TY - BOOK TI - Ultra-efficient Solid-State Lighting: Likely Characteristics, Economic Benefits, Technological Approaches DA - 2013/// PY - 2013/// ER - TY - JOUR TI - Three-Dimensional Mapping of Quantum Wells in a GaN/InGaN Core-Shell Nanowire Light-Emitting Diode Array AU - Riley, J. R. AU - Padalkar, S. AU - Li, Q. M. AU - Lu, P. AU - Koleske, D. D. AU - Wierer, J. J. AU - Wang, G. T. AU - Lauhon, L. J. T2 - Nano Letters AB - Correlated atom probe tomography, cross-sectional scanning transmission electron microscopy, and cathodoluminescence spectroscopy are used to analyze InGaN/GaN multiquantum wells (QWs) in nanowire array light-emitting diodes (LEDs). Tomographic analysis of the In distribution, interface morphology, and dopant clustering reveals material quality comparable to that of planar LED QWs. The position-dependent CL emission wavelength of the nonpolar side-facet QWs and semipolar top QWs is correlated with In composition. DA - 2013/// PY - 2013/// DO - 10.1021/nl4021045 VL - 13 IS - 9 SP - 4317-4325 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000330158900056&KeyUID=WOS:000330158900056 ER - TY - JOUR TI - Comparison between blue lasers and light-emitting diodes for future solid-state lighting AU - Wierer, J. J. AU - Tsao, J. Y. AU - Sizov, D. S. T2 - Laser & Photonics Reviews AB - Abstract Solid‐state lighting (SSL) is now the most efficient source of high color quality white light ever created. Nevertheless, the blue InGaN light‐emitting diodes (LEDs) that are the light engine of SSL still have significant performance limitations. Foremost among these is the decrease in efficiency at high input current densities widely known as “efficiency droop.” Efficiency droop limits input power densities, contrary to the desire to produce more photons per unit LED chip area and to make SSL more affordable. Pending a solution to efficiency droop, an alternative device could be a blue laser diode (LD). LDs, operated in stimulated emission, can have high efficiencies at much higher input power densities than LEDs can. In this article, LEDs and LDs for future SSL are explored by comparing: their current state‐of‐the‐art input‐power‐density‐dependent power‐conversion efficiencies; potential improvements both in their peak power‐conversion efficiencies and in the input power densities at which those efficiencies peak; and their economics for practical SSL. DA - 2013/// PY - 2013/// DO - 10.1002/lpor.201300048 VL - 7 IS - 6 SP - 963-993 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000328150300016&KeyUID=WOS:000328150300016 ER - TY - JOUR TI - Spatial Mapping of Efficiency of GaN/InGaN Nanowire Array Solar Cells Using Scanning Photocurrent Microscopy AU - Howell, S. L. AU - Padalkar, S. AU - Yoon, K. AU - Li, Q. M. AU - Koleske, D. D. AU - Wierer, J. J. AU - Wang, G. T. AU - Lauhon, L. J. T2 - Nano Letters AB - GaN-InGaN core-shell nanowire array devices are characterized by spectrally resolved scanning photocurrent microscopy (SPCM). The spatially resolved external quantum efficiency is correlated with structure and composition inferred from atomic force microscope (AFM) topography, scanning transmission electron microscope (STEM) imaging, Raman microspectroscopy, and scanning photocurrent microscopy (SPCM) maps of the effective absorption edge. The experimental analyses are coupled with finite difference time domain simulations to provide mechanistic understanding of spatial variations in carrier generation and collection, which is essential to the development of heterogeneous novel architecture solar cell devices. DA - 2013/// PY - 2013/// DO - 10.1021/nl402331u VL - 13 IS - 11 SP - 5123-5128 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000327111700021&KeyUID=WOS:000327111700021 ER - TY - CHAP TI - Introduction Part B. Ultra-efficient Solid-State Lighting: Likely Characteristics, Economic Benefits, Technological Approaches AU - Tsao, Jeff Y. AU - Wierer, Jonathan J., Jr. AU - Rohwer, Lauren E. S. AU - Coltrin, Michael E. AU - Crawford, Mary H. AU - Simmons, Jerry A. AU - Hung, Po-Chieh AU - Saunders, Harry AU - Sizov, Dmitry S. AU - Bhat, Raj AU - Zah, Chung-En AU - Seong, TY AU - Han, J AU - Amano, H AU - Morkoc, H T2 - Iii-Nitride Based Light Emitting Diodes and Applications AB - Technologies for artificial lighting, as illustrated on the left side of Fig. 2.1, have made tremendous progress over the centuries: from fire, with an efficiency of about a tenth of a percent; to incandescent lamps, with an efficiency of about 4 %; to gas discharge lamps, with an efficiency of about 20 %; and soon to solid-state lighting (SSL), with efficiencies that in principle could approach 100 %. At this point in time, there is virtually no question that SSL will eventually displace its predecessor technologies. A remaining question, however, is what the final efficiency of SSL will be. Will it be, as illustrated on the right side of Fig. 2.1, 50 %, which is what the community (Haitz and Tsao in Phys. Status Solidi A 208:17–29, 2011) has long targeted as its “efficient” lighting goal? Will it be 70 % or higher, which is what some (Phillips et al. in Laser Photon. Rev. 1:307–333, 2007) have called the “ultra-efficient” lighting goal? Or will it be even beyond an effective efficiency of 100 %, something that might be enabled by smart lighting (Kim and Schubert in Science 308:1274–1278, 2005), in which one doesn’t just engineer the efficiency with which light is produced, but the efficiency with which light is used? In this chapter, we give a perspective on the future of SSL, with a focus on ultra-high efficiencies. We ask, and sketch answers to, three questions. First, what are some of the likely characteristics of ultra-efficient SSL? Second, what are some of the economic benefits of ultra-efficient SSL? And, third, what are some of the challenges associated with the various technological approaches that could be explored for ultra-efficient SSL? PY - 2013/// DO - 10.1007/978-94-007-5863-6_2 VL - 126 SP - 11-26 PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000348907300003&KeyUID=WOS:000348907300003 ER - TY - JOUR TI - Asking Photons Where They Have Been AU - Danan, A. AU - Farfurnik, D. AU - Bar-Ad, S. AU - Vaidman, L. T2 - Physical Review Letters AB - We present surprising experimental evidence regarding the past of photons passing through an interferometer. The information about the positions through which the photons pass in the interferometer is retrieved from modulations of the detected signal at the vibration frequencies of mirrors the photons bounce off. From the analysis we conclude that the past of the photons is not represented by continuous trajectories, although a "common sense" analysis adopted in various welcher weg measurements, delayed-choice which-path experiments, and counterfactual communication demonstrations yields a single trajectory. The experimental results have a simple explanation in the framework of the two-state vector formalism of quantum theory. DA - 2013/// PY - 2013/// DO - 10.1103/physrevlett.111.240402 VL - 111 IS - 24 ER - TY - JOUR TI - An Integrated Boost Resonant Converter for Photovoltaic Applications AU - York, Ben AU - Yu, Wensong AU - Lai, Jih-Sheng T2 - IEEE Transactions on Power Electronics AB - Effective photovoltaic power conditioning requires efficient power conversion and accurate maximum power point tracking to counteract the effects of panel mismatch, shading, and general variance in power output during a daily cycle. In this paper, the authors propose an integrated boost resonant converter with low component count, galvanic isolation, simple control, as well as high efficiency across a wide input and load range. Provided is a discussion of the converter synthesis, key operational features, converter design procedure, and loss analysis, as well as experimental verification by way of a 250-W prototype with a California Energy Commission efficiency of 96.8%. DA - 2013/3// PY - 2013/3// DO - 10.1109/tpel.2012.2207127 VL - 28 IS - 3 SP - 1199-1207 J2 - IEEE Trans. Power Electron. OP - SN - 0885-8993 1941-0107 UR - http://dx.doi.org/10.1109/tpel.2012.2207127 DB - Crossref ER - TY - JOUR TI - Interferometric direction finding with a metamaterial detector AU - Venkatesh, Suresh AU - Shrekenhamer, David AU - Xu, Wangren AU - Sonkusale, Sameer AU - Padilla, Willie AU - Schurig, David T2 - Appl. Phys. Lett. AB - We present measurements and analysis demonstrating useful direction finding of sources in the S band (2–4 GHz) using a metamaterial detector. An augmented metamaterial absorber that supports magnitude and phase measurement of the incident electric field, within each unit cell, is described. The metamaterial is implemented in a commercial printed circuit board process with off-board back-end electronics. We also discuss on-board back-end implementation strategies. Direction finding performance is analyzed for the fabricated metamaterial detector using simulated data and the standard algorithm, MUtiple SIgnal Classification. The performance of this complete system is characterized by its angular resolution as a function of radiation density at the detector. Sources with power outputs typical of mobile communication devices can be resolved at kilometer distances with sub-degree resolution and high frame rates. DA - 2013/// PY - 2013/// DO - 10.1063/1.4851936 VL - 103 IS - 25 SP - 254103 ER - TY - JOUR TI - Materials Selections and Growth Conditions for Large-Area, Multilayered, Visible Negative Index Metamaterials Formed by Nanotransfer Printing AU - Gao, Li AU - Kim, Youngmin AU - Vazquez-Guardado, Abraham AU - Shigeta, Kazuki AU - Hartanto, Steven AU - Franklin, Daniel AU - Progler, Christopher J. AU - Bogart, Gregory R. AU - Rogers, John A. AU - Chanda, Debashis T2 - Advanced Optical Materials AB - Nanotransfer printing is used to fabricate large-area visible 3D negative index metamaterials. Material growth aspects of nanotransfer printing are explored for multilayered metamaterials, and alternative dielectrics and deposition conditions are introduced that enabled nearly ideal geometries with excellent optical properties. 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 - 2013/// PY - 2013/// DO - 10.1002/adom.201300356 VL - 2 IS - 3 SP - 256-261 ER - TY - THES TI - DC Bus Current Ripple Management in Single Phase PWM Inverters AU - Vishnu, M DA - 2013/// PY - 2013/// ER - TY - CONF TI - Battery-free multichannel digital ECG biotelemetry using UHF RFID techniques AU - Besnoff, J. S. AU - Deyle, T. AU - Harrison, R. R. AU - Reynolds, M. S. AB - We propose to leverage UHF RFID techniques to yield a continuously wearable, battery-free wireless multichannel ECG telemetry device that is potentially disposable, low-cost and suitable for integration with multiple electrodes in a flexible circuit assembly. Such a device could have broad applicability, ranging from initial patient assessment by first responders, to continuous monitoring in various clinical settings. We employ a recently described single-chip data acquisition system including RF power harvesting to eliminate the need for a battery. The single-chip system includes 14 channels of integrated biopotential amplification, an 11-bit ADC, and a 5 Mbps digital backscatter telemetry link. We present an initial characterization of the telemetry chip in this application including battery-free, wireless 3 and 5 channel ECG recordings made from an ambulatory human subject at a range of ≈ 1 meter. C2 - 2013/4// C3 - 2013 IEEE International Conference on RFID (RFID) DA - 2013/4// DO - 10.1109/rfid.2013.6548130 PB - Institute of Electrical and Electronics Engineers (IEEE) ER - TY - CONF TI - Single-wire RF transmission lines for implanted devices AU - Besnoff, Jordan S. AU - Reynolds, Matthew S. AB - We consider the use of insulated single wires as transmission lines to carry 100 MHz - 3 GHz radio frequency (RF) signals among devices implanted in biological tissue. In contrast to near-field magnetically coupled links, the use of transmission lines to carry RF signals results in higher efficiency for a given implant package size once the antenna is included, albeit with the disadvantage of tissue displacement along the path of the wire. We present a theory based on the work of Goubau and Rao that describes the transmission line loss of a single insulated wire in a lossy dielectric medium. We experimentally verify the characteristic impedance and insertion loss of transmission lines formed by thin wires insulated with Teflon fluorinated ethylene propylene (FEP). We consider media including 0.91% saline (a homogeneous tissue proxy), muscle tissue, and brain tissue, and present a launcher design based on a dielectric loaded coaxial sleeve. For example, in the saline proxy, a single FEP-insulated conductor of only 0.127 mm diameter presents a measured return loss of 10 dB in a 50Ω system, with a measured insertion loss of only 1 dB/cm at 1 GHz. C2 - 2013/10// C3 - 2013 IEEE Biomedical Circuits and Systems Conference (BioCAS) DA - 2013/10// DO - 10.1109/biocas.2013.6679679 PB - Institute of Electrical and Electronics Engineers (IEEE) ER - TY - CONF TI - Understanding Impact of New Additive Manufacturing Techniques on Power Electronics Design AU - Hopkins, D.C. T2 - IEEE Applied Power Electronics Conference C2 - 2013/3/18/ CY - Long Beach, California DA - 2013/3/18/ PY - 2013/3/18/ ER - TY - JOUR TI - Conceptual Development Using 3D Printing Technologies for 8kV SiC Power Module Package AU - Ke, Haotao AU - Xu, Yang AU - Hopkins, Douglas C T2 - International Symposium on Microelectronics AB - Post-silicon power devices, SiC or GaN for example, have many advantages over traditional silicon devices, particularly for smaller size and higher thermal densities. Although these devices are in the early stage of development, many applications have been identified, such as hybrid vehicles and the smart grid. For power packaging, there is now a greater challenge of much higher voltage, faster switching speed and much smaller package size (higher density). All of these issues call for newer approaches in power packaging. The microelectronics area has been developing stacked 3D technology along with printed 3D circuit technologies. Of been interested are the 3D printing technologies that can implement complicated structures, such as multilevel interconnects and selective dielectric field enhancements, besides introducing rapid prototyping in the early power stage design cycle. The 3D printing technology, introduced in the late 1980's, is now becoming prevalent. Commercial printers can create high-resolution structures in ceramic, metals (e.g. titanium, copper and aluminum) and polymers. The conceptual design proposed in this paper will incorporate a hybrid approach of traditional structures over-printed with polymers, or more advanced structures over-printed with metal and ceramic. The design focuses on packaging 1 cm × 1 cm SiC Schottky diode, which has a blocking capability of 8kV with a final target at 15kV. Early use of the package, in keeping with rapid prototyping, is to provide a test vehicle for the device, and prove the application of 3D printed material to high voltage power modules. This paper will present the necessity for packaging new SiC devices, review device characteristics, introduce the use of extruded 3D printing materials for a hybrid structure, and use of jetted/extruded layer-by-layer buildup for total, direct structure creation. Characterization of some available dielectric and metal printable materials, and a test methodology for electrical, thermal and mechanical performance will be discussed. An early-stage example will be shown and extrapolated to higher-level conceptual designs. DA - 2013/1/1/ PY - 2013/1/1/ DO - 10.4071/isom-2013-wp62 VL - 2013 IS - 1 SP - 000758-000763 LA - en OP - SN - 2380-4505 UR - http://dx.doi.org/10.4071/isom-2013-wp62 DB - Crossref ER - TY - CONF TI - Applications and design styles for 3DIC AU - Franzon, Paul D AU - Rotenberg, Eric AU - Tuck, James AU - Davis, W Rhett AU - Zhou, Huiyang AU - Schabel, Joshua AU - Zhang, Zhenquian AU - Park, J AU - Dwiel, Brandon AU - Forbes, Elliott AU - others T2 - IEEE C2 - 2013/// C3 - 2013 IEEE International Electron Devices Meeting DA - 2013/// SP - 29-4 ER - TY - CHAP TI - Batteries AU - Rahimi-Eichi, H. AU - Chow, M.-Y. T2 - The World Scientific Handbook of Energy A2 - Crawley, G.M. PY - 2013/// SP - 405–426 PB - World Scientific Publishing Company Inc. and Imperial College Press ER - TY - CHAP TI - Tracking Pedestrian with Multi-component Online Deformable Part-Based Model AU - Xie, Yi AU - Pei, Mingtao AU - Liu, Zhao AU - Wu, Tianfu T2 - Computer Vision – ACCV 2012 A2 - Lee, K.M. A2 - Matsushita, Y. A2 - Rehg, J.M. A2 - Hu, Z. T3 - Lecture Notes in Computer Science AB - In this work we present a novel online algorithm to track pedestrian by integrating both the bottom-up and the top-down models of pedestrian. Motivated by the observation that the appearance of a pedestrian changes a lot in different perspectives or poses, the proposed bottom-up model has multiple components to represent distinct groups of the pedestrian appearances. Also, similar pedestrian appearances have several common salient local patterns and their structure is relatively stable. So, each component of the proposed bottom-up model uses an online deformable part-based model (OLDPM) containing one root and several shared parts to represent the flexible structure and salient local patterns of an appearance. We term the bottom-up model multi-component OLDPM in this paper. We borrow an offline trained class specific pedestrian model [19] as the top-down model. The top-down model is used to extend the bottom-up model with a new OLDPM when a new appearance can’t be covered by the bottom-up model. The multi-component OLDPM has three advantages compared with other models. First, through an incremental support vector machine (INCSVM) [2] associated with the each component, the OLDPM of each component can effectively adapt to the pedestrian appearance variations of a specified perspective and pose. Second, OLDPM can efficiently generate match penalty maps of parts preserving the 2bit binary pattern (2bitBP) [10] through robust real-time pattern matching algorithm [16], and can search over all possible configurations in an image in linear-time by distance transforms algorithm [5]. Last but not least, parts can be shared among components to reduce the computational complexity for matching. We compare our method with four cutting edge tracking algorithms over seven visual sequences and provide quantitative and qualitative performance comparisons. PY - 2013/// DO - 10.1007/978-3-642-37431-9_51 SP - 664–676 PB - Springer SN - 9783642374302 9783642374319 SV - 7726 UR - http://dx.doi.org/10.1007/978-3-642-37431-9_51 ER - TY - CHAP TI - Coupling-and-Decoupling: A Hierarchical Model for Occlusion-Free Car Detection AU - Li, Bo AU - Wu, Tianfu AU - Hu, Wenze AU - Pei, Mingtao T2 - Computer Vision – ACCV 2012 A2 - Lee, K.M. A2 - Matsushita, Y. A2 - Rehg, J.M. A2 - Hu, Z. T3 - Lecture Notes in Computer Science AB - Handling occlusions in object detection is a long-standing problem. This paper addresses the problem of X-to-X-occlusion-free object detection (e.g. car-to-car occlusions in our experiment) by utilizing an intuitive coupling-and-decoupling strategy. In the “coupling” stage, we model the pair of occluding X’s (e.g. car pairs) directly to account for the statistically strong co-occurrence (i.e. coupling). Then, we learn a hierarchical And-Or directed acyclic graph (AOG) model under the latent structural SVM (LSSVM) framework. The learned AOG consists of, from the top to bottom, (i) a root Or-node representing different compositions of occluding X pairs, (ii) a set of And-nodes each of which represents a specific composition of occluding X pairs, (iii) another set of And-nodes representing single X’s decomposed from occluding X pairs, and (iv) a set of terminal-nodes which represent the appearance templates for the X pairs, single X’s and latent parts of the single X’s, respectively. The part appearance templates can also be shared among different single X’s. In detection, a dynamic programming (DP) algorithm is used and as a natural consequence we decouple the two single X’s from the X-to-X occluding pairs. In experiments, we test our method on roadside cars which are collected from real traffic video surveillance environment by ourselves. We compare our model with the state-of-the-art deformable part-based model (DPM) and obtain better detection performance. PY - 2013/// DO - 10.1007/978-3-642-37331-2_13 SP - 164–175 PB - Springer SN - 9783642373305 9783642373312 SV - 7724 UR - http://dx.doi.org/10.1007/978-3-642-37331-2_13 ER - TY - JOUR TI - Interference suppression for the LTE uplink AU - Çelebi, Mehmet Bahadır AU - Güvenç, İsmail AU - Arslan, Hüseyin AU - Qaraqe, Khalid A. T2 - Physical Communication AB - Abstract Interference cancellation is expected to have significant importance for next-generation wireless communication systems due to various co-channel deployment scenarios and denser frequency reuse. In this study, an interference cancellation receiver that exploits the unique characteristics of single-carrier frequency-division multiple access based systems is proposed. The proposed receiver suppresses the co-channel dominant interference by blanking frequency-domain samples where the desired and interfering signals overlap. In order to improve the performance, demodulation and regeneration stages can be introduced and repeated multiple times. Further enhancement is possible by initially accommodating a group of reliable symbols before the iterations. The simulation results indicate that proposed methods work particularly well for low overlap ratios compared to interference coordination and no cancellation schemes. DA - 2013/12// PY - 2013/12// DO - 10.1016/J.PHYCOM.2013.05.004 VL - 9 SP - 23-44 J2 - Physical Communication LA - en OP - SN - 1874-4907 UR - http://dx.doi.org/10.1016/J.PHYCOM.2013.05.004 DB - Crossref ER - TY - CHAP TI - From conventional bioceramics to modern expeditious bioactive glasses AU - Mozafari, Masoud AU - Shabafrooz, Vahid AU - Vashaee, Daryoosh AU - Tayebi, Lobat T2 - Frontiers in Ceramic Science – Synthesis and Characterization, Processing and its New Emerging Applications PY - 2013/// ER - TY - CONF TI - Modeling and simulation of a Microcontroller based power factor correction converter AU - Ahmmed, P. AU - Saha, S. S. AU - Sunny, S. M. N. A. AU - Hossain, M. I. AU - Rafee, M. I. J. AB - A Microcontroller based power factor correction (PFC) converter is proposed, which is not affected by harmonic distortion in current and voltage wave shapes. This paper describes the design and simulation of a single-phase PFC converter using Atmel's AVR Microcontroller. It involves sensing and measuring the power factor from the load using ADC; implementing faster algorithm to process the data using discrete time filter which requires least amount of memory; and triggering appropriate capacitors in order to compensate the excessive reactive components. A power factor near to unity is thus achieved, which results higher efficiency and low-THD AC output. A provision for measuring the power is also discussed. C2 - 2013/// C3 - 2013 International Conference on Informatics, Electronics and Vision (ICIEV) DA - 2013/// DO - 10.1109/ICIEV.2013.6572713 VL - SP - 1-4 M1 - ER - TY - THES TI - Decoupled control strategy of grid interactive inverter system with optimal LCL filter design AU - Anurag, Anup DA - 2013/// PY - 2013/// M3 - PhD thesis PB - National Institute of Technology ER - TY - CONF TI - Welcome to ICCD 2013! AU - Byrd, G. AU - Schneider, K. AU - Chang, N. AU - Ozev, S. AB - On behalf of the organizing and program committees, we welcome you to the 31 st IEEE International Conference on Computer Design. ICCD is co-sponsored by the IEEE Computer Society and the IEEE Circuits and Systems Society. It covers a broad range of topics at all levels of computer system design, from logic and circuits to architecture and applications, including the tools and processes used for design, test, verification, and security. This makes it a fertile environment for cross-layer discussions and interactions. C2 - 2013/// C3 - 2013 IEEE 31st International Conference on Computer Design, ICCD 2013 DA - 2013/// DO - 10.1109/ICCD.2013.6657012 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84892493679&partnerID=MN8TOARS ER - TY - CONF TI - Exploiting Uniform Vector Instructions for GPGPU Performance, Energy Efficiency, and Opportunistic Reliability Enhancement AU - Xiang, P. AU - Yang, Y. AU - Mantor, M. AU - Rubin, N. AU - Hsu, L. AU - Zhou, H. T2 - 27th International ACM Conference on International Conference on Supercomputing AB - State-of-art graphics processing units (GPUs) employ the single-instruction multiple-data (SIMD) style execution to achieve both high computational throughput and energy efficiency. As previous works have shown, there exists significant computational redundancy in SIMD execution, where different execution lanes operate on the same operand values. Such value locality is referred to as uniform vectors. In this paper, we first show that besides redundancy within a uniform vector, different vectors can also have the identical values. Then, we propose detailed architecture designs to exploit both types of redundancy. For redundancy within a uniform vector, we propose to either extend the vector register file with token bits or add a separate small scalar register file to eliminate redundant computations as well as redundant data storage. For redundancy across different uniform vectors, we adopt instruction reuse, proposed originally for CPU architectures, to detect and eliminate redundancy. The elimination of redundant computations and data storage leads to both significant energy savings and performance improvement. Furthermore, we propose to leverage such redundancy to protect arithmetic-logic units (ALUs) and register files against hardware errors. Our detailed evaluation shows that our proposed design has low hardware overhead and achieves performance gains, up to 23.9% and 12.0% on average, along with energy savings, up to 24.8% and 12.6% on average, as well as a 21.1% and 14.1% protection coverage for ALUs and register files, respectively. C2 - 2013/6// C3 - Proceedings of the 27th International ACM Conference on International Conference on Supercomputing CY - Eugene, Oregon DA - 2013/6// PY - 2013/// DO - 10.1145/2464996.2465022 SP - 433-442 PB - Association for Computing Machinery ER - TY - JOUR TI - Analyzing locality of memory references in GPU architectures AU - Gupta, S. AU - Xiang, P. AU - Zhou, H. T2 - MSPC '13: Proceedings of the ACM SIGPLAN Workshop on Memory Systems Performance and Correctness AB - In this paper we advocate formal locality analysis on memory references of GPGPU kernels. We investigate the locality of reference at different cache levels in the memory hierarchy. At the L1 cache level, we look into the locality behavior at the warp-, the thread block- and the streaming multiprocessor-level. Using matrix multiplication as a case study, we show that our locality analysis accurately captures some interesting and counter-intuitive behavior of the memory accesses. We believe that such analysis will provide very useful insights in understanding the memory accessing behavior and optimizing the memory hierarchy in GPU architectures. DA - 2013/6// PY - 2013/6// DO - 10.1145/2492408.2492423 VL - 6 ER - TY - JOUR TI - Multilayer bioactive glass/zirconium titanate thin films in bone tissue engineering and regenerative dentistry AU - Mozafari, Masoud AU - Salahinejad, Erfan AU - Shabafrooz, Vahid AU - Yazdimamaghani, Mostafa AU - Vashaee, Daryoosh AU - Tayebi, Lobat T2 - International Journal of Nanomedicine AB - Surface modification, particularly coatings deposition, is beneficial to tissue-engineering applications. In this work, bioactive glass/zirconium titanate composite thin films were prepared by a sol-gel spin-coating method. The surface features of the coatings were studied by scanning electron microscopy, atomic force microscopy, and spectroscopic reflection analyses. The results show that uniform and sound multilayer thin films were successfully prepared through the optimization of the process variables and the application of carboxymethyl cellulose as a dispersing agent. Also, it was found that the thickness and roughness of the multilayer coatings increase nonlinearly with increasing the number of the layers. This new class of nanocomposite coatings, comprising the bioactive and inert components, is expected not only to enhance bioactivity and biocompatibility, but also to protect the surface of metallic implants against wear and corrosion. DA - 2013/4// PY - 2013/4// DO - 10.2147/IJN.S42659 VL - 8 IS - 1 SP - 1665-1672 SN - 1178-2013 UR - http://dx.doi.org/10.2147/IJN.S42659 KW - bioactive glass KW - zirconium titanate KW - spin-coating KW - microstructural properties KW - bone/dental applications KW - tissue engineering ER - TY - JOUR TI - Erratum to “Effects of heat-treatment on physical, microstructural and optical characteristics of PbS luminescent nanocrystals” [Physica E: Low-dimens. Syst. Nanostruct. 44 (2012) 1429–1435 ] AU - Mozafari, Masoud AU - Moztarzadeh, Fathollah AU - Vashaee, Daryoosh AU - Tayebi, Lobat T2 - Physica E: Low-dimensional Systems and Nanostructures DA - 2013/1// PY - 2013/1// DO - 10.1016/j.physe.2012.10.015 VL - 47 SP - 324 J2 - Physica E: Low-dimensional Systems and Nanostructures LA - en OP - SN - 1386-9477 UR - http://dx.doi.org/10.1016/j.physe.2012.10.015 DB - Crossref ER - TY - JOUR TI - The effect of hyaluronic acid on biofunctionality of gelatin-collagen intestine tissue engineering scaffolds AU - Shabafrooz, Vahid AU - Mozafari, Masoud AU - Köhler, Gerwald A. AU - Assefa, Senait AU - Vashaee, Daryoosh AU - Tayebi, Lobat T2 - Journal of Biomedical Materials Research Part A AB - Abstract The creation of engineered intestinal tissue has recently stimulated new endeavors with the ultimate goal of intestinal replacement for massive resections of bowel. In this context, we investigated the effect of hyaluronic acid (HA) on the physicochemical characteristics of gelatin–collagen scaffolds and its cytocompatibilty to the human intestinal epithelial Caco‐2 cell line in vitro . Gelatin/collagen hybrid scaffolds with different concentrations of HA were prepared by solvent casting and freeze‐drying techniques and subsequent chemical crosslinking by genipin. The morphologies of the scaffolds were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. In vitro tests were carried out in phosphate‐buffered saline (PBS) solution to study the swelling ratio and the biostability of the scaffolds. It was found that the porous structure of the scaffolds could be tailored by further addition of HA. Moreover, both the swelling ratio and the degradation rate of the scaffold increased by addition of HA. A resazurin‐based cell viability assay was employed to determine the viability and estimate the number of scaffold‐adherent Caco‐2 cells. The assay indicated that the scaffolds were all cytocompatible. We concluded that addition of less than 15% HA to scaffolds with a composition of 9:1 gelatin:collagen results only in incremental improvement in the structural characteristics and cytocompatibility of the gelatin–collagen scaffolds. However, the scaffolds with 25% HA exhibited remarkable enhancement in physicochemical characteristics of the scaffolds including cell viability, growth, and attachment as well as their physical structure. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 3130–3139, 2014. DA - 2013/10/17/ PY - 2013/10/17/ DO - 10.1002/JBM.A.34984 VL - 102 IS - 9 SP - 3130-3139 J2 - J. Biomed. Mater. Res. LA - en OP - SN - 1549-3296 UR - http://dx.doi.org/10.1002/JBM.A.34984 DB - Crossref KW - hyaluronic acid KW - gelatin KW - collagen KW - scaffolds KW - porosity KW - freeze-drying KW - intestine KW - tissue engineering ER - TY - JOUR TI - Electrochemical Tattoo Biosensors for Real-Time Noninvasive Lactate Monitoring in Human Perspiration AU - Jia, Wenzhao AU - Bandodkar, Amay J. AU - Valdés-Ramírez, Gabriela AU - Windmiller, Joshua R. AU - Yang, Zhanjun AU - Ramírez, Julian AU - Chan, Garrett AU - Wang, Joseph T2 - Analytical Chemistry AB - The present work describes the first example of real-time noninvasive lactate sensing in human perspiration during exercise events using a flexible printed temporary-transfer tattoo electrochemical biosensor that conforms to the wearer's skin. The new skin-worn enzymatic biosensor exhibits chemical selectivity toward lactate with linearity up to 20 mM and demonstrates resiliency against continuous mechanical deformation expected from epidermal wear. The device was applied successfully to human subjects for real-time continuous monitoring of sweat lactate dynamics during prolonged cycling exercise. The resulting temporal lactate profiles reflect changes in the production of sweat lactate upon varying the exercise intensity. Such skin-worn metabolite biosensors could lead to useful insights into physical performance and overall physiological status, hence offering considerable promise for diverse sport, military, and biomedical applications. DA - 2013/7/5/ PY - 2013/7/5/ DO - 10.1021/ac401573r VL - 85 IS - 14 SP - 6553-6560 J2 - Anal. Chem. LA - en OP - SN - 0003-2700 1520-6882 UR - http://dx.doi.org/10.1021/ac401573r DB - Crossref ER - TY - JOUR TI - Magnetic Nanoclusters Exhibiting Protein-Activated Near-Infrared Fluorescence AU - Daniele, Michael A. AU - Shaughnessy, Margaret L. AU - Roeder, Ryan AU - Childress, Anthony AU - Bandera, Yuriy P. AU - Foulger, Stephen T2 - ACS Nano AB - Composite nanoclusters with chemical, magnetic, and biofunctionality offer broad opportunities for targeted cellular imaging. A key challenge is to load a high degree of targeting, imaging, and therapeutic functionality onto stable metal-oxide nanoparticles. Here we report a route for producing magnetic nanoclusters (MNCs) with alkyne surface functionality that can be utilized as multimodal imaging probes. We form MNCs composed of magnetic Fe3O4 nanoparticles and poly(acrylic acid-co-propargyl acrylate) by the co-precipitation of iron salts in the presence of copolymer stabilizers. The MNCs were surface-modified with near-infrared (NIR) emitting fluorophore used in photodynamic therapy, an azide-modified indocyanine green. The fluorophores engaged and complexed with bovine serum albumin, forming an extended coverage of serum proteins on the MNCs. These proteins isolated indocyanine green fluorophores from the aqueous environment and induced an effective “turn-on” of NIR emission. DA - 2013/1/22/ PY - 2013/1/22/ DO - 10.1021/nn3037368 VL - 7 IS - 1 SP - 203–213 SN - 1936-0851 1936-086X UR - http://dx.doi.org/10.1021/nn3037368 KW - biomedical imaging KW - magnetic colloid KW - click chemistry KW - biodetection ER - TY - JOUR TI - Biomolecular Gradients via Semiconductor Gradients: Characterization of Amino Acid Adsorption to InxGa1–xN Surfaces AU - Bain, Lauren E AU - Jewett, Scott A AU - Mukund, Aadhithya Hosalli AU - Bedair, Salah M AU - Paskova, Tania M AU - Ivanisevic, Albena T2 - ACS Applied Materials & Interfaces AB - The band gap of indium gallium nitride can be tuned by varying the compositional ratio of indium to gallium, spanning the entire visible region and extending into the near-infrared and near-ultraviolet. This tunability allows for device optimization specific to different applications, including as a biosensor or platform for studying biological interactions. However, these rely on chemically dependent interactions between the device surface and the biostructures of interest. This study presents a material gradient of changing In:Ga composition and the subsequent evaluation of amino acid adsorption to this surface. Arginine is adsorbed to the surface in conditions both above and below the isoelectric point, providing insight to the role of electrostatic interactions in interface formation. These electrostatics are the driving force of the observed adsorption behaviors, with protonated amino acid demonstrating increased adsorption as a function of native surface oxide buildup. We thus present a gradient inorganic substrate featuring varying affinity for amino acid adhesion, which can be applied in generating gradient architectures for biosensors and studying cellular behaviors without application of specialized patterning processes. DA - 2013/7/23/ PY - 2013/7/23/ DO - 10.1021/AM4015555 VL - 5 IS - 15 SP - 7236-7243 J2 - ACS Appl. Mater. Interfaces LA - en OP - SN - 1944-8244 1944-8252 UR - http://dx.doi.org/10.1021/AM4015555 DB - Crossref KW - III-V semiconductor KW - indium gallium nitride KW - X-ray photoelectron spectroscopy KW - surface gradient KW - amino acid KW - atomic force microscopy ER - TY - JOUR TI - A universal-input high-power-factor power supply without electrolytic capacitor for multiple lighting LED lamps AU - Ma, Hongbo AU - Lai, Jih-Sheng Jason AU - Feng, Quanyuan AU - Yu, Wensong AU - Zheng, Cong T2 - International Journal of Circuit Theory and Applications AB - SUMMARY The AC–DC power supply for LED lighting application requires a long lifetime while maintaining high‐efficiency, high power factor and low cost. However, a typical design uses electrolytic capacitor as storage capacitor, which is not only bulky but also with short life span, thus hampering performance improvement of the entire LED lighting system. In this article, a SEPIC‐derived power factor correction topology is proposed as the first stage for driving multiple lighting LED lamps. Along with a relatively large voltage ripple allowable in a two‐stage design, the proposal of LED lamp driver is able to eliminate the electrolytic capacitor while maintaining high power factor and high efficiency. To further increase the efficiency of LED driver, we introduced and used the twin‐bus buck converter as the second‐stage current regulator with Pulse Width Modulation (PWM) dimming function. The basic operating principle and the deign consideration are discussed in detail. A 50‐W prototype has been built and tested to verify the proposal. Copyright © 2011 John Wiley & Sons, Ltd. DA - 2013/5// PY - 2013/5// DO - 10.1002/cta.816 VL - 41 IS - 5 SP - 514–534 SN - 0098-9886 UR - http://dx.doi.org/10.1002/cta.816 KW - electrolytic capacitor KW - SEPIC derived KW - multiple lighting LED lamps KW - universal input voltage KW - power factor correction (PFC) KW - PWM dimming 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 - 2013/4/8/ PY - 2013/4/8/ DO - 10.1063/1.4796125 VL - 102 IS - 14 SP - 149902 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.4796125 DB - Crossref ER - TY - JOUR TI - A potentiometric tattoo sensor for monitoring ammonium in sweat AU - Guinovart, Tomàs AU - Bandodkar, Amay J. AU - Windmiller, Joshua R. AU - Andrade, Francisco J. AU - Wang, Joseph T2 - The Analyst AB - The development and analytical characterization of a novel ion-selective potentiometric cell in a temporary-transfer tattoo platform for monitoring ammonium levels in sweat is presented. The fabrication of this skin-worn sensor, which is based on a screen-printed design, incorporates all-solid-state potentiometric sensor technology for both the working and reference electrodes, in connection to ammonium-selective polymeric membrane based on the nonactin ionophore. The resulting tattooed potentiometric sensor exhibits a working range between 10(-4) M to 0.1 M, well within the physiological levels of ammonium in sweat. Testing under stringent mechanical stress expected on the epidermis shows that the analytical performance is not affected by factors such as stretching or bending. Since the levels of ammonium are related to the breakdown of proteins, the new wearable potentiometric tattoo sensor offers considerable promise for monitoring sport performance or detecting metabolic disorders in healthcare. Such combination of the epidermal integration, screen-printed technology and potentiometric sensing represents an attractive path towards non-invasive monitoring of a variety of electrolytes in human perspiration. DA - 2013/// PY - 2013/// DO - 10.1039/c3an01672b VL - 138 IS - 22 SP - 7031 J2 - Analyst LA - en OP - SN - 0003-2654 1364-5528 UR - http://dx.doi.org/10.1039/c3an01672b DB - Crossref ER - TY - JOUR TI - Solid-state Forensic Finger sensor for integrated sampling and detection of gunshot residue and explosives: towards ‘Lab-on-a-finger’ AU - Bandodkar, Amay J. AU - O'Mahony, Aoife M. AU - Ramírez, Julian AU - Samek, Izabela A. AU - Anderson, Sean M. AU - Windmiller, Joshua R. AU - Wang, Joseph T2 - The Analyst AB - Increasing security needs require field-deployable, on-the-spot detection tools for the rapid and reliable identification of gunshot residue (GSR) and nitroaromatic explosive compounds. This manuscript presents a simple, all-solid-state, wearable fingertip sensor for the rapid on-site voltammetric screening of GSR and explosive surface residues. To fabricate the new Forensic Fingers, we screen-print a three-electrode setup onto a nitrile finger cot, and coat another finger cot with an ionogel electrolyte layer. The new integrated sampling/detection methodology relies on ‘voltammetry of microparticles’ (VMP) and involves an initial mechanical transfer of trace amounts of surface-confined analytes directly onto the fingertip-based electrode contingent. Voltammetric measurements of the sample residues are carried out upon bringing the working electrode (printed on the index finger cot) in direct contact with a second finger cot coated with an ionogel electrolyte (worn on the thumb), thus completing the solid-state electrochemical cell. Sampling and screening are performed in less than four minutes and generate distinct voltammetric fingerprints which are specific to both GSR and explosives. The use of the solid, flexible ionogel electrolyte eliminates any liquid handling which can resolve problems associated with leakage, portability and contamination. A detailed study reveals that the fingertip detection system can rapidly identify residues of GSR and nitroaromatic compounds with high specificity, without compromising its attractive behavior even after undergoing repeated mechanical stress. This new integrated sampling/detection fingertip strategy holds considerable promise as a rapid, effective and low-cost approach for on-site crime scene investigations in various forensic scenarios. DA - 2013/// PY - 2013/// DO - 10.1039/c3an01179h VL - 138 IS - 18 SP - 5288 J2 - Analyst LA - en OP - SN - 0003-2654 1364-5528 UR - http://dx.doi.org/10.1039/c3an01179h DB - Crossref ER - TY - JOUR TI - Epidermal Biofuel Cells: Energy Harvesting from Human Perspiration AU - Jia, Wenzhao AU - Valdés-Ramírez, Gabriela AU - Bandodkar, Amay J. AU - Windmiller, Joshua R. AU - Wang, Joseph T2 - Angewandte Chemie International Edition AB - No sweat, no gain: Flexible biofuel cells functionalized with lactate oxidase (LOx) and platinum as anode and cathode materials harvested biochemical energy from human perspiration (see picture). Substantial power was generated from human sweat in real-life scenarios. 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 - 2013/5/31/ PY - 2013/5/31/ DO - 10.1002/anie.201302922 VL - 52 IS - 28 SP - 7233-7236 J2 - Angew. Chem. Int. Ed. LA - en OP - SN - 1433-7851 UR - http://dx.doi.org/10.1002/anie.201302922 DB - Crossref KW - biofuel cells KW - electrochemistry KW - energy harvesting KW - enzyme catalysis KW - epidermal electronics ER - TY - JOUR TI - Tattoo-based potentiometric ion-selective sensors for epidermal pH monitoring AU - Bandodkar, Amay J. AU - Hung, Vinci W. S. AU - Jia, Wenzhao AU - Valdés-Ramírez, Gabriela AU - Windmiller, Joshua R. AU - Martinez, Alexandra G. AU - Ramírez, Julian AU - Chan, Garrett AU - Kerman, Kagan AU - Wang, Joseph T2 - The Analyst AB - This article presents the fabrication and characterization of novel tattoo-based solid-contact ion-selective electrodes (ISEs) for non-invasive potentiometric monitoring of epidermal pH levels. The new fabrication approach combines commercially available temporary transfer tattoo paper with conventional screen printing and solid-contact polymer ISE methodologies. The resulting tattoo-based potentiometric sensors exhibit rapid and sensitive response to a wide range of pH changes with no carry-over effects. Furthermore, the tattoo ISE sensors endure repetitive mechanical deformation, which is a key requirement of wearable and epidermal sensors. The flexible and conformal nature of the tattoo sensors enable them to be mounted on nearly any exposed skin surface for real-time pH monitoring of the human perspiration, as illustrated from the response during a strenuous physical activity. The resulting tattoo-based ISE sensors offer considerable promise as wearable potentiometric sensors suitable for diverse applications. DA - 2013/// PY - 2013/// DO - 10.1039/c2an36422k VL - 138 IS - 1 SP - 123-128 J2 - Analyst LA - en OP - SN - 0003-2654 1364-5528 UR - http://dx.doi.org/10.1039/c2an36422k DB - Crossref ER - TY - CONF TI - Power spectrum blind sampling using minimum mean square error and weighted least squares AB - We present a new power spectrum recovery method in the context of power spectrum blind sampling. As sampling device we propose a multicoset sampler, which provides sub-Nyquist rate samples. A weighted least squares (WLS) criterion is adopted with the aim to define a power spectrum recovery algorithm that minimizes the mean square error (MSE) of the correlation estimate of the input signal. It is analytically shown that the optimal weighting matrix is equal to the inverse of the covariance matrix of the correlation estimate of the sub-Nyquist rate samples. The derived weight can also be shown to be optimal in MSE sense for power spectrum estimation. We also provide an optimization framework for the design of multicoset sampling patterns that minimize the MSE of the compressive WLS power spectrum estimator. The resulting integer nonlinear programming problem is solved by using exhaustive search. C2 - 2013/// C3 - Conference Record - Asilomar Conference on Signals, Systems and Computers DA - 2013/// DO - 10.1109/ACSSC.2013.6810249 SP - 153-157 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84901252003&partnerID=MN8TOARS ER - TY - CONF TI - A class of circular sparse rulers for compressive power spectrum estimation AU - Dominguez-Jimenez, M.E. AU - Gonzalez-Prelcic, N. C2 - 2013/// C3 - European Signal Processing Conference DA - 2013/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84901365760&partnerID=MN8TOARS ER - TY - CONF TI - Undergraduate research and the smart grid: REU-Site: Engineering the grid AU - Lunardi, L. C2 - 2013/// C3 - ASEE Annual Conference and Exposition, Conference Proceedings DA - 2013/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84884333631&partnerID=MN8TOARS ER - TY - CHAP TI - Optoelectronic Devices AU - Lunardi, L. AU - Mokkapati, S. AU - Jagadish, C. T2 - Guide to State-of-the-Art Electron Devices AB - This chapter covers the advances on semiconductor devices that manipulate light, convert photons to electrons, and their applications. Some devices are designed for generation of light. The materials used in all these devices have steered the applications from communications, to medical instrumentation, scanners, and consumer electronics in a way thatsemiconductor optoelectronics became ubiquitous. PY - 2013/// DO - 10.1002/9781118517543.ch20 SP - 265-274 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84986915862&partnerID=MN8TOARS ER - TY - JOUR TI - Decoupled Control Strategy of Grid Interactive Inverter System with Optimal LCL Filter Design AU - Babu, B. Chitti AU - Anurag, Anup AU - Sowmya, Tontepu AU - Marandi, Debati AU - Bal, Satarupa T2 - International Journal of Emerging Electric Power Systems AB - Abstract This article presents a control strategy for a three-phase grid interactive voltage source inverter that links a renewable energy source to the utility grid through a LCL-type filter. An optimized LCL-type filter has been designed and modeled so as to reduce the current harmonics in the grid, considering the conduction and switching losses at constant modulation index ( M a ). The control strategy adopted here decouples the active and reactive power loops, thus achieving desirable performance with independent control of active and reactive power injected into the grid. The startup transients can also be controlled by the implementation of this proposed control strategy: in addition to this, optimal LCL filter with lesser conduction and switching copper losses as well as core losses. A trade-off has been made between the total losses in the LCL filter and the Total Harmonic Distortion (THD%) of the grid current, and the filter inductor has been designed accordingly. In order to study the dynamic performance of the system and to confirm the analytical results, the models are simulated in the MATLAB/Simulink environment, and the results are analyzed. DA - 2013/9/6/ PY - 2013/9/6/ DO - 10.1515/ijeeps-2013-0015 VL - 14 IS - 5 SP - 477-486 OP - SN - 2194-5756 1553-779X UR - http://dx.doi.org/10.1515/ijeeps-2013-0015 DB - Crossref KW - active and reactive power control KW - current controller KW - grid-connected inverter KW - LCL-type filter KW - inductor losses ER - TY - JOUR TI - Design and Analysis of Improved Soft Switching DC–DC Boost Converter for Low Power Photovoltaic Applications AU - Bal, Satarupa AU - Anurag, Anup AU - Babu, B. Chitti T2 - Journal of Low Power Electronics DA - 2013/10/1/ PY - 2013/10/1/ DO - 10.1166/jolpe.2013.1267 VL - 9 IS - 3 SP - 303-312 J2 - Journal of Low Power Electronics LA - en OP - SN - 1546-1998 UR - http://dx.doi.org/10.1166/jolpe.2013.1267 DB - Crossref KW - Zero Voltage Switching (ZVS) KW - Zero Current Switching (ZCS) KW - Soft Switching KW - Perturbation and Observation (P&O) Method KW - Photovoltaic (PV) Array KW - DC-DC Boost Converter ER - TY - CONF TI - The viability of distributed antennas for massive MIMO systems AB - Massive multiple-input multiple-output (MIMO) is a breakthrough communication technique for providing high spectral efficiency. The idea is to deploy a very large number of antennas at each base station and to use multiuser MIMO transmission to serve a smaller number of users. In this paper, the viability of using distributed antennas for massive MIMO on the uplink is investigated for a particular spatial correlation channel model. Both maximal ratio combining (MRC) and minimum mean squared error (MMSE) beamforming are found to provide higher performance in several distributed settings. An algorithm for remote radio head selection is proposed that allows MRC to approach the performance achieved by the MMSE beamforming solution yet retaining its lower complexity. C2 - 2013/// C3 - Conference Record - Asilomar Conference on Signals, Systems and Computers DA - 2013/// DO - 10.1109/ACSSC.2013.6810508 SP - 1318-1323 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84901278795&partnerID=MN8TOARS ER - TY - CONF TI - Precision limits of low-energy GNSS receivers C2 - 2013/// C3 - 26th International Technical Meeting of the Satellite Division of the Institute of Navigation, ION GNSS 2013 DA - 2013/// VL - 4 SP - 2828-2834 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84898958688&partnerID=MN8TOARS ER - TY - CONF TI - Multi-user real-time wireless video with perceptual constraints AB - The current military and civil ground based surveillance and reconnaissance is characterized by a large number of sensor assets, feeding resource constrained analysis nodes, and constrained by extremely limited transport bandwidth. The complexity of such systems is captured by the Networks of Systems (NoS) concept which use tools from wireless engineering and control theory. In this paper, the role of perceptual quality constraints on video-based NoS is investigated. An algorithm to determine the feasible set of nodes and optimal packet schedule via a Markov decision process, given their perceptual constraints and channel qualities is proposed. The H.264/SVC codec is used for compression, while the visual information fidelity pixel-domain (VIFP) full-reference image quality assessment model is used to measure perceptual quality. The algorithm is implemented in custom C;; software with over-the-air transmissions using 802.11 WLAN hardware. Real-time encoding is done for over-the-air transmission of the video. The results indicate that gains of 10-30% can be realized for a three node system. C2 - 2013/// C3 - Conference Record - Asilomar Conference on Signals, Systems and Computers DA - 2013/// DO - 10.1109/ACSSC.2013.6810480 SP - 1183-1187 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84901269861&partnerID=MN8TOARS ER - TY - CONF TI - Video quality-maximizing resource allocation and scheduling with statistical delay guarantees AB - Real-time video demands quality-of-service (QoS) guarantees such as delay bounds for end-user satisfaction. Due to the stochastic nature of wireless fading channels, deterministic delay bounds are prohibitively difficult to guarantee. Instead, this paper proposes providing statistical delay guarantees using the concept of effective capacity. A multiuser setup is considered whereby different users have (possibly different) delay QoS constraints. The resource allocation policy that maximizes the sum video quality is derived and has a useful intuitive interpretation: 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, termed source spectral efficiency. Scheduling policies are also proposed to select a maximal user subset such that all selected users can meet their statistical delay requirement. Results show that QoS-aware scheduling and resource allocation enable supporting significantly more users under the same resource constraints. C2 - 2013/// C3 - GLOBECOM - IEEE Global Telecommunications Conference DA - 2013/// DO - 10.1109/GLOCOM.2013.6831324 SP - 1736-1740 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84904125372&partnerID=MN8TOARS ER - TY - JOUR TI - The practical challenges of interference alignment AU - El Ayach, O. AU - Peters, S. AU - Heath, R.W. T2 - IEEE Wireless Communications AB - Interference alignment is a revolutionary wireless transmission strategy that reduces the impact of interference. The idea of interference alignment is to coordinate multiple transmitters so that their mutual interference aligns at the receivers, facilitating simple interference cancellation techniques. Since interference alignment's inception, researchers have investigated its performance and proposed several improvements. Research efforts have been primarily focused on verifying interference alignment's ability to achieve the maximum degrees of freedom (an approximation of sum capacity), developing algorithms for determining alignment solutions, and designing transmission strategies that relax the need for perfect alignment but yield better performance. This article provides an overview of the concept of interference alignment as well as an assessment of practical issues including performance in realistic propagation environments, the role of channel state information at the transmitter, and the practicality of interference alignment in large networks. DA - 2013/// PY - 2013/// DO - 10.1109/MWC.2013.6472197 VL - 20 IS - 1 SP - 35-42 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84874978120&partnerID=MN8TOARS ER - TY - CONF TI - Multimode precoding in millimeter wave MIMO transmitters with multiple antenna sub-arrays AU - El Ayach, O. AU - Heath, R.W. AU - Rajagopal, S. AU - Pi, Z. AB - Millimeter wave (mmWave) systems must use beamforming to overcome the heavy attenuation at mmWave frequencies and establish high-quality communication links with reasonably high spectral efficiency. When received signal power is sufficiently large and the propagation channel is sufficiently rich, beamforming with multiple data streams, known as precoding, could further increase data rates in mmWave systems. The high cost of digital devices in mmWave systems, however, implies that precoding is predominantly done in the analog domain, making mmWave precoding significantly more constrained than traditional multiple-input multiple-output (MIMO) solutions. In this paper, we propose an iterative precoding algorithm for a practical mmWave transmitter architecture in which all precoding is done in the analog domain. In addition to precoding, the proposed algorithm allows the mmWave system to adapt the rank of its transmission in response to varying propagation conditions. We present numerical results showing that the proposed multimode precoding algorithm allows systems to achieve large data rates, in some cases approaching channel capacity. C2 - 2013/// C3 - GLOBECOM - IEEE Global Telecommunications Conference DA - 2013/// DO - 10.1109/GLOCOM.2013.6831611 SP - 3476-3480 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84904102799&partnerID=MN8TOARS ER - TY - JOUR TI - Single-user MIMO versus multi-user MIMO in distributed antenna systems with limited feedback T2 - Eurasip Journal on Advances in Signal Processing AB - This article investigates the performance of cellular networks employing distributed antennas in addition to the central antennas of the base station. Distributed antennas are likely to be implemented using remote radio units, which is enabled by a low latency and high bandwidth dedicated link to the base station. This facilitates coherent transmission from potentially all available antennas at the same time. Such distributed antenna system (DAS) is an effective way to deal with path loss and large-scale fading in cellular systems. DAS can apply precoding across multiple transmission points to implement single-user MIMO (SU-MIMO) and multi-user MIMO (MU-MIMO) transmission. The throughput performance of various SU-MIMO and MU-MIMO transmission strategies is investigated in this article, employing a Long-Term evolution (LTE) standard compliant simulation framework. The previously theoretically established cell-capacity improvement of MU-MIMO in comparison to SU-MIMO in DASs is confirmed under the practical constraints imposed by the LTE standard, even under the assumption of imperfect channel state information (CSI) at the base station. Because practical systems will use quantized feedback, the performance of different CSI feedback algorithms for DASs is investigated. It is shown that significant gains in the CSI quantization accuracy and in the throughput of especially MU-MIMO systems can be achieved with relatively simple quantization codebook constructions that exploit the available temporal correlation and channel gain differences. DA - 2013/// PY - 2013/// DO - 10.1186/1687-6180-2013-54 VL - 2013 IS - 1 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84886693758&partnerID=MN8TOARS KW - Distributed antenna systems KW - Remote radio units KW - Channel state information estimation KW - Limited feedback communication KW - Quantized feedback KW - Single-user MIMO KW - Multi-user MIMO KW - LTE ER - TY - JOUR TI - Predictive vector quantization for multicell cooperation with delayed limited feedback AU - Bhagavatula, R. AU - Heath, R.W. T2 - IEEE Transactions on Wireless Communications AB - Base station cooperation can use knowledge of the users' channel state information (CSI) at the transmitters to manage co-channel interference. A reasonable way to provide CSI to the base stations is through a finite rate limited feedback channel. Existing multicell limited feedback techniques require a large amount of feedback, which incurs an overhead penalty on the uplink. In this paper, a new feedback approach based on predictive vector quantization (PVQ) is proposed to reduce feedback requirements in multicell systems and provide high resolution CSI at base stations by exploiting temporal correlation in the channels. Transmitter and receiver structures are proposed to implement predictive limited feedback accounting for delay, for signals on the Grassmann manifold. Simulations show that the proposed PVQ framework yields higher sum-rates than memoryless quantization approaches for multicell limited feedback, in a cooperative system using intercell interference nulling. DA - 2013/// PY - 2013/// DO - 10.1109/TWC.2013.040413.112037 VL - 12 IS - 6 SP - 2588-2597 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84880145400&partnerID=MN8TOARS KW - Limited feedback KW - multicell coordination KW - predictive quantization KW - MIMO KW - Base stations KW - cellular networks KW - channel state information ER - TY - JOUR TI - Multicell cooperative systems with multiple receive antennas AU - Hwang, I. AU - Chae, C.