TY - JOUR TI - Synaptic plasticity functions in an organic electrochemical transistor AU - Gkoupidenis, Paschalis AU - Schaefer, Nathan AU - Strakosas, Xenofon AU - Fairfield, Jessamyn A. AU - Malliaras, George G. T2 - Applied Physics Letters AB - Synaptic plasticity functions play a crucial role in the transmission of neural signals in the brain. Short-term plasticity is required for the transmission, encoding, and filtering of the neural signal, whereas long-term plasticity establishes more permanent changes in neural microcircuitry and thus underlies memory and learning. The realization of bioinspired circuits that can actually mimic signal processing in the brain demands the reproduction of both short- and long-term aspects of synaptic plasticity in a single device. Here, we demonstrate the implementation of neuromorphic functions similar to biological memory, such as short- to long-term memory transition, in non-volatile organic electrochemical transistors (OECTs). Depending on the training of the OECT, the device displays either short- or long-term plasticity, therefore, exhibiting non von Neumann characteristics with merged processing and storing functionalities. These results are a first step towards the implementation of organic-based neuromorphic circuits. DA - 2015/12/28/ PY - 2015/12/28/ DO - 10.1063/1.4938553 UR - https://doi.org/10.1063/1.4938553 ER - TY - JOUR TI - Neuromorphic Functions in PEDOT:PSS Organic Electrochemical Transistors AU - Gkoupidenis, Paschalis AU - Schaefer, Nathan AU - Garlan, Benjamin AU - Malliaras, George G. T2 - Advanced Materials AB - Depressive short-term synaptic plasticity functions are implemented with a simple polymer poly(3,4ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) organic electrochemical transistor device. These functions are a first step toward the realization of organic-based neuroinspired platforms with spatiotemporal information processing capabilities. DA - 2015/10// PY - 2015/10// DO - 10.1002/adma.201503674 VL - 27 IS - 44 SP - 7176-7180 ER - TY - JOUR TI - Vibrational state-selective resonant two-photon photoelectron spectroscopy of AuS- via a spin-forbidden excited state AU - Liu, Hong-Tao AU - Huang, Dao-Ling AU - Liu, Yuan AU - Cheung, Ling-Fung AU - Dau, Phuong Diem AU - Ning, Chuan-Gang AU - Wang, Lai-Sheng T2 - Journal of Physical Chemistry Letters AB - Vibrational state-selective resonant two-photon photoelectron spectra have been obtained via a triplet intermediate state ((3)Σ(-)) of AuS(-) near its detachment threshold using high-resolution photoelectron imaging of cryogenically cooled AuS(-) anions. Four vibrational levels of the (3)Σ(-) excited state are observed to be below the detachment threshold. Resonant two-photon absorptions through these levels yield vibrational state-selective photoelectron spectra to the (2)Σ final state of neutral AuS with broad and drastically different Franck-Condon distributions, reflecting the symmetries of the vibrational wave functions of the (3)Σ(-) intermediate state. The (3)Σ(-) excited state is spin-forbidden from the (1)Σ(+) ground state of AuS(-) and is accessed due to strong relativistic effects. The nature of the (3)Σ(-) excited state is confirmed by angular distributions of the photoelectron images and quantum calculations. DA - 2015/// PY - 2015/// DO - 10.1021/acs.jpclett.5b00053 VL - 6 IS - 4 SP - 637-642 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84923376070&partnerID=MN8TOARS ER - TY - JOUR TI - Calculation of photodetachment cross sections and photoelectron angular distributions of negative ions using density functional theory AU - Liu, Yuan AU - Ning, Chuangang T2 - Journal of Chemical Physics AB - Recently, the development of photoelectron velocity map imaging makes it much easier to obtain the photoelectron angular distributions (PADs) experimentally. However, explanations of PADs are only qualitative in most cases, and very limited works have been reported on how to calculate PAD of anions. In the present work, we report a method using the density-functional-theory Kohn-Sham orbitals to calculate the photodetachment cross sections and the anisotropy parameter β. The spherical average over all random molecular orientation is calculated analytically. A program which can handle both the Gaussian type orbital and the Slater type orbital has been coded. The testing calculations on Li−, C−, O−, F−, CH−, OH−, NH2−, O2−, and S2− show that our method is an efficient way to calculate the photodetachment cross section and anisotropy parameter β for anions, thus promising for large systems. DA - 2015/// PY - 2015/// DO - 10.1063/1.4932978 VL - 143 IS - 14 SP - 144310 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84944267513&partnerID=MN8TOARS ER - TY - JOUR TI - Selective layer disordering in intersubband Al0.028Ga0.972N/AlN superlattices with silicon nitride capping layer AU - Wierer, Jonathan J., Jr. AU - Allerman, Andrew A. AU - Skogen, Erik J. AU - Tauke-Pedretti, Anna AU - Vawter, Gregory A. AU - Montano, Ines T2 - Applied Physics Express AB - Selective layer disordering in an intersubband Al0.028Ga0.972N/AlN superlattice using a silicon nitride (SiNx) capping layer is demonstrated. The SiNx capped superlattice exhibits suppressed layer disordering under high-temperature annealing. Additionally, the rate of layer disordering is reduced with increased SiNx thickness. The layer disordering is caused by Si diffusion, and the SiNx layer inhibits vacancy formation at the crystal surface and ultimately, the movement of Al and Ga atoms across the heterointerfaces. Patterning of the SiNx layer results in selective layer disordering, an attractive method to integrate active and passive III–nitride-based intersubband devices. DA - 2015/// PY - 2015/// DO - 10.7567/APEX.8.061004 VL - 8 IS - 6 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000358071400004&KeyUID=WOS:000358071400004 ER - TY - JOUR TI - Performance and Breakdown Characteristics of Irradiated Vertical Power GaN P-i-N Diodes AU - King, M. P. AU - Armstrong, A. M. AU - Dickerson, J. R. AU - Vizkelethy, G. AU - Fleming, R. M. AU - Campbell, J. AU - Wampler, W. R. AU - Kizilyalli, I. C. AU - Bour, D. P. AU - Aktas, O. AU - Nie, H. AU - Disney, D. AU - Wierer, J. AU - Allerman, A. A. AU - Moseley, M. W. AU - Leonard, F. AU - Talin, A. A. AU - Kaplar, R. J. T2 - Ieee Transactions on Nuclear Science AB - Electrical performance and defect characterization of vertical GaN P-i-N diodes before and after irradiation with 2.5 MeV protons and neutrons is investigated. Devices exhibit increase in specific on-resistance following irradiation with protons and neutrons, indicating displacement damage introduces defects into the $p$ -GaN and $n^{-}$ drift regions of the device that impact on-state device performance. The breakdown voltage of these devices, initially above 1700 V, is observed to decrease only slightly for particle fluence $ < {10^{13}} ~\hbox{cm}^{ - 2}$ . The unipolar figure of merit for power devices indicates that while the on-resistance and breakdown voltage degrade with irradiation, vertical GaN P-i-Ns remain superior to the performance of the best available, unirradiated silicon devices and on-par with unirradiated modern SiC-based power devices. DA - 2015/// PY - 2015/// DO - 10.1109/tns.2015.2480071 VL - 62 IS - 6 SP - 2912-2918 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000367732600074&KeyUID=WOS:000367732600074 ER - TY - JOUR TI - On the increased efficiency in InGaN-based multiple quantum wells emitting at 530-590 nm with AlGaN interlayers AU - Koleske, D. D. AU - Fischer, A. J. AU - Bryant, B. N. AU - Kotula, P. G. AU - Wierer, J. J. T2 - Journal of Crystal Growth AB - InGaN/AlGaN/GaN-based multiple quantum wells (MQWs) with AlGaN interlayers (ILs) are investigated, specifically to examine the fundamental mechanisms behind their increased radiative efficiency at wavelengths of 530–590 nm. The AlzGa1−zN (z~0.38) IL is ~1–2 nm thick, and is grown after and at the same growth temperature as the ~3 nm thick InGaN quantum well (QW). This is followed by an increase in temperature for the growth of a ~10 nm thick GaN barrier layer. The insertion of the AlGaN IL within the MQW provides various benefits. First, the AlGaN IL allows for growth of the InxGa1−xN QW well below typical growth temperatures to achieve higher x (up to~0.25). Second, annealing the IL capped QW prior to the GaN barrier growth improves the AlGaN IL smoothness as determined by atomic force microscopy, improves the InGaN/AlGaN/GaN interface quality as determined from scanning transmission electron microscope images and x-ray diffraction, and increases the radiative efficiency by reducing non-radiative defects as determined by time-resolved photoluminescence measurements. Finally, the AlGaN IL increases the spontaneous and piezoelectric polarization induced electric fields acting on the InGaN QW, providing an additional red-shift to the emission wavelength as determined by Schrodinger-Poisson modeling and fitting to the experimental data. The relative impact of increased indium concentration and polarization fields on the radiative efficiency of MQWs with AlGaN ILs is explored along with implications to conventional longer wavelength emitters. DA - 2015/// PY - 2015/// DO - 10.1016/j.jcrysgro.2014.12.034 VL - 415 SP - 57-64 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000349603500011&KeyUID=WOS:000349603500011 ER - TY - JOUR TI - Growth temperature dependence of Si doping efficiency and compensating deep level defect incorporation in Al0.7Ga0.3N AU - Armstrong, Andrew M. AU - Moseley, Michael W. AU - Allerman, Andrew A. AU - Crawford, Mary H. AU - Wierer, Jonathan J., Jr. T2 - Journal of Applied Physics AB - The growth temperature dependence of Si doping efficiency and deep level defect formation was investigated for n-type Al0.7Ga0.3N. It was observed that dopant compensation was greatly reduced with reduced growth temperature. Deep level optical spectroscopy and lighted capacitance-voltage were used to understand the role of acceptor-like deep level defects on doping efficiency. Deep level defects were observed at 2.34 eV, 3.56 eV, and 4.74 eV below the conduction band minimum. The latter two deep levels were identified as the major compensators because the reduction in their concentrations at reduced growth temperature correlated closely with the concomitant increase in free electron concentration. Possible mechanisms for the strong growth temperature dependence of deep level formation are considered, including thermodynamically driven compensating defect formation that can arise for a semiconductor with very large band gap energy, such as Al0.7Ga0.3N. DA - 2015/// PY - 2015/// DO - 10.1063/1.4920926 VL - 117 IS - 18 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000354984500042&KeyUID=WOS:000354984500042 ER - TY - JOUR TI - Detection and modeling of leakage current in AlGaN-based deep ultraviolet light-emitting diodes AU - Moseley, Michael W. AU - Allerman, Andrew A. AU - Crawford, Mary H. AU - Wierer, Jonathan J., Jr. AU - Smith, Michael L. AU - Armstrong, Andrew M. T2 - Journal of Applied Physics AB - Current-voltage (IV) characteristics of two AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) with differing densities of open-core threading dislocations (nanopipes) are analyzed. A three-diode circuit is simulated to emulate the forward-bias IV characteristics of the DUV-LEDs, but is only able to accurately model the lower leakage current, lower nanopipe density DUV-LED. It was found that current leakage through the nanopipes in these structures is rectifying, despite nanopipes being previously established as inherently n-type. Using defect-sensitive etching, the nanopipes are revealed to terminate within the p-type GaN capping layer of the DUV-LEDs. The circuit model is modified to account for another p-n junction between the n-type nanopipes and the p-type GaN, and an excellent fit to the forward-bias IV characteristics of the leaky DUV-LED is achieved. DA - 2015/// PY - 2015/// DO - 10.1063/1.4908543 VL - 117 IS - 9 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000351134400036&KeyUID=WOS:000351134400036 ER - TY - JOUR TI - Defect-reduction mechanism for improving radiative efficiency in InGaN/GaN light-emitting diodes using InGaN underlayers AU - Armstrong, Andrew M. AU - Bryant, Benjamin N. AU - Crawford, Mary H. AU - Koleske, Daniel D. AU - Lee, Stephen R. AU - Wierer, Jonathan J., Jr. T2 - Journal of Applied Physics AB - The influence of a dilute InxGa1-xN (x ∼ 0.03) underlayer (UL) grown below a single In0.16Ga0.84N quantum well (SQW), within a light-emitting diode (LED), on the radiative efficiency and deep level defect properties was studied using differential carrier lifetime (DCL) measurements and deep level optical spectroscopy (DLOS). DCL measurements found that inclusion of the UL significantly improved LED radiative efficiency. At low current densities, the non-radiative recombination rate of the LED with an UL was found to be 3.9 times lower than the LED without an UL, while the radiative recombination rates were nearly identical. This suggests that the improved radiative efficiency resulted from reduced non-radiative defect concentration within the SQW. DLOS measurement found the same type of defects in the InGaN SQWs with and without ULs. However, lighted capacitance-voltage measurements of the LEDs revealed a 3.4 times reduction in a SQW-related near-mid-gap defect state for the LED with an UL. Quantitative agreement in the reduction of both the non-radiative recombination rate (3.9×) and deep level density (3.4×) upon insertion of an UL corroborates deep level defect reduction as the mechanism for improved LED efficiency. DA - 2015/// PY - 2015/// DO - 10.1063/1.4916727 VL - 117 IS - 13 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000352645100037&KeyUID=WOS:000352645100037 ER - TY - JOUR TI - Defect-enabled electrical current leakage in ultraviolet light-emitting diodes AU - Moseley, Michael W. AU - Allerman, Andrew A. AU - Crawford, Mary H. AU - Wierer, Jonathan J., Jr. AU - Smith, Michael L. AU - Biedermann, Laura B. T2 - Physica Status Solidi a-Applications and Materials Science AB - Electrical current leakage paths in AlGaN‐based ultraviolet (UV) light‐emitting diodes (LEDs) are identified using conductive atomic force microscopy. Open‐core threading dislocations are found to conduct current through insulating Al 0.7 Ga 0.3 N layers. A defect‐sensitive H 3 PO 4 etch reveals these open‐core threading dislocations as 1–2 µm wide hexagonal etch pits visible with optical microscopy. Additionally, closed‐core threading dislocations are decorated with smaller and more numerous nanometer‐scale pits, which are quantifiable by atomic‐force microscopy. The performances of UV‐LEDs fabricated on similar Si‐doped Al 0.7 Ga 0.3 N templates are found to have a strong correlation to the density of these electrically conductive open‐core dislocations, while the total threading dislocation densities of the UV‐LEDs remain relatively unchanged. DA - 2015/// PY - 2015/// DO - 10.1002/pssa.201400182 VL - 212 IS - 4 SP - 723-726 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000352820100002&KeyUID=WOS:000352820100002 ER - TY - JOUR TI - Advantages of III-nitride laser diodes in solid-state lighting AU - Wierer, Jonathan J., Jr. AU - Tsao, Jeffrey Y. T2 - Physica Status Solidi a-Applications and Materials Science AB - III‐nitride laser diodes (LDs) are an interesting light source for solid‐state lighting (SSL). Modelling of LDs is performed to reveal the potential advantages over traditionally used light‐emitting diodes (LEDs). The first, and most notable, advantage is LDs have higher efficiency at higher currents when compared to LEDs. This is because Auger recombination that causes efficiency droop can no longer grow after laser threshold. Second, the same phosphor‐converted methods used with LEDs can also be used with LDs to produce white light with similar color rendering and color temperature. Third, producing white light from color mixed emitters is equally challenging for both LEDs and LDs, with neither source having a direct advantage. Fourth, the LD emission is directional and can be more readily captured and focused, leading to the possibility of novel and more compact luminaires. Finally, the smaller area and higher current density operation of LDs provides them with a potential cost advantage over LEDs. These advantages make LDs a compelling source for future SSL. DA - 2015/// PY - 2015/// DO - 10.1002/pssa.201431700 VL - 212 IS - 5 SP - 980-985 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000354405000014&KeyUID=WOS:000354405000014 ER - TY - CONF TI - Enhanced coherence properties and solid-state spin ensemble magnetometry using optimized dynamical decoupling AU - Farfurnik, D. T2 - Israel Physical Society Annual Meeting C2 - 2015/12// C3 - The Israel Physical Society Annual Meeting CY - Bar Ilan University, Ramat Gan, Israel DA - 2015/12// PY - 2015/12// ER - TY - JOUR TI - Response: Commentary: “Asking photons where they have been” - without telling them what to say AU - Danan, Ariel AU - Farfurnik, Demitry AU - Bar-Ad, Shimshon AU - Vaidman, Lev T2 - Frontiers in Physics AB - GENERAL COMMENTARY article Front. Phys., 30 June 2015Sec. Optics and Photonics Volume 3 - 2015 | https://doi.org/10.3389/fphy.2015.00048 DA - 2015/6// PY - 2015/6// DO - 10.3389/fphy.2015.00048 VL - 3 ER - TY - JOUR TI - Optimizing a dynamical decoupling protocol for solid-state electronic spin ensembles in diamond AU - Farfurnik, D. AU - Jarmola, A. AU - Pham, L. M. AU - Wang, Z. H. AU - Dobrovitski, V. V. AU - Walsworth, R. L. AU - Budker, D. AU - Bar-Gill, N. T2 - Physical Review B AB - We demonstrate significant improvements of the spin coherence time of a dense ensemble of nitrogen-vacancy (NV) centers in diamond through optimized dynamical decoupling (DD). Cooling the sample down to $77$ K suppresses longitudinal spin relaxation $T_1$ effects and DD microwave pulses are used to increase the transverse coherence time $T_2$ from $\sim 0.7$ ms up to $\sim 30$ ms. We extend previous work of single-axis (CPMG) DD towards the preservation of arbitrary spin states. Following a theoretical and experimental characterization of pulse and detuning errors, we compare the performance of various DD protocols. We identify that the optimal control scheme for preserving an arbitrary spin state is a recursive protocol, the concatenated version of the XY8 pulse sequence. The improved spin coherence might have an immediate impact on improvements of the sensitivities of AC magnetometry. Moreover, the protocol can be used on denser diamond samples to increase coherence times up to NV-NV interaction time scales, a major step towards the creation of quantum collective NV spin states. DA - 2015/8// PY - 2015/8// DO - 10.1103/physrevb.92.060301 VL - 92 IS - 6 ER - TY - CONF TI - 3D Packaging for High Density And High Performance GaN-Based Circuits AU - Hopkins, Douglas C. T2 - 2015 IEEE Applied Power Electronics Conference and Exposition (APEC) C2 - 2015/// C3 - 2015 IEEE Applied Power Electronics Conference and Exposition (APEC) CY - Charlotte, NC DA - 2015/// PY - 2015/3/15/ ER - TY - ER - TY - CONF TI - Impact analysis of different inputs and outputs block sizes of DFT-SCFDMA system AU - Pervej, M.F. AU - Sarkar, M.Z.I. AU - Islam, M.T. AB - The Bit Error Rate (BER) and Peak to Average Power Ratio (PAPR) are the major concerns for wireless communication. This paper aims to analyze these two important parameters for different inputs and outputs block sizes of the discrete Fourier transform (DFT) based single carrier frequency division multiple access (SCFDMA) system by using the conventional raised cosine (RC) and square root raised cosine (RRC) pulse shaping filters for different sub-carrier mapping schemes (e.g. interleaved frequency division multiple access (IFDMA), localized frequency division multiple access (LFDMA) and distributed frequency division multiple access (DFDMA)). Note that DFT based SCFDMA system is being adopted for uplink communication in the long term evolution (LTE) for its lower PAPR. The suitable block size of SCFDMA is crucial to improve wireless communication performances in terms of BER and PAPR, because if the block sizes vary then the PAPR also changes. Therefore, this paper analyzes the impact of the input and output block sizes of the system on enhancement of the system performances. Taking help from the numerical analysis and evaluation, this paper shows the way to choose the proper input and output block size to have a significantly lower PAPR and BER. C2 - 2015/// C3 - 2nd International Conference on Electrical Engineering and Information and Communication Technology, iCEEiCT 2015 DA - 2015/// DO - 10.1109/ICEEICT.2015.7307372 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84962159109&partnerID=MN8TOARS ER - TY - CONF TI - Effect of signal length in cross-correlation based underwater network size estimation AU - Hossen, M.A. AU - Chowdhury, S.A.H. AU - Anower, M.S. AU - Hossen, S. AU - Pervej, M.F. AU - Hasan, M.M. AB - Signal length possesses a very important role in size estimation of underwater wireless sensor network (UWSN). As size estimation is very tough in UWSN s using conventional protocol techniques, a cross-correlation based technique is introduced to estimate the number of nodes. In UWSN, The greater the signal length, the more energy is required to perform the estimation. In this paper, we observe the effect of signal length (N s ) over the number of estimated nodes (N) in a spherical region of an underwater acoustic sensor network (UASN) using three sensors and investigate the error in node estimation for different N s . As the theoretical required N s is infinity (N s = 10 6 samples is used in simulation), using minimum N s how it is possible to go through a successful estimation process i.e., accurate node estimation is being observed and discussed. C2 - 2015/// C3 - 2nd International Conference on Electrical Engineering and Information and Communication Technology, iCEEiCT 2015 DA - 2015/// DO - 10.1109/ICEEICT.2015.7307476 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84962182191&partnerID=MN8TOARS ER - TY - CONF TI - W-Band Sparse Synthetic Aperture for Computational Imaging AU - Venkatesh, Suresh AU - Viswanathan, Naren AU - Schurig, David AB - We present a sparse synthetic aperture system at W-Band (75 – 110 GHz) using sub-harmonic mixer modules. The active system consists of a scanned transmitter module, a fixed receiver module and a vector network analyzer as the back end. For this scanned synthetic aperture system we construct a complete analytical forward model and solve the inverse problem to reconstruct the scene using least squares technique. We demonstrate standoff diffraction limited imaging of 2D and 3D targets and achieve a cross range resolution of 3 mm and a depth range resolution of 4 mm respectively. Furthermore, we also show that the positions of the transmitter can be further optimized using finely gridded scattered electric field information from a specific target. This optimization technique helps to reduce the number of measurements significantly by using measurements above a certain threshold SNR for the scene reconstruction. C2 - 2015/// C3 - Imaging and Applied Optics 2015 DA - 2015/// DO - 10.1364/aoms.2015.jt5a.17 PB - The Optical Society ER - TY - CONF TI - Receiver/transmitter configuration optimization for compressed computational millimeter-wave imaging AU - Venkatesh, Suresh AU - Viswanathan, Naren AU - Schurig, David AB - Millimeter wave (mmw) imaging is gaining popularity in surveillance systems as it provides good tradeoff between high resolution (optical/IR imaging) and high penetration depth (microwave). Conventional mmw Fourier transform based holographic imaging systems (D.M. Sheen et. al., MTT, IEEE Transactions on, vol.49, no.9, Sep 2001) require as many measurements as the required space-bandwidth product (M) of the target image. However, in compressed imaging systems (Guy Lipworth et. al., JOSA A, Vol. 30, Issue 8, 2013), apriori knowledge of the target object to be imaged can considerably reduce the number of measurements required. General priors such as sparsity can almost always be used, but more target specific priors can be used for further reducing the number of measurements needed. C2 - 2015/7// C3 - 2015 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium) DA - 2015/7// DO - 10.1109/usnc-ursi.2015.7303304 PB - Institute of Electrical & Electronics Engineers (IEEE) ER - TY - JOUR TI - Polarization-independent actively tunable colour generation on imprinted plasmonic surfaces AU - Franklin, Daniel AU - Chen, Yuan AU - Vazquez-Guardado, Abraham AU - Modak, Sushrut AU - Boroumand, Javaneh AU - Xu, Daming AU - Wu, Shin-Tson AU - Chanda, Debashis T2 - Nature Communications AB - Structural colour arising from nanostructured metallic surfaces offers many benefits compared to conventional pigmentation based display technologies, such as increased resolution and scalability of their optical response with structure dimensions. However, once these structures are fabricated their optical characteristics remain static, limiting their potential application. Here, by using a specially designed nanostructured plasmonic surface in conjunction with high birefringence liquid crystals, we demonstrate a tunable polarization-independent reflective surface where the colour of the surface is changed as a function of applied voltage. A large range of colour tunability is achieved over previous reports by utilizing an engineered surface which allows full liquid crystal reorientation while maximizing the overlap between plasmonic fields and liquid crystal. In combination with imprinted structures of varying periods, a full range of colours spanning the entire visible spectrum is achieved, paving the way towards dynamic pixels for reflective displays. DA - 2015/// PY - 2015/// DO - 10.1038/ncomms8337 VL - 6 SP - 7337 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84931281928&partnerID=MN8TOARS ER - TY - JOUR TI - Multi-spectral infrared spectroscopy for robust plastic identification AU - Vázquez-Guardado, Abraham AU - Money, Mason AU - McKinney, Nathaniel AU - Chanda, Debashis T2 - Applied Optics AB - The identification and classification of plastics plays an important role in waste management and recycling processes. Present electrical and optical sorting techniques lack the required resolution for accurate identification in a high throughput manner for a diverse set of plastics commonly found in municipal waste. In this work a multi-spectral infrared spectroscopic technique is employed to construct a unique fingerprint library of 12 plastic resin groups that are commonly encountered in municipal waste. We test the proposed method in a blind plastic identification experiment, which shows excellent unbiased identification accuracy. This simple optical technique in combination with the multi-spectral library will enable high throughput and accurate detection of various plastics from recovered solid waste. DA - 2015/// PY - 2015/// DO - 10.1364/AO.54.007396 VL - 54 IS - 24 SP - 7396-7405 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84942374630&partnerID=MN8TOARS ER - TY - CONF TI - Exploration and topological mapping with Hexbugs AU - Dirafzoon, Alireza AU - Lobaton, Edgar AU - Bozkurt, Alper AB - In this demonstration, we present a topological mapping system to be used with biobotic insects in order to sketch maps of unknown arenas using only neighbor to neighbor interactions among the agents. Biobotic insects fuse the locomotory advantages of insects with wireless sensing technology in form of electronic backpacks to function as search and rescue agents. Our mapping approach is designed for emergency response scenarios, where traditional mapping approaches may fail due to lack of localization information. We demonstrate the performance of our proposed approach instead using Hexbugs, which emulate the natural random motion of biobots. The Hexbugs are dispersed into a maze with unknown structure (Fig. 1), and their local interactions are captured through a visual tracking system. Such information is then exploited into a data analysis engine in order to robustly find the topological structure of the maze. C2 - 2015/4/13/ C3 - Proceedings of the 14th International Conference on Information Processing in Sensor Networks DA - 2015/4/13/ DO - 10.1145/2737095.2737137 PB - ACM UR - http://dx.doi.org/10.1145/2737095.2737137 KW - Topological Mapping KW - Swram Robotics KW - Cyborg Insect Networks ER - TY - CHAP TI - FreePDK15: An Open-Source Predictive Process Design Kit for 15nm FinFET Technology AU - Bhanushali, K. AU - Davis, W.R. T2 - ISPD '15: Proceedings of the 2015 Symposium on International Symposium on Physical Design AB - This paper discusses design rules and layout guidelines for an open source predictive process design kit (PDK) for multi-gate 15nm FinFET devices. Additional design rules are introduced considering process variability, and challenges involved in fabrication beyond 20nm. Particularly, double patterning lithography is assumed and a unique set of design rules are developed for critical dimensions. In order to improve the FinFET layout density, Middle-of-line local interconnect layers are implemented for the FinFET layout. The rules are further validated by running Calibre design-rule checks on Virtuoso layout of an Inverter and NAND4 cells. As part of the validation process, the area of a FreePDK15 inverter was compared to the area of an inverter in 45nm bulk MOS process and the ratio was found to be 1:6. This kit primarily aims to support introduction of sub-20nm FinFET devices into research and universities. PY - 2015/// DO - 10.1145/2717764.2717782 SP - 165-170 ER - TY - CONF TI - High Altitude Infrasound Measurements using Balloon-Borne Arrays C2 - 2015/12// C3 - American Geophysical Union, Fall Meeting 2015 DA - 2015/12// UR - https://ui.adsabs.harvard.edu/abs/2015AGUFM.S54B..06B/abstract ER - TY - JOUR TI - Single-wire radio frequency transmission lines in biological tissue AU - Besnoff, Jordan S. AU - Reynolds, Matthew S. T2 - Applied Physics Letters AB - We present an approach for implanting radio frequency transmission lines in biological tissue, using a single insulated wire surrounded by tissue as a variant of the Goubau single-wire transmission line (SWTL) in air. We extend the Goubau SWTL model to include SWTLs surrounded by lossy dielectrics such as tissue by assuming a propagating mode component in the tissue. We show that a thin wire of radius 63.5 μm, coated with biocompatible fluorinated ethylene propylene dielectric, exhibits a measured loss of only 1 dB/cm at a frequency of 915 MHz. The model fit to the measured insertion loss is within ±0.3 dB/cm across the 100 MHz to 3 GHz band. This SWTL presents excellent impedance matching to 50 Ω as evidenced by a measured median return loss better than 10 dB across the 100 MHz to 3 GHz range. This approach represents an alternative to near-field magnetic coupling for implanted systems where tissue displacement by a single, thin wire can be tolerated. DA - 2015/5/4/ PY - 2015/5/4/ DO - 10.1063/1.4919799 VL - 106 IS - 18 SP - 183705 ER - TY - JOUR TI - Tattoo-based noninvasive glucose monitoring: A proof-of-concept study AU - Bandodkar, A.J. AU - Jia, W. AU - Yardimci, C. AU - Wang, X. AU - Ramirez, J. AU - Wang, J. T2 - Analytical Chemistry AB - We present a proof-of-concept demonstration of an all-printed temporary tattoo-based glucose sensor for noninvasive glycemic monitoring. The sensor represents the first example of an easy-to-wear flexible tattoo-based epidermal diagnostic device combining reverse iontophoretic extraction of interstitial glucose and an enzyme-based amperometric biosensor. In-vitro studies reveal the tattoo sensor’s linear response toward physiologically relevant glucose levels with negligible interferences from common coexisting electroactive species. The iontophoretic-biosensing tattoo platform is reduced to practice by applying the device on human subjects and monitoring variations in glycemic levels due to food consumption. Correlation of the sensor response with that of a commercial glucose meter underscores the promise of the tattoo sensor to detect glucose levels in a noninvasive fashion. Control on-body experiments demonstrate the importance of the reverse iontophoresis operation and validate the sensor specificity. This preliminary investigation indicates that the tattoo-based iontophoresis-sensor platform holds considerable promise for efficient diabetes management and can be extended toward noninvasive monitoring of other physiologically relevant analytes present in the interstitial fluid. DA - 2015/// PY - 2015/// DO - 10.1021/ac504300n VL - 87 IS - 1 SP - 394-398 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84920495168&partnerID=MN8TOARS ER - TY - CONF TI - Additive Manufacturing In Power Electronics Packaging AU - Hopkins, D.C. AU - Ke, H. T2 - IEEE Applied Power Electronics Conference C2 - 2015/// CY - Charlotte, NC DA - 2015/// PY - 2015/3/15/ ER - TY - CONF TI - 3D Power Electronics Packaging and Additive Manufacturing AU - Hopkins, D.C. T2 - 3rd IEEE Workshop on Wide Bandgap Power Devices and Applications C2 - 2015/11// CY - Blacksburg, VA DA - 2015/11// PY - 2015/11// ER - TY - CONF TI - Additive Manufacturing (a.k.a. 3D Printing) for Designing Power Electronic Systems AU - Hopkins, D.C. T2 - Manufacturing Conference 2015 (MFGCON) C2 - 2015/10/20/ CY - Raleigh, NC DA - 2015/10/20/ PY - 2015/10/20/ ER - TY - CONF TI - Physical Rf Circuit Techniques And The Implications On Future Power Module Design AU - Morgan, A.J. AU - Hopkins, D.C. AU - McKeown, M. T2 - International Microelectronics Assembly & Packaging Society, Northeast Symposium C2 - 2015/5// DA - 2015/5// PY - 2015/5// ER - TY - CONF TI - The Evolution and Future Development of Power Electronics as an Essential Element of Power Generation/Delivery, Energy Efficiency, and Industrial Automation AU - Lawrence, R. AU - Hopkins, D.C. T2 - North Carolina IEEE Power Electronic Society (PELS) Chapter Seminar C2 - 2015/12/12/ CY - Raleigh, NC DA - 2015/12/12/ PY - 2015/12/12/ ER - TY - JOUR TI - A Robust, Composite Packaging Approach for a High Voltage 6.5kV IGBT and Series Diode AU - Morgan, Adam AU - De, Ankan AU - Ke, Haotao AU - Zhao, Xin AU - Vechalapu, Kasunaidu AU - Hopkins, Douglas C. AU - Bhattacharya, Subhashish T2 - International Symposium on Microelectronics AB - The main motivation of this work is to design, fabricate, test, and compare an alternative, robust packaging approach for a power semiconductor current switch. Packaging a high voltage power semiconductor current switch into a single power module, compared to using separate power modules, offers cost, performance, and reliability advantages. With the advent of Wide-Bandgap (WBG) semiconductors, such as Silicon-Carbide, singular power electronic devices, where a device is denoted as a single transistor or rectifier unit on a chip, can now operate beyond 10kV–15kV levels and switch at frequencies within the kHz range. The improved voltage blocking capability reduces the number of series connected devices within the circuit, but challenges power module designers to create packages capable of managing the electrical, mechanical, and thermal stresses produced during operation. The non-sinusoidal nature of this stress punctuated with extremely fast changes in voltage and current, with respect to time, leads to non-ideal electrical and thermal performance. An optimized power semiconductor series current switch is fabricated using an IGBT (6500V/25A die) and SiC JBS Diode (6000V/10A), packaged into a 3D printed housing, to create a composite series current switch package (CSCSP). The final chosen device configuration was simulated and verified in an ANSYS software package. Also, the thermal behavior of such a composite package was simulated and verified using COMSOL. The simulated results were then compared with empirically obtained data, in order to ensure that the thermal ratings of the power devices were not exceeded; directly affecting the maximum attainable frequency of operation for the CSCSP. Both power semiconductor series current switch designs are tested and characterized under hard switching conditions. Special attention is given to ensure the voltage stress across the devices is significantly reduced. DA - 2015/10/1/ PY - 2015/10/1/ DO - 10.4071/isom-2015-wp17 VL - 2015 IS - 1 SP - 000359-000364 LA - en OP - SN - 2380-4505 UR - http://dx.doi.org/10.4071/isom-2015-wp17 DB - Crossref ER - TY - CONF TI - Source Mark: A Source-Level Approach for Identifying Architecture and Optimization Agnostic Regions for Performance Analysis AU - Agrawal, Abhinav AU - Wibowo, Bagus AU - Tuck, James T2 - IEEE C2 - 2015/// C3 - 2015 IEEE International Symposium on Workload Characterization DA - 2015/// SP - 160-171 ER - TY - CONF TI - Runtime checking C programs AU - Milewicz, Reed AU - Vanka, Rajesh AU - Tuck, James AU - Quinlan, Daniel AU - Pirkelbauer, Peter C2 - 2015/// C3 - Proceedings of the 30th Annual ACM Symposium on Applied Computing DA - 2015/// SP - 2107-2114 ER - TY - CONF TI - Revisiting ILP Designs for Throughput-Oriented GPGPU Architecture AU - Xiang, P. AU - Yang, Y. AU - Mantor, M. AU - Rubin, N. AU - Zhou, H. T2 - 2015 15th IEEE/ACM International Symposium on Cluster, Cloud and Grid Computing AB - Many-core architectures such as graphics processing units (GPUs) rely on thread-level parallelism (TLP)to overcome pipeline hazards. Consequently, each core in a many-core processor employs a relatively simple in-order pipeline with limited capability to exploit instruction-level parallelism (ILP). In this paper, we study the ILP impact on the throughput-oriented many-core architecture, including data bypassing, score boarding and branch prediction. We show that these ILP techniques significantly reduce the performance dependency on TLP. This is especially useful for applications, whose resource usage limits the hardware to run a high number of threads concurrently. Furthermore, ILP techniques reduce the demand on on-chip resource to support high TLP. Given the workload-dependent impact from ILP, we propose heterogeneous GPGPU architecture, consisting of both the cores designed for high TLP and those customized with ILPtechniques. Our results show that our heterogeneous GPUarchitecture achieves high throughput as well as high energy and area-efficiency compared to homogenous designs. C2 - 2015/5// C3 - Proceedings of the 2015 15th IEEE/ACM International Symposium on Cluster, Cloud and Grid Computing CY - Shenzhen, China DA - 2015/5// PY - 2015/5/4/ DO - 10.1109/CCGrid.2015.14 SP - 121-130 PB - IEEE SN - 9781479980062 KW - GPGPU KW - Heterogeneous KW - ILP KW - Energy ER - TY - CONF TI - Locality-Driven Dynamic GPU Cache Bypassing AU - Li, C. AU - Song, S. AU - Dai, H. AU - Sidelnik, A. AU - Hari, S. AU - Zhou, H. T2 - 29th International conference on supercomputing AB - This paper presents novel cache optimizations for massively parallel, throughput-oriented architectures like GPUs. L1 data caches (L1 D-caches) are critical resources for providing high-bandwidth and low-latency data accesses. However, the high number of simultaneous requests from single-instruction multiple-thread (SIMT) cores makes the limited capacity of L1 D-caches a performance and energy bottleneck, especially for memory-intensive applications. We observe that the memory access streams to L1 D-caches for many applications contain a significant amount of requests with low reuse, which greatly reduce the cache efficacy. Existing GPU cache management schemes are either based on conditional/reactive solutions or hit-rate based designs specifically developed for CPU last level caches, which can limit overall performance. C2 - 2015/6// C3 - ICS '15: Proceedings of the 29th ACM on International Conference on Supercomputing CY - Newport Beach/Irvine, CA DA - 2015/6// PY - 2015/6/8/ DO - 10.1145/2751205.2751237 SP - 61-77 PB - ACM KW - GPU architecture Optimization KW - Locality KW - Cache Bypassing ER - TY - CONF TI - An Optimized AMPM-based Prefetcher Coupled with Configurable Cache Line Sizing AU - Jia, Q. AU - Padia, M.B. AU - Amboju, K. AU - Zhou, H. C2 - 2015/6// C3 - JILP Workshop on Computer Architecture Competitions (JWAC): 2nd Data Prefetching Championship (DPC2) DA - 2015/6// ER - TY - JOUR TI - Wearable temporary tattoo sensor for real-time trace metal monitoring in human sweat AU - Kim, Jayoung AU - de Araujo, William R. AU - Samek, Izabela A. AU - Bandodkar, Amay J. AU - Jia, Wenzhao AU - Brunetti, Barbara AU - Paixão, Thiago R.L.C. AU - Wang, Joseph T2 - Electrochemistry Communications AB - A wearable electrochemical sensor for non-invasive monitoring of trace metals in human perspiration is described. The temporary tattoo-based printable stripping-voltammetric sensor has been applied for real-time monitoring of zinc in sweat using a bismuth/Nafion film electrode during physical activity. The Zn temporary tattoo sensor withstands repeated mechanical stress and displays a well-defined Zn response during on-body testing. Such a non-invasive stripping-voltammetric detection could be readily expanded to epidermal measurements of other relevant heavy metals. DA - 2015/2// PY - 2015/2// DO - 10.1016/j.elecom.2014.11.024 VL - 51 SP - 41-45 J2 - Electrochemistry Communications LA - en OP - SN - 1388-2481 UR - http://dx.doi.org/10.1016/j.elecom.2014.11.024 DB - Crossref KW - Wearable sensors KW - Stripping voltammetry KW - Zinc KW - Temporary tattoo sensor KW - Sweat ER - TY - JOUR TI - Highly Stretchable Fully-Printed CNT-Based Electrochemical Sensors and Biofuel Cells: Combining Intrinsic and Design-Induced Stretchability AU - Bandodkar, Amay J. AU - Jeerapan, Itthipon AU - You, Jung-Min AU - Nuñez-Flores, Rogelio AU - Wang, Joseph T2 - Nano Letters AB - We present the first example of an all-printed, inexpensive, highly stretchable CNT-based electrochemical sensor and biofuel cell array. The synergistic effect of utilizing specially tailored screen printable stretchable inks that combine the attractive electrical and mechanical properties of CNTs with the elastomeric properties of polyurethane as a binder along with a judiciously designed free-standing serpentine pattern enables the printed device to possess two degrees of stretchability. Owing to these synergistic design and nanomaterial-based ink effects, the device withstands extremely large levels of strains (up to 500% strain) with negligible effect on its structural integrity and performance. This represents the highest stretchability offered by a printed device reported to date. Extensive electrochemical characterization of the printed device reveal that repeated stretching, torsional twisting, and indenting stress has negligible impact on its electrochemical properties. The wide-range applicability of this platform to realize highly stretchable CNT-based electrochemical sensors and biofuel cells has been demonstrated by fabricating and characterizing potentiometric ammonium sensor, amperometric enzyme-based glucose sensor, enzymatic glucose biofuel cell, and self-powered biosensor. Highly stretchable printable multianalyte sensor, multifuel biofuel cell, or any combination thereof can thus be realized using the printed CNT array. Such combination of intrinsically stretchable printed nanomaterial-based electrodes and strain-enduring design patterns holds considerable promise for creating an attractive class of inexpensive multifunctional, highly stretchable printed devices that satisfy the requirements of diverse healthcare and energy fields wherein resilience toward extreme mechanical deformations is mandatory. DA - 2015/12/29/ PY - 2015/12/29/ DO - 10.1021/acs.nanolett.5b04549 VL - 16 IS - 1 SP - 721-727 J2 - Nano Lett. LA - en OP - SN - 1530-6984 1530-6992 UR - http://dx.doi.org/10.1021/acs.nanolett.5b04549 DB - Crossref KW - Printed electronics KW - electrochemical sensors KW - carbon nanotubes KW - biofuel cells KW - stretchable devices ER - TY - JOUR TI - Microfluidics: Microfluidic Strategies for Design and Assembly of Microfibers and Nanofibers with Tissue Engineering and Regenerative Medicine Applications (Adv. Healthcare Mater. 1/2015) AU - Daniele, Michael A. AU - Boyd, Darryl A. AU - Adams, André A. AU - Ligler, Frances S. T2 - Advanced Healthcare Materials AB - Recent applications in tissue engineering and regenerative medicine have highlighted the utility of microfluidic fiber fabrication. On page 11 M. A. Daniele and team show how this process uses microflow shaping to generate a core-sheath profile, which can be subsequently solidified into microfibers of various shapes and chemistries, providing the capability to incorporate and organize both fragile biomolecules and cell-cultures within individual fibers and bioactive textiles. DA - 2015/1// PY - 2015/1// DO - 10.1002/ADHM.201570002 VL - 4 IS - 1 SP - 2-2 J2 - Adv. Healthcare Mater. LA - en OP - SN - 2192-2640 UR - http://dx.doi.org/10.1002/ADHM.201570002 DB - Crossref ER - TY - JOUR TI - A single-stage integrated bridgeless AC/DC converter for electrolytic capacitor-less LED lighting applications AU - Ma, Hongbo AU - Zheng, Cong AU - Yu, Wensong AU - Lai, Jih-Sheng Jason T2 - International Journal of Circuit Theory and Applications AB - Summary In this paper, a single‐stage integrated bridgeless AC/DC converter is proposed. As compared to its counterpart that is composed of totem‐pole boost power factor correction (PFC) cascade fly‐back DC/DC converter, the studied circuit has less components number while overcoming the limits of the totem‐pole type. Thus, it is suitable to the low‐power LED lighting applications. Furthermore, when both PFC inductors L b and magmatic inductance L m of the transformer TR1 operate at discontinuous current mode, the bus voltage v CB can be used to decouple the ac input and constant dc output power. Thus, the approach of increasing bus voltage ripple is employed to eliminate electrolytic capacitors and obtain long operation lifetime. Additionally, it is able to be compatible with our studied twin‐bus configuration for increasing the overall efficiency. A 50‐W hardware prototype has been designed, fabricated, and tested in the laboratory to verify the proposed converter validity. Copyright © 2014 John Wiley & Sons, Ltd. DA - 2015/6// PY - 2015/6// DO - 10.1002/CTA.1970 VL - 43 IS - 6 SP - 742–755 SN - 0098-9886 UR - http://dx.doi.org/10.1002/CTA.1970 KW - bridgeless KW - AC-DC KW - electrolytic capacitor KW - single-stage KW - power factor correction (PFC) ER - TY - JOUR TI - Erratum: “Experimental demonstration of the equivalence of inductive and strongly coupled magnetic resonance wireless power transfer” [Appl. Phys. Lett. 102, 053904 (2013)] AU - Ricketts, David S. AU - Chabalko, Matthew J. AU - Hillenius, Andrew T2 - Applied Physics Letters AB - First Page DA - 2015/7/27/ PY - 2015/7/27/ DO - 10.1063/1.4926660 VL - 107 IS - 4 SP - 049901 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.4926660 DB - Crossref ER - TY - BOOK TI - The Struggle for Pakistan: A Muslim Homeland and Global Politics. By Ayesha Jalal. Cambridge, Mass.: Belknap Press of Harvard University Press, 2014. 435 pp. $35.00 (cloth, ISBN 9780674052895). AU - Gilmartin, David AU - Jalal, Ayesha AB - The Struggle for Pakistan: A Muslim Homeland and Global Politics. By Ayesha Jalal. Cambridge, Mass.: Belknap Press of Harvard University Press, 2014. 435 pp. $35.00 (cloth, ISBN 9780674052895). - Volume 74 Issue 4 DA - 2015/11// PY - 2015/11// DO - 10.1017/S0021911815001473 VL - 74 PB - Cambridge University Press (CUP) SE - 1056–1057 UR - http://dx.doi.org/10.1017/S0021911815001473 ER - TY - JOUR TI - Ferroelectric and magnetic properties of multiferroic BiFeO3-La0.7Sr0.3MnO3 heterostructures integrated with Si (100) AU - Singamaneni, Srinivasa Rao AU - Prater, J. T. AU - Nori, S. AU - Kumar, D. AU - Lee, Bongmook AU - Misra, V. AU - Narayan, J. T2 - Journal of Applied Physics AB - We report on the electrical, ferroelectric, and magnetic properties of BiFeO3 (BFO)-La0.7Sr0.3MnO3 heterostructures deposited epitaxially onto Si(100) substrates. Temperature dependent (200–350 K) current-voltage (I-V), switching spectroscopy piezo-response force microscopy (SSPFM), and temperature dependent (5–300 K) anisotropic magnetization measurements have been performed. The BFO (100-nm thick)-based device structures were fabricated with a 250 nm thick La0.7Sr0.3MnO3 bottom electrode and 200 μm circular top Pt electrodes. I-V measurements performed at various temperatures indicated that the devices retained their as-deposited characteristics and exhibited non-leaky behavior up to at least 50 cycles. The temperature-dependent measurements showed clear diode-like behavior and resistive (hysteretic) switching behaviour. Characteristic butterfly loops (of several cycles) were observed in the PFM amplitude signals of the BFO film. In addition, the phase signal indicated a clear (180°) switching behavior at the switching voltage of 4–5 V, providing unambiguous evidence for the occurrence of ferroelectricity in BFO films integrated on Si (100). The temperature- and angle-dependent zero field cooled isothermal (5 K) magnetization measurements were consistent with the presence of uniaxial magnetic anisotropy. This work makes an important step for the fabrication of CMOS-compatible BFO devices for memory applications. DA - 2015/5/7/ PY - 2015/5/7/ DO - 10.1063/1.4913811 VL - 117 IS - 17 SP - 17D908 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.4913811 DB - Crossref ER - TY - JOUR TI - Self-Healing Inks for Autonomous Repair of Printable Electrochemical Devices AU - Bandodkar, Amay J. AU - Mohan, Vinu AU - López, Cristian S. AU - Ramírez, Julian AU - Wang, Joseph T2 - Advanced Electronic Materials AB - The synthesis of self-healing printable inks for fabricating all-printed inexpensive smart electrochemical devices that can self-heal upon mechanical damage is reported. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. DA - 2015/11/9/ PY - 2015/11/9/ DO - 10.1002/aelm.201500289 VL - 1 IS - 12 SP - 1500289 J2 - Adv. Electron. Mater. LA - en OP - SN - 2199-160X UR - http://dx.doi.org/10.1002/aelm.201500289 DB - Crossref ER - TY - JOUR TI - All‐Printed Stretchable Electrochemical Devices AU - Bandodkar, Amay J. AU - Nuñez‐Flores, Rogelio AU - Jia, Wenzhao AU - Wang, Joseph T2 - Advanced Materials AB - The fabrication and characterization of all-printed, inexpensive, stretchable electrochemical devices is described. These devices are based on specially engineered inks that can withstand severe tensile strain, as high as 100%, without any significant effect on their electrochemical properties. Such stretchable electrochemical devices should be attractive for diverse sensing and energy applications. DA - 2015/4/9/ PY - 2015/4/9/ DO - 10.1002/adma.201500768 VL - 27 IS - 19 SP - 3060-3065 J2 - Adv. Mater. LA - en OP - SN - 0935-9648 1521-4095 UR - http://dx.doi.org/10.1002/adma.201500768 DB - Crossref KW - electrochemical devices KW - screen printing KW - stretchable electronics ER - TY - JOUR TI - Biocompatible Enzymatic Roller Pens for Direct Writing of Biocatalytic Materials: “Do-it-Yourself” Electrochemical Biosensors AU - Bandodkar, Amay J. AU - Jia, Wenzhao AU - Ramírez, Julian AU - Wang, Joseph T2 - Advanced Healthcare Materials AB - The development of enzymatic‐ink‐based roller pens for direct drawing of biocatalytic sensors, in general, and for realizing renewable glucose sensor strips, in particular, is described. The resulting enzymatic‐ink pen allows facile fabrication of high‐quality inexpensive electrochemical biosensors of any design by the user on a wide variety of surfaces having complex textures with minimal user training. Unlike prefabricated sensors, this approach empowers the end user with the ability of “on‐demand” and “on‐site” designing and fabricating of biocatalytic sensors to suit their specific requirement. The resulting devices are thus referred to as “do‐it‐yourself” sensors. The bio­active pens produce highly reproducible biocatalytic traces with minimal edge roughness. The composition of the new enzymatic inks has been optimized for ensuring good biocatalytic activity, electrical conductivity, biocompati­bility, reproducible writing, and surface adherence. The resulting inks are characterized using spectroscopic, viscometric, electrochemical, thermal and microscopic techniques. Applicability to renewable blood glucose testing, epidermal glucose monitoring, and on‐leaf phenol detection are demonstrated in connection to glucose oxidase and tyrosinase‐based carbon inks. The “do‐it‐yourself” renewable glucose sensor strips offer a “fresh,” reproducible, low‐cost biocatalytic sensor surface for each blood test. The ability to directly draw biocatalytic conducting traces even on unconventional surfaces opens up new avenues in various sensing applications in low‐resource settings and holds great promise for diverse healthcare, environmental, and defense domains. DA - 2015/2/26/ PY - 2015/2/26/ DO - 10.1002/adhm.201400808 VL - 4 IS - 8 SP - 1215-1224 J2 - Adv. Healthcare Mater. LA - en OP - SN - 2192-2640 UR - http://dx.doi.org/10.1002/adhm.201400808 DB - Crossref KW - biosensors KW - diabetes KW - direct writing KW - electrodes KW - fabrication ER - TY - JOUR TI - Tattoo-Based Wearable Electrochemical Devices: A Review AU - Bandodkar, Amay J. AU - Jia, Wenzhao AU - Wang, Joseph T2 - Electroanalysis AB - Abstract This article provides an overview of the recent advances in the field of skin‐worn tattoo‐based wearable electrochemical devices, including electrolyte and metabolite sensors, biofuel cells and batteries. Temporary tattoos are attractive platforms for fabricating skin‐worn devices. Body‐compliant wearable electrochemical devices on temporary tattoos couple highly favorable substrate‐skin elasticity with an attractive electrochemical performance. For example, tattoo‐based “skin‐like” sensors can be used for real‐time non‐invasive analysis of key electrolytes and metabolites, leading to remarkable sensing capabilities. Continued progress has been made also towards developing skin‐worn flexible energy harvesting and storage devices to power wearable health monitors and other devices. Key requirements and challenges that confront researchers in this exciting area of skin‐worn electrochemical devices are discussed. DA - 2015/1/8/ PY - 2015/1/8/ DO - 10.1002/elan.201400537 VL - 27 IS - 3 SP - 562-572 J2 - Electroanalysis LA - en OP - SN - 1040-0397 UR - http://dx.doi.org/10.1002/elan.201400537 DB - Crossref KW - Wearable sensors KW - Non-invasive monitoring KW - Printable flexible devices KW - Skin KW - Screen printing KW - Biofuel cells KW - Batteries KW - Electrochemical sensors ER - TY - CONF TI - Impact of reactive power injection outside feed-in hours on the reliability of photovoltaic inverters AU - Anurag, Anup AU - Yang, Yongheng AU - Blaabjerg, Frede T2 - 2015 IEEE 6th International Symposium on Power Electronics for Distributed Generation Systems (PEDG) AB - Current energy paradigm of mixed renewables seems to urgently require reactive power provision at various feed-in points of the utility grid. Photovoltaic (PV) inverters are able to provide reactive power in a decentralized manner at the grid-connection point even outside active power feed-in operation, especially at night. This serves as a motivation for utilizing the PV inverters at night for reactive power compensation. Thus, a detailed analysis on the impact of reactive power injection by PV inverters outside feed-in operation on the thermal performance and also the reliability is performed in this paper. A thermal analysis based on the mission profile (i.e. solar irradiance and ambient temperature) has been incorporated, so as to determine the additional temperature rise in the components (IGBTs and diodes) outside feed-in operation for different values of reactive power injection. Consequently, the analysis enables the translation from long-term mission profiles to device thermal loading, considering the operation at night. An analytical lifetime model is then used for lifetime quantization based on the Palgrem Miner rule. Thereafter, considering the lifetime reduction of the PV inverter for different values of reactive power injection an assessment of the economic impacts is made. This analysis can be useful in choosing between conventional reactive power devices or PV inverters for injecting reactive power to the grid. C2 - 2015/6// C3 - 2015 IEEE 6th International Symposium on Power Electronics for Distributed Generation Systems (PEDG) DA - 2015/6// DO - 10.1109/pedg.2015.7223032 PB - IEEE SN - 9781479985869 UR - http://dx.doi.org/10.1109/pedg.2015.7223032 DB - Crossref ER - TY - CONF TI - Reliability analysis of single-phase PV inverters with reactive power injection at night considering mission profiles AU - Anurag, Anup AU - Yang, Yongheng AU - Blaabjerg, Frede T2 - 2015 IEEE Energy Conversion Congress and Exposition AB - The widespread adoption of mixed renewables urgently require reactive power exchange at various feed-in points of the utility grid. Photovoltaic (PV) inverters are able to provide reactive power in a decentralized manner at the grid-connection points even outside active power feed-in operation, especially at night when there is no solar irradiance. This serves as a motivation for utilizing the PV inverters at night for reactive power compensation. Thus, an analysis on the impact of reactive power injection by PV inverters outside feed-in operation on the thermal performance and the reliability has been performed in this paper. A thermal analysis is incorporated to determine the additional temperature rise in the power switching components outside the feed-in operation. This analysis enables the translation from long-term mission profiles (three different mission profiles) to device thermal loading, considering the operation outside active feed-in hours. An analytical lifetime model is then employed for lifetime quantization based on the Palgrem Miner rule. Thereafter, considering the lifetime reduction of the PV inverter under different mission profiles with reactive power injection at night, the impact of PV sites on the economic value of the inverter is assessed. This analysis can be useful in choosing between conventional reactive power compensation devices or PV inverters for injecting reactive power to the grid. C2 - 2015/9// C3 - 2015 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2015/9// DO - 10.1109/ecce.2015.7309961 PB - IEEE SN - 9781467371513 UR - http://dx.doi.org/10.1109/ecce.2015.7309961 DB - Crossref ER - TY - JOUR TI - Comprehensive Analysis and Experimental Validation of an Improved Mathematical Modeling of Photovoltaic Array AU - Bal, Satarupa AU - Anurag, Anup AU - Nanda, Mrutyunjaya AU - Sourav, Suman T2 - Advances in Power Electronics AB - This paper proposes a simple, accurate, and easy to model approach for the simulation of photovoltaic (PV) array and also provides a comparative analysis of the same with two other widely used models. It is highly imperative that the maximum power point (MPP) is achieved effectively and thus a simple and robust mathematical model is necessary that poses less mathematical complexity as well as low data storage requirement, in which the maximum power point tracking (MPPT) algorithm can be realized in an effective way. Further, the resemblance of the P-V and I-V curves as obtained on the basis of experimental data should also be taken into account for theoretical validation. In addition, the study incorporates the root mean square deviation (RMSD) from the experimental data, the fill factor (FF), the efficiency of the model, and the time required for simulation. Two models have been used to investigate the I-V and P-V characteristics. Perturb and Observe method has been adopted for MPPT. The MPP tracking is realized using field programmable gate array (FPGA) to prove the effectiveness of the proposed approach. All the systems are modeled and simulated in MATLAB/Simulink environment. DA - 2015/// PY - 2015/// DO - 10.1155/2015/654092 VL - 2015 SP - 1-11 J2 - Advances in Power Electronics LA - en OP - SN - 2090-181X 2090-1828 UR - http://dx.doi.org/10.1155/2015/654092 DB - Crossref ER - TY - CONF TI - Vce-based chip temperature estimation methods for high power IGBT modules during power cycling — A comparison AU - Amoiridis, Anastasios AU - Anurag, Anup AU - Ghimire, Pramod AU - Munk-Nielsen, Stig AU - Baker, Nick T2 - 2015 17th European Conference on Power Electronics and Applications (EPE'15 ECCE-Europe) AB - Temperature estimation is of great importance for performance and reliability of IGBT power modules in converter operation as well as in active power cycling tests. It is common to be estimated through Thermo-Sensitive Electrical Parameters such as the forward voltage drop (V ce ) of the chip. This experimental work evaluates the validity and accuracy of two V ce based methods applied on high power IGBT modules during power cycling tests. The first method estimates the chip temperature when low sense current is applied and the second method when normal load current is present. Finally, a correction factor that eliminates the series resistance contribution on the V ce measured at high current, is proposed. C2 - 2015/9// C3 - 2015 17th European Conference on Power Electronics and Applications (EPE'15 ECCE-Europe) DA - 2015/9// DO - 10.1109/epe.2015.7309449 PB - IEEE SN - 9789075815221 UR - http://dx.doi.org/10.1109/epe.2015.7309449 DB - Crossref ER - TY - JOUR TI - Thermal Performance and Reliability Analysis of Single-Phase PV Inverters With Reactive Power Injection Outside Feed-In Operating Hours AU - Anurag, Anup AU - Yang, Yongheng AU - Blaabjerg, Frede T2 - IEEE Journal of Emerging and Selected Topics in Power Electronics AB - Reactive power support by photovoltaic (PV) systems is of increasing interest, when compared with the conventional reactive power compensation devices. The PV inverters can exchange reactive power with the utility grid in a decentralized manner even outside feed-in operation, especially at night when there is no solar irradiance. However, reactive power injection causes additional power losses in the switching components leading to a temperature rise in the devices. Thus, this paper analyzes the impact of reactive power injection by PV inverters outside feed-in operation on the thermal performance of their power switching components. A thermal analysis based on the mission profile (i.e., solar irradiance and ambient temperature) has been incorporated, so as to determine the additional temperature rise in the components induced by the operation outside feed-in hours. An analytical lifetime model has been used. The damage produced on the transistors has been quantified using the Palmgren-Miner rule. A reliability analysis has been carried out on a PV inverter with and without the injection of reactive power into the utility grid at night. Economic impacts of injecting reactive power from PV inverters outside feed-in operating hours have been analyzed thereafter. This analysis can be helpful to make a better choice while choosing between conventional reactive power devices or PV inverters for injecting reactive power to the grid. DA - 2015/12// PY - 2015/12// DO - 10.1109/jestpe.2015.2428432 VL - 3 IS - 4 SP - 870-880 J2 - IEEE J. Emerg. Sel. Topics Power Electron. OP - SN - 2168-6777 2168-6785 UR - http://dx.doi.org/10.1109/jestpe.2015.2428432 DB - Crossref KW - Photovoltaic (PV) inverters KW - Q at night KW - reactive ower injection KW - reliability KW - thermal performance ER - TY - CONF TI - Uplink massive MIMO SIR analysis: how do antennas scale with users? AU - Bai, T. AU - Heath, R.W. AB - Massive multiple-input multiple-output (MIMO) is a potential physical layer technology for 5G cellular networks. This paper leverages stochastic geometry to derive the uplink signal-to- interference (SIR) distribution in massive MIMO networks. Based on the derived expressions, a scaling law between the number of base station antennas and scheduled users per cell is provided to preserve the uplink SIR distribution, where the impacts of correlation in small-scale fading and power control in the form of fractional path loss compensation are taken account. Numerical results verify the analysis, and show that fractional power control with a compensation fraction of 0.5 is nearly optimal for the average achievable rate in certain cases. C2 - 2015/// C3 - 2015 IEEE Global Communications Conference, GLOBECOM 2015 DA - 2015/// DO - 10.1109/GLOCOM.2014.7417688 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84964872728&partnerID=MN8TOARS ER - TY - CONF TI - Threshold-based antenna selection algorithm for dense cloud radio access networks AU - Park, J. AU - Heath, R.W. AB - In this paper, we propose a threshold-based antenna selection algorithm for uplink dense cloud radio access networks (C- RANs), where a baseband processor unit (BBU) cloud is separately placed from densely deployed remote radio heads (RRHs). The proposed algorithm consists of two phases. In the first phase, each RRH determines whether to be included or not in a candidate set by using a predefined selection threshold. In the second phase, a RRH is randomly selected within the candidate set made in the first phase. By modeling the network with a homogeneous Poisson point process (PPP), the signal- to-interference ratio (SIR) complementary cumulative distribution function (CCDF) is derived when applying the proposed algorithm. Exploiting the derived expression, an approximate optimum selection threshold that maximizes the SIR coverage performance is obtained in terms of relevant system parameters, chiefly the SIR target, the pathloss exponent, and the RRH and user densities. Simulations demonstrate the performance of the obtained selection threshold. The key advantage of the proposed algorithm is its simplicity. Since the complexity caused by selecting a RRH is reasonable irrespective of the density of the RRH while guaranteeing the certain performance, the proposed algorithm is easily applied in a C-RAN where the RRHs are densely deployed. C2 - 2015/// C3 - 2015 IEEE Global Communications Conference, GLOBECOM 2015 DA - 2015/// DO - 10.1109/GLOCOM.2014.7417757 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84964887790&partnerID=MN8TOARS ER - TY - CONF TI - Spectral efficiency of massive MIMO systems with D2D underlay AU - Lin, X. AU - Heath, R.W. AU - Andrews, J.G. AB - This paper studies the interplay between massive MIMO and device-to-device (D2D) networking in a single cell setting, where cellular uplink resources are shared by D2D. The spatial positions of underlaid D2D transmitters are modeled by a Poisson point process. All the transmissions (both cellular and D2D) are SIMO (i.e., single-input multiple-output) with the base station (BS) having a very large antenna array. Assuming perfect channel state information at the receivers, we study cellular and D2D spectral efficiency. In the asymptotic regime where the number of BS antennas goes to infinity, we find that the received signal-to-interference-plus-noise ratio (SINR) of any cellular user increases unboundedly and the effects of noise, fast fading, and the interfering signals from the other co-channel cellular users and the infinite D2D transmitters vanish completely. In the non-asymptotic regime, we derive simple analytical lower bounds for both cellular and D2D spectral efficiency, which allow for efficient numerical evaluation. C2 - 2015/// C3 - IEEE International Conference on Communications DA - 2015/// DO - 10.1109/ICC.2015.7249006 VL - 2015-September SP - 4345-4350 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84953741766&partnerID=MN8TOARS ER - TY - CONF TI - Retrospective interference alignment for two-cell uplink MIMO cellular networks with delayed CSIT AU - Shin, W. AU - Han, Y. AU - Lee, J. AU - Lee, N. AU - Heath, R.W. AB - In this paper, we propose a new retrospective interference alignment for two-cell multiple-input multiple-output (MIMO) interfering multiple access channels (IMAC) with the delayed channel state information at the transmitters (CSIT). It is shown that having delayed CSIT can strictly increase the sum-DoF compared to the case of no CSIT. The key idea is to align multiple interfering signals from adjacent cells onto a small dimensional subspace over time by fully exploiting the previously received signals as side information with outdated CSIT in a distributed manner. Remarkably, we show that the retrospective interference alignment can achieve the optimal sum-DoF in the context of two-cell two-user scenario by providing a new outer bound. C2 - 2015/// C3 - IEEE International Conference on Communications DA - 2015/// DO - 10.1109/ICC.2015.7248973 VL - 2015-September SP - 4144-4150 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84953749958&partnerID=MN8TOARS ER - TY - JOUR TI - Spectral efficiency of dynamic coordinated beamforming: A stochastic geometry approach AU - Lee, N. AU - Morales-Jimenez, D. AU - Lozano, A. AU - Heath, R.W. T2 - IEEE Transactions on Wireless Communications AB - This paper characterizes the performance of coordinated beamforming with dynamic clustering. A downlink model based on stochastic geometry is put forth to analyze the performance of such a base station (BS) coordination strategy. Analytical expressions for the complementary cumulative distribution function (CCDF) of the instantaneous signal-to-interference ratio (SIR) are derived in terms of relevant system parameters, chiefly the number of BSs forming the coordination clusters, the number of antennas per BS, and the pathloss exponent. Utilizing this CCDF, with pilot overheads further incorporated into the analysis, we formulate the optimization of the BS coordination clusters for a given fading coherence. Our results indicate that: 1) coordinated beamforming is most beneficial to users that are in the outer part of their cells yet in the inner part of their coordination cluster and that 2) the optimal cluster cardinality for the typical user is small and it scales with the fading coherence. Simulation results verify the exactness of the SIR distributions derived for stochastic geometries, which are further compared with the corresponding distributions for deterministic grid networks. DA - 2015/// PY - 2015/// DO - 10.1109/TWC.2014.2337305 VL - 14 IS - 1 SP - 230-241 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84921323055&partnerID=MN8TOARS KW - Coordinated beamforming KW - dynamic clustering KW - stochastic geometry ER - TY - JOUR TI - Space-Time Physical-Layer Network Coding AU - Lee, N. AU - Heath, R.W. T2 - IEEE Journal on Selected Areas in Communications AB - A space-time physical-layer network coding (ST-PNC) method is presented for information exchange among multiple users over fully connected multiway relay networks. The method involves two steps: 1) side-information learning and 2) space-time relay transmission. In the first step, different sets of users are scheduled to send signals over networks, and the remaining users and relays overhear the transmitted signals, thereby learning the interference patterns. In the second step, multiple relays cooperatively send out linear combinations of signals received in the previous phase using space-time precoding so that all users efficiently exploit their side information in the form of 1) what they sent and 2) what they overheard in decoding. This coding concept is illustrated through two simple network examples. It is shown that ST-PNC improves the sum of degrees of freedom (sum-DoF) of the network compared to existing interference management methods. With ST-PNC, the sum-DoF of a general multiway relay network without channel knowledge at the users is characterized in terms of relevant system parameters, chiefly the number of users, the number of relays, and the number of antennas at relays. A major implication of the derived results is that efficiently harnessing both transmitted and overheard signals as side information brings significant performance improvements to fully connected multiway relay networks. DA - 2015/// PY - 2015/// DO - 10.1109/JSAC.2014.2384351 VL - 33 IS - 2 SP - 323-336 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84924978325&partnerID=MN8TOARS KW - Physical-layer network coding KW - space-time precoding KW - multi-way relay channels ER - TY - JOUR TI - Power control for D2D underlaid cellular networks: Modeling, algorithms, and analysis AU - Lee, N. AU - Lin, X. AU - Andrews, J.G. AU - Heath, R.W. T2 - IEEE Journal on Selected Areas in Communications AB - This paper proposes a random network model for a device-to-device (D2D) underlaid cellular system using stochastic geometry and develops centralized and distributed power control algorithms. The goal of centralized power control is twofold: ensure that the cellular users have sufficient coverage probability by limiting the interference created by underlaid D2D users, while scheduling as many D2D links as possible. For the distributed power control method, the optimal on-off power control strategy is proposed, which maximizes the sum rate of the D2D links. Expressions are derived for the coverage probabilities of cellular, D2D links, and the sum rate of the D2D links in terms of the density of D2D links and the path-loss exponent. The analysis reveals the impact of key system parameters on the network performance. For example, the bottleneck of D2D underlaid cellular networks is the cross-tier interference between D2D links and the cellular user, not the D2D intratier interference when the density of D2D links is sparse. Simulation results verify the exactness of the derived coverage probabilities and the sum rate of D2D links. DA - 2015/// PY - 2015/// DO - 10.1109/JSAC.2014.2369612 VL - 33 IS - 1 SP - 1-13 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84922808929&partnerID=MN8TOARS KW - Power control KW - device-to-device communication KW - cellular networks KW - Poisson point process KW - stochastic geometry ER - TY - JOUR TI - The interplay between massive MIMO and underlaid D2D networking AU - Lin, X. AU - Heath, R.W. AU - Andrews, J.G. T2 - IEEE Transactions on Wireless Communications AB - In a device-to-device (D2D) underlaid cellular network, the uplink spectrum is reused by the D2D transmissions, causing mutual interference with the ongoing cellular transmissions. Massive MIMO is appealing in such a context as the base station's (BS's) large antenna array can nearly null the D2D-to-BS interference. The multi-user transmission in massive MIMO, however, may lead to increased cellular-to-D2D interference. This paper studies the interplay between massive MIMO and underlaid D2D networking in a multi-cell setting. We investigate cellular and D2D spectral efficiencies under both perfect and imperfect channel state information (CSI) at the receivers that employ partial zero-forcing. Compared to the case without D2D, there is a loss in cellular spectral efficiency due to D2D underlay. With perfect CSI, the loss can be completely overcome if the number of canceled D2D interfering signals is scaled with the number of BS antennas at an arbitrarily slow rate. With imperfect CSI, in addition to pilot contamination, a new asymptotic effect termed underlay contamination arises. In the non-asymptotic regime, simple analytical lower bounds are derived for both the cellular and D2D spectral efficiencies. DA - 2015/// PY - 2015/// DO - 10.1109/TWC.2015.2404435 VL - 14 IS - 6 SP - 3337-3351 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84933059825&partnerID=MN8TOARS KW - Massive MIMO KW - device-to-device KW - cellular networks KW - spectral efficiency KW - stochastic geometry ER - TY - JOUR TI - Rate adaptation and admission control for video transmission with subjective quality constraints AU - Chen, C. AU - Zhu, X. AU - De Veciana, G. AU - Bovik, A.C. AU - Heath, R.W. T2 - IEEE Journal on Selected Topics in Signal Processing AB - Adapting video data rate during streaming can effectively reduce the risk of playback interruptions caused by channel throughput fluctuations. The variations in rate, however, also introduce video quality fluctuations and thus potentially affects viewers' Quality of Experience (QoE). We show how the QoE of video users can be improved