TY - JOUR TI - Silicon impurity-induced layer disordering of AlGaN/AlN superlattices AU - Wierer, J. J., Jr. AU - Allerman, A. A. AU - Li, Q. T2 - Applied Physics Letters AB - Impurity-induced layer disordering is demonstrated in Al0.1Ga0.9N/AlN superlattices grown by metal-organic vapor phase epitaxy. During growth at temperatures as low as 885 °C and under post growth annealing at 1000 °C in N2 the heterointerfaces of Si-doped (Si concentration &gt;8×1019 cm−3) superlattices exhibit layer disordering (intermixing) while the unintentionally doped superlattices remain stable. Shifts in the intersubband energy transitions and scanning transmission electron microscope images showing changes in the layer abruptness are used to verify layer disordering due to Si diffusion in Al0.1Ga0.9N/AlN superlattices. DA - 2010/// PY - 2010/// DO - 10.1063/1.3478002 VL - 97 IS - 5 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000281059500023&KeyUID=WOS:000281059500023 ER - TY - JOUR TI - The impact of piezoelectric polarization and nonradiative recombination on the performance of (0001) face GaN/InGaN photovoltaic devices AU - Wierer, J. J., Jr. AU - Fischer, A. J. AU - Koleske, D. D. T2 - Applied Physics Letters AB - The impact of piezoelectric polarization and nonradiative recombination on the short-circuit current densities (Jsc) of (0001) face GaN/InGaN photovoltaic devices is demonstrated. P-i-n diodes consisting of 170 nm thick intrinsic In0.09Ga0.91N layers sandwiched by GaN layers exhibit low Jsc∼40 μA/cm2. The piezoelectric polarization at the GaN/InGaN heterointerfaces creates drift currents opposite in direction needed for efficient carrier collection. Also, nonradiative recombination centers produce short carrier lifetimes, limiting Jsc. Alternative structures with intrinsic InGaN layers sandwiched by n-type InGaN or graded InyGa1−yN (y=0–0.09) layer and a p-type In0.015Ga0.985N layer have favorable potentials, longer carrier lifetimes, and improve Jsc to ∼0.40 mA/cm2. DA - 2010/// PY - 2010/// DO - 10.1063/1.3301262 VL - 96 IS - 5 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000274319500007&KeyUID=WOS:000274319500007 ER - TY - CHAP TI - Taste disorders AU - Schiffman, S.S. T2 - Encyclopedia of Perception A2 - Goldstein, E.B. PY - 2010/// PB - Sage Publications ER - TY - CONF TI - Power Electronics in a Smart-Grid Distribution System AU - Hopkins, Douglas C. T2 - 25th Annual IEEE Conference on Applied Power Electronics Conference and Exposition (APEC) C2 - 2010/2/21/ C3 - 25th Annual IEEE Conference on Applied Power Electronics Conference and Exposition (APEC) CY - Palm Springs, CA DA - 2010/2/21/ PY - 2010/2/21/ ER - TY - JOUR TI - An Improved Zero-Voltage Switching Inverter Using Two Coupled Magnetics in One Resonant Pole AU - Yu, Wensong AU - Lai, Jih-Sheng AU - Park, Sung-Yeul T2 - IEEE Transactions on Power Electronics AB - A novel soft-switching inverter using two small coupled magnetics in one resonant pole is proposed to ensure the main switches operating at zero-voltage switching from zero load to full load and the auxiliary switches at zero-current switching with load adaptability and small current stress. Since independent coupled magnetics structure avoids the unwanted magnetizing current freewheeling loop, the size of the coupled magnetics can be minimized with low magnetizing inductance, and the saturable inductor can be eliminated. Detailed circuit operation is described, and voltage-second balance condition of the magnetics is expressed mathematically. A 4-kW hardware prototype has been designed, fabricated, and tested to verify the validity of the novel circuit and the improved performance of the proposed soft-switching inverter. Experimental results show an excellent agreement with analytical results. Since the measured efficiency from 20% to 100% load consistently shows above 97.8% and peaks at 98.2%, the proposed inverter is very attractive for high-efficiency applications where energy saving is a major concern. DA - 2010/4// PY - 2010/4// DO - 10.1109/tpel.2009.2030197 VL - 25 IS - 4 SP - 952-961 J2 - IEEE Trans. Power Electron. OP - SN - 0885-8993 1941-0107 UR - http://dx.doi.org/10.1109/tpel.2009.2030197 DB - Crossref ER - TY - CONF TI - On the Design of a KANSEI Robot Testbed for Understanding Human Machine Interaction AU - Livingston, F. AU - Grant, E. AU - Lee, G. T2 - International Conference on KANSEI Engineering and Emotion Research C2 - 2010/// C3 - International Conference on KANSEI Engineering and Emotion Research CY - Paris, France DA - 2010/// PY - 2010/// ER - TY - CONF TI - A methodology for remote virtual interaction in teleimmersive environments AU - Vasudevan, Ram AU - Lobaton, Edgar AU - Kurillo, Gregorij AU - Bajcsy, Ruzena AU - Bernardin, Tony AU - Hamann, Bernd AU - Nahrstedt, Klara AB - Though the quality of imaging devices, the accuracy of algorithms that construct 3D data, and the hardware available to render such data have all improved, the algorithms available to calibrate, reconstruct, and then visualize such data are difficult to use, extremely noise sensitive, and unreasonably slow. In this paper, we describe a multi-camera system that creates a highly accurate (on the order of a centimeter), 3D reconstruction of an environment in real time (under 30 ms) that allows for remote interaction between users. The paper addresses the aforementioned deficiencies by featuring an overview of the technology and algorithms used to calibrate, reconstruct, and render objects in the system. The algorithm produces partial 3D meshes, instead of dense point clouds, which are combined on the renderer to create a unified model of the environment. The chosen representation of the data allows for high compression ratios for transfer to remote sites. We demonstrate the accuracy and speed of our results on a variety of benchmarks and data collected from our own system. C2 - 2010/2/22/ C3 - Proceedings of the first annual ACM SIGMM conference on Multimedia systems DA - 2010/2/22/ DO - 10.1145/1730836.1730871 PB - ACM UR - http://dx.doi.org/10.1145/1730836.1730871 ER - TY - CONF TI - Real-time stereo-vision system for 3D teleimmersive collaboration AU - Vasudevan, Ram AU - Zhou, Zhong AU - Kurillo, Gregorij AU - Lobaton, Edgar AU - Bajcsy, Ruzena AU - Nahrstedt, Klara AB - Though the variety of desktop real time stereo vision systems has grown considerably in the past several years, few make any verifiable claims about the accuracy of the algorithms used to construct 3D data or describe how the data generated by such systems, which is large in size, can be effectively distributed. In this paper, we describe a system that creates an accurate (on the order of a centimeter), 3D reconstruction of an environment in real time (under 30 ms) that also allows for remote interaction between users. This paper addresses how to reconstruct, compress, and visualize the 3D environment. In contrast to most commercial desktop real time stereo vision systems our algorithm produces 3D meshes instead of dense point clouds, which we show allows for better quality visualizations. The chosen representation of the data also allows for high compression ratios for transfer to remote sites. We demonstrate the accuracy and speed of our results on a variety of benchmarks. C2 - 2010/7// C3 - 2010 IEEE International Conference on Multimedia and Expo DA - 2010/7// DO - 10.1109/icme.2010.5582538 PB - IEEE UR - http://dx.doi.org/10.1109/icme.2010.5582538 KW - 3D video KW - compression KW - real time KW - teleimmersion ER - TY - JOUR TI - A Distributed Topological Camera Network Representation for Tracking Applications AU - Lobaton, Edgar AU - Vasudevan, Ramanarayan AU - Bajcsy, Ruzena AU - Sastry, Shankar T2 - IEEE Transactions on Image Processing AB - Sensor networks have been widely used for surveillance, monitoring, and tracking. Camera networks, in particular, provide a large amount of information that has traditionally been processed in a centralized manner employing a priori knowledge of camera location and of the physical layout of the environment. Unfortunately, these conventional requirements are far too demanding for ad-hoc distributed networks. In this article, we present a simplicial representation of a camera network called the camera network complex (CN-complex), that accurately captures topological information about the visual coverage of the network. This representation provides a coordinate-free calibration of the sensor network and demands no localization of the cameras or objects in the environment. A distributed, robust algorithm, validated via two experimental setups, is presented for the construction of the representation using only binary detection information. We demonstrate the utility of this representation in capturing holes in the coverage, performing tracking of agents, and identifying homotopic paths. DA - 2010/10// PY - 2010/10// DO - 10.1109/tip.2010.2052273 VL - 19 IS - 10 SP - 2516-2529 UR - http://dx.doi.org/10.1109/tip.2010.2052273 KW - Multitarget tracking KW - network coverage KW - sensor networks KW - simplicial homology KW - smart camera networks ER - TY - CONF TI - Comparison of Learning on the Design of a KANSEI Robot Testbed for Understanding Human-Machine Interaction AU - Livingston, Fred AU - Grant, Edward AU - Lee, Gordon C2 - 2010/// C3 - International Conference on KANSEI Engineering and Emotion Research DA - 2010/// ER - TY - CONF TI - Creating 3D Specific Systems: Architecture, Design and CAD AU - Franzon, P. AU - Davis, W.R. AU - Thorolfsson, T. AU - Melamed, S.L. T2 - Intlernational Microelectronics and Packaging Society (iMAPS) Symposium AB - 3D stacking and integration can provide significant system advantages. Following a brief technology review, this abstract explores application drivers, design and CAD for 3D ICs. The main 3D exploitation explored in detail is that of logic on memory. This application is explored in a specific DSP example, showing a 25% power advantage when implemented in 3D compared with 2D. Finally critical areas that need better solutions are explored. These include cost management, design planning, test management, and thermal management. C2 - 2010/11/2/ C3 - International Symposium on Microelectronics CY - Raleigh, NC DA - 2010/11/2/ PY - 2010/// DO - 10.4071/isom-2010-TA1-Paper4 VL - 2010 SP - 23-27 M1 - 1 ER - TY - CONF TI - Algorithm and hardware complexity reduction techniques for k-best sphere decoders AU - Moezzi-Madani, N. AU - Thorolfsson, T. AU - Davis, W.R. T2 - Great Lakes Symposium on VLSI (GLSVLSI AB - MIMO (Multi-Input Multi-Output) technology is garnering more interest in new wireless communication standards. In this work, we introduce three techniques to reduce the power consumption of MIMO detectors and increase their data rate. We decrease the complexity of the K-best sphere decoder effectively by using the MMSE-SQRD channel processing technique. This technique results in a smaller K which results in a great reduction in power consumption compared to the K-best detectors using ZF-SQRD with the same BER/throughput performance. We also propose a child reduction technique that reduces the number of multiplications and additions which results in 8% power reduction. Also, we utilized the odd-even merge algorithm for the merge unit which is on the critical path of the circuit, to achieve the best power/throughput tradeoff. We implemented a 4*4 16QAM detector in a commercial 0.18µm CMOS process; synthesis results show that the detector works at the maximum data rate of 768Mbps with the area of 91KGates. C2 - 2010/5// C3 - GLSVLSI '10: Proceedings of the 20th symposium on Great lakes symposium on VLSI DA - 2010/5// PY - 2010/// DO - 10.1145/1785481.1785589 SP - 471-476 ER - TY - CONF TI - A Low-Area Flexible MIMO Detector for WiFi/WiMAX Standards AU - Moezzi-Madani, N. AU - Thorolfsson, T. AU - Davis, W.R. T2 - 2010 Design, Automation & Test in Europe Conference & Exhibition (DATE 2010) AB - MIMO wireless technology is required to increase the data rates for a broad range of applications, including low cost mobile devices. In this paper we present a very low area reconfigurable MIMO detector which achieves a high throughput of 103Mbps and uses 27 Kilo Gates when implemented in a commercial 180nm CMOS process. The low area is achieved by the proposed in-place architecture. This architecture implements the K-best algorithm and reduces area 4-fold compared to the widely used multi-stage architecture, while provides reconfigurability in terms of antenna configuration during real-time operation. C2 - 2010/// C3 - 2010 Design, Automation & Test in Europe Conference & Exhibition (DATE 2010) CY - Dresden, Germany DA - 2010/// PY - 2010/3/8/ DO - 10.1109/DATE.2010.5457073 ER - TY - JOUR TI - Low Power Hypercube Divided Memory FFT Engine Using 3D Integration AU - Thorolfsson, T. AU - Melamed, S. AU - Davis, W.R. AU - Franzon, P.D. T2 - ACM Transactions on Design Automation of Electronic Systems AB - In this article we demonstrate a floating point FFT processor that leverages both 3D integration and a unique hypercube memory division scheme to reduce the power consumption of a 1024 point FFT down to 4.227 μJ . The hypercube memory division scheme lowers the energy per memory access by 59.2% and increases the total required area by 16.8%. The use of 3D integration reduces the logic power by 5.2%. We describe the tool flow required to realize the 3D implementation and perform a thermal analysis of it. DA - 2010/11// PY - 2010/11// DO - 10.1145/1870109.1870114 VL - 16 IS - 1 SP - 1-25 KW - Design KW - 3DIC KW - scaling KW - TSV KW - FFT ER - TY - CONF TI - Thermal Adaptive Clock Design for 3D Integrated Circuits AU - Chen, X. AU - Davis, W.R. T2 - Semiconductor Research Corporation (SRC) TECHCON C2 - 2010/9/13/ DA - 2010/9/13/ PY - 2010/9/13/ ER - TY - CONF TI - Modeling Layout-Dependent Stress Effects: Opportunities for OpenDFM AU - Davis, W.R. T2 - Design Automation Conference (DAC) Open Design-for-Manufacturability (OpenDFM) Workshop C2 - 2010/6/13/ DA - 2010/6/13/ PY - 2010/6/13/ ER - TY - CONF TI - Investigation of tier-swapping to improve the thermal profile of memory-on-logic 3DICs AU - Melamed, S. AU - Thorolfsson, T. AU - Srinivasan, A. AU - Cheng, E. AU - Franzon, P. AU - Davis, W.R. T2 - International Workshop on Thermal Investigations of ICs and Systems (THERMINIC) C2 - 2010/10// DA - 2010/10// PY - 2010/10/6/ ER - TY - JOUR TI - Investigating Control of Vision Based Autonomous Navigation in the Image Plane AU - Gupta, Rachana Ashok AU - Snyder, Wesley AU - Pitts, W Shepherd T2 - SAE International Journal of Commercial Vehicles DA - 2010/10/5/ PY - 2010/10/5/ DO - 10.4271/2010-01-2005 VL - 3 IS - 1 SP - 250-258 UR - http://dx.doi.org/10.4271/2010-01-2005 ER - TY - JOUR TI - Nanostructured conducting polymer based reagentless capacitive immunosensor AU - Bandodkar, A.J. AU - Dhand, C. AU - Arya, S.K. AU - Pandey, M.K. AU - Malhotra, B.D. T2 - Biomedical Microdevices DA - 2010/// PY - 2010/// DO - 10.1007/s10544-009-9360-2 VL - 12 IS - 1 SP - 63-70 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77950863204&partnerID=MN8TOARS KW - Polyaniline KW - Electrophoretic deposition KW - Parallel plate capacitor KW - Immunosensor ER - TY - CONF TI - Augmenting Bucholz Relay Using Embedded Mems Gas Sensor AU - Bhat, K.P. AU - Hopkins, D.C. T2 - 2010 IEEE PES Transmission and Distribution Conference C2 - 2010/// CY - New Orleans, LA DA - 2010/// PY - 2010/4/19/ ER - TY - CONF TI - Solid-State Protection: Dual-use for Microgrids AU - Hopkins, D.C. T2 - Advanced Energy Conference C2 - 2010/// CY - New York, NY DA - 2010/// PY - 2010/11/8/ ER - TY - CONF TI - Development and Testing of a 350 ̊C SiC MCPM with Cast Metal Matrix Composites AU - Hopkins, D.C. AU - Guo, Y.B. AU - Aravamudhan, A. AU - Scofield, J.D. T2 - International Electronics Packaging Symposium C2 - 2010/// CY - Niskayuna, NY DA - 2010/// PY - 2010/9/9/ ER - TY - JOUR TI - Development of a SiC SSPC Module with Advanced High Temperature Packaging AU - Hopkins, Douglas C AU - Guo, Yuan-Bo AU - Dwyer, Herbert E AU - Scofield, James D. T2 - Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) AB - Development of a multi-chip power module (MCPM) is reported that uses advanced metal-matrix composite aluminum packaging to manage high thermally induced stresses in devices that incur 350°C transients. The MCPM uses parallel SiC devices to control 120A DC nominal, 1200A fault in a 270V DC system. Electrical system modeling is presented to characterize electrical fault transients that induce electrical and thermal stresses in the semiconductors and packaging. The characterization of the advanced aluminum-based packaging system, which uses composites, such as AlSiC, and direct bonded aluminum (DBA), is discussed to manage the thermal stresses and transient heat flow. DA - 2010/1/1/ PY - 2010/1/1/ DO - 10.4071/hitec-dhopkins-wp25 VL - 2010 IS - HITEC SP - 000310-000315 LA - en OP - SN - 2380-4491 UR - http://dx.doi.org/10.4071/hitec-dhopkins-wp25 DB - Crossref ER - TY - CONF TI - A MEMS Sensor for Gas Detection in High Voltage Oil Filled Equipment AU - Bhat, Krishna Prasad AU - Oh, Kwang W. AU - Hopkins, Douglas C. T2 - 2010 IEEE Industry Applications Society Annual Meeting AB - This paper addresses protection of oil insulated power equipment, e.g. transformers, using a 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. A MEMS sensor is described to augment or replace such sensors. The proposed device is immersed within the insulating fluid, e.g. oil, and primarily consists of multiple micro scale turbines centrally shafted to a MEMS generator. The device utilizes relative differences in velocity, pressure and flow rate, of gas emanating from stressed or degrading insulation. A differential electrical output is produced which can be RF or photon coupled to a user interface. C2 - 2010/10// C3 - 2010 IEEE Industry Applications Society Annual Meeting DA - 2010/10// DO - 10.1109/ias.2010.5615297 PB - IEEE SN - 9781424463930 UR - http://dx.doi.org/10.1109/ias.2010.5615297 DB - Crossref ER - TY - CONF TI - Mmt: Exploiting fine-grained parallelism in dynamic memory management AU - Tiwari, Devesh AU - Lee, Sanghoon AU - Tuck, James AU - Solihin, Yan T2 - IEEE C2 - 2010/// C3 - 2010 IEEE International Symposium on Parallel & Distributed Processing (IPDPS) DA - 2010/// SP - 1-12 ER - TY - CONF TI - Design Trade-offs for Memory Level Parallelism on an Asymmetric Multicore System AU - Patsilaras, George AU - Choudhary, Niket K AU - Tuck, James C2 - 2010/// C3 - Pespma 2010-Workshop on Parallel Execution of Sequential Programs on Multi-core Architecture DA - 2010/// ER - TY - JOUR TI - Special Issue on Artificial Immune Systems: Theory and Applications AU - Gao, Xiao-Zhi AU - Chow, Mo-Yuen AU - Pelta, David AU - Timmis, Jon T2 - Neural Computing and Applications AB - Natural immune systems are sophisticated and complex defense and maintenance systems with remarkable capabilities, such as learning, memory, and adaptation. The immune system can be viewed in two parts: the innate immune system and the adaptive immune system. The innate immune system is inherited from birth, and endows on the host non-specific recognition of pathogenic material. The adaptive (or acquired) immune system is afforded by the specific recognition of pathogenic material, and adapts over the lifetime of the host through a process of cloning, mutation, and selection. During the past decade, numerous novel computational models and algorithms have been developed based on such immunological principles. Artificial Immune Systems (AIS), inspired by the natural immune systems, are an emerging kind of soft computing paradigm. Applied to a wide variety of applications, the AIS have recently gained considerable research interest from different communities. Their successful industry applications include robotics, optimization, fault tolerance, process control, etc. This special issue focuses on presenting the latest work in the theory and applications of artificial immune systems. The topics of interest for this special issue include, but are not limited to: Immunological modeling Population and network based immune algorithms Architectures and frameworks inspired by immune systems Novel developments in AIS, such as danger theory and cognitive immune paradigm Applications of AIS (including industrial employment of artificial immune algorithms) Hardware implementation of AIS Immunoinformatics Fusion of artificial immune systems and other soft computing methods Theoretical analysis of AIS Prospective authors are invited to submit their full papers to the guest editors before the deadline. DA - 2010/6// PY - 2010/6// DO - 10.1007/s00521-007-0136-4 VL - 19 IS - 4 SP - 647-647 SN - 0941-0643 1433-3058 UR - http://dx.doi.org/10.1007/s00521-007-0136-4 ER - TY - CONF TI - Accelerating MATLAB Image Processing Toolbox Functions on GPUs AU - Kong, J. AU - Dimitrov, M. AU - Yang, Y. AU - Liyanage, J. AU - Cao, L. AU - Staples, J. AU - Mantor, M. AU - Zhou, H. T2 - 3rd Workshop on General-Purpose Computation on Graphics Processing Units AB - In this paper, we present our effort in developing an open-source GPU (graphics processing units) code library for the MATLAB Image Processing Toolbox (IPT). We ported a dozen of representative functions from IPT and based on their inherent characteristics, we grouped these functions into four categories: data independent, data sharing, algorithm dependent and data dependent. For each category, we present a detailed case study, which reveals interesting insights on how to efficiently optimize the code for GPUs and highlight performance-critical hardware features, some of which have not been well explored in existing literature. Our results show drastic speedups for the functions in the data-independent or data-sharing category by leveraging hardware support judiciously; and moderate speedups for those in the algorithm-dependent category by careful algorithm selection and parallelization. For the functions in the last category, fine-grain synchronization and data-dependency requirements are the main obstacles to an efficient implementation on GPUs. C2 - 2010/3// C3 - Proceedings of the 3rd Workshop on General-Purpose Computation on Graphics Processing Units CY - Pittsburgh, Pennsylvania, USA DA - 2010/3// PY - 2010/3// DO - 10.1145/1735688.1735703 SP - 75-85 PB - Association for Computing Machinery SN - 9781605589350 ER - TY - JOUR TI - Ultra-low leakage and high breakdown Schottky diodes fabricated on free-standing GaN substrate AU - Wang, Yaqi AU - Alur, Siddharth AU - Sharma, Yogesh AU - Tong, Fei AU - Thapa, Resham AU - Gartland, Patrick AU - Issacs-Smith, Tamara AU - Ahyi, Claude AU - Williams, John AU - Park, Minseo AU - Johnson, Mark AU - Paskova, Tanya AU - Preble, Edward A AU - Evans, Keith R T2 - Semiconductor Science and Technology AB - Vertical Schottky diodes were fabricated on the bulk GaN substrate with decreasing impurity concentration from N-face to Ga-face. An array of circular Pt Schottky contacts and a full backside Ti/Al/Ni/Au ohmic contact were prepared on the Ga-face and the N-face of the n-GaN substrate, respectively. The Schottky diode exhibits a minimum specific on-state resistance of 1.3 mΩ cm2 and a maximum breakdown voltage of 600 V, resulting in a figure-of- merit of 275 MW cm−2. An ultra-low reverse leakage current density of 3.7 × 10−4 A cm−2 at reverse bias of 400 V was observed. Temperature-dependent I–V measurements were also carried out to study the forward and reverse transportation mechanisms. DA - 2010/12/24/ PY - 2010/12/24/ DO - 10.1088/0268-1242/26/2/022002 VL - 26 IS - 2 SP - 022002 J2 - Semicond. Sci. Technol. OP - SN - 0268-1242 1361-6641 UR - http://dx.doi.org/10.1088/0268-1242/26/2/022002 DB - Crossref ER - TY - THES TI - Adaptive integer kernels and dyadic approximation error analysis for state-of-the-art video codecs AU - Wong, Chau-Wai DA - 2010/// PY - 2010/// PB - The Hong Kong Polytechnic University ER - TY - CONF TI - Wideband spectral estimation from compressed measurements exploiting spectral a priori information in cognitive radio systems AB - In Cognitive Radio scenarios channelization information from primary network may be available to the spectral monitor. Under this assumption we propose a spectral estimation algorithm from compressed measurements of a multichannel wideband signal. The analysis of the Cramer-Rao Lower Bound (CRLB) for this estimation problem shows the importance of detecting the underlaying sparsity pattern of the signal. To this end we describe a Bayesian based iterative algorithm that discovers the set of active signals conforming the band and simultaneously reconstructs the spectrum. This iterative spectral estimator is shown to perform close to a Genie-Aided CRLB that includes full knowledge about the sparsity pattern of the channels. C2 - 2010/// C3 - ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings DA - 2010/// DO - 10.1109/ICASSP.2010.5496152 SP - 2958-2961 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78049400013&partnerID=MN8TOARS KW - Spectral estimation KW - compressive sampling KW - cognitive radio ER - TY - CONF TI - Amorphous InGaZnO logic gates for transparent electronics AU - Luo, H. AU - Wellenius, P. AU - Lunardi, L. AU - Muth, J.F. AB - In this paper we present, transparent logic showing good performance from inverters, NAND and NOR gates, all deposited at room temperature. The significance of these results is that construction of these basic digital logic building blocks with high gain and fast response demonstrate the viability for amorphous oxide digital logic to be utilized in transparent, and flexible electronic systems. C2 - 2010/// C3 - Device Research Conference - Conference Digest, DRC DA - 2010/// DO - 10.1109/DRC.2010.5551866 SP - 121-122 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77957605970&partnerID=MN8TOARS ER - TY - JOUR TI - Unequal power allocation for JPEG transmission over MIMO systems T2 - IEEE Transactions on Image Processing AB - With the introduction of multiple transmit and receive antennas in next generation wireless systems, real-time image and video communication are expected to become quite common, since very high data rates will become available along with improved data reliability. New joint transmission and coding schemes that explore advantages of multiple antenna systems matched with source statistics are expected to be developed. Based on this idea, we present an unequal power allocation scheme for transmission of JPEG compressed images over multiple-input multiple-output systems employing spatial multiplexing. The JPEG-compressed image is divided into different quality layers, and different layers are transmitted simultaneously from different transmit antennas using unequal transmit power, with a constraint on the total transmit power during any symbol period. Results show that our unequal power allocation scheme provides significant image quality improvement as compared to different equal power allocations schemes, with the peak-signal-to-noise-ratio gain as high as 14 dB at low signal-to-noise-ratios. DA - 2010/// PY - 2010/// DO - 10.1109/TIP.2009.2032346 VL - 19 IS - 2 SP - 410-421 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-76849110426&partnerID=MN8TOARS KW - Distortion model KW - joint source-channel coding KW - JPEG KW - multiple-input multiple-output systems KW - unequal error protection KW - unequal power allocation ER - TY - JOUR TI - Opportunistic scheduling in multiuser OFDM systems with clustered feedback T2 - Wireless Personal Communications DA - 2010/// PY - 2010/// DO - 10.1007/s11277-008-9502-5 VL - 52 IS - 1 SP - 209-225 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-73349120952&partnerID=MN8TOARS KW - OFDMA KW - Scheduling KW - Limited feedback ER - TY - CONF TI - Online adaptive modulation and coding with support vector machines AB - Optimizing the performance of adaptive modulation and coding (AMC) in practice has proven challenging. Prior research has struggled to find link quality metrics that are suitable for look-up-tables and simultaneously provide an injective mapping to error rate in wireless links that feature selective channels with hardware nonlinearities and non-Gaussian noise effects. This paper proposes a novel online support vector machine algorithm, compatible with accurate multidimensional link quality metrics, that is able to optimize AMC to the unique (potentially dynamic) hardware characteristics of each wireless device in selective channels. IEEE 802.11n simulations show that our proposed algorithm allows each individual wireless device to optimize the operating point in the rate/reliability tradeoff through frame-by-frame error evaluation. These simulations also show that our algorithm displays identical performance to alternative online AMC algorithms while drastically reducing complexity. C2 - 2010/// C3 - 2010 European Wireless Conference, EW 2010 DA - 2010/// DO - 10.1109/EW.2010.5483527 SP - 718-724 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77954440908&partnerID=MN8TOARS ER - TY - CONF TI - Two-way transmission capacity of wireless ad-hoc networks AB - The transmission capacity of an ad-hoc network is the maximum density of active transmitters in a unit area, given an outage constraint at each receiver for a fixed rate of transmission. Most prior work on finding the transmission capacity of ad-hoc networks has focused only on one-way communication where a source communicates with destination and no data is sent from destination to the source. In practice, however, two-way or bidirectional data transmission is required to support control functions like packet acknowledgements and channel feedback. This paper develops the concept of transmission capacity for two-way wireless ad-hoc networks, by incorporating the concept of a two-way outage with different rate requirements in both directions. Upper and lower bounds on the two-way transmission capacity are derived for frequency division duplexing, under the assumption that the channel coefficients are independent on different carrier frequencies. The derived bounds are used to derive the optimal solution for bidirectional bandwidth allocation that maximizes the two-way transmission capacity, which is shown to perform better than allocating bandwidth proportional to the desired rate in both directions. C2 - 2010/// C3 - IEEE International Symposium on Information Theory - Proceedings DA - 2010/// DO - 10.1109/ISIT.2010.5513314 SP - 1688-1692 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77955670406&partnerID=MN8TOARS ER - TY - JOUR TI - The feasibility of interference alignment over measured MIMO-OFDM channels AU - El Ayach, O. AU - Peters, S.W. AU - Heath, R.W. T2 - IEEE Transactions on Vehicular Technology AB - Interference alignment (IA) has been shown to achieve the maximum achievable degrees of freedom in the interference channel. This results in sum rate scaling linearly with the number of users in the high signal-to-noise-ratio (SNR) regime. Linear scaling is achieved by precoding the transmitted signals to align interference subspaces at the receivers given channel knowledge of all transmit-receive pairs, effectively reducing the number of discernible interferers. The theory of IA was derived under assumptions about the richness of scattering in the propagation channel; practical channels do not guarantee such ideal characteristics. This paper presents the first experimental study of IA in measured multiple-input-multiple-output orthogonal frequency-division-multiplexing (MIMO-OFDM) interference channels. Our measurement campaign includes a variety of indoor and outdoor measurement scenarios at The University of Texas at Austin. We show that IA achieves the claimed scaling factors, or degrees of freedom, in several measured channel settings for a three-user two-antenna-per-node setup. In addition to verifying the claimed performance, we characterize the effect of Kronecker spatial correlation on sum rate and present two other correlation measures, which we show to be more tightly related to the achieved sum rate. DA - 2010/// PY - 2010/// DO - 10.1109/TVT.2010.2082005 VL - 59 IS - 9 SP - 4309-4321 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78149417620&partnerID=MN8TOARS KW - Channel measurements KW - interference alignment (IA) KW - multiple-input-multiple-output (MIMO) KW - software-defined radio ER - TY - CONF TI - Sum-rate of mimo two-way relaying with imperfect CSI AB - In this paper we analyze pilot-aided channel estimation for the multiple-input multiple-output amplify-and-forward two-way relay channel. We use a linear minimum mean-square estimator for estimating the composite channel at each communicating terminal and by using the notion of “worst-case noise” we derive lower-bounds for the transmission sum-rate in both directions of the established bi-directional relay link. C2 - 2010/// C3 - ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings DA - 2010/// DO - 10.1109/ICASSP.2010.5495978 SP - 3418-3421 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78049355341&partnerID=MN8TOARS KW - Multiple-input multiple-output (MIMO) KW - channel estimation KW - amplify-and-forward relay ER - TY - CONF TI - Predictive limited feedback for cooperative transmission AB - In multicell cooperation, knowledge of the users' channel state information (CSI) at the base stations can be used to improve sum-rates and reduce outages. Users estimate and feedback CSI of the desired and multiple interfering channels in cooperation-based systems. Existing multicell limited feedback techniques are memoryless quantization approaches, which result in large feedback overhead. In this paper, a novel technique is proposed using predictive vector quantization to reduce feedback requirements associated with multicell systems by exploiting temporal correlation in channels. An approach to further reduce feedback overhead by transmitting back only the normalized vector directions is also presented, using linear prediction. Simulations are used to show that the proposed predictive framework yields higher sum-rates with fewer bits as compared to existing multicell limited feedback strategies. C2 - 2010/// C3 - Conference Record - Asilomar Conference on Signals, Systems and Computers DA - 2010/// DO - 10.1109/ACSSC.2010.5757728 SP - 1237-1241 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-79957992534&partnerID=MN8TOARS ER - TY - JOUR TI - Limited feedback for temporally correlated MIMO channels with other cell interference T2 - IEEE Transactions on Signal Processing AB - Limited feedback improves link reliability with a small amount of feedback from the receiver to the transmitter. In cellular systems, the performance of limited feedback will be degraded in the presence of other cell interference, when the base stations have limited or no coordination. This paper establishes the degradation in sum rate of users in a cellular system, due to uncoordinated other cell interference and feedback delay. A goodput metric is defined as the rate when the bits are successfully received at the mobile station, and used to derive an upper bound on the performance of limited feedback systems with delay. This paper shows that the goodput gained from having delayed limited feedback decreases