-B. AU - Lee, J. AU - Heath, R. T2 - IEEE Wireless Communications AB - Multicell cooperation may play an important role in achieving high performance in cellular systems. Multicell cooperation with a single receive antenna at the mobile station has been widely investigated. Applying cooperation with multiple receive antennas, allowed in several emerging wireless standards, has met with some challenges. This is primarily because the transmit precoding/beamforming vector and receive processing have to be jointly optimized in multiple cells to combat out-of-cell interference. In this article, we first discuss the role of the receive antennas in a multicell environment, and then review recently proposed multicell cooperative algorithms and receive antenna techniques for different interference statistics. Finally, we highlight recent work on the fundamental limits of cooperation and the possibility of overcoming such limits by using multiple receive antennas in multicell cooperative networks. DA - 2013/// PY - 2013/// DO - 10.1109/MWC.2013.6472199 VL - 20 IS - 1 SP - 50-58 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84874992843&partnerID=MN8TOARS ER - TY - JOUR TI - Modeling heterogeneous network interference using poisson point processes T2 - IEEE Transactions on Signal Processing AB - Cellular systems are becoming more heterogeneous with the introduction of low power nodes including femtocells, relays, and distributed antennas. Unfortunately, the resulting interference environment is also becoming more complicated, making evaluation of different communication strategies challenging in both analysis and simulation. Leveraging recent applications of stochastic geometry to analyze cellular systems, this paper proposes to analyze downlink performance in a fixed-size cell, which is inscribed within a weighted Voronoi cell in a Poisson field of interferers. A nearest out-of-cell interferer, out-of-cell interferers outside a guard region, and cross-tier interferers are included in the interference calculations. Bounding the interference power as a function of distance from the cell center, the total interference is characterized through its Laplace transform. An equivalent marked process is proposed for the out-of-cell interference under additional assumptions. To facilitate simplified calculations, the interference distribution is approximated using the Gamma distribution with second order moment matching. The Gamma approximation simplifies calculation of the success probability and average rate, incorporates small-scale and large-scale fading, and works with co-tier and cross-tier interference. Simulations show that the proposed model provides a flexible way to characterize outage probability and rate as a function of the distance to the cell edge. DA - 2013/// PY - 2013/// DO - 10.1109/TSP.2013.2262679 VL - 61 IS - 16 SP - 4114-4126 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84880831887&partnerID=MN8TOARS KW - Wireless communication KW - cellular networks KW - MIMO KW - stochastic geometry KW - interference ER - TY - CONF TI - Link adaptation in MIMO-OFDM with practical impairments AB - Performing link adaptation in multiple-input-multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems is challenging due to the problem of mapping the channel state information to a frame error rate (FER) value. This difficulty comes from the spatial and frequential selectivity of the channel, which makes the different symbols in a codeword to observe different signal to noise ratio values. Moreover, practical impairments like non-Gaussian noise, different frame lengths, or channel nonlinearities can severely affect the adaptation procedure in real scenarios. In this paper we study different FER prediction techniques, which can be classified in parametric, non-parametric and semi-parametric. We evaluate the performance of the FER predictors under practical impairments, and compare the achieved throughput when used in conjunction with link adaptation algorithms. C2 - 2013/// C3 - Conference Record - Asilomar Conference on Signals, Systems and Computers DA - 2013/// DO - 10.1109/ACSSC.2013.6810579 SP - 1649-1653 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84901272256&partnerID=MN8TOARS ER - TY - CONF TI - Learning based link adaptation in multiuser MIMO-OFDM C2 - 2013/// C3 - European Signal Processing Conference DA - 2013/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84901343679&partnerID=MN8TOARS ER - TY - JOUR TI - Interference coordination: Random clustering and adaptive limited feedback AU - Akoum, S. AU - Heath, R.W. T2 - IEEE Transactions on Signal Processing AB - Interference coordination improves data rates and reduces outages in cellular networks. Accurately evaluating the gains of coordination, however, is contingent upon using a network topology that models realistic cellular deployments. In this paper, we model the base stations locations as a Poisson point process to provide a better analytical assessment of the performance of coordination. Since interference coordination is only feasible within clusters of limited size, we consider a random clustering process where cluster stations are located according to a random point process and groups of base stations associated with the same cluster coordinate. We assume channel knowledge is exchanged among coordinating base stations, and we analyze the performance of interference coordination when channel knowledge at the transmitters is either perfect or acquired through limited feedback. We apply intercell interference nulling (ICIN) to coordinate interference inside the clusters. The feasibility of ICIN depends on the number of antennas at the base stations. Using tools from stochastic geometry, we derive the probability of coverage and the average rate for a typical mobile user. We show that the average cluster size can be optimized as a function of the number of antennas to maximize the gains of ICIN. To minimize the mean loss in rate due to limited feedback, we propose an adaptive feedback allocation strategy at the mobile users. We show that adapting the bit allocation as a function of the signals' strength increases the achievable rate with limited feedback, compared to equal bit partitioning. Finally, we illustrate how this analysis can help solve network design problems such as identifying regions where coordination provides gains based on average cluster size, number of antennas, and number of feedback bits. DA - 2013/// PY - 2013/// DO - 10.1109/TSP.2013.2238933 VL - 61 IS - 7 SP - 1822-1834 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84897583701&partnerID=MN8TOARS KW - Adaptive feedback bit partitioning KW - base stations KW - cellular networks KW - channel state information (CSI) KW - clustering KW - clustering algorithms KW - interference cancellation KW - limited CSI feedback KW - MIMO KW - multicell coordination KW - stochastic geometry ER - TY - JOUR TI - Location-specific coverage in heterogeneous networks AU - Bai, T. AU - Heath, R.W. T2 - IEEE Signal Processing Letters AB - Cellular networks are taking on a more heterogeneous character with the introduction of low power nodes. Besides the aggregate performance over the entire network, it is also of interest to evaluate the coverage probability conditioning on a specific user location in a cell. This letter proposes a method to compute the location-specific coverage probability inside the inscribing ball of a weighted Voronoi cell in heterogeneous networks. Simulations show that the proposed closed-form approximation accurately characterizes the coverage probability at locations of interest inside the inscribing ball. Moreover the expression can also be applied to evaluate the performance at locations outside the inscribing ball with minor loss. DA - 2013/// PY - 2013/// DO - 10.1109/LSP.2013.2272400 VL - 20 IS - 9 SP - 873-876 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84880807471&partnerID=MN8TOARS KW - Coverage probability KW - heterogeneous cellular networks KW - stochastic geometry KW - wireless communication ER - TY - CONF TI - Interference alignment - Recent results and future directions AU - Ayach, O.E. AU - Heath, R.W. AB - Interference alignment (IA) is a cooperative transmission strategy that can mitigate the effects of interference in distributed wireless networks. As its name suggests, the idea of alignment is to structure interference such that multiple interfering signals overlap at the receiver. The alignment property enables efficient interference cancellation. This article provides a brief review of the concept of interference alignment, with a focus on linear precoding-based IA strategies for the multiple-input multiple-output (MIMO) interference channel, and surveys some of the authors' recent results on the subject, with a special focus on making IA more practical. The key concepts discussed range from algorithmic improvements to early IA solutions, to managing the overhead associated with user cooperation. The article highlights some active areas, and future directions, in IA research. C2 - 2013/// C3 - IEEE Radio and Wireless Symposium, RWS DA - 2013/// DO - 10.1109/RWS.2013.6486689 SP - 205-207 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84876778132&partnerID=MN8TOARS ER - TY - JOUR TI - Fundamental limits of cooperation AU - Lozano, A. AU - Heath, R.W. AU - Andrews, J.G. T2 - IEEE Transactions on Information Theory AB - Cooperation is viewed as a key ingredient for interference management in wireless networks. This paper shows that cooperation has fundamental limitations. First, it is established that in systems that rely on pilot-assisted channel estimation, the spectral efficiency is upper-bounded by a quantity that does not depend on the transmit powers; in this framework, cooperation is possible only within clusters of limited size, which are subject to out-of-cluster interference whose power scales with that of the in-cluster signals. Second, an upper bound is also shown to exist if the cooperation extends to an entire (large) system operating as a single cluster; here, pilot-assisted transmission is necessarily transcended. Altogether, it is concluded that cooperation cannot in general change an interference-limited network to a noise-limited one. Consequently, the existing literature that routinely assumes that the high-power spectral efficiency scales with the log-scale transmit power provides only a partial characterization. The complete characterization proposed in this paper subdivides the high-power regime into a degree-of-freedom regime, where the scaling with the log-scale transmit power holds approximately, and a saturation regime, where the spectral efficiency hits a ceiling that is independent of the power. Using a cellular system as an example, it is demonstrated that the spectral efficiency saturates at power levels of operational relevance. DA - 2013/// PY - 2013/// DO - 10.1109/TIT.2013.2253153 VL - 59 IS - 9 SP - 5213-5226 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84880148105&partnerID=MN8TOARS KW - Cooperative systems KW - interference KW - wireless communications KW - wireless networks ER - TY - JOUR TI - MIMO interference alignment in random access networks AU - Nosrat-Makouei, B. AU - Ganti, R.K. AU - Andrews, J.G. AU - Heath, R.W. T2 - IEEE Transactions on Communications AB - In this paper, we analyze a multiple-input multiple-output (MIMO) interference channel where nodes are randomly distributed on a plane as a spatial Poisson cluster point process. A Poisson cluster point process consists of clusters with fixed number of points randomly distributed as with the cluster centers distributed randomly on the plane. The nodes in each cluster use interference alignment (IA) to suppress intra-cluster interference but unlike most work on IA, we do not neglect inter-cluster interference. We also connect the accuracy of channel state information to the distance between the nodes, i.e., the quality of CSI degrades with increasing distance. Accounting for the training and feedback overhead, we derive the transmission capacity of this MIMO IA ad hoc network and then compare it to open-loop (interference-blind) spatial multiplexing. Finally, we present exemplary system setups where spatial multiplexing outperforms IA due to the imperfect channel state information or the non-aligned inter-cluster interference. DA - 2013/// PY - 2013/// DO - 10.1109/TCOMM.2013.111213.120518 VL - 61 IS - 12 SP - 5042-5055 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891739623&partnerID=MN8TOARS KW - Transmission capacity KW - interference channels KW - interference alignment KW - multiple-input multiple-output (MIMO) KW - zero forcing KW - channel estimation KW - analog feedback KW - wireless networks KW - ad hoc networks ER - TY - JOUR TI - Joint transmit precoding for the relay interference broadcast channel T2 - IEEE Transactions on Vehicular Technology AB - Relays in cellular systems are interference limited. The highest end-to-end sum rates are achieved when the relays are jointly optimized with the transmit strategy. Unfortunately, interference couples the links together, making joint optimization challenging. Further, the end-to-end multihop performance is sensitive to rate mismatch when some links have a dominant first link, whereas others have a dominant second link. This paper proposes an algorithm for designing the linear transmit precoders at the transmitters and relays of the relay interference broadcast channel, which is a generic model for relay-based cellular systems, to maximize the end-to-end sum rates. First, the relays are designed to maximize the second-hop sum rates. Next, approximate end-to-end rates that depend on the time-sharing fraction and the second-hop rates are used to formulate a sum-utility maximization problem to design the transmitters. This problem is solved by iteratively minimizing the weighted sum of mean square errors (MSEs). Finally, the norms of the transmit precoders at the transmitters are adjusted to eliminate rate mismatch. The proposed algorithm allows for distributed implementation and has fast convergence. Numerical results show that the proposed algorithm outperforms a reasonable application of single-hop interference management strategies separately on two hops. DA - 2013/// PY - 2013/// DO - 10.1109/TVT.2012.2228888 VL - 62 IS - 3 SP - 1201-1215 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84879584011&partnerID=MN8TOARS KW - Cooperative systems KW - distributed algorithms KW - interference channels KW - multiple-input multiple-output (MIMO) KW - relay communication KW - relay interference broadcast channel KW - wireless communication ER - TY - CONF TI - HF MIMO NVIS measurements with co-located dipoles for future tactical communications AB - Multiple antennas in transceivers can increase system spectral efficiency, reduce transmit power, enable robustness to interference, and increase overall reliability through multiple-input multiple-output processing (MIMO). Consequently, high frequency (HF) networks, which feature extreme spectrum scarcity and unreliability, are prime for MIMO exploitation. Unfortunately, the desired antenna spacing for MIMO is proportional to the wavelength (tens of meters at HF). One promising approach is to utilize two antennas in a single antenna footprint through cross-polarization. This configuration has not yet been fully validated for MIMO at HF. In this paper, we demonstrate MIMO capabilities in near vertical incidence sky-wave (NVIS) propagation through a measurement campaign. This paper shows that MIMO is a game changer for HF NVIS with up to 2.27 times higher data rate, up to 9 times less transmit power, and more than 3 times fewer link failures. This paper also provides critical channel metrics for baseband designers of future MIMO HF protocols as demonstrated in our companion paper. C2 - 2013/// C3 - Proceedings - IEEE Military Communications Conference MILCOM DA - 2013/// DO - 10.1109/MILCOM.2013.210 SP - 1250-1255 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84897699725&partnerID=MN8TOARS ER - TY - CONF TI - General chairs' welcome AB - On behalf of the IEEE Global Conference on Signal and Information Processing (GlobalSIP) Organizing Committee, we would like to cordially welcome you to Austin, Texas. Austin is known as the Live Music Capital of the World. Indeed, Austin offers many opportunities to experience music just a stones throw away from the convention center, but it also has much to offer residents and visitors. Austin is also the capital of Texas and is home to the University of Texas at Austin, leading technology companies, and a number of emerging startups in diverse areas from signal processing, communications, semiconductors, and gaming. Several annual events are held in Austin including the Formula 1 US Grand Prix, the Austin City Limits Music Festival (ACL), and the South-by-Southwest music, film, and interactive conference and festival (SXSW also called “Southy-By”). C2 - 2013/// C3 - 2013 IEEE Global Conference on Signal and Information Processing, GlobalSIP 2013 - Proceedings DA - 2013/// DO - 10.1109/GlobalSIP.2013.6736790 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84897674585&partnerID=MN8TOARS ER - TY - CONF TI - Coverage in dense millimeter wave cellular networks AB - The millimeter wave (mmWave) spectrum holds promise for future cellular systems. MmWave cellular deployments are likely to be dense to achieve good coverage. This paper proposes a simplified approach to evaluate the coverage probability in dense mmWave networks. By simplifying a framework that incorporates blockages, analytical expressions are derived to compute the coverage probability. The results show that the average cell size should scale with the average size of the line-of-sight region to maintain the same coverage probability in a dense network, and that the optimum base station density should be dense enough but not too dense. C2 - 2013/// C3 - Conference Record - Asilomar Conference on Signals, Systems and Computers DA - 2013/// DO - 10.1109/ACSSC.2013.6810669 SP - 2062-2066 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84901248233&partnerID=MN8TOARS ER - TY - JOUR TI - Cooperative algorithms for MIMO amplify-and-forward relay networks T2 - IEEE Transactions on Signal Processing AB - Interference is a common impairment in wireless communication systems. Multi-hop relay networks use a set of intermediate nodes called relays to facilitate communication between multiple transmitters and multiple receivers through multiple hops. Relay based communication is especially sensitive to interference because the interference impacts both the received signal at the relay, and the received signal at the destination. Interference alignment is a signaling technique that provides high multiplexing gain in the interference channel. In this paper, inspired by an algorithmic approach for interference alignment, three cooperative algorithms are proposed to find suboptimal solutions for end-to-end sum-rate maximization problem in a multiple-antenna amplify-and-forward (AF) relay interference channel. The first algorithm aims at minimizing the sum power of enhanced noise from the relays and interference at the receivers. The second and third algorithms aim at minimizing matrix-weighted sum mean square errors with either equality or inequality power constraints to utilize a connection between mean square error and mutual information. The resulting iterative algorithms are convergent to points that we conjecture to be stationary points of the corresponding problems. Simulations show that the proposed algorithms achieve higher end-to-end sum-rates and multiplexing gains that existing strategies for AF relays, decode-and-forward relays, and direct transmission. The first algorithm outperforms the other algorithms at high signal-to-noise ratio (SNR) but performs worse than them at low SNR. Thanks to power control, the third algorithm outperforms the second algorithm at the cost of additional overhead. DA - 2013/// PY - 2013/// DO - 10.1109/TSP.2012.2236832 VL - 61 IS - 5 SP - 1272-1287 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84873922560&partnerID=MN8TOARS KW - Interference alignment KW - joint source-relay design KW - relay beamforming KW - relay interference channel KW - relay-aided interference alignment KW - two-hop interference channel ER - TY - CONF TI - Base station cooperation with dynamic clustering in super-dense cloud-RAN AU - Lee, N. AU - Heath, R.W. AU - Morales-Jimenez, D. AU - Lozano, A. AB - In this paper, a downlink cellular model based on stochastic geometry is put forth in order to analyze the performance of base station (BS) cooperation with dynamic clustering in highly dense BS deployments. Utilizing the proposed model, a closed-form expression for the complementary cumulative distribution function of the instantaneous signal-to-interference ratio (SIR) is derived in terms of relevant system parameters, chiefly the number of cooperating base stations and the path-loss exponent. From the derived SIR distribution, some of the benefits of cooperation can be characterized. Through simulation, the derived SIR distribution is verified and further compared with the corresponding distribution for a deterministic grid model. C2 - 2013/// C3 - 2013 IEEE Globecom Workshops, GC Wkshps 2013 DA - 2013/// DO - 10.1109/GLOCOMW.2013.6825084 SP - 784-788 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84902986739&partnerID=MN8TOARS ER - TY - JOUR TI - Degrees of freedom for the two-cell two-hop MIMO interference channel: Interference-free relay transmission and spectrally efficient relaying protocol AU - Lee, N. AU - Heath, R.W. T2 - IEEE Transactions on Information Theory AB - This paper considers the two-cell two-hop multiple-input-multiple-output (MIMO) interference channel, where two source groups consisting of multiple users with a single antenna wish to communicate with two multiantenna destinations by sharing two multiantenna relays. For such a channel, an inner bound on the degrees of freedom is derived for different channel knowledge assumptions and relay operations. Assuming global channel knowledge at the relays and full-duplex relay operation, it is shown that two cascaded interfering links can be decomposed into two independent parallel relay channels while sharing the spectrum. The key to showing this result is a novel amplify-and-forward interference-free relay transmission method, which performs interference-shaping during reception and interference neutralization during transmission. Assuming that the relays have global channel knowledge only for the first hop, a spectrally efficient relaying protocol is proposed that overcomes the loss due to half-duplex relaying constraint. The proposed protocol improves performance compared to a trivial time-division-multiple access method for the two-cell two-hop MIMO interference channel. DA - 2013/// PY - 2013/// DO - 10.1109/TIT.2013.2237753 VL - 59 IS - 5 SP - 2882-2896 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84876771480&partnerID=MN8TOARS KW - Interference channel KW - interference shaping KW - multihop KW - multiple-input-multiple-output (MIMO) ER - TY - JOUR TI - Cascaded orthogonal space-time block codes for wireless multi-hop relay networks T2 - Eurasip Journal on Wireless Communications and Networking AB - Distributed space–time block coding is a diversity technique to mitigate the effects of fading in multi-hop wireless networks, where multiple relay stages are used by a source to communicate with its destination. This article proposes a new distributed space–time block code called the cascaded orthogonal space–time block code (COSTBC) for the case where the source and destination are equipped with multiple antennas and each relay stage has one or more multiple antenna relays. Each relay stage is assumed to have receive channel state information (CSI) for all the channels from the source and all relays from previous stages to itself, while the destination is assumed to have receive CSI for all the channels. To construct the COSTBC, multiple orthogonal space–time block codes (OSTBCs) are used in cascade by the source and each relay stages. In the COSTBC, each relay stage separates the constellation symbols of the OSTBC sent by the preceding relay stage using its CSI, and then transmits another OSTBC to the next relay stage. COSTBCs are shown to achieve the maximum diversity gain in a multi-hop wireless network with linear decoding complexity thanks to the connection to OSTBCs. Several explicit constructions of COSTBCs are also provided, and their performance is simulated in different relay configurations. DA - 2013/// PY - 2013/// DO - 10.1186/1687-1499-2013-113 VL - 2013 IS - 1 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84878055233&partnerID=MN8TOARS ER - TY - JOUR TI - Antenna subset modulation for secure millimeter-wave wireless communication T2 - IEEE Transactions on Communications AB - The small carrier wavelength at millimeter-wave (mm-Wave) frequencies enables featuring a large number of co-located antennas. This paper exploits the potential of large antenna arrays to develop a low-complexity directional modulation technique, Antenna Subset Modulation (ASM), for point-to-point secure wireless communication. The main idea in ASM is to modulate the radiation pattern at the symbol rate by driving only a subset of antennas in the array. This results in a directional radiation pattern that projects a sharply defined constellation in the desired direction and expanded further randomized constellation in other directions. Two techniques for implementing ASM are proposed. The first technique selects an antenna subset randomly for every symbol. While randomly switching antenna subsets does not affect the symbol modulation for a desired receiver along the main direction, it effectively randomizes the amplitude and phase of the received symbol for an eavesdropper along a sidelobe. Using a simplified statistical model, an expression for the average uncoded symbol error rate (SER) is derived as a function of the observation angle. To overcome the problem of large sidelobes in random antenna subset switching, the second technique uses an optimized antenna subset selection procedure based on simulated annealing to achieve superior performance compared with random selection. Numerical comparisons of the SER performance and secrecy capacity of the proposed techniques against those of conventional array transmission are presented to highlight the potential of ASM. DA - 2013/// PY - 2013/// DO - 10.1109/TCOMM.2013.061013.120459 VL - 61 IS - 8 SP - 3231-3245 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84883296165&partnerID=MN8TOARS KW - Antenna subset modulation KW - directional modulation KW - secure millimeter-wave communication KW - secrecy capacity ER - TY - JOUR TI - Effects of channel aging in massive MIMO systems AU - Truong, K.T. AU - Heath, R.W. T2 - Journal of Communications and Networks AB - Multiple-input multiple-output (MIMO) communication may provide high spectral efficiency through the deployment of a very large number of antenna elements at the base stations. The gains from massive MIMO communication come from the use of multiuser MIMO on the uplink and downlink, but with a large excess of antennas at the base station compared to the number of served users. Initial work on massive MIMO did not fully address several practical issues associated with its deployment. This paper considers the impact of channel aging on the performance of massive MIMO systems. The effects of channel variation are characterized as a function of different system parameters assuming a simple model for the channel time variations at the transmitter. Channel prediction is proposed to overcome channel aging effects. The analytical results on aging show how capacity is lost due to time variation in the channel. Numerical results in a multiceli network show that massive MIMO works even with some channel variation and that channel prediction could partially overcome channel aging effects. DA - 2013/// PY - 2013/// DO - 10.1109/JCN.2013.000065 VL - 15 IS - 4 SP - 338-351 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84885409411&partnerID=MN8TOARS KW - Channel aging KW - channel prediction KW - large-scale antenna systems KW - massive multi-input multi-output (MIMO) KW - outdated channel state information (CSI) ER - TY - CONF TI - Coverage and area spectral efficiency in downlink random cellular networks with channel estimation error AU - Wu, Y. AU - McKay, M.R. AU - Heath, R.W. AB - We investigate the impact of channel estimation on the performance of downlink random cellular networks. First, we derive a new closed-form expression for the coverage probability under certain practical conditions. We show that the coverage probability is dependent on the user and base station (BS) densities solely through their ratio for arbitrary pilot-training length. Next, we derive the optimal pilot-training length that maximizes the area spectral efficiency (ASE) in several asymptotic regimes, and capture the dependence of this optimal length on the ratio between the user and BS densities. The ASE loss due to training is shown to be less significant in small cell networks with a larger base station density. C2 - 2013/// C3 - ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings DA - 2013/// DO - 10.1109/ICASSP.2013.6638492 SP - 4404-4408 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84890544304&partnerID=MN8TOARS ER - TY - CONF TI - Coverage analysis for millimeter wave cellular networks with blockage effects AB - Millimeter wave (mmWave) is promising for the fifth generation cellular systems. The sensitivity of mmWave signals to blockages, such as buildings in cities, however, makes the network performance hard to predict. Using concepts from stochastic geometry and random shape theory, this paper proposes an analytical framework to incorporate the blockage effects and evaluate the performance of mmWave cellular networks, in terms of coverage probability and achievable rate. Leveraging prior work on a blockage model, a stochastic characterization of the regions covered by line-of-sight (LOS) and non-LOS links is obtained, which allows different path loss laws to be applied to the LOS and non-LOS links, respectively. Based on the proposed framework, analytical expressions for the mmWave downlink coverage probability are derived, and then the network performance is examined. Numerical results show that millimeter wave (mmWave) networks can provide comparable coverage probability and much higher data rates than microwave networks. C2 - 2013/// C3 - 2013 IEEE Global Conference on Signal and Information Processing, GlobalSIP 2013 - Proceedings DA - 2013/// DO - 10.1109/GlobalSIP.2013.6736994 SP - 727-730 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84897678368&partnerID=MN8TOARS ER - TY - CONF TI - Degrees of freedom of completely-connected multi-way interference networks AU - Lee, N. AU - Heath, R.W. AB - This paper considers a fully-connected interference network with a relay in which multiple users equipped with a single antenna want to exchange multiple unicast messages with other users in the network by sharing the relay equipped with multiple antennas. For such a network, the optimal degrees of freedom (DoF) are derived by providing both converse and achievability. Further, considering single-antenna relays in the three-user fully-connected interference network, it is shown that three distributed relays with a single antenna is sufficient to achieve the optimal DoF. A major implication of the derived DoF results is that a relay with multiple antennas or distributed relays employing a single antenna increases the capacity scaling law of the multi-user interference network when multiple directional information flows are considered, even if the networks are fully-connected and all nodes operate in half-duplex. These results verify the intuition that the relay is useful in increasing DoF for the multi-way the interference network. C2 - 2013/// C3 - IEEE International Symposium on Information Theory - Proceedings DA - 2013/// DO - 10.1109/ISIT.2013.6620491 SP - 1571-1575 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84890357702&partnerID=MN8TOARS ER - TY - CONF TI - Antenna Subset Modulation for secure millimeter-wave wireless communication AU - Valliappan, N. AU - Heath, R.W. AU - Lozano, A. AB - This paper exploits the potential of large antenna arrays at millimeter-wave (mm-Wave) frequencies to develop a low-complexity directional modulation technique, Antenna Subset Modulation (ASM), for point-to-point secure wireless communication. The main idea in ASM is to modulate the radiation pattern at the symbol rate by driving only a subset of antennas in the array. This results in a directional radiation pattern that projects a sharply defined constellation in the desired direction and randomizes the constellation in other directions. To implement ASM, a simple antenna selection technique that selects an antenna subset randomly for every symbol is proposed. While randomly switching antenna subsets does not affect the symbol modulation for a desired receiver along the main direction, it effectively randomizes the amplitude and phase of the received symbol for an eavesdropper along a sidelobe. Statistical analysis and numerical examples are presented to highlight the superior performance and secrecy capacity achieved by ASM. C2 - 2013/// C3 - 2013 IEEE Globecom Workshops, GC Wkshps 2013 DA - 2013/// DO - 10.1109/GLOCOMW.2013.6825166 SP - 1258-1263 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84902985644&partnerID=MN8TOARS ER - TY - JOUR TI - A current perspective on distributed antenna systems for the downlink of cellular systems AU - Heath, R. AU - Peters, S. AU - Wang, Y. AU - Zhang, J. T2 - IEEE Communications Magazine AB - Providing uniformly high capacity in cellular systems is challenging due to fading, path loss, and interference. A partial solution to this problem is the deployment of distributed antenna systems, where transmission points are distributed throughout the cell using coax cable or fiber, instead of being centrally located on a single tower. This article reviews how distributed antenna systems are evolving to provide higher performance on the downlink in cellular systems. Research trends in distributed antennas for the downlink of cellular systems are described along with current progress on their integration into commercial wireless cellular standards. A key observation is that distributed antenna systems are tightly integrated into the cellular architecture, and incorporate physical layer technologies like MIMO communication and multiuser MIMO to provide higher data rates. DA - 2013/// PY - 2013/// DO - 10.1109/MCOM.2013.6495775 VL - 51 IS - 4 SP - 161-167 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84876279935&partnerID=MN8TOARS ER - TY - JOUR TI - Adaptive quantization on a grassmann-manifold for limited feedback beamforming systems AU - Schwarz, S. AU - Heath, R.W. AU - Rupp, M. T2 - IEEE Transactions on Signal Processing AB - In this paper we examine delay limited adaptive quantization on the Grassmann manifold of 1-dimensional subspaces in n-dimensional space. Due to strict delay limits, vector quantization over multiple time instants cannot be applied to exploit the temporal correlation of the source signal. Instead, a vector predictive quantizer is proposed that combines prediction and differential quantization algorithms to achieve an efficient quantization of the correlated Grassmannian source. The proposed predictor is based on adaptive finite impulse response filters to adjust to the temporal statistics of the source signal. It is shown that the prediction error in the tangent space associated with the Grassmann manifold behaves approximately Gaussian, provided its norm is sufficiently small. The proposed quantization algorithm is applied to channel state information quantization in multi-user beamforming wireless communication systems. Large throughput gains are demonstrated in comparison to memoryless quantization, due to reduced multi-user interference. DA - 2013/// PY - 2013/// DO - 10.1109/TSP.2013.2270466 VL - 61 IS - 18 SP - 4450-4462 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84883013264&partnerID=MN8TOARS KW - Adaptive quantization KW - channel state information KW - Grassmann manifold KW - limited feedback KW - LTE KW - multi-user MIMO KW - OFDMA KW - quantized feedback ER - TY - JOUR TI - A markov decision model for adaptive scheduling of stored scalable videos AU - Chen, C. AU - Heath, R.W. AU - Bovik, A.C. AU - De Veciana, G. T2 - IEEE Transactions on Circuits and Systems for Video Technology AB - We propose two scheduling algorithms that seek to optimize the quality of scalably coded videos that have been stored at a video server before transmission. The first scheduling algorithm is derived from a Markov decision process (MDP) formulation developed here. We model the dynamics of the channel as a Markov chain and reduce the problem of dynamic video scheduling to a tractable Markov decision problem over a finite-state space. Based on the MDP formulation, a near-optimal scheduling policy is computed that minimizes the mean square error. Using insights taken from the development of the optimal MDP-based scheduling policy, the second proposed scheduling algorithm is an online scheduling method that only requires easily measurable knowledge of the channel dynamics, and is thus viable in practice. Simulation results show that the performance of both scheduling algorithms is close to a performance upper bound also derived in this paper. DA - 2013/// PY - 2013/// DO - 10.1109/TCSVT.2013.2254896 VL - 23 IS - 6 SP - 1081-1095 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84878813576&partnerID=MN8TOARS KW - Scheduling algorithm KW - videos transport KW - wireless communication ER - TY - CONF TI - A dynamic system model of time-varying subjective quality of video streams over HTTP AB - Newly developed HTTP-based video streaming technology enables flexible rate-adaptation in varying channel conditions. The users' Quality of Experience (QoE) of rate-adaptive HTTP video streams, however, is not well understood. Therefore, designing QoE-optimized rate-adaptive video streaming algorithms remains a challenging task. An important aspect of understanding and modeling QoE is to be able to predict the up-to-the-moment subjective quality of video as it is played. We propose a dynamic system model to predict the time-varying subjective quality (TVSQ) of rate-adaptive videos that is transported over HTTP. For this purpose, we built a video database and measured TVSQ via a subjective study. A dynamic system model is developed using the database and the measured human data. We show that the proposed model can effectively predict the TVSQ of rate-adaptive videos in an online manner, which is necessary to be able to conduct QoE-optimized online rate-adaptation for HTTP-based video streaming. C2 - 2013/// C3 - ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings DA - 2013/// DO - 10.1109/ICASSP.2013.6638329 SP - 3602-3606 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84890462158&partnerID=MN8TOARS ER - TY - JOUR TI - A distributed algorithm using interference pricing for relay interference channels AU - Truong, K.T. AU - Heath, R.W. T2 - Eurasip Journal on Advances in Signal Processing AB - Relays in cellular systems are sensitive to interference. A good relay design will transmit in a way that avoids excess out-of-cell interference. This article proposes a two-step algorithm for relay design for the relay interference channel, which models a relay-based cellular system. The transmitters and relays are equipped with multiple antennas while the receivers are equipped with a single antenna. In the first step, we propose to apply existing single-hop strategies to design the transmission parameters of the transmitters. In the second step, we propose to modify the interference pricing approach to design the relays. Interference pricing is used to provide the relays with information on how interference impacts the end-to-end achievable rates. A new method is proposed to compute interference prices via an approximation of the end-to-end achievable rate to integrate information about the relationship of the parameters in the two hops to alleviate mismatch between the rates on two hops experienced by the direct application of prior algorithms, which are designed specifically for the single-hop interference channel. Simulations show that the proposed algorithm outperforms the other designs, including the naive approach of applying the single-hop interference pricing strategies on two hops. DA - 2013/// PY - 2013/// DO - 10.1186/1687-6180-2013-26 VL - 2013 IS - 1 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84879567396&partnerID=MN8TOARS ER - TY - CONF TI - Adaptive quantization on the Grassmann-manifold for limited feedback multi-user MIMO systems AU - Schwarz, S. AU - Heath, R.W. AU - Rupp, M. AB - We propose an adaptive quantization algorithm for subspace tracking on the Grassmann-manifold of p-dimensional subspaces in the n-dimensional Euclidean space. This quantization problem arises naturally in limited feedback based wireless communication systems, which apply precoding for interference cancellation and alignment. The proposed algorithm exploits the differential geometry associated with the Grassmann-manifold for efficient differential and predictive quantization. The algorithm is applied to channel state information quantization in a multi-user block-diagonalization based wireless communication system, demonstrating large throughput gains compared to memoryless quantization. C2 - 2013/// C3 - ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings DA - 2013/// DO - 10.1109/ICASSP.2013.6638617 SP - 5021-5025 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84890520684&partnerID=MN8TOARS ER - TY - CHAP TI - Simulation and Experimental Characterization of a Unified Memory Device with Two Floating-Gates AU - Di Spigna, Neil AU - Schinke, Daniel AU - Jayanti, Srikant AU - Misra, Veena AU - Franzon, Paul T2 - VLSI-SoC: From Algorithms to Circuits and System-on-Chip Design AB - The operation of a novel unified memory device using two floating-gates is described through experimental characterization of a fabricated proof-of-concept device and confirmed through simulation. The dynamic, nonvolatile, and concurrent modes of the device are described in detail. Simulations show that the device compares favorably to conventional memory devices. Applications enabled by this unified memory device are discussed, highlighting the dramatic impact this device could have on next generation memory architectures. PY - 2013/// DO - 10.1007/978-3-642-45073-0_12 SP - 217-233 OP - PB - Springer Berlin Heidelberg SN - 9783642450723 9783642450730 UR - http://dx.doi.org/10.1007/978-3-642-45073-0_12 DB - Crossref ER - TY - CHAP TI - Efficient GPU Implementation of the Integral Histogram AU - Poostchi, Mahdieh AU - Palaniappan, Kannappan AU - Bunyak, Filiz AU - Becchi, Michela AU - Seetharaman, Guna T2 - Computer Vision - ACCV 2012 Workshops AB - The integral histogram for images is an efficient preprocessing method for speeding up diverse computer vision algorithms including object detection, appearance-based tracking, recognition and segmentation. Our proposed Graphics Processing Unit (GPU) implementation uses parallel prefix sums on row and column histograms in a cross-weave scan with high GPU utilization and communication-aware data transfer between CPU and GPU memories. Two different data structures and communication models were evaluated. A 3-D array to store binned histograms for each pixel and an equivalent linearized 1-D array, each with distinctive data movement patterns. Using the 3-D array with many kernel invocations and low workload per kernel was inefficient, highlighting the necessity for careful mapping of sequential algorithms onto the GPU. The reorganized 1-D array with a single data transfer to the GPU with high GPU utilization, was 60 times faster than the CPU version for a 1K ×1K image reaching 49 fr/sec and 21 times faster for 512×512 images reaching 194 fr/sec. The integral histogram module is applied as part of the likelihood of features tracking (LOFT) system for video object tracking using fusion of multiple cues. PY - 2013/// DO - 10.1007/978-3-642-37410-4_23 SP - 266-278 OP - PB - Springer Berlin Heidelberg SN - 9783642374098 9783642374104 UR - http://dx.doi.org/10.1007/978-3-642-37410-4_23 DB - Crossref ER - TY - JOUR TI - Long-Range Smectic Coupling of Phase Separated Domains in Ternary Mixture Lipid Multilayers AU - Ma, Yicong AU - Tayebi, Lobat AU - Vashaee, Daryoosh AU - Chen, Gang AU - Parikh, Atul AU - Sinha, Sunil T2 - Biophysical Journal AB - Lipid multilayers serve as suitable and convenient bio-mimetic systems and are broadly used for studies of lipid membrane structure and function. It is known that many mixed lipid systems undergo phase separation as a function of temperature. Here we report that, in multilayers, the lateral phase separation in the bilayers is accompanied by long-range columnar order of the two phases along the normal to the bilayers arising from the coupling of two-dimensional intra-layer phase separation and inter-layer smectic ordering. Quantitative analysis of real-time dynamical experiments of confocal florescence microscopy reveal an interplay between intra-layer domain growth and inter-layer coupling, while X-ray reflectivity studies establish that the phase-separated domains are correlated normal to the lamellae over hundreds of bilayers. Through reconstruction of relative electron density profiles, XRR data also offer insight into differences in the domain structure on nm length scales. The microscopic understanding of two coexisting and domain-aligned multilamellar phases advanced by our experiments shed new light on the role of water in organizing membrane phases in stacked bilayers - a phenomenon of possible relevance to the mechanism of inter-layer lipid-lipid interactions in biological membranes. DA - 2013/1// PY - 2013/1// DO - 10.1016/j.bpj.2012.11.3268 VL - 104 IS - 2 SP - 588a J2 - Biophysical Journal LA - en OP - SN - 0006-3495 UR - http://dx.doi.org/10.1016/j.bpj.2012.11.3268 DB - Crossref ER - TY - JOUR TI - Bridgeless electrolytic capacitor-less valley-fill AC/DC converter for offline Twin-Bus light-emitting diode lighting application AU - Ma, Hongbo AU - Gu, Bin AU - Feng, Quanyuan AU - Lai, Jih-Sheng (Jason) AU - Zheng, Cong AU - Yu, Wensong T2 - IET Power Electronics AB - To match the key features of light-emitting diode (LED) lighting source and further save power, LED lighting driver also requires long life, while maintaining high efficiency, high power factor, pulse-width modulation dimming and low cost. However, a typical LED lighting driver has the following drawbacks: (i) utilise bulky electrolytic capacitor as storage capacitor with short lifetime; (ii) employ a low-frequency diode bridge as the rectifier cell; and (iii) engage multiple stages cascade structure for multiple LED strings. To overcome the aforementioned shortages, this study proposed a bridgeless electrolytic capacitor-less AC/DC converter for offline LED lighting application. In the proposed converter, the conventional diode rectified bridge is replaced by Totem-pole bridgeless configuration for reducing the number of semiconductors in the line-current path. Meanwhile, the valley-fill circuit is introduced to further reduce the capacitor size. As comparison to its counterpart, the proposed circuit requires only one quarter of the capacitor energy when considering the energy amount (CV2) as the capacitor sizing criterion. Furthermore, the isolation type of the studied circuit is compatible with Twin-Bus configuration for achieving higher overall system efficiency. Finally, the experimental results, taken from a laboratory prototype rated at 50 W, are presented to verify the effectiveness of the proposed converter. DA - 2013/7/1/ PY - 2013/7/1/ DO - 10.1049/IET-PEL.2012.0708 VL - 6 IS - 6 SP - 1132-1141 LA - en OP - SN - 1755-4535 1755-4543 UR - http://dx.doi.org/10.1049/IET-PEL.2012.0708 DB - Crossref ER - TY - JOUR TI - Ultrathin-barrier AlN/GaN heterostructures grown by rf plasma-assisted molecular beam epitaxy on freestanding GaN substrates AU - Storm, D.F. AU - Deen, D.A. AU - Katzer, D.S. AU - Meyer, D.J. AU - Binari, S.C. AU - Gougousi, T. AU - Paskova, T. AU - Preble, E.A. AU - Evans, K.R. AU - Smith, David J. T2 - Journal of Crystal Growth AB - We report the structural and electrical properties of ultrathin-barrier AlN/GaN heterostructures grown on freestanding GaN substrates by rf plasma-assisted molecular beam epitaxy. Structures with barrier thicknesses between 1.5 nm and 7.5 nm were grown and characterized. We observe that AlN/GaN structures with barriers of 3.0 nm exhibit the highest Hall mobility, approximately 1700 cm2/Vs. Furthermore, the Hall mobility is much diminished in heterostructures with AlN barriers thicker than 4.5 nm, coincident with the onset of strain relaxation. DA - 2013/10// PY - 2013/10// DO - 10.1016/J.JCRYSGRO.2013.05.029 VL - 380 SP - 14-17 J2 - Journal of Crystal Growth LA - en OP - SN - 0022-0248 UR - http://dx.doi.org/10.1016/J.JCRYSGRO.2013.05.029 DB - Crossref KW - Molecular beam epitaxy KW - Nitrides KW - Semiconducting III-V materials KW - High electron mobility transistors ER - TY - JOUR TI - Protein triggered fluorescence switching of near-infrared emitting nanoparticles for contrast-enhanced imaging AU - Jetty, Ragini AU - Bandera, Yuriy P. AU - Daniele, Michael A. AU - Hanor, David AU - Hung, Hsin-I. AU - Ramshesh, Venkat AU - Duperreault, Megan F. AU - Nieminen, Anna-Liisa AU - Lemasters, John J. AU - Foulger, Stephen H. T2 - Journal of Materials Chemistry B AB - Sub-100 nm colloidal particles which are surface-functionalized with multiple environmentally-sensitive moieties have the potential to combine imaging, early detection, and the treatment of cancer with a single type of long-circulating “nanodevice”. Deep tissue imaging is achievable through the development of particles which are surface-modified with fluorophores that operate in the near-infrared (NIR) spectrum and where the fluorophore's signal can be maximized by “turning-on” the fluorescence only in the targeted tissue. We present a general approach for the synthesis of NIR emitting nanoparticles that exhibit a protein triggered activation/deactivation of the emission. Dispersing the particles into an aqueous solution, such as phosphate buffered saline (PBS), resulted in an aggregation of the hydrophobic fluorophores and a cessation of emission. The emission can be reinstated, or activated, by the conversion of the surface-attached fluorophores from an aggregate to a monomeric species with the addition of an albumin. This activated probe can be deactivated and returned to a quenched state by a simple tryptic digestion of the albumin. The methodology for emission switching offers a path to maximize the signal from the typically weak quantum yield inherent in NIR fluorophores. DA - 2013/// PY - 2013/// DO - 10.1039/C3TB20681E VL - 1 IS - 36 SP - 4542 J2 - J. Mater. Chem. B LA - en OP - SN - 2050-750X 2050-7518 UR - http://dx.doi.org/10.1039/C3TB20681E DB - Crossref ER - TY - JOUR TI - Microfabrication: Rapid and Continuous Hydrodynamically Controlled Fabrication of Biohybrid Microfibers (Adv. Funct. Mater. 6/2013) AU - Daniele, Michael A. AU - North, Stella H. AU - Naciri, Jawad AU - Howell, Peter B. AU - Foulger, Stephen H. AU - Ligler, Frances S. AU - Adams, André A. T2 - Advanced Functional Materials AB - Hydrodynamic shaping is used as a versatile method for the in situ encapsulation of bacteria in microfibers. On page 698 André A. Adams and co-workers report the production of biohybrid microfibers by hydrodynamic shaping of a cell-containing pre-gel and inert sheath fluid, subsequently polymerized via photoinitiation. DA - 2013/2/11/ PY - 2013/2/11/ DO - 10.1002/ADFM.201370031 VL - 23 IS - 6 SP - 697-697 J2 - Adv. Funct. Mater. LA - en OP - SN - 1616-301X UR - http://dx.doi.org/10.1002/ADFM.201370031 DB - Crossref ER - TY - JOUR TI - Microstructures: 3D Printing of Free Standing Liquid Metal Microstructures (Adv. Mater. 36/2013) AU - Ladd, Collin AU - So, Ju-Hee AU - Muth, John AU - Dickey, Michael D. T2 - Advanced Materials AB - A direct-write method for writing 3D freestanding, liquid-metal microcomponents from the binary eutectic alloy of gallium and indium at room temperature is described in work by Prof. Michael Dickey, Prof. John Muth, and co-workers on page 5081. The smallest components fabricated by the technique are of the order of 10 μm in size, and smaller–sized structures may be possible. The technique allows the formation of mechanically stable structures and is capable of printing wires, spheres, arches, and interconnects. DA - 2013/9// PY - 2013/9// DO - 10.1002/ADMA.201370225 VL - 25 IS - 36 SP - 4953-4953 J2 - Adv. Mater. LA - en OP - SN - 0935-9648 UR - http://dx.doi.org/10.1002/ADMA.201370225 DB - Crossref ER - TY - CONF TI - Transient overvoltage rating and BIL of the transformerless intelligent power substation AU - Carr, J. AU - Wang, Z. AU - Bhattacharya, S. AU - Patel, D. AB - The overvoltage impulse protection of the transformerless intelligent power substation (TIPS) is explored in this paper. Two failure mechanisms, excess current causing thermal failure of the devices and excess component to ground voltage causing failure of the insulation, are considered. A variety of grounding, protection, and filter circuits were analyzed. It was found that the current and voltage do not exceed the limits of safety if the midpoint of the TIPS DC bus capacitor bank is grounded. A recommended protection scheme was proposed based on these results, consisting of a MOV at the input to the TIPS to divert surge currents and a reactive connection to ground to limit the device currents without resulting in a large voltage between the midpoint and ground. A large voltage was found to fall across the input filter, which should be designed with sufficient BIL to withstand this voltage. C2 - 2013/// C3 - IEEE Power and Energy Society General Meeting DA - 2013/// DO - 10.1109/PESMG.2013.6672424 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84893178752&partnerID=MN8TOARS ER - TY - CONF TI - Vehicle-to-grid scheme based on inductive power transfer for advanced distribution automation AU - Javanbakht, P. AU - Mohagheghi, S. AU - Parkhideh, B. AU - Dutta, S. AU - Chattopadhyay, R. AU - Bhattacharya, S. AB - The latest technological advances in battery and converter technology, along with government mandates on energy independence and resilience, are expected to pave the way for higher deployment of plug-in electric vehicles (PEV) in the transportation fleet. These vehicles, when equipped with bidirectional energy transfer capabilities, can function as mobile energy resources and can be utilized in a Vehicle-to-Grid (V2G) scheme in order to temporarily inject energy back into the power grid, thereby functioning as energy storage systems. The forecasted increase in the number of these dispersed vehicles can potentially turn them into a significant energy resource that can be used by the utilities for ancillary services or even for long-term integration with the power system. The notion of energy injection through V2G schemes has been conceptually investigated in the literature for charging stations or single residential charging devices. In all these case studies, the vehicle needs to be parked, and a connection be established by the driver, for the duration of the battery charge or discharge. This paper looks into V2G through the employment of contactless means for energy transfer, namely inductive power transfer (IPT). IPT adds flexibility to V2G schemes by allowing energy exchange with vehicles in motion or when the driver is not physically present to establish a connection. The performance of IPT for bidirectional power flow has been shown through simulation as well as experimental results. Also, statistical analysis are provided that demonstrate the large scale integration of these vehicles into the grid. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 DA - 2013/// DO - 10.1109/ECCE.2013.6647127 SP - 3250-3257 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891073969&partnerID=MN8TOARS ER - TY - CONF TI - Ultra high voltage IGBTs in 4H-SiC AU - Ryu, S. AU - Capell, C. AU - Jonas, C. AU - Lemma, Y. AU - O’Loughlin, M. AU - Clayton, J. AU - Van Brunt, E. AU - Lam, K. AU - Richmond, J. AU - Burk, A. AU - Grider, D. AU - Allen, S. AU - Palmour, J. AU - Agarwal, A. AU - Kadavelugu, A. AU - Bhattacharya, S. AB - A 1 cm × 1 cm 4H-SiC N-IGBT exhibited a blocking voltage of 20.7 kV with a leakage current of 140 μA, which represents the highest blocking voltage reported from an MOS semiconductor power switching device to date. The device showed a V F of 6.4 V at an I C of 20 A, and a differential R on,sp of 28 mΩ-cm 2 . Temperature insensitive on-state characteristics were demonstrated. Switching measurements with a supply voltage of 8 kV were performed, and a turn-off time of 720 ns and a turn-off loss of 5.4 mJ were measured at 25°C, for a 8.4 mm × 8.4 mm device with 140 μm drift layer and 5 μm Field Stop buffer layer. It was demonstrated that the charge injection from the backside can be controlled by varying the thickness of the Field-Stop buffer layer. A 55 kW, 1.7 kV to 7 kV boost converter operating at 5 kHz was demonstrated using the 4H-SiC N-IGBT, and an efficiency value of 97.8% was reported. C2 - 2013/// C3 - 1st IEEE Workshop on Wide Bandgap Power Devices and Applications, WiPDA 2013 - Proceedings DA - 2013/// DO - 10.1109/WiPDA.2013.6695557 SP - 36-39 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84893540558&partnerID=MN8TOARS ER - TY - CONF TI - Performance evaluation and control of modular multilevel converter under system fault conditions AU - Narwal, A. AU - Kim, S. AU - Yousefpoor, N. AU - Bhattacharya, S. AB - For industrial applications requiring medium and high-power supplies modular multilevel converter (MMC) based voltage source converters (VSC) offer advantages over traditional VSCs. These include achievement of higher voltage levels with utilization of lower voltage power semiconductor devices. The control structure of MMC for fault operating condition is proposed in this paper, and dynamic performance of the MMC based on the proposed control structures is further investigated in PSCAD/EMTDC environment. Real Time Digital Simulator (RTDS) results are also presented to verify the controller performance under normal and fault operating conditions. C2 - 2013/// C3 - IECON Proceedings (Industrial Electronics Conference) DA - 2013/// DO - 10.1109/IECON.2013.6700171 SP - 6299-6304 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84893562203&partnerID=MN8TOARS ER - TY - CONF TI - Power dispatch strategy in microgrid integrated with solid state transformer AU - Yu, J. AU - Wu, Z. AU - Bhattacharya, S. AB - The Future Renewable Electric Energy Delivery and Management (FREEDM) System smoothly integrate and manage a variety of controllable loads, DRER (distributed renewable energy resource) and DESD (distributed energy storage device) through the revolutionary solid state transformer (SST). The distributed grid intelligence integrated with the SST facilitates the optimal power dispatch for a residential distribution system. This paper presents a mathematical formulation to determine the optimal power dispatch strategy in order to minimize the operational cost as well as the emission pollution. In this paper, a multi-objective immune particle swarm optimization (MIPSO) based computational intelligence approach is adopted to find the Pareto solution. Several numerical simulation studies demonstrate the effectiveness and accuracy of the proposed power dispatch strategy in a residential distribution system. More analysis indicates that the fitting degree between load profile and output of renewable energy generators (such as PV cells) is an identifier, which would be applied as a reference to make power exchange schedule between micro grid and utility grid. C2 - 2013/// C3 - IEEE Power and Energy Society General Meeting DA - 2013/// DO - 10.1109/PESMG.2013.6672265 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84893156032&partnerID=MN8TOARS ER - TY - CONF TI - Electric arc furnace compensation using LaGrange minimization AU - White, L.W. AU - Battacharya, S. AB - Electric Arc Furnaces (EAFs) are generally moderated by ancillary compensation to remove the time-varying reactive component from the utility load; the compensation strategy is fundamentally based upon an application of the Clarke transformation which does not use the zero component; as a result, the highly unbalanced EAF currents have a component that remains uncompensated. The present work uses LaGrange minimization to determine inactive currents that are then used to direct a Static Compensator (STATCOM). Where there is significant unbalance, the technique results in reduced line currents and improvements to the magnitude and stability of power delivered to the arc. The real power delivered by the STATCOM under the LaGrange technique is zero; where there is no line imbalance the results are identical to those produced by use of the Clarke transformation. The LaGrange scheme is compared directly to the Clarke transformation-based compensation scheme by the use of a PSCad model. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 DA - 2013/// DO - 10.1109/ECCE.2013.6646987 SP - 2253-2256 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891091177&partnerID=MN8TOARS ER - TY - CONF TI - Overloading and overvoltage evaluation of a Transformerless Intelligent Power Substation AU - Carr, J. AU - Wang, Z. AU - Bhattacharya, S. AU - Hatua, K. AU - Madhusoodhanan, S. AB - The Transformerless Intelligent Power Substation (TIPS) has been proposed as a replacement for the traditional distribution transformer in future power grids due to its improved voltage and power quality regulation capabilities. This system provides several benefits, but the use of power electronic devices imposes limitations on the TIPS's overloading and temporary overvoltage withstand capabilities. The overloading limits and the behavior of the TIPS under the temporary overvoltage impulse are examined in this paper, laying the groundwork to develop methods to mitigate these limitations. C2 - 2013/// C3 - IEEE Power and Energy Society General Meeting DA - 2013/// DO - 10.1109/PESMG.2013.6672840 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84893191278&partnerID=MN8TOARS ER - TY - CONF TI - Investigation of enhancement in pool boiling heat transfer of a binary temperature sensitive magnetic fluid AU - Karimi-Moghaddam, G. AU - Gould, R.D. AU - Bhattacharya, Subhashish AB - In this paper, the performance of pool boiling heat transfer using a binary temperature sensitive magnetic fluid in the presence of a non-uniform magnetic field is investigated numerically. By using a binary magnetic fluid, enhanced boiling heat transfer is obtained by thermomagnetic convection without deterioration of properties of the fluid. This work is aimed at gaining a qualitative understanding the magnetic field effects on boiling heat transfer enhancement of magnetic fluids. In order to accomplish this, the boiling process and the effects of position of the external magnetic field on flow pattern and heat transfer are investigated in a 2D rectangular domain using COMSOL Multiphysics simulation software. Finally, the boiling curves for a binary temperature sensitive magnetic fluid and its base fluid (without magnetic particles) are compared for various applied heat flux magnitudes. C2 - 2013/// C3 - ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) DA - 2013/// DO - 10.1115/IMECE2013-66308 VL - 8 B UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84903487625&partnerID=MN8TOARS ER - TY - CONF TI - Integration of multi-terminal DC to DC hub architecture with solid state transformer for renewable energy integration AU - Dutta, S. AU - Bhattacharya, S.R.S. AB - In this paper an alternate to the DC to DC stage of a single phase solid state transformer is proposed comprising of a Multi limb core (MLC) transformer. Further two important operation conditions of a single phase solid state transformer (SST) with cascaded series connected converter topology is studied: soft startup from auxiliary DC source to avoid any inrush current on the DC capacitors and the control interaction between the cascaded converters under severe voltage sag. The voltage balance in the cascaded structure under extreme voltage sag is the primary concern and a solution is proposed. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 DA - 2013/// DO - 10.1109/ECCE.2013.6647345 SP - 4793-4800 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891084431&partnerID=MN8TOARS ER - TY - CONF TI - A reliable photovoltaic integrated UPS system with modified maximum power point tracking (MPPT) algorithm AU - Juvekar, S. AU - Brandmeyer, J. AU - Compton, B. AU - Liu, Y. AU - Bhattacharya, S. AB - This paper presents a new approach to integrate a fluctuating renewable power source like PV array into a conventional UPS by only modifying existing UPS firmware without needing any additional power converter. The paper also presents PV-UPS integrated system simulation developed using MATLAB/SIMULINK and hardware testing results for a 550kVA UPS interfaced with 30kW of solar panels. Proposed solution is modular, scalable, can work together with existing conventional UPSs on site or even upgrade them to interface PV power and still be as reliable as a conventional UPS. The proposed solution will allow utilities to do peak shaving and will help customers to reduce energy bills and extend battery time while providing same excellent power quality as conventional UPS. Unlike PV inverters which are forced to go offline during utility outage, proposed system shall continue to support critical loads during outages which is especially important for areas where utility interruptions are common. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 DA - 2013/// DO - 10.1109/ECCE.2013.6647306 SP - 4526-4531 PB - IEEE UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891135659&partnerID=MN8TOARS ER - TY - CONF TI - A flexible low-voltage ride-through operation for the distributed generation converters AU - Chen, H.-C. AU - Lee, C.-T. AU - Cheng, P.-T. AU - Teodorescu, R. AU - Blaabjerg, F. AU - Bhattacharya, S. AB - With more and more distributed energy resources (DERs) are installed in the utility grid, the utility requires the DER generation system to remain grid-connected and injects reactive and active power to support grid voltage during voltage sags. In this paper, a positive- and negative-sequence current injection method is proposed to meet the low-voltage ride through (LVRT) requirement. The proposed method predefined a current constraint to avoid the overcurrent during the LVRT operation and adjust the positive-sequence reactive current to reduce the DC-bus voltage ripple. Comparisons of the proposed method and other LVRT techniques are also presented. C2 - 2013/// C3 - Proceedings of the International Conference on Power Electronics and Drive Systems DA - 2013/// DO - 10.1109/PEDS.2013.6527230 SP - 1354-1359 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84880729315&partnerID=MN8TOARS ER - TY - CONF TI - A non-dimensional analysis to characterize thermomagnetic convection of a temperature sensitive magnetic fluid in a flow loop AU - Karimi-Moghaddam, G. AU - Gould, R.D. AU - Bhattacharya, Subhashish AB - This paper presents results from theoretical and numerical studies of a single-phase, temperature sensitive magnetic fluid operating under steady-state laminar flow conditions in a partially heated thermomagnetic circulation loop under the influence of an external magnetic field (created by a solenoid). A one-dimensional theoretical model has been developed using scaling arguments to characterize thermomagnetic circulation in this loop in terms of the geometric length scales, magnetic fluid properties, and strength of the imposed magnetic field. In parallel to this theoretical analysis, supporting numerical simulations using COMSOL Multiphysics simulation software have been undertaken to obtain data for use in this 1D model. A correlation for the non-dimensional heat transfer (Nusselt number) as a function of the appropriate magnetic Rayleigh number and a correlation for the mass flow rate based on the system’s properties are developed. C2 - 2013/// C3 - ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) DA - 2013/// DO - 10.1115/IMECE2013-66313 VL - 8 B UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84903451690&partnerID=MN8TOARS ER - TY - CONF TI - Channel-Adaptive Spectrum Detection and Sensing Strategy for Cognitive Radio Ad-Hoc Networks AU - Lu, Yuan AU - Duel-Hallen, A. AB - In Cognitive Radio (CR) networks, multiple secondary network users (SUs) attempt to communicate over wide potential spectrum without causing significant interference to the Primary Users (PUs). A spectrum sensing algorithm is a critical component of any sensing strategy. Performance of conventional spectrum detection methods is severely limited when the average SNR of the fading channel between the PU transmitter and the SU sensor is low. Advanced detection techniques only partially remedy this problem. Cooperative sensing can combat channel fading, but requires a large number of cooperating SUs and/or diversity branches. A key limitation of conventional approaches is that the sensing threshold is determined from the miss detection rate averaged over the fading distribution. In this paper, the threshold is adapted to the instantaneous PU-to-SU Channel State Information (CSI) under the prescribed collision probability constraint, and a novel sensing strategy design is proposed for an overlay CR ad hoc network where the instantaneous false alarm probability is incorporated into the belief update and the reward computation. It is demonstrated that the proposed sensing approach improves SU confidence, randomizes sensing decisions, and significantly improves SU network throughput while satisfying the collision probability constraint to the PUs in the low average PU-to-SU SNR region. Moreover, the proposed adaptive sensing strategy is robust to mismatched and correlated fading CSI. In addition, threshold adaptation at a single SU sensor outperforms conventional cooperative sensing unless the number of cooperating SUs is very large. Finally, joint adaptation to PU channel gain and SU link CSI is proposed to further improve CR throughput and reduce SU collisions. C2 - 2013/// C3 - 2013 51st Annual Allerton Conference on Communication, Control, and Computing (Allerton) CY - Piscataway, NJ, USA DA - 2013/// DO - 10.1109/Allerton.2013.6736692 SP - 1408 - 14 UR - http://dx.doi.org/10.1109/Allerton.2013.6736692 ER - TY - CONF TI - A Generalized Model using Genetic Algorithm for Optimization of Material Gain of the Active layer of a MQW Edge Emitting Laser with Unequal Well Width AB - In this work, a computational model for optimization of material gain of the active region of a multiple quantum well (MQW) edge emitting laser (EEL) using genetic algorithm has been developed. Through this optimization procedure, the values of the width of quantum wells (QW), width of barriers, lattice temperature, injection carrier density and number of QWs which are related to material gain of the active region are optimized for optimizing the design of a MQW EEL. For the above mentioned optimization the numerical simulation of the optical gain expression of MQW EEL along with the solution of the Schrodinger's equation has been performed using MATLAB. The developed optimization based design technique has been applied for the design of (i) a 1550nm In 0.72 Ga 0.28 As 0.82 P 0.18 / In 0.42 Ga 0.58 As 0.82 P 0.18 MQW EEL having 3 QWs and also (ii) for a 1550nm In 0.72 Ga 0.28 As 0.82 P 0.18 /In 0.42 Ga 0.58 As 0.82 P 0.18 MQW EEL having 5 QWs for testing the validity. The computation indicates clearly that the optimization based computational model works well and can be easily used for the design of MQW EELs. C2 - 2013/// C3 - International Conference on Electrical Information and Communication Technology (EICT) DA - 2013/// DO - 10.1109/EICT.2014.6777814 UR - https://publons.com/publon/30967577/ ER - TY - CHAP TI - Activity Video Analysis via Operator-Based Local Embedding AU - Bian, Xiao AU - Krim, Hamid T2 - Lecture Notes in Computer Science AB - High dimensional data sequences, such as video clips, can be modeled as trajectories in a high dimensional space, and usually exhibit a low dimensional structure intrinsic to each distinct class of data sequence [1]. In this paper, we proposed a novel geometric framework to investigate the temporal relations as well as spatial features in a video sequence. Important visual features are preserved by mapping a high dimensional video sequence to operators in a circulant operator space (image operator space). The corresponding operator sequence is subsequently embedded into a low dimensional space, in which the temporal dynamics of each sequence is well preserved. In addition, an algorithm for human activity video classification is implemented by employing Markov models in the low dimensional embedding space, and illustrating examples and classification performance are presented. PY - 2013/// DO - 10.1007/978-3-642-40020-9_95 SP - 845-852 OP - PB - Springer Berlin Heidelberg SN - 9783642400193 9783642400209 UR - http://dx.doi.org/10.1007/978-3-642-40020-9_95 DB - Crossref ER - TY - CHAP TI - A Subspace Learning of Dynamics on a Shape Manifold: A Generative Modeling Approach AU - Yi, Sheng AU - Krim, Hamid T2 - Lecture Notes in Computer Science AB - In this paper, we propose a novel subspace learning of shape dynamics. In comparison with the previous works, our method is invertible and better characterises the nonlinear geometry of a shape manifold while being computationally more efficient. In this work, with a parallel moving frame on a shape manifold, each path of shape dynamics is uniquely represented in a subspace spanned by the moving frame, given an initial condition (the starting point and the starting frame). Given the parallelism of the frame and ensured by a Levi-Civita connection, and a path on a shape manifold, the parallel moving frame along the path is uniquely determined up to the choice of the starting frame. PY - 2013/// DO - 10.1007/978-3-642-40020-9_8 SP - 84-91 OP - PB - Springer Berlin Heidelberg SN - 9783642400193 9783642400209 UR - http://dx.doi.org/10.1007/978-3-642-40020-9_8 DB - Crossref ER - TY - CHAP TI - Towards Minimal Barcodes AU - González-Díaz, Rocío AU - Jiménez, María-José AU - Krim, Hamid T2 - Graph-Based Representations in Pattern Recognition AB - In the setting of persistent homology computation, a useful tool is the persistence barcode representation in which pairs of birth and death times of homology classes are encoded in the form of intervals. Starting from a polyhedral complex K (an object subdivided into cells which are polytopes) and an initial order of the set of vertices, we are concerned with the general problem of searching for filters (an order of the rest of the cells) that provide a minimal barcode representation in the sense of having minimal number of “k-significant” intervals, which correspond to homology classes with life-times longer than a fixed number k. As a first step, in this paper we provide an algorithm for computing such a filter for k = 1 on the Hasse diagram of the poset of faces of K. PY - 2013/// DO - 10.1007/978-3-642-38221-5_20 SP - 184-193 OP - PB - Springer Berlin Heidelberg SN - 9783642382208 9783642382215 UR - http://dx.doi.org/10.1007/978-3-642-38221-5_20 DB - Crossref ER - TY - CHAP TI - Optimal Operator Space Pursuit: A Framework for Video Sequence Data Analysis AU - Bian, Xiao AU - Krim, Hamid T2 - Computer Vision – ACCV 2012 AB - High dimensional data sequences, such as video clips, can be modeled as trajectories in a high dimensional space and, and usually exhibit a low dimensional structure intrinsic to each distinct class of data sequence [1]. In this paper, we exploit a fibre bundle formalism to model various realizations of each trajectory, and characterize these high dimensional data sequences by an optimal operator subspace. Each operator is calculated as a matched filter corresponding to a standard Gaussian output with the data as input. The low dimensional structure intrinsic to the data is further explored, by minimizing the dimension of the operator space under data driven constraints. The dimension minimization problem is reformulated as a convex nuclear norm minimization problem, and an associated algorithm is proposed. Moreover, a fast method with superior performance for video based human activity classification is implemented by searching for an optimal operator space and adapted to the data. Illustrating examples demonstrating the performance of this approach are presented. PY - 2013/// DO - 10.1007/978-3-642-37444-9_59 SP - 760-769 OP - PB - Springer Berlin Heidelberg SN - 9783642374432 9783642374449 UR - http://dx.doi.org/10.1007/978-3-642-37444-9_59 DB - Crossref ER - TY - CONF TI - A Unified View of Non-monotonic Core Selection and Application Steering in Heterogeneous Chip Multiprocessors AU - Navada, S. AU - Choudhary, N.K. AU - Wadhavkar, S.V. AU - Rotenberg, E. C2 - 2013/9// C3 - Proceedings of the 22nd IEEE/ACM International Conference on Parallel Architectures and Compilation Techniques (PACT-22) DA - 2013/9// SP - 133–144 ER - TY - JOUR TI - HMM-Based Malicious User Detection for Robust Collaborative Spectrum Sensing AU - He, Xiaofan AU - Dai, Huaiyu AU - Ning, Peng T2 - IEEE Journal on Selected Areas in Communications AB - Collaborative spectrum sensing improves the spectrum state estimation accuracy but is vulnerable to the potential attacks from malicious secondary cognitive radio (CR) users, and thus raises security concerns. One promising malicious user detection method is to identify their abnormal statistical spectrum sensing behaviors. From this angle, two hidden Markov models (HMMs) corresponding to honest and malicious users respectively are adopted in this paper to characterize their different sensing behaviors, and malicious user detection is achieved via detecting the difference in the corresponding HMM parameters. To obtain the HMM estimates, an effective inference algorithm that can simultaneously estimate two HMMs without requiring separated training sequences is also developed. By using these estimates, high malicious user detection accuracy can be achieved at the fusion center, leading to more robust and reliable collaborative spectrum sensing performance (substantially enlarged operational regions) in the presence of malicious users, as compared to the baseline approaches. Different fusion methods are also discussed and compared. DA - 2013/11// PY - 2013/11// DO - 10.1109/jsac.2013.131119 VL - 31 IS - 11 SP - 2196-2208 J2 - IEEE J. Select. Areas Commun. OP - SN - 0733-8716 UR - http://dx.doi.org/10.1109/jsac.2013.131119 DB - Crossref KW - Cognitive radio network KW - security KW - collaborative spectrum sensing KW - malicious user detection KW - Byzantine attacks KW - HMM ER - TY - JOUR TI - Structured Variational Methods for Distributed Inference in Networked Systems: Design and Analysis AU - Dai, Huaiyu AU - Zhang, Yanbing AU - Liu, Juan T2 - IEEE Transactions on Signal Processing AB - In this paper, a variational message passing framework is proposed for distributed inference in networked systems. Based on this framework, structured variational methods are explored to take advantage of both the simplicity of variational approximation (for inter-cluster processing) and the quality of more accurate inference (for intra-cluster processing). To investigate the convergence performance of our inference approach, we distinguish the inter- and intra-cluster inference algorithms as vertex and edge processes, respectively. Based on an analysis on the intracluster inference procedure, the overall performance of structured variational methods, modeled as a mixed vertex-edge process, is quantitatively characterized via a coupling approach. The tradeoff between performance and complexity of this inference approach is also addressed. DA - 2013/8// PY - 2013/8// DO - 10.1109/tsp.2013.2264463 VL - 61 IS - 15 SP - 3827-3839 J2 - IEEE Trans. Signal Process. OP - SN - 1053-587X 1941-0476 UR - http://dx.doi.org/10.1109/tsp.2013.2264463 DB - Crossref KW - Convergence analysis KW - distributed inference KW - Markov chain KW - variational methods ER - TY - JOUR TI - A-DFA AU - Becchi, Michela AU - Crowley, Patrick T2 - ACM Transactions on Architecture and Code Optimization AB - Modern network intrusion detection systems need to perform regular expression matching at line rate in order to detect the occurrence of critical patterns in packet payloads. While Deterministic Finite Automata (DFAs) allow this operation to be performed in linear time, they may exhibit prohibitive memory requirements. Kumar et al. [2006a] have proposed Delayed Input DFAs (D2FAs), which provide a trade-off between the memory requirements of the compressed DFA and the number of states visited for each character processed, which in turn affects the memory bandwidth required to evaluate regular expressions. In this article we introduce Amortized time − bandwidth overhead DFAs ( A − DFAs ), a general compression technique that results in at most N ( k + 1)/ k state traversals when processing a string of length N , k being a positive integer. In comparison to the D2FA approach, our technique achieves comparable levels of compression with lower provable bounds on memory bandwidth (or greater compression for a given bandwidth bound). Moreover, the A-DFA algorithm has lower complexity, can be applied during DFA creation, and is suitable for scenarios where a compressed DFA needs to be dynamically built or updated. Finally, we show how to combine A-DFA with alphabet reduction and multistride DFAs, two techniques aimed at reducing the memory space and bandwidth requirement of DFAs, and discuss memory encoding schemes suitable for A-DFAs. DA - 2013/4/1/ PY - 2013/4/1/ DO - 10.1145/2445572.2445576 VL - 10 IS - 1 SP - 1-26 J2 - TACO LA - en OP - SN - 1544-3566 UR - http://dx.doi.org/10.1145/2445572.2445576 DB - Crossref KW - Algorithms KW - Design KW - Performance KW - Security KW - Deep packet inspection KW - regular expressions KW - deterministic finite automata KW - memory compression ER - TY - JOUR TI - Scheduling concurrent applications on a cluster of CPU–GPU nodes AU - Ravi, Vignesh T. AU - Becchi, Michela AU - Jiang, Wei AU - Agrawal, Gagan AU - Chakradhar, Srimat T2 - Future Generation Computer Systems AB - Heterogeneous architectures comprising a multi-core CPU and many-core GPU(s) are increasingly being used within cluster and cloud environments. In this paper, we study the problem of optimizing the overall throughput of a set of applications deployed on a cluster of such heterogeneous nodes. We consider two different scheduling formulations. In the first formulation, we consider jobs that can be executed on either the GPU or the CPU of a single node. In the second formulation, we consider jobs that can be executed on the CPU, GPU, or both, of any number of nodes in the system. We have developed scheduling schemes addressing both of the problems. In our evaluation, we first show that the schemes proposed for first formulation outperform a blind round-robin scheduler and approximate the performances of an ideal scheduler that involves an impractical exhaustive exploration of all possible schedules. Next, we show that the scheme proposed for the second formulation outperforms the best of existing schemes for heterogeneous clusters, TORQUE and MCT, by up to 42%. Additionally, we evaluate the robustness of our proposed scheduling policies under inaccurate inputs to account for real execution scenarios. We show that, with up to 20% of inaccuracy in the input, the degradation in performance is marginal (less than 7%) on the average. DA - 2013/10// PY - 2013/10// DO - 10.1016/j.future.2013.06.002 VL - 29 IS - 8 SP - 2262-2271 J2 - Future Generation Computer Systems LA - en OP - SN - 0167-739X UR - http://dx.doi.org/10.1016/j.future.2013.06.002 DB - Crossref KW - Scheduling KW - CPU-GPU systems ER - TY - JOUR TI - Diet Alters Both the Structure and Taxonomy of the Ovine Gut Microbial Ecosystem AU - Ellison, M. J. AU - Conant, G. C. AU - Cockrum, R. R. AU - Austin, K. J. AU - Truong, H. AU - Becchi, M. AU - Lamberson, W. R. AU - Cammack, K. M. T2 - DNA Research AB - We surveyed the ruminal metagenomes of 16 sheep under two different diets using Illumina pair-end DNA sequencing of raw microbial DNA extracted from rumen samples. The resulting sequence data were bioinformatically mapped to known prokaryotic 16S rDNA sequences to identify the taxa present in the samples and then analysed for the presence of potentially new taxa. Strikingly, the majority of the microbial individuals found did not map to known taxa from 16S sequence databases. We used a novel statistical modelling approach to compare the taxonomic distributions between animals fed a forage-based diet and those fed concentrated grains. With this model, we found significant differences between the two groups both in the dominant taxa present in the rumen and in the overall shape of the taxa abundance curves. In general, forage-fed animals have a more diverse microbial ecosystem, whereas the concentrate-fed animals have ruminal systems more heavily dominated by a few taxa. As expected, organisms from methanogenic groups are more prevalent in forage-fed animals. Finally, all of these differences appear to be grounded in an underlying common input of new microbial individuals into the rumen environment, with common organisms from one feed group being present in the other, but at much lower abundance. DA - 2013/10/29/ PY - 2013/10/29/ DO - 10.1093/dnares/dst044 VL - 21 IS - 2 SP - 115-125 J2 - DNA Research LA - en OP - SN - 1340-2838 1756-1663 UR - http://dx.doi.org/10.1093/dnares/dst044 DB - Crossref KW - Ovis aries KW - microbiome KW - 16S subunit ER - TY - CHAP TI - Nano Bulk Thermoelectrics: Concepts, Techniques, and Modeling AU - Satyala, Nikhil AU - Norouzzadeh, Payam AU - Vashaee, Daryoosh T2 - Lecture Notes in Nanoscale Science and Technology AB - The beneficial effects of nanostructured material systems have provided a significant momentum to accomplish high-efficiency thermoelectric materials for power generation and cooling applications. The quantum size effects have been widely explored in order to shrink the contribution of lattice thermal conductivity of the thermoelectric systems, thereby enhancing the overall figure-of-merit. Modifying the nanoscale level structural features and the creation of additional phonon scattering sites in the form of grain boundary interfaces became the basis for fabrication of nanostructured materials. The requirement of specific physical features in nanostructured thermoelectrics also brought a variety of changes to the fabrication processes. In this chapter, we review some of the prominent techniques for fabrication of such nanostructured material systems. An overview of the concepts and techniques for theoretical modeling of the charge carrier and phonon transport mechanisms in the interfacial regions is presented. Further, the constructive effects of nanostructuring in thermoelectric materials are discussed based on a theoretical approach via Boltzmann transport equation under the relaxation time approximation. The calculations are used to demonstrate the advantages and disadvantages of nanoscale effects in the well-known material systems of Si x Ge1−x and Mg2Si. PY - 2013/10/28/ DO - 10.1007/978-3-319-02012-9_4 SP - 141-183 OP - PB - Springer International Publishing SN - 9783319020112 9783319020129 UR - http://dx.doi.org/10.1007/978-3-319-02012-9_4 DB - Crossref ER - TY - JOUR TI - Multilayer zirconium titanate thin films prepared by a sol–gel deposition method AU - Salahinejad, E. AU - Hadianfard, M.J. AU - Macdonald, D.D. AU - Mozafari, M. AU - Vashaee, D. AU - Tayebi, L. T2 - Ceramics International AB - Zirconium titanate multilayer thin films were prepared by an aqueous particulate sol–gel process followed by spin coating. The obtained structures were studied by transmission electron microscope, scanning electron microscope, atomic force microscope, and spectroscopic reflection analyses. According to the results, sound thin films up to three layers were developed, accompanied by an increase in thickness and roughness by increasing the number of the layers. It was also found that the coatings consist of globular nanoparticles with an average diameter of 50 nm. Considering the contribution of roughness to biological responses, the optimization of the surface characteristics to meet an optimal performance seems to be a challenging issue, which demands future studies. DA - 2013/3// PY - 2013/3// DO - 10.1016/j.ceramint.2012.07.058 VL - 39 IS - 2 SP - 1271-1276 J2 - Ceramics International LA - en OP - SN - 0272-8842 UR - http://dx.doi.org/10.1016/j.ceramint.2012.07.058 DB - Crossref KW - Films KW - Sol-gel processes KW - Electron microscopy KW - Microstructure-final ER - TY - JOUR TI - Synthesis, characterization, and thermoelectric properties of nanostructured bulk p-type MnSi1.73, MnSi1.75, and MnSi1.77 AU - Zamanipour, Zahra AU - Shi, Xinghua AU - Mozafari, Masoud AU - Krasinski, Jerzy S. AU - Tayebi, Lobat AU - Vashaee, Daryoosh T2 - Ceramics International AB - P-type higher manganese silicide (HMS) has attracted considerable interest due to its remarkable thermoelectric (TE) properties and potential applications at intermediate and high temperature TE devices. In this study, a series of nanostructured bulk p-type HMS materials with different compositions of MnSix (where x=1.73, 1.75 and 1.77) were synthesized via mechanical ball milling and hot-press sintering. The X-ray diffraction analysis of the synthesized materials showed that increasing the Si contents yields to a slight shift to higher diffraction angles. The increase in Si content further resulted in a decrease in electrical conductivity and increase in Seebeck coefficient. The power factor of all three compositions are approximately identical. However, the lowest thermal conductivity was achieved in MnSi1.75 and resulted in the highest figure-of-merit among all the compositions. DA - 2013/4// PY - 2013/4// DO - 10.1016/j.ceramint.2012.08.086 VL - 39 IS - 3 SP - 2353-2358 J2 - Ceramics International LA - en OP - SN - 0272-8842 UR - http://dx.doi.org/10.1016/j.ceramint.2012.08.086 DB - Crossref KW - Higher manganese silicide KW - Thermoelectric properties KW - Nanostructured materials ER - TY - JOUR TI - The effect of hyaluronic acid on biofunctionality of gelatin-collagen intestine tissue engineering scaffolds AU - Shabafrooz, Vahid AU - Mozafari, Masoud AU - Köhler, Gerwald A. AU - Assefa, Senait AU - Vashaee, Daryoosh AU - Tayebi, Lobat T2 - Journal of Biomedical Materials Research Part A AB - The creation of engineered intestinal tissue has recently stimulated new endeavors with the ultimate goal of intestinal replacement for massive resections of bowel. In this context, we investigated the effect of hyaluronic acid (HA) on the physicochemical characteristics of gelatin–collagen scaffolds and its cytocompatibilty to the human intestinal epithelial Caco-2 cell line in vitro. Gelatin/collagen hybrid scaffolds with different concentrations of HA were prepared by solvent casting and freeze-drying techniques and subsequent chemical crosslinking by genipin. The morphologies of the scaffolds were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. In vitro tests were carried out in phosphate-buffered saline (PBS) solution to study the swelling ratio and the biostability of the scaffolds. It was found that the porous structure of the scaffolds could be tailored by further addition of HA. Moreover, both the swelling ratio and the degradation rate of the scaffold increased by addition of HA. A resazurin-based cell viability assay was employed to determine the viability and estimate the number of scaffold-adherent Caco-2 cells. The assay indicated that the scaffolds were all cytocompatible. We concluded that addition of less than 15% HA to scaffolds with a composition of 9:1 gelatin:collagen results only in incremental improvement in the structural characteristics and cytocompatibility of the gelatin–collagen scaffolds. However, the scaffolds with 25% HA exhibited remarkable enhancement in physicochemical characteristics of the scaffolds including cell viability, growth, and attachment as well as their physical structure. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 3130–3139, 2014. DA - 2013/10/17/ PY - 2013/10/17/ DO - 10.1002/jbma.34984 VL - 102 IS - 9 SP - 3130-3139 J2 - J. Biomed. Mater. Res. LA - en OP - SN - 1549-3296 UR - http://dx.doi.org/10.1002/jbm.a.34984 DB - Crossref ER - TY - JOUR TI - Synthesis and Characterization of Encapsulated Nanosilica Particles with an Acrylic Copolymer by in Situ Emulsion Polymerization Using Thermoresponsive Nonionic Surfactant AU - Yazdimamaghani, Mostafa AU - Pourvala, Tannaz AU - Motamedi, Elaheh AU - Fathi, Babak AU - Vashaee, Daryoosh AU - Tayebi, Lobat T2 - Materials AB - Nanocomposites of encapsulated silica nanoparticles were prepared by in situ emulsion polymerization of acrylate monomers. The synthesized material showed good uniformity and dispersion of the inorganic components in the base polymer, which enhances the properties of the nanocomposite material. A nonionic surfactant with lower critical solution temperature (LCST) was used to encapsulate the silica nanoparticles in the acrylic copolymer matrix. This in situ method combined the surface modification and the encapsulation in a single pot, which greatly simplified the process compared with other conventional methods requiring separate processing steps. The morphology of the encapsulated nanosilica particles was investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM), which confirmed the uniform distribution of the nanoparticles without any agglomerations. A neat copolymer was also prepared as a control sample. Both the neat copolymer and the prepared nanocomposite were characterized by Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analyses (TGA), dynamic mechanical thermal analysis (DMTA) and the flame resistance test. Due to the uniform dispersion of the non-agglomerated nanoparticles in the matrix of the polymer, TGA and flame resistance test results showed remarkably improved thermal stability. Furthermore, DMTA results demonstrated an enhanced storage modulus of the nanocomposite samples compared with that of the neat copolymer, indicating its superior mechanical properties. DA - 2013/8/28/ PY - 2013/8/28/ DO - 10.3390/ma6093727 VL - 6 IS - 9 SP - 3727-3741 J2 - Materials LA - en OP - SN - 1996-1944 UR - http://dx.doi.org/10.3390/ma6093727 DB - Crossref KW - silica nanoparticles KW - thermoresponsive nonionic surfactant KW - cloud point KW - emulsion polymerization ER - TY - JOUR TI - Energy Harvesting Capability of Lipid-Merocyanine Macromolecules: A New Design and Performance Model Development AU - Tayebi, Lobat AU - Mozafari, Masoud AU - El-khouri, Rita AU - Rouhani, Parvaneh AU - Vashaee, Daryoosh T2 - Photochemistry and Photobiology AB - Abstract Light induced cis/trans isomerization in the family of merocyanine ( MC ) dyes offers a recyclable proton pumping ability which can potentially be used in hybrid bio‐electronic devices. In this article, a hexadecyl MC dye is embedded in lipid molecules to make a macromolecular configuration of a lipid/hexadecyl MC membrane. Lipid molecules play a critical role in stabilizing the dye in a membrane structure for practical use in energy devices. In this study, we first examined the proton pumping characteristic of the lipid/hexadecyl MC membrane in a conventional photoelectrochemical cell. Next, a major modification in the cell was introduced by eliminating I 2 / I ‐electrolyte which resulted in a two‐fold increase in the open circuit voltage compared with that of the conventional cell. In addition, the charging time in the new cell was reduced approximately four orders of magnitude. This research demonstrated that the newly designed lipid‐ MC cell can act as a promising bioelectronic device based on the green energy of photoinduced MC dye proton pumping. DA - 2013/11/28/ PY - 2013/11/28/ DO - 10.1111/php.12193 VL - 90 IS - 3 SP - 517-521 J2 - Photochem Photobiol LA - en OP - SN - 0031-8655 UR - http://dx.doi.org/10.1111/php.12193 DB - Crossref ER - TY - JOUR TI - 3D conductive nanocomposite scaffold for bone tissue engineering AU - Tayebi AU - Shahini, Aref AU - Yazdimamaghani, Mostafa AU - Walker, Kenneth Jimmy AU - Eastman, Margaret AU - Hatami-Marbini, Hamed AU - Smith, Brenda AU - Ricci, John L. AU - Madihally, Sundar AU - Vashaee, Daryoosh T2 - International Journal of Nanomedicine AB - Bone healing can be significantly expedited by applying electrical stimuli in the injured region. Therefore, a three-dimensional (3D) ceramic conductive tissue engineering scaffold for large bone defects that can locally deliver the electrical stimuli is highly desired. In the present study, 3D conductive scaffolds were prepared by employing a biocompatible conductive polymer, ie, poly(3,4-ethylenedioxythiophene) poly(4-styrene sulfonate) (PEDOT:PSS), in the optimized nanocomposite of gelatin and bioactive glass. For in vitro analysis, adult human mesenchymal stem cells were seeded in the scaffolds. Material characterizations using hydrogen-1 nuclear magnetic resonance, in vitro degradation, as well as thermal and mechanical analysis showed that incorporation of PEDOT:PSS increased the physiochemical stability of the composite, resulting in improved mechanical properties and biodegradation resistance. The outcomes indicate that PEDOT:PSS and polypeptide chains have close interaction, most likely by forming salt bridges between arginine side chains and sulfonate groups. The morphology of the scaffolds and cultured human mesenchymal stem cells were observed and analyzed via scanning electron microscope, micro-computed tomography, and confocal fluorescent microscope. Increasing the concentration of the conductive polymer in the scaffold enhanced the cell viability, indicating the improved microstructure of the scaffolds or boosted electrical signaling among cells. These results show that these conductive scaffolds are not only structurally more favorable for bone tissue engineering, but also can be a step forward in combining the tissue engineering techniques with the method of enhancing the bone healing by electrical stimuli. DA - 2013/12// PY - 2013/12// DO - 10.2147/ijn.s54668 SP - 167 J2 - IJN LA - en OP - SN - 1178-2013 UR - http://dx.doi.org/10.2147/ijn.s54668 DB - Crossref KW - conductive polymers KW - bone scaffold KW - gelatin KW - bioactive glass nanoparticles KW - PEDOT:PSS KW - conductive scaffold ER - TY - JOUR TI - Surface modification of magnesium alloy implants by nanostructured bredigite coating AU - Razavi, Mehdi AU - Fathi, Mohammadhossein AU - Savabi, Omid AU - Mohammad Razavi, Seyed AU - Hashemi Beni, Batoul AU - Vashaee, Daryoosh AU - Tayebi, Lobat T2 - Materials Letters AB - Magnesium and its alloys have been recently investigated as biodegradable metallic biomaterials for bone implants. However, rapid corrosion rate and low bioactivity have been two limiting factors for their biomedical applications. In this work we aimed to improve these two properties for AZ91 magnesium alloy using the nanostructured bredigite (Ca7MgSi4O16) coating made by micro-arc oxidation and electrophoretic deposition methods. The results indicated that this surface treatment enhanced both corrosion resistance and the bioactivity of AZ91 substrate, making it suitable for biomedical applications. DA - 2013/12// PY - 2013/12// DO - 10.1016/j.matlet.2013.09.068 VL - 113 SP - 174-178 J2 - Materials Letters LA - en OP - SN - 0167-577X UR - http://dx.doi.org/10.1016/j.matlet.2013.09.068 DB - Crossref KW - Biomaterials KW - Bioceramics KW - Corrosion ER - TY - JOUR TI - Preparation of Al–SiC–Al2O3 metal matrix composite powder by mechanochemical reaction between Al, SiO2 and C AU - Karbasi, Maryam AU - Taheri, Mina AU - Tayebi, Lobat AU - Razavi, Mehdi AU - Vashaee, Daryoosh T2 - Micro & Nano Letters AB - In this Letter, Al–SiC–Al2O3 metal matrix nanocomposite powder was successfully synthesised employing a mechanical alloying technique, through a mechanochemical reaction among aluminium (Al), silicon dioxide (SiO2) and carbon (C). For commercial purposes, the materials (Al, SiO2 and C powders) and also the method of synthesis (mechanical alloying) is considered to be cost-effective for production of Al–SiC–Al2O3 nanocomposite. The structural evaluation of powder particles after different milling times was conducted by X-ray diffractometry, and scanning electron microscopy. The results showed that during ball milling Al, SiO2 and C reacted through a mechanochemical reaction producing Al–SiC–Al2O3 metal matrix nanocomposite powder after 50 h of ball milling and annealing at a temperature of 650°C for 1 h. The crystallite sizes of phases remained in nanometric scale. DA - 2013/9/1/ PY - 2013/9/1/ DO - 10.1049/mnl.2013.0419 VL - 8 IS - 9 SP - 519-522 LA - en OP - SN - 1750-0443 UR - http://dx.doi.org/10.1049/mnl.2013.0419 DB - Crossref KW - alumina KW - aluminium KW - ball milling KW - crystallites KW - mechanical alloying KW - nanocomposites KW - powders KW - scanning electron microscopy KW - silicon compounds KW - X-ray diffraction KW - Al-SiC-Al2O3 KW - time 1 hour KW - temperature 650 degC KW - crystallite sizes KW - ball milling KW - scanning electron microscopy KW - X-ray diffractometry KW - milling time KW - mechanical alloying KW - nanocomposite powder KW - mechanochemical reaction KW - metal matrix composite powder ER - TY - JOUR TI - Digital holographic microscopy of the myelin figure structural dynamics and the effect of thermal gradient AU - Fathi, Narges AU - Moradi, Ali-Reza AU - Habibi, Mehdi AU - Vashaee, Daryoosh AU - Tayebi, Lobat T2 - Biomedical Optics Express AB - Myelin figures (MFs) are cylindrical multilamellar lipid tubes that can be found in various healthy and diseased living cells. Their formation and dynamics involve some of the most mysterious configurations that lipid molecules can adopt under certain conditions. They have been studied with different microscopy methods. Due to the frequent coiling of their structure, the usual methods of microscopy fail to give precise quantitative information about their dynamics. In this paper, we introduced Digital Holographic Microscopy (DHM) as a useful method to calculate the precise dynamical volume, thickness, surface and length of the myelin figures. As an example of DHM imaging of myelin figures, their structure and growth rate in the presence and absence of temperature gradient have been studied in this work. We showed that the thickness of a myelin figure can be changed during the first few seconds. However, after approximately ten seconds, the thickness stabilizes and does not alter significantly. We further studied the effect of the thermal gradient on the length growth. The calculation of the length growth from the measurement of the myelin figure volume shows that the length (L) grows in time (t) as [Formula: see text]at the early stage of the myelin protrusion in both the presence and the absence of the thermal gradient. However, thermal gradient facilitates the growth and increases its rate. DA - 2013/5/24/ PY - 2013/5/24/ DO - 10.1364/boe.4.000950 VL - 4 IS - 6 SP - 950 J2 - Biomed. Opt. Express LA - en OP - SN - 2156-7085 2156-7085 UR - http://dx.doi.org/10.1364/boe.4.000950 DB - Crossref ER - TY - JOUR TI - On the estimation of the unknown reactivity coefficients in a CANDU reactor AU - Tayebi, Lobat AU - Vashaee, Daryoosh T2 - Annals of Nuclear Energy AB - A space-time kinetics based inverse architecture method is suggested to analyze the reactivity variations associated with power excursions in a generic CANDU reactor. It is intended to provide diagnosis tools to gain enhanced control thereby ensuring safe operation of the plant. A methodology for analyzing the data available from the in core flux detectors and extracting the unknown reactivity coefficients is presented. The proposed system uses a reference model in conjunction with an optimal estimator. The reference model is composed of a state space representation of the space-time dynamics of neutron flux in the core, based on modal expansion approximation, and a time domain optimal estimator filter. We investigated three different estimation techniques based on recursive prediction error method (RPEM), dual extended Kalman filter (DEKF), and joint extended Kalman filter (JEKF). We compared their applicability to the estimation of coolant-void dynamic reactivity in loss-of-coolant accident in a CANDU reactor. The state equations also include the characteristics of the detector responses. The thermal hydraulic models were not included in the calculations. Two different types of detectors are considered in this analysis, the over prompt responsive Platinum detector of the reactor shutdown systems, and the under delayed responsive Vanadium detector of the flux mapping system. DA - 2013/3// PY - 2013/3// DO - 10.1016/j.anucene.2012.07.025 VL - 53 SP - 447-457 J2 - Annals of Nuclear Energy LA - en OP - SN - 0306-4549 UR - http://dx.doi.org/10.1016/j.anucene.2012.07.025 DB - Crossref KW - CANDU reactor KW - Parameter estimation KW - Space-time kinetics KW - Coolant void ER - TY - JOUR TI - Nanostructured zirconium titanate fibers prepared by particulate sol–gel and cellulose templating techniques AU - Rouhani, P. AU - Salahinejad, E. AU - Kaul, R. AU - Vashaee, D. AU - Tayebi, L. T2 - Journal of Alloys and Compounds AB - In this paper, a method for cost-effective production of nanostructured zirconium titanate (ZrTiO4) fibers is introduced. In this method, ZrTiO4 fibers were synthesized by a sol–gel technique using cellulose fibers as the template. The resultant structures were studied by transmission electron microscopy, X-ray diffraction, scanning electron microscopy, and Brunauer–Emmett–Teller (BET) analyses. The photocatalytic activity of the fiber was compared to that of ZrTiO4 powders prepared by the same sol–gel method, in dark and under UVA and UVC radiations. According to the results, after calcination accompanied by the template removal, the ZrTiO4 fiber consists of uniformly-deposited, crystalline nanoparticles. This nanostructured fiber exhibited a higher surface area and a higher porosity compared with the ZrTiO4 powders, resulting in considerably higher photocatalytic characteristics, as confirmed by the experiment. The large surface area and the enhanced photocatalytic activity of the ZrTiO4 fibers also offer applications in sensors and bioactive films. DA - 2013/8// PY - 2013/8// DO - 10.1016/j.jallcom.2013.03.142 VL - 568 SP - 102-105 J2 - Journal of Alloys and Compounds LA - en OP - SN - 0925-8388 UR - http://dx.doi.org/10.1016/j.jallcom.2013.03.142 DB - Crossref KW - Ceramics KW - Nanostructured materials KW - Sol-gel processes KW - Catalysis ER - TY - JOUR TI - A new double-layer sol–gel coating to improve the corrosion resistance of a medical-grade stainless steel in a simulated body fluid AU - Salahinejad, E. AU - Hadianfard, M.J. AU - Macdonald, D.D. AU - Mozafari, M. AU - Vashaee, D. AU - Tayebi, L. T2 - Materials Letters AB - One of the effective ways to overcome some of the drawbacks of oxide coatings for corrosion protection of metal surfaces is the incorporation of an organic component into the inorganic network, although, commonly, film adhesion is disadvantageously affected. In this work, for the first time, by exploiting both inorganic and organic–inorganic coatings, a new double-layer thin film, which comprises ZrTiO4 as the bottom layer and ZrTiO4–PMMA as the top layer, was deposited on a medical-grade stainless steel substrate via a sol–gel spin coating method. According to potentiodynamic polarization experiments in a simulated body fluid, the substrate coated with this film exhibited superior corrosion resistance, compared with the same steel coated with purely inorganic ZrTiO4 and hybrid ZrTiO4–PMMA films. The superior corrosion resistance of the newly developed coating was found to be due to simultaneously the good adhesion of the lower, inorganic film and the low defect density of the upper, hybrid film. DA - 2013/4// PY - 2013/4// DO - 10.1016/j.matlet.2013.01.111 VL - 97 SP - 162-165 J2 - Materials Letters LA - en OP - SN - 0167-577X UR - http://dx.doi.org/10.1016/j.matlet.2013.01.111 DB - Crossref KW - Sol-gel preparation KW - Corrosion KW - Electron microscopy KW - Adhesion ER - TY - JOUR TI - Surface Modification of Stainless Steel Orthopedic Implants by Sol–Gel ZrTiO4 and ZrTiO4–PMMA Coatings AU - Salahinejad, E. AU - Hadianfard, M. J. AU - Macdonald, D. D. AU - Sharifi(Asl), S. AU - Mozafari, M. AU - Walker, K. J. AU - Rad, A. Tahmasbi AU - Madihally, S. V. AU - Vashaee, D. AU - Tayebi, L. T2 - Journal of Biomedical Nanotechnology AB - In this paper, the biocompatibility of a medical-grade stainless steel coated with sol-gel derived, nanostructured inorganic ZrTiO4 and hybrid ZrTiO4-PMMA thin films is correlated with surface characteristics. The surfaces of the samples are characterized by atomic force microscopy, the sessile drop technique, and electrochemical corrosion experiments. The viability of adult human mesenchymal stem cells on the surfaces after one day of culture is also assessed quantitatively and morphologically. According to the results, both of the coatings improve the hydrophilicity, corrosion resistance, and thereby cytocompatibility of the substrate. Despite the higher corrosion protection by the hybrid coating, the sample coated with the inorganic thin film exhibits a better cell response, suggesting the domination of wettability. In summary, the ZrTiO4-based sol-gel films can be considered to improve the biocompatibility of metallic implants. DA - 2013/8/1/ PY - 2013/8/1/ DO - 10.1166/jbn.2013.1619 VL - 9 IS - 8 SP - 1327-1335 J2 - j biomed nanotechnol LA - en OP - SN - 1550-7033 UR - http://dx.doi.org/10.1166/jbn.2013.1619 DB - Crossref KW - Sol-Gel Coating KW - Water Contact Angle KW - Corrosion Resistance KW - Cytocompatibility KW - Zirconium Titanate ER - TY - JOUR TI - Interlamellar Organization of Phase Separated Domains in Multi-Component Lipid Multilayers: Energetic Considerations AU - Tayebi, Lobat AU - Parikh, Atul AU - Vashaee, Daryoosh T2 - International Journal of Molecular Sciences AB - A recent experimental study [1] has demonstrated the alignment of phase separated domains across hundreds of bilayer units in multicomponent stacked lipid bilayers. The origin of this alignment is the interlamellar coupling of laterally phase separated domains. Here, we develop a theoretical model that presents the energetics description of this phenomenon based on the minimization of the free energy of the system. Specifically, we use solution theory to estimate the competition between energy and entropy in different stacking configurations. The model furnishes an elemental phase diagram, which maps the domain distributions in terms of the strength of the intra- and inter-layer interactions and estimates the value of inter-layer coupling for complete alignment of domains in the stacks of five and ten bilayers. The area fraction occupied by co-existing phases was calculated for the system of the minimum free energy, which showed a good agreement with experimental observations. DA - 2013/2/8/ PY - 2013/2/8/ DO - 10.3390/ijms14023824 VL - 14 IS - 2 SP - 3824-3833 J2 - IJMS LA - en OP - SN - 1422-0067 UR - http://dx.doi.org/10.3390/ijms14023824 DB - Crossref KW - lipid multilayers KW - phase separation KW - aligned domains KW - energetic considerations KW - lipid rafts ER - TY - JOUR TI - Comparison of boron precipitation in p-type bulk nanostructured and polycrystalline silicon germanium alloy AU - Zamanipour, Zahra AU - Krasinski, Jerzy S. AU - Vashaee, Daryoosh T2 - Journal of Applied Physics AB - Boron precipitation process and its effect on electronic properties of p-type bulk nanostructured silicon germanium (Si0.8Ge0.2) compared with large grain polycrystalline Si0.8Ge0.2 have been studied. The structures were synthesized and their thermoelectric properties were measured versus temperature during heating and cooling cycles. The experimental data showed stronger temperature variation of Seebeck coefficient, carrier concentration, and conductivity in the nanostructured Si0.8Ge0.2 compared with the polycrystalline form indicating stronger boron precipitation in this structure. The electrical properties of both samples were calculated using a multi-band semi-classical model. The theoretical calculations confirm that the increase of boron precipitation in the nanostructured Si0.8Ge0.2 is responsible for its higher thermal instability. Since the thermoelectric properties of the nanostructured sample degrade as a result of thermal cycling, the material is appropriate only for continuous operation at high temperature without cooling. DA - 2013/4/14/ PY - 2013/4/14/ DO - 10.1063/1.4801388 VL - 113 IS - 14 SP - 143715 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.4801388 DB - Crossref ER - TY - JOUR TI - The effect of phase heterogeneity on thermoelectric properties of nanostructured silicon germanium alloy AU - Zamanipour, Zahra AU - Salahinejad, Erfan AU - Norouzzadeh, Payam AU - Krasinski, Jerzy S. AU - Tayebi, Lobat AU - Vashaee, Daryoosh T2 - Journal of Applied Physics AB - Detailed examination of the nanostructured bulk Si0.80Ge0.20 alloy synthesized by mechanical alloying and hot-press methods revealed that the alloy composition can unintentionally deviate from its nominal value. The phase deviation is difficult to be detected with x-ray diffraction due to the continuous solid solution characteristics of the Si-Ge alloy. Differential thermal analysis, in particular, showed that the synthesized nanostructured bulk Si0.80Ge0.20 alloy was a composition of two unintentional phases. The dominant phase was Si0.88Ge0.12 with admixture of Si0.58Ge0.42 in a much lower concentration. The two-phase structure is difficult to be detected in X-ray diffraction analysis and is often neglected. Thermoelectric properties of Si1−xGex significantly depend on the Ge content in the synthesized alloy. The thermoelectric properties of the synthesized material were studied experimentally and theoretically. The comparison of the data of the mixed phase nanostructured alloy with those of the single phase Si0.80Ge0.20 alloy showed enhancement in Seebeck coefficient and reduction in thermal conductivity of the former material. It was found using model calculations that these differences are due to the existence of the Si0.88Ge0.12 phase in the two-phase structure that results in the reduction of the bipolar diffusion part of the thermal conductivity and the bipolar effect in the Seebeck coefficient at high temperature. The results can stimulate a new route for enhancing the thermoelectric properties of silicon germanium alloy based on multicomponent material design. DA - 2013/7/14/ PY - 2013/7/14/ DO - 10.1063/1.4813474 VL - 114 IS - 2 SP - 023705 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.4813474 DB - Crossref ER - TY - JOUR TI - Enhancement of thermoelectric power factor of silicon germanium films grown by electrophoresis deposition AU - Nozariasbmarz, Amin AU - Tahmasbi Rad, Armin AU - Zamanipour, Zahra AU - Krasinski, Jerzy S. AU - Tayebi, Lobat AU - Vashaee, Daryoosh T2 - Scripta Materialia AB - A method based on electrophoresis deposition is demonstrated for making efficient silicon germanium thermoelectric films. The film showed a thermoelectric power factor an order of magnitude larger than the previously reported values. Theoretical modeling of the charge carrier transport showed that the enhancement of power factor is due to the large carrier mobility of the film. The method offers a cost-effective approach extendable to other materials for making efficient miniature thermoelectric devices. DA - 2013/10// PY - 2013/10// DO - 10.1016/j.scriptamat.2013.06.025 VL - 69 IS - 7 SP - 549-552 J2 - Scripta Materialia LA - en OP - SN - 1359-6462 UR - http://dx.doi.org/10.1016/j.scriptamat.2013.06.025 DB - Crossref KW - Thermoelectric materials KW - Thin films KW - Silicon germanium KW - Electrical properties ER - TY - JOUR TI - Prediction of a large number of electron pockets near the band edges in type-VIII clathrate Si46and its physical properties from first principles AU - Norouzzadeh, Payam AU - Myles, Charles W AU - Vashaee, Daryoosh T2 - Journal of Physics: Condensed Matter AB - The material design of type-VIII clathrate Si46 is presented based on first principles. The structural, electronic, elastic, vibrational, and thermodynamic properties of this hypothetical material are presented. Our results predict that type-VIII clathrate Si46 is an indirect semiconductor with a bandgap of 1.24 eV. The band structure revealed an interestingly large number of electron pockets near both conduction and valance band edges. Such a large density of states near the band edges, which is higher than that of the best thermoelectric materials discovered so far, can result in a large thermoelectric power factor (>0.004 W m−1 K−2) making it a promising candidate for thermoelectric applications. The elastic properties as well as the vibrational modes and the phonon state densities of this material were also calculated. Our calculations predict that the heat capacity at constant volume (isochoric) of this clathrate increases smoothly with temperature and approaches the Dulong–Petit value near room temperature. The electronic band structure shows a large number of valleys closely packed around the valance band edge, which is rare among the known semiconducting materials. These valleys can contribute to transport at high temperature resulting in a possibly high performance (ZT > 1.5) p-type thermoelectric material. DA - 2013/10/31/ PY - 2013/10/31/ DO - 10.1088/0953-8984/25/47/475502 VL - 25 IS - 47 SP - 475502 J2 - J. Phys.: Condens. Matter OP - SN - 0953-8984 1361-648X UR - http://dx.doi.org/10.1088/0953-8984/25/47/475502 DB - Crossref ER - TY - JOUR TI - Electronic, elastic, vibrational, and thermodynamic properties of type-VIII clathrates Ba8Ga16Sn30 and Ba8Al16Sn30 by first principles AU - Norouzzadeh, Payam AU - Myles, Charles W. AU - Vashaee, Daryoosh T2 - Journal of Applied Physics AB - We present the results of studying electronic, elastic, vibrational, and thermodynamic properties of type-VIII clathrates Ba8Ga16Sn30 Ba8Al16Sn30 calculated from a first-principles approach. The calculations utilize the generalized gradient approximation to density functional theory. The results indicate that the Ba8Ga16Sn30 and Ba8Al16Sn30 are indirect semiconductors with fundamental band gaps of 160 meV and 315 meV, respectively. It was also found that the stiffness of Al containing type-VIII clathrate does not show any significant change against the uniform pressure, shearing, and linear strains. The phonon spectrum and the phonon state densities of these compounds as well as the Raman and infrared active modes were further calculated and the effects of replacing the Ga with Al atoms on the properties of interest were discussed. The calculated elastic, vibrational, and thermodynamic properties along with Raman and IR spectra are reported for the first time. The identification of the Raman and infrared active modes will be especially useful for the experimental characterizations of these compounds. Our calculations show that the heat capacities of these clathrates increase smoothly with temperature and approach the Dulong-Petit value at about room temperature, which agrees with the existing experimental data. DA - 2013/10/28/ PY - 2013/10/28/ DO - 10.1063/1.4826213 VL - 114 IS - 16 SP - 163509 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.4826213 DB - Crossref ER - TY - RPRT TI - DC Bus Current Ripple Management in Single Phase PWM Inverters AU - Iyer, V.M. A3 - Indian Institute of Science Bangalore DA - 2013/6// PY - 2013/6// M3 - project report PB - Indian Institute of Science Bangalore UR - http://www.ee.iisc.ac.in/new/people/faculty/vjohn/pdf/ME2013_VishnuM.pdf ER - TY - JOUR TI - Passive energy storage using distributed electric loads with thermal storage AU - Lu, Ning AU - Vanouni, Maziar T2 - Journal of Modern Power Systems and Clean Energy AB - This paper presents the concept of controlling distributed electric loads with thermal energy storage as a passive electric energy storage system (PEESS). Examples of such loads include different types of thermostatically controlled appliances (TCAs) such as hot water heaters, air conditioners, and refrigerators. Each TCA can be viewed as a thermal cell that stores electricity as thermal energy. A centralized control mechanism can be used to control the timing of each thermal cell to consume electric energy so that the aggregated electricity consumption of the thermal cells will vary against a baseline consumption. Thus, when the aggregated consumption is higher than the baseline, the PEESS is charging; otherwise, the PEESS is discharging. The overall performance of a PEESS will be equivalent to that of a battery energy storage device. This paper presents the configuration and formulates the control of a PEESS. The modeling results demonstrate the feasibility of implementing the PEESS. DA - 2013/// PY - 2013/// DO - 10.1007/s40565-013-0033-z VL - 1 IS - 3 SP - 264-274 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000209527300009&KeyUID=WOS:000209527300009 ER - TY - JOUR TI - Parameter Selection for a Centralized Thermostatically Controlled Appliances Load Controller Used for Intra-Hour Load Balancing AU - Zhang, Yu AU - Lu, Ning T2 - Ieee Transactions on Smart Grid AB - This paper presents a novel dynamic parameter selection process to optimize the performance of a centralized load controller designed to provide intra-hour load balancing services using thermostatically controlled appliances (TCAs). An optimal set of control parameters for the controller are selected by exhaustive simulations of control variables such as the sampling time of the forecaster, the magnitude of the load balancing signal, and the temperature deadband. The effects of TCA lock-off times, ambient temperatures, heat gains, and two-way communication delays on the controller design are also modeled. Customer comfort, device life cycles, and control errors are used as metrics to evaluate the performance. The results demonstrate that the optimized controller offers satisfactory performance considering all the operational uncertainties. DA - 2013/// PY - 2013/// DO - 10.1109/tsg.2013.2258950 VL - 4 IS - 4 SP - 2100-2108 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000328064100038&KeyUID=WOS:000328064100038 KW - Ancillary service KW - demand response KW - direct load control KW - load management KW - optimal parameter selection KW - renewable integration KW - smart grid KW - thermostatically controlled appliances ER - TY - CHAP TI - Design Considerations of a Centralized Load Controller Using Thermostatically Controlled Appliances for Continuous Regulation Reserves AU - Lu, Ning AU - Ieee T2 - 2013 Ieee Power and Energy Society General Meeting PY - 2013/// SP - PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000331874300120&KeyUID=WOS:000331874300120 ER - TY - JOUR TI - Design Considerations of a Centralized Load Controller Using Thermostatically Controlled Appliances for Continuous Regulation Reserves AU - Lu, Ning AU - Zhang, Yu T2 - Ieee Transactions on Smart Grid AB - This paper presents design considerations for a centralized load controller to control thermostatically controlled appliances (TCAs) for continuous regulation reserves (CRRs). The controller logics for setting up the baseline load, generating priority lists, issuing dispatch commands, and tuning the simplified forecaster model using measurement data are described. To study the impacts of different control parameter settings on control performance and device lifetimes, a system consisting of 1000 heating, ventilating, and air-conditioning (HVAC) units in their heating modes is modeled to provide a CRR 24 hours a day. Four cases are modeled to evaluate the impact of forecasting errors, minimum HVAC turn-off times, response delays, and consumer overrides. The results demonstrate that a centralized TCA load controller can provide robust, good quality CRRs with reduced communication needs for the two-way communication network and inexpensive load control devices. Most importantly, because the controller precisely controls the aggregated HVAC load shapes while maintaining load diversity, the controllable and measurable load services that it provides can be used for many other demand response applications, such as peak shaving, load shifting, and arbitrage. DA - 2013/// PY - 2013/// DO - 10.1109/tsg.2012.2222944 VL - 4 IS - 2 SP - 914-921 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000325487800029&KeyUID=WOS:000325487800029 KW - Air conditioning KW - ancillary service KW - demand response KW - direct load control KW - HVAC KW - load balancing KW - load following KW - regulation service KW - renewable integration KW - smart grid KW - thermostatically controlled appliances ER - TY - BOOK TI - Demand-side Management of Air Conditioning Cooling Loads for Intra-hour Load Balancing AU - Zhang, Yu AU - Lu, Ning AU - Ieee DA - 2013/// PY - 2013/// PB - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000320500800116&KeyUID=WOS:000320500800116 ER - TY - CHAP TI - A Comparison of Forecast Error Generators for Modeling Wind and Load Uncertainty AU - Lu, Ning AU - Diao, Ruisheng AU - Hafen, Ryan P. AU - Samaan, Nader AU - Makarov, Yuri V. AU - Ieee T2 - 2013 Ieee Power and Energy Society General Meeting PY - 2013/// SP - PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000331874303159&KeyUID=WOS:000331874303159 ER - TY - CONF TI - A 60 GHz Doherty power amplifier with 14% PAE at 6-dB back off AU - Sarkar, A. AU - Floyd, B. C2 - 2013/9// C3 - Proceedings SRC Techcon Conference DA - 2013/9// ER - TY - CONF TI - Spin logic via controlled correlation in a topological insulator-nanomagnet hybrid structure AU - Duan, Xiaopeng AU - Semenov, Yuriy G AU - Kim, Ki Wook T2 - 2013 71st Annual Device Research Conference (DRC) AB - A magnetic switching device implemented with a majority-gate logic structure is explored as a potential candidate for beyond-CMOS technology. Specifically, a novel switching mechanism is envisioned that relies on the unique magneto-electric properties of a hybrid structure consisting of topological insulator (TI), insulating ferromagnet (FM) and graphene (Gr) in the Bennett clocking operation scheme (Fig. 1A). A circuit layout is proposed and the logic operation demonstrated in a 1-bit adder. C2 - 2013/6// C3 - 71st Device Research Conference DA - 2013/6// DO - 10.1109/drc.2013.6633829 PB - IEEE SN - 9781479908141 9781479908110 9781479908127 UR - http://dx.doi.org/10.1109/drc.2013.6633829 DB - Crossref ER - TY - CONF TI - Rationale for a 3D heterogeneous multi-core processor AU - Rotenberg, Eric AU - Dwiel, Brandon H. AU - Forbes, Elliott AU - Zhang, Zhenqian AU - Widialaksono, Randy AU - Chowdhury, Rangeen Basu Roy AU - Tshibangu, Nyunyi AU - Lipa, Steve AU - Davis, W. Rhett AU - Franzon, Paul AU - al. T2 - 2013 IEEE 31st International Conference on Computer Design (ICCD) AB - Single-ISA heterogeneous multi-core processors are comprised of multiple core types that are functionally equivalent but microarchitecturally diverse. This paradigm has gained a lot of attention as a way to optimize performance and energy. As the instruction-level behavior of the currently executing program varies, it is migrated to the most efficient core type for that behavior. C2 - 2013/10// C3 - 2013 IEEE 31st International Conference on Computer Design (ICCD) CY - Asheville, NC DA - 2013/10// PY - 2013/10/6/ DO - 10.1109/iccd.2013.6657038 SP - 154–168 PB - IEEE SN - 9781479929870 UR - http://dx.doi.org/10.1109/iccd.2013.6657038 DB - Crossref ER - TY - CONF TI - Design and test of 2.5D and 3D stacked ICs AU - Franzon, Paul T2 - 2013 IEEE 22nd Conference on Electrical Performance of Electronic Packaging and Systems (EPEPS) AB - Three dimensional chips stacked using Through Silicon Via (TSV) technology has been under consideration and the subject of intensive research for several years now. Soon the technologies will become available through standard fabs. Will the technology be an instant hit, a niche, or a flop? What is needed to ensure it reaches hit status? What are the basic manufacturing steps and flows? This tutorial will discuss these question mainly in the context of the opportunities and challenges that face the designer. What are the significant opportunities presented by 3DIC? What problems will the designer face that will need clever solutions? What are the potential solution paths? C2 - 2013/10// C3 - 2013 IEEE 22nd Conference on Electrical Performance of Electronic Packaging and Systems DA - 2013/10// DO - 10.1109/epeps.2013.6703444 PB - IEEE SN - 9781479907076 9781479907052 UR - http://dx.doi.org/10.1109/epeps.2013.6703444 DB - Crossref ER - TY - CONF TI - Applications and design styles for 3DIC AU - Franzon, P.D. AU - Rotenberg, E. AU - Tuck, J. AU - Davis, W.R. AU - Zhou, H. AU - Schabel, J. AU - Zhang, Z. AU - Park, J. AU - Dwiel, B. AU - Forbes, E. AU - Huh, Joonmoo AU - Priyadarshi, S. AU - Lipa, S. AU - Thorolfsson, T. T2 - 2013 IEEE International Electron Devices Meeting (IEDM) AB - 3D technologies offer significant potential to improve raw performance and performance per unit power. After exploiting TSV technologies for cost reduction and increasing memory bandwidth, the next frontier is to create more sophisticated solutions that promise further increases in power/performance beyond those attributable to memory interfaces alone. These include heterogeneous integration and exploitation of the high amounts of interconnect available to provide for customization. Challenges include the creation of physical standards and the design of sophisticated static and dynamic thermal management methods. C2 - 2013/12// C3 - 2013 IEEE International Electron Devices Meeting CY - Washington, DC DA - 2013/12// PY - 2013/12/9/ DO - 10.1109/iedm.2013.6724717 PB - IEEE SN - 9781479923069 UR - http://dx.doi.org/10.1109/iedm.2013.6724717 DB - Crossref ER - TY - CONF TI - 3D volumetric ultrasound imaging with a 32×32 CMUT array integrated with front-end ICs using flip-chip bonding technology AU - Bhuyan, A. AU - Choe, J. W. AU - Lee, Byung Chul AU - Wygant, I. AU - Nikoozadeh, A. AU - Oralkan, O. AU - Khuri-Yakub, B. T. T2 - 2013 IEEE International Solid-State Circuits Conference (ISSCC 2013) AB - 3D ultrasound imaging is becoming increasingly prevalent in the medical field. Compared to conventional 2D imaging systems, 3D imaging can provide a detailed view of tissue structures that makes diagnosis easier for the physicians. In addition, 2D image slices can be formed at various orientations to the transducer, making the examination less dependent on the skill of the sonographer. However, various challenges exist in developing a 3D imaging system, such as integration of a large number of elements, as well as post-processing of datasets received from a large number of channels. 