by rate adaptation and admission control. We conducted a subjective study wherein we found that viewers' QoE was strongly correlated with the empirical cumulative distribution function (eCDF) of the predicted video quality. Based on this observation, we propose a rate-adaptation algorithm that can incorporate QoE constraints on the empirical cumulative quality distribution per user. We then propose a threshold-based admission control policy to block users whose empirical cumulative quality distribution is not likely to satisfy their QoE constraint. We further devise an online adaptation algorithm to automatically optimize the threshold. Extensive simulation results show that the proposed scheme can reduce network resource consumption by 40% over conventional average-quality maximized rate-adaptation algorithms. DA - 2015/// PY - 2015/// DO - 10.1109/JSTSP.2014.2337277 VL - 9 IS - 1 SP - 22-36 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84921790863&partnerID=MN8TOARS KW - Quality of experience KW - video transport KW - rate adaptation KW - admission control KW - wireless networks ER - TY - CONF TI - Performance evaluation of ITLinQ and FlashLinQ for overlaid device-to-device communication AU - Mungara, R.K. AU - Zhang, X. AU - Lozano, A. AU - Heath, R.W. AB - We present a performance evaluation of ITLinQ and FlashLinQ, the two most popular schemes proposed to date to channelize D2D transmissions, i.e., to parse transmissions into noninterfering sets to be allocated to separate channels. Recognizing that it captures well the spatial characteristics of D2D networks, a stochastic geometry setting is utilized for this evaluation with the parameters of either scheme optimized in order to maximize the system spectral efficiency (bits/s/Hz per unit area). Although independently formulated and seemingly based on different principles, both schemes are found to exercise similar mechanisms to avoid situations of excessive interference, yielding substantial improvements with respect to unchannelized networks. C2 - 2015/// C3 - 2015 IEEE International Conference on Communication Workshop, ICCW 2015 DA - 2015/// DO - 10.1109/ICCW.2015.7247246 SP - 596-601 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84947721844&partnerID=MN8TOARS ER - TY - CONF TI - Performance analysis of pair-wise dynamic multi-user joint transmission AU - Park, J. AU - Lee, N. AU - Heath, R.W. AB - This paper characterizes the performance of multiuser joint transmission (MU-JT) with pair-wise dynamic base station (BS) clustering. For analyzing the performance of such BS cooperation method, a tractable model is presented by means of stochastic geometry. Using tools of stochastic geometry, a tight lower bound of the instantaneous signal-to-interference ratio (SIR) distribution is derived in a closed form in terms of relevant system parameters: the path-loss exponent and the topologies of users in the BS cooperative region. Our key finding is that the pair-wise dynamic BS cooperation through MU-JT provides a better rate coverage performance than that of single-user joint transmission (SU-JT) over the entire range of the rate threshold when each user is close enough to the associated BS. Through simulations, the exactness of the derived analytical expression is verified. C2 - 2015/// C3 - IEEE International Conference on Communications DA - 2015/// DO - 10.1109/ICC.2015.7248946 VL - 2015-September SP - 3981-3986 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84953715868&partnerID=MN8TOARS ER - TY - JOUR TI - Performance Analysis of Cooperative Wireless Networks with Unreliable Backhaul Links AU - Khan, T.A. AU - Orlik, P. AU - Kim, K.J. AU - Heath, R.W. T2 - IEEE Communications Letters AB - A cooperative wireless network, where a cluster of K single-antenna transmitters jointly serve a single-antenna receiver, is considered. Each transmitter is connected to the control unit (CU) via independent but unreliable backhaul links. The CU sends a common message to each transmitter over backhaul links, which upon successful reception, jointly transmit this message to the intended receiver. To facilitate analysis, a general expression is derived for the complementary cumulative distribution function of a sum of K independent random variables, where each random variable is a product of an exponential and a Bernoulli random variable. This result is applied to find a simple closed-form expression that characterizes the system outage performance as a function of network parameters and node geometry. The analytical model is validated using numerical simulations. As an application, the derived expression is also used for investigating the impact of backhaul assignment on the system performance. DA - 2015/// PY - 2015/// DO - 10.1109/LCOMM.2015.2442991 VL - 19 IS - 8 SP - 1386-1389 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84939423495&partnerID=MN8TOARS KW - Cooperative wireless networks KW - backhaul KW - Bernoulli-weighted exponential ER - TY - CONF TI - Optimizing the target error rate for link adaptation AU - Park, S. AU - Daniels, R.C. AU - Heath, R.W. AB - Wireless link adaptation configures the physical layer of the transmitter in the presence of dynamic channel conditions to maximize link performance under error rate reliability constraints. Typically, error rate reliability targets are defined externally and remain fixed, regardless of the physical layer configuration. In this paper, we allow link adaptation to define its own error rate reliability target. We derive a closed form expression for the optimal target block error rate (BLER) that maximizes the throughput with hybrid automatic repeat request (HARQ). This expression shows that the optimal BLER target is inversely proportional to the SINR. We conduct LTE simulations with link adaptation that exploits the optimal BLER target to reinforce the utility of our derived BLER target expression and to showcase that a performance improvements of up to 30% in throughput can be obtained through dynamic BLER targets for link adaptation. C2 - 2015/// C3 - 2015 IEEE Global Communications Conference, GLOBECOM 2015 DA - 2015/// DO - 10.1109/GLOCOM.2014.7417770 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84964851012&partnerID=MN8TOARS ER - TY - CONF TI - Near maximum-likelihood detector with one-bit ADCs for multiuser massive MIMO systems AU - Choi, J. AU - Heath, R.W. AB - In massive multiple-input multiple-output (MIMO) systems, deploying a high-resolution analog-to-digital converter (ADC) for each antenna element may not be power and cost efficient. Assuming each antenna is connected to a pair of one-bit ADCs, i.e., one for each real and imaginary component of the received signal, a near maximum likelihood (nML) detector for uplink multiuser massive MIMO systems is proposed in this paper. The proposed nML detector is based on a standard convex optimization technique and becomes optimal when the number of receive antennas at the base station goes to infinity. Simulation results show that the proposed nML detector can simultaneously support multiple users using higher-order constellations, e.g., 16 quadrature amplitude modulation, and performs much better than a simple zeroforcing (ZF)-type detector. C2 - 2015/// C3 - 2015 IEEE 6th International Workshop on Computational Advances in Multi-Sensor Adaptive Processing, CAMSAP 2015 DA - 2015/// DO - 10.1109/CAMSAP.2015.7383820 SP - 397-400 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963800557&partnerID=MN8TOARS ER - TY - CONF TI - MmWave ad hoc network coverage and capacity AU - Thornburg, A. AU - Bai, T. AU - Heath, R.W. AB - Ad hoc networks consistently under perform compared to cellular networks. Protocols either create residual interference that leads to poor signal-to-interference-plus-noise ratios or try to coordinate transmissions leading to fewer transmission opportunities. Communication with millimeter-wave (mmWave) devices offers the potential for higher bandwidth communication channels and reduced interference in ad hoc networks. This paper uses a stochastic geometry approach to characterize the coverage probability of a mmWave ad hoc network with directional antennas and random building blockages. The coverage probability in the presence of noise and both line-of-sight and non-line-of-sight interference is analyzed and used to derive the transmission capacity. Performance of mmWave is then analyzed in terms of area spectral efficiency and rate coverage. The results show that mmWave networks support larger densities, higher area spectral efficiencies, and better rate coverage compared to traditional, lower-frequency ad hoc networks. C2 - 2015/// C3 - IEEE International Conference on Communications DA - 2015/// DO - 10.1109/ICC.2015.7248504 VL - 2015-September SP - 1310-1315 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84953712917&partnerID=MN8TOARS ER - TY - CONF TI - On the spatial spectral efficiency of ITLinQ AU - Mungara, R.K. AU - Zhang, X. AU - Lozano, A. AU - Heath, R.W. AB - Device-to-device (D2D) communication allows serving local wireless traffic bypassing the system's infrastructure. The interference in D2D can be controlled by carefully allocating users to orthogonal channels. This paper analytically characterizes the spectral efficiency of the ITLinQ channelization technique. The analysis relies on a stochastic geometry formulation, which enables obtaining compact expressions while opening the door to an optimization of ITLinQ's parameters. C2 - 2015/// C3 - Conference Record - Asilomar Conference on Signals, Systems and Computers DA - 2015/// DO - 10.1109/ACSSC.2014.7094779 VL - 2015-April SP - 1806-1810 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84940483413&partnerID=MN8TOARS ER - TY - CONF TI - Multi-layer precoding for full-dimensional massive MIMO systems AU - Alkhateeb, A. AU - Leus, G. AU - Heath, R.W. AB - Full-dimensional massive multiple-input multiple-output (MIMO) systems boost sum spectral efficiency by offering orders of magnitude increase in multiplexing gains. In time division duplexing systems, however, the reuse of the uplink training pilots among cells results in channel estimation errors, which lead to downlink inter-cell interference, especially for cell-edge users, even with large numbers of antennas. Handling this interference with conventional network MIMO techniques is challenging due to the high channel dimensionality. Further, large antenna precoding and combining implementation is associated with high hardware complexity. In this paper, we propose multi-layer precoding to enable efficient and low complexity full-dimensional MIMO operation. Multi-layer precoding (i) leverages the directional characteristics of large-scale MIMO channels to manage inter-cell interference with low channel requirements, and (ii) allows for an efficient implementation using low-complexity hybrid analog/digital architectures. We present and evaluate a specific multi-layer precoding design for full-dimensional MIMO systems. Simulation results show the potential gains of multi-layer precoding compared with traditional pilot-contaminated massive MIMO setups despite the low channel knowledge requirements and the low-complexity implementation. C2 - 2015/// C3 - Conference Record - Asilomar Conference on Signals, Systems and Computers DA - 2015/// DO - 10.1109/ACSSC.2014.7094563 VL - 2015-April SP - 815-819 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84940528813&partnerID=MN8TOARS ER - TY - JOUR TI - Loss Visibility Optimized Real-Time Video Transmission over MIMO Systems AU - Abdel Khalek, A. AU - Caramanis, C. AU - Heath, R.W. T2 - IEEE Transactions on Multimedia AB - The structured nature of video data motivates introducing video-aware decisions that make use of this structure for improved video transmission over wireless networks . In this paper, we introduce an architecture for real-time video transmission over multiple-input multiple-output (MIMO) wireless communication systems using loss visibility side information . We quantify the perceptual importance of a packet through the packet loss visibility and use the loss visibility distribution to provide a notion of relative packet importance . To jointly achieve high video quality and low latency, we define the optimization objective function as the throughput weighted by the loss visibility of each packet, a proxy for the total perceptual value of successful packets per unit of time. We solve the problem of mapping video packets to MIMO subchannels and adapting per-stream rates to maximize the proposed objective . We show that the solution enables jointly reaping gains in terms of improved video quality and lower latency. Optimized packet-stream mapping enables transmission of more relevant packets over more reliable streams while unequal modulation opportunistically increases the transmission rate on the stronger streams to enable low latency delivery of high priority packets. Tested on H.264-encoded video sequences, for a 4 ×4 MIMO system with three spatial streams, the proposed architecture achieves 8 dB power reduction for the same video quality and supports 2.4× higher throughput due to unequal modulation. Furthermore, the gains are achieved at the expense of few bits of cross-layer overhead rather than a complex cross-layer design. DA - 2015/// PY - 2015/// DO - 10.1109/TMM.2015.2468196 VL - 17 IS - 10 SP - 1802-1817 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84960857916&partnerID=MN8TOARS KW - Limited feedback KW - loss visibility KW - multiple-input multiple-output (MIMO) KW - packet loss KW - unequal error protection KW - video signal processing ER - TY - CONF TI - Millimeter wave power transfer and information transmission AU - Wang, L. AU - Elkashlan, M. AU - Heath, R.W. AU - Di Renzo, M. AU - Wong, K.-K. AB - Compared to the existing lower frequency wireless power transfer, millimeter wave (mmWave) power transfer takes advantage of the high-dimensional multi-antenna and narrow beam transmission. In this paper we introduce wireless power transfer for mmWave cellular networks. Here, we consider users with large energy storage that are recharged by the mmWave base stations prior to uplink information transmission, and analyze the average harvested energy and average achievable rate. Numerical results corroborate our analysis and show that the serving base station plays a dominant role in wireless power transfer, and the contribution of the interference power from the interfering base stations is negligible, even when the interfering base stations are dense. By examining the average achievable rate in the uplink, when increasing the base station density, a transition from a noise-limited regime to an interference-limited regime is observed. C2 - 2015/// C3 - 2015 IEEE Global Communications Conference, GLOBECOM 2015 DA - 2015/// DO - 10.1109/GLOCOM.2014.7417676 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84964904801&partnerID=MN8TOARS ER - TY - CONF TI - Low complexity hybrid sparse precoding and combining in millimeter wave MIMO systems AU - Rusu, C. AU - Mendez-Rial, R. AU - Gonzalez-Prelcicy, N. AU - Heath, R.W. AB - Millimeter wave (mmWave) multiple-input multipleoutput (MIMO) communication with large antenna arrays has been proposed to enable gigabit per second communication for next generation cellular systems and local area networks. A key difference relative to lower frequency solutions is that in mmWave systems, precoding/combining can not be performed entirely at digital baseband, due to the high cost and power consumption of some components of the radio frequency (RF) chain. In this paper we develop a low complexity algorithm for finding hybrid precoders that split the precoding/combining process between the analog and digital domains. Our approach exploits sparsity in the received signal to formulate the design of the precoder/combiners as a compressed sensing optimization problem. We use the properties of the matrix containing the array response vectors to find first an orthonormal analog precoder, since sparse approximation algorithms applied to orthonormal sensing matrices are based on simple computations of correlations. Then, we propose to perform a local search to refine the analog precoder and compute the baseband precoder. We present numerical results demonstrate substantial improvements in complexity while maintaining good spectral efficiency. C2 - 2015/// C3 - IEEE International Conference on Communications DA - 2015/// DO - 10.1109/ICC.2015.7248509 VL - 2015-September SP - 1340-1345 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84953433844&partnerID=MN8TOARS ER - TY - JOUR TI - Limited Feedback Hybrid Precoding for Multi-User Millimeter Wave Systems AU - Alkhateeb, A. AU - Leus, G. AU - Heath, R.W. T2 - IEEE Transactions on Wireless Communications AB - Antenna arrays will be an important ingredient in millimeter-wave (mmWave) cellular systems. A natural application of antenna arrays is simultaneous transmission to multiple users. Unfortunately, the hardware constraints in mmWave systems make it difficult to apply conventional lower frequency multiuser MIMO precoding techniques at mmWave. This paper develops low-complexity hybrid analog/digital precoding for downlink multiuser mmWave systems. Hybrid precoding involves a combination of analog and digital processing that is inspired by the power consumption of complete radio frequency and mixed signal hardware. The proposed algorithm configures hybrid precoders at the transmitter and analog combiners at multiple receivers with a small training and feedback overhead. The performance of the proposed algorithm is analyzed in the large dimensional regime and in single-path channels. When the analog and digital precoding vectors are selected from quantized codebooks, the rate loss due to the joint quantization is characterized, and insights are given into the performance of hybrid precoding compared with analog-only beamforming solutions. Analytical and simulation results show that the proposed techniques offer higher sum rates compared with analog-only beamforming solutions, and approach the performance of the unconstrained digital beamforming with relatively small codebooks. DA - 2015/// PY - 2015/// DO - 10.1109/TWC.2015.2455980 VL - 14 IS - 11 SP - 6481-6494 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84959441538&partnerID=MN8TOARS KW - Millimeter wave communication KW - multi-user hybrid precoding KW - limited-feedback ER - TY - JOUR TI - Metrocell antennas: The positive impact of a narrow vertical beamwidth and electrical downtilt AU - Li, X. AU - Heath, R.W. AU - Linehan, K. AU - Butler, R. T2 - IEEE Vehicular Technology Magazine AB - This article discusses the positive impact that metrocell antennas with a narrow vertical beamwidth and electrical downtilt can have on heterogeneous cellular networks. Using a model of random cell placement based on a Poisson distribution, along with an innovative three-dimensional (3-D) building model that quantifies blockage due to shadowing, it is demonstrated that the network spectral efficiency and average user through-put both increase as the vertical beamwidth decreases and downtilt is applied to metrocell transmission. Moreover, the network becomes more energy efficient. Importantly, these additional gains in network performance can be achieved without any cooperation or exchange of information between macrocell base stations (BSs) and metrocells. DA - 2015/// PY - 2015/// DO - 10.1109/MVT.2015.2410993 VL - 10 IS - 3 SP - 51-59 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84941027855&partnerID=MN8TOARS ER - TY - CONF TI - Interference statistics in a random mmWave ad hoc network AU - Thornburg, A. AU - Bai, T. AU - Heath, R.W. AB - Wireless communication at millimeter wave (mmWave) frequencies is attractive for cellular, local area, and ad hoc networks due to the potential for channels with large bandwidths. As a byproduct of directional beamforming and propagation differences, some studies have claimed that mmWave networks will be noise rather than interference limited. This paper presents a derivation of the instantaneous interference-to-noise ratio (INR) distribution of a mmWave ad hoc network. Random network model of transmitters represented by a Poisson point process with a narrowband channel model is used to derive an approximation of the INR distribution. The analysis shows that the shape of the INR distribution is determined largely by the line-of-sight interferers, which depends on the overall network density and building blockage. A main conclusion drawn is that even with highly directional beamforming, interference can only sometimes be neglected in an ad hoc network. With a reasonable choice of system parameters, the interference is nearly always stronger than the noise power in dense networks. C2 - 2015/// C3 - ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings DA - 2015/// DO - 10.1109/ICASSP.2015.7178502 VL - 2015-August SP - 2904-2908 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84946070491&partnerID=MN8TOARS ER - TY - CONF TI - Interference in finite-sized highly dense millimeter wave networks AU - Venugopal, K. AU - Valenti, M.C. AU - Heath, R.W. AB - The potential of millimeter wave (mmWave) frequencies for device-to-device communication among wearable electronics is enormous for applications requiring Gbps through-put. In a dense usage scenario such as inside a train car or airplane cabin, many devices may be present within close proximity where interference is significant. Previous work that models interference in wireless networks has leveraged stochastic geometry and often assumes an infinite number of interferers. In the indoor wearables setting, a finite network may be a more realistic assumption. This paper analyzes mmWave networks with a finite number of interferers that are located in fixed positions. The paper considers the effect of blockages, which are primarily caused by the human bodies present in the operating environment. Expressions for coverage and rate are developed, which capture the effects of key antenna characteristics such as directivity and gain. C2 - 2015/// C3 - 2015 Information Theory and Applications Workshop, ITA 2015 - Conference Proceedings DA - 2015/// DO - 10.1109/ITA.2015.7308984 SP - 175-180 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84961855527&partnerID=MN8TOARS ER - TY - CONF TI - Frequency selective hybrid precoding in millimeter wave OFDMA systems AU - Park, S. AU - Heath, R.W. AB - Hybrid precoding, a combination of analog and digital precoding, is an attempt to reach a compromise between complexity and performance. By exploiting more than one RF chain, hybrid precoding enables a millimeter wave (mmWave) system to take advantage of both spatial multiplexing and beamforming gain. A major challenge with hybrid precoding is its configuration in wideband systems. The reason is that the analog beamforming weights are the same across the entire band. In this paper, we propose a frequency selective hybrid precoding technique for a mmWave orthogonal frequency division multiple access system. We propose an algorithm to jointly optimize the wideband analog beamformers and the per- subcarrier digital precoders. We compare an upper bound with our solution and show that our optimized approach achieves good performance in terms of beamforming gain in the sense that it minimizes the loss caused by allocating multiple users to different subcarriers with a limited number of radio frequency chains. C2 - 2015/// C3 - 2015 IEEE Global Communications Conference, GLOBECOM 2015 DA - 2015/// DO - 10.1109/GLOCOM.2014.7417763 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84964880233&partnerID=MN8TOARS ER - TY - CONF TI - Ergodic capacity in mmWave ad hoc network with imperfect beam alignment AU - Thornburg, A. AU - Heath, R.W. AB - Millimeter wave (mmWave) technology has several technical hurdles to overcome before becoming an integral next-generation wireless technology. One such hurdle is the alignment of the steerable mmWave antenna array. This paper quantifies both the ergodic capacity of a mmWave ad hoc network with perfect alignment and the loss in ergodic capacity when error is introduced. First, we leverage stochastic geometry to evaluate the ergodic capacity (bits/sec/Hz/area) in the network. Next, we compare two antenna models that are commonly used: sectored and Gaussian. Lastly, we derive expressions that quantify the loss in ergodic capacity per user when alignment error occurs at the receiver and transmitter. Our results show that even relatively small errors in alignment can lead to significant ergodic capacity reduction. C2 - 2015/// C3 - Proceedings - IEEE Military Communications Conference MILCOM DA - 2015/// DO - 10.1109/MILCOM.2015.7357653 VL - 2015-December SP - 1479-1484 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84959310159&partnerID=MN8TOARS ER - TY - JOUR TI - Index Coding With Coded Side-Information AU - Lee, N. AU - Dimakis, A.G. AU - Heath, R.W. T2 - IEEE Communications Letters AB - This letter investigates a new class of index coding problems. One sender broadcasts packets to multiple users, each desiring a subset, by exploiting prior knowledge of linear combinations of packets. We refer to this class of problems as index coding with coded side-information. Our aim is to characterize the minimum index code length that the sender needs to transmit to simultaneously satisfy all user requests. We show that the optimal binary vector index code length is equal to the minimum rank (minrank) of a matrix whose elements consist of the sets of desired packet indices and side-information encoding matrices. This is the natural extension of matrix minrank in the presence of coded side information. Using the derived expression, we propose a greedy randomized algorithm to minimize the rank of the derived matrix. DA - 2015/// PY - 2015/// DO - 10.1109/LCOMM.2015.2388477 VL - 19 IS - 3 SP - 319-322 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84924856040&partnerID=MN8TOARS KW - Index coding and coded side-information ER - TY - CONF TI - Energy coverage in millimeter wave energy harvesting networks AU - Khan, T.A. AU - Alkhateeb, A. AU - Heath, R.W. AB - Wireless energy harvesting in millimeter wave (mmWave) cellular networks is attractive, thanks to the large antenna arrays and the anticipated dense deployment of these systems. The signal propagation at mmWave frequencies, however, shows peculiar propagation characteristics such as extreme sensitivity to building blockages. This work analyzes the energy harvesting performance at receivers powered by a mmWave cellular network. Leveraging tools from stochastic geometry, analytical expressions are derived to characterize the energy coverage probability at a typical receiver in terms of the cellular network density, the antenna geometry parameters, and the channel parameters. Results show that there typically exists an optimum transmit antenna beamwidth that maximizes the network-wide energy coverage probability for many operating scenarios. Simulation results further suggest that mmWave energy harvesting could provide a substantial performance boost compared to lower frequency solutions. C2 - 2015/// C3 - 2015 IEEE Globecom Workshops, GC Wkshps 2015 - Proceedings DA - 2015/// DO - 10.1109/GLOCOMW.2015.7414219 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84971264181&partnerID=MN8TOARS ER - TY - CONF TI - Dictionary-free hybrid precoders and combiners for mmWave MIMO systems AU - Mendez-Rial, R. AU - Rusu, C. AU - Gonzalez-Prelcic, N. AU - Heath, R.W. AB - The high cost and power consumption of the radio frequency chain and data converters at mmWave frequencies introduce hardware limitations into the design of MIMO precoders and combiners. MmWave hybrid precoding overcomes this limitation by dividing the spatial signal processing between the radio frequency and baseband domains. Analog networks of phase shifters have been proposed to implement the radio frequency precoders, since they achieve a good compromise between complexity and performance. In this paper, we propose a low complexity hybrid precoding design for the architecture based on phase shifters. The new method is a greedy algorithm based on the orthogonal matching pursuit algorithm, but replacing the costly correlation operations over a dictionary with the element-wise normalization of the first singular vector of the residual. The main advantage is that the design avoids any assumption on the antenna array geometry. Additionally, numerical results show the superiority of the proposed method in terms of achievable spectral efficiency over other previous solutions. C2 - 2015/// C3 - IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC DA - 2015/// DO - 10.1109/SPAWC.2015.7227018 VL - 2015-August SP - 151-155 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84953407083&partnerID=MN8TOARS ER - TY - CONF TI - Compressed sensing based multi-user millimeter wave systems: How many measurements are needed? AU - Alkhateeby, A. AU - Leusz, G. AU - Heath, R.W. AB - Millimeter wave (mmWave) systems will likely employ directional beamforming with large antenna arrays at both the transmitters and receivers. Acquiring channel knowledge to design these beamformers, however, is challenging due to the large antenna arrays and small signal-to-noise ratio before beamforming. In this paper, we propose and evaluate a downlink system operation for multi-user mmWave systems based on compressed sensing channel estimation and conjugate analog beamforming. Adopting the achievable sum-rate as a performance metric, we show how many compressed sensing measurements are needed to approach the perfect channel knowledge performance. The results illustrate that the proposed algorithm requires an order of magnitude less training overhead compared with traditional lower-frequency solutions, while employing mmWave-suitable hardware. They also show that the number of measurements need to be optimized to handle the trade-off between the channel estimate quality and the training overhead. C2 - 2015/// C3 - ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings DA - 2015/// DO - 10.1109/ICASSP.2015.7178503 VL - 2015-August SP - 2909-2913 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84946012070&partnerID=MN8TOARS ER - TY - JOUR TI - Enabling 5G: Energy and spectrally efficient communication systems AU - Tafazolli, R. AU - Palazzo, S. AU - Payarõ, M. AU - Heath, R.W. T2 - Transactions on Emerging Telecommunications Technologies AB - Transactions on Emerging Telecommunications TechnologiesVolume 26, Issue 1 p. 1-2 Editorial Enabling 5G: energy and spectrally efficient communication systems Rahim Tafazolli, Rahim Tafazolli r.tafazolli@surrey.ac.uk Centre for Communication Systems Research, University of Surrey, UKSearch for more papers by this authorSergio Palazzo, Sergio Palazzo palazzo@diit.unict.it University of Catania, ItalySearch for more papers by this authorMiquel Payaró, Miquel Payaró miquel.payaro@cttc.es Centre Tecnològic de Telecomunicacions de Catalunya, SpainSearch for more papers by this authorRobert W. Heath Jr., Robert W. Heath Jr. rheath@utexas.edu The University of Texas at Austin, TX, USASearch for more papers by this author Rahim Tafazolli, Rahim Tafazolli r.tafazolli@surrey.ac.uk Centre for Communication Systems Research, University of Surrey, UKSearch for more papers by this authorSergio Palazzo, Sergio Palazzo palazzo@diit.unict.it University of Catania, ItalySearch for more papers by this authorMiquel Payaró, Miquel Payaró miquel.payaro@cttc.es Centre Tecnològic de Telecomunicacions de Catalunya, SpainSearch for more papers by this authorRobert W. Heath Jr., Robert W. Heath Jr. rheath@utexas.edu The University of Texas at Austin, TX, USASearch for more papers by this author First published: 05 December 2014 https://doi.org/10.1002/ett.2917Citations: 4Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume26, Issue1Special Issue: Enabling 5G: energy and spectrally efficient communication systemsJanuary 2015Pages 1-2 RelatedInformation DA - 2015/// PY - 2015/// DO - 10.1002/ett.2917 VL - 26 IS - 1 SP - 1-2 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84928885792&partnerID=MN8TOARS ER - TY - JOUR TI - Distributed space-time interference alignment with moderately delayed CSIT AU - Lee, N. AU - Tandon, R. AU - Heath, R.W. T2 - IEEE Transactions on Wireless Communications AB - This paper proposes an interference alignment method with distributed and delayed channel state information at the transmitter (CSIT) for a class of interference networks. The core idea of the proposed method is to align interference signals over time at the unintended receivers in a distributed manner. With the proposed method, achievable tradeoffs between the sum of degrees of freedom (sum-DoF) and feedback delay of CSI are characterized in both the X-channel and three-user interference channel to reveal the impact on how the CSI feedback delay affects the sum-DoF of the interference networks. A major implication of derived results is that distributed and moderately delayed CSIT is useful to strictly improve the sum-DoF over the case of no CSI at the transmitter in a certain class of interference networks. For a class of X-channels, the results show how to optimally use distributed and moderately delayed CSIT to yield the same sum-DoF as instantaneous and global CSIT. Furthermore, leveraging the proposed transmission method and the known outer bound results, the sum-capacity of the two-user X-channel with a particular set of channel coefficients is characterized within a constant number of bits. DA - 2015/// PY - 2015/// DO - 10.1109/TWC.2014.2363475 VL - 14 IS - 2 SP - 1048-1059 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84922905910&partnerID=MN8TOARS KW - Space-time interference alignment KW - delayed CSIT KW - interference networks ER - TY - JOUR TI - Coverage and rate analysis for millimeter-wave cellular networks AU - Bai, T. AU - Heath, R.W. T2 - IEEE Transactions on Wireless Communications AB - Millimeter wave (mmWave) holds promise as a carrier frequency for fifth generation cellular networks. Because mmWave signals are sensitive to blockage, prior models for cellular networks operated in the ultra high frequency (UHF) band do not apply to analyze mmWave cellular networks directly. Leveraging concepts from stochastic geometry, this paper proposes a general framework to evaluate the coverage and rate performance in mmWave cellular networks. Using a distance-dependent line-of-site (LOS) probability function, the locations of the LOS and non-LOS base stations are modeled as two independent non-homogeneous Poisson point processes, to which different path loss laws are applied. Based on the proposed framework, expressions for the signal-to-noise-and-interference ratio (SINR) and rate coverage probability are derived. The mmWave coverage and rate performance are examined as a function of the antenna geometry and base station density. The case of dense networks is further analyzed by applying a simplified system model, in which the LOS region of a user is approximated as a fixed LOS ball. The results show that dense mmWave networks can achieve comparable coverage and much higher data rates than conventional UHF cellular systems, despite the presence of blockages. The results suggest that the cell size to achieve the optimal SINR scales with the average size of the area that is LOS to a user. DA - 2015/// PY - 2015/// DO - 10.1109/TWC.2014.2364267 VL - 14 IS - 2 SP - 1100-1114 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84922879239&partnerID=MN8TOARS KW - Millimeter wave KW - fifth generation cellular networks KW - stochastic geometry KW - performance analysis ER - TY - JOUR TI - Distributed real-time implementation of interference alignment with analog feedback AU - Lee, S. AU - Gerstlauer, A. AU - Heath, R.W. T2 - IEEE Transactions on Vehicular Technology AB - Interference alignment (IA) is a precoding technique that aligns interfering signals at receivers. It is known that IA achieves the maximum degrees of freedom over an interference channel under ideal assumptions. The real-world performance of IA depends on a range of practical issues, such as imperfect synchronization, channel estimation, and feedback. Practical issues have been studied in simulations and prototypes, but fully distributed operation of IA network nodes has not been considered. In this paper, we present the first investigation of real-time IA performance on a fully distributed 2 $\times$ 2 multiple-input–multiple-output (MIMO) prototype system with three physically independent user pairs. Over-the-air algorithms for time and frequency synchronization, as well as analog feedback, are studied and implemented. Sum rates are illustrated as a function of complexity and accuracy of different alignment, synchronization, and feedback algorithms. Corresponding tradeoffs are evaluated using an iterative IA method, the injection of residual frequency offset into synchronization, and analog versus quantization-based limited feedback approaches. We demonstrate that, while considering all possible error sources in estimation, synchronization, and feedback, the theoretical multiplexing gain of IA can be reached in practical systems with a constant sum rate loss that remains within 5 bits/Hz/s compared with an ideal simulation. DA - 2015/// PY - 2015/// DO - 10.1109/TVT.2014.2357391 VL - 64 IS - 8 SP - 3513-3525 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84939520224&partnerID=MN8TOARS KW - Interference alignment (IA) KW - prototyping ER - TY - JOUR TI - Delay-constrained video transmission: Quality-driven resource allocation and scheduling AU - Khalek, A.A. AU - Caramanis, C. AU - Heath, R.W. T2 - IEEE Journal on Selected Topics in Signal Processing AB - Real-time video demands quality-of-service (QoS) guarantees such as delay bounds for end-user satisfaction. Furthermore, the tolerable delay varies depending on the use case such as live streaming or two-way video conferencing. Due to the inherently stochastic nature of wireless fading channels, deterministic delay bounds are difficult to guarantee. Instead, we propose providing statistical delay guarantees using the concept of effective capacity. We consider a multiuser setup whereby different users have (possibly different) delay QoS constraints. We derive the resource allocation policy that maximizes the sum video quality and applies to any quality metric with concave rate-quality mapping. We show that the optimal operating point per user is such that the rate-distortion slope is the inverse of the supported video source rate per unit bandwidth, a key metric we refer to as the source spectral efficiency. We extend the resource allocation policy to capture video quality-driven adaptive user-subcarrier assignment in wideband channels as well as capture the impact of adaptive modulation and coding. We also solve the alternative problem of fairness-based resource allocation whereby the objective is to maximize the minimum video quality across users. Finally, we derive user admission and scheduling policies that enable selecting a maximal user subset such that all selected users can meet their statistical delay requirement. Results show that video users with differentiated QoS requirements can achieve similar video quality with vastly different resource requirements. Thus, QoS-aware scheduling and resource allocation enable supporting significantly more users under the same resource constraints. DA - 2015/// PY - 2015/// DO - 10.1109/JSTSP.2014.2332304 VL - 9 IS - 1 SP - 60-75 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84921810289&partnerID=MN8TOARS KW - Resource allocation KW - statistical QoS KW - rate distortion theory KW - perceptual video quality KW - effective capacity ER - TY - CONF TI - Channel estimation and hybrid combining for mmWave: Phase shifters or switches? AU - Mendez-Rial, R. AU - Rusu, C. AU - Alkhateeb, A. AU - Gonzalez-Prelcic, N. AU - Heath, R.W. AB - Precoding/combining and large antenna arrays are essential in millimeter wave (mmWave) systems. In traditional MIMO systems, precoding/combining is usually done digitally at baseband with one radio frequency (RF) chain and one analog-to-digital converter (ADC) per antenna. The high cost and power consumption of RF chains and ADCs at mmWave frequencies make an all-digital processing approach prohibitive. When only a limited number of RF chains is available, hybrid architectures that split the precoding/combining processing into the analog and digital domains are attractive. A previously proposed hybrid solution employs phase shifters and mixers in the RF precoding/combining stage. It obtains near optimal spectral efficiencies with a reduced number of RF channels. In this paper we propose a different hybrid architecture, which simplifies the hardware at the receiver by replacing the phase shifters with switches. We present a new approach for compressed sensing based channel estimation for the hybrid architectures. Given the channel estimate, we propose a novel algorithm that jointly designs the antenna subsets selected and the baseband combining. Using power consumption calculations and achievable rates, we compare the performance of hybrid combining with antenna switching and phase shifting, showing that antenna selection is preferred in a range of operating conditions. C2 - 2015/// C3 - 2015 Information Theory and Applications Workshop, ITA 2015 - Conference Proceedings DA - 2015/// DO - 10.1109/ITA.2015.7308971 SP - 90-97 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84961836201&partnerID=MN8TOARS ER - TY - CONF TI - Base station cluster patterns for semi-static multi-cell cooperation in irregular network topologies AU - Park, J. AU - Lee, N. AU - Heath, R.W. AB - This paper proposes a clustering strategy for semi-static mul-ticell cooperation. Semi-static multicell cooperation exploits multiple predefined base station (BS) cluster patterns for improving cell-edge user throughput. The proposed clustering guarantees that every user communicates with their two closest BSs, so that users are protected from the dominant interferer. The key idea of the proposed clustering is to use the 2nd-order Voronoi region to form BS clusters. Each of the formed BS clusters is mapped into a particular cluster pattern by exploiting the edge-coloring in graph theory. Through simulations, the performance is compared to that of other conventional strategies. Our major finding is that the proposed clustering provides performance gains for cell-edge users compared to that of the conventional strategies. C2 - 2015/// C3 - 2015 23rd European Signal Processing Conference, EUSIPCO 2015 DA - 2015/// DO - 10.1109/EUSIPCO.2015.7362823 SP - 2441-2445 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963988180&partnerID=MN8TOARS ER - TY - CONF TI - Channel estimation in millimeter wave MIMO systems with one-bit quantization AU - Mo, J. AU - Schniter, P. AU - Prelcic, N.G. AU - Heath, R.W. AB - We develop channel estimation agorithms for millimeter wave (mmWave) multiple input multiple output (MIMO) systems with one-bit analog-to-digital converters (ADCs). Since the mmWave MIMO channel is sparse due to the propagation characteristics, the estimation problem is formulated as a one-bit compressed sensing problem. We propose a modified EM algorithm that exploits sparsity and has better performance than the conventional EM algorithm. We also present a second solution using the generalized approximate message passing (GAMP) algorithm to solve this optimization problem. The simulation results show that GAMP can reduce mean squared error in the important low and medium SNR regions. C2 - 2015/// C3 - Conference Record - Asilomar Conference on Signals, Systems and Computers DA - 2015/// DO - 10.1109/ACSSC.2014.7094595 VL - 2015-April SP - 957-961 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84940470523&partnerID=MN8TOARS ER - TY - JOUR TI - Capacity Analysis of One-Bit Quantized MIMO Systems with Transmitter Channel State Information AU - Mo, J. AU - Heath, R.W. T2 - IEEE Transactions on Signal Processing AB - With bandwidths on the order of a gigahertz in emerging wireless systems, high-resolution analog-to-digital convertors (ADCs) become a power consumption bottleneck. One solution is to employ low resolution one-bit ADCs. In this paper, we analyze the flat fading multiple-input multiple-output (MIMO) channel with one-bit ADCs. Channel state information is assumed to be known at both the transmitter and receiver. For the multiple-input single-output channel, we derive the exact channel capacity. For the single-input multiple-output and MIMO channel, the capacity at infinite signal-to-noise ratio (SNR) is found. We also derive upper bound at finite SNR, which is tight when the channel has full row rank. In addition, we propose an efficient method to design the input symbols to approach the capacity achieving solution. We incorporate millimeter wave channel characteristics and find the bounds on the infinite SNR capacity. The results show how the number of paths and number of receive antennas impact the capacity. DA - 2015/// PY - 2015/// DO - 10.1109/TSP.2015.2455527 VL - 63 IS - 20 SP - 5498-5512 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84959378939&partnerID=MN8TOARS KW - Analog-to-digital convertor KW - millimeter wave KW - MIMO channel KW - one-bit quantization ER - TY - CONF TI - An indoor correlated shadowing model AU - Zhang, X. AU - Baccelli, F. AU - Heath, R.W. AB - A Manhattan Poisson line process divides the plane into an infinite number of rectangular rooms with walls extending infinitely along the axes. When the path loss is dominated by the penetration through each of the walls, a Poisson field of transmitters creates a heavy tailed interference at a randomly picked room, whose distribution is tractable in the Laplace domain. Interference correlation at different rooms is explicitly available. This model gives the first tractable mathematical abstraction to indoor physical environments where wireless signals are shadowed by (common) walls. Applying the analytical results leads to a formula for success probabilities of a transmission attempt between two given rooms. C2 - 2015/// C3 - 2015 IEEE Global Communications Conference, GLOBECOM 2015 DA - 2015/// DO - 10.1109/GLOCOM.2014.7417557 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84964810170&partnerID=MN8TOARS ER - TY - CONF TI - Augmented covariance estimation with a cyclic approach in DOA AU - Mendez-Rial, R. AU - Gonzalez-Prelcic, N. AU - Heath, R.W. AB - High resolution direction-of-arrival (DOA) estimation is an important problem in many array signal processing applications. This paper proposes an augmented covariance estimator for DOA estimation. The new method exploits the periodicity of the covariance lags when the DOAs are assumed on a discrete grid with a certain resolution. Then, it achieves twice the resolution of typical methods such as the direct augmentable approach or forward backward spatial smoothing. When the sources are not on the discrete grid, an interpolated array manifold technique is proposed to mitigate the grid mismatch error. C2 - 2015/// C3 - ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings DA - 2015/// DO - 10.1109/ICASSP.2015.7178478 VL - 2015-August SP - 2784-2788 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84946045711&partnerID=MN8TOARS ER - TY - CONF TI - Asymptotic SINR for millimeter wave massive MIMO cellular networks AU - Bai, T. AU - Heath, R.W. AB - Thanks to the small wavelength at millimeter wave (mmWave) frequency, it is promising to combine massive multiple-input and multiple-output (MIMO) with mmWave. MmWave massive MIMO will differ from the conventional massive MIMO, due to the differences in propagation and hardware constraints. This paper proposes a stochastic geometry framework for evaluating the performance in large-scale mmWave massive MIMO networks. Based on the system model, analytical expressions are provided for the asymptotic signal-to-interference-plus-noise ratio (SINR) distributions in both uplink and downlink, when the number of base station antennas goes to infinity. Numerical results indicate a fast convergence in the SINR distribution to its asymptotic equivalence in dense mmWave networks. A comparison with conventional massive MIMO shows that mmWave massive MIMO achieves a higher cell throughput with sufficiently dense deployments. C2 - 2015/// C3 - IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC DA - 2015/// DO - 10.1109/SPAWC.2015.7227112 VL - 2015-August SP - 620-624 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84953374573&partnerID=MN8TOARS ER - TY - JOUR TI - Artificial-noise-aided secure multi-antenna transmission with limited feedback AU - Zhang, X. AU - McKay, M.R. AU - Zhou, X. AU - Heath, R.W. T2 - IEEE Transactions on Wireless Communications AB - We present an optimized secure multi-antenna transmission approach based on artificial-noise-aided beamforming, with limited feedback from a desired single-antenna receiver. To deal with beamformer quantization errors as well as unknown eavesdropper channel characteristics, our approach is aimed at maximizing throughput under dual performance constraints-a connection outage constraint on the desired communication channel and a secrecy outage constraint to guard against eavesdropping. We propose an adaptive transmission strategy that judiciously selects the wiretap coding parameters, as well as the power allocation between the artificial noise and the information signal. This optimized solution reveals several important differences with respect to solutions designed previously under the assumption of perfect feedback. We also investigate the problem of how to most efficiently utilize the feedback bits. The simulation results indicate that a good design strategy is to use approximately 20% of these bits to quantize the channel gain information, with the remainder to quantize the channel direction, and this allocation is largely insensitive to the secrecy outage constraint imposed. In addition, we find that 8 feedback bits per transmit antenna is sufficient to achieve approximately 90% of the throughput attainable with perfect feedback. DA - 2015/// PY - 2015/// DO - 10.1109/TWC.2015.2391261 VL - 14 IS - 5 SP - 2742-2754 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84929330256&partnerID=MN8TOARS KW - Artificial noise KW - adaptive transmission KW - limited feedback KW - physical-layer security KW - power allocation ER - TY - CONF TI - Analysis of self-body blocking effects in millimeter wave cellular networks AU - Bai, T. AU - Heath, R.W. AB - The millimeter wave (mmWave) spectrum is a strong candidate carrier frequency for access channels in fifth generation cellular networks. Unfortunately, the human body heavily attenuates mmWave signals. This paper evaluates the impact of self-body blocking (the blocking of the direct link by the handset user's body) in mmWave cellular networks using a stochastic geometric network model. A mathematical model for self-body blocking is proposed, allowing for position changes, and used to compute signal-to-interference-plus-noise ratio (SINR) distributions with two possible user association rules. The results characterize how self-body blocking impacts the SINR coverage. Even including self-body blocking, mmWave cellular systems can still outperform convention systems at lower frequencies, in terms of the achievable rate, due to the larger bandwidth. C2 - 2015/// C3 - Conference Record - Asilomar Conference on Signals, Systems and Computers DA - 2015/// DO - 10.1109/ACSSC.2014.7094804 VL - 2015-April SP - 1921-1925 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84940531598&partnerID=MN8TOARS ER - TY - CONF TI - Achievable rates of multi-user millimeter wave systems with hybrid precoding AU - Alkhateeb, A. AU - Heath, R.W. AU - Leus, G. AB - Millimeter wave (mmWave) systems will likely employ large antenna arrays at both the transmitters and receivers. A natural application of antenna arrays is simultaneous transmission to multiple users, which requires multi-user precoding at the transmitter. Hardware constraints, however, make it difficult to apply conventional lower frequency MIMO precoding techniques at mmWave. This paper proposes and analyzes a low complexity hybrid analog/digital beamforming algorithm for downlink multi-user mmWave systems. Hybrid precoding involves a combination of analog and digital processing that is motivated by the requirement to reduce the power consumption of the complete radio frequency and mixed signal hardware. The proposed algorithm configures hybrid precoders at the transmitter and analog combiners at multiple receivers with a small training and feedback overhead. For this algorithm, we derive a lower bound on the achievable rate for the case of single-path channels, show its asymptotic optimality at large numbers of antennas, and make useful insights for more general cases. Simulation results show that the proposed algorithm offers higher sum rates compared with analog-only beamforming, and approaches the performance of the unconstrained digital precoding solutions. C2 - 2015/// C3 - 2015 IEEE International Conference on Communication Workshop, ICCW 2015 DA - 2015/// DO - 10.1109/ICCW.2015.7247346 SP - 1232-1237 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84947718364&partnerID=MN8TOARS ER - TY - CONF TI - Adaptive hybrid precoding and combining in MmWave multiuser MIMO systems based on compressed covariance estimation AB - In this paper we propose an adaptive multi user (MU) single-cell hybrid precoding strategy that iteratively designs the precoders/combiners exploiting the reciprocity of time division duplex (TDD) millimeter wave systems. The minimum mean square error (MMSE) criterion is considered to design the combiners, which relies on second order statistics of the channel. The covariance of the received signal at the antenna array is estimated online from compressed measurements, leveraging the sparse nature of mmWave channels. The proposed method avoids the explicit estimation of the channel matrix associated to each user, reducing the training overhead, and achieving sum spectral efficiencies comparable to the ones obtained with block diagonalization. C2 - 2015/// C3 - 2015 IEEE 6th International Workshop on Computational Advances in Multi-Sensor Adaptive Processing, CAMSAP 2015 DA - 2015/// DO - 10.1109/CAMSAP.2015.7383774 SP - 213-216 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963928899&partnerID=MN8TOARS ER - TY - CONF TI - An attack on antenna subset modulation for millimeter wave communication AB - Antenna subset modulation (ASM) is a physical layer security technique that is well suited for millimeter wave communication systems. The key idea is to vary the radiation pattern at the symbol rate by selecting one from a subset of patterns with a similar main lobe and different side lobes. This paper shows that ASM is not robust to an eavesdropper that makes multiple simultaneous measurements at multiple angles. The measurements are combined and used to formulate an estimation problem to undo the effects of the side lobe randomization. Simulations show the performance of the estimation algorithms and how the eavesdropper can effectively recover the information if the signal-to-noise ratio exceeds a certain threshold. Using fewer active radio frequency chains makes it harder for the attacker to recover the transmit symbol, at the expense of more grating lobes. C2 - 2015/// C3 - ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings DA - 2015/// DO - 10.1109/ICASSP.2015.7178504 VL - 2015-August SP - 2914-2918 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84946070681&partnerID=MN8TOARS ER - TY - CONF TI - Advanced limited feedback designs for FD-MIMO using uniform planar arrays AU - Choi, J. AU - Lee, K. AU - Love, D.J. AU - Kim, T. AU - Heath, R.W. AB - Massive multiple-input multiple-output (MIMO) with uniform planar arrays (UPAs), which is often referred to as full-dimension (FD) MIMO, is being strongly considered for future wireless communication standards. FD-MIMO can control transmit and receive beams in both the horizontal and vertical domains and fully exploit the large number of antennas of massive MIMO. It is widely accepted that Kronecker-product codebooks using a discrete Fourier transform (DFT) structure are suitable to quantize the downlink channel at the user for FD-MIMO systems relying on frequency division duplexing (FDD). In this paper, we numerically study the characteristics of FD-MIMO channels using a three-dimensional (3D) channel model that captures realistic channel properties. Based on the study, we identify a limitation of conventional Kronecker-product codebooks and propose advanced channel quantization techniques that can further improve channel quantization quality. C2 - 2015/// C3 - 2015 IEEE Global Communications Conference, GLOBECOM 2015 DA - 2015/// DO - 10.1109/GLOCOM.2014.7417281 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84964886837&partnerID=MN8TOARS ER - TY - CONF TI - Adaptive one-bit compressive sensing with application to low-precision receivers at mmWave AU - Rusu, C. AU - Mendez-Rial, R. AU - Gonzalez-Prelcic, N. AU - Heath, R.W. AB - Multiple input multiple output (MIMO) systems employing large antenna arrays are the basic architecture for millimeter wave (mmWave) systems. Due to the higher bandwidths to be used at mmWave, the corresponding sampling rates of high-resolution analog-to-digital converters (ADCs) are also very high, so that ADCs become the most power hungry devices in the reception chain. One solution is to employ low resolution, i.e. one-bit, ADCs. We develop an adaptive one-bit compressed sensing scheme that can be used at low-resolution mmWave receivers for channel estimation. The simulation results show that the adaptive one-bit compressed sensing scheme outperforms the fixed one in the context of mmWave channel estimation. C2 - 2015/// C3 - 2015 IEEE Global Communications Conference, GLOBECOM 2015 DA - 2015/// DO - 10.1109/GLOCOM.2014.7417853 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84964910034&partnerID=MN8TOARS ER - TY - JOUR TI - Accuracy in the palm of your hand: Centimeter positioning with a smartphone-quality GNSS antenna AU - Pesyna, K.M. AU - Heath, R.W. AU - Humphreys, T.E. T2 - GPS World DA - 2015/// PY - 2015/// VL - 26 IS - 2 SP - 16-31 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84964573502&partnerID=MN8TOARS ER - TY - CONF TI - A stochastic geometry approach to analyzing cellular networks with semi-static clustering AU - Khan, T.A. AU - Zhang, X. AU - Heath, R.W. AB - Static base-station clustering allows clustered transmitters to jointly serve a group of users and thus eliminate the intra-cluster interference. The network performance is then bottlenecked by the cluster-edge users. Semi-static clustering can help improve the performance along the cluster edges by time-sharing between different clustering patterns. We propose a simple clustering and user scheduling algorithm to gauge the performance gain of semi-static clustering. Under a stochastic geometry framework, we derive analytical expressions for the coverage and rate of a user at a given location. As the cluster size goes to infinity, we show that the outage probability of semi-static clustering decays at the same order as that of static clustering. Thus, in the asymptotic regime, the performance gain provided by semi- static clustering can be characterized by a linear factor. Numerical results demonstrate the gain of semi-static clustering in the non-asymptotic regime. C2 - 2015/// C3 - 2015 IEEE Global Communications Conference, GLOBECOM 2015 DA - 2015/// DO - 10.1109/GLOCOM.2014.7417282 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84964887314&partnerID=MN8TOARS ER - TY - JOUR TI - Bacterial Nanobioreactors–Directing Enzyme Packaging into Bacterial Outer Membrane Vesicles AU - Alves, Nathan J. AU - Turner, Kendrick B. AU - Daniele, Michael A. AU - Oh, Eunkeu AU - Medintz, Igor L. AU - Walper, Scott A. T2 - ACS Applied Materials & Interfaces AB - All bacteria shed outer membrane vesicles (OMVs) loaded with a diverse array of small molecules, proteins, and genetic cargo. In this study we sought to hijack the bacterial cell export pathway to simultaneously produce, package, and release an active enzyme, phosphotriesterase (PTE). To accomplish this goal the SpyCatcher/SpyTag (SC/ST) bioconjugation system was utilized to produce a PTE-SpyCatcher (PTE-SC) fusion protein and a SpyTagged transmembrane porin protein (OmpA-ST), known to be abundant in OMVs. Under a range of physiological conditions the SpyTag and SpyCatcher domains interact with one another and form a covalent isopeptide bond driving packaging of PTE into forming OMVs. The PTE-SC loaded OMVs are characterized for size distribution, number of vesicles produced, cell viability, packaged PTE enzyme kinetics, OMV loading efficiency, and enzyme stability following iterative cycles of freezing and thawing. The PTE-loaded OMVs exhibit native-like enzyme kinetics when assayed with paraoxon as a substrate. PTE is often toxic to expression cultures and has a tendency to lose activity with improper handling. The coexpression of OmpA-ST with PTE-SC, however, greatly improved the overall PTE production levels by mitigating toxicity through exporting of the PTE-SC and greatly enhanced packaged enzyme stability against iterative cycles of freezing and thawing. DA - 2015/10/29/ PY - 2015/10/29/ DO - 10.1021/ACSAMI.5B08811 VL - 7 IS - 44 SP - 24963-24972 J2 - ACS Appl. Mater. Interfaces LA - en OP - SN - 1944-8244 1944-8252 UR - http://dx.doi.org/10.1021/ACSAMI.5B08811 DB - Crossref KW - outer membrane vesicle (OMV) KW - phosphotriesterase (PTE) KW - directed packaging enzyme KW - E. coli KW - SpyCatcher KW - SpyTag ER - TY - JOUR TI - Low-voltage PV power integration into medium voltage grid using high-voltage SiC devices AU - Chattopadhyay, R. AU - Bhattacharya, S. AU - Foureaux, N.C. AU - Pires, I.A. AU - De Paula, H. AU - Moraes, L. AU - Cortizio, P.C. AU - Silva, S.M. AU - Filho, B.C. AU - Brito, J.A.D.S. T2 - IEEJ Journal of Industry Applications AB - High voltage high power semiconductor devices are being used for grid integration of renewable energy sources. 1200V/100A SiC-MOSFETs, 1700V SiC-MOSFETs, 1700V SiC-Schottky diodes, 10kV SiC-MOSFETs, and 10kV JBS diodes have proved to be useful for high-voltage applications. High-voltage SiC devices enable high-switching frequency operation thus reducing the size of the parasitic element. This paper focuses on an alternative approach to the 0.9MW PV power plant currently being constructed in Brazil. The objective of the use of high power SiC devices for integration of the PV power plant into 13.8kV grid is to provide higher efficiency and reduced size and volume. DA - 2015/// PY - 2015/// DO - 10.1541/ieejjia.4.767 VL - 4 IS - 6 SP - 767-775 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85015067417&partnerID=MN8TOARS KW - medium voltage grid KW - PV plant KW - renewable energy source KW - SiC. dual active bridge (DAB) ER - TY - JOUR TI - A Transformerless Intelligent Power Substation: A three-phase SST enabled by a 15-kV SiC IGBT AU - Mainali, K. AU - Tripathi, A. AU - Madhusoodhanan, S. AU - Kadavelugu, A. AU - Patel, D. AU - Hazra, S. AU - Hatua, K. AU - Bhattacharya, S. T2 - IEEE Power Electronics Magazine AB - The solid-state transformer (SST) is a promising power electronics solution that provides voltage regulation, reactive power compensation, dc-sourced renewable integration, and communication capabilities, in addition to the traditional step-up/step-down functionality of a transformer. It is gaining widespread attention for medium-voltage (MV) grid interfacing to enable increases in renewable energy penetration, and, commercially, the SST is of interest for traction applications due to its light weight as a result of medium-frequency isolation. The recent advancements in silicon carbide (SiC) power semiconductor device technology are creating a new paradigm with the development of discrete power semiconductor devices in the range of 10-15 kV and even beyond-up to 22 kV, as recently reported. In contrast to silicon (Si) IGBTs, which are limited to 6.5-kV blocking, these high-voltage (HV) SiC devices are enabling much simpler converter topologies and increased efficiency and reliability, with dramatic reductions of the size and weight of the MV power-conversion systems. DA - 2015/// PY - 2015/// DO - 10.1109/MPEL.2015.2449271 VL - 2 IS - 3 SP - 31-43 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84960131504&partnerID=MN8TOARS ER - TY - JOUR TI - Quantitative assessment of solid renal masses by contrast-enhanced ultrasound with time–intensity curves: how we do it AU - King, Kevin G. AU - Gulati, Mittul AU - Malhi, Harshawn AU - Hwang, Darryl AU - Gill, Inderbir S. AU - Cheng, Phillip M. AU - Grant, Edward G. AU - Duddalwar, Vinay A. T2 - Abdominal Imaging DA - 2015/6/3/ PY - 2015/6/3/ DO - 10.1007/S00261-015-0468-Y VL - 40 IS - 7 SP - 2461-2471 J2 - Abdom Imaging LA - en OP - SN - 0942-8925 1432-0509 UR - http://dx.doi.org/10.1007/S00261-015-0468-Y DB - Crossref KW - Renal mass KW - Contrast-enhanced ultrasound KW - Time-intensity curve KW - Renal cell carcinoma KW - Oncocytoma KW - Angiomyolipoma ER - TY - JOUR TI - Respiratory rate monitoring using infrared sensors AU - Erden, Fatih AU - Cetin, A. Enis T2 - 2015 9th International Conference on Electrical and Electronics Engineering (ELECO) AB - Respiratory rate is an essential parameter in many practical applications such as patient and elderly people monitoring. In this paper, a novel contact-free system is introduced to detect the human breathing activity. The system, which consists of two pyro-electric infrared (PIR) sensors, is capable of estimating the respiratory rate and detecting the sleep apnea. Sensors' signals corresponding to the thoracic movements of a human being are sampled using a microprocessor and analyzed on a general-purpose computer. Sampled signals are processed using empirical mode decomposition (EMD) and a new average magnitude difference function (AMDF) is used to detect the periodicity and the period of the processed signals. The resulting period, by using the fact that breathing is almost a periodic activity, is monitored as the respiratory rate. The new AMDF provides a way to fuse the data from the multiple sensors and generate a more reliable estimation of the respiratory rate. DA - 2015/11// PY - 2015/11// DO - 10.1109/eleco.2015.7394631 ER - TY - JOUR TI - Examination of EV-grid integration using real driving and transformer loading data AU - Erden, Fatih AU - Kisacikoglu, Mithat C. AU - Gurec, Ozan H. T2 - 2015 9th International Conference on Electrical and Electronics Engineering (ELECO) AB - The growing environmental concerns and the increase in oil prices will lead to the proliferation of electric vehicles (EVs) in the near future. The increase in the number of EVs, while providing green and inexpensive solutions to transportation needs, may cause constraints on the operation of the utility grid that should be investigated. In this paper, the real user driving information is collected from individual data tracking devices of passenger vehicle owners instead of assuming randomly distributed trip characteristics. The collected trip data are first analyzed to generate a statistical model of the trip characteristics in terms of home arrival times and state of charge (SOC) levels. The resulting model is then used to simulate and analyze the impact of EV integration in a real grid with different EV penetration levels. For this, real distribution transformer data provided by Başkent Electric Distribution Co. is used. The proposed method produces more realistic results in comparison to the studies assuming random scenarios. DA - 2015/11// PY - 2015/11// DO - 10.1109/eleco.2015.7394445 ER - TY - CONF TI - Investigation of Performance Characteristics of an Al0.8Ga0.2N-delta-GaN QW Laser Considering Structural Parameters AB - We have designed Al0.8Ga0.2N-delta-GaN Quantum Well (QW) Laser to investigate the performance characteristics of device like square momentum matrix element at zone center, spontaneous emission rate and optical gain, with structural parameters like delta width, well width, barrier width and injection carrier density. A Self Consistent model using 6-band k.p method incorporating strain effect due to lattice mismatch, valence band mixing effect, carrier screening effect and both spontaneous and piezoelectric polarization effect has been adopted to calculate the electronic properties of the structure. With the variation of the structural parameters, the detail illustration of the variations of the device characteristics are demonstrated in this work. From the investigation, it has been found that the structure shows a maximum optical output of 6636.8 cm 1 at 425nm emission wavelength for 7A delta width, 12A well width, 60A barrier width and 5×1019 cm 3 carrier density at 300K. Detail relationship between the performance parameters of the structure has been elaborated in this work to obtain the conditions for maximum output of the structure. The calculated device properties are compared favourably with the values reported previously in the literature. C2 - 2015/// C3 - IEEE International Conference on Telecommunications and Photonics (ICTP) DA - 2015/// DO - 10.1109/ICTP.2015.7427936 UR - https://publons.com/publon/30967569/ ER - TY - JOUR TI - Optical Gain Optimization of Al0.8Ga0.2N-Delta-GaN Quantum Well Laser in Ultraviolet Spectra Using Genetic Algorithm T2 - ECS Transactions AB - An AlGaN based quantum well laser with GaN delta layer and AlN barrier layers has been designed and characterized for obtaining electronic and optical characteristics. The band structure was calculated with self-consistent 6-band k.p formalism including valence-band mixing effect, strain and polarization effect. A Genetic Algorithm based optimization has been performed to optimize the optical gain taking well width, delta width and barrier width into consideration. The Optimization of both TE and TM polarized optical gain exhibits good improvement than previously published work. The peak optical gain as obtained in analysis is 3589.5 cm −1 while the peak spontaneous emission rate is 12.94×10 28 s -1 cm -3 eV -1 at 246.89nm for 5×10 19 cm -3 carrier density. The optimum TE optical gain is found to be 6479.1 cm -1 for 11Å QW with 7Å delta layer at 279nm wavelength and optimum TM gain is found to be 116.95 cm -1 for 20Å QW with 3Å delta layer at 289.8nm wavelength. DA - 2015/// PY - 2015/// DO - 10.1149/06912.0081ECST UR - https://publons.com/publon/30971212/ ER - TY - JOUR TI - Characterization of InN - In0.25Ga0.75N Quantum Well Laser Structure for 1330 nm Wavelength T2 - ECS Transactions AB - A nitride based wurtzite-strained QW laser with 12Å InN well layer, 15Å In 0.25 Ga 0.75 N barrier layer and GaN SCH layer has been designed and characterized at 1330nm wavelength. To determine the electronic properties, a self-consistent method with 6-bands k.p formalism considering valence-band mixing effect, strain and polarization effect followed by Poisson's equation has been used. The interband momentum matrix elements, optical gain, spontaneous emission rate, and radiative current density have been calculated to analyze the optical properties of the laser. Due to the strain effect, the wave-function overlap integral was obtained as 43.27%. The structure is TE polarized with C1-HH1 and C1-LH1 dominating transitions, while the spontaneous emission rate per energy interval per unit volume was 7.21×10 27 s -1 cm -3 eV -1 at 1329.55nm. Furthermore, the radiative recombination rate and the radiative current density were 7.77×10 29 s -1 cm -3 and 149.19 Acm -2 , respectively. The optical gain of the structure is 5261.52cm -1 at 1336.7nm for TE-polarization. DA - 2015/// PY - 2015/// DO - 10.1149/06912.0071ECST UR - https://publons.com/publon/30971214/ ER - TY - CHAP TI - Hardware Synthesis from Functional Embedded Domain-Specific Languages: A Case Study in Regular Expression Compilation AU - Graves, Ian AU - Procter, Adam AU - Harrison, William L. AU - Becchi, Michela AU - Allwein, Gerard T2 - Lecture Notes in Computer Science AB - Although FPGAs have the potential to bring software-like flexibility and agility to the hardware world, designing for FPGAs remains a difficult task divorced from standard software engineering norms. A better programming flow would go far towards realizing the potential of widely deployed, programmable hardware. We propose a general methodology based on domain specific languages embedded in the functional language Haskell to bridge the gap between high level abstractions that support programmer productivity and the need for high performance in FPGA circuit implementations. We illustrate this methodology with a framework for regular expression to hardware compilers, written in Haskell, that supports high programmer productivity while producing circuits whose performance matches and, indeed, exceeds that of a state of the art, hand-optimized VHDL-based tool. For example, after applying a novel optimization pass, throughput increased an average of $$28.3\,\%$$ over the state of the art tool for one set of benchmarks. All code discussed in the paper is available online [1]. PY - 2015/// DO - 10.1007/978-3-319-16214-0_4 SP - 41-52 OP - PB - Springer International Publishing SN - 9783319162133 9783319162140 UR - http://dx.doi.org/10.1007/978-3-319-16214-0_4 DB - Crossref ER - TY - JOUR TI - Nanocomposites: Sweet Substrate: A Polysaccharide Nanocomposite for Conformal Electronic Decals (Adv. Mater. 