doubly exponentially as the delay increases. The analysis is extended to precoded spatial multiplexing systems where it is shown that the same upper bound can be used to evaluate the decay in the achievable sum rate. To reduce the effects of interference, zero forcing interference nulling is applied at the receiver, where it is shown that the effect of the interference on the achievable sum rate can be suppressed by nulling out the interferer. Numerical results show that the decay rate of the goodput decreases when the codebook quantization size increases and when the Doppler shift in the channel decreases. DA - 2010/// PY - 2010/// DO - 10.1109/TSP.2010.2055860 VL - 58 IS - 10 SP - 5219-5232 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77956718998&partnerID=MN8TOARS KW - Cellular systems KW - feedback delay KW - goodput KW - imperfect CSI KW - limited feedback precoding KW - multiple-input-multiple-output (MIMO) KW - other-cell interference KW - rate outage KW - temporally correlated channels ER - TY - JOUR TI - Impact of mutual coupling on adaptive switching between MIMO transmission strategies and antenna configurations T2 - Wireless Personal Communications DA - 2010/// PY - 2010/// DO - 10.1007/s11277-008-9513-2 VL - 52 IS - 1 SP - 69-87 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-73349116581&partnerID=MN8TOARS KW - MIMO KW - Adaptive switching KW - Reconfigurable antenna arrays KW - Mutual coupling ER - TY - JOUR TI - Multimode antenna selection for MIMO amplify-and-forward relay systems T2 - IEEE Transactions on Signal Processing AB - Obtaining the most from multiple-antenna relay systems requires algorithms that configure the source and relay adaptively to instantaneous channel conditions. In this paper, we define an antenna selection mode of operation as the number of selected transmit antennas at the source (which is equal to the number of data substreams), the substream-to-antenna mapping at the source, the number of selected transmit antennas at the relay, and the substream-to-antenna mapping at the relay. We develop dualmode and multimode antenna selection algorithms to choose the mode that is most likely to deliver the lowest vector symbol error rate assuming the overall data rate is fixed. The effective condition numbers of both the two-hop channel and the relay channel are derived to give intuition on how the spatial characteristics of the constituent channels affect mode selection and to derive low complexity algorithms. Link-level simulations show that our proposed algorithms usually select the best mode, thus improving the diversity performance of spatial multiplexing relay systems and providing array gains over the existing single-stream relay transmission strategies. The two-hop multimode algorithms are shown by system-level simulations to improve the reliability of transmission and extend spatial multiplexing capability to cell-edge users in a multi-cell network. DA - 2010/// PY - 2010/// DO - 10.1109/TSP.2010.2053364 VL - 58 IS - 11 SP - 5845-5859 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-79953813194&partnerID=MN8TOARS KW - Adaptive antenna selection KW - amplify-and-forward KW - MIMO relay channel KW - multimode antenna selection KW - mutiple-antenna relay KW - multiple-input multiple-output (MIMO) KW - two-hop channel KW - nonregenerative ER - TY - JOUR TI - MIMO two-way amplify-and-forward relaying with imperfect receiver CSI AU - Panah, A.Y. AU - Heath, R.W. T2 - IEEE Transactions on Vehicular Technology AB - In this paper, we investigate the effects of channel estimation error on the receiver of multiple-input-multiple-output (MIMO) amplify-and-forward (AF) two-way relaying. The estimation is conducted via training using known pilot symbols transmitted from the terminals, which is a method commonly referred to as pilot symbol-aided modulation. In this context, linear minimum mean square estimation (LMMSE) of composite and individual channels is analyzed. We show that orthogonal pilots, i.e., pilot sequences that are orthogonal over the antenna arrays and the communicating terminals, minimize the composite and individual mean square errors. Using notions of worst-case noise, we obtain lower bounds on the sum rate of information transmission in both directions of the bidirectional relay link and show that the orthogonal pilots perform well against the bound. DA - 2010/// PY - 2010/// DO - 10.1109/TVT.2010.2070087 VL - 59 IS - 9 SP - 4377-4387 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78149429387&partnerID=MN8TOARS KW - Channel estimation KW - multiple-input-multiple-output (MIMO) communications KW - sum-rate KW - two-way relaying ER - TY - CONF TI - Link adaptation in MIMO-OFDM with non-uniform constellation selection over spatial streams through supervised learning AB - Supervised learning has been used to develop practical link adaptation algorithms for MIMO-OFDM under an equal rate per stream assumption. In this paper we develop supervised learning algorithms that select from non-uniform rates per stream. We show that the straightforward application of existing supervised learning link adaptation algorithms exhibits complexity that scales with the number of spatial streams. Therefore, we propose a decoupled stream link adaptation algorithm which reduces the complexity below the original supervised learning algorithm with uniform spatial streams. We further show that the performance loss of decoupled link adaptation is reduced in systems with non-uniform constellations per spatial stream. IEEE 802.11n and uncoded MIMO-OFDM simulations are used to validate the proposed algorithms. C2 - 2010/// C3 - ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings DA - 2010/// DO - 10.1109/ICASSP.2010.5496020 SP - 3314-3317 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78049354402&partnerID=MN8TOARS KW - MIMO-OFDM KW - link adaptation KW - supervised learning KW - non-uniform spatial streams KW - IEEE 802.11n ER - TY - CONF TI - Multiuser MIMO in distributed antenna systems AB - Distributed antenna systems (DAS) add remote radio units with one or more antennas to enhance coverage and capacity in cellular systems. DAS works by connecting the remote radio units to the base station via a high bandwidth and low latency link. This paper analyzes multiuser multiple input multiple output (MIMO) DAS and compares it with multiuser MIMO communication without DAS in terms of per-user throughput and area spectral efficiency. Zero-forcing transmit beamforming is used at the transmitter. To facilitate rapid simulation and design space exploration, approximations of the ergodic rate are proposed for each technique assuming path-loss, small-scale Rayleigh fading, and out-of-cell interference. Treating all the remote radio units as a super MIMO transmitter gives the best performance even accounting for out-of-cell interference, though gains diminish for higher numbers of active users. C2 - 2010/// C3 - Conference Record - Asilomar Conference on Signals, Systems and Computers DA - 2010/// DO - 10.1109/ACSSC.2010.5757721 SP - 1202-1206 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-79957978588&partnerID=MN8TOARS ER - TY - CONF TI - Maximum sum-rate interference alignment algorithms for MIMO channels AB - Alternating minimization algorithms are typically used to find interference alignment (IA) solutions for multiple-input multiple-output (MIMO) interference channels with more than K=3 users. For these scenarios many IA solutions exit, and the initial point determines which one is obtained upon convergence. In this paper, we propose a new iterative algorithm that aims at finding the IA solution that maximizes the average sum-rate. At each step of the alternating minimization algorithm, either the precoders or the decoders are moved along the direction given by the gradient of the sum-rate. Since IA solutions are defined by a set of subspaces, the gradient optimization is performed on the Grassmann manifold. The step size of the gradient ascent algorithm is annealed to zero over the iterations in such a way that during the last iterations only the interference leakage is being minimized and a perfect alignment solution is finally reached. Simulation examples are provided showing that the proposed algorithm obtains IA solutions with significant higher throughputs than the conventional IA algorithms. C2 - 2010/// C3 - GLOBECOM - IEEE Global Telecommunications Conference DA - 2010/// DO - 10.1109/GLOCOM.2010.5683919 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-79551622757&partnerID=MN8TOARS ER - TY - CONF TI - Limited feedback with joint CSI quantization for multicell cooperative generalized eigenvector beamforming AB - Existing work on limited feedback for cooperative multicell beamforming quantizes the desired and interfering channel state information (CSI) using separate codebooks. In this paper, it is shown that comparatively higher sum-rates can be obtained by jointly quantizing the desired and interfering CSI using a single codebook. A selection criterion is developed for random vector quantization (RVQ) to show that joint quantization with RVQ yields higher sum-rates than those obtained using separate codebooks. The generalized Lloyd algorithm is then used to generate codebooks using the codeword design strategy proposed in this paper. Simulations are used to show that the proposed joint quantization approaches perform almost as well as the full CSI case. C2 - 2010/// C3 - ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings DA - 2010/// DO - 10.1109/ICASSP.2010.5496190 SP - 2838-2841 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78049376001&partnerID=MN8TOARS KW - Cooperative systems KW - Array signal processing KW - Limited feedback KW - Channel state information KW - Joint quantization ER - TY - CONF TI - Limited feedback beamforming for temporally correlated MIMO channels with other cell interference AB - Limited feedback beamforming improves link reliability with a small amount of feedback from the receiver to the transmitter. The performance of such a closed loop MIMO system is unknown in interference limited cellular environments, when the base stations have limited or no coordination. This paper establishes the degradation in throughput due to uncoordinated other cell interference and delay on the feedback channel. Under a Markov channel assumption, the paper shows that the throughput gain of cell edge users decays doubly exponentially as the delay increases. Numerical results illustrate how the decay rate decreases when the codebook size increases. C2 - 2010/// C3 - ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings DA - 2010/// DO - 10.1109/ICASSP.2010.5496108 SP - 3054-3057 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78049362293&partnerID=MN8TOARS KW - Limited feedback beamforming KW - MIMO systems KW - Markov model KW - other cell interference ER - TY - CONF TI - Interference alignment with analog CSI feedback AB - Interference alignment has been used to derive and realize the maximum multiplexing gain of the MIMO interference channel. Interference alignment requires some form of channel state information at the transmitter. This paper proposes analog CSI feedback as an alternative to limited feedback or reciprocity based alignment. We show that the maximum degrees of freedom of the K-user interference channel are preserved with the suggested feedback strategy, and that the mean loss in sum rate incurred by imperfect CSI is bounded by a constant provided that the signal-to-noise ratio is comparable in both forward and reverse channels. Finally, demonstrate the performance of the proposed strategy through simulation. C2 - 2010/// C3 - Proceedings - IEEE Military Communications Conference MILCOM DA - 2010/// DO - 10.1109/MILCOM.2010.5680216 SP - 1644-1648 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-79951606689&partnerID=MN8TOARS ER - TY - JOUR TI - An energy-based comparison of long-hop and short-hop routing in MIMO networks AU - Lo, C.K. AU - Vishwanath, S. AU - Heath, R.W. T2 - IEEE Transactions on Vehicular Technology AB - This paper considers the problem of selecting either routes that consist of long hops or routes that consist of short hops in a network of multiple-antenna nodes, where each transmitting node employs spatial multiplexing. This distance-dependent route selection problem is approached from the viewpoint of energy efficiency, where a route is selected with the objective of minimizing the transmission energy consumed while satisfying a target outage criterion at the final destination. Deterministic line networks and two-dimensional random networks are considered. It is shown that when 1) the number of hops traversed between the source and destination grows large or 2) when the target success probability approaches one or 3) when the number of transmit and/or receive antennas grows large, short-hop routing requires less energy than long-hop routing. It is also shown that if both routing strategies are subject to the same delay constraint, long-hop routing requires less energy than short-hop routing as the target success probability approaches one. In addition, numerical analysis indicates that given loose outage constraints, only a small number of transmit antennas are needed for short-hop routing to have its maximum advantage over long-hop routing, while given stringent outage constraints, the advantage of short-hop over long-hop routing always increases with additional transmit antennas. DA - 2010/// PY - 2010/// DO - 10.1109/TVT.2009.2033075 VL - 59 IS - 1 SP - 394-405 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-76849101090&partnerID=MN8TOARS KW - Large-antenna limits KW - multiple antennas KW - random networks KW - relays ER - TY - JOUR TI - Adaptation in convolutionally coded MIMO-OFDM wireless systems through supervised learning and SNR ordering AU - Daniels, R.C. AU - Caramanis, C.M. AU - Heath, R.W. T2 - IEEE Transactions on Vehicular Technology AB - Multiple-input-multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) wireless systems use link adaptation to exploit the dynamic nature of wireless environments. Link adaptation maximizes throughput while maintaining target reliability by adaptively selecting the modulation order and coding rate. Link adaptation is extremely challenging, however, due to the difficulty in predicting error rates in OFDM with binary convolutional codes, bit interleaving, MIMO processing, and real channel impairments. This paper proposes a new machine-learning framework that exploits past observations of the error rate and the associated channel-state information to predict the best modulation order and coding rate for new realizations of the channel state without modeling the input-output relationship of the wireless transceiver. Our approach is enabled through our new error-rate expression that is only parameterized by postprocessing signal-to-noise ratios (SNRs), ordered over subcarriers and spatial streams. Using ordered SNRs, we propose a low-dimensional feature set that enables machine learning to increase the accuracy of link adaptation. An IEEE 802.11n simulation study validates the application of this machine-learning framework in real channels and demonstrates the improved performance of SNR ordering as it compares with competing link-quality metrics. DA - 2010/// PY - 2010/// DO - 10.1109/TVT.2009.2029693 VL - 59 IS - 1 SP - 114-126 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-76849102593&partnerID=MN8TOARS ER - TY - CONF TI - Grassmannian predictive frequency domain compression for limited feedback beamforming AB - Frequency domain channel correlation can be exploited to reduce feedback in limited feedback beamforming multiple-input multiple-output orthogonal frequency division multiplexing wireless systems. Prior methods rely on downsampling, interpolation, or clustering the channel state information in the frequency domain. The resulting compressed samples are quantized using one-shot quantization on the Grassmann manifold. The resolution, unfortunately, is limited. We propose a new frequency domain compression technique to obtain high resolution channel state information. The key idea is to use predictive coding on the Grassmann manifold, exploiting the correlation between adjacent subcarriers. C2 - 2010/// C3 - 2010 Information Theory and Applications Workshop, ITA 2010 - Conference Proceedings DA - 2010/// DO - 10.1109/ITA.2010.5454127 SP - 173-177 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77952740579&partnerID=MN8TOARS ER - TY - JOUR TI - Adaptive MIMO transmission techniques for broadband wireless communication systems T2 - IEEE Communications Magazine AB - Link adaptation is a way to increase data rates in wireless systems by adapting transmission parameters such as the modulation and coding rate. While link adaptation in single antenna systems is now mature, its application to multiple-input multiple-output communication links, presented in several emerging wireless standards, has been challenging. The main reason is that the space-time transmission strategy can also be adjusted in MIMO communication links, introducing a new dimension for adaptation. This means that practical MIMO link adaptation algorithms must also provide a dynamic adaptation between diversity and multiplexing modes of operation. This article reviews a recently proposed framework for adaptive MIMO architectures and shows how to use this framework to reduce adaptive control overhead. We also discuss practical implementation issues. Simulations in an IEEE 802.16e (mobile WiMAX) system illustrate the frame-work's potential improvements in data rates. DA - 2010/// PY - 2010/// DO - 10.1109/MCOM.2010.5458371 VL - 48 IS - 5 SP - 112-118 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77952154883&partnerID=MN8TOARS KW - MIMO KW - Wireless communication KW - Signal to noise ratio KW - Switches KW - Phase shift keying KW - Encoding ER - TY - JOUR TI - A new double-directional channel model including antenna patterns, array orientation, and depolarization AU - Bhagavatula, R. AU - Oestges, C. AU - Heath, R.W. T2 - IEEE Transactions on Vehicular Technology AB - Multiple-input-multiple-output (MIMO) wireless channel models are often too simplistic to accurately model wireless propagation effects or too complex and/or site specific to be used for analytical purposes. In this paper, we develop a double-directional MIMO channel model that accounts for important propagation effects like scattering, clustering, and channel depolarization and antenna effects like antenna diversity, cross polarization, and random array orientation, while still retaining an intuitive representation. The proposed model can be parameterized using channel measurements obtained from site-specific measurement campaigns or from standard-based channel models. We show, using simulations, that the proposed model captures channel and antenna effects not included in other models, like the third-generation partnership program (3GPP) spatial channel model, the WINNER, and the IEEE 802.11n channel model. We use the model to study the impact of random orientation and channel depolarization on the data rates of a MIMO system. DA - 2010/// PY - 2010/// DO - 10.1109/TVT.2010.2045775 VL - 59 IS - 5 SP - 2219-2231 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77953767895&partnerID=MN8TOARS KW - Antenna diversity KW - channel depolarization KW - mobile orientation KW - multiple-input-multiple-output (MIMO) channel modeling ER - TY - CONF TI - Augmenting commercial wireless transceivers with time-of-arrival positioning AB - The augmentation of commercial wireless hardware with time-of-arrival (ToA) estimation enables pervasive wireless networks to serve additionally as positioning systems. ToA-augmented wireless links offer the ability to provide accurate localization in environments not served by global navigation satellite systems (GNSS) with greater accuracy than inertial sensing systems and wireless fingerprinting. In this paper we propose the augmentation of IEEE 802.11 commercial hardware with ToA through an add-on hardware module. Two processing architectures are introduced, loopback and loopback with probing, to leverage the ToA module. The calibration of local device clocks due to unstable frequency references is also presented. Finally, a discussion of positioning algorithms with simulations demonstrates the efficacy of the proposed ToA module to provide high-precision, low-cost positioning without the addition of significant system infrastructure. C2 - 2010/// C3 - Record - IEEE PLANS, Position Location and Navigation Symposium DA - 2010/// DO - 10.1109/PLANS.2010.5507271 SP - 982-987 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77955027019&partnerID=MN8TOARS ER - TY - CONF TI - Adaptive transmit antenna selection in mimo amplify-and-forward relay channels AB - Obtaining the most from multiple-antenna relay systems requires adapting the number of substreams based on channel conditions. In this paper, we develop algorithms for selecting dynamically the number of data streams and the transmit antenna subsets at both the source and relay to minimize the vector symbol error rate at a fixed overall rate. An antenna selection mode of operation is defined by the number of transmit antennas and the substream-to-antenna mapping at the source and relay. We propose three suboptimal multimode algorithms that aim to select the best mode based on the knowledge of channel conditions. The algorithms are shown by Monte Carlo simulations to achieve the full diversity order and to provide considerable gains over the existing designs. C2 - 2010/// C3 - ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings DA - 2010/// DO - 10.1109/ICASSP.2010.5496117 SP - 3022-3025 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78049376997&partnerID=MN8TOARS KW - MIMO relay KW - antenna selection KW - amplify-and-forward KW - multi-antenna relay ER - TY - CONF TI - A simple SINR characterization for linear interference alignment over uncertain MIMO channels AB - This paper provides a simple closed-form SINR expression for interference alignment over MIMO channels with channel uncertainty. Assuming linear processing (specifically, zero-forcing) at the transmitters and receivers and a complex Gaussian interference channel, we show that random matrix theory can be successfully applied to find the SINR distribution of each stream for each user with channel uncertainty. Perfect channel knowledge constitutes a special case. This SINR distribution allows easy calculation of useful performance metrics like symbol error-rate and achievable sum rate. C2 - 2010/// C3 - IEEE International Symposium on Information Theory - Proceedings DA - 2010/// DO - 10.1109/ISIT.2010.5513649 SP - 2288-2292 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77955694616&partnerID=MN8TOARS ER - TY - CONF TI - Coordinated single-cell vs multi-cell transmission with limited-capacity backhaul AB - Base station coordination is an efficient technique to transcend the limits on spectral efficiency imposed by intercell interference. In this paper, we compare the performance of different coordination strategies with different amount of channel state information (CSI) and data sharing among the coordinating base stations. We focus on the effect of limited backhaul capacity in a two-cell network. Contrary to the common belief, we show that coordination strategies with no data and only limited CSI sharing is preferred to those with full data and CSI sharing when the backhaul capacity is relatively low and the edge SNR is high. C2 - 2010/// C3 - Conference Record - Asilomar Conference on Signals, Systems and Computers DA - 2010/// DO - 10.1109/ACSSC.2010.5757724 SP - 1217-1221 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-79957984126&partnerID=MN8TOARS ER - TY - CONF TI - Cognitive cooperation for the downlink of frequency reuse small cells C2 - 2010/// C3 - 2010 2nd International Workshop on Cognitive Information Processing, CIP2010 DA - 2010/// DO - 10.1109/CIP.2010.5604251 SP - 111-115 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78349284430&partnerID=MN8TOARS ER - TY - JOUR TI - 60 GHz wireless: Up close and personal T2 - IEEE Microwave Magazine AB - To meet the needs of next-generation high-data-rate applications, 60 GHz wireless networks must deliver Gb/s data rates and reliability at a low cost. In this article, we surveyed several ongoing challenges, including the design of cost-efficient and low-loss on-chip and in-package antennas and antenna arrays, the characterization of CMOS processes at millimeter-wave frequencies, the discovery of efficient modulation techniques that are suitable for the unique hardware impairments and frequency selective channel characteristics at millimeter-wave frequencies, and the creation of MAC protocols that more effectively coordinate 60 GHz networks with directional antennas. Solving these problems not only provides for wireless video streaming and interconnect replacement, but also moves printed and magnetic media such as books and hard drives to a lower cost, higher reliability semiconductor form factor with wireless connectivity between and within devices. DA - 2010/// PY - 2010/// DO - 10.1109/MMM.2010.938581 VL - 11 IS - 7 SUPPL. UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78649845496&partnerID=MN8TOARS KW - OFDM KW - Wireless communication KW - Dipole antennas KW - Phased arrays KW - Modulation KW - Frequency domain analysis ER - TY - JOUR TI - Effects of nanoscale porosity on thermoelectric properties of SiGe AU - Lee, Hohyun AU - Vashaee, Daryoosh AU - Wang, D. Z. AU - Dresselhaus, Mildred S. AU - Ren, Z. F. AU - Chen, Gang T2 - Journal of Applied Physics AB - The recent achievement of the high thermoelectric figure of merit in nanograined materials is attributed to the successful optimization of the consolidation process. Despite a thermal conductivity reduction, it has been experimentally observed that the porous nanograined materials have lower thermoelectric figure of merit than their bulk counterpart due to significant reduction in the electrical conductivity. In this paper, nanoscale porosity effects on electron and phonon transport are modeled to predict and explain thermoelectric properties in porous nanograined materials. Electron scattering at the pores is treated quantum mechanically while phonon transport is treated using a classical picture. The modeling results show that the charge carriers are scattered more severely in nanograined materials than the macroscale porous materials, due to a higher number density of scattering sites. Porous nanograined materials have enhanced Seebeck coefficient due to energy filtering effect and low thermal conductivity, which are favorable for thermoelectric applications. However, the benefit is not large enough to overcome the deficit in the electrical conductivity, so that a high sample density is necessary for nanograined SiGe. DA - 2010/5// PY - 2010/5// DO - 10.1063/1.3388076 VL - 107 IS - 9 SP - 094308 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.3388076 DB - Crossref ER - TY - CHAP TI - Local Occlusion Detection under Deformations Using Topological Invariants AU - Lobaton, Edgar AU - Vasudevan, Ram AU - Bajcsy, Ruzena AU - Alterovitz, Ron T2 - Computer Vision – ECCV 2010 AB - Occlusions provide critical cues about the 3D structure of man-made and natural scenes. We present a mathematical framework and algorithm to detect and localize occlusions in image sequences of scenes that include deforming objects. Our occlusion detector works under far weaker assumptions than other detectors. We prove that occlusions in deforming scenes occur when certain well-defined local topological invariants are not preserved. Our framework employs these invariants to detect occlusions with a zero false positive rate under assumptions of bounded deformations and color variation. The novelty and strength of this methodology is that it does not rely on spatio-temporal derivatives or matching, which can be problematic in scenes including deforming objects, but is instead based on a mathematical representation of the underlying cause of occlusions in a deforming 3D scene. We demonstrate the effectiveness of the occlusion detector using image sequences of natural scenes, including deforming cloth and hand motions. PY - 2010/// DO - 10.1007/978-3-642-15558-1_8 SP - 101-114 OP - PB - Springer Berlin Heidelberg SN - 9783642155574 9783642155581 UR - http://dx.doi.org/10.1007/978-3-642-15558-1_8 DB - Crossref ER - TY - JOUR TI - Radiation-induced defects in GaN AU - Son, N T AU - Hemmingsson, C G AU - Morishita, N AU - Ohshima, T AU - Paskova, T AU - Evans, K R AU - Usui, A AU - Isoya, J AU - Monemar, B AU - Janzén, E T2 - Physica Scripta AB - Radiation-induced defects in n-type GaN irradiated by 2 MeV electrons at room temperature were studied by electron paramagnetic resonance (EPR). Four EPR spectra, labelled D1–D4, were observed in irradiated n-type GaN. The D1 spectrum is a broad line (∼10–12 mT in line width) with an isotropic g-value g∼2.03 and can be detected in all the studied samples in the temperature range of 4–300 K. The D2 centre has an electron spin S=1/2 and shows a clear hyperfine structure due to interaction with three equivalent 14N. The g-values of the axial configuration are determined to be g∥=2.001 and g⊥=1.999. On the basis of the observed hyperfine structure, formation conditions and annealing behaviour, the D2 defect was assigned to the gallium vacancy–oxygen pair in the negative charge state, (VGaON)–. DA - 2010/11/1/ PY - 2010/11/1/ DO - 10.1088/0031-8949/2010/T141/014015 VL - T141 SP - 014015 J2 - Phys. Scr. OP - SN - 0031-8949 1402-4896 UR - http://dx.doi.org/10.1088/0031-8949/2010/T141/014015 DB - Crossref ER - TY - JOUR TI - Effect of Fe doping on the terahertz conductivity of GaN single crystals AU - Kadlec, Filip AU - Kadlec, Christelle AU - Paskova, Tanya AU - Evans, Keith T2 - Journal of Physics D: Applied Physics AB - Bulk single crystals of GaN with different degrees of Fe doping were studied using time-domain terahertz spectroscopy at high temperatures. Features due to free carriers were observed in the complex permittivity spectra with a pronounced dependence on both doping and temperature. Fitting the spectra using the Drude model made it possible to deduce a defect ionization energy of 16 meV in the undoped sample while the spectra of doped samples are consistent with an ionization energy of 60 meV. Also, the free carrier concentrations at temperatures from 300 to 900 K were estimated. DA - 2010/3/23/ PY - 2010/3/23/ DO - 10.1088/0022-3727/43/14/145401 VL - 43 IS - 14 SP - 145401 J2 - J. Phys. D: Appl. Phys. OP - SN - 0022-3727 1361-6463 UR - http://dx.doi.org/10.1088/0022-3727/43/14/145401 DB - Crossref ER - TY - JOUR TI - InGaN staircase electron injector for reduction of electron overflow in InGaN light emitting diodes AU - Ni, X. AU - Li, X. AU - Lee, J. AU - Liu, S. AU - Avrutin, V. AU - Özgür, Ü. AU - Morkoç, H. AU - Matulionis, A. AU - Paskova, T. AU - Mulholland, G. AU - Evans, K. R. T2 - Applied Physics Letters AB - Ballistic and quasiballistic electron transport across the active InGaN layer are shown to be responsible for electron overflow and electroluminescence efficiency droop at high current levels in InGaN light emitting diodes both experimentally and by first-order calculations. An InGaN staircase electron injector with step-like increased In composition, an “electron cooler,” is proposed for an enhanced thermalization of the injected hot electrons to reduce the overflow and mitigate the efficiency droop. The experimental data show that the staircase electron injector results in essentially the same electroluminescence performance for the diodes with and without an electron blocking layer, confirming substantial electron thermalization. On the other hand, if no InGaN staircase electron injector is employed, the diodes without the electron blocking layer have shown significantly lower (three to five times) electroluminescence intensity than the diodes with the blocking layer. These results demonstrate a feasible method for the elimination of electron overflow across the active region, and therefore, the efficiency droop in InGaN light emitting diodes. DA - 2010/7/19/ PY - 2010/7/19/ DO - 10.1063/1.3465658 VL - 97 IS - 3 SP - 031110 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.3465658 DB - Crossref KW - ballistic transport KW - electroluminescence KW - gallium compounds KW - hot carriers KW - III-V semiconductors KW - indium compounds KW - light emitting diodes KW - wide band gap semiconductors ER - TY - JOUR TI - Effect of hot phonon lifetime on electron velocity in InAlN/AlN/GaN heterostructure field effect transistors on bulk GaN substrates AU - Leach, J. H. AU - Zhu, C. Y. AU - Wu, M. AU - Ni, X. AU - Li, X. AU - Xie, J. AU - Özgür, Ü. AU - Morkoç, H. AU - Liberis, J. AU - Šermukšnis, E. AU - Matulionis, A. AU - Paskova, T. AU - Preble, E. AU - Evans, K. R. T2 - Applied Physics Letters AB - We report on electron velocities deduced from current gain cutoff frequency measurements on GaN heterostructure field effect transistors (HFETs) with InAlN barriers on Fe-doped semi-insulating bulk GaN substrates. The intrinsic transit time is a strong function of the applied gate bias, and a minimum intrinsic transit time occurs for gate biases corresponding to two-dimensional electron gas densities near 9.3×1012 cm−2. This value correlates with the independently observed density giving the minimum longitudinal optical phonon lifetime. We expect the velocity, which is inversely proportional to the intrinsic transit time, to be limited by scattering with non equilibrium (hot) phonons at the high fields present in the HFET channel, and thus, we interpret the minimum intrinsic transit time in terms of the hot phonon decay. At the gate bias associated with the minimum transit time, we determined the average electron velocity for a 1.1 μm gate length device to be 1.75±0.1×107 cm/sec. DA - 2010/3/29/ PY - 2010/3/29/ DO - 10.1063/1.3358392 VL - 96 IS - 13 SP - 133505 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.3358392 DB - Crossref KW - aluminium compounds KW - electron density KW - electron gas KW - field effect transistors KW - gallium compounds KW - indium compounds ER - TY - JOUR TI - Carrier velocity in InAlN/AlN/GaN heterostructure field effect transistors on Fe-doped bulk GaN substrates AU - Leach, J. H. AU - Wu, M. AU - Ni, X. AU - Li, X. AU - Xie, J. AU - Özgür, Ü. AU - Morkoç, H. AU - Paskova, T. AU - Preble, E. AU - Evans, K. R. AU - Lu, Chang-Zhi T2 - Applied Physics Letters AB - We report microwave characteristics of field effect transistors employing InAlN/AlN/GaN heterostructures grown on low-defect-density bulk Fe-doped GaN substrates. We achieved unity current gain cutoff frequencies of 14.3 and 23.7 GHz for devices with gate lengths of 1 and 0.65 μm, respectively. Measurements as a function of applied bias allow us to estimate the average carrier velocity in the channel to be ∼1.0×107 cm/sec for a 1 μm device. Additionally, we found nearly no gate lag in the devices, which is considered a precondition for good performance under large signal operation. DA - 2010/3/8/ PY - 2010/3/8/ DO - 