2D transducer arrays are typically integrated with custom ICs in the probe handle to perform some intermediate beamforming and to reduce the number of cable connections to the imaging system. Capacitive micromachined ultrasonic transducers (CMUTs) have emerged as an alternative to piezoelectric transducers. Being a MEMS device, they greatly benefit from flexibility and ease of fabrication, and can be seamlessly integrated with electronics. Previous work demonstrates 3D stacking of CMUTs and dummy ICs with an intermediate interposer layer. However, that represents more of a mechanical demonstration of 3D integration. In this paper, we present a fully functional 3D ultrasound imaging system comprising a 32×32 2D CMUT array, 3D-stacked with front-end ICs using flip-chip bonding technology. The imaging system is capable of capturing real-time volumetric ultrasound data, and displaying 2D and 3D ultrasound images. C2 - 2013/2// C3 - 2013 IEEE International Solid-State Circuits Conference Digest of Technical Papers DA - 2013/2// DO - 10.1109/isscc.2013.6487786 PB - IEEE SN - 9781467345163 9781467345156 9781467345149 UR - http://dx.doi.org/10.1109/isscc.2013.6487786 DB - Crossref ER - TY - CONF TI - GPU-based real-time imaging software suite for medical ultrasound AU - Choe, Jung Woo AU - Nikoozadeh, Amin AU - Oralkan, Omer AU - Khuri-Yakub, Butrus T. T2 - 2013 IEEE International Ultrasonics Symposium (IUS) AB - We developed a GPU-based real-time imaging software suite for medical ultrasound imaging to provide a fast real-time imaging platform for various probe geometries and imaging schemes. The imaging software receives raw RF data from a data acquisition system, and processes them on GPU to reconstruct real-time images. The most general-purpose imaging program in the suite displays three cross-sectional images for arbitrary probe geometry and various imaging schemes including conventional beamforming, synthetic beamforming, and plane-wave compounding. The other imaging programs in the software suite, derived from the general-purpose imaging program, are optimized for their own purposes, such as displaying a rotating B-mode plane and its maximum intensity projection (MIP), photoacoustic imaging, and real-time volume-rendering. Real-time imaging was successfully demonstrated using each of the imaging programs in the software suite. C2 - 2013/7// C3 - 2013 IEEE International Ultrasonics Symposium (IUS) DA - 2013/7// DO - 10.1109/ultsym.2013.0525 PB - IEEE SN - 9781467356862 9781467356848 UR - http://dx.doi.org/10.1109/ultsym.2013.0525 DB - Crossref KW - Real-time imaging KW - Volumetric imaging KW - GPU KW - CMUT ER - TY - CONF TI - A 32×32 integrated CMUT array for volumetric ultrasound imaging AU - Bhuyan, Anshuman AU - Chang, Chienliu AU - Choe, Jung Woo AU - Lee, Byung Chul AU - Nikoozadeh, Amin AU - Oralkan, Omer AU - Khuri-Yakub, Butrus T. T2 - 2013 IEEE International Ultrasonics Symposium (IUS) AB - Real-time 3D volumetric ultrasound imaging systems require transmit and receive circuitry to generate the ultrasound beam and process the received echo signals. Since a 2D array is required for 3D imaging, the complexity of building such a system is significantly higher, e.g., front-end electronics need to be interfaced to the transducer, a large number of elements need to be interfaced to the backend system and a large dataset needs to be processed. In this work, we present a 3D imaging system using capacitive micromachined ultrasonic transducer (CMUT) technology that addresses many of the challenges in building such a system. The transducer is a 5-MHz CMUT array with an 8 mm × 8 mm aperture size. The aperture consists of 1024 elements (32×32) with an element pitch of 250 µm. An integrated circuit (IC) is integrated very close to the CMUT array. It consists of a transmit beamformer and receive circuitry to improve the noise performance of the overall system. Simultaneous multi-beam transmit is also incorporated in the IC to improve the imaging frame rate. The CMUT is flip-chip bonded to the IC and the final assembly measured 9.2 mm × 9.2 mm. The assembly was then interfaced with an FPGA and a backend system (comprising of a data acquisition system and PC). The FPGA provided the digital I/O signals for the IC and the backend system was used to process the received RF echo data (from the IC) and reconstruct the volume image using a phased array imaging approach. Imaging experiments were performed using wire phantoms. Real-time volumetric images were captured at 5 volumes per second and are presented in this paper. C2 - 2013/7// C3 - 2013 IEEE International Ultrasonics Symposium (IUS) DA - 2013/7// DO - 10.1109/ultsym.2013.0141 PB - IEEE SN - 9781467356862 9781467356848 UR - http://dx.doi.org/10.1109/ultsym.2013.0141 DB - Crossref KW - 3D volumetric imaging KW - capacitive micromachined ultrasonic transducer (CMUT) KW - 2D array KW - phased array imaging KW - ultrasound KW - real-time KW - flip-chip bonding KW - integrated circuits ER - TY - CONF TI - Small-world networks empowered large machine-to-machine communications AU - Gu, Lei AU - Lin, Shih-Chun AU - Chen, Kwang-Cheng T2 - 2013 IEEE Wireless Communications and Networking Conference (WCNC) AB - Cloud-based machine-to-machine communications emerge to facilitate services through linkage between cyber and physical worlds. In addition to great challenges in a large network of machine/sensor swarm, effective network architecture involving interconnection of wireless infrastructure and multi-hop ad hoc networking in the machine swarm remains open. Inspired by the small-world phenomenon in social networks, we may establish a short-cut path under a heterogeneous network architecture through wireless infrastructure and cloud, by connecting to data aggregators or access points in the machine swarm, such that end-to-end delay can be significantly reduced. Our mathematical analysis on network diameter and average delay, along with verifications by simulations, demonstrate spectral and energy efficiency of our proposed heterogeneous network architecture in large machine-to-machine communication networks. C2 - 2013/4// C3 - 2013 IEEE Wireless Communications and Networking Conference (WCNC) DA - 2013/4// DO - 10.1109/wcnc.2013.6554795 PB - IEEE SN - 9781467359399 9781467359382 9781467359375 UR - http://dx.doi.org/10.1109/wcnc.2013.6554795 DB - Crossref ER - TY - CONF TI - End-to-end delay reduction via in-network computation in cognitive radio sensor networks AU - Lin, Shih-Chun T2 - 2013 IEEE Global Communications Conference (GLOBECOM 2013) AB - To potentially alleviate the spectrum shortage for sensor networks of tremendous number of nodes, cognitive radio technology, and thus multi-hop opportunistic and concurrent transmissions overlaying with the primary system suggest an attractive facilitation of large-scale sensor networks. However, it is shown to result in significant end-to-end delay to prohibit practical applications. Noting the nature of traffic in sensor networks, with the aid of distributed source coding and broadcasting in wireless communication, we develop in-network computation to reduce requisite transmissions and to accommodate more concurrent transmissions within given spectrum. Without end-to-end table to significantly save control signaling, a greedy networking algorithm schedules traffic among cooperative relay paths and achieves great delay reduction under various communication scenarios. Such in-network computation further suggests a new design paradigm of communication-computation tradeoff in multi-hop cognitive sensor networks and thus machine-to-machine communications. C2 - 2013/12// C3 - 2013 IEEE Global Communications Conference (GLOBECOM) DA - 2013/12// DO - 10.1109/glocom.2013.6831105 PB - IEEE SN - 9781479913534 UR - http://dx.doi.org/10.1109/glocom.2013.6831105 DB - Crossref ER - TY - CONF TI - Multi-dimensional wide-area visualization of power system dynamics using Synchrophasors AU - Thakur, Sidharth AU - Chakrabortty, Aranya T2 - 2013 IEEE Power & Energy Society General Meeting AB - Majority of the traditional visualization techniques for Synchrophasor-based wide-area monitoring of large power grids are based on displaying measured values of voltage, phase angle, currents, and frequencies at discrete points in space, thereby providing only limited insight into the spatio-temporal relationships between the dynamic features embedded in the measured signals. To bridge this gap, we present several geospatial and multi-dimensional visualization methods that correlate various dynamic attributes of phase angle and power oscillations, and explicitly quantify their spatio-temporal couplings, on both absolute and relative scales. In particular, we focus on four main attributes, namely, modal frequency, damping factor, residues, and modal energy. We show how the proposed methods can interpret the interdependencies of these respective features over space and time leading to more global situational awareness, how they can be visualized in real-time using 3-dimensional plots, and, most importantly, how they can be used for robust outlier detection and baseline modification in large PMU datasets. C2 - 2013/// C3 - 2013 IEEE Power & Energy Society General Meeting DA - 2013/// DO - 10.1109/pesmg.2013.6672612 PB - IEEE SN - 9781479913039 UR - http://dx.doi.org/10.1109/pesmg.2013.6672612 DB - Crossref ER - TY - CONF TI - A multi-user network testbed for wide-area monitoring and control of power systems using distributed synchrophasors AU - Weiss, Matthew AU - Chakrabortty, Aranya AU - Xin, Yufeng T2 - the the fourth international conference AB - In this poster we describe an advanced hardware-in-loop simulation facility for real-time demonstration and validation of power system monitoring and control algorithms, currently under construction at NC State University. This facility integrates a real-time power system emulation lab with the GENI network and its associated cloud testbeds. The dynamic responses from the power system emulator are captured via real hardware Phasor Measurement Units (PMU) that are synchronized with the time-scale of the simulations via a common GPS reference. These responses are then sent to the computing and storage resource in GENI using the IEEE C37.118 protocol, running the smart grid control and management application simulations via QoS-guaranteed communications channels, all provisioned in a dynamic fashion. C2 - 2013/// C3 - Proceedings of the the fourth international conference on Future energy systems - e-Energy '13 DA - 2013/// DO - 10.1145/2487166.2487212 PB - ACM Press SN - 9781450320528 UR - http://dx.doi.org/10.1145/2487166.2487212 DB - Crossref ER - TY - CONF TI - A study on group communication in distributed wide-area measurement system networks in large power systems AU - Xin, Yufeng AU - Chakrabortty, Aranya T2 - 2013 IEEE Global Conference on Signal and Information Processing (GlobalSIP) AB - Future wide-area measurement and control applications in large electric power systems will require a new decentralized architecture that scales up with the rapidly growing deployment of Phasor Measurement Units (PMUs). The emerging cloud computing paradigm that allows dynamic creation of virtual machines to form virtual data centers would help better support this new architecture through more efficient and flexible use of the networking and computing resources. However, this paradigm shift poses new technical challenges to the underneath communication and computing infrastructure leading to new problem formulations and solution approaches. Given that the primary communication pattern in the decentralized system will consist of various types of real-time group communication methods, in this paper we present a preliminary study on two problems, namely communication group formation and routing, that are fundamental to the envisioned new communication architecture. C2 - 2013/12// C3 - 2013 IEEE Global Conference on Signal and Information Processing DA - 2013/12// DO - 10.1109/globalsip.2013.6736935 PB - IEEE SN - 9781479902484 UR - http://dx.doi.org/10.1109/globalsip.2013.6736935 DB - Crossref ER - TY - JOUR TI - Many-Body Effects in Valleytronics: Direct Measurement of Valley Lifetimes in Single-Layer MoS2 AU - Mai, Cong AU - Barrette, Andrew AU - Yu, Yifei AU - Semenov, Yuriy G. AU - Kim, Ki Wook AU - Cao, Linyou AU - Gundogdu, Kenan T2 - Nano Letters AB - Single layer MoS2 is an ideal material for the emerging field of "valleytronics" in which charge carrier momentum can be finely controlled by optical excitation. This system is also known to exhibit strong many-body interactions as observed by tightly bound excitons and trions. Here we report direct measurements of valley relaxation dynamics in single layer MoS2, by using ultrafast transient absorption spectroscopy. Our results show that strong Coulomb interactions significantly impact valley population dynamics. Initial excitation by circularly polarized light creates electron-hole pairs within the K-valley. These excitons coherently couple to dark intervalley excitonic states, which facilitate fast electron valley depolarization. Hole valley relaxation is delayed up to about 10 ps due to nondegeneracy of the valence band spin states. Intervalley biexciton formation reveals the hole valley relaxation dynamics. We observe that biexcitons form with more than an order of magnitude larger binding energy compared to conventional semiconductors. These measurements provide significant insight into valley specific processes in 2D semiconductors. Hence they could be used to suggest routes to design semiconducting materials that enable control of valley polarization. DA - 2013/12/13/ PY - 2013/12/13/ DO - 10.1021/nl403742j VL - 14 IS - 1 SP - 202-206 J2 - Nano Lett. LA - en OP - SN - 1530-6984 1530-6992 UR - http://dx.doi.org/10.1021/nl403742j DB - Crossref KW - MoS2 KW - valley relaxation KW - transient absorption KW - many-body interactions KW - transition metal dichalcogenides KW - two-dimensional materials ER - TY - CHAP TI - Innovations in Ultrasound Instrumentation for Image Guidance AU - Khuri-Yakub, Pierre AU - Oralkan, Ömer AU - Nikoozadeh, Amin T2 - Intraoperative Imaging and Image-Guided Therapy PY - 2013/11/25/ DO - 10.1007/978-1-4614-7657-3_11 SP - 163-171 OP - PB - Springer New York SN - 9781461476566 9781461476573 UR - http://dx.doi.org/10.1007/978-1-4614-7657-3_11 DB - Crossref ER - TY - JOUR TI - Precise Neural Stimulation in the Retina Using Focused Ultrasound AU - Menz, M. D. AU - Oralkan, O. AU - Khuri-Yakub, P. T. AU - Baccus, S. A. T2 - Journal of Neuroscience AB - Focused ultrasound is a promising noninvasive technology for neural stimulation. Here we use the isolated salamander retina to characterize the effect of ultrasound on an intact neural circuit and compared these effects with those of visual stimulation of the same retinal ganglion cells. Ultrasound stimuli at an acoustic frequency of 43 MHz and a focal spot diameter of 90 μm delivered from a piezoelectric transducer evoked stable responses with a temporal precision equal to strong visual responses but with shorter latency. By presenting ultrasound and visual stimulation together, we found that ultrasonic stimulation rapidly modulated visual sensitivity but did not change visual temporal filtering. By combining pharmacology with ultrasound stimulation, we found that ultrasound did not directly activate retinal ganglion cells but did in part activate interneurons beyond photoreceptors. These results suggest that, under conditions of strong localized stimulation, timing variability is largely influenced by cells beyond photoreceptors. We conclude that ultrasonic stimulation is an effective and spatiotemporally precise method to activate the retina. Because the retina is the most accessible part of the CNS in vivo, ultrasonic stimulation may have diagnostic potential to probe remaining retinal function in cases of photoreceptor degeneration, and therapeutic potential for use in a retinal prosthesis. In addition, because of its noninvasive properties and spatiotemporal resolution, ultrasound neurostimulation promises to be a useful tool to understand dynamic activity in pharmacologically defined neural pathways in the retina. DA - 2013/3/6/ PY - 2013/3/6/ DO - 10.1523/jneurosci.3521-12.2013 VL - 33 IS - 10 SP - 4550-4560 J2 - Journal of Neuroscience LA - en OP - SN - 0270-6474 1529-2401 UR - http://dx.doi.org/10.1523/jneurosci.3521-12.2013 DB - Crossref ER - TY - JOUR TI - A comparison between conventional and collapse-mode capacitive micromachined ultrasonic transducers in 10-MHz 1-D arrays AU - Park, Kwan Kyu AU - Oralkan, O. AU - Khuri-Yakub, B. T. T2 - IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control AB - This paper presents a comprehensive comparison between a collapse-mode and a conventional-mode capacitive micromachined ultrasonic transducer (CMUT); both devices have a 1-μm-thick silicon plate and operate at 10 MHz when biased at 100 V. The radii of the circular plates and the gap heights are modified to meet the design specifications required for a fair comparison. Finite element analysis (FEA) shows that the collapse-mode CMUT has higher output pressure sensitivity (46.5 kPa/V) than the conventional CMUT (13.1 kPa/V), and achieves a 3-dB fractional bandwidth (FBW) of 124% compared with 128% for the conventional mode. These results were validated by experiments performed on devices fabricated in a 1-D phased array configuration using the local oxidation of silicon (LOCOS)/wafer-bonding process. The measured output pressure sensitivity and the FBW of the collapse-mode and the conventional CMUTs at 100 V were 26.4 kPa/V and 103% and 12.7 kPa/V and 111%, respectively. The maximum output pressure of the collapse-mode CMUT was 1.19 MPa at 10 MHz, which was much higher than the conventional CMUT (0.44 MPa). However, the second harmonic distortion (SHD) level of the collapse-mode CMUT is higher than the conventional CMUT at the same excitation condition. Even with higher electric field in the cavity, the collapse-mode CMUT was as stable as the conventional CMUT in a long-term test. A 30-h test with a total of 3.2 × 10 9 cycles of 30 V ac excitation resulted in no significant degradation in the performance of the collapse-mode devices. DA - 2013/6// PY - 2013/6// DO - 10.1109/tuffc.2013.2688 VL - 60 IS - 6 SP - 1245-1255 J2 - IEEE Trans. Ultrason., Ferroelect., Freq. Contr. OP - SN - 0885-3010 UR - http://dx.doi.org/10.1109/tuffc.2013.2688 DB - Crossref ER - TY - JOUR TI - GPU-Based Real-Time Volumetric Ultrasound Image Reconstruction for a Ring Array AU - Choe, Jung Woo AU - Nikoozadeh, A. AU - Oralkan, O. AU - Khuri-Yakub, B. T. T2 - IEEE Transactions on Medical Imaging AB - Synthetic phased array (SPA) beamforming with Hadamard coding and aperture weighting is an optimal option for real-time volumetric imaging with a ring array, a particularly attractive geometry in intracardiac and intravascular applications. However, the imaging frame rate of this method is limited by the immense computational load required in synthetic beamforming. For fast imaging with a ring array, we developed graphics processing unit (GPU)-based, real-time image reconstruction software that exploits massive data-level parallelism in beamforming operations. The GPU-based software reconstructs and displays three cross-sectional images at 45 frames per second (fps). This frame rate is 4.5 times higher than that for our previously-developed multi-core CPU-based software. In an alternative imaging mode, it shows one B-mode image rotating about the axis and its maximum intensity projection, processed at a rate of 104 fps . This paper describes the image reconstruction procedure on the GPU platform and presents the experimental images obtained using this software. DA - 2013/7// PY - 2013/7// DO - 10.1109/tmi.2013.2253117 VL - 32 IS - 7 SP - 1258-1264 J2 - IEEE Trans. Med. Imaging OP - SN - 0278-0062 1558-254X UR - http://dx.doi.org/10.1109/tmi.2013.2253117 DB - Crossref KW - Capacitive micromachined ultrasonic transducer (CMUT) KW - graphics processing unit (GPU) KW - maximum intensity projection (MIP) KW - real-time imaging KW - ring array KW - ultrasound imaging KW - volumetric imaging ER - TY - JOUR TI - Dynamic Response of Model Lipid Membranes to Ultrasonic Radiation Force AU - Prieto, Martin Loynaz AU - Oralkan, Ömer AU - Khuri-Yakub, Butrus T. AU - Maduke, Merritt C. T2 - PLoS ONE AB - Low-intensity ultrasound can modulate action potential firing in neurons in vitro and in vivo. It has been suggested that this effect is mediated by mechanical interactions of ultrasound with neural cell membranes. We investigated whether these proposed interactions could be reproduced for further study in a synthetic lipid bilayer system. We measured the response of protein-free model membranes to low-intensity ultrasound using electrophysiology and laser Doppler vibrometry. We find that ultrasonic radiation force causes oscillation and displacement of lipid membranes, resulting in small (<1%) changes in membrane area and capacitance. Under voltage-clamp, the changes in capacitance manifest as capacitive currents with an exponentially decaying sinusoidal time course. The membrane oscillation can be modeled as a fluid dynamic response to a step change in pressure caused by ultrasonic radiation force, which disrupts the balance of forces between bilayer tension and hydrostatic pressure. We also investigated the origin of the radiation force acting on the bilayer. Part of the radiation force results from the reflection of the ultrasound from the solution/air interface above the bilayer (an effect that is specific to our experimental configuration) but part appears to reflect a direct interaction of ultrasound with the bilayer, related to either acoustic streaming or scattering of sound by the bilayer. Based on these results, we conclude that synthetic lipid bilayers can be used to study the effects of ultrasound on cell membranes and membrane proteins. DA - 2013/10/23/ PY - 2013/10/23/ DO - 10.1371/journal.pone.0077115 VL - 8 IS - 10 SP - e77115 J2 - PLoS ONE LA - en OP - SN - 1932-6203 UR - http://dx.doi.org/10.1371/journal.pone.0077115 DB - Crossref ER - TY - CHAP TI - Measurement-Based Methods for Model Reduction of Power Systems Using Synchrophasors AU - Chakrabortty, Aranya AU - Chow, J. T2 - Power Electronics and Power Systems AB - Wide-area analysis and control of large-scale electric power systems are highly dependent on the idea of aggregation. For example, one often hears power system operators mentioning how “Northern Washington” oscillates against “Southern California” in response to various disturbance events. The main question here is whether we can analytically construct dynamic electromechanical models for these conceptual, aggregated generators representing Washington and California, which in reality are some hypothetical combinations of hundreds of actual generators. In this chapter we present an overview of several new results on how to construct such simplified interarea models of large power systems by using dynamic measurements available from phasor measurement units (PMUs) installed at limited points on the transmission lines. Our examples of study are motivated by widely encountered power transfer paths in the Western Electricity Coordinating Council (WECC), namely a two-area radial system representing the WA-MT flow, a star-connected three-area system resembling the Pacific AC Intertie, and a generic multi-area system with more than one dominant slow mode of oscillation. PY - 2013/// DO - 10.1007/978-1-4614-1803-0_8 SP - 159-197 OP - PB - Springer New York SN - 9781461418023 9781461418030 UR - http://dx.doi.org/10.1007/978-1-4614-1803-0_8 DB - Crossref ER - TY - JOUR TI - Measurement Bounds for Sparse Signal Ensembles via Graphical Models AU - Duarte, M. F. AU - Wakin, M. B. AU - Baron, D. AU - Sarvotham, S. AU - Baraniuk, R. G. T2 - IEEE Transactions on Information Theory AB - In compressive sensing, a small collection of linear projections of a sparse signal contains enough information to permit signal recovery. Distributed compressive sensing extends this framework by defining ensemble sparsity models, allowing a correlated ensemble of sparse signals to be jointly recovered from a collection of separately acquired compressive measurements. In this paper, we introduce a framework for modeling sparse signal ensembles that quantifies the intra- and intersignal dependences within and among the signals. This framework is based on a novel bipartite graph representation that links the sparse signal coefficients with the measurements obtained for each signal. Using our framework, we provide fundamental bounds on the number of noiseless measurements that each sensor must collect to ensure that the signals are jointly recoverable. DA - 2013/7// PY - 2013/7// DO - 10.1109/tit.2013.2252051 VL - 59 IS - 7 SP - 4280-4289 J2 - IEEE Trans. Inform. Theory OP - SN - 0018-9448 1557-9654 UR - http://dx.doi.org/10.1109/tit.2013.2252051 DB - Crossref KW - Compressive sensing (CS) KW - random projections KW - signal ensembles KW - sparsity ER - TY - CONF TI - Understanding Failure Dynamics in the Smart Electric Grid AU - Dubey, A AU - Karsai, G AU - Mahadevan, N AU - Srivastava, A AU - Liu, CC AU - Lukic, S C2 - 2013/// C3 - NSF Energy Cyber Physical System Workshop, Washington DC DA - 2013/// ER - TY - CONF TI - Distance estimation algorithm for plug-in hybrid electric vehicle control strategy AU - Ravey, Alexandre AU - Wang, Rui AU - Lukic, Srdjan AU - Miraoui, Abdellatif T2 - IEEE C2 - 2013/// C3 - 2013 IEEE Transportation Electrification Conference and Expo (ITEC) DA - 2013/// SP - 1-4 ER - TY - JOUR TI - Cutting the cord: Static and dynamic inductive wireless charging of electric vehicles AU - Lukic, Srdjan AU - Pantic, Zeljko T2 - IEEE Electrification Magazine DA - 2013/// PY - 2013/// VL - 1 IS - 1 SP - 57-64 ER - TY - JOUR TI - 2013 Index IEEE Electrification Magazine Vol. AU - Akin, B AU - Balamurali, A AU - Bhavaraju, V AU - Bunzel, S AU - Cairoli, P AU - Carnicero, A AU - Clark, R AU - Cuzner, R AU - Dougal, R AU - Emadi, A AU - others T2 - Cryogenics DA - 2013/// PY - 2013/// VL - 40 SP - 56 ER - TY - JOUR TI - Reducing Migration-Induced Misses In An Over-Subscribed Multiprocessor System AU - REZA, SAJJID AU - BYRD, GREGORY T. T2 - Parallel Processing Letters AB - In a large multiprocessor server platform using multicore chips, the scheduler often migrates a thread or process, in order to achieve better load balancing or ensure fairness among competing scheduling entities. Each migration incurs a severe performance impact from the loss of cache and Translation Lookaside Buffer (TLB) footprints and subsequent higher cache misses and page walks. Such impact is likely to be more severe in virtualized environments, where high over-subscription of CPUs is very common for server consolidation workloads or virtual desktop infrastructure deployment, causing frequent migrations and context switches. We demonstrate the performance benefit of preserving a portion of L2 cache—in particular, MRU cache lines—and warming the destination L2 cache by prefetching those cache lines under different migration scenarios. We observed a 1.5-27% reduction in CPI (cycles per instruction) following a migration. We also study the effectiveness of preserving TLB entries over a context switch or migration. DA - 2013/3// PY - 2013/3// DO - 10.1142/s0129626413500060 VL - 23 IS - 01 SP - 1350006 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84875530850&partnerID=MN8TOARS KW - Process migration KW - cache KW - server consolidation KW - virtualization ER - TY - JOUR TI - Magneto-quasistatic tracking of an American football: A goal-line measurement [measurements corner] AU - Arumugam, D.D. AU - Griffin, J.D. AU - Stancil, D.D. AU - Ricketts, D.S. T2 - IEEE Antennas and Propagation Magazine AB - An American football was tracked using a long-range magneto-quasistatic position and orientation measurement system. A low-weight emitter that emitted a low-frequency quasistatic magnetic field was embedded within an American football. The emitter weighed a total of 26.5 g, which was within the manufacturing tolerance of an American football, and did not alter the dynamics of the ball. Measurements of a person carrying the football along the goal line of an American football field are described, along with a description of the construction of the magneto-quasistatic tracking system. The technique demonstrated measurements with a distance accuracy of 15 cm and an azimuthal orientation accuracy of 2.45° for measurements conducted along the goal line of an American football field. DA - 2013/// PY - 2013/// DO - 10.1109/MAP.2013.6474504 VL - 55 IS - 1 SP - 137-146 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84874844969&partnerID=MN8TOARS KW - Electromagnetic fields KW - magnetoquasistatics KW - radio position measurement KW - radio tracking KW - football ER - TY - CONF TI - An active position sensing tag for sports visualization in American football AU - Arumugam, D.D. AU - Sibley, M. AU - Griffin, J.D. AU - Stancil, D.D. AU - Ricketts, D.S. AB - Remote experience and visualization in sporting events can be significantly improved by providing accurate tracking information of the players and objects in the event. Sporting events such as American football or rugby have proved difficult for camera- and radio-based tracking due to blockage of the line-of-sight, or proximity of the ball to groups of players. Magnetoquasistatic fields have been shown to enable accurate position and orientation sensing in these environments [1]-[3]. In this work, we introduce a magnetoquasistatic tag developed for tracking an American football during game-play. We describe its integration into an American football and demonstrate its use in game-play during a collegiate American football practice. C2 - 2013/// C3 - 2013 IEEE International Conference on RFID, RFID 2013 DA - 2013/// DO - 10.1109/RFID.2013.6548141 SP - 96-103 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84881340615&partnerID=MN8TOARS ER - TY - CONF TI - A stepped-frequency continuous wave ranger for aiding pedestrian navigation AU - Downey, J. AU - Paramesh, J. AU - Stancil, D. AU - Mukherjee, T. AB - Pedestrian navigation is readily enabled by GPS in outdoor environments. However, there are many locations - indoors, urban canyons and underground - where the GPS signal is unreliable or unavailable. Compact, MEMS inertial navigation, augmented by a Shoe Ranging Sensor (SRS) that measures scalar range between shoes, greatly reduces navigational error over large distances in simulations. Existing sensors have insufficient measurement dynamic range or environmental resiliency. Here, the authors report on an SRS based on stepped-frequency continuous wave radar with RMS ranging accuracy of 0.59 mm and 1 m range. This is an order-of-magnitude more accuracy over recent ultra-wideband rangers. C2 - 2013/// C3 - WiSNet 2013 - Proceedings: 2013 IEEE Topical Conference on Wireless Sensors and Sensor Networks - 2013 IEEE Radio and Wireless Week, RWW 2013 DA - 2013/// DO - 10.1109/WiSNet.2013.6488623 SP - 28-30 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84876012098&partnerID=MN8TOARS ER - TY - CONF TI - SVC and STATCOM application in Electric Arc Furnace efficiency improvement AU - Kashani, M.G. AU - Babaei, S. AU - Bhattacharya, Subhashish AB - Electric Arc Furnaces (EAF) are high power industrial loads which cause power quality problems at all voltage levels due to their unbalanced and nonlinear characteristics. The rapid, stochastic large swings in real and reactive power required by the arc furnace causes voltage drops, rapid voltage variation and distortion across the ac supply network. These voltage drops and fluctuations not only have negative impact on the power system quality and other loads, but also have an effect on the arc furnace operation, power output and efficiency. Hence, some sort of reactive compensation is required to limit the voltage disturbances injected by arc furnace into the electric power system. In this paper, an accurate electric arc furnace model, whose parameters have been set according to a 80 MVA actual arc furnace, is studied. A Static VAR Compensator (SVC) is simulated in PSCad and Real Time Digital Simulation (RTDS)/RSCAD platform for the purpose of comparison of voltage regulation at EAF bus. It is shown that the SVC mitigates the reactive power fluctuations in addition to providing the fundamental reactive power, and regulates the Point of Common Coupling (PCC) bus voltage precisely during the arc furnace operation. To verify the PSCad simulation results and make a comparison, a real time simulation study based on Real Time Digital Simulation (RTDS)/RSCAD platform has been performed in this case. On the other hand, a 80 MVA static synchronous compensator (STATCOM) is simulated in PSCad. It is illustrated that the SVC is inherently limited in its ability to respond rapidly to the fluctuating arc furnace load. It is found that the transient performance of the EAF voltage in case which equipped with the STATCOM is better than the case equipped with SVC. It is also demonstrated that although the voltage regulation by the SVC compensates a portion of the reactive power fluctuation, it is completely unable to supply any portion of the fluctuating real power drawn by the arc furnace, while the STATCOM can supply those components of active and reactive power fluctuation. The STATCOM will not normally have a source of real power connected to its DC terminals. It is therefore unable to supply sustained real power or real power fluctuations. With suitable choice of DC capacitor, however, it is capable of supplying in large part the fluctuating real power requirement of the furnace. C2 - 2013/// C3 - 2013 4th IEEE International Symposium on Power Electronics for Distributed Generation Systems, PEDG 2013 - Conference Proceedings DA - 2013/// DO - 10.1109/pedg.2013.6785641 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84899437744&partnerID=MN8TOARS ER - TY - CONF TI - Real-time Hardware-in-the-Loop simulation of convertible static transmission controller for transmission grid management AU - Yousefpoor, N. AU - Azidehak, A. AU - Bhattacharya, Subhashish AU - Parkhideh, B. AU - Celanovic, I. AU - Genic, A. AB - We propose a Convertible Static Transmission Controller (CSTC) concept that enables coordinated power flow control with emphasis on large penetration of renewable energy resources based transmission in a meshed network. CSTS can be connected across the substation power transformer and reconfigured for different modes of operation to perform as a versatile transmission controller with several functions including: power flow control for transmission of renewable resources, and as a transformer back-up for disaster management and/or life extension purposes. Different connecting configuration options, i.e. shunt-shunt, series-shunt, and series-series can be obtained. In this paper, we demonstrated the viability of the proposed concept using Typhoon HIL400 ultra-high fidelity Hardware-in-the-Loop (HIL) system in three different modes of operation. HIL simulations are used to verify the validity of the proposed control architecture for CSTC operation during both normal and unbalanced power system conditions for different connecting configurations. C2 - 2013/// C3 - 2013 IEEE 14th Workshop on Control and Modeling for Power Electronics, COMPEL 2013 DA - 2013/// DO - 10.1109/compel.2013.6626403 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84889049526&partnerID=MN8TOARS ER - TY - CONF TI - Protection of a transformerless intelligent power substation AU - Madhusoodhanan, S. AU - Patel, D. AU - Bhattacharya, Subhashish AU - Carr, J.A. AU - Wang, Z. AB - The Transformerless Intelligent Power Substation (TIPS) is being developed as an alternative to the conventional line frequency transformers at the 13.8 kV distribution grid - 480 V utility grid interface. The Front End Converter (FEC) of TIPS is composed of newly developed 15 kV/20 A Silicon Carbide (SiC) IGBTs and series connected 10 kV/10 A SiC Junction Barrier Schottky (JBS) diodes. The low device current ratings open up a big challenge in the protection of these devices in the event of faults on the a.c side or on the d.c bus as well as during high surge voltage on the line. This paper covers a detailed study of the various components of the fault protection system in terms of their breaking time, breaking current and fault coordination. The evaluation is also done with respect to different fault types like 3-phase to ground fault and single phase to ground fault at various points of the system. The effect of fault on passive elements is also considered. C2 - 2013/// C3 - 2013 4th IEEE International Symposium on Power Electronics for Distributed Generation Systems, PEDG 2013 - Conference Proceedings DA - 2013/// DO - 10.1109/pedg.2013.6785610 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84899427434&partnerID=MN8TOARS ER - TY - CONF TI - Reactive power scheduler for voltage regulation of distributed energy systems AU - Safayet, A. AU - Husain, I. AU - Sozer, Y. AB - A new reactive power scheduler control algorithm for the distributed voltage regulation with PQ inverters is proposed in this research. An elegant approach to achieve voltage regulation in utility grid is proposed through appropriate control of the renewable energy systems. PQ inverter capable of producing the reactive power is used to either achieve local voltage regulation or produce the reactive power commanded from the outer voltage regulator in the upper hierarchy of the grid management system. The proposed PQ scheduler and PQ inverters will work harmoniously in the local substation with minimum communication interface. The proposed control techniques achieve efficient utilization of the PQ inverters with maximum efficiency. The proposed energy network and the control algorithms are modeled at the system level to verify the effectiveness of the proposed system architecture. C2 - 2013/// C3 - 2013 ieee energy conversion congress and exposition (ecce) DA - 2013/// DO - 10.1109/ecce.2013.6647092 SP - 2996-3002 ER - TY - CONF TI - Grid harmonics and voltage unbalance effect elimination for three-phase PLL grid synchronization algorithm AU - Safayet, A. AU - Husain, I. AU - Elrayyah, A. AU - Sozer, Y. AB - The conventional synchronous reference frame phase locked loop (SRF-PLL) works perfectly for synchronization of utility interactive systems with grid that has no imperfections such as harmonics, unbalanced voltage or frequency fluctuation. However, the power grid suffers from these types of imperfections. For large distributed systems such as solar, onshore and offshore wind or wave energy, there is a need for synchronization with the frequency and phase angle of the three-phase grid contaminated with harmonics. For three-phase systems, the other imperfection of the grid that needs to be eliminated before feeding the grid voltage to PLL is the voltage unbalance. The proposed algorithm demonstrates a method to eliminate both the three-phase grid voltage harmonics and unbalance effects to improve the steady state performance of grid synchronization with high bandwidth PLL. C2 - 2013/// C3 - 2013 ieee energy conversion congress and exposition (ecce) DA - 2013/// DO - 10.1109/ecce.2013.6647133 SP - 3299-3304 ER - TY - CONF TI - Design considerations and performance evaluation of 1200 V, 100 a SiC MOSFET based converter for high power density application AU - Hazra, S. AU - Madhusoodhanan, S. AU - Bhattacharya, Subhashish AU - Moghaddam, G.K. AU - Hatua, K. AB - Silicon Carbide (SiC) MOSFET is capable of achieving better efficiency, power density and reliability of power converters due to its low on-state resistance, high temperature operation capability and lower switching losses compared to silicon (Si) IGBT. Operation of power converters at higher switching frequency using SiC devices allows reduction in filter size and hence improves the power to weight ratio of the converter. This paper presents switching characterization of 1200 V, 100 A SiC MOSFET module and compares efficiency of a Two Level Voltage Source Converter (2L-VSC) using SiC MOSFETs and Si IGBTs. Also, various design considerations of the 1200 V, 100 A SiC MOSFET based 2L-VSC including gate drive design, bus bar packaging and thermal management have been elaborated. The designed and developed 2L-VSC is operated to supply 35 kVA load at 20 kHz switching frequency with DC bus voltage at 800 V and the experimental results are presented. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 DA - 2013/// DO - 10.1109/ECCE.2013.6647272 SP - 4278-4285 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891136369&partnerID=MN8TOARS ER - TY - CONF TI - Kinect-based system for automated control of terrestrial insect biobots AU - Whitmire, E. AU - Latif, T. AU - Bozkurt, A. AB - Centimeter scale mobile biobots offer unique advantages in uncertain environments. Our previous experimentation has demonstrated neural stimulation techniques in order to control the motion of Madagascar hissing cockroaches. These trials relied on stimulation by a human operator using a remote control. We have developed a Kinect-based system for computer operated automatic control of cockroaches. Using image processing techniques and a radio transmitter, this platform both detects the position of the roach biobot and sends stimulation commands to an implanted microcontroller-based receiver. The work presented here enables repeatable experimentation and allows precise quantification of the line following capabilities of the roach biobot. This system will help refine our model for the stimulation response of the insect and improve our ability to direct them in increasingly dynamic situations. C2 - 2013/// C3 - 2013 35th annual international conference of the ieee engineering in medicine and biology society (embc) DA - 2013/// DO - 10.1109/embc.2013.6609789 SP - 1470-1473 ER - TY - CONF TI - Electromagnetic levitation platform for wireless study of insect flight neurophysiology AU - Verderber, A. AU - McKnight, M. AU - Bozkurt, A. AB - An electromagnetic levitation platform for use in a light emitting diode (LED) arena based virtual reality environment was developed for wireless recording of neural and neuromuscular signals from the flight related muscle groups in Manduca sexta. The platform incorporates the use of Early Metamorphosis Insertion Technology to implant recording electrodes into the flight muscles of late stage pupal moths. Analysis of the insects' response to changes in the LED arena rotation direction indicate that this setup could be used to perform a variety of flight behavior studies during yaw maneuvers. C2 - 2013/// C3 - 2013 35th annual international conference of the ieee engineering in medicine and biology society (embc) DA - 2013/// DO - 10.1109/embc.2013.6609851 SP - 1720-1723 ER - TY - CONF TI - integration of multi-terminal dc to dc hub architecture with solid state transformer for renewable energy integration AU - Dutta, S. AU - Roy, S. AU - Bhattacharya, S. C2 - 2013/// C3 - 2013 ieee energy conversion congress and exposition (ecce) DA - 2013/// SP - 4793-4800 ER - TY - CONF TI - Tandem InGaP/GaAs-quantum well solar cells and their potential improvement through phosphorus carry-over management in multiple quantum well structures AU - Samberg, J. P. AU - Bradshaw, G. K. AU - Carlin, C. Z. AU - Colter, P. C. AU - Edmondson, K. AU - Hong, W. AU - Fetzer, C. AU - Karam, N. AU - El-Masry, N. A. AU - Bedair, S. M. AB - InGaP/GaAs/Ge multijunction solar cell (MJSC) efficiency can be increased through improved current matching among the subcells with multiple quantum wells (MQWs) being promising for this purpose. In this study we show that InGaAs/GaAsP QWs utilizing high phosphorus composition barriers can be successfully incorporated into the GaAs subcell of an InGaP/GaAs tandem solar cell. This InGaP/GaAs-MQW device has an enhanced short circuit current density when compared to that of a standard InGaP/GaAs tandem device with minimal impact on either GaAs or InGaP subcell open circuit voltage. Additionally, phosphorus carry-over in the MQW structure is investigated through the use of photoluminescence (PL). It is demonstrated that the phosphorus carry-over can be overcome through the utilization of thick GaAs transition layers at the GaAsP→InGaAs interfaces, resulting in a MQW with an extended absorption edge. C2 - 2013/// C3 - 2013 ieee 39th photovoltaic specialists conference (pvsc) DA - 2013/// DO - 10.1109/pvsc.2013.6744479 SP - 1737-1740 ER - TY - CONF TI - Predictive current mode control of single phase dual active bridge DC to DC converter AU - Dutta, S. AU - Bhattacharya, Subhashish AB - In this digest a review of various current control strategies in a bidirectional isolated DC to DC converter is shown. Average current control, peak current control and predictive current control is proposed for the single phase topology. A comparison between the controllers is shown with simulation results and experimental verification. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 DA - 2013/// DO - 10.1109/ecce.2013.6647451 SP - 5526-5533 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891133680&partnerID=MN8TOARS ER - TY - CONF TI - Power management strategy for DC microgrid interfaced to distribution system based on solid state transformer AU - Yu, X. W. AU - She, X. AU - Ni, X. J. AU - Wang, G. Y. AU - Huang, A. AB - A typical DC microgrid, which can be enabled by Solid State Transformer (SST), is investigated in this paper. One unidirectional DC/DC converter for photovoltaic (PV), one bidirectional DC/DC converters for battery, and a SST based on distribution system level, are included in the proposed DC microgrid system. In order to manage the system operation, a distributed power management strategy is proposed. In the proposed control algorithm, not only the DC microgrid system can interface to the distribution system, but each module in the system can be distributed based on its own characteristics. Experimental results verify that the proposed power management strategy can be applied to a DC microgrid stably and achieve good performance. C2 - 2013/// C3 - 2013 ieee energy conversion congress and exposition (ecce) DA - 2013/// DO - 10.1109/ecce.2013.6647394 SP - 5131-5136 ER - TY - CONF TI - Power flow analysis for 3-port 3-phase dual active bridge dc/dc converter and design validation using high frequency planar transformer AU - Baek, S. AU - Roy, S. AU - Bhattacharya, Subhashish AU - Kim, S. AB - In this paper, an inductor-integrated three-winding shell-type planar transformer is designed and analyzed for three-port dual-active bridge (DAB) dc/dc converters in wye wye-delta connection. The steady-state operation principle of the proposed topology has been studied and design parameters of the isolation transformer are analytically determined. The proposed geometry and design method for the ac-link transformer allows us to integrate a large number of bulky inductors required for three phase DAB operation to the transformer without additional connections and unanticipated parasitic effects. It also considerably simplifies the equivalent leakage inductance circuit model and power flow analysis. This configuration is suitable for high power and high step up/down ratio dc/dc converter applications which requires series and/or parallel combination of converters. The experimental and FEM simulation results from prototypes are presented and it validates the theoretical considerations and feasibility of the proposed approach for isolated dc/dc converter applications such as solid-state transformer (SST). C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 DA - 2013/// DO - 10.1109/ecce.2013.6646727 SP - 388-395 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891090658&partnerID=MN8TOARS ER - TY - CONF TI - Performance investigation of hybrid converter systems for mobile mining applications AU - Mirzaee, H. AU - Beddingfield, R. AU - Bhattacharya, Subhashish AU - Parkhideh, B. AB - To supply the AC high power drive systems, several Active Front-Ends (AFEs) with DC choppers are currently used to ensure reliable operation and an acceptable harmonic current spectrum. Recently, integration of the energy storage system with the mining equipment as an example of large mobile multimotor applications has received industry attention, especially for peak load shaving and energy management of the mines. Currently, the regenerative energy is often burnt into the choppers. The industry is motivated to capture this regenerative energy since it can be as high as 60% of the motoring power, as high as 3MJ in every operation cycle and 24 MW peak power. Hybrid approach for the front-end converter system has shown a technology path to deploy on-board energy storage without sacrificing the efficiency and reliability of the entire system. This paper addresses the dynamic performance analysis of such systems through detailed simulation and laboratory scale experiments. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 DA - 2013/// DO - 10.1109/ecce.2013.6646788 SP - 825-831 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891046405&partnerID=MN8TOARS ER - TY - CONF TI - Performance comparison of 1200V 100A SiC MOSFET and 1200V 100A silicon IGBT AU - Wang, G. Y. AU - Wang, F. AU - Magai, G. AU - Lei, Y. AU - Huang, A. AU - Das, M. AB - This paper presents the characteristics of the first commercial 1200V 100A SiC MOSFET module and compares it with state-of-the-art silicon IGBT with the same rating. The results show that the 1200V SiC MOSFET has faster switching speed and much lower loss compared with silicon IGBT. Moreover, the silicon IGBT switching loss will increase significantly for higher operation temperature, while the SiC MOSFET switching loss is almost the same for different temperature. A loss model has been implemented in PLECs in order to simulation the losses. An 11kW singlephase inverter prototype with 600V dc bus and 380Vac output voltage has been built for evaluating and comparing the SiC MOSFET and Si IGBT performance. The test results match with the simulation very well and show that with 40 kHz switching frequency the inverter efficiency can be increased to 98.5% from 96.5% if replacing the Si IGBT with the SiC MOSFET module. C2 - 2013/// C3 - 2013 ieee energy conversion congress and exposition (ecce) DA - 2013/// DO - 10.1109/ecce.2013.6647124 SP - 3230-3234 ER - TY - CONF TI - Oscillatory angle control scheme for PWM static synchronous compensators under unbalanced conditions and system faults AU - Babaei, S. AU - Bhattacharya, Subhashish 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. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 DA - 2013/// DO - 10.1109/ECCE.2013.6646949 SP - 1970-1977 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891134988&partnerID=MN8TOARS ER - TY - CONF TI - Modeling an InGaP/AlGaAs tunnel junction containing an AlAs diffusion barrier AU - Hauser, J. AU - Carlin, Z. AU - Harmon, J. AU - Bradshaw, G. AU - Samberg, J. AU - Colter, P. AU - Bedair, S. AB - Cost improvements in concentrated photovoltaic (CPV) systems can be achieved by operating at increased solar concentration. Current multijunction CPV systems are limited to about 1000× concentration by the performance of the tunnel junctions (TJ) which connect the subcells. The TJ requires materials which are doped in excess of 10 19 cm -3 in order to operate effectively, and so are susceptible to diffusion during the growth of subsequent layers. This paper considers a tunnel junction comprised of tellurium doped n + -InGaP and carbon doped p + -AlGaAs with a several monolayers of AlAs at the interface. The diffusion profile of the dopants was found and used to calculate the tunneling current through a junction. Due to uncertainty in the diffusion constants of C and Te in the three layers, the tunneling current was calculated for several values of Dt. The diffusion constant ratio in the AlAs was taken as a fraction of the diffusion constant in the other two layers. A significant increase in peak tunneling current was seen for Dt>1×10 -14 cm 2 when a three monolayer thick AlAs barrier was present. C2 - 2013/// C3 - 2013 ieee 39th photovoltaic specialists conference (pvsc) DA - 2013/// DO - 10.1109/pvsc.2013.6744883 SP - 2082-2085 ER - TY - CONF TI - Inductive power transfer by means of multiple frequencies in the magnetic link AU - Pantic, Zeljko AU - Lee, Kibok AU - Lukic, Srdjan T2 - IEEE AB - In this paper we explore the concept of transmitting and receiving power wirelessly at multiple frequencies. This proposed frequency multiplex is achieved by using multi-resonant tanks at the transmitter and receiver to amplify and extract power at multiple frequencies. Frequency multiplexed IPT system is a new concept that has numerous advantages over the state of the art: (1) low switching frequency converters can be used to drive high-frequency IPT systems, (2) emission standards may become easier to meet by spreading the power transfer over a spectrum of frequencies, (3) single-frequency receivers tuned to different frequencies can be charged simultaneously even though their coils are at close proximity and mutually coupled, etc. In this paper we develop the theory of source and receiver resonant tank design, and present the complete methodology for determining the system quality factor, effective resistance and power transfer at each frequency. We present a case study of a system that transfers equal amounts of power at 25 kHz and 75 kHz through simulations and experiments. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition DA - 2013/// DO - 10.1109/ecce.2013.6647080 SP - 2912-2919 ER - TY - CONF TI - Finite element based analytical model for controller development of switched reluctance machines AU - Mikail, R. AU - Husain, I. AU - Islam, M. AB - This paper presents a novel method of modeling SRM including mutual coupling effect based on Finite Element Analysis (FEA). Once the machine geometry and design is completed in FEA, it is required to analyze the performance of the machine at different operating conditions with different control methods. Designing control algorithm with FEA in the loop is not convenient because of the complexity and simulation time involved. An analytical model performing similar to the FEA model and including the mutual coupling effect is desired variable speeds of operation. The self and mutual λ-i-θ during tuning of the control algorithm at different modes and characteristics of the machine can be derived from the FEA on the λ-i-θ characteristics of the machine is developed which can model and stored in a look-up table. A state space model based be readily coupled to any controller model. The method incorporates the mutual coupling effect which cannot be neglected for accurate modeling and good controller performance. C2 - 2013/// C3 - 2013 ieee energy conversion congress and exposition (ecce) DA - 2013/// DO - 10.1109/ecce.2013.6646801 SP - 920-925 ER - TY - CONF TI - Field containment in dynamic wireless charging systems through source-reciever interaction AU - Lee, Kibok AU - Pantic, Zeljko AU - Lukic, Srdjan T2 - IEEE AB - This paper presents a new topology appropriate for dynamic wireless charging of electric vehicles. We propose a source coil made from multiple lumped coils powered by a single inverter, with the receiver coil mounted on the vehicle. The proposed system uses the reflected reactance from the receiver to automatically limit the field strength in uncoupled portions of the source-receiver system, thus allowing the system to more easily meet the electromagnetic field emission standards without complex shielding circuits, switches, electronics and communication systems. The power transfer is at its peak when the source-receiver coils pair is strongly coupled resulting in improved system-level efficiency. The analysis is supported by simulation and experiments. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition DA - 2013/// DO - 10.1109/ecce.2013.6647183 SP - 3658-3663 ER - TY - CONF TI - Experimental validation of modular transformer converter based convertible static transmission controller for transmission grid management AU - Yousefpoor, N. AU - Azidehak, A. AU - Bhattacharya, Subhashish AU - Parkhideh, B. AB - For power flow control with specific attention to renewable energy resources based transmission in a meshed network, less complex coordinated control can be obtained with the proposed Convertible Static Transmission Controller (CSTC) concept which is connected across the substation power transformer and can be reconfigured to the required modes of operation. Convertible Static Transmission Controller (CSTC) is a versatile transmission controller which can perform several functions including power flow control for renewable resources transmission and transformer back-up for disaster management or life extension purposes. Different connecting configuration options (shunt-shunt, series-shunt, and series-series) can be obtained in the proposed transmission controller. In this paper, the control structure of CSTC in different modes of operation is presented, and dynamic performance of the CSTC based on the proposed control structures is further investigated in three different connecting configurations in PSCAD/EMTDC environment. Lab-scale experimental results are also presented to evaluate the performance of CSTC in three different modes of operation. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 DA - 2013/// DO - 10.1109/ecce.2013.6647036 SP - 2597-2604 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891109040&partnerID=MN8TOARS ER - TY - CONF TI - Evaluation of 15 kV SiC N-IGBT and P-IGBT for complementary inverter topology with zero dv/dt stress on gate drivers AU - Kadavelugu, A. AU - Bhattacharya, Subhashish AU - Ryu, S.-H. AU - Grider, D. AU - Agarwal, A. AU - Leslie, S. AB - The complementary inverter topology with N-channel and P-channel switching devices is a known method of eliminating dv/dt stress on the gate drivers. In the Silicon (Si) based applications, this advantage did not gain wide attention due to inherent inefficiency of the P-type devices, and the matured technology to handle the dv/dt stress levels produced by these devices with highest blocking voltage rating of 6.5 kV. On the other hand, the ultrahigh voltage (> 12 kV) SiC devices generate high dv/dt due to their high speed switching. This requires meticulous design of the gate drivers for reliable operation of high power converters. As an easy alternative, the option of using a complementary inverter has been explored in this paper. Both N-channel and P-channel IGBTs with blocking capability of 15 kV have been investigated for the complementary structure. The N-IGBT is found to be more efficient than the P-IGBT, based on the experimental switching characterization results at 6 kV and 5 A. The results of the 3 kV half-bridge complementary inverter prototype are also presented. The option of trade-off of P-IGBT field-stop buffer layer parameters (thickness, doping concentration and lifetime) for better switching characteristics can provide the use of complementary topologies a promising alternative for high power conversion. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 DA - 2013/// DO - 10.1109/ecce.2013.6647026 SP - 2522-2527 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891060348&partnerID=MN8TOARS ER - TY - CONF TI - Device characterization and performance of 1200V/45A SiC JFET module AU - Baliga, V. AU - Hazra, S. AU - Singh, S. AU - Roy, S. AU - Bhattacharya, Subhashish AU - Paulakonis, J. AU - Notani, S. AB - This paper evaluates the hard-switching performance of a novel cascode configuration of a 1200V/45A SiC JFET module. The device is first characterized and then switched up to 600V through double pulse testing. The capacitive effects of the device are analyzed and account for a significant current spike during turn-on. The switching behavior due to the gate drive circuitintroduction of varied gate resistances is discussed and analyzed. The switching behavior allows for the extraction of rise time, fall time, dV/dt, di/dt, and the switching losses - E on and E off - while applying these varying gate resistances. The gate drive circuit is discussed and the hardware and test setup are shown and presented. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 DA - 2013/// DO - 10.1109/ecce.2013.6646711 SP - 273-278 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891141152&partnerID=MN8TOARS ER - TY - CONF TI - Determination of carrier recombination lifetime in InGaAs quantum wells from external quantum efficiency measurements AU - Bradshaw, G. K. AU - Carlin, C. Z. AU - Samberg, J. P. AU - Colter, P. C. AU - Bedair, S. M. AB - GaAs cells containing multiple quantum wells (MQW) of strained InGaAs/GaAsP can enhance efficiency in multijunction solar cells. Determination of carrier recombination lifetime in the InGaAs well is useful to understand material quality and carrier transport across the structure. GaAs p-i-n structures with and without strain balanced In 0.17 Ga 0.83 As wells and GaAs 0.25 P 0.75 barriers were grown by MOCVD on p-type GaAs substrates. The GaAsP barrier thickness was varied between devices to intentionally influence carrier transport. A decrease in EQE was observed as barrier width was increased, which was attributed to an increase in tunneling lifetime, τ tn . While this EQE decrease is undesirable in practical devices, it is useful for determining the recombination lifetime, τ r , of the InGaAs wells. The decrease in EQE was observed only at wavelengths of light greater than 600 nm, indicating that minority carrier electrons generated in the base are responsible for the reduction in EQE. Shorter wavelengths (<;600 nm) of light are almost completely absorbed before reaching the base and primarily generate holes in the emitter. The tunneling lifetime and the currents generated in the p-i-n structures were modeled to calculate the EQE of a GaAs control and both thick and thin barrier MQW devices. The probability of transport through the entire MQW structure, P tot , was varied until the calculated EQE fit the experimental data. The value of P tot was then correlated to the only unknown parameter, the recombination lifetime. Using this method the recombination lifetime in In 0.17 Ga 0.83 As in the QW was determined to be 110 ns, which agrees with values found in previous time resolved photoluminescence measurements of metamorphic InGaAs films. C2 - 2013/// C3 - 2013 ieee 39th photovoltaic specialists conference (pvsc) DA - 2013/// DO - 10.1109/pvsc.2013.6744143 SP - 264-267 ER - TY - CONF TI - DC-side series active power filter for STATCOM performance under system faults AU - Babaei, S. AU - Bhattacharya, Subhashish AB - Voltage-Sourced Converter (VSC) based Static Synchronous Compensator (STATCOM) is used in transmission and distribution systems for the purpose of voltage regulation and reactive power compensation. In the transmission level, angle-controlled STATCOMs are of primary interest due to their high efficiency and excellent waveform quality. This type of the STATCOM is fired at line frequency to lower the switching losses. There are considerable numbers of angle-controlled STATCOMs installed in the different utilities in the United States. Despite the high efficiency and good voltage quality, this type of the STATCOM is showing poor performance under AC-system faults. They are usually tripped under severe unbalanced condition and system faults to protect the switches from huge negative sequence current flow. This paper provides a solution to improve the transmission level STATCOM performance under power system faults. Proposed solution is based on adding a single phase inverter in series with converter DC-bus. This single phase inverter generates controllable oscillations with twice the line frequency on the DC-link voltage which will be reflected as negative sequence voltage at VSC output terminals. Generated negative sequence voltage limits the fault negative sequence current flow on the STATCOM tie line. Based on the proposed Solution one specific controller is designed which provides the capability of simultaneous controlling of the both positive and negative sequence voltages. The results are supported by detailed simulation studies on the New York Power Authority (NYPA) STATCOM model using the PSCAD/EMTDC. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 DA - 2013/// DO - 10.1109/ecce.2013.6647405 SP - 5207-5214 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891093461&partnerID=MN8TOARS ER - TY - CONF TI - Control technique for 15 kV SiC IGBT based active front end converter of a 13.8 kV grid tied 100 kVA transformerless intelligent power substation AU - Madhusoodhanan, S. AU - Bhattacharya, Subhashish AU - Hatua, K. AB - This paper discusses the control technique adopted for a 3-Level Neutral Point Clamped (3L-NPC) converter, which is the rectifier stage of a 100 kVA solid state transformer known as the Transformerless Intelligent Power Substation (TIPS) interfacing with 13.8 kV grid. Due to high voltage (13.8 kV) and low power (100 kVA) specification for the rectifier, the control technique needs to be specially designed to control very low magnitude of line current (4.184 A r.m.s). Due to dead time in the converter and harmonic voltage present in the grid, the rectifier current is rich in lower order harmonics (6m±1). Moreover due to very high grid voltage, limiting starting inrush current within the converter current rating is a serious issue. A unified control technique is discussed to mitigate the above mentioned problems. Also the proposed control technique addresses the grid voltage unbalance and d.c bus mid-point voltage unbalance issue faced by the rectifier stage of TIPS. Simulation and SiC IGBT prototype experimental results verify the proposed techniques. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 DA - 2013/// DO - 10.1109/ecce.2013.6647331 SP - 4697-4704 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891067107&partnerID=MN8TOARS ER - TY - CONF TI - Control of Active Mobile Substations under system faults AU - Yousefpoor, N. AU - Azidehak, A. AU - Bhattacharya, Subhashish AU - Parkhideh, B. AB - While conventional mobile substations are used to bypass the whole substation in case of loss or maintenance of power transformers, Active Mobile Substations (AMS) can be used both in normal conditions as a power router and in contingencies as a recovery transformer. The AMS is a mobile substation with integrated power electronics. By controlling its throughput power, it can be connected across different transformers of the grid. This paper explores transmission-level active mobile substations that provide back-up in case of power transformer failure or forced reduced operation scenarios in addition to power flow control for seasonal renewable energy transmission. The AMS must be designed to operate satisfactorily under typical fault and unbalanced conditions. In this paper, component design considerations in development of the AMS under unbalanced operating condition will be provided, and a new control strategy is proposed to control AMS under unbalanced operating conditions when component design is not sufficient to prevent overcurrent and trips. Detailed PSCAD simulation for the proposed control scheme is performed and results are presented. Experimental results are also shown to verify the proposed control method under unbalanced operating conditions. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 DA - 2013/// DO - 10.1109/ECCE.2013.6646948 SP - 1962-1969 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891048215&partnerID=MN8TOARS ER - TY - CONF TI - Comparative evaluation of SiC devices for PWM buck rectifier based active front end converter for MV grid interface AU - Madhusoodhanan, S. AU - Cho, Y. AU - Kadavelugu, A. AU - Bhattacharya, Subhashish AU - Grider, D. AU - Ryu, S.-H. AU - Agarwal, A. AU - Leslie, S. AB - In this paper a new method for implementation of a 3-phase medium voltage rectifier is presented for Active Front End grid interface applications. A current source based PWM buck rectifier with Silicon Carbide (SiC) devices, different from the traditional GTO based current source rectifier, is used to grid tie with 3-phase, 4.16 kV grid. The power level considered is 100 kVA. Simplicity of construction, very high efficiency, better input line current control and small volume are the main advantages of this system. Due to low switching losses compared with traditional GTOs, PWM operation of the rectifier at higher switching frequencies is possible. A detailed simulation shows the validity of the proposed method. Efficiency comparison of the PWM Buck rectifier with 10 kV/10 A SiC MOSFET and 15 kV/20 A SiC IGBT as the active devices is also presented. Low voltage hardware prototype based high frequency switching validation is also carried out. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 DA - 2013/// DO - 10.1109/ecce.2013.6647097 SP - 3034-3041 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891099153&partnerID=MN8TOARS ER - TY - CONF TI - Cogging torque reduction in flux-switching permanent magnet machines by rotor pole shaping AU - Sikder, C. AU - Husain, I. AU - Ouyang, W. AB - Cogging torque in flux-switching permanent magnet machines (FSPMs) is relatively high compared with 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-EMF and average electromagnetic torque have also been investigated. C2 - 2013/// C3 - 2013 ieee energy conversion congress and exposition (ecce) DA - 2013/// DO - 10.1109/ecce.2013.6646890 SP - 1555-1562 ER - TY - CONF TI - Closed loop D-Q control of high-voltage high-power three-phase dual active bridge converter in presence of real transformer parasitic parameters AU - Tripathi, A.K. AU - Mainali, K. AU - Patel, D. AU - Bhattacharya, Subhashish AU - Hatua, K. AB - Three-phase Dual Active Bridge (DAB) Y : Y/Δ composite topology offers advantage of nearly sinusoidal converter-currents without pulse-width modulation, which can be utilized for D-Q mode control implementation. D-Q control is smooth and regulates power-factor of DAB which ensures zero voltage switching (ZVS) operation of the DAB converter at wide-range loading conditions. A practical DAB high-frequency transformer has certain limitations like small leakage-inductance, limited magnetizing-inductance and unwanted parasitic-capacitance's which distort the primary-side currents at the rated high-voltage because primary inter-turn capacitance is high in per-unit for a real 100kW transformerdesign. This problem can be solved by using secondary currents and estimated magnetizing current to emulate primary-currents for D-Q control. Parasitic are introduced in the LV TIPS set-up by adding lumped elements to emulate real HV-transformer with objective to test the controls in worst case scenario. This paper proposes the solutions for some of the practical implementation problems of the control algorithm for the DAB. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 DA - 2013/// DO - 10.1109/ecce.2013.6647446 SP - 5488-5495 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891099254&partnerID=MN8TOARS ER - TY - CONF TI - Characterization of 15 kV SiC n-IGBT and its application considerations for high power converters AU - Kadavelugu, A. AU - Bhattacharya, Subhashish AU - Ryu, S.-H. AU - Brunt, E. Van AU - Grider, D. AU - Agarwal, A. AU - Leslie, S. AB - The 4H-SiC n-IGBT is a promising power semiconductor device for medium voltage power conversion. Currently, Cree has successfully built 15 kV n-IGBTs. These IGBTs are pivotal for the smart grid power conversion systems and medium voltage drives. The need for complex multi-level topologies or series connected devices can be eliminated, while achieving reduced power loss, by using the SiC IGBT. In this paper, characteristics of the 15 kV n-IGBT have been reported for the first time. The turn-on and turn-off transitions of the 15 kV, 20 A IGBT have been experimentally evaluated up to 11 kV. This is highest switching characterization voltage ever reported on a single power semiconductor device. The paper includes static characteristics up to 25 A (forward) and 12 kV (blocking). The dependency of the power loss with voltage, current and temperature are provided. In addition, the basic converter design considerations using this ultrahigh voltage IGBT for high power conversion applications are presented. Also, a comparative evaluation is reported with an IGBT with thicker field-stop buffer layer as a means to show flexibility in choosing the IGBT design parameters based on the power converter frequency and power rating specification. Finally, power loss comparison of the IGBTs and MOSFET is provided to consummate the results for a complete reference. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 DA - 2013/// DO - 10.1109/ecce.2013.6647027 SP - 2528-2535 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891115267&partnerID=MN8TOARS ER - TY - CONF TI - Bidirectional soft-switched AC/AC high frequency link converter AU - De, A. AU - Roy, S. AU - Bhattacharya, Subhashish AB - This paper investigates a soft-switching partial-resonant link AC/AC converter. The proposed converter uses 12 unidirectional switches and overcomes the various shortcomings of conventional AC Link schemes. The switching operations occur at zero voltage instants thus lowering the switching losses. The input and output current is harmonic free and the controller also allows setting of desired power factor. It can perform buck and boost operations and has bi-directional power flow capability. As the converter operates at high switching frequency, it offers both improved performance and considerable reduction of volume, weight and cost. Detailed simulation results are presented and prototype converter system has been built and tested. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 DA - 2013/// DO - 10.1109/ecce.2013.6647430 SP - 5377-5384 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891133946&partnerID=MN8TOARS ER - TY - CONF TI - A multi-loop control system for series DC active filter in a medium-voltage DC amplifier AU - Mirzaee, H. AU - Bhattacharya, Subhashish AU - Bala, S. AB - In order to cope with increasing power demand onboard future combatant ships, US navy has embarked on medium-voltage dc as the next generation integrated power system. A viable dc power supply system solution for such ships is based on the mature technology of multi-pulse thyristor bridge front-end rectifiers. Due to the intrinsic ripple characteristic associated with thyristor commutations in such front-ends, a high bandwidth series dc active filter can be used to smooth out the dc-bus. In this paper, we propose a new multi-loop feedback and feed-forward control system for the series dc active filter in order to meet the stringent dc-bus ripple attenuation and disturbance rejection requirements. Analysis and simulations results show promise of multi-loop control scheme. Experimental results of the 12kVA/400Vdc laboratory test-bed with feed-forward control are provided. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 DA - 2013/// DO - 10.1109/ecce.2013.6647403 SP - 5193-5198 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891093183&partnerID=MN8TOARS ER - TY - CONF TI - A cost effective power sharing strategy for a cascaded multilevel converter based Solid state transformer AU - She, X. AU - Huang, A. Q. AU - Ni, X. J. AB - This paper proposes a power sharing strategy for DC/DC stage of a cascaded multilevel converter based solid state transformer. It is revealed that the equalization of the active power component of duty cycles in the cascaded multilevel rectifier stage can be a good indicator of power balance in the DC/DC stage. Additionally, the power balance of the DC/DC stage can guarantee the voltage balance in the rectifier stage if the differences among the power devices are negligible. Based on this principle, a novel power balance controller without sensing any current in the DC/DC stage is proposed. Both simulation and experimental results in a seven-level three-stage solid state transformer are provided for verifying the proposed method. C2 - 2013/// C3 - 2013 ieee energy conversion congress and exposition (ecce) DA - 2013/// DO - 10.1109/ecce.2013.6646725 SP - 372-379 ER - TY - CONF TI - A control structure for line-frequency-switched STATCOMs under system faults AU - Babaei, S. AU - Bhattacharya, Subhashish AB - Voltage-Sourced Converter (VSC) based Static Synchronous Compensator (STATCOM) is used for voltage regulation in transmission and distribution systems. Comparing with PWM STATCOMs, Angle-controlled STATCOMs are fired at line frequency to lower the system losses. In recent years, angle-controlled STATCOMs have been deployed by utility owners for the purpose of voltage regulation, voltage stability improvement and increasing operational functionality. Despite the superior feature on voltage waveform quality and efficiency, the practical angle-controlled STATCOMs suffer from the over-current (and trips) and possible saturation of the interfacing transformers caused by negative sequence current during unbalanced conditions and system faults. This paper specifically proposes a control structure to improve the angle-controlled STATCOMs performance under unbalanced conditions and system faults. The main improvement is to decrease the negative sequence current and DC-link voltage oscillations substantially under power line faults through the control and not the components design. PSCAD/EMTDC and experimental results verify the validity of the proposed control structure under unbalanced conditions and system faults. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 DA - 2013/// DO - 10.1109/ecce.2013.6647037 SP - 2605-2612 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891087871&partnerID=MN8TOARS ER - TY - CONF TI - 15 kV SiC IGBT based three-phase three-level modular-leg power converter AU - Patel, D.C. AU - Kadavelugu, A. AU - Madhusoodhanan, S. AU - Bhattacharya, Subhashish AU - Hatua, K. AU - Leslie, S. AU - Ryu, S.-H. AU - Grider, D. AU - Agarwal, A. AB - The 15kV /20A, 4H-SiC n-IGBT is the state-of-the-art high voltage power semiconductor device. The transformerless intelligent power substation (TIPS) [1] for 13.8kV grid interfacing is built using this device. It is proposed to use a three-phase, three-level, diode clamped topology as the front end converter (FEC) in TIPS. A modular-leg structure has been employed for FEC. In modular-leg structure, each phase-leg will have its own DC-link capacitors and a low inductance bus-bar. However, modular-leg structure adds complexity in DC bus over-load protection, which is studied in this paper. Experimental results of modular-leg converter at 3kV DC link voltage and scale down prototype of AC switch for DC bus fault protection are presented. C2 - 2013/// C3 - 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 DA - 2013/// DO - 10.1109/ecce.2013.6647132 SP - 3291-3298 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84891113691&partnerID=MN8TOARS ER - TY - CONF TI - Investigation of intermediate dielectric for dual floating gate MOSFET AU - Sarkar, B. AU - Jayanti, S. AU - Spigna, N. Di AU - Lee, B. AU - Misra, V. AU - Franzon, Paul AB - A dual floating gate transistor offers potential as a unified memory, with simultaneous volatile and non-volatile storage. The quality of the dielectric between the two floating gates is critical to achieving the required dynamic cycle endurance. This paper reports on the results of early experiments into the material choice and process for this dielectric. C2 - 2013/// C3 - 2013 13th Non-Volatile Memory Technology Symposium (NVMTS) DA - 2013/// DO - 10.1109/nvmts.2013.6851052 ER - TY - JOUR TI - Compact spatial heterodyne interferometer using polarization gratings AU - Kudenov, Michael W. AU - Miskiewicz, Matthew N. AU - Escuti, Michael J. AU - Coward, Jim T2 - POLARIZATION SCIENCE AND REMOTE SENSING VI AB - Spatial heterodyne interferometry (SHI) is a spectral measurement technique based on Fourier Transform Spectroscopy (FTS). One main benefit of an FTS lies in its higher spectral resolving power over direct measurement (dispersive) systems; however, accessing this higher resolving power can result in longer measurement times without heterodyning techniques. In this paper, the calibration and modeling of a polarization SHI is detailed, based on the Jones matrix formalism. With this, we explore non-ideal aspects of the polarization grating, such as zero-order light leakage. This light leakage causes crosstalk that can introduce errors in the spectral calibration. To minimize error, a calibration procedure is introduced based on a linear operator theory. Finally, the Jones matrix model and calibration procedure are validated through a series of experiments. DA - 2013/// PY - 2013/// DO - 10.1117/12.2024104 VL - 8873 SP - SN - 1996-756X KW - Polarization KW - spatial heterodyne KW - Fourier transform spectroscopy KW - polarization gratings KW - birefringence KW - interferometry ER - TY - CONF TI - On the efficient wireless power transfer in resonant multi-receiver systems AU - Ricketts, D. S. AU - Chabalko, M. J. AB - In this paper we present an analysis of resonant wireless power transfer in systems with multiple receivers. We show that maximum power transfer can be achieved when the source is impedance matched to the set of receivers, i.e. matched to their equivalent impedance as seen by the source. The interaction of the receivers, or coupled modes, simply represent an interdependence of impedances that can be modeled and impedance matched. We explore three methods to achieve impedance matching: frequency tuning, impedance transformation and resonant tuning and show that the later two can achieve the maximum theoretical power transfer for a wide range of coupling between receivers. C2 - 2013/// C3 - 2013 ieee international symposium on circuits and systems (iscas) DA - 2013/// DO - 10.1109/iscas.2013.6572455 SP - 2779-2782 ER - TY - CONF TI - Modeling of dense metallic grids for transparent transmission lines and antennas AU - Adams, J. J. AU - Bernhard, J. T. C2 - 2013/// C3 - 2013 ieee antennas and propagation society international symposium (apsursi) DA - 2013/// SP - 700-701 ER - TY - CONF TI - Investigation of close-in passive intermodulation distortion on antennas AU - Steer, M. B. AU - Wetherington, J. M. AU - Wilkerson, J. R. AB - Passive intermodulation distortion (PIM) generated on antennas is experimentally investigated and shown to agree with calculations based on an electro-thermal origin. Two-tone testing is used in the investigations with tone spacings ranging from 3 Hz to 100 kHz. The two-tone measurement system has a minimum spurious-free dynamic range of 125 dB at 3 Hz tone separation. Results show that at least some of the PIM generated by an antenna is due to electro-thermal effects but it is apparent that there are sources of PIM that cannot be described by electro-thermal effects alone. C2 - 2013/// C3 - 2013 ieee antennas and propagation society international symposium (apsursi) DA - 2013/// DO - 10.1109/aps.2013.6711784 SP - 2251-2252 ER - TY - CONF TI - Exploring early design tradeoffs in 3DIC AU - Franzon, P. D. AU - Priyadarshi, S. AU - Lipa, S. AU - Davis, W. R. AU - Thorolfsson, T. T2 - 2013 IEEE International Symposium on Circuits and Systems (ISCAS) AB - This The key to gaining substantial benefit from the use of 3DIC technology is to create 3D specific designs that do more than recast a 2D optimal design into the third dimension. This paper explores some of the approaches to creating 3D specific designs and the CAD tools that can help in that exploration. The power advantages of 3D design are illustrated in details. Results from different partitioning approaches (function, modular and circuit) are presented, together with early results from a thermal pathfinding tool. C2 - 2013/// C3 - 2013 IEEE International Symposium on Circuits and Systems (ISCAS) CY - Beijing, China DA - 2013/// PY - 2013/5/19/ DO - 10.1109/iscas.2013.6571901 SP - 545–549 ER - TY - CONF TI - Continuous shape estimation of continuum robots using X-ray images AU - Lobaton, Edgar J. AU - Fu, Jinghua AU - Torres, Luis G. AU - Alterovitz, Ron AB - We present a new method for continuously and accurately estimating the shape of a continuum robot during a medical procedure using a small number of X-ray projection images (e.g., radiographs or fluoroscopy images). Continuum robots have curvilinear structure, enabling them to maneuver through constrained spaces by bending around obstacles. Accurately estimating the robot's shape continuously over time is crucial for the success of procedures that require avoidance of anatomical obstacles and sensitive tissues. Online shape estimation of a continuum robot is complicated by uncertainty in its kinematic model, movement of the robot during the procedure, noise in X-ray images, and the clinical need to minimize the number of X-ray images acquired. Our new method integrates kinematics models of the robot with data extracted from an optimally selected set of X-ray projection images. Our method represents the shape of the continuum robot over time as a deformable surface which can be described as a linear combination of time and space basis functions. We take advantage of probabilistic priors and numeric optimization to select optimal camera configurations, thus minimizing the expected shape estimation error. We evaluate our method using simulated concentric tube robot procedures and demonstrate that obtaining between 3 and 10 images from viewpoints selected by our method enables online shape estimation with errors significantly lower than using the kinematic model alone or using randomly spaced viewpoints. C2 - 2013/5// C3 - 2013 IEEE International Conference on Robotics and Automation DA - 2013/5// DO - 10.1109/icra.2013.6630653 SP - 725–732 PB - IEEE UR - http://dx.doi.org/10.1109/icra.2013.6630653 ER - TY - CONF TI - Towards a smart bandage with functional near infrared spectroscopy capability AU - Dieffenderfer, J. AU - Bair, M. C. AU - Bozkurt, A. AB - This paper presents our efforts towards a smart bandage with incorporated miniaturized wireless functional near infrared spectroscopy system as a sensor node for wearable body area networks. The built prototype was used to successfully transmit deoxygenation of forearm muscle tissue during pressure cuff induced ischemia through an established Bluetooth link. The system can run over 4 hours continuously sampling at 150 Hz with provided 90mAh lithium polymer batteries and transmit data to distances more than 75 meters. C2 - 2013/// C3 - Ieee topical conference on biomedical wireless technologies networks and DA - 2013/// DO - 10.1109/biowireless.2013.6613659 SP - 13-15 ER - TY - CONF TI - Topological mapping of unknown environments using an unlocalized robotic swarm AU - Dirafzoon, Alireza AU - Lobaton, Edgar AB - Mapping and exploration are essential tasks for swarm robotic systems. These tasks become extremely challenging when localization information is not available. In this paper, we explore how stochastic motion models and weak encounter information can be exploited to learn topological information about an unknown environment. Our system behavior mimics a probabilistic motion model of cockroaches, as it is inspired by current biobotic (cyborg insect) systems. We employ tools from algebraic topology to extract spatial information of the environment based on neighbor to neighbor interactions among the biologically inspired agents with no need for localization data. This information is used to build a map of persistent topological features of the environment. We analyze the performance of our estimation and propose a switching control mechanism for the motion models to extract features of complex environments in an effective way. C2 - 2013/11// C3 - 2013 IEEE/RSJ International Conference on Intelligent Robots and Systems DA - 2013/11// DO - 10.1109/iros.2013.6697160 SP - 5545–5551 PB - IEEE UR - http://dx.doi.org/10.1109/iros.2013.6697160 ER - TY - CONF TI - Thermal requirements in future 3D processors AU - Franzon, Paul AU - Bar-Cohen, Avi T2 - 2013 IEEE International 3D Systems Integration Conference (3DIC) AB - This paper reports on a study in which the projected thermal load of future 3D optimized embedded computers was explored. The approach taken was to project the performance, power consumption and area of a reasonably power-efficient 7 nm, 6672 core baseline conventionally packaged (“2D”) design, and 3D alternatives to this design. The 3D alternatives have improved power efficiency over the baseline 2D design, due to their reduced interconnect power consumptions and reduced processing overhead. The most efficient set of designs use more aggressive 3D-specific strategies to increase power efficiency at the expense of increased heat flux. The most efficient design is 38% more power efficient than the baseline 2D design, but has 13x the heat flux of that design. The value of that heat flux was 5.4 W/mm 2 . Further optimizations increase the thermal flux even further. Specifically creating architecture optimized to floating point operations, increases the heat flux to 17 W/mm 2 while improving the computing efficiency by another 2x. C2 - 2013/10// C3 - 2013 IEEE International 3D Systems Integration Conference (3DIC) DA - 2013/10// DO - 10.1109/3dic.2013.6702402 PB - IEEE SN - 9781467364843 UR - http://dx.doi.org/10.1109/3dic.2013.6702402 DB - Crossref ER - TY - CONF TI - TSV-based, modular and collision detectable face-to-back shared bus design AU - Zhang, Z. Q. AU - Franzon, Paul AB - In this paper, we present a shared backbone bus solution specially tuned for modular 3DIC post-silicon-stacking. The proposed solution allows multiple parallel TSV-based channels to be placed and shared among various stacked components, which is uniquely supported by the dense connection pitch of the Face-to-back TSV bonding technology. To support the plug-n-play features, a distributed arbitration and collision detection structure is designed and evaluated. A demo of 16-channel shared bus is synthesized and verified under .13 μm technology. The conservative power estimate is 0.20 pJ/bit and bandwidth per area is 0.984 Tbps/mm 2 . C2 - 2013/// C3 - 2013 ieee international 3d systems integration conference (3dic) DA - 2013/// DO - 10.1109/3dic.2013.6702399 ER - TY - CONF TI - Solid state transformer in the future smart electrical system AU - She, X. AU - Huang, A. AB - The concept of the solid state transformer has been investigated extensively in the past decade with the emphasis mainly focused on the circuit topology investigation. With the technology being more and more mature and acceptable, the application issue of solid state transformer in the future smart electrical system needs to be investigated. This paper characterizes and summarizes the main features of the solid state transformer, and correspondingly presents possible application areas of solid state transformer in the future smart electrical system. The future distribution system architecture is proposed and a new wind energy system is presented based on the multifunctional utilization of SST. Simulation results are given to demonstrate the proposal. C2 - 2013/// C3 - 2013 ieee power and energy society general meeting (pes) DA - 2013/// DO - 10.1109/pesmg.2013.6672768 ER - TY - CONF TI - Proposing a electricity market framework for the energy internet AU - Su, W. C. AU - Huang, A. Q. AB - Smart Grid is drawing increasing attentions and reshaping the traditional view of power systems in the last decade. The Future Renewable Electric Energy Delivery and Management (FREEDM) Systems provide a promising solution to accommodate the high penetration of intermittent renewable energy resources and the emerging Smart Grid technologies. As a future automated and flexible electric power distribution system, the envisioned FREEDM systems enable the customers to fully participate in a deregulated electricity market. The customers are not only the price-takers but also the electricity suppliers by locally operating and managing their own Distributed Generators (DGs), Distributed Energy Storage Devices (DESDs), and dispatchable loads. This paper proposes a novel framework for a deregulated electricity market to enable the “Energy Internet” in a residential distribution system. It can achieve the flexible energy/power dispatch by allowing the customers to maximize their own benefits and compete with each other. Some game-theoretic methodologies (e.g., Nikaido-Isoda function and relaxation algorithm) are applied to determine the equilibrium solutions in a deregulated electricity market. A numerical case study is performed to validate the proposed approach. Accordingly, the numerical simulation results demonstrate the effectiveness and accuracy of the proposed framework for clearing the deregulated electricity market price enabling the “Energy Internet”. C2 - 2013/// C3 - 2013 ieee power and energy society general meeting (pes) DA - 2013/// DO - 10.1109/pesmg.2013.6672224 ER - TY - CONF TI - Power comparison of 2D, 3D and 2.5D interconnect solutions and power optimization of interposer interconnects AU - Karim, M. A. AU - Franzon, Paul AU - Kumar, A. AB - This paper compares the power efficiency of multiple 2D, 2.5D and 3D interconnect scenarios, specifically DDR3 with PCB, DDR3 with interposers, LPDDR2(3) with POP, wide I/Os with through-silicon vias (TSVs) and interposers and 32 nm technology CMOS drivers with TSVs and on-chip wires. It was found that DDR3 with PCB is the lowest power efficiency (15.65 mW/Gbps) and custom designed CMOS drivers optimized for the 2.5D and 3D give the highest power efficiency (0.23mW/Gbps). Optimization of a Back End of the Line (BEOL) 65 nm interposer interface is also presented for Wide IO interface to find maximize power efficiency. Power efficiency for different interposer trace lengths (5mm-40mm) and pitches (4.6μm-11.05μm) was analyzed. It was found that power efficiency decreases linearly with the increase of pitch and length of the interposer traces both in one stack and 4 stack die of Wide IO. C2 - 2013/// C3 - 2013 IEEE 63rd Electronic Components and Technology Conference (ECTC) DA - 2013/// DO - 10.1109/ectc.2013.6575674 SP - 860–866 ER - TY - CONF TI - Network coordinated distributed demand management for optimal large-scale charging of PHEVs/PEVs AU - Asr, N. R. AU - Chow, M. Y. AB - Designing efficient demand management policies for charging Plug-in Hybrid Electrical Vehicles (PHEVs) and Plug-in Electrical Vehicles (PEVs) is becoming a vital issue as increasing numbers of these vehicles are being introduced to the power grid. In order to avoid overloads and satisfy customer preferences in terms of the time and cost of charging, a distribution-level charging algorithm can be formulated to solve a constrained optimization problem. In this paper, we have developed a novel network distributed algorithm for optimal charging of PHEVs/PEVs within a consensus algorithm framework. In our design, the global optimal power allocation under all local and global constraints is reached by peer-to-peer coordination of charging stations. Therefore, the need for a central control unit is eliminated. In this way, the single node congestion is avoided when the size of the problem is increased, and the system gains robustness against single link/node failures. C2 - 2013/// C3 - 2013 ieee power and energy society general meeting (pes) DA - 2013/// DO - 10.1109/pesmg.2013.6672367 ER - TY - CONF TI - Machine learning based posture estimation for a wireless canine machine interface AU - Brugarolas, R. AU - Roberts, D. AU - Sherman, B. AU - Bozkurt, A. AB - Effective training and accurate interpretation of canine behaviors are essential for dog welfare and to obtain the maximum benefits provided by working dogs. We are developing a canine body area network based interface to incorporate electronic sensing and computational behavior modeling into canine training, where computers will be able to provide real time feedback to trainers about canine behavior. In this study, we investigated the accuracy of machine learning algorithms in identifying canine posture through wireless inertial sensing with 3-axis accelerometers and 3-axis gyroscopes. Data was collected from two dogs performing a sequence of 5 postures (sit, stand, lie, stand on two legs, and eat off the ground). A two-stage cascade learning technique was used: one for differentiating samples of behaviors of interest from transitions between behaviors, and one for posture classification of the behaviors. The algorithms achieved high posture classification accuracies demonstrating potential to enable a real time canine computer interface. C2 - 2013/// C3 - Ieee topical conference on biomedical wireless technologies networks and DA - 2013/// DO - 10.1109/biowireless.2013.6613658 SP - 10-12 ER - TY - JOUR TI - Hardware-in-the-Loop Simulations and Verifications of Smart Power Systems Over an Exo-GENI Testbed AU - Chakrabortty, Aranya AU - Xin, Yufeng T2 - 2013 SECOND GENI RESEARCH AND EDUCATIONAL EXPERIMENT WORKSHOP (GREE) AB - In this paper we describe an advanced hardware-in- loop simulation facility for real-time demonstration and validation of power system monitoring and control algorithms, currently under construction at NC State University. This facility integrates a real-time power system emulation lab with the GENI network and its associated cloud testbeds. The dynamic responses from the power system emulator are captured via real hardware Phasor Measurement Units (PMU) that are synchronized with the time-scale of the simulations via a common GPS reference. These responses are then sent to the computing and storage resource in GENI using the IEEE C37.118 protocol, running the smart grid control and management application simulations via QoS-guaranteed communications channels, all provisioned in a dynamic fashion. DA - 2013/// PY - 2013/// DO - 10.1109/gree.2013.12 SP - 16-19 ER - TY - CONF TI - Face-to-face bus design with built-in self-test in 3D ICS AU - Zhang, Z. Q. AU - Noia, B. AU - Chakrabarty, K. AU - Franzon, Paul AB - This paper presents a bus structure, synchronization and test scheme for fast data transfer between logic dies in stacked 3D ICs using face-to-face (F2F) micro-bumps. The proposed design permits different designs, such as microprocessor, co-processor and accelerator, to be integrated together vertically with high bandwidth and low power, which is uniquely enabled by the dense F2F micro-bumps. We propose a new teleport-register-file structure and corresponding clock gating and switching techniques to synchronize data across multiple clock domains. Simultaneous bi-directional transfer is supported and 50% reduction of flip-flops compared with conventional synchronizer design. Moreover, a lightweight built-in-self-test (BIST) unit is integrated into the bus. The BIST unit allows for rapid stuck-at and transition fault testing of the 3D bus interconnects and associated logic, without the need for an external tester. BIST allows field testing and test/validation at later stages of 3D integration. The BIST architecture utilizes the architectures and functions inherent to the bus and requires little extra hardware or dedicated interconnects between dies. Functionality and performance demos are verified and simulated under .13 μm technology. The energy cost estimate is 0.22 pJ/bit and maximum bandwidth per area is 1.42 Tb/mm 2 . C2 - 2013/// C3 - 2013 ieee international 3d systems integration conference (3dic) DA - 2013/// DO - 10.1109/3dic.2013.6702395 ER - TY - CONF TI - Dynamic adaptive anti-jamming via controlled mobility AU - He, X. F. AU - Dai, H. Y. AU - Ning, P. AB - In this work, the mobility of network nodes is explored as a new promising approach for jamming defense. To fulfill it, properly designed node motion that can intelligently adapt to the jammer's action is crucial. In our study, anti-jamming mobility control is investigated in the context of the single and multiple commodity flow problems, in the presence of one intelligent mobile jammer which can respond to the evasion of legitimate nodes as well. Based on spectral graph theory, two new spectral quantities, single- and multi-weighted Cheeger constants and corresponding eigenvalue variants, are constructed to direct motions of the defender and the attacker in this dynamic adaptive competition. Both analytical and simulation results are presented to justify the effectiveness of the proposed approach. C2 - 2013/// C3 - 2013 IEEE Conference on Communications and Network Security (CNS) DA - 2013/// DO - 10.1109/cns.2013.6682686 SP - 1-9 ER - TY - CONF TI - Distributed energy management under smart grid plug-and-play operations AU - Zhang, Z. AU - Zhang, Y. AU - Chow, M. Y. AB - With the increasing penetration of distributed generation, the plug-and-play energy resources or energy storage devices will become a required functionality of future power systems. Effective distributed control algorithms could be embedded in distributed controllers to allocate energy among the generating systems economically when a plug-and-play operation is performed. The Incremental Cost Consensus (ICC) algorithm can solve this kind of Economic Dispatch Problem (EDP) in a distributed fashion. Several case studies are presented to demonstrate the performance of the ICC algorithm under smart grid plug-and-play operations. C2 - 2013/// C3 - 2013 ieee power and energy society general meeting (pes) DA - 2013/// DO - 10.1109/pesmg.2013.6672509 ER - TY - CONF TI - Design of controller for L2 cache mapped in Tezzaron stacked DRAM AU - Tshibangu, N. M. AU - Franzon, P. D. AU - Rotenberg, E. AU - Davis, W. R. T2 - 2013 IEEE International 3D Systems Integration Conference (3DIC) AB - 3DIC technology allows implementation of fast and dense memory by allowing multiple layers of DRAM to be fabricated in a single die called Die-stacking technology. This creates opportunity to explore usage of DRAM as fast last level cache by exploiting mapping of data and tag in the same bank. This Paper investigates the implementation of such a cache controller using 3-layer 256 MB Tezzaron Octopus stacked DRAM. This memory provides a fast data access through burst-4 and burst-8 mode. To avoid multiple row activation, the entire set is confined in one row of 2KB. For a 64B cache block, 32 lines of data can be obtained in one row. In this design, only two cache blocks are used for tag while 30 blocks are used for data yielding a 30-way set associative L2 cache. Given the performance of Tezzaron memory, a low hit time of approximately 20 cycles was achieved. This hit latency includes precharge and row activation delays. This access latency was used in Gem5 full-system simulator to estimate the performance compared to a standard 2D SRAM L2 cache. An average of 15% on performance is achieved on different benchmarks while providing an average 27% on energy saving. C2 - 2013/10/2/ C3 - 2013 IEEE International 3D Systems Integration Conference (3DIC) CY - San Francisco, CA DA - 2013/10/2/ PY - 2013/10/2/ DO - 10.1109/3dic.2013.6702397 ER - TY - CONF TI - Design of 60 GHz contact less probe system for RDL in passive silicon interposer AU - Suh, E. J. AU - Franzon, Paul AB - A probe design for detecting discontinuities of a redistribution layer (RDL) on TSV silicon interposer is presented in this paper. The probe is a 60 GHz contactless system based on a quarter-wavelength directional coupler, using the capacitive coupling effects between two signal traces. The probes consists of one ground plane and one signal trace embedded in BCB, low dielectric constant insulator. The length, width, and thickness of the contactless probe are 749.3 um, 100.584 um, and 10.414 um, respectively. A time-domain reflectometery (TDR) pulse with 10 ps rise time makes it possible to obtain high resolution. A variation of the probe's TDR signal through two capacitance coupling effects indicates the location of the open or short circuit fault where RDL has. Reaching a peak and dip of the probe's TDR signal represents the open and short circuit sites, respectively. C2 - 2013/// C3 - 2013 ieee international 3d systems integration conference (3dic) DA - 2013/// DO - 10.1109/3dic.2013.6702352 ER - TY - CONF TI - Design considerations of a centralized load controller using thermostatically controlled appliances for continuous regulation reserves AU - Lu, N. AB - This paper presents design considerations for a centralized load controller to control thermostatically controlled appliances (TCAs) for continuous regulation reserves (CRRs). The controller logics for setting up the baseline load, generating priority lists, issuing dispatch commands, and tuning the simplified forecaster model using measurement data are described. To study the impacts of different control parameter settings on control performance and device lifetimes, a system consisting of 1000 heating, ventilating, and air-conditioning (HVAC) units in their heating modes is modeled to provide a ±1-MW CRR 24 hours a day. Four cases are modeled to evaluate the impact of forecasting errors, minimum HVAC turn-off times, response delays, and consumer overrides. The results demonstrate that a centralized TCA load controller can provide robust, good quality CRRs with reduced communication needs for the two-way communication network and inexpensive load control devices. Most importantly, because the controller precisely controls the aggregated HVAC load shapes while maintaining load diversity, the controllable and measurable load services that it provides can be used for many other demand response applications, such as peak shaving, load shifting, and arbitrage. C2 - 2013/// C3 - 2013 ieee power and energy society general meeting (pes) DA - 2013/// DO - 10.1109/pesmg.2013.6672203 ER - TY - CONF TI - Consensus-based distributed energy management with real-time pricing AU - Asr, N. R. AU - Zhang, Z. AU - Chow, M. Y. AB - Energy management is becoming a crucial issue in the future power grid system as more controllable energy resources and responsive loads with communications abilities are being introduced into the smart grid. This paper proposes a novel distributed approach to deal with energy management in the smart grid under dispatchable distributed generators and responsive loads using real-time pricing (RTP) and consensus networks to maximize the social welfare. In our algorithm, each distributed generation/consumer unit, in response to the local price of energy, decides on its optimal power generation/ consumption level to maximize its benefit at the device level. However, the consensus-based coordination of price among local retailers drives the behavior of the overall system toward the global optimum, despite the greedy behavior of the generation and consumer units. The main features of our algorithm are computational and communicational scalability, as well as privacy of information. C2 - 2013/// C3 - 2013 ieee power and energy society general meeting (pes) DA - 2013/// DO - 10.1109/pesmg.2013.6672511 ER - TY - CONF TI - Comprehensive lost minimization strategy for parallel plug-in hybrid electric vehicles AU - Hu, C. J. AU - Huang, A. Q. AU - Gao, Y. M. AB - Plug-in hybrid electric vehicles (PHEVs) have two energy inputs, the petroleum fuel and electric energy from the utility grid. Due to the different operation costs, the energy management has significant effects on the fuel economy. In this paper, an energy management strategy, stemmed from the AER-focused and blended strategy, is developed. It features the “smart” utilization of the stored electric energy and meanwhile provides intensive electric range. A traffic pattern identification algorithm is proposed. Using the historic and current traffic data, the algorithm can identify the highway and urban traffic pattern, which provides the guidance of the “smart” utilization. In addition, an innovative real time control algorithm for charge sustenance is proposed. It computs the comprehensive energy loss of the hybrid drive train. The operation points with the minimum comprehensive energy loss is found to be the optimized engine and motor operation points. Simulation results show that significant improvement of fuel efficiency can be achieved. C2 - 2013/// C3 - 2013 IEEE Transportation Electrification Conference and Expo (ITEC) DA - 2013/// DO - 10.1109/itec.2013.6573501 ER - TY - CONF TI - Circuit/channel co-design methodology for multimode signaling AU - Yan, Z. AU - Franzon, Paul AU - Aygun, K. AU - Braunisch, H. AB - As higher density of interconnects and packages are demanded, crosstalk noise is becoming more important in input/output (I/O) design. The multimode signaling scheme offers effective crosstalk cancellation in high density links. This paper presents a new circuit/channel co-design methodology for high density links with multimode signaling. A detailed design approach is introduced and a detailed channel design optimization example is provided to validate this method. The optimized channel shows over 60% root mean square (RMS) jitter reduction compared with single-ended signaling. The printed circuit board (PCB) and package routing density of the optimized channel are 300% and 97% higher compared with a practical benchmark channel, respectively, and still shows 31% jitter reduction. C2 - 2013/// C3 - 2013 IEEE 63rd Electronic Components and Technology Conference (ECTC) DA - 2013/// DO - 10.1109/ectc.2013.6575750 SP - 1356–1361 ER - TY - CONF TI - Behavior recognition based on machine learning algorithms for a wireless canine machine interface AU - Brugarolas, R. AU - Loftin, R. T. AU - Yang, P. AU - Roberts, D. L. AU - Sherman, B. AU - Bozkurt, A. AB - Training and handling working dogs is a costly process and requires specialized skills and techniques. Less subjective and lower-cost training techniques would not only improve our partnership with these dogs but also enable us to benefit from their skills more efficiently. To facilitate this, we are developing a canine body-area-network (cBAN) to combine sensing technologies and computational modeling to provide handlers with a more accurate interpretation for dog training. As the first step of this, we used inertial measurement units (IMU) to remotely detect the behavioral activity of canines. Decision tree classifiers and Hidden Markov Models were used to detect static postures (sitting, standing, lying down, standing on two legs and eating off the ground) and dynamic activities (walking, climbing stairs and walking down a ramp) based on the heuristic features of the accelerometer and gyroscope data provided by the wireless sensing system deployed on a canine vest. Data was collected from 6 Labrador Retrievers and a Kai Ken. The analysis of IMU location and orientation helped to achieve high classification accuracies for static and dynamic activity recognition. C2 - 2013/// C3 - 2013 IEEE International Conference on Body Sensor Networks (BSN) DA - 2013/// DO - 10.1109/bsn.2013.6575505 ER - TY - CONF TI - Adaptive online battery parameters/SOC/capacity co-estimation AU - Rahimi-Eichi, H. AU - Chow, M. Y. AB - Total capacity is one of the most important parameters to characterize the performance and application of a battery. Although the nominal capacity is provided by the manufacturer, the actual capacity is subject to change with cycling effect, temperature and even storage ageing of the battery. Following our previous publications in which we developed an online adaptive parameters/state of charge (SOC) co-estimation algorithm to identify the parameters of the dynamic model of the battery and accordingly design an observer to estimate the SOC. In this paper, first we show that the parameters identification and SOC estimation results are not dependent on the correct approximation of the capacity. Afterwards, using the estimated SOC, we design another observer to estimate the actual capacity of the battery. C2 - 2013/// C3 - 2013 IEEE Transportation Electrification Conference and Expo (ITEC) DA - 2013/// DO - 10.1109/itec.2013.6574502 ER - TY - JOUR TI - Adaptive Cache Bypassing for Inclusive Last Level Caches AU - Gupta, Saurabh AU - Gao, Hongliang AU - Zhou, Huiyang T2 - IEEE 27TH INTERNATIONAL PARALLEL AND DISTRIBUTED PROCESSING SYMPOSIUM (IPDPS 2013) AB - Cache hierarchy designs, including bypassing, replacement, and the inclusion property, have significant performance impact. Recent works on high performance caches have shown that cache bypassing is an effective technique to enhance the last level cache (LLC) performance. However, commonly used inclusive cache hierarchy cannot benefit from this technique because bypassing inherently breaks the inclusion property. This paper presents a solution to enabling cache bypassing for inclusive caches. We introduce a bypass buffer to an LLC. Bypassed cache lines skip the LLC while their tags are stored in this bypass buffer. When a tag is evicted from the bypass buffer, it invalidates the corresponding cache lines in upper level caches to ensure the inclusion property. Our key insight is that the lifetime of a bypassed line, assuming a well-designed bypassing algorithm, should be short in upper level caches and is most likely dead when its tag is evicted from the bypass buffer. Therefore, a small bypass buffer is sufficient to maintain the inclusion property and to reap most performance benefits of bypassing. Furthermore, the bypass buffer facilitates bypassing algorithms by providing the usage information of bypassed lines. We show that a top performing cache bypassing algorithm, which is originally designed for non-inclusive caches, performs comparably for inclusive caches equipped with our bypass buffer. The usage information collected from the bypass buffer also significantly reduces the cost of hardware implementation compared to the original design. DA - 2013/// PY - 2013/// DO - 10.1109/ipdps.2013.16 SP - 1243-1253 SN - 1530-2075 KW - Last level cache KW - cache bypassing KW - cache replacement policy KW - inclusion property ER - TY - CONF TI - A novel method for control of distributed storage devices in distribution: Ripple voltage injection with frequency droop AU - Fregosi, D. AU - Bhattacharya, Subhashish AB - Ripple voltage injection has been used to control distributed loads to implement demand response. In this paper, we propose a novel technique to improve ripple control by utilizing frequency droop to control the power flow of distributed storage devices. Droop enables an arbitrary number of distributed devices to communicate bi-directionally to achieve power sharing. The response time of such a system is defined by the control and does not change as the number of storage devices increases. By controlling distributed storage through ripple control, communication systems on the grid are freed to perform other functions. The proposed control technique is explained and design and simulation are presented for the application of controlling electric vehicle chargers on a distribution feeder for frequency support. C2 - 2013/// C3 - IEEE Power and Energy Society General Meeting DA - 2013/// DO - 10.1109/pesmg.2013.6672278 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84893185579&partnerID=MN8TOARS ER - TY - CONF TI - A control method for angle-controlled STATCOMs under system faults AU - Babaei, S. AU - Parkhideh, B. AU - Bhattacharya, Subhashish AU - Fardanesh, B. AB - Voltage-Sourced Converter (VSC) based Synchronous Static Compensator (STATCOM) is used for voltage regulation in transmission and distribution systems. Comparing with PWM STATCOMs, angle-controlled STATCOMs are fired once with the line frequency to lower the system losses. In recent years, angle-controlled STATCOMs have been deployed by utility owners for the purpose of voltage regulation, voltage stability improvement and increasing operational functionality. Despite the superior feature on voltage waveform quality and efficiency, the practical angle-controlled STATCOMs suffer from the over-current (and trips) and possible saturation of the interfacing transformers caused by negative sequence current during unbalanced conditions and faults. This paper specifically proposes a control structure to improve the angle-controlled STATCOMs performance under unbalanced conditions and faults. The main improvement is to decrease the negative sequence current and DC-link voltage oscillations substantially under power line faults through the control and not the component design. PSCAD/EMTDC and Real Time Digital Simulation (RTDS) results verify the validity of the proposed control structure under fault conditions. C2 - 2013/// C3 - IEEE Power and Energy Society General Meeting DA - 2013/// DO - 10.1109/pesmg.2013.6672943 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84893199035&partnerID=MN8TOARS ER - TY - CONF TI - A comparison of forecast error generators for modeling wind and load uncertainty AU - Lu, N. AU - Diao, R. S. AU - Hafen, R. P. AU - Samaan, N. AU - Makarov, Y. V. AB - This paper presents four algorithms to generate random forecast error time series, including a truncated-normal distribution model, a state-space based Markov model, a seasonal autoregressive moving average (ARMA) model, and a stochastic-optimization based model. The error time series are used to create real-time (RT), hour-ahead (HA), and day-ahead (DA) wind and load forecast time series that statistically match historically observed forecasting data sets, used for variable generation integration studies. A comparison is made using historical DA load forecast and actual load values to generate new sets of DA forecasts with similar stoical forecast error characteristics. This paper discusses and compares the capabilities of each algorithm to preserve the characteristics of the historical forecast data sets. C2 - 2013/// C3 - 2013 ieee power and energy society general meeting (pes) DA - 2013/// DO - 10.1109/pesmg.2013.6672978 ER - TY - CONF TI - A compact inductively coupled connector for mobile devices AU - Zhao, W. X. AU - Gadfort, P. AU - Erickson, E. AU - Franzon, Paul AB - A nested inductive connector, consisting of a single power channel and one or more data channels, is proposed as replacement for legacy conductive connectors in mobile devices. Advantages include minimized space in the mobile device, waterproofing, orientation independence, and resistance to stress through a breakaway mechanism. A simulation and analysis of relevant parameters, such as the transfer coefficients for both the power and data channels as well as crosstalk, of the connector design for a simple 2-layer PCB is presented. As an example, the proposed connector is utilized as a replacement for a standard TRS headphone jack found on many mobile devices. The connect or features an AC to DC rectifier, data transmitting circuits, as well as a Class-D power amplifier to drive a pair of headphones. C2 - 2013/// C3 - 2013 IEEE 63rd Electronic Components and Technology Conference (ECTC) DA - 2013/// DO - 10.1109/ectc.2013.6575919 SP - 2385–2390 ER - TY - CONF TI - Understanding blackholes in large-scale cognitive radio networks under generic failures AU - Sun, L. AU - Wang, Wenye 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. Therefore, many solutions, such as routing protocols and restoration algorithms, are proposed to deal with Blackholes by identifying alternative paths to bypass these holes such that the effect of Blackholes can be mitigated. These advancements are based on an underlying premise that there exists at least one alternative path in the network. However, such a hypothesis remains an open question. In other words, we do not know whether the network is resilient to Blackholes or whether an alternative path exists. The answer to this question can complement our understanding of designing routing protocols, as well as topology evolution in the presence of random failures. 