9/2015) AU - Daniele, Michael A. AU - Knight, Adrian J. AU - Roberts, Steven A. AU - Radom, Kathryn AU - Erickson, Jeffrey S. T2 - Advanced Materials AB - On page 1600, M. A. Daniele and co-workers report the development of a flexible, robust, and green decal system for transferring circuitry to complex surfaces, such as biological tissue. The decal, a bilayer film of nanocellulose and pullulan, is characterized and utilized to support and transfer simple conductive traces. By taking full advantage of the chemical and mechanical robustness of the nanocellulose, these “polysaccharide circuit boards” show promise as a biocompatible substrate for wearable bioelectronics. DA - 2015/3// PY - 2015/3// DO - 10.1002/ADMA.201570064 VL - 27 IS - 9 SP - 1636-1636 J2 - Adv. Mater. LA - en OP - SN - 0935-9648 UR - http://dx.doi.org/10.1002/ADMA.201570064 DB - Crossref ER - TY - JOUR TI - 3D hydrodynamic focusing microfluidics for emerging sensing technologies AU - Daniele, Michael A. AU - Boyd, Darryl A. AU - Mott, David R. AU - Ligler, Frances S. T2 - Biosensors and Bioelectronics AB - While the physics behind laminar flows has been studied for 200 years, understanding of how to use parallel flows to augment the capabilities of microfluidic systems has been a subject of study primarily over the last decade. The use of one flow to focus another within a microfluidic channel has graduated from a two-dimensional to a three-dimensional process and the design principles are only now becoming established. This review explores the underlying principles for hydrodynamic focusing in three dimensions (3D) using miscible fluids and the application of these principles for creation of biosensors, separation of cells and particles for sample manipulation, and fabrication of materials that could be used for biosensors. Where sufficient information is available, the practicality of devices implementing fluid flows directed in 3D is evaluated and the advantages and limitations of 3D hydrodynamic focusing for the particular application are highlighted. DA - 2015/5// PY - 2015/5// DO - 10.1016/J.BIOS.2014.07.002 VL - 67 SP - 25-34 J2 - Biosensors and Bioelectronics LA - en OP - SN - 0956-5663 UR - http://dx.doi.org/10.1016/J.BIOS.2014.07.002 DB - Crossref KW - Microfluidics KW - Sensors KW - Hydrodynamic focusing KW - Flow cytometry KW - Microfluidic fabrication ER - TY - JOUR TI - Computational approaches to identify regulators of plant stress response using high-throughput gene expression data AU - Koryachko, Alexandr AU - Matthiadis, Anna AU - Ducoste, Joel J. AU - Tuck, James AU - Long, Terri A. AU - Williams, Cranos T2 - Current Plant Biology AB - Insight into biological stress regulatory pathways can be derived from high-throughput transcriptomic data using computational algorithms. These algorithms can be integrated into a computational approach to provide specific testable predictions that answer biological questions of interest. This review conceptually organizes a wide variety of developed algorithms into a classification system based on desired type of output predictions. This classification is then used as a structure to describe completed approaches in the literature, with a focus on project goals, overall path of implemented algorithms, and biological insight gained. These algorithms and approaches are introduced mainly in the context of research on the model plant species Arabidopsis thaliana under stress conditions, though the nature of computational techniques makes these approaches easily applicable to a wide range of species, data types, and conditions. DA - 2015/9// PY - 2015/9// DO - 10.1016/J.CPB.2015.04.001 VL - 3-4 SP - 20-29 J2 - Current Plant Biology LA - en OP - SN - 2214-6628 UR - http://dx.doi.org/10.1016/J.CPB.2015.04.001 DB - Crossref KW - Stress response KW - Transcription factors KW - Gene regulatory networks KW - Algorithms KW - Arabidopsis thaliana ER - TY - JOUR TI - An entropy-based persistence barcode AU - Chintakunta, Harish AU - Gentimis, Thanos AU - Gonzalez-Diaz, Rocio AU - Jimenez, Maria-Jose AU - Krim, Hamid T2 - Pattern Recognition AB - In persistent homology, the persistence barcode encodes pairs of simplices meaning birth and death of homology classes. Persistence barcodes depend on the ordering of the simplices (called a filter) of the given simplicial complex. In this paper, we define the notion of “minimal” barcodes in terms of entropy. Starting from a given filtration of a simplicial complex K, an algorithm for computing a “proper” filter (a total ordering of the simplices preserving the partial ordering imposed by the filtration as well as achieving a persistence barcode with small entropy) is detailed, by way of computation, and subsequent modification, of maximum matchings on subgraphs of the Hasse diagram associated to K. Examples demonstrating the utility of computing such a proper ordering on the simplices are given. DA - 2015/2// PY - 2015/2// DO - 10.1016/J.PATCOG.2014.06.023 VL - 48 IS - 2 SP - 391-401 J2 - Pattern Recognition LA - en OP - SN - 0031-3203 UR - http://dx.doi.org/10.1016/J.PATCOG.2014.06.023 DB - Crossref KW - Persistent homology KW - Persistence barcodes KW - Hasse diagram KW - Simplicial complexes KW - Entropy KW - Filtration KW - Filter ER - TY - JOUR TI - An acoustic filter based on layered structure AU - Ma, Jianguo AU - Steer, Michael B. AU - Jiang, Xiaoning T2 - Applied Physics Letters AB - Acoustic filters (AFs) are key components to control wave propagation in multi-frequency systems. We present a design which selectively achieves acoustic filtering with a stop band and passive amplification at the high- and low-frequencies, respectively. Measurement results from the prototypes closely match the design predictions. The AF suppresses the high frequency aliasing echo by 14.5 dB and amplifies the low frequency transmission by 8.0 dB, increasing an axial resolution from 416 to 86 μm in imaging. The AF design approach is proved to be effective in multi-frequency systems. DA - 2015/3/16/ PY - 2015/3/16/ DO - 10.1063/1.4915100 VL - 106 IS - 11 SP - 111903 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.4915100 DB - Crossref ER - TY - JOUR TI - Microfabrication of conical microfunnels for drug delivery applications AU - Liu, L.W.Y. AU - Inal, J. AU - Steer, M.B. AU - Virdee, B.S. T2 - Micro & Nano Letters AB - A cost-effective fabrication methodology for the mass production of conical microfunnels for drug delivery applications is presented. The fabrication methodology originates from a technique previously used for fabricating suspended or hollow microstructures. The process comprises six stages: in stage 1, a UV-opaque resin substrate is formed by mixing photocurable SU-8 with a UV-opaque impurity; in stage 2, an embossing stamp with an array of microrods is fabricated; in stage 3, the upper surface of the UV-opaque resin substrate (from the first stage) is mechanically deformed by stamping with the embossing stamp from stage 2; in stage 4, the regions in which microfunnels are photolithographically defined are selectively exposed to UV light; in stage 5, the wafer from stage 4 is subjected to heat and then developed in 1-methoxy-2-propanol acetate; finally, a hole on the tip of each microfunnel is formed by dry etching with oxygen plasma. The sharpness of the funnel tips can be flexibly adjusted by changing the stroke speed of the stamping in stage 3. The overall process can be carried out photolithographically with conventional photolithographic equipment. Using the proposed fabrication methodology, a matrix of polymeric microfunnels tapering from the base measuring 300 μm to the tip measuring 50 μm over a funnel height of 100 μm has been fabricated. Each fabricated microfunnel features a wide base and a sharp tip so that it has sufficient mechanical strength and sharpness to pierce the human skin. The conical geometry used in this study had a volume in excess of 24.4 nl. DA - 2015/7/1/ PY - 2015/7/1/ DO - 10.1049/MNL.2014.0659 VL - 10 IS - 7 SP - 355-357 LA - en OP - SN - 1750-0443 UR - http://dx.doi.org/10.1049/MNL.2014.0659 DB - Crossref KW - microfabrication KW - drug delivery systems KW - mass production KW - deformation KW - photolithography KW - etching KW - mechanical strength KW - skin KW - biomedical equipment KW - microfabrication KW - conical microfunnels KW - drug delivery applications KW - mass production KW - microstructures KW - UV-opaque resin substrate KW - photocurable SU-8 KW - UV-opaque impurity KW - mechanical deformation KW - embossing stamp KW - microfunnels KW - UV light KW - 1-methoxy-2-propanol acetate KW - dry etching KW - oxygen plasma KW - conventional photolithographic equipment KW - polymeric microfunnels KW - mechanical strength KW - human skin KW - conical geometry ER - TY - JOUR TI - Contrast-enhanced ultrasound (CEUS) of cystic and solid renal lesions: a review AU - Gulati, Mittul AU - King, Kevin G. AU - Gill, Inderbir S. AU - Pham, Vivian AU - Grant, Edward AU - Duddalwar, Vinay A. T2 - Abdominal Imaging DA - 2015/1/15/ PY - 2015/1/15/ DO - 10.1007/S00261-015-0348-5 VL - 40 IS - 6 SP - 1982-1996 J2 - Abdom Imaging LA - en OP - SN - 0942-8925 1432-0509 UR - http://dx.doi.org/10.1007/S00261-015-0348-5 DB - Crossref KW - Contrast-enhanced ultrasound KW - Renal mass KW - Renal cyst KW - Renal cell carcinoma ER - TY - JOUR TI - Respiratory Rate Monitoring Using Infrared Sensors AU - Erden, F. AU - Cetin, A. E. AU - Ieee T2 - 2015 9th International Conference on Electrical and Electronics Engineering (Eleco) DA - 2015/// PY - 2015/// SP - 1136-1140 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000380410800196&KeyUID=WOS:000380410800196 ER - TY - JOUR TI - Examination of EV-Grid Integration Using Real Driving and Transformer Loading Data AU - Erden, F. AU - Kisacikoglu, M. C. AU - Gurec, O. H. AU - Ieee T2 - 2015 9th International Conference on Electrical and Electronics Engineering (Eleco) DA - 2015/// PY - 2015/// SP - 364-368 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000380410800066&KeyUID=WOS:000380410800066 ER - TY - JOUR TI - Contact-free measurement of respiratory rate using infrared and vibration sensors AU - Erden, Fatih AU - Alkar, Ali Ziya AU - Cetin, Ahmet Enis T2 - Infrared Physics & Technology AB - Respiratory rate is an essential parameter in many practical applications such as apnea detection, patient monitoring, and elderly people monitoring. In this paper, we describe a novel method and a contact-free multi-modal system which is capable of detecting human breathing activity. The multimodal system, which uses both differential pyro-electric infrared (PIR) and vibration sensors, can also estimate the respiratory rate. Vibration sensors pick up small vibrations due to the breathing activity. Similarly, PIR sensors pick up the thoracic movements. Sensor signals are sampled using a microprocessor board and analyzed on a laptop computer. Sensor signals are processed using wavelet analysis and empirical mode decomposition (EMD). Since breathing is almost periodic, a new multi-modal average magnitude difference function (AMDF) is used to detect the periodicity and the period in the processed signals. By fusing the data of two different types of sensors we achieve a more robust and reliable contact-free human breathing activity detection system compared to systems using only one specific type of sensors. DA - 2015/11/1/ PY - 2015/11/1/ DO - 10.1016/j.infrared.2015.09.005 VL - 73 SP - 88-94 UR - https://doi.org/10.1016/j.infrared.2015.09.005 KW - Average magnitude difference function (AMDF) KW - Empirical mode decomposition (EMD) KW - PIR sensor KW - Respiratory rate KW - Vibration sensor KW - Wavelet transform ER - TY - JOUR TI - A robust system for counting people using an infrared sensor and a camera AU - Erden, Fatih AU - Alkar, Ali Ziya AU - Cetin, Ahmet Enis T2 - Infrared Physics & Technology AB - Abstract In this paper, a multi-modal solution to the people counting problem in a given area is described. The multi-modal system consists of a differential pyro-electric infrared (PIR) sensor and a camera. Faces in the surveillance area are detected by the camera with the aim of counting people using cascaded AdaBoost classifiers. Due to the imprecise results produced by the camera-only system, an additional differential PIR sensor is integrated to the camera. Two types of human motion: (i) entry to and exit from the surveillance area and (ii) ordinary activities in that area are distinguished by the PIR sensor using a Markovian decision algorithm. The wavelet transform of the continuous-time real-valued signal received from the PIR sensor circuit is used for feature extraction from the sensor signal. Wavelet parameters are then fed to a set of Markov models representing the two motion classes. The affiliation of a test signal is decided as the class of the model yielding higher probability. People counting results produced by the camera are then corrected by utilizing the additional information obtained from the PIR sensor signal analysis. With the proof of concept built, it is shown that the multi-modal system can reduce false alarms of the camera-only system and determines the number of people watching a TV set in a more robust manner. DA - 2015/// PY - 2015/// DO - 10.1016/j.infrared.2015.07.019 VL - 72 SP - 127-134 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000362146700017&KeyUID=WOS:000362146700017 KW - Infrared sensors KW - Markov models KW - Multi-modal systems KW - People counting ER - TY - CHAP TI - GLES: A Practical GPGPU Optimizing Compiler Using Data Sharing and Thread Coarsening T2 - Languages and Compilers for Parallel Computing AB - Writing optimized CUDA programs for General Purpose Graphics Processing Unit (GPGPU) is complicated and error-prone. Most of the former compiler optimization methods are impractical for many applications that contain divergent control flows, and they failed to fully exploit optimization opportunities in data sharing and thread coarsening. In this paper, we present GLES, an optimizing compiler for GPGPU programs. GLES proposes two optimization techniques based on divergence analysis. The first one is data sharing optimization for data reuse and bandwidth enhancement. The other one is thread granularity coarsening for reducing redundant instructions. Our experiments on 6 real-world programs show that GPGPU programs optimized by GLES achieve similar performance compared with manually tuned GPGPU programs. Furthermore, GLES is not only applicable to a much wider range of GPGPU programs than the state-of-art GPGPU optimizing compiler, but it also achieves higher or close performance on 8 out of 9 benchmarks. PY - 2015/// DO - 10.1007/978-3-319-17473-0_3 UR - http://dx.doi.org/10.1007/978-3-319-17473-0_3 KW - GPGPU KW - Optimization KW - Compiler ER - TY - CONF TI - Stochastic geometry based energy-efficient base station density optimization in cellular networks AB - In the research of green networks, considering the base station (BS) density from the perspective of energy efficiency is very meaningful for both network deployment and BS sleeping based power saving. In this paper, we optimize the BS density for energy efficiency in cellular networks by the stochastic geometry theory. First, we model the distribution of base stations and user equipment (UE) as spatial Poisson point process (PPP). Based on such model, we derive the closed-form expressions of the average achievable data rate, the network energy consumption and the network energy efficiency with respect to the network load. Then, we optimize the BS density for network energy efficiency maximization by adopting the Newton iteration method. Our study reveals that we can improve the network energy efficiency by deploying the suitable amount of BSs or switching on/off proportion of the BSs according to the network load. The simulation results validate the theoretical analysis, and show that when the right amount of BSs is deployed according to the network load, the network energy efficiency can be maximized and the maximum energy efficiency is a fixed value once the network parameters are given. C2 - 2015/3// C3 - 2015 IEEE Wireless Communications and Networking Conference (WCNC) DA - 2015/3// DO - 10.1109/wcnc.2015.7127709 UR - http://dx.doi.org/10.1109/wcnc.2015.7127709 ER - TY - JOUR TI - Single-Hop Transport Throughput of Secondary Networks in Spectrum Sharing Systems AU - Li, Chengzhi AU - Dai, Huaiyu T2 - IEEE Transactions on Mobile Computing AB - In order to improve the spectrum efficiency, spectrum sharing systems allow multiple systems to utilize the same spectrum with different priorities. Typically, the primary network performs as a stand-alone network while the secondary one accesses the spectrum only if it does no harm to the primary receivers. In this paper, the configuration of the secondary network is of our interest and we explore its single-hop transport throughput (STT) with outage constraints imposed on both networks. STT is a new metric that inherits the merits of both the traditional transport capacity and transmission capacity, incorporating transmission distance and outage probability into a uniform framework. Given the settings of the primary network, we first evaluate the limit of the secondary STT, single-hop transport capacity (STC). Then, we investigate STT with secondary receivers randomly located in the field of interest. To provide a comprehensive view of achievable secondary network throughputs, three models regarding the selection of receivers are considered: optimally selected, randomly selected, and the nearest neighbors. Our theoretical analysis are well substantiated by numerical and simulation results. DA - 2015/8/1/ PY - 2015/8/1/ DO - 10.1109/tmc.2014.2363091 VL - 14 IS - 8 SP - 1726-1736 J2 - IEEE Trans. on Mobile Comput. OP - SN - 1536-1233 UR - http://dx.doi.org/10.1109/tmc.2014.2363091 DB - Crossref KW - Cognitive radio KW - network throughput KW - outage analysis and transmission capacity ER - TY - JOUR TI - Market Mechanisms for Buying Random Wind AU - Tang, Wenyuan AU - Jain, Rahul T2 - IEEE Transactions on Sustainable Energy AB - The intermittent nature of wind power leads to the question of how wind power producers can participate in a deregulated electricity market. In the proposed auction paradigm, wind farms bid probability distributions of generation, instead of bidding cost functions as thermal units do. Our focus is to design incentive compatible mechanisms that elicit truthful information of strategic agents who supply stochastic resource. We first study the aggregators problem of how to select the wind farms, which have the most desirable distributions. We then study the independent system operators (ISOs) problem of how to price wind energy for stochastic economic dispatch. DA - 2015/10// PY - 2015/10// DO - 10.1109/tste.2015.2460745 VL - 6 IS - 4 SP - 1615-1623 J2 - IEEE Trans. Sustain. Energy OP - SN - 1949-3029 1949-3037 UR - http://dx.doi.org/10.1109/tste.2015.2460745 DB - Crossref KW - Game theory KW - mechanism design KW - renewable energy integration KW - smart grid KW - stochastic resource auction ER - TY - JOUR TI - Learning Near-Optimal Cost-Sensitive Decision Policy for Object Detection AU - Wu, Tianfu AU - Zhu, Song-Chun T2 - IEEE Transactions on Pattern Analysis and Machine Intelligence AB - Many popular object detectors, such as AdaBoost, SVM and deformable part-based models (DPM), compute additive scoring functions at a large number of windows in an image pyramid, thus computational efficiency is an important consideration in real time applications besides accuracy. In this paper, a decision policy refers to a sequence of two-sided thresholds to execute early reject and early accept based on the cumulative scores at each step. We formulate an empirical risk function as the weighted sum of the cost of computation and the loss of false alarm and missing detection. Then a policy is said to be cost-sensitive and optimal if it minimizes the risk function. While the risk function is complex due to high-order correlations among the two-sided thresholds, we find that its upper bound can be optimized by dynamic programming efficiently. We show that the upper bound is very tight empirically and thus the resulting policy is said to be near-optimal. In experiments, we show that the decision policy outperforms state-of-the-art cascade methods significantly, in several popular detection tasks and benchmarks, in terms of computational efficiency with similar accuracy of detection. DA - 2015/5/1/ PY - 2015/5/1/ DO - 10.1109/tpami.2014.2359653 VL - 37 IS - 5 SP - 1013-1027 J2 - IEEE Trans. Pattern Anal. Mach. Intell. OP - SN - 0162-8828 2160-9292 UR - http://dx.doi.org/10.1109/tpami.2014.2359653 DB - Crossref KW - Decision policy KW - cost-sensitive computing KW - risk minimization KW - dynamic programming KW - object detection ER - TY - JOUR TI - Biobotic Insect Sensor Networks for Search and Rescue AU - Bozkurt, A. AU - Lobaton, E. AU - Sichitiu, M. T2 - Journal of Homeland Defense & Security Information Analysis Center DA - 2015/// PY - 2015/// VL - 2 IS - 2 ER - TY - CHAP TI - Green Chemical and Biological Synthesis of Nanoparticles and Their Biomedical Applications AU - Razavi, Mehdi AU - Salahinejad, Erfan AU - Fahmy, Mina AU - Yazdimamaghani, Mostafa AU - Vashaee, Daryoosh AU - Tayebi, Lobat T2 - Green Processes for Nanotechnology PY - 2015/// DO - 10.1007/978-3-319-15461-9_7 SP - 207-235 OP - PB - Springer International Publishing SN - 9783319154602 9783319154619 UR - http://dx.doi.org/10.1007/978-3-319-15461-9_7 DB - Crossref ER - TY - CHAP TI - Electrophoretic Deposition (EPD): Fundamentals and Applications from Nano- to Microscale Structures AU - Amrollahi, Pouya AU - Krasinski, Jerzy S. AU - Vaidyanathan, Ranji AU - Tayebi, Lobat AU - Vashaee, Daryoosh T2 - Handbook of Nanoelectrochemistry PY - 2015/9/14/ DO - 10.1007/978-3-319-15266-0_7 SP - 561-591 OP - PB - Springer International Publishing SN - 9783319152653 9783319152660 UR - http://dx.doi.org/10.1007/978-3-319-15266-0_7 DB - Crossref ER - TY - CHAP TI - Metamorphic neural interfaces with insects for remote controlled biobots AU - Bozkurt, Alper T2 - Handbook of Bioelectronics A2 - Carrara, Sandro A2 - Iniewski, Krzysztof AB - Muscles are the mechanical actuators of the body controlled by neurons. We use these actuators to perform many actions during the activities of our daily life. Moreover, we have benefited throughout history from the muscle power of larger animals, for farming, transportation, and industry. However, the muscle power of insects has not yet been exploited reliably or reproducibly, although insects possess a much higher ratio of muscle force to body mass than most large domesticated mammals. The novel field of insect–machine interfaces (IMI) combines microtechnology and neuroengineering to benefit from the muscle power of insects in a “biobotic” manner. To facilitate this, Early Metamorphosis Insertion Technology (EMIT) provides a novel neurotechnological pathway for integrating microelectronic sensing and actuation platforms into insects during metamorphosis. Metamorphic development not only provides an elegant and effective method of mechanically affixing artificial systems in or on an insect, but also produces a reliable bioelectrical interface without any observable short-term adverse effect on insect flight behavior. As an application of biobotic control of insect locomotion, the first steps towards flight and gait navigation in moths and cockroaches are presented in this chapter. PY - 2015/9/5/ DO - 10.1017/cbo9781139629539.016 SP - 183-194 OP - PB - Cambridge University Press SN - 9781139629539 UR - http://dx.doi.org/10.1017/cbo9781139629539.016 DB - Crossref ER - TY - JOUR TI - In vivo assessments of bioabsorbable AZ91 magnesium implants coated with nanostructured fluoridated hydroxyapatite by MAO/EPD technique for biomedical applications AU - Razavi, Mehdi AU - Fathi, Mohammadhossein AU - Savabi, Omid AU - Vashaee, Daryoosh AU - Tayebi, Lobat T2 - Materials Science and Engineering: C AB - Although magnesium (Mg) is a unique biodegradable metal which possesses mechanical property similar to that of the natural bone and can be an attractive material to be used as orthopedic implants, its quick corrosion rate restricts its actual clinical applications. To control its rapid degradation, we have modified the surface of magnesium implant using fluoridated hydroxyapatite (FHA: Ca10(PO4)6OH2 − xFx) through the combined micro-arc oxidation (MAO) and electrophoretic deposition (EPD) techniques, which was presented in our previous paper. In this article, the biocompatibility examinations were conducted on the coated AZ91 magnesium alloy by implanting it into the greater trochanter area of rabbits. The results of the in vivo animal test revealed a significant enhancement in the biocompatibility of FHA/MAO coated implant compared to the uncoated one. By applying the FHA/MAO coating on the AZ91 implant, the amount of weight loss and magnesium ion release in blood plasma decreased. According to the histological results, the formation of the new bone increased and the inflammation decreased around the implant. In addition, the implantation of the uncoated AZ91 alloy accompanied by the release of hydrogen gas around the implant; this release was suppressed by applying the coated implant. Our study exemplifies that the surface coating of magnesium implant using a bioactive ceramic such as fluoridated hydroxyapatite may improve the biocompatibility of the implant to make it suitable as a commercialized biomedical product. DA - 2015/3// PY - 2015/3// DO - 10.1016/j.msec.2014.11.020 VL - 48 SP - 21-27 J2 - Materials Science and Engineering: C LA - en OP - SN - 0928-4931 UR - http://dx.doi.org/10.1016/j.msec.2014.11.020 DB - Crossref KW - Bioabsorbable magnesium alloy KW - Coating KW - Surface modification KW - Fluoridated hydroxyapatite KW - in vivo ER - TY - JOUR TI - Development of Inexpensive SiGe–FeSi2 Thermoelectric Nanocomposites AU - Abudakka, Mohamed AU - Nozariasbmarz, Amin AU - Tayebi, Lobat AU - Krasisnki, Jerzy S. AU - Vashaee, Daryoosh T2 - Energy Harvesting and Systems AB - Abstract This investigation presents cost-effective fabrication of n-type silicon germanium–iron disilicide nanocomposites using low-cost low-purity germanium–germanium oxide powder. Moreover, the probability of the reduction of oxide powders during the synthesis process was studied. X-ray diffraction (XRD) analysis indicated reduction of germanium oxide impurity in the synthesized material. Scanning electron microscopy (SEM) along with the energy-dispersive spectrometer (EDS) showed a structure of dispersed iron disilicide particles embedded in silicon germanium matrix. The nanocomposite structure showed a moderate figure-of-merit, ZT, equal to 0.8. The ZT enhancement was related to both the nanocomposite structure and the reduction of germanium oxide. DA - 2015/1/1/ PY - 2015/1/1/ DO - 10.1515/ehs-2014-0039 VL - 2 IS - 1-2 OP - SN - 2329-8774 2329-8766 UR - http://dx.doi.org/10.1515/ehs-2014-0039 DB - Crossref ER - TY - CHAP TI - Smart Hybrid House Test Systems in a Solid-state Transformer Supplied Microgrid AU - Yan, Jiahong AU - Zhu, Xiangqi AU - Lu, Ning AU - Ieee T2 - 2015 Ieee Power & Energy Society General Meeting PY - 2015/// SP - PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000371397504026&KeyUID=WOS:000371397504026 ER - TY - CHAP TI - Control and Size Energy Storage Systems for Managing Energy Imbalance of Variable Generation Resources AU - Ke, Xinda AU - Lu, Ning AU - Jin, Chunlian AU - Ieee T2 - 2015 Ieee Power & Energy Society General Meeting PY - 2015/// SP - PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000371397504079&KeyUID=WOS:000371397504079 ER - TY - CHAP TI - A Modified Priority List-Based MILP Method for Solving Large-Scale Unit Commitment Problems AU - Ke, Xinda AU - Lu, Ning AU - Wu, Di AU - Kintner-Meyer, Michael AU - Ieee T2 - 2015 Ieee Power & Energy Society General Meeting PY - 2015/// SP - PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000371397504036&KeyUID=WOS:000371397504036 ER - TY - CONF TI - Defense Applications of 3DIC AU - Franzon, P. C2 - 2015/3// C3 - Proceedings Gomactech 2015 DA - 2015/3// ER - TY - JOUR TI - Wireless Software-defined Networks (W-SDNs) and Network Function Virtualization (NFV) for 5G Cellular Systems: An Overview and Qualitative Evaluation AU - Akyildiz, I.F. AU - Lin, S.-C. AU - Wang, P. T2 - Computer Network (Elsevier) Journal DA - 2015/12// PY - 2015/12// VL - 93 SP - 66–79 ER - TY - CONF TI - Characterization of the Mechanical Stress Impact on Device Electrical Performance in the CMOS and III-V HEMT/HBT Heterogeneous Integration Environment AU - Wyers, E.J. AU - Harris, T.R. AU - Massad, J.E. AU - Franson, P.D. C2 - 2015/3// C3 - Proceedings Gomactech 2015 DA - 2015/3// ER - TY - CONF TI - Augmenting Human Odor Assessments of Cabin Air Quality of Automobiles by Instrumental Measurement AU - Nagle, H.T. AU - Gutierrez-Osuna, R. AU - Suslick, R.K. AU - Persaud, K. AU - Hodges, R.D. AU - Covington, J. AU - Luckey, G. AU - Crowell, J. AU - Schiffman, S.S. T2 - ISOEN 2015 C2 - 2015/// C3 - Proceedings of the Sixteenth International Symposium on Olfaction and Electronic Noses CY - Dijon, France DA - 2015/// PY - 2015/// ER - TY - CONF TI - Computing in 3D AU - Franzon, Paul D. AU - Rotenberg, Eric AU - Davis, W. Rhett AU - Tuck, James AU - Davis, W. Rhett AU - Zhou, Huiyang AU - Schabel, Joshua AU - Zhang, Zhenquian AU - Dwiel, J. Brandon AU - Forbes, Elliott AU - Huh, Joonmoo AU - Tshibangu, Marcus AU - Lipa, Steve T2 - 2015 International 3D Systems Integration Conference (3DIC) AB - 3DIC technology refers to stacking and interconnecting chips and substrates (“interposers”) with Through Silicon Vias (TSVs). Industry is gearing up for widespread introduction of this technology with the 22 nm node. We have been pursuing a range of approaches to enable low power computing. As well as 3DIC these include heterogeneous computing, powered optimized SIMD units, optimized memory hierarchies, and MPI with post-silicon customized interconnect. Heterogeneous computing refers to the concept of building a mix of CPUs and memories that in turn enable in-situ tuning of the compute load to the compute resources. We introduce the concept of Fast Thread Migration using 3DIC technologies. We present the design of a power optimized SIMD unit in which over half of the power is employed in the FP units. A parallel computer is built using an MPI paradigm. Codes are analyzed so that the MPI interconnect can be power optimized post-silicon. Emerging 3D memories have potential to be employed as Level 2 and Level 3 caches, and this is explored using the Tezzaron 3D memory. As scaling and power optimization occurs, the main memory increasingly dominates the power consumption. Possible extensions to Cortical Processing are discussed. C2 - 2015/8// C3 - 2015 International 3D Systems Integration Conference (3DIC) CY - Sendai, Japan DA - 2015/8// PY - 2015/8/31/ DO - 10.1109/3dic.2015.7334571 PB - IEEE SN - 9781467393850 UR - http://dx.doi.org/10.1109/3dic.2015.7334571 DB - Crossref ER - TY - CONF TI - Thermal simulation of heterogeneous GaN/ InP/silicon 3DIC stacks AU - Harris, T. Robert AU - Wyers, Eric J. AU - Wang, Lee AU - Graham, Samuel AU - Pavlidis, Georges AU - Franzon, Paul D. AU - Davis, W. Rhett T2 - 2015 International 3D Systems Integration Conference (3DIC) AB - Integration of materials such as GaN, InP, SiGe, and Si is a natural extension of the 3D-IC perspective and provides a unique solution for high performance circuits. In this approach, application of a component is no longer dependent on semiconductor material selection. In this paper, preliminary results are presented which examine the thermal performance of the technology. A thermal analysis prototype solution in Mentor Graphics Calibre ® provides surface heat maps based on IC layout, material property, and geometric configuration files. Chiplets are connected by heterogeneous interconnect (HIC). Differences in thermal performance of GaN and InP chiplets are explored by varying the number of HICs. Two methods for building up the model of a test chip are compared. One method uses custom scripts to place discrete blocks in the model to represent HICs, while the other uses thermal material properties extracted from the layout. Measurements presented confirm simulated results. C2 - 2015/8// C3 - 2015 International 3D Systems Integration Conference (3DIC) CY - Sendai, Japan DA - 2015/8// PY - 2015/8/31/ DO - 10.1109/3dic.2015.7334616 SP - 1–3 PB - IEEE SN - 9781467393850 UR - http://dx.doi.org/10.1109/3dic.2015.7334616 DB - Crossref ER - TY - CONF TI - Characterization of the mechanical stress impact on device electrical performance in the CMOS and III–V HEMT/HBT heterogeneous integration environment AU - Wyers, Eric J. AU - Harris, T. Robert AU - Pitts, W. Shep AU - Massad, Jordan E. AU - Franzon, Paul D. T2 - 2015 International 3D Systems Integration Conference (3DIC) AB - The stress impact of the CMOS and III–V heterogeneous integration environment on device electrical performance is being characterized. Measurements from a partial heterogeneous integration fabrication run will be presented to provide insight into how the backside source vias, alternatively referred to as through-silicon-carbide vias (TSCVs), used within the heterogeneous integration environment impacts GaN HEMT device-level DC performance. C2 - 2015/8// C3 - 2015 International 3D Systems Integration Conference (3DIC) DA - 2015/8// DO - 10.1109/3dic.2015.7334597 PB - IEEE SN - 9781467393850 UR - http://dx.doi.org/10.1109/3dic.2015.7334597 DB - Crossref ER - TY - CONF TI - Computing in 3D AU - Franzon, Paul AU - Rotenberg, Eric AU - Tuck, James AU - Davis, W. Rhett AU - Zhou, Huiyang AU - Schabel, Joshua AU - Zhang, Zhenquian AU - Dwiel, J. Brandon AU - Forbes, Elliott AU - Huh, Joonmoo AU - Lipa, Steve T2 - 2015 IEEE Custom Integrated Circuits Conference - CICC 2015 AB - 3D technologies offer significant potential to improve total performance and performance per unit of power. After exploiting TSV technologies for cost reduction and increasing memory bandwidth, the next frontier is to create sophisticated logic on logic solutions that promise further increases in performance/power beyond those attributable to memory interfaces alone. These include heterogeneous integration for computing and exploitation of the high amounts of 3D interconnect available to reduce total interconnect power. Challenges include access for prototype quantities and the design of sophisticated static and dynamic thermal management methods and technologies, as well as test. C2 - 2015/9// C3 - 2015 IEEE Custom Integrated Circuits Conference (CICC) DA - 2015/9// DO - 10.1109/cicc.2015.7338401 SP - 1-6 PB - IEEE SN - 9781479986828 UR - http://dx.doi.org/10.1109/cicc.2015.7338401 DB - Crossref ER - TY - CONF TI - QoS-aware virtualization-enabled routing in Software-Defined Networks AU - Xifra Porxas, Alba AU - Lin, Shih-Chun AU - Luo, Min T2 - 2015 IEEE International Conference on Signal Processing for Communications (ICC) AB - Software-Defined Networking (SDN) has been recognized as the next-generation networking paradigm. It is a fast-evolving technology that decouples the network control plane from the data forwarding plane. A logically centralized controller is responsible for all the control decisions and communication among the forwarding elements. However, current traffic engineering techniques and state-of-the-art routing algorithms do not effectively use the merits of SDNs, such as global centralized visibility, control and data plane decoupling, network management simplification and portability. In this paper, a multi-tenancy management framework is proposed to fulfill the quality-of-services (QoSs) requirements through tenant isolation, prioritization and flow allocation. First, a network virtualization algorithm is provided to isolate and prioritize tenants from different clients. Second, a novel routing scheme, called QoS-aware Virtualization-enabled Routing (QVR), is presented. It combines the proposed virtualization technique and a QoS-aware framework to enable flow allocation with respect to different tenant applications. Simulation results confirm that the proposed QVR algorithm surpasses the conventional algorithms with less traffic congestion and packet delay. This facilitates reliable and efficient data transportation in generalized SDNs. Therefore, it yields to service performance improvement for numerous applications and enhancement of client isolation. C2 - 2015/6// C3 - 2015 IEEE International Conference on Communications (ICC) DA - 2015/6// DO - 10.1109/icc.2015.7249242 PB - IEEE SN - 9781467364324 UR - http://dx.doi.org/10.1109/icc.2015.7249242 DB - Crossref ER - TY - CONF TI - Diversity-Multiplexing Tradeoff in Cognitive Machine-to-Machine Networks AU - Lin, Shih-Chun AU - Gu, Lei T2 - GLOBECOM 2015 - 2015 IEEE Global Communications Conference AB - Machine-to-Machine (M2M) communication enables many applications, which require ubiquitous wireless connections among objects and the surrounding environment. A general cognitive M2M network (CM2M) consists of multi-radio systems, involving primary system (PS) and secondary system(s) of cognitive machines under heterogeneous wireless architecture. However, inherited from dynamic spectrum access (DSA) ability of cognitive radio technology, uni- directional opportunistic wireless fading links exist in multi-hop CM2M network and the conventional flow control mechanisms at link level cannot be applied anymore. In many cases, effective end-to-end quality-of-service (QoS) control is also needed to provide reliable data transportation. In addition, emerging multi- user multiple input multiple output (MU-MIMO) technology coherently coordinates the transmission and reception among multiple base stations, leveraging the advantage of MIMO communications based on one-hop physical layer transmission. In this paper, through the exploitation of network coding and MU-MIMO, we develop a novel opportunistic QoS control (OQC) scheme for multi-hop CM2M network. OQC control utilizes the cooperative relaying at session level with the proposed Qos guarantees, realizing diversity-multiplexing tradeoff for session traffic. In particular, the statistical QoS guarantee is first proposed to work with our prior routing design, called SAOR. Furthermore, overlaying the proposed guarantees with the routing algorithm, OQC scheme employs the diversity mode to deal with PS's opportunistic nature and wireless fading, and utilizes the spatial multiplexing mode to obtain the maximum end-to-end throughput. Performance evaluations show the remarkable improvement of end-to-end delay violation probability for cognitive machines' traffic in multi-hop CM2M networks, thus enabling great M2M applications. C2 - 2015/12// C3 - 2015 IEEE Global Communications Conference (GLOBECOM) DA - 2015/12// DO - 10.1109/glocom.2015.7417283 PB - IEEE SN - 9781479959525 UR - http://dx.doi.org/10.1109/glocom.2015.7417283 DB - Crossref ER - TY - JOUR TI - Statistical Dissemination Control in Large Machine-to-Machine Communication Networks AU - Lin, Shih-Chun AU - Gu, Lei AU - Chen, Kwang-Cheng T2 - IEEE Transactions on Wireless Communications AB - Cloud based machine-to-machine (M2M) communications have emerged to achieve ubiquitous and autonomous data transportation for future daily life in the cyber-physical world. In light of the need of network characterizations, we analyze the connected M2M network in the machine swarm of geometric random graph topology, including degree distribution, network diameter, and average distance (i.e., hops). Without the need of end-to-end information to escape catastrophic complexity, information dissemination appears an effective way in machine swarm. To fully understand practical data transportation, G/G/1 queuing network model is exploited to obtain average end-to-end delay and maximum achievable system throughput. Furthermore, as real applications may require dependable networking performance across the swarm, quality of service (QoS) along with large network diameter creates a new intellectual challenge. We extend the concept of small-world network to form shortcuts among data aggregators as infrastructure-swarm two-tier heterogeneous network architecture, then leverage the statistical concept of network control instead of precise network optimization, to innovatively achieve QoS guarantees. Simulation results further confirm the proposed heterogeneous network architecture to effectively control delay guarantees in a statistical way and to facilitate a new design paradigm in reliable M2M communications. DA - 2015/4// PY - 2015/4// DO - 10.1109/twc.2014.2376952 VL - 14 IS - 4 SP - 1897-1910 J2 - IEEE Trans. Wireless Commun. OP - SN - 1536-1276 UR - http://dx.doi.org/10.1109/twc.2014.2376952 DB - Crossref KW - Machine-to-machine communications KW - network topology KW - small-world networks KW - information dissemination KW - quality-of-service guarantees KW - statistical control KW - Internet of things KW - ad hoc networks ER - TY - JOUR TI - Distributed Cross-Layer Protocol Design for Magnetic Induction Communication in Wireless Underground Sensor Networks AU - Lin, Shih-Chun AU - Akyildiz, Ian F. AU - Wang, Pu AU - Sun, Zhi T2 - IEEE Transactions on Wireless Communications AB - Wireless underground sensor networks (WUSNs) enable many applications such as underground pipeline monitoring, power grid maintenance, mine disaster prevention, and oil upstream monitoring among many others. While the classical electromagnetic waves do not work well in WUSNs, the magnetic induction (MI) propagation technique provides constant channel conditions via small size of antenna coils in the underground environments. In this paper, instead of adopting currently layered protocols approach, a distributed cross-layer protocol design is proposed for MI-based WUSNs. First, a detailed overview is given for different communication functionalities from physical to network layers as well as the QoS requirements of applications. Utilizing the interactions of different layer functionalities, a distributed environment-aware protocol, called DEAP, is then developed to satisfy statistical QoS guarantees and achieve both optimal energy savings and throughput gain concurrently. Simulations confirm that the proposed cross-layer protocol achieves significant energy savings, high throughput efficiency and dependable MI communication for WUSNs. DA - 2015/7// PY - 2015/7// DO - 10.1109/twc.2015.2415812 VL - 14 IS - 7 SP - 4006-4019 J2 - IEEE Trans. Wireless Commun. OP - SN - 1536-1276 UR - http://dx.doi.org/10.1109/twc.2015.2415812 DB - Crossref KW - Wireless underground sensor network KW - magnetic induction communication KW - cross-layer optimization KW - Pareto optimal front KW - distributed power control KW - distributed protocol ER - TY - JOUR TI - SoftAir: A software defined networking architecture for 5G wireless systems AU - Akyildiz, Ian F. AU - Wang, Pu AU - Lin, Shih-Chun T2 - Computer Networks AB - One of the main building blocks and major challenges for 5G cellular systems is the design of flexible network architectures which can be realized by the software defined networking paradigm. Existing commercial cellular systems rely on closed and inflexible hardware-based architectures both at the radio frontend and in the core network. These problems significantly delay the adoption and deployment of new standards, impose significant challenges in implementing and innovation of new techniques to maximize the network capacity and accordingly the coverage, and prevent provisioning of truly- differentiated services which are able to adapt to growing and uneven and highly variable traffic patterns. In this paper, a new software-defined architecture, called SoftAir, for next generation (5G) wireless systems, is introduced. Specifically, the novel ideas of network function cloudification and network virtualization are exploited to provide a scalable, flexible and resilient network architecture. Moreover, the essential enabling technologies to support and manage the proposed architecture are discussed in details, including fine-grained base station decomposition, seamless incorporation of Openflow, mobility- aware control traffic balancing, resource-efficient network virtualization, and distributed and collaborative traffic classification. Furthermore, the major benefits of SoftAir architecture with its enabling technologies are showcased by introducing software- defined traffic engineering solutions. The challenging issues for realizing SoftAir are also discussed in details. DA - 2015/7// PY - 2015/7// DO - 10.1016/j.comnet.2015.05.007 VL - 85 SP - 1-18 J2 - Computer Networks LA - en OP - SN - 1389-1286 UR - http://dx.doi.org/10.1016/j.comnet.2015.05.007 DB - Crossref KW - Software-defined networking KW - 5G wireless system KW - Wireless software-defined networks KW - Network function cloudification KW - Network virtualization KW - Software-defined traffic engineering ER - TY - CONF TI - Ensuring localizability of node attacks in consensus networks via feedback graph design AU - Nudell, Thomas R. AU - Chakrabortty, Aranya T2 - 2015 American Control Conference (ACC) AB - In this paper we consider the problem of localizability of attacks in continuous-time consensus networks. In our previous work [1] we showed that if a consensus network is divided into clusters, then a supervisor can successfully localize the cluster in which an attack may have been launched by simply inspecting the sign patterns of the residues corresponding to the slow poles of its input-output transfer function (TF). A necessary condition for localizability, however, was that the attack must enter through a node that guarantees this TF to be minimal. In case the attacker knows the identity of the so-called zero nodes from where the TFs are non-minimal, and chooses to launch the attack at any of them, then the supervisor cannot localize the attack.We show that this problem can be bypassed by designing a state-feedback controller that equivalently changes the algebraic properties of the underlying network graph, and thereby restores minimality of the TF. We illustrate the approach by simulating a three-area, 30-node graph, and highlighting the performance trade-offs that come as a price of localizability. C2 - 2015/7// C3 - 2015 American Control Conference (ACC) DA - 2015/7// DO - 10.1109/acc.2015.7170759 PB - IEEE SN - 9781479986842 UR - http://dx.doi.org/10.1109/acc.2015.7170759 DB - Crossref ER - TY - CONF TI - Odor assessment of automobile interior components using ion mobility spectrometry AU - Li, Juan AU - Gutierrez-Osuna, Ricardo AU - Hodges, Ryan D. AU - Luckey, Gail AU - Crowell, Joel AU - Schiffman, Susan S. AU - Nagle, H. Troy T2 - 2015 IEEE Sensors AB - Evaluating and improving odors emitted from automobile interior parts can help automotive companies fulfill prospective customers' expectations of odor character and health impacts. Extending our previous work on machine-versus-human odor assessment for intact automobile cabin interiors, in this study we evaluated odors generated from individual interior parts using a human panel and ion mobility spectrometry (IMS). We used image processing to extract geometric features from IMS dispersion fields, and built predictive models for three odor assessment parameters (intensity, irritation, and pleasantness) by means of partial least squares regression. Using cross validation, we achieved statistically significant correlations in the range from 0.483 to 0.616 with a sample set of 48 interior automobile parts. These results support the feasibility of replacing a human panel by machine-olfaction for the assessment of odor quality of interior automobile parts. C2 - 2015/11// C3 - 2015 IEEE SENSORS DA - 2015/11// DO - 10.1109/icsens.2015.7370105 PB - IEEE SN - 9781479982035 UR - http://dx.doi.org/10.1109/icsens.2015.7370105 DB - Crossref ER - TY - JOUR TI - Compressive Imaging via Approximate Message Passing With Image Denoising AU - Tan, Jin AU - Ma, Yanting AU - Baron, Dror T2 - IEEE Transactions on Signal Processing AB - We consider compressive imaging problems, where images are reconstructed from a reduced number of linear measurements. Our objective is to improve over existing compressive imaging algorithms in terms of both reconstruction error and runtime. To pursue our objective, we propose compressive imaging algorithms that employ the approximate message passing (AMP) framework. AMP is an iterative signal reconstruction algorithm that performs scalar denoising at each iteration; in order for AMP to reconstruct the original input signal well, a good denoiser must be used. We apply two wavelet based image denoisers within AMP. The first denoiser is the "amplitude-scaleinvariant Bayes estimator" (ABE), and the second is an adaptive Wiener filter; we call our AMP based algorithms for compressive imaging AMP-ABE and AMP-Wiener. Numerical results show that both AMP-ABE and AMP-Wiener significantly improve over the state of the art in terms of runtime. In terms of reconstruction quality, AMP-Wiener offers lower mean square error (MSE) than existing compressive imaging algorithms. In contrast, AMP-ABE has higher MSE, because ABE does not denoise as well as the adaptive Wiener filter. DA - 2015/4// PY - 2015/4// DO - 10.1109/tsp.2015.2408558 VL - 63 IS - 8 SP - 2085-2092 J2 - IEEE Trans. Signal Process. OP - SN - 1053-587X 1941-0476 UR - http://dx.doi.org/10.1109/tsp.2015.2408558 DB - Crossref KW - Approximate message passing KW - compressive imaging KW - image denoising KW - wavelet transform ER - TY - CONF TI - Approximate message passing in coded aperture snapshot spectral imaging AU - Tan, Jin AU - Ma, Yanting AU - Rueda, Hoover AU - Baron, Dror AU - Arce, Gonzalo R. T2 - 2015 IEEE Global Conference on Signal and Information Processing (GlobalSIP) AB - We consider a compressive hyperspectral imaging reconstruction problem, where three-dimensional spatio-spectral information about a scene is sensed by a coded aperture snapshot spectral imager (CASSI). The approximate message passing (AMP) framework is utilized to reconstruct hyperspectral images from CASSI measurements, and an adaptive Wiener filter is employed as a three-dimensional image denoiser within AMP. We call our algorithm "AMP-3D-Wiener." The simulation results show that AMP-3D-Wiener outperforms existing widely-used algorithms such as gradient projection for sparse reconstruction (GPSR) and two-step iterative shrinkage/thresholding (TwIST) given the same amount of runtime. Moreover, in contrast to GPSR and TwIST, AMP-3D-Wiener need not tune any parameters, which simplifies the reconstruction process. C2 - 2015/12// C3 - 2015 IEEE Global Conference on Signal and Information Processing (GlobalSIP) DA - 2015/12// DO - 10.1109/globalsip.2015.7418268 PB - IEEE SN - 9781479975914 UR - http://dx.doi.org/10.1109/globalsip.2015.7418268 DB - Crossref ER - TY - CONF TI - High-frequency, high-current transformer designs for Silicon Carbide based LLC converters AU - Iyer, V. M. AU - Prabhakaran, S. AU - Vijayan, P. T2 - 2015 IEEE Energy Conversion Congress and Exposition (ECCE) AB - The introduction of 1200 V Silicon Carbide (SiC) based technologies has enabled the use of high performance LLC converters for high input voltage (>500 VDC) applications such as datacenter power conversion. In this paper, we describe performance of the magnetics for a 2 kW-level LLC converter, operating at 100 kHz with SiC devices. We present magnetics designed for high converter efficiencies (> 96%) at high-current outputs (65 A). We focus on the design considerations to minimize the leakage inductance of a center-tapped transformer with a high voltage transformation ratio. We present a variety of winding strategies and show the efficacy of a hybrid solution that combines foil windings with litz winding for the application described. We demonstrate the performance improvements through finite element simulations and measurements from several prototypes. C2 - 2015/9// C3 - 2015 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2015/9// DO - 10.1109/ECCE.2015.7310454 SP - 5650-5656 DB - IEEE Xplore ER - TY - JOUR TI - Low-frequency dc bus ripple cancellation in single phase pulse-width modulation inverters AU - Iyer, Vishnu Mahadeva AU - John, Vinod T2 - IET Power Electronics AB - This study presents a topology for a single-phase pulse-width modulation (PWM) converter which achieves low-frequency ripple reduction in the dc bus even when there are grid frequency variations. A hybrid filter is introduced to absorb the low-frequency current ripple in the dc bus. The control strategy for the proposed filter does not require the measurement of the dc bus ripple current. The design criteria for selecting the filter components are also presented in this study. The effectiveness of the proposed circuit has been tested and validated experimentally. A smaller dc-link capacitor is sufficient to keep the low-frequency bus ripple to an acceptable range in the proposed topology. DA - 2015/2/12/ PY - 2015/2/12/ DO - 10.1049/iet-pel.2014.0320 VL - 8 IS - 4 SP - 497-506 LA - en SN - 1755-4543 UR - https://digital-library.theiet.org/content/journals/10.1049/iet-pel.2014.0320 DB - digital-library.theiet.org Y2 - 2019/3/2/ ER - TY - JOUR TI - Systems and methods for wireless power transfer AU - Lukic, Srdjan AU - Pantic, Zeljko AU - Kibok, LEE DA - 2015/12// PY - 2015/12// N1 - US Patent App. 14/764,558 RN - US Patent App. 14/764,558 ER - TY - CONF TI - Counterfeit detection using paper PUF and mobile cameras AU - Wong, Chau-Wai AU - Wu, Min T2 - IEEE AB - This work studies the paper authentication problem by exploiting optical features through mobile imaging devices to characterize the unique, physically unclonable properties of paper surface. Prior work showing high matching accuracy either used a consumer-level scanner for estimating a projected normal vector field of the surface of the paper as the feature for authentication, or used an industrial camera with controlled lighting to obtain an appearance image of the surface as the feature. In comparison, past explorations based on mobile cameras were very limited and have not had substantial success in obtaining consistent appearance images due to the uncontrolled nature of the ambient light. We show in this work that images captured by mobile cameras can be directly used for authentication by exploiting the camera flashlight to create a semi-controlled lighting condition. We have proposed new algorithms to demonstrate that the microscopic normal vector field of paper surface can be estimated by using multiple camera-captured images of different viewpoints. Our findings can relax the restricted imaging setups to enable paper authentication under a more casual, ubiquitous setting of a mobile imaging device, which may facilitate duplicate detection of paper documents and merchandise packaging. C2 - 2015/11// C3 - 2015 IEEE International Workshop on Information Forensics and Security (WIFS) DA - 2015/11// DO - 10.1109/wifs.2015.7368579 PB - IEEE ER - TY - CONF TI - A Study on PUF characteristics for counterfeit detection AU - Wong, Chau-Wai AU - Wu, Min T2 - IEEE AB - Low-cost physically unclonable functions (PUFs) can be deployed with consumer products to deter counterfeiting. An intrinsic physical property - unique textures of paper or other surface - has received strong interest. Extrinsically introduced features, such as randomly positioned bubbles and fiber segments, have also been deployed in the industry to facilitate authentication. This paper carries out a study to gain a better understanding in the factors affecting the authentication performance, with a consideration of the friendliness under mobile imaging. Comparisons are made for paper-based PUFs of different characteristics. It is found that the density of foreground objects have a dominant impact on the authentication performance. C2 - 2015/9// C3 - 2015 IEEE International Conference on Image Processing (ICIP) DA - 2015/9// DO - 10.1109/icip.2015.7351079 SP - 1643-1647 PB - IEEE ER - TY - JOUR TI - Towards Optimal Link Patterns for Robustness of Interdependent Networks against Cascading Failures AU - Chattopadhyay, Srinjoy AU - Dai, Huaiyu T2 - 2015 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM) AB - In this work we consider the optimal design of interconnection links for an interdependent system of networks. In contrast to existing literature, we explicitly exploit the information of intra- layer node degrees to design more robust interdependency structure against cascading failures triggered by random attacks. Built on solid mathematical models, we characterize the optimal design for the one-to-one structure, with complete interdependence and partial interdependence. We also extend the study to the one-to-many structure and targeted attack model. Simulation results are provided to corroborate the theoretical results. DA - 2015/// PY - 2015/// DO - 10.1109/glocom.2015.7417333 SP - SN - 2576-6813 KW - Interdependent networks KW - optimal inter-links KW - targeted attack KW - network robustness ER - TY - CONF TI - Mismatched estimation in large linear systems AU - Ma, Y. T. AU - Baron, Dror AU - Beirami, A. AB - We study the excess mean square error (EMSE) above the minimum mean square error (MMSE) in large linear systems where the posterior mean estimator (PME) is evaluated with a postulated prior that differs from the true prior of the input signal. We focus on large linear systems where the measurements are acquired via an independent and identically distributed random matrix, and are corrupted by additive white Gaussian noise (AWGN). The relationship between the EMSE in large linear systems and EMSE in scalar channels is derived, and closed form approximations are provided. Our analysis is based on the decoupling principle, which links scalar channels to large linear system analyses. Numerical examples demonstrate that our closed form approximations are accurate. C2 - 2015/// C3 - 2015 ieee international symposium on information theory (isit) DA - 2015/// DO - 10.1109/isit.2015.7282557 SP - 760–764 ER - TY - CONF TI - Green city: A low-cost testbed for distributed control algorithms in smart grid AU - Becerra, A. C. AU - Zeng, W. T. AU - Chow, M. Y. AU - Rodriiuez-Andina, J. J. AB - As a type of Cyber-Physical Systems (CPSs), Smart Grid has been adding more communication and control capabilities to improve power efficiency and availability. Especially, more and more distributed control algorithms have been developed for Smart Grids because of their flexibility and robustness. In order to deploy them in real electric power systems, distributed control algorithms must be tested, not only in theoretical simulations, but also in testbeds subject to real world constraints that can provide feedback to make the algorithm robust. Implementations of these algorithms in a Smart Grid environment are facing many cyber-physical challenges such as possible communication failures or imperfections, noisy signals, etc. These challenges can lead to increasing economical expenditure or cause failure of the power system. There exist different approaches for testing distributed control algorithms, from using state-of-the-art facilities to software or hardware-in-the-loop simulations. To better emulate real-world electric grid operation scenarios with low capital investment, in this paper the Green City (GC) testbed is proposed as a suitable platform for both control theory researchers in Smart Grid, and for engineering education, allowing students to learn through hands-on experiences. GC has been conceived as a multi-agent networked CPS with the following main features: 1- Smart Grid environment emulation with low-cost physical elements; 2- Fast prototyping capability of distributed control algorithms for Smart Grid. C2 - 2015/// C3 - Iecon 2015 - 41st annual conference of the ieee industrial electronics society DA - 2015/// DO - 10.1109/iecon.2015.7392385 SP - 1948-1953 ER - TY - CONF TI - Economic benefits of plug-in electric vehicles using V2G for grid performance-based regulation service AU - Zeng, W. AU - Gibeau, J. AU - Chow, M. Y. AB - With advancement of the vehicle-to-grid (V2G) technologies, plug-in electric vehicles (PEVs) are able to connect to the electric grid and participate in the grid regulation markets. Thus the large-scale PEV penetration into transportation systems will play an essential role for the grid support in the future. In this paper, a comprehensive daily economic benefit model for the PEV is formulated to analyze its costs and revenues of adopting unidirectional and bidirectional V2G technologies to provide grid performance-based regulation (PBR) services. Case studies considering three different types of PEVs with different charging rates and V2G capabilities are discussed. The simulation results quantitatively demonstrate the economic profit of PEVs to participate in the grid regulation service market. The sensitivities of the profit to battery sizes and charging rates are also analyzed. C2 - 2015/// C3 - Iecon 2015 - 41st annual conference of the ieee industrial electronics society DA - 2015/// DO - 10.1109/iecon.2015.7392772 SP - 4322-4327 ER - TY - JOUR TI - Dynamic IDS Configuration in the Presence of Intruder Type Uncertainty AU - He, Xiaofan AU - Dai, Huaiyu AU - Ning, Peng AU - Dutta, Rudra T2 - 2015 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM) AB - Intrusion detection systems (IDSs) assume increasingly importance in past decades as information systems become ubiquitous. Despite the abundance of intrusion detection algorithms developed so far, there is still no single detection algorithm or procedure that can catch all possible intrusions; also, simultaneously running all these algorithms may not be feasible for practical IDSs due to resource limitation. For these reasons, effective IDS configuration becomes crucial for real-time intrusion detection. However, the uncertainty in the intruder's type and the (often unknown) dynamics involved with the target system pose challenges to IDS configuration. Considering these challenges, the IDS configuration problem is formulated as an incomplete information stochastic game in this work, and a new algorithm, Bayesian Nash-Q learning, that combines conventional reinforcement learning with a Bayesian type identification procedure is proposed. Numerical results show that the proposed algorithm can identify the intruder's type with high fidelity and provide effective configuration. DA - 2015/// PY - 2015/// DO - 10.1109/glocom.2015.7417158 SP - SN - 2334-0983 ER - TY - CONF TI - Data center energy efficiency and power quality: An alternative approach with solid state transformer AU - Zhabelova, G. AU - Yavarian, A. AU - Vyatkin, V. AU - Huang, A. Q. AB - Data center evolved to become large power consumers. Its supporting infrastructure, such as cooling and power distribution, consumes resources e.g. electric power and money. In fact, most money is spent on power conditioning and cooling systems. Therefore, the efficiency of data center and power quality are important topics and can be addressed by careful design. There is a need for research into application of innovative design and state-of-the-art technology for optimizing power supply in data centers. The paper investigates potential of a state-of-the-art technology such as solid state transformer (SST). The simulation proves that SST has potential to improve operational efficiency. SST shows better control of voltage, current and reactive power of the facility, eliminating need for additional devices such as power conditioners and reducing power loss. These results lead to the next stage of the project that involves developing an optimal data center design with SST and investigating data center potential in demand response applications. C2 - 2015/// C3 - Iecon 2015 - 41st annual conference of the ieee industrial electronics society DA - 2015/// DO - 10.1109/iecon.2015.7392279 SP - 1294-1300 ER - TY - JOUR TI - Towards the Non-Visual Monitoring of Canine Physiology in Real-Time by Blind Handlers AU - Mealin, Sean AU - Winters, Mike AU - Dominguez, Ignacio X. AU - Marrero-Garcia, Michelle AU - Bozkurt, Alper AU - Sherman, Barbara L. AU - Roberts, David L. T2 - 12TH ADVANCES IN COMPUTER ENTERTAINMENT TECHNOLOGY CONFERENCE (ACE15) AB - One of the challenges to working with canines is that whereas humans are primarily vocal communicators, canines are primarily postural and behavioral communicators. It can take years to gain some level of proficiency at reading canine body language, even under the best of circumstances. In the case of guide dogs and visually-impaired handlers, this task is even more difficult. Luckily, new technology designed to help monitor canines may prove useful in helping handlers, especially those with visual impairments, to better understand and interpret what their working partners are feeling or saying. DA - 2015/// PY - 2015/// DO - 10.1145/2832932.2837018 SP - ER - TY - JOUR TI - Knowledge Engineering for Unsupervised Canine Posture Detection from IMU Data AU - Winters, Michael AU - Brugarolas, Rita AU - Majikes, John AU - Mealin, Sean AU - Yuschak, Sherrie AU - Sherman, Barbara L. AU - Bozkurt, Alper AU - Roberts, David T2 - 12TH ADVANCES IN COMPUTER ENTERTAINMENT TECHNOLOGY CONFERENCE (ACE15) AB - Training animals is a process that requires a significant investment of time and energy on the part of the trainer. One of the most basic training tasks is to train dogs to perform postures on cue. While it might be easy for a human trainer to see when an animal has performed the desired posture, it is much more difficult for a computer to determine this. Most work in this area uses accelerometer and/or gyroscopic data to produce data from an animal's current state, but this has limitations. Take for example a normal standing posture. From an accelerometer's perspective, it closely resembles the "laying down" posture, but the posture can look very different if the animal is standing still, versus walking, versus running, and might look completely different from a "standing on incline" posture. A human trainer can instantly tell the difference between these postures and behaviors, but the process is much more difficult for a computer. DA - 2015/// PY - 2015/// DO - 10.1145/2832932.2837015 SP - KW - Animal-computer interaction KW - Classification algorithms KW - canine training KW - accelerometers KW - animal-machine interfaces ER - TY - CONF TI - Grid connected CM noise considerations of a three-phase multi-stage SST AU - Tripathi, A. AU - Madhusoodhanan, S. AU - Mainali, K. AU - Kadavelugu, A. AU - Patel, D. AU - Bhattacharya, Subhashish AU - Hatua, K. AB - Solid State Transformer (SST) is an alternative to the conventional distribution transformer for smart grid applications. By employing a compact Medium-Frequency (MF) transformer for isolation, the SST has merits on size and weight. It also provides flexible utilization as a FACTS component. The switching converters are a potential source of Common-Mode (CM) and HF EMI noises. These noises are more nuisance in a SiC device based SST which switches at a high dV/dT at the Medium-Voltage (MV) level resulting in high CM voltages. The SST floating metalic surfaces such as heatsink and the output must be grounded for safety and smooth operation. However there are various significant low impedance paths present, including the parasitics of the compact transformer, which may conduct CM noise to the grid. The generated CM noise may affect the controls. This paper presents the CM and grounding challenges in the multistage integration of a three-phase SST system based on 15kV SiC IGBTs termed as Transformerless Intelligent Power Substation (TIPS). The TIPS interfaces MV 13.8kV and LV 480V grids using MV ac-dc, MV to LV dc-dc dual active bridge and LV dc-ac inverter stages. A study on the CM noise in the TIPS and a passive filter solution for its attenuation is presented in this paper. A time domain simulation considering the passive filter specification is also presented. The experimental results for line to line 3.64kV MV grid integration are presented. A LV prototype is used to verify the complete grounding and the CM choke design at a scaled-down condition. C2 - 2015/// C3 - 9th International Conference on Power Electronics - ECCE Asia: "Green World with Power Electronics", ICPE 2015-ECCE Asia DA - 2015/// DO - 10.1109/icpe.2015.7167873 SP - 793-800 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84961872947&partnerID=MN8TOARS ER - TY - CONF TI - Turn-on capability of 22 kV SiC Fmitter Turn-off (ETO) Thyristor AU - Liang, L. AU - Huang, A. Q. AU - Sung, W. J. AU - Lee, M. C. AU - Song, X. Q. AU - Peng, C. AU - Cheng, L. AU - Palmour, J. AU - Scozzie, C. AB - The turn-on characteristics for the SiC p-ETO are researched in this paper. By establishing the two-dimensional numerical model of the SiC p-ETO, the influence of the device parameters and external circuit conditions on the turn-on speed is discussed. The experiments agree with the simulated results well. The npn turn-on mode of ETO is captured in a high di/dt experiment, which proves the existence of the FBSOA for this time hence the possibility of its application in converters without di/dt snubber. According to the intrinsic temperature limitation of the SiC material, the simulation shows that the peak power density of the SiC p-ETO during turn-on could reach several tens of MW/cm2. C2 - 2015/// C3 - WiPDA 2015 3rd IEEE Workshop on Wide Bandgap Power Devices and Applications DA - 2015/// DO - 10.1109/wipda.2015.7369275 SP - 192-195 ER - TY - CONF TI - Thermomagnetic liquid cooling: A novel variable speed motor drives thermal management solution AU - Karimi-Moghaddam, G. AU - Gould, R. D. AU - Bhattacharya, S. AB - Liquid cooling for thermal management has been extensively applied in high power electronic systems. However, the use of pumps may introduce reliability and mechanical limitations such as vibration, noise, leakage, and considerable power consumption. It has been shown that temperature sensitive ferrofluids in the presence of temperature field and magnetic field gradients are able to produce a liquid flow without a mechanical pump. This paper presents results from experiments using a single-phase, Mn-Zn ferrite based ferrofluid operating under transient and steady laminar flow conditions in a partially heated thermomagnetic circulation loop under the influence of an external magnetic field created by a solenoid. The effects of several operational factors on the system performance are discussed. Additionally, the self-regulating feature of this cooling system is demonstrated as the heat load is increased a larger heat dissipation rate can be managed due to a stronger thermomagnetic convection effect. C2 - 2015/// C3 - 2015 IEEE International Electric Machines & Drives Conference (IEMDC) DA - 2015/// DO - 10.1109/iemdc.2015.7409303 SP - 1768-1773 ER - TY - JOUR TI - Runtime Checking C Programs AU - Milewicz, Reed AU - Vanka, Rajesh AU - Tuck, James AU - Quinlan, Daniel AU - Pirkelbauer, Peter T2 - 30TH ANNUAL ACM SYMPOSIUM ON APPLIED COMPUTING, VOLS I AND II AB - The C Programming Language is known for being an efficient language that can be compiled on almost any architecture and operating system. However the absence of dynamic safety checks and a relatively weak type system allows programmer oversights that are hard to spot. In this paper, we present RTC, a runtime monitoring tool that instruments unsafe code and monitors the program execution. RTC is built on top of the ROSE compiler infrastructure. RTC finds memory bugs and arithmetic overflows and underflows, and run-time type violations. Most of the instrumentations are directly added to the source file and only require a minimal runtime system. As a result, the instrumented code remains portable. In tests against known error detection benchmarks, RTC found 98% of all memory related bugs and had zero false positives. In performance tests conducted with well known algorithms, such as binary search and MD5, we determined that the unoptimized overhead rate is between a factor of 1.8 and a factor of 77 respectively. DA - 2015/// PY - 2015/// DO - 10.1145/2695664.2695906 SP - 2107-2114 ER - TY - CONF TI - Power management strategy of hybrid electric vehicles based on particle swarm optimization AU - Hu, C. J. AU - Gao, Y. M. AU - Alex, Q. H. AB - The Power management strategy of HEV using global optimization techniques can achieve optimum control solution. However, the “a priori” nature of the trip information and heavy computational cost prohibit it from being utilized in real world application. In this paper, a power management strategy using particle swarm optimization (PSO) is proposed. The aim is to achieve real time implementation and sub-optimal control solution without requiring the “a priori” knowledge of the driving cycle. Using pricewise linearization, at each time step, normalized comprehensive energy loss for each power split scenario is obtained and normalized over the traveling distance. The power split strategy that minimizes the normalized comprehensive energy loss is considered optimal. However, searching for the optimal power split is mathematically challenging and time consuming. To address the real time implementation, PSO algorithm is employed as the global minima searching tool. Simulation study on a series-parallel configuration passenger vehicle has been performed. In addition, Dynamic Programming (DP) technique has also been implemented in the simulation for the comparison purpose. The simulation results demonstrated that the proposed control strategy is able to achieve comparable fuel economy with global optimization while feasible for real time implementation. C2 - 2015/// C3 - 2015 IEEE Transportation Electrification Conference and Expo (ITEC) DA - 2015/// DO - 10.1109/itec.2015.7165795 ER - TY - CONF TI - Performance evaluation of series connected 1700V SiC MOSFET devices AU - Vechalapu, K. AU - Bhattacharya, Subhashish AU - Aleoiza, E. AB - The low voltage SiC (Silicon carbide) MOSFET (1.2 kV to 1.7 kV) increases the switching frequency limits of a power electronic converter several folds compared to low voltage Si IGBTs. Significant increase in efficiency and power density of voltage source converters can be achieved. However, for medium-voltage high-power converter applications Silicon (Si) devices (4.5 kV and 6.5 kV IGBT) are still dominant. To explore the capability of low voltage SiC devices for medium or high voltage applications, series connection of 1.7 kV/300 A SiC MOSFET modules has been investigated in this paper. A simple RC snubber method has been used for dynamic voltage sharing to offset the turn-off delays due to mismatch on device's characteristics and/or gate signals. Experimental switching characterization with different values of RC snubbers have been carried out to find the optimal RC snubber which gives minimum voltage sharing difference, snubber losses and total semiconductor losses. This paper also intends to show an optimization of the RC snubber for series connection of a limited number of 1.7kV SiC MOSFETs for 6 kV dc bus and for a generalized dc bus voltage. C2 - 2015/// C3 - WiPDA 2015 - 3rd IEEE Workshop on Wide Bandgap Power Devices and Applications DA - 2015/// DO - 10.1109/wipda.2015.7369327 SP - 184-191 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963541072&partnerID=MN8TOARS ER - TY - CONF TI - Performance evaluation and characterization of 6500V asymmetric SiC NPNP Thyristor based current switch AU - De, A. AU - Bhattacharya, Subhashish AU - Singh, R. AB - The main motivation of this work is to evaluate performance and characteristics of a 6.5kV SiC Thyristor based current switch (series connected active switch and diode). A unique series resonant testing circuit has been proposed to characterize this switch. The device has been tested in several soft and hard turn on and off transitions. Conceptual simulation and hardware results have been presented. It has been shown that SiC Thyristor exhibit fast turn-on transitions (~200ns). This coupled with the fact that SiC-JBS Diode (connected in series) has fast reverse voltage commutation leads to an efficient and robust switch combination for a high voltage, high power and high frequency converter. The collected data has been used to estimate overall device losses of a high voltage and high power resonant soft-switched converter. C2 - 2015/// C3 - WiPDA 2015 - 3rd IEEE Workshop on Wide Bandgap Power Devices and Applications DA - 2015/// DO - 10.1109/wipda.2015.7369324 SP - 10-15 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963613100&partnerID=MN8TOARS ER - TY - CONF TI - Loss analysis of GaN Devices in an isolated bidirectional DC-DC converter AU - Xue, F. AU - Yu, R. Y. AU - Guo, S. X. AU - Yu, Wensong AU - Huang, A. Q. AB - GaN devices have emerged as a possible replacement for silicon devices in various power conversion applications and as an enabler of new applications not previously possible. This paper presents a 600V Gallium-Nitride (GaN) device based isolated bidirectional DC-DC converter applied in battery energy storage systems. Apart from the features of low turn-off loss, low output capacitance and low drain-source on-state resistance, the most salient one in our bidirectional DC-DC converter application is the ultra-fast freewheeling "body diode" that GaN devices have when compared with Si devices. To distinguish the above mentioned performances of GaN from those of the comparable Si devices, a figure of merit for power devices operating in synchronous rectifying mode is proposed. The converter's operating principle is analyzed in steady state. Switching losses of high voltage and low voltage side switches are simulated based on detailed PSpice models. The converter's safe operation area is extended by using GaN device is explained by calculating the loss in hard switching mode. A thermal simulation is conducted to predict its temperature. Experimental results are presented for a 1 kW, 380-to-12 V prototype DC-DC converter, which demonstrate the validity of the analysis and simulation. C2 - 2015/// C3 - WiPDA 2015 3rd IEEE Workshop on Wide Bandgap Power Devices and Applications DA - 2015/// DO - 10.1109/wipda.2015.7369261 SP - 201–205 ER - TY - CONF TI - Excess carrier mapping technique -A new parameter extraction method for 4H-SiC ambipolar power devices AU - Lee, M. C. AU - Song, X. Q. AU - Huang, A. C2 - 2015/// C3 - WiPDA 2015 3rd IEEE Workshop on Wide Bandgap Power Devices and Applications DA - 2015/// SP - 51-55 ER - TY - CONF TI - Electrical machines for power generation in oscillating wave energy conversion system - a comparative study AU - Hazra, S. AU - Bhattacharya, S. AB - In this paper, system level design of an oscillating wave energy conversion system (WECS) using doubly-fed induction generator (DFIG) is compared with systems using squirrel-cage induction generator (SCIG) and permanent magnet synchronous generator (PMSG). The comparative study is carried out considering major hardware components and their rating requirements for each system. Although, SCIG and PMSG based systems are more simple and reliable, DFIG can enable compact and cost effective systems especially for high power WECS design. DFIG can generate power above its nominal rating at super-synchronous rotor speed and hence can offer an attractive solution for the oscillating power pattern of WECS. Moreover, rotor side control of the DFIG enables one to work with lower voltage and power level which effectively reduces the ratings of the power converters and other passive elements in the system. The system design comparison is performed with a wave energy converter (WEC) modeled for maximum power output around 500 kW. System operation with singly-fed generator (SCIG) and doubly-fed generator (DFIG) have been studied through simulation in real time simulator (OPAL-RT). The results of the comparison are shown with details of the major component rating of each system. C2 - 2015/// C3 - 2015 IEEE International Electric Machines & Drives Conference (IEMDC) DA - 2015/// DO - 10.1109/iemdc.2015.7409267 SP - 1538-1544 ER - TY - CONF TI - Comparative evaluation of 6kV Si and SiC power devices for medium voltage power flectronics applications AU - Song, X. Q. AU - Huang, A. Q. AU - Ni, X. J. AU - Zhang, L. Q. AB - In order to better assist researchers to select the appropriate power device for medium voltage power electronics applications, this paper presents a comparative evaluation on three typical 6kV level Si and SiC power devices, including 6.5kV/25A Si IGBT from ABB, 6.5kV/15A normally off SiC JFET from USCi and a FREEDM System Center developed 6kV/26A SiC series-connected JFET. The 6.5kV Si IGBT and 6.5kV SiC JFET are packaged in the same module to minimize the effect of different parasitic inductance on the comparison. The 6kV SiC series-connected JFET is developed based on one 1.2kV SiC MOSFET from Cree and four 1.2kV SiC JFETs from Infineon, in this paper, named FREEDM Super-Cascode. A short introduction on the three selected devices are first given, then their forward conduction and switching performances are compared. Also, some additional features are discussed and compared, including the device size, cost, gate driver circuit complexity. C2 - 2015/// C3 - WiPDA 2015 3rd IEEE Workshop on Wide Bandgap Power Devices and Applications DA - 2015/// DO - 10.1109/wipda.2015.7369289 SP - 160-165 ER - TY - CONF TI - A new AlGaN/GaN power HFET employing partial deep trench drain structure for high voltage application AU - Ji, I. H. AU - Lee, B. AU - Wang, S. Z. AU - Misra, Veena AU - Huang, A. Q. AB - A new AlGaN/GaN heterojuction field effect transistor (HFET) employing the partial deep trench drain structure for high voltage application has been proposed and verified successfully to achieve low leakage current and small Rdson. In order to reduce leakage current and on-resistance of HFET devices, we propose a partial deep trench on drain edge adjacent to access region for the first time, which contributes to reducing the surface electric field under the off-state. In addition, trenched area under drain Ohmic metal enhances Ohmic contact on the surface of AlGaN layer which reduces contact resistivity of drain Ohmic contact. The proposed deep trench drain successfully reduces Ohmic contact resistance under the on-state and leakage current under the off-state at the same time. C2 - 2015/// C3 - WiPDA 2015 3rd IEEE Workshop on Wide Bandgap Power Devices and Applications DA - 2015/// DO - 10.1109/wipda.2015.7369277 SP - 147–149 ER - TY - CONF TI - 3.38 Mhz operation of 1.2kV SiC MOSFET with integrated ultra-fast gate drive AU - Guo, S. X. AU - Zhang, L. Q. AU - Lei, Y. AU - Li, X. AU - Xue, F. AU - Yu, Wensong AU - Huang, A. Q. AB - With the commercialization of wide bandgap power devices such as SiC MOSFETs and JBS diodes, power electronics converters used in the harsh environments such as hybrid electric vehicles and aerospace attract more and more attentions. The low loss, high temperature and fast switching capabilities are utilized in the converters to improve the power density and efficiency. However, the EMI problem caused by the fast switching is a major constrain for improving switching frequency. For this reason, an integrated SiC module with 1.2kV MOSFET and ultra-fast gate drive circuits is proposed and developed. Two 1.2kV SiC MOSFETs bare dies and two high current gate driver chips are integrated in a compact integrated module package to reduce the parasitic inductance. 