10.1063/1.3358192 VL - 96 IS - 10 SP - 102109 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.3358192 DB - Crossref ER - TY - JOUR TI - Wavelength-stable cyan and green light emitting diodes on nonpolar m-plane GaN bulk substrates AU - Detchprohm, Theeradetch AU - Zhu, Mingwei AU - Li, Yufeng AU - Zhao, Liang AU - You, Shi AU - Wetzel, Christian AU - Preble, Edward A. AU - Paskova, Tanya AU - Hanser, Drew T2 - Applied Physics Letters AB - We report the development of 480 nm cyan and 520 nm green light emitting diodes (LEDs) with a highly stable emission wavelength. The shift is less than 3 nm when the drive current density is changed from 0.1 to 38 A/cm2. LEDs have been obtained in GaInN-based homoepitaxy on nonpolar m-plane GaN bulk substrates. For increasing emission wavelength we find a large number of additional dislocations generated within the quantum wells (2×108 to ∼1010 cm2) and a decrease in the electroluminescence efficiency. This suggests that the strain induced generation of defects plays a significant role in the performance limitations. DA - 2010/2// PY - 2010/2// DO - 10.1063/1.3299257 VL - 96 IS - 5 SP - 051101 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.3299257 DB - Crossref KW - current density KW - dislocations KW - electroluminescence KW - gallium compounds KW - III-V semiconductors KW - indium compounds KW - light emitting diodes KW - semiconductor quantum wells KW - wide band gap semiconductors ER - TY - JOUR TI - Proximity effects of beryllium-doped GaN buffer layers on the electronic properties of epitaxial AlGaN/GaN heterostructures AU - Storm, D.F. AU - Katzer, D.S. AU - Deen, D.A. AU - Bass, R. AU - Meyer, D.J. AU - Roussos, J.A. AU - Binari, S.C. AU - Paskova, T. AU - Preble, E.A. AU - Evans, K.R. T2 - Solid-State Electronics AB - AlGaN/GaN/Be:GaN heterostructures have been grown by rf-plasma molecular beam epitaxy on free-standing semi-insulating GaN substrates, employing unintentionally-doped (UID) GaN buffer layers with thicknesses, d UID , varying between 50 nm and 500 nm. We have found that the heterostructures with UID buffers thicker than 200 nm exhibit much improved Hall properties and inter-device isolation current compared to heterostructures with d UID < 200 nm. The output conductance of devices fabricated on these heterostructures increases as d UID decreases below 200 nm, and devices with gate lengths of 240 nm and 1 μm exhibited no significant difference in output conductance. Evidence of buffer trapping is observed in devices for which d UID ⩽ 100 nm. The observed effects are tentatively explained by the presence of parallel conduction paths in samples with non-optimized UID buffer thickness. DA - 2010/11// PY - 2010/11// DO - 10.1016/j.sse.2010.05.041 VL - 54 IS - 11 SP - 1470-1473 J2 - Solid-State Electronics LA - en OP - SN - 0038-1101 UR - http://dx.doi.org/10.1016/j.sse.2010.05.041 DB - Crossref KW - Gallium nitride KW - High electron mobility transistor KW - Molecular beam epitaxy KW - Homoepitaxy KW - Doping ER - TY - JOUR TI - Revealing extended defects in HVPE-grown GaN AU - Weyher, J.L. AU - łucznik, B. AU - Grzegory, I. AU - Smalc-Koziorowska, J. AU - Paskova, T. T2 - Journal of Crystal Growth AB - In this communication we will summarize the results of a complementary study of structural and chemical non-homogeneities that are present in thick HVPE-grown GaN layers. It will be shown that complex extended defects are formed during HVPE growth, and are clearly visible after photo-etching on both Ga-polar surface and on any non-polar cleavage or section planes. Large chemical (electrically active) defects, such as growth striations, overgrown or empty pits (pinholes) and clustered irregular inclusions, are accompanied by non-uniform distribution of crystallographic defects (dislocations). Possible reasons of formation of these complex structures are discussed. The nature of defects revealed by selective etching was subsequently confirmed using TEM, orthodox etching and compared with the CL method. The non-homogeneities were studied in GaN crystals grown in different laboratories showing markedly different morphological characteristics. DA - 2010/9// PY - 2010/9// DO - 10.1016/j.jcrysgro.2010.04.021 VL - 312 IS - 18 SP - 2611-2615 J2 - Journal of Crystal Growth LA - en OP - SN - 0022-0248 UR - http://dx.doi.org/10.1016/j.jcrysgro.2010.04.021 DB - Crossref KW - Etching KW - Defects KW - Hydride vapor phase epitaxy KW - Nitrides ER - TY - JOUR TI - Effect of Fe doping on optical properties of freestanding semi-insulating HVPE GaN:Fe AU - Gladkov, P. AU - Humlíček, J. AU - Hulicius, E. AU - Šimeček, T. AU - Paskova, T. AU - Evans, K. T2 - Journal of Crystal Growth AB - Systematic study of optical properties of undoped and Fe-doped substrates grown by hydride vapor phase epitaxy has revealed a strong dependence of the photoluminescence, transmission, reflectivity and ellipsometric spectra on the Fe-doping level. The changes of the near-band-gap transmission, reflectivity and photoluminescence has been observed and ascribed to the absorption introduced by the density of states tails, and the Fe3+ -ions incorporated in the GaN-lattice. Several approaches towards quantifying the Fe-doping level are suggested. DA - 2010/4// PY - 2010/4// DO - 10.1016/j.jcrysgro.2009.11.032 VL - 312 IS - 8 SP - 1205-1209 J2 - Journal of Crystal Growth LA - en OP - SN - 0022-0248 UR - http://dx.doi.org/10.1016/j.jcrysgro.2009.11.032 DB - Crossref KW - Fe-doping KW - Optical characterization KW - Hydride vapor phase epitaxy KW - Nitrides ER - TY - JOUR TI - In Situ Raman Analysis of a Bulk GaN-Based Schottky Rectifier Under Operation AU - Xu, Hui AU - Alur, Siddharth AU - Wang, Yaqi AU - Cheng, An-Jen AU - Kang, Kilho AU - Sharma, Yogeshkumar AU - Park, Minseo AU - Ahyi, Claude AU - Williams, John AU - Gu, Chaokang AU - Hanser, Andrew AU - Paskova, Tanya AU - Preble, Edward A. AU - Evans, Keith R. AU - Zhou, Yi T2 - Journal of Electronic Materials DA - 2010/6/16/ PY - 2010/6/16/ DO - 10.1007/S11664-010-1304-3 VL - 39 IS - 10 SP - 2237-2242 J2 - Journal of Elec Materi LA - en OP - SN - 0361-5235 1543-186X UR - http://dx.doi.org/10.1007/S11664-010-1304-3 DB - Crossref KW - GaN KW - Schottky rectifier KW - Raman spectroscopy ER - TY - JOUR TI - Physical Properties of AlGaN/GaN Heterostructures Grown on Vicinal Substrates AU - Grenko, J. A. AU - Reynolds, C. L., Jr. AU - Barlage, D. W. AU - Johnson, M. A. L. AU - Lappi, S. E. AU - Ebert, C. W. AU - Preble, E. A. AU - Paskova, T. AU - Evans, K. R. T2 - Journal of Electronic Materials DA - 2010/3/27/ PY - 2010/3/27/ DO - 10.1007/S11664-010-1153-0 VL - 39 IS - 5 SP - 504-516 J2 - Journal of Elec Materi LA - en OP - SN - 0361-5235 1543-186X UR - http://dx.doi.org/10.1007/S11664-010-1153-0 DB - Crossref KW - GaN KW - vicinal surfaces ER - TY - JOUR TI - The effect of ballistic and quasi-ballistic electrons on the efficiency droop of InGaN light emitting diodes AU - Ni, X. AU - Li, X. AU - Lee, J. AU - Liu, S. AU - Avrutin, V. AU - Özgür, Ü. AU - Morkoç, H. AU - Matulionis, A. AU - Paskova, T. AU - Mulholland, G. AU - Evans, K. R. T2 - physica status solidi (RRL) - Rapid Research Letters AB - Abstract The effect of hot electrons on electroluminescence of m ‐plane double heterostructure light emitting diodes (with a single 6 nm active layer of In 0.20 Ga 0.80 N) is investigated. Diodes with an electron blocking layer (Al 0.15 Ga 0.85 N) demonstrate from 3 to 5 times higher electroluminescence efficiency than those without a blocking layer. The lower electroluminescence efficiency in devices without the blocking layer is ex‐ plained in terms of electron overflow caused by ballistic and quasi‐ballistic transport of injected electrons across the InGaN active region. The same mechanism explains the decrease, observed at high current densities, of the electroluminescence efficiency (efficiency droop) in the In 0.20 Ga 0.80 N diodes with the Al 0.15 Ga 0.85 N blocking layer. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) DA - 2010/6/8/ PY - 2010/6/8/ DO - 10.1002/pssr.201004147 VL - 4 IS - 8-9 SP - 194-196 J2 - phys. stat. sol. (RRL) LA - en OP - SN - 1862-6254 UR - http://dx.doi.org/10.1002/pssr.201004147 DB - Crossref KW - nitride semiconductors KW - InGaN KW - LEDs KW - efficiency KW - hot electrons ER - TY - JOUR TI - Cyan and green light emitting diode on non-polar m -plane GaN bulk substrate AU - Detchprohm, Theeradetch AU - Zhu, Mingwei AU - You, Shi AU - Li, Yufeng AU - Zhao, Liang AU - Preble, Edward A. AU - Paskova, Tanya AU - Hanser, Drew AU - Wetzel, Christian T2 - physica status solidi (c) AB - Abstract We report the development of non‐polar light emitting diodes (LEDs) covering the emission spectra from 480 to 520 nm (dominant wavelength), i.e. from cyan to the green region. The devices are obtained via GaInN‐based homoepitaxy on non‐polar m ‐plane GaN bulk substrate. Owing to the absence of piezoelectric polarization, these LEDs exhibit stable emission color with a wavelength shift less than 3 nm when the drive current density is changed from 0.1–30 A/cm 2 . However, we observe a decreasing electroluminescence efficiency as the emission wavelengths increases from cyan to green. We tentatively attribute this to a higher density of defects in the longer wavelength structures. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) DA - 2010/4/30/ PY - 2010/4/30/ DO - 10.1002/pssc.200983611 VL - 7 IS - 7-8 SP - 2190-2192 J2 - Phys. Status Solidi (c) LA - en OP - SN - 1862-6351 1610-1642 UR - http://dx.doi.org/10.1002/pssc.200983611 DB - Crossref KW - GaInN/GaN KW - quantum wells KW - MOVPE KW - defects KW - electroluminescence KW - LEDs ER - TY - JOUR TI - Mg-related acceptors in GaN AU - Monemar, B. AU - Paskov, P. P. AU - Pozina, G. AU - Hemmingsson, C. AU - Bergman, J. P. AU - Amano, H. AU - Akasaki, I. AU - Figge, S. AU - Hommel, D. AU - Paskova, T. AU - Usui, A. T2 - physica status solidi (c) AB - Abstract Photoluminescence spectra of c ‐plane Mg doped GaN samples grown by MOVPE on bulk GaN templates reveal previously unknown properties, like the presence of several Mg‐related acceptors. The use of unstrained samples allows a study of both bound exciton (BE) and donor‐acceptor pair (DAP) spectra. Two main acceptors A1 and A2 are observed strongly in BE spectra as well as in DAP spectra, they have similar binding energies, i.e. about 220 meV. The common assignment of the deeper blue PL emission at 2.8–3.0 eV to a deep donor‐shallow acceptor transition is questioned, and discussed in connection with the compensation problem in p‐GaN. It seems like the Fermi level in p‐GaN is controlled by a set of Mg‐related acceptors at energies 0.2–0.6 eV from the valence band top. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) DA - 2010/6/10/ PY - 2010/6/10/ DO - 10.1002/pssc.200983436 VL - 7 IS - 7-8 SP - 1850-1852 J2 - Phys. Status Solidi (c) LA - en OP - SN - 1862-6351 1610-1642 UR - http://dx.doi.org/10.1002/pssc.200983436 DB - Crossref KW - GaN KW - MOVPE KW - doping KW - impurity levels KW - photoluminescence ER - TY - JOUR TI - Various misfit dislocations in green and yellow GaInN/GaN light emitting diodes AU - Zhu, Mingwei AU - You, Shi AU - Detchprohm, Theeradetch AU - Paskova, Tanya AU - Preble, Edward A. AU - Wetzel, Christian T2 - physica status solidi (a) AB - Abstract We report the growth and structural characteristics of green and yellow (529–576 nm) GaInN/GaN light emitting diodes (LEDs) grown on two types of c ‐plane substrates – bulk GaN and sapphire. In this longer wavelength range, depending on the substrate, we find different strain relaxation mechanisms within the GaInN/GaN quantum well (QW) region. In optimized epitaxy, structures on sapphire that contain a low density of threading dislocations (TDs) within the n ‐GaN show virtually no generation of additional misfit dislocations (MDs) (<10 8 cm −2 ) or V ‐defects within the QW region for emission wavelengths up to 571 nm. On bulk GaN substrate, however, where much fewer TDs reach the QWs, strain relaxation is observed by inclined dislocation pairs in green emitters and a high density of edge‐type MDs in yellow emitters. The electroluminescence line width, as well as the efficiency droop, was found to increase with dislocation density in the QWs. DA - 2010/5/17/ PY - 2010/5/17/ DO - 10.1002/pssa.200983645 VL - 207 IS - 6 SP - 1305-1308 J2 - phys. stat. sol. (a) LA - en OP - SN - 1862-6300 UR - http://dx.doi.org/10.1002/pssa.200983645 DB - Crossref KW - dislocations KW - electroluminescence KW - GaInN/GaN KW - LEDs KW - MOVPE ER - TY - CHAP TI - Green Secure Processors: Towards Power-Efficient Secure Processor Design AU - Chhabra, Siddhartha AU - Solihin, Yan T2 - Transactions on Computational Science X AB - With the increasing wealth of digital information stored on computer systems today, security issues have become increasingly important. In addition to attacks targeting the software stack of a system, hardware attacks have become equally likely. Researchers have proposed Secure Processor Architectures which utilize hardware mechanisms for memory encryption and integrity verification to protect the confidentiality and integrity of data and computation, even from sophisticated hardware attacks. While there have been many works addressing performance and other system level issues in secure processor design, power issues have largely been ignored. In this paper, we first analyze the sources of power (energy) increase in different secure processor architectures. We then present a power analysis of various secure processor architectures in terms of their increase in power consumption over a base system with no protection and then provide recommendations for designs that offer the best balance between performance and power without compromising security. We extend our study to the embedded domain as well. We also outline the design of a novel hybrid cryptographic engine that can be used to minimize the power consumption for a secure processor. We believe that if secure processors are to be adopted in future systems (general purpose or embedded), it is critically important that power issues are considered in addition to performance and other system level issues. To the best of our knowledge, this is the first work to examine the power implications of providing hardware mechanisms for security. PY - 2010/// DO - 10.1007/978-3-642-17499-5_13 SP - 329-351 OP - PB - Springer Berlin Heidelberg SN - 9783642174988 9783642174995 UR - http://dx.doi.org/10.1007/978-3-642-17499-5_13 DB - Crossref ER - TY - CHAP TI - An Analysis of Secure Processor Architectures AU - Chhabra, Siddhartha AU - Solihin, Yan AU - Lal, Reshma AU - Hoekstra, Matthew T2 - Transactions on Computational Science VII AB - Security continues to be an increasingly important concern in the design of modern systems. Many systems may have security requirements such as protecting the integrity and confidentiality of data and code stored in the system, ensuring integrity of computations, or preventing the execution of unauthorized code. Making security guarantees has become even harder with the emergence of hardware attacks where the attacker has physical access to the system and can bypass any software security mechanisms employed. To this end, researchers have proposed Secure Processor architectures that provide protection against hardware attacks using platform features. In this paper, we analyze three of the currently proposed secure uniprocessor designs in terms of their security, complexity of hardware required and performance overheads: eXecute Only Memory (XOM), Counter mode encryption and Merkle tree based authentication, and Address Independent Seed Encryption and Bonsai Merkle Tree based authentication. We then provide a discussion on the issues in securing multiprocessor systems and survey one design each for Shared Memory Multiprocessors and Distributed Shared Memory Multiprocessors. Finally, we discuss future directions in Secure Processor research which have largely been ignored forming the weakest link in the security afforded by the proposed schemes, namely, Secure booting and Secure configuration. We identify potential issues which can serve to form the foundation of further research in secure processors. PY - 2010/// DO - 10.1007/978-3-642-11389-5_6 SP - 101-121 OP - PB - Springer Berlin Heidelberg SN - 9783642113888 9783642113895 UR - http://dx.doi.org/10.1007/978-3-642-11389-5_6 DB - Crossref ER - TY - JOUR TI - Spectra and energy levels of Eu3+ in cubic phase Gd2O3 AU - Smith, Eric R. AU - Gruber, John B. AU - Wellenius, Patrick AU - Muth, John F. AU - Everitt, Henry O. T2 - physica status solidi (b) AB - In pulsed laser deposition of the sesquioxide semiconductor Gd2O3, adjusting the chamber oxygen pressure controls the crystalline structure of the host. This technique was used to deposit thin films of nominally 1.6% by weight europium-doped, cubic phase Gd2O3 using 50 mTorr of oxygen. Structural measurements using high-resolution transmission electron microscopy and selected area electron diffraction confirm the films were polycrystalline, cubic phase Eu:Gd2O3. The spectroscopic assignment of emission lines to specific radiative transitions within the trivalent Eu ion is confirmed by theoretical analysis of the appropriate crystal field Hamiltonian. Detailed crystal-field splittings are presented for the 5DJ=0-2 and 7FJ=0-5 multiplet manifolds of Eu3+ in this host material. DA - 2010/5/14/ PY - 2010/5/14/ DO - 10.1002/pssb.200945602 VL - 247 IS - 7 SP - 1807-1813 J2 - phys. stat. sol. (b) LA - en OP - SN - 0370-1972 1521-3951 UR - http://dx.doi.org/10.1002/pssb.200945602 DB - Crossref KW - crystal field calculations KW - photoluminescence KW - rare earth doped semiconductors ER - TY - CHAP TI - How the Public Views Strategies Designed to Reduce the Threat of Botnets AU - Rowe, Brent AU - Wood, Dallas AU - Reeves, Douglas T2 - Trust and Trustworthy Computing AB - Botnets pose a growing threat to the nation’s critical digital infrastructure and general level of cybersecurity. Several strategies for reducing the threat of botnets have been outlined in the cyber security literature. These strategies typically call for both Internet Service Providers (ISPs) and home Internet users to adopt a greater share of the responsibility for overall security. However, to date no study has attempted to determine how accepting the public would be of these strategies. This study takes the first step in filling that gap. The results of this pilot survey suggest that, in general, individuals would be willing to spend additional time each month meeting security requirements set by their ISPs. The results also suggest that although only 50% of respondents would be willing to pay their ISP more per month to protect themselves from cyber threats, more people would be willing to do so if they perceived ISPs as being effective or very effective at reducing such threats. The findings provide important guidance for policy makers and ISPs seeking to gain support for such strategies. PY - 2010/// DO - 10.1007/978-3-642-13869-0_25 SP - 337-351 OP - PB - Springer Berlin Heidelberg SN - 9783642138683 9783642138690 UR - http://dx.doi.org/10.1007/978-3-642-13869-0_25 DB - Crossref ER - TY - CONF TI - Validation of battery energy storage control for wind farm dispatching AU - Teleke, S. AU - Baran, M.E. AU - Bhattacharya, S. AU - Huang, A. AB - Integrating a Battery Energy Storage System (BESS) with a large wind farm can smooth out the intermittent power from the wind farm. This paper focuses on the experimental validation of the proposed control strategy for the BESS. The paper considers a rule based control scheme, which is the solution of the optimal control problem defined, to incorporate the operating constraints of the BESS, such as state of charge limits, charge/discharge current limits and lifetime. The goal of the control is to have the BESS provide as much smoothing as possible so that the wind farm can be dispatched on an hourly basis based on the forecasted wind conditions. The effectiveness of this control strategy has been tested by using an actual wind farm data and it is shown that optimal dispatching is achieved with the proposed method. Finally, the method is verified with an experiment and the details of the implementation are explained. C2 - 2010/// C3 - IEEE PES General Meeting, PES 2010 DA - 2010/// DO - 10.1109/PES.2010.5589640 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78649570830&partnerID=MN8TOARS ER - TY - CONF TI - Series active filter control and implementation for utility interface of multiple adjustable speed drives AU - Bhattacharya, S. AU - Mirzaee, H. AB - The control of Series Active Filter (SAF) to meet IEEE 519 standard for harmonic voltage source front-end based multiple adjustable speed motor drives, is reported in this paper. The series active filter design, control, implementation and issues in the practical application for utility interface of multiple three-phase six-pulse diode rectifier with dc side capacitor fed 480V, 150kW motor drives are investigated. The simulation and experimental results validate series active filter performance for utility interface of multiple ASDs under practical utility conditions. C2 - 2010/// C3 - IECON Proceedings (Industrial Electronics Conference) DA - 2010/// DO - 10.1109/IECON.2010.5675126 SP - 2663-2668 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78751534269&partnerID=MN8TOARS ER - TY - CONF TI - The issue of plug-in hybrid electric vehicles' grid integration and its control solution AU - Zhou, X. AU - Li, J. AU - Liang, Z. AU - Huang, A. AU - Bhattacharya, S. AB - In this paper, a bi-directional battery charger is applied as an interface between plug-in hybrid electric vehicles and the grid. The major issue of using power electronics interface for grid integration of PHEVs is high frequency resonance. This resonance is caused by a high order filter, which is composed of the charger's LC filter and the grid impedance. An active damping method is proposed to mitigate the resonance. The modeling and controller design are presented. The damping performance to both the converter output harmonics and the grid harmonics are analyzed. The proposed controller can effectively reduce the high frequency resonance on the grid current. The proposed method is verified by the simulation and experiment. C2 - 2010/// C3 - 2010 IEEE Energy Conversion Congress and Exposition, ECCE 2010 - Proceedings DA - 2010/// DO - 10.1109/ECCE.2010.5617710 SP - 3596-3603 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78650135071&partnerID=MN8TOARS ER - TY - JOUR TI - Rule-based control of battery energy storage for dispatching intermittent renewable sources AU - Teleke, S. AU - Baran, M.E. AU - Bhattacharya, S. AU - Huang, A.Q. T2 - IEEE Transactions on Sustainable Energy AB - Integrating a battery energy storage system (BESS) with a solar photovoltaic (PV) system or a wind farm can make these intermittent renewable energy sources more dispatchable. This paper focuses on the development of a control strategy for optimal use of the BESS for this purpose. The paper considers a rule-based control scheme, which is the solution of the optimal control problem defined, to incorporate the operating constraints of the BESS, such as state of charge limits, charge/discharge current limits, and lifetime. The goal of the control is to have the BESS provide as much smoothing as possible so that the renewable resource can be dispatched on an hourly basis based on the forecasted solar/wind conditions. The effectiveness of this control strategy has been tested by using an actual PV system and wind farm data and it is shown that the BESS can indeed help to cope with variability in wind's and solar's generation. DA - 2010/// PY - 2010/// DO - 10.1109/TSTE.2010.2061880 VL - 1 IS - 3 SP - 117-124 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77957007183&partnerID=MN8TOARS KW - Battery energy storage system (BESS) KW - closed loop optimal control KW - dispatchability KW - photovoltaic (PV) system KW - rule-based control KW - wind energy ER - TY - CONF TI - Performance comparison of 1200V silicon and SiC devices for UPS application AU - McBryde, J. AU - Kadavelugu, A. AU - Compton, B. AU - Bhattacharya, S. AU - Das, M. AU - Agarwal, A. T2 - Glendale, AZ AB - In this paper, a comparative study of 1200V Silicon IGBTs with Silicon Carbide (SiC) MOSFETs is presented for a 6kVA single-phase 230V online Uninterruptible Power Supply (UPS) system. The UPS is first tested with the 1200V silicon IGBT/Diode devices (2 parallel 34A IGBT/diode) and then the inverter devices are replaced by next generation SiC 1200V MOSFET/Diode devices (2 parallel 20A MOSFET/10A Diode co-packs). The UPS efficiency is compared with two different sets of devices, at different loading and gate driving conditions. SiC MOSFETs significantly improve the efficiency of the UPS at light load conditions. The experimental results are presented at 20kHz switching frequency. C2 - 2010/// C3 - IECON Proceedings (Industrial Electronics Conference) DA - 2010/// DO - 10.1109/IECON.2010.5675125 SP - 2657-2662 PB - IEEE UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78751483327&partnerID=MN8TOARS ER - TY - CONF TI - Modeling of the impact of diode junction capacitance on high voltage high frequency rectifiers based on 10kV SiC JBS diodes AU - Du, Y. AU - Wang, G. AU - Wang, J. AU - Bhattacharya, S. AU - Huang, A.Q. AB - There is strong industrial need to boost the power density of the high voltage generators, for example, in medical radiology applications. 10 kV SiC JBS diode is potential candidate to be employed in the high voltage high frequency rectifier in future high voltage generator applications. However, the impact of the relatively large diode junction capacitance of SiC JBS diode cannot be neglected at high frequency and high voltage conditions. An electric circuit model is proposed to describe this effect for full bridge and half bridge high voltage diode rectifiers based on mathematical derivations. The effect of junction capacitance is to decrease the output voltage and to increase the ratio of capacitive reactive power in the circuit, which can be represented by an equivalent shunt capacitor with input source and ideal diode rectifier. The model is validated by simulation results, and can be used for the further design of the high voltage generators. C2 - 2010/// C3 - 2010 IEEE Energy Conversion Congress and Exposition, ECCE 2010 - Proceedings DA - 2010/// DO - 10.1109/ECCE.2010.5618065 SP - 105-111 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78650087880&partnerID=MN8TOARS ER - TY - CONF TI - Identifying techniques, topologies and features for maximizing the efficiency of a distribution grid with solid state power devices AU - Stefanski, K. AU - Qin, H. AU - Chowdhury, B.H. AU - Kimball, J.W. AU - Bhattacharya, S. AB - The FREEDM grid utilizes solid state transformers (SST) and solid state fault interruption devices (FID) which may lead to unfavorable operating losses as compared to a conventional grid. Various SST topologies and switching techniques are identified for minimizing losses and a performance evaluation is made to determine the efficiency of the FREEDM distribution network to improve the overall efficiency. Losses include conductors, SSTs, FIDs, and conventional distribution transformers tested under various loading levels. Compared to a conventional distribution network, the FREEDM grid has a slight reduction in losses. By choosing the proper distribution line configuration, conductor type, switching devices and switching techniques, the power losses on the system may be minimized further. C2 - 2010/// C3 - North American Power Symposium 2010, NAPS 2010 DA - 2010/// DO - 10.1109/NAPS.2010.5618966 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78650040405&partnerID=MN8TOARS ER - TY - CONF TI - Instantiation of solid state fault isolation devices for future power electronic based distribution systems AU - Vodyakho, O. AU - Steurer, M. AU - Edrington, C. AU - Karady, G. AU - Bhattacharya, S. AB - This paper addresses the timely issues of modeling of, and defining selection criteria for, a solid state fault isolation device (FID) to be used in power electronic based distribution systems (PEDS). Circuit interruption requirements and FID location in power electronics based distribution system are discussed in this paper. The paper subsequently derives the FID parameters by mapping the characteristics of a conventional medium-voltage distribution system onto that of the PEDS envisioned under a new multi-university Engineering Research Center funded by the National Science Foundation. A design of a high frequency solid state transformer (SST) is presented and evaluated. An average-value simulation model of a SST, as the interface of the PEDS to the legacy system, is used to derive key parameters of the FID. The simulation and experimental results validated the feasibility of the proposed FID topology. Finally, the conceptual Power Hardware-in-the-Loop simulation setup for testing the FID under various system conditions is presented. C2 - 2010/// C3 - IEEE PES General Meeting, PES 2010 DA - 2010/// DO - 10.1109/PES.2010.5590129 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78649617239&partnerID=MN8TOARS ER - TY - CONF TI - Comparison of 10-kV SiC power devices in solid-state transformer AU - Wang, J. AU - Wang, G. AU - Bhattacharya, S. AU - Huang, A.Q. AB - The characteristics and losses of 10-kV SiC MOSFETs, p-IGBTs and emitter turn-off thyristors (ETOs) were compared using the experimental measurements, PSPICE simulations and numerical simulations. Using the extracted loss information and method of loss calculation in the AC/DC rectifier and DC/DC converter, the frequency capability of these 10-kV SiC power devices in a 20 kVA solid-state transformer (SST) was investigated and compared in the same total power loss density of 300 W/cm 2 and junction temperature of 125°C. The comparison shows that 10-kV SiC MOSFETs have the highest switching frequency capability amongst the discussed 10-kV SiC device types in the AC/DC rectifier stage and DC/DC converter stage of the SST. C2 - 2010/// C3 - 2010 IEEE Energy Conversion Congress and Exposition, ECCE 2010 - Proceedings DA - 2010/// DO - 10.1109/ECCE.2010.5617759 SP - 3284-3289 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78650148187&partnerID=MN8TOARS ER - TY - CONF TI - Digital Flickermeter design and implementation based on IEC standard AU - Fregosi, D. AU - White, L.W. AU - Green, E. AU - Watterson, J. AU - Bhattacharya, S. AB - The present work describes the design and implementation of a IEC 61000-4-15 digital Flickermeter on a National Instruments CompactRIO Controller; the Flickermeter is configured for use on 120 VAC, 60 Hz systems. The IEC Flickermeter Standard defines an instrument that quantifies human perception of the magnitude and frequency of voltage change supplied to a gas-filled filament lamp with a single `perceived flicker' value. A physical instrument for use in measuring the level of flicker that might appear in real-world scenarios is described. The instrument is a faithful reproduction of the Flickermeter defined by the IEC Standard. The Flickermeter has been validated by importing calibration points through a file stored in the processor's memory. Additionally, a physical calibrator with the necessary accuracy was implemented on a separate CompactRIO Controller, allowing validation through the use of a physical signal. The digital Flickermeter, as tested, is in full compliance with the IEC 61000-4-15 Standard meeting mandated error rates at all test points. C2 - 2010/// C3 - 2010 IEEE Energy Conversion Congress and Exposition, ECCE 2010 - Proceedings DA - 2010/// DO - 10.1109/ECCE.2010.5618422 SP - 4521-4526 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78650128886&partnerID=MN8TOARS KW - Lighting KW - Measurement KW - Modeling KW - Power Quality KW - Standards ER - TY - CONF TI - Analysis of static voltage balance of series connected self-power emitter turn-off thyristors AU - Chen, Q. AU - Huang, A. AU - Bhattacharya, S. AB - Self-power emitter turn-off thyristor (SPETO) is a high power switching device which could provide power for its gate driver during operation. Self-power function is a major benefit, whereas it brings an issue of large power loss on parallel resistors when two or more SPETOs are in series connection and static voltage balance between them is expected. In this paper, the root reason causing large power loss on parallel resistors is analyzed; a solution that could greatly reduce the power loss is proposed and verified by experimental results. C2 - 2010/// C3 - 2010 IEEE Energy Conversion Congress and Exposition, ECCE 2010 - Proceedings DA - 2010/// DO - 10.1109/ECCE.2010.5618426 SP - 4547-4550 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78650136965&partnerID=MN8TOARS ER - TY - CONF TI - Comparisons of 6.5kV 25A Si IGBT and 10-kV SiC MOSFET in solid-state transformer application AU - Wang, G. AU - Huang, X. AU - Wang, J. AU - Zhao, T. AU - Bhattacharya, S. AU - Huang, A.Q. AB - A 6.5 kV 25 A dual IGBT module is customized and packaged specially for high voltage low current application like solid state transformer and its characteristics and losses have been tested under the low current operation and compared with 10 kV SiC MOSFET. Based on the test results, the switching losses under different frequencies in a 20 kVA Solid-State Transformer (SST) has been calculated for both devices. The result shows 10 kV SiC MOSFET has 7-10 times higher switching frequency capability than 6.5 kV Si IGBT in the SST application. C2 - 2010/// C3 - 2010 IEEE Energy Conversion Congress and Exposition, ECCE 2010 - Proceedings DA - 2010/// DO - 10.1109/ECCE.2010.5618069 SP - 100-104 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78650117900&partnerID=MN8TOARS ER - TY - CONF TI - Design considerations of high voltage and high frequency three phase transformer for Solid State Transformer Application AU - Leung, C.