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. C2 - 2013/// C3 - 2013 proceedings ieee infocom DA - 2013/// DO - 10.1109/infcom.2013.6566859 SP - 728–736 ER - TY - JOUR TI - Snapshot Imaging Mueller Matrix Instrument AU - Kudenov, Michael W. AU - Mallik, Sushmit AU - Escuti, Michael J. AU - Hagen, Nathan AU - Oka, Kazuhiko AU - Dereniak, Eustace L. T2 - ELECTRO-OPTICAL REMOTE SENSING, PHOTONIC TECHNOLOGIES, AND APPLICATIONS VII; AND MILITARY APPLICATIONS IN HYPERSPECTRAL IMAGING AND HIGH SPATIAL RESOLUTION SENSING AB - A novel way to measure the Mueller matrix image enables a sample's diattenuation, retardance, and depolarization to be measured within a single camera integration period. Since the Mueller matrix components are modulated onto coincident carrier frequencies, the described technique provides unique solutions to image registration problems for moving objects. In this paper, a snapshot imaging Mueller matrix polarimeter is theoretically described, and preliminary results shows it to be a viable approach for use in surface characterization of moving objects. DA - 2013/// PY - 2013/// DO - 10.1117/12.2028546 VL - 8897 SP - SN - 1996-756X KW - Polarization KW - Mueller matrix polarimetry KW - polarization gratings KW - snapshot imaging ER - TY - JOUR TI - Reliable Wireless Communication Networks for Demand Response Control AU - Zheng, Lei AU - Lu, Ning AU - Cai, Lin T2 - IEEE TRANSACTIONS ON SMART GRID AB - This paper presents methodologies for deriving reliability performance of wireless communication networks to support demand response (DR) control. First, the impact of communication impairments on a direct DR control program is investigated. Second, the outage probability of a wireless link is modelled and quantified, considering the multipath fading, shadowing, and random path loss given the location distribution of smart meters. Third, the distributions of packet delivery ratio are derived for two wireless network architectures: the single-hop infrastructure-based network and the multi-hop mesh network. Simulation results verify the above reliability models and provide important insights on the coverage of wireless communication networks considering the reliability requirements of DR programs. DA - 2013/3// PY - 2013/3// DO - 10.1109/tsg.2012.2224892 VL - 4 IS - 1 SP - 133-140 SN - 1949-3061 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000325485600013&KeyUID=WOS:000325485600013 KW - Communications reliability KW - demand response KW - network topology KW - outage probability KW - smart grid ER - TY - CONF TI - Performance regions in compressed sensing from noisy measurements AU - Zhu, J. A. AU - Baron, Dror AB - In this paper, compressed sensing with noisy measurements is addressed. The theoretically optimal reconstruction error is studied by evaluating Tanaka's equation. The main contribution is to show that in several regions, which have different measurement rates and noise levels, the reconstruction error behaves differently. This paper also evaluates the performance of the belief propagation (BP) signal reconstruction method in the regions discovered. When the measurement rate and the noise level lie in a certain region, BP is suboptimal with respect to Tanaka's equation, and it may be possible to develop reconstruction algorithms with lower error in that region. C2 - 2013/// C3 - 2013 47th Annual Conference on Information Sciences and Systems (CISS) DA - 2013/// DO - 10.1109/ciss.2013.6552256 ER - TY - CONF TI - Panorama creation using a team of robots AU - Huang, Y. Q. AU - Snyder, W. AB - A system is presented which allows a single human to teleoperate a team of camera-equipped robots. This paper emphasizes the image processing required to take a number of views and construct a single panorama which provides a sense of a 3-D environment to the operator who finds it easy to comprehend the environment and to control the team using something as simple as a joystick. Since the cameras have diverse poses, their output images must be distorted to provide smooth alignment. This is accomplished by correspondence finding, triangular tessellation and warping of a portion of each view. The panorama which gives a 180° field-of-view is projected onto a semi-circular array of monitors to provide the operator with a sensation of both forward and peripheral views. C2 - 2013/// C3 - 2013 IEEE Workshop on Robot Vision (WORV) DA - 2013/// DO - 10.1109/worv.2013.6521922 SP - 108-113 ER - TY - CONF TI - Optimization of wireless power transfer for mobile receivers using automatic digital capacitance tuning AU - Ricketts, D. S. AU - Chabalko, M. J. AU - Hillenius, A. C2 - 2013/// C3 - 2013 european microwave conference (eumc) DA - 2013/// SP - 515-518 ER - TY - JOUR TI - Multiobjective Control of PEM Fuel Cell System With Improved Durability AU - She, Yun AU - Baran, Mesut E. AU - She, Xu T2 - IEEE TRANSACTIONS ON SUSTAINABLE ENERGY AB - A critical design goal of a fuel-cell-based renewable energy system in a smart grid scenario is to enable high efficiency while extending durability. This is particularly emphasized when the fuel-cell system becomes widely used. Towards this goal, the effort in this research paper is to develop multiobjective controllers to simultaneously realize both output tracking and durability improvement. More specifically, two types of controller are developed. With assumptions of knowledge of system parameters, the first controller enables exponentially stability of the closed-loop system. Then, with practical considerations of robustness, an adaptive extension of the first controller is developed, which is capable of handling possible mismatch between real parameters and parameters obtained from the manufacturer or system identification methods. The performance and stability is theoretically guaranteed by a Lyapunov-based proof. Together with theoretical analysis, several scenarios are considered and tested via Matlab/simulink-based simulation. DA - 2013/1// PY - 2013/1// DO - 10.1109/tste.2012.2203324 VL - 4 IS - 1 SP - 127-135 SN - 1949-3029 KW - Durability KW - energy conversion KW - multiobjective control KW - proton exchange membrane (PEM) fuel cell KW - renewable energy KW - smart grid ER - TY - CONF TI - Is link signature dependable for wireless security? AU - He, X. F. AU - Dai, H. Y. AU - Shen, W. B. AU - Ning, P. AB - A fundamental assumption of link signature based security mechanisms is that the wireless signals received at two locations separated by more than half a wavelength are essentially uncorrelated. However, it has been observed that in certain circumstances (e.g., with poor scattering and/or a strong line-of-sight (LOS) component), this assumption is invalid. In this paper, a Correlation ATtack (CAT) is proposed to demonstrate the potential vulnerability of the link signature based security mechanisms in such circumstances. Based on statistical inference, CAT explicitly exploits the spatial correlations to reconstruct the legitimate link signature from the observations of multiple adversary receivers deployed in vicinity. Our findings are verified through theoretical analysis, well-known channel correlation models, and experiments on USRP platforms and GNURadio. C2 - 2013/// C3 - 2013 proceedings ieee infocom DA - 2013/// DO - 10.1109/infcom.2013.6566763 SP - 200-204 ER - TY - JOUR TI - Effect of GaAs interfacial layer on the performance of high bandgap tunnel junctions for multijunction solar cells AU - Samberg, Joshua P. AU - Carlin, C. Zachary AU - Bradshaw, Geoff K. AU - Colter, Peter C. AU - Harmon, Jeffrey L. AU - Allen, J. B. AU - Hauser, John R. AU - Bedair, S. M. T2 - APPLIED PHYSICS LETTERS AB - The effect of the heterojunction interface on the performance of high bandgap InxGa1−xP:Te/Al0.6Ga0.4As:C tunnel junctions (TJs) was investigated. The insertion of 30 Å of GaAs:Te at the junction interface resulted in a peak current of 1000 A/cm2 and a voltage drop of ∼3 mV for 30 A/cm2 (2000× concentration). The presence of this GaAs interfacial layer also improved the uniformity across the wafer. Modeling results are consistent with experimental data and were used to explain the observed enhancement in TJ performance. This architecture could be used within multijunction solar cells to extend the range of usable solar concentration with minimal voltage drop. DA - 2013/9/2/ PY - 2013/9/2/ DO - 10.1063/1.4819917 VL - 103 IS - 10 SP - SN - 1077-3118 ER - TY - JOUR TI - Computationally-Efficient, Generalized Expressions for the Proximity-Effect in Multi-Layer, Multi-Turn Tubular Coils for Wireless Power Transfer Systems AU - Pantic, Zeljko AU - Lukic, Srdjan T2 - IEEE TRANSACTIONS ON MAGNETICS AB - Wireless power transfer (WPT) based on magnetic induction is used in numerous applications where physical contact between the power source and the load is not desired. For efficient power transfer, the resonant coils should have a low equivalent series resistance at the resonant frequency and have a high packing factor while being simple to manufacture. Coils made from hollow copper tubes might be an acceptable alternative to Litz wire designs due to low skin-effect resistance, easy manufacturing, and simplicity in implementing active cooling; however, the lack of an analytical model for complex coil designs poses a difficulty in systematically assessing its benefits and limitations. This paper presents a new method, based on the Fourier series, for evaluating proximity-effect losses in a multi-turn, multi-layer tubular coil. The model evaluates the proximity factor G p as a function of coil and tube parameters, which can be incorporated into the design and optimization procedures. The derivations are supported by simulations that compare analytic and finite element models (FEM) of current density distribution in the coil. The model is further validated via experimental measurements of the resulting equivalent series resistance for two prototype coils. DA - 2013/11// PY - 2013/11// DO - 10.1109/tmag.2013.2264486 VL - 49 IS - 11 SP - 5404-5416 SN - 1941-0069 KW - Model of a tubular coil KW - skin and proximity effect modeling KW - tubular conductor KW - wireless power transfer ER - TY - CONF TI - Characterizing link connectivity for opportunistic mobile networking: Does mobility suffice? AU - Lee, C. H. AU - Kwak, J. AU - Eun, D. Y. AB - With recent drastic growth in the number of users carrying smart mobile devices, it is not hard to envision opportunistic ad-hoc communications taking place with such devices carried by humans. This leads to, however, a new challenge to the conventional link-level metrics, solely defined based on user mobility, such as inter-contact time, since there are many constraints including limited battery power that prevent the wireless interface of each user from being always `on' for communication. By taking into account the process of each user's availability jointly with mobility-induced contact/inter-contact process, we investigate how each of them affects the link-level connectivity depending on their relative operating time scales. We then identify three distinct regimes in each of which (1) the so-called impact of mobility on network performance prevails; (2) such impact of mobility disappears or its extent is not that significant; (3) the user availability process becomes dominant. Our findings not only caution that mobility alone is not sufficient to characterize the link-level dynamics, which in turn can lead to highly misleading results, but also suggest the presence of many uncharted research territories for further exploration. C2 - 2013/// C3 - 2013 proceedings ieee infocom DA - 2013/// DO - 10.1109/infcom.2013.6567009 SP - 2076-2084 ER - TY - CONF TI - Characterization and performance comparison of reverse blocking SiC and Si based switch AU - De, A. AU - Roy, S. AU - Bhattacharya, Subhashish AU - Divan, D.M. AB - In this paper a custom made Reverse Voltage Blocking 1200V SiC switch or “current switch” (1200V SiC MOSFET in series with a 1200V SiC JBS diode) is compared with various other combinations of Reverse Voltage Blocking switches (with 1200V Si-IGBT, SiC MOSFET and Si-PIN diodes and SiC JBS diodes). The devices are tested under Reverse Voltage Commutation, Switch Overlap (turn on at non-zero current but zero voltage) and Hard Switching conditions. Test circuits have been constructed and tested at different dc voltage levels with various combinations of devices. The custom made current switch results show remarkable reduction of loss owing to reduced leakage inductance of the package. A new form of switching characteristic has been noticed and presented in this paper. The main motivation of the paper is to make a fair judgment on device selection for current stiff based hard and soft switching topologies. C2 - 2013/// C3 - 1st IEEE Workshop on Wide Bandgap Power Devices and Applications, WiPDA 2013 - Proceedings DA - 2013/// DO - 10.1109/wipda.2013.6695567 SP - 80-83 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84893572618&partnerID=MN8TOARS ER - TY - CONF TI - An analytical investigation of the effect of varied buffer layer designs on the turn-off speed for 4H-SiC IGBTs AU - Lee, M. C. AU - Huang, X. AU - Huang, A. AU - Brunt, E. AB - We propose a criterion to quantify the relationship between buffer layer parameters at a given total charge and turn-off speed for 4H-SiC IGBTs. Three phases of voltage ramp are analytically discussed during the inductive load turn-off by solving each corresponding continuity equation. Extra emphasis will be placed on Phase II - a transition phase in between the initial voltage ramp and punch-through. C2 - 2013/// C3 - 2013 1st IEEE Workshop on Wide Bandgap Power Devices and Applications (WiPDA) DA - 2013/// DO - 10.1109/wipda.2013.6695559 SP - 44-47 ER - TY - JOUR TI - An Empirical Study of Communication Infrastructures Towards the Smart Grid: Design, Implementation, and Evaluation AU - Lu, Xiang AU - Wang, Wenye AU - Ma, Jianfeng T2 - IEEE TRANSACTIONS ON SMART GRID AB - The smart grid features ubiquitous interconnections of power equipments to enable two-way flows of electricity and information for various intelligent power management applications, such as accurate relay protection and timely demand response. To fulfill such pervasive equipment interconnects, a full-fledged communication infrastructure is of great importance in the smart grid. There have been extensive works on disparate layouts of communication infrastructures in the smart grid by surveying feasible wired or wireless communication technologies, such as power line communications and cellular networks. Nevertheless, towards an operable, cost-efficient and backward-compatible communication solution, more comprehensive and practical understandings are still urgently needed regarding communication requirements, applicable protocols, and system performance. Through such comprehensive understandings, we are prone to answer a fundamental question, how to design, implement and integrate communication infrastructures with power systems. In this paper, we address this issue in a case study of a smart grid demonstration project, the Future Renewable Electric Energy Delivery and Management (FREEDM) systems. By investigating communication scenarios, we first clarify communication requirements implied in FREEDM use cases. Then, we adopt a predominant protocol framework, Distributed Network Protocol 3.0 over TCP/IP (DNP3 over TCP/IP), to practically establish connections between electric devices for data exchanges in a small-scale FREEDM system setting, Green Hub. Within the real-setting testbed, we measure the message delivery performance of the DNP3-based communication infrastructure. Our results reveal that diverse timing requirements of message deliveries are arguably primary concerns in a way that dominates viabilities of protocols or schemes in the communication infrastructure of the smart grid. Accordingly, although DNP3 over TCP/IP is widely considered as a smart grid communication solution, it cannot satisfy communication requirements in some time-critical scenarios, such as relay protections, which claim a further optimization on the protocol efficiency of DNP3. DA - 2013/3// PY - 2013/3// DO - 10.1109/tsg.2012.2225453 VL - 4 IS - 1 SP - 170-183 SN - 1949-3061 KW - Communication infrastructures KW - DNP3 over TCP/IP KW - field deployment and performance evaluations KW - FREEDM systems KW - smart grid KW - system design ER - TY - JOUR TI - An Efficient, Watt-Level Microwave Rectifier Using an Impedance Compression Network (ICN) With Applications in Outphasing Energy Recovery Systems AU - Xu, Junfeng AU - Ricketts, David S. T2 - IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS AB - We present a transmission line based impedance compression network (ICN) for application in RF-to-dc conversion. We show that the ICN is able to significantly compress the undesired input impedance variation that occurs when there is a large variation of input power. We designed and measured an ICN for a 4 W, 4.6 GHz rectifier and show that the impedance is significantly compressed with the ICN. We then demonstrate the ICN in an outphasing system where we achieve up to a 37% improvement in efficiency at back-off power and an overall more efficient design over large input power variation. DA - 2013/10// PY - 2013/10// DO - 10.1109/lmwc.2013.2278276 VL - 23 IS - 10 SP - 542-544 SN - 1558-1764 KW - Amplifier KW - efficiency KW - impedance compression network (ICN) KW - outphasing KW - rectifier ER - TY - JOUR TI - Sensitive Vibration Detection Using Ground-Penetrating Radar AU - Wetherington, Joshua M. AU - Steer, Michael B. T2 - IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS AB - A high-dynamic-range vibration detection system is presented based on analog cancellation. The prototype system operates at 900 MHz and is shown to detect vibrational displacement as low as 11 nm for a rectangular aluminum plate at a standoff distance of 2 m. By operating at a lower frequency than previous radar vibrometers, the system gains ground-penetrating capability and is shown to detect vibrations through 13 cm of sand. A fundamental relationship is introduced relating the minimum detectable vibration displacement to the standoff distance and system dynamic range. DA - 2013/12// PY - 2013/12// DO - 10.1109/lmwc.2013.2284779 VL - 23 IS - 12 SP - 680-682 SN - 1558-1764 KW - Acousto-electromagnetic coupling KW - cancellation system KW - nonlinear measurement ER - TY - JOUR TI - Review of snapshot spectral imaging technologies AU - Hagen, Nathan AU - Kudenov, Michael W. T2 - OPTICAL ENGINEERING AB - Within the field of spectral imaging, the vast majority of instruments used are scanning devices. Recently, several snapshot spectral imaging systems have become commercially available, providing new functionality for users and opening up the field to a wide array of new applications. A comprehensive survey of the available snapshot technologies is provided, and an attempt has been made to show how the new capabilities of snapshot approaches can be fully utilized. DA - 2013/9// PY - 2013/9// DO - 10.1117/1.oe.52.9.090901 VL - 52 IS - 9 SP - SN - 1560-2303 KW - snapshot KW - imaging spectrometry KW - hyperspectral imaging KW - multispectral imaging KW - advantage KW - throughput KW - remote sensing KW - standoff detection ER - TY - JOUR TI - Reliability of AlGaN/GaN high electron mobility transistors on low dislocation density bulk GaN substrate: Implications of surface step edges AU - Killat, N. AU - Montes Bajo, M. AU - Paskova, T. AU - Evans, K. R. AU - Leach, J. AU - Li, X. AU - Oezguer, Ue AU - Morkoc, H. AU - Chabak, K. D. AU - Crespo, A. AU - Gillespie, J. K. AU - Fitch, R. AU - Kossler, M. AU - Walker, D. E. AU - Trejo, M. AU - Via, G. D. AU - Blevins, J. D. AU - Kuball, M. T2 - APPLIED PHYSICS LETTERS AB - Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation N. Killat, M. Montes Bajo, T. Paskova, K. R. Evans, J. Leach, X. Li, Ü. Özgür, H. Morkoç, K. D. Chabak, A. Crespo, J. K. Gillespie, R. Fitch, M. Kossler, D. E. Walker, M. Trejo, G. D. Via, J. D. Blevins, M. Kuball; Reliability of AlGaN/GaN high electron mobility transistors on low dislocation density bulk GaN substrate: Implications of surface step edges. Appl. Phys. Lett. 4 November 2013; 103 (19): 193507. https://doi.org/10.1063/1.4829062 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioApplied Physics Letters Search Advanced Search |Citation Search DA - 2013/11/4/ PY - 2013/11/4/ DO - 10.1063/1.4829062 VL - 103 IS - 19 SP - SN - 1077-3118 ER - TY - JOUR TI - Inversion by metalorganic chemical vapor deposition from N-to Ga-polar gallium nitride and its application to multiple quantum well light-emitting diodes AU - Hosalli, A. M. AU - Van Den Broeck, D. M. AU - Bharrat, D. AU - El-Masry, N. A. AU - Bedair, S. M. T2 - APPLIED PHYSICS LETTERS AB - We demonstrate a metalorganic chemical vapor deposition growth approach for inverting N-polar to Ga-polar GaN by using a thin inversion layer grown with high Mg flux. The introduction of this inversion layer allowed us to grow p-GaN films on N-polar GaN thin film. We have studied the dependence of hole concentration, surface morphology, and degree of polarity inversion for the inverted Ga-polar surface on the thickness of the inversion layer. We then use this approach to grow a light emitting diode structure which has the MQW active region grown on the advantageous N-polar surface and the p-layer grown on the inverted Ga-polar surface. DA - 2013/12/2/ PY - 2013/12/2/ DO - 10.1063/1.4841755 VL - 103 IS - 23 SP - SN - 1077-3118 ER - TY - JOUR TI - Gossip-Based Information Spreading in Mobile Networks AU - Zhang, Huazi AU - Zhang, Zhaoyang AU - Dai, Huaiyu T2 - IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS AB - In this paper, we analyze the effect of mobility on information spreading in geometric networks through natural random walks. Specifically, our focus is on epidemic propagation via mobile gossip, a variation from its static counterpart. Our contributions are twofold. Firstly, we propose a new performance metric, mobile conductance, which allows us to separate the details of mobility models from the study of mobile spreading time. Secondly, we utilize geometrical properties to explore this metric for several popular mobility models, and offer insights on the corresponding results. Large scale network simulation is conducted to verify our analysis. DA - 2013/11// PY - 2013/11// DO - 10.1109/twc.2013.100113.130619 VL - 12 IS - 11 SP - 5918-5928 SN - 1558-2248 KW - Conductance KW - gossip KW - information spreading KW - mobile networks KW - mobility models ER - TY - JOUR TI - Automatic Parallelization of Fine-Grained Metafunctions on a Chip Multiprocessor AU - Lee, Sanghoon AU - Tuck, James T2 - ACM TRANSACTIONS ON ARCHITECTURE AND CODE OPTIMIZATION AB - Due to the importance of reliability and security, prior studies have proposed inlining metafunctions into applications for detecting bugs and security vulnerabilities. However, because these software techniques add frequent, fine-grained instrumentation to programs, they often incur large runtime overheads. In this work, we consider an automatic thread extraction technique for removing these fine-grained checks from a main application and scheduling them on helper threads. In this way, we can leverage the resources available on a CMP to reduce the latency and overhead of fine-grained checking codes. Our parallelization strategy extracts metafunctions from a single threaded application and executes them in customized helper threads—threads constructed to mirror relevant fragments of the main program’s behavior in order to keep communication and overhead low. To get good performance, we consider optimizations that reduce communication and balance work among many threads. We evaluate our parallelization strategy on Mudflap, a pointer-use checking tool in GCC. To show the benefits of our technique, we compare it to a manually parallelized version of Mudflap. We run our experiments on an architectural simulator with support for fast queueing operations. On a subset of SPECint 2000, our automatically parallelized code using static load balance is only 19% slower, on average, than the manually parallelized version on a simulated eight-core system. In addition, our automatically parallelized code using dynamic load balance is competitive, on average, to the manually parallelized version on a simulated eight-core system. Furthermore, all the applications except parser achieve better speedups with our automatic algorithms than with the manual approach. Also, our approach introduces very little overhead in the main program—it is kept under 100%, which is more than a 5.3× reduction compared to serial Mudflap. DA - 2013/12// PY - 2013/12// DO - 10.1145/2541228.2541237 VL - 10 IS - 4 SP - SN - 1544-3973 KW - Automatic parallelization KW - helper computing KW - chip multiprocessor ER - TY - CONF TI - Supervisory control of convertible static transmission controller in shunt-shunt mode of operation AU - Yousefpoor, N. AU - Kim, S. AU - Bhattacharya, Subhashish AU - Parkhideh, B. AB - The Convertible static transmission controller is a versatile device which can be installed across a transmission transformer to extend the life time of existing transformers by partially bypassing and conditioning the substation throughput power. The proposed technology can provide several integration options with multiple operational modes. From the supervisory control point of view, a control algorithm is required to set the reference values of active and reactive power flow of CSTC converters based on the desired operating points for transformer active and reactive power. In this paper, the algebraic model of CSTC in shunt-shunt mode of operation is derived. Algebraic model of CSTC is used for steady state and transient stability analysis. Algebraic model will present the behavior of transformer power flow with respect to various operating points of CSTC converters. The P-Q transformer operating range can be obtained based on the proposed algebraic model. Dynamic performance of the CSTC system is also investigated in PSCAD/EMTDC environment. Simulation results will be presented to verify the proposed algebraic model of CSTC in shunt-shunt mode of operation based on steady state results. C2 - 2013/// C3 - IECON Proceedings (Industrial Electronics Conference) DA - 2013/// DO - 10.1109/iecon.2013.6699322 SP - 1314-1319 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84893579665&partnerID=MN8TOARS ER - TY - CONF TI - Simplifying the homology of networks via strong collapses AU - Wilkerson, A. C. AU - Moore, T. J. AU - Swami, A. AU - Krim, H. AB - There has recently been increased interest in applications of topology to areas ranging from control and sensing, to social network analysis, to high-dimensional point cloud data analysis. Here we use simplicial complexes to represent the group relationship structure in a network. We detail a novel algorithm for simplifying homology and “hole location” computations on a complex by reducing it to its core using a strong collapse. We show that the homology and hole locations are preserved and provide motivation for interest in this reduction technique with applications in sensor and social networks. Since the complexity of finding “holes” is quintic in the number of simplices, the proposed reduction leads to significant savings in complexity. C2 - 2013/// C3 - International conference on acoustics speech and signal processing DA - 2013/// DO - 10.1109/icassp.2013.6638666 SP - 5258-5262 ER - TY - CONF TI - SiC Symmetric Blocking Terminations Using Orthogonal Positive Bevel Termination and Junction Termination Extension AU - Huang, X. AU - Baliga, B. J. AU - Huang, A. Q. AU - Suvorov, A. AU - Capell, C. AU - Cheng, L. AU - Agarwal, A. AB - Symmetric blocking power semiconductor switches require two edge terminations, one for the reverse blocking junction and the other one for the forward blocking junction. In this work, we demonstrated 1100V SiC symmetric blocking edge terminations using orthogonal positive bevel (OPB) termination and a one-zone Junction Termination Extension (JTE). The OPB was formed by orthogonally sawing 45° V-shape trenches into the SiC wafer with a diamond-coated dicing blade. The surface damage was then repaired with dry-etch in SF 6 /O 2 plasma, which reduced the leakage current by around two orders of magnitude. As limited by field reach-through, both the OPB and the JTE terminations show breakdown voltage of 1100V. The P + P - N + diodes fabricated on the same wafer with the OPB termination showed 1610V avalanche breakdown which was around 83% of ideal value. C2 - 2013/// C3 - Proceedings of the international symposium on power semiconductor DA - 2013/// DO - 10.1109/ispsd.2013.6694475 SP - 179-182 ER - TY - CONF TI - Sensitivity Analysis of Lithium-Ion Battery Model to Battery Parameters AU - Rahimi-Eichi, H. AU - Balagopal, B. AU - Chow, M. Y. AU - Yeo, T. J. AB - Different models have been proposed so far to represent the dynamic characteristics of batteries. These models contain a number of parameters and each of them represents an internal characteristic of the battery. Since the battery is an entity that works based on many electrochemical reactions, the battery parameters are subject to change due to different conditions of state of charge (SOC), C-rate, temperature and ageing. Referring to our previous work on online identification of the battery parameters, the change in the parameters even during one charging cycle is an experimental fact at least for many lithium-ion batteries. In this paper, the terminal voltage is used as the output to investigate the effect of changes in the parameters on the battery model. Therefore, we analyze the sensitivity of the model to the parameters and validate the analysis by comparing it with the simulation results. Since the output of the model is one of the main components in estimation of the state of charge (SOC), the sensitivity analysis determines the need to update each of the battery parameters in the SOC estimation structure. C2 - 2013/// C3 - 39th annual conference of the ieee industrial electronics society (iecon 2013) DA - 2013/// DO - 10.1109/iecon.2013.6700257 SP - 6794-6799 ER - TY - CONF TI - Network cooperative distributed pricing control system for large-scale optimal charging of PHEVs/PEVs AU - Rahbari-Asr, N. AU - Chow, M. Y. AU - Yang, Z. Y. AU - Chen, J. M. AB - Efficient demand management policies at the grid side are required for large scale charging of Plug-in Hybrid Electric Vehicles and Plug-in Electric vehicles (PHEVs/PEVs). The SoC level and Charging Cost should be optimized while the aggregate load is kept under a safety limit to avoid overloads. Conventionally, optimal managing of the charging rates requires gathering and processing data in a center. However, as the scale of the problem increases to consider thousands of charging stations distributed over a vast geographical area, the central approach suffers from vulnerability to single node/link failures as well as scalability. This paper introduces a novel decentralized network cooperative approach for controlling the PHEV/PEV charging rates. In this approach, each charging station acts as a local retailer of energy, selling the power to the plugged in vehicle while coordinating the price with its neighbors. In response to the offered price, the Smart-Charger of the vehicle adjusts the charging current to maximize the utility of the PHEV/PEV user. By iteratively repeating this process, the convergence to the global optimum is attained without the requirement for any central unit. Robustness to single link/node failures is another advantage of our method. C2 - 2013/// C3 - 39th annual conference of the ieee industrial electronics society (iecon 2013) DA - 2013/// DO - 10.1109/iecon.2013.6700146 SP - 6148-6153 ER - TY - JOUR TI - Integrated Circuits for Volumetric Ultrasound Imaging With 2-D CMUT Arrays AU - Bhuyan, Anshuman AU - Choe, Jung Woo AU - Lee, Byung Chul AU - Wygant, Ira O. AU - Nikoozadeh, Amin AU - Oralkan, Omer AU - Khuri-Yakub, Butrus T. T2 - IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS AB - Real-time volumetric ultrasound imaging systems require transmit and receive circuitry to generate ultrasound beams and process received echo signals. The complexity of building such a system is high due to requirement of the front-end electronics needing to be very close to the transducer. A large number of elements also need to be interfaced to the back-end system and image processing of a large dataset could affect the imaging volume rate. In this work, we present a 3-D imaging system using capacitive micromachined ultrasonic transducer (CMUT) technology that addresses many of the challenges in building such a system. We demonstrate two approaches in integrating the transducer and the front-end electronics. The transducer is a 5-MHz CMUT array with an 8 mm × 8 mm aperture size. The aperture consists of 1024 elements (32 × 32) with an element pitch of 250 μm. An integrated circuit (IC) consists of a transmit beamformer and receive circuitry to improve the noise performance of the overall system. The assembly was interfaced with an FPGA and a back-end system (comprising of a data acquisition system and PC). The FPGA provided the digital I/O signals for the IC and the back-end system was used to process the received RF echo data (from the IC) and reconstruct the volume image using a phased array imaging approach. Imaging experiments were performed using wire and spring targets, a ventricle model and a human prostrate. Real-time volumetric images were captured at 5 volumes per second and are presented in this paper. DA - 2013/12// PY - 2013/12// DO - 10.1109/tbcas.2014.2298197 VL - 7 IS - 6 SP - 796-804 SN - 1940-9990 KW - 2D array KW - capacitive micromachined ultrasonic transducer (CMUT) KW - flip-chip bonding KW - integrated circuits KW - phased array imaging KW - ultrasound KW - volumetric imaging ER - TY - CONF TI - Hierarchical power management for DC microgrid in islanding mode and solid state transformer enabled mode AU - Yu, X. W. AU - She, X. AU - Huang, A. AB - A hierarchical power management scheme is proposed in this paper for a typical DC Microgrid. Different from other Microgrids, the DC Microgrid can interface to the distribution system by Solid-State transformer (SST). The hierarchical power management strategy includes three control levels: 1) primary control for DC Microgrid to implement distributed operation 2) secondary control for the DC Microgrid bus voltage recovery to achieve seamless mode switch 3) tertiary control to manage the battery charge and discharge. The DC Microgrid can operate in islanding mode, including the individual control for distributed renewable energy source (DRER) and distributed energy storage device (DESD). In addition, the DC microgrid can operate in SST-enabled mode to interface to the distribution system. The DC Micorgrid can seamlessly switch between islanding mode and SST-enable mode. The consideration of state of charge (SOC) for battery is also involved into the tertiary control. To this end, a lab test-bed is constructed to verify the system performance. Lastly, several typical case studies are carried out and the experimental results verify the proposed power management strategy. C2 - 2013/// C3 - 39th annual conference of the ieee industrial electronics society (iecon 2013) DA - 2013/// DO - 10.1109/iecon.2013.6699381 SP - 1656-1661 ER - TY - CONF TI - Electric power resource provisioning for large scale public EV charging facilities AU - Bayram, I. S. AU - Michailidis, G. AU - Devetsikiotis, M. C2 - 2013/// C3 - 2013 IEEE International Conference on Smart Grid Communications (SmartGridComm) DA - 2013/// SP - 133-138 ER - TY - CONF TI - A novel control principle for a high frequency transformer based multiport converter for integration of renewable energy sources AU - Hazra, S. AU - Bhattacharya, Subhashish AU - Chakraborty, C. AB - This paper presents a novel approach to control power flow inside a high frequency transformer based multiport DC-DC converter. A multiport converter can interface a number of power sources and sinks with control of power flow among them. In a renewable energy sources (RES) integration scheme, the multiport converter operates like an accumulator where it collects power from each RES and dispatches it to the load port. Typically, power flow between any two ports happens through the leakage inductance of the transformer by imposing a required phase shift between fundamental component of two square wave voltages, impressed at the ports. However, each port is connected with the other ports by some inductance and hence the power flow from a particular source port to load port is not decoupled and can not be controlled independently. This paper proposes decoupling of source ports by eliminating the load port leakage inductance with a negative inductance, emulated by voltage injection in series with leakage inductance. A three port transformer based system is simulated to validate the principle. A scaled prototype of the three port transformer is designed and the effect of load port leakage inductance is analyzed through experiment. C2 - 2013/// C3 - IECON Proceedings (Industrial Electronics Conference) DA - 2013/// DO - 10.1109/iecon.2013.6700467 SP - 7984-7989 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84893563302&partnerID=MN8TOARS ER - TY - JOUR TI - 3D Printing of Free Standing Liquid Metal Microstructures AU - Ladd, Collin AU - So, Ju-Hee AU - Muth, John AU - Dickey, Michael D. T2 - ADVANCED MATERIALS AB - This paper describes a method to direct-write 3D liquid metal microcomponents at room temperature. The thin oxide layer on the surface of the metal allows the formation of mechanically stable structures strong enough to stand against gravity and the large surface tension of the liquid. The method is capable of printing wires, arrays of spheres, arches, and interconnects. 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 - 2013/9// PY - 2013/9// DO - 10.1002/adma.201301400 VL - 25 IS - 36 SP - 5081-5085 SN - 1521-4095 KW - direct-write KW - 3D printing KW - liquid metal KW - egain KW - stretchable electronics ER - TY - CONF TI - Using battery management systems to augment inter-area oscillation control in wind-integrated power systems AU - Chandra, S. AU - Gayme, D. F. AU - Chakrabortty, Aranya AB - This paper presents a control design for shaping the inter-area oscillations of a wind-integrated power system through coordination between a wind power controller and a controlled battery energy system (BES). We consider a continuum representation of the power system dynamics subject to two point source forcings from wind and battery power, each injected at specified electrical distances along the transfer path. The inter-area oscillation modes of a wind-integrated power system have previously been shown to be highly dependent on the location where wind power is injected, as a result of which a particular injection site may produce a desired spectral response. A wind power controller may be used to achieve the response in an arbitrary location but the effect is limited to small frequency ranges. In the present work, we design co-dependent linear controllers for the wind power and the BES in charging mode, and show that the addition of this controlled BES greatly improves the spectral matching within the inter-area oscillation range. We illustrate the performance of our controllers using power system models inspired by US west coast transfer paths such as the Pacific AC Inter-tie. C2 - 2013/// C3 - 2013 american control conference (acc) DA - 2013/// DO - 10.1109/acc.2013.6580748 SP - 5809–5814 ER - TY - JOUR TI - Toward stimulated interaction of surface phonon polaritons AU - Kong, B. D. AU - Trew, R. J. AU - Kim, K. W. T2 - Journal of Applied Physics AB - Thermal emission spectra mediated by surface phonon polariton are examined by using a theoretical model that accounts for generation processes. Specifically, the acoustic phonon fusion mechanism is introduced to remedy theoretical deficiencies of the near thermal equilibrium treatments. The model clarifies the thermal excitation mechanism of surface phonon polaritons and the energy transfer path under non-zero energy flow. When applied to GaAs and SiC semi-infinite surfaces, the nonequilibrium model predicts that the temperature dependence of the quasi-monochromatic peak can exhibit distinctly different characteristics of either sharp increase or slow saturation depending on the materials, which is in direct contrast with the estimate made by the near-equilibrium model. The proposed theoretical tool can accurately analyze the nonequilibrium steady states, potentially paving a pathway to demonstrate stimulated interaction/emission of thermally excited surface phonon polaritons. DA - 2013/12/21/ PY - 2013/12/21/ DO - 10.1063/1.4851717 VL - 114 IS - 23 SP - 233508 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.4851717 DB - Crossref ER - TY - CONF TI - Topology identification for dynamic equivalent models of large power system networks AU - Nabavi, S. AU - Chakrabortty, Aranya AB - In this paper we propose two algorithms to identify the equivalent topology of reduced-order models of power systems using measurements of phase angles and frequencies available from Phasor Measurement Units (PMUs). We first show that the topology identification problem can be posed as a parameter estimation problem. Thereafter, we extract the slow oscillatory component of the PMU measurements using subspace identification methods and use them for identifying the topological parameters via conventional ℓ 2 minimization approach. Next, we consider the problem of identifying a sparse equivalent network topology using a ℓ 1 /ℓ 2 minimization technique. We illustrate our results using a IEEE 39-bus model. C2 - 2013/// C3 - 2013 american control conference (acc) DA - 2013/// DO - 10.1109/acc.2013.6579989 SP - 1138–1143 ER - TY - JOUR TI - Spectroscopic investigation of coupling among asymmetric InGaN/GaN multiple quantum wells grown on non-polar a-plane GaN substrates AU - Roberts, A. T. AU - Mohanta, A. AU - Everitt, H. O. AU - Leach, J. H. AU - Broeck, D. AU - Hosalli, A. M. AU - Paskova, T. AU - Bedair, S. M. T2 - APPLIED PHYSICS LETTERS AB - Low defect density asymmetric multiple quantum wells (MQWs) of InGaN/GaN grown on non-polar a-plane GaN substrates were investigated using time-integrated and time-resolved photoluminescence spectroscopy. Comparison of these spectra with the predicted emission energies reveals that these QWs may be spectrally resolved at low temperatures. However, a combination of thermal activation and resonant tunneling of carriers increasingly coupled the QWs, favoring emission from the lowest energy QWs with increasing temperature in a manner analogous to MQWs composed of other non-polar semiconductor materials but unlike most InGaN MQWs grown on polar substrates and influenced by the strong polarization-dependent effects. DA - 2013/10/28/ PY - 2013/10/28/ DO - 10.1063/1.4827536 VL - 103 IS - 18 SP - SN - 1077-3118 ER - TY - JOUR TI - SUCRALOSE, A SYNTHETIC ORGANOCHLORINE SWEETENER: OVERVIEW OF BIOLOGICAL ISSUES AU - Schiffman, Susan S. AU - Rother, Kristina I. T2 - JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH-PART B-CRITICAL REVIEWS AB - Sucralose is a synthetic organochlorine sweetener (OC) that is a common ingredient in the world's food supply. Sucralose interacts with chemosensors in the alimentary tract that play a role in sweet taste sensation and hormone secretion. In rats, sucralose ingestion was shown to increase the expression of the efflux transporter P-glycoprotein (P-gp) and two cytochrome P-450 (CYP) isozymes in the intestine. P-gp and CYP are key components of the presystemic detoxification system involved in first-pass drug metabolism. The effect of sucralose on first-pass drug metabolism in humans, however, has not yet been determined. In rats, sucralose alters the microbial composition in the gastrointestinal tract (GIT), with relatively greater reduction in beneficial bacteria. Although early studies asserted that sucralose passes through the GIT unchanged, subsequent analysis suggested that some of the ingested sweetener is metabolized in the GIT, as indicated by multiple peaks found in thin-layer radiochromatographic profiles of methanolic fecal extracts after oral sucralose administration. The identity and safety profile of these putative sucralose metabolites are not known at this time. Sucralose and one of its hydrolysis products were found to be mutagenic at elevated concentrations in several testing methods. Cooking with sucralose at high temperatures was reported to generate chloropropanols, a potentially toxic class of compounds. Both human and rodent studies demonstrated that sucralose may alter glucose, insulin, and glucagon-like peptide 1 (GLP-1) levels. Taken together, these findings indicate that sucralose is not a biologically inert compound. DA - 2013/10/3/ PY - 2013/10/3/ DO - 10.1080/10937404.2013.842523 VL - 16 IS - 7 SP - 399-451 SN - 1521-6950 ER - TY - CONF TI - MOOCs, OOCs, flips and hybrids: The new world of higher education AU - Franzon, Paul AB - A combination of new teaching methods, tools together with cloud services promises to deliver greater efficiency to higher education with improved teaching outcomes. C2 - 2013/// C3 - Proceedings ieee international conference on microelectronic systems DA - 2013/// DO - 10.1109/mse.2013.6566692 SP - 13–13 ER - TY - CONF TI - Introduction to wide-area control of power systems AU - Chakrabortty, Aranya AU - Khargonekar, P. P. AB - A key element in the development of smart power transmission systems over the past decade is the tremendous advancement of the Wide-Area Measurement System (WAMS) technology, also commonly referred to as the Synchrophasor technology. Sophisticated digital recording devices called Phasor Measurement Units or PMUs are currently being installed at different points in the North American grid, especially under the smart grid initiatives of the US Department of Energy, to record and communicate GPS-synchronized, high sampling rate (6-60 samples/sec), dynamic power system data. Significant research efforts have been made on techniques to useWAMS for monitoring and situational awareness of large power networks dispersed across wide geographical areas. In contrast, use of WAMS for automatic feedback control has received less attention from the research community. The objective of this paper is to bridge this gap by formulating wide-area control problems for oscillation damping, voltage control, wide-area protection, and disturbance localization. We present the main research challenges that need to be overcome to realize the benefits of wide area control in power systems. Our discussion begins with a review of the fundamental physical models of different characteristic components of a large transmission-level power grid such as synchronous generators, transmission lines, and loads, followed by a description of how these subsystem-level models can be integrated to form the overall system model. We pose ten distinct control-theoretic problems. The first two problems are on using PMU measurements from selected nodes in the system to identify such system models in different resolutions in real-time, and the remaining on how the identified models can be used for designing output-feedback based damping controllers, for understanding voltage fluctuations at different nodes of the network graph, and for detecting malicious inputs entering the system dynamics via faults or extraneous attacks. We also propose two new control paradigms, namely a scheduling approach for appropriate controller selection based on online estimation of oscillation modes, and distributed phasor-based control using model estimation. We illustrate our ideas via representative examples, many of which are inspired by well-known power transfer paths in the US west coast grid, also referred to as the Western Electricity Coordinating Council (WECC). C2 - 2013/// C3 - 2013 american control conference (acc) DA - 2013/// DO - 10.1109/acc.2013.6580901 SP - 6758–6770 ER - TY - JOUR TI - Generating and analyzing non-diffracting vector vortex beams AU - Li, Yanming AU - Dudley, Angela AU - Mhlanga, Thandeka AU - Escuti, Michael J. AU - Forbes, Andrew T2 - LASER BEAM SHAPING XIV AB - We experimentally generate non-diffracting vector vortex beams by using a Spatial Light Modulator (SLM) and an azimuthal birefringent plate (q-plate). The SLM generates scalar Bessel beams and the q-plate converts them to vector vortex beams. Both single order Bessel beam and superposition cases are studied. The polarization and the azimuthal modes of the generated beams are analyzed. The results of modal decompositions on polarization components are in good agreement with theory. We demonstrate that the generated beams have cylindrical polarization and carry polarization dependent Orbital Angular Momentum (OAM). DA - 2013/// PY - 2013/// DO - 10.1117/12.2027249 VL - 8843 SP - SN - 1996-756X KW - vector beam KW - orbital angular momentum KW - optical vortex KW - Bessel beam ER - TY - JOUR TI - Deriving common malware behavior through graph clustering AU - Park, Younghee AU - Reeves, Douglas S. AU - Stamp, Mark T2 - COMPUTERS & SECURITY AB - Detection of malicious software (malware) continues to be a problem as hackers devise new ways to evade available methods. The proliferation of malware and malware variants requires new advanced methods to detect them. This paper proposes a method to construct a common behavioral graph representing the execution behavior of a family of malware instances. The method generates one common behavioral graph by clustering a set of individual behavioral graphs, which represent kernel objects and their attributes based on system call traces. The resulting common behavioral graph has a common path, called HotPath, which is observed in all the malware instances in the same family. The proposed method shows high detection rates and false positive rates close to 0%. The derived common behavioral graph is highly scalable regardless of new instances added. It is also robust against system call attacks. DA - 2013/11// PY - 2013/11// DO - 10.1016/j.cose.2013.09.006 VL - 39 SP - 419-430 SN - 1872-6208 KW - Malware KW - Dynamic analysis KW - Graph clustering KW - Intrusion detection KW - Virtualization ER - TY - CONF TI - Convergence and recovery analysis of the secure distributed control methodology for D-NCS AU - Zeng, W. T. AU - Chow, M. Y. AB - Distributed control algorithms (e.g., consensus algorithms) are vulnerable to the misbehaving agent compromised by cyber attacks in the Distributed Networked Control Systems (D-NCS). In this paper we continue our work on a proposed secure distributed control methodology that is capable of performing a secure consensus computation in D-NCS in the presence of misbehaving agents. The methodology is introduced first and proven to be effective through convergence analysis. Then, we extend our secure distributed control methodology to the leaderless consensus network by introducing and adding two recovery schemes into the current secure distributed control framework to guarantee accurate convergence in the presence of misbehaving agents. All phases of our method are distributed. That is, at each step of the detection, mitigation, identification, update, and recovery, each agent only uses local and one-hop neighbors' information. The simulation results are presented to demonstrate the effectiveness of the proposed methods. C2 - 2013/// C3 - 2013 IEEE International Symposium on Industrial Electronics (ISIE) DA - 2013/// DO - 10.1109/isie.2013.6563743 ER - TY - JOUR TI - Characterization of the sequence and expression pattern of LFY homologues from dogwood species (Cornus) with divergent inflorescence architectures AU - Liu, Juan AU - Franks, Robert G. AU - Feng, Chun-Miao AU - Liu, Xiang AU - Fu, Cheng-Xin AU - Xiang, Qiu-Yun T2 - ANNALS OF BOTANY AB - LFY homologues encode transcription factors that regulate the transition from vegetative to reproductive growth in flowering plants and have been shown to control inflorescence patterning in model species. This study investigated the expression patterns of LFY homologues within the diverse inflorescence types (head-like, umbel-like and inflorescences with elongated internodes) in closely related lineages in the dogwood genus (Cornus s.l.). The study sought to determine whether LFY homologues in Cornus species are expressed during floral and inflorescence development and if the pattern of expression is consistent with a function in regulating floral development and inflorescence architectures in the genus.Total RNAs were extracted using the CTAB method and the first-strand cDNA was synthesized using the SuperScript III first-strand synthesis system kit (Invitrogen). Expression of CorLFY was investigated by RT-PCR and RNA in situ hybridization. Phylogenetic analyses were conducted using the maximum likelihood methods implemented in RAxML-HPC v7.2.8.cDNA clones of LFY homologues (designated CorLFY) were isolated from six Cornus species bearing different types of inflorescence. CorLFY cDNAs were predicted to encode proteins of approximately 375 amino acids. The detection of CorLFY expression patterns using in situ RNA hybridization demonstrated the expression of CorLFY within the inflorescence meristems, inflorescence branch meristems, floral meristems and developing floral organ primordia. PCR analyses for cDNA libraries derived from reverse transcription of total RNAs showed that CorLFY was also expressed during the late-stage development of flowers and inflorescences, as well as in bracts and developing leaves. Consistent differences in the CorLFY expression patterns were not detected among the distinct inflorescence types.The results suggest a role for CorLFY genes during floral and inflorescence development in dogwoods. However, the failure to detect expression differences between the inflorescence types in the Cornus species analysed suggests that the evolutionary shift between major inflorescence types in the genus is not controlled by dramatic alterations in the levels of CorLFY gene transcript accumulation. However, due to spatial, temporal and quantitative limitations of the expression data, it cannot be ruled out that subtle differences in the level or location of CorLFY transcripts may underlie the different inflorescence architectures that are observed across these species. Alternatively, differences in CorLFY protein function or the expression or function of other regulators (e.g. TFL1 and UFO homologues) may support the divergent developmental trajectories. DA - 2013/11// PY - 2013/11// DO - 10.1093/aob/mct202 VL - 112 IS - 8 SP - 1629-1641 SN - 1095-8290 KW - Cornus KW - dogwood KW - inflorescence evolution KW - LFY homologues KW - CorLFY expression KW - RTPCR KW - in situ hybridization ER - TY - JOUR TI - Ally Friendly Jamming: How to Jam Your Enemy and Maintain Your Own Wireless Connectivity at the Same Time AU - Shen, Wenbo AU - Ning, Peng AU - He, Xiaofan AU - Dai, Huaiyu T2 - 2013 IEEE SYMPOSIUM ON SECURITY AND PRIVACY (SP) AB - This paper presents a novel mechanism, called Ally Friendly Jamming, which aims at providing an intelligent jamming capability that can disable unauthorized (enemy) wireless communication but at the same time still allow authorized wireless devices to communicate, even if all these devices operate at the same frequency. The basic idea is to jam the wireless channel continuously but properly control the jamming signals with secret keys, so that the jamming signals are unpredictable interference to unauthorized devices, but are recoverable by authorized ones equipped with the secret keys. To achieve the ally friendly jamming capability, we develop new techniques to generate ally jamming signals, to identify and synchronize with multiple ally jammers. This paper also reports the analysis, implementation, and experimental evaluation of ally friendly jamming on a software defined radio platform. Both the analytical and experimental results indicate that the proposed techniques can effectively disable enemy wireless communication and at the same time maintain wireless communication between authorized devices. DA - 2013/// PY - 2013/// DO - 10.1109/sp.2013.22 SP - 174-188 SN - 1081-6011 KW - Wireless KW - friendly jamming KW - interference cancellation ER - TY - CONF TI - A graph-theoretic algorithm for disturbance localization in large power grids using residue estimation AU - Nudell, Thomas R. AU - Chakrabortty, Aranya T2 - 2013 American Control Conference (ACC) AB - In this paper we consider the problem of localizing unknown disturbances in large power systems using a measurement-based graph theoretic method. We first show that the aggregate electro-mechanical model of the power system, under certain assumptions, can be analyzed analogously to a generic n th -order asymmetric networked dynamic system. Considering that the network exhibits a clustering structure leading to slow and fast eigenvalues, we propose an input localization method based on the properties of the weak nodal domains corresponding to the first p dominant slow eigenvalues. In particular, we prove that for systems defined over p-area complete graphs the input localization is unique. We provide simulation results to illustrate our algorithm. C2 - 2013/6// C3 - 2013 American Control Conference DA - 2013/6// DO - 10.1109/acc.2013.6580367 SP - 3467-3472 PB - IEEE SN - 9781479901784 9781479901777 9781479901753 UR - http://dx.doi.org/10.1109/acc.2013.6580367 DB - Crossref ER - TY - JOUR TI - A Roadside Scattering Model for the Vehicle-to-Vehicle Communication Channel AU - Cheng, Lin AU - Stancil, Daniel D. AU - Bai, Fan T2 - IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS AB - Achieving accurate and effective modeling of the vehicle-to-vehicle (V2V) communication channel has proven to be a challenging task, particularly owing to the highly dynamic nature of vehicular environments. V2V channels generally may have contributions from the line-of-sight path, reflections from large stationary and moving objects such as bridges and other vehicles, and a diffuse base from large numbers of small stationary objects in the environment. We propose a new geometrical model for the diffuse component based on scattering objects distributed along the roadside, and use this model to predict the Doppler spectrum and angle-of-arrival distribution associated with this component for various V2V scenarios. In contrast with previous roadside scattering models that sum the contributions from large numbers of randomly-generated scattering objects, our model assumes a uniform linear distribution along the roadside. This permits a computationally efficient, closed-form model. Comparisons with on-road measurement data as well as the double ring model demonstrate the validity and effectiveness of the proposed model. DA - 2013/9// PY - 2013/9// DO - 10.1109/jsac.2013.sup.0513040 VL - 31 IS - 9 SP - 449-459 SN - 1558-0008 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84883458078&partnerID=MN8TOARS KW - Propagation channel KW - geometrical modeling KW - VANET ER - TY - JOUR TI - A Battery Management System Using an Active Charge Equalization Technique Based on a DC/DC Converter Topology AU - Yarlagadda, Sriram AU - Hartley, Tom T. AU - Husain, Iqbal T2 - IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS AB - An active charge equalization technique based on a dc/dc converter topology is proposed in this paper. The technique achieves cell balancing of batteries in a stack in terms of both voltage and charge as the pack is being charged/discharged and in idle periods to maximize the energy and reliability of stack operation. A set of MOSFET switches controlled by a voltage monitoring circuit ensures that each battery module has the same output voltage by transferring charge from an individual battery module with the highest voltage to a weak module. An overvoltage and overdischarge protection circuit is presented to reduce the degradation of battery life and to operate each battery within the voltage limits. DA - 2013/// PY - 2013/// DO - 10.1109/tia.2013.2264794 VL - 49 IS - 6 SP - 2720-2729 SN - 1939-9367 KW - Battery KW - battery protection KW - cell balancing KW - charge equalization KW - management system ER - TY - JOUR TI - Successful aging through digital games: Socioemotional differences between older adult gamers and Non-gamers AU - Allaire, Jason C. AU - McLaughlin, Anne Collins AU - Trujillo, Amanda AU - Whitlock, Laura A. AU - LaPorte, Landon AU - Gandy, Maribeth T2 - COMPUTERS IN HUMAN BEHAVIOR AB - The purpose of this investigation was to examine differences in psychological functioning (e.g., well-being, affect, depression, and social functioning) between older adults who play digital games compared to those older adults that do not play digital games. Analysis was conducted on a sample of 140 independently living older adults with an average age of 77.47 years (SD = 7.31). Participants were divided into three groups (Regular, Occasional Gamers, and Non-gamers) – 60% of the sample was either a Regular or Occasional Gamer. Differences among the groups were found for well-being, negative affect, social functioning, and depression with Regular and Occasional Gamers performing better, on average, than Non-gaming older adults. Findings suggest that playing may serve as a positive activity associated with successful aging. DA - 2013/7// PY - 2013/7// DO - 10.1016/j.chb.2013.01.014 VL - 29 IS - 4 SP - 1302-1306 SN - 1873-7692 KW - Aging KW - Digital games KW - Well-being KW - Depression ER - TY - JOUR TI - Spray characteristics of a swirl atomiser in trigger sprayers using water-ethanol mixtures AU - Yao, Shanshan AU - Fang, Tiegang T2 - CANADIAN JOURNAL OF CHEMICAL ENGINEERING AB - Abstract Pressure swirl atomisers are widely used in both industry and daily life. It is critical to understand the spray transient behaviour for better design of these systems. This paper presents an experimental study of conical liquid sheets breakup from a swirl atomiser nozzle in trigger sprayers. Spray and atomisation characteristics were measured and analysed. Water–ethanol mixtures were used to simulate different fluids on the breakup and atomisation quality of the spray development process with a wide range of surface tension while maintaining relatively small changes in fluid viscosity and density. The spray images were taken by a high speed digital camera and post‐processed to analyse the global spray structure, spray cone angle, and breakup length. The droplet size and its distribution were measured using a laser diffraction technique. It was observed that the surface waves grow rapidly on the cone‐shaped liquid sheets and breakup into liquid ligaments and droplets during the initial stage of fluid dispensing. Then the spray transitions into the developed stage. Near the end of the dispensing process, the liquid cone collapses with poor atomisation (large droplets) due to momentum loss. The comparison between different fluids showed that the spray cone angle and liquid breakup length decreased with the increase of ethanol percentage ratio. The percentiles parameters, Sauter mean diameter (SMD) and particle size distribution were measured and compared for different locations. High surface tension fluids produce larger droplets than lower surface tension fluids, which have the same trend as the percentiles parameters and SMD. Results also show that droplet size and its distribution depend on the location of the measurement. Generally speaking, smaller droplet size is found for a location away from the nozzle axis in the vertical direction. In the horizontal direction, larger droplet sizes are found for a location closer to the nozzle exit. © 2013 Canadian Society for Chemical Engineering DA - 2013/7// PY - 2013/7// DO - 10.1002/cjce.21821 VL - 91 IS - 7 SP - 1312-1324 SN - 0008-4034 KW - swirl atomiser KW - trigger sprayer KW - spray atomisation KW - droplet size distribution KW - visualisation ER - TY - JOUR TI - Special Section on Vehicular Networks and Communication Systems: From Laboratory into Reality AU - Bai, Fan AU - Hartenstein, Hannes AU - Gruteser, Marco AU - Kravets, Robin AU - Zhang, Tao AU - Stancil, Daniel D. T2 - IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY AB - The nine papers in this special section mainly deal with vehicular wireless networks, covering a rich variety of research topics ranging from vehicular channel modeling to safety application design. DA - 2013/11// PY - 2013/11// DO - 10.1109/tvt.2013.2286434 VL - 62 IS - 9 SP - 4146-4149 SN - 1939-9359 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84888111231&partnerID=MN8TOARS ER - TY - CONF TI - Signal reconstruction in linear mixing systems with different error metrics AU - Tan, J. AU - Baron, Dror AB - We consider the problem of reconstructing a signal from noisy measurements in linear mixing systems. The reconstruction performance is usually quantified by standard error metrics such as squared error, whereas we consider any additive error metric. Under the assumption that relaxed belief propagation (BP) can compute the posterior in the large system limit, we propose a simple, fast, and highly general algorithm that reconstructs the signal by minimizing the user-defined error metric. For two example metrics, we provide performance analysis and convincing numerical results. Finally, our algorithm can be adjusted to minimize the l error, which is not additive. Interestingly, l minimization only requires to apply a Wiener filter to the output of relaxed BP. C2 - 2013/// C3 - 2013 Information Theory and Applications Workshop (ITA) DA - 2013/// DO - 10.1109/ita.2013.6502925 ER - TY - JOUR TI - Properties of atomic layer deposited dielectrics for AlGaN/GaN device passivation AU - Ramanan, Narayanan AU - Lee, Bongmook AU - Kirkpatrick, Casey AU - Suri, Rahul AU - Misra, Veena T2 - SEMICONDUCTOR SCIENCE AND TECHNOLOGY AB - In order to minimize ac–dc dispersion, reduce gate leakage and maximize ac transconductance, there is a critical need to identify optimal interfaces, low-k passivation dielectrics and high-k gate dielectrics. In this paper, an investigation of different atomic layer deposited (ALD) passivation dielectrics on AlGaN/GaN-based hetero-junction field effect transistors (HFETs) was performed. Angle-resolved x-ray photoelectron spectroscopy revealed that HCl/HF and NH4OH cleans resulted in a reduction of native oxide and carbon levels at the GaN surface. The role of high temperature anneals, following the ALD, on the effectiveness of passivation was also explored. Gate-lag measurements on HFETs passivated with a thin ALD high-k Al2O3 or HfAlO layer capped with a thick plasma enhanced chemical vapor deposited (PECVD) low-k SiO2 layer, annealed at 600–700 °C, were found to be as good as or even better than those with conventional PECVD silicon nitride passivation. Further, it was observed that different passivation dielectric stacks required different anneal temperatures for improved gate-lag behavior compared to the as-deposited case. DA - 2013/7// PY - 2013/7// DO - 10.1088/0268-1242/28/7/074004 VL - 28 IS - 7 SP - SN - 1361-6641 ER - TY - JOUR TI - Passive orientation measurement using magnetoquasistatic fields and coupled magnetic resonances AU - Arumugam, D.D. AU - Ricketts, D.S. T2 - Electronics Letters AB - A passive position orientation measurement method is presented which leverages the spatial variation of the reflected