0Ω gate resistor therefore can be used in this module to improve the device at maximum speed. Noise free operation of the tested module is verified even under extremely high dV/dt and dI/dt conditions. The ultra-low turn-off loss of the module is being demonstrated. Finally, the integrated module is demonstrated in two megahertz converters: an 800W 1.5MHz synchronous boost converter and a 3.38MHz half bridge inverter. The era for high voltage-megahertz switching has arrived. C2 - 2015/// C3 - WiPDA 2015 3rd IEEE Workshop on Wide Bandgap Power Devices and Applications DA - 2015/// DO - 10.1109/wipda.2015.7369298 SP - 390–395 ER - TY - CONF TI - An intrusion-resilient distributed optimization algorithm for modal estimation in power systems AU - Nabavi, S. AU - Chakrabortty, Aranya AB - In this paper we present an intrusion-resilient distributed algorithmic approach to estimate the electro-mechanical oscillation modes of a large power system using Synchrophasor measurements. For this, we first show how to distribute the centralized Prony method over a network consisting of several computational areas using a distributed variant of alternating direction method of multipliers (D-ADMM). We then add a cross-verification step to show the resiliency of this algorithm against the cyber-attacks that may happen in the form of data manipulation. We illustrate the robustness of our method in face of intrusion for a case study on IEEE 68-bus power system. C2 - 2015/// C3 - 2015 54th IEEE conference on decision and control (CDC) DA - 2015/// DO - 10.1109/cdc.2015.7402084 SP - 39–44 ER - TY - CONF TI - Understanding the influence of E-a and band-offset toward the conductance modulation in Al2O3 and HfO2 synaptic RRAM AU - Sarkar, B. AU - Lee, B. AU - Misra, Veena AB - This work highlights the contribution of E a and band-offset toward conductance change in RRAM dielectrics. Both Al 2 O 3 and HfO 2 RRAM showed a gradual conductance change suitable for synaptic applications, and the lower E a of the dielectric helps in generating higher number of vacancies during set and higher band-offset of the dielectric limiting the TAT current during reset resulting in a higher conductance change in Al 2 O 3 RRAM compared to HfO 2 RRAM. C2 - 2015/// C3 - 2015 73rd Annual Device Research Conference (DRC) DA - 2015/// DO - 10.1109/drc.2015.7175599 SP - 149–150 ER - TY - CONF TI - Ultra-low power sensing platform for personal health and personal environmental monitoring AU - Misra, Veena AU - Lee, B. AU - Manickam, P. AU - Lim, M. AU - Pasha, S. K. AU - Mills, S. AU - Bhansali, S. AB - The vision of the NSF Center on Advanced Self-Powered Systems of Integrated Sensors and Technologies (ASSIST) is to develop nano-enabled technologies to achieve a paradigm shift towards long-term health and wellness management. To achieve this, the center is building self-powered, wearable and multimodal sensing systems for correlation of environmental exposures to physiological parameters. This paper presents the latest advances in environmental and personal health sensors that have ultra-low power consumption and are highly selective and sensitive to enable real time, continuous, and wearable platforms. C2 - 2015/// C3 - 2015 IEEE International Electron Devices Meeting (IEDM) DA - 2015/// DO - 10.1109/iedm.2015.7409687 ER - TY - CONF TI - Thermal design considerations for medium voltage power converters with 15 kV SiC IGBTs AU - Madhusoodhanan, S. AU - Mainali, K. AU - Tripathi, A. AU - Kadavelugu, A. AU - Patel, D. AU - Bhattacharya, Subhashish AB - Medium Voltage (MV) Silicon Carbide (SiC) devices such as the 15 kV SiC IGBT have better thermal handling capability compared to Silicon (Si) based devices. These devices also have lower switching and conduction losses, at high switching frequencies and high power levels, respectively. The maximum safe operating junction temperature for the 15 kV SiC IGBT is 175 °C. This enables high power density design of the MV converters using this device. Heat sink with forced air cooling is sufficient for dissipating the heat generated during converter operation. In this paper, the thermal design of 3-phase MV converters based on 15 kV/40 A SiC N-IGBT is discussed. The design is carried out based on experimental loss data and the continuous heat-run test of the device. It is supported by analytical calculations and FEM simulations in COMSOL Multiphysics simulation software. Hardware prototypes of the converters are developed and experimental results are given. C2 - 2015/// C3 - 2015 IEEE 6th International Symposium on Power Electronics for Distributed Generation Systems, PEDG 2015 DA - 2015/// DO - 10.1109/PEDG.2015.7223105 SP - 265–272 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84954159835&partnerID=MN8TOARS ER - TY - CONF TI - The state of the art approaches to estimate the state of health (SOH) and state of function (SOF) of lithium ion batteries AU - Balagopal, B. AU - Chow, M. Y. AB - This paper discusses the commonly used techniques to estimate the state of health (SOH) and state of function (SOF) of lithium ion batteries and their limitations. Factors affecting the health and SOF of the battery are discussed in this paper. The SOH of the battery is mainly represented by the capacity degradation and the increase in the internal resistance. The other indices that could represent the battery's health are also briefly discussed. The different techniques that are used to estimate the capacity and internal resistance of the battery are discussed along with their limitations. The concept of SOF and its relationship with SOC, SOH and temperature are discussed along with the commonly used techniques to estimate the SOF of the battery. This paper also discusses the limitations in the definition and estimation of the SOF. C2 - 2015/// C3 - Proceedings 2015 ieee international conference on industrial informatics (indin) DA - 2015/// DO - 10.1109/indin.2015.7281923 SP - 1302-1307 ER - TY - CONF TI - Stationary energy storage system based on modular high voltage battery modules AU - Xue, F. AU - Zhao, Y. L. AU - Yu, R. Y. AU - Yu, Wensong AU - Huang, A. Q. AB - This paper focuses on the design and control of a stationary energy storage system based on multiple modular high voltage battery modules. The system achieves bi-directional power flow directly from 400V dc grid to the 12V battery modules via a bi-directional dc-dc converter with high conversion ratio as an interface. One merit of such a system is its extensibility and scalability for higher power rating for future use by dispatching more battery modules together. A 2kWh energy storage system prototype which is made up by one grid-connected solid state transformer (SST) emulator and two bi-directional dc-dc converters are designed, fabricated and tested. Based on the modified droop control, a double-loop digital control system for the SST emulator and a single-loop digital control system for the dc-dc converter are implemented respectively. At last, experimental results are presented to verify the proposed distributed control strategy. C2 - 2015/// C3 - 2015 IEEE First International Conference on DC microgrids (ICDCM) DA - 2015/// DO - 10.1109/icdcm.2015.7152028 ER - TY - CONF TI - Silver nanowire strain sensors for wearable body motion tracking AU - Yao, S. S. AU - Lee, J. S. AU - James, K. AU - Miller, J. AU - Narasimhan, V. AU - Dickerson, A. J. AU - Zhu, X. AU - Zhu, Y. AB - This paper demonstrates a wearable body motion tracking technology in the form of data glove to measure the instantaneous bending positions of individual finger knuckles. Attached to the glove is a highly stretchable and flexible silver nanowire (AgNW) based capacitive strain sensor which can adapt to curvilinear surfaces. The sensor shows a linear response to large tensile strain up to 60% with less than 5 msec response time. Such kind of merits enable many applications, e.g. Virtue Reality, gaming, and robot control, which desire natural human-machine interactions associated with typical human motions such as finger movements, walking, running and jumping, etc. C2 - 2015/// C3 - 2015 ieee sensors DA - 2015/// DO - 10.1109/icsens.2015.7370650 SP - 1823-1826 ER - TY - JOUR TI - Safety Can Be Dangerous: Secure Communications Impair Smart Grid Stability Under Emergencies AU - Wei, Mingkui AU - Wang, Wenye T2 - 2015 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM) AB - Smart grid features real-time monitoring and control by integrating advanced communication networks into traditional power grids. This integration, however, makes smart grid vulnerable to cyber attacks, i.e., the anomalies caused by attackers in the communication network can affect ordinary operations of the power grid and result in severe physical damage. To protect smart grid from cyber attacks, many traditional countermeasures, such as message encryption, have been proposed to be directly migrated to fit this system. In this regard, the very first fundamental questions that need to be addressed are how to evaluate and compare the physical impacts of cyber attacks and countermeasures, and whether traditional cyber security countermeasures can result in satisfactory performance in smart grid. Motivated by these questions, we establish a small-scale smart grid prototype, and use both experiments and cross-domain simulations to evaluate and compare the reaction of the power system under cyber attacks, with and without the presence of traditional countermeasures. Our study reveals that traditional countermeasures can not be readily migrated to protect smart grid in particular, and shows that during system emergencies where prompt system reactions are critical, the extra latency caused by message encryption and decryption can result in more than 10 times in the magnitude of voltage collapse. Our work indicates that traditional countermeasures may not fit smart grid, the newly emerging cyber- physical system, which has strict time constraint. Therefore it is essential for researchers to seek solutions to address smart grid specific security threats. DA - 2015/// PY - 2015/// DO - 10.1109/glocom.2015.7417012 SP - SN - 2334-0983 ER - TY - CONF TI - Robust multi-target tracking in outdoor traffic scenarios via persistence topology based robust motion segmentation AU - Chattopadhyay, Somrita AU - Ge, Qian AU - Wei, Chunpeng AU - Lobaton, Edgar AB - In this paper, we present a motion segmentation based robust multi-target tracking technique for on-road obstacles. Our approach uses depth imaging information, and integrates persistence topology for segmentation and min-max network flow for tracking. To reduce time as well as computational complexity, the max flow problem is solved using a dynamic programming algorithm. We classify the sensor reading into regions of stationary and moving parts by aligning occupancy maps obtained from the disparity images and then, incorporate Kalman filter in the network flow algorithm to track the moving objects robustly. Our algorithm has been tested on several real-life stereo datasets and the results show that there is an improvement by a factor of three on robustness when comparing performance with and without the topological persistent detections. We also perform measurement accuracy of our algorithm using popular evaluation metrics for segmentation and tracking, and the results look promising. C2 - 2015/12// C3 - 2015 IEEE Global Conference on Signal and Information Processing (GlobalSIP) DA - 2015/12// DO - 10.1109/globalsip.2015.7418308 SP - 805–809 PB - IEEE UR - http://dx.doi.org/10.1109/globalsip.2015.7418308 ER - TY - CONF TI - Non-volatile memory host controller interface performance analysis in high-performance I/O systems AU - Awad, A. AU - Kettering, B. AU - Solihin, Y. AB - Emerging non-volatile memories (NVMs), such as Phase-Change Memory (PCM), Spin-Transfer Torque RAM (STT-RAM) and Memristor, are very promising candidates for replacing NAND-Flash Solid-State Drives (SSDs) and Hard Disk Drives (HDDs) for many reasons. First, their read/write latencies are orders of magnitude faster. Second, some emerging NVMs, such as memristors, are expected to have very high densities, which allow deploying a much higher capacity without requiring increased physical space. While the percentage of the time taken for data movement over low-speed buses, such as Peripheral Component Interconnect (PCI), is negligible for the overall read/write latency in HDDs, it could be dominant for emerging fast NVMs. Therefore, the trend has moved toward using very fast interconnect technologies, such as PCI Express (PCIe) which is hundreds of times faster than the traditional PCI. Accordingly, new host controller interfaces are used to communicate with I/O devices to exploit the parallelism and low-latency features of emerging NVMs through high-speed interconnects. In this paper, we investigate the system performance bottlenecks and overhead of using the standard state-of-the-art Non-Volatile Memory Express (NVMe), or Non-Volatile Memory Host Controller Interface (NVMHCI) Specification [1] as representative for NVM host controller interfaces. C2 - 2015/// C3 - Ieee international symposium on performance analysis of systems and DA - 2015/// DO - 10.1109/ispass.2015.7095793 SP - 145-154 ER - TY - CONF TI - Near field wireless power transfer and quadrature amplitude modulated (QAM) communication link AU - Besnoff, Jordan AU - Ricketts, David S. AB - We present a near field wireless power transfer (NF-WPT) link which is also capable of data communication through complex, quadrature amplitude (QAM) load modulation. We present a method for designing a 4QAM constellation that allows for minimal degradation of the NF-WPT link efficiency by minimizing the complex reflection coefficient. Using a modulation board and a resonant 4-coil NF-WPT system we demonstrate 307.2kbps data transmission, representing a 12.7% fractional bandwidth, over a distance of 1-coil diameter (29cm) at a carrier frequency of 2.428MHz. Efficiency of the NF-WPT is only reduced from 68% to approximately 63.1% when used for data communication as well as power transfer. C2 - 2015/5// C3 - 2015 IEEE Wireless Power Transfer Conference (WPTC) DA - 2015/5// DO - 10.1109/wpt.2015.7139131 PB - Institute of Electrical and Electronics Engineers (IEEE) ER - TY - JOUR TI - Nash Bargaining in Beamforming Games with Quantized CSI in Two-user Interference Channels AU - Lee, Jung Hoon AU - Dai, Huaiyu T2 - 2015 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM) AB - In this paper, we consider a beamforming game of the transmitters in a two-user multiple-input single- output interference channel using limited feedback and investigate how each transmitter should find a strategy from the quantized channel state information (CSI). In the beamforming game, each transmitter (a player) tries to maximize the achievable rate (a payoff function) via a proper beamforming strategy. In our case, each transmitter's beamforming strategy is represented by a linear combining factor between the maximum-ratio transmission (MRT) and the zero-forcing (ZF) beamforming vectors, which is shown to be a Pareto optimal achieving strategy. With the perfect CSI, each transmitter can know the exact achievable rate region, and hence can find the beamforming strategy corresponding to any point in the achievable rate region. With limited feedback, however, the transmitters can only conjecture the achievable rate region from the quantized CSI, so their optimal strategies may not be optimal anymore. Considering the quantized CSI at the transmitter, we first find the Nash equilibrium in a non-cooperative game. Then, in a cooperative (Nash bargaining) game, we find a Nash bargaining solution and test its validity. Finally, we propose three bargaining solutions that improve the validity of the cooperation or the average Nash product. Our proposed bargaining solutions utilize the codebook structure; instead of each quantized channel itself, its Voronoi region is considered. DA - 2015/// PY - 2015/// DO - 10.1109/glocom.2015.7417263 SP - SN - 2334-0983 KW - Beamforming KW - Nash bargaining KW - limited feedback KW - multiple-input single-output KW - interference channels ER - TY - CONF TI - Modular multilevel converter based medium voltage DC amplifier for ship board power system AU - Vechalapu, K. AU - Bhattacharya, Subhashish AB - In this paper, the Modular Multilevel Cascaded Converter based on Double-Star Bridge Cells(MMCC-DSBC) for Medium Voltage DC (MVDC) amplifier is proposed. The medium voltage DC (MVDC) amplifier system is required to validate new technologies, new high power non-linear loads based on power electronics, in all electric ships as part of the proposed medium voltage (MVDC) ship power system. Thyristor based medium voltage DC amplifier (6 kV to 24 kV DC from 4.2 kV (L-L) AC three phase system) with Series Active Inverter (SAI) and DC side transformer in series with DC bus has been reported in the literature, where the series active Inverter compensates the slow dynamics of the Thyristor converter and facilitates fast dynamic response for step changing loads. However, this system has disadvantages as shown in Table III. This paper first shows a control method for AC to DC operation of MMCC-DSBC converter to control the wide DC output voltage in both buck and boost modes from fixed AC source. The simulation results show that the MMCC-DSBC converter provides a variable DC voltage from 6 kV to 24 kV DC and also the extended wide range of output DC voltage - 1 kV to 24 kV - from fixed 4.2 kV (L-L) AC three phase system. It is also shown that this topology will provide fast dynamic response compared to Thyristor based Line Commutated Converter (LCC) without the need of Series Active Inverter, DC side transformer in series with DC bus. This paper also shown the the control method to operate the MMCC-DSBC converter in STATCOM mode-to provide reactive power support to the AC side grid-during DC side pole to pole fault. Simulation results are presented on EMTDC/PSCAD platform to validate the controls. C2 - 2015/// C3 - 2015 IEEE 6th International Symposium on Power Electronics for Distributed Generation Systems, PEDG 2015 DA - 2015/// DO - 10.1109/PEDG.2015.7223098 SP - 419–426 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84954128604&partnerID=MN8TOARS ER - TY - CONF TI - Modeling time-sensitive information diffusion in online social networks AU - Xu, X. AU - Chen, X. AU - Eun, D. Y. AB - After a piece of information is released in Online Social Networks (OSNs), will it spread to the entire network or reach only a small population of users? In a time window of interest, how many users will forward or comment on this information? Limited effort has been made at this point to develop an effective model to address these issues, as the timesensitive nature of information spreading and the complexity of network structure make it a very challenging task. In this paper, we propose a continuous-time model for information diffusion with time-varying diffusion (infection) rate to address these issues, and provide an interface between our proposed model and the well-studied SI model with constant diffusion rate. We prove that there exists an elegant time-rescaling relationship between these two cases, such that any available result on the standard SI model can readily carry over to our time-varying case. We then show how the shape of the time-dependent infection rate will influence the temporal evolution of the size of infection and the time until the information reaches a given node on a graph. This also explains why some information stops spreading before reaching the entire population. Simulation results on Digg graph validate our findings. C2 - 2015/// C3 - 2015 ieee conference on computer communications workshops (infocom wkshps) DA - 2015/// DO - 10.1109/infcomw.2015.7179419 SP - 408-413 ER - TY - CONF TI - Modal Q as a bounding metric for MIMO antenna optimization AU - Yang, B. B. AU - Adams, J. J. C2 - 2015/// C3 - 2015 31st International Review of Progress in Applied Computational Electromagnetics (ACES) vol 31 DA - 2015/// ER - TY - JOUR TI - Jamming Games in Underwater Sensor Networks with Reinforcement Learning AU - Xiao, Liang AU - Li, Qiangda AU - Chen, Tianhua AU - Cheng, En AU - Dai, Huaiyu T2 - 2015 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM) AB - Jamming attacks that can further lead to denial of service attacks have thrown serious threats to underwater sensor networks (UWSNs). However, due to the narrow bandwidth of underwater acoustic signals and time variant propagation environments, jamming in UWSNs cannot be fully addressed by spread spectrum techniques, one type of widely-used antijamming methods in wireless networks for decades. In this work, we investigate jamming attacks in underwater sensor networks. More specifically, the interactions between the underwater sensors and jammers in UWSNs are formulated as an underwater jamming game, in which the players choose their transmit power levels to maximize their individual utilities based on the signal to interference plus noise ratio of the legal signals and transmission costs. The Nash equilibrium (NE) of a static jamming game is presented in a closed-form expression for the jamming scenario with known acoustic channel gains. For the dynamic and unknown underwater environments, we propose a reinforcement learning-based anti-jamming method for UWSNs, in which each sensor chooses its transmit power without knowing the channel gain of the jammers. Simulations are performed to evaluate the NE in the static jamming game in underwater sensor networks and to validate the efficacy of the proposed anti-jamming power control scheme against jamming in dynamic environments. DA - 2015/// PY - 2015/// DO - 10.1109/glocom.2015.7417192 SP - SN - 2334-0983 KW - Jamming KW - underwater sensor networks KW - reinforcement learning KW - game theory ER - TY - CONF TI - Integrated DC/DC parallel PnP PV architecture method for powering residential buildings AU - Najm, E. M. AU - Huang, A. Q. AB - This paper proposes a novel integrated plug and play (PnP) DC/DC parallel PV architecture for powering residential buildings. The scheme is based on low cost PV converters (first stage) integrated into one mechanical enclosure along with a second stage grid tied centralized inverter or converter in the case of DC powered applications. The technique limits the requirements of the first stage converters to operation in the maximum power point tracking (MPPT) while supporting power curtailment. All communications to the grid or to other applications are proposed to be provided by the said centralized inverter or converter. Furthermore, a novel approach to improve the racking installation time is also proposed in this paper. The outcome of the said configuration as well as the proposed racking improvement method is a lower cost and simpler to implement PnP system. System configuration and the proposed improved racking installation diagrams as well as experimental results are illustrated in this paper. C2 - 2015/// C3 - 2015 IEEE First International Conference on DC microgrids (ICDCM) DA - 2015/// DO - 10.1109/icdcm.2015.7152071 SP - 371-376 ER - TY - CONF TI - Incremental cost consensus(ICC) and leaderless ICC implementations in FREEDM AU - Feng, L. AU - McMillin, B. AU - Santiago, A. P. AU - Zhang, Z. C2 - 2015/// C3 - 2015 IEEE Power & Energy Society Innovative Smart Grid Technologies Conference (ISGT) DA - 2015/// ER - TY - CONF TI - Incorporating big data analysis in speed profile classification for range estimation AU - Rahimi-Eichi, H. AU - Jeon, P. B. AU - Chow, M. Y. AU - Yeo, T. J. AB - Incorporation of data from multiple resources and various structures is necessary for accurate estimation of the driving range for electric vehicles. In addition to the parameters of the vehicle model, states of the battery, weather information, and road grade, the driving behavior of the driver in different regions is a critical factor in predicting the speed/acceleration profile of the vehicle. Following our previously proposed big data analysis framework for range estimation, in this paper we implement and compare different techniques for speed profile generation. Moreover we add the big data analysis classification results to especially improve the performance of the Markov Chain approach. The quantitative results show the significant influence of considering the big data analysis results on range estimation. C2 - 2015/// C3 - Proceedings 2015 ieee international conference on industrial informatics (indin) DA - 2015/// DO - 10.1109/indin.2015.7281921 SP - 1290-1295 ER - TY - CONF TI - GaN transistor based Bi-directional DC-DC converter for stationary energy storage device for 400V DC microgrid AU - Xue, F. AU - Yu, R. Y. AU - Yu, Wensong AU - Huang, A. Q. AB - This paper presents a novel GaN transistor based bidirectional isolated DC-DC converter for stationary energy storage device (SESD) for 400V DC microgrid. The improvements achieved in the application includes: first, benefitting from the internal ultra-fast free-wheeling diode, the converter's operation range can be expended to light load conditions (switches operate in hard switching). The light load efficiency can be greatly increased. Second, because of its low switching loss and on state resistance, the heavy load efficiency is increased. Third, the snubber inductor which is indispensable in Si device based converter can now be omitted in the GaN version. The power stage design as well as a loss analysis of GaN is based on a steady state analysis and PSpice simulation. Experimental results are presented for a 500 W bidirectional dc-dc converter prototype. C2 - 2015/// C3 - 2015 IEEE First International Conference on DC microgrids (ICDCM) DA - 2015/// DO - 10.1109/icdcm.2015.7152029 ER - TY - JOUR TI - Feasibility of a wearable, sensor-based motion tracking system AU - Mohammadzadeh, Farrokh F. AU - Liu, Shijing AU - Bond, Kyle A. AU - Nam, Chang S. T2 - 6TH INTERNATIONAL CONFERENCE ON APPLIED HUMAN FACTORS AND ERGONOMICS (AHFE 2015) AND THE AFFILIATED CONFERENCES, AHFE 2015 AB - The objective of this study was to develop and evaluate the feasibility of a wearable, sensor-based motion tracking system that provides an economical and quantitative means of recording upper limb motion for physical rehabilitation. The tracking system is comprised of a wirelessly connected network of inertial measurement units (IMUs), each containing a gyroscope and an accelerometer. Two IMUs were rigidly attached to each subject's forearm and upper arm. A trajectorizing algorithm was developed to estimate the three dimensional upper limb motion based on the measurements of the IMUs. A major advantage of the algorithm is that it allows the IMUs to be attached with arbitrary orientation to each limb and no manual anthropomorphic measurements need to be performed. By recording specific, known motions, the sensors can be calibrated with respect to their orientation in space and with respect to their orientation relative to their respective body segments. During the experiment, healthy subjects performed elbow flexion-extension motions that were recorded using the IMUs. To validate the system including the accuracy of recorded data and the correctness of the trajectorizing algorithm, an optical motion capture system was also used to record the same motions. Results showed that the proposed motion tracking system measured the elbow joint angles of the flexion-extension motions with high consistency with the measurements obtained from the optical motion capture system. Statistical analysis showed that joint angles between two systems are highly correlated. The error of elbow joint angles measured by our system yielded small root mean square error (RMSE) and small median absolute deviation (MAD). These results suggest that an IMU-based (more specifically, a gyroscope-based) motion tracking system can be realistically used to accurately track a patient's motion without the need of numerous sensors or an overly complicated set-up. DA - 2015/// PY - 2015/// DO - 10.1016/j.promfg.2015.07.128 VL - 3 SP - 192-199 SN - 2351-9789 KW - Healthcare KW - Motion tracking KW - Wearable wireless sensor ER - TY - CONF TI - Emulating cache organizations on real hardware using performance cloning AU - Wang, Y. P. AU - Solihin, Y. AB - Computer system designers need a deep understanding of end users' workload in order to arrive at an optimum design. Unfortunately, many end users will not share their software to designers due to the proprietary or confidential nature of their software. Researchers have proposed workload cloning, which is a process of extracting statistics that summarize the behavior of users' workloads through profiling, followed by using them to drive the generation of a representative synthetic workload (clone). Clones can be used in place of the original workloads to evaluate computer system performance, helping designers to understand the behavior of users workload on the simulated machine models without the users having to disclose proprietary or sensitive information about the original workload. In this paper, we propose infusing environment-specific information into the clone. This Environment-Specific Clone (ESC) enables the simulation of hypothetical cache configurations directly on a machine with a different cache configuration. We validate ESC on both real systems as well as cache simulations. Furthermore, we present a case study of how page mapping affects cache performance. ESC enables such a study at native machine speed by infusing the page mapping information into clones, without needing to modify the OS or hardware. We then analyze the factors that determine how page mapping impact cache performance, and how various applications are affected differently. C2 - 2015/// C3 - Ieee international symposium on performance analysis of systems and DA - 2015/// DO - 10.1109/ispass.2015.7095815 SP - 298-307 ER - TY - CONF TI - Distributed energy storage device based on a novel bidirectional DC-DC converter with 650V GaN transistors AU - Xue, F. AU - Yu, R. Y. AU - Yu, Wensong AU - Huang, A. Q. AB - This paper presents a distributed energy storage device (DESD) based on a novel isolated bidirectional DC-DC converter with 650V GaN transistors. The device integrates a low-voltage (13.2V) Li-ion battery pack, an embedded bidirectional DC-DC converter and wireless communication system. The three parts are packaged together, thus it can be directly connected to high-voltage (380V) DC grid, enabling a modular approach for battery energy storage systems. Two 650V enhancement mode GaN transistors are used at the high voltage side. Compared with Si device, three improvements can be achieved in the application: expanding the operation range to light load, reducing switching loss and EMI, increasing the total efficiency of charging and discharging operation. The power stage design as well as a loss analysis of GaN is based on a steady state analysis and PSpice simulation. A 400V to 12V DC, 1kW converter for 1kWh DESD prototype is designed, fabricated, and tested. Experimental results verify the validity of the proposed DESD and the performance improved by using GaN transistors. C2 - 2015/// C3 - Ieee international symposium on power electronics for distributed DA - 2015/// DO - 10.1109/pedg.2015.7223038 SP - 369–374 ER - TY - JOUR TI - Claim What You Need: A Text-Mining Approach on Android Permission Request Authorization AU - Wei, Mingkui AU - Gong, , Xi AU - Wang, Wenye T2 - 2015 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM) AB - Android is one of the most popular mobile operating systems nowadays, whose popularity, however, also attracts even more crafty developers to develop malicious softwares, or malwares, to exploit illegitimate means for profit. As a basic countermeasure, Android enforces the permission request scheme, in which an application (App) is required to present to the user the system resources (permissions) it will access, and ask user's approval before installation. However, this approach has been proven ineffective as it delegates the whole responsibility of decision- making to the user, who usually lacks the professional knowledge to comprehend the interpretation of a permission. Alternatively, many current researches focus on identifying potential malwares based on attributes of individual Apps, such as inspecting their source code, which, unfortunately, fall in another extreme which tend to make the decision for the user. Nevertheless, from the user's perspective, a satisfactory solution should be an approach which assists users to make the decision of the App installation on their own, by providing them with lucid reasons and requiring minimum professional knowledge. Based on the observation that the description of an App is the most direct interface to communicate its functionality to the user, in this paper we are motivated to explore the relationship between the description and the requested permissions of an App, and further build a model to predict proper permissions based on its description. Our evaluation with Apps collected from the Google Play Market shows that our prediction can achieve as high as 87% accuracy. In this regard, provide a user has full understanding of the description of an App, our model can act as an effective reminder to the user if the App tries to stealthily request permissions that are inconsistent with its description, which is a major character commonly exploited by malwares. DA - 2015/// PY - 2015/// DO - 10.1109/glocom.2015.7417472 SP - SN - 2334-0983 ER - TY - CONF TI - Characterizing conductive yarns for pressure sensors applications AU - Grant, E. AU - Livingston, Fred AU - Craver, M. AU - Hegarty-Craver, M. AU - McMaster, S. AB - Compression therapy is used to treat and manage chronic venous disease, deep venous thrombosis, and lymphedema. While successful, the means by which compression therapy improves vascular health remains unclear. Portable and wearable health monitoring devices have gained acceptance for managing such chronic conditions. Here, conductive knitted structures are experimented upon to test their suitability for use as wearable pressure sensors. C2 - 2015/// C3 - 2015 IEEE SENSORS - Proceedings DA - 2015/// DO - 10.1109/ICSENS.2015.7370189 SP - 108–111 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84962900952&partnerID=MN8TOARS ER - TY - CONF TI - Beamforming games with quantized CSI in two-user interference channels AU - Lee, J. H. AU - Dai, H. Y. AB - We consider a beamforming game of the transmitters in a two-user multiple-input single-output interference channel using limited feedback and investigate how each transmitter should find a strategy from the quantized channel state information (CSI). In the beamforming game, each transmitter (a player) tries to maximize the achievable rate (a payoff function) via a proper beamforming strategy. With the perfect CSI, each transmitter can know the exact achievable rate region, and hence can find the beamforming strategy corresponding to any point in the achievable rate region. With limited feedback, however, the transmitters can only conjecture the achievable rate region from the quantized CSI, so their optimal strategies may not be optimal anymore. Considering the quantized CSI at the transmitter, we first find the Nash equilibrium in a non-cooperative game. Then, we consider a cooperative game and modify the Nash bargaining solution. C2 - 2015/// C3 - 2015 International Conference on ICT Convergence (ICTC) DA - 2015/// DO - 10.1109/ictc.2015.7354802 SP - 1303-1306 ER - TY - CONF TI - Automatic data placement into GPU on-chip memory resources AU - Li, C. AU - Yang, Y. AU - Lin, Zhen AU - Huiyang AB - Although graphics processing units (GPUs) rely on thread-level parallelism to hide long off-chip memory access latency, judicious utilization of on-chip memory resources, including register files, shared memory, and data caches, is critical to application performance. However, explicitly managing GPU on-chip memory resources is a non-trivial task for application developers. More importantly, as on-chip memory resources vary among different GPU generations, performance portability has become a daunting challenge. In this paper, we tackle this problem with compiler-driven automatic data placement. We focus on programs that have already been reasonably optimized either manually by programmers or automatically by compiler tools. Our proposed compiler algorithms refine these programs by revising data placement across different types of GPU on-chip resources to achieve both performance enhancement and performance portability. Among 12 benchmarks in our study, our proposed compiler algorithm improves the performance by 1.76× on average on Nvidia GTX480, and by 1.61× on average on GTX680. C2 - 2015/// C3 - 2015 IEEE/ACM International Symposium on Code Generation and Optimization (CGO) DA - 2015/// DO - 10.1109/cgo.2015.7054184 SP - 23–33 ER - TY - CONF TI - Analyzing graphics processor unit (GPU) instruction set architectures AU - Mayank, K. AU - Dai, H. W. AU - Wei, J. Z. AU - Huiyang AB - Because of their high throughput and power efficiency, massively parallel architectures like graphics processing units (GPUs) become a popular platform for generous purpose computing. However, there are few studies and analyses on GPU instruction set architectures (ISAs) although it is wellknown that the ISA is a fundamental design issue of all modern processors including GPUs. C2 - 2015/// C3 - Ieee international symposium on performance analysis of systems and DA - 2015/// DO - 10.1109/ispass.2015.7095794 SP - 155–156 ER - TY - CONF TI - A two-layer coalitional game among rational cognitive radio users AU - fairness.}, Address= {Piscataway, N.J., U.S.A.} AU - {Yuan Lu and Duel-Hallen, A.}, Author= AU - Copyright= AB - In cognitive radio (CR) networks, secondary users (SUs) sense the spectrum to identify and possibly transmit over temporarily unoccupied channels that are licensed to primary users (PUs). However, when the received PU signal is weak, spectrum sensing by individual SUs becomes unreliable. To improve sensing accuracy, SUs can form disjoint coalitions and cooperate to discover idle time slots. These spectrum opportunities are then shared among the coalition members in a coordinated manner. It is proposed to decouple the coalition formation and the access (payoff) allocation problems by modeling these processes as a two-layer coalitional game. This game fosters cooperation by providing each SU with the access opportunities it deserves. Numerical results demonstrate that the proposed game outperforms previously investigated collaborative sensing and access approaches in terms of energy efficiency, throughput, and fairness. C2 - 2015/// C3 - 2015 49th Annual Conference on Information Sciences and Systems (CISS). Proceedings DA - 2015/// DO - 10.1109/ciss.2015.7086824 SP - – , UR - http://dx.doi.org/10.1109/CISS.2015.7086824 N1 - Keywords= {cognitive radio;energy conservation;game theory;radio spectrum management;signal detection;wireless channels;two-layer coalitional game;rational cognitive radio users;CR networks;secondary users;spectrum sensing accuracy improvement;primary users;received PU signal;individual SU;disjoint coalition member;idle time slots;coalition formation;access allocation problems;collaborative sensing;access approach;energy efficiency;temporarily unoccupied channels;}, Pages= {6 RN - Keywords= {cognitive radio;energy conservation;game theory;radio spectrum management;signal detection;wireless channels;two-layer coalitional game;rational cognitive radio users;CR networks;secondary users;spectrum sensing accuracy improvement;primary users;received PU signal;individual SU;disjoint coalition member;idle time slots;coalition formation;access allocation problems;collaborative sensing;access approach;energy efficiency;temporarily unoccupied channels;}, Pages= {6 ER - TY - CONF TI - A low-power integrated circuit for interfacing a capacitive micromachined ultrasonic transducer (CMUT) based resonant gas sensor AU - Kumar, M. AU - Seok, C. AU - Mahmud, M. M. AU - Zhang, X. AU - Oralkan, Omer AB - In this work we present a complete end-to-end interface for a capacitive micromachined ultrasonic transducer (CMUT) intended for low-power gas sensing applications. A prototype chip was designed in a 0.18-μm BiCMOS process. Different blocks (a BJT-based Colpitts oscillator, an inverter-based oscillator, a sine-to-square wave converter, a digital frequency counter, and a parallel-to-serial converter) required for the complete system are discussed, designed, and tested for their standalone performance. Consequently, a complete system interfaced with a 3.6-MHz CMUT and providing a digital frequency output is presented. With duty cycling for one measurement per minute the system consumed 10 μW power. C2 - 2015/// C3 - 2015 ieee sensors DA - 2015/// DO - 10.1109/icsens.2015.7370639 SP - 1781–1784 ER - TY - CONF TI - A compact, high-gain Q-band stacked power amplifier in 45nm SOI CMOS with 19.2dBm P-sat and 19% PAE AU - Tai, W. AU - Ricketts, D. S. C2 - 2015/// C3 - Ieee topical conference on power amplifiers for wireless and radio DA - 2015/// SP - 34-36 ER - TY - CONF TI - A capacitive micromachined ultrasonic transducer (CMUT) array as a low-power multi-channel volatile organic compound (VOC) sensor AU - Mahmud, M. M. AU - Kumar, M. AU - Zhang, X. AU - Yamaner, F. Y. AU - Nagle, H. T. AU - Oralkan, O. T2 - 2015 IEEE Sensors AB - In this study we extend our work on low-power CMUT chemical sensors from a single element to an array as a way to improve selectivity to volatile organic compound (VOC) analytes. A single channel of our sensor array comprises of a polymer-functionalized CMUT resonator in the feedback loop of a Colpitts oscillator, which consumes 0.76 mW, when operated continuously. Using our anodic-bonding based fabrication process, we fabricated 6-, 8-, and 15-channel prototype arrays with a standard deviation of 1 % in the parallel resonant frequency (4.5 MHz) in a 7×9-mm2 die area. We measured the response of three channels, one uncoated, one with a polyisobutylene (PIB) layer, and one with a polyvinyl alcohol (PVA) layer, to 20-ppm toluene vapor. Initial measurements show 1:13:37 ratio in the response of reference: PVA:PIB channels. C2 - 2015/11// C3 - 2015 IEEE SENSORS DA - 2015/11// DO - 10.1109/icsens.2015.7370208 SP - 181–184 PB - IEEE SN - 9781479982035 UR - http://dx.doi.org/10.1109/icsens.2015.7370208 DB - Crossref ER - TY - CONF TI - Wearable wireless sensors for chronic respiratory disease monitoring AU - Dieffenderfer, J. P. AU - Goodell, H. AU - Bent, B. AU - Beppler, E. AU - Jayakumar, R. AU - Yokus, M. AU - Jur, J. S. AU - Bozkurt, A. AU - Peden, D. AB - We present a wearable sensor system consisting of a wristband and chest patch to enable the correlation of individual environmental exposure to health response for understanding impacts of ozone on chronic asthma conditions. The wrist worn device measures ambient ozone concentration, heart rate via plethysmography (PPG), three-axis acceleration, ambient temperature, and ambient relative humidity. The chest patch measures heart rate via electrocardiography (ECG) and PPG, respiratory rate via PPG, wheezing via a microphone, and three-axis acceleration. The data from each sensor is continually streamed to a peripheral data aggregation device, and is subsequently transferred to a dedicated server for cloud storage. The current generation of the system uses only commercially-off-the-shelf (COTS) components where the entire electronic structure of the wristband has dimensions of 3.1×4.1×1.2 cm3 while the chest patch electronics has a dimensions of 3.3×4.4×1.2 cm3. The power consumptions of the wristband and chest patch are 78 mW and 33 mW respectively where using a 400 mAh lithium polymer battery would operate the wristband for around 15 hours and the chest patch for around 36 hours. C2 - 2015/// C3 - 2015 IEEE 12th International Conference on Wearable and Implantable Body Sensor Networks (BSN) DA - 2015/// DO - 10.1109/bsn.2015.7299411 ER - TY - CONF TI - Wearable SpO(2) and sleep posture monitoring system for obstructive sleep apnea patients AU - Brugarolas, R. AU - Valero-Sarmiento, J. M. AU - Brna, A. C2 - 2015/// C3 - 2015 Virtual Conference on Application of Commercial Sensors DA - 2015/// ER - TY - CONF TI - The future interaction between virtual aggregator-TSO-DSO to increase DG penetration AU - Sbordone, D. A. AU - Di Pietra, B. AU - Carlini, E. M. AU - Devetsikiotis, M. AB - The increasing integration of massive quantities of generation from Renewable Energy Sources (RES) constitutes a challenge for the pan-European system. Reserve provision for the balancing of the network is an important service that, in principle, should be provided by all the units connected to the network, including RES generators themselves as well as flexible loads and storage systems. However, these resources have big peculiarities tied with their relevant technologies and could, beyond providing local services within the distribution grids (e.g. voltage regulation, congestion management), be available to provide reserve for the entire system, through the connection points to the transmission grid. This paper shows a more advanced dispatching management of distribution systems by resorting to more advanced Information and Communications Technology(ICT) systems able to transform distribution from a “passive” into an “active” system and market architectures able to incorporate scattered bids coming from distributed generation and active load. A delicate point is the interface between transmission and distribution that has to be managed in a coordinated manner between Transmission System Operators (TSO) and Distribution System Operators (DSOs) in order to achieve an overall efficiency target. ICT should also be key to allow a strict real-time coordination of the different subjects that are in charge to actuate the provision of ancillary services. Further, the paper shows as new actors could appear in the system like the “aggregators” who interface with the Market Operator to submit the bids for the provision of the services, with the local TSO to receive the consequent dispatching orders, with to the aggregated distributed resources (generation, flexible demand, storage) and with to the involved DSOs, in order to communicate how each dispatching order will in turn be dispatched among the distributed resources it aggregates. C2 - 2015/// C3 - 2015 International Conference on Smart Grid and Clean Energy Technologies (ICSGCE) DA - 2015/// DO - 10.1109/icsgce.2015.7454296 SP - 201-205 ER - TY - CONF TI - Textile sensor system for electrocardiogram monitoring AU - Gonzales, L. AU - Walker, K. AU - Keller, K. AU - Beckman, D. AU - Goodell, H. AU - Wright, G. AU - Rhone, C. AU - Emery, A. AU - Gupta, Rachana AB - Wearable self-powered medical devices have long been a goal of the medical community. The ability to constantly monitor the patient's vital signs for abnormalities, in addition to alerting first responders to immediate problems, would allow for more rapid medical treatment. As the population of the United States ages, low-cost and ubiquitous medical devices will improve the ability of medical personnel to diagnose potential health issues early, thus increasing the survival rate and decreasing the potential complications. Electrocardiograms are a major focus of the medical community due to the prevalence of heart issues among elderly Americans, and as the cost of sensors and wireless communication decreases, new devices are possible. This paper describes a Bluetooth-based, dry electrode electrocardiogram monitoring system seamlessly integrated into a T-shirt. The shirt used three dry silver-based electrodes to collect the ECG signal and streamed the resulting signal to an Android smartphone for analysis. C2 - 2015/// C3 - 2015 Virtual Conference on Application of Commercial Sensors DA - 2015/// DO - 10.1109/vcacs.2015.7439568 ER - TY - CONF TI - Spectral estimation in highly transient data AU - Emrani, S. AU - Krim, H. AB - We propose a new framework for estimating different frequencies in piece-wise periodic signals with time varying amplitude and phase. Through a 3-dimensional delay embedding of the introduced model, we construct a union of intersecting planes where each plane corresponds to one frequency. The equations of each of these planes only depend on the associated frequency, and are used to calculate the tone in each segment. A sparse subspace clustering technique is utilized to find the segmentation of the data, and the points in each cluster are used to compute the normal vectors. In the presence of white Gaussian noise, principal component analysis is used to robustly perform this computation. Experimental results demonstrate the effectiveness of the proposed framework. C2 - 2015/// C3 - 2015 23rd european signal processing conference (eusipco) DA - 2015/// DO - 10.1109/eusipco.2015.7362678 SP - 1721-1725 ER - TY - JOUR TI - SourceMark: A Source-Level Approach for Identifying Architecture and Optimization Agnostic Regions for Performance Analysis AU - Agrawal, Abhinav AU - Wibowo, Bagus AU - Tuck, James T2 - 2015 IEEE INTERNATIONAL SYMPOSIUM ON WORKLOAD CHARACTERIZATION (IISWC) AB - Computer architects often evaluate performance on only parts of a program and not the entire program due to long simulation times that could take weeks or longer to finish. However, choosing regions of a program to evaluate in a way that is consistent and correct with respect to different compilers and different architectures is very challenging and has not received sufficient attention. The need for such tools is growing in importance given the diversity of architectures and compilers in use today. In this work, we propose a technique that identifies regions of a desired granularity for performance evaluation. We use a source-to-source compiler that inserts software marks into the program's source code to divide the execution into regions with a desired dynamic instruction count. An evaluation framework chooses from among a set of candidate marks to find ones that are both consistent across different architectures or compilers and can yield a low run-time instruction overhead. Evaluated on a set of SPEC applications, with a region size of about 100 million instructions, our technique has a dynamic instruction overhead as high as 3.3% with an average overhead of 0.47%. We also demonstrate the scalability of our technique by evaluating the dynamic instruction overhead for regions of finer granularity and show similar small overheads, of the applications we studied, we were unable to find suitable fine grained regions only for 462.libquantum and 444.namd. Our technique is an effective alternative to traditional binary-level approaches. We have demonstrated that a source-level approach is robust, that it can achieve low overhead, and that it reduces the effort for bringing up new architectures or compilers into an existing evaluation framework. DA - 2015/// PY - 2015/// DO - 10.1109/iiswc.2015.27 SP - 160-171 ER - TY - CONF TI - Self-powered wearable sensor platforms for wellness AU - Misra, V. AU - Lach, J. AU - Bozkurt, A. AU - Calhoun, B. AU - Datta, S. AU - Oralkan, O. C2 - 2015/// C3 - 2015 International Conference on Compilers, Architecture and Synthesis for Embedded Systems (CASES) DA - 2015/// SP - 187-187 ER - TY - CONF TI - Investigation of series DC active filter and hybrid AC active filter performance in medium voltage DC amplfier AU - Beddingfield, R. AU - Davis, A. AU - Mirzaee, H. AU - Bhattacharya, Subhashish AB - To further improve energy management, the US navy is exploring medium-voltage DC as the power supply of choice for next generation integrated power systems (NGIPS). Using the mature technology of multi-pulse thyristor bridge rectifiers, viable topologies are proposed that meet power density expectations. However, due to the non-linear ripple associated with thyristor commutations in such active front-ends (AFEs), a high bandwidth series AC active filter is used to smooth out the current harmonics. Similarly, a high bandwidth hybrid DC active filter is used for DC bus smoothing and improved dynamic performance. This paper will investigate the combined performance and consequential interactions of both active filters. C2 - 2015/// C3 - 2015 IEEE Electric Ship Technologies Symposium, ESTS 2015 DA - 2015/// DO - 10.1109/ests.2015.7157880 SP - 161-166 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84945919142&partnerID=MN8TOARS ER - TY - CONF TI - G2G: Privacy-preserving group matching for proximity-based mobile social networks AU - Zhu, X. Y. AU - Chen, Z. B. AU - Wang, Wenye AB - The explosive development of mobile devices and position systems makes it possible and meaningful for Proximity-based Mobile Social Networks (PMSNs), in which social group networking is among the most prominent features. In order to choose a suitable friend group, a group needs to find another group in vicinity and computes the matching degree based on their attributes. Then, they decide whether to make new social interactions through WiFi/Bluetooth interfaces embedded in their mobile devices according to the matching information. However, since group attributes usually contain some sensitive information, users may have increasing privacy concerns and do not want to reveal them to strangers. In this paper, we propose G2G, a novel privacy-preserving group matching mechanism, which can support group matching with preserving the privacy of all group members by applying permutation function. Considering a few potential attacks, we design an enhanced version G2G+, which can further improve group privacy. By detailed analysis and evaluation, we demonstrate that the proposed schemes have a desirable performance on security, efficiency and communication traffic. C2 - 2015/// C3 - 2015 IEEE/CIC International Conference on Communications in China (ICCC) DA - 2015/// DO - 10.1109/iccchina.2015.7448721 ER - TY - CONF TI - Emergence of core-periphery structure from local node dominance in social networks AU - Gamble, J. AU - Chintakunta, H. AU - Krim, H. AB - There has been growing evidence recently for the view that social networks can be divided into a well connected core, and a sparse periphery. This paper describes how such a global description can be obtained from local "dominance" relation ships between vertices, to naturally yield a distributed algorithm for such a decomposition. It is shown that the resulting core describes the global structure of the network, while also preserving shortest paths, and displaying "expander-like" properties. Moreover, the periphery obtained from this de composition consists of a large number of connected com ponents, which can be used to identify communities in the network. These are used for a `divide-and-conquer' strategy for community detection, where the peripheral components are obtained as a pre-processing step to identify the small sets most likely to contain communities. The method is illustrated using a real world network (DBLP co-authorship network), with ground-truth communities. C2 - 2015/// C3 - 2015 23rd european signal processing conference (eusipco) DA - 2015/// DO - 10.1109/eusipco.2015.7362716 SP - 1910-1914 ER - TY - CONF TI - Design and implementation of a sensorimotor network for chemical sensing using a mobile robot platform AU - Craver, M. AU - Grant, E. AB - Many current robotic systems are application-specific and have difficulty if the environment changes. These controllers do not scale well with increased task complexity, and rely on widely used high quality sensors. However, biological systems exhibit impressive adaptability. Therefore, self-organizing architectures should be incorporated into robotic systems to allow for emergent intelligence and robustness given less than optimal sensors and environments. In this study, a flat, fully-connected sensorimotor architecture was implemented on the EvBot III platform for the application of chemical sensing. The network was trained to associate increased alcohol concentration with increased battery charge. Seven training and testing experiments were conducted using different learning protocols. Although the sensorimotor network was shown to be a good initial step towards robotic reflex behavior, the robot was unable to successfully learn to home to the alcohol source. C2 - 2015/// C3 - 2015 IEEE International Conference on Multisensor Fusion and Integration for Intelligent Systems (MFI) DA - 2015/// DO - 10.1109/mfi.2015.7295806 SP - 184-189 ER - TY - CONF TI - Design and development of a 7.2 kV/200A hybrid circuit breaker based on 15 kV SiC emitter turn-off (ETO) thyristor AU - Huang, A. AU - Peng, C. AU - Song, X. Q. AB - This paper deals with the design of a 7.2 kV, 200 A hybrid AC circuit breaker employing a 15 kV Silicon Carbide (SiC) Emitter Turn-off (ETO) thyristor device as the main semiconductor switch and presents the test results to verify the functions of both the high voltage and low voltage electronic components of the medium voltage hybrid circuit breaker. The hybrid circuit breaker consists a fast acting mechanical switch, a low voltage commutating switch in series with that mechanical switch, a single 15 kV SiC ETO Thyristor device, and a stack of MOVs. This paper focuses on the electronic parts and a companion paper would elucidate the principle and operation of the fast acting mechanical switch. To fulfill bidirectional interruption capability of the high voltage semiconductor device, the SiC ETO is equipped with a low cost silicon diode bridge; a snubber capacitor is equipped in parallel with this diode bridge to alleviate voltage stress of the ETO during turn-off transients. A compact low voltage commutating switch based on silicon MOSFETs has been built and tested up to the full current rating. C2 - 2015/// C3 - 2015 IEEE Electric Ship Technologies Symposium (ESTS) DA - 2015/// DO - 10.1109/ests.2015.7157909 SP - 306-311 ER - TY - CONF TI - Design and characterization of breath analysis system for BAC prediction AU - Novak, T. AU - Thumula, N. AU - Chen, M. AU - Chen, Z. Q. C2 - 2015/// C3 - 2015 Virtual Conference on Application of Commercial Sensors DA - 2015/// ER - TY - CONF TI - Beyond the classroom and into the workplace: A learning experience for minority engineering students at north carolina state university AU - Pittman, B. C. C2 - 2015/// C3 - Edulearn15: 7th international conference on education and new learning technologies DA - 2015/// SP - 3936-3939 ER - TY - CONF TI - A resilient distributed energy management algorithm for economic dispatch in the presence of misbehaving generation units AU - Zeng, W. T. AU - Zhang, Y. AU - Chow, M. Y. C2 - 2015/// C3 - 2015 Resilience Week (RSW) DA - 2015/// SP - 12-16 ER - TY - CONF TI - A low-power wearable substance monitoring device AU - Howell, J. AU - Nag, A. AU - McKnight, M. AU - Narsipur, S. AU - Adelegan, O. AB - Alcohol and illicit drug abuse has become a major problem in recent years. According to US Census, there are approximately 40 million teenagers between the age of 10-19, and 20% of them have used an illegal substance at least once in their lifetime. Therefore, by extrapolation, there are potentially 8 million drug abuse cases across the board. This opens up a major requirement for drug monitoring and devices capable of monitoring drug abusers or helping addicts recover. Previous research has shown that certain quantifiable physiological parameters become altered following illicit drug or alcohol consumption. A solution that addresses the problem of detecting drug abuse is the core focus of this research. Initial steps have been focused on developing a device in the form of a wrist-watch that is capable of measuring selected physiological parameters using commercially available sensors. An Android application with algorithms capable of determining if the user is under the influence of alcohol or drugs has been developed and tested. C2 - 2015/// C3 - 2015 Virtual Conference on Application of Commercial Sensors DA - 2015/// DO - 10.1109/vcacs.2015.7439567 ER - TY - CONF TI - A Wearable bioimpedance spectroscopy system for characterizing fluid distribution in the lower limbs AU - Hegarty-Craver, M. AU - Grant, E. AU - Reid, L. AB - Compression therapy is used to treat and manage many vascular conditions. Unfortunately, the mechanism by which compression affects the body has remained largely uncharacterized because there are no wearable systems for continuously assessing blood flow and swelling. In this study, a wearable bioimpedance spectroscopy system was designed to measure changes in limb impedance. This system applied stimuli at frequencies ranging from 10-100 kHz while maintaining a constant current level. During controlled laboratory and wear tests, the system was found to be capable of resolving small changes in impedance. The newly designed system was an improvement over similar portable bioimpedance systems because it was smaller, consumed less power, and could select between a range of frequencies to study different physiological information. C2 - 2015/// C3 - 2015 IEEE International Conference on Multisensor Fusion and Integration for Intelligent Systems (MFI) DA - 2015/// DO - 10.1109/mfi.2015.7295829 SP - 328-333 ER - TY - CONF TI - 6.5 kV Si/SiC hybrid power module: An ideal next step? AU - Huang, A. Q. AU - Song, X. Q. AU - Zhang, L. Q. AB - Silicon carbide (SiC) power switches such as JFET or MOSFET have demonstrated their superior advantages over silicon (Si) power devices such as IGBT, especially in terms of significantly reduced switching losses. A major issue facing large scale adoption of SiC power devices is still the much higher cost. This paper proposes that Si/SiC hybrid power module (HPM) should be a natural next step moving forward for high voltage applications to address the cost issue. In the proposed Si/SiC HPM, a SiC JFET is connected in parallel with Si IGBT to combine the advantages of both IGBT and JFET. A 6.5 kV HPM is developed based on Si IGBT and SiC JFET as an example to demonstrate its superior cost/performance. The switching loss can be reduced by more than 70% at a cost of about 70% higher compared to Si IGBT. This work is especially essential for high voltage applications such as medium voltage motor drive, FACTS and HVDC systems. C2 - 2015/// C3 - 2015 IEEE International Workshop on Integrated Power Packaging (IWIPP) DA - 2015/// DO - 10.1109/iwipp.2015.7295979 SP - 64-67 ER - TY - CONF TI - Wide bandwidth for high-speed communication in mid-range, resonant WPT and RFID systems AU - Besnoff, Jordan AU - Ricketts, David S. AB - In this paper we present an experimental wireless power transfer (WPT) prototype that has achieved a 118 kHz power transfer bandwidth operating at the maximum achievable efficiency. Using a simulation and analytical model we show that the power transfer bandwidth of an optimally tuned WPT system is determined by the loaded Q of the system and not by the Q of the resonant tanks. This observation lead to the realization of a WPT communication system that can transmit data at high data rates greater than 8% of the carrier frequency, a data rate significantly greater than has previously been proposed for resonant WPT and RFID systems. C2 - 2015/9// C3 - 2015 European Microwave Conference (EuMC) DA - 2015/9// DO - 10.1109/eumc.2015.7345721 SP - 147-150 PB - Institute of Electrical and Electronics Engineers (IEEE) ER - TY - CONF TI - Using real-time system design methods to integrate SMPS control software with application software AU - Juneja, A. AU - Dean, A.G. AU - Bhattacharya, Subhashish AB - A switch-mode power supply (SMPS) converts power efficiently between different voltage levels, making power optimizations through voltage scaling feasible. SMPS controllers are generally dedicated hardware (analog/digital circuits, microcontroller (MCU), digital signal processor (DSP)), and so are expensive to add to very low cost embedded applications. In this work, we show how to integrate SMPS control software into the MCU running application software, which reduces system cost while increasing the design space and flexibility for developers. Real-time system design methods are employed to ensure SMPS voltage regulation quality, while retaining the original embedded application behavior. Our methods apply to a wide range of software task schedulers, from simple interrupt-based foreground/background systems to sophisticated preemptive real-time kernels (RTOS). We demonstrate our methods on a position-logging embedded system, with multiple voltage domains controlled in software, resulting in power savings. C2 - 2015/// C3 - 2015 IEEE Energy Conversion Congress and Exposition, ECCE 2015 DA - 2015/// DO - 10.1109/ecce.2015.7310485 SP - 5880-5887 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963563112&partnerID=MN8TOARS ER - TY - CONF TI - Three-phase 4.16 kV medium voltage grid tied AC-DC converter based on 15 kV/40 a SiC IGBTs AU - Madhusoodhanan, S. AU - Tripathi, A. AU - Mainali, K. AU - Kadavelugu, A. AU - Patel, D. AU - Bhattacharya, Subhashish AU - Hatua, K. AB - Recently, with the emergence of Wide Bandgap semiconductor devices having higher blocking voltage capabilities and higher switching speed, ac-dc converters for Medium Voltage (MV) and Low Voltage (LV) dc micro-grid applications are becoming popular. In this paper, the first time experimental demonstration of such a 3-phase, isolated ac-dc power converter based on the newly developed 15 kV/40 A SiC IGBT is presented for 4.16 kV ac distribution grid interface. The presented converter consists of two bidirectional stages — the 4.16 kV ac to 8 kV dc front end converter followed by an 8 kV dc to 480 V dc dual active bridge converter with high frequency isolation. These stages are switched at 5 kHz and 10 kHz respectively. The converter design is presented along with experimental validation on a prototype at 9.6 kW. C2 - 2015/// C3 - 2015 IEEE Energy Conversion Congress and Exposition, ECCE 2015 DA - 2015/// DO - 10.1109/ecce.2015.7310594 SP - 6675-6682 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963600033&partnerID=MN8TOARS ER - TY - JOUR TI - Spatial Locality-Aware Cache Partitioning for Effective Cache Sharing AU - Gupta, Saurabh AU - Zhou, Huiyang T2 - 2015 44TH INTERNATIONAL CONFERENCE ON PARALLEL PROCESSING (ICPP) AB - In modern multi-core processors, last-level caches (LLCs) are typically shared among multiple cores. Previous works have shown that such sharing is beneficial as different workloads have different needs for cache capacity, and logical partitioning of capacity can improve system performance. However, what is missing in previous works on partitioning shared LLCs is that the heterogeneity in spatial locality among workloads has not been explored. In other words, all the cores use the same block/line size in shared LLCs. In this work, we highlight that exploiting spatial locality enables much more effective cache sharing. The fundamental reason is that for many memory intensive workloads, their cache capacity requirements can be drastically reduced when a large block size is employed, therefore they can effectively donate more capacity to other workloads. To leverage spatial locality for cache partitioning effectively, we first propose a simple yet effective mechanism to measure both spatial and temporal locality at run-time. The locality information is then used to determine both the proper block size and the capacity assigned to each workload. Our experiments show that our Spatial Locality-aware Cache Partitioning (SLCP) significantly outperforms the previous works. We also present several case studies that dissect the effectiveness of SLCP compared to the existing approaches. DA - 2015/// PY - 2015/// DO - 10.1109/icpp.2015.24 SP - 150-159 SN - 0190-3918 KW - shared last level cache KW - cache partitioning KW - spatial locality KW - cache management KW - high bandwidth memory ER - TY - CONF TI - Sparse null space basis pursuit and analysis dictionary learning for high-dimensional data analysis AU - Bian, X. AU - Krim, H. AU - Bronstein, A. AU - Dai, L. Y. AB - Sparse models in dictionary learning have been successfully applied in a wide variety of machine learning and computer vision problems, and have also recently been of increasing research interest. Another interesting related problem based on a linear equality constraint, namely the sparse null space problem (SNS), first appeared in 1986, and has since inspired results on sparse basis pursuit. In this paper, we investigate the relation between the SNS problem and the analysis dictionary learning problem, and show that the SNS problem plays a central role, and may be utilized to solve dictionary learning problems. Moreover, we propose an efficient algorithm of sparse null space basis pursuit, and extend it to a solution of analysis dictionary learning. Experimental results on numerical synthetic data and real-world data are further presented to validate the performance of our method. C2 - 2015/// C3 - International conference on acoustics speech and signal processing DA - 2015/// DO - 10.1109/icassp.2015.7178678 SP - 3781-3785 ER - TY - CONF TI - Soft switching characterization of 15 kV SiC n-IGBT and performance evaluation for high power converter applications AU - Vechalapu, K. AU - Tripathi, A. AU - Mainali, K. AU - Baliga, B.J. AU - Bhattacharya, Subhashish AB - The 15 kV SiC IGBT with 2 μm and 5 μm field-stop buffer layer thicknesses are two state of the art HV SiC devices. These 15 kV SiC IGBTs generate high dv/dt with two slopes in punch through and non-punch through regions. To design 15 kV SiC IGBT with reduced dv/dt and single slope dv/dt similar to 10-15 kV SiC MOSFET, requires significantly larger drift epitaxial layer thickness and it increases the size and cost of the 15 kV SiC IGBT. This paper presents the zero voltage switching (ZVS) characteristics of 15 kV SiC N-IGBTs to reduce the dv/dt at switching pole along with reduction in the switching losses and increase in the switching frequency limits with external snubber capacitor. The ZVS characteristics are reported up to 9 kV dc bus voltage at 25°C and 150°C for both IGBTs. This paper also reports continuous mode experimental demonstration of zero voltage switching (ZVS) of 5 μm 15 kV IGBT in a medium voltage half bridge converter up to 7 kV dc bus voltage and calculation of power dissipation per IGBT module and its comparison of switching frequency limits with hard switching of half bridge converter. C2 - 2015/// C3 - 2015 IEEE Energy Conversion Congress and Exposition, ECCE 2015 DA - 2015/// DO - 10.1109/ecce.2015.7310246 SP - 4151-4158 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963579482&partnerID=MN8TOARS ER - TY - CONF TI - Real-time multiple DOA estimation of speech sources in wireless acoustic sensor networks AU - Ayllon, D. AU - Gil-Pita, R. AU - Rosa-Zurera, M. AU - Krim, H. AB - Indoor localization of multiple speech sources in wireless acoustic sensor networks (WASNs) is an open and interesting problem with many practical applications, but the presence of noise and reverberations complicates the problem. In this paper, a distributed algorithm for multiple DOA estimation of speech sources in WASNs is presented. The method exploits the sparsity of speech sources in the time-frequency domain to obtain DOA estimations locally in each node of the network. The DOA estimations of different nodes are further combined to increase the accuracy of the local DOA estimations. Since the local DOAs are estimated using only the microphones of the same node, the synchronization between input channels and localization of the microphones from different nodes are not an issue. C2 - 2015/// C3 - International