-K. AU - Baek, S. AU - Dutta, S. AU - Bhattacharya, S. AB - The three-phase Solid State Transformer (SST) is one of the key elements in the Future Renewable Electric Energy Delivery and Management (FREEDM) System. The SST consists of an input rectifier, Dual Active Bridge (DAB) bidirectional dc-dc converter and followed by an inverter for ac voltage output. The DAB converter is a bidirectional dc-dc converter using high frequency transformers to step up or down the voltages at high frequency for a reduction in size while maintaining high efficiency and reliability. The single phase high-frequency high-voltage transformer for two-level DAB has been reported by the authors [2]. In this paper, high frequency three-phase transformer for multi-level (3-level) and multi-phase (three-phase) DAB is designed for three-phase multilevel SST. There are two proposed topologies and for each topology the high voltage and high frequency transformer is designed at 3 kHz and 20 kHz. The proposed transformer designs for electromagnetic, thermal and mechanical analysis are validated with the simulation of Finite Element Analysis software. C2 - 2010/// C3 - 2010 IEEE Energy Conversion Congress and Exposition, ECCE 2010 - Proceedings DA - 2010/// DO - 10.1109/ECCE.2010.5618234 SP - 1551-1558 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78650099327&partnerID=MN8TOARS ER - TY - CONF TI - Advanced lithium ion battery modeling and power stage integration technique AU - Ramamurthy, A. AU - Notani, S. AU - Bhattacharya, S. AB - This paper focuses on the system modeling aspect of energy storage, power conversion and digital power control involved in non-renewable power systems. Lithium based batteries, the energy storage devices were modeled at different state of charges (SOC) using Electro chemical Impedance Spectroscopy (EIS). EIS based impedance measurements were fitted to a standard electrochemical battery model. The AC impedance model of the battery was integrated to the power supply control loop. The battery impedance changes with SOC of the battery and its effect on the control loop was observed. Based on the battery impedance based control loop performance, a dynamic compensation technique was proposed to optimally stabilize different control loops in the battery charging cycle. The system model and design aspects were verified using a synchronous buck based charging system. C2 - 2010/// C3 - 2010 IEEE Energy Conversion Congress and Exposition, ECCE 2010 - Proceedings DA - 2010/// DO - 10.1109/ECCE.2010.5618249 SP - 1485-1492 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78650151456&partnerID=MN8TOARS KW - Lithium Batteries KW - EIS KW - Battery model KW - Control Loop ER - TY - CONF TI - A medium-voltage DC (MVDC) with series active injection for shipboard power system applications AU - Mirzaee, H. AU - Dutta, S. AU - Bhattacharya, S. AB - Modern electric ships utilize a medium-voltage zonal dc distribution system to meet the ever increasing power demand while keeping the power density as low as possible. Power electronics building blocks (PEBBs) composed of different DC/AC and DC/DC converters are used to convert the main DC bus voltage to appropriate dc and ac voltage levels suited for the loads in such a system. Due to the fact that most of these power electronic converters present a constant power load (CPL) with negative incremental impedance at the input terminal, the interaction of these converters under different system configurations with the main AC-DC rectifier of the MVDC system might induce voltage oscillations on the main DC-bus. In this paper, a novel method of series active injection on the dc-side is proposed to smooth out disturbances on the main DC-bus. This has resulted in much smoother DC-bus voltage enabling the system to use less amount of passive storage elements on dc-side which is very beneficial to ship's limited onboard space. The simulation results presented verify the operation and functionality of the proposed system. C2 - 2010/// C3 - 2010 IEEE Energy Conversion Congress and Exposition, ECCE 2010 - Proceedings DA - 2010/// DO - 10.1109/ECCE.2010.5618184 SP - 2865-2870 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78650154309&partnerID=MN8TOARS KW - Medium-voltage DC (MVDC) KW - Series Active Injection KW - Shipboard Power System KW - Power Electronic Building Blocks (PEBB) KW - Constant Power Loads (CPL) ER - TY - CONF TI - A simplified space vector based current controller for any general N-level converter AU - Li, J. AU - Zhou, X. AU - Liang, Z. AU - Bhattacharya, S. AU - Huang, A.Q. AB - This paper proposes a simplified current controller for any general N-level converter based on space vector (SV) theory. Through the presented mapping technique between the subhexagon of the N-level converter and the hexagon of the two-level converter, the proper output voltage vector of the N-level converter can be identified to suppress harmonic current content in steady state and attain fast current response in transient state. Meanwhile, the redundant switching states of the voltage vectors can be used to reduce or balance the device power losses, and regulate floating capacitor voltages. The controller complexity is greatly reduced due to the use of very simple lookup tables, thus it can be easily extended to any general N-level converter. The proposed scheme is explained for a five-level active NPC converter and the simulation results are presented to prove its correctness. C2 - 2010/// C3 - 2010 IEEE Energy Conversion Congress and Exposition, ECCE 2010 - Proceedings DA - 2010/// DO - 10.1109/ECCE.2010.5618277 SP - 2156-2163 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78650165482&partnerID=MN8TOARS ER - TY - JOUR TI - Guest Editorial Special Issue on Light-Emitting Diodes AU - Kumar, M.J. AU - Lunardi, L. AU - Meneghesso, G. AU - Pearton, S.J. AU - Schubert, E.F. T2 - IEEE Transactions on Electron Devices AB - There are eight invited papers and 12 contributed papers in this special issue on light-emitting diodes. DA - 2010/1// PY - 2010/1// DO - 10.1109/ted.2009.2035570 VL - 57 IS - 1 SP - 7-11 UR - http://dx.doi.org/10.1109/ted.2009.2035570 ER - TY - CONF TI - Improving privacy and lifetime of PCM-based main memory AU - Kong, Jingfei AU - Zhou, Huiyang T2 - Networks (DSN) AB - Phase change memory (PCM) is a promising technology for computer memory systems. However, the non-volatile nature of PCM poses serious threats to computer privacy. The low programming endurance of PCM devices also limits the lifetime of PCM-based main memory (PRAM). In this paper, we first adopt counter-mode encryption for privacy protection and show that encryption significantly reduces the effectiveness of some previously proposed wear-leveling techniques for PRAM. To mitigate such adverse impact, we propose simple, yet effective extensions to the encryption scheme. In addition, we propose to reuse the encryption counters as age counters and to dynamically adjust the strength of error correction code (ECC) to extend the lifetime of PRAM. Our experiments show that our mechanisms effectively achieve privacy protection and lifetime extension for PRAM with very low performance overhead. C2 - 2010/6// C3 - 2010 IEEE/IFIP International Conference on Dependable Systems & Networks (DSN) DA - 2010/6// DO - 10.1109/dsn.2010.5544298 PB - IEEE SN - 9781424475001 UR - http://dx.doi.org/10.1109/dsn.2010.5544298 DB - Crossref ER - TY - JOUR TI - VOC GAS LEAK DETECTION USING PYRO-ELECTRIC INFRARED SENSORS AU - Erden, Fatih AU - Soyer, E. Birey AU - Toreyin, B. Ugur AU - Cetin, A. Enis AU - IEEE T2 - 2010 Ieee International Conference on Acoustics, Speech, and Signal Processing AB - In this paper, we propose a novel method for detecting and monitoring Volatile Organic Compounds (VOC) gas leaks by using a Pyro-electric (or Passive) Infrared (PIR) sensor whose spectral range intersects with the absorption bands of VOC gases. A continuous time analog signal is obtained from the PIR sensor. This signal is discretized and analyzed in real time. Feature parameters are extracted in wavelet domain and classified using a Markov Model (MM) based classifier. Experimental results are presented. DA - 2010/// PY - 2010/// DO - 10.1109/ICASSP.2010.5495500 SP - 1682-1685 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000287096001167&KeyUID=WOS:000287096001167 KW - VOC gas leak detection KW - pyro-electric infrared (PIR) sensor KW - wavelet transform KW - Markov Models ER - TY - CONF TI - EXACT: Explicit Dynamic-Branch Prediction with Active Updates AU - Al-Otoom, Muawya AU - Forbes, Elliott AU - Rotenberg, Eric T2 - the 7th ACM international conference AB - Branches that depend directly or indirectly on load instructions are a leading cause of mispredictions by state-of-the-art branch predictors. For a branch of this type, there is a unique dynamic instance of the branch for each unique combination of producer-load addresses. Based on this definition, a study of mispredictions reveals two related problems: C2 - 2010/// C3 - Proceedings of the 7th ACM international conference on Computing frontiers - CF '10 DA - 2010/// DO - 10.1145/1787275.1787321 SP - 165–176 PB - ACM Press SN - 9781450300445 UR - http://dx.doi.org/10.1145/1787275.1787321 KW - branch prediction KW - superscalar processors KW - microarchitecture ER - TY - JOUR TI - A Numerical Study of the Bottom-Up and Top-Down Inference Processes in And-Or Graphs AU - Wu, Tianfu AU - Zhu, Song-Chun T2 - International Journal of Computer Vision AB - This paper presents a numerical study of the bottom-up and top-down inference processes in hierarchical models using the And-Or graph as an example. Three inference processes are identified for each node A in a recursively defined And-Or graph in which stochastic context sensitive image grammar is embedded: the α(A) process detects node A directly based on image features, the β(A) process computes node A by binding its child node(s) bottom-up and the γ(A) process predicts node A top-down from its parent node(s). All the three processes contribute to computing node A from images in complementary ways. The objective of our numerical study is to explore how much information each process contributes and how these processes should be integrated to improve performance. We study them in the task of object parsing using And-Or graph formulated under the Bayesian framework. Firstly, we isolate and train the α(A), β(A) and γ(A) processes separately by blocking the other two processes. Then, information contributions of each process are evaluated individually based on their discriminative power, compared with their respective human performance. Secondly, we integrate the three processes explicitly for robust inference to improve performance and propose a greedy pursuit algorithm for object parsing. In experiments, we choose two hierarchical case studies: one is junctions and rectangles in low-to-middle-level vision and the other is human faces in high-level vision. We observe that (i) the effectiveness of the α(A), β(A) and γ(A) processes depends on the scale and occlusion conditions, (ii) the α(face) process is stronger than the α processes of facial components, while β(junctions) and β(rectangle) work much better than their α processes, and (iii) the integration of the three processes improves performance in ROC comparisons. DA - 2010/5/7/ PY - 2010/5/7/ DO - 10.1007/s11263-010-0346-6 VL - 93 IS - 2 SP - 226-252 J2 - Int J Comput Vis LA - en OP - SN - 0920-5691 1573-1405 UR - http://dx.doi.org/10.1007/s11263-010-0346-6 DB - Crossref KW - Bottom-up/Top-down inference KW - a-beta-gamma process KW - Information contribution KW - Hierarchical model KW - And-Or graph KW - Object parsing ER - TY - JOUR TI - Statistical Feature Selection From Massive Data in Distribution Fault Diagnosis AU - Cai, Yixin AU - Chow, Mo-Yuen AU - Lu, Wenbin AU - Li, Lexin T2 - IEEE Transactions on Power Systems AB - Selecting proper features to identify the root cause is a critical step in distribution fault diagnosis. Power engineers usually select features based on experience. However, engineers cannot be familiar with every local system, especially in fast growing regions. With the advancing information technologies and more powerful sensors, utilities can collect much more data on their systems than before. The phenomenon will be even more substantial for the anticipating Smart Grid environments. To help power engineers select features based on the massive data collected, this paper reviews two popular feature selection methods: 1) hypothesis test, 2) stepwise regression, and introduces another two: 3) stepwise selection by Akaike's Information Criterion, and 4) LASSO/ALASSO. These four methods are compared in terms of their model requirements, data assumptions, and computational cost. With real-world datasets from Progress Energy Carolinas, this paper also evaluates these methods and compares fault diagnosis performance by accuracy, probability of detection and false alarm ratio. This paper discusses the advantages and limitations of each method for distribution fault diagnosis as well. DA - 2010/5// PY - 2010/5// DO - 10.1109/tpwrs.2009.2036924 VL - 25 IS - 2 SP - 642-648 J2 - IEEE Trans. Power Syst. OP - SN - 0885-8950 1558-0679 UR - http://dx.doi.org/10.1109/tpwrs.2009.2036924 DB - Crossref KW - Akaike's information criteria KW - classification KW - fault cause identification KW - feature selection KW - hypothesis test KW - LASSO KW - logistic regression KW - power distribution systems KW - smart grid KW - stepwise regression ER - TY - RPRT TI - THE WIDE-AREA ENERGY STORAGE AND MANAGEMENT SYSTEM PHASE II Final Report - Flywheel Field Tests AU - Lu, Ning AU - Makarov, Yuri V. AU - Weimar, Mark R. AU - Rudolph, Frank AU - Murthy, Shashikala AU - Arseneaux, Jim AU - Loutan, Clyde AU - Chowdhury, S. A3 - Office of Scientific and Technical Information (OSTI) AB - This research was conducted by Pacific Northwest National Laboratory (PNNL) operated for the U.S. department of Energy (DOE) by Battelle Memorial Institute for Bonneville Power Administration (BPA), California Institute for Energy and Environment (CIEE) and California Energy Commission (CEC). A wide-area energy management system (WAEMS) is a centralized control system that operates energy storage devices (ESDs) located in different places to provide energy and ancillary services that can be shared among balancing authorities (BAs). The goal of this research is to conduct flywheel field tests, investigate the technical characteristics and economics of combined hydro-flywheel regulation services that can be shared between Bonneville Power Administration (BPA) and California Independent System Operator (CAISO) controlled areas. This report is the second interim technical report for Phase II of the WAEMS project. This report presents: 1) the methodology of sharing regulation service between balancing authorities, 2) the algorithm to allocate the regulation signal between the flywheel and hydro power plant to minimize the wear-and-tear of the hydro power plants, 3) field results of the hydro-flywheel regulation service (conducted by the Beacon Power), and 4) the performance metrics and economic analysis of the combined hydro-flywheel regulation service. DA - 2010/8/31/ PY - 2010/8/31/ DO - 10.2172/991592 PB - Office of Scientific and Technical Information (OSTI) UR - http://dx.doi.org/10.2172/991592 DB - Crossref ER - TY - RPRT TI - The Wide-area Energy Management System Phase 2 Final Report AU - Lu, Ning AU - Makarov, Yuri V. AU - Weimar, Mark R. A3 - Office of Scientific and Technical Information (OSTI) AB - The higher penetration of intermittent generation resources (including wind and solar generation) in the Bonneville Power Administration (BPA) and California Independent System Operator (CAISO) balancing authorities (BAs) raises issue of requiring expensive additional fast grid balancing services in response to additional intermittency and fast up and down power ramps in the electric supply system. The overall goal of the wide-area energy management system (WAEMS) project is to develop the principles, algorithms, market integration rules, a functional design, and a technical specification for an energy storage system to help cope with unexpected rapid changes in renewable generation power output. The resulting system will store excess energy, control dispatchable load and distributed generation, and utilize inter-area exchange of the excess energy between the California ISO and Bonneville Power Administration control areas. A further goal is to provide a cost-benefit analysis and develop a business model for an investment-based practical deployment of such a system. There are two tasks in Phase 2 of the WAEMS project: the flywheel field tests and the battery evaluation. Two final reports, the Wide-area Energy Management System Phase 2 Flywheel Field Tests Final Report and the Wide-area Energy Storage and Management System Battery Storage Evaluation, were written to summarize the results of the two tasks. DA - 2010/8/31/ PY - 2010/8/31/ DO - 10.2172/1000162 PB - Office of Scientific and Technical Information (OSTI) UR - http://dx.doi.org/10.2172/1000162 DB - Crossref ER - TY - CHAP TI - Unit Commitment Considering Generation Flexibility and Environmental Constraints AU - Lu, Shuai AU - Makarov, Yuri V. AU - Zhu, Yunhua AU - Lu, Ning AU - Kumar, Nirupama Prakash AU - Chakrabarti, Bhujanga B. AU - Ieee T2 - Ieee Power and Energy Society General Meeting 2010 PY - 2010/// SP - PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000287611905101&KeyUID=WOS:000287611905101 ER - TY - JOUR TI - Smart-Grid Security Issues AU - Khurana, Himanshu AU - Hadley, Mark AU - Lu, Ning AU - Frincke, Deborah A. T2 - Ieee Security & Privacy AB - This article has given a broadbrush description of issues related to smart-grid security. Designing solutions in at this stage, before widespread deployment, would be beneficial; in some cases solutions exist, whereas in others research investments will be needed. Several open questions about goals still require discussion, especially around such topics as how (and how much) privacy can be supported. DA - 2010/// PY - 2010/// DO - 10.1109/msp.2010.49 VL - 8 IS - 1 SP - 81-85 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000274527500016&KeyUID=WOS:000274527500016 ER - TY - JOUR TI - Climate Change Impacts on Residential and Commercial Loads in the Western US Grid AU - Lu, Ning AU - Taylor, Todd AU - Jiang, Wei AU - Jin, Chunlian AU - Correia, James, Jr. AU - Leung, L. Ruby AU - Wong, Pak Chung T2 - Ieee Transactions on Power Systems AB - This paper presents a multidisciplinary modeling approach to quickly quantify climate change impacts on energy consumption, peak load, and load composition of residential and commercial buildings. This research focuses on addressing the impact of temperature changes on the building cooling load in ten major cities across the Western United States and Canada. Our results have shown that by the mid-century, building yearly energy consumption and peak load will increase in the Southwest. Moreover, the peak load months will spread out to not only the summer months but also spring and autumn months. The Pacific Northwest will experience more hot days in the summer months. The penetration levels of air-conditioning (a/c) systems in this region are likely to increase significantly over the years. As a result, some locations in the Pacific Northwest may be shifted from winter peaking to summer peaking. Overall, the Western U.S. grid may see more simultaneous peaks across the North and South in summer months. Increased cooling load will result in a significant increase in the motor load, which consumes more reactive power and requires stronger voltage support from the grid. This study suggests an increasing need for the industry to implement new technology to increase the efficiency of temperature-sensitive loads and apply proper protection and control to prevent possible adverse impacts of a/c motor loads. DA - 2010/// PY - 2010/// DO - 10.1109/tpwrs.2009.2030387 VL - 25 IS - 1 SP - 480-488 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000273930800050&KeyUID=WOS:000273930800050 KW - Climate change KW - commercial load KW - fault-induced delayed voltage recovery KW - load composition KW - load modeling KW - power system stability KW - residential load KW - temperature sensitivity ER - TY - CHAP TI - An Evaluation of the Flywheel Potential for Providing Regulation Service in California AU - Lu, N. AU - Weimar, M. R. AU - Makarov, Y. V. AU - Rudolph, F. J. AU - Murthy, S. N. AU - Arseneaux, J. AU - Loutan, C. AU - Ieee T2 - Ieee Power and Energy Society General Meeting 2010 PY - 2010/// SP - PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000287611901134&KeyUID=WOS:000287611901134 ER - TY - CONF TI - Packaging of large and low-pitch size 2D ultrasonic transducer arrays AU - Lin, Der-Song AU - Zhuang, Xuefeng AU - Wodnicki, Robert AU - Woychik, Charles. G. AU - Kupnik, Mario AU - Oralkan, Ö AU - Khuri-Yakub, Butrus T. T2 - 23rd IEEE International Conference on Micro Electro Mechanical Systems (MEMS 2010) AB - The successful packaging and electronics integration of large 2D array devices with small pitch-sizes, such as fully populated 2D ultrasonic transducer arrays, require a flexible, simple, and reliable integration approach. One example for such electronics integration is based on through silicon vias (TSVs) with under-bump metallization (UBM) stack for solder bumping. In this paper, we demonstrate such an approach by successfully integrating a fully populated 2D ultrasonic transducer array. Our integration is based on a previously reported TSV technology (trench-frame technology), based on trench-isolated interconnects with supporting frame. We successfully combined the trench-frame technology with a simple UBM preparation technique - electro plating or chemical plating techniques with passivation layers for UBM pad definition are not required. Our results show high shear strength (26.5 g) of the UBM, which is essential for successful flip-chip bonding. The yield of the interconnections is 100% with excellent solder-ball-height uniformity (¿ = 0.9 ¿m). As demonstrated in this paper, this allows for a large-scale assembly of a tiled array by using an interposer. A design guideline for finer element-pitch design was developed suggesting that fusion bonding strength and the length of pillars are the main design parameters. C2 - 2010/1// C3 - Proceedings of the 2010 IEEE 23rd International Conference on Micro Electro Mechanical Systems (MEMS) DA - 2010/1// DO - 10.1109/memsys.2010.5442455 SP - 508–511 PB - IEEE SN - 9781424457618 9781424457649 UR - http://dx.doi.org/10.1109/memsys.2010.5442455 ER - TY - CONF TI - Thermal Investigatoin of Tier Swapping to Improve the Thermal Profile of Memory-on-Logic 3DICs AU - Melamed, S. AU - Thorolfsson, T. AU - Srinivasan, A. AU - Cheng, E. AU - Franozn, P. AU - Davis, W. C2 - 2010/// C3 - IEEE THERMINIC DA - 2010/// SP - 1–6 ER - TY - CONF TI - The NCSU Tezzaron design kit AU - Lipa, S. AU - Thorolfsson, T. AU - Franzon, P. T2 - 2010 IEEE International 3D Systems Integration Conference (3DIC) AB - A collection of slides from the authors' conference is given. Topics include NCSU design kit user guide, Verilog memory model, and lessons learned in assembling the reticle. C2 - 2010/// C3 - 2010 IEEE International 3D Systems Integration Conference (3DIC) DA - 2010/// DO - 10.1109/3dic.2010.5751418 SP - 1–15 PB - IEEE SN - 9781457705267 UR - http://dx.doi.org/10.1109/3dic.2010.5751418 ER - TY - CONF TI - Creating 3D specific systems: Architecture, design and CAD AU - Franzon, Paul D AU - Davis, W Rhett AU - Thorolffson, Thor T2 - 2010 Design, Automation & Test in Europe Conference & Exhibition (DATE 2010) AB - 3D stacking and integration can provide system advantages. Following a brief technology review, this abstract explores application drivers, design and CAD for 3D ICs. The main application area explored in detail is that of logic on memory. This application is explored in a specific DSP example. Finally critical areas that need better solutions are explored. These include design planning, test management, and thermal management. C2 - 2010/3// C3 - 2010 Design, Automation & Test in Europe Conference & Exhibition (DATE 2010) CY - Dresden, Germany DA - 2010/3// PY - 2010/3/8/ DO - 10.1109/date.2010.5457086 SP - 1684-1688 PB - IEEE SN - 9783981080162 9781424470549 9783981080162 UR - http://dx.doi.org/10.1109/date.2010.5457086 DB - Crossref ER - TY - CONF TI - A zero power consumption Multi-Capacitor structure for voltage summing in high-speed FFE AU - Su, Bruce AU - Pitts, W. Shepherd AU - Franzon, Paul D. AU - Wilson, John T2 - 2010 IEEE 19th Conference on Electrical Performance of Electronic Packaging and Systems (EPEPS) AB - Conventional current-mode summation utilized in feed-forward equalization (FFE) has disadvantages in power consumption and linearity and thus becomes less attractive when high-speed low-power equalization is required. A Multi-Capacitor (MultiCap) structure is presented to overcome these disadvantages by supporting voltage-mode summation. This passive structure replaces the current-summation block of the transmit FFE and has zero power consumption. A set of equations are derived to estimate the useable value of the MultiCap, of which the range is bounded by I/O pitch, receiver sensitivity, and other parameters. The parasitics of this device are proven to be negligible. Simulation in 0.13μm standard CMOS process shows that the MultiCap structure could enable a power saving of more than 90% over the conventional current-mode FFE. C2 - 2010/10// C3 - 19th Topical Meeting on Electrical Performance of Electronic Packaging and Systems DA - 2010/10// DO - 10.1109/epeps.2010.5642532 PB - IEEE SN - 9781424468652 UR - http://dx.doi.org/10.1109/epeps.2010.5642532 DB - Crossref ER - TY - CONF TI - Logic-on-logic 3D integration and placement AU - Thorolfsson, Thorlindur AU - Luo, Guojie AU - Cong, Jason AU - Franzon, Paul D. T2 - 2010 IEEE International 3D Systems Integration Conference (3DIC) AB - In this paper we describe three 3D standard cell placement algorithms, which are: “3D Placement using Sequential Off-the-Shelf 2D Placement Tools”, “True-3D Analytical Placement with mPL” and “3D Placement using Simultaneous 2D Placements with mPL”. We use these algorithms to place three case studies in a real face-to-face 3D integration process. The three case studies are a 2 point FFT butterfly processing element (PE), an Advanced Encryption Standard encryption block (AES) and a multiple-input and multiple-output wireless decoder (MIMO). The placements are then fully routed and compared to 2D placements in terms of performance and power consumption. Using this methodology we show that using 3D face-to-face integration with microbumps in conjunction with the three placement algorithms we can improve the maximum clock speed of AES module by 15.3% and the PE by 22.6%, while reducing the power of the AES module and the PE by 2.6% and 12.9% respectively. C2 - 2010/11// C3 - 2010 IEEE International 3D Systems Integration Conference (3DIC) DA - 2010/11// DO - 10.1109/3dic.2010.5751451 PB - IEEE SN - 9781457705267 UR - http://dx.doi.org/10.1109/3dic.2010.5751451 DB - Crossref ER - TY - CONF TI - Thermal isolation in 3D chip stacks using vacuum gaps and capacitive or inductive communications AU - Franzon, Paul AU - Wilson, John AU - Li, Ming T2 - 2010 IEEE International 3D Systems Integration Conference (3DIC) AB - In a 3D chip stack, it is important to thermally isolate any DRAMs from high power processors, so that the former can operate at low junction temperatures. One way to do this is to use the combination of a vacuum gap, formed using standard semiconductor processing, together with capacitive or inductive signaling across the gap. Simulation shows that the DRAM can operate at a temperature 47°C cooler than the CPU. C2 - 2010/11// C3 - 2010 IEEE International 3D Systems Integration Conference (3DIC) DA - 2010/11// DO - 10.1109/3dic.2010.5751431 PB - IEEE SN - 9781457705267 9781457705274 UR - http://dx.doi.org/10.1109/3dic.2010.5751431 DB - Crossref ER - TY - CONF TI - Miniaturized ultrasound imaging probes enabled by CMUT arrays with integrated frontend electronic circuits AU - Khuri-Yakub, B T AU - Oralkan, Ömer AU - Nikoozadeh, A AU - Wygant, I O AU - Zhuang, S AU - Gencel, M AU - Choe, Jung Woo AU - Stephens, D N AU - de la Rama, A AU - Chen, P AU - Lin, Feng AU - Dentinger, A AU - Wildes, D AU - Thomenius, K AU - Shivkumar, K AU - Mahajan, A AU - Seo, Chi Hyung AU - O'Donnell, M AU - Truong, Uyen AU - Sahn, D J T2 - 2010 32nd Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC 2010) AB - Capacitive micromachined ultrasonic transducer (CMUT) arrays are conveniently integrated with frontend integrated circuits either monolithically or in a hybrid multichip form. This integration helps with reducing the number of active data processing channels for 2D arrays. This approach also preserves the signal integrity for arrays with small elements. Therefore CMUT arrays integrated with electronic circuits are most suitable to implement miniaturized probes required for many intravascular, intracardiac, and endoscopic applications. This paper presents examples of miniaturized CMUT probes utilizing 1D, 2D, and ring arrays with integrated electronics. C2 - 2010/8// C3 - 2010 Annual International Conference of the IEEE Engineering in Medicine and Biology DA - 2010/8// DO - 10.1109/iembs.2010.5627580 PB - IEEE SN - 9781424441235 9781424441242 UR - http://dx.doi.org/10.1109/iembs.2010.5627580 DB - Crossref ER - TY - CONF TI - Simulating capacitive micromachined ultrasonic transducers (CMUTs) using field II AU - Baek, David AU - Oralkan, Omer AU - Kupnik, Mario AU - Willatzen, Morten AU - Khuri-Yakub, Butrus T. AU - Jensen, Jorgen Arendt T2 - 2010 International Ultrasonics Symposium AB - Field II has been a recognized simulation tool for piezoceramic medical transducer arrays for more than a decade. The program has its strength in doing fast computations of the spatial impulse response (SIR) from array elements by dividing the elements into smaller mathematical elements (ME)s from which it calculates the SIR responses. The program features predefined models for classical transducer geometries, but currently none for the fast advancing CMUTs. This work addresses the assumptions required for modeling CMUTs with Field II. It is shown that rectangular array elements, populated with cells, can be well approximated by neglecting the cells. Further, it is demonstrated that scaling of the SIR translates into better computational efficiency. C2 - 2010/10// C3 - 2010 IEEE International Ultrasonics Symposium DA - 2010/10// DO - 10.1109/ultsym.2010.5935580 PB - IEEE SN - 9781457703829 9781457703812 UR - http://dx.doi.org/10.1109/ultsym.2010.5935580 DB - Crossref ER - TY - CONF TI - Monitoring radiofrequency catheter ablation using thermal strain imaging AU - Seo, Chi Hyung AU - Stephens, Douglas AU - Cannata, Jonathan AU - Dentinger, Aaron AU - Lin, Feng AU - Park, Suhyun AU - Wildes, Douglas AU - Thomenius, Kai AU - Chen, Peter AU - Nguyen, Tho AU - Delarama, Alan AU - Jeong, Jong Seob AU - Mahajan, Aman AU - Shivkumar, Kalyanam AU - Oralkan, Omer AU - Sahn, David AU - Khuri-Yakub, Pierre AU - O'Donnell, Matthew T2 - 2010 IEEE Ultrasonics Symposium (IUS) AB - A method to monitor ablative therapy by examining slope changes in the thermal strain curve caused by speed of sound with temperature is introduced. The variation of sound speed with temperature rise for most soft tissue follows a similar pattern to that of water. Unlike most liquids, the sound speed of tissue increases with temperature. However, at temperatures above about 50°C, there is no further increase in the sound speed and the temperature coefficient may become slightly negative. For ablation therapy, an irreversible injury to tissue and a complete heart block occurs in the range of 48-50°C for a short period in accordance with the well known Arrhenius equation. Using these two properties, we propose a potential tool to detect the moment when tissue damage occurs using the reduced slope in the thermal strain curve as a function of heating time. Using a prototype intracardiac echocardiography (ICE) array for imaging and a catheter for RF ablation, we were able to observe an obvious slope change in the thermal strain curve in an excised tissue sample. The method was further tested in-vivo, using a specially equipped ablation tip and an 11 MHz microlinear (ML) ICE array mounted on the tip of a catheter. As with in-vitro experiments, the thermal strain curve showed a plateau and a change in the sign of the slope. C2 - 2010/10// C3 - 2010 IEEE International Ultrasonics Symposium DA - 2010/10// DO - 10.1109/ultsym.2010.5935567 PB - IEEE SN - 9781457703829 UR - http://dx.doi.org/10.1109/ultsym.2010.5935567 DB - Crossref ER - TY - CONF TI - Design optimization for a 2-D sparse transducer array for 3-D ultrasound imaging AU - Choe, Jung Woo AU - Oralkan, Omer AU - Khuri-Yakub, Pierre T. T2 - 2010 IEEE Ultrasonics Symposium (IUS) AB - In 3-D ultrasound imaging where 2-D transducer arrays with more than hundreds of elements are used, sparse arrays can be used to reduce the number of active ultrasound channels. Under a restriction of desired number of active channels, we can maximize the image quality by optimally choosing the positions of active elements. Here we use the method of simulated annealing to find the optimal configuration of a 2-D sparse array. This algorithm tries to minimize the value of an objective function defined as the energy ratio between the nonfocal and focal regions in the point spread function (PSF). Optimal configurations were found for the cases of choosing 16, 20, 24, 28, and 32 transmit and receive elements from a 16×16-element rectangular transducer array. With only 32 transmit and 32 receive elements, we could achieve an energy ratio of 16%, compared to 6% of the full array, which is the gold standard utilizing all the 256 elements for both transmit and receive. Using Field II, we simulated imaging with the optimal sparse arrays, for off-axis targets as well as on-axis targets, and the resulting images were compared with those from some other configurations, such as full-transmit full-receive, full-transmit x-receive, x-transmit boundary-receive, and so on. C2 - 2010/10// C3 - 2010 IEEE International Ultrasonics Symposium DA - 2010/10// DO - 10.1109/ultsym.2010.5935854 PB - IEEE SN - 9781457703829 UR - http://dx.doi.org/10.1109/ultsym.2010.5935854 DB - Crossref ER - TY - CONF TI - 3-D Deep penetration photoacoustic imaging with a 2-D CMUT array AU - Ma, Te-Jen AU - Kothapalli, Sri Rajasekhar AU - Vaithilingam, Srikant AU - Oralkan, Omer AU - Kamaya, Aya AU - Wygant, Ira O. AU - Zhuang, Xuefeng AU - Gambhir, Sanjiv S. AU - Jeffrey, R. Brooke AU - Khuri-Yakub, Butrus T. AU - al. T2 - 2010 IEEE Ultrasonics Symposium (IUS) AB - In this work, we demonstrate 3-D photoacoustic imaging of optically absorbing targets embedded as deep as 5 cm inside a highly scattering background medium using a 2-D capacitive micromachined ultrasonic transducer (CMUT) array with a center frequency of 5.5 MHz. 3-D volumetric images and 2-D maximum intensity projection images are presented to show the objects imaged at different depths. Due to the close proximity of the CMUT to the integrated frontend circuits, the CMUT array imaging system has a low noise floor. This makes the CMUT a promising technology for deep tissue photoacoustic imaging. C2 - 2010/10// C3 - 2010 IEEE International Ultrasonics Symposium DA - 2010/10// DO - 10.1109/ultsym.2010.5935647 PB - IEEE SN - 9781457703829 UR - http://dx.doi.org/10.1109/ultsym.2010.5935647 DB - Crossref ER - TY - CONF TI - Forward-looking intracardiac imaging catheters using fully integrated CMUT arrays AU - Nikoozadeh, Amin AU - Oralkan, Omer AU - Gencel, Mustafa AU - Choe, Jung Woo AU - Stephens, Douglas N. AU - de la Rama, Alan AU - Chen, Peter AU - Lin, Feng AU - Dentinger, Aaron AU - Wildes, Douglas AU - Thomenius, Kai AU - Shivkumar, Kalyanam AU - Mahajan, Aman AU - Seo, Chi Hyung AU - O'Donnell, Matthew AU - Truong, Uyen AU - Sahn, David J. AU - Khuri-Yakub, Pierre T. T2 - 2010 IEEE Ultrasonics Symposium (IUS) AB - Atrial fibrillation, the most common type of cardiac arrhythmia, now affects more than 2.2 million adults in the US alone. Currently, electrophysiological interventions are performed