magnetoquasistatic field from a mobile loop to determine the loop's spatial orientation. The azimuthal orientation was measured from 0° to 360° at a distance of 1 m from the fixed measurement loop. Inverting the theoretical expressions to estimate orientation from measured field values resulted in an average and RMS error of 3.15° and 4.55°, respectively. This technique offers a means to accurately determine the orientation of the mobile loop through purely passive methods. DA - 2013/8/1/ PY - 2013/8/1/ DO - 10.1049/EL.2013.0766 VL - 49 IS - 16 SP - 999-1001 LA - en OP - SN - 0013-5194 1350-911X UR - http://dx.doi.org/10.1049/EL.2013.0766 DB - Crossref ER - TY - JOUR TI - On the Forwarding Performance under Heterogeneous Contact Dynamics in Mobile Opportunistic Networks AU - Lee, Chul-Ho AU - Eun, Do Young T2 - IEEE TRANSACTIONS ON MOBILE COMPUTING AB - In this paper, we focus on how the heterogeneous contact dynamics of mobile nodes impact the performance of forwarding algorithms in mobile opportunistic networks (MONs). To this end, we consider two representative heterogeneous network models, each of which captures heterogeneity among node pairs (individual) and heterogeneity in underlying environment (spatial), respectively, and examine the full extent of difference in delay performance they cause on forwarding algorithms through formal stochastic comparisons. We first show that these heterogeneous models correctly capture non-Poisson contact dynamics observed in real traces. We then rigorously establish stochastic/convex ordering relationships on the delay performance of direct forwarding and multicopy two-hop relay protocol under these heterogeneous models and the corresponding homogeneous model, all of which have the same average intercontact time of a random pair of nodes. In particular, we demonstrate that the heterogeneous models predict an entirely opposite ordering relationship in delay performance depending on which of the two heterogeneity structures is captured. We also provide simulation results including the delay performance of epidemic routing protocol to support the analytical findings. Our results thus suggest that the heterogeneity in mobile nodes' contact dynamics should be properly taken into account for the performance evaluation of forwarding algorithms. Our results will also be useful for better design of forwarding algorithms correctly exploiting the heterogeneity structure. DA - 2013/6// PY - 2013/6// DO - 10.1109/tmc.2012.84 VL - 12 IS - 6 SP - 1107-1119 SN - 1558-0660 KW - Mobile opportunistic networks KW - heterogeneous contact dynamics KW - non-Poisson contact dynamics KW - forwarding performance KW - stochastic/convex ordering relationships ER - TY - JOUR TI - ON SOME RECENT ATTEMPTS TO RESOLVE THE DEBATE BETWEEN INTERNALISTS AND EXTERNALISTS AU - Mabrito, Robert T2 - SOUTHERN JOURNAL OF PHILOSOPHY AB - Abstract An important debate in moral philosophy concerns the thesis of internalism, of which the characteristic idea is that there is a conceptual link between moral judgment and motivation. According to the internalist, to judge that something is right is to be motivated to do it (at least under certain conditions). Externalists are those who deny the truth of internalism. There are two ways that either party to this debate may argue for their preferred position. The indirect approach requires defending an account of moral judgment and showing (for internalists) that it entails there is a conceptual link between moral judgment and motivation or (for externalists) that it entails there is no such link. In contrast, the direct approach requires arguing in favor of one position without assuming any particular account of moral judgment. In this paper, I examine two attempts—one by M ichael S mith and one by S igrún S vavarsdóttir—to resolve this debate between internalists and externalists by using the direct approach. S mith attempts to do so in favor of internalism while S vavarsdóttir makes the attempt in favor of externalism. I conclude that both attempts fail. DA - 2013/6// PY - 2013/6// DO - 10.1111/sjp.12013 VL - 51 IS - 2 SP - 179-205 SN - 0038-4283 ER - TY - JOUR TI - Measurement of ultra-low power oscillators using adaptive drift cancellation with applications to nano-magnetic spin torque oscillators AU - Tamaru, S. AU - Ricketts, D. S. T2 - REVIEW OF SCIENTIFIC INSTRUMENTS AB - This work presents a technique for measuring ultra-low power oscillator signals using an adaptive drift cancellation method. We demonstrate this technique through spectrum measurements of a sub-pW nano-magnet spin torque oscillator (STO). We first present a detailed noise analysis of the standard STO characterization apparatus to estimate the background noise level, then compare these results to the noise level of three measurement configurations. The first and second share the standard configuration but use different spectrum analyzers (SA), an older model and a state-of-the-art model, respectively. The third is the technique proposed in this work using the same old SA as for the first. Our results show that the first and second configurations suffer from a large drift that requires ~30 min to stabilize each time the SA changes the frequency band, even though the SA has been powered on for longer than 24 h. The third configuration introduced in this work, however, shows absolutely no drift as the SA changes frequency band, and nearly the same noise performance as with a state-of-the-art SA, thus providing a reliable method for measuring very low power signals for a wide variety of applications. DA - 2013/5// PY - 2013/5// DO - 10.1063/1.4804650 VL - 84 IS - 5 SP - SN - 0034-6748 ER - TY - JOUR TI - Internode Mobility Correlation for Group Detection and Analysis in VANETs AU - Li, Yujin AU - Zhao, Ming AU - Wang, Wenye T2 - IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY AB - Recent studies on mobility-assisted schemes for routing and topology control and on mobility-induced link dynamics have presented significant findings on the properties of a pair of nodes (e.g., the intermeeting time and link life time) or a group of nodes (e.g., network connectivity and partitions). In contrast to the study on the properties of a set of nodes rather than individuals, many works share a common ground with respect to node mobility, i.e., independent mobility in multihop wireless networks. Nonetheless, in vehicular ad hoc networks (VANETs), mobile devices installed on vehicles or held by humans are not isolated; however, they are dependent on each other. For example, the speed of a vehicle is influenced by its close-by vehicles, and vehicles on the same road move at similar speeds. Therefore, the gap between our understanding of the impact of independent mobility and our interest in the properties of correlated mobility in VANETs, along with the real systems altogether, declare an interesting question. How can we measure the internode mobility correlation, such as to uncover the node groups and network components, and explore their impact on link dynamics and network connectivity? Bearing this question in mind, we first examine several traces and find that node mobility exhibits spatial locality and temporal locality correlations, which are closely related to node grouping. To study the properties of these groups on the fly, we introduce a new metric, i.e., dual-locality ratio (DLR), which quantifies mobility correlation of nodes. In light of taking spatial and temporal locality dimensions into account, the DLR can be used to effectively identify stable user groups, which in turn can be used for network performance enhancement. DA - 2013/11// PY - 2013/11// DO - 10.1109/tvt.2013.2264689 VL - 62 IS - 9 SP - 4590-4601 SN - 1939-9359 KW - Correlated mobility KW - group detection KW - vehicular ad hoc networks ER - TY - JOUR TI - Improved high-temperature device transport properties and off-state characteristics of AlGaN/GaN power devices with atomic layer deposition (ALD) HfAlO high-k dielectric AU - Lee, B. AU - Choi, Y. H. AU - Kirkpatrick, C. AU - Huang, A. Q. AU - Misra, V. T2 - SEMICONDUCTOR SCIENCE AND TECHNOLOGY AB - The effect of the atomic layer deposition (ALD) HfAlO high-k dielectric on device transport properties and breakdown characteristics of an AlGaN/GaN metal?oxide?semiconductor hetero-junction field-effect transistor (MOS-HFET) was evaluated based on temperature-dependent measurements. It was found that the MOS-HFET device with a HfAlO gate dielectric shows high-channel mobility greater than the Schottky HFET device for the measured temperature range (25?150??C). In the case of off-state breakdown characteristics, the MOS-HFET device greatly suppressed gate leakage currents for measured temperatures (25?200??C) resulting in improvements in off-state breakdown characteristics. In contrast, large gate/drain leakage currents were observed for the Schottky HFET device at high temperature (>100??C) resulting in about 200?V of breakdown voltage reduction. It was also found that the ALD HfAlO layer reduced surface leakage current by passivating the GaN surface effectively. Therefore, the MOS-HFET structure with the HfAlO gate dielectric is very attractive for GaN-based high-power and high-temperature device applications. DA - 2013/7// PY - 2013/7// DO - 10.1088/0268-1242/28/7/074016 VL - 28 IS - 7 SP - SN - 1361-6641 ER - TY - JOUR TI - Gallium nitride devices for power electronic applications AU - Baliga, B. Jayant T2 - SEMICONDUCTOR SCIENCE AND TECHNOLOGY AB - Recent success with the fabrication of high-performance GaN-on-Si high-voltage HFETs has made this technology a contender for power electronic applications. This paper discusses the properties of GaN that make it an attractive alternative to established silicon and emerging SiC power devices. Progress in development of vertical power devices from bulk GaN is reviewed followed by analysis of the prospects for GaN-on-Si HFET structures. Challenges and innovative solutions to creating enhancement-mode power switches are reviewed. DA - 2013/7// PY - 2013/7// DO - 10.1088/0268-1242/28/7/074011 VL - 28 IS - 7 SP - SN - 1361-6641 ER - TY - JOUR TI - Efficient In-Network Computing with Noisy Wireless Channels AU - Li, Chengzhi AU - Dai, Huaiyu T2 - IEEE TRANSACTIONS ON MOBILE COMPUTING AB - In this paper, we study distributed function computation in a noisy multihop wireless network. We adopt the adversarial noise model, for which independent binary symmetric channels are assumed for any point-to-point transmissions, with (not necessarily identical) crossover probabilities bounded above by some constant $(\epsilon)$. Each node takes an $(m)$-bit integer per instance, and the computation is activated after each node collects $(N)$ readings. The goal is to compute a global function with a certain fault tolerance in this distributed setting; we mainly deal with divisible functions, which essentially cover the main body of interest for wireless applications. We focus on protocol designs that are efficient in terms of communication complexity. We first devise a general protocol for evaluating any divisible functions, addressing both one-shot $((N = O(1)))$ and block computation, and both constant and large $(m)$ scenarios. We also analyze the bottleneck of this general protocol in different scenarios, which provides insights into designing more efficient protocols for specific functions. In particular, we endeavor to improve the design for two exemplary cases: the identity function, and size-restricted type-threshold functions, both focusing on the constant $(m)$ and $(N)$ scenario. We explicitly consider clustering, rather than hypothetical tessellation, in our protocol design. DA - 2013/11// PY - 2013/11// DO - 10.1109/tmc.2012.185 VL - 12 IS - 11 SP - 2167-2177 SN - 1536-1233 KW - Distributed computing KW - noisy multihop network KW - clustering ER - TY - JOUR TI - Dynamic Service Contract Enforcement in Service-Oriented Networks AU - Jarma, Yesid AU - Boloor, Keerthana AU - Amorim, Marcelo Dias AU - Viniotis, Yannis AU - Callaway, Robert D. T2 - IEEE TRANSACTIONS ON SERVICES COMPUTING AB - In recent years, service-oriented architectures (SOA) have emerged as the main solution for the integration of legacy systems with new technologies in the enterprise world. A service is usually governed by a client service contract (CSC) that specifies, among other requirements, the rate at which a service should be accessed, and limits it to no more than a number of service requests during an observation period. Several approaches, using both static and dynamic credit-based strategies, have been developed to enforce the rate specified in the CSC. Existing approaches have problems related to starvation, approximations used in calculations, and rapid credit consumption under certain conditions. In this paper, we propose and validate DoWSS, a doubly weighted algorithm for service traffic shaping. We show via simulation that DoWSS possesses several advantages: It eliminates the approximation issues, prevents starvation, and contains the rapid credit consumption issue in existing credit-based approaches. DA - 2013/// PY - 2013/// DO - 10.1109/tsc.2011.45 VL - 6 IS - 1 SP - 130-142 SN - 1939-1374 KW - Service-oriented networks KW - web services KW - service traffic shaping KW - contract enforcement KW - middleware appliances KW - appliance cluster KW - credit-based algorithm ER - TY - JOUR TI - Data-Aided Noise Reduction for Long-Range Fading Prediction in Adaptive Modulation Systems AU - Jia, Tao AU - Duel-Hallen, Alexandra AU - Hallen, Hans T2 - IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY AB - The long-range prediction (LRP) of fading signals enables adaptive transmission methods for rapidly varying mobile radio channels encountered in vehicular communications, but its performance is severely degraded by the additive noise and interference. A data-aided noise reduction (DANR) method is proposed to enhance the accuracy of fading prediction and to improve the spectral efficiency of adaptive modulation systems enabled by the LRP. The DANR includes an adaptive pilot transmission mechanism, robust noise reduction (NR), and decision-directed channel estimation. Due to improved prediction accuracy and low pilot rates, the DANR results in higher spectral efficiency than previously proposed NR techniques, which rely on oversampled pilots. It is also demonstrated that DANR-aided LRP increases the coding gain of adaptive trellis-coded modulation (ATCM). Finally, for low-to-medium signal-to-noise ratio (SNR) values, we show that LRP-enabled adaptive modulation performs better for realistic reflector configurations than for the conventional Jakes model (JM) data set. DA - 2013/6// PY - 2013/6// DO - 10.1109/tvt.2013.2241090 VL - 62 IS - 5 SP - 2358-2362 SN - 1939-9359 UR - http://dx.doi.org/10.1109/TVT.2013.2241090 KW - Adaptive modulation KW - adaptive signal processing KW - fading channels KW - prediction methods ER - TY - JOUR TI - Crosstalk-Canceling Multimode Interconnect Using Transmitter Encoding AU - Kim, HoonSeok AU - Won, Chanyoun AU - Franzon, Paul D. T2 - IEEE TRANSACTIONS ON VERY LARGE SCALE INTEGRATION (VLSI) SYSTEMS AB - A new implementation approach to cancel crosstalk using modal decomposition on a multiconductor transmission bundle is presented. The proposed approach requires a CODEC only at the transmitter, not at both the transmitter and receiver. This gives potential for more flexibility, lower power, better scaling, and ease of implementation. A circuit is presented along with the simulation results. DA - 2013/8// PY - 2013/8// DO - 10.1109/tvlsi.2012.2213281 VL - 21 IS - 8 SP - 1562-1567 SN - 1063-8210 KW - Crosstalk cancellation KW - encoding KW - modal decomposition KW - multiconductor transmission KW - multimode interconnect ER - TY - JOUR TI - Comparison of the performance of inverse transformation methods from OSA-UCS to CIEXYZ AU - Cao, Renbo AU - Trussell, H. Joel AU - Shamey, Renzo T2 - JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION AB - The Optical Society of America’s Uniform Color Scales (OSA-UCS) is one of the color spaces that most closely approximate a “true” uniform color space. Different techniques have been used to convert OSA-UCS-based color specification parameters, L, j, and g, to the CIE tristimulus values, X, Y, and Z. However, none of these methods provides a direct method of inverting OSA-UCS to CIEXYZ values. Thus, numerical algorithms, such as the Newton–Raphson method, have been employed to obtain the transformations. The relative low accuracy and long computation time of this method makes it undesirable for practical applications. An artificial neural network (ANN) was employed to convert OSA-UCS to CIEXYZ. Its performance was compared with that of numerical methods. After optimization, ANN gave a better performance with a mean error (ΔEXYZ) of 1.0×10−4 and a conversion time of less than 1 s for 1891 samples. DA - 2013/8// PY - 2013/8// DO - 10.1364/josaa.30.001508 VL - 30 IS - 8 SP - 1508-1515 SN - 1520-8532 ER - TY - JOUR TI - Battery Management System An Overview of Its Application in the Smart Grid and Electric Vehicles AU - Rahimi-Eichi, Habiballah AU - Ojha, Unnati AU - Baronti, Federico AU - Chow, Mo-Yuen T2 - IEEE INDUSTRIAL ELECTRONICS MAGAZINE AB - With the rapidly evolving technology of the smart grid and electric vehicles (EVs), the battery has emerged as the most prominent energy storage device, attracting a significant amount of attention. The very recent discussions about the performance of lithium-ion (Li-ion) batteries in the Boeing 787 have confirmed so far that, while battery technology is growing very quickly, developing cells with higher power and energy densities, it is equally important to improve the performance of the battery management system (BMS) to make the battery a safe, reliable, and cost-efficient solution. The specific characteristics and needs of the smart grid and EVs, such as deep charge/discharge protection and accurate state-of-charge (SOC) and state-of-health (SOH) estimation, intensify the need for a more efficient BMS. The BMS should contain accurate algorithms to measure and estimate the functional status of the battery and, at the same time, be equipped with state-of-the-art mechanisms to protect the battery from hazardous and inefficient operating conditions. DA - 2013/6// PY - 2013/6// DO - 10.1109/mie.2013.2250351 VL - 7 IS - 2 SP - 4-16 SN - 1941-0115 ER - TY - JOUR TI - A Bounded and Discretized Nelder-Mead Algorithm Suitable for RFIC Calibration AU - Wyers, Eric J. AU - Steer, Michael B. AU - Kelley, C. T. AU - Franzon, Paul D. T2 - IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS I-REGULAR PAPERS AB - This paper describes a calibration technique for noisy and nonconvex circuit responses based on the Nelder-Mead direct search algorithm. As Nelder-Mead is intended for unconstrained optimization problems, we present an implementation of the algorithm which is suitable for bounded and discretized RFIC calibration problems. We apply the proposed algorithm to the problem of spurious tone reduction via VCO control line ripple minimization for a PLL operating at a frequency of 12 GHz. For this nonconvex calibration test case, we show that a gradient descent-based algorithm has difficulty in reducing the VCO control line ripple, while the proposed algorithm reduces the relative power of the first harmonic reference spurs by at least 10 dBc and effectively enables design complexity reduction in the supporting analog calibration circuitry. DA - 2013/7// PY - 2013/7// DO - 10.1109/tcsi.2012.2230496 VL - 60 IS - 7 SP - 1787-1799 SN - 1558-0806 KW - Calibration KW - derivative-free optimization KW - Nelder-Mead direct search algorithm KW - PLL spurious tone reduction KW - radio frequency integrated circuit calibration ER - TY - JOUR TI - Wireless Mesh Network in Smart Grid: Modeling and Analysis for Time Critical Communications AU - Xu, Yi AU - Wang, Wenye T2 - IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS AB - Communication networks are an indispensable component in the smart grid power systems by providing the essential information exchange functions among the electrical devices that are located distributively in the grid. In particular, wireless networks will be deployed widely in the smart grid for data collection and remote control purposes. In this paper, we model the smart grid wireless networks and present the communication delay analysis in typical wireless network deployment scenarios in the grid. As the time critical communications are coupled with the power system protections in the smart grid, it is important to understand the delay performance of the smart grid wireless networks. Our results provide the delay bounds that can help design satisfactory wireless networks to meet the demanding communication requirements in the smart grid. DA - 2013/7// PY - 2013/7// DO - 10.1109/twc.2013.061713.121545 VL - 12 IS - 7 SP - 3360-3371 SN - 1536-1276 KW - Wireless network KW - smart grid KW - time critical communication KW - network performance KW - communication delay ER - TY - JOUR TI - Wind Energy System With Integrated Functions of Active Power Transfer, Reactive Power Compensation, and Voltage Conversion AU - She, Xu AU - Huang, Alex Q. AU - Wang, Fei AU - Burgos, Rolando T2 - IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS AB - As the power of wind energy system increases, the control of their active and reactive power becomes increasingly more important from a system standpoint given that these are typical frequency and voltage control parameters. In this paper, a family of wind energy systems with integrated functions of active power transfer, reactive power compensation, and voltage conversion is proposed. The proposed wind energy systems using solid-state transformer (SST) can effectively suppress the voltage fluctuation caused by the transient nature of wind energy without additional reactive power compensator and, as such, may enable the large penetration of wind farm (WF) into the power grid. To this end, a simulation study for WF driven by squirrel-cage induction generators is presented to verify the effectiveness of the proposed system. In addition, a modular-type high-voltage and high-power three-phase SST topology is presented for the proposed system, and its basic building block, which is a single-phase SST, is analyzed. The functions of SST in the presented wind energy system are verified in a single-phase laboratory prototype with scaled-down experiments. Lastly, cost issue of the proposed technology is analyzed with comparison to the traditional one. DA - 2013/10// PY - 2013/10// DO - 10.1109/tie.2012.2216245 VL - 60 IS - 10 SP - 4512-4524 SN - 1557-9948 KW - Power electronic transformer KW - reactive power compensation KW - solid-state transformer (SST) KW - voltage regulation KW - wind energy KW - wind generation ER - TY - JOUR TI - Wheeze detection and location using spectro-temporal analysis of lung sounds AU - Emrani, Saba AU - Krim, Hamid T2 - 29TH SOUTHERN BIOMEDICAL ENGINEERING CONFERENCE (SBEC 2013) AB - Wheezes are abnormal lung sounds, which usually imply obstructive airways diseases. The objective of this study is to design an automatic wheeze detector for a wearable health monitoring system, which is able to locate the wheezes inside the respiratory cycle with high accuracy, and low computational complexity. We compute important features of wheezes, which we classify as temporal and spectral characteristics and employed to analyze recorded lung sounds including wheezes from patients with asthma. Time-frequency (TF) technique as well as wavelet packet decomposition (WPD) is used for this purpose. Experimental results verify the promising performance of described methods. DA - 2013/// PY - 2013/// DO - 10.1109/sbec.2013.27 SP - 37-38 SN - 1086-4105 ER - TY - JOUR TI - Unified Active Filter and Energy Storage System for an MW Electric Vehicle Charging Station AU - Bai, Sanzhong AU - Lukic, Srdjan M. T2 - IEEE TRANSACTIONS ON POWER ELECTRONICS AB - A network of fast-charging stations is of great importance for widespread adoption of electric vehicles (EV) if the so-called range anxiety issue is to be resolved. As with petrol stations, we expect that multiple chargers will be co-located to form charging stations. This layout allows for the fast-charging station to make use of a common rectifier stage and several dc/dc stages to charge multiple EVs. This paper builds on our previous work where we proposed a novel dc-side filter for the 12-pulse rectifier and investigated the power profile for a MW fast-charging station. In this paper, we propose a novel control approach for the filter, based on the virtual resistor injection, which results in further reduction in dc ripple, ac-side harmonics, and filter VA ratings. We also demonstrate that, with the proposed topology and control, the filter stage can be used as dc-side energy storage system. DA - 2013/12// PY - 2013/12// DO - 10.1109/tpel.2013.2245146 VL - 28 IS - 12 SP - 5793-5803 SN - 1941-0107 KW - AC-DC 12-pulse diode rectifier KW - energy storage KW - fast-charging station KW - harmonics mitigation KW - virtual impedance ER - TY - JOUR TI - Torque-Ripple Minimization of Switched Reluctance Machines Through Current Profiling AU - Mikail, Rajib AU - Husain, Iqbal AU - Sozer, Yilmaz AU - Islam, Mohammad S. AU - Sebastian, Tomy T2 - IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS AB - This paper presents a novel method of profiling the phase currents to minimize the torque ripple of a switched reluctance machine. The method is a combination of machine design and control algorithm. The minimization is accomplished in three steps: The first step is to design a machine that has symmetric torque characteristics with an extended flat portion, the second step is to find the required current profile through simulation, and the third step is the fine tuning of the profile. The simulation is done to verify the method through a coupling of the finite-element-based machine model and the Matlab/Simulink-based dynamic controller model. The coupled simulation considers the nonlinearities, electrical loss, magnetic loss, and mutual coupling. Experimental verification validated the torque-ripple minimization procedure. DA - 2013/// PY - 2013/// DO - 10.1109/tia.2013.2252592 VL - 49 IS - 3 SP - 1258-1267 SN - 0093-9994 KW - Coupled simulation KW - current profiling KW - end of line calibration KW - FEA KW - fine tuning KW - Fourier series KW - interpolation KW - mutual coupling KW - ripple minimization ER - TY - JOUR TI - Terahertz Spectra of Biotin Based on First Principle, Molecular Mechanical, and Hybrid Simulations AU - Bykhovski, Alexei AU - Woolard, Dwight T2 - IEEE TRANSACTIONS ON TERAHERTZ SCIENCE AND TECHNOLOGY AB - Terahertz (THz) absorption of biotin was simulated using the first principle and the density functional theory (DFT) both in the harmonic approximation and with corrections for the anharmonicity. Anharmonicity corrections were calculated using two different approaches. First, the perturbation theory-based first principle calculations were performed to include third- and fourth-order anharmonicity corrections in atomic displacements to harmonic vibrational states. Second, the atom-centered density matrix propagation molecular dynamics model that provides a good energy conservation was used to calculate the atomic trajectories, velocities, and a dipole moment time history of biotin at low and room temperatures. Predicted low-THz lines agree well with the experimental spectra. The influence of the polyethylene (PE) matrix embedment on the THz spectra of biotin at the nanoscale was studied using the developed hybrid DFT/molecular mechanical approach. While PE is almost transparent at THz frequencies, additional low-THz lines are predicted in the biotin/PE system, which reflects a dynamic interaction between biotin and a surrounding PE cavity. DA - 2013/7// PY - 2013/7// DO - 10.1109/tthz.2013.2267413 VL - 3 IS - 4 SP - 357-362 SN - 2156-342X KW - Biotin KW - first principle KW - hybrid KW - terahertz (THZ) ER - TY - JOUR TI - Temporal Response of the Underwater Optical Channel for High-Bandwidth Wireless Laser Communications AU - Cochenour, Brandon AU - Mullen, Linda AU - Muth, John T2 - IEEE JOURNAL OF OCEANIC ENGINEERING AB - This paper describes a high-sensitivity, high-dynamic range experimental method for measuring the frequency response of the underwater optical channel in the forward direction for the purpose of wireless optical communications. Historically, there have been few experimental measurements of the frequency response of the underwater channel, particularly with regard to wireless communication systems. In this work, the frequency response is measured out to 1 GHz over a wide range of water clarities (approximately 1-20 attenuation lengths). Both spatial and temporal dispersions are measured as a function of pointing angle between the transmitter and the receiver. We also investigate the impact of scattering function and receiver field of view. The impact of these results to the link designer is also presented. DA - 2013/10// PY - 2013/10// DO - 10.1109/joe.2013.2255811 VL - 38 IS - 4 SP - 730-742 SN - 1558-1691 KW - Communications KW - laser KW - optical KW - propagation KW - scattering KW - underwater KW - wireless ER - TY - JOUR TI - Locality principle revisited: A probability-based quantitative approach AU - Gupta, Saurabh AU - Xiang, Ping AU - Yang, Yi AU - Zhou, Huiyang T2 - JOURNAL OF PARALLEL AND DISTRIBUTED COMPUTING AB - This paper revisits the fundamental concept of the locality of references and proposes to quantify it as a conditional probability: in an address stream, given the condition that an address is accessed, how likely the same address (temporal locality) or an address within its neighborhood (spatial locality) will be accessed in the near future. Previous works use reuse distance histograms as a measure of temporal locality. For spatial locality, some ad hoc metrics have been proposed as a quantitative measure. In contrast, our conditional probability-based locality measure has a clear mathematical meaning and provides a theoretically sound and unified way to quantify both temporal and spatial locality. We showcase that our quantified locality measure can be used to evaluate compiler optimizations, to analyze the locality at different levels of memory hierarchy, to optimize the cache architecture to effectively leverage the locality, and to examine the effect of data prefetching mechanisms. DA - 2013/7// PY - 2013/7// DO - 10.1016/j.jpdc.2013.01.010 VL - 73 IS - 7 SP - 1011-1027 SN - 1096-0848 KW - Locality of references KW - Probability KW - Memory hierarchy KW - Last level cache KW - Cache replacement policy KW - Data prefetching KW - Locality optimizations ER - TY - JOUR TI - Integrated Electric Motor Drive and Power Electronics for Bidirectional Power Flow Between the Electric Vehicle and DC or AC Grid AU - Khan, Mehnaz Akhter AU - Husain, Iqbal AU - Sozer, Yilmaz T2 - IEEE TRANSACTIONS ON POWER ELECTRONICS AB - This paper presents an integrated traction machine and converter topology that has bidirectional power flow capability between an electric vehicle and the dc or ac supply or grid. The inductances of the traction motor windings are used for bidirectional converter operation to transfer power eliminating the need for extra inductors for the charging and vehicle-to-grid converter operations. These operations are in addition to the vehicle traction mode operation. The electric powertrain system size and weight can be minimized with this approach. The concept has been analyzed with finite-element- coupled simulation with dynamic analysis software. Experimental results are also provided with electric machines. The interleaving technique has been used with the inductors to share the current and reduce the converter switching stresses. DA - 2013/12// PY - 2013/12// DO - 10.1109/tpel.2013.2258471 VL - 28 IS - 12 SP - 5774-5783 SN - 1941-0107 KW - Bidirectional converter KW - electric vehicle KW - integrated converter KW - machine inductance KW - vehicle-to-grid (V2G) ER - TY - CONF TI - Hetero(2) 3d integration: A scheme for optimizing efficiency/cost of chip multiprocessors AU - Priyadarshi, S. AU - Choudhary, N. AU - Dwiel, B. AU - Upreti, A. AU - Rotenberg, E. AU - Davis, R. AU - Franzon, P. T2 - International Symposium on Quality Electronic Design (ISQED) AB - Timing the transition of a processor design to a new technology poses a provocative tradeoff. On the one hand, transitioning as early as possible offers a significant competitive advantage, by bringing improved designs to market early. On the other hand, an aggressive strategy may prove to be unprofitable, due to the low manufacturing yield of a technology that has not had time to mature. We propose exploiting two complementary forms of heterogeneity to profitably exploit an immature technology for Chip Multiprocessors (CMP). First, 3D integration facilitates a technology alloy. The CMP is split across two dies, one fabricated in the old technology and the other in the new technology. The alloy derives benefit from the new technology while limiting cost exposure. Second, to compensate for lower efficiency of old-technology cores, we exploit application and microarchitectural heterogeneity: applications which gain less from technology scaling are scheduled on old-technology cores, moreover, these cores are retuned to optimize this class of application. For a defect density ratio of 200 between 45nm and 65nm, Hetero 2 3D gives 3.6× and 1.5× higher efficiency/cost compared to 2D and 3D homogeneous implementations, respectively, with only 6.5% degradation in efficiency. We also present a sensitivity analysis by sweeping the defect density ratio. The analysis reveals the defect density break-even points, where homogeneous 2D and 3D designs in 45nm achieve the same efficiency/cost as Hetero 2 3D, marking significant points in the maturing of the technology. C2 - 2013/// C3 - Proceedings of the fourteenth international symposium on quality electronic design (ISQED 2013) CY - Santa Clara, CA DA - 2013/// PY - 2013/3/4/ DO - 10.1109/isqed.2013.6523582 SP - 1–7 ER - TY - JOUR TI - Enhanced Quench Propagation in Bi2Sr2CaCu2Ox and YBa2Cu3O7-x Coils via a Nanoscale Doped-Titania-Based Thermally Conducting Electrical Insulator AU - Ishmael, Sasha AU - Luo, Haojun AU - White, Marvis AU - Hunte, Frank AU - Liu, X. T. AU - Mandzy, Natalia AU - Muth, John F. AU - Naderi, Golsa AU - Ye, Liyang AU - Hunt, Andrew T. AU - Schwartz, Justin T2 - IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY AB - The significant amount of energy stored in a large high-field superconducting magnet can be sufficient to destroy the coil in the event of an unprotected quench. For magnets based on high-temperature superconductors (HTSs), such as Bi 2 Sr 2 CaCu 2 O x (Bi2212) and YBa 2 Cu 3 O 7-x (YBCO), quench protection is particularly challenging due to slow normal zone propagation. A previous computational study showed that the quench behavior of HTS magnets is significantly improved if the turn-to-turn electrical insulation is thermally conducting, enhancing 3-D normal zone propagation. Here, a new doped-titania electrical insulation with high thermal conductivity is evaluated. The thermal conductivity of the insulation is measured at cryogenic temperatures, and its chemical compatibility with Bi2212 round wires is determined. Thin layers of the insulation are deposited onto the surface of Bi2212 and YBCO wires, which are then wound into small coils to study the quench behavior. Results show that the critical current and homogeneity of Bi2212 coils are improved relative to coils reacted with mullite insulation. Relative to similar coils with conventional insulation (mullite for Bi2212 and Kapton for YBCO), the turn-to-turn quench propagation is increased by a factor of 2.8 in Bi2212 coils at 4.2 K and self-field and by a factor of 2.5 in YBCO coils at 4.2 K and 5 T. These results indicate that doped-titania insulation may significantly improve Bi2212 and YBCO coils. Increased normal zone propagation velocity enhances quench detection and quench protection, and the thinness of the insulation relative to the most common alternatives increases the magnet winding pack current density and reduces the coil specific heat. DA - 2013/10// PY - 2013/10// DO - 10.1109/tasc.2013.2269535 VL - 23 IS - 5 SP - SN - 1558-2515 KW - Bi2Sr2CaCu2Ox KW - high-temperature superconductor (HTS) KW - insulation KW - quench detection KW - quench protection KW - thermal conductivity KW - YBa2Cu3O7-x ER - TY - CONF TI - Channel-adaptive sensing strategy for Cognitive Radio ad hoc networks AU - Lu, Yuan AU - Duel-Hallen, A. AB - In Cognitive Radio (CR) ad hoc networks, secondary users (SU) attempt to utilize valuable spectral resources without causing significant interference to licensed primary users (PU). While there is a large body of research on spectrum opportunity detection, exploitation, and adaptive transmission in CR, most existing approaches focus only on avoiding PU activity when making sensing decisions. Since the myopic sensing strategy results in congestion and poor throughput, several collision-avoidance sensing approaches were investigated in the literature. However, they provide limited improvement. A channel-aware myopic sensing strategy that adapts the reward to the fading channel state information (CSI) of the SU link is proposed. This CSI varies over the CR spectrum and from one SU pair to another due to multipath and shadow fading, thus randomizing sensing decisions and increasing the network throughput. The proposed joint CSI adaptation at the medium access control (MAC) and physical layers provides large throughput gain over randomized sensing strategies and/or conventional adaptive transmission methods. The performance of the proposed CSI-aided sensing strategy is validated for practical network scenarios and demonstrated to be robust to CSI mismatch, sensing errors, and spatial channel correlation. C2 - 2013/// C3 - 2013 IEEE 10th Consumer Communications and Networking Conference (CCNC) CY - Piscataway, NJ, USA DA - 2013/// DO - 10.1109/ccnc.2013.6488485 SP - 466 - 71 UR - http://dx.doi.org/10.1109/CCNC.2013.6488485 ER - TY - JOUR TI - Broadband Equivalent Circuit Models for Antenna Impedances and Fields Using Characteristic Modes AU - Adams, Jacob J. AU - Bernhard, Jennifer T. T2 - IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION AB - An approach for modeling antenna impedances and radiation fields in terms of fundamental eigenmodes is presented. Our method utilizes the simple frequency behavior of the characteristic modes to develop fundamental building blocks that superimpose to create the total response. In this paper, we study the modes of a dipole, but the method may be applied to more complicated structures as the modes retain many of their characteristics. We show that the eigenmode-based approach results in a more accurate model for the same complexity compared to a typical series RLC resonator model. Higher order modes can be more accurately modeled with added circuit complexity, but we show that this may not always be necessary. Because this method is based on the physical behavior of the fundamental modes, it also accurately connects circuit models to radiation patterns and other field behavior. To demonstrate this, we show that far field patterns, gain, and beam width of a dipole can be accurately extrapolated over a decade of bandwidth using data at two frequency points. DA - 2013/8// PY - 2013/8// DO - 10.1109/tap.2013.2261852 VL - 61 IS - 8 SP - 3985-3994 SN - 1558-2221 KW - Characteristic modes KW - circuit model KW - eigenmode KW - eigenvalue ER - TY - JOUR TI - A High Step-Up Three-Port DC-DC Converter for Stand-Alone PV/Battery Power Systems AU - Chen, Yen-Mo AU - Huang, Alex Q. AU - Yu, Xunwei T2 - IEEE TRANSACTIONS ON POWER ELECTRONICS AB - A three-port dc-dc converter integrating photovoltaic (PV) and battery power for high step-up applications is proposed in this paper. The topology includes five power switches, two coupled inductors, and two active-clamp circuits. The coupled inductors are used to achieve high step-up voltage gain and to reduce the voltage stress of input side switches. Two sets of active-clamp circuits are used to recycle the energy stored in the leakage inductors and to improve the system efficiency. The operation mode does not need to be changed when a transition between charging and discharging occurs. Moreover, tracking maximum power point of the PV source and regulating the output voltage can be operated simultaneously during charging/discharging transitions. As long as the sun irradiation level is not too low, the maximum power point tracking (MPPT) algorithm will be disabled only when the battery charging voltage is too high. Therefore, the control scheme of the proposed converter provides maximum utilization of PV power most of the time. As a result, the proposed converter has merits of high boosting level, reduced number of devices, and simple control strategy. Experimental results of a 200-W laboratory prototype are presented to verify the performance of the proposed three-port converter. DA - 2013/11// PY - 2013/11// DO - 10.1109/tpel.2013.2242491 VL - 28 IS - 11 SP - 5049-5062 SN - 1941-0107 KW - DC microgrid KW - energy storage KW - high step-up application KW - hybrid power system KW - renewable energy source KW - three-port converter ER - TY - JOUR TI - The Implementation of a High Performance GPGPU Compiler AU - Yang, Yi AU - Zhou, Huiyang T2 - INTERNATIONAL JOURNAL OF PARALLEL PROGRAMMING DA - 2013/12// PY - 2013/12// DO - 10.1007/s10766-012-0228-3 VL - 41 IS - 6 SP - 768-781 SN - 1573-7640 KW - GPU KW - Compiler KW - Optimization KW - Vectorization KW - OpenCL ER - TY - JOUR TI - Supplementary Energy Storage and Hybrid Front-End Converters for High-Power Mobile Mining Equipment AU - Parkhideh, Babak AU - Mirzaee, Hesam AU - Bhattacharya, Subhashish T2 - IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS AB - To supply the high-power ac-drive systems of the mining equipment, several active front ends with dc choppers are used to ensure reliable operation and an acceptable harmonic current spectrum. Recently, the integration of the energy storage system with the mining equipment has received industry attention, particularly for peak load shaving and smarter energy management of the mines. Currently, the regenerative energy is often burned into the choppers and is not fed back to the grid. The industry is motivated to capture this regenerative energy since it can be as high as 60% of the motoring power, as high as 3 MJ in every operation cycle, and as high as 24-MW peak power. Therefore, there is a possibility of large cost reductions and component rating reduction. In this paper, we investigate the operation of the current state-of-the-art front-end converter systems for multimotor applications. In particular, we propose power conversion configurations and methodology to determine the suitable energy storage technology for the development of the multimotor mobile mining equipment that has encouraging incentives for both the manufacturers and the mine operators. DA - 2013/// PY - 2013/// DO - 10.1109/tia.2013.2257637 VL - 49 IS - 4 SP - 1863-1872 SN - 1939-9367 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84880876687&partnerID=MN8TOARS KW - Active power filters KW - coal mining KW - energy efficiency KW - energy harvesting KW - energy management KW - energy storage KW - hybrid power electronic systems KW - mining equipment KW - power conversion harmonics KW - supercapacitors ER - TY - JOUR TI - Software thread integration for instruction-level parallelism AU - So, W. AU - Dean, A. G. T2 - ACM Transactions on Embedded Computing Systems AB - Multimedia applications require a significantly higher level of performance than previous workloads of embedded systems. They have driven digital signal processor (DSP) makers to adopt high-performance architectures like VLIW (Very-Long Instruction Word). Despite many efforts to exploit instruction-level parallelism (ILP) in the application, the speed is a fraction of what it could be, limited by the difficulty of finding enough independent instructions to keep all of the processor's functional units busy. DA - 2013/// PY - 2013/// DO - 10.1145/2501626.2512466 VL - 13 IS - 1 ER - TY - JOUR TI - Minority Carrier Transport and Their Lifetime in InGaAs/GaAsP Multiple Quantum Well Structures AU - Carlin, Conrad Zachary AU - Bradshaw, Geoffrey Keith AU - Samberg, Joshua Paul AU - Colter, Peter C. AU - Bedair, Salah M. T2 - IEEE TRANSACTIONS ON ELECTRON DEVICES AB - Minority carrier transport across InGaAs/GaAsP multiple quantum wells is studied by measuring the response of p-i-n and n-i-p GaAs solar cell structures. It is observed that the spectral response depends critically upon the width of the GaAsP barriers and the device polarity. Electron tunneling is not as efficient as hole tunneling due to a higher conduction band barrier. The spectral response depends on the relative magnitude of the carrier lifetime as compared with the tunneling lifetime. This paper deduces an estimated electron lifetime of 110 ns in In0.14Ga0.86As wells and 25 ns in In0.17Ga0.83As wells, which agree with published results. DA - 2013/8// PY - 2013/8// DO - 10.1109/ted.2013.2268421 VL - 60 IS - 8 SP - 2532-2536 SN - 1557-9646 KW - Indium Gallium Arsenide KW - quantum wells KW - tunneling ER - TY - JOUR TI - Method for non-optical quantification of in situ local soft tissue biomechanics AU - Tarsi, Grant M. AU - Gould, Russell A. AU - Chung, Jaebum A. AU - Xu, Andrew Z. AU - Bozkurt, Alper AU - Butcher, Jonathan T. T2 - JOURNAL OF BIOMECHANICS AB - Soft tissues exhibit significant biomechanical changes as they grow, adapt, and remodel under a variety of normal and pathogenic stimuli. Biomechanical measurement of intact soft tissues is challenging because of its large strain and nonlinear behavior. Tissue distention through applied vacuum pressure is an attractive method for acquiring local biomechanical information minimally invasive and non-destructive, but the current requirement for optical strain measurement limits its use. In this study, we implemented a novel flexible micro-electrode array placed within a cylindrical probe tip. We hypothesized that upon tissue distention, contact with each electrode would result in a precipitous voltage drop (from the resistive connection formed between input and output electrodes) across the array. Hence, tissue distention (strain) can be derived directly from the electrode array geometry. In pilot studies, we compared the electrode array measurements directly against optical deformation measurements in-situ of agar tissue phantoms and freshly isolated porcine tissue. Our results demonstrate that the probe derived stress–strain profiles and modulus measurements were statistically indistinguishable from optical measurement. We further show that electrode geometry can be scaled down to 50 μm in size (length and width) and spaced 50 μm apart without impairing measurement accuracy. These results establish a promising new method for minimally invasive local soft tissue biomechanical measurement, which may be useful for applications such as disease diagnosis and health monitoring. DA - 2013/7/26/ PY - 2013/7/26/ DO - 10.1016/j.jbiomech.2013.05.014 VL - 46 IS - 11 SP - 1938-1942 SN - 0021-9290 KW - Flexible electronics KW - Microelectrode device KW - Pipette aspiration KW - Biopsy KW - Diagnosis ER - TY - JOUR TI - Interface properties of Ga(As,P)/(In,Ga)As strained multiple quantum well structures AU - Samberg, Joshua P. AU - Alipour, Hamideh M. AU - Bradshaw, Geoffrey K. AU - Carlin, C. Zachary AU - Colter, Peter C. AU - LeBeau, James M. AU - El-Masry, N. A. AU - Bedair, Salah M. T2 - APPLIED PHYSICS LETTERS AB - (In,Ga)As/Ga(As,P) multiple quantum wells (MQWs) with GaAs interface layers have been characterized with photoluminescence (PL) and high resolution scanning transmission electron microscopy (STEM). By growing (In,Ga)As/Ga(As,P) MQWs with asymmetric GaAs interfacial layers, we found that phosphorus carry-over had a profound effect on the absorption edge of the (In,Ga)As wells. Evidence for this phosphorus was initially determined via PL and then definitively proven through STEM and energy dispersive x-ray spectroscopy. We show that the phosphorus carry-over can be prevented with sufficiently thick GaAs transition layers. Preliminary results for GaAs p-i-n solar cells utilizing the improved MQWs are presented. DA - 2013/8/12/ PY - 2013/8/12/ DO - 10.1063/1.4818548 VL - 103 IS - 7 SP - SN - 0003-6951 ER - TY - CONF TI - Gradient based centralized optimal volt/var control strategy for smart distribution system AU - Shen, Z. AU - Baran, Mesut AB - With the development of enabling power electronic devices, such as the solid state transformer (SST) [1], the concept of a novel future renewable electric energy delivery and management system [2] is raised. The Future Renewable Electric Energy Delivery and Management (FREEDM) system is a smart distribution system that can accommodate distributed renewable energy, distributed energy storage devices, and plug-in hybrid electric vehicles (PHEVs), As the complexity of the power system increases, the need for a sophisticated power system operation and control method is becoming a critical issue. The new devices shouldn't disturb normal system operations, and the capabilities of these devices should help support the customer needs and enhance system performance. Therefore, this paper develops a centralized Volt/Var control strategy to minimize power system losses while maintaining voltage profiles within acceptable limits. C2 - 2013/// C3 - 2013 IEEE PES Innovative Smart Grid Technologies (ISGT) DA - 2013/// DO - 10.1109/isgt.2013.6497865 ER - TY - JOUR TI - Gallium nitride nanowires by maskless hot phosphoric wet etching AU - Bharrat, D. AU - Hosalli, A. M. AU - Van Den Broeck, D. M. AU - Samberg, J. P. AU - Bedair, S. M. AU - El-Masry, N. A. T2 - APPLIED PHYSICS LETTERS AB - We demonstrate gallium nitride (GaN) nanowires formation by controlling the selective and anisotropic etching of N-polar GaN in hot phosphoric acid. Nanowires of ∼109/cm,2 total height of ∼400 nm, and diameters of 170–200 nm were obtained. These nanowires have both non-polar {11¯00}/ {112¯0} and semi-polar {1011¯} facets. X–Ray Diffraction characterization shows that screw dislocations are primarily responsible for preferential etching to create nanowires. Indium gallium nitride multi-quantum wells (MQWs) grown on these GaN nanowires showed a blue shift in peak emission wavelength of photoluminescence spectra, and full width at half maximum decreased relative to MQWs grown on planar N-polar GaN, respectively. DA - 2013/8/19/ PY - 2013/8/19/ DO - 10.1063/1.4819272 VL - 103 IS - 8 SP - SN - 1077-3118 ER - TY - JOUR TI - GaN polarity determination by photoelectron diffraction AU - Romanyuk, O. AU - Jiricek, P. AU - Paskova, T. AU - Bieloshapka, I. AU - Bartos, I. T2 - APPLIED PHYSICS LETTERS AB - A nondestructive approach to determine the wurtzite GaN crystal polarity based on X-ray photoelectron diffraction is proposed. The approach, utilizing the ratio of photoemitted electron currents excited by a standard laboratory X-ray source from the N 1s level in the (101¯0) plane at polar angles of 20° and 25°, is tested on GaN crystals. The photoelectron intensity ratio I20/I25 is larger or smaller than unity for GaN(0001) or GaN(0001¯), respectively. The approach can be used for polarity determination of other binary wurtzite crystals. The atom with the smaller electron scattering cross-section should be used as the emitter. DA - 2013/8/26/ PY - 2013/8/26/ DO - 10.1063/1.4819761 VL - 103 IS - 9 SP - SN - 1077-3118 ER - TY - JOUR TI - Fault Analysis on Distribution Feeders With High Penetration of PV Systems AU - Hooshyar, Hossein AU - Baran, Mesut E. T2 - IEEE TRANSACTIONS ON POWER SYSTEMS AB - Fault current profile on a PV-dominated distribution feeder is rather different than a conventional feeder. To estimate the fault current profile on such a feeder, the paper proposes a new method which extends the capability of conventional short-circuit analysis method. The paper also shows that this time-varying fault current profile makes it also more difficult to estimate the time it will take for an overcurrent relay/device to interrupt such a fault current. The paper proposes a method for estimation of this operating time also. Performance of the proposed methods has been assessed by simulations on a sample distribution feeder. DA - 2013/8// PY - 2013/8// DO - 10.1109/tpwrs.2012.2227842 VL - 28 IS - 3 SP - 2890-2896 SN - 1558-0679 KW - Fault analysis KW - overcurrent relay KW - photovoltaic (PV) KW - PSCAD/EMTDC ER - TY - JOUR TI - Effect of etching with cysteamine assisted phosphoric acid on gallium nitride surface oxide formation AU - Wilkins, S. J. AU - Paskova, T. AU - Ivanisevic, A. T2 - JOURNAL OF APPLIED PHYSICS AB - In-situ functionalization of polar GaN was performed by adding cysteamine to a phosphoric acid etchant in order to study its effect on photoluminescence and oxide formation on the surfaces. The functionalization was characterized by atomic force microscopy, x-ray photoelectron spectroscopy, photoluminescence (PL), and water contact angle measurements. Two sets of polar GaN samples with different dislocation densities were evaluated, thin GaN layers residing on sapphire and thick free-standing GaN separated from sapphire substrate aiming to reveal the effect of material quality on in-situ functionalization. The addition of cysteamine to the phosphoric acid solution was found to result in: (i) decreased surface roughness, (ii) no change to hydrophobicity, (iii) decreased oxygen content especially at high-temperature treatments. The effect of the in-situ functionalization on the PL efficiency was more pronounced in the free-standing sample than in the film residing on the sapphire, which was attributed to a higher crystal quality free from strain. DA - 2013/8/14/ PY - 2013/8/14/ DO - 10.1063/1.4817899 VL - 114 IS - 6 SP - SN - 1089-7550 ER - TY - JOUR TI - Discussion of "Online Tracking of Thevenin Equivalent Parameters Using PMU Measurements" AU - Vanouni, Maziar T2 - IEEE TRANSACTIONS ON POWER SYSTEMS AB - The paper points out that PMU measurements cannot be used directly to estimate TEC parameters due to the phase drift brought about by the continuous change of frequency in real power systems. Therefore, a method has been presented to eliminate the effect of the phase drift and to synchronize the PMU measurements so that the synchronized samples can be used to identify TEC. DA - 2013/5// PY - 2013/5// DO - 10.1109/tpwrs.2013.2254332 VL - 28 IS - 2 SP - 1899-1899 SN - 1558-0679 ER - TY - JOUR TI - WELFARE AND PARADOX AU - Mabrito, Robert T2 - JOURNAL OF PHILOSOPHICAL RESEARCH AB - The basic idea of a desire theory of welfare is that how good a life is for the person who lives it is a matter of how many of that person’s desires are satisfied. The more satisfied desires the better the life. That it is possible for a person to desire that his or her life go badly is thought to pose problems for such a view. Indeed, some have recently argued that the possibility of such desires entails that a desire theory of welfare leads to paradox. In this paper, I present this purported paradox for the desire theory of welfare, offer a new solution to it, and defend it from objections that have been made to other responses. DA - 2013/// PY - 2013/// DO - 10.5840/jpr20133815 VL - 38 SP - 299-322 SN - 2153-7984 ER - TY - CONF TI - Ultra-broadband wavelength conversion sensor using thermochromic liquid crystals AU - Chen, I. A. AU - Park, S. W. AU - Chen, G. AU - Wang, C. AU - Bethea, C. AU - Martini, R. AU - Woolard, D. C2 - 2013/// C3 - Terahertz, rf, millimeter, and submillimeter-wave technology and applications vi DA - 2013/// VL - 8624 ER - TY - JOUR TI - The impact of manipulating surface topography on the hydrologic restoration of a forested coastal wetland AU - Jarzemsky, Robert D. AU - Burchell, Michael R., II AU - Evans, Robert O. T2 - ECOLOGICAL ENGINEERING AB - A wetland, converted to agriculture in the mid-1970s, was restored to re-establish a non-riverine wet hardwood forest community in eastern North Carolina. Three surface techniques were implemented during construction to determine their effect on successfully restoring target wetland hydrology. The surface treatments, replicated within a randomized complete block design, were: plugging field ditches without altering the land surface (PLUG), plugging the field ditches and roughening the surface (ROUGH), and plugging the field ditches and removing the field crown (CR). Hydrologic conditions for the restoration and a nearby reference site were evaluated based on three years of monitoring data. Daily water table depths between the restoration and reference were within 11 cm on average. An initial evaluation found inconsistencies of treatment effect between blocks, and an as-built survey later confirmed surface elevations within Block 3 deviated from the intended design and was excluded from further analysis. Water table and outflow conditions for the remaining treatment plots and the reference were evaluated using several hydrologic criteria. The CR treatment was found to produce the wettest surface conditions and exported the lowest volume of outflow. For the majority of criterion considered, CR also produced significantly wetter conditions than the reference. The PLUG and ROUGH treatments produced similar hydrologic conditions and tracked closely with the median hydrologic conditions in the reference. Based on the results of this study and several others in low lying coastal areas, plugging pre-existing field ditches may be adequate to restore jurisdictional wetland hydrology and match reference hydrologic conditions. However, surface roughening is low cost method to increase surface storage and introduce microtopographic diversity. For many areas, the removal of existing field crown may be cost-prohibitive and produce wetter than desired conditions. Crown removal should be reserved for sites which have borderline historic wetland hydrologic characteristics. DA - 2013/9// PY - 2013/9// DO - 10.1016/j.ecoleng.2013.06.002 VL - 58 SP - 35-43 SN - 1872-6992 KW - Wetland hydrology KW - Restoration KW - Microtopography ER - TY - JOUR TI - Terahertz Spectra of Biotin Based on First Principle, Molecular Mechanical, and Hybrid Simulations AU - Bykhovski, Alexei AU - Woolard, Dwight T2 - IEEE JOURNAL OF BIOMEDICAL AND HEALTH INFORMATICS AB - Terahertz (THz) absorption of biotin was simulated using the first principle and the density functional theory (DFT) both in the harmonic approximation and with corrections for the anharmonicity. Anharmonicity corrections were calculated using two different approaches. First, the perturbation theory-based first principle calculations were performed to include third- and fourth-order anharmonicity corrections in atomic displacements to harmonic vibrational states. Second, the atom-centered density matrix propagation molecular dynamics model that provides a good energy conservation was used to calculate the atomic trajectories, velocities, and a dipole moment time history of biotin at low and room temperatures. Predicted low-THz lines agree well with the experimental spectra. The influence of the polyethylene (PE) matrix embedment on the THz spectra of biotin at the nanoscale was studied using the developed hybrid DFT/molecular mechanical approach. While PE is almost transparent at THz frequencies, additional low-THz lines are predicted in the biotin/PE system, which reflects a dynamic interaction between biotin and a surrounding PE cavity. DA - 2013/7// PY - 2013/7// DO - 10.1109/jbhi.2013.2253786 VL - 17 IS - 4 SP - 768-773 SN - 2168-2194 KW - Biotin KW - first principle KW - hybrid KW - terahertz (THZ) ER - TY - CONF TI - Short-circuit capability of 1200V SiC MOSFET and JFET for fault protection AU - Huang, X. AU - Wang, G. Y. AU - Li, Y. S. AU - Huang, A. Q. AU - Baliga, B. J. AB - The short-circuit capability of power switches is crucial for the fault protection. In this paper, 1200V SiC MOSFET and normally-off SiC JFET have been characterized and their short-circuit capabilities have been studied and analyzed at 400V DC bus voltage. Due to different physics in the channels, SiC MOSFET and SiC JFET show different types of temperature coefficient. During the short-circuit operation, the saturation current, I sat , of SiC MOSFET increases for several microseconds before the gentle decreasing while that of SiC JFET decreases drastically from the very beginning. The SiC MOSFETs failed after short-circuit operations of 80μs and 50μs at 10V and 15V gate bias respectively while the SiC JFET could survive a short-circuit time more than 1.4msec. C2 - 2013/// C3 - 2013 twenty-eighth annual ieee applied power electronics conference and exposition (apec 2013) DA - 2013/// DO - 10.1109/apec.2013.6520207 SP - 197-200 ER - TY - JOUR TI - Photoacoustic Imaging of the Bladder A Pilot Study AU - Kamaya, Aya AU - Vaithilingam, Srikant AU - Chung, Benjamin I. AU - Oralkan, Omer AU - Khuri-Yakub, Butrus T. T2 - JOURNAL OF ULTRASOUND IN MEDICINE AB - Photoacoustic imaging is a promising new technology that combines tissue optical characteristics with ultrasound transmission and can potentially visualize tumor depth in bladder cancer. We imaged simulated tumors in 5 fresh porcine bladders with conventional pulse-echo sonography and photoacoustic imaging. Isoechoic biomaterials of different optical qualities were used. In all 5 of the bladder specimens, photoacoustic imaging showed injected biomaterials, containing varying degrees of pigment, better than control pulse-echo sonography. Photoacoustic imaging may be complementary to diagnostic information obtained by cystoscopy and urine cytologic analysis and could potentially obviate the need for biopsy in some tumors before definitive treatment. DA - 2013/7// PY - 2013/7// DO - 10.7863/ultra.32.7.1245 VL - 32 IS - 7 SP - 1245-1250 SN - 1550-9613 KW - bladder cancer KW - bladder tumor depth KW - bladder tumor staging KW - noninvasive bladder cancer staging KW - optoacoustic imaging KW - photoacoustic imaging ER - TY - CONF TI - Performance analysis and characterization of current switch under reverse voltage commutation, overlap voltage bump and zero current switching AU - De, A. AU - Roy, S. AU - Bhattacharya, Subhashish AU - Divan, D.M. AB - Diode reverse recovery is notorious for increasing switching losses in current stiff converters. A lot of effort has been made over the years to mitigate the reverse recovery losses. However, there exists ways to use this feature to achieve zero voltage transition in the same converter thereby, mitigating the loss incurred as compared to hard switched turn off. An attempt has been made in this paper to demonstrate the behavior of several devices working under Reverse voltage commutation, hard switched and zero current turn off condition. Test Circuits have been constructed and tested at various voltage levels with various combinations of devices. A new form of switching characteristic has been noticed and presented in this paper. The main motivation of the paper is to make a fair judgment on device