conference on acoustics speech and signal processing DA - 2015/// DO - 10.1109/icassp.2015.7178463 SP - 2709-2713 ER - TY - CONF TI - Permanent magnet transverse flux machine with overlapping stator poles AU - Ahmed, A. AU - Wan, Z. AU - Husain, I. AB - A Transverse Flux Machine (TFM) topology with ring winding configuration is proposed. A novel approach for stator pole configuration is presented that ensures lower leakage between adjacent poles. The unique stator pole configuration permits an overlapping region between adjacent stator poles resulting in a significant improvement in space utilization that helps attain higher torque-to-volume ratio. In addition, the innovative pole design reduces the end winding length which helps reduce the copper mass. Simulation results are presented based on 3D Finite Element Analysis (FEA). Significant performance improvement was achieved compared to similar transverse flux machines. C2 - 2015/// C3 - 2015 ieee energy conversion congress and exposition (ecce) DA - 2015/// DO - 10.1109/ecce.2015.7309770 SP - 791-798 ER - TY - CONF TI - Operation of hybrid multi-terminal DC system under normal and DC fault operating conditions AU - Acharya, Sayan AU - Azidehak, A. AU - Vechalapu, K. AU - Kashani, M. AU - Chavan, G. AU - Bhattacharya, Subhashish AU - Yousefpoor, N. AB - Recently, multi-terminal DC (MTDC) system has received more attention in the power transmission areas. Development of modular structured power converter topologies has now enabled the power converter technology to attain high voltage high power ratings. Compared to current source converter technology, voltage source converters have several benefits including higher power quality, independent control of active and reactive power etc. This paper focuses on a unique MTDC system consisting of terminals with different converter topologies especially considering the fact that each of the terminals may be manufactured by different vendors. In this particular configuration, the MTDC system consists of four terminals namely two advanced modular multi-level converter with high frequency isolation, one standard modular multi-level converter (MMC) with half bridge sub modules and the fourth terminal is modular DC-DC converter which integrates PV along with a Battery energy storage system with the DC grid directly. This paper presents a system level study of hybrid MTDC System. Also the DC fault contingency case has been explored thoroughly. An algorithm has been proposed to prevent the system damage. All the cases have been demonstrated with the PSCAD simulation results. To show the system practically works in real time, the system is also evaluated in a unique real time platform, consisting of interconnected RTDS and OPAL RT systems. C2 - 2015/// C3 - 2015 IEEE Energy Conversion Congress and Exposition, ECCE 2015 DA - 2015/// DO - 10.1109/ecce.2015.7310417 SP - 5386-5393 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963585191&partnerID=MN8TOARS ER - TY - CONF TI - On the detection of abandoned objects with a moving camera using robust subspace recovery and sparse representation AU - Jardim, E. AU - Bian, X. AU - Silva, E. A. B. AU - Netto, S. L. AU - Krim, H. AB - We consider the application of sparse-representation and robust-subspace-recovery techniques to detect abandoned objects in a target video acquired with a moving camera. In the proposed framework, the target video is compared to a previously acquired reference video, which is assumed to have no abandoned objects. The detection method explores the low-rank similarities among the reference and target videos, as well as the sparsity of the differences between the two video sequences caused by the unexpected object in the target video. A three-step procedure is then presented adapting a previous low-rank and sparse image representation to the problem at hand. Performance of the proposed technique is verified using a large video database for abandoned-object detection in a cluttered environment. Results demonstrate the technique effectiveness even in the presence of some significant camera shake along its trajectory. C2 - 2015/// C3 - International conference on acoustics speech and signal processing DA - 2015/// DO - 10.1109/icassp.2015.7178179 SP - 1295-1299 ER - TY - CONF TI - MVDC microgrids enabled by 15kV SiC IGBT based flexible three phase dual active bridge isolated DC-DC converter AU - Tripathi, A. AU - Mainali, K. AU - Madhusoodhanan, S. AU - Patel, D. AU - Kadavelugu, A. AU - Hazra, S. AU - Bhattacharya, Subhashish AU - Hatua, K. AB - The Dual Active Bridge (DABC) dc-dc converter is an integral part of the recently popular Medium-Voltage (MV) dc micro-grid application due to its high-power density. The advent of 15kV SiC IGBT and 10kV SiC MOSFET, has enabled a non-cascaded MV and Medium-Frequency (MF) DABC converter which is expected to have higher MTBF than the cascaded H-bridge topology due to relatively small number of switches. A composite DABC three-level three-phase topology earlier proposed for MV-MF application, has dual secondary side bridges to meet the rated load conditions. The duty-ratio control of the primary and the independent operation of dual secondary bridges as a single active bridge, can be utilized to solve the light load ZVS problem. This paper presents flexible operating modes of this MV DABC for ZVS and higher efficiency. The MV DABC simulations are presented to bring out the advantages of this topology in wide range load and voltage-ratio conditions. This paper reports 8kV experimental validation of this DABC while using 15kV/40A SiC IGBTs on the MV side. C2 - 2015/// C3 - 2015 IEEE Energy Conversion Congress and Exposition, ECCE 2015 DA - 2015/// DO - 10.1109/ecce.2015.7310462 SP - 5708-5715 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963593747&partnerID=MN8TOARS ER - TY - JOUR TI - Intra-Operation Dynamic Voltage Scaling AU - Moore, Daniel R. AU - Dean, Alexander G. T2 - 2015 IEEE 3RD INTERNATIONAL CONFERENCE ON CYBER-PHYSICAL SYSTEMS, NETWORKS, AND APPLICATIONS CPSNA 2015 AB - Embedded peripheral devices are often specified with a range of performance characteristics that are determined by their supply voltage. Recent research explored the benefits of modulating peripheral supply voltage with task-level granularity. With Intra-Operation Dynamic Voltage Scaling (IODVS), we further reduce the energy consumption of peripheral devices by modulating the peripheral supply voltage at critical states occurring during operation of the peripheral device. IODVS is designed to have minimal impact on CPU utilization through the use of a lookup table that designates an ideal voltage on a per-state basis. IODVS is unique in that during high-performance states such as data-transmission, peripherals can have the high supply voltage required to reduce overall energy-delay product. Likewise, during low-performance states such as mandatory delays, the system decreases peripheral domain voltage thus reducing energy consumption without adversely affecting performance or correctness. We demonstrate this method on various peripherals common to wireless sensor nodes and have found total energy savings of up to 40%. DA - 2015/// PY - 2015/// DO - 10.1109/cpsna.2015.22 SP - 70-77 KW - Keywords Embedded Systems KW - Dynamic Voltage Scaling (DVS) KW - Dynamic Power Management (DPM) KW - low-power KW - low-energy KW - wireless sensor node (WSN) KW - energy-aware design ER - TY - CONF TI - Economic impact of data integrity attacks on distributed DC optimal power flow algorithm AU - Duan, J. AU - Zeng, W. T. AU - Chow, M. Y. AB - A variety of distributed energy management algorithms are being developed for DC optimal power flow (DCOPF) application owing to their flexibility and scalability in the presence of high distributed Energy Resources (DERs) penetration. However, these algorithms are vulnerable to malicious cyber attacks due to the absence of control centers. In this paper, we study and analyze the economic impact of the data integrity attack to distributed DC-OPF algorithms. In particular, we demonstrate how a malicious generator could gain more economic profit by compromising the distributed controller of its bus, modifying the information sent to neighboring buses and manipulating the power dispatch commands. To our best knowledge, this is the first paper to show the economic impact of malicious attacks in distributed DC-OPF. By revealing such potential financial risks, this paper conveys the message that besides the efforts of designing novel distributed energy management algorithms to address the DERs integration challenges, it is equally important to protect the distributed energy management algorithms from possible malicious attacks to avoid potential economic loss. The economic impact of the data integrity attack is illustrated in the Future Renewable Electric Energy Delivery and Management (FREEDM) system. C2 - 2015/// C3 - 2015 north american power symposium (naps) DA - 2015/// DO - 10.1109/naps.2015.7335167 ER - TY - CONF TI - Doubly-fed induction generator enabled power generation in ocean wave energy conversion system AU - Hazra, S. AU - Dean, A.G. AU - Bhattacharya, Subhashish AB - This paper proposes a power architecture to utilize doubly-fed induction generator (DFIG) for power generation from oscillating wave energy converter (WEC). Unlike in wind energy conversion system, the stator circuit of the DFIG can not be tied directly with the grid in wave energy conversion system (WECS). In WECS, the speed of the DFIG oscillates from one direction to another. Due to the change of direction of the speed, the stator of the DFIG is proposed to be connected with the grid with switched phase sequence. Also, at low operating speed the DFIG slip speed increases which requires higher voltage rating of the rotor side converter. Therefore, to operate the DFIG with limited rotor side voltage the stator circuit is short circuited at low speed. With these modifications, the DFIG based power architecture is proposed to generate power from WECS. In this paper, the overall hardware and control architecture and system operation are presented. System operation is validated through simulation in MATLAB-Simulink platform. For simulation of the whole system, a WEC model is considered. C2 - 2015/// C3 - 2015 IEEE Energy Conversion Congress and Exposition, ECCE 2015 DA - 2015/// DO - 10.1109/ecce.2015.7310637 SP - 6978-6985 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963576837&partnerID=MN8TOARS ER - TY - CONF TI - Distributed optimal generation dispatch considering transmission losses AU - Zhang, Y. AU - Chow, M. Y. AB - Economically dispatching the generation is essential to the efficient operations of a power system. As an approximation to the nonconvex AC optimal power flow (ACOPF) problem, the convex DC optimal power flow (DCOPF) problem is used in many studies. In this paper, the DCOPF with transmission line losses (DCOPFL) is formulated to better approximate the ACOPF problem. A Cooperative Distributed Optimal Dispatch (CDOD) algorithm is proposed to solve the DCOPFL problem in a distributed manner. The convergence and correctness of the CDOD algorithm are verified through two representative case studies. The DCOPFL is also verified to have the smallest approximation error comparing with DCOPF and economic dispatch considering transmission losses (EDL) by taking ACOPF solution as reference. C2 - 2015/// C3 - 2015 north american power symposium (naps) DA - 2015/// DO - 10.1109/naps.2015.7335143 ER - TY - CONF TI - Discontinuous mode sparse Dyna-C rectifier for efficient AC/DC power conversion AU - De, A. AU - Bhattacharya, Subhashish AB - The paper investigates a soft-switching buck-boost AC/DC converter. The proposed converter uses 4 active switches and overcomes the various shortcomings of conventional rectifiers. The proposed controller facilitates discontinuous mode of operation that leads to zero current turn on and turn off. A nonlinear average phase charge based controller is presented which ensures zero harmonic current in the input phases. The switching scheme has been so arranged that the diodes always turn off at zero voltage thereby reducing the reverse recovery stress and losses. These modifications lead to a considerable reduction of switching loss and device stress as compared to the conventional control scheme of Dyna-C. Owing to soft switching states, the frequency of operation can be pushed even higher thereby reducing the size of the passive components. An alternate switching pattern has also been discussed which enables soft switched turn off of active switches. Design guidelines to construct an optimized inductor has also been discussed. Simulation and initial experimental results are presented to validate operation of the control scheme. A comparison study has been carried out to choose the appropriate set of devices for this application. The research shows that SiC-MOS with low cost Si-PiN Diode results in impressive reduction in overall losses. The topology is expected to offer compact, fast, efficient and inexpensive solution to the present AC/DC power conversion requirements. C2 - 2015/// C3 - 2015 IEEE Energy Conversion Congress and Exposition, ECCE 2015 DA - 2015/// DO - 10.1109/ecce.2015.7310606 SP - 6762-6769 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963576495&partnerID=MN8TOARS ER - TY - CONF TI - Development of 6kV SiC hybrid power switch based on 1200V SiC JFET and MOSFET AU - Ni, X. J. AU - Gao, R. AU - Song, X. Q. AU - Huang, A. Q. AU - Yu, Wensong AB - Series-connected power switch provides a viable solution to implement high voltage and high frequency converters. By using the commercially available 1200V Silicon Carbide (SiC) Junction Field Effect Transistor (JFET) and Metal Oxide semiconductor Filed-effect Transistor (MOSFET), a 6 kV SiC hybrid power switch concept and its application are demonstrated. To solve the parameter deviation issue in the series device structure, an optimized voltage control method is introduced, which can guarantee the equal voltage sharing under both static and dynamic state. Without Zener diode arrays, this strategy can significantly reduce the turn-off switching loss. Moreover, this hybrid MOSFET-JFETs concept is also presented to suppress the silicon MOSFET parasitic capacitance effect. In addition, the positive gate drive voltage greatly accelerates turn-on speed and decreases the switching loss. Compared with the conventional super-JFETs, the proposed scheme is suitable for series-connected device, and can achieve better performance. The effectiveness of this method is validated by simulations and experiments, and promising results are obtained. C2 - 2015/// C3 - 2015 ieee energy conversion congress and exposition (ecce) DA - 2015/// DO - 10.1109/ecce.2015.7310240 SP - 4113–4118 ER - TY - CONF TI - Design of a modular E-core flux concentrating axial flux machine AU - Husain, T. AU - Sozer, Y. AU - Husain, I. AU - Muljadi, E. AB - In this paper a novel E-Core axial flux machine is proposed. The machine has a double stator-single rotor configuration with flux concentrating ferrite magnets, and pole windings across each leg of an E-Core stator. E-Core stators with the proposed flux-concentrating rotor arrangement result in better magnet utilization and higher torque density. The machine also has a modular structure facilitating simpler construction. This paper presents a single phase and a three-phase version of the E-Core machine. Case study for a 1.1 kW, 400 rpm machine for both the single phase and three-phase axial flux machine is presented. The results are verified through 3D finite element analysis. C2 - 2015/// C3 - 2015 ieee energy conversion congress and exposition (ecce) DA - 2015/// DO - 10.1109/ecce.2015.7310392 SP - 5203-5210 ER - TY - CONF TI - Concentrated winding segmented rotor switched reluctance machine (SRM) using three-phase standard inverters AU - Kabir, M. A. AU - Husain, I. AB - Two new topologies of three-phase segmented rotor switched reluctance machine (SRM) that enables the use of standard voltage source inverters (VSIs) for its operation are presented. The topologies has shorter end-turn length, axial length compared to SRM topologies that use three-phase inverters; compared to the conventional SRM (CSRM), these new topologies has the advantage of shorter flux paths that results in lower core losses. FEA based optimization have been performed for a given design specification. The new concentrated winding segmented SRMs demonstrate competitive performance with three-phase standard inverters compared to CSRM. C2 - 2015/// C3 - 2015 ieee energy conversion congress and exposition (ecce) DA - 2015/// DO - 10.1109/ecce.2015.7310443 SP - 5567-5572 ER - TY - CONF TI - Comparison of DC fault current limiting capability of various modular structured multilevel converters within a multi-terminal DC grid AU - Acharya, Sayan AU - Vechalapu, K. AU - Bhattacharya, Subhashish AU - Yousefpoor, N. AB - With the development of Modular structured Voltage Source Converters (VSC), Multi-Terminal DC (MTDC) transmission systems have now become a feasible solution to transmit power at high voltage which greatly improves the electric power transmission system. The MTDC grid has lower capital costs and lower losses than an equivalent AC transmission system. Thus for long distance power transmission MTDC grid becomes a very attractive solution. Since the MTDC network is now built based on VSCs, it automatically offers better quality of transmitted power along with more flexibility in power transmission over the conventional current source converters. However, VSC based MTDC transmission systems are vulnerable to DC side fault and expensive DC circuit breakers are required to protect them against DC fault. This paper compares the DC short circuit fault response of different modular multi-level converters (MMC) inside a MTDC system. For the comparison purpose two different kind of MMC topologies have been considered namely, Modular Multi-level Converter (MMC) with High Frequency DC/DC Isolation Stage and MMC with full bridge sub modules. The paper analyzes the fault current limiting capabilities of each of the converters. PSCAD simulation is also done to prove the relevance of the analysis. C2 - 2015/// C3 - 2015 IEEE Energy Conversion Congress and Exposition, ECCE 2015 DA - 2015/// DO - 10.1109/ecce.2015.7310107 SP - 3184-3191 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963525471&partnerID=MN8TOARS ER - TY - CONF TI - CSI-based device-free gesture detection AU - Xiong, H. AU - Gong, F. Y. AU - Qu, L. AU - Du, C. L. AU - Harfoush, K. C2 - 2015/// C3 - 2015 12th International Conference on High-Capacity Optical Networks and Enabling/Emerging Technologies (HONET) DA - 2015/// SP - 122-126 ER - TY - CONF TI - Auto-inspection and permitting with a PV Utility Interface (PUI) for residential plug-and-play solar photovoltaic unit AU - Khan, M.T.A. AU - Norris, G. AU - Chattopadhyay, R. AU - Husain, I. AU - Bhattacharya, Subhashish AB - Renewable energy resources are becoming popular with mass adoption in residential and commercial applications because of gradual cost reduction along with continuous technical advancements. Photovoltaic (PV) energy is one of the biggest players of renewable energy installations although soft costs remain as a major barrier for higher penetration of PV systems. To significantly lower the soft costs related to residential photovoltaic system installations, a Plug-and-Play (PnP) system has been designed which allows for a quick, low-cost installation. The method is much less invasive and labor intensive than traditional installation methods involving drilling holes through walls and installing additional panel boxes within the house. This paper presents the PnP electrical system, with emphasis on the controls, software, and system level communications within the system. A PV Utility Interface (PUI) circuit has been developed for automated electrical safety checks and authentication for implementing the PnP PV system. A data protocol has been used to deal with the master-slave controller setup in the system. C2 - 2015/// C3 - 2015 IEEE Energy Conversion Congress and Exposition, ECCE 2015 DA - 2015/// DO - 10.1109/ecce.2015.7310469 SP - 5763-5770 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963549051&partnerID=MN8TOARS ER - TY - CONF TI - Assessment of volt/var control schemes at power distribution level AU - Shi, Yue AU - Baran, Mesut AB - This paper proposes a general approach to assess the effectiveness of a Volt/Var control (VVC) scheme for a power distribution system. It first provides a comprehensive list of possible performance metrics for VVC. Then, a power flow based method is proposed to estimate the metrics considered. To illustrate the approach, a case study for a given VVC scheme on a test feeder with high PV penetration is also presented. C2 - 2015/// C3 - 2015 north american power symposium (naps) DA - 2015/// DO - 10.1109/naps.2015.7335108 ER - TY - CONF TI - An improved distance relay model with directional element, and memory polarization for TCD based fault propagation studies AU - Jain, R AU - Lukic, SM AU - Chhokra, A AU - Mahadevan, N AU - Dubey, A AU - Karsai, G T2 - IEEE AB - Modern Power Systems have evolved into a very complex network of multiple sources, lines, breakers, loads and others. The performance of these interdependent components decide the reliability of the power systems. A tool called “Reasoner” is being developed to deduce fault propagations using a Temporal Causal Diagram (TCD) approach. It translates the physical system as a Cause-effect model. This work discusses the development of an advanced distance relay model, which monitors the system, and challenges the operation of reasoner for refinement. Process of generation of a Fault and Discrepancy Mapping file from the test system is presented. This file is used by the reasoner to scrutinize relays' responses for active system faults, and hypothesize potential mis-operations (or cyber faults) with a confidence metric. Analyzer (relay model) is integrated to OpenDSS for fault analysis. The understanding of the system interdependency (fault propagation behavior) using reasoner can make the grid more robust against cascaded failures. C2 - 2015/// C3 - 2015 North American Power Symposium (NAPS) DA - 2015/// DO - 10.1109/naps.2015.7335206 SP - 1-6 ER - TY - CONF TI - An Isolated Bi-directional high-frequency-AC link DC-AC converter using hybrid SiC switches with carrier-based unipolar modulation technique AU - Wang, M. Q. AU - Huang, Q. Y. AU - Yu, Wensong AU - Huang, A. Q. AB - A novel isolated bi-directional soft-switched high-frequency-AC (HFAC) link DC-AC converter using SiC MOSFET and IGBT hybrid switches is presented in this paper. The DC-AC converter is composed of a full-bridge (FB) inverter cascaded with a cycloconverter through a high-frequency transformer. In order to increase the converter efficiency, and to push the transformer frequency to 50-100 kHz, SiC MOSFETs are preferable devices compared to the traditional IGBTs or SCRs. A unipolar-SPWM-oriented modulation technique is proposed to realize zero-voltage-switching (ZVS) for FB and zero-current-switching (ZCS) for cycloconverter, and to suppress the voltage spikes introduced by the transformer leakage inductance as well. With the novel modulation technique, half of the AC switches in the cycloconverter work under transformer frequency and the rest work at line frequency (60 Hz). Therefore a SiC-IGBT hybrid switch structure is proposed for the cycloconverter. Simulation model and a 400 VDC to 240 VAC, 3 kW prototype have been developed to validate the effectiveness and performance of the proposed unipolar soft-switching modulation technique and the hybrid switch structure. C2 - 2015/// C3 - 2015 IEEE 2nd International Future Energy Electronics Conference (IFEEC) DA - 2015/// DO - 10.1109/ifeec.2015.7361625 ER - TY - CONF TI - A past mechanical switch for medium voltage hybrid DC and AC circuit breakers AU - Peng, C. AU - Husain, I. AU - Huang, A. AU - Lequesne, B. AU - Briggs, R. C2 - 2015/// C3 - 2015 ieee energy conversion congress and exposition (ecce) DA - 2015/// SP - 5211-5218 ER - TY - CONF TI - A novel control approach for protection of multi-terminal VSC based HVDC transmission system against DC faults AU - Mobarez, M. AU - Kashani, M.G. AU - Chavan, G. AU - Bhattacharya, Subhashish AB - Overall performance of the voltage source converters (VSCs) has improved during the recent years. Improvement of the VSCs along with the attractive features of the VSC based high voltage direct current (HVDC) transmission systems over the thyristor based HVDC transmission systems make it possible to build multiterminal (MT) VSC HVDC transmission systems. However, the VSCs are vulnerable against dc side faults and a method needs to be employed to extinguish the dc fault current. In this paper, three different configurations of solid state dc circuit breakers (CB) for protection purposes are studied. Moreover, a new control method to protect the VSCs against the dc side fault is proposed, the new method makes it possible to extinguish the dc fault current with the existing ac breakers on the ac side or with the lower rating solid state (SS) DCCBs. The performance of the SS DCCBs and the proposed method are studied using Real Time Digital Simulator (RTDS). C2 - 2015/// C3 - 2015 IEEE Energy Conversion Congress and Exposition, ECCE 2015 DA - 2015/// DO - 10.1109/ecce.2015.7310254 SP - 4208-4213 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963632405&partnerID=MN8TOARS ER - TY - CONF TI - 6.5kV FREEDM-Pair: Ideal high power switch capitalizing on Si and SiC AU - Song, X. Q. AU - Huang, A. Q. AB - 6.5kV Si IGBTs have been used widely in median voltage drives, HVDC, FACTs and traction systems. However, the large switching losses of the Si IGBT limit its switching frequency to only 100Hz to 1kHz. On the other hand, wide bandgap (WBG)power devices such as Silicon Carbide (SiC) MOSFET or JFET have demonstrated their superior advantages over Si IGBT, especially in terms of significantly reduced switching losses. A major issue facing large scale adoption of SiC power devices is still the much higher cost. This paper proposes that the FREEDM-Pair, a Si/SiC hybrid switch, should be an ideal and cost effective switch for high power applications. In the proposed FREEDM-Pair, a SiC MOSFET is connected in parallel with Si IGBT to combine the advantages of IGBT and MOSFET. A 6.5kV FREEDM-Pair is developed as an example to demonstrate its superior cost/performance. Experimental results demonstrated 70% switching loss reduction and the FREEDM-Pair cost is estimated to be only 50% higher than 6.5kV Si IGBT. C2 - 2015/// C3 - 2015 17th european conference on power electronics and applications (epe'15 ecce-europe) DA - 2015/// DO - 10.1109/epe.2015.7309243 ER - TY - JOUR TI - The Struggle for Pakistan: A Muslim homeland and global politics AU - Gilmartin, D. T2 - Journal of Asian Studies DA - 2015/// PY - 2015/// VL - 74 IS - 4 SP - 1056-1057 ER - TY - CONF TI - Solid state transformer (SST) as an energy router: Economic dispatch based energy routing strategy AU - Hambridge, S. AU - Huang, A. Q. AU - Yu, R. Y. AB - The Solid State Transformer (SST) is a revolutionary technology being developed by the authors. It has a tremendous number of features, which include power management, fault management and energy management. Its autonomous and distributed power management capability enables large-scale integration of distributed energy resources (DER) into the power grid. Specifically, it supports AC or DC connected Energy Cells: a combination of DERs, energy storage devices and loads. The SST can achieve real-time power flow regulation via the Energy Cell, therefore forming the foundation of its capability to become a real-time Energy Router. This paper introduces an economic based energy routing strategy that utilizes energy storage to reduce consumption of grid power. Predictive photovoltaic and load forecasting are used to optimize charging and discharging of energy storage. This rule-based algorithm is implemented and demonstrated in a SST enabled 380 V DC Energy Cell. C2 - 2015/// C3 - 2015 ieee energy conversion congress and exposition (ecce) DA - 2015/// DO - 10.1109/ecce.2015.7309991 SP - 2355-2360 ER - TY - CONF TI - Single-phase distributed generation synchronization with a distorted or weak grid AU - Alkuhayli, A. AU - Safayet, A. AU - Husain, I. AB - Fast and accurate synchronization of power electronics interfaced distributed generation to the grid or a microgrid is an important step in the management and utilization of the distributed energy resources. Several synchronization algorithms have been proposed to improve the phase tracking of the grid voltage. However, when the grid is weak or distorted, the synchronization process may suffer from poor frequency regulation. Therefore, Sliding Discrete Fourier Transform Phase-locked-loop (SDFT-PLL) algorithm is proposed to extract an accurate angle of the fundamental voltage while rejecting the harmonics in a distorted or weak grid. The SDFT-PLL algorithm and simulation results to validate this method are presented in this paper. C2 - 2015/// C3 - 2015 ieee energy conversion congress and exposition (ecce) DA - 2015/// DO - 10.1109/ecce.2015.7309819 SP - 1143-1148 ER - TY - CONF TI - Reactive power management for overvoltage prevention at high PV penetration in low voltage distribution system AU - Safayet, A. AU - Fajri, P. AU - Husain, I. AB - In this paper, a new approach for reactive power management based on inverter's capacity and sensitivity to the critical bus has been presented. The approach addresses the voltage rise and reverse power flow issue when residential renewable energy sources such as rooftop solar panels produce more energy than the local load demand. The overvoltage issues are controlled by active management of reactive power flow. This method improves the voltage regulation of distributed system with high penetration of renewable energy sources while utilizing the inverters' reactive power capacity. C2 - 2015/// C3 - 2015 ieee energy conversion congress and exposition (ecce) DA - 2015/// DO - 10.1109/ecce.2015.7309941 SP - 1988-1994 ER - TY - CONF TI - Performance evaluation of 15 kV SiC IGBT based medium voltage grid connected three-phase three-level NPC converter AU - Madhusoodhanan, S. AU - Mainali, K. AU - Tripathi, A. AU - Patel, D. AU - Kadavelugu, A. AU - Bhattacharya, Subhashish AU - Hatua, K. AB - Cascaded converters are generally used for Medium Voltage (MV) grid connected applications due to the limitation in the voltage rating of available Silicon (Si) power devices. These converters find application in Active Power Filters, STATCOM or as Active Front End Converters for Solid State Transformers at the distribution voltage levels. The wide bandgap semiconductor devices have enabled the grid connected operation of non-cascaded converters. This results in high power density, less number of switching devices, high efficiency and control simplicity for three-phase MV grid interface. 15 kV SiC IGBT is one such device which can be switched at 5 kHz between MV and zero levels with forced air cooling. However, this device in a grid connected non-cascaded converter introduces few additional challenges which are analyzed in this paper. The paper investigates the performance of the grid connected converter using 15 kV SiC IGBT through simulations and experiments till 4.16 kV, 3-phase operation. The concerned areas of study are Total Harmonic Distortion (THD) at low currents, effect of practical sensor-feedback path errors, effect of switching ripple on the distribution transformer, effect of filter parasitic capacitance and elimination of high common mode current. C2 - 2015/// C3 - 2015 IEEE Energy Conversion Congress and Exposition, ECCE 2015 DA - 2015/// DO - 10.1109/ecce.2015.7310184 SP - 3710-3717 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963604269&partnerID=MN8TOARS ER - TY - CONF TI - Multi-layer tubular conductor for high Q-factor wireless power transfer system resonators AU - Etemadrezaei, M. AU - Lukic, Srdjan AB - In this paper we investigate multi-layer tubular conductor for multi-MHz Wireless Power Transfer (WPT) systems high-Q (quality factor) resonators. The conductor layers thickness and current sharing between them are optimized at 13.56 MHz, showing significant reduction in conductor AC resistance (R AC ). Capacitive ballast is used as a practical method for current sharing between layers and operation of coil near resonance. A two-layer conductor is designed, fabricated and characterized showing 18.1% reduction in R AC at 27.93 MHz using capacitive ballast. C2 - 2015/// C3 - 2015 ieee energy conversion congress and exposition (ecce) DA - 2015/// DO - 10.1109/ecce.2015.7310096 SP - 3111–3118 ER - TY - JOUR TI - MeToo: Stochastic Modeling of Memory Traffic Timing Behavior AU - Wang, Yipeng AU - Solihin, Yan AU - Balakrishnan, Ganesh T2 - 2015 INTERNATIONAL CONFERENCE ON PARALLEL ARCHITECTURE AND COMPILATION (PACT) AB - The memory subsystem (memory controller, bus, andDRAM) is becoming a bottleneck in computer system performance. Optimizing the design of the multicore memory subsystem requires good understanding of the representative workload. A common practice in designing the memory subsystem is to rely on trace simulation. However, the conventional method of relying on traditional traces faces two major challenges. First, many software users are apprehensive about sharing their code (source or binaries) due to the proprietary nature of the code or secrecy of data, so representative traces are sometimes not available. Second, there is a feedback loop where memory performance affects processor performance, which in turnalters the timing of memory requests that reach the bus. Such feedback loop is difficult to capture with traces. In this paper, we present MeToo, a framework for generating synthetic memory traffic for memory subsystem design exploration. MeToo uses a small set of statistics that summarizes the performance behavior of the original applications, and generates synthetic traces or executables stochastically, allowing applications to remain proprietary. MeToo uses novel methods for mimicking the memory feedback loop. We validate MeToo clones, and show very good fit with the original applications' behavior, with an average error of only 4.2%, which is a small fraction of the errors obtained using geometric inter-arrival(commonly used in queueing models) and uniform inter-arrival. DA - 2015/// PY - 2015/// DO - 10.1109/pact.2015.36 SP - 457-467 SN - 1089-795X KW - workload cloning KW - memory subsystem KW - memory controller KW - memory bus KW - DRAM ER - TY - CONF TI - Effect of brake power distribution on dynamic programming technique in plug-in series hybrid electric vehicle control strategy AU - Hafiz, F. AU - Fajri, P. AU - Husain, I. AB - Plug-in Hybrid Electric Vehicle (PHEV) control strategies have received much attention in recent years for their significant impact in reducing the overall fuel cost. Dynamic programming (DP) is a control method which calculates every possible outcome at each step to find out the optimal supervisory control trajectory. In this work, DP is applied to a PHEV control strategy using a backward looking powertrain model while demonstrating the effect of considering the regenerative braking power distribution. A case study with a Series PHEV model is considered using DP based powertrain control strategy with different drive cycles to demonstrate the importance of considering brake power distribution on the cost-to-go function of these vehicles. The simulation results show that there is significant deviation from the optimal trajectory especially in heavy stop and go traffic situations while brake power distribution is considered. C2 - 2015/// C3 - 2015 ieee energy conversion congress and exposition (ecce) DA - 2015/// DO - 10.1109/ecce.2015.7309675 SP - 100-105 ER - TY - CONF TI - Dynamic performance evaluation of hybrid multi-terminal HVAC/HVDC grid AU - Acharya, Sayan AU - Bhattacharya, Subhashish AU - Yousefpoor, N. AB - The multi-terminal DC grid can be integrated to the existing meshed AC grid system to provide back-up in case of transmission line failure and enhance power transmission capacity and flexibility in existing ac grids. In addition to that, Power oscillations can also be damped effectively through modulation of both active and reactive power of a voltage source converter (VSC) based multi-terminal DC grid. In this paper, the ability of the multi-terminal DC grid to effectively damp the power oscillation in an interconnected AC grid has been investigated. Also, VSC based MTDC transmission systems are vulnerable to DC side fault. This paper demonstrates a control method of a dc fault resilient voltage source converter that has ultra-fast electronic isolation capability following dc fault which can be protected against dc fault. To verify the control structure, the dynamic performance of the integrated multi-terminal DC grid in a reduced order three-bus AC equivalent power system is investigated through hardware-in-the-loop testing. Controller hardware-in-the-loop simulation of the embedded multi-terminal DC grid in a meshed AC power system is performed by Real Time Digital Simulator (RTDS), and RTDS results are presented to verify the control structure. C2 - 2015/// C3 - 2015 IEEE Energy Conversion Congress and Exposition, ECCE 2015 DA - 2015/// DO - 10.1109/ecce.2015.7309982 SP - 2287-2293 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963549008&partnerID=MN8TOARS ER - TY - JOUR TI - Dual-Mode Integrated Circuit for Imaging and HIFU With 2-D CMUT Arrays AU - Jang, Ji Hoon AU - Rasmussen, Morten Fischer AU - Bhuyan, Anshuman AU - Yoon, Hyo-Seon AU - Moini, Azadeh AU - Chang, Chienliu AU - Watkins, Ronald D. AU - Choe, Jung Woo AU - Nikoozadeh, Amin AU - Stephens, Douglas AU - Oralkan, Oemer AU - Pauly, Kim Butts AU - Khuri-Yakub, Butrus T2 - 2015 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS) AB - Successful high intensity focused ultrasound (HIFU) operation requires a reliable guidance and monitoring method such as magnetic resonance imaging (MRI) or ultrasound imaging. However, both widely used modalities are typically separate from the HIFU system, which makes co-registration of HIFU with cross-sectional imaging difficult. In this paper, we present a dual-mode integrated circuit (IC) that can perform both ultrasound imaging and HIFU with a single 2D capacitive micromachined ultrasonic transducer (CMUT) array, combining these two systems for ease of use. The dual-mode IC consists of pulsers, transmit beamforming circuitry, and low-noise amplifiers for imaging mode and switches for HIFU mode. By turning this switching network on and off, the system can alternately operate the imaging mode and HIFU mode on demand. The dual-mode IC was designed and fabricated in the 0.18-µm HV 4LM process provided by Maxim Inc. We fabricated a 32×32-element CMUT array that has a center frequency of 5 MHz using a sacrificial release process and flip-chip bonded this CMUT array to the IC. With the back-end system, real-time volumetric imaging on the wire phantom and HIFU ablation on ex-vivo tissue were performed respectively. DA - 2015/// PY - 2015/// DO - 10.1109/ultsym.2015.0166 SP - SN - 1948-5719 ER - TY - CONF TI - Design, analysis and implementation of discontinuous mode Dyna-C AC/AC converter for solid state transformer applications AU - De, A. AU - Bhattacharya, Subhashish AB - The paper presents an improved control strategy for Dynamic Current (Dyna-C) Converter. Dyna-C is a bidirectional current-source based AC/AC converter for Solid State Transformer (SST) application. The proposed controller facilitates discontinuous mode operation which leads to zero current turn on and turn off. A non-linear average phase charge based controller is presented which ensures zero harmonic current in the input phase currents. The switching scheme has been so arranged that the diodes always turn off at zero voltage thereby reducing the reverse recovery stress and losses. These modifications lead to a considerable reduction of switching loss and device stress as compared to the conventional control scheme of Dyna-C. Owing to soft switching states, the frequency of operation can therefore be pushed further higher thereby reducing the size of the passive components. An alternate switching pattern has also been discussed which enables soft switched turn off of active switches. Design Considerations of packaging such a switch structure has also been discussed. It has been shown that direct connection of Emitter of IGBT to the Anode of the Diode leads to considerably lower parasitic inductance. Design guidelines to construct an optimized inductor has also been discussed. Simulation and experimental results are presented to validate operation of the control scheme. A comparison study has been carried out to choose the appropriate set of devices for this application. It has been shown that SiC-MOS with low cost Si-PiN Diode shows impressive reduction in overall losses. C2 - 2015/// C3 - 2015 IEEE Energy Conversion Congress and Exposition, ECCE 2015 DA - 2015/// DO - 10.1109/ecce.2015.7310369 SP - 5030-5037 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963520581&partnerID=MN8TOARS ER - TY - CONF TI - Design of high-frequency broadband CMUT arrays AU - Zhang, Xiao AU - Yamanery, F. Yalcin AU - Adelegan, Oluwafemi AU - Oralkan, Omer T2 - 2015 IEEE International Ultrasonics Symposium (IUS) AB - In this work we demonstrate a high-frequency (29-MHz) broadband (100% FBW) CMUT 1D array. The devices are fabricated using anodic bonding with only three photolithography steps. We also discuss the design guidelines for high-frequency broadband CMUTs using the simulations. A high fill factor and a thin plate are important for the broadband design. Small cell size is required for the increased center frequency. To improve the transducer sensitivity and to keep the collapse voltage low, the gap height should be small and a high-k dielectric insulation layer should be employed. The fabrication steps we report in this paper have good potential to meet the high-frequency broadband CMUT design requirements. So far we have demonstrated that we can define a 50-nm gap, bond to a post as narrow as 2 µm, and pattern a high-k dielectric layer on the bottom electrode. C2 - 2015/10// C3 - 2015 IEEE International Ultrasonics Symposium (IUS) DA - 2015/10// DO - 10.1109/ultsym.2015.0167 SP - PB - IEEE SN - 9781479981823 UR - http://dx.doi.org/10.1109/ultsym.2015.0167 DB - Crossref KW - High frequency transducer array KW - Broadband KW - CMUT KW - Anodic bonding KW - Glass ER - TY - CONF TI - Design consideration of an MMC-HVDC system based on 4500V/4000A emitter turn-off (ETO) thyristor AU - Falahi, G. AU - Huang, A. Q. AB - Excessive power loss is a major concern in high voltage and high power applications and is considered one of the main drawbacks of VSC-HVDC system when compared with traditional HVDC system based on thyristor technology. This is primarily caused by high switching loss associated with switching devices used in the VSC-HVDC. This issue can be largely addressed by using the emerging MMC-HVDC topology, which requires much lower switching frequency than traditional VSC-HVDC. Emitter turn-off thyristor (ETO) is one of the best high power switching devices packed with many advanced features. ETO thyristor based MMC-HVDC system is therefore an extremely attractive choice for ultra-high voltage and high power HVDCs. This paper discusses the operation principle of ETO based MMC-HVDC as well as its design and loss comparison with other solutions. C2 - 2015/// C3 - 2015 ieee energy conversion congress and exposition (ecce) DA - 2015/// DO - 10.1109/ecce.2015.7310149 SP - 3462-3467 ER - TY - CONF TI - Control of modular dual active bridge DC/DC converter for photovoltaic integration AU - Azidehak, A. AU - Chattopadhyay, R. AU - Acharya, Sayan AU - Tripathi, A.K. AU - Kashani, M.G. AU - Chavan, G. AU - Bhattacharya, Subhashish AB - The DC transmission system provides a cost effective solution for long distance power transmission compared to the AC transmission system. Hence, this has increased the emphasis on the development of the DC transmission system. Development of power converter with modular structure has now made it possible to achieve higher voltage and power level. This opens the possibility for further development of a multi-terminal DC grid. Now once the DC grid system has been formed, it is also important to include more renewable energy sources directly to the DC grid. Therefore, a power conversion stage is required to condition the available power from a source to the grid. This paper shows the operation and control of such a kind of converter system which integrates the solar cell to the DC grid directly. The paper mainly focuses on control of the series connected DAB that have been integrated to HVDC power network. In order to deliver power in HVDC system, the total number of DABs must be high enough to achieve the DC link voltage. The control in that case must be a combination of current and voltage control. In order to validate the proposed control, complete system has been implemented on Opal-RT™ and hardware in the loop (HIL) using external controller has also been implemented to show the system operation. C2 - 2015/// C3 - 2015 IEEE Energy Conversion Congress and Exposition, ECCE 2015 DA - 2015/// DO - 10.1109/ecce.2015.7310140 SP - 3400-3406 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963537568&partnerID=MN8TOARS ER - TY - CONF TI - Control of dynamic VAR compensator based on current source converter AU - De, A. AU - Bhattacharya, Subhashish AB - The paper proposes a current source based Dynamic VAR Compensator (DVC) control strategy. The switching unit in this DVC topology is composed of series connected switch and diode also termed as the “current switch”. The proposed controller has been designed to force discontinuous conduction mode operation thus fundamentally different from the traditional constant current source based control system operation. This naturally facilitates zero current turn-on, zero voltage switch overlap and zero current turn off. Two of the switches undergo hard switched turn off only once in a switching time period. The switching scheme has been managed in such a way that the diodes are always turned off at zero voltage thereby minimizing the reverse recovery loss and stress. This effectively reduces the switching losses and allows the switching frequency to be designed considerably higher. High Switching frequency facilitates faster response and high power density. An average model of this DVC converter has been used in an IEEE-34 BUS system to validate the VAR compensation capability. It has been shown that this effectively improves the feeder voltage profile. The ill effects of partial clouding over roof-top PV cells have also been shown, and its mitigation by the DVC. The proposed VAR compensator algorithm can adjust capacitive reactive power as well as inductive reactive power, which can be adapted to a wide range of load. C2 - 2015/// C3 - 2015 IEEE Energy Conversion Congress and Exposition, ECCE 2015 DA - 2015/// DO - 10.1109/ecce.2015.7310146 SP - 3442-3448 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963625762&partnerID=MN8TOARS ER - TY - CONF TI - Comparative evaluation of 15 kV SiC MOSFET and 15 kV SiC IGBT for medium voltage converter under same dv/dt conditions AU - Vechalapu, K. AU - Bhattacharya, Subhashish AU - Brunt, E. Van AU - Ryu, S.-H. AU - Grider, D. AU - Palmour, J.W. AB - The 15 kV SiC MOSFET and 15 kV SiC IGBT are two state-of-the-art high voltage SiC devices. These high voltage SiC devices enable simple two level converters for medium voltage source converter compared to the complex three level and multilevel topologies with Silicon devices. This paper presents the detailed experimental results for the characterization of 15 kV SiC MOSFET module at 10 kV and 12 kV DC bus for two different configuration of device under test. This paper also presents the switching loss comparison of 15 kV SiC MOSFET with 15 kV SiC IGBT for the same dv/dt. Based on loss data obtained from experiments, this paper finally reports the switching frequency limits of 15 kV SiC MOSFET for 10 kV DC bus, 3-Phase two level converter and Bi-directional DC-DC phase leg converter with 10 kV output voltage and comparative evaluation of 15 kV SiC MOSFET and 15 kV SiC IGBT for the same dv/dt in a unidirectional DC-DC boost hard switching converter for 10 kV output voltage. C2 - 2015/// C3 - 2015 IEEE Energy Conversion Congress and Exposition, ECCE 2015 DA - 2015/// DO - 10.1109/ecce.2015.7309787 SP - 927-934 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84963553261&partnerID=MN8TOARS ER - TY - CONF TI - Bi-sparsity pursuit for robust subspace recovery AU - Bian, X. AU - Krim, H. AB - The success of sparse models in computer vision and machine learning in many real-world applications, may be attributed in large part, to the fact that many high dimensional data are distributed in a union of low dimensional subspaces. The underlying structure may, however, be adversely affected by sparse errors, thus inducing additional complexity in recovering it. In this paper, we propose a bi-sparse model as a framework to investigate and analyze this problem, and provide as a result, a novel algorithm to recover the union of subspaces in presence of sparse corruptions. We additionally demonstrate the effectiveness of our method by experiments on real-world vision data. C2 - 2015/// C3 - 2015 ieee international conference on image processing (icip) DA - 2015/// DO - 10.1109/icip.2015.7351462 SP - 3535-3539 ER - TY - CONF TI - Axial flux segmental rotor flux-switching synchronous motor AU - Kabir, M. A. AU - Ahmed, A. AU - Husain, I. AB - A novel three-phase, concentrated winding, axial flux, segmental rotor, flux-switching synchronous motor is presented. The proposed topology has rotor segments made of only iron laminations and operates with flux-switching principle. Compared to existing axial flux permanent magnet (AFPM) topologies, the proposed machine contains reduced amount of permanent magnets located only in its stator. This approach makes the assembly easier and reduce the cost compared to conventional AFPM. Moreover, the proposed topologies have higher torque density and torque-to-weight ratio compared to reported axial flux SRMs (AFSRMs). Detailed design and operation of the proposed machine is presented; the performance of the machine is evaluated for an in-wheel traction application. C2 - 2015/// C3 - 2015 ieee energy conversion congress and exposition (ecce) DA - 2015/// DO - 10.1109/ecce.2015.7309963 SP - 2148-2152 ER - TY - CONF TI - Analytical modeling of a novel transverse flux machine for direct drive wind turbine applications AU - Hasan, I. AU - Husain, T. AU - Uddin, M. W. AU - Sozer, Y. AU - Husain, I. AU - Muljadi, E. AB - This paper presents a nonlinear analytical model of a novel double sided flux concentrating Transverse Flux Machine (TFM) based on the Magnetic Equivalent Circuit (MEC) model. The analytical model uses a series-parallel combination of flux tubes to predict the flux paths through different parts of the machine including air gaps, permanent magnets (PM), stator, and rotor. The two-dimensional MEC model approximates the complex three-dimensional flux paths of the TFM and includes the effects of magnetic saturation. The model is capable of adapting to any geometry which makes it a good alternative for evaluating prospective designs of TFM as compared to finite element solvers which are numerically intensive and require more computation time. A single phase, 1 kW, 400 rpm machine is analytically modeled and its resulting flux distribution, no-load EMF and torque, verified with Finite Element Analysis (FEA). The results are found to be in agreement with less than 5% error, while reducing the computation time by 25 times. C2 - 2015/// C3 - 2015 ieee energy conversion congress and exposition (ecce) DA - 2015/// DO - 10.1109/ecce.2015.7309965 SP - 2161-2168 ER - TY - CONF TI - A universal restart strategy for permanent magnet synchronous machines AU - Lee, Kibok AU - Lukic, Srdjan AU - Ahmed, Sara T2 - IEEE AB - In many industrial settings, momentary power disruptions commonly occur, resulting in tripping of large electric machines, which then have to be brought to zero speed before the machine can be restarted. This approach can result in frequent interruptions in an industrial process, which can have negative effects on productivity. A more practical control implementation would restart the machine back to the original speed as soon as power is restored, not having to wait for the machine to be at a standstill. This concept is known as flying restart. In this paper we propose an approach to implement the universal restart for PMSM through a simple identification algorithm which determines the speed and position of the machine back-emf so that the correct voltage vector can be applied and thus minimize the inrush current during the restart. Beyond the development of the basic algorithm, implementation issues will be considered to provide general guideline for the application of the developed algorithm. C2 - 2015/// C3 - 2015 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2015/// DO - 10.1109/ecce.2015.7309712 SP - 373-380 ER - TY - CONF TI - A unified framework for wireless connectivity study subject to general interference attack AU - Liu, Y. AU - Li, C. Z. AU - Yin, C. C. AU - Dai, H. Y. AB - Connectivity is crucial to ensure information availability and survivability for wireless networks. In this paper, we propose a unified framework to study the connectivity of wireless networks under a general type of interference attack, which can address diverse applications including Cognitive Radio, Jamming attack and shadowing effect. By considering the primary users, jammers and deep fading as unified Interferers, we investigate a 3-dimensional connectivity region, defined as the set of key system parameters - the density of users, the density of Interferers and the interference range of Interferers - with which the network is connected. Further we study the impact of the Interferers' settings on node isolation probability, which is a fundamental local connectivity metric. Through percolation theory, the sufficient and necessary conditions for global connectivity are also derived. Our study is supported by simulation results. C2 - 2015/// C3 - 2015 ieee international conference on communications (icc) DA - 2015/// DO - 10.1109/icc.2015.7249471 SP - 7174-7179 ER - TY - CONF TI - A stochastic multi-channel spectrum access game with incomplete information AU - He, X. F. AU - Dai, H. Y. AU - Ning, P. AU - Dutta, R. AB - To ensure continuous functioning and satisfactory performance, a wireless communication system has to not only learn and adapt to the unknown and ever-changing wireless environment, but also strategically deal with the usually unfamiliar peers. Incomplete information stochastic game (SG) is a promising model for the corresponding analysis and strategy design. In this work, an exemplary multi-channel spectrum access game (SAG) with unknown environment dynamics and limited information of the other player is considered to illustrate the proposed solution for the corresponding incomplete information SG. To find the best communication strategy in the face of uncertainty, a joint reinforcement learning and type identification algorithm is developed, which is provably convergent under certain technical conditions. Numerical results show that using the proposed algorithm, a wireless user can gradually achieve the same performance as that in the corresponding complete information game. C2 - 2015/// C3 - 2015 ieee international conference on communications (icc) DA - 2015/// DO - 10.1109/icc.2015.7249082 SP - 4799-4804 ER - TY - CONF TI - A new modulation technique to reduce leakage current without compromising modulation index in PV systems AU - Chen, Z. P. AU - Yu, Wensong AU - Ni, X. J. AU - Huang, A. AB - The transformerless grid-connected PV system suffers from leakage current and neutral voltage imbalance if three-level inverters are utilized. This paper first investigates the common-mode voltage (CM voltage) reduction/elimination methods in three-phase PV inverters, especially three-level inverters. Several mainstream common-mode voltage reduction/elimination methods, including AZSPWM, 2MV1Z, 3MV, 3MV120, are compared in terms of CM voltage reduction/elimination performance, switching losses, modulation index, linear region and neutral point voltage balancing ability. Then a new topology and modulation scheme are proposed, which reduce the frequency of the CM voltage to the order of line frequency and could reach a 100% modulation index. This method is discussed in detail and is verified by simulation. C2 - 2015/// C3 - 2015 ieee energy conversion congress and exposition (ecce) DA - 2015/// DO - 10.1109/ecce.2015.7309724 SP - 460–465 ER - TY - CONF TI - A high efficiency flyback micro-inverter with a new adaptive snubber for photovoltaic applications AU - Rezaei, M. A. AU - Lee, K. J. AU - Huang, A. Q. AB - Based on the hybrid operation of interleaved flyback micro-inverter in Discontinuous and Boundary Conduction Modes (DCM and BCM), a novel adaptive snubber is proposed in this paper. The proposed snubber limits the drain-to-source voltage overshoot of the flyback's main switch during the turn-off process, enabling the use of lower voltage MOSFETs. It also recovers the stored energy in the leakage inductance of the flyback transformer and provides soft switching for the main flyback switch by limiting the rising slope of the MOSFET voltage during the turn off process resulting in higher efficiency. Exploiting the natural resonant of the flyback converter in BCM the adopted controller provides ZVS and ZCS for the main switch during the BCM operation. The operation of the flyback micro-inverter with associated controllers is analytically studied, and considerations for an optimum design aiming to higher efficiency are presented. Performance of the flyback micro-inverter with the proposed adaptive snubber and the corresponding controllers are experimentally verified based on a 250W interleaved flyback micro-inverter hardware setup. C2 - 2015/// C3 - 2015 ieee energy conversion congress and exposition (ecce) DA - 2015/// DO - 10.1109/ecce.2015.7310126 SP - 3308-3313 ER - TY - CONF TI - A dynamic measurement method for parasitic capacitances of high voltage SiC MOSFETs AU - Song, X. Q. AU - Huang, A. Q. AU - Lee, M. J. AU - Wang, G. Y. AB - The voltage dependent parasitic capacitances in high voltage semiconductor power devices such as MOSFET, JFET and IGBT play a vital role in the understanding and modeling of the device switching performance. In this paper, a simple but effective parasitic capacitance measurement method is proposed. The output capacitance C oss and the reverse transfer capacitance C rss can be measured simultaneously and directly in the proposed parasitic capacitance tester (PCT). The input capacitance C iss is measured based on gate driver waveforms during the turn on transient. To verify the effectiveness of the proposed method, a 10kV SiC MOSFET parasitic capacitances are measured as an example. The measured parasitic capacitance results are compared with those from a conventional LCR meter and theoretical calculation. Furthermore, a Matlab/Simulink compact circuit model for the 10kV SiC MOSFET is developed based on the measured parasitic capacitances, whose results also validate the effectiveness of the proposed method. C2 - 2015/// C3 - 2015 ieee energy conversion congress and exposition (ecce) DA - 2015/// DO - 10.1109/ecce.2015.7309788 SP - 935-941 ER - TY - CONF TI - Smart hybrid house test systems in a solid-state transformer supplied microgrid AU - Yan, J. H. AU - Zhu, X. Q. AU - Lu, N. AB - This paper presents the design and setup, considerations, and preliminary results of an AC/DC hybrid smart house test system. Rapid growth of rooftop photovoltaic (PV) in distribution systems makes it viable to supply a residential home with both AC and DC power sources. Solid-state transformers (SST) used as energy routers for rerouting power during normal and emergency situations are being developed in the FREEDM center at North Carolina State University. To provide a load test system for studying the control and monitoring of such an SST supplied AC/DC mixed power supply system, an 1-SST AC/DC hybrid smart house test system is built. The test system consists of a solid state transformer (SST), on-site photovoltaic panels, energy storage devices and three AC/DC smart houses with a home energy management system (HEMS). A demonstration case is presented to illustrate the operation of the test system for algorithm development and validation. C2 - 2015/// C3 - 2015 ieee power & energy society general meeting DA - 2015/// DO - 10.1109/pesgm.2015.7286550 ER - TY - JOUR TI - Revenue Optimization Frameworks for Multi-Class PEV Charging Stations AU - Kong, Cuiyu AU - Bayram, Islam Safak AU - Devetsikiotis, Michael T2 - IEEE ACCESS AB - The charging power of plug-in electric vehicles (PEVs) decreases significantly when the state of charge (SoC) gets closer to the fully charged state, which leads to a longer charging duration. Each time when the battery is charged at high rates, it incurs a significant degradation cost that shortens the battery life. Furthermore, the differences between demand preferences, battery types, and charging technologies make the operation of the charging stations a complex problem. Even though some of these issues have been addressed in the literature, the charging station modeling with battery models and different customer preferences have been neglected. To that end, this paper proposes two queueing-based optimization frameworks. In the first one, the goal is to maximize the system revenue for single class customers by limiting the requested SoC targets. The PEV cost function is composed of battery degradation cost, the waiting cost in the queue, and the admission fee. Under this framework, the charging station is modeled as a $M/G/S/K$ queue, and the system performance is assessed based on the numerical and simulation results. In the second framework, we describe an optimal revenue model for multi-class PEVs, building upon the approach utilized in the first framework. Two charging strategies are proposed: 1) a dedicated charger model and 2) a shared charger model for the multi-class PEVs. We evaluate and compare these strategies. Results show that the proposed frameworks improve both the station performance and quality of service provided to customers. The results show that the system revenue is more than doubled when compared with the baseline scenario which includes no limitations on the requested SoC. DA - 2015/// PY - 2015/// DO - 10.1109/access.2015.2498105 VL - 3 SP - 2140-2150 SN - 2169-3536 KW - Electric vehicle KW - queuing system KW - multi-class KW - dedicated chargers KW - shared chargers ER - TY - CONF TI - Online convergence factor tuning for robust cooperative distributed economic dispatch AU - Zhang, Y. AU - Asr, N. R. AU - Chow, M. Y. AB - Solving economic dispatch problem (EDP) in a distributed way has attracted lots of attention in recent years due to its scalability and robustness to single points of failure. Robust distributed system Incremental Cost Estimation (RICE) algorithm has been proposed to solve the classic EDP in a distributed way considering communications information losses. However, assuring the stability of the algorithm without knowing the global information of the system is a challenging issue. This paper provides a distributed online approach to tune a certain parameter of the algorithm called “convergence factor” using only local information to assure the algorithm is stable. To do this, a local energy function is defined for each agent. As the algorithm proceeds, each agent uses a decaying mechanism to tune its convergence factor to ensure that its local energy function is within a certain bound. The summation of local energy functions represents an energy function for the entire network. Therefore, if each agent uses the tuning mechanism, the energy of the system would be forced to be constrained and the system will become stable. The effectiveness of the proposed approach is verified through several case studies. C2 - 2015/// C3 - 2015 ieee power & energy society general meeting DA - 2015/// DO - 10.1109/pesgm.2015.7285652 ER - TY - CONF TI - Load scheduling with price uncertainty and temporally-coupled constraints in smart grids AU - Deng, R. L. AU - Yang, Z. Y. AU - Chen, J. M. AU - Chow, M. Y. AB - Summary form only given. Recent years have witnessed the significant growth in electricity consumption. The emerging smart grid aims to address the ever-increasing load through appropriate scheduling, i.e., to shift the energy demand from peak to off-peak periods by pricing tariffs as incentives. Under the real-time pricing environment, due to the uncertainty of future prices, load scheduling is formulated as an optimization problem with expectation and temporally-coupled constraints. Instead of resorting to stochastic dynamic programming that is generally prohibitive to be explicitly solved, we propose dual decomposition and stochastic gradient to solve the problem. That is, the primal problem is firstly dually decomposed into a series of separable subproblems, and then the price uncertainty in each subproblem is addressed by stochastic gradient based on the statistical knowledge of future prices. In addition, we propose an online approach to further alleviate the impact of price prediction error. Numerical results are provided to validate our theoretical analysis. C2 - 2015/// C3 - 2015 ieee power & energy society general meeting DA - 2015/// DO - 10.1109/pesgm.2015.7286257 ER - TY - CONF TI - Lateral silicon photodiodes with extremely low dark current for visible and infra-red applications AU - Mehta, J. AU - Lunardi, Leda AB - We present two lateral p-i-n photodiodes for operation in the 400-900nm wavelength range. The design is compatible with typical 180nm CMOS process and yields high responsivity and low dark current independent of the geometry. C2 - 2015/// C3 - 2015 photonics conference (ipc) DA - 2015/// DO - 10.1109/ipcon.2015.7323594 SP - 446-447 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84964890183&partnerID=MN8TOARS ER - TY - CONF TI - Joint scheduling of large-scale appliances and batteries via distributed mixed optimization AU - Yang, Z. Y. AU - Long, K. Y. AU - You, P. C. AU - Chow, M. Y. C2 - 2015/// C3 - 2015 ieee power & energy society general meeting DA - 2015/// ER - TY - CONF TI - Hybrid excitation topologies for three-phase mutually coupled reluctance machine with standard inverters AU - Kabir, M. A. AU - Husain, I. AB - New winding configurations for mutually coupled salient pole switched reluctance machines (MCSRMs) have been proposed that enables the application of three-phase standard inverters for variable speed drives. The proposed topologies comprise phase windings carrying balanced three phase currents from standard inverters along with DC excitation coils in the stator slots. Both concentrated and distributed hybrid winding configurations are proposed and performances of these MCSRMs are compared with that of the conventional SRM under the same machine geometry and phase excitation levels. The analysis and results show that the proposed machine configurations with standard inverters are more suitable for low cost, variable speed drives with higher power densities and lower torque ripples compared to conventional SRM drives. C2 - 2015/// C3 - 2015 ieee power & energy society general meeting DA - 2015/// DO - 10.1109/pesgm.2015.7286004 ER - TY - JOUR TI - Handwritten, Soft Circuit Boards and Antennas Using Liquid Metal Nanoparticles AU - Lin, Yiliang AU - Cooper, Christopher AU - Wang, Meng AU - Adams, Jacob J. AU - Genzer, Jan AU - Dickey, Michael D. T2 - SMALL AB - Soft conductors are created by embedding liquid metal nanoparticles between two elastomeric sheets. Initially, the particles form an electrically insulating composite. Soft circuit boards can be handwritten by a stylus, which sinters the particles into conductive traces by applying localized mechanical pressure to the elastomeric sheets. Antennas with tunable frequencies are formed by sintering nanoparticles in microchannels. DA - 2015/12/22/ PY - 2015/12/22/ DO - 10.1002/smll.201502692 VL - 11 IS - 48 SP - 6397-6403 SN - 1613-6829 ER - TY - JOUR TI - Guest Editorial New Trends of Demand Response in Smart Grids AU - Yang, Zaiyue AU - Chow, Mo-Yuen AU - Hu, Guoqiang AU - Zhang, Yan T2 - IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS AB - The papers in this special section focus on technological and system developments in designing power grids. The power grid is a large interconnected infrastructure for delivering electricity from power plants to end users. Now, traditional grids are facing kinds of challenges, and the world is proposing to modernize legacy and make strides toward smart grid. It is widely recognized that demand response is the core feature of smart grid, which can be formally defined as “changes in electric use by demand-side resources from their normal consumption patterns in response to changes in the price of electricity, or to incentive payments designed to induce lower electricity use at times of high wholesale market prices or when system reliability is jeopardized. With the support of the advanced information and communication technologies, demand response is able to improve the efficiency, reliability, economics, and sustainability of power generation, distribution, and utilization. DA - 2015/12// PY - 2015/12// DO - 10.1109/tii.2015.2490623 VL - 11 IS - 6 SP - 1505-1508 SN - 1941-0050 ER - TY - BOOK TI - Geometric methods in signal and image analysis AU - Krim, H. AU - Hamza, A. B. AB - This comprehensive guide offers a new approach for developing and implementing robust computational methodologies that uncover the key geometric and topological information from signals and images. With the help of detailed real-world examples and applications, readers will learn how to solve complex signal and image processing problems in fields ranging from remote sensing to medical imaging, bioinformatics, robotics, security, and defence. With an emphasis on intuitive and application-driven arguments, this text covers not only a range of methods in use today, but also introduces promising new developments for the future, bringing the reader up-to-date with the state of the art in signal and image analysis. Covering basic principles as well as advanced concepts and applications, and with examples and homework exercises, this is an invaluable resource for graduate students, researchers, and industry practitioners in a range of fields including signal and image processing, biomedical engineering, and computer graphics. DA - 2015/// PY - 2015/// DO - 10.1017/cbo9781139523967 PB - Cambridge, United Kingdom: Cambridge University Press SN - 9781107033900 ER - TY - CONF TI - Fabrication of capacitive micromachined ultrasonic transducers with through-glass-via interconnects AU - Zhang, Xiao AU - Yamanery, F. Yalcin AU - Oralkan, Omer T2 - 2015 IEEE International Ultrasonics Symposium (IUS) AB - This paper introduces a novel fabrication method for capacitive micromachined ultrasonic transducer (CMUT) arrays amenable to 3D integration. The work demonstrates that MEMS structures can be directly built on a through-glass-via (TGV) substrate. The key feature of this new approach is the combination of TGV interconnects with a vibrating silicon-plate structure formed by anodic bonding. This method simplifies the overall fabrication process for CMUTs with through-wafer interconnects by eliminating the need for an insulating lining for vias or isolation trenches. Fabrication of CMUTs on a glass substrate and use of copper-filled vias as interconnects can help reduce the parasitic interconnect capacitance and resistance, improving device performance and reliability. This work is especially important for fabricating 2D CMUT arrays and integrating them closely with supporting electronic circuits. C2 - 2015/10// C3 - 2015 IEEE International Ultrasonics Symposium (IUS) DA - 2015/10// DO - 10.1109/ultsym.2015.0060 SP - PB - IEEE SN - 9781479981823 UR - http://dx.doi.org/10.1109/ultsym.2015.0060 DB - Crossref KW - CMUT KW - TGV KW - Anodic bonding KW - 3D integration KW - Glass ER - TY - CONF TI - Equilibria analysis of power systems using a numerical homotopy method AU - Chandra, S. AU - Mehta, D. AU - Chakrabortty, Aranya AB - In this paper, we present a homotopy based numerical continuation algorithm to efficiently compute all feasible equilibria of a complex power system model. The dynamic characteristics of conventional power systems are undergoing a sea change due to the impact of large-scale integration of renewables, storage elements, new type of loads etc. Several parameters of these components affect the power system operation leading to multiple feasible equilibria which may be intractable by the traditional load flow techniques. In contrast, our algorithm finds all the feasible solutions over a certain parameter space. We illustrate the results through the simulation of a 5-machine power system model with wind, storage elements, and dynamic loads. We observed that the wind velocity and the reference to the wind bus voltage strongly affect the number and the stability of the system equilibria. Knowledge of these equilibria can benefit small-signal stability assessment and system level planning. C2 - 2015/// C3 - 2015 ieee power & energy society general meeting DA - 2015/// DO - 10.1109/pesgm.2015.7285823 ER - TY - CONF TI - Distributed real-time demand response in multiseller"Cmultibuyer smart distribution grid AU - Deng, R. L. AU - Yang, Z. Y. AU - Hou, F. AU - Chow, M. Y. AU - Chen, J. M. AB - Demand response is a key solution in smart grid to address the ever-increasing peak energy consumption. With multiple utility companies, users will decide from which utility company to buy electricity and how much to buy. Consequently, how to devise distributed real-time demand response in the multiseller̈Cmultibuyer environment emerges as a critical problem in future smart grid. In this paper, we focus on the real-time interactions among multiple utility companies and multiple users. We propose a distributed real-time demand response algorithm to determine each user's demand and each utility company's supply simultaneously. By applying dual decomposition, the original problem is firstly decoupled into single-seller̈Cmultibuyer subsystems; then, the demand response problem in each subsystem can be distributively solved. The major advantage of this approach is that each utility company and user locally solve subproblems to perform energy allocation, instead of requiring a central controller or any third party. Therefore, privacy is guaranteed because no entity needs to reveal or exchange private information. Numerical results are presented to verify efficiency and effectiveness of the proposed approach. C2 - 2015/// C3 - 2015 ieee power & energy society general meeting DA - 2015/// DO - 10.1109/pesgm.2015.7286260 ER - TY - CONF TI - Cooperative distributed scheduling for storage devices in microgrids using dynamic KKT multipliers and consensus networks AU - Rahbari-Asr, N. AU - Zhang, Y. AU - Chow, M. Y. AB - Scheduling of storage devices in microgrids with multiple renewable energy resources is crucial for their optimal and reliable operation. With proper scheduling, the storage devices can capture the energy when the renewable generation is high and utility energy price is low, and release it when the demand is high or utility energy price is expensive. This scheduling is a multi-step optimization problem where different time-steps are dependent on each other. Conventionally, this problem is solved centrally. The central controller should have access to the real-time states of the system as well as the predicted load and renewable generation information. It should also have