under fluoroscopy guidance, which besides its harmful ionizing radiation does not provide adequate soft-tissue resolution. Intracardiac echocardiography (ICE) provides realtime anatomical information that has proven valuable in reducing the fluoroscopy time and enhancing procedural success. We developed two types of forward-looking ICE catheters using capacitive micromachined ultrasonic transducer (CMUT) technology: MicroLinear (ML) and ring catheters. The ML catheter enables real-time forward-looking 2-D imaging using a 24-element 1-D CMUT phased-array that is designed for a center frequency of 10 MHz. The ring catheter uses a 64-element ring CMUT array that is also designed for a center frequency of 10 MHz. However, this ring-shaped 2-D array enables real-time forward-looking volumetric imaging. In addition, this catheter provides a continuous central lumen that enables convenient delivery of other devices such as RF ablation catheter, EP diagnostic catheter, biopsy devices, etc. Both catheters are equipped with custom front-end IC's that are integrated with the CMUT arrays at the tip of the catheters. The integration of the IC's with the CMUT arrays was accomplished using custom flexible PCB's. We also developed several image reconstruction schemes for the ring catheter on a PC-based imaging platform from VeraSonics. We performed a variety of bench-top characterizations to validate the functionality and performance of our fully integrated CMUT arrays. Using both catheters, we demonstrated in vivo images of the heart in a porcine animal model. We have successfully prototyped the first CMUT-based ICE catheters and proven the capabilities of the CMUT technology for implementing high-frequency miniature transducer arrays with integrated electronics. C2 - 2010/10// C3 - 2010 IEEE International Ultrasonics Symposium DA - 2010/10// DO - 10.1109/ultsym.2010.5935817 PB - IEEE SN - 9781457703829 UR - http://dx.doi.org/10.1109/ultsym.2010.5935817 DB - Crossref ER - TY - CONF TI - Ultrasound compatible RF ablation electrode design for catheter based guidance of RF ablation — In vivo results with thermal strain imaging AU - Stephens, Douglas N. AU - Cannata, Jonathan AU - Seo, Chi Hyung AU - Jeong, Jong-Seob AU - Sun, Enwei AU - Cao, Wenwu AU - Nikoozadeh, Amin AU - Oralkan, Omer AU - de la Rama, Alan AU - Nguyen, Tho AU - Dentinger, Aaron AU - Lin, Feng AU - Park, Suhyun AU - Wildes, Douglas AU - Thomenius, Kai E. AU - Shung, K. K. AU - Shivkumar, Kalyanam AU - Mahajan, Aman AU - Truong, Uyen AU - O'Donnell, Matthew AU - Khuri-Yakub, Pierre AU - Sahn, David J. T2 - 2010 International Ultrasonics Symposium AB - Currently the feedback guidance of intracardiac radiofrequency ablation (RFA) is very limited, offering only a catheter electrode (not tissue) temperature estimation and a means to titrate radiofrequency (RF) power delivery to the tissue. Our "MicroLinear" (ML) forward imaging ultrasound catheter design, now at a true 9F (3mm) in size, has been optimized with several features to simultaneously permit, a) high quality intracardiac steering and imaging, b) tracking of 3D position with electroanatomical mapping, c) RF ablation, and d) tissue thermal strain (TS) estimation for direct tissue temperature feedback. Two types of ML catheters have been built and tested in 3 porcine animal models. The first type, in its third generation, is based on a PZT transducer array; the second type, in its second generation, is based on a CMUT array with custom integrated interface circuitry. Both types of devices are true 9F in size and performed well in imaging tests in recent in vivo studies. Both the ML-PZT and ML-CMUT arrays, as described previously, have a fine pitch (65 and 63 micron respectively) 24 element phased arrays operating at 14 MHz which project a B-mode plane directly out from the tip of the catheter. Intracardiac imaging performance was documented to show that the very small array apertures of the ML design (1.2mm × 1.58mm, and 1.1mm × 1.4mm) permit good, high resolution imaging to depths as great as 4 cm. The ML-PZT catheter was equipped with a special low profile ablation tip which allowed simultaneous imaging and ablation at the distal end of the catheter. TS data were acquired during tissue ablations in right atrium (RA) and right ventricle (RV). The TS data of the RF ablations were processed off line. In vivo use of this new technology has shown for the first time the very substantial potential for a single, low profile catheter to simultaneously image within the heart and perform intracardiac ablation therapy with tissue temperature guidance produced from the incorporation of TS imaging. Work is underway to further assess the temperature estimation accuracy and to integrate the TS processing for real time displays. C2 - 2010/10// C3 - 2010 IEEE International Ultrasonics Symposium DA - 2010/10// DO - 10.1109/ultsym.2010.5935664 PB - IEEE SN - 9781457703812 9781457703829 9781457703805 UR - http://dx.doi.org/10.1109/ultsym.2010.5935664 DB - Crossref ER - TY - CONF TI - Highly sensitive detection of DMMP using a CMUT-based chemical sensor AU - Lee, H J AU - Park, K K AU - Kupnik, M AU - Oralkan, O AU - Khuri-Yakub, B T T2 - 2010 Ninth IEEE Sensors Conference (SENSORS 2010) AB - We present ppt-level detection of dimethyl methylphosphonate (DMMP), a common simulant used in detector calibrations for sarin gas, using a new capacitive micromachined ultrasonic transducer (CMUT) design with a mass sensitivity improved from 130 zg/Hz/μm 2 to 48.8 zg/Hz/μm 2 . A low-noise oscillator using the CMUT as the frequency selective component exhibits an Allan deviation of 0.55 Hz at the presence of air flow. The CMUT resonant sensor was functionalized with a 50-nm thick proprietary polymer layer (Sandia National Laboratory, Albuquerque, NM). Our sensor performance was reliably measured at the MIT Lincoln Laboratory where the accurate delivery of low concentrations of gases was ensured through stringent calibrations. Our sensor response to various concentrations of DMMP in air (10 ppb-1 ppm) showed an excellent volume sensitivity of 30.6 pptv/Hz. Based on the system noise floor, we achieved a mass resolution of 26.9 zg/μm 2 and a limit of detection of 16.8 pptv. In addition, the sensor showed good selectivity to DMMP. C2 - 2010/11// C3 - 2010 IEEE Sensors DA - 2010/11// DO - 10.1109/icsens.2010.5690493 PB - IEEE SN - 9781424481705 UR - http://dx.doi.org/10.1109/icsens.2010.5690493 DB - Crossref ER - TY - CONF TI - Zero-bias resonant sensor with an oxide-nitride layer as charge trap AU - Park, Kwan Kyu AU - Kupnik, Mario AU - Lee, Hyunjoo J AU - Oralkan, O AU - Khuri-Yakub, Butrus T T2 - 2010 Ninth IEEE Sensors Conference (SENSORS 2010) AB - We report on a capacitive resonant sensor with an oxide-nitride (ON) layer used as charge trap. The main idea is that we intentionally inject charges into the ON layer by biasing the device for 30 s with 160% of the pull-in voltage. We use a capacitive micromachined ultrasonic transducer (CMUT) to demonstrate this idea. The CMUT is fabricated via high temperature assisted direct wafer bonding after a local oxidation of silicon (LOCOS) to form evacuated cavities (vacuum gaps), and, thus, the device inherently has the ON layer beneath single crystal silicon plates and vacuum gaps. Therefore, this device is ideal for this work. It allows us to test an elegant charge injection mechanism. By simply pulling in the plate a high electric field strength (~ 8.9 MV/cm) is created in the ON layer for a designated time, which results in charge injection. These charges stay trapped in the ON layer and create an intrinsic electric field in the vacuum gaps, which would otherwise require an external dc bias voltage of 44% of the pull-in voltage. We successfully implemented a 5.3-MHz oscillator with this zero bias resonator and achieved excellent noise performance of 0.06 Hz of Allan deviation. C2 - 2010/11// C3 - 2010 IEEE Sensors DA - 2010/11// DO - 10.1109/icsens.2010.5690742 PB - IEEE SN - 9781424481705 UR - http://dx.doi.org/10.1109/icsens.2010.5690742 DB - Crossref ER - TY - CONF TI - Spectrum Aware Opportunistic Routing in Cognitive Radio Networks AU - Lin, Shih-Chun AU - Chen, Kwang-Cheng T2 - GLOBECOM 2010 - 2010 IEEE Global Communications Conference AB - Cognitive radio (CR) emerges as a key technology to enhance spectrum efficiency and thus creates opportunistic transmissions over links. Supporting the routing function on top of numerous opportunistic links is a must to route packets in a general cognitive radio network (CRN) consisting of multi-radio systems. However, there lacks complete understanding of these highly dynamic available links and a reliable end-to-end transportation mechanism over CRN. Aspiring to meet this need, we propose novel spectrum aware opportunistic routing (SAOR) algorithm suited for the CRN under wireless fading channels. With innovative establishment of the spectrum map from local sensing information and the derivation of the routing metric for opportunistic links known as opportunistic link transmission (OLT), the opportunistic path metrics, and the CR node metrics, the promising SAOR employs a cooperative scheme to enable multi-path transmissions and maintains the statistical QoS guaranteed throughput for practical applications. Numerical results confirm that SAOR enjoys less delay with guaranteed throughput, not only in CRN, but also in general wireless network. C2 - 2010/12// C3 - 2010 IEEE Global Telecommunications Conference GLOBECOM 2010 DA - 2010/12// DO - 10.1109/glocom.2010.5683924 PB - IEEE SN - 9781424456369 UR - http://dx.doi.org/10.1109/glocom.2010.5683924 DB - Crossref ER - TY - CONF TI - Optimal placement of PMUs for identification of power system models using noisy measurement data AU - Chakrabortty, Aranya AU - Szczodrak, Marta A T2 - Energy Society General Meeting AB - In this paper we address the problem of placing Phasor Measurement Units (PMUs) on a long transmission line connecting two areas of a power system network. Dynamic measurements of electrical signals such as magnitudes and phases of bus voltages and line currents, corrupted with Gaussian noise, are available from these PMUs. Our objective is to determine the best locations for their placement such that, given a particular measured noisy signal, the error in identifying a two-machine interarea equivalent model of the two-area power system is minimum. We first show that the identification problem is equivalent to estimating four essential model parameters, namely the two intra-area reactances, and the inertias of the two aggregated machines. We then formulate the Cramer-Rao bounds for the estimates of these four unknown parameters, and show that the bounds are functions of the PMU location. We finally state the condition for finding the optimal PMU location to achieve the tightest Cramer-Rao bound. C2 - 2010/7// C3 - IEEE PES General Meeting DA - 2010/7// DO - 10.1109/pes.2010.5589445 PB - IEEE SN - 9781424465491 UR - http://dx.doi.org/10.1109/pes.2010.5589445 DB - Crossref ER - TY - CONF TI - Building a dynamic electromechanical model for the pacific AC intertie using PMU measurements AU - Chakrabortty, A AU - Salazar, A T2 - Energy Society General Meeting AB - In this paper we present several new results on how to construct simplified inter-area models of large power networks by using dynamic measurements available from phasor measurement units (PMUs) installed at specific points on the transmission line. Our example of study in this paper is a widely encountered realistic system, namely the Pacific AC intertie, which closely resembles a star-connected three-area power system. We derive analytical results showing how the voltage, phase angle and frequency oscillations at different buses on the transfer path of this intertie can be used to estimate the essential parameters of the three-machine equivalent model of this three-area system. We illustrate the results with actual disturbance event data from the WECC. C2 - 2010/7// C3 - IEEE PES General Meeting DA - 2010/7// DO - 10.1109/pes.2010.5589513 PB - IEEE SN - 9781424465491 UR - http://dx.doi.org/10.1109/pes.2010.5589513 DB - Crossref ER - TY - CONF TI - Macroscopic modeling of large power systems using distributed dynamic measurements with dependence on network topology AU - Chakrabortty, Aranya AU - Chow, Joe H. T2 - 2010 49th IEEE Conference on Decision and Control (CDC) 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 electro-mechanical models for these conceptual, aggregated generators representing Washington and California, which in reality are some hypothetical combinations of thousands of actual generators. We address this problem in this paper and present several new results on how to construct simplified macroscopic models of large power networks by using dynamic measurements available from specific points on the network edges. Our examples of study are motivated by widely encountered power transfer paths in the US west coast power system, namely, a two-node radial network and a star-connected three-node system. C2 - 2010/12// C3 - 49th IEEE Conference on Decision and Control (CDC) DA - 2010/12// DO - 10.1109/cdc.2010.5717012 PB - IEEE SN - 9781424477456 UR - http://dx.doi.org/10.1109/cdc.2010.5717012 DB - Crossref KW - Power networks KW - model reduction KW - parameter estimation ER - TY - CONF TI - Optimal sensor placement for parametric model identification of electrical networks, part I: Open loop estimation AU - Chakrabortty, Aranya AU - Martin, Clyde F. T2 - 2010 49th IEEE Conference on Decision and Control (CDC) AB - In this paper we present an algorithm for placing sensors optimally along the edges of a large network of electrical oscillators to identify a parametric model for the network using dynamic measurements of electrical signals such as magnitudes and phase angles of voltages and currents, corrupted with Gaussian noise. We pose the identification problem as estimation of four essential parameters for each edge, namely the real and imaginary components of the edge-weight (or, equivalently the resistance and reactance along the transmission line), and the inertias of the two machines connected by this edge. We then formulate the Cramer-Rao bounds for the estimates of these four unknown parameters, and show that the bounds are functions of the sensor locations. We finally state the condition for finding the optimal sensor location to achieve the tightest Cramer-Rao bound. C2 - 2010/12// C3 - 49th IEEE Conference on Decision and Control (CDC) DA - 2010/12// DO - 10.1109/cdc.2010.5717926 PB - IEEE SN - 9781424477456 UR - http://dx.doi.org/10.1109/cdc.2010.5717926 DB - Crossref KW - Power networks KW - Cramer-Rao bound KW - swing equation KW - parameter estimation ER - TY - CONF TI - Optimal sensor placement for parametric model identification of electrical networks, Part II: Estimation under output feedback AU - Chakrabortty, Aranya AU - Martin, Clyde F. T2 - 2010 49th IEEE Conference on Decision and Control (CDC) AB - In this paper we present an algorithm for choosing optimal measurement points on the edges of a network of dynamic electrical oscillators such that the noise-corrupted electrical signals measured by sensors at that point can be used for generating the most accurate estimates for the network model. Assuming that the measured outputs are fed back to the network nodes to increase system damping we show that the Cramer-Rao bounds for the model estimates are functions of the sensor locations on every edge in the network. We finally state the condition for finding the optimal sensor locations to achieve the tightest Cramer-Rao bounds. An interesting observation is that unlike the algorithm derived in Part-I of this paper, where the open-loop configuration of the system allows us to optimize the bounds in a distributed fashion for each individual edge, here the problem no longer has that decoupled structure under the influence of feedback and must be carried out in a centralized way. C2 - 2010/12// C3 - 49th IEEE Conference on Decision and Control (CDC) DA - 2010/12// DO - 10.1109/cdc.2010.5717928 PB - IEEE SN - 9781424477456 UR - http://dx.doi.org/10.1109/cdc.2010.5717928 DB - Crossref KW - Power networks KW - Cramer-Rao bound KW - swing equation KW - parameter estimation ER - TY - CONF TI - A SiGe BiCMOS 16-element phased-array transmitter for 60GHz communications AU - Valdes-Garcia, Alberto AU - Nicolson, Sean AU - Lai, Jie-Wei AU - Natarajan, Arun AU - Chen, Ping-Yu AU - Reynolds, Scott AU - Zhan, Jing-Hong Conan AU - Floyd, Brian T2 - 2010 IEEE International Solid- State Circuits Conference - (ISSCC) AB - The demonstration of multi-Gb/s links in the 60GHz band has created new opportunities for wireless communications [1,2]. Due to the directional nature of millimeter-wave (mm-Wave) propagation, beam steering enables longer-range non-line-of-sight (NLOS) links at these frequencies. A phased-array architecture is attractive for an integrated 60GHz transmitter (Tx) since it can attain both beam steering and higher EIRP through spatial combining. An all-RF 16-element 40-to-45GHz Tx for satellite applications [3], a 6-element 60GHz Tx with IF-path phase-shift [4], and a bi-directional 4-element 60GHz Tx/Rx with RF phase shifters [5] have been recently demonstrated in silicon. This work presents a fully-integrated phased-array Tx which supports multi-Gb/s NLOS IEEE 802.15.3c links. In addition to beamsteering, the IC has the following major features: an on-chip power sensor at each element, 3 temperature sensors, LO leakage and I/Q phase and amplitude adjustment, front-end OP 1dB programmability, and an integrated modulator for pi/2-BPSK/MSK signaling (common mode in 802.15.3c). The IC integrates 2240 NPNs, 323,000 FETs and hundreds of transmission lines and is fabricated in the IBM 8HP 0.12µm SiGe BiCMOS process (f T = 200GHz). C2 - 2010/2// C3 - 2010 IEEE International Solid-State Circuits Conference - (ISSCC) DA - 2010/2// DO - 10.1109/isscc.2010.5433956 VL - 53 SP - 218-219 PB - IEEE SN - 9781424460335 UR - http://dx.doi.org/10.1109/isscc.2010.5433956 DB - Crossref ER - TY - CONF TI - Silicon millimeter-wave radios for 60 GHz and beyond AU - Floyd, B. AU - Valdes Garcia, A. AU - Reynolds, S. AU - Natarajan, A. AU - Liu, D. AU - Gaucher, B. AU - Nakano, D. AU - Katayama, Y. T2 - 2010 International Symposium on VLSI Technology, Systems, and Applications (VLSI-TSA 2010) AB - This paper provides an overview of a 60GHz transceiver chipset implemented in 0.12μm SiGe BiCMOS technology, prototype 60GHz antennas and packages developed for that chipset, and a 60GHz phased-array receiver front-end. The transceiver chipset achieves 6dB noise figure in the receiver and 10dBm output compression point in the transmitter. Folded-dipole and patch antenna arrays developed for the 60GHz chipset show >90% efficiencies and broad bandwidths. These antennas were attached to the SiGe RF chips, and the packaged chipset has been used to transmit an uncompressed high-definition video stream at 2Gb/s, with even higher data rates possible. Finally, a 60GHz RF-combined phased-array receiver front-end is discussed which uses a hybrid parallel/series phase-shifting architecture and which achieves full spatial coverage with reduced phase-shifter requirements. C2 - 2010/4// C3 - Proceedings of 2010 International Symposium on VLSI Technology, System and Application DA - 2010/4// DO - 10.1109/vtsa.2010.5488970 SP - 12-13 PB - IEEE SN - 9781424450633 UR - http://dx.doi.org/10.1109/vtsa.2010.5488970 DB - Crossref ER - TY - CONF TI - A 16-element phased-array receiver IC for 60-GHz communications in SiGe BiCMOS AU - Reynolds, Scott K. AU - Natarajan, Arun S. AU - Tsai, Ming-Da AU - Nicolson, Sean AU - Zhan, Jing-Hong Conan AU - Liu, Duixian AU - Kam, Dong G. AU - Huang, Oscar AU - Valdes-Garcia, Alberto AU - Floyd, Brian A. AU - al., T2 - 2010 IEEE Radio Frequency Integrated Circuits Symposium AB - A 0.12-μm SiGe phased-array Rx IC for beam-steered wireless communication in the 60-GHz band is described. It has 16 RF phase-shifting front-ends with 11° digital phase resolution and hybrid passive-active RF signal combining. It achieves 7.4-7.9 dB NF (not including 12-dB array gain) over the 4 IEEE channels. The IC has a double-conversion superheterodyne Rx core with a maximum of 72 dB of power gain in 1-dB steps, and the on-chip synthesizer achieves <; -90 dBc/Hz Rx phase noise at 1MHz offset. The IC draws 1.8 W at 2.7 V with a die area of 38 mm 2 . It has been packaged with 16 antennas in a 288-pin organic BGA and phased-array beamsteering has been demonstrated, along with 5+ Gb/s wireless links using 16-QAM OFDM. C2 - 2010/// C3 - 2010 IEEE Radio Frequency Integrated Circuits Symposium DA - 2010/// DO - 10.1109/rfic.2010.5477306 SP - 461-464 PB - IEEE SN - 9781424462407 UR - http://dx.doi.org/10.1109/rfic.2010.5477306 DB - Crossref KW - Phased-arrays KW - beam steering KW - 60 GHz KW - millimeter-wave KW - receiver KW - SiGe ER - TY - CONF TI - Microstrip to CPW transitions for package applications AU - Liu, Duixian AU - Floyd, B T2 - 2010 IEEE International Symposium Antennas and Propagation and CNC-USNC/URSI Radio Science Meeting AB - We have presented MS-to-CPW transitions that are easy to design and implement while maintaining good impedance match and low insertion loss. These transitions are very useful for antenna evaluations using probes and for RF package applications. C2 - 2010/7// C3 - 2010 IEEE Antennas and Propagation Society International Symposium DA - 2010/7// DO - 10.1109/aps.2010.5561028 PB - IEEE SN - 9781424449675 9781424449682 UR - http://dx.doi.org/10.1109/aps.2010.5561028 DB - Crossref ER - TY - CONF TI - An LTCC superstrate patch antenna for 60-GHz package applications AU - Liu, Duixian AU - Chen, HoChung AU - Floyd, B T2 - 2010 IEEE International Symposium Antennas and Propagation and CNC-USNC/URSI Radio Science Meeting AB - In this paper we present an aperture-coupled superstrate patch antenna with an embedded air cavity. This package eliminates the RFIC chip cavity to simplify the manufacturing process. The package presented is based on low-temperature co-fired ceramic (LTCC) technology; however, the package structure can be implemented in a variety of technologies, including PCB/MLO. C2 - 2010/7// C3 - 2010 IEEE Antennas and Propagation Society International Symposium DA - 2010/7// DO - 10.1109/aps.2010.5561139 PB - IEEE SN - 9781424449675 9781424449682 UR - http://dx.doi.org/10.1109/aps.2010.5561139 DB - Crossref ER - TY - CONF TI - Low-cost antenna-in-package solutions for 60-GHz phased-array systems AU - Kam, Dong Gun AU - Liu, Duixian AU - Natarajan, Arun AU - Reynolds, Scott AU - Floyd, Brian A. T2 - 2010 IEEE 19th Conference on Electrical Performance of Electronic Packaging and Systems (EPEPS) AB - A low-cost, fully-integrated antenna-in-package solution for 60-GHz phased-array system is demonstrated. Sixteen patch antennas are integrated into a 28 mm × 28 mm ball grid array together with a flip-chip attached phased-array transmitter or receiver chip. The packages have first been fabricated using low temperature co-fired ceramic technology, and then built using conventional printed circuit board processes for lower manufacturing cost. Antenna chamber measurement has shown ~5 dBi unit antenna gain across the 60-GHz frequency band covering all four IEEE 802.15.3c channels. The packaged transmitter and receiver chipsets, each mounted on an evaluation board, have demonstrated beam-steered, non-line-of-sight links with data rates up to 5.3 Gb/s. C2 - 2010/10// C3 - 19th Topical Meeting on Electrical Performance of Electronic Packaging and Systems DA - 2010/10// DO - 10.1109/epeps.2010.5642554 SP - 93-96 PB - IEEE SN - 9781424468652 UR - http://dx.doi.org/10.1109/epeps.2010.5642554 DB - Crossref ER - TY - JOUR TI - Influence of electron-electron scattering on transport characteristics in monolayer graphene AU - Li, X. AU - Barry, E. A. AU - Zavada, J. M. AU - Nardelli, M. Buongiorno AU - Kim, K. W. T2 - Applied Physics Letters AB - The influence of electron-electron scattering on the distribution function and transport characteristics of intrinsic monolayer graphene is investigated via an ensemble Monte Carlo simulation. Due to the linear dispersion relation in the vicinity of the Dirac points, it is found that pair-wise collisions in graphene do not conserve the ensemble average velocity in contrast to conventional semiconductors with parabolic energy bands. Numerical results indicate that electron-electron scattering can lead to a decrease in the low field mobility by more than a factor of 2 for moderate electron densities. The corresponding degradation in the saturation velocity is more modest at around 15%. At high densities, the impact gradually diminishes due to increased degeneracy. DA - 2010/8/23/ PY - 2010/8/23/ DO - 10.1063/1.3483612 VL - 97 IS - 8 SP - 082101 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.3483612 DB - Crossref ER - TY - CONF TI - An equivalent circuit for collapse operation mode of CMUTs AU - Olcum, Selim AU - Yamaner, F. Yalcin AU - Bozkurt, Ayhan AU - Koymen, Hayrettin AU - Atalar, Abdullah T2 - 2010 IEEE Ultrasonics Symposium (IUS) AB - Collapse mode of operation of the capacitive micromachined ultrasonic transducers (CMUTs) was shown to be a very effective way for achieving high output pressures. However, no accurate model exists for understanding the mechanics and limits of the collapse mode. In this work, we extend the analyses made for CMUTs working in uncollapsed mode to collapsed mode. We have developed an equivalent nonlinear electrical circuit that can accurately simulate the mechanical behavior of a CMUT under any large signal electrical excitation. The static and dynamic deflections of a membrane predicted by the model are compared with the finite element simulations. The equivalent circuit model can estimate the static deflection within 1% and the transient behavior of a CMUT membrane within 3% accuracy. The circuit model is also compared to experimental results of pulse excitation applied to fabricated collapse mode CMUTs. The model is suitable as a powerful design and optimization tool for the collapsed as well as the uncollapsed case of CMUTs. C2 - 2010/10// C3 - 2010 IEEE International Ultrasonics Symposium DA - 2010/10// DO - 10.1109/ultsym.2010.5935697 PB - IEEE SN - 9781457703829 UR - http://dx.doi.org/10.1109/ultsym.2010.5935697 DB - Crossref ER - TY - CONF TI - Optimizing CMUT geometry for high power AU - Yamaner, F. Yalcin AU - Olcum, Selim AU - Bozkurt, Ayhan AU - Koymen, Hayrettin AU - Atalar, Abdullah T2 - 2010 IEEE Ultrasonics Symposium (IUS) AB - Capacitive micromachined ultrasonic transducers (CMUTs) have demonstrated various advantages over piezoelectric transducers. However, current CMUT designs produce low output pressures with high harmonic distortions. Optimizing the transducer parameters requires an iterative solution and is too time consuming using finite element (FEM) modelling tools. In this work, we present a method of designing high output pressure CMUTs with relatively low distortion. We analyze the behavior of a membrane under high voltage continuous wave operation using a nonlinear electrical circuit model. The radiation impedance of an array of CMUTs is accurately represented using an RLC circuit in the model. The maximum membrane swing without collapse is targeted in the transmit mode. Using SPICE simulation of the parametric circuit model, we design the CMUT cell with optimized parameters such as the membrane radius (a), thickness (t m ), insulator thickness (t i ) and gap height (t g ). The model also predicts the amount of second harmonic at the output. To verify the accuracy of the results, we built a FEM model with the same CMUT parameters. The design starts by choosing t i for the given input voltage level. First, a is selected for the maximum radiation resistance of the array at the operating frequency. Second, t m is found for the resonance at the input frequency. Third, t g is chosen for the maximum membrane swing. Under this condition, a frequency shift in the resonant frequency occurs. Second and third steps are repeated until convergence. This method results in a CMUT array with a high output power and with low distortion. C2 - 2010/10// C3 - 2010 IEEE International Ultrasonics Symposium DA - 2010/10// DO - 10.1109/ultsym.2010.5935942 PB - IEEE SN - 9781457703829 UR - http://dx.doi.org/10.1109/ultsym.2010.5935942 DB - Crossref ER - TY - CONF TI - An MCMC Approach to Lossy Compression of Continuous Sources AU - Baron, Dror AU - Weissman, Tsachy T2 - 2010 Data Compression Conference AB - Motivated by the Markov chain Monte Carlo (MCMC) relaxation method of Jalali and Weissman, we propose a lossy compression algorithm for continuous amplitude sources that relies on a finite reproduction alphabet that grows with the input length. Our algorithm asymptotically achieves the optimum rate distortion (RD) function universally for stationary ergodic continuous amplitude sources. However, the large alphabet slows down the convergence to the RD function, and is thus an impediment in practice. We thus propose an MCMC-based algorithm that uses a (smaller) adaptive reproduction alphabet. In addition to computational advantages, the reduced alphabet accelerates convergence to the RD function, and is thus more suitable in practice. C2 - 2010/// C3 - 2010 Data Compression Conference DA - 2010/// DO - 10.1109/dcc.2010.11 PB - IEEE SN - 9781424464258 UR - http://dx.doi.org/10.1109/dcc.2010.11 DB - Crossref KW - Lossy compression KW - rate distortion theory KW - stationary ergodic sources KW - universal compression ER - TY - JOUR TI - Bayesian Compressive Sensing Via Belief Propagation AU - Baron, Dror AU - Sarvotham, Shriram AU - Baraniuk, Richard G. T2 - IEEE Transactions on Signal Processing AB - Compressive sensing (CS) is an emerging field based on the revelation that a small collection of linear projections of a sparse signal contains enough information for stable, sub-Nyquist signal acquisition. When a statistical characterization of the signal is available, Bayesian inference can complement conventional CS methods based on linear programming or greedy algorithms. We perform asymptotically optimal Bayesian inference using belief propagation (BP) decoding, which represents the CS encoding matrix as a graphical model. Fast computation is obtained by reducing the size of the graphical model with sparse encoding matrices. To decode a length-N signal containing K large coefficients, our CS-BP decoding algorithm uses O(K log(N)) measurements and O(N log 2 (N)) computation. Finally, although we focus on a two-state mixture Gaussian model, CS-BP is easily adapted to other signal models. DA - 2010/1// PY - 2010/1// DO - 10.1109/tsp.2009.2027773 VL - 58 IS - 1 SP - 269-280 J2 - IEEE Trans. Signal Process. OP - SN - 1053-587X 1941-0476 UR - http://dx.doi.org/10.1109/tsp.2009.2027773 DB - Crossref KW - Bayesian inference KW - belief propagation KW - compressive sensing KW - fast algorithms KW - sparse matrices ER - TY - JOUR TI - A Fully Integrated 16-Element Phased-Array Transmitter in SiGe BiCMOS for 60-GHz Communications AU - Valdes-Garcia, Alberto AU - Nicolson, Sean T. AU - Lai, Jie-Wei AU - Natarajan, Arun AU - Chen, Ping-Yu AU - Reynolds, Scott K. AU - Zhan, Jing-Hong Conan AU - Kam, Dong G. AU - Liu, Duixian AU - Floyd, Brian AU - al., T2 - IEEE Journal of Solid-State Circuits AB - A phased-array transmitter (TX) for multi-Gb/s non-line-of-sight links in the four frequency channels of the IEEE 802.15.3c standard (58.32 to 64.8 GHz) is fully integrated in a 0.12-μm SiGe BiCMOS process. It consists of an up-conversion core followed by a 1:16 power distribution tree, 16 phase-shifting front-ends, and a digital control unit. The TX core is a two-step sliding-IF up-conversion chain with frequency synthesizer that features 40 dB of gain programmability, I/Q balance and LO leakage correction, and a modulator for 802.15.3c common-mode signaling. The tradeoffs involved in the implementation of a 1:16 power distribution network are analyzed and a hybrid passive/active distribution tree architecture is introduced. Each of the 16 front-ends consists of a balanced passive phase shifter and a variable-gain, 3-stage PA that features oP 1dB programmability through the bias control of the its final stage. All of the chip features are digitally controllable and individual memory arrays are integrated at each front-end to enable fast beam steering through a high-speed parallel interface. The IC occupies 44 mm and is fully characterized on wafer. The TX delivers 9 to 13.5 dBm oPidB per element at 60.48 GHz with a total power consumption of 3.8 to 6.2 W. Each element attains a phase-shift range >360° with an amplitude variation <;±1 dB across phase settings and adjacent elements. Measurement results from a packaged IC in an antenna chamber are also presented including the demonstration of spatial power combining up to +40 dBm EIRP and 16-element radiation patterns. DA - 2010/12// PY - 2010/12// DO - 10.1109/jssc.2010.2074951 VL - 45 IS - 12 SP - 2757-2773 J2 - IEEE J. Solid-State Circuits OP - SN - 0018-9200 1558-173X UR - http://dx.doi.org/10.1109/jssc.2010.2074951 DB - Crossref KW - 60-GHz transmitter KW - 802153c KW - millimeter-wave KW - phased-array KW - SiGe BiCMOS ER - TY - CONF TI - Analyzing and scaling parallelism for network routing protocols AU - Dhanotia, Abhishek AU - Grover, Sabina AU - Byrd, Greg T2 - 2010 IEEE International Symposium on Workload Characterization (IISWC) AB - The serial nature of legacy code in routing protocol implementations has inhibited a shift to multicore processing in the control plane, even though there is much inherent parallelism. In this paper, we investigate the use of multicore as the compute platform for routing applications using BGP, the ubiquitous protocol for routing in the Internet backbone, as a representative application. We develop a scalable multithreaded implementation for BGP and evaluate its performance on several multicore configurations using a fully configurable multicore simulation environment. We implement several optimizations at the software and architecture levels, achieving a speedup of 6.5 times over the sequential implementation, which translates to a throughput of ~170K updates per second. Subsequently, we propose a generic architecture and parallelization methodology which can be applied to all routing protocol implementations to achieve significant performance improvement. C2 - 2010/12// C3 - IEEE International Symposium on Workload Characterization (IISWC'10) DA - 2010/12// DO - 10.1109/iiswc.2010.5650317 PB - IEEE SN - 9781424492978 UR - http://dx.doi.org/10.1109/iiswc.2010.5650317 DB - Crossref ER - TY - CONF TI - Use of inductive power transfer for electric vehicles AU - Lukic, Srdjan M AU - Saunders, Marshall AU - Pantic, Zeljko AU - Hung, Steve AU - Taiber, Joachim T2 - IEEE C2 - 2010/// C3 - IEEE PES General Meeting DA - 2010/// SP - 1-6 ER - TY - JOUR TI - Solar-assisted electric auto rickshaw three-wheeler AU - Mulhall, Priscilla AU - Lukic, Srdjan M AU - Wirasingha, Sanjaka G AU - Lee, Young-Joo AU - Emadi, Ali T2 - IEEE transactions on vehicular technology DA - 2010/// PY - 2010/// VL - 59 IS - 5 SP - 2298-2307 ER - TY - CONF TI - Review of non-isolated bi-directional DC-DC converters for plug-in hybrid electric vehicle charge station application at municipal parking decks AU - Du, Yu AU - Zhou, Xiaohu AU - Bai, Sanzhong AU - Lukic, Srdjan AU - Huang, Alex T2 - IEEE C2 - 2010/// C3 - 2010 Twenty-Fifth Annual IEEE Applied Power Electronics Conference and Exposition (APEC) DA - 2010/// SP - 1145-1151 ER - TY - CONF TI - Performance characterization and optimization of various circuit topologies to combine batteries and ultra-capacitors AU - Govindaraj, Arvind AU - King, Mathew AU - Lukic, Srdjan M T2 - IEEE C2 - 2010/// C3 - IECON 2010-36th Annual Conference on IEEE Industrial Electronics Society DA - 2010/// SP - 1850-1857 ER - TY - CONF TI - Optimum design of an EV/PHEV charging station with DC bus and storage system AU - Bai, Sanzhong AU - Yu, Du AU - Lukic, Srdjan T2 - IEEE C2 - 2010/// C3 - 2010 IEEE Energy Conversion Congress and Exposition DA - 2010/// SP - 1178-1184 ER - TY - CONF TI - Optimal resonant tank design considerations for primary track compensation in inductive power transfer systems AU - Pantic, Z. AU - Bhattacharya, S. AU - Lukic, S. T2 - IEEE AB - In this paper, design of a primary resonant tank for resonant converters compensation in an Inductive Power Transfer (IPT) system is analyzed and some criteria for selecting its reactive components are established. The optimization goal is to maximize the transferred power, while limiting the number of compensation components to no more than two reactive components. Additionally, VA limits of the inverter are taken into consideration. Current track requirements are relaxed and instead of constant track current, small track load dependency is allowed, which is acceptable in practice. The theoretical investigations and calculations, as well as simulations for two important practical cases considered are presented in the paper. It is shown that LC compensation structure allows maximum delivered power, but not for the case when the impedances of compensation elements are the same as it would be expected. Additionally, the impact of converter ratings and allowed load dependent track current variation on the optimal design are investigated through the set of numerical simulations. C2 - 2010/// C3 - 2010 IEEE Energy Conversion Congress and Exposition, ECCE 2010 - Proceedings DA - 2010/// DO - 10.1109/ECCE.2010.5618093 SP - 1602-1609 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78650149637&partnerID=MN8TOARS KW - Inductive power transfer KW - compensation tank design KW - resonant converter ER - TY - CONF TI - New method for current and voltage measuring offset correction in an induction motor sensorless drive AU - Pantic, Zeljko AU - Ballal, Siddharth AU - Lukic, Srdjan T2 - IEEE C2 - 2010/// C3 - 2010 IEEE Energy Conversion Congress and Exposition DA - 2010/// SP - 23-30 ER - TY - CONF TI - Investigations into the minimization of electrical costs for traction-type elevators AU - White, L.W. AU - Lukic, S.M. AU - Bhattacharya, S. T2 - IEEE AB - This work examines the real-time utilization of energy in an operating elevator drive system with a goal, not of improving efficiency per se, but rather of reducing the cost paid by the system owner for the operation of the equipment. Several load-leveling and peak-shaving schemes using ultracapacitors are reviewed, including (1) off-peak energy storage for on-peak use, (2) energy storage to reduce the utility demand cost, (3) energy storage to reduce inrush peaks, and (4) energy storage to redirect regenerated energy. Each of these schemes is developed to demonstrate technical acceptability and then evaluated with respect to cost effectiveness. C2 - 2010/// C3 - 2010 IEEE Energy Conversion Congress and Exposition, ECCE 2010 - Proceedings DA - 2010/// DO - 10.1109/ECCE.2010.5618473 SP - 4285-4292 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78650153772&partnerID=MN8TOARS KW - Capacitive energy storage KW - Elevators KW - Energy management KW - Energy storage KW - Life cycle costing KW - Power demand KW - Power system economics ER - TY - CONF TI - High-frequency high-efficiency DC-DC converter for distributed energy storage modularization AU - Du, Yu AU - Wang, Mengqi AU - Meitl, Ryan T AU - Lukic, Srdjan AU - Huang, Alex Q T2 - IEEE C2 - 2010/// C3 - IECON 2010-36th Annual Conference on IEEE Industrial Electronics Society DA - 2010/// SP - 1832-1837 ER - TY - JOUR TI - Power management for multi-module energy storage systems in electric, hybrid electric, and fuel cell vehicles AU - Lukic, Srdjan AU - Emadi, Ali DA - 2010/12// PY - 2010/12// N1 - US Patent 7,859,202 RN - US Patent 7,859,202 ER - TY - JOUR TI - Design and optimization of circular magnetic structures for lumped inductive power transfer systems. AU - Li, Yan-Ling AU - He, Zheng-You AU - Sun, Yue AU - Dai, Xin AU - Chen, BM AU - Davoudi, A AU - Jatskevich, J AU - Dong, L AU - Ma, H AU - Xu, F AU - others T2 - Information Technology Journal DA - 2010/// PY - 2010/// VL - 12 IS - 9 SP - Pages-452 ER - TY - CONF TI - DC zonal micro-grid architecture and control AU - She, Xu AU - Lukic, Srdjan AU - Alex, Q Huang T2 - IEEE C2 - 2010/// C3 - IECON 2010-36th Annual Conference on IEEE Industrial Electronics Society DA - 2010/// SP - 2988-2993 ER - TY - CONF TI - A digital current control for switched reluctance motor drives AU - Shao, Baiming AU - Lukic, Srdjan M AU - Emadi, Ali T2 - IEEE C2 - 2010/// C3 - 2010 IEEE International Symposium on Industrial Electronics DA - 2010/// SP - 1163-1168 ER - TY - CONF TI - Toward understanding characteristics of Dedicated Short Range Communications (DSRC) from a perspective of vehicular network engineers AU - Bai, F. AU - Stancil, D.D. AU - Krishnan, H. AB - IEEE 802.11p-based Dedicated Short Range Communications (DSRC) is considered a promising wireless technology for enhancing transportation safety and improving highway efficiency. Here, using a large set of empirical measurement data taken in a rich variety of realistic driving environments, we attempt to characterize communication properties of DSRC as well as to analyze the causes of communication loss. Specifically, from a perspective of vehicular network engineers, the fundamental characteristic of DSRC communications is Packet Delivery Ratio (PDR). We investigate the impact of both uncontrollable environmental factors and controllable radio parameters on DSRC characteristics. Moreover, we also examine temporal correlation, spatial correlation and symmetric correlation of DSRC characteristics under realistic vehicular environments. C2 - 2010/// C3 - Proceedings of the Annual International Conference on Mobile Computing and Networking, MOBICOM DA - 2010/// DO - 10.1145/1859995.1860033 SP - 329-340 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78649279855&partnerID=MN8TOARS ER - TY - CONF TI - EXperience with a wireless network testbed based on signal propagation emulation AU - Borries, K. AU - Wang, X. AU - Judd, G. AU - Steenkiste, P. AU - Stancil, D. AB - The evaluation of wireless research is challenging because signals traveling through the ether are affected by the physical environment, including movement by people and objects. As a result, testbed experiments are hard to control and are non-repeatable. We have developed a wireless networking testbed based on digital signal propagation emulation that provides control over the signal propagation environment. The testbed has been in regular use for research and education since early 2007. In this paper we present measurements illustrating the properties of the emulator testbed. We also compare the results of various experiments on the emulator with simulation results to shed some light on when the increased accuracy of the emulator testbed is important. Finally, we use the experience gained on the emulator to identify classes of experiments for which the emulator is well suited, compared with other evaluation platforms. C2 - 2010/// C3 - 2010 European Wireless Conference, EW 2010 DA - 2010/// DO - 10.1109/EW.2010.5483538 SP - 833-840 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77954441199&partnerID=MN8TOARS ER - TY - CONF TI - Dynamic channel equalization for IEEE 802.11p waveforms in the vehicle-to-vehicle channel AU - Fernandez, J.A. AU - Stancil, D.D. AU - Bai, F. AB - The IEEE 802.11p standard (or Dedicated Short Range Communication, DSRC) [1] has been proposed to be the standard for vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications. Since the IEEE 802.11a-based DSRC standard is not fully customized for outdoor, highly mobile channels, the performance of DSRC standard might degrade in a challenging V2V channel. In this paper, we develop several equalization schemes that are able to closely track the V2V channel dynamics and thus improve performance at the physical layer. Through a set of empirical experiments, we show that the performance (in terms of Packet Error Rate) can be significantly improved from 41% (using a simple Least Square Estimator) to 19% (using a Spectral Temporal Averaging Estimator). C2 - 2010/// C3 - 2010 48th Annual Allerton Conference on Communication, Control, and Computing, Allerton 2010 DA - 2010/// DO - 10.1109/ALLERTON.2010.5706954 SP - 542-551 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-79952419235&partnerID=MN8TOARS ER - TY - BOOK TI - Communication Systems for Car-2-X Networks AU - Stancil, D.D. AU - Bai, F. AU - Cheng, L. AB - This chapter provides an overview of the architectures and environments for Vehicle-to-Infrastructure (V2I) and Vehicle-to-Vehicle (V2V) communication. Antenna requirements and channel properties are discussed with an emphasis on the car-to-car environment. The impact of channel properties on Orthogonal Frequency Division Multiplexing (OFDM) is discussed together with its implications and recommendations for the IEEE 802.11p standard. The protocol requirements for Dedicated Short Range Communications (DSRC) applications differ substantially from those of conventional wireless networks. The chapter discusses the use of multiple channels for medium access, as well as broadcast and unicast protocols. Single-hop and multi-hop protocols are discussed, including techniques for enhancing the reliability for safety-critical applications. Next, the technical portion ends with a discussion of network layer challenges related to mobility, such as mobile IP and dynamic address allocation schemes. The chapter concludes with a discussion of future directions and challenges. Controlled Vocabulary Terms communication systems; OFDM; vehicular ad hoc networks DA - 2010/// PY - 2010/// DO - 10.1002/9780470661314.ch3 SE - 45-81 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84886202089&partnerID=MN8TOARS ER - TY - JOUR TI - A low-power shoe-embedded radar for aiding pedestrian inertial navigation AU - Zhou, C. AU - Downey, J. AU - Stancil, D. AU - Mukherjee, T. T2 - IEEE Transactions on Microwave Theory and Techniques AB - Navigation in global positioning system (GPS)-denied or GPS-inhibited environments such as urban canyons, mountain areas, and indoors is often accomplished with an inertial measurement unit (IMU). For portable navigation, miniaturized IMUs suffer from poor accuracy due to bias, bias drift, and noise. We propose to use a low-power shoe-embedded radar as an aiding sensor to identify zero velocity periods during which the individual IMU sensor biases can be observed. The proposed radar sensor can also be used to detect the vertical position and velocity of the IMU relative to the ground in real time, which provides additional independent information for sensor fusion. The impacts of the noise and interference on the system performance have been analyzed analytically. A prototype sensor has been constructed to demonstrate the concept, and experimental results show that the proposed sensor is promising for position and velocity sensing. DA - 2010/// PY - 2010/// DO - 10.1109/TMTT.2010.2063810 VL - 58 IS - 10 SP - 2521-2528 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77958007826&partnerID=MN8TOARS KW - Direct conversion KW - inertial navigation KW - position and velocity sensor KW - zero velocity update (ZUPT) ER - TY - CONF TI - Understanding how off-chip memory bandwidth partitioning in chip multiprocessors affects system performance AU - Liu, F. AU - Jiang, X. W. AU - Solihin, Y. AB - Chip Multi-Processor (CMP) architectures have recently become a mainstream computing platform. Recent CMPs allow cores to share expensive resources, such as the last level cache and off-chip pin bandwidth. To improve system performance and reduce the performance volatility of individual threads, last level cache and off-chip bandwidth partitioning schemes have been proposed. While how cache partitioning affects system performance is well understood, little is understood regarding how bandwidth partitioning affects system performance, and how bandwidth and cache partitioning interact with one another. In this paper, we propose a simple yet powerful analytical model that gives us an ability to answer several important questions: (1) How does off-chip bandwidth partitioning improve system performance? (2) In what situations the performance improvement is high or low, and what factors determine that? (3) In what way cache and bandwidth partitioning interact, and is the interaction negative or positive? (4) Can a theoretically optimum bandwidth partition be derived, and if so, what factors affect it? We believe understanding the answers to these questions is very valuable to CMP system designers in coming up with strategies to deal with the scarcity of off-chip bandwidth in future CMPs with many cores on a chip. C2 - 2010/// C3 - International symposium on high-performance computer DA - 2010/// DO - 10.1109/hpca.2010.5416655 SP - 57-68 ER - TY - CONF TI - MMT: Exploiting Fine Grained Parallelism in Dynamic Memory Management AU - Tiwari, D. AU - Tuck, J. AU - Solihin, Y. AB - Dynamic memory management is one of the most expensive but ubiquitous operations in many C/C++ applications. Additional features such as security checks, while desirable, further worsen memory management overheads. With advent of multicore architecture, it is important to investigate how dynamic memory management overheads for sequential applications can be reduced. In this paper, we propose a new approach for accelerating dynamic memory management on multicore architecture, by offloading dynamic management functions to a separate thread that we refer to as memory management thread (MMT). We show that an efficient MMT design can give significant performance improvement by extracting parallelism while being agnostic to the underlying memory management library algorithms and data structures. We also show how parallelism provided by MMT can be beneficial for high overhead memory management tasks, for example, security checks related to memory management. We evaluate MMT on heap allocation-intensive benchmarks running on an Intel core 2 quad platform for two widely-used memory allocators: Doug Lea's and PHKmalloc allocators. On average, MMT achieves a speedup ratio of 1.19× for both allocators, while both the application and memory management libraries are unmodified and are oblivious to the parallelization scheme. For PHKmalloc with security checks turned on, MMT reduces the security check overheads from 21% to only 1% on average. C2 - 2010/// C3 - International Parallel and Distributed Processing Symposium DA - 2010/// DO - 10.1109/ipdps.2010.5470428 ER - TY - CONF TI - Design Tradeoffs for Memory-Level Parallelism on an Asymmetric Multicore System AU - Patsilaras, G. AU - Choudhary, N. AU - Tuck, J. C2 - 2010/// C3 - Workshop on Parallel Execution of Sequential Programs on Multi-core Architectures DA - 2010/// ER - TY - CONF TI - CHOP: Adaptive filter-based DRAM caching for CMP server platforms AU - Jiang, X. W. AU - Madan, N. AU - Zhao, L. AU - Upton, M. AU - Iyer, R. AU - Makineni, S. AU - Newell, D. AU - Solihin, Y. AU - Balasubramonian, R. AB - As manycore architectures enable a large number of cores on the die, a key challenge that emerges is the availability of memory bandwidth with conventional DRAM solutions. To address this challenge, integration of large DRAM caches that provide as much as 5× higher bandwidth and as low as 1/3rd of the latency (as compared to conventional DRAM) is very promising. However, organizing and implementing a large DRAM cache is challenging because of two primary tradeoffs: (a) DRAM caches at cache line granularity require too large an on-chip tag area that makes it undesirable and (b) DRAM caches with larger page granularity require too much bandwidth because the miss rate does not reduce enough to overcome the bandwidth increase. In this paper, we propose CHOP (Caching HOt Pages) in DRAM caches to address these challenges. We study several filter-based DRAM caching techniques: (a) a filter cache (CHOP-FC) that profiles pages and determines the hot subset of pages to allocate into the DRAM cache, (b) a memory-based filter cache (CHOP-MFC) that spills and fills filter state to improve the accuracy and reduce the size of the filter cache and (c) an adaptive DRAM caching technique (CHOP-AFC) to determine when the filter cache should be enabled and disabled for DRAM caching. We conduct detailed simulations with server workloads to show that our filter-based DRAM caching techniques achieve the following: (a) on average over 30% performance improvement over previous solutions, (b) several magnitudes lower area overhead in tag space required for cache-line based DRAM caches, (c) significantly lower memory bandwidth consumption as compared to page-granular DRAM caches. C2 - 2010/// C3 - International symposium on high-performance computer DA - 2010/// DO - 10.1109/hpca.2010.5416642 SP - 233-244 ER - TY - CONF TI - Ultimate scalability of TaN metal floating gate with incorporation of High-K blocking dielectrics for flash memory applications AU - Jayanti, S. AU - Yang, X. Y. AU - Suri, R. AU - Misra, Veena AB - We have investigated ultrathin TaN metal floating gate (FG) with Hf based high-K interpoly dielectrics (IPD) for NAND Flash applications. In an attempt to investigate the memory behavior as the FG thickness is reduced, scalability of TaN FG down to 1 nm thickness has been explored. We have demonstrated excellent memory performance with program-erase (P-E) window as large as 16V. Our results indicate that high-K based IPD in conjunction with ultra-thin TaN metal FG can enable further scaling of NAND Flash memory beyond conventional oxide-nitride-oxide (ONO) based IPD technology. C2 - 2010/// C3 - 2010 international electron devices meeting - technical digest DA - 2010/// DO - 10.1109/iedm.2010.5703301 ER - TY - CONF TI - Normally-off AlGaN/GaN-on-Si MOSHFETs with TaN floating gates and ALD SiO2 tunnel dielectrics AU - Lee, B. AU - Kirkpatrick, C. AU - Yang, X. Y. AU - Jayanti, S. AU - Suri, R. AU - Roberts, J. AU - Misra, Veena AB - In this work, we have demonstrated a normally-off AlGaN/GaN metal-oxide semiconductor heterojunction field effect transistor (MOSHFET) wherein the enhancement mode operation is enabled by charge storage within a metal floating gate embedded in a dielectric stack and negative charges in the tunnel oxide. By combining ALD SiO 2 and TaN floating gate (FG), up to 6V of V T shift after pulse programming (corresponding ~1.2×10 13 charges/cm 2 stored within the FG) is obtained which results in a normally-off device with low gate leakage and good transconductance. C2 - 2010/// C3 - 2010 international electron devices meeting - technical digest DA - 2010/// DO - 10.1109/iedm.2010.5703401 ER - TY - JOUR TI - Multimode Transceiver for High-Density Interconnects: Measurement and Validation AU - Choi, Yongjin AU - Braunisch, Henning AU - Ayguen, Kemal AU - Franzon, Paul D. T2 - 2010 PROCEEDINGS 60TH ELECTRONIC COMPONENTS AND TECHNOLOGY CONFERENCE (ECTC) AB - The demand for high-density links is increasing as the trend towards more cost-effective and high-throughput systems continues. Whereas the conventional single-ended and differential signaling schemes need a guaranteed interpair spacing which imposes certain bounds on maximum achievable signaling density, multimode signaling can be utilized to further increase it. In this paper, first, the exacerbated crosstalk caused by highly-coupled lines is illustrated to demonstrate the motivation for multimode signaling. A multimode signaling transceiver is then designed to prove the concept of multimode signaling. The measurement results of the decoded receiver output demonstrate that this scheme is able to reduce the effective crosstalk in a multi-wire link. DA - 2010/// PY - 2010/// DO - 10.1109/ectc.2010.5490738 SP - 1733-1738 SN - 2377-5726 ER - TY - CONF TI - Microgrid planning and operation: solar energy and wind energy AU - Su, W. C. AU - Yuan, Z. Y. AU - Chow, M. Y. AB - Economic, technology and environmental incentives are changing the features of electricity generation and transmission. Centralized power systems are giving way to local scale distributed generations. At present, there is a need to assess the effects of large numbers of distributed generators and short-term storage in Microgrid. To accommodate the high demand of renewable energy and the environment policy, the planning and operation of Micro-source generators has been studied using HOMER. Simulation results show a case study of an optimal microgrid configuration on Ontario area in Canada. Sensitivity variables are specified to examine the effect of uncertainties (e.g. diesel price and average wind speed), especially in a long-term planning. The effect of air emission penalties on Microgrid planning is also well presented. C2 - 2010/// C3 - Ieee power and energy soceity general meeting 2010 DA - 2010/// DO - 10.1109/pes.2010.5589391 ER - TY - CONF TI - Evaluation of distribution fault diagnosis algorithms using ROC curves AU - Cai, Y. X. AU - Chow, M. Y. AU - Lu, W. B. AU - Li, L. X. AB - In power distribution fault data, the percentage of faults with different causes could be very different and varies from region to region. This data imbalance issue seriously affects the performance evaluation of fault diagnosis algorithms. Due to the limitations of conventional accuracy (ACC) and geometric mean (G-mean) measures, this paper discusses the application of Receiver Operating Characteristic (ROC) curves in evaluating distribution fault diagnosis performance. After introducing how to obtain ROC curves, Artificial Neural Networks (ANN), Logistic Regression (LR), Support Vector Machines (SVM), Artificial Immune Recognition Systems (AIRS), and K-Nearest Neighbor (KNN) algorithm are compared using ROC curves and Area Under the Curve (AUC) on real-world fault datasets from Progress Energy Carolinas. Experimental results show that AIRS performs best most of the time and ANN is potentially a good algorithm with a proper decision threshold. C2 - 2010/// C3 - Ieee power and energy soceity general meeting 2010 DA - 2010/// DO - 10.1109/pes.2010.5588154 ER - TY - JOUR TI - Comprehensive Dynamic Battery Modeling for PHEV Applications AU - Zhang, Hanlei AU - Chow, Mo-Yuen T2 - IEEE POWER AND ENERGY SOCIETY GENERAL MEETING 2010 AB - With the increasing demand in PHEV safety, performance, etc., the PHEV applications require a battery model which can accurately reflect and predict the battery performance under different dynamic loads, environmental conditions, and battery conditions. An accurate battery model is the basis of the precise battery state (state of charge, state of health and state of function) estimation. And the precise battery state information can be used to enable the optimal control over the battery's charging/discharging process, therefore to manage the battery to its optimal usage, prolong the battery life, and enable vehicle to grid and vehicle to home applications fitting into the future smart grid scenario. One of the challenges in constructing such a model is to accurately reflect the highly nonlinear battery I-V performance, such as the battery's relaxation effect and the hysteresis effect. This paper will mainly focus on the relaxation effect modeling. The relaxation effect will be modeled through series connected RC circuits. Accuracy analysis demonstrates that with more RC circuit the battery model gives better accuracy, yet increases the total computational time. Therefore, to select an appropriate battery model for a certain PHEV application is formulated as a multi-objective optimization problem balancing between the model accuracy and the computational complexity within the constraints set by the minimum accuracy required and the maximum computational time allowed. This multi-objective optimization problem is mapped into a weighted optimization problem to solve. DA - 2010/// PY - 2010/// DO - 10.1109/pes.2010.5590108 SP - SN - 1944-9925 KW - Electric battery model KW - plug-in hybrid electric KW - vehicle (PHEV) KW - battery relaxation effect KW - accuracy analysis KW - computational complexity analysis KW - multi-objective optimization ER - TY - JOUR TI - ADAPTIVE SAMPLING FOR OUTPUT DEVICE CHARACTERIZATION AU - Trussell, H. J. AU - Nanjappan, J. T2 - 2010 IEEE INTERNATIONAL CONFERENCE ON IMAGE PROCESSING AB - We develop a method of adaptive sampling for use with image output devices, e.g., displays and projectors, that can produce improved results over sampling the input space with a fixed rectangular grid in a multidimensional space. Fixed sampling requires knowledge of the function shape to be effective. Even then the sampling can be grossly inefficient in some regions and grossly undersampled in others. Our method produces a more efficient sampling over the whole gamut of the device output of oddly shaped gamuts, while producing good results for more usual functions. This increased efficiency is important, since measuring samples is the most time-consuming part of the characterization process. DA - 2010/// PY - 2010/// DO - 10.1109/icip.2010.5651556 SP - 537-540 SN - 1522-4880 KW - Color KW - display KW - characterization KW - calibration ER - TY - CONF TI - A digital testbed for FREEDM system development AU - Baran, Mesut AU - Steurer, M. AB - In this paper, a notional Future Renewable Electric Energy Delivery and Management (FREEDM) system has been developed based on a real distribution feeder. The goal is to develop a digital testbed which can be used to show capabilities of this system, and to help the development of especially the new system components and the control schemes for this system. Two digital testbeds have been developed, one to represent the small scale green hub that will be realized in the center's test facilities at North Carolina State University and the other is a more detailed notional system that can be used for large scale system level analysis and design. C2 - 2010/// C3 - Ieee power and energy soceity general meeting 2010 DA - 2010/// DO - 10.1109/pes.2010.5589690 ER - TY - JOUR TI - 3D FACE RECOGNITION BASED ON EVOLUTION OF ISO-GEODESIC DISTANCE CURVES AU - Miao, Shun AU - Krim, Hamid T2 - 2010 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH, AND SIGNAL PROCESSING AB - This paper presents a novel 3D face recognition method by means of the evolution of iso-geodesic distance curves. Specifically, the proposed method compares two neighboring iso-geodesic distance curves, and formalizes the evolution between them as a one-dimensional function, named evolution angle function, which is Euclidean invariant. The novelty of this paper consists in formalizing 3D face by an evolution angle functions, and in computing the distance between two faces by that of two functions. Experiments on Face Recognition Grand Challenge (FRGC) ver2.0 shows that our approach works very well on both neutral faces and non-neutral faces. By introducing a weight function, we also show a very promising result on non-neutral face database. DA - 2010/// PY - 2010/// DO - 10.1109/icassp.2010.5495363 SP - 1134-1137 SN - 1520-6149 KW - Face recognition KW - Geometric modeling KW - Image registration KW - Pattern classification ER - TY - CONF TI - Topology-incurred delay for information dissemination in large multi-channel cognitive radio networks AU - Sun, L. AU - Wang, Wenye AB - Cognitive Radio (CR) networks have become an important component of the modern communication infrastructure due to their capability of improving spectrum usage efficiency by exploiting channels opportunistically. In CR networks, the network topology changes very frequently because of the temporarily available channels and dynamic transmitting parameters (e.g. transmission power and transmitting frequency), which may even result in network disconnectivity from time to time. Hence an interesting and open question is that: are there bounds on end-to-end delay between a source-destination pair with Euclidean distance d apart in such networks? These bounds are required for time-critical applications. This paper first investigates the nature of topology-incurred end-to-end delay in large multi-channel CR networks and then identifies the conditions under which the asymptotic topology-incurred delay scales linearly with the Euclidean distance (d); that is, the conditions under which the end-to-end delay is bounded. The results in this paper are validated through extensive simulations and can advance our understanding of CR network performance. C2 - 2010/// C3 - 2010 ieee global telecommunications conference globecom 2010 DA - 2010/// DO - 10.1109/glocom.2010.5683925 ER - TY - CONF TI - Speculative parallelization of partial reduction variables AU - Han, Liang AU - Liu, Wei AU - Tuck, James M AB - Reduction variables are an important class of cross-thread dependence that can be parallelized by exploiting the associativity and commutativity of their operation. In this paper, we define a class of shared variables called partial reduction variables (PRV). These variables either cannot be proven to be reductions or they violate the requirements of a reduction variable in some way. C2 - 2010/// C3 - Proceedings of the 8th annual IEEE/ACM international symposium on Code generation and optimization DA - 2010/// DO - 10.1145/1772954.1772975 SP - 141-150 ER - TY - JOUR TI - Performance Modeling of Virtual Collaborative Environments AU - Gavaskar, Nilesh AU - Kallitsis, Michael G. AU - Devetsikiotis, Michael AU - Michailidis, George AU - Montoya, Mitzi T2 - 2010 IEEE GLOBECOM WORKSHOPS AB - In this paper, we present a framework for performance modeling of virtual collaborative environments (VCE). Our model could be used as benchmarking tool for assessing the quality of experience of participants in a virtual environment. Our framework is designed to assess Second Life type of environments but could easily be extended to any kind of virtual worlds. We examine the case of users communicating via chatting and voice. We capture the performance for both cases and using response surface methodology techniques we derive a utility function that yields the performance of the examined environment given the available computing and communication resources. We propose a pricing scheme and based on this we formulate optimization problems for optimal resource allocation for VCEs. DA - 2010/// PY - 2010/// DO - 10.1109/glocomw.2010.5700165 SP - 1383-1387 SN - 2166-0069 ER - TY - CONF TI - Information theoretic optimal broadband matching for communication systems AU - Taluja, P. S. AU - Hughes, B. L. AB - We present an information theoretic perspective on optimal broadband matching. Most of the broadband matching and communication theory literature assumes a frequency-flat reflection coefficient. We derive the optimal capacity and matching network characteristic for a broadband system from an information theoretic view point while incorporating the broadband matching limitations. We also propose an iterative algorithm to arrive at the optimal solution. We illustrate by an example that a white characteristic for a matching network is often sub- optimal for a system with a non-white transfer function. C2 - 2010/// C3 - 2010 ieee global telecommunications conference globecom 2010 DA - 2010/// DO - 10.1109/glocom.2010.5683273 ER - TY - CONF TI - Heuristic-based request scheduling subject to a percentile response time SLA in a distributed cloud AU - Boloor, K. AU - Chirkova, R. AU - Salo, T. AU - Viniotis, Y. AB - We consider geographically distributed data centers forming a collectively managed cloud computing system hosting multiple applications, each subject to Service Level Agreements (SLA). The Service Level Agreements for each application require the response time of a certain percentile of the input requests to be less than a specified value, with the non-conforming requests being charged a penalty. We present a novel approach of heuristic-based request scheduling at each server, in each of the geographically distributed data centers, to globally minimize the penalty charged to the cloud computing system. We evaluate two variants of our heuristic-based approach, one based on the simulated annealing method of neighborhood searches and another based on gi-FIFO scheduling, which has been analytically proven to be the best schedule for percentile goals in a single machine, multi-class problem. We also compare our approaches with First In First Out (FIFO) and Weighted Round Robin (WRR) scheduling policies. C2 - 2010/// C3 - 2010 ieee global telecommunications conference globecom 2010 DA - 2010/// DO - 10.1109/glocom.2010.5683946 ER - TY - CONF TI - Fairness schemes in 802.16j mobile multihop relay networks AU - Kim, Y. C. AU - Sichitiu, Mihail L. AB - Multihop relaying in WiMAX networks is considered a cost effective way to extend the coverage of the base stations, increase cell capacity, or both. In this paper, we consider deploying non-transparent relay stations for coverage extension and study the issue of fairness schemes in such networks. Since there are access and relay zones in both downlink and uplink frames and simultaneous transmissions are possible in the access zone, it is challenging to schedule resources optimally for serving subscriber stations in a fair manner. We evaluate the performance of well known fairness schemes such as max-min and proportional fairness in such networks. We also propose a new scheduling scheme, named subsection fairness that can achieve better throughput than traditional fairness schemes by maximizing bandwidth utilization. Our numerical results evaluate the performance of each scheduling scheme in terms of cell throughput and fairness. C2 - 2010/// C3 - 2010 ieee global telecommunications conference globecom 2010 DA - 2010/// DO - 10.1109/glocom.2010.5683326 ER - TY - JOUR TI - An apparatus for P2P classification in Netflow traces AU - Gossett, Andrew M. AU - Papapanagiotou, Ioannis AU - Devetsikiotis, Michael T2 - 2010 IEEE GLOBECOM WORKSHOPS AB - Application classification from Netflow traces is a challenging process due to the lack of payload information. It is even becoming more challenging when the applications running in the network tend to hide under well known ports, encrypt packets and are distributed. In this paper, we propose an in-the-box apparatus for Netflow classification of Bit Torrent applications. The apparatus includes several device optimizations