selection for various soft-switch based topologies. C2 - 2013/// C3 - Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC DA - 2013/// DO - 10.1109/apec.2013.6520636 SP - 2429-2435 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84879373029&partnerID=MN8TOARS ER - TY - CONF TI - Operation and design considerations of FID at distribution voltages AU - Watterson, J. AU - White, L. AU - Bhattacharya, Subhashish AU - Widener, C. AU - Bosworth, M. AU - Vodyakho, O. AU - Steurer, M. AU - Neumayr, D. AU - Edrington, C. AB - This paper addresses the theory, construction, and testing of a novel prototype Solid State Fault Isolation Device (SSFID) that serves as an enabling technology for the multi-university, National Science Foundation funded Future Renewable Electrical Energy Distribution and Management (FREEDM) initiative. This initiative focuses on performing the fundamental research and devising breakthrough technologies to aid in the conversion of today's conventional grid to a more flexible and effective Power Electronics Distribution System (PEDS). The SSFID, the device on which this paper focuses, provides high speed (micro-seconds) sectionalizing and re-closing abilities that will support the use and function of other components of the FREEDM system that are being designed and tested by the other universities involved in the initiative. Its functional parameters and requirements are discussed and a prototype design, as well as its testing results, is presented. C2 - 2013/// C3 - Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC DA - 2013/// DO - 10.1109/apec.2013.6520601 SP - 2206-2211 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84879360229&partnerID=MN8TOARS ER - TY - JOUR TI - On the Capacity Region of Cognitive Multiple Access over White Space Channels AU - Zhang, Huazi AU - Zhang, Zhaoyang AU - Dai, Huaiyu T2 - IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS AB - Opportunistically sharing the white spaces, or the temporarily unoccupied spectrum licensed to the primary user (PU), is a practical way to improve the spectrum utilization. In this paper, we consider the fundamental problem of rate regions achievable for multiple secondary users (SUs) which send their information to a common receiver over such a white space channel. In particular, the PU activities are treated as on/off side information, which can be obtained causally or non-causally by the SUs. The system is then modeled as a multi-switch channel and its achievable rate regions are characterized in some scenarios. Explicit forms of outer and inner bounds of the rate regions are derived by assuming additional side information, and they are shown to be tight in some special cases. An optimal rate and power allocation scheme that maximizes the sum rate is also proposed. The numerical results reveal the impacts of side information, channel correlation and PU activity on the achievable rates, and also verify the effectiveness of our rate and power allocation scheme. Our work may shed some light on the fundamental limit and design tradeoffs in practical cognitive radio systems. DA - 2013/11// PY - 2013/11// DO - 10.1109/jsac.2013.131105 VL - 31 IS - 11 SP - 2517-2527 SN - 1558-0008 KW - Cognitive multiple access channel (CogMAC) KW - cognitive radio KW - white space channel KW - three-switch channel KW - capacity region KW - optimal rate and power allocation ER - TY - JOUR TI - Magneto-quasistatic tracking of an American football: A goal-line measurement AU - Arumugam, D. D. AU - Griffin, J. D. AU - Stancil, D. D. AU - Ricketts, D. S. T2 - IEEE Antennas and Propagation Magazine DA - 2013/// PY - 2013/// VL - 55 IS - 1 SP - 137-146 ER - TY - JOUR TI - Growth and Characterization of InxGa1-xAs/GaAs1-yPy Strained-Layer Superlattices with High Values of y (similar to 80%) AU - Samberg, J. P. AU - Carlin, C. Z. AU - Bradshaw, G. K. AU - Colter, P. C. AU - Bedair, S. M. T2 - JOURNAL OF ELECTRONIC MATERIALS AB - Strained-layer superlattice (SLS) structures, such as InGaAs/GaAsP lattice matched to GaAs, have shown great potential in absorption devices such as photodetectors and triple-junction photovoltaic cells. However, until recently they have been somewhat hindered by their usage of low-phosphorus GaAsP barriers. High-P-composition GaAsP was developed as the barrier for InGaAs/GaAsP strained-layer superlattice (SLS) structures, and the merits of using such a high composition of phosphorus are discussed. It is believed that these barriers represent the highest phosphorus content to date in such a structure. By using high-composition GaAsP the carriers are collected via tunneling (for barriers ≤30 Å) as opposed to thermionic emission. Thus, by utilizing thin, high-content GaAsP barriers one can increase the percentage of the intrinsic in a p-i-n structure that is composed of InGaAs wells in addition to increasing the number of periods that can be grown for given depletion width. However, standard SLSs of this type inherently possess undesirable compressive strain and quantum size effects (QSEs) that cause the optical absorption of the thin InGaAs SLS wells to shift to higher energies relative to that of bulk InGaAs of the same composition. To circumvent these deleterious QSEs, stress-balanced, pseudomorphic InGaAs/GaAsP staggered SLSs were grown. Staggering was achieved by removing a portion of one well and adding it to an adjacent well. The spectral response obtained from device characterization indicated that staggering resulted in thicker InGaAs films with reduced cutoff energy. Additionally, these data confirm that tunneling is a very effective means for carrier transport in the SLS. DA - 2013/5// PY - 2013/5// DO - 10.1007/s11664-012-2375-0 VL - 42 IS - 5 SP - 912-917 SN - 0361-5235 KW - Superlattice KW - strain-balanced KW - tunneling KW - InGaAs KW - GaAsP KW - photovoltaic ER - TY - JOUR TI - Generating and measuring nondiffracting vector Bessel beams AU - Dudley, Angela AU - Li, Yanming AU - Mhlanga, Thandeka AU - Escuti, Michael AU - Forbes, Andrew T2 - OPTICS LETTERS AB - Nondiffracting vector Bessel beams are of considerable interest due to their nondiffracting nature and unique high-numerical-aperture focusing properties. Here we demonstrate their creation by a simple procedure requiring only a spatial light modulator and an azimuthally varying birefringent plate, known as a q-plate. We extend our control of both the geometric and dynamic phases to perform a polarization and modal decomposition on the vector field. We study both single-charged Bessel beams as well as superpositions and find good agreement with theory. Since we are able to encode nondiffracting modes with circular polarizations possessing different orbital angular momenta, we suggest these modes will be of interest in optical trapping, microscopy, and optical communication. DA - 2013/9/1/ PY - 2013/9/1/ DO - 10.1364/ol.38.003429 VL - 38 IS - 17 SP - 3429-3432 SN - 1539-4794 ER - TY - JOUR TI - Electric Power Allocation in a Network of Fast Charging Stations AU - Bayram, I. Safak AU - Michailidis, George AU - Devetsikiotis, Michael AU - Granelli, Fabrizio T2 - IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS AB - In order to increase the penetration of electric vehicles, a network of fast charging stations that can provide drivers with a certain level of quality of service (QoS) is needed. However, given the strain that such a network can exert on the power grid, and the mobility of loads represented by electric vehicles, operating it efficiently is a challenging and complex problem. In this paper, we examine a network of charging stations equipped with an energy storage device and propose a scheme that allocates power to them from the grid, as well as routes customers. We examine three scenarios, gradually increasing their complexity. In the first one, all stations have identical charging capabilities and energy storage devices, draw constant power from the grid and no routing decisions of customers are considered. It represents the current state of affairs and serves as a baseline for evaluating the performance of the proposed scheme. In the second scenario, power to the stations is allocated in an optimal manner from the grid and in addition a certain percentage of customers can be routed to nearby stations. In the final scenario, optimal allocation of both power from the grid and customers to stations is considered. The three scenarios are evaluated using real traffic traces corresponding to weekday rush hour from a large metropolitan area in the US. The results indicate that the proposed scheme offers substantial improvements of performance compared to the current mode of operation; namely, more customers can be served with the same amount of power, thus enabling the station operators to increase their profitability. Further, the scheme provides guarantees to customers in terms of the probability of being blocked (and hence not served) by the closest charging station to their location. Overall, the paper addresses key issues related to the efficient operation, both from the perspective of the power grid and the drivers satisfaction, of a network of charging stations. DA - 2013/7// PY - 2013/7// DO - 10.1109/jsac.2013.130707 VL - 31 IS - 7 SP - 1235-1246 SN - 1558-0008 KW - Electric Vehicles KW - Stochastic Charging Station Model KW - Performance Evaluation ER - TY - JOUR TI - Are expressivists guilty of wishful thinking? AU - Mabrito, Robert T2 - PHILOSOPHICAL STUDIES DA - 2013/9// PY - 2013/9// DO - 10.1007/s11098-012-0003-8 VL - 165 IS - 3 SP - 1069-1081 SN - 0031-8116 KW - Dorr KW - Expressivism KW - Non-cognitivism KW - Wishful thinking ER - TY - JOUR TI - Analysis and modeling of parallel three-phase boost converters using three-phase coupled inductor AU - Lim, C. S. AU - Lee, K. J. AU - Kim, R. Y. AU - Hyun, D. S. T2 - Journal of Electrical Engineering & Technology DA - 2013/// PY - 2013/// VL - 8 IS - 5 SP - 1086-1095 ER - TY - CONF TI - A multi-terminal DC to DC converter topology with power accumulation from renewable energy sources with unregulated DC voltages AU - Dutta, S. AU - Roy, S. AU - Bhattacharya, Subhashish AB - The following paper details out a converter topology which can act as an accumulator of power from different renewable energy sources (RES). Due to the intermittent nature of power availability from RES the DC buses are assumed unregulated. The proposed topology decouples individual voltage sources and reduces unwanted circulation of reactive power between the busses due to mismatch in voltage levels, and at the same time accumulates the power and produces a regulated DC output. The magnetic design of the transformer core has been shown and the topology has been verified with hardware experimental results. C2 - 2013/// C3 - Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC DA - 2013/// DO - 10.1109/apec.2013.6520440 SP - 1124-1130 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84879384693&partnerID=MN8TOARS ER - TY - CONF TI - A fully autonomous power management strategy for DC microgrid bus voltages AU - Yu, X. W. AU - Huang, A. AU - Burgos, R. AU - Li, J. AU - Du, Y. AB - A typical DC microgrid is investigated in this paper. Two unidirectional DC/DC converters for photovoltaic (PV), and two bidirectional DC/DC converters for batteries are included in the proposed DC microgrid system embodying multiple renewable energy sources and energy storage devices. In order to manage the system operation, a fully autonomous power management strategy, namely adaptive DC bus voltage signal, is proposed. In the proposed control algorithm, the DC microgrid system can operate in islanding mode, DC source-connection mode, featuring seamless transitions between these two modes. Experimental results verify that the proposed power management strategy can be applied to a DC microgrid stably and achieve good performance. C2 - 2013/// C3 - 2013 twenty-eighth annual ieee applied power electronics conference and exposition (apec 2013) DA - 2013/// DO - 10.1109/apec.2013.6520706 SP - 2876-2881 ER - TY - JOUR TI - A Byzantine Attack Defender in Cognitive Radio Networks: The Conditional Frequency Check AU - He, Xiaofan AU - Dai, Huaiyu AU - Ning, Peng T2 - IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS AB - Security concerns are raised for collaborative spectrum sensing due to its vulnerabilities to the potential attacks from malicious secondary users. Most existing malicious user detection methods are reputation-based, which become incapable when the malicious users dominate the network. On the other hand, although Markovian models characterize the spectrum state behavior more precisely, there is a scarcity of malicious user detection methods which fully explore this feature. In this paper, a new malicious user detection method using two proposed conditional frequency check (CFC) statistics is developed under the Markovian model for the spectrum state. With the assistance of one trusted user, the proposed method can achieve high malicious user detection accuracy (≥ 95%) for arbitrary percentage of malicious users that may even be equipped with more advanced sensing devices, and can thus improve the collaborative spectrum sensing performance significantly. Simulation results are provided to verify the theoretical analysis and effectiveness of the proposed method. DA - 2013/5// PY - 2013/5// DO - 10.1109/twc.2013.031313.121551 VL - 12 IS - 5 SP - 2512-2523 SN - 1558-2248 KW - Cognitive radio network KW - collaborative spectrum sensing KW - malicious user detection KW - security ER - TY - JOUR TI - 74 GHz, 17.2 dBm power amplifier in 45 nm SOI CMOS AU - Tai, W. AU - Ricketts, D. S. T2 - ELECTRONICS LETTERS AB - A millimetre-wave power amplifier (PA) fabricated in 45 nm SOI CMOS is reported that achieves 17.2 dBm saturated output power at 74 GHz without power combining using a 2.2 V supply, over twice the output power of previously reported single CMOS PAs. The peak gain and PAE are 14.3 dB and 11.1%, respectively. The PA also achieves a 3 dB bandwidth of 31 GHz while occupying a small die area of 0.23 mm2. DA - 2013/6/6/ PY - 2013/6/6/ DO - 10.1049/el.2013.1052 VL - 49 IS - 12 SP - 758-+ SN - 0013-5194 ER - TY - JOUR TI - Physics based modeling of gate leakage current due to traps in AlGaN/GaN HFETs AU - Goswami, A. AU - Trew, R. J. AU - Bilbro, G. L. T2 - SOLID-STATE ELECTRONICS AB - Abstract A new model for the gate leakage current in AlGaN/GaN HFETs is demonstrated. The model is completely physical and is based on the formulation of space charge limited current flow. Two levels of shallow traps in the AlGaN surface layer are considered to evaluate the model. The depth of the traps is consistent with the reports presented in the literature. The model adequately explains the measured gate leakage current and for the first time, predicts accurately the experimentally observed change in slope of the gate leakage current versus the gate to drain voltage. DA - 2013/2// PY - 2013/2// DO - 10.1016/j.sse.2012.10.005 VL - 80 SP - 23-27 SN - 1879-2405 KW - AlGaN/GaN HFET reliability KW - Gate leakage KW - HEMTs KW - Semiconductor device modeling ER - TY - JOUR TI - Multifacet semipolar formation by controlling the groove depth via lateral sidewall epitaxy AU - Frajtag, P. AU - Nepal, N. AU - Paskova, T. AU - Bedair, S. M. AU - El-Masry, N. A. T2 - JOURNAL OF CRYSTAL GROWTH AB - We demonstrate InxGa1−xN/GaN light emitting diode structures with different sets of multifacet semipolar formation grown laterally on m-plane sidewalls formed by stripe patterning on preliminary grown c-plane GaN template. It was found that regrowth on shallow side walls within the GaN template resulted in a single semipolar (11¯01) facet, while deeper side walls led to multifacet semipolar formation. Very deep etching through the entire GaN template reaching the underlying sapphire substrates resulted in a combination of semipolar (11¯01) and nonpolar (11¯00) facets. The results indicate that the depth of the groove patterning can be used as a tool for controlling the set of semipolar facet formation. In addition, the growth rate in different crystallographic directions was studied and possible factors affecting the growth rates are discussed. DA - 2013/3/15/ PY - 2013/3/15/ DO - 10.1016/j.jcrysgro.2012.12.039 VL - 367 SP - 88-93 SN - 1873-5002 KW - Crystal structure KW - Metalorganic vapor phase epitaxy KW - InGaN KW - Nitrides ER - TY - JOUR TI - Intrinsic electrical transport properties of monolayer silicene and MoS2from first principles AU - Li, Xiaodong AU - Mullen, Jeffrey T. AU - Jin, Zhenghe AU - Borysenko, Kostyantyn M. AU - Buongiorno Nardelli, M. AU - Kim, Ki Wook T2 - Physical Review B AB - The electron-phonon interaction and related transport properties are investigated in monolayer silicene and MoS${}_{2}$ by using a density functional theory calculation combined with a full-band Monte Carlo analysis. In the case of silicene, the results illustrate that the out-of-plane acoustic phonon mode may play the dominant role unlike its close relative, graphene. The small energy of this phonon mode, originating from the weak $sp$${}^{2}$ $\ensuremath{\pi}$ bonding between Si atoms, contributes to the high scattering rate and significant degradation in electron transport. In MoS${}_{2}$, the longitudinal acoustic phonons show the strongest interaction with electrons. The key factor in this material appears to be the $Q$ valleys located between the $\ensuremath{\Gamma}$ and $K$ points in the first Brillouin zone as they introduce additional intervalley scattering. The analysis also reveals the potential impact of extrinsic screening by other carriers and/or adjacent materials. Finally, the effective deformation potential constants are extracted for all relevant intrinsic electron-phonon scattering processes in both materials. DA - 2013/3/15/ PY - 2013/3/15/ DO - 10.1103/physrevb.87.115418 VL - 87 IS - 11 SP - J2 - Phys. Rev. B LA - en OP - SN - 1098-0121 1550-235X UR - http://dx.doi.org/10.1103/PhysRevB.87.115418 DB - Crossref ER - TY - JOUR TI - First-principles calculation of thermal transport in metal/graphene systems AU - Mao, R. AU - Kong, B. D. AU - Gong, C. AU - Xu, S. AU - Jayasekera, T. AU - Cho, K. AU - Kim, K. W. T2 - Physical Review B AB - Thermal properties in the metal/graphene (Gr) systems are analyzed by using an atomistic phonon transport model based on Landauer formalism and first-principles calculations. The specific structures under investigation include chemisorbed Ni(111)/Gr, physisorbed Cu(111)/Gr and Au(111)/Gr, as well as Pd(111)/Gr with intermediate characteristics. Calculated results illustrate a strong dependence of thermal transfer on the details of interfacial microstructures. In particular, it is shown that the chemisorbed case provides a generally smaller interfacial thermal resistance than the physisorbed due to the stronger bonding. However, our calculation also indicates that the weakly chemisorbed interface of Pd/Gr may be an exception, with the largest thermal resistance among the considered. Further examination of the electrostatic potential and interatomic force constants reveal that the mixed bonding force between the Pd and C atoms results in incomplete hybridization of Pd and graphene orbital states at the junction, leading effectively to two phonon interfaces and a larger than expected thermal resistance. Comparison with available experimental data shows good agreement. The result clearly suggests the feasibility of phonon engineering for thermal property optimization at the interface. DA - 2013/4/5/ PY - 2013/4/5/ DO - 10.1103/physrevb.87.165410 VL - 87 IS - 16 SP - J2 - Phys. Rev. B LA - en OP - SN - 1098-0121 1550-235X UR - http://dx.doi.org/10.1103/PhysRevB.87.165410 DB - Crossref ER - TY - JOUR TI - Extension of the KLI approximation toward the exact optimized effective potential AU - Iafrate, G. J. AU - Krieger, J. B. T2 - Journal of Chemical Physics DA - 2013/// PY - 2013/// VL - 138 IS - 9 ER - TY - JOUR TI - A Low-Bandwidth Camera Sensor Platform with Applications in Smart Camera Networks AU - Chen, Phoebus AU - Hong, Kirak AU - Naikal, Nikhil AU - Sastry, S. Shankar AU - Tygar, Doug AU - Yan, Posu AU - Yang, Allen Y. AU - Chang, Lung-Chung AU - Lin, Leon AU - Wang, Simon AU - Lobaton, Edgar AU - Oh, Songhwai AU - Ahammad, Parvez T2 - ACM TRANSACTIONS ON SENSOR NETWORKS AB - Smart camera networks have recently emerged as a new class of sensor network infrastructure that is capable of supporting high-power in-network signal processing and enabling a wide range of applications. In this article, we provide an exposition of our efforts to build a low-bandwidth wireless camera network platform, called CITRIC, and its applications in smart camera networks. The platform integrates a camera, a microphone, a frequency-scalable (up to 624 MHz) CPU, 16 MB FLASH, and 64 MB RAM onto a single device. The device then connects with a standard sensor network mote to form a wireless camera mote. With reasonably low power consumption and extensive algorithmic libraries running on a decent operating system that is easy to program, CITRIC is ideal for research and applications in distributed image and video processing. Its capabilities of in-network image processing also reduce communication requirements, which has been high in other existing camera networks with centralized processing. Furthermore, the mote easily integrates with other low-bandwidth sensor networks via the IEEE 802.15.4 protocol. To justify the utility of CITRIC, we present several representative applications. In particular, concrete research results will be demonstrated in two areas, namely, distributed coverage hole identification and distributed object recognition. DA - 2013/3// PY - 2013/3// DO - 10.1145/2422966.2422978 VL - 9 IS - 2 SP - SN - 1550-4867 UR - http://dx.doi.org/10.1145/2422966.2422978 KW - Algorithms KW - Wireless Sensor Networks KW - Camera Sensor Architecture ER - TY - JOUR TI - Variation-Aware Circuit Macromodeling and Design Based on Surrogate Models AU - Zhu, Ting AU - Yelten, Mustafa Berke AU - Steer, Michael B. AU - Franzon, Paul D. T2 - SIMULATION AND MODELING METHODOLOGIES, TECHNOLOGIES AND APPLICATIONS AB - This paper presents surrogate model-based methods to generate circuit performance models, device models, and high-speed IO buffer macromodels. Circuit performance models are built with design parameters and parametric variations, and they can be used for fast and systematic design space exploration and yield analysis. Surrogate models of the main device characteristics are generated in order to assess the effects of variability in analog circuits. A new variation-aware IO buffer macromodel is developed by integrating surrogate modeling and a physically-based model structure. The new IO model provides both good accuracy and scalability for signal integrity analysis. DA - 2013/// PY - 2013/// DO - 10.1007/978-3-642-34336-0_17 VL - 197 SP - 255-269 SN - 2194-5365 KW - Surrogate Modeling KW - Macromodel KW - Variation-Aware KW - Circuit KW - Device Model KW - Design Exploration KW - IO Buffer ER - TY - JOUR TI - Riparian buffer located in an upland landscape position does not enhance nitrate-nitrogen removal AU - Johnson, Sara R. AU - Burchell, Michael R., II AU - Evans, Robert O. AU - Osmond, Deanna L. AU - Gilliam, J. Wendell T2 - ECOLOGICAL ENGINEERING AB - Relatively narrow (<50 m) riparian buffers strategically reestablished in correct landscape positions have been shown to significantly reduce agricultural non-point source pollution to streams. Because of this, conservation programs have been established to encourage landowners to enroll lands near surface waters to improve water quality. Former cropland enrolled in a conservation program was evaluated to determine its effectiveness in reducing nitrate-nitrogen (NO3−-N) in shallow groundwater. This conservation buffer (CB) was up to 80 m wide and was planted with loblolly pine (Pinus taeda). It was situated upslope of an existing 30–60 m wide riparian hardwood forest buffer (EHB) located within the floodplain of an intermittent stream. Shallow groundwater NO3−-N, groundwater hydrology, total organic carbon, and soil redox potential were measured throughout both the CB and the EHB for 18 months. Groundwater NO3−-N concentrations, often 5–15 mg L−1 within the CB, were not significantly reduced from concentrations that entered from the agricultural field edge. However, a decrease in NO3−-N concentration was observed within the EHB (17–83%). The hydrology of the CB coupled with relatively low organic carbon contributed to a low denitrification potential and lack of NO3−-N reduction compared with the EHB. While the CB enrollment likely provided additional habitat benefits it did not appear to provide treatment of groundwater NO3−-N. It is our conclusion that landscape position is a more important defining variable for buffer site selection than buffer width if NO3−-N reduction is a primary goal. DA - 2013/3// PY - 2013/3// DO - 10.1016/j.ecoleng.2012.11.006 VL - 52 SP - 252-261 SN - 1872-6992 KW - Riparian buffer KW - Conservation programs KW - Groundwater KW - Hydrology KW - Nitrate KW - NO3--N ER - TY - JOUR TI - Monolignol Pathway 4-Coumaric Acid: Coenzyme A Ligases in Populus trichocarpa: Novel Specificity, Metabolic Regulation, and Simulation of Coenzyme A Ligation Fluxes AU - Chen, Hsi-Chuan AU - Song, Jina AU - Williams, Cranos M. AU - Shuford, Christopher M. AU - Liu, Jie AU - Wang, Jack P. AU - Li, Quanzi AU - Shi, Rui AU - Gokce, Emine AU - Ducoste, Joel AU - Muddiman, David C. AU - Sederoff, Ronald R. AU - Chiang, Vincent L. T2 - PLANT PHYSIOLOGY AB - 4-Coumaric acid:coenzyme A ligase (4CL) is involved in monolignol biosynthesis for lignification in plant cell walls. It ligates coenzyme A (CoA) with hydroxycinnamic acids, such as 4-coumaric and caffeic acids, into hydroxycinnamoyl-CoA thioesters. The ligation ensures the activated state of the acid for reduction into monolignols. In Populus spp., it has long been thought that one monolignol-specific 4CL is involved. Here, we present evidence of two monolignol 4CLs, Ptr4CL3 and Ptr4CL5, in Populus trichocarpa. Ptr4CL3 is the ortholog of the monolignol 4CL reported for many other species. Ptr4CL5 is novel. The two Ptr4CLs exhibited distinct Michaelis-Menten kinetic properties. Inhibition kinetics demonstrated that hydroxycinnamic acid substrates are also inhibitors of 4CL and suggested that Ptr4CL5 is an allosteric enzyme. Experimentally validated flux simulation, incorporating reaction/inhibition kinetics, suggested two CoA ligation paths in vivo: one through 4-coumaric acid and the other through caffeic acid. We previously showed that a membrane protein complex mediated the 3-hydroxylation of 4-coumaric acid to caffeic acid. The demonstration here of two ligation paths requiring these acids supports this 3-hydroxylation function. Ptr4CL3 regulates both CoA ligation paths with similar efficiencies, whereas Ptr4CL5 regulates primarily the caffeic acid path. Both paths can be inhibited by caffeic acid. The Ptr4CL5-catalyzed caffeic acid metabolism, therefore, may also act to mitigate the inhibition by caffeic acid to maintain a proper ligation flux. A high level of caffeic acid was detected in stem-differentiating xylem of P. trichocarpa. Our results suggest that Ptr4CL5 and caffeic acid coordinately modulate the CoA ligation flux for monolignol biosynthesis. DA - 2013/3// PY - 2013/3// DO - 10.1104/pp.112.210971 VL - 161 IS - 3 SP - 1501-1516 SN - 0032-0889 ER - TY - JOUR TI - Molecular sentinel-on-chip for SERS-based biosensing AU - Wang, Hsin-Neng AU - Dhawan, Anuj AU - Du, Yan AU - Batchelor, Dale AU - Leonard, Donovan N. AU - Misra, Veena AU - Vo-Dinh, Tuan T2 - PHYSICAL CHEMISTRY CHEMICAL PHYSICS AB - The development of DNA detection techniques on large-area plasmonics-active platforms is critical for many medical applications such as high-throughput screening, medical diagnosis and systems biology research. Here, we report for the first time a unique "molecular sentinel-on-chip" (MSC) technology for surface-enhanced Raman scattering (SERS)-based DNA detection. This unique approach allows label-free detection of DNA molecules on chips developed on a wafer scale using large area nanofabrication methodologies. To develop plasmonics-active biosensing platforms in a repeatable and reproducible manner, we employed a combination of deep UV lithography, atomic layer deposition, and metal deposition to fabricate triangular-shaped nanowire (TSNW) arrays having controlled sub-10 nm gap nanostructures over an entire 6 inch wafer. The detection of a DNA sequence of the Ki-67 gene, a critical breast cancer biomarker, on the TSNW substrate illustrates the usefulness and potential of the MSC technology as a novel SERS-based DNA detection method. DA - 2013/// PY - 2013/// DO - 10.1039/c3cp00076a VL - 15 IS - 16 SP - 6008-6015 SN - 1463-9076 ER - TY - JOUR TI - Effect of fabric substrate and coating material on the quality of conductive printing AU - Suh, Minyoung AU - Carroll, Katherine E. AU - Grant, Edward AU - Oxenham, William T2 - JOURNAL OF THE TEXTILE INSTITUTE AB - This paper reports an investigation into the effect of fabric substrates and coating materials on the electrical and mechanical performance of printed antennas. Inductively coupled antennas were printed on fabrics using silver ink. To assure printability and protection, a printing structure was configured, consisting of surface coating, conductive printing, and protective coating. In order to simulate a realistic situation, three fabric substrates (denim, broadcloth, and single jersey) were selected from woven and knit fabrics for everyday wear. Three coating materials (acrylic, polyurethane, and silicone) were chosen from conventional conformal coating materials for printed circuit boards. Experimental results verified that fabric substrates can be selected to fit specific end-use application since it is shown that antenna performance was not significantly affected. Silicone coating is suggested to support antenna performance since this gave the least impairment in the fabrics as mechanical performance. DA - 2013/2/1/ PY - 2013/2/1/ DO - 10.1080/00405000.2012.714107 VL - 104 IS - 2 SP - 213-222 SN - 0040-5000 KW - smart textiles KW - conductive printing KW - protective coating KW - printed antenna KW - inductive coupling ER - TY - JOUR TI - Diversity Limits of Compact Broadband Multi-Antenna Systems AU - Taluja, Pawandeep S. AU - Hughes, Brian L. T2 - IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS AB - In order to support multiple antennas on compact wireless devices, transceivers are often designed with matching networks that compensate for mutual coupling. Some works have suggested that when optimal matching is applied to such a system, performance at the center frequency can be improved at the expense of an apparent reduction in the system bandwidth. This paper addresses the question of how coupling impacts bandwidth in the context of circular arrays. It will be shown that mutual coupling creates eigen-modes (virtual antennas) with diverse frequency responses, using the standard matching techniques. We shall also demonstrate how common communications techniques such as Diversity-OFDM would need to be optimized in order to compensate for these effects. DA - 2013/2// PY - 2013/2// DO - 10.1109/jsac.2013.130219 VL - 31 IS - 2 SP - 326-337 SN - 1558-0008 KW - multiple antennas KW - mutual coupling KW - broadband matching KW - MIMO KW - OFDM ER - TY - JOUR TI - Analytical Modeling of IGBTs: Challenges and Solutions AU - Baliga, B. J. T2 - IEEE TRANSACTIONS ON ELECTRON DEVICES AB - With the availability of advanced computing capability, it is fashionable to analyze and design insulated-gate bipolar transistors (IGBTs) using sophisticated 2-D and 3-D numerical simulation tools. However, analytical modeling of IGBTs allows a deeper understanding of the physics of operation, which can foster innovation. This paper reviews 1-D analytical models developed for the IGBT on-state characteristics, switching behavior, and safe operating area for symmetric (nonpunchthrough) and asymmetric (punchthrough) devices. DA - 2013/2// PY - 2013/2// DO - 10.1109/ted.2012.2222415 VL - 60 IS - 2 SP - 535-543 SN - 1557-9646 KW - Blocking KW - insulated-gate bipolar transistor (IGBT) KW - modeling KW - ON state KW - safe operating area KW - silicon carbide KW - switching ER - TY - JOUR TI - An AFM/STM multi-mode nanofabrication approach allowing in situ surface modification and characterisation AU - Hu, Weihua AU - Bain, J. AU - Ricketts, D. T2 - MICRO & NANO LETTERS AB - A report is presented on a new multi-mode nanofabrication method that uses a compliant conductive atomic force microscope (AFM) probe for both AFM and scanning tunnelling microscope (STM) operation and it is demonstrated that these modes can be switched ‘on-the-fly’ during the measurement or fabrication of nanostructures. The authors oxidised Ti with the same conductive AFM probe in AFM and STM modes, alternately in a continuous writing step. An in-plane Ti–TiOx–Ti junction was fabricated by combining AFM and STM modes and electrically characterised by taking current images in conductive AFM mode. After measurement, additional features were written to increase the electrical isolation, thus realising in situ nanoscale modification. DA - 2013/1// PY - 2013/1// DO - 10.1049/mnl.2012.0859 VL - 8 IS - 1 SP - 43-46 SN - 1750-0443 ER - TY - JOUR TI - A Compact Physical AlGaN/GaN HFET Model AU - Hou, Danqiong AU - Bilbro, Griff L. AU - Trew, Robert J. T2 - IEEE TRANSACTIONS ON ELECTRON DEVICES AB - We introduce a physics-based compact model for AlGaN/GaN heterojunction field-effect transistors (HFETs) that is suitable for both RF microwave and switched-mode power supply (SMPS) applications, so that RF techniques can help determine HFET performance in SMPS applications. Such simulations can predict the on-resistance, slew rate, and breakdown voltage from the physical design of the transistor. Starting from an expression for the drain-source conduction current, charge distribution and displacement current are determined. The new model was implemented in Verilog-A and implemented in AWRDE, the design environment from Applied Wave Research. The HFET model was validated by comparison with Silvaco simulations and with data from an AlGaN/GaN HFET S-band amplifier. The new model accurately predicts device performance for dc, small-signal, and large-signal operations. DA - 2013/2// PY - 2013/2// DO - 10.1109/ted.2012.2227323 VL - 60 IS - 2 SP - 639-645 SN - 1557-9646 KW - AlGaN/GaN heterojunction field-effect transistor (FET) (HFET) models KW - HFET compact models KW - nitride-based HFETs ER - TY - JOUR TI - New Method to Achieve AC Harmonic Elimination and Energy Storage Integration for 12-Pulse Diode Rectifiers AU - Bai, Sanzhong AU - Lukic, Srdjan M. T2 - IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS AB - The 12-pulse rectifier is often used to supply high-power industrial loads. Its ability to effectively and cheaply mitigate the harmonics on the ac side has ensured its dominance in the industry even as active front ends become cheaper and more reliable. Despite its many benefits, the 12-pulse rectifier is not able to reduce the ac-side harmonics to a level acceptable by the pertinent IEEE standards without additional filtering. In this paper, we outline a novel method to profile the rectifier output current to be triangular which results in low ac-side harmonics. The novelty in the proposed approach is that we exploit the dc-side filter design to minimize the volt-amperes (VA) rating of the current source used to profile the dc-side rectifier current. Additional benefits of the proposed method include lower VA rating of the dc filter, simple integration of dc energy storage, and effective ac harmonic control even when the initial rectifier current is discontinuous. DA - 2013/7// PY - 2013/7// DO - 10.1109/tie.2012.2196903 VL - 60 IS - 7 SP - 2547-2554 SN - 1557-9948 KW - Active power filter KW - energy storage KW - harmonics KW - 12-pulse diode rectifier ER - TY - JOUR TI - Multi-twist retarders: broadband retardation control using self-aligning reactive liquid crystal layers AU - Komanduri, Ravi K. AU - Lawler, Kristopher F. AU - Escuti, Michael J. T2 - OPTICS EXPRESS AB - We report on a family of complex birefringent elements, called Multi-Twist Retarders (MTRs), which offer remarkably effective control of broadband polarization transformation. MTRs consist of two or more twisted liquid crystal (LC) layers on a single substrate and with a single alignment layer. Importantly, subsequent LC layers are aligned directly by prior layers, allowing simple fabrication, achieving automatic layer registration, and resulting in a monolithic film with a continuously varying optic axis. In this work, we employ a numerical design method and focus on achromatic quarter- and half-wave MTRs. In just two or three layers, these have bandwidths and general behavior that matches or exceeds all traditional approaches using multiple homogenous retarders. We validate the concept by fabricating several quarter-wave retarders using a commercial polymerizeable LC, and show excellent achromaticity across bandwidths of 450-650 nm and 400-800 nm. Due to their simple fabrication and many degrees of freedom, MTRs are especially well suited for patterned achromatic retarders, and can easily achieve large bandwidth and/or low-variation of retardation within visible through infrared wavelengths. DA - 2013/1/14/ PY - 2013/1/14/ DO - 10.1364/oe.21.000404 VL - 21 IS - 1 SP - 404-420 SN - 1094-4087 ER - TY - JOUR TI - Loss minimisation in lambda/4 impedance transformers using multiple lambda/4 segments AU - Li, C. AU - Ricketts, D. S. T2 - ELECTRONICS LETTERS AB - Presented is an analysis of loss in quarter-wavelength impedance transformers. It is shown that the loss of an impedance transformer, S 21, is a function not only of the dielectric and conductor loss, but also the transformation ratio. S 21 is derived as a function of both loss and transformation ratio and it is shown that for high transformation ratios, using two or even three quarter-wavelength impedance transformers results in an overall lower loss. DA - 2013/2/14/ PY - 2013/2/14/ DO - 10.1049/el.2012.3382 VL - 49 IS - 4 SP - 274-276 SN - 0013-5194 ER - TY - JOUR TI - Experimental demonstration of the equivalence of inductive and strongly coupled magnetic resonance wireless power transfer AU - Ricketts, David S. AU - Chabalko, Matthew J. AU - Hillenius, Andrew T2 - APPLIED PHYSICS LETTERS AB - In this work, we show experimentally that wireless power transfer (WPT) using strongly coupled magnetic resonance (SCMR) and traditional induction are equivalent. We demonstrate that for a given coil separation, and to within 4%, strongly coupled magnetic resonance and traditional induction produce the same theoretical efficiency of wireless power transfer versus distance. Moreover, we show that the difference between traditional induction and strongly coupled magnetic resonance is in the implementation of the impedance matching network where strongly coupled magnetic resonance uses the mini-loop impedance match. The mini-loop impedance mach provides a low-loss, high-ratio impedance transformation that makes it desirable for longer distance wireless power transfer, where large impedance transformations are needed to maximize power transfer. DA - 2013/2/4/ PY - 2013/2/4/ DO - 10.1063/1.4788748 VL - 102 IS - 5 SP - SN - 0003-6951 ER - TY - JOUR TI - Athermalized channeled spectropolarimetry using a biaxial potassium titanyl phosphate crystal AU - Craven-Jones, Julia AU - Way, Brandyn M. AU - Kudenov, Michael W. AU - Mercier, Jeffrey A. T2 - OPTICS LETTERS AB - Channeled spectropolarimeters measure the polarization state of light as a function of wavelength. Typically, a channeled spectropolarimeter uses high-order retarders made of uniaxial crystal to amplitude modulate the measured spectrum with the Stokes polarization information. A primary limitation of these instruments is the thermal variability of the retarders, which necessitates frequent system recalibration. Past work has addressed this issue by implementing an athermalized retarder produced from two uniaxial crystals. However, reducing the complexity of an athermalized retarder is advantageous for minimizing size and weight requirements. In this Letter, a technique for producing a thermally stable channeled spectropolarimeter using biaxial retarders is presented. This technique preserves a constant phase over an appreciable temperature range. Proof-of-concept results from a KTP-based athermal partial channeled spectropolarimeter are presented from 500 to 750 nm for temperature changes up to 26°C. Spectropolarimetric reconstructions produced from this system vary by <=2.6% RMS when the retarder experiences a 13°C increase in temperature above 21°C ambient, <=5.2% for a 20°C increase, and <=6.7% for a 26°C increase. DA - 2013/5/15/ PY - 2013/5/15/ DO - 10.1364/ol.38.001657 VL - 38 IS - 10 SP - 1657-1659 SN - 0146-9592 ER - TY - JOUR TI - Architecting against Software Cache-Based Side-Channel Attacks AU - Kong, Jingfei AU - Aciicmez, Onur AU - Seifert, Jean-Pierre AU - Zhou, Huiyang T2 - IEEE TRANSACTIONS ON COMPUTERS AB - Using cache-like architectural components including data caches, instruction caches, or branch target buffers as a side channel, software cache-based side-channel attacks are able to derive secret keys used in cryptographic operations through legitimate software activities. Existing software solutions are typically application specific and incur substantial performance overhead. Recent hardware proposals against attacks on data caches, although effective in reducing performance overhead, may still be vulnerable to advanced attacks. Furthermore, efficient defenses against attacks on other cache structures, including instruction caches and branch target buffers, are missing. In this paper, we propose hardware-software integrated approaches to defend against software cache-based attacks comprehensively. For attacks on data caches, we propose to use preloading, informing loads, and informing loads with software random permutation to secure the partition-locked cache (PLcache), the random permutation (RPcache) and regular caches, respectively. These approaches present different tradeoffs between hardware complexity and performance overhead. To defend against attacks on instruction caches, we show that the PLcache with preloading and the RPcache provide good protection. To defend against attacks based on branch target buffers, we propose to adopt a new update policy to eliminate potential information leaking. Our experiments show that the proposed schemes not only provide strong security protection but also incur small performance overhead. DA - 2013/7// PY - 2013/7// DO - 10.1109/tc.2012.78 VL - 62 IS - 7 SP - 1276-1288 SN - 0018-9340 KW - Cache memories KW - private/public key cryptosystems KW - side-channel attacks KW - architectural support for computer security ER - TY - JOUR TI - Analysis of Electronic Structure, Binding, and Vibrations in Biotin-Streptavidin Complexes Based on Density Functional Theory and Molecular Mechanics AU - Bykhovski, Alexei AU - Zhang, Weidong AU - Jensen, James AU - Woolard, Dwight T2 - JOURNAL OF PHYSICAL CHEMISTRY B AB - In this work, the biotin-streptavidin complex was studied with density functional theory (DFT), molecular mechanical methods (MM), and a hybrid DFT/MM approach in order to obtain the theoretical predictions for electronic structures, binding, optical transitions, harmonic vibrations, and absorption spectra. It was demonstrated that biotin solvation in water can reduce the binding strength to streptavidin by more than half. All studied properties, including the biotin binding and the UV absorption of the biotin-streptavidin complex, are predicted to be protonation state dependent. The absorption edge of the complex calculated with TDDFT/MM was found to be virtually insensitive to the choice of the MM force field and strongly dependent on the type of embedding of the DFT partition. Both UV and terahertz light absorption spectra are predicted to be sensitive to the presence of biotin in the streptavidin tetramer. DA - 2013/1/10/ PY - 2013/1/10/ DO - 10.1021/jp3075833 VL - 117 IS - 1 SP - 25-37 SN - 1520-6106 ER - TY - JOUR TI - An asynchronous scheduled MAC protocol for wireless sensor networks AU - Jang, Beakcheol AU - Lim, Jun Bum AU - Sichitiu, Mihail L. T2 - COMPUTER NETWORKS AB - Wireless sensor networks (WSNs) comprise a number of autonomous sensors and one or more sinks to cooperatively monitor physical or environmental conditions. Energy efficiency is a key design factor of a MAC protocol for WSNs. Due to the importance of the problem, a number of energy efficient MAC protocols have been developed for WSNs. Preamble-sampling based MAC protocols (e.g., B-MAC and X-MAC) have overheads due to their preambles, and are inefficient at large wakeup intervals. SCP-MAC, a synchronous scheduled energy-efficient scheduling MAC protocol, minimizes the preamble by combining preamble sampling and scheduling techniques; however, it does not prevent energy loss due to overhearing; in addition, due to its synchronization procedure, it results in increased contention and delay. In this paper, we present an energy efficient MAC protocol for WSNs that avoids overhearing and reduces contention and delay by asynchronously scheduling the wakeup time of neighboring nodes. We provide an energy consumption analysis for multi-hop networks. To validate our design and analysis, we implement the proposed scheme in TinyOS. Experimental results show that AS-MAC considerably reduces energy consumption, packet loss and delay when compared with existing energy efficient MAC protocols. DA - 2013/1/16/ PY - 2013/1/16/ DO - 10.1016/j.comnet.2012.09.002 VL - 57 IS - 1 SP - 85-98 SN - 1872-7069 KW - Wireless sensor networks KW - Medium access control KW - Duty cycling KW - Low power listening KW - AS-MAC KW - SCP-MAC ER - TY - JOUR TI - Voltage and Power Balance Control for a Cascaded H-Bridge Converter-Based Solid-State Transformer AU - Zhao, Tiefu AU - Wang, Gangyao AU - Bhattacharya, Subharshish AU - Huang, Alex Q. T2 - IEEE TRANSACTIONS ON POWER ELECTRONICS AB - The solid-state transformer (SST) is an interface device between ac distribution grids and dc distribution systems. The SST consists of a cascaded multilevel ac/dc rectifier stage, a dual active bridge (DAB) converter stage with high-frequency transformers to provide a regulated 400-V dc distribution, and an optional dc/ac stage that can be connected to the 400-V dc bus to provide residential 120/240 V $_{\rm ac}$ . However, due to dc-link voltage and power unbalance in the cascaded modules, the unbalanced dc-link voltages and power increase the stress of the semiconductor devices and cause overvoltage or overcurrent issues. This paper proposes a new voltage and power balance control for the cascaded H-Bridge converter-based SST. Based on the single-phase dq model, a novel voltage and the power control strategy is proposed to balance the rectifier capacitor voltages and the real power through parallel DAB modules. Furthermore, the intrinsic power constraints of the cascaded H-Bridge voltage balance control are derived and analyzed. With the proposed control methods, the dc-link voltage and the real power through each module can be balanced. The SST switching model simulation and the prototype experiments are presented to verify the performance of the proposed voltage and power balance controller. DA - 2013/4// PY - 2013/4// DO - 10.1109/tpel.2012.2216549 VL - 28 IS - 4 SP - 1523-1532 SN - 1941-0107 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84878813627&partnerID=MN8TOARS KW - Cascaded H-Bridge converter KW - dq vector control KW - solid-state transformer (SST) KW - voltage and power balance ER - TY - JOUR TI - Vector-Controlled Voltage-Source-Converter-Based Transmission Under Grid Disturbances AU - Parkhideh, Babak AU - Bhattacharya, Subhashish T2 - IEEE TRANSACTIONS ON POWER ELECTRONICS AB - Voltage-source converter (VSC)-based transmission systems have attractive potential features in terms of power flow control and stability of the network. Although relatively low switching frequency operation of high-power converters (9-15 times the line frequency) is desirable, it makes them sensitive to power network imbalances when they may be needed the most. This paper specifically proposes a control structure to improve the performance of high-power vector-controlled back-to-back VSC systems for conventional and emerging utility applications. The main improvement is to suppress the possible dc-link voltage fluctuations under power line faults and unbalanced conditions. The proposed controller structure is designed based on regulating the converter system's states locally in dq synchronous reference frame without sequence components extraction or resonant notch compensator. RTDS results verify the validity of the proposed control architecture during normal and unbalanced power system conditions. DA - 2013/2// PY - 2013/2// DO - 10.1109/tpel.2012.2204071 VL - 28 IS - 2 SP - 661-672 SN - 1941-0107 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84867080235&partnerID=MN8TOARS KW - High-voltage direct current (HVDC) KW - Lyapunov methods KW - power systems faults KW - pulsewidth modulation (PWM) voltage-source converter (VSC) KW - recovery transformer KW - RTDS KW - vector-controlled VSC KW - wind power ER - TY - JOUR TI - Shallow acceptor complexes in p-type ZnO AU - Reynolds, J. G. AU - Reynolds, C. L., Jr. AU - Mohanta, A. AU - Muth, J. F. AU - Rowe, J. E. AU - Everitt, H. O. AU - Aspnes, D. E. T2 - APPLIED PHYSICS LETTERS AB - We show that N-doped ZnO films grown on sapphire can exhibit significant (∼1018 cm−3) room-temperature p-type behavior when sufficient nitrogen (N) is incorporated and the material is annealed appropriately. Substitutional N on the oxygen (O) sublattice is a deep acceptor; however, shallow acceptor complexes involve N, H, and zinc vacancies (VZn). Combining secondary ion mass spectrometry, Raman-scattering, photoluminescence, and Hall-effect data, we establish the evolution of N from its initial incorporation on a Zn site to a final shallow acceptor complex VZn_NO_H+ with an ionization energy of ca. 130 meV. This complex is responsible for the observed p-type behavior. DA - 2013/4/15/ PY - 2013/4/15/ DO - 10.1063/1.4802753 VL - 102 IS - 15 SP - SN - 1077-3118 ER - TY - JOUR TI - Scheduling Partition for Order Optimal Capacity in Large-Scale Wireless Networks AU - Xu, Yi AU - Wang, Wenye T2 - IEEE TRANSACTIONS ON MOBILE COMPUTING AB - The capacity scaling property specifies the change of network throughput when network size increases. It serves as an essential performance metric in large-scale wireless networks. Existing results have been obtained based on the assumption of using a globally planned link transmission schedule in the network, which is however not feasible in large wireless networks due to the scheduling complexity. The gap between the well-known capacity results and the infeasible assumption on link scheduling potentially undermines our understanding of the achievable network capacity. In this paper, we propose the scheduling partition methodology that decomposes a large network into small autonomous scheduling zones and implements a localized scheduling algorithm independently in each partition. We prove the sufficient and the necessary conditions for the scheduling partition approach to achieve the same order of capacity as the widely assumed global scheduling strategy. In comparison to the network dimension $(\sqrt{n})$, scheduling partition size $(\Theta (r(n)))$ is sufficient to obtain the optimal capacity scaling, where $(r(n))$ is the node transmission radius and much smaller than $(\sqrt{n})$. We finally propose a distributed partition protocol and a localized scheduling algorithm as our scheduling solution for maximum capacity in large wireless networks. DA - 2013/4// PY - 2013/4// DO - 10.1109/tmc.2012.113 VL - 12 IS - 4 SP - 666-679 SN - 1536-1233 KW - Wireless multihop networks KW - capacity scaling KW - link scheduling KW - network decomposition KW - network design ER - TY - JOUR TI - Realization of pure frequency modulation of DFB laser via combined optical and electrical tuning AU - Tian, C. AU - Chen, I. C. A. AU - Park, S. W. AU - Martini, R. T2 - Optics Express DA - 2013/// PY - 2013/// VL - 21 IS - 7 SP - 8401-8408 ER - TY - JOUR TI - Observation of terahertz absorption signatures in microliter DNA solutions AU - Zhang, W. AU - Brown, E. R. AU - Rahman, M. AU - Norton, M. L. T2 - Applied Physics Letters DA - 2013/// PY - 2013/// VL - 102 IS - 2 ER - TY - JOUR TI - Feasibility of a MEMS Sensor for Gas Detection in HV Oil-Insulated Transformer AU - Bhat, Krishna Prasad AU - Oh, Kwang W. AU - Hopkins, Douglas C. T2 - IEEE Transactions on Industry Applications AB - This paper addresses protection of oil-insulated transformers, using a microelectromechanical systems (MEMS) sensor system to augment or replace existing protection techniques. Traditional technologies used for protection and analysis involve pressure and temperature sensing, gas chromatography, and/or a Buchholz relay. The proposed MEMS device is immersed within the insulating fluid, e.g., oil, and primarily consists of multiple microscale turbines centrally shafted to a MEMS generator. The device utilizes relative differences in the velocity, pressure, and flow rate of fluid caused by electric faults. A differential electrical output is produced, which can be coupled to a remote recorder. DA - 2013/1// PY - 2013/1// DO - 10.1109/tia.2012.2229681 VL - 49 IS - 1 SP - 316-321 J2 - IEEE Trans. on Ind. Applicat. OP - SN - 0093-9994 1939-9367 UR - http://dx.doi.org/10.1109/TIA.2012.2229681 DB - Crossref N1 - \urlhttps://ieeexplore.ieee.org/document/6361292/ ; \urlhttps://www.researchgate.net/profile/DC_Hopkins/publication/260706240_Feasibility_of_a_MEMS_Sensor_for_Gas_Detection_in_HV_Oil-Insulated_Transformer/links/54170b2f0cf2218008bec49d.pdf RN - \urlhttps://ieeexplore.ieee.org/document/6361292/ ; \urlhttps://www.researchgate.net/profile/DC_Hopkins/publication/260706240_Feasibility_of_a_MEMS_Sensor_for_Gas_Detection_in_HV_Oil-Insulated_Transformer/links/54170b2f0cf2218008bec49d.pdf KW - Fault diagnosis KW - fluid flow measurement KW - fluidic microsystems KW - gas detectors KW - microelectromechanical systems (MEMS) KW - oil insulation KW - power transformers ER - TY - JOUR TI - Cyber security in the Smart Grid: Survey and challenges AU - Wang, Wenye AU - Lu, Zhuo T2 - COMPUTER NETWORKS AB - The Smart Grid, generally referred to as the next-generation power system, is considered as a revolutionary and evolutionary regime of existing power grids. More importantly, with the integration of advanced computing and communication technologies, the Smart Grid is expected to greatly enhance efficiency and reliability of future power systems with renewable energy resources, as well as distributed intelligence and demand response. Along with the silent features of the Smart Grid, cyber security emerges to be a critical issue because millions of electronic devices are inter-connected via communication networks throughout critical power facilities, which has an immediate impact on reliability of such a widespread infrastructure. In this paper, we present a comprehensive survey of cyber security issues for the Smart Grid. Specifically, we focus on reviewing and discussing security requirements, network vulnerabilities, attack countermeasures, secure communication protocols and architectures in the Smart Grid. We aim to provide a deep understanding of security vulnerabilities and solutions in the Smart Grid and shed light on future research directions for Smart Grid security. DA - 2013/4/7/ PY - 2013/4/7/ DO - 10.1016/j.comnet.2012.12.017 VL - 57 IS - 5 SP - 1344-1371 SN - 1872-7069 KW - Smart Grid KW - Cyber security KW - Attacks and countermeasures KW - Cryptography KW - Security protocols ER - TY - JOUR TI - Carrier Transport and Improved Collection in Thin-Barrier InGaAs/GaAsP Strained Quantum Well Solar Cells AU - Bradshaw, Geoffrey K. AU - Carlin, C. Zachary AU - Samberg, Joshua P. AU - El-Masry, Nadia A. AU - Colter, Peter C. AU - Bedair, Salah M. T2 - IEEE JOURNAL OF PHOTOVOLTAICS AB - Multiple quantum wells (MQW) lattice matched to GaAs consisting of In 0.14 Ga 0.76 As wells balanced with GaAs 0.24 P 0.76 barriers have been used to extend the absorption of GaAs subcells to longer wavelengths for use in an InGaP/GaAs/Ge triple-junction photovoltaic cell. Thin barriers with high-phosphorus composition are capable of balancing the strain from the InGaAs wells; thus, creating conditions to allow for thicker wells and for carrier tunneling to dominate transport across the structure. As a result, a larger percentage of the depletion region is occupied by InGaAs quantum wells that absorb wavelengths beyond 875 nm and the indium composition is not limited by thermionic emission requirements. Measurements at elevated temperatures and reverse bias suggest that a thermally assisted tunneling mechanism is responsible for transport through the barriers. DA - 2013/1// PY - 2013/1// DO - 10.1109/jphotov.2012.2216858 VL - 3 IS - 1 SP - 278-283 SN - 2156-3381 KW - III-V multijunction solar cells KW - multiple quantum wells KW - thermionic emission KW - tunneling ER - TY - JOUR TI - Behavioural modelling of amplifier asymmetry in the time domain AU - Jang, W. AU - Kriplani, N. M. AU - Steer, M. B. T2 - INTERNATIONAL JOURNAL OF NUMERICAL MODELLING-ELECTRONIC NETWORKS DEVICES AND FIELDS AB - SUMMARY Power amplifier asymmetry is captured by a behavioural model that contains multiple slices representing the amplifier's nonlinearity and long‐term, that is low frequency, memory. The simulation is performed entirely in the time domain, and the expense associated with performing a purely transient radio frequency (RF) simulation is circumvented by scaling down the carrier frequency by two orders of magnitude. This leads to a manageable transient simulation with results scaling back to the original carrier frequency. The model is empirical and can be easily implemented in any general purpose circuit simulation environment. The baseband portion of the model parameters was extracted and the simulation result was compared with measurement, thereby demonstrating that a nonlinear and accurate transient analysis routine can be effectively employed to capture memory‐related RF power amplifier phenomena. Copyright © 2012 John Wiley & Sons, Ltd. DA - 2013/// PY - 2013/// DO - 10.1002/jnm.1842 VL - 26 IS - 2 SP - 112-126 SN - 1099-1204 KW - power amplifier KW - behavioural modelling KW - memory effects KW - transient simulation ER - TY - JOUR TI - Analysis and Comparison of Medium Voltage High Power DC/DC Converters for Offshore Wind Energy Systems AU - Chen, Wu AU - Huang, Alex Q. AU - Li, Chushan AU - Wang, Gangyao AU - Gu, Wei T2 - IEEE TRANSACTIONS ON POWER ELECTRONICS AB - Offshore wind farm with an internal medium-voltage dc (MVDC)-grid collection connected HVDC transmission may be an option to harvest offshore wind energy. High-power MV dc/dc converters with high-step-up conversion ratios are the key components for the internal MVDC grid. In this paper, a high-efficiency step-up resonant switched-capacitor converter for offshore wind energy system is studied, which is characterized by the soft-switching condition for all switches and diodes. This significantly reduces switching losses and higher switching frequency is feasible to reduce the overall system volume and weight. The comparisons with other two kinds of topologies are also presented; moreover, the possible specification requirements of high power MV dc/dc converters are analyzed and set. The operation principle of the proposed converter has been successfully verified by simulation and experiment results. DA - 2013/4// PY - 2013/4// DO - 10.1109/tpel.2012.2215054 VL - 28 IS - 4 SP - 2014-2023 SN - 1941-0107 KW - High power KW - medium-voltage dc (MVDC) converter KW - MVDC grid KW - offshore wind farm ER - TY - JOUR TI - A Generalized Markov Graph Model: Application to Social Network Analysis AU - Wang, Tian AU - Krim, Hamid AU - Viniotis, Yannis T2 - IEEE JOURNAL OF SELECTED TOPICS IN SIGNAL PROCESSING AB - In this paper we propose a generalized Markov Graph model for social networks and evaluate its application in social network synthesis, and in social network classification. The model reveals that the degree distribution, the clustering coefficient distribution as well as a newly discovered feature, a crowding coefficient distribution, are fundamental to characterizing a social network. The application of this model to social network synthesis leads to a capacity to generate networks dominated by the degree distribution and the clustering coefficient distribution. Another application is a new social network classification method based on comparing the statistics of their degree distributions and clustering coefficient distributions as well as their crowding coefficient distributions. In contrast to the widely held belief that a social network graph is solely defined by its degree distribution, the novelty of this paper consists in establishing the strong dependence of social networks on the degree distribution, the clustering coefficient distribution and the crowding coefficient distribution, and in demonstrating that they form minimal information to classify social networks as well as to design a new social network synthesis tool. We provide numerous experiments with published data and demonstrate very good performance on both counts. DA - 2013/4// PY - 2013/4// DO - 10.1109/jstsp.2013.2246767 VL - 7 IS - 2 SP - 318-332 SN - 1941-0484 KW - Complex networks KW - pattern recognition KW - classification KW - Markov graph model ER - TY - JOUR TI - Modeling and Optimizing the Performance-Security Tradeoff on D-NCS Using the Coevolutionary Paradigm AU - Zeng, Wente AU - Chow, Mo-Yuen T2 - IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS AB - Distributed networked control systems (D-NCS) are vulnerable to various network attacks when the network is not secured; thus, D-NCS must be well protected with security mechanisms (e.g., cryptography), which may adversely affect the dynamic performance of the D-NCS because of limited system resources. This paper addresses the tradeoff between D-NCS security and its real-time performance and uses the Intelligent Space (iSpace) for illustration. A tradeoff model for a system's dynamic performance and its security is presented. This model can be used to allocate system resources to provide sufficient protection and to satisfy the D-NCS's real-time dynamic performance requirements simultaneously. Then, the paper proposes a paradigm of the performance-security tradeoff optimization based on the coevolutionary genetic algorithm (CGA) for D-NCS. A Simulink-based test-bed is implemented to illustrate the effectiveness of this paradigm. The results of the simulation show that the CGA can efficiently find the optimal values in a performance-security tradeoff model for D-NCS. DA - 2013/2// PY - 2013/2// DO - 10.1109/tii.2012.2209662 VL - 9 IS - 1 SP - 394-402 SN - 1941-0050 KW - Coevolutionary genetic algorithm (CGA) KW - distributed networked control systems (D-NCS) KW - iSpace ER -