the capability to send dispatch commands to each storage device. However, as the number of devices increases, the centralized approach would not be scalable and will be vulnerable to single point of failure. Combining the idea of dynamic KKT multipliers with consensus networks, this paper introduces a novel algorithm that can optimally schedule the storage devices in a microgrid solely through peer-to-peer coordination of devices with their neighbors without using a central controller. C2 - 2015/// C3 - 2015 ieee power & energy society general meeting DA - 2015/// DO - 10.1109/pesgm.2015.7286376 ER - TY - CONF TI - Convergence analysis of ADMM-based power system mode estimation under asynchronous wide-area communication delays AU - Zhang, J. H. AU - Nabavi, S. AU - Chakrabortty, Aranya AU - Xin, Y. F. AB - In our recent paper [1], we proposed a distributed PMU-PDC architecture for estimating power system oscillation modes by integrating a Prony-based algorithm with Alternating Direction Method of Multipliers (ADMM). A critical assumption behind the proposed method was that the communication between local PDCs and the central averager is completely synchronized. In realistic wide-area networks, however, such synchronous communication may not always be possible. In this paper we address this issue of asynchronous communication, and its impact on the convergence of the distributed estimation. We first impose a probability model for the communication delays between the central PDC and the local PDCs, and then implement two strategies of averaging at the central PDC based on a chosen delay threshold. We carry out simulations to show possible instabilities and sensitivities of the ADMM convergence on delay distribution parameters under these two averaging strategies. Our results exhibit a broad view of how the convergence of distributed estimation algorithms in physical processes depends strongly on the uncertainties in the underlying communications in a generic cyber-physical system. C2 - 2015/// C3 - 2015 ieee power & energy society general meeting DA - 2015/// DO - 10.1109/pesgm.2015.7286038 ER - TY - CONF TI - Control and size energy storage systems for managing energy imbalance of variable generation resources AU - Ke, X. D. AU - Lu, N. AU - Jin, C. L. AB - Summary form only given: This paper presents control algorithms and sizing strategies for using energy storage to manage energy imbalance for variable generation resources. The control objective is to minimize the hourly generation imbalance between the actual and the scheduled generation of wind farms. Three control algorithms are compared: (1) tracking minute-by-minute power imbalance; (2) postcompensation; and (3) precompensation. Measured data from a wind farm are used in the study. The results show that tracking minute-by-minute power imbalance achieves the best performance by keeping hourly energy imbalance zero. However, the energy storage system (ESS) will be significantly oversized. Postcompensation reduces the power rating of the ESS but the hourly energy imbalance may not be reduced to zero when a large and long-lasting power imbalance occurs. A linear regression forecasting algorithm is developed for a two-stage precompensation algorithm to precharge or predischarge the ESS based on the predicted energy imbalance. An equivalent charge cycle estimation method is proposed to evaluate the effect of providing the energy balancing service on battery life. The performance comparison shows that the precompensation method reduces the size of the ESS by 30% with satisfactory performance. C2 - 2015/// C3 - 2015 ieee power & energy society general meeting DA - 2015/// DO - 10.1109/pesgm.2015.7286609 ER - TY - CONF TI - Control and dynamic performance evaluation of Multi-Terminal DC grid AU - Yousefpoor, N. AU - Bhattacharya, Subhashish AB - In this paper, the operation of Voltage Source Converter (VSC) based Multi-Terminal DC (MTDC) transmission system consisting of three different power converter topologies is evaluated. The high frequency isolated modular converter is used as the VSC configuration for two terminals. The Modular Multi-level Converter (MMC) and three-phase AC/DC converters are also used as the VSC configuration for the other two terminals. In the high frequency isolated modular converter configuration, several H-bridge modules are connected in cascade. From the MTDC system control point of view, a droop control structure with dead-band controller is proposed for MTDC grid control. The dynamic performance of a four-terminal DC grid is further investigated in PSCAD/EMTDC environment. Simulation results are presented to verify the performance of multi-terminal DC grid based on the proposed control method. C2 - 2015/// C3 - IEEE Power and Energy Society General Meeting DA - 2015/// DO - 10.1109/pesgm.2015.7286382 VL - 2015-September UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84956855351&partnerID=MN8TOARS ER - TY - JOUR TI - ALD gate dielectrics for improved threshold voltage stability in AlGaN/GaN MOS-HFETs for power applications AU - Ramanan, Narayanan AU - Lee, Bongmook AU - Misra, Veena T2 - SEMICONDUCTOR SCIENCE AND TECHNOLOGY AB - Dielectrics by atomic layer deposition (ALD) are sought after for fabricating AlGaN/GaN based metal oxide semiconductor heterojunction field effect transistors (MOS-HFETs) for power applications. The ideal gate dielectric is required to suppress gate leakage and minimize threshold voltage (VT) instability by hosting minimal interface traps. Additionally, with the need for an enhancement mode device, it is preferable if it minimizes VT shift in the negative direction. For the first time, we compare popular ALD dielectrics like SiO2, Al2O3, HfO2 and HfAlO with identical electrical thickness on AlGaN/GaN, thereby ensuring identical electrostatic conditions across different dielectrics. High-k ALD dielectrics (HfAlO, HfO2 and Al2O3) are found to suppress gate leakage but host a high density of interface traps with AlGaN, thereby resulting in significant VT instability. ALD SiO2 gate dielectric, annealed in N2 above 600 °C, is a promising gate dielectric candidate which provides the most stable and least negative shift in VT while also substantially suppressing gate leakage below that of an HFET. DA - 2015/12// PY - 2015/12// DO - 10.1088/0268-1242/30/12/125017 VL - 30 IS - 12 SP - SN - 1361-6641 KW - power transistors KW - semiconductor-insulator interfaces KW - semiconductor device reliability KW - high-k gate dielectrics KW - atomic layer deposition (ALD) KW - AlGaN/GaN KW - MOSHFET ER - TY - CONF TI - A novel transverse flux machine for vehicle traction aplications AU - Wan, Z. AU - Ahmed, A. AU - Husain, I. AU - Muljadi, E. AB - A novel transverse flux machine topology for electric vehicle traction application using ferrite magnets is presented in this paper. The proposed transverse flux topology utilizes novel magnet arrangements in the rotor that are similar to Halbacharray to boost flux linkage; on the stator side, cores are alternately arranged around a pair of ring windings in each phase to make use of the entire rotor flux that eliminates end windings. Analytical design considerations and finite element methods are used for an optimized design of a scooter in-wheel motor. Simulation results from Finite Element Analysis (FEA) show the motor achieved comparable torque density to conventional rare-earth permanent magnet machines. This machine is a viable candidate for direct drive applications with low cost and high torque density. C2 - 2015/// C3 - 2015 ieee power & energy society general meeting DA - 2015/// DO - 10.1109/pesgm.2015.7286494 ER - TY - CONF TI - A modified priority list-based MILP method for solving large-scale unit commitment problems AU - Ke, X. D. AU - Lu, N. AU - Wu, D. AU - Kintner-Meyer, M. AB - This paper presents a two-step modified priority list (MPL) based mixed integer linear programming (MILP) method for improving the computational speed of unit commitment (UC) programs while preserving optimality. In the first step, the heuristics of UC results for a given generation fleet are investigated to develop the MPL. A subset of the generators are determined to be online (committed) or offline (uncommitted) within a planning period (e.g., a week), based on the demand curve and generator priority list. Then, for generators whose on/off status is predetermined, the corresponding binary variables are removed from the MILP solving process. After this simplification, the remaining problem can be solved much faster using an off-the-shelf MILP solver, based on the branch-and-bound algorithm. Scale factors are used to adjust the tradeoff between solution speed and level of optimality. Simulation results show that the proposed method can significantly speed up the large-scale UC problem with negligible compromise in optimality by selecting appropriate scale factors. C2 - 2015/// C3 - 2015 ieee power & energy society general meeting DA - 2015/// DO - 10.1109/pesgm.2015.7286561 ER - TY - CONF TI - A Wide-area SVC controller design using a dynamic equivalent model of WECC AU - Weiss, M. AU - Chakrabortty, Aranya AU - Ashrafi, F. H. AU - Jamehbozorg, A. AU - Ahu-Jaradeh, B. N. AB - In our recent work [1] we constructed a reduced-order five-area model of the Western Electricity Coordinating Council (WECC) power system using mathematically derived parameters from real PMU data. These parameters include inter and intra-area impedances, inertias, and damping values for aggregate machines representing five geographic areas. In this paper we use this reduced-order model as a tool to design an SVC controller to damp the inter-machine oscillation modes, which in the full-order model corresponds to inter-area oscillations. The controller input is chosen via statistical variance analysis, and its parameters are tuned to improve slow mode damping. The model is implemented in a real-time digital simulator, and emulated for various disturbance scenarios to illustrate the effectiveness of the SVC using a metric for dynamic performance. The resulting closed-loop response is promising in aiding damping of inter-area modes in the WECC, especially at a time of increasing penetration of wind and other renewable resources. C2 - 2015/// C3 - 2015 ieee power & energy society general meeting DA - 2015/// DO - 10.1109/pesgm.2015.7286605 ER - TY - JOUR TI - Voltage stability enhancement using thermostatically controlled appliances as a comfort-constrained virtual generator AU - Wang, Dan AU - Jia, Hongjie AU - Wang, Chengshan AU - Lu, Ning AU - Fan, Menghua AU - Zhou, Yue AU - Qi, Yebai T2 - INTERNATIONAL TRANSACTIONS ON ELECTRICAL ENERGY SYSTEMS AB - Conventional direct load-shedding for achieving static voltage stability lacks considerations on both customer comfort and energy efficiency, resulting in higher cost and emission. A novel security-based, optimal load-shedding strategy considering customer comfort settings is presented in this paper. A temperature priority list method is used to model the virtual generator (VG) consisting of thermostatically controlled appliances (TCAs). To illustrate the control process and performance evaluation of the proposed load-shedding scheme, a modified IEEE 6-bus test system is used. Three heat, ventilation, and air-conditioning (HVAC) groups are numerically simulated to respond to optimal load shedding signals. Reduced responsive load population, variations of temperature dead-bands, and different outdoor temperature profiles are modeled to evaluate the capacity variations of the VG and its control performance. The results demonstrate that TCAs can provide satisfactory voltage stability. Copyright © 2015 John Wiley & Sons, Ltd. DA - 2015/12// PY - 2015/12// DO - 10.1002/etep.2048 VL - 25 IS - 12 SP - 3509-3522 SN - 2050-7038 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000367676900018&KeyUID=WOS:000367676900018 KW - voltage stability enhancement KW - demand response KW - indirect load control KW - HVAC KW - regulation service KW - thermostatically controlled loads ER - TY - CONF TI - Tunable GaInP solar cell lattice matched to GaAs AU - Sayed, I. E. H. AU - Carlin, C. Z. AU - Hagar, B. AU - Colter, P. C. AU - Bedair, S. M. AB - A new strain-balanced multiple quantum well (MQW) approach to tune the Ga 0.51 In 0.49 P bandgap is demonstrated. This approach is based on Ga 1-x In x P/Ga 1-y In y P (x > y) or Ga 1-x In x As z P 1-z /Ga 1-y In y P (x > y) structures, strain balanced and lattice matched to GaAs in a p-i-n solar cell structure. A red shift in the absorption edge and an increase in the short circuit current were observed. Carriers generated in quantum wells due to transitions between the quantum levels are transported across the barriers via thermionic emission. The proposed structure allows more flexibility in the design of current multi-junction solar cells and future cells with more than four junctions. C2 - 2015/// C3 - 2015 ieee 42nd photovoltaic specialist conference (pvsc) DA - 2015/// DO - 10.1109/pvsc.2015.7356081 ER - TY - CONF TI - Start-up scheme for solid state transformers connected to medium voltage grids AU - Mainali, K. AU - Madhusoodhanan, S. AU - Tripathi, A. AU - Patel, D. AU - Bhattacharya, Subhashish AB - The development of the high voltage wideband gap semiconductor SiC power devices has enabled the solid state transformer (SST) technology in connecting a medium voltage grid to a low voltage grid. Though, these power devices have superior loss and switching characteristics compared to Si power devices, they have limited inrush current handling capability. The large inrush currents that flow into the SST from the grids when commissioning the SST system can be detrimental to the SiC devices. A proper start-up scheme is required to address this issue. Reported literatures on SST are focused on different topologies and their control aspects. This paper is focused in developing the safe start-up schemes for SST system connecting medium voltage grid to low voltage grid. The paper presents the simulation results and experimental verifications of the proposed SST start-up scheme. C2 - 2015/// C3 - Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC DA - 2015/// DO - 10.1109/apec.2015.7104473 VL - 2015-May SP - 1014-1021 M1 - May UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84937922109&partnerID=MN8TOARS ER - TY - CONF TI - Solid-state transformer interfaced PMSG wind energy conversion system AU - Gao, R. AU - Husain, I. AU - Wang, F. AU - Huang, A. Q. AB - The solid-state transformer (SST) has been regarded as an emerging technology where emphasis is mainly on the design of the device. To explore its system integration opportunities, this paper proposes and demonstrates a SST interfaced permanent magnet synchronous generator (PMSG) wind energy conversion system. The system integration issues along with wind turbine level control methods have been presented and simulated for power management. Moreover, the lab hardware prototype has been set up, which consists of an induction motor based wind turbine emulator (WTE), PMSG, pulse-width modulation (PWM) rectifier, SST, and resistive load bank. Experiments have been carried out to validate the proposed system and control strategy. C2 - 2015/// C3 - 2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015) DA - 2015/// DO - 10.1109/apec.2015.7104517 SP - 1310-1317 ER - TY - CONF TI - Quadrature amplitude modulated (QAM) communication link for near and mid-range RFID systems AU - Besnoff, Jordan AU - Ricketts, David AB - We present the theory and design equations for leveraging vector modulation in the form of M-ary quadrature amplitude modulation (QAM) for LF near and mid-range RFID systems, which can allow for the design of high bandwidth passive near and mid-range devices. The theory is developed through the impedance transformations that occur in coupled coil antennas. Using the developed theory along with system simulations, we determine the necessary load impedances for 4-QAM constellations at various distances for a carrier frequency of approximately 2.4 MHz and present 3 prototype boards that yield the desired reflections. The achievable data rates are investigated through a custom IQ demodulator, and we show that for communication distances of 17 cm, 29 cm, and 45 cm, which represent scaled coil diameter distances, data rates of 409.6 kbps, 307.2 kbps, and 153.6 kbps can be achieved. This corresponds to bandwidth percentages of 17%, 12%, and 6.5%, which surpasses the bandwidth percentage of typical NFC communication systems of about 3% for a carrier of 13.56 MHz (424 kbps). C2 - 2015/4// C3 - 2015 IEEE International Conference on RFID (RFID) DA - 2015/4// DO - 10.1109/rfid.2015.7113086 SP - 151-157 PB - Institute of Electrical and Electronics Engineers (IEEE) ER - TY - CONF TI - Power-weighting-based multiple input and multiple output control strategy for single-phase PV cascaded H-bridge multilevel grid-connected inverter AU - Huang, Q. Y. AU - Wang, M. Q. AU - Yu, Wensong AU - Huang, A. Q. AB - This paper presents a power-weighting-based multiple input and multiple output control strategy and performance improvements schemes for single-phase PV cascaded H-bridge multilevel grid-connected inverter. The truly individual MPPT block for each H-bridge converter realizes independent MPPT, and the sum of each voltage reference provides the system voltage reference for the voltage loop. And the sum of each PV voltage is the system voltage feedback. The output of the voltage controller delivers the peak value of the sinusoidal current reference. The output of this central current controller is assigned directly according to the PV power weighting factors to create the coordinated control signals for PWM generation of each H-bridge respectively. This approach makes the control structure for this cascaded multilevel inverter have only one central dual loop controller, and the PWM generation will be decoupled from the voltage controllers. This feature is similar with the single H-bridge inverter's dual loop control. Furthermore, to improve the dynamic response of the voltage loops, a sample and hold block at double line frequency is included in each voltage loop. Therefore, the voltage loop bandwidth will increase to 25~30Hz and the MPPT speed will be much faster as well. Besides, the power-based duty-ratio feed-forward technique is proposed to improve the current loop performance. Finally, simulated and experimental results are provided to verify the performance of the proposed control approaches. C2 - 2015/// C3 - 2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015) DA - 2015/// DO - 10.1109/apec.2015.7104646 SP - 2148–2153 ER - TY - CONF TI - Modular isolated DC-DC converter with multi-limb transformer for interfacing of renewable energy sources AU - Chattopadhyay, R. AU - Bhattacharya, Subhashish AB - This paper presents a modular isolated scalable three phase dual active bridge(DAB) DC-DC converter configuration using three multi limb high frequency transformers. The proposed converter has the advantage of having multiple low and high voltage dc links, which can be used at different power levels. The converter has three high voltage dc links which can be used for cascaded inverters or can be connected in series to provide a high dc link voltage for medium voltage grid-tie inverter. Multiple number of renewable energy sources(RES) can be connected to the low voltage side dc links to feed power to the grid. The paper work contains converter configuration, equivalent circuit of multi limb transformer, control of converter for a single renewable energy source and multiple renewable energy sources. C2 - 2015/// C3 - Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC DA - 2015/// DO - 10.1109/apec.2015.7104785 VL - 2015-May SP - 3039-3046 M1 - May UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84937960339&partnerID=MN8TOARS ER - TY - CONF TI - Medium voltage power converter design and demonstration using 15 kV SiC N-IGBTs AU - Kadavelugu, A. AU - Mainali, K. AU - Patel, D. AU - Madhusoodhanan, S. AU - Tripathi, A. AU - Hatua, K. AU - Bhattacharya, Subhashish AU - Ryu, S.-H. AU - Grider, D. AU - Leslie, S. AB - This paper summarizes the different steps that have been undertaken to design medium voltage power converters using the state-of-the-art 15 kV SiC N-IGBTs. The 11 kV switching characterization results, 11 kV high dv/dt gate driver validation, and the heat-run test results of the SiC IGBT at 10 kV, 550 W/cm 2 (active area) have been recently reported as individual topics. In this paper, it is attempted to link all these individual topics and present them as a complete subject from the double pulse tests to the converter design, for evaluating these novel high voltage power semiconductor devices. In addition, the demonstration results of two-level H-Bridge and three-level NPC converters, both at 10 kV dc input, are being presented for the first-time. Lastly, the performance of two-chip IGBT modules for increased current capability and demonstration of three-level poles, built using these modules, at 10 kV dc input with sine-PWM and square-PWM modulation for rectifier and dc-dc stages of a three-phase solid state transformer are presented. C2 - 2015/// C3 - Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC DA - 2015/// DO - 10.1109/apec.2015.7104530 VL - 2015-May SP - 1396-1403 M1 - May UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84937857287&partnerID=MN8TOARS ER - TY - CONF TI - Learning rule for associative memory in recurrent neural networks AU - Jacob, T. AU - Snyder, W. AB - We present a new learning rule for intralayer connections in neural networks. The rule is based on Hebbian learning principles and is derived from information theoretic considerations. A simple network trained using the rule is shown to have associative memory like properties. The network acts by building connections between correlated data points, under constraints. C2 - 2015/// C3 - 2015 international joint conference on neural networks (ijcnn) DA - 2015/// DO - 10.1109/ijcnn.2015.7280532 ER - TY - CONF TI - GaN HEMT based 250W CCM photovoltaic micro-inverter AU - McLamara, J. W. AU - Huang, A. Q. AB - The high speed, conductivity, and voltage blocking capability of the GaN HEMT facilitates higher efficiency, and smaller size of switched mode power supply designs. Characteristics such as these are important in the solar energy field, in which every extra Watt of harvestable power is extremely valuable. In this paper, the design and experimental results of a 250W 240VAC photo-voltaic micro-inverter utilizing commercially available enhancement-mode GaN HEMTs are presented. The design philosophy is centered on leveraging the advantages of GaN while applying analytics to maximizing efficiency and minimizing device stress. To that end, the nuances of employing GaN devices with respect to parasitic resonance, layout dependent performance, and thermal considerations are also presented for the purpose of executing a robust design. C2 - 2015/// C3 - 2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015) DA - 2015/// DO - 10.1109/apec.2015.7104359 SP - 246-253 ER - TY - CONF TI - GaN FET based CubeSat Electrical Power System AU - Singh, S. AU - Shrivastav, A. AU - Bhattacharya, Subhashish AB - This paper deals with the development of high efficiency, compact and flexible Electrical Power System (EPS) for a Cube Satellite (CubeSat). The EPS is responsible for harnessing power from solar panels, battery charging and multi-domain voltage output regulation within the CubeSat. This work builds upon the results and learnings obtained from an EPS which uses Silicon MOSFETs. The hardware and software aspects of the development of such photovoltaic battery based power management systems are examined. The introduction of digital controller provides flexibility and intelligence but also introduces controller design challenges with simultaneous execution of multiple control loops. The EPS behaves like a standalone photo-voltaic battery charging system that harnesses solar energy to charge the battery banks. This entails the development of maximum power point tracking techniques as well as battery charging methods such as constant-current/constant-voltage charging. A dual loop control methodology with output current control is implemented to regulate the output current when charging the battery. This new EPS uses GaN FETs with an aim to increase efficiency and have all the functionalities of its silicon counterpart in smaller dimensions. C2 - 2015/// C3 - Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC DA - 2015/// DO - 10.1109/apec.2015.7104529 VL - 2015-May SP - 1388-1395 M1 - May UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84937840289&partnerID=MN8TOARS ER - TY - CONF TI - Evaluation of design variables in Thompson coil based operating mechanisms for ultra-fast opening in hybrid AC and DC circuit breakers AU - Peng, C. AU - Husain, I. AU - Huang, A. Q. AB - The paper presents the operation transient analysis and multi-physics complexities in the design of a Thompson coil based ultra-fast mechanical switch for hybrid AC and DC circuit breakers. The electromagnetic, mechanical and thermal behavior of the switch has been analyzed through simulation using a multi-physics finite element software. The design variables have been classified into lumped circuit and geometric parameters; the sensitivity analysis by means of systematic and comprehensive simulations on these parameters helped establish the design guidelines. The switch has been designed with optimization for both the circuit parameters and geometrical dimensions of components targeting 2 mm travel for separation within 1 ms. C2 - 2015/// C3 - 2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015) DA - 2015/// DO - 10.1109/apec.2015.7104673 SP - 2325-2332 ER - TY - CONF TI - Distributed Energy Storage Device integration with three phase distribution grid using a Transformerless Intelligent Power Substation AU - Madhusoodhanan, S. AU - Tripathi, A. AU - Mainali, K. AU - Patel, D. AU - Kadavelugu, A. AU - Bhattacharya, Subhashish AB - The advent of SiC devices has resulted in the development of 3-phase, Medium Voltage (MV) grid tied Solid State Transformers (SSTs). One such SST is the 100 kVA Transformerless Intelligent Power Substation (TIPS) based on 15 kV SiC IGBTs and 1200 V SiC MOSFETs which interconnects the 13.8 kV distribution grid with the 480 V utility grid. TIPS has an ac-dc-dc-ac multi-module configuration. The availability of 800 V dc and 480 V ac terminals in the system allows for the integration of Distributed Energy Storage Devices (DESDs) with the 13.8 kV MV grid. These DESDs store the energy derived from the renewable sources like solar, wind and wave. The complex nature of the overall system makes the power flow control very challenging during integration. This paper investigates the steady state and transient behavior of the TIPS system when integrated with a battery model representing the DESD. Complete system simulation is carried out using the switching model of the converters along with the dynamic model of the battery and a feeder model similar to IEEE-34 bus system. Experimental verification is done on TIPS prototype at scaled down voltage and power levels. C2 - 2015/// C3 - Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC DA - 2015/// DO - 10.1109/apec.2015.7104422 VL - 2015-May SP - 670-677 M1 - May UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84937940471&partnerID=MN8TOARS ER - TY - CONF TI - Design methodology of series DC coupling transformer in a medium-voltage DC amplifier system AU - Beddingfield, R. AU - De, A. AU - Mirzae, H. AU - Bhattacharya, Subhashish AB - The medium-voltage dc amplifier is a controllable dc source for the purpose of testing medium-voltage dc system technologies for shipboard applications. In a medium-voltage dc amplifier system, a dc active filter with a series dc coupling transformer is an integral component of the system required for both steady-state and dynamic voltage injection. This paper describes the design aspects and methodology for the series dc coupling transformer in such a system. The design of the transformer is one of the most critical aspects of this system as it has to withstand large continuous dc current offset without saturating. Based on system performance requirements, design criteria for the transformer is defined and two transformer designs based on two Iron-based magnetic materials are evaluated for a 12 kVA, 300 Vdc laboratory-scale amplifier test bed. An optimal design methodology is also proposed in this paper. Various design compromises have been studied and reported. The practical transformer design considerations and feasibility study for a medium-voltage dc amplifier system are given. C2 - 2015/// C3 - Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC DA - 2015/// DO - 10.1109/apec.2015.7104350 VL - 2015-May SP - 183-190 M1 - May UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84937857830&partnerID=MN8TOARS ER - TY - CONF TI - DC assisted bipolar switched reluctance machine AU - Husain, T. AU - Sozer, Y. AU - Husain, I. AB - In this paper, a sinusoidally excited four-phase switched reluctance machine (SRM) with modified DC assisted windings is presented. The proposed four-phase SRM configuration with modified DC windings has reduced number of controllable phases and power converter devices. The DC winding configuration is modified from its traditional form by taking advantage of the machine's inherent 90 degree phase shift between adjacent phases to achieve the desired simplification in the drive. Different power electronic converters that can be used with the proposed winding configuration have also been investigated. The proposed concepts are then verified through coupled FEA circuit simulations on a case study motor. C2 - 2015/// C3 - 2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015) DA - 2015/// DO - 10.1109/apec.2015.7104360 SP - 254-261 ER - TY - CONF TI - Current commutation in a medium voltage hybrid DC circuit breaker using 15 kV vacuum switch and SiC devices AU - Peng, C. AU - Huang, A. Q. AU - Song, X. Q. AB - Analysis and experimental study of current commutation in an ultra-fast, current limiting, hybrid DC circuit breaker for medium voltage applications is reported in this paper. The hybrid DCCB consists a fast acting 15 kV mechanical switch, a low voltage commutating switch, a single 15 kV Silicon Carbide Emitter Turn Off Thyristor (ETO) device, and a stack of MOVs. The proof-of-concept prototype is able to conduct 45 A normal current and interrupt a maximum of more than 100 A fault current at medium voltage level in less than 4 milliseconds, which is one order of magnitude faster compared to conventional mechanical circuit breakers that typically take 40-100 ms. This paper has presented the operation principle of a hybrid DC circuit breaker and analyzed the current commutation process. Based on the analysis, guidelines are given in the paper to select and design the commutating switch. C2 - 2015/// C3 - 2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015) DA - 2015/// DO - 10.1109/apec.2015.7104661 SP - 2244-2250 ER - TY - CONF TI - Auxiliary power supply for solid state transformer with ultra high voltage capacitive driving AU - Zong, S. AU - Zhu, Q. L. AU - Yu, Wensong AU - Huang, A. Q. AB - This paper proposes an auxiliary power supply (APS) for solid state transformers (SST), which is able to handle extremely high input voltage. Input series output parallel (ISOP) structure is used and only one controller IC is adopted to regulate the output voltage, which simplifies the structure and reduces the cost effectively. Capacitive driving is used to drive multiple switches in different modules of the APS. The proposed capacitive driving method is able to transfer gate signal and driving energy simultaneously even for thousands of volts, which largely reduces the cost and size of the APS. Finally the proposed auxiliary power supply is verified and demonstrated through a 12W prototype. C2 - 2015/// C3 - 2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015) DA - 2015/// DO - 10.1109/apec.2015.7104472 SP - 1008–1013 ER - TY - JOUR TI - Atomic Layer Deposition of SnO2 for Selective Room Temperature Low ppb Level O-3 Sensing AU - Mills, Steven AU - Lim, Michael AU - Lee, Bongmook AU - Misra, Veena T2 - ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY AB - This work demonstrates ultra-low power ozone sensors for real time, continuous, and portable monitoring. Atomic Layer Deposition (ALD) of SnO2 enables precise control of ultrathin film thickness on the order of the Debye length to enhance sensitivity at room temperature. Correlation between ozone concentration and the rate of resistance change is used to maintain fast response times and ultraviolet (UV) illumination hastens recovery. ALD SnO2 ultrathin film sensors realize room temperature operation with highly selective detection of 50 ppb ozone with average power consumption of 150 μW making them well suited for real time, portable environmental monitoring systems. DA - 2015/// PY - 2015/// DO - 10.1149/2.0111510jss VL - 4 IS - 10 SP - S3059-S3061 SN - 2162-8769 ER - TY - JOUR TI - Application of AlGaN/GaN Heterostructures for Ultra-Low Power Nitrogen Dioxide Sensing AU - Lim, Michael AU - Mills, Steven AU - Lee, Bongmook AU - Misra, Veena T2 - ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY AB - Ultra-low power room temperature NO2 sensors are demonstrated using AlGaN/GaN. The chemically stable semiconductor was sensitized to increase the sensitivity to enable ultra-low power, low ppb level detection without additional heaters. Sensors were sensitized by two methods, ultra-thin ALD SnO2 and surface enhancement by ICP-RIE in BCl3 gas. Both sensitization techniques demonstrate room temperature response, while the unsensitized sensors did not respond. At room temperature, surface enhanced sensors show a significant increase in sensitivity compared to SnO2 sensitized sensors. Sensitized sensors have fast response times and ultra-low power consumption to enable wearable monitoring systems with high spatial resolution of NO2. DA - 2015/// PY - 2015/// DO - 10.1149/2.0101510jss VL - 4 IS - 10 SP - S3034-S3037 SN - 2162-8769 ER - TY - CONF TI - An isolated bi-directional soft-switched DC-AC converter using wide-band-gap devices with novel carrier-based unipolar modulation technique under synchronous rectification AU - Wang, M. Q. AU - Huang, Q. Y. AU - Yu, Wensong AU - Huang, A. Q. AB - A novel carrier-based unipolar-SPWM-oriented modulation technique with synchronous rectification for isolated bi-directional soft-switched high-frequency-AC (HFAC) link DC-AC converter using SiC MOSFET is presented in this paper. The DC-AC converter is composed of a full-bridge (FB) inverter cascaded with a cycloconverter through a high-frequency transformer. In order to increase the efficiency and power density, we proposed to utilize SiC MOSFETs for the converter. A carrier-based unipolar-SPWM-oriented modulation technique is proposed to realize zero-voltage-switching (ZVS) for FB and zero-current or zero-voltage-switching (ZVS/ZCS) for cycloconverter in all load range, and to suppress the voltage spikes introduced by the transformer leakage inductance as well. Synchronous rectification is implemented to further increase the converter efficiency. With the novel modulation technique, 1/4 of the AC switches in the cycloconverter are always on which eliminates 1/4 of the switching loss. Simulation model and a 400 VDC to 240 VAC, 1.2 kW prototype have been developed to validate the effectiveness and performance of the proposed unipolar soft-switching modulation technique and SiC converter. C2 - 2015/// C3 - 2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015) DA - 2015/// DO - 10.1109/apec.2015.7104672 SP - 2317–2324 ER - TY - CONF TI - An integrated high efficiency ultra-low power single chip DC/AC inverter for driving liquid crystal electro-optic lenses AU - Li, X. M. AU - Huang, A. AB - An integrated high efficiency, ultra-low power liquid crystal driver for electro-optic diffractive lenses is presented in this paper. The proposed LC driver provides an adjustable 3V to 15V RMS square wave output voltage to drive a liquid crystal in the electro-optic lens, which can be modeled as a 5nF capacitive load. This application is powered by a 3V lithium button cell or energy harvest devices. A reconfigurable hysteretic 2×/3×/4×/5× switched capacitor charge pump is developed for DC-DC conversion to maintain high power efficiency over the entire output power range. An improved H-bridge driving scheme is used to reduce the DC/AC inversion power loss. In addition, an auto-sink scheme is developed to speed up output transaction from high to low in different output modes. Implemented in a 0.25μm 5V V GS , 12-45V V DS BCD technology, the proposed LC driver achieves peak power efficiency of 98%. The transaction time of LC driver output from high to low is 48us, which is 219 times faster than that when auto-sink scheme is disabled. C2 - 2015/// C3 - 2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015) DA - 2015/// DO - 10.1109/apec.2015.7104811 SP - 3208-3211 ER - TY - CONF TI - A novel bi-directional DC-DC converter for distributed energy storage device AU - Xue, F. AU - Yu, R. Y. AU - Yu, Wensong AU - Huang, A. Q. AU - Du, Y. AB - This paper presents a high efficiency, low-cost bidirectional isolated dc--dc converter for distributed energy storage device (DESD). Derived from dual active bridge (DAB), the proposed converter consists of a half-bridge circuit at high voltage side and a push-pull circuit with active clamp at low voltage side. The proposed topology is attractive in low voltage and high current applications and it also reduces the number of switching transistors such that the cost and complexity are considerably reduced. With single phase-shift control strategy, all the switches operate in zero-voltage switching (ZVS) condition without increasing circuit complexity. Besides, planar transformer is implemented where the low voltage windings consist of PCB trace and external copper foils. A 380V to 12V DC, 500W DESD hardware prototype has been designed, fabricated, and tested. Experimental results verify the validity of the proposed bi-directional converter, which has 97.3% peak efficiency and maintains greater than 92% efficiency over a load range between 100W and 600W. C2 - 2015/// C3 - 2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015) DA - 2015/// DO - 10.1109/apec.2015.7104489 SP - 1126–1130 ER - TY - CONF TI - A medium voltage bidirectional DC-DC converter combining resonant and dual active bridge converters AU - Wang, L. AU - Zhu, Q. L. AU - Yu, Wensong AU - Huang, A. Q. AB - In this paper, an isolated bidirectional dc-dc converter for medium voltage application is proposed. It combines the resonant converter and dual active bridge converter (DAB). Under normal load condition, this isolated converter operates at resonant point to achieve zero voltage (ZVS) turn on at primary side and zero current (ZCS) turn off at secondary side. When over current happens, the voltage across the resonant capacitor will be clamped by paralleled diode and the converter will automatically switch to resonant and DAB mixed operation mode, therefore cycle-by-cycle over current protection is achieved with constant switching frequency. Different operation modes are analyzed for the proposed circuits using time domain waveform and state trajectory. Detailed theoretical analysis and design procedure for transformer, resonant tank and semiconductor devices are discussed. Performance of the proposed circuit is verified by a 3 kV to 200 V, 2.5 kW experimental prototype with high voltage SiC devices. C2 - 2015/// C3 - 2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015) DA - 2015/// DO - 10.1109/apec.2015.7104486 SP - 1104–1111 ER - TY - CONF TI - 4H-SiC 15kV n-IGBT physics-based sub-circuit model implemented in Simulink/Matlab AU - Lee, M. C. AU - Wang, G. Y. AU - Huang, A. Q. AB - A physics-based 15kV 4H-SiC n-IGBT sub-circuit model implemented in Simulink/Matlab is demonstrated in this work. Two-phase voltage ramp during the switching before and after punch through is well predicted. Simulated with a simple 4H-SiC Schottky diode model, the switching results is experimentally verified. The current bump during turn-off and current overshoot during turn-on are well-predicted and can be explained by the instantaneous output capacitances of the IGBT and Schottky diode. The computing speed for the full turn-on and off with stray inductance is approximately 2 minutes. C2 - 2015/// C3 - 2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015) DA - 2015/// DO - 10.1109/apec.2015.7104478 SP - 1051-1057 ER - TY - CONF TI - 3D FEA based squirrel cage rotor model for design tradeoffs and performance analysis AU - Kabir, M. A. AU - Mikail, R. AU - Englebretson, S. AU - Husain, I. AB - An accurate rotor resistance estimation model of squirrel cage induction motors (SCIMs) is developed in 3D FEA. 2D transient analysis was utilized for excitations in the 3D model to improve its accuracy over previous 2D and analytical methods. Rated and starting performance from the FEA model match with the nominal and locked-rotor performance of a 3-phase, 460 V, 1 hp test machine. A modified ring model has been proposed and machine torque-slip characteristics and nominal performance have been analyzed. The effect of slot opening and 4 classes of SCIM bar geometry have been investigated to analyze their relative performance. Finally, four different ring and bar combinations are suggested, with the modified rotor structure presenting gain in starting and rated performance compared to the test machine. Results present the design tradeoffs and performance analysis, first for a 1 hp SCIM and then extended for a higher power (10 hp) machine. C2 - 2015/// C3 - 2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015) DA - 2015/// DO - 10.1109/apec.2015.7104732 SP - 2696-2702 ER - TY - CONF TI - Voltage source based voltage-to-time converter AU - Stout, T. AU - Dean, A. AB - Voltage-to-time converter (VTC) circuits are used as the core component of single-slope analog to digital converters (ADCs). These VTC circuits have traditionally depended on the use of a constant current source as part of their implementation in order to have good linearity. An alternative approach is presented where only voltage sources and a few discrete components are needed without sacrificing linearity. This circuit can be realized in hardware using general purpose IO (GPIO) pins that are available on all microcontrollers, FPGAs, and CPLDs. This provides more flexibility than current source based VTCs that rely on specialized hardware, allowing for a full ADC to be built using GPIO pins with no specialized ADC hardware. C2 - 2015/// C3 - 2015 ieee 58th international midwest symposium on circuits and systems (mwscas) DA - 2015/// DO - 10.1109/mwscas.2015.7282107 ER - TY - CONF TI - The first demonstration of symmetric blocking SiC gate turn-off (GTO) thyristor AU - Sung, Woongje AU - Huang, Alex Q. AU - Baliga, B. J. AU - Ji, Inhwan AU - Ke, Haotao AU - Hopkins, Douglas C. T2 - 2015 IEEE 27th International Symposium on Power Semiconductor Devices & IC's (ISPSD) AB - This paper reports the development of symmetric blocking SiC p-GTO thyristors. The proposed thyristor structure features a positive bevel edge termination implemented by orthogonal dicing technique. In this paper, a detailed design of the device structure, forward current-voltage characteristics, and symmetric blocking capabilities are discussed. C2 - 2015/5// C3 - 2015 IEEE 27th International Symposium on Power Semiconductor Devices & IC's (ISPSD) DA - 2015/5// DO - 10.1109/ispsd.2015.7123438 SP - 257–260 PB - IEEE SN - 9781479962594 9781479962617 UR - http://dx.doi.org/10.1109/ISPSD.2015.7123438 DB - Crossref N1 - \urlhttps://ieeexplore.ieee.org/document/7123438/ RN - \urlhttps://ieeexplore.ieee.org/document/7123438/ ER - TY - CONF TI - Static and dynamic performance characterization and comparison of 15 kV SiC MOSFET and 15 kV SiC n-IGBTs AU - Wang, G. Y. AU - Huang, A. Q. AU - Wang, F. AU - Song, X. Q. AU - Ni, X. J. AU - Ryu, S. H. AU - Grider, D. AU - Schupbach, M. AU - Palmour, J. AB - This paper presents the static and dynamic performance of 15 kV SiC IGBTs with 2 um and 5 um field-stop buffer layer thicknesses respectively and compares them with 15 kV SiC MOSFET in term of loss and switching capability. Their switching energy for different gate resistors and temperature have been reported and compared. A 5 kHz 10.5 kW 8 kV boost converter has been built and tested using these three devices respectively. The MOSFET based boost converter has the highest efficiency 99.39% which is the highest reported efficiency for a high voltage SiC device based converter. PLECS loss models can be developed for these devices based on the characterization data to simplify the simulation of a variety circuits or applications which potentially utilize these devices. C2 - 2015/// C3 - Proceedings of the international symposium on power semiconductor DA - 2015/// DO - 10.1109/ispsd.2015.7123431 SP - 229-232 ER - TY - CONF TI - SiC reversely switched dynistor (RSD) for pulse power application AU - Liang, L. AU - Huang, A. Q. AU - Liu, C. AU - Chang, W. G. AB - This paper reports the world's first SiC reversely switched dynistor (RSD) work. The device structure of 1200V SiC RSD is designed. The two-dimensional numerical model of SiC RSD is established with full consideration of the SiC material parameters and the important physical effects in power device. The blocking characteristics and turn-on characteristics are simulated. The operation principle based on the turn-on controlled by the reverse plasma injection is explained. The influence factors on the switching performance, especially on the residual voltage, including the device parameters and the external conditions, are discussed. The experiment reports the high di/dt pulse output acquired recently based on Si RSD integrated module. The di/dt of 8.85kA/μs is acquired at 1500V discharge voltage, with the peak current of 3.7kA. C2 - 2015/// C3 - Proceedings of the international symposium on power semiconductor DA - 2015/// DO - 10.1109/ispsd.2015.7123447 SP - 293-296 ER - TY - CONF TI - Protecting privacy of topology in consensus networks AU - Katewa, V. AU - Chakrabortty, Aranya AU - Gupta, V. AB - Consider a set of agents implementing the discrete time consensus algorithm. At each time step, all agents also transmit their states to a central estimator that wishes to identify the underlying topology and eigenvalues of the network. It does so by using a nonlinear least squares (NLS) algorithm to identify the state evolution matrix used in the consensus algorithm. We present a mechanism to protect the differential privacy of this topology from an eavesdropper who may have unauthorized access to the estimator. In this mechanism, every agent purposely adds noise to its measurements before transmission to the estimator. The noise is designed to ensure that the eavesdropper cannot uniquely identify the topology with a specified confidence level. Numerical results are presented to describe the corresponding trade-off in estimation accuracy as a function of the level of differential privacy achieved. C2 - 2015/// C3 - 2015 american control conference (acc) DA - 2015/// DO - 10.1109/acc.2015.7171103 SP - 2476–2481 ER - TY - JOUR TI - Probabilistic total transfer capability analysis based on static voltage stability region integrated with a modified distributed-level nodal-loading model AU - Dan, Wang AU - Yue, Zhou AU - HongJie, Jia AU - ChengShan, Wang AU - Ning, Lu AU - MengHua, Fan T2 - SCIENCE CHINA-TECHNOLOGICAL SCIENCES DA - 2015/12// PY - 2015/12// DO - 10.1007/s11431-015-5964-3 VL - 58 IS - 12 SP - 2072-2084 SN - 1869-1900 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000367028400009&KeyUID=WOS:000367028400009 KW - voltage stability enhancement KW - demand response KW - demand-side management KW - indirect load control KW - heat pump KW - regulation service ER - TY - CONF TI - On the efficiency-optimal Markov chains for distributed networking applications AU - Lee, C. H. AU - Eun, D. Y. AB - The Metropolis-Hastings (MH) algorithm, in addition to its application for Markov Chain Monte Carlo sampling or simulation, has been popularly used for constructing a random walk that achieves a given, desired stationary distribution over a graph. Applications include crawling-based sampling of large graphs or online social networks, statistical estimation or inference from massive scale of networked data, efficient searching algorithms in unstructured peer-to-peer networks, randomized routing and movement strategies in wireless sensor networks, to list a few. Despite its versatility, the MH algorithm often causes self-transitions of its resulting random walk at some nodes, which is not efficient in the sense of the Peskun ordering - a partial order between off-diagonal elements of transition matrices of two different Markov chains, and in turn results in deficient performance in terms of asymptotic variance of time averages and expected hitting times with slower speed of convergence. To alleviate this problem, we present simple yet effective distributed algorithms that are guaranteed to improve the MH algorithm over time when running on a graph, and eventually reach `efficiency-optimality', while ensuring the same desired stationary distribution throughout. C2 - 2015/// C3 - 2015 ieee conference on computer communications (infocom) DA - 2015/// DO - 10.1109/infocom.2015.7218566 ER - TY - CONF TI - On aggregate control of clustered consensus networks AU - Boker, A. M. AU - Nudell, T. R. AU - Chakrabortty, Aranya AB - In this paper we address the problem of controlling the slow-time-scale dynamics of clustered consensus networks. Using time-scale separation arising from clustering, we first decompose the actual network model into an approximate model, and define the controller at every node as the sum of two independent state-feedback controls, one for the fast dynamics and another for the slow. We show that the slow controller is identical for every node belonging to the same cluster, indicating that only a single aggregate slow controller needs to be designed per area. This reduces the computational complexity of the design significantly. Applying results from singular perturbation theory, we show that when these individual controllers are implemented on the actual network, the closed-loop response is close to that obtained from the approximate models, provided that the clustering is strong. The design procedure is demonstrated by a simulation example. C2 - 2015/// C3 - 2015 american control conference (acc) DA - 2015/// DO - 10.1109/acc.2015.7172204 SP - 5527–5532 ER - TY - CONF TI - Improving learning and adaptation in security games by exploiting information asymmetry AU - He, X. F. AU - Dai, H. Y. AU - Ning, P. AB - With the advancement of modern technologies, the security battle between a legitimate system (LS) and an adversary is becoming increasingly sophisticated, involving complex interactions in unknown dynamic environments. Stochastic game (SG), together with multi-agent reinforcement learning (MARL), offers a systematic framework for the study of information warfare in current and emerging cyber-physical systems. In practical security games, each player usually has only incomplete information about the opponent, which induces information asymmetry. This work exploits information asymmetry from a new angle, considering how to exploit local information unknown to the opponent to the player's advantage. Two new MARL algorithms, termed minimax-PDS and WoLF-PDS, are proposed, which enable the LS to learn and adapt faster in dynamic environments by exploiting its private local information. The proposed algorithms are provably convergent and rational, respectively. Also, numerical results are presented to show their effectiveness through two concrete anti-jamming examples. C2 - 2015/// C3 - 2015 ieee conference on computer communications (infocom) DA - 2015/// DO - 10.1109/infocom.2015.7218560 ER - TY - JOUR TI - Highly efficient conductance control in a topological insulator based magnetoelectric transistor AU - Duan, Xiaopeng AU - Li, Xi-Lai AU - Li, Xiaodong AU - Semenov, Yuriy G. AU - Kim, Ki Wook T2 - Journal of Applied Physics AB - The spin-momentum interlocked properties of the topological insulator (TI) surface states are exploited in a transistor-like structure for efficient conductance control in the TI-magnet system. Combined with the electrically induced magnetization rotation as part of the gate function, the proposed structure takes advantage of the magnetically modulated TI electronic band dispersion in addition to the conventional electrostatic barrier. The transport analysis coupled with the magnetic simulation predicts super-steep current-voltage characteristics near the threshold along with the GHz operating frequencies. Potential implementation to a complementary logic is also examined. The predicted characteristics are most suitable for applications requiring low power or those with small signals. DA - 2015/12/14/ PY - 2015/12/14/ DO - 10.1063/1.4937407 VL - 118 IS - 22 SP - 224502 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.4937407 DB - Crossref ER - TY - CONF TI - High voltage Si/SiC hybrid switch: An ideal next step for SiC AU - Song, X. Q. AU - Huang, A. Q. AU - Lee, M. C. AU - Peng, C. AB - Silicon carbide (SiC) power switches such as MOSFET or JFET have demonstrated their superior advantages over silicon (Si) power devices such as IGBT, especially in terms of significantly reduced switching losses. A major issue facing large scale adoption of SiC power devices is still the much higher cost. This paper proposes that Si/SiC hybrid switch should be a natural next step moving forward for high voltage applications to address the cost issue. In the proposed Si/SiC hybrid switch, a SiC MOSFET is connected in parallel with Si IGBT to combine the advantages of IGBT and MOSFET. This concept can also works well with SiC JFET. A 6.5 kV Si IGBT and SiC MOSFET hybrid switch is developed as an example to demonstrate its superior cost/performance. The switching loss can be reduced by more than 70% at a cost of only 50% higher compared to Si IGBT. This work is especially essential for high voltage applications such as medium voltage motor drive, FACTS and HVDC systems. C2 - 2015/// C3 - Proceedings of the international symposium on power semiconductor DA - 2015/// DO - 10.1109/ispsd.2015.7123446 SP - 289-292 ER - TY - CONF TI - Exploring the impact of wind penetration on power system equilibrium using a numerical continuation approach AU - Chandra, S. AU - Mehta, D. AU - Chakrabortty, Aranya AB - In this paper we investigate how the equilibrium characteristics of conventional power systems may change with an increase in wind penetration. We first derive a differentialalgebraic model of a power system network consisting of synchronous generators, loads and a wind power plant modeled by wind turbines and doubly-fed induction generators (DFIG). The models of these three components are coupled via nonlinear power flow equations. In contrast to the traditional approach for solving the power flows via iterative methods that often lead to a local solution, we apply a recently developed parameterhomotopy based numerical continuation algorithm to compute all possible solutions. The method obtains all the solutions of the power flow equations over multiple values of the wind penetration. We observe that depending on the penetration limit and the setpoint value for the magnitude of the wind bus voltage, the system may exhibit several undesired or even unstable equilibria. We illustrate these results through a detailed simulation of a 5-machine power system model with wind injection, and highlight how the solutions may be helpful for small-signal stability assessment. C2 - 2015/// C3 - 2015 american control conference (acc) DA - 2015/// DO - 10.1109/acc.2015.7172011 SP - 4339–4344 ER - TY - CONF TI - Dual-vector phase rotator for Doherty beamformers AU - Greene, K. AU - Floyd, Brian AB - A 28-GHz dual-vector phase rotator is introduced, having the capability of generating two quadrature output signals that track one another in phase. The 4-bit dual-vector rotator was implemented in IBM 0.12-μm SiGe BiCMOS technology and achieves full 360o phase shifting, RMS phase and amplitude errors of <; 5 degrees and <; 0.8 dB, respectively for both output vectors, and 10-12 dB of gain. Output 1-dB compression points for both quadrature outputs is -6.5 to -4.4 dBm, suitable for directly driving a Doherty amplifier in a 28-GHz beamformer. C2 - 2015/// C3 - Proceedings of the 2015 ieee radio frequency integrated circuits symposium (rfic 2015) DA - 2015/// DO - 10.1109/rfic.2015.7337772 VL - 2015-November SP - 331–334 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84975761262&partnerID=MN8TOARS ER - TY - CONF TI - An experimental microgrid for laboratory activities AU - Sbordone, D. A. AU - Huq, K. M. M. AU - Baran, Mesut AB - This paper introduces development of a small scale microgrid which consists of a PV system, an energy storage device, and a load. The system is intended for conducting experiments to demonstrate and/or investigate different design and control issues related to microgrids. The system has also a data acquisition and power management component in order to facilitate monitoring and management of the system in different operating conditions. Hence, the system can be used for both education and research purposes. Two experiments have been provided to illustrate the flexibility of the proposed microgrid. C2 - 2015/// C3 - 2015 IEEE 15th International Conference on Environment and Electrical Engineering (IEEE EEEIC 2015) DA - 2015/// DO - 10.1109/eeeic.2015.7165188 SP - 363–367 ER - TY - CONF TI - A model predictive control design for selective modal damping in power systems AU - Jain, A. AU - Biyik, E. AU - Chakrabortty, Aranya AB - This paper presents a novel real-time predictive control technique to damp dominant inter-area oscillation modes in power systems. We first show that conventional Power System Stabilizers (PSS) in synchronous generators are best suited to damp only the intra-area oscillation modes, and participate poorly in inter-area damping. We then design a centralized Model Predictive Controller (MPC) to provide supplementary control to these conventional PSSs based on a Selective Discrete Fourier Transform (SDFT) approach. The SDFT extracts the energies associated with the inter-area frequency components in the output spectrum of the system, and uses this information to construct a weighting matrix Q. The MPC is then formulated as a quadratic minimization of the outputs using Q, resulting in damping only the inter-area modes of interest. In reality, however, the most dominant DFT magnitudes will not be known ahead of time since they are decided by the location of the disturbance. Therefore, we next augment the MPC design by predicting the dominant DFT magnitudes in the desired low frequency range using online measured data, and tuning Q accordingly. We illustrate the effectiveness of the proposed approach using an IEEE 39-bus prototype power system model for the New England system. C2 - 2015/// C3 - 2015 american control conference (acc) DA - 2015/// DO - 10.1109/acc.2015.7172007 SP - 4314–4319 ER - TY - CONF TI - A global identifiability condition for consensus networks on tree graphs AU - Nabavi, S. AU - Chakrabortty, Aranya AU - Khargonekar, P. P. AB - In this paper we present a sufficient condition that guarantees identifiability of linear network dynamic systems exhibiting continuous-time weighted consensus protocols with acyclic structure. Each edge of the underlying network graph G is defined by a constant parameter, referred to as the weight of the edge, while each node is defined by a scalar state whose dynamics evolve as the weighted linear combination of its difference with the states of its neighboring nodes. Following the classical definitions of identifiability and indistinguishability, we first derive a condition that ensures the identifiability of the edge weights of G in terms of the associated transfer function. Using this characterization, we propose a sensor placement algorithm that guarantees identifiability of the edge weights. We describe our results using illustrative examples. C2 - 2015/// C3 - 2015 american control conference (acc) DA - 2015/// DO - 10.1109/acc.2015.7170999 SP - 1830–1835 ER - TY - CONF TI - A 55-GHz power-efficient frequency quadrupler with high harmonic rejection in 0.1-mu m SiGe BiCMOS technology AU - Yeh, Y. S. AU - Floyd, Brian AB - This paper presents a V-band frequency quadrupler in 0.1-μm SiGe BiCMOS technology with 3-dB bandwidth from 44.8 to 57.2 GHz. The circuit employs cascode stacks comprising in-phase class-C common-emitter and anti-phase class-AB cascode devices to obtain current pulses at ×4 frequency. Four such cascodes driven with differential and tunable quadrature increase the 4 th harmonic output power while suppressing all other harmonics 22 dB or more. Measurements show >7.4-dBm 4 th harmonic output power, and >5.2% power efficiency for the core of the multiplier. C2 - 2015/// C3 - Proceedings of the 2015 ieee radio frequency integrated circuits symposium (rfic 2015) DA - 2015/// DO - 10.1109/rfic.2015.7337756 VL - 2015-November SP - 267–270 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84975774977&partnerID=MN8TOARS ER - TY - CONF TI - 22 kV SiC emitter turn-off (ETO) thyristor and Its dynamic performance including SOA AU - Song, X. Q. AU - Huang, A. Q. AU - Lee, M. C. AU - Peng, C. AU - Cheng, L. AU - O'Brien, H. AU - Ogunniyi, A. AU - Scozzie, C. AU - Palmour, J. AB - Ultra-high voltage (>10 kV) power devices based on SiC are gaining significant attentions since Si power devices are typically at lower voltage levels. In this paper, a world record 22kV Silicon Carbide (SiC) p-type ETO thyristor is developed and reported as a promising candidate for ultra-high voltage applications. The device is based on a 2cm 2 22kV p type gate turn off thyristor (p-GTO) structure. Its static as well as dynamic performances are analyzed, including the anode to cathode blocking characteristics, forward conduction characteristics at different temperatures, turn-on and turn-off dynamic performances. The turn-off energy at 6kV, 7kV and 8kV respectively is also presented. In addition, theoretical boundary of the reverse biased safe operation area (RBSOA) of the 22kV SiC ETO is obtained by simulations and the experimental test also demonstrated a wide RBSOA. C2 - 2015/// C3 - Proceedings of the international symposium on power semiconductor DA - 2015/// DO - 10.1109/ispsd.2015.7123443 SP - 277-280 ER - TY - JOUR TI - Stretch-Triggered Drug Delivery from Wearable Elastomer Films Containing Therapeutic Depots AU - Di, Jin AU - Yao, Shanshan AU - Ye, Yanqi AU - Cui, Zheng AU - Yu, Jicheng AU - Ghosh, Tushar K. AU - Zhu, Yong AU - Gu, Zhen T2 - ACS NANO AB - Mechanical force-based stimulus provides a simple and easily accessible manner for spatiotemporally controlled drug delivery. Here we describe a wearable, tensile strain-triggered drug delivery device consisting of a stretchable elastomer and microgel depots containing drug loaded nanoparticles. By applying a tensile strain to the elastomer film, the release of drug from the microdepot is promoted due to the enlarged surface area for diffusion and Poisson's ratio-induced compression on the microdepot. Correspondingly, both sustained drug release by daily body motions and pulsatile release by intentional administration can be conveniently achieved. Our work demonstrated that the tensile strain, applied to the stretchable device, facilitated release of therapeutics from microdepots for anticancer and antibacterial treatments. Moreover, polymeric microneedles were further integrated with the stretch-responsive device for transcutaneous delivery of insulin and regulation of blood glucose levels of chemically induced type 1 diabetic mice. DA - 2015/9// PY - 2015/9// DO - 10.1021/acsnano.5b03975 VL - 9 IS - 9 SP - 9407-9415 SN - 1936-086X KW - drug delivery KW - wearable devices KW - stimuli-responsive KW - nanoparticles KW - microdepots ER - TY - JOUR TI - Snapshot retinal imaging Mueller matrix polarimeter AU - Wang, Yifan AU - Kudenov, Michael AU - Kashani, Amir H. AU - Schwiegerling, Jim AU - Escuti, Michael T2 - POLARIZATION SCIENCE AND REMOTE SENSING VII AB - Early diagnosis of glaucoma, which is a leading cause for visual impairment, is critical for successful treatment. It has been shown that Imaging polarimetry has advantages in early detection of structural changes in the retina. Here, we theoretically and experimentally present a snapshot Mueller Matrix Polarimeter fundus camera, which has the potential to record the polarization-altering characteristics of retina with a single snapshot. It is made by incorporating polarization gratings into a fundus camera design. Complete Mueller Matrix data sets can be obtained by analyzing the polarization fringes projected onto the image plane. In this paper, we describe the experimental implementation of the snapshot retinal imaging Mueller matrix polarimeter (SRIMMP), highlight issues related to calibration, and provide preliminary images acquired from the camera. DA - 2015/// PY - 2015/// DO - 10.1117/12.2188480 VL - 9613 SP - SN - 0277-786X KW - Glaucoma KW - polarimeter KW - snapshot KW - Mueller matrix KW - fundus camera ER - TY - CONF TI - Pump-free feedback control of a frequency reconfigurable liquid metal monopole AU - Wang, M. AU - Khan, M. R. AU - Trlica, C. AU - Dickey, Michael AU - Adams, Jacob AB - We demonstrate a pump-free method to control the length of liquid metal in a capillary as a means to change the operating frequency of a monopole antenna. An applied DC voltage controls the surface tension of the liquid metal filament, causing it to lengthen or contract, varying the antenna's resonant length. A closed-loop feedback system tracks the antenna's operating frequency and adjusts the applied voltage to shape the liquid metal towards the desired response. Measurements show that the process is controlled and fully reversible, dynamically adjusting to a programmed frequency. C2 - 2015/// C3 - 2015 ieee international symposium on antennas and propagation & usnc/ursi national radio science meeting DA - 2015/// DO - 10.1109/aps.2015.7305500 SP - 2223–2224 ER - TY - JOUR TI - Probabilistic-Based Available Transfer Capability Assessment Considering Existing and Future Wind Generation Resources AU - Du, Pengwei AU - Li, Weifeng AU - Ke, Xinda AU - Lu, Ning AU - Ciniglio, Orlando A. AU - Colburn, Mitchel AU - Anderson, Phillip M. T2 - IEEE TRANSACTIONS ON SUSTAINABLE ENERGY AB - This paper presents a probabilistic-based approach for available transfer capability (ATC) assessment. A composite algorithm is developed to generate ensembles of future wind generation scenarios for the existing and planned wind sites using both measured and model-produced wind data. Then, the ensembles of wind and load are used to calculate their respective probability density functions (pdfs), which are subsequently used to calculate the probabilistic-based ATC for a selected transmission corridor. The method has been tested and validated using historical and operational data provided by the Idaho Power Co. The results show that the method can effectively quantify the uncertainties in the ATC assessment introduced by variable generation resources and load variations. As a result, the grid planners will inform the likelihood for the transmission corridor to exceed its transfer capacity in any targeted future years as well as the duration of such events. DA - 2015/10// PY - 2015/10// DO - 10.1109/tste.2015.2425354 VL - 6 IS - 4 SP - 1263-1271 SN - 1949-3029 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000361680800010&KeyUID=WOS:000361680800010 KW - Available transfer capacity KW - composite methods KW - renewable integration KW - stochastic planning KW - transmission planning KW - uncertainty quantification KW - variable generation resources KW - wind scenario generation ER - TY - CONF TI - Physics-based circuit models for MIMO antennas using characteristic modes AU - Adams, J. J. AU - Yang, B. B. C2 - 2015/// C3 - 2015 ieee international symposium on antennas and propagation & usnc/ursi national radio science meeting DA - 2015/// SP - 852-853 ER - TY - JOUR TI - Non-nutritive sweeteners in breast milk: perspective on potential implications of recent findings AU - Rother, Kristina I. AU - Sylvetsky, Allison C. AU - Schiffman, S. S. T2 - Archives of Toxicology AB - We recently determined that nonnutritive (NNS) sweeteners ingested by lactating mothers are passed to their infants in breast milk (Sylvetsky et al., 2015). Three NNS including sucralose, acesulfame-K (ace-K), and saccharin were found in the breast milk of 65% of twenty lactating women who had been enrolled in the study, irrespective of their history of NNS usage. While most of the mothers reported NNS intake during the day prior to collection of the breast milk sample, NNS were also found in samples from women who were not aware of consuming NNS. The findings that NNS are present in breast milk raises several issues regarding infant exposure to these nonnutritive compounds and highlights the need for future research studying the potential short- and long-term effects of exposure to NNS early in life. DA - 2015/10/14/ PY - 2015/10/14/ DO - 10.1007/s00204-015-1611-9 VL - 89 IS - 11 SP - 2169-2171 J2 - Arch Toxicol LA - en OP - SN - 0340-5761 1432-0738 UR - http://dx.doi.org/10.1007/s00204-015-1611-9 DB - Crossref ER - TY - CONF TI - No time to demodulate - fast physical layer verification of friendly jamming AU - Shen, W. B. AU - Liu, Y. AU - He, X. F. AU - Dai, H. Y. AU - Ning, P. AB - Jamming attacks are well-known threats to wireless communications, but on the other hand they provide insights for researchers to design novel approaches to protect wireless communications. In recent years, friendly jamming is used by a number of research works to achieve the wireless medium access control. However, in these works, the friendly jammer relies on bit-level information to distinguish the allies' wireless transmissions from the enemies', which requires the received signals to be processed through demodulation steps and thus introduces a non-trivial reaction time delay for the friendly jammer. This reaction delay is undesirable as the transmissions need to be jammed while they are still on the air. To address this problem, we propose fast friendly jamming, which eliminates the need for demodulation and enables the friendly jammer to verify the received signals directly on the physical layer. We have implemented a prototype of the proposed techniques based on GNURadio and USRP, and performed real-world experiments to validate the proposed techniques. The experiment results show that the proposed techniques reduce the normal reaction delay of the friendly jammer by 81.9%-85.7%, and achieve the accurate distinction between allies' and enemies' transmissions. C2 - 2015/// C3 - 2015 ieee military communications conference (milcom 2015) DA - 2015/// DO - 10.1109/milcom.2015.7357518 SP - 653-658 ER - TY - CONF TI - Multi-resonant AgNW/PDMS patch antenna for biaxial strain sensing AU - Muchler, C. AU - Cui, Z. AU - Zhu, Y. AU - Adams, J. J. C2 - 2015/// C3 - 2015 ieee international symposium on antennas and propagation & usnc/ursi national radio science meeting DA - 2015/// SP - 1878-1879 ER - TY - JOUR TI - Growth and Characterization of High-Quality, Relaxed In (y) Ga1-y N Templates for Optoelectronic Applications AU - Van Den Broeck, D. M. AU - Bharrat, D. AU - Liu, Z. AU - El-Masry, N. A. AU - Bedair, S. M. T2 - JOURNAL OF ELECTRONIC MATERIALS DA - 2015/11// PY - 2015/11// DO - 10.1007/s11664-015-3989-9 VL - 44 IS - 11 SP - 4161-4166 SN - 1543-186X KW - InGaN KW - metal organic chemical vapor deposition (MOCVD) KW - relaxation KW - semibulk ER - TY - CONF TI - Design considerations of packaging a high voltage current switch AU - De, A. AU - Morgan, A. AU - Bhattacharya, Subhashish AU - Hopkins, D.C. AB - In this paper an attempt has been made to demonstrate various package design considerations to accommodate series connection of high voltage Si-IGBT (6500V/25A die) and SiC-Diode (6500V/25A die). The effects of connecting the cathode of the series diode to the collector of the IGBT versus connecting the emitter of the IGBT to the anode of the series diode has been analyzed in regards to gate terminal operation and the parasitic line inductance of the structure. ANSYS Q3D/MAXWELL software have been used to analyze and extract parasitic inductance and capacitances in the package along with electromagnetic fields, electric potentials, and current density distributions throughout the package for variable parameters. SIMPLIS-SIMETRIX is used to simulate typical switch behavior for different parasitic parameters under hard switched conditions. Various simulation results have then been used to redesign and justify the optimized package structure for the final current switch design. The thermal behavior of such a package is also conducted in COMSOL in order to ensure that the thermal ratings of the power devices is not exceeded, and to understand where potentially harmful hotspots could arise and estimate the maximum attainable frequency of operation. The main motivation of this work is to enumerate detailed design considerations for packing a high voltage current switch package. C2 - 2015/// C3 - ASME 2015 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems, InterPACK 2015, collocated with the ASME 2015 13th International Conference on Nanochannels, Microchannels, and Minichannels DA - 2015/// DO - 10.1115/IPACK2015-48714 VL - 3 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84953889244&partnerID=MN8TOARS ER - TY - JOUR TI - Complete Intrinsic Coincident Polarimetry using Stacked Organic Photovoltaics AU - Roy, S. Gupta AU - Awartani, O. M. AU - Sen, P. AU - O'Connor, B. T. AU - Kudenov, M. W. T2 - POLARIZATION SCIENCE AND REMOTE SENSING VII AB - Measuring the 2 dimensional Stokes vector, to determine the polarization state of light, finds application in multiple areas, including the characterization of aerosol size distributions, target identification, quality control by evaluating the distribution of stress birefringence, resolving data channels in telecommunications, and for evaluating biological tissues in medical imaging. Conventional methods, such as channeled and division of focal plane polarimeters, usually limit spatial resolution, while others, like division of aperture or division of amplitude polarimeters, have higher complexity and less compactness. To help solve these issues, we have developed a system that uses semitransparent organic photovoltaics (OPVs) as photodetectors. The active area of the devices consist of biaxially oriented polymer films, which enables the device to preferentially absorb certain polarized states of incident light, depending on the orientation of the polymer chains. Taking advantage of the cells’ transparency and ease of processing, compared to inorganic materials, enables multiple devices to be “stacked” along the optical axis. Presently, experiments have been conducted to detect linear polarization states of light. We use three stacked OPVs, where each device can measure one of the first three Stokes parameters simultaneously, thereby ensuring high spatial and temporal resolution with inherent spatial registration. In this paper, the fabrication of the OPVs and the design and calibration technique is documented, along with experimental data, supporting the hypothesis. DA - 2015/// PY - 2015/// DO - 10.1117/12.2188972 VL - 9613 SP - SN - 0277-786X KW - Polarimetry KW - polarimeters KW - Stokes vector KW - organic photovoltaics KW - strain aligned polymer chains KW - inherent spatial registration ER - TY - JOUR TI - Rethinking the Public through the Lens of Sovereignty AU - Gilmartin, David T2 - SOUTH ASIA-JOURNAL OF SOUTH ASIAN STUDIES AB - The interrelationships of the various, seemingly