and requires low processing power. It was developed by reverse engineering the Bit Torrent protocol and by identifying connection patterns. The accuracy of the algorithm reaches high values specifically for Bit Torrent peers that use the DHT protocol. DA - 2010/// PY - 2010/// DO - 10.1109/glocomw.2010.5700160 SP - 1361-1366 SN - 2166-0069 ER - TY - CONF TI - Age invariant regime for multi-source content update in mobile opportunistic networks AU - Kim, S. AU - Eun, D. Y. AB - In the multi-source content update scenario where each mobile node can be both a publisher and subscriber and opportunistic contacts are used for spreading out up-to-date contents, the age of contents would be the main interest in performance evaluation. We can simplify the overall age dynamics in this scenario by two parameters, which are content update rate and contact rate among mobile users. In this paper, we analyze how the age of time-evolving contents changes in publish/subscribe scenario when Poisson update and contact are assumed, and show that there exists an age-invariant regime where the average age does not depend on content update rate or contact rate. We also compare the age-invariant regime in publish/subscribe scenario with that of service provider content update case, and show a stark contact in those regimes. Then, we extend our study into existing mobility models that generate non-Poisson contacts, show that there still exists an age-invariant regime where Poisson assumptions suffice to capture the age dynamics, and specify a general rule of thumb that decides the scope of this regime. Our work that shows the existence of an age-invariant regime is in sharp contact to previous works that highlighted the impact of mobility models under single message scenario. C2 - 2010/// C3 - 2010 ieee global telecommunications conference globecom 2010 DA - 2010/// DO - 10.1109/glocom.2010.5683934 ER - TY - CONF TI - A Distributed Wake-up Scheduling for Opportunistic Forwarding in Wireless Sensor Networks AU - Lee, C. H. AU - Eun, D. Y. AB - In wireless sensor networks (WSNs), sensor nodes are typically subjected to energy constraints and often prone to topology changes. While duty cycling has been widely used for energy conservation in WSNs, random walks have been popular for many delay-tolerant applications in WSNs due to their many inherent desirable properties. In this paper, we consider an opportunistic forwarding under an asynchronous and heterogeneous duty cycling. We first show that its resulting packet trajectory can be interpreted as a continuous-time random walk, and then provide an analytical formula for its end-to-end delay. Since the extremely large end-to-end delay is still undesirable even for most delay-tolerant applications, we develop a distributed wake-up scheduling algorithm in which each node autonomously adjusts its (heterogeneous) wake-up rate based only on its own degree information so as to improve the worst-case end-to-end delay. In particular, we prove that our algorithm outperforms pure homogeneous duty cycling, where every node uses the same wake-up rate, in its guaranteed asymptotic upper bound of the worst-case delay for any graph. In addition, we show that our proposed algorithm brings out more than 35% performance improvement on average when compared with pure homogeneous duty cycling, under various settings of random geometric graphs via numerical evaluations and independent simulation results. C2 - 2010/// C3 - 2010 ieee global telecommunications conference globecom 2010 DA - 2010/// DO - 10.1109/glocom.2010.5683254 ER - TY - JOUR TI - State-Switching Control Technique for Switched Reluctance Motor Drives: Theory and Implementation AU - Lukic, Srdjan M. AU - Emadi, Ali T2 - IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS AB - Switched reluctance motors (SRMs) exhibit advantageous features such as low inertia, fault tolerance, high efficiency, and simple design. However, its control is fairly complex due to nonlinear characteristics of the magnetic flux linkage seen on the stator windings. Several memory and/or processor intensive solutions have been proposed to deal with the control problem, constraining the use of the motor to high-cost and high-performance applications. The focus of this paper is to develop a simple controller for the SRM based on state-switching digital control. The concept of state-switching digital control is to control the motor state (speed) by applying a high or a low energy pulse-above and below the desired steady state of the motor. Such a controller can be implemented in low-complexity analog circuitry. This paper presents two methods of motor control: one for single-speed applications and another for variable speed applications. In addition, this paper derives the control equations and disturbance rejection response. Simulation and experimental results for various operating modes are presented. DA - 2010/9// PY - 2010/9// DO - 10.1109/tie.2009.2038942 VL - 57 IS - 9 SP - 2932-2938 SN - 1557-9948 KW - Speed control KW - switched reluctance motors (SRMs) ER - TY - JOUR TI - Optimal Control of Battery Energy Storage for Wind Farm Dispatching AU - Teleke, Sercan AU - Baran, Mesut E. AU - Bhattacharya, Subhashish AU - Huang, Alex Q. T2 - IEEE TRANSACTIONS ON ENERGY CONVERSION AB - Integrating a battery energy storage system (BESS) with a large wind farm can make a wind farm more dispatchable. This paper focuses on development of a control strategy for optimal use of the BESS for this purpose. The paper considers an open-loop optimal control scheme to incorporate the operating constraints of the BESS, such as state of charge limits, charge/discharge current limits, and lifetime. The goal of the control is to have the BESS to provide as much smoothing as possible, so that the wind farm can be dispatched on an hourly basis based on the forecasted wind conditions. The effectiveness of this control strategy has been tested by using an actual wind farm data. Furthermore, a real-time implementation strategy using model predictive control is also proposed. Finally, it is shown that the control strategy is very important in improving the BESS performance for this application. DA - 2010/9// PY - 2010/9// DO - 10.1109/tec.2010.2041550 VL - 25 IS - 3 SP - 787-794 SN - 1558-0059 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77956056892&partnerID=MN8TOARS KW - Battery energy storage system (BESS) KW - dispatchability KW - model predictive control (MPC) KW - optimal control KW - wind energy ER - TY - JOUR TI - Low-Frequency Noise Measurements of AlGaN/GaN Metal-Oxide-Semiconductor Heterostructure Field-Effect Transistors With HfAlO Gate Dielectric AU - Kayis, Cemil AU - Leach, Jacob H. AU - Zhu, C. Y. AU - Wu, Mo AU - Li, X. AU - Oezguer, Uemit AU - Morkoc, Hadis AU - Yang, X. AU - Misra, Veena AU - Handel, Peter H. T2 - IEEE ELECTRON DEVICE LETTERS AB - We report on the low-frequency phase-noise measurements of AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors employing HfAlO as the gate dielectric. Some devices tested exhibited noise spectra deviating from the well-known 1/f γ spectrum. These devices showed broad peaks in the noise spectral density versus frequency plots, which shifted toward higher frequencies at elevated temperatures. The temperature dependence of the frequency position of this peak allowed us to determine the energy level of these excess traps as 0.22 ± 0.06 eV below the conduction band for the bias conditions employed. DA - 2010/9// PY - 2010/9// DO - 10.1109/led.2010.2055823 VL - 31 IS - 9 SP - 1041-1043 SN - 0741-3106 KW - Gate dielectric KW - generation-recombination (G-R) KW - metal-oxide-semiconductor heterostructure field-effect transistor (MOS-HFET) KW - noise measurement ER - TY - JOUR TI - Long Range Passive UHF RFID System Using HVAC Ducts AU - Nikitin, Pavel V. AU - Arumugam, Darmindra D. AU - Chabalko, Matthew J. AU - Henty, Benjamin E. AU - Stancil, Daniel D. T2 - PROCEEDINGS OF THE IEEE AB - In this paper, the use of hollow metal heating, ventilating, and air-conditioning (HVAC) ducts as a potential communication channel between passive ultrahigh-frequency (UHF) radio-frequency identification (RFID) readers and tags is studied. HVAC ducts behave as electromagnetic waveguides with much lower signal attenuation compared to free-space propagation. This low-loss electromagnetic environment allows one to greatly increase the communication range of passive UHF RFID systems and build, for example, a long range passive sensor network spanning an entire infrastructure such as a large building. In this work, it is shown both theoretically and experimentally that the read range of passive UHF RFID systems can be increased by multiple times compared to operation in a free-space environment. DA - 2010/9// PY - 2010/9// DO - 10.1109/jproc.2010.2047821 VL - 98 IS - 9 SP - 1629-1635 SN - 0018-9219 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77956063007&partnerID=MN8TOARS KW - HVAC duct communications KW - radio frequency identification tags KW - wireless sensor networks ER - TY - JOUR TI - Location-Aided Fast Distributed Consensus in Wireless Networks AU - Li, Wenjun AU - Dai, Huaiyu AU - Zhang, Yanbing T2 - IEEE TRANSACTIONS ON INFORMATION THEORY AB - Existing works on distributed consensus explore linear iterations based on reversible Markov chains, which contribute to the slow convergence of the algorithms. It has been observed that by overcoming the diffusive behavior of reversible chains, certain nonreversible chains lifted from reversible ones mix substantially faster than the original chains. In this paper, the idea of Markov chain lifting is studied to accelerate the convergence of distributed consensus, and two general pseudoalgorithms are presented. These pseudoalgorithms are then instantiated through a class of location-aided distributed averaging (LADA) algorithms for wireless networks, where nodes' coarse location information is used to construct nonreversible chains that facilitate distributed computing and cooperative processing. Our first LADA algorithm is designed for grid networks; for a k × k grid network, it achieves an ε-averaging time of O ( k log(ε -1 )). Based on this algorithm, in a wireless network with transmission range r , an ε-averaging time of O ( r -1 log(ε -1 )) can be attained through a centralized algorithm. Subsequently, a distributed LADA algorithm is presented, achieving the same scaling law in averaging time as the centralized scheme in wireless networks for all r satisfying the connectivity requirement; the constructed chain also attains the optimal scaling law in terms of an important mixing metric, the fill time, in its class. Finally, a cluster-based LADA algorithm is proposed, which, requiring no central coordination, provides the additional benefit of reduced message complexity compared with the distributed LADA algorithm. DA - 2010/12// PY - 2010/12// DO - 10.1109/tit.2010.2081030 VL - 56 IS - 12 SP - 6208-6227 SN - 1557-9654 KW - Clustering KW - distributed computation KW - distributed consensus KW - message complexity KW - mixing time KW - nonreversible Markov chains KW - time complexity ER - TY - JOUR TI - InAs/GaSb broken-gap heterostructure laser for terahertz spectroscopic sensing application AU - Zhang, W. D. AU - Woolard, D. L. T2 - IEEE Transactions on Nanotechnology DA - 2010/// PY - 2010/// VL - 9 IS - 5 SP - 575-581 ER - TY - JOUR TI - Hybrid Ab Initio/Empirical Modeling of the Conformations and Light-Induced Transitions in Stilbene-Derivatives Bonded to DNA AU - Bykhovski, Alexei D. AU - Woolard, Dwight L. T2 - IEEE TRANSACTIONS ON NANOTECHNOLOGY AB - Modeling and simulation techniques are presented, which are both physically accurate and computationally efficient for treating complex organic structures that have relevance to sensing and characterization, including structures with covalent bonding to biological (i.e., DNA) molecules. The theoretical study of large and complex biological molecular systems is very challenging because ab initio quantum mechanical methods are usually too computationally demanding and alternative empirical approaches are often insufficient for describing the internal interactions and dynamics. The goal of this research is to provide detailed insight into the molecular interaction mechanisms (e.g., terahertz (THz) frequency spectral absorption), which can be used to define novel types of bioelectronic-sensing devices. Therefore, a mixed ab initio/molecular mechanical-modeling approach is implemented and applied to the study of stilbene-DNA conjugates that offer switchable spectral characteristics that may be useful for detection and identification purposes. In particular, results are generated for two conformations of a TGCGCA-DNA duplex with trimethoxystilbene carboxamide (TMS) end capping that are confirmed by experimental data. The model is also used to derive the influences of DNA sequence and/or TMS orientation on the conformation, electronic states, and atomic vibrations of single- and doubled-stranded variants of the TGCGCA-DNA duplex. These results, which include very distinct absorption spectra in the THz to UV range, demonstrate that hybrid methodologies can bridge the gap in understanding electronic and atomic structure, and light-induced interactions in complex bioorganic systems. DA - 2010/9// PY - 2010/9// DO - 10.1109/tnano.2010.2060349 VL - 9 IS - 5 SP - 565-574 SN - 1536-125X KW - Bioelectronic sensing KW - DNA KW - stilbene KW - terahertz (THz) ER - TY - CONF TI - Ferromagnetism and near infrared luminescence in neodymium and erbium doped gallium nitride via diffusion AU - Luen, M. O. AU - Nepal, N. AU - Frajtag, P. AU - Zavada, J. M. AU - Brown, E. AU - Hommerich, U. AU - Bedair, S. M. AU - El Masry, N. A. C2 - 2010/// C3 - Novel materials and devices for spintronics DA - 2010/// DO - 10.1557/proc-1183-ff06-01 VL - 1183 SP - 45-50 ER - TY - JOUR TI - Examining the auditory nerve fiber response to high rate cochlear implant stimulation: Chronic sensorineural hearing loss and facilitation AU - Heffer, L. F. AU - Sly, D. J. AU - Fallon, J. B. AU - White, M. W. AU - Shepherd, R. K. AU - O'Leary, S. J. T2 - Journal of Neurophysiology DA - 2010/// PY - 2010/// VL - 104 IS - 6 SP - 3124-3135 ER - TY - JOUR TI - Er-doped GaN and InxGa1-xN for optical communications AU - Dahal, R. AU - Lin, J. Y. AU - Jiang, H. X. AU - Zavada, J. M. T2 - Rare earth doped iii-nitrides for optoelectronic and spintronic applications DA - 2010/// PY - 2010/// VL - 124 SP - 115-157 ER - TY - JOUR TI - Enhanced Control of Voltage Source Converters for DC Shipboard Power Systems AU - Teleke, Sercan AU - Bhattacharya, Subhashish AU - Baran, Mesut T2 - NAVAL ENGINEERS JOURNAL AB - In this paper, an enhanced control scheme for a pulse-width-modulated (PWM) voltage source converter (VSC) is proposed for a DC zonal shipboard power system (SPS). First, the main design parameters of VSC such as switching frequency and DC-link capacitance are investigated and optimized for the SPS application. Then, the nonideal operating conditions such as sudden load change, sudden supply voltage change, and unbalanced supply voltage are considered. To address these issues, the VSC control strategy has been enhanced by (i) adopting a different PWM strategy that changes the carrier frequency under nonideal operating conditions, (ii) adding a negative-sequence controller, and (iii) implementing an instantaneous phase locked loop (PLL). The results show that the proposed controller shows indeed a satisfactory performance for this specific application and it can also operate at unity displacement power factor under nonideal conditions. DA - 2010/// PY - 2010/// DO - 10.1111/j.1559-3584.2010.00239.x VL - 122 IS - 1 SP - 81-91 SN - 1559-3584 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78650143229&partnerID=MN8TOARS ER - TY - JOUR TI - Criticality-driven Superscalar Design Space Exploration AU - Navada, Sandeep AU - Choudhary, Niket K. AU - Rotenberg, Eric T2 - PACT 2010: PROCEEDINGS OF THE NINETEENTH INTERNATIONAL CONFERENCE ON PARALLEL ARCHITECTURES AND COMPILATION TECHNIQUES AB - It has become increasingly difficult to perform design space exploration (DSE) of computer systems with a short turnaround time because of exploding design spaces, increasing design complexity and long-running workloads. Researchers have used classical search/optimization techniques like simulated annealing, genetic algorithms, etc., to accelerate the DSE. While these techniques are better than an exhaustive search, a substantial amount of time must still be dedicated to DSE. This is a serious bottleneck in reducing research/development time. These techniques do not perform the DSE quickly enough, primarily because they do not leverage any insight as to how the different design parameters of a computer system interact to increase or degrade performance at a design point and treat the computer system as a "black-box". DA - 2010/// PY - 2010/// DO - 10.1145/1854273.1854308 SP - 261-272 KW - design space exploration KW - criticality model KW - bottleneck analysis KW - superscalar processors KW - simulated annealing ER - TY - JOUR TI - Collaborative Quickest Spectrum Sensing via Random Broadcast in Cognitive Radio Systems AU - Li, Husheng AU - Dai, Huaiyu AU - Li, Chengzhi T2 - IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS AB - Quickest detection is applied in spectrum sensing in cognitive radio systems when multiple secondary users collaborate with limited communication time slots. When the transmissions of sensing results are not coordinated to avoid confliction, random broadcast is used to exchange information. A necessary condition for the optimal broadcast probability, as a function of the log likelihood ratio of local observation, is obtained using variational analysis. To alleviate the difficulty of computing the optimal broadcast probability, a simple threshold broadcast scheme is proposed. Simulation shows that the proposed threshold broadcast scheme can achieve substantial performance gain (less than 60% in detection delay for the same false alarm rate) over schemes of random broadcast without regulation and single-user spectrum sensing. DA - 2010/7// PY - 2010/7// DO - 10.1109/twc.2010.07.091667 VL - 9 IS - 7 SP - 2338-2348 SN - 1558-2248 KW - Cognitive radio KW - spectrum sensing KW - quickest detection KW - random broadcast ER - TY - JOUR TI - Acoustic Indicators for Targeted Detection of Stored Product and Urban Insect Pests by Inexpensive Infrared, Acoustic, and Vibrational Detection of Movement AU - Mankin, R. W. AU - Hodges, R. D. AU - Nagle, H. T. AU - Schal, C. AU - Pereira, R. M. AU - Koehler, P. G. T2 - JOURNAL OF ECONOMIC ENTOMOLOGY AB - Crawling and scraping activity of three stored-product pests, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), and Stegobium paniceum (L.) (Coleoptera: Anobiidae), and two urban pests, Blattella germanica (L.) (Blattodea: Blattellidae) and Cimex lectularius L. (Hemiptera: Cimicidae), were monitored individually by infrared sensors, microphones, and a piezoelectric sensor in a small arena to evaluate effects of insect locomotory behavior and size on the ability of an inexpensively constructed instrument to detect insects and distinguish among different species. Adults of all species could be detected when crawling or scraping. The smallest insects in the study, first-fourth-instar C. lectularius nymphs, could not be detected easily when crawling, but could be detected when scraping. Sound and vibration sensors detected brief, 3-10-ms impulses from all tested species, often grouped in distinctive trains (bursts), typical of impulses in previous acoustic detection experiments. To consider the potential for targeting or focusing detection on particular species of interest, indicators were developed to assess the likelihood of detection of C. lectularius. Statistically significant differences were found between C. lectularius and other species in distributions of three measured variables: infrared signal durations, sound impulse-burst durations, and sound pressure levels (energy) of impulses that best matched an averaged spectrum (profile) of scraping behavior. Thus, there is potential that signals collected by an inexpensive, polymodal-sensor instrument could be used in automated trapping systems to detect a targeted species, 0.1 mg or larger, in environments where servicing of traps is difficult or when timeliness of trapping information is important. DA - 2010/10// PY - 2010/10// DO - 10.1603/ec10126 VL - 103 IS - 5 SP - 1636-1646 SN - 1938-291X KW - bed bug KW - cockroach KW - rice weevil KW - red flour beetle KW - drugstore beetle ER - TY - JOUR TI - Transient-voltage-clamp circuit design based on constant load line impedance for voltage regulator module AU - Lim, S. AU - Fan, J. W. AU - Huang, A. Q. T2 - IEEE Transactions on Industrial Electronics AB - A transient-voltage-clamp (TVC) circuit acts as a replacement of bulk capacitors, which is required for voltage regulator (VR) module (VRM) to clamp output voltage spikes. With the TVC circuit, VRM size is greatly reduced with similar transient performance. This paper presents a new TVC circuit. This TVC circuit is designed based on the constant load line impedance which is recently given by Intel's VRM11.0. The TVC circuit works in parallel with VR decoupling capacitors to achieve faster voltage regulation. The impedances of the VR, output capacitors, and the proposed TVC circuit are analyzed. The TVC circuit design procedure is described, and the transient performance and power consumption are discussed. The theoretical analysis is verified by simulation results. Moreover, the proposed TVC circuit is fabricated with a 0.6-μm CMOS process, and experimental results verify the simulation results and theoretical analysis. DA - 2010/// PY - 2010/// DO - 10.1109/tie.2010.2042419 VL - 57 IS - 12 SP - 4085-4094 ER - TY - CONF TI - Towards efficient designs for in-network computing with noisy wireless channels AU - Li, C. Z. AU - Dai, H. Y. AB - In this paper we study distributed function computation in a noisy multi-hop wireless network, in which n nodes are uniformly and independently distributed in a unit square. 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 ¿. Each node holds an m-bit integer per instance and the computation is started 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 covers 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; its bottleneck in different scenarios is also analyzed. Based on this analysis, we then endeavor to improve the design for two special cases: identity function, and some restricted type-threshold functions, both focusing on the constant m and N scenario. C2 - 2010/// C3 - 2010 proceedings ieee infocom DA - 2010/// DO - 10.1109/infcom.2010.5462023 ER - TY - JOUR TI - Surface polar phonon dominated electron transport in graphene AU - Li, X. AU - Barry, E. A. AU - Zavada, J. M. AU - Buongiorno Nardelli, M. AU - Kim, K. W. T2 - Applied Physics Letters AB - The effects of surface polar phonons on the electronic transport properties of monolayer graphene are studied by using a Monte Carlo simulation. Specifically, the low-field electron mobility and saturation velocity are examined for different substrates (SiC, SiO2, and HfO2) in comparison to the intrinsic case. While the results show that the low-field mobility can be substantially reduced by the introduction of surface polar phonon scattering, corresponding degradation of the saturation velocity is not observed for all three substrates at room temperature. It is also found that surface polar phonons can influence graphene’s electrical resistivity even at low temperature, leading potentially to inaccurate estimation of the acoustic phonon deformation potential constant. DA - 2010/12/6/ PY - 2010/12/6/ DO - 10.1063/1.3525606 VL - 97 IS - 23 SP - 232105 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.3525606 DB - Crossref ER - TY - JOUR TI - SPECIAL SECTION ON ENERGY STORAGE SYSTEMS: INTERFACE, POWER ELECTRONICS, AND CONTROL AU - Franquelo, Leopoldo G. AU - Lukic, Srdjan M. AU - Vazquez, Sergio AU - Atcitty, Stan T2 - IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS AB - The 15 papers in this special section focus on energy storage systems. DA - 2010/12// PY - 2010/12// DO - 10.1109/tie.2010.2075110 VL - 57 IS - 12 SP - 3878-3880 SN - 1557-9948 ER - TY - JOUR TI - Polarization Gratings: A Novel Polarimetric Component for Astronomical Instruments AU - Packham, C. AU - Escuti, M. AU - Ginn, J. AU - Oh, C. AU - Quijano, I. AU - Boreman, G. T2 - PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC AB - Polarization gratings (PGs) have been recently been developed for ultraefficient liquid crystal displays, nonmechanical optical beam steering, and telecommunication devices at optical and near-infrared wavelengths (0.4–2.0 µm). A PG simultaneously acts as both a spectroscopic and polarimetric disperser for circularly polarized light. With the use of a quarter-wave retarder (or analog) to convert linearly to circularly polarized light, these devices can be used as linear polarimetric analyzers. PGs offer high throughput and high levels of birefringence and can currently be constructed inexpensively to diameters of 150 mm, and development projects are in progress to double that size. In this article we report on the characterization of a PG sample at mid-infrared wavelengths (2–40 µm), including the birefringence, throughput, spectral response, and cold cycling survivability. We discuss these devices in the context of astronomical polarimetry, especially as the polarimetric components for a conceptual study of a SOFIA-based polarimeter. DA - 2010/12// PY - 2010/12// DO - 10.1086/657904 VL - 122 IS - 898 SP - 1471-1482 SN - 1538-3873 ER - TY - CONF TI - On the connectivity analysis over large-scale hybrid wireless networks AU - Yi, C. AU - Wang, Wenye AB - Many real systems are hybrid networks which include infrastructure nodes in multi-hop wireless networks, such as sinks in sensor networks and mesh routers in mesh networks. However, we have very little understanding of network connectivity in such networks. Therefore, in this paper, we consider hybrid networks denoted by H(¿, ß) with ad hoc nodes and base stations and prove how base stations can improve the connectivity of ad hoc nodes in subcritical phase, that is, the ad hoc node density, ¿ ¿ is lower than the critical density ¿ ¿ c . We find that with the existence of a positive density of base stations, i.e., the density of base stations ¿ ß > 0 which have the same transmission range as ad hoc nodes, the number of connected ad hoc nodes is ¿(n) with probability nearly 1, where n is the number of ad hoc nodes. However, the size of connected ad hoc component scales linearly with ¿ ß when it is lower than c 1 (¿ ¿ ) with probability nearly 1, which demonstrates a tremendous benefit of using base stations to enhance the connectivity of ad hoc nodes. Further, we study a hybrid network architecture that makes a significant connectivity improvement with transmission range r ß larger than r ¿ for ad hoc nodes. Therefore, our results provide a theoretical understanding of to what extent ad hoc nodes can benefit from base stations in multi-hop wireless networks. C2 - 2010/// C3 - 2010 proceedings ieee infocom DA - 2010/// DO - 10.1109/infcom.2010.5462106 ER - TY - CONF TI - On order gain of backoff misbehaving nodes in CSMA/CA-based wireless networks AU - Lu, Z. AU - Wang, Wenye AU - Wang, C. AB - Backoff misbehavior, in which a wireless node deliberately manipulates its backoff time, can induce significant network problems, such as severe unfairness and denial-of-service. Although great progress has been made towards the design of countermeasures to backoff misbehavior, little attention has been focused on quantifying the gain of backoff misbehaviors. In this paper, we define and study two general classes of backoff misbehavior to assess the gain that misbehaving nodes can obtain. The first class, called continuous misbehavior, keeps manipulating the backoff time unless it is disabled by countermeasures. The second class is referred to as intermittent misbehavior, which tends to evade the detection by countermeasures by performing misbehavior sporadically. Our approach is to introduce a new performance metric, namely order gain, which is to characterize the performance benefits of misbehaving nodes in comparison to legitimate nodes. Through analytical studies, simulations, and experiments, we demonstrate the impact of a wide range of backoff misbehaviors on network performance with respect to the number of users in CSMA/CA-based wireless networks. C2 - 2010/// C3 - 2010 proceedings ieee infocom DA - 2010/// DO - 10.1109/infcom.2010.5462002 ER - TY - CONF TI - Improving cache performance by combining cost-sensitivity and locality principles in cache replacement algorithms AU - Sheikh, R. AU - Kharbutli, M. C2 - 2010/// C3 - 2010 ieee international conference on computer design DA - 2010/// SP - 76-83 ER - TY - JOUR TI - Guest Editors' Introduction: Special Issue on Modeling and Simulation of Cross-Layer Interactions in Communication Networks AU - Devetsikiotis, Michael AU - Granelli, Fabrizio T2 - ACM TRANSACTIONS ON MODELING AND COMPUTER SIMULATION AB - introduction Share on Guest editors' introduction: Special issue on modeling and simulation of cross-layer interactions in communication networks Authors: Michael Devetsikiotis North carolina state university North carolina state universityView Profile , Fabrizio Granelli University of trento University of trentoView Profile Authors Info & Claims ACM Transactions on Modeling and Computer SimulationVolume 21Issue 1December 2010 Article No.: 1pp 1–4https://doi.org/10.1145/1870085.1870086Published:17 December 2010Publication History 0citation178DownloadsMetricsTotal Citations0Total Downloads178Last 12 Months2Last 6 weeks0 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my Alerts New Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access DA - 2010/12// PY - 2010/12// DO - 10.1145/1870085.1870086 VL - 21 IS - 1 SP - SN - 1049-3301 ER - TY - JOUR TI - Global optimization by adapted diffusion AU - Poliannikov, O. V. AU - Zhizhina, E. AU - Krim, H. T2 - IEEE Transactions on Signal Processing AB - In this paper, we study a diffusion stochastic dynamics with a general diffusion coefficient. The main result is that adapting the diffusion coefficient to the Hamiltonian allows to escape local wide minima and to speed up the convergence of the dynamics to the global minima. We prove the convergence of the invariant measure of the modified dynamics to a measure concentrated on the set of global minima and show how to choose a diffusion coefficient for a certain class of Hamiltonians. DA - 2010/// PY - 2010/// DO - 10.1109/tsp.2010.2071867 VL - 58 IS - 12 SP - 6119-6125 ER - TY - JOUR TI - Energy Storage Systems for Transport and Grid Applications AU - Vazquez, Sergio AU - Lukic, Srdjan M. AU - Galvan, Eduardo AU - Franquelo, Leopoldo G. AU - Carrasco, Juan M. T2 - IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS AB - Energy storage systems (ESSs) are enabling technologies for well-established and new applications such as power peak shaving, electric vehicles, integration of renewable energies, etc. This paper presents a review of ESSs for transport and grid applications, covering several aspects as the storage technology, the main applications, and the power converters used to operate some of the energy storage technologies. Special attention is given to the different applications, providing a deep description of the system and addressing the most suitable storage technology. The main objective of this paper is to introduce the subject and to give an updated reference to nonspecialist, academic, and engineers in the field of power electronics. DA - 2010/12// PY - 2010/12// DO - 10.1109/tie.2010.2076414 VL - 57 IS - 12 SP - 3881-3895 SN - 1557-9948 KW - Batteries KW - compressed air energy storage (CAES) KW - energy storage KW - flywheel KW - fuel cell KW - power conversion KW - power electronics KW - renewable energy KW - supercapacitors KW - superconductive magnetic energy storage (SMES) KW - thermoelectric energy storage (TEES) ER - TY - JOUR TI - Electron spin relaxation in carbon nanotubes AU - Semenov, Y. G. AU - Zavada, J. M. AU - Kim, K. W. T2 - Physical Review B AB - The long-standing problem of inexplicably short spin relaxation in carbon nanotubes is examined. The curvature-mediated spin-orbital interaction is shown to induce fluctuating electron spin precession causing efficient relaxation in a manner analogous to the Dyakonov-Perel mechanism. Our calculations in single-walled semiconducting nanotubes estimate longitudinal (spin-flip) and transversal (decoherence) relaxation times as short as 150 and 130 ps at room temperature along with a pronounced anisotropic dependence. Interference of electrons originating from different valleys can lead to even faster dephasing. The results can help clarify the measured data, resolving discrepancies in the literature. DA - 2010/10/27/ PY - 2010/10/27/ DO - 10.1103/physrevb.82.155449 VL - 82 IS - 15 SP - J2 - Phys. Rev. B LA - en OP - SN - 1098-0121 1550-235X UR - http://dx.doi.org/10.1103/PhysRevB.82.155449 DB - Crossref ER - TY - JOUR TI - Concurrent visual multiple lane detection for autonomous vehicles AU - Gupta, Rachana Ashok AU - Snyder, Wesley AU - Pitts, W. Shepherd T2 - 2010 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA) AB - This paper proposes a monocular vision solution to simultaneous detection of multiple lanes in navigable regions/urban roads using accumulator voting. Unlike other approaches in literature, this paper first examines the extent of lane parameters required for continuous control of any vehicle manually or autonomously. The accumulator-based algorithm is designed using this fundamental control knowledge to vote for the required lane parameters (position of lanes and steering angle required) in the image plane. The novel accumulator voting scheme is called "Parametric Transform for Multi-lane Detection". This paper not only adapts predictive control in the image plane, but also detects multiple lanes in the scene concurrently in the form of multiple peaks in the accumulator. This method is robust to shadows and invariant to color, texture, and width of the road. Finally, the method is designed for dashed/continuous lines. DA - 2010/// PY - 2010/// DO - 10.1109/robot.2010.5509389 SP - 2416-2422 SN - 2577-087X ER - TY - CONF TI - Characterizing the spread of correlated failures in large wireless networks AU - Xu, Y. AU - Wang, Wenye AB - Correlated failures pose a great challenge for the normal functioning of large wireless networks, because an initial local failure may trigger a global sequence of related failures. Given their potentially devastating impact, we characterize the spread of correlated failures in this paper, which lays the foundation for evaluating and improving the failure resilience of existing wireless networks. We model the failure contagiousness as two generic functions: the failure impact radius distribution function f r (x) and the failure connection function g(x). By using the percolation theory, we determine the respective characteristic