contradictory, uses of the public as a concept are best understood by relating the concept to sovereignty. The concept of the public thus gained particular structural meaning in colonial India through the state's efforts to legitimise its authority as the embodiment of a discourse of reason in the nineteenth century, with the courts serving as a critical model for the public. With the emergence of the concept of the sovereignty of the people in the twentieth century, the nature of the public was significantly transformed, and gained increasing significance as an arena for the open performance of the autonomous self. DA - 2015/7/3/ PY - 2015/7/3/ DO - 10.1080/00856401.2015.1055422 VL - 38 IS - 3 SP - 371-386 SN - 1479-0270 KW - Law KW - performance KW - public KW - reason KW - sovereignty ER - TY - JOUR TI - Reliable antifuse one-time-programmable scheme with charge pump for postpackage repair of DRAM AU - Li, X. AU - Zhong, H. C. AU - Tang, Z. H. AU - Jia, C. T2 - IEEE Transactions on Very Large Scale Integration (VLSI) Systems DA - 2015/// PY - 2015/// VL - 23 IS - 9 SP - 1956-1960 ER - TY - JOUR TI - Reliable and scalable communication for the power grid AU - Zimmer, C. AU - Mueller, F. T2 - Cyber physical systems approach to smart electric power grid AB - Future smart power grids require constant data availability for actuation of control decisions. The job of ensuring the timely arrival of data falls onto the network that connects these intelligent devices. This network needs to be fault tolerant. When nodes, devices or communication links fail along a default route of a message from A to B, the underlying hardware and software layers should ensure that this message will actually be delivered as long as alternative routes exist. Existence and discovery of multi-route pathways is essential in ensuring delivery of critical data. In this work, we present methods of developing network topologies of smart devices that enable multi-route discovery in an intelligent power grid. This is accomplished through the utilization of software overlays that (1) maintain a digital structure for the physical network and (2) identify new routes in the case of faults. The resulting cyber network structure is scalable, reliable and inexpensive to build by extending existing infrastructure. DA - 2015/// PY - 2015/// DO - 10.1007/978-3-662-45928-7_8 SP - 195-217 ER - TY - JOUR TI - Investigation of Lanthanum Silicate Conditions on 4H-SiC MOSFET Characteristics AU - Yang, Xiangyu AU - Lee, Bongmook AU - Misra, Veena T2 - IEEE Transactions on Electron Devices AB - The lanthanum silicate interface engineering has been shown to dramatically improve the mobility of 4H-silicon carbide (SiC) MOSFETs. We studied the impact of post deposition annealing (PDA) conditions and the initial lanthanum oxide (La 2 O 3 ) thickness on the MOSFET performance. The combination of 900 °C PDA and 1 nm La 2 O 3 leads to highest field-effect mobility. Higher PDA temperature leads to mobility reduction due to lower lanthanum concentration at the SiC/dielectric interface. The peak mobility and threshold voltage show strong dependence on the initial La 2 O 3 thickness. DA - 2015/11// PY - 2015/11// DO - 10.1109/ted.2015.2480047 VL - 62 IS - 11 SP - 3781-3785 J2 - IEEE Trans. Electron Devices OP - SN - 0018-9383 1557-9646 UR - http://dx.doi.org/10.1109/TED.2015.2480047 DB - Crossref KW - Atomic layer deposition (ALD) KW - ALD SiO2 KW - lanthanum silicate (LaSiOx) KW - mobility KW - silicon carbide (SiC) ER - TY - JOUR TI - Intrusion Detection for CPS Real-Time Controllers AU - Zimmer, Christopher AU - Bhat, Balasubramany AU - Mueller, Frank AU - Mohan, Sibin T2 - CYBER PHYSICAL SYSTEMS APPROACH TO SMART ELECTRIC POWER GRID AB - Security in CPS-based real-time embedded systems controlling the power grid has been an afterthought, but it is becoming a critical issue as CPS systems are networked and inter-dependent. This work presents a set of mechanisms for timebased intrusion detection, i.e., the execution of unauthorized instructions in realtime CPS environments. The novelty is the utilization of information obtained by static timing analysis for intrusion detection. Real-time CPS systems are unique in that timing bounds on code sections are readily available since they are required for schedulability analysis.We demonstrate how micro-timings can be exploited for multiple granularity levels of application code to track execution progress. Through bounds checking of these micro-timings, we develop techniques to detect intrusions (1) in a self-checking manner by the application and (2) through the operating system scheduler, which are novel contributions to the real-time/embedded systems domain to the best of our knowledge. DA - 2015/// PY - 2015/// DO - 10.1007/978-3-662-45928-7_12 SP - 329-358 SN - 1860-4676 ER - TY - JOUR TI - International Education AU - Xu, Yan AU - Fu, Haipeng AU - Ma, Jianguo AU - Trussell, Henry Joel T2 - PROCEEDINGS OF THE IEEE AB - With the globalization of economy and liberalization of trade, the international education trade market is becoming an increasingly important part of international service trade. Education resources are distributed internationally, and exchanges and cooperation of education among different nations are becoming increasingly frequent. As a result, education in various countries interacts and competes with each other, which eventually promotes the globalized education. DA - 2015/10// PY - 2015/10// DO - 10.1109/jproc.2015.2475435 VL - 103 IS - 10 SP - 1691-1697 SN - 1558-2256 ER - TY - JOUR TI - In-situ fabricated transparent conducting nanofiber-shape polyaniline/coral-like TiO2 thin film: Application in bifacial dye-sensitized solar cells AU - Bahramian, Alireza AU - Vashaee, Daryoosh T2 - SOLAR ENERGY MATERIALS AND SOLAR CELLS AB - Dye-sensitized solar cell (DSSC) is the most promising of third generation solar cells for large scale applications due its low cost, flexibility, and scalable manufacturability. However, enhancing the efficiency of the DSSC is still highly desired. In this study, we designed a novel bifacial DSSC based on a transparent Polyaniline (PANI) films as counter electrode (CE) associated with coral-like TiO2 nanostructured films, which can be used as the photoanode. PANI-based CEs were prepared by a facile in situ polymerization, while coral-like TiO2 films were chemically synthesized at low temperature through the sol–gel process. Owing to the light irradiation from both the front and the rear sides, it is expected that higher density of dye molecules should be excited. In addition, due to the excellent light scattering of the coal-like TiO2 and high specific surface area of PANI nanofibers (NFs), more carriers are generated. Both these factors resulted in the increase of the conversion efficiency. The bifacial DSSC fabricated by combining the PANI NFs-based film and the coral-like TiO2 film in the presence of the expensive N719 dye molecules showed the efficiency of 8.22% corresponding to the both-side irradiation. In comparison, similar cells employing either a cross-linked PANI- or Pt-based CE showed efficiencies of 7.81% and 7.75%, respectively. The results of the similar cells in the presence of the low cost CoPC dye molecules showed efficiencies of 0.29%, 0.22%, and 0.27%, for DSSCs comprised of PANI NFs-, cross-linked PANI-, and Pt-based CEs, respectively. The low fabrication cost as well as the improved light absorption highlights the potential application of the coral-like TiO2 and PANI NFs-based films in fabrication of bifacial DSSCs. DA - 2015/12// PY - 2015/12// DO - 10.1016/j.solmat.2015.07.011 VL - 143 SP - 284-295 SN - 1879-3398 KW - Polyaniline nanofibers KW - Coral-like TiO2 nanostructures KW - Transparent thin films KW - Bifacial dye-sensitized solar cell KW - Conversion efficiency ER - TY - JOUR TI - Distributed Optimization Algorithms for Wide-Area Oscillation Monitoring in Power Systems Using Interregional PMU-PDC Architectures AU - Nabavi, Seyedbehzad AU - Zhang, Jianhua AU - Chakrabortty, Aranya T2 - IEEE TRANSACTIONS ON SMART GRID AB - In this paper, we present a set of distributed algorithms for estimating the electro-mechanical oscillation modes of large power system networks using synchrophasors. With the number of phasor measurement units (PMUs) in the North American grid scaling up to the thousands, system operators are gradually inclining toward distributed cyber-physical architectures for executing wide-area monitoring and control operations. Traditional centralized approaches, in fact, are anticipated to become untenable soon due to various factors such as data volume, security, communication overhead, and failure to adhere to real-time deadlines. To address this challenge, we propose three different communication and computational architectures by which estimators located at the control centers of various utility companies can run local optimization algorithms using local PMU data, and thereafter communicate with other estimators to reach a global solution. Both synchronous and asynchronous communications are considered. Each architecture integrates a centralized Prony-based algorithm with several variants of alternating direction method of multipliers (ADMM). We discuss the relative advantages and bottlenecks of each architecture using simulations of IEEE 68-bus and IEEE 145-bus power system, as well as an Exo-GENI-based software defined network. DA - 2015/9// PY - 2015/9// DO - 10.1109/tsg.2015.2406578 VL - 6 IS - 5 SP - 2529-2538 SN - 1949-3061 KW - Alternating direction method of multipliers (ADMM) KW - distributed optimization KW - phasor measurement units (PMUs) KW - Prony KW - wide area oscillation monitoring ER - TY - JOUR TI - Condition Monitoring, Diagnosis, Prognosis, and Health Management for Wind Energy Conversion Systems AU - Qiao, Wei AU - Zhang, Pinjia AU - Chow, Mo-Yuen T2 - IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS AB - The articles in this special section focus on condition monitoring, diagnosis, prognosis, and information management. These technologies and applications are effective means to reduce the downtime and the maintenance cost, and to improve the reliability, capacity factor, and lifespan of wind energy conversion systems. These important issues have drawn more and more attention during the last decade, and significant research effort is being taken by both the academia and the industry to advance the technologies for the condition monitoring, diagnosis, prognosis, and health management of wind energy conversion systems. This Special Section aims to provide a platform for academic and industrial communities to report the most recent findings in this field. DA - 2015/10// PY - 2015/10// DO - 10.1109/tie.2015.2464785 VL - 62 IS - 10 SP - 6533-6535 SN - 1557-9948 ER - TY - JOUR TI - Compact 0.92/2.45-GHz Dual-Band Directional Circularly Polarized Microstrip Antenna for Handheld RFID Reader Applications AU - Liu, Qiang AU - Shen, Junyu AU - Yin, Jungang AU - Liu, Hongli AU - Liu, Yuanan T2 - IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION AB - This paper presents a compact 0.92/2.45-GHz dual-band directional circularly polarized (CP) microstrip antenna for handheld radio-frequency identification (RFID) reader applications. The proposed antenna comprises a wideband dual-feed network and two stacked concentric patches assembled by two orthogonally placed vertical probes. The dual-feed network feeds quadrature signals across the RFID bands between 0.92 and 2.45 GHz. The two stacked concentric patches provide resonance frequencies in fundamental mode for lower band and higher band, respectively. Additionally, the antenna features only one connection port and same sense CP radiation at two bands, beneficial to cost and complexity reductions of the dual-band front end of RFID readers. The measurement results show the performances of return loss (RL) >10 dB, 3-dB gain variation, and axial ratio (AR) <;3 dB are achieved on the bands 0.911-0.933 GHz and 2.40- 2.57 GHz. The measured peak gains are 3.8 dBic at 0.926 GHz and 8.9 dBic at 2.48 GHz. In addition, the antenna provides symmetrical patterns with wide-angle half-power beamwidths and wide-angle 3-dB AR beamwidths. The size of the antenna 110 × 110 × 6.6 mm 3 is much smaller than reported dual-band one port RFID directional CP reader antennas. The antenna appropriates to both ultra-high frequency (UHF) and industrial scientific and medical (ISM) bands in handheld RFID reader applications. DA - 2015/9// PY - 2015/9// DO - 10.1109/tap.2015.2452954 VL - 63 IS - 9 SP - 3849-3856 SN - 1558-2221 KW - Circularly polarized (CP) KW - compact KW - directional KW - dual-band KW - microstrip antenna KW - radio-frequency identification (RFID) ER - TY - JOUR TI - Cogging Torque Reduction in Flux-Switching Permanent-Magnet Machines by Rotor Pole Shaping AU - Sikder, Chandan AU - Husain, Iqbal AU - Ouyang, Wen T2 - IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS AB - Cogging torque in flux-switching permanent-magnet (FSPM) machines is relatively high compared with that of other types of PM machines because of their unique doubly salient structure. Reducing the cogging torque in the FSPM machine is of particular importance to make it a viable alternative to conventional rotor-PM machines. A new pole shaping method has been proposed to reduce the cogging torque. The validity of the proposed method has been confirmed by analytical methods and finite-element-analysis-based simulation. The influence of the proposed pole shaping method on the back-electromotive force (EMF) and average electromagnetic torque has also been investigated. DA - 2015/// PY - 2015/// DO - 10.1109/tia.2015.2416238 VL - 51 IS - 5 SP - 3609-3619 SN - 1939-9367 KW - Cogging torque KW - flux reversal machine (FRM) KW - flux-switching permanent-magnet (FSPM) machine KW - pole shaping ER - TY - JOUR TI - Clustering and Differential Alignment Algorithm: Identification of Early Stage Regulators in the Arabidopsis thaliana Iron Deficiency Response AU - Koryachko, Alexandr AU - Matthiadis, Anna AU - Muhammad, Durreshahwar AU - Foret, Jessica AU - Brady, Siobhan M. AU - Ducoste, Joel J. AU - Tuck, James AU - Long, Terri A. AU - Williams, Cranos T2 - PLOS ONE AB - Time course transcriptome datasets are commonly used to predict key gene regulators associated with stress responses and to explore gene functionality. Techniques developed to extract causal relationships between genes from high throughput time course expression data are limited by low signal levels coupled with noise and sparseness in time points. We deal with these limitations by proposing the Cluster and Differential Alignment Algorithm (CDAA). This algorithm was designed to process transcriptome data by first grouping genes based on stages of activity and then using similarities in gene expression to predict influential connections between individual genes. Regulatory relationships are assigned based on pairwise alignment scores generated using the expression patterns of two genes and some inferred delay between the regulator and the observed activity of the target. We applied the CDAA to an iron deficiency time course microarray dataset to identify regulators that influence 7 target transcription factors known to participate in the Arabidopsis thaliana iron deficiency response. The algorithm predicted that 7 regulators previously unlinked to iron homeostasis influence the expression of these known transcription factors. We validated over half of predicted influential relationships using qRT-PCR expression analysis in mutant backgrounds. One predicted regulator-target relationship was shown to be a direct binding interaction according to yeast one-hybrid (Y1H) analysis. These results serve as a proof of concept emphasizing the utility of the CDAA for identifying unknown or missing nodes in regulatory cascades, providing the fundamental knowledge needed for constructing predictive gene regulatory networks. We propose that this tool can be used successfully for similar time course datasets to extract additional information and infer reliable regulatory connections for individual genes. DA - 2015/8/28/ PY - 2015/8/28/ DO - 10.1371/journal.pone.0136591 VL - 10 IS - 8 SP - SN - 1932-6203 ER - TY - JOUR TI - A Real-Time Attack Localization Algorithm for Large Power System Networks Using Graph-Theoretic Techniques AU - Nudell, Thomas R. AU - Nabavi, Seyedbehzad AU - Chakrabortty, Aranya T2 - IEEE TRANSACTIONS ON SMART GRID AB - We develop a graph-theoretic algorithm for localizing the physical manifestation of attacks or disturbances in large power system networks using real-time synchrophasor measurements. We assume the attack enters through the electro-mechanical swing dynamics of the synchronous generators in the grid as an unknown additive disturbance. Considering the grid to be divided into coherent areas, we pose the problem as to localize which area the attack may have entered using relevant information extracted from the phasor measurement data. Our approach to solve this problem consists of three main steps. We first run a phasor-based model reduction algorithm by which a dynamic equivalent of the clustered network can be identified in real-time. Second, in parallel, we run a system identification in each area to identify a transfer matrix model for the full-order power system. Thereafter, we exploit the underlying graph-theoretic properties of the identified reduced-order topology, create a set of localization keys, and compare these keys with a selected set of transfer function residues. We validate our results using a detailed case study of the two-area Kundur model and the IEEE 39-bus power system. DA - 2015/9// PY - 2015/9// DO - 10.1109/tsg.2015.2406571 VL - 6 IS - 5 SP - 2551-2559 SN - 1949-3061 KW - Algebraic graph theory KW - attack localization KW - identification KW - nodal domains KW - power system ER - TY - JOUR TI - A Pulse-Injection-Based Sensorless Position Estimation Method for a Switched Reluctance Machine Over a Wide Speed Range AU - Ofori, Ernest AU - Husain, Tausif AU - Sozer, Yilmaz AU - Husain, Iqbal T2 - IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS AB - In this paper, a pulse-injection-based method for determining the rotor position of a switched reluctance motor (SRM) over its entire speed range is presented. In this method, a single high-frequency pulse is injected in an idle phase to determine the rotor position at high speeds. The proposed method estimates the rotor position through analysis of the resultant current after voltage pulse injection. A low-speed sensorless method previously developed based on pulse injection has also been extended to improve robustness against varying operating conditions. The developed pulse injection with varying duty ratios provided uniform sensing thresholds over varying dc bus voltages. The low- and high-speed methods are integrated together to provide a robust wide-speed-range rotor position estimator for SRM. DA - 2015/// PY - 2015/// DO - 10.1109/tia.2015.2420618 VL - 51 IS - 5 SP - 3867-3876 SN - 1939-9367 KW - High-speed operation KW - sensorless control KW - signal injection method KW - switched reluctance motor (SRM) ER - TY - JOUR TI - 21st Century Pong AU - Byrd, Greg T2 - COMPUTER AB - Cornell University students built a system that tracks a Ping-Pong ball in real time and keeps score. The Web extra at https://youtu.be/r7VtgzPPYy4 is a video demonstration in which Cornell students Pol Rosello (CS), Taylor Pritchard (ECE), and Frank Xie (ECE), describe and demonstrate their Table Tennis Tracker system. The system analyzes a video stream to track the location of the ball and to automatically keep score. Video provided by Dr. Bruce Land. DA - 2015/10// PY - 2015/10// DO - 10.1109/mc.2015.306 VL - 48 IS - 10 SP - 80-84 SN - 1558-0814 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84959421337&partnerID=MN8TOARS ER - TY - JOUR TI - Polarity of GaN with polar {0001} and semipolar {10(1)over-bar1}, {20(2)over-bar1}, {11(2)over-bar2} orientations by x-ray photoelectron diffraction AU - Romanyuk, Oleksandr AU - Jiricek, Petr AU - Paskova, Tania AU - Bartos, Igor T2 - JOURNAL OF MATERIALS RESEARCH DA - 2015/10/14/ PY - 2015/10/14/ DO - 10.1557/jmr.2015.153 VL - 30 IS - 19 SP - 2881-2892 SN - 2044-5326 ER - TY - JOUR TI - Nonlinear magnetic dynamics in a nanomagnet–topological insulator heterostructure AU - Duan, Xiaopeng AU - Li, Xi-Lai AU - Semenov, Yuriy G. AU - Kim, Ki Wook T2 - Physical Review B AB - Magnetization dynamics of a nanomagnet, when strongly coupled with a topological insulator (TI) via the proximity interaction, is examined theoretically in the presence of electrical current on the TI surface under realistic transport conditions. Due to the spin-momentum interlock, the magnetic state and TI electron transport depend significantly on each other. Such an interdependence leads to a variety of nonlinear dynamical responses in all transport regimes including the scattering dominant diffusive cases. Generation of the anomalous Hall current, in particular, is found to be a key to the unique features that have not been observed previously. For instance, the anomalous Hall current can result in antiparallel alignment of the final magnetization state in reference to the effective driving magnetic field by inducing an extra term that counters the damping effect. Similarly the calculation also reveals steady oscillation of the magnetization under a broad range of conditions, offering a robust mechanism for highly efficient magnetization reversal and/or spin wave excitation under a dc bias. DA - 2015/9/18/ PY - 2015/9/18/ DO - 10.1103/physrevb.92.115429 VL - 92 IS - 11 SP - J2 - Phys. Rev. B LA - en OP - SN - 1098-0121 1550-235X UR - http://dx.doi.org/10.1103/PhysRevB.92.115429 DB - Crossref ER - TY - JOUR TI - NITRIDES AND OXYNITRIDE MATERIALS Introduction AU - Redwing, Joan AU - Lences, Zoltan AU - Xie, Rong-Jun AU - Paskova, Tania T2 - JOURNAL OF MATERIALS RESEARCH DA - 2015/10/14/ PY - 2015/10/14/ DO - 10.1557/jmr.2015.303 VL - 30 IS - 19 SP - 2845-2845 SN - 2044-5326 ER - TY - JOUR TI - Fabrication of ideal geometric-phase holograms with arbitrary wavefronts AU - Kim, Jihwan AU - Li, Yanming AU - Miskiewicz, Matthew N. AU - Oh, Chulwoo AU - Kudenov, Michael W. AU - Escuti, Michael J. T2 - OPTICA AB - Throughout optics and photonics, phase is normally controlled via an optical path difference. Although much less common, an alternative means for phase control exists: a geometric phase (GP) shift occurring when a light wave is transformed through one parameter space, e.g., polarization, in such a way as to create a change in a second parameter, e.g., phase. In thin films and surfaces where only the GP varies spatially—which may be called GP holograms (GPHs)—the phase profile of nearly any (physical or virtual) object can in principle be embodied as an inhomogeneous anisotropy manifesting exceptional diffraction and polarization behavior. Pure GP elements have had poor efficiency and utility up to now, except in isolated cases, due to the lack of fabrication techniques producing elements with an arbitrary spatially varying GP shift at visible and near-infrared wavelengths. Here, we describe two methods to create high-fidelity GPHs, one interferometric and another direct-write, capable of recording the wavefront of nearly any physical or virtual object. We employ photoaligned liquid crystals to record the patterns as an inhomogeneous optical axis profile in thin films with a few μm thickness. We report on eight representative examples, including a GP lens with F/2.3 (at 633 nm) and 99% diffraction efficiency across visible wavelengths, and several GP vortex phase plates with excellent modal purity and remarkably small central defect size (e.g., 0.7 and 7 μm for topological charges of 1 and 8, respectively). We also report on a GP Fourier hologram, a fan-out grid with dozens of far-field spots, and an elaborate phase profile, which showed excellent fidelity and very low leakage wave transmittance and haze. Together, these techniques are the first practical bases for arbitrary GPHs with essentially no loss, high phase gradients (∼rad/μm), novel polarization functionality, and broadband behavior. DA - 2015/11/20/ PY - 2015/11/20/ DO - 10.1364/optica.2.000958 VL - 2 IS - 11 SP - 958-964 SN - 2334-2536 ER - TY - JOUR TI - Cycling Through Cyberspace AU - Byrd, Greg T2 - COMPUTER AB - Students at the University of Brasília set out to build a better exercise bike. The Web extra at http://youtu.be/NCSb_sDJL7c is a video demonstration of the Bike-X simulator, a virtual cycling experience designed by engineering students at the University of Brasília's Gama Campus. DA - 2015/8// PY - 2015/8// DO - 10.1109/mc.2015.220 VL - 48 IS - 8 SP - 72-75 SN - 1558-0814 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84939488306&partnerID=MN8TOARS ER - TY - JOUR TI - Creating Analytic Online Homework for Digital Signal Processing [sp Education] AU - Trussell, H. Joel AU - Baron, Dror T2 - IEEE Signal Processing Magazine AB - An article by W.L. Everitt in the 1962 50th anniversary issue of Proceedings of the IEEE, ?Engineering Education?Circa 2012 A.D.,? was one of many predictive articles that appeared in that issue [1]. One of Everitt?s observations was the distinction between training and education. He then predicted that, in the future, training will be done primarily with computers, remarking, ?Relieved of the necessity of spending most of their time on the training function, devoted teachers will be able to concentrate their efforts on ?education?.? DA - 2015/9// PY - 2015/9// DO - 10.1109/msp.2015.2438992 VL - 32 IS - 5 SP - 112-118 J2 - IEEE Signal Process. Mag. OP - SN - 1053-5888 UR - http://dx.doi.org/10.1109/msp.2015.2438992 DB - Crossref ER - TY - JOUR TI - A review of in situ surface functionalization of gallium nitride via beaker wet chemistry AU - Pearce, Brady L. AU - Wilkins, Stewart J. AU - Paskova, Tania AU - Ivanisevic, Albena T2 - JOURNAL OF MATERIALS RESEARCH DA - 2015/10/14/ PY - 2015/10/14/ DO - 10.1557/jmr.2015.132 VL - 30 IS - 19 SP - 2859-2870 SN - 2044-5326 ER - TY - JOUR TI - A non-uniform multi-rate control strategy for a Markov chain-driven Networked Control System AU - Cuenca, Ángel AU - Ojha, Unnati AU - Salt, Julián AU - Chow, Mo-Yuen T2 - Information Sciences AB - In this work, a non-uniform multi-rate control strategy is applied to a kind of Networked Control System (NCS) where a wireless path tracking control for an Unmanned Ground Vehicle (UGV) is carried out. The main aims of the proposed strategy are to face time-varying network-induced delays and to avoid packet disorder. A Markov chain-driven NCS scenario will be considered, where different network load situations, and consequently, different probability density functions for the network delay are assumed. In order to assure mean-square stability for the considered NCS, a decay-rate based sufficient condition is enunciated in terms of probabilistic Linear Matrix Inequalities (LMIs). Simulation results show better control performance, and more accurate path tracking, for the scheduled (delay-dependent) controller than for the non-scheduled one (i.e. the nominal controller when delays appear). Finally, the control strategy is validated on an experimental test-bed. DA - 2015/11// PY - 2015/11// DO - 10.1016/j.ins.2015.05.035 VL - 321 SP - 31-47 J2 - Information Sciences LA - en OP - SN - 0020-0255 UR - http://dx.doi.org/10.1016/j.ins.2015.05.035 DB - Crossref KW - Networked Control System KW - Unmanned ground vehicle KW - Network delay KW - Packet disorder KW - Multi-rate control system KW - PID controller ER - TY - JOUR TI - 275-285 GHz balanced frequency quadrupler chain in 45 nm SOI CMOS AU - Abbasi, M. AU - Ricketts, D. S. T2 - ELECTRONICS LETTERS AB - A 280 GHz broadband balanced frequency quadrupler chain is presented. The quadrupler can be used to generate as high as 200 μW over a −3 dB bandwidth of 275–285 GHz, which enables emerging applications in sub-millimetre-wave communications and remote sensing. The circuit is designed and fabricated in a 45 nm silicon on insulator (SOI) CMOS technology and occupies an area of 0.21 mm2 including the pads. The chip consumes 85 mA dc current from a 1.1 V supply. DA - 2015/9/3/ PY - 2015/9/3/ DO - 10.1049/el.2015.2100 VL - 51 IS - 18 SP - SN - 1350-911X KW - silicon-on-insulator KW - frequency multipliers KW - CMOS analogue integrated circuits KW - submillimetre wave integrated circuits KW - frequency quadrupler KW - silicon on insulator CMOS technology KW - SOI CMOS KW - submillimetre-wave communications KW - remote sensing KW - frequency 275 GHz to 285 GHz KW - size 45 nm KW - size 0 KW - 21 mm KW - current 85 mA KW - voltage 1 KW - 1 V KW - Si ER - TY - JOUR TI - Understanding the gradual reset in Pt/Al2O3/Ni RRAM for synaptic applications AU - Sarkar, Biplab AU - Lee, Bongmook AU - Misra, Veena T2 - SEMICONDUCTOR SCIENCE AND TECHNOLOGY AB - In this work, a study has been performed to understand the gradual reset in Al2O3 resistive random-access memory (RRAM). Concentration of vacancies created during the forming or set operation is found to play a major role in the reset mechanism. The reset was observed to be gradual when a significantly higher number of vacancies are created in the dielectric during the set event. The vacancy concentration inside the dielectric was increased using a multi-step forming method which resulted in a diffusion-dominated gradual filament dissolution during the reset in Al2O3 RRAM. The gradual dissolution of the filament allows one to control the conductance of the dielectric during the reset. RRAM devices with gradual reset show excellent endurance and retention for multi-bit storage. Finally, the conductance modulation characteristics realizing synaptic learning are also confirmed in the RRAM. DA - 2015/10// PY - 2015/10// DO - 10.1088/0268-1242/30/10/105014 VL - 30 IS - 10 SP - SN - 1361-6641 KW - RRAM KW - forming KW - set KW - reset KW - synapse KW - diffusion ER - TY - JOUR TI - Strain induced room temperature ferromagnetism in epitaxial magnesium oxide thin films AU - Jin, Zhenghe AU - Nori, Sudhakar AU - Lee, Yi-Fang AU - Kumar, D. AU - Wu, Fan AU - Prater, J. T. AU - Kim, Ki Wook AU - Narayan, Jagdish T2 - Journal of Applied Physics AB - We report on the epitaxial growth and room-temperature ferromagnetic properties of MgO thin films deposited on hexagonal c-sapphire substrates by pulsed laser deposition. The epitaxial nature of the films has been confirmed by both θ-2θ and φ-scans of X-ray diffraction pattern. Even though bulk MgO is a nonmagnetic insulator, we have found that the MgO films exhibit ferromagnetism and hysteresis loops yielding a maximum saturation magnetization up to 17 emu/cc and large coercivity, Hc = 1200 Oe. We have also found that the saturation magnetization gets enhanced and that the crystallization degraded with decreased growth temperature, suggesting that the origin of our magnetic coupling could be point defects manifested by the strain in the films. X-ray (θ-2θ) diffraction peak shift and strain analysis clearly support the presence of strain in films resulting from the presence of point defects. Based on careful investigations using secondary ion mass spectrometer and X-ray photoelectron spectroscopy studies, we have ruled out the possibility of the presence of any external magnetic impurities. We discuss the critical role of microstructural characteristics and associated strain on the physical properties of the MgO films and establish a correlation between defects and magnetic properties. DA - 2015/10/28/ PY - 2015/10/28/ DO - 10.1063/1.4934498 VL - 118 IS - 16 SP - 165309 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.4934498 DB - Crossref ER - TY - JOUR TI - Guidance in Selecting Advanced Control Techniques for Switched Reluctance Machine Drives in Emerging Applications AU - Sozer, Yilmaz AU - Husain, Iqbal AU - Torrey, David A. T2 - IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS AB - This paper presents advancements in the control techniques of switched reluctance machines (SRMs) for traction and automotive applications. The high performance of the SRM drive system is embodied in the smooth torque output and high-efficiency control methods in the motoring and generating modes of operation. Wide speed operating ranges for both motoring and generating operations are considered. An SRM designed and built for an off-road traction application is used as an application example. Simulation results for the proposed techniques using an SRM system designed for off-road traction application are presented. DA - 2015/// PY - 2015/// DO - 10.1109/tia.2015.2444357 VL - 51 IS - 6 SP - 4505-4514 SN - 1939-9367 KW - Control KW - direct torque control (DTC) KW - excitation KW - switched reluctance machine (SRM) KW - torque ripple KW - traction ER - TY - JOUR TI - Control of High-Frequency Isolated Modular Converter AU - Yousefpoor, Nima AU - Parkhideh, Babak AU - Azidehak, Ali AU - Kim, Sungmin AU - Bhattacharya, Subhashish T2 - IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS AB - Recently, voltage-source converter (VSC)-based high-voltage dc (HVDC) transmission systems have gained more attention. In this paper, a control method for a modular VSC-based HVDC transmission system with high-frequency isolation referred to as high-frequency isolated modular converter is proposed. In the high-frequency isolated modular converter configuration, several floating dc capacitors in all three phases are connected in series, and voltage balancing control of these floating dc capacitors is required. In this paper, an appropriate control structure with the capacitor voltage balancing controller is proposed. The proposed control scheme consists of three layers to control terminal dc bus voltage and balance dc capacitor voltages of each building block. Detailed PSCAD simulation results are presented to evaluate the performance of high-frequency isolated modular converter. Controller hardware-in-the-loop simulation of the high-frequency isolated modular converter is also performed by real-time digital simulator (RTDS), and RTDS results are presented to verify the control structure. Finally, laboratory-scale experimental results are presented to validate the proposed control method. DA - 2015/// PY - 2015/// DO - 10.1109/tia.2015.2457402 VL - 51 IS - 6 SP - 4634-4641 SN - 1939-9367 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84957878360&partnerID=MN8TOARS KW - Capacitor voltage balancing controller KW - high-frequency isolated modular converter KW - high-voltage dc (HVDC) transmission systems KW - voltage-source converter (VSC) ER - TY - JOUR TI - Biomineralization and biocompatibility studies of bone conductive scaffolds containing poly(3,4-ethylenedioxythiophene): poly(4-styrene sulfonate) (PEDOT:PSS) AU - Yazdimamaghani, Mostafa AU - Razavi, Mehdi AU - Mozafari, Masoud AU - Vashaee, Daryoosh AU - Kotturi, Hari AU - Tayebi, Lobat T2 - JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE DA - 2015/12// PY - 2015/12// DO - 10.1007/s10856-015-5599-8 VL - 26 IS - 12 SP - SN - 1573-4838 ER - TY - JOUR TI - Tracking Cows Wirelessly AU - Byrd, Greg T2 - COMPUTER AB - A student team from NC State designed and built a prototype wireless network to monitor the milking and weighing of cows. DA - 2015/6// PY - 2015/6// DO - 10.1109/mc.2015.154 VL - 48 IS - 6 SP - 60-63 SN - 1558-0814 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84933557206&partnerID=MN8TOARS ER - TY - JOUR TI - Thermal conductivity of nanostructured SixGe1-x in amorphous limit by molecular dynamics simulation AU - Norouzzadeh, Payam AU - Nozariasbmarz, Amin AU - Krasinski, Jerzy S. AU - Vashaee, Daryoosh T2 - JOURNAL OF APPLIED PHYSICS AB - We report the thermal conductivity of amorphous SixGe1−x compound calculated versus composition and temperature. The result sets the minimum value of thermal conductivity which is achievable by nanostructuring. We employed molecular dynamics with Tersoff's potential for the calculations. It was found that, contrary to the crystalline SixGe1−x, the thermal conductivity of amorphous phase is a weak function of the material composition. For the most popular composition Si0.8Ge0.2, the thermal conductivity of the amorphous phase is less than 1 W m−1 K−1 with small reduction as the temperature increases from 300 K to 1400 K. The thermal conductivity of amorphous SixGe1−x for any value of x is approximately an order of magnitude smaller than the minimum thermal conductivity of crystalline SixGe1−x alloy, which occurs near x = 0.5. It is known that alloying with germanium is more efficient than nanostructuring to reduce the thermal conductivity of silicon; however, it was found that the amorphization process is even more effective than alloying for that purpose. It was also shown that the reduction of the thermal conductivity of silicon due to alloying with germanium is more efficient in crystalline phase than in amorphous phase. DA - 2015/6/7/ PY - 2015/6/7/ DO - 10.1063/1.4921536 VL - 117 IS - 21 SP - SN - 1089-7550 ER - TY - JOUR TI - Solid-State Transformer and MV Grid Tie Applications Enabled by 15 kV SiC IGBTs and 10 kV SiC MOSFETs Based Multilevel Converters AU - Madhusoodhanan, Sachin AU - Tripathi, Awneesh AU - Patel, Dhaval AU - Mainali, Krishna AU - Kadavelugu, Arun AU - Hazra, Samir AU - Bhattacharya, Subhashish AU - Hatua, Kamalesh T2 - IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS AB - Medium-voltage (MV) SiC devices have been developed recently which can be used for three-phase MV grid tie applications. Two such devices, 15 kV SiC insulated-gate bipolar transistor (IGBT) and 10 kV SiC MOSFET, have opened up the possibilities of looking into different converter topologies for the MV distribution grid interface. These can be used in MV drives, active filter applications, or as the active front end converter for solid-state transformers (SSTs). The transformerless intelligent power substation (TIPS) is one such application for these devices. TIPS is proposed as a three-phase SST interconnecting a 13.8 kV distribution grid with a 480 V utility grid. It is an all SiC device-based multistage SST. This paper focuses on the advantages, design considerations, and challenges associated with the operation of converters using these devices keeping TIPS as the topology of reference. The efficiency of the TIPS topology is also calculated using the experimentally measured loss data of the devices and the high-frequency transformer. Experimental results captured on a developed prototype of TIPS along with its measured efficiency are also given. DA - 2015/// PY - 2015/// DO - 10.1109/tia.2015.2412096 VL - 51 IS - 4 SP - 3343-3360 SN - 1939-9367 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84937880113&partnerID=MN8TOARS KW - Active front-end converter (FEC) KW - mediumvoltage (MV) grid tie application KW - silicon carbide (SiC) KW - solid-state transformer (SST) ER - TY - JOUR TI - Robust blind image watermarking based on chaotic mixtures AU - Liu, Niansheng AU - Li, Huajian AU - Dai, Huaiyu AU - Guo, Donghui AU - Chen, Deming T2 - NONLINEAR DYNAMICS DA - 2015/5// PY - 2015/5// DO - 10.1007/s11071-015-1946-z VL - 80 IS - 3 SP - 1329-1355 SN - 1573-269X KW - Blind watermarking KW - Chaotic map KW - Wavelet transform KW - Robustness KW - Security ER - TY - JOUR TI - Phase Response of High to Very High Frequency Metal/Anomaly Detector AU - Heinz, Daniel C. AU - Brennan, Michael L. AU - Steer, Michael B. AU - Melber, Adam W. AU - Cua, John T. T2 - DETECTION AND SENSING OF MINES, EXPLOSIVE OBJECTS, AND OBSCURED TARGETS XX AB - In this paper the phase response and reflection coefficient notch of a metal/anomaly detector design that operates in the high to very high frequency range is studied. This design uses a high-Q tuned loop antenna for metal/anomaly detection. By measuring the reflection coefficient or voltage standing wave ratio a frequency notch can be detected. Tuning to the optimal location for detector performance can be accomplished by monitoring both the depth of the notch and the phase response. It has been experimentally observed that there are three regions of interest relative to the notch and phase response of the detector. One is at the frequency where the phase response is on a near vertical line of substantial phase shift and the notch is near its deepest depth. The second and third are at slightly higher and lower frequencies, where the slope of the phase shift line is reduced and the notch is still deep, but slightly removed from the frequency of maximum depth. As would be expected, initial experimentation indicates that the region of maximum detection performance, in terms of relative change in phase response, occurs when the phase response is at the center of the near vertical phase shift response near the location of the deepest notch. However, there may be advantages to the other two regions, since the response is more stable and less prone to false alarms. Performance results for various combinations of phase response and notch depth will be shown. DA - 2015/// PY - 2015/// DO - 10.1117/12.2182083 VL - 9454 SP - SN - 0277-786X KW - Detector KW - High Frequency KW - Very High Frequency KW - Metal KW - Anomaly KW - Phase ER - TY - JOUR TI - Performance Analysis of Bidirectional DC-DC Converters for Electric Vehicles AU - Khan, Mehnaz Akhter AU - Ahmed, Adeeb AU - Husain, Iqbal AU - Sozer, Yilmaz AU - Badawy, Mohamed T2 - IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS AB - This paper presents the performance analysis and comparison of two types of bidirectional dc-dc converters-cascaded buck-boost capacitor in the middle and cascaded buck-boost inductor in the middle for use in plug-in electric and hybrid electric vehicles. The comparison of the two converters is based on device requirements, rating of switches and components, control strategy, and performance. Each of the converter topologies has some advantages over the other in certain aspects. Efficiency analysis has been carried out for specific scenarios in vehicle applications. The simulation and experimental results are provided for both converter types. DA - 2015/// PY - 2015/// DO - 10.1109/tia.2015.2388862 VL - 51 IS - 4 SP - 3442-3452 SN - 1939-9367 KW - Bidirectional KW - cascaded buck-boost KW - comparison KW - dc-dc converter KW - electric vehicle ER - TY - JOUR TI - Graph-Theoretic Methods for Measurement-Based Input Localization in Large Networked Dynamic Systems AU - Nudell, Thomas R. AU - Chakrabortty, Aranya T2 - IEEE TRANSACTIONS ON AUTOMATIC CONTROL AB - In this paper, we consider the problem of localizing disturbance inputs in first-order linear time-invariant (LTI) consensus networks using measurement-based graph-theoretic methods. We consider every node and edge of the network graph to be characterized with physical weights, and show that the resulting system dynamics can be represented in terms of an asymmetric Laplacian matrix L m . Assuming the network graph to be divided into p coherent clusters, we next propose an input localization algorithm based on the properties of the weak nodal domains corresponding to the first p-1 slow eigenvalues of L m . The algorithm takes in sensor measurements of the states from selected nodes, runs a system identification routine to construct the input-output transfer matrix, and compares the signs of the residues of the component transfer functions to a nominal localization key to determine in which cluster(s)the disturbance input may have entered. We prove that for systems defined over a specific class of graphs, referred to as p-area complete graphs, the localization is unique. We also state the extension of this result for second-order synchronization networks. We illustrate the algorithms by applying them to large-scale power system networks. DA - 2015/8// PY - 2015/8// DO - 10.1109/tac.2015.2398911 VL - 60 IS - 8 SP - 2114-2128 SN - 1558-2523 KW - Algebraic graph theory KW - consensus networks KW - fault localization KW - identification KW - nodal domains ER - TY - JOUR TI - Distributed Real-Time Demand Response in Multiseller-Multibuyer Smart Distribution Grid AU - Deng, Ruilong AU - Yang, Zaiyue AU - Hou, Fen AU - Chow, Mo-Yuen AU - Chen, Jiming T2 - IEEE TRANSACTIONS ON POWER SYSTEMS AB - Demand response is a key solution in smart grid to address the ever-increasing peak energy consumption. With multiple utility companies, users will decide from which utility company to buy electricity and how much to buy. Consequently, how to devise distributed real-time demand response in the multiseller–multibuyer environment emerges as a critical problem in future smart grid. In this paper, we focus on the real-time interactions among multiple utility companies and multiple users. We propose a distributed real-time demand response algorithm to determine each user's demand and each utility company's supply simultaneously. By applying dual decomposition, the original problem is firstly decoupled into single-seller–multibuyer subsystems; then, the demand response problem in each subsystem can be distributively solved. The major advantage of this approach is that each utility company and user locally solve subproblems to perform energy allocation, instead of requiring a central controller or any third party. Therefore, privacy is guaranteed because no entity needs to reveal or exchange private information. Numerical results are presented to verify efficiency and effectiveness of the proposed approach. DA - 2015/9// PY - 2015/9// DO - 10.1109/tpwrs.2014.2359457 VL - 30 IS - 5 SP - 2364-2374 SN - 1558-0679 KW - Dual decomposition KW - optimization KW - smart grid KW - supply and demand ER - TY - JOUR TI - Design Considerations of a 15-kV SiC IGBT-Based Medium-Voltage High-Frequency Isolated DC-DC Converter AU - Tripathi, Awneesh K. AU - Mainali, Krishna AU - Patel, Dhaval C. AU - Kadavelugu, Arun AU - Hazra, Samir AU - Bhattacharya, Subhashish AU - Hatua, Kamalesh T2 - IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS AB - A dual active bridge (DAB) is a zero-voltage switching (ZVS) high-power isolated dc-dc converter. The development of a 15-kV SiC insulated-gate bipolar transistor switching device has enabled a noncascaded medium voltage (MV) isolated dc-dc DAB converter. It offers simple control compared to a cascaded topology. However, a compact-size high frequency (HF) DAB transformer has significant parasitic capacitances for such voltage. Under high voltage and high dV/dT switching, the parasitics cause electromagnetic interference and switching loss. They also pose additional challenges for ZVS. The device capacitance and slowing of dV/dT play a major role in deadtime selection. Both the deadtime and transformer parasitics affect the ZVS operation of the DAB. Thus, for the MV-DAB design, the switching characteristics of the devices and MV HF transformer parasitics have to be closely coupled. For the ZVS mode, the current vector needs to be between converter voltage vectors with a certain phase angle defined by deadtime, parasitics, and desired converter duty ratio. This paper addresses the practical design challenges for an MV-DAB application. DA - 2015/// PY - 2015/// DO - 10.1109/tia.2015.2394294 VL - 51 IS - 4 SP - 3284-3294 SN - 1939-9367 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84937876123&partnerID=MN8TOARS KW - Deadtime KW - dual active bridge (DAB) KW - isolated dc-dc converter KW - medium voltage (MV) KW - parasitic capacitance KW - SiC insulated-gate bipolar transistor (IGBT) KW - zero-voltage switching (ZVS) ER - TY - JOUR TI - Control of DC-fault-resilient voltage source converter-based HVDC transmission system under DC fault operating condition AU - Yousefpoor, N. AU - Narwal, A. AU - Bhattacharya, Subhashish T2 - IEEE Transactions on Industrial Electronics AB - Voltage source converter (VSC)-based high-voltage direct current (HVDC) transmission systems have attractive advantages compared to classical thyristor-based HVDC transmission systems. However, VSC-based HVDC transmission systems are vulnerable to dc side fault, and expensive dc circuit breakers are required to protect them against dc fault. This paper proposes a control method of a dc fault-resilient VSC which can be protected against dc fault without using expensive dc circuit breakers. In the VSC configuration, several H-bridge modules are connected in cascade, so the voltage balancing control of several floating dc capacitors is required. In this paper, an appropriate control structure with the capacitor voltage balancing controller is proposed. The appropriate control algorithm for dc fault operation and recovery after dc fault is also proposed. PSCAD simulation results are presented to validate the proposed control structure under normal and dc fault operating conditions. Real-time-digital-simulator results are also presented to verify the control structure. DA - 2015/// PY - 2015/// DO - 10.1109/TIE.2014.2371431 VL - 62 IS - 6 SP - 3683-3690 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84929378724&partnerID=MN8TOARS KW - Capacitor voltage balancing controller KW - dc fault KW - high-voltage direct current (HVDC) transmission systems KW - recovery after dc fault KW - voltage source converter (VSC) ER - TY - JOUR TI - Comparison of the Stability of Functionalized GaN and GaP AU - Wilkins, Stewart J. AU - Paskova, Tania AU - Reynolds, C. Lewis, Jr. AU - Ivanisevic, Albena T2 - CHEMPHYSCHEM AB - Surface functionalization via 1 H,1 H,2 H,2H-perfluoro octanephosphonic acid was done in the presence of phosphoric acid to provide a simplified surface passivation technique for gallium nitride (GaN) and gallium phosphide (GaP). In an effort to identify the leading causes of surface instabilities, hydrogen peroxide was utilized as an additional chemical modification to cap unsatisfied bonds. The stability of the surfaces was studied in an aqueous environment and subsequently characterized. A physical characterization was carried out to evaluate the surface roughness and water hydrophobicity pre and post stability testing via atomic force microscopy and water goniometry. Surface-chemistry changes and solution leaching were quantified by X-ray photoelectron spectroscopy and inductively coupled plasma mass spectrometry. The results indicate a sensitivity to hydroxyl terminated species for both GaN and GaP under aqueous environments, as the increase of the degree of leaching was more significant for hydrogen peroxide treated samples. The results support the notion that hydroxyl species act as precursors to gallium oxide formation and lead to subsequent instability in aqueous solutions. DA - 2015/6/8/ PY - 2015/6/8/ DO - 10.1002/cphc.201500105 VL - 16 IS - 8 SP - 1687-1694 SN - 1439-7641 KW - adsorption KW - gallium KW - mass spectrometry KW - peroxide KW - photoelectron spectroscopy ER - TY - JOUR TI - A probability transition matrix based decentralized electric vehicle charging method for load valley filling AU - Zhan, Kaiqiao AU - Hu, Zechun AU - Song, Yonghua AU - Lu, Ning AU - Xu, Zhiwei AU - Jia, Long T2 - ELECTRIC POWER SYSTEMS RESEARCH AB - This paper presents a decentralized control method to schedule EV (electric vehicle) charging loads to fill the overnight load valley while meeting customers’ charging requirements. A PTM (probability transition matrix) is calculated at the aggregator side as the control signal to guide EV charging processes based on submitted EV charging schedules. Elements of the PTM represent the transition probabilities of moving a charging load from one time period to another. At the EV side, each EV individually updates its charging schedule according to its charging requirements and the PTM. Then the updated schedules are sent back to the aggregator. This process is repeated iteratively until convergence. In this method, no optimal control problems need to be solved locally so that its implementation on the EV side requires low computation capability. Simulation results show that the proposed method can create desired EV charging schedules for load valley filling within only several iterations, making it suitable for real-time implementation. DA - 2015/8// PY - 2015/8// DO - 10.1016/j.epsr.2015.03.013 VL - 125 SP - 1-7 SN - 1873-2046 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000358101200001&KeyUID=WOS:000358101200001 KW - Electric vehicle KW - Load valley filling KW - Decentralized charging control KW - Smart grid KW - Probability transition matrix KW - Aggregators ER - TY - JOUR TI - Wide color gamut multi-twist retarders AU - Homburg, Kathryn J. AU - Brickson, Leandra L. AU - Escuti, Michael J. T2 - EMERGING LIQUID CRYSTAL TECHNOLOGIES X AB - We show how highly chromatic Multi-Twist Retarder (MTR) films can be used to create a single-film color filter wherein the color may be selected only by the MTR orientation angle. By this approach, we can create multi- color images with just an MTR between polarizers. We study the design method and limits of the available color gamut possibilities in this approach, and experimentally demonstrate several designs of continuous and discrete patterns. This technique may be useful in art, displays, microscopy, and remote sensing. DA - 2015/// PY - 2015/// DO - 10.1117/12.2084853 VL - 9384 SP - SN - 1996-756X KW - color filter KW - waveplate KW - multi-twist retarder KW - liquid crystals KW - imaging KW - art ER - TY - JOUR TI - Unsplittable Load Balancing in a Network of Charging Stations Under QoS Guarantees AU - Bayram, Islam Safak AU - Michailidis, George AU - Devetsikiotis, Michael T2 - IEEE TRANSACTIONS ON SMART GRID AB - The operation of the power grid is becoming more stressed, due to the addition of new large loads represented by Electric Vehicles (EVs) and a more intermittent supply due to the incorporation of renewable sources. As a consequence, the coordination and control of projected EV demand in a network of fast charging stations becomes a critical and challenging problem. In this paper, we introduce a game theoretic based decentralized control mechanism to alleviate negative impacts from the EV demand. The proposed mechanism takes into consideration the non-uniform spatial distribution of EVs that induces uneven power demand at each charging facility, and aims to: (i) avoid straining grid resources by offering price incentives so that customers accept being routed to less busy stations, (ii) maximize total revenue by serving more customers with the same amount of grid resources, and (iii) provide charging service to customers with a certain level of Quality-of-Service (QoS), the latter defined as the long term customer blocking probability. We examine three scenarios of increased complexity that gradually approximate real world settings. The obtained results show that the proposed framework leads to substantial performance improvements in terms of the aforementioned goals, when compared to current state of affairs. DA - 2015/5// PY - 2015/5// DO - 10.1109/tsg.2014.2362994 VL - 6 IS - 3 SP - 1292-1302 SN - 1949-3061 KW - Demand response KW - distributed control KW - electric vehicles (EVs) KW - game theory KW - performance evaluation ER - TY - JOUR TI - Ultraspectral Imaging and the Snapshot Advantage AU - Kudenov, Michael W. AU - Roy, Subharup Gupta AU - Pantalone, Brett AU - Maione, Bryan T2 - MICRO- AND NANOTECHNOLOGY SENSORS, SYSTEMS, AND APPLICATIONS VII AB - Ultraspectral sensing has been investigated as a way to resolve terrestrial chemical fluorescence within solar Fraunhofer lines. Referred to as Fraunhofer Line Discriminators (FLDs), these sensors attempt to measure "band filling" of terrestrial fluorescence within these naturally dark regions of the spectrum. However, the method has challenging signal to noise ratio limitations due to the low fluorescence emission signal of the target, which is exacerbated by the high spectral resolution required by the sensor (<0.1 nm). To now, many Fraunhofer line discriminators have been scanning sensors; either pushbroom or whiskbroom, which require temporal and/or spatial scanning to acquire an image. In this paper, we attempt to quantify the snapshot throughput advantage in ultraspectral imaging for FLD. This is followed by preliminary results of our snapshot FLD sensor. The system has a spatial resolution of 280x280 pixels and a spectral resolving power of approximately 10,000 at a 658 nm operating wavelength. DA - 2015/// PY - 2015/// DO - 10.1117/12.2176980 VL - 9467 SP - SN - 1996-756X KW - Snapshot KW - ultraspectral KW - interferometry KW - imaging KW - Fraunhofer KW - fluorescence KW - tradestudy ER - TY - JOUR TI - Type VIII Si based clathrates: prospects for a giant thermoelectric power factor AU - Norouzzadeh, Payam AU - Krasinski, Jerzy S. AU - Myles, Charles W. AU - Vashaee, Daryoosh T2 - PHYSICAL CHEMISTRY CHEMICAL PHYSICS AB - Si46-VIII based clathrates filled with selected alkali and alkali-earth elements are predicted to have giant thermoelectric power factors. DA - 2015/// PY - 2015/// DO - 10.1039/c5cp00729a VL - 17 IS - 14 SP - 8850-8859 SN - 1463-9084 ER - TY - JOUR TI - Optimal Resource Allocation in Random Access Cooperative Cognitive Radio Networks AU - Pandian, Mani Bharathi AU - Sichitiu, Mihail L. AU - Dai, Huaiyu T2 - IEEE TRANSACTIONS ON MOBILE COMPUTING AB - Cooperative cognitive radio networks (CCRNs) incorporates cooperative communication into cognitive radio networks, in which, primary users lease their spectrum to secondary users, and in exchange, the primary users leverage secondary users as cooperative relays to enhance their own throughput. Mobile operators offload their Internet traffic to privately owned Wi-Fi access points (APs), much to the inconvenience of non-cellular users served by the APs. However, by employing the CCRN scheme, the mobile operator can lease a licensed channel to the AP, effectively doubling its capacity. In this paper, we propose an implementation of the CCRN framework applied to IEEE 802.11 WLANs. The cooperation is cast as a two-player bargaining game where the two players are the primary users (users of the mobile operator) and the secondary users (users of the AP before spectrum leasing) who bargain for either throughput share or channel access time share. The optimal resource allocation that ensures efficiency as well as fairness among users is provided by the Nash solution. Simulation results show that the users achieve higher throughput via the proposed CCRN scheme, thus providing the mobile operator (e.g., AT&T) and the private Wi-Fi provider (e.g., a Starbucks coffee shop) with incentives for cooperation. DA - 2015/6// PY - 2015/6// DO - 10.1109/tmc.2014.2343968 VL - 14 IS - 6 SP - 1245-1258 SN - 1558-0660 KW - Cooperative cognitive radio networks KW - WLAN optimization KW - Wi-Fi KW - spectrum leasing KW - game theory ER - TY - JOUR TI - In vivo biocompatibility of Mg implants surface modified by nanostructured merwinite/PEO AU - Razavi, Mehdi AU - Fathi, Mohammadhossein AU - Savabi, Omid AU - Vashaee, Daryoosh AU - Tayebi, Lobat T2 - Journal of Materials Science: Materials in Medicine DA - 2015/4/17/ PY - 2015/4/17/ DO - 10.1007/s10856-015-5514-3 VL - 26 IS - 5 SP - J2 - J Mater Sci: Mater Med LA - en OP - SN - 0957-4530 1573-4838 UR - http://dx.doi.org/10.1007/s10856-015-5514-3 DB - Crossref ER - TY - JOUR TI - Flexible Technologies for Self-Powered Wearable Health and Environmental Sensing AU - Misra, Veena AU - Bozkurt, Alper AU - Calhoun, Benton AU - Jackson, Thomas N. AU - Jur, Jesse S. AU - Lach, John AU - Lee, Bongmook AU - Muth, John AU - Oralkan, Oemer AU - Oeztuerk, Mehmet AU - Trolier-McKinstry, Susan AU - Vashaee, Daryoosh AU - Wentzloff, David AU - Zhu, Yong T2 - PROCEEDINGS OF THE IEEE AB - This article provides the latest advances from the NSF Advanced Self-powered Systems of Integrated sensors and Technologies (ASSIST) center. The work in the center addresses the key challenges in wearable health and environmental systems by exploring technologies that enable ultra-long battery lifetime, user comfort and wearability, robust medically validated sensor data with value added from multimodal sensing, and access to open architecture data streams. The vison of the ASSIST center is to use nanotechnology to build miniature, self-powered, wearable, and wireless sensing devices that can enable monitoring of personal health and personal environmental exposure and enable correlation of multimodal sensors. These devices can empower patients and doctors to transition from managing illness to managing wellness and create a paradigm shift in improving healthcare outcomes. This article presents the latest advances in high-efficiency nanostructured energy harvesters and storage capacitors, new sensing modalities that consume less power, low power computation, and communication strategies, and novel flexible materials that provide form, function, and comfort. These technologies span a spatial scale ranging from underlying materials at the nanoscale to body worn structures, and the challenge is to integrate them into a unified device designed to revolutionize wearable health applications. DA - 2015/4// PY - 2015/4// DO - 10.1109/jproc.2015.2412493 VL - 103 IS - 4 SP - 665-681 SN - 1558-2256 KW - Atomic layer deposition KW - CMUT KW - environmental monitoring KW - environmental sensor KW - flexible electrode KW - motion harvesting KW - physiological sensor KW - piezoelectric KW - PZT KW - self-powered KW - silver nanowire KW - TEG KW - thermoelectrics KW - ultra-low power KW - ultra-low power SOC KW - volatile organic compound sensor KW - wearable device ER - TY - JOUR TI - Effect of ion substitution on properties of bioactive glasses: A review AU - Rabiee, Sayed Mahmood AU - Nazparvar, Neda AU - Azizian, Misaq AU - Vashaee, Daryoosh AU - Tayebi, Lobat T2 - Ceramics International AB - Bioactive glasses and glass-ceramics have recently found key applications in biomedicine, mainly for bone repair and replacement. Recent developments in the field of tissue engineering have re-invigorated the quest to enhance the physical and biomedical effectiveness of bioactive glasses and glass-ceramics by incorporation of different elements into the composition of these materials. Although most elements are included in the bioactive glass for the therapeutic benefits (e.g., Ag and Sr), they influence the structure and bioactivity of the glass. This review systematically discusses the influence of the addition of silver (Ag), magnesium (Mg), strontium (Sr), zinc (Zn), aluminum (Al), potassium (P), fluoride (F) and zirconia (ZrO2) elements on the chemical, physical and therapeutic properties of bioactive glasses and glass-ceramics, which are expected to play an important role in the future of bone regenerative medicine. This article describes where these dopant ions fit into the glass structure and how these affect the delivery and properties of the glass as a whole. DA - 2015/7// PY - 2015/7// DO - 10.1016/j.ceramint.2015.02.140 VL - 41 IS - 6 SP - 7241-7251 J2 - Ceramics International LA - en OP - SN - 0272-8842 UR - http://dx.doi.org/10.1016/j.ceramint.2015.02.140 DB - Crossref KW - Glass-ceramics KW - Bioactive glass KW - Ion substitution ER - TY - JOUR TI - Distortion-free broadband holograms: A novel class of elements utilizing the wavelength-independent geometric phase AU - Xiang, Xiao AU - Miskiewicz, Matthew N. AU - Escuti, Michael J. T2 - PRACTICAL HOLOGRAPHY XXIX: MATERIALS AND APPLICATIONS AB - We demonstrate a novel class of elements called Far-Field Geometric Phase Holograms (FGPH) capable of producing far-field output images free of chromatic distortion for a broad range of input wavelengths. The FGPH utilizes the geometric phase which applies the same phase profile to any incident wave regardless of wavelength. Thus, the fidelity of an image produced by an FGPH is the same for all wavelengths. However, being a diffractive element, the FGPH is still dispersive in that the size of a generated image depends on the replay wavelength according to the diffraction equation. In this paper, we give theory for the ideal FGPH element, describing its replay characteristics and unique polarization properties. We experimentally realize an FGPH element using photo-aligned liquid crystals patterned with a direct-write system. We characterize the fabricated element and show the theory to be valid. Generally, this new class of polarization sensitive elements can produce broadband undistorted images with high diffraction efficiency. DA - 2015/// PY - 2015/// DO - 10.1117/12.2084722 VL - 9386 SP - SN - 1996-756X KW - geometric phase KW - Fourier transform hologram ER - TY - JOUR TI - Coordinate-free quantification of coverage in dynamic sensor networks AU - Gamble, Jennifer AU - Chintakunta, Harish AU - Krim, Hamid T2 - SIGNAL PROCESSING AB - We present a methodology for analyzing coverage properties in dynamic sensor networks. The dynamic sensor network under consideration is studied through a series of snapshots, and is represented by a sequence of simplicial complexes, built from the communication graph at each time point. A method from computational topology called zigzag persistent homology takes this sequence of simplicial complexes as input, and returns a 'barcode' containing the birth and death times of homological features in this sequence. We derive useful statistics from this output for analyzing time-varying coverage properties.In addition, we propose a method which returns specific representative cycles for these homological features, at each point along the birth-death intervals. These representative cycles are then used to track coverage holes in the network, and obtain size estimates for individual holes at each time point. A weighted barcode, incorporating the size information, is then used as a visual and quantitative descriptor of the dynamic network coverage. Graphical abstractDisplay Omitted HighlightsEach sensor has only a list of its neighboring sensors, with no coordinates, or inter-sensor distance information.Using these snapshots of local information, we describe the dynamic coverage properties of the network.Quantitative output is a weighted barcode, obtained using zigzag persistent homology.Estimated hole size and duration are encoded in this barcode.Method is able to distinguish between different sensor network mobility patterns. DA - 2015/9// PY - 2015/9// DO - 10.1016/j.sigpro.2015.02.013 VL - 114 SP - 1-18 SN - 1872-7557 KW - Dynamic sensor network KW - Coverage problem KW - Homology KW - Coordinate-free ER - TY - JOUR TI - Control-Flow Decoupling: An Approach for Timely, Non-Speculative Branching AU - Sheikh, Rami AU - Tuck, James AU - Rotenberg, Eric T2 - IEEE TRANSACTIONS ON COMPUTERS AB - Mobile and PC/server class processor companies continue to roll out flagship core microarchitectures that are faster than their predecessors. Meanwhile placing more cores on a chip coupled with constant supply voltage puts per-core energy consumption at a premium. Hence, the challenge is to find future microarchitecture optimizations that not only increase performance but also conserve energy. Eliminating branch mispredictions-which waste both time and energy-is valuable in this respect. In this paper, we explore the control-flow landscape by characterizing mispredictions in four benchmark suites. We find that a third of mispredictions-per-1K-instructions (MPKI) come from what we call separable branches: branches with large control-dependent regions (not suitable for if-conversion), whose backward slices do not depend on their control-dependent instructions or have only a short dependence. We propose control-flow decoupling (CFD) to eradicate mispredictions of separable branches. The idea is to separate the loop containing the branch into two loops: the first contains only the branch's predicate computation and the second contains the branch and its control-dependent instructions. The first loop communicates branch outcomes to the second loop through an architectural queue. Microarchitecturally, the queue resides in the fetch unit to drive timely, non-speculative branching. On a microarchitecture configured similar to Intel's Sandy Bridge core, CFD increases performance by up to 55 percent, and reduces energy consumption by up to 49 percent (for CFD regions). Moreover, for some applications, CFD is a necessary catalyst for future complexity-effective large-window architectures to tolerate memory latency. DA - 2015/8// PY - 2015/8// DO - 10.1109/tc.2014.2361526 VL - 64 IS - 8 SP - 2182-2203 SN - 1557-9956 KW - Microarchitecture KW - software/hardware codesign KW - branch prediction KW - predication KW - pre-execution KW - separable branches KW - isa extensions KW - instruction level parallelism ER - TY - JOUR TI - Camouflage Traffic: Minimizing Message Delay for Smart Grid Applications under Jamming AU - Lu, Zhuo AU - Wang, Wenye AU - Wang, Cliff T2 - IEEE TRANSACTIONS ON DEPENDABLE AND SECURE COMPUTING AB - Smart grid is a cyber-physical system that integrates power infrastructures with information technologies. To facilitate efficient information exchange, wireless networks have been proposed to be widely used in the smart grid. However, the jamming attack that constantly broadcasts radio interference is a primary security threat to prevent the deployment of wireless networks in the smart grid. Hence, spread spectrum systems, which provide jamming resilience via multiple frequency and code channels, must be adapted to the smart grid for secure wireless communications, while at the same time providing latency guarantee for control messages. An open question is how to minimize message delay for timely smart grid communication under any potential jamming attack. To address this issue, we provide a paradigm shift from the case-by-case methodology, which is widely used in existing works to investigate well-adopted attack models, to the worst-case methodology, which offers delay performance guarantee for smart grid applications under any attack. We first define a generic jamming process that characterizes a wide range of existing attack models. Then, we show that in all strategies under the generic process, the worst-case message delay is a U-shaped function of network traffic load. This indicates that, interestingly, increasing a fair amount of traffic can in fact improve the worst-case delay performance. As a result, we demonstrate a lightweight yet promising system, transmitting adaptive camouflage traffic (TACT), to combat jamming attacks. TACT minimizes the message delay by generating extra traffic called camouflage to balance the network load at the optimum. Experiments show that TACT can decrease the probability that a message is not delivered on time in order of magnitude. DA - 2015/// PY - 2015/// DO - 10.1109/tdsc.2014.2316795 VL - 12 IS - 1 SP - 31-44 SN - 1941-0018 KW - Smart grid KW - wireless applications KW - performance modeling KW - worst-case analysis KW - message delay KW - jamming attacks ER - TY - JOUR TI - Bevel Junction Termination Extension-A New Edge Termination Technique for 4H-SiC High-Voltage Devices AU - Sung, Woongje AU - Huang, Alex Q. AU - Baliga, B. Jayant T2 - IEEE ELECTRON DEVICE LETTERS AB - A new edge termination method, referred to as a bevel junction termination extension (Bevel-JTE), is presented for high-voltage silicon carbide devices. The 4H-SiC PiN rectifiers, with a breakdown voltage of 1600 V (~95% of the theoretical value), were fabricated using Bevel-JTEs. The Bevel-JTE technique significantly reduces the chip size by decreasing space occupied by edge termination while providing broad process latitude for parameter variations, such as implantation dose and activation anneal condition. DA - 2015/6// PY - 2015/6// DO - 10.1109/led.2015.2427654 VL - 36 IS - 6 SP - 594-596 SN - 1558-0563 KW - Edge termination KW - bevel dicing KW - junction termination extension (JTE) KW - PiN diode KW - 4H-SiC ER - TY - JOUR TI - A Universal Parallel Two-Pass MDL Context Tree Compression Algorithm AU - Krishnan, Nikhil AU - Baron, Dror T2 - IEEE JOURNAL OF SELECTED TOPICS IN SIGNAL PROCESSING AB - Computing problems that handle large amounts of data necessitate the use of lossless data compression for efficient storage and transmission. We present a novel lossless universal data compression algorithm that uses parallel computational units to increase the throughput. The length- N input sequence is partitioned into B blocks. Processing each block independently of the other blocks can accelerate the computation by a factor of B, but degrades the compression quality. Instead, our approach is to first estimate the minimum description length (MDL) context tree source underlying the entire input, and then encode each of the B blocks in parallel based on the MDL source. With this two-pass approach, the compression loss incurred by using more parallel units is insignificant. Our algorithm is work-efficient, i.e., its computational complexity is O(N/B). Its redundancy is approximately Blog(N/B) bits above Rissanen's lower bound on universal compression performance, with respect to any context tree source whose maximal depth is at most log(N/B). We improve the compression by using different quantizers for states of the context tree based on the number of symbols corresponding to those states. Numerical results from a prototype implementation suggest that our algorithm offers a better trade-off between compression and throughput than competing universal data compression algorithms. DA - 2015/6// PY - 2015/6// DO - 10.1109/jstsp.2015.2403800 VL - 9 IS - 4 SP - 741-748 SN - 1941-0484 KW - Big data KW - computational complexity KW - data compression KW - distributed computing KW - minimum description length KW - parallel algorithms KW - redundancy KW - two-pass code KW - universal compression KW - work-efficient algorithms ER - TY - JOUR TI - Unified codebook design for vector channel quantization in MIMO broadcast channels AU - Lee, J. H. AU - Choi, W. T2 - IEEE Transactions on Signal Processing DA - 2015/// PY - 2015/// VL - 63 IS - 10 SP - 2509-2519 ER - TY - JOUR TI - Snapshot Imaging Fraunhofer Line Discriminator for Detection of Plant Fluorescence AU - Roy, S. Gupta AU - Kudenov, M. W. T2 - ALGORITHMS AND TECHNOLOGIES FOR MULTISPECTRAL, HYPERSPECTRAL, AND ULTRASPECTRAL IMAGERY XXI AB - Non-invasive quantification of plant health is traditionally accomplished using reflectance based metrics, such as the normalized difference vegetative index (NDVI). However, measuring plant fluorescence (both active and passive) to determine photochemistry of plants has gained importance. Due to better cost efficiency, lower power requirements, and simpler scanning synchronization, detecting passive fluorescence is preferred over active fluorescence. In this paper, we propose a high speed imaging approach for measuring passive plant fluorescence, within the hydrogen alpha Fraunhofer line at ~656 nm, using a Snapshot Imaging Fraunhofer Line Discriminator (SIFOLD). For the first time, the advantage of snapshot imaging for high throughput Fraunhofer Line Discrimination (FLD) is cultivated by our system, which is based on a multiple-image Fourier transform spectrometer and a spatial heterodyne interferometer (SHI). The SHI is a Sagnac interferometer, which is dispersion compensated using blazed diffraction gratings. We present data and techniques for calibrating the SIFOLD to any particular wavelength. This technique can be applied to quantify plant fluorescence at low cost and reduced complexity of data collection. DA - 2015/// PY - 2015/// DO - 10.1117/12.2176906 VL - 9472 SP - SN - 1996-756X KW - plant fluorescence KW - snapshot imaging KW - Fraunhofer line discriminator KW - multiple image Fourier transform spectrometer KW - spatial heterodyne interferometer KW - Sagnac interferometer ER - TY - JOUR TI - Regenerative influence of nanostructured bredigite (Ca7MgSi4O16)/anodic spark coating on biodegradable AZ91 magnesium alloy implants for bone healing AU - Razavi, Mehdi AU - Fathi, Mohammadhossein AU - Savabi, Omid AU - Vashaee, Daryoosh AU - Tayebi, Lobat T2 - Materials Letters AB - Magnesium has been recently introduced as a novel biodegradable material for bone healing. However, the fast degradation of this material results in the fast release of hydrogen which limits its clinical applications. In view of that, in the present study, we attempt to overcome this drawback using a bredigite (Ca7MgSi4O16) coating. In our previous work, we have coated AZ91 magnesium implants with bredigite through the combination of anodic spark deposition (ASD) and electrophoretic deposition (EPD) techniques. As continuation to that work, in this paper, we have focused on the in vivo examination of the bredigite/ASD compared to the plain ASD coated and the uncoated AZ91 substrates. The results of the in vivo animal test in the greater trochanter of rabbits indicated improved regeneration of bone and less bone inflammation upon employing bredigite/ASD coated implants. In addition, an enhancement in in vivo biodegradation was observed by the reduction in magnesium ion released in the blood plasma. In summary, a surface treatment using bredigite on magnesium implants promotes their bone healing capabilities for future clinical applications. DA - 2015/9// PY - 2015/9// DO - 10.1016/j.matlet.2015.04.129 VL - 155 SP - 97-101 J2 - Materials Letters LA - en OP - SN - 0167-577X UR - http://dx.doi.org/10.1016/j.matlet.2015.04.129 DB - Crossref KW - Magnesium implant KW - Bredigite coating KW - Surface coating KW - Bone regeneration KW - Biocompatibility ER - TY - JOUR TI - Passive Standoff Imaging using Spatial-Spectral Multiplexing AU - Woodard, Ethan R. AU - Kudenov, Michael W. T2 - ALGORITHMS AND TECHNOLOGIES FOR MULTISPECTRAL, HYPERSPECTRAL, AND ULTRASPECTRAL IMAGERY XXI AB - The concept of a passive far-field imaging system, using a unique spatial-spectral multiplexing (SSM) technique, is presented. The described SSM technique uses spectrally resolved interferometry to multiplex a scene’s angular spectrum onto the power spectrum, while dispersion characteristics are implemented to heterodyne the channeled spectrum into the spectral range of visible light. In this paper, the theory of the design is detailed and an analysis of the spatial and spectral tradespace of the system are discussed. Applications for this imaging technique are primarily focused in remote sensing and far-field target identification. DA - 2015/// PY - 2015/// DO - 10.1117/12.2177272 VL - 9472 SP - SN - 1996-756X KW - spatial-spectral multiplexing KW - channeled spectrum KW - angular coherence compensation KW - remote sensing ER - TY - JOUR TI - On Topology and Resilience of Large-Scale Cognitive Radio Networks Under Generic Failures AU - Sun, Lei AU - Wang, Wenye AU - Lu, Zhuo T2 - IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS AB - It has been demonstrated that in wireless networks, blackholes, which are typically generated by isolated node failures, and augmented by failure correlations, can easily result in devastating impact on network performance. In order to address this issue, we focus on the topology of Cognitive Radio Networks (CRNs) because of their phenomenal benefits in improving spectrum efficiency through opportunistic communications. Particularly, we first define two metrics, namely the failure occurrence probability p and failure connection function g(·), to characterize node failures and their spreading properties, respectively. Then we prove that each blackhole is exponentially bounded based on percolation theory. By mapping failure spreading using a branching process, we further derive an upper bound on the expected size of blackholes. With the observations from our analysis, we are able to find a sufficient condition for a resilient CRN in the presence of blackholes through analysis and simulations. DA - 2015/6// PY - 2015/6// DO - 10.1109/twc.2015.2404919 VL - 14 IS - 6 SP - 3390-3401 SN - 1558-2248 KW - Resilience KW - cognitive radio networks KW - topology KW - generic failures ER - TY - JOUR TI - Nonmechanical Laser Beam Steering Based on Polymer Polarization Gratings: Design Optimization and Demonstration AU - Kim, Jihwan AU - Miskiewicz, Matthew N. AU - Serati, Steve AU - Escuti, Michael J. T2 - JOURNAL OF LIGHTWAVE TECHNOLOGY AB - We present a wide-angle, nonmechanical laser beam steerer based on polymer polarization gratings with an optimal design approach for maximizing field-of-regard (FOR). The steering design offers exponential scaling of the number of steering angles, called suprabinary steering. The design approach can be easily adapted for any 1-D or 2-D (e.g, symmetric or asymmetric FOR) beam steering. We simulate a system using a finite difference and ray tracing tools and fabricate coarse beam steerer with 65° FOR with ~8° resolution at 1550 nm. We demonstrate high optical throughput (84%-87%) that can be substantially improved by optimizing substrates and electrode materials. This beam steerer can achieve very low sidelobes and supports comparatively large beam diameters paired with a very thin assembly and low beam walk-off. We also demonstrate using a certain type of LC variable retarder that the total switching time from any steering angle to another can be 1.7 ms or better. DA - 2015/5/15/ PY - 2015/5/15/ DO - 10.1109/jlt.2015.2392694 VL - 33 IS - 10 SP - 2068-2077 SN - 1558-2213 KW - Beam steering KW - diffractive optics KW - holography KW - lidar KW - liquid crystals KW - optical communications KW - polarization grating KW - radar ER - TY - JOUR TI - NoCMsg: A Scalable Message-Passing Abstraction for Network-on-Chips AU - Zimmer, Christopher AU - Mueller, Frank T2 - ACM TRANSACTIONS ON ARCHITECTURE AND CODE OPTIMIZATION AB - The number of cores of contemporary processors is constantly increasing and thus continues to deliver ever higher peak performance (following Moore’s transistor law). Yet high core counts present a challenge to hardware and software alike. Following this trend, the network-on-chip (NoC) topology has changed from buses over rings and fully connected meshes to 2D meshes. This work contributes NoCMsg, a low-level message-passing abstraction over NoCs, which is specifically designed for large core counts in 2D meshes. NoCMsg ensures deadlock-free messaging for wormhole Manhattan-path routing over the NoC via a polling-based message abstraction and non--flow-controlled communication for selective communication patterns. Experimental results on the TilePro hardware platform show that NoCMsg can significantly reduce communication times by up to 86% for single packet messages and up to 40% for larger messages compared to other NoC-based message approaches. On the TilePro platform, NoCMsg outperforms shared memory abstractions by up to 93% as core counts and interprocess communication increase. Results for fully pipelined double-precision numerical codes show speedups of up to 64% for message passing over shared memory at 32 cores. Overall, we observe that shared memory scales up to about 16 cores on this platform, whereas message passing performs well beyond that threshold. These results generalize to similar NoC-based platforms. DA - 2015/4// PY - 2015/4// DO - 10.1145/2701426 VL - 12 IS - 1 SP - SN - 1544-3973 KW - Experimentation KW - Tracing KW - Compression KW - Multicore architectures KW - shared memory KW - message passing ER - TY - JOUR TI - Modulated optical sensitivity with nanostructured gallium nitride AU - Wilkins, S. J. AU - Slomski, M. J. AU - Paskova, T. AU - Weyher, J. L. AU - Ivanisevic, A. T2 - APPLIED PHYSICS LETTERS AB - Surface functionalization via etching of high aspect ratio gallium nitride (GaN) nanostructures provides a way to modulate the optical properties in addition to properties gained from unique topographical formations. In this study, planar layered (heteroepitaxy) and bulk free-standing gallium nitride were modified via a phosphonic acid (1H,1H,2H,2H-perfluorooctanephosphonic acid) assisted phosphoric acid etch in conjunction with an aqueous KOH + K2S2O8 formed gallium nitride nanostructured surface. Despite the high defect concentrations in the thin planar and nanostructured GaN layer, the nanostructured GaN sample produced improved photoluminescence intensities versus the high quality bulk free-standing gallium nitride. Subsequent treatments with additive and additive-free phosphoric etches provided a means of additional optical manipulation in the form of red-shifting the near-band-edge (NBE) emission of the nanostructured GaN sample and increasing the maximum NBE photoluminescence intensity. DA - 2015/4/13/ PY - 2015/4/13/ DO - 10.1063/1.4918739 VL - 106 IS - 15 SP - SN - 1077-3118 ER - TY - JOUR TI - Measuring graphene adhesion using atomic force microscopy with a microsphere tip AU - Jiang, Tao AU - Zhu, Yong T2 - NANOSCALE AB - Van der Waals adhesion between graphene and various substrates has an important impact on the physical properties, device applications and nanomanufacturing processes of graphene. Here we report a general, high-throughput and reliable method that can measure adhesion energies between ultraflat graphene and a broad range of materials using atomic force microscopy with a microsphere tip. In our experiments, only van der Waals force between the tip and a graphene flake is measured. The Maugis-Dugdale theory is employed to convert the measured adhesion force using AFM to the adhesion energy. The ultraflatness of monolayer graphene on mica eliminates the effect of graphene surface roughness on the adhesion, while roughness of the microsphere tip is addressed by the modified Rumpf model. Adhesion energies of monolayer graphene to SiO2 and Cu are obtained as 0.46 and 0.75 J m(-2), respectively. This work provides valuable insight into the mechanism of graphene adhesion and can readily extend to the adhesion measurement for other 2D nanomaterials. DA - 2015/// PY - 2015/// DO - 10.1039/c5nr02480c VL - 7 IS - 24 SP - 10760-10766 SN - 2040-3372 ER - TY - JOUR TI - Low-cost compact circularly polarized directional antenna for universal UHF RFID handheld reader applications AU - Liu, Q. AU - Shen, J. Y. AU - Liu, H. L. AU - Wu, Y. L. AU - Su, M. AU - Liu, Y. N. T2 - IEEE Antennas and Wireless Propagation Letters DA - 2015/// PY - 2015/// VL - 14 ER - TY - JOUR TI - Joint Scheduling of Large-Scale Appliances and Batteries Via Distributed Mixed Optimization AU - Yang, Zaiyue AU - Long, Keyu AU - You, Pengcheng AU - Chow, Mo-Yuen T2 - IEEE TRANSACTIONS ON POWER SYSTEMS AB - This paper investigates joint scheduling problem of large-scale smart appliances and batteries (e.g., in a smart building), to minimize electricity payment, user's dissatisfaction and battery loss under kinds of constraints. Due to the binary nature of charge and discharge states of battery, this problem is formulated as a constrained mixed-integer nonlinear program. In order to solve it efficiently, a distributed mixed optimization approach is proposed. First, Lagrangian relaxation is applied to decompose the original problem into two sets of subproblems, each of which corresponds to scheduling on appliance/battery. Then, the battery scheduling subproblem is formulated as a mixed-integer linear program and tackled by Benders decomposition. The main advantages of the proposed approach are the distributed implementation and low computational complexity, as shown by simulations. DA - 2015/7// PY - 2015/7// DO - 10.1109/tpwrs.2014.2354071 VL - 30 IS - 4 SP - 2031-2040 SN - 1558-0679 KW - Benders decomposition KW - demand-side management KW - distributed mixed optimization KW - Lagrangian relaxation ER - TY - JOUR TI - High-performance emulation of heterogeneous systems using adaptive time dilation AU - Lee, Hee Won AU - Sichitiu, Mihail L. AU - Thuente, David T2 - INTERNATIONAL JOURNAL OF HIGH PERFORMANCE COMPUTING APPLICATIONS AB - Building a testbed for evaluating the performance of large-scale heterogeneous systems can be costly and inefficient. Emulation is often used to evaluate the performance of a system in a controlled environment. Time dilation allows virtual machines (VMs) to emulate higher performance than that of their physical machine. We present an approach using adaptive time dilation to emulate large-scale distributed systems composed of heterogeneous machines and Operating Systems (OSs). In our implementation, VMs are globally synchronized. To evaluate our system, distributed VMs running Linux, Windows, FreeBSD, and Junos are emulated on general-purpose physical machines. DA - 2015/// PY - 2015/// DO - 10.1177/1094342014554789 VL - 29 IS - 2 SP - 166-183 SN - 1741-2846 KW - Emulation KW - time dilation KW - virtual time KW - virtualization KW - virtual machines KW - testbeds KW - heterogeneous systems KW - distributed applications ER - TY - JOUR TI - Four-quadrant torque ripple minimization of switched reluctance machine through current profiling with mitigation of rotor eccentricity problem and sensor errors AU - Mikail, R. AU - Husain, I. AU - Islam, M. S. AU - Sozer, Y. AU - Sebastian, T. T2 - IEEE Transactions on Industry Applications AB - This paper presents a method of profiling the phase currents to minimize the torque ripple of switched reluctance machines (SRMs) operating in four-quadrant mode over the entire speed range of operation. The method is based on machine and controller design through coupled simulation of the finite-element-based machine model and the dynamic controller model. The method considers the mutual coupling effect between conducting phases. The research quantifies the effect of sensor error and manufacturing build variations on the level of torque ripple minimization. The mitigation processes to address the issues in mass production are also presented. DA - 2015/// PY - 2015/// DO - 10.1109/tia.2014.2365715 VL - 51 IS - 3 SP - 2097-2104 ER - TY - JOUR TI - Experimental demonstration of the equivalence of inductive and strongly coupled magnetic resonance wireless power transfer (vol 102, 053904, 2013) AU - Ricketts, D. S. AU - Chabalko, M. J. AU - Hillenius, A. T2 - Applied Physics Letters DA - 2015/// PY - 2015/// VL - 107 IS - 4 ER - TY - JOUR TI - Characterizing link connectivity in opportunistic networks AU - Lee, C. H. AU - Eun, D. Y. T2 - Opportunistic Mobile Social Networks DA - 2015/// PY - 2015/// SP - 71-97 ER - TY - JOUR TI - Accurate characterization and understanding of interface trap density trends between atomic layer deposited dielectrics and AlGaN/GaN with bonding constraint theory AU - Ramanan, Narayanan AU - Lee, Bongmook AU - Misra, Veena T2 - Applied Physics Letters AB - Many dielectrics have been proposed for the gate stack or passivation of AlGaN/GaN based metal oxide semiconductor heterojunction field effect transistors, to reduce gate leakage and current collapse, both for power and RF applications. Atomic Layer Deposition (ALD) is preferred for dielectric deposition as it provides uniform, conformal, and high quality films with precise monolayer control of film thickness. Identification of the optimum ALD dielectric for the gate stack or passivation requires a critical investigation of traps created at the dielectric/AlGaN interface. In this work, a pulsed-IV traps characterization method has been used for accurate characterization of interface traps with a variety of ALD dielectrics. High-k dielectrics (HfO2, HfAlO, and Al2O3) are found to host a high density of interface traps with AlGaN. In contrast, ALD SiO2 shows the lowest interface trap density (&lt;2 × 1012 cm−2) after annealing above 600 °C in N2 for 60 s. The trend in observed trap densities is subsequently explained with bonding constraint theory, which predicts a high density of interface traps due to a higher coordination state and bond strain in high-k dielectrics. DA - 2015/6/15/ PY - 2015/6/15/ DO - 10.1063/1.4922799 VL - 106 IS - 24 SP - 243503 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.4922799 DB - Crossref ER - TY - JOUR TI - A reconfigurable liquid metal antenna driven by electrochemically controlled capillarity AU - Wang, M. AU - Trlica, C. AU - Khan, M. R. AU - Dickey, M. D. AU - Adams, J. J. T2 - JOURNAL OF APPLIED PHYSICS AB - We describe a new electrochemical method for reversible, pump-free control of liquid eutectic gallium and indium (EGaIn) in a capillary. Electrochemical deposition (or removal) of a surface oxide on the EGaIn significantly lowers (or increases) its interfacial tension as a means to induce the liquid metal in (or out) of the capillary. A fabricated prototype demonstrates this method in a reconfigurable antenna application in which EGaIn forms the radiating element. By inducing a change in the physical length of the EGaIn, the operating frequency of the antenna tunes over a large bandwidth. This purely electrochemical mechanism uses low, DC voltages to tune the antenna continuously and reversibly between 0.66 GHz and 3.4 GHz resulting in a 5:1 tuning range. Gain and radiation pattern measurements agree with electromagnetic simulations of the device, and its measured radiation efficiency varies from 41% to 70% over its tuning range. DA - 2015/5/21/ PY - 2015/5/21/ DO - 10.1063/1.4919605 VL - 117 IS - 19 SP - SN - 1089-7550 ER - TY - JOUR TI - A Three-Mask Process for Fabricating Vacuum-Sealed Capacitive Micromachined Ultrasonic Transducers Using Anodic Bonding AU - Yamaner, F. Yalcin AU - Zhang, Xiao AU - Oralkan, Omer T2 - IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL AB - This paper introduces a simplified fabrication method for vacuum-sealed capacitive micromachined ultrasonic transducer (CMUT) arrays using anodic bonding. Anodic bonding provides the established advantages of wafer-bondingbased CMUT fabrication processes, including process simplicity, control over plate thickness and properties, high fill factor, and ability to implement large vibrating cells. In addition to these, compared with fusion bonding, anodic bonding can be performed at lower processing temperatures, i.e., 350°C as opposed to 1100°C; surface roughness requirement for anodic bonding is more than 10 times more relaxed, i.e., 5-nm rootmean- square (RMS) roughness as opposed to 0.5 nm for fusion bonding; anodic bonding can be performed on smaller contact area and hence improves the fill factor for CMUTs. Although anodic bonding has been previously used for CMUT fabrication, a CMUT with a vacuum cavity could not have been achieved, mainly because gas is trapped inside the cavities during anodic bonding. In the approach we present in this paper, the vacuum cavity is achieved by opening a channel in the plate structure to evacuate the trapped gas and subsequently sealing this channel by conformal silicon nitride deposition in the vacuum environment. The plate structure of the fabricated CMUT consists of the single-crystal silicon device layer of a silicon-on-insulator wafer and a thin silicon nitride insulation layer. The presented fabrication approach employs only three photolithographic steps and combines the advantages of anodic bonding with the advantages of a patterned metal bottom electrode on an insulating substrate, specifically low parasitic series resistance and low parasitic shunt capacitance. In this paper, the developed fabrication scheme is described in detail, including process recipes. The fabricated transducers are characterized using electrical input impedance measurements in air and hydrophone measurements in immersion. A representative design is used to demonstrate immersion operation in conventional, collapse-snapback, and collapse modes. In collapsemode operation, an output pressure of 1.67 MPa pp is shown at 7 MHz on the surface of the transducer for 60-Vpp, 3-cycle sinusoidal excitation at 30-V dc bias. DA - 2015/5// PY - 2015/5// DO - 10.1109/tuffc.2014.006794 VL - 62 IS - 5 SP - 972-982 SN - 1525-8955 ER - TY - JOUR TI - A Survey on Demand Response in Smart Grids: Mathematical Models and Approaches AU - Deng, Ruilong AU - Yang, Zaiyue AU - Chow, Mo-Yuen AU - Chen, Jiming T2 - IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS AB - The smart grid is widely considered to be the informationization of the power grid. As an essential characteristic of the smart grid, demand response can reschedule the users' energy consumption to reduce the operating expense from expensive generators, and further to defer the capacity addition in the long run. This survey comprehensively explores four major aspects: 1) programs; 2) issues; 3) approaches; and 4) future extensions of demand response. Specifically, we first introduce the means/tariffs that the power utility takes to incentivize users to reschedule their energy usage patterns. Then we survey the existing mathematical models and problems in the previous and current literatures, followed by the state-of-the-art approaches and solutions to address these issues. Finally, based on the above overview, we also outline the potential challenges and future research directions in the context of demand response. DA - 2015/6// PY - 2015/6// DO - 10.1109/tii.2015.2414719 VL - 11 IS - 3 SP - 570-582 SN - 1941-0050 KW - Convex optimization KW - demand response KW - game theory KW - renewable energy KW - smart grid ER - TY - JOUR TI - A Novel Framework for Pulse Pressure Wave Analysis Using Persistent Homology AU - Emrani, Saba AU - Saponas, T. Scott AU - Morris, Dan AU - Krim, Hamid T2 - IEEE SIGNAL PROCESSING LETTERS AB - Four characteristic points of pulse pressure waves-the systolic peak, the anacrotic notch, the dicrotic notch, and the diastolic foot-are used to estimate various aspects of cardiovascular function, such as heart rate and augmentation index. We propose a novel approach to extracting these characteristic points using a topological signal processing framework. We characterize the topology of the signals using a collection of persistence intervals, which are encapsulated in a persistence diagram. The characteristic points are identified based on their time of occurrence and their distance from the identity line in the persistence diagram. We validate this approach by collecting radial pulse pressure data from twenty-eight participants using a wearable tonometer, and computing the peripheral augmentation index using a traditional derivative-based method and our novel persistence-based method. The augmentation index values computed using the two methods are statistically indistinguishable, suggesting that this representation merits further exploration as a tool for analyzing pulse pressure waves. DA - 2015/11// PY - 2015/11// DO - 10.1109/lsp.2015.2441068 VL - 22 IS - 11 SP - SN - 1558-2361 KW - Algebraic topology algorithms KW - pulse pressure waves KW - topological signal analysis KW - wearable sensors ER - TY - JOUR TI - A Multitier Study on Various Stacking Topologies of TSV-Based PDN Systems Using On-Chip Decoupling Capacitor Models AU - Charles, Gary AU - Franzon, Paul D. T2 - IEEE TRANSACTIONS ON COMPONENTS PACKAGING AND MANUFACTURING TECHNOLOGY AB - We studied the impedance characteristics of through-silicon via (TSV)-based power delivery networks (PDNs) for hierarchical on-die simulation and interconnect noise analysis. This paper compares the quality of power delivery in 3-D stacking scenarios for three distinct chip stacking topologies: 1) face-to-back (F2B); 2) face-to-face (F2F); and 3) back-to-back (B2B). Quantitatively, this paper compared the impedance noise level between the three stacking topologies and found the PDN impedance noise of F2F chip stacking to be relatively lower than F2B and B2B chip stacking topologies. A power delivery impedance below 1 Ω for F2F chip stacking topology was possible up to 2 GHz. However, for F2B and B2B chip stacking, the PDN impedance could not get beyond sub-1 Ω. The impedance was simulated between 0.1 and 20 GHz. Among power grid and power and ground TSV models presented in this paper, we also present and implemented a metal-insulator-metal capacitor model written as a complex impedance equation. With capacitor dimensions similar to the unit cell gird size (200 μm × 200 μm), the capacitance density (per unit area) ranged from 0.062 pF/μm 2 to 5.325 fF/μm 2 . DA - 2015/4// PY - 2015/4// DO - 10.1109/tcpmt.2015.2416196 VL - 5 IS - 4 SP - 541-550 SN - 2156-3985 KW - Back-to-back (B2B) KW - face-to-back (F2B) KW - face-to-face (F2F) KW - on-chip decoupling capacitors KW - power distribution network (PDN) KW - segmentation method KW - through silicon via (TSV) ER - TY - JOUR TI - 3D-printed spherical dipole antenna integrated on small RF node AU - Adams, J.J. AU - Slimmer, S.C. AU - Bernhard, J.T. AU - Lewis, J.A. T2 - Electronics Letters AB - New three-dimensional (3D) printing techniques enable the integration of an antenna directly onto the package of a small wireless sensor node. This volume-filling approach ensures near-optimal bandwidth performance of the small antenna, increasing a system's battery life, data rate or range. Simulated results show that the fabricated spherical antenna's bandwidth-efficiency product is more than half of the fundamental limit and radiation pattern measurements exhibit a dipole pattern with −0.7 dBi gain. DA - 2015/4/30/ PY - 2015/4/30/ DO - 10.1049/el.2015.0256 VL - 51 IS - 9 SP - 661-662 LA - en OP - SN - 0013-5194 1350-911X UR - http://dx.doi.org/10.1049/el.2015.0256 DB - Crossref ER - TY - JOUR TI - Towards characterizing the pressure profiles of medical compression hosiery: an investigation of current measurement devices and techniques AU - Hegarty-Craver, Meghan AU - Kwon, Cassandra AU - Oxenham, William AU - Grant, Edward AU - Reid, Lawrence, Jr. T2 - JOURNAL OF THE TEXTILE INSTITUTE AB - Medical compression hosiery is prescribed according to the pressure it applies to a limb. There are many devices available for measuring this pressure, but differences in the design of the systems used, measurement locations, protocols, and operators result in different pressures being measured for the same garment. This article explores the construction of these compression-measuring devices and the sensing involved in order to highlight the potential causes of these discrepancies. The Tension–Elongation profiles of six compression hosiery samples were then measured, and a method of verifying the point pressure measurements from current techniques was proposed and tested. The results of this analysis show that there was an average discrepancy of 1–5 mmHg between point pressure measurements and those predicted from the Tension–Elongation profiles. With respect to on-body measurements, this technique predicted a maximum change in pressure of 3 mmHg for the samples tested. DA - 2015/7/3/ PY - 2015/7/3/ DO - 10.1080/00405000.2014.941535 VL - 106 IS - 7 SP - 757-767 SN - 1754-2340 KW - body measurement KW - compression garments KW - medical textiles KW - interface pressure KW - measurement and verification ER - TY - JOUR TI - Special Section on Monitoring, Visualization, and State Estimation for Distribution Systems AU - Aminifar, Farrokh AU - Meliopoulos, Sakis AU - Baran, Mesut AU - Romero-Agueero, Julio AU - Pahwa, Anil AU - Grijalva, Santiago AU - Madani, Vahid AU - Giri, Jay T2 - IEEE TRANSACTIONS ON SMART GRID AB - Inherited from legacy technologies, electric distribution systems are aging infrastructures whose component failures have a significant role in customer electricity interruptions. Low visibility and controllability of the distribution grid are a common practice today across the globe. In this circumstance, elements of the distribution grid including overhead distribution lines, underground cables, breakers, sectionalizers, etc. are being operated with very limited real-time data acquisition and virtually no remote control capability. The majority of failures are not detected by system operators unless interrupted customers notify them by phone. Very often (and particularly in municipal areas with underground networks), a distribution system is scattered across a large (and cumbersome) geographical region. Therefore, fault location and service restoration by nature is a difficult and prolonged process. Most of the associated tasks such as restoration are manually implemented, which necessitates dispatching field crew to the affected regions. The lack of controllability of the distribution system, specifically, related to balancing loads with available generation, impedes islanded operation of distribution system at the event of main grid failure. For example, while transmission systems have generator inertia and governor controls which stabilize frequency during emergencies, distribution systems do not have such automated actions. As a result, during emergencies, various distributed energy resources (DERs) that might be available are most likely switched off instead of serving some portions of the affected customers. DA - 2015/7// PY - 2015/7// DO - 10.1109/tsg.2015.2436011 VL - 6 IS - 4 SP - 1999-2001 SN - 1949-3061 ER - TY - JOUR TI - Receivers for Multifrequency Wireless Power Transfer: Design for Minimum Interference AU - Pantic, Zeljko AU - Lee, Kibok AU - Lukic, Srdjan M. T2 - IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS AB - Inductive (or wireless) power transfer is proving to be an effective way to deliver power over short distances in a wide range of applications. Frequently, there is a need to deliver power from a single transmitter to multiple mutually coupled receivers. In this paper, we quantify how the power delivered to each receiver is affected due to the resonant frequency shift resulting from receiver mutual coupling. We show that the effect on power delivered is quite severe, especially in high-quality-factor systems. We develop the mathematical framework and demonstrate experimentally that the problem disappears if each receiver is tuned at one of the frequencies emitted by a single transmitter. We adopt the concept of frequency traps as a method to completely decouple the receivers. DA - 2015/3// PY - 2015/3// DO - 10.1109/jestpe.2014.2356853 VL - 3 IS - 1 SP - 234-241 SN - 2168-6785 KW - Cross coupling KW - inductive power transfer (IPT) KW - multireceiver systems KW - multiresonant receivers KW - multiresonant wireless power transfer ER - TY - JOUR TI - Passive Intermodulation Distortion in Antennas AU - Wilkerson, Jonathan R. AU - Kilgore, Ian M. AU - Gard, Kevin G. AU - Steer, Michael B. T2 - IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION AB - An analytic formulation of passive intermodulation distortion (PIM) in antennas is presented for PIM introduced by electro-thermal modulation of conductivity by current-related losses. A silver rectangular patch antenna was fabricated using a sapphire substrate isolating the thermal process from other possible sources. Two-tone testing at 990 MHz using a sweep of the tone separation from 3 Hz to 100 kHz is reported. Both transmitted and reflected PIM are characterized using a high dynamic range two-tone test system incorporating an analog canceler achieving a dynamic range of 125 dB at 1-Hz tone separation for reflection measurements, and 100 dB at 10-Hz tone separation for transmission measurements with each tone set to 32.3 dBm. DA - 2015/2// PY - 2015/2// DO - 10.1109/tap.2014.2379947 VL - 63 IS - 2 SP - 474-482 SN - 1558-2221 KW - Antenna distortion KW - intermodulation distortion KW - microstrip patch antenna KW - nonlinear distortion KW - passive intermodulation distortion (PIM) KW - two-tone test ER - TY - JOUR TI - Equally Efficient Inter layer Exciton Relaxation and Improved Absorption in Epitaxial and Nonepitaxial MoS2/WS2 Heterostructures AU - Yu, Yifei AU - Hu, Shi AU - Su, Liqin AU - Huang, Lujun AU - Liu, Yi AU - Jin, Zhenghe AU - Purezky, Alexander A. AU - Geohegan, David B. AU - Kim, Ki Wook AU - Zhang, Yong AU - Cao, Linyou T2 - NANO LETTERS AB - Semiconductor heterostructures provide a powerful platform for the engineering of excitons. Here we report the excitonic properties of two-dimensional (2D) heterostructures that consist of monolayer MoS2 and WS2 stacked epitaxially or non-epitaxially in the vertical direction. We find similarly efficient interlayer relaxation and transition of excitons in both the epitaxial and nonepitaxial heterostructures. This is manifested by a two orders of magnitude decrease in the photoluminescence and the appearance of an extra absorption peak at low energy region. The MoS2/WS2 heterostructures show weak interlayer coupling and can essentially act as atomicscale heterojunctions with the intrinsic bandstructures of the two monolayers largely preserved. They are particularly promising for the applications that request efficient dissociation of excitons and strong light absorption, including photovoltaics, solar fuels, photodetectors, and optical modulators. Our results also indicate that 2D heterostructures promise unprecedented capabilities to engineer excitons from the atomic level without concerns of interfacial imperfection. DA - 2015/1// PY - 2015/1// DO - 10.1021/nl5038177 VL - 15 IS - 1 SP - 486-491 SN - 1530-6992 KW - Molybdenum disulfide KW - tungsten disulfide KW - van der Waals epitaxy KW - interlayer charge transfer KW - two-dimensional heterojunction ER - TY - JOUR TI - Anti-Jamming transmission Stackelberg game with observation errors AU - Xiao, L. AU - Chen, T. H. AU - Liu, J. L. AU - Dai, H. Y. T2 - IEEE Communications Letters AB - As smart jammers that can analyze the ongoing radio transmission with flexible and powerful control on jamming signals throw serious threats on cognitive radio networks, game theory provides a powerful approach to study the interactions between smart jammers and secondary users (SUs). In this work, the power control strategy of an SU against a smart jammer under power constraints is formulated as a Stackelberg game. The jammer as the follower of the game chooses the jamming power according to the observed ongoing transmission, while the SU as the leader determines its transmit power based on the estimated jamming power. The impact of the observation accuracy of the jammer regarding the transmit power of the SU is investigated. The Stackelberg equilibrium of the anti-jamming game is derived and compared with the Nash equilibrium of the game. Simulation results show that the transmission of an SU benefits from the observation error of the jammer with a higher signal-to-interference-plus-noise ratio and utility. DA - 2015/// PY - 2015/// DO - 10.1109/lcomm.2015.2418776 VL - 19 IS - 6 SP - 949-952 ER - TY - JOUR TI - A control structure for PWM-controlled static synchronous compensators under unbalanced conditions and grid faults AU - Babaei, Saman AU - Bhattacharya, Subhashish T2 - INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS AB - Grid connected Voltage Source Converters (VSCs) are the heart of many applications with power quality concerns due to their reactive power controllability. Among the widely used grid-connected applications of the VSCs, the Static Synchronous Compensators (STATCOMs) are commonly used for compensating the voltage quality problems that come from voltage sag and swell. In spite of superior feature of fast voltage regulation and reactive power support functionality, VSC-based STATCOMs have the major drawback of being sensitive to the grid disturbances, especially the unbalanced condition and faults. Moreover, when the STATCOMs are used in the Distributed Generation (DG) applications or reactive power support of the sensitive industrial load, the unbalanced condition becomes even more intolerable. Protection system usually trips due to over current or highly distorted current caused by negative sequence current flow under unbalanced conditions and system faults. This paper propose an alternative control structure to keep the VSC-based STATCOM online during the unbalanced condition and system faults by limiting the negative sequence current. This eliminates the need to redesign/overdesign of the STACOM power components and over rating of the semiconductor switches to operate under fault current. Converter MVA rating reduction will decrease the cost significantly. Proposed controller performance has been verified by simulation and Hardware-In-the-Loop test. DA - 2015/10// PY - 2015/10// DO - 10.1016/j.ijepes.2015.02.035 VL - 71 SP - 160-173 SN - 1879-3517 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84925149499&partnerID=MN8TOARS KW - PWM-controlled STATCOM KW - AC-system fault KW - Voltage regulation ER - TY - JOUR TI - A Little Ingenuity Solves an Elephant-Sized Problem AU - Byrd, Greg T2 - COMPUTER AB - A student team from NC State has designed a collar to help control wild elephants that threaten human property and life in Africa and Asia. The Web extra at https://youtu.be/aQV_BkOL4vA is a video showing how students from North Carolina State University designed a collar to keep elephants away from farms and villages. In this field test in South Africa, a buzzing sound from the collar causes an elephant to turn away from the protected area. Video by Emma Besaw. The second Web extra at http://youtu.be/ap1dSwCc6fY is a video in which editor Greg Byrd introduces the new Student Design Showcase column, dedicated to innovative, interesting student projects from computer science and engineering. DA - 2015/4// PY - 2015/4// DO - 10.1109/mc.2015.94 VL - 48 IS - 4 SP - 74-77 SN - 1558-0814 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84928143216&partnerID=MN8TOARS ER - TY - JOUR TI - Thermoelectric figure of merit of bulk FeSi2-Si0.8Ge0.2 nanocomposite and a comparison with beta-FeSi2 AU - Mohebali, Milad AU - Liu, Yin AU - Tayebi, Lobat AU - Krasinski, Jerzy S. AU - Vashaee, Daryoosh T2 - RENEWABLE ENERGY AB - Among various thermoelectric (TE) materials, iron disilicide (FeSi2) has relatively low cost and non-toxic characteristics which make it appropriate for large scale applications. To enhance the dimensionless figure of merit (ZT) of this material, a composite of FeSi2–Si0.8Ge0.2 with high fraction of α-FeSi2 was prepared by mechanical alloying and sintering. The process was followed by thermal annealing to transform α to β phase FeSi2 through a slow peritectoid reaction (several hours). The thermoelectric properties were significantly improved upon the completion of the phase transformation. At temperatures above 900 °C, FeSi2 component rapidly changed from β to α phase (several minutes) leading to sudden increase of the thermal conductivity. For comparison, the thermoelectric alloy of β-FeSi2 was prepared through a similar process. The effect of sintering conditions and annealing time were studied and a comparison was drawn between the thermoelectric properties of β-FeSi2 and FeSi2–Si0.8Ge0.2 nanocomposite. Overall, (FeSi2)0.75(Si0.8Ge0.2)0.25 showed 170% enhancement in ZT compared with β-FeSi2 making it suitable for medium to high temperature applications (500 °C −850 °C). DA - 2015/2// PY - 2015/2// DO - 10.1016/j.renene.2014.08.059 VL - 74 SP - 940-947 SN - 0960-1481 KW - Thermoelectric KW - Nanocomposite KW - Iron disilicide KW - Silicon germanium ER - TY - JOUR TI - N-body: A social mobility model with support for larger populations AU - Zhao, Chen AU - Sichitiu, Mihail L. AU - Rhee, Injong T2 - AD HOC NETWORKS AB - An accurate reproduction of real human movement is essential in simulations of MANETs in order to obtain meaningful performance results. Existing models capturing real world mobility features often require knowledge of the underlying dynamics of the target scenario, therefore limiting the application scope. In this paper we tackle this problem from a different perspective. Rather than considering the details of the target scenario, we extract features from a sample trace, and synthesize traces that have similar features. In particular, as human activities are often socially organized, resulting in a tendency of forming groups, we propose an N-body mobility model that captures the group forming tendency from traces of a small number of nodes, and reproduces them in mobility traces of a larger population. Through simulation we show that the N-body model is capable of synthesizing the group forming behavior similar to that observed from sample traces. DA - 2015/2// PY - 2015/2// DO - 10.1016/j.adhoc.2014.10.005 VL - 25 SP - 185-196 SN - 1570-8713 KW - Mobility model KW - Network generation KW - Ad hoc networks ER - TY - JOUR TI - Integrated data-model analysis facilitated by an Instrumental Model AU - Yeates, Devin R. AU - Li, Wenjun AU - Westmoreland, Phillip R. AU - Speight, William AU - Russi, Trent AU - Packard, Andrew AU - Frenklach, Michael T2 - PROCEEDINGS OF THE COMBUSTION INSTITUTE AB - Abstract A paradigm is described and demonstrated for rigorously evaluating model-versus-data agreement while extracting new insights for improving the model and experiment. “Bound-to-Bound Data Collaboration” (B2B-DC) is augmented with an Instrumental Model, integrating uncertainty quantification of the reactor model, chemical model, and data analysis. The subject of analysis is a fuel-lean C2H2/O2/Ar premixed laminar flat flame, mapped with VUV-photoionization molecular-beam mass spectrometry at the Advanced Light Source of Lawrence Berkeley National Laboratory. Experimental signals were modeled with a CHEMKIN flame code augmented with an Instrumental Model. Consistency of the model and raw experimental data are determined as a quantitative measure of their agreement. Features of the mole-fraction profiles are predicted for O, OH, C2H3, and background contributions to H2O measurements. Also computed are posterior distributions of the initial targets and model parameters, as well as their correlations. This approach to model-versus-data assessment promises to advance the science and practical utility of modeling, establishing validity rigorously while identifying and ranking the impacts of specific model and data uncertainties for model and data improvements. DA - 2015/// PY - 2015/// DO - 10.1016/j.proci.2014.05.090 VL - 35 SP - 597-605 SN - 1873-2704 KW - Uncertainty quantification KW - Model validation KW - Premixed flame KW - Data Collaboration KW - Instrumental Model ER - TY - JOUR TI - In situ preparation of iron oxide nanoparticles in natural hydroxyapatite/chitosan matrix for bone tissue engineering application AU - Heidari, Fatemeh AU - Bahrololoom, Mohammad E. AU - Vashaee, Daryoosh AU - Tayebi, Lobat T2 - CERAMICS INTERNATIONAL AB - Magnetic materials inside bone scaffolds are known to be a promoting factor for bone healing especially when the therapy is accompanied by application of external magnetic stimulation. In this study we employed a new route to synthesize iron oxide nanoparticles inside hydroxyapatite/chitosan bone scaffolds. Hydroxyapatite and chitosan are both natural compounds and were prepared from bovine cortical bone and shrimp shell, respectively. The morphology and composition of the synthesized materials were characterized employing scanning electron microscopy and FTIR spectroscopy. The iron oxide mean particle size inside the scaffold matrix was estimated to be in the range of 10–40 nm by particle size analyzer and transmission electron microscopy. The X-ray powder diffraction pattern indicated that the magnetite crystal size was about 23.5 nm. Magnetic measurements specified that the saturated magnetic intensity (Ms) was approximately 3.04 emu/g and the coercive force was 128.39 Oe. The results revealed that the as-prepared magnetite was super-paramagnetic. DA - 2015/3// PY - 2015/3// DO - 10.1016/j.ceramint.2014.10.153 VL - 41 IS - 2 SP - 3094-3100 SN - 1873-3956 KW - Nanocomposite KW - Chitosan KW - Hydroxyapatite KW - Magnetite KW - Bone tissue engineering ER - TY - JOUR TI - Improving the Centralized Control of Thermostatically Controlled Appliances by Obtaining the Right Information AU - Vanouni, Maziar AU - Lu, Ning T2 - IEEE TRANSACTIONS ON SMART GRID AB - This letter presents a performance enhancement for a previously developed direct load control scheme that controls (toggles on/off) thermostatically controlled appliances (TCAs) through two-way communication infrastructure for providing load balancing services. In addition to device operating temperature and on/off status (TCA states), two more pieces of information, rates of temperature increase and decrease (RTI/RTD), are calculated at each TCA and communicated to the central controller. By communicating the RTI/RTD to the central controller, the same or even better control performance can be achieved at 2-3 times longer sampling periods, showing significant reduction of the communication needs from each TCA to the central controller. DA - 2015/3// PY - 2015/3// DO - 10.1109/tsg.2014.2357211 VL - 6 IS - 2 SP - 946-948 SN - 1949-3061 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000350338100048&KeyUID=WOS:000350338100048 KW - Direct load control (DLC) KW - load balancing services (LBSs) KW - smart grid KW - thermostatically controlled appliances (TCAs) KW - two-way communication ER - TY - JOUR TI - Design and operation of silver nanowire based flexible and stretchable touch sensors AU - Cui, Zheng AU - Poblete, Felipe R. AU - Cheng, Guangming AU - Yao, Shanshan AU - Jiang, Xiaoning AU - Zhu, Yong T2 - JOURNAL OF MATERIALS RESEARCH DA - 2015/1/14/ PY - 2015/1/14/ DO - 10.1557/jmr.2014.347 VL - 30 IS - 1 SP - 79-85 SN - 2044-5326 ER - TY - JOUR TI - The Effect of Multivalley Bandstructure on Thermoelectric Properties of Al (x) Ga1-x As AU - Norouzzadeh, Payam AU - Vashaee, Daryoosh T2 - JOURNAL OF ELECTRONIC MATERIALS DA - 2015/2// PY - 2015/2// DO - 10.1007/s11664-014-3535-1 VL - 44 IS - 2 SP - 636-644 SN - 1543-186X KW - Multivalley KW - bandstructure KW - thermoelectric KW - boltzmann transport ER - TY - JOUR TI - Surface modification of biodegradable porous Mg bone scaffold using polycaprolactone/bioactive glass composite AU - Yazdimamaghani, Mostafa AU - Razavi, Mehdi AU - Vashaee, Daryoosh AU - Tayebi, Lobat T2 - Materials Science and Engineering: C AB - A reduction in the degradation rate of magnesium (Mg) and its alloys is in high demand to enable these materials to be used in orthopedic applications. For this purpose, in this paper, a biocompatible polymeric layer reinforced with a bioactive ceramic made of polycaprolactone (PCL) and bioactive glass (BG) was applied on the surface of Mg scaffolds using dip-coating technique under low vacuum. The results indicated that the PCL-BG coated Mg scaffolds exhibited noticeably enhanced bioactivity compared to the uncoated scaffold. Moreover, the mechanical integrity of the Mg scaffolds was improved using the PCL-BG coating on the surface. The stable barrier property of the coatings effectively delayed the degradation activity of Mg scaffold substrates. Moreover, the coatings induced the formation of apatite layer on their surface after immersion in the SBF, which can enhance the biological bone in-growth and block the microcracks and pore channels in the coatings, thus prolonging their protective effect. Furthermore, it was shown that a three times increase in the concentration of PCL-BG noticeably improved the characteristics of scaffolds including their degradation resistance and mechanical stability. Since bioactivity, degradation resistance and mechanical integrity of a bone substitute are the key factors for repairing and healing fractured bones, we suggest that PCL-BG is a suitable coating material for surface modification of Mg scaffolds. DA - 2015/4// PY - 2015/4// DO - 10.1016/j.msec.2015.01.041 VL - 49 SP - 436-444 J2 - Materials Science and Engineering: C LA - en OP - SN - 0928-4931 UR - http://dx.doi.org/10.1016/j.msec.2015.01.041 DB - Crossref ER - TY - JOUR TI - Recovery From Linear Measurements With Complexity-Matching Universal Signal Estimation AU - Zhu, Junan AU - Baron, Dror AU - Duarte, Marco F. T2 - IEEE TRANSACTIONS ON SIGNAL PROCESSING AB - We study the compressed sensing (CS) signal estimation problem where an input signal is measured via a linear matrix multiplication under additive noise. While this setup usually assumes sparsity or compressibility in the input signal during recovery, the signal structure that can be leveraged is often not known a priori. In this paper, we consider universal CS recovery, where the statistics of a stationary ergodic signal source are estimated simultaneously with the signal itself. Inspired by Kolmogorov complexity and minimum description length, we focus on a maximum a posteriori (MAP) estimation framework that leverages universal priors to match the complexity of the source. Our framework can also be applied to general linear inverse problems where more measurements than in CS might be needed. We provide theoretical results that support the algorithmic feasibility of universal MAP estimation using a Markov chain Monte Carlo implementation, which is computationally challenging. We incorporate some techniques to accelerate the algorithm while providing comparable and in many cases better reconstruction quality than existing algorithms. Experimental results show the promise of universality in CS, particularly for low-complexity sources that do not exhibit standard sparsity or compressibility. DA - 2015/3/15/ PY - 2015/3/15/ DO - 10.1109/tsp.2015.2393845 VL - 63 IS - 6 SP - 1512-1527 SN - 1941-0476 KW - Compressed sensing KW - MAP estimation KW - Markov chain Monte Carlo KW - universal algorithms ER - TY - JOUR TI - Optimization of direct-write polarization gratings AU - Miskiewicz, Matthew N. AU - Escuti, Michael J. T2 - OPTICAL ENGINEERING AB - We recently reported on a mathematical formalism for analyzing the result of a direct-write scanning system applied to photoaligned liquid crystal films. We use that formalism to study the direct-write recording of polarization gratings (PGs). First, we evaluate three scan paths in simulation and experiment, describe their tradeoffs and practical constraints, and identify the most favorable. Second, we explore the parameter space of direct-write PGs in simulation, which includes four dimensions in general: grating period, line spacing, beam size, and spatially averaged fluence. Using this analysis, we predict that a certain portion of the parameter space should be optimal, leading to high diffraction efficiency and well-aligned PGs. Finally, we experimentally fabricate and characterize nine PGs with scan parameters within and around this optimal parameter space and conclude that the prediction is validated. This work is the first in-depth study of direct-write PGs; it identifies many challenges and solutions, and shows, for the first time, direct-write recorded PGs with quality equivalent to those recorded via holography. In particular, we demonstrate a PG (20 μm period) with first-order diffraction efficiency 99.5%, 0.2% haze, and polarization contrast of 2000. DA - 2015/2// PY - 2015/2// DO - 10.1117/1.oe.54.2.025101 VL - 54 IS - 2 SP - SN - 1560-2303 KW - polarization gratings KW - liquid crystals KW - photoalignment KW - direct-write KW - lithography KW - diffraction ER - TY - JOUR TI - MCAS-MAC: A multichannel asynchronous scheduled MAC protocol for wireless sensor networks AU - Lim, Jun Bum AU - Jang, Beakcheol AU - Sichitiu, Mihail L. T2 - COMPUTER COMMUNICATIONS AB - Due to their energy efficiency, many duty cycling-based MAC protocols have been proposed in WSNs. Although these protocols considerably reduce energy consumption by minimizing idle listening and overhearing, the energy efficiency comes at the cost of decreased packet delivery ratio and increased delay. In this paper, we present a multichannel asynchronous scheduled MAC protocol, called MCAS-MAC, which inherits the basic asynchronous scheduling operation from AS-MAC and adds back-to-back packet transmissions and multichannel support for high traffic dense WSN. Using RaPTEX, we evaluate the performance of MCAS-MAC by comparing it with existing duty cycling MAC protocols including BMAC, SMAC and AS-MAC. DA - 2015/2/1/ PY - 2015/2/1/ DO - 10.1016/j.comcom.2014.10.008 VL - 56 SP - 98-107 SN - 1873-703X KW - MAC KW - Duty cycling KW - AS-MAC KW - Wireless sensor networks KW - MCAS-MAC ER - TY - JOUR TI - In Vitro Analysis of Electrophoretic Deposited Fluoridated Hydroxyapatite Coating on Micro-arc Oxidized AZ91 Magnesium Alloy for Biomaterials Applications AU - Razavi, Mehdi AU - Fathi, Mohammadhossein AU - Savabi, Omid AU - Vashaee, Daryoosh AU - Tayebi, Lobat T2 - METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE DA - 2015/3// PY - 2015/3// DO - 10.1007/s11661-014-2694-2 VL - 46A IS - 3 SP - 1394-1404 SN - 1543-1940 ER - TY - JOUR TI - Fabrication of Si and Ge vertical nanowire for transistor applications AU - Chu, C. H. AU - Huang, M. K. AU - Wu, G. F. AU - Chu, C. L. AU - Hsu, S. H. AU - Luo, G. L. T2 - International Journal of Nanotechnology DA - 2015/// PY - 2015/// VL - 12 IS - 1-2 SP - 74-86 ER - TY - JOUR TI - Experimental characterization of Fabry-Perot resonances of magnetostatic volume waves in near-field metamaterials AU - Chabalko, Matthew J. AU - Ricketts, David S. T2 - APPLIED PHYSICS LETTERS AB - In this work, we report on the experimental demonstration of magnetoquasistatic volume wave resonances in a 2-dimensional near field metamaterial (MM). Previous works have described only theoretically the magnetostatic waves in near field MMs and have reported peaks and valleys in the mutual coupling of MM enhanced wireless power transfer that they have attributed to Fabry-Perot resonances, however, neither has been experimentally measured nor characterized. We report on the direct magnetic field measurement of magnetostatic volume waves in a 2D near-field MM and show that the periodic peaks and valleys in mutual coupling observed previously are indeed due to a Fabry-Perot oscillation. In addition, we show that these resonances can be predicted from experimentally extracted permeability and the dimensions of the system. DA - 2015/2/9/ PY - 2015/2/9/ DO - 10.1063/1.4907046 VL - 106 IS - 6 SP - SN - 1077-3118 ER - TY - JOUR TI - Cooling Devices in Demand Response: A Comparison of Control Methods AU - Wai, Chon Hou AU - Beaudin, Marc AU - Zareipour, Hamidreza AU - Schellenberg, Antony AU - Lu, Ning T2 - IEEE TRANSACTIONS ON SMART GRID AB - Demand response plays an important role in the development of the smart grid, which can effectively manage society's energy consumption. Cooling devices, such as refrigerators and freezers, are ideal devices for demand-response programs because their energy states can be controlled without reducing the lifestyle and comfort of the residents. Conversely, managing air conditioning and space heating would affect a resident's comfort level. Direct compressor control and thermostat control methods have been proposed in the past for controlling cooling devices but they are never studied concurrently. This paper proposes a new control mechanism and compares the effectiveness of the three control mechanisms for cooling devices in demand response. In addition, this paper illustrates the need for a damping strategy to mitigate demand oscillations that occur from synchronous fleet control. DA - 2015/1// PY - 2015/1// DO - 10.1109/tsg.2014.2358579 VL - 6 IS - 1 SP - 249-260 SN - 1949-3061 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000346731400025&KeyUID=WOS:000346731400025 KW - Cooling devices KW - demand response KW - smart grid KW - state-queuing ER - TY - JOUR TI - Control and Size Energy Storage Systems for Managing Energy Imbalance of Variable Generation Resources AU - Ke, Xinda AU - Lu, Ning AU - Jin, Chunlian T2 - IEEE TRANSACTIONS ON SUSTAINABLE ENERGY AB - This paper presents control algorithms and sizing strategies for using energy storage to manage energy imbalance for variable generation resources. The control objective is to minimize the hourly generation imbalance between the actual and the scheduled generation of wind farms. Three control algorithms are compared: 1)tracking minute-by-minute power imbalance; 2)postcompensation; and 3)precompensation. Measured data from a wind farm are used in the study. The results show that tracking minute-by-minute power imbalance achieves the best performance by keeping hourly energy imbalance zero. However, the energy storage system (ESS) will be significantly oversized. Postcompensation reduces the power rating of the ESS but the hourly energy imbalance may not be reduced to zero when a large and long-lasting power imbalance occurs. A linear regression forecasting algorithm is developed for a two-stage precompensation algorithm to precharge or predischarge the ESS based on the predicted energy imbalance. An equivalent charge cycle estimation method is proposed to evaluate the effect of providing the energy balancing service on battery life. The performance comparison shows that the precompensation method reduces the size of the ESS by 30% with satisfactory performance. DA - 2015/1// PY - 2015/1// DO - 10.1109/tste.2014.2355829 VL - 6 IS - 1 SP - 70-78 SN - 1949-3029 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000346733200008&KeyUID=WOS:000346733200008 KW - Ancillary service KW - energy management KW - energy storage KW - operation scheduling KW - renewable integration KW - wind forecast ER - TY - JOUR TI - CUDA-NP: Realizing Nested Thread-Level Parallelism in GPGPU Applications AU - Yang, Yi AU - Li, Chao AU - Zhou, Huiyang T2 - JOURNAL OF COMPUTER SCIENCE AND TECHNOLOGY AB - Parallel programs consist of series of code sections with different thread-level parallelism (TLP). As a result, it is rather common that a thread in a parallel program, such as a GPU kernel in CUDA programs, still contains both sequential code and parallel loops. In order to leverage such parallel loops, the latest NVIDIA Kepler architecture introduces dynamic parallelism, which allows a GPU thread to start another GPU kernel, thereby reducing the overhead of launching kernels from a CPU. However, with dynamic parallelism, a parent thread can only communicate with its child threads through global memory and the overhead of launching GPU kernels is non-trivial even within GPUs. In this paper, we first study a set of GPGPU benchmarks that contain parallel loops, and highlight that these benchmarks do not have a very high loop count or high degree of TLP. Consequently, the benefits of leveraging such parallel loops using dynamic parallelism are too limited to offset its overhead. We then present our proposed solution to exploit nested parallelism in CUDA, referred to as CUDA-NP. With CUDA-NP, we initially enable a high number of threads when a GPU program starts, and use control flow to activate different numbers of threads for different code sections. We implement our proposed CUDA-NP framework using a directive-based compiler approach. For a GPU kernel, an application developer only needs to add OpenMP-like pragmas for parallelizable code sections. Then, our CUDA-NP compiler automatically generates the optimized GPU kernels. It supports both the reduction and the scan primitives, explores different ways to distribute parallel loop iterations into threads, and efficiently manages on-chip resource. Our experiments show that for a set of GPGPU benchmarks, which have already been optimized and contain nested parallelism, our proposed CUDA-NP framework further improves the performance by up to 6.69 times and 2.01 times on average. DA - 2015/1// PY - 2015/1// DO - 10.1007/s11390-015-1500-y VL - 30 IS - 1 SP - 3-19 SN - 1860-4749 KW - GPGPU KW - nested parallelism KW - compiler KW - local memory ER - TY - JOUR TI - Automating Analytical Homework AU - Trussell, H. J. T2 - PROCEEDINGS OF THE IEEE AB - Discusses the distinction between training and education and examines how current technologies and software programs have and will shape engineering education and the development of skills sets in the future. DA - 2015/1// PY - 2015/1// DO - 10.1109/jproc.2014.2374751 VL - 103 IS - 1 SP - 2-7 SN - 1558-2256 ER - TY - JOUR TI - 4-Coumaroyl and Caffeoyl Shikimic Acids Inhibit 4-Coumaric Acid: Coenzyme A Ligases and Modulate Metabolic Flux for 3-Hydroxylation in Monolignol Biosynthesis of Populus trichocarpa AU - Lin, Chien-Yuan AU - Wang, Jack P. AU - Li, Quanzi AU - Chen, Hsi-Chuan AU - Liu, Jie AU - Loziuk, Philip AU - Song, Jina AU - Williams, Cranos AU - Muddiman, David C. AU - Sederoff, Ronald R. AU - Chiang, Vincent L. T2 - MOLECULAR PLANT AB - Downregulation of 4-coumaric acid:coenzyme A ligase (4CL) can reduce lignin content in a number of plant species. In lignin precursor (monolignol) biosynthesis during stem wood formation in Populus trichocarpa, two enzymes, Ptr4CL3 and Ptr4CL5, catalyze the coenzyme A (CoA) ligation of 4-coumaric acid to 4-coumaroyl-CoA and caffeic acid to caffeoyl-CoA. CoA ligation of 4-coumaric acid is essential for the 3-hydroxylation of 4-coumaroyl shikimic acid. This hydroxylation results from sequential reactions of 4-hydroxycinnamoyl-CoA:shikimic acid hydroxycinnamoyl transferases (PtrHCT1 and PtrHCT6) and 4-coumaric acid 3-hydroxylase 3 (PtrC3H3). Alternatively, 3-hydroxylation of 4-coumaric acid to caffeic acid may occur through an enzyme complex of cinnamic acid 4-hydroxylase 1 and 2 (PtrC4H1 and PtrC4H2) and PtrC3H3. We found that 4-coumaroyl and caffeoyl shikimic acids are inhibitors of Ptr4CL3 and Ptr4CL5. 4-Coumaroyl shikimic acid strongly inhibits the formation of 4-coumaroyl-CoA and caffeoyl-CoA. Caffeoyl shikimic acid inhibits only the formation of 4-coumaroyl-CoA. 4-Coumaroyl and caffeoyl shikimic acids both act as competitive and uncompetitive inhibitors. Metabolic flux in wild-type and PtrC3H3 downregulated P. trichocarpa transgenics has been estimated by absolute protein and metabolite quantification based on liquid chromatography–tandem mass spectrometry, mass action kinetics, and inhibition equations. Inhibition by 4-coumaroyl and caffeoyl shikimic acids may play significant regulatory roles when these inhibitors accumulate. DA - 2015/1/5/ PY - 2015/1/5/ DO - 10.1016/j.molp.2014.12.003 VL - 8 IS - 1 SP - 176-187 SN - 1752-9867 KW - monolignol biosynthesis KW - Populus trichocarpa KW - metabolic flux KW - reaction and inhibition kinetics KW - LC-MS/MS KW - 4-coumaroyl and caffeoyl shikimic acids ER - TY - JOUR TI - Wearable silver nanowire dry electrodes for electrophysiological sensing AU - Myers, Amanda C. AU - Huang, He AU - Zhu, Yong T2 - RSC ADVANCES AB - We present wearable dry electrodes made of silver nanowires for long-term electrophysiological sensing such as electrocardiography and electromyography. DA - 2015/// PY - 2015/// DO - 10.1039/c4ra15101a VL - 5 IS - 15 SP - 11627-11632 SN - 2046-2069 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84921993993&partnerID=MN8TOARS ER - TY - JOUR TI - The Historiography of India's Partition: Between Civilization and Modernity AU - Gilmartin, David T2 - JOURNAL OF ASIAN STUDIES AB - More than sixty-five years after the partition of the Indian subcontinent in 1947, controversy about partition, its causes and its effects, continues. Yet the emphases in these debates have changed over the years, and it is perhaps time, in the wake of India's recent elections, to take stock once again of how these debates have developed in the last several decades and where they are heading. What gives these controversies particular significance is that they are not just about that singular event, but about the whole trajectory of India's modern history, as interpreted through partition's lens—engaging academic historians, even as they continue to be deeply enmeshed in ongoing political conflict in South Asia, and, indeed, in the world more broadly. DA - 2015/2// PY - 2015/2// DO - 10.1017/s0021911814001685 VL - 74 IS - 1 SP - 23-41 SN - 1752-0401 ER - TY - JOUR TI - Spotlighting Student Innovation AU - Byrd, Greg T2 - COMPUTER AB - This new column provides a space for undergraduates in computer engineering and science to share their capstone project designs. DA - 2015/2// PY - 2015/2// DO - 10.1109/mc.2015.54 VL - 48 IS - 2 SP - 75-76 SN - 1558-0814 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84923869694&partnerID=MN8TOARS ER - TY - JOUR TI - Significant degradability enhancement in multilayer coating of polycaprolactone-bioactive glass/gelatin-bioactive glass on magnesium scaffold for tissue engineering applications AU - Yazdimamaghani, Mostafa AU - Razavi, Mehdi AU - Vashaee, Daryoosh AU - Pothineni, Venkata Raveendra AU - Rajadas, Jayakumar AU - Tayebi, Lobat T2 - Applied Surface Science AB - Magnesium (Mg) is a promising candidate to be used in medical products especially as bone tissue engineering scaffolds. The main challenge for using Mg in biomedical applications is its high degradation rate in the body. For this reason, in this study, a multilayer polymeric layer composed of polycaprolactone (PCL) and gelatin (Gel) reinforced with bioactive glass (BaG) particles has been applied on the surface of Mg scaffolds. The materials characteristics of uncoated Mg scaffold, Mg scaffold coated only with PCL-BaG and Mg scaffold coated with PCL-BaG and Gel-BaG have been analyzed and compared in detail. Scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (FTIR) were utilized for microstructural studies. In vitro bioactivity and biodegradation evaluations were carried out by submerging the scaffolds in simulated body fluid (SBF) at pre-determined time points. The results demonstrated that Mg scaffold coated with PCL-BaG and Gel-BaG exhibited significant improvement in biodegradability. DA - 2015/5// PY - 2015/5// DO - 10.1016/j.apsusc.2015.02.120 VL - 338 SP - 137-145 J2 - Applied Surface Science LA - en OP - SN - 0169-4332 UR - http://dx.doi.org/10.1016/j.apsusc.2015.02.120 DB - Crossref KW - Mg scaffold KW - Biodegradation KW - Coating KW - Surface modification KW - Bone tissue engineering ER - TY - JOUR TI - Reuse-based optimization for prebond and post-bond testing of 3-D-stacked ICS AU - Agrawal, M. AU - Chakrabarty, K. AU - Widialaksono, R. T2 - IEEE Transactions on Computer-aided Design of Integrated Circuits and Systems DA - 2015/// PY - 2015/// VL - 34 IS - 1 SP - 122-135 ER - TY - JOUR TI - Non-destructive assessment of the polarity of GaN nanowire ensembles using low-energy electron diffraction and x-ray photoelectron diffraction AU - Romanyuk, O. AU - Fernandez-Garrido, S. AU - Jiricek, P. AU - Bartos, I. AU - Geelhaar, L. AU - Brandt, O. AU - Paskova, T. T2 - APPLIED PHYSICS LETTERS AB - We investigate GaN nanowire ensembles spontaneously formed in plasma-assisted molecular beam epitaxy by non-destructive low-energy electron diffraction (LEED) and x-ray photoelectron diffraction (XPD). We show that GaN nanowire ensembles prepared on AlN-buffered 6H-SiC(0001¯) substrates with well-defined N polarity exhibit similar LEED intensity-voltage curves and angular distribution of photo-emitted electrons as N-polar free-standing GaN layers. Therefore, as in the case of GaN layers, LEED and XPD are found to be suitable techniques to assess the polarity of GaN nanowire ensembles on a macroscopic scale. The analysis of GaN nanowire ensembles prepared on bare Si(111) allows us to conclude that, on this non-polar substrate, the majority of nanowires is also N-polar. DA - 2015/1/12/ PY - 2015/1/12/ DO - 10.1063/1.4905651 VL - 106 IS - 2 SP - SN - 1077-3118 ER - TY - JOUR TI - Non-Rigid Image Registration under Non-Deterministic Deformation Bounds AU - Ge, Qian AU - Lokare, Namita AU - Lobaton, Edgar T2 - 10TH INTERNATIONAL SYMPOSIUM ON MEDICAL INFORMATION PROCESSING AND ANALYSIS AB - Image registration aims to identify the mapping between corresponding locations in an anatomic structure. Most traditional approaches solve this problem by minimizing some error metric. However, they do not quantify the uncertainty behind their estimates and the feasibility of other solutions. In this work, it is assumed that two images of the same anatomic structure are related via a Lipschitz non-rigid deformation (the registration map). An approach for identifying point correspondences with zero false-negative rate and high precision is introduced under this assumption. This methodology is then extended to registration of regions in an image which is posed as a graph matching problem with geometric constraints. The outcome of this approach is a homeomorphism with uncertainty bounds characterizing its accuracy over the entire image domain. The method is tested by applying deformation maps to the LPBA40 dataset. DA - 2015/// PY - 2015/// DO - 10.1117/12.2072530 VL - 9287 SP - SN - 1996-756X UR - http://dx.doi.org/10.1117/12.2072530 KW - Non-rigid image registration KW - Lipschitz deformation KW - Uncertainty quantification ER - TY - JOUR TI - Modified surface chemistry, potential, and optical properties of polar gallium nitride via long chained phosphonic acids AU - Wilkins, Stewart J. AU - Paskova, Tania AU - Ivanisevic, Albena T2 - APPLIED SURFACE SCIENCE AB - Surface potential, chemistry, topography, and optical properties were modulated utilizing the attachment of phosphonic acids (11-mercaptoundecylphosphonic acid, 1H,1H,2H,2H-perfluorooctanephosphonic acid, and 1,8-octanediphosphonic acid) with phosphoric acid to polar (c-plane) GaN. These changes were identified using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) with kelvin probe force microscopy (KPFM), photoluminescence (PL), and water contact angle. The results indicated that the attachment of phosphonic groups to gallium nitride strongly depends on the formation of a native oxide layer and subsequent passivation. It was seen that a fluorine terminated phosphonic acid increased the overall surface oxide versus other groups, as well as reduced the surface potential and improved the photoluminescence relative to other treatments. Sulfur terminated phosphonic acid demonstrated a similar reduction in surface potential and oxide formation to fluorine based phosphonic acid; however, improvements of optical luminescence on the same scale were not achieved. DA - 2015/2/1/ PY - 2015/2/1/ DO - 10.1016/j.apsusc.2014.11.179 VL - 327 SP - 498-503 SN - 1873-5584 KW - In situ functionalization KW - Polar KW - Gallium nitride KW - X-ray photoelectron spectroscopy KW - Kelvin probe microscopy ER - TY - JOUR TI - In-Plane Alignment in Organic Solar Cells to Probe the Morphological Dependence of Charge Recombination AU - Awartani, Omar AU - Kudenov, Michael W. AU - Kline, R. Joseph AU - Brendan T. O'Connor, T2 - ADVANCED FUNCTIONAL MATERIALS AB - Bulk heterojunction (BHJ) organic solar cells are fabricated with the polymer semiconductor aligned in the plane of the film to probe charge recombination losses associated with aggregates characterized by varying degrees of local order. 100% uniaxial strain is applied on ductile poly(3‐hexylthiophene):phenyl‐C61‐butyric acid methyl ester (P3HT:PCBM) BHJ films and characterize the resulting morphology with ultraviolet‐visible absorption spectroscopy and grazing incidence X‐ray diffraction. It is found that the strained films result in strong alignment of the highly ordered polymer aggregates. Polymer aggregates with lower order and amorphous regions also align but with a much broader orientation distribution. The solar cells are then tested under linearly polarized light where the light is selectively absorbed by the appropriately oriented polymer, while maintaining a common local environment for the sweep out of photogenerated charge carriers. Results show that charge collection losses associated with a disordered BHJ film are circumvented, and the internal quantum efficiency is independent of P3HT local aggregate order near the heterojunction interface. Uniquely, this experimental approach allows for selective excitation of distinct morphological features of a conjugated polymer within a single BHJ film, providing insight into the morphological origin of recombination losses. DA - 2015/2/25/ PY - 2015/2/25/ DO - 10.1002/adfm.201403377 VL - 25 IS - 8 SP - 1296-1303 SN - 1616-3028 ER - TY - JOUR TI - High Mobility 4H-SiC Lateral MOSFETs Using Lanthanum Silicate and Atomic Layer Deposited SiO2 AU - Yang, Xiangyu AU - Lee, Bongmook AU - Misra, Veena T2 - IEEE ELECTRON DEVICE LETTERS AB - We report high mobility Si-face 4H-SiC MOSFET results via a novel interface engineering technique using a gate-stack consisting of lanthanum silicate (LaSiO x ) and atomic layer deposited SiO 2 . Peak field effect mobility of 132.6 cm 2 /V · s has been achieved while maintaining a positive threshold voltage (3.1 V). From the peak field effect mobility's dependence on measurement temperatures, it has been found that the mobility of La containing MOSFET is limited by phonon scattering. DA - 2015/4// PY - 2015/4// DO - 10.1109/led.2015.2399891 VL - 36 IS - 4 SP - 312-314 SN - 1558-0563 KW - Atomic layer deposition KW - lanthanum silicate KW - mobility KW - SiC ER - TY - JOUR TI - Delay Optimal Scheduling for Energy Harvesting Based Communications AU - Liu, Juan AU - Dai, Huaiyu AU - Chen, Wei T2 - IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS AB - Green communications have been attracting increased research interest recently. Equipped with a rechargeable battery, a source node can harvest energy from ambient environments and rely on this free and regenerative energy supply to transmit packets. Due to the uncertainty of available energy from harvesting, however, intolerably large latency and packet loss could be induced, if the source always waits for harvested energy. To overcome this problem, one Reliable Energy Source (RES) can be resorted to for a prompt delivery of backlogged packets. Naturally, there exists a tradeoff between the packet delivery delay and power consumption from the RES. In this paper, we address the delay optimal scheduling problem for a bursty communication link powered by a capacity-limited battery storing harvested energy together with one RES. The proposed scheduling scheme gives priority to the usage of harvested energy, and resorts to the RES when necessary based on the data and energy queueing processes, with an average power constraint from the RES. Through two-dimensional Markov chain modeling and linear programming formulation, we derive the optimal threshold-based scheduling policy together with the corresponding transmission parameters. Our study includes three exemplary cases that capture some important relations between the data packet arrival process and energy harvesting capability. Our theoretical analysis is corroborated by simulation results. DA - 2015/3// PY - 2015/3// DO - 10.1109/jsac.2015.2391972 VL - 33 IS - 3 SP - 452-466 SN - 1558-0008 KW - Energy harvesting KW - packet scheduling KW - Markov chain KW - queueing delay KW - delay-power tradeoff ER - TY - JOUR TI - Comparison of Methods for Accurate Characterization of Interface Traps in GaN MOS-HFET Devices AU - Ramanan, Narayanan AU - Lee, Bongmook AU - Misra, Veena T2 - IEEE TRANSACTIONS ON ELECTRON DEVICES AB - Reliability of dielectrics is a critical concern in GaN metal-oxide-semiconductor-heterojunction-field-effect transistor (MOS-HFET) devices for use in high-voltage power and RF applications. Accurate characterization of interface traps is essential toward developing an understanding of the reliability issues associated with this system and to evaluate the effectiveness of different dielectrics proposed for use in the gate-stack or the passivation of the access regions. Using small-signal equivalent circuit models and TCAD simulations, it is found that conductance and capacitance methods for trap density estimation potentially have severely constrained detection limits and can probe only shallow traps. In contrast, a pulsed-IV method, used along with UV irradiation, can accurately detect a wide range of trap densities over the entire wide bandgap. The effectiveness of this method is also experimentally demonstrated using an AlGaN/GaN MOS-HFET device with HfAlO gate dielectric. DA - 2015/2// PY - 2015/2// DO - 10.1109/ted.2014.2382677 VL - 62 IS - 2 SP - 546-553 SN - 1557-9646 KW - Heterojunctions KW - millimeter wave transistors KW - power transistors KW - semiconductor device reliability KW - semiconductor-insulator interfaces ER - TY - JOUR TI - A Five-Parameter Model of the AlGaN/GaN HFET AU - Bilbro, Griff L. AU - Trew, Robert J. T2 - IEEE TRANSACTIONS ON ELECTRON DEVICES AB - We introduce an analytic expression for the drain current Id(V gs , V ds ) of an AlGaN/GaN heterojunction field-effect transistor (HFET) as a function of its gate and drain voltages. We derive the function from a compact physical model of conduction current in the HFET. The proposed expression for the current is configured by five parameters, which can be expressed in terms of the geometry and materials of a device. We extend the model to small-signal RF operation by embedding it in a 12-parameter RLC network that represents terminal feed impedances and device parasitics. We adjust the parameters of the extended model to simultaneously fit dc and RF measurements of an industrial transistor. DA - 2015/4// PY - 2015/4// DO - 10.1109/ted.2015.2394376 VL - 62 IS - 4 SP - 1157-1162 SN - 1557-9646 KW - AlGaN/GaN KW - analytic KW - compact model KW - continuously differentiable KW - dc KW - HEMT KW - heterojunction field-effect transistor (HFET) KW - physical KW - physics based KW - RF ER -