regimes of f r (x) and g(x) in which correlated failures will and will not percolate in the network. As our model represents various failure scenarios, the results are generally applicable in understanding the spread of a wide range of correlated failures. C2 - 2010/// C3 - 2010 proceedings ieee infocom DA - 2010/// DO - 10.1109/infcom.2010.5462009 ER - TY - JOUR TI - Behavioural modelling and impact analysis of physical impairments in quadrature modulators AU - Li, M. AU - Hoover, L. AU - Gard, K. G. AU - Steer, M. B. T2 - IET MICROWAVES ANTENNAS & PROPAGATION AB - Non-linear distortion and linear static errors (DC offset and gain/phase imbalance) are the major analogue impairments in microwave I/Q quadrature modulators. They can adversely impact the performance of the systems using them, especially for direct-conversion transceiver systems. The impacts of these impairments were investigated for three different modulator applications: double sideband modulation, zero intermediate frequency (IF) single sideband (SSB) orthogonal frequency-division multiplexing (OFDM) modulation and low-IF SSB OFDM modulation. A behavioural model for characterising the non-linear response and the linear static errors was developed. The non-linear characteristic of each input was modelled by a complex power series based on amplitude-to-amplitude modulation and amplitude-to-phase modulation measurements. The linear static errors were modelled as three static error terms added into the complex power series based on a four-DC-point vector network analyser measurement. The non-linear model was validated by measurements with three types of signals representing the three modulator applications. DA - 2010/12// PY - 2010/12// DO - 10.1049/iet-map.2009.0278 VL - 4 IS - 12 SP - 2144-2154 SN - 1751-8733 ER - TY - CONF TI - case study: gpu-based implementation of sequence pair based floorplanning using cuda AU - Choi, W. H. AU - Liu, X. C2 - 2010/// C3 - 2010 ieee international symposium on circuits and systems DA - 2010/// SP - 917-920 ER - TY - JOUR TI - Understanding the Behavior and Implications of Context Switch Misses AU - Liu, Fang AU - Solihin, Yan T2 - ACM TRANSACTIONS ON ARCHITECTURE AND CODE OPTIMIZATION AB - One of the essential features in modern computer systems is context switching, which allows multiple threads of execution to time-share a limited number of processors. While very useful, context switching can introduce high performance overheads, with one of the primary reasons being the cache perturbation effect. Between the time a thread is switched out and when it resumes execution, parts of its working set in the cache may be perturbed by other interfering threads, leading to (context switch) cache misses to recover from the perturbation. The goal of this article is to understand how cache parameters and application behavior influence the number of context switch misses the application suffers from. We characterize a previously unreported type of context switch misses that occur as the artifact of the interaction of cache replacement policy and an application's temporal reuse behavior. We characterize the behavior of these “reordered misses” for various applications, cache sizes, and various amount of cache perturbation. As a second contribution, we develop an analytical model that reveals the mathematical relationship between cache design parameters, an application's temporal reuse pattern, and the number of context switch misses the application suffers from. We validate the model against simulation studies and find that it is sufficiently accurate in predicting the trends of context switch misses with regard to various cache perturbation amount. The mathematical relationship provided by the model allows us to derive insights into precisely why some applications are more vulnerable to context switch misses than others. Through a case study on prefetching, we find that prefetching tends to aggravate the number of context switch misses and a less aggresive prefetching technique can reduce the number of context switch misses the application suffers from. We also investigate how cache sizes affect context switch misses. Our study shows that under relatively heavy workloads in the system, the worst-case number of context switch misses an application suffers from tends to increase proportionally with cache sizes, to the extent that may completely negate the reduction in other types of cache misses. DA - 2010/12// PY - 2010/12// DO - 10.1145/1880043.1880048 VL - 7 IS - 4 SP - SN - 1544-3973 KW - Algorithms KW - Design KW - Experimentation KW - Performance KW - Context switch misses KW - stack distance profiling KW - analytical model KW - prefetching ER - TY - JOUR TI - Transport Capacity and Connectivity of Cognitive Radio Networks with Outage Constraint AU - Li, Chengzhi AU - Dai, Huaiyu T2 - 2010 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY AB - In this paper we study two basic properties, capacity and connectivity, of Cognitive Radio networks. Our goal is to quantitatively characterize the relationship and tradeoff among key system parameters involved in these properties, incorporating channel randomness and interference into the performance analysis. In particular, we explore the characterization of a capacity metric, single-hop transport capacity, with respect to arbitrarily and randomly located receivers, and investigate a fundamental connectivity metric, node isolation probability. The tradeoff between capacity and connectivity is also revealed. DA - 2010/// PY - 2010/// DO - 10.1109/isit.2010.5513267 SP - 1743-1747 ER - TY - CONF TI - Thermal analysis and verification of a mounted monolithic integrated circuit AU - Harris, T.R. AU - Melamed, S. AU - Luniya, S. AU - Davis, W.R. AU - Steer, M.B. AU - Doxsee, L.E. AU - Obermiller, K. AU - Hawkinson, C. T2 - IEEE SoutheastCon 2010 (SoutheastCon) AB - As circuit density increases and high-power applications are facilitated, thermal considerations become paramount a design concern. In this paper, a high power monolithic microwave integrated circuit (MMIC) is modeled by the fREEDA multi-physics simulator and measured for validation. While validation is the crux of any simulation model, it is known that thermal measurements accurate to a high resolution are problematic. As such, the thermal profile of integrated circuits cannot be measured directly with infrared thermal imaging due to unequivalent emissivities of materials. It becomes necessary to use an absorptive ink to approximate a blackbody so that the infrared emissions can be used to infer temperature. The impact and effect of this thermal imaging technique is investigated in this work by comparing measurements with detailed thermal simulations with and without the surface treatment. Thermal analysis uses the finite element method and a reduced-order model based on cuboids with effective thermal conductivities. The end goal is to provide a simulation tool to designers, which can be extended to any project which requires attention to thermal preference. C2 - 2010/// C3 - Proceedings of the IEEE SoutheastCon 2010 (SoutheastCon) CY - Concord, NC DA - 2010/// PY - 2010/3/18/ DO - 10.1109/secon.2010.5453924 SP - 37-40 KW - MMIC KW - electrothermal KW - heat transfer KW - simulators KW - compact modeling KW - fREEDA ER - TY - JOUR TI - The integration of novel EAP-based Braille cells for use in a refreshable tactile display AU - Di Spigna, N. AU - Chakraborti, P. AU - Winick, D. AU - Yang, P. AU - Ghosh, T. AU - Franzon, P. T2 - ELECTROACTIVE POLYMER ACTUATORS AND DEVICES (EAPAD) 2010 AB - Structures demonstrating the viability of both the hydraulic and latching Braille dot, and the dielectric elastomer fiber Braille dot have been fabricated and characterized. A hydraulic proof-of-concept structure has achieved the necessary volumetric change required to lift a Braille dot over 0.5mm at voltages under 1000V and at speeds under 100ms. Long bimorphs have been fabricated that demonstrate large tip displacements over 2mm that could be used to mechanically latch the Braille rod in the 'up' position to achieve the force requirement. The addition of radial prestrain in dielectric elastomer tubes has reduced the wall thickness and directed the strain in the axial direction which has had a dramatic impact on their resulting characteristics. The required bias voltage for the dielectric elastomer fiber Braille dot has been reduced from 15.5kV to 8.75kV while the Braille head tip displacement of a fabricated prototype has almost tripled on average and now also exceeds the required displacement for a refreshable Braille display. Finally, potential solutions to the current shortcomings of both designs in meeting all of the requirements for such a display are discussed. DA - 2010/// PY - 2010/// DO - 10.1117/12.847666 VL - 7642 SP - SN - 1996-756X KW - Braille KW - blind KW - PVDF KW - electroactive polymers KW - dielectric elastomer KW - visual impairments KW - bimorph ER - TY - CONF TI - Review and evaluation of security threats on the communication networks in the smart grid AU - Lu, Z. AU - Lu, X. A. AU - Wang, Wenye AU - Wang, C. AB - The smart grid, generally referred to as the next-generation power electric system, relies on robust communication networks to provide efficient, secure, and reliable information delivery. Thus, the network security is of critical importance in the smart grid. In this paper, we aim at classifying and evaluating the security threats on the communication networks in the smart grid. Based on a top-down analysis, we categorize the goals of potential attacks against the smart grid communication networks into three types: network availability, data integrity and information privacy. We then qualitatively analyze both the impact and feasibility of the three types of attacks. Moreover, since network availability is the top priority in the security objectives for the smart grid, we use experiments to quantitatively evaluate the impact of denial-of-service (DoS) attacks on a power substation network. Our work provides initial experimental data of DoS attacks against a power network and shows that the network performance degrades dramatically only when the DoS attack intensity approaches to the maximum. C2 - 2010/// C3 - Military communications conference, 2010 (milcom 2010) DA - 2010/// DO - 10.1109/milcom.2010.5679551 SP - 1830–1835 ER - TY - JOUR TI - Quality of Service Shared Cache Management in Chip Multiprocessor Architecture AU - Guo, Fei AU - Solihin, Yan AU - Zhao, Li AU - Iyer, Ravishankar T2 - ACM TRANSACTIONS ON ARCHITECTURE AND CODE OPTIMIZATION AB - The trends in enterprise IT toward service-oriented computing, server consolidation, and virtual computing point to a future in which workloads are becoming increasingly diverse in terms of performance, reliability, and availability requirements. It can be expected that more and more applications with diverse requirements will run on a Chip Multi-Processor (CMP) and share platform resources such as the lowest level cache and off-chip bandwidth. In this environment, it is desirable to have microarchitecture and software support that can provide a guarantee of a certain level of performance, which we refer to as performance Quality of Service . In this article, we investigated a framework would be needed to manage the shared cache resource for fully providing QoS in a CMP. We found in order to fully provide QoS, we need to specify an appropriate QoS target for each job and apply an admission control policy to accept jobs only when their QoS targets can be satisfied. We also found that providing strict QoS often leads to a significant reduction in throughput due to resource fragmentation. We proposed throughput optimization techniques that include: (1) exploiting various QoS execution modes, and (2) a microarchitecture technique, which we refer to as resource stealing, that detects and reallocates excess cache capacity from a job while preserving its QoS target. We designed and evaluated three algorithms for performing resource stealing, which differ in how aggressive they are in stealing excess cache capacity, and in the degree of confidence in meeting QoS targets. In addition, we proposed a mechanism to dynamically enable or disable resource stealing depending on whether other jobs can benefit from additional cache capacity. We evaluated our QoS framework with a full system simulation of a 4-core CMP and a recent version of the Linux Operating System. We found that compared to an unoptimized scheme, the throughput can be improved by up to 47%, making the throughput significantly closer to a non-QoS CMP. DA - 2010/12// PY - 2010/12// DO - 10.1145/1880037.1880039 VL - 7 IS - 3 SP - SN - 1544-3973 KW - Design KW - Performance KW - Cache KW - chip multi-processors KW - CMP KW - multicore architecture KW - quality of service KW - QoS KW - performance KW - resource stealing ER - TY - CONF TI - New inductor current feedback control with active harmonics injection for inverter stage of solid state transformer AU - Zhou, X. AU - Liu, Y. AU - Bhattacharya, Subhashish AU - Huang, A. AB - Solid state transformer (SST) is considered the key unit for power processing and conversion in the future distributed renewable energy network. The role of SST is to enable the active management of distributed energy resources, energy storage devices and different type of loads in a distribution grid. Inverter stage of SST supplies sinusoidal voltage to the users. In this paper an improved inductor current control based on active harmonics injection is proposed to overcome the drawback of inferior performance of conventional inductor current feedback control for the nonlinear loads. The inductor current overshoot during the load transient is investigated by using both capacitor current feedback control and inductor current feedback control. The inductor current feedback control has the capability to limit current overshoot even with a smaller inductor, which shows the potential to further reduce the size and weight of the passive components. C2 - 2010/// C3 - IECON Proceedings (Industrial Electronics Conference) DA - 2010/// DO - 10.1109/iecon.2010.5675216 SP - 593-598 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78751540900&partnerID=MN8TOARS ER - TY - CONF TI - Improvement of gate drive for self-power emitter turn-off thyristor (speto) AU - Chen, Q. A. AU - Huang, A. Q. AB - Self-power emitter turn-off thyristor (SPETO) is a high power switching device which could provide power for its gate drive during operation. Self-power function reduces the system cost and makes the mechanical structure compact, whereas it may bring extra harmonic when SPETO is being utilized in power utilities. In this paper, the impact of self-power function on extra harmonic is analyzed. The ideas to improve SPETO gate drive hence reduce extra harmonic are presented and verified by simulation. C2 - 2010/// C3 - Iecon 2010: 36th annual conference of the ieee industrial electronics society DA - 2010/// DO - 10.1109/iecon.2010.5675201 ER - TY - JOUR TI - High efficiency quasi-ternary design for nonmechanical beam-steering utilizing polarization gratings AU - Kim, Jihwan AU - Miskiewicz, Matthew N. AU - Serati, Steve AU - Escuti, Michael J. T2 - ADVANCED WAVEFRONT CONTROL: METHODS, DEVICES, AND APPLICATIONS VIII AB - We introduce and demonstrate a quasi-ternary nonmechanical beam steering design based on Polarization Gratings (PGs). That uses a single wave plate and N PGs to generate 2(N+1)-1 steering angles. When compared to conventional binary (2N) or ternary (3N) liquid crystal PG steering designs, this technique uses fewer elements arranged in a simpler configuration to obtain the same number of steering angles. This advantageous property can be achieved by selecting proper diffraction angles and alignment of the PGs. Due to fewer elements per stage, losses due to electrode absorption and Fresnel reflections are reduced, thereby increasing the overall steering efficiency. Using this approach, we demonstrate a four-stage (N = 4) quasi-ternary beam steering device that achieves 52° Field Of Regard (FOR) with 1.7° resolution (31 steering angles) at 1550 nm wavelength. DA - 2010/// PY - 2010/// DO - 10.1117/12.860885 VL - 7816 SP - SN - 1996-756X KW - Non-mechanical beam steering KW - laser radar KW - laser beam steering KW - lidar KW - polarization grating KW - liquid crystals ER - TY - JOUR TI - Effect of controlled drainage on water and nitrogen balances in drained lands AU - Skaggs, R. W. AU - Youssef, M. A. AU - Gilliam, J. W. AU - Evans, R. O. T2 - Transactions of the ASABE AB - Field studies have shown that subsurface drainage systems can be managed to conserve water and reduce losses of nitrogen (N) to surface waters. The practice, called controlled drainage (CD) or drainage water management (DWM), is a viable alternative for reducing N loads from drained cropland, including millions of acres in the Midwest. This article reviews past studies on the effect of CD on drainage volumes and N losses for a wide range of soils and climatological conditions and uses simulations to examine mechanisms affecting the practice. Results published in the literature show that CD has reduced drainage volumes and N losses in drainage waters by 17% to over 80%, depending on soil properties, crops, drainage intensities, control strategies, and location. This study resulted in the following conclusions. CD reduces subsurface drainage and raises water tables, while increasing ET, seepage, and surface runoff. Seepage, which depends on soil properties and site conditions, is an important factor that often governs the effectiveness of CD. Experiments to determine the effect of CD on drainage volumes and N losses should be conducted on the field or watershed scale so that impacts of seepage are properly represented. Increases in ET in response to CD are important but are rarely greater than 10%. The effect of this increase in water use on drainage water loss is also less than 10% for most locations. CD reduces N losses in drainage water by about the same percentage as its effect on subsurface drainage volume in most cases. The effect of CD on N loss to surface waters depends on denitrification, both in the profile and in reduced zones along seepage paths. For soils that do not develop reduced zones, the effect of CD on N loss may be substantially less than its effect on drainage volume. DA - 2010/// PY - 2010/// DO - 10.13031/2013.35810 VL - 53 IS - 6 SP - 1843-1850 ER - TY - CONF TI - Design considerations of high voltage and high frequency transformer for solid state transformer application AU - Baek, S. AU - Du, Y. AU - Wang, G. AU - Bhattacharya, Subhashish AB - This paper presents overall design considerations of the high-voltage and high-frequency (HV-HF) transformer in dc/dc converter stages of solid state transformer (SST). SST is a new concept of an interface for direct connection between the distribution line and local customers which can be considered as another generation source as well from the local smart-grid point of view. Therefore, the size and weight reduction are the main objectives of this system. Therefore, increasing operating frequency to minimize the bulky magnetic elements and solid insulation become necessary. Especially, the inductance of transformer plays a crucial role in Dual-Active Bridge (DAB) converter to determine the power transfer, therefore, the inductance optimization depending on winding structures is investigated and a high voltage insulation is carefully designed to support 15kV in this paper. A comprehensive electromagnetic analysis is conducted to validate the proposed design by finite element analysis (FEA) and experimental result with 2kVA scale-down transformer is analyzed first and, finally, 3 versions of 7kVA HV-HF transformer are built and tested for SST application. C2 - 2010/// C3 - IECON Proceedings (Industrial Electronics Conference) DA - 2010/// DO - 10.1109/IECON.2010.5674991 SP - 421-426 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78751474139&partnerID=MN8TOARS ER - TY - JOUR TI - Authenticating Primary Users' Signals in Cognitive Radio Networks via Integrated Cryptographic and Wireless Link Signatures AU - Liu, Yao AU - Ning, Peng AU - Dai, Huaiyu T2 - 2010 IEEE SYMPOSIUM ON SECURITY AND PRIVACY AB - To address the increasing demand for wireless bandwidth, cognitive radio networks (CRNs) have been proposed to increase the efficiency of channel utilization; they enable the sharing of channels among secondary (unlicensed) and primary (licensed) users on a non-interference basis. A secondary user in a CRN should constantly monitor for the presence of a primary user's signal to avoid interfering with the primary user. However, to gain unfair share of radio channels, an attacker (e.g., a selfish secondary user) may mimic a primary user's signal to evict other secondary users. Therefore, a secure primary user detection method that can distinguish a primary user's signal from an attacker's signal is needed. A unique challenge in addressing this problem is that Federal Communications Commission (FCC) prohibits any modification to primary users. Consequently, existing cryptographic techniques cannot be used directly. In this paper, we develop a novel approach for authenticating primary users' signals in CRNs, which conforms to FCC's requirement. Our approach integrates cryptographic signatures and wireless link signatures (derived from physical radio channel characteristics) to enable primary user detection in the presence of attackers. Essential to our approach is a {\em helper node} placed physically close to a primary user. The helper node serves as a "bridge" to enable a secondary user to verify cryptographic signatures carried by the helper node's signals and then obtain the helper node's authentic link signatures to verify the primary user's signals. A key contribution in our paper is a novel physical layer authentication technique that enables the helper node to authenticate signals from its associated primary user. Unlike previous techniques for link signatures, our approach explores the geographical proximity of the helper node to the primary user, and thus does not require any training process. DA - 2010/// PY - 2010/// DO - 10.1109/sp.2010.24 SP - 286-301 SN - 1081-6011 KW - cognitive radio networks KW - primary user detection KW - link signatures ER - TY - JOUR TI - An optimal design of magnetostrictive material (MsM) based energy harvester AU - Hu, Jingzhen AU - Yuan, Fuh-Gwo AU - Xu, Fujun AU - Huang, Alex Q. T2 - SENSORS AND SMART STRUCTURES TECHNOLOGIES FOR CIVIL, MECHANICAL, AND AEROSPACE SYSTEMS 2010 AB - In this study, an optimal vibration-based energy harvesting system using magnetostrictive material (MsM) has been designed to power the Wireless Intelligent Sensor Platform (WISP), developed at North Carolina State University. A linear MsM energy harvesting device has been modeled and optimized to maximize the power output. The effects of number of MsM layers and glue layers, and load matching on the output power of the MsM energy harvester have been analyzed. From the measurement, the open circuit voltage can reach 1.5 V when the MsM cantilever beam operates at the 2nd natural frequency 324 Hz. The AC output power is 0.97 mW, giving power density 279 μW/cm3. Since the MsM device has low open circuit output voltage characteristics, a full-wave quadrupler has been designed to boost the rectified output voltage. To deliver the maximum output power to the load, a complex conjugate impedance matching between the load and the MsM device has been implemented using a discontinuous conduction mode (DCM) buck-boost converter. The maximum output power after the voltage quadrupler is now 705 μW and power density reduces to 202.4 μW/cm3, which is comparable to the piezoelectric energy harvesters given in the literature. The output power delivered to a lithium rechargeable battery is around 630 μW, independent of the load resistance. DA - 2010/// PY - 2010/// DO - 10.1117/12.847623 VL - 7647 SP - SN - 1996-756X KW - Magnetostrictive material KW - energy harvesting KW - impedance matching KW - voltage quadrupler KW - buck-boost converter ER - TY - CONF TI - An efficient 13.56 MHz active back-telemetry rectifier in standard CMOS technology AU - Bawa, G. AU - Huang, A. Q. AU - Ghovanloo, M. AB - In this paper, we present the design of a high-frequency (HF) rectifier implemented in a 0.5-μm 3M/2P 5V standard CMOS process for wireless power transmission across short-range inductive links. The rectifier has been optimized for 13.56 MHz ISM band, and achieves power conversion efficiency (PCE) of ~83% and voltage conversion ratio >92% in post-layout simulations. We have successfully incorporated a dual-mode back-telemetry capability in this rectifier with little area or efficiency overhead, which tolerates wide load-fluctuations at the secondary side. With these improvements, this active back-telemetry rectifier (ABTR) is geared towards increasing the overall system efficiency, data transfer rate, and reading range in applications such as implantable microelectronic devices (IMD) and radio frequency identification (RFID). C2 - 2010/// C3 - 2010 ieee international symposium on circuits and systems DA - 2010/// DO - 10.1109/iscas.2010.5537296 SP - 1201-1204 ER - TY - JOUR TI - A new family of unsteady boundary layers over a stretching surface AU - Fang, Tiegang AU - Zhang, Ji AU - Yao, Shanshan T2 - APPLIED MATHEMATICS AND COMPUTATION AB - In this paper, a new family of unsteady boundary layers over a stretching flat surface was proposed and studied. This new class of unsteady boundary layers involves the flows over a constant speed stretching surface from a slot, and the slot is moving at a certain speed. Depending on the slot moving parameter, the flow can be treated as a stretching sheet problem or a shrinking sheet problem. Both the momentum and thermal boundary layers were studied. Under special conditions, the solutions reduce to the unsteady Rayleigh problem and the steady Sakiadis stretching sheet problem. Solutions only exist for a certain range of the slot moving parameter, α. Two solutions are found for −53.55° < α < −45°. There are also two solution branches for the thermal boundary layers at any given Prandtl number in this range. Compared with the upper solution branch, the lower solution branch leads to simultaneous reduction in wall drag and heat transfer rate. The results also show that the motion of the slot greatly affects the wall drag and heat transfer characteristics near the wall and the temperature and velocity distributions in the fluids. DA - 2010/12/15/ PY - 2010/12/15/ DO - 10.1016/j.amc.2010.09.031 VL - 217 IS - 8 SP - 3747-3755 SN - 1873-5649 KW - Similarity solution KW - Unsteady boundary layer KW - Stretching surface KW - Shrinking surface ER - TY - CONF TI - A comparison study of control strategies for ZVS resonant converters AU - Bai, Sanzhong AU - Pantic, Zeljko AU - Lukic, Srdjan T2 - IEEE AB - This paper studies three fundamental switching patterns for resonant converters to achieve Zero Voltage Switching (ZVS) operation. To evaluate the performance of the three control methods, three resonant topologies are taken into consideration: series resonant, parallel resonant and series-parallel resonant. The criteria functions for ZVS operation are derived for each control method and topology. The results show that the Asymmetrical Clamped Mode control (ACM) can guarantee lower switching frequency than other two control methods while keeping ZVS operation. Moreover, the circulating power for each control method is analyzed. The relationships between the switching frequency and the maximum power transfer of the three resonant topologies are derived and the series-parallel resonant topology shows a superior characteristic. Experiment results are given to verify some of the results. C2 - 2010/// C3 - IECON 2010-36th Annual Conference on IEEE Industrial Electronics Society DA - 2010/// DO - 10.1109/iecon.2010.5675019 SP - 256-262 ER - TY - CONF TI - A MEMS Blue/Green retroreflecting modulator for underwater optical communications AU - Cox, W. C. AU - Gray, K. F. AU - Simpson, J. A. AU - Cochenour, B. AU - Hughes, B. L. AU - Muth, J. F. AB - Short range, high bandwidth underwater optical communications links are potentially useful for retrieving stored information from underwater systems. However many underwater systems have limited power capacity or limited weight budget. The use of a modulating retroreflector eliminates the need for a transmitting laser on the data bearing platform and reduces the pointing requirements by retroreflecting the modulated light back to the interrogating source. Blue/green operation of a MEMS Fabry-Perot modulator was demonstrated at data rates of 500 kbps and 1 Mbps in a 7.7 meter tank with water conditions varied by the addition of Maalox as a scattering agent. C2 - 2010/// C3 - Oceans 2010 DA - 2010/// DO - 10.1109/oceans.2010.5664432 ER - TY - CONF TI - 5 mbps optical wireless communication with error correction coding for underwater sensor nodes AU - Simpson, J. A. AU - Cox, W. C. AU - Krier, J. R. AU - Cochenour, B. AU - Hughes, B. L. AU - Muth, J. F. AB - One issue with underwater sensors is how to efficiently transfer large amounts of data collected by the node to an interrogating platform such as an underwater vehicle. It is often impractical to make a physical connection between the node and the vehicle which suggests an acoustic or optical wireless solution. For large amounts of data, the high bandwidth of underwater optical wireless is an advantage. A small, low-cost platform to demonstrate the potential of an optical wireless communications interface for underwater sensor nodes is demonstrated. To enhance the reliability and robustness of the optical wireless communication digital signal processing and error correction techniques are used. The system was tested in 3 and 7.7 meter tanks at 5 Mbps with the turbidity of the water controlled by the addition of Maalox. C2 - 2010/// C3 - Oceans 2010 DA - 2010/// DO - 10.1109/oceans.2010.5664429 ER - TY - MPCT TI - The Prepared Mind: Engineering Entrepreneurs Program at NC State DA - 2010/// PY - 2010/// PB - NCSU Engineering Entrepreneurs Program ER - TY - JOUR TI - Tanh cascode cell amplifier - an arbitrary transfer characteristics amplifier AU - Ding, M. AU - Gard, K. G. T2 - Electronics Letters DA - 2010/// PY - 2010/// VL - 46 IS - 22 SP - 1495-1496 ER - TY - JOUR TI - Slip Magnetohydrodynamic Viscous Flow over a Permeable Shrinking Sheet AU - Tie-Gang, Fang AU - Ji, Zhang AU - Shan-Shan, Yao T2 - CHINESE PHYSICS LETTERS AB - The magnetohydrodynamic (MHD) flow under slip conditions over a shrinking sheet is solved analytically. The solution is given in a closed form equation and is an exact solution of the full governing Navier-Stokes equations. Interesting solution behavior is observed with multiple solution branches for certain parameter domain. The effects of the mass transfer, slip, and magnetic parameters are discussed. DA - 2010/12// PY - 2010/12// DO - 10.1088/0256-307x/27/12/124702 VL - 27 IS - 12 SP - SN - 0256-307X ER - TY - JOUR TI - Optimization of homoepitaxially grown AlGaN/GaN heterostructures AU - Grenko, J. A. AU - Ebert, C. W. AU - Reynolds, C. L., Jr. AU - Duscher, G. J. AU - Barlage, D. W. AU - Johnson, M. A. L. AU - Preble, E. A. AU - Paskova, T. AU - Evans, K. R. T2 - PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE AB - Abstract We report on the growth of Al 0.25 Ga 0.75 N/GaN heterostructures on low dislocation density semi‐insulating c ‐axis GaN substrates by metalorganic vapor phase epitaxy (MOVPE). A room temperature (RT) Hall mobility ( µ RT ) up to 2065 cm 2 V −1 s −1 at sheet density ( n s ) of 8.25 × 10 12 cm −2 has been measured. This work compliments prior studies in which we observed a buffer‐induced modulation of the RT two‐dimensional electron gas (2DEG) n s and µ RT by varying the GaN buffer layer thickness. Here, we focus on the optimization of the heterostructure 2DEG properties by elimination of silicon doping in the Al 0.25 Ga 0.75 N barrier and unintentional Al in the not‐intentionally doped (n.i.d.) GaN buffer layer. The 15% improvement in µ RT and n s relative to previous results is consistent with those predicted by Poisson solver calculations. Use of thick GaN buffers has minimized the theoretical mobility reduction based on intersubband scattering and has enabled us to determine the 2DEG sheet density associated with the polarization field ( $n_{{\rm s}}^{{\rm polar}} $ ) to be ∼5 × 10 12 cm −2 . DA - 2010/10// PY - 2010/10// DO - 10.1002/pssa.200925508 VL - 207 IS - 10 SP - 2292-2299 SN - 1862-6300 KW - AlGaN KW - GaN KW - heterostructures KW - mobility KW - MOCVD KW - two-dimensional electron gas ER - TY - CONF TI - High-voltage high-frequency transformer design for a 7.2kV to 120V/240V 20kVA solid state transformer AU - Du, Y. AU - Baek, S. AU - Bhattacharya, Subhashish AU - Huang, A.Q. AB - Solid state transformer (SST) exhibits good features such as high power density, small volume and weight, controlled power factor, voltage sag ride through, etc. compared with traditional line frequency transformer. The 7.2 kV AC to 120V/240V AC 20 kVA solid state transformer is a key component of the future renewable electric energy delivery and management (FREEDM) systems as the interface between the 7.2 kV distribution grid and the low voltage residential micro-grid. Three cascaded 6.7 kVA high-voltage high-frequency transformers operating at 3 kHz are employed to convert voltage from 3800 V high voltage DC link of each cascaded stage to 400 V low voltage DC link. The transformer is required to withstand at least 15 kV high frequency voltage insulation continuously. Transformer magnetic core materials were reviewed and compared. Winding layout alternatives for leakage, magnetizing inductance and insulation were compared. An insulation strategy based on split core and separate winding structure with inserted insulation layer between the C cores was proposed. One 6.7 kVA high voltage high frequency transformer prototype was built and the test results were reported. C2 - 2010/// C3 - IECON Proceedings (Industrial Electronics Conference) DA - 2010/// DO - 10.1109/iecon.2010.5674828 SP - 493-498 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-78751558902&partnerID=MN8TOARS ER - TY - JOUR TI - Encapsulation of organic solar cells with ultrathin barrier layers deposited by ozone-based atomic layer deposition AU - Sarkar, Smita AU - Culp, Jason H. AU - Whyland, Jon T. AU - Garvan, Margret AU - Misra, Veena T2 - ORGANIC ELECTRONICS AB - Ultrathin Al2O3 layers, deposited using atomic layer deposition (ALD), have been utilized as the primary barrier layers for encapsulation of organic solar cells. This work shows that the encapsulation characteristics of a barrier layer can be accentuated by replacing H2O with O3 as the ALD oxidant. The Al2O3 layers deposited using O3 offered superior device encapsulation compared to the films deposited using H2O. The organic solar cell efficiency has also been studied as a function of Al2O3 thickness and effective encapsulation has been monitored for two different ALD temperatures. DA - 2010/12// PY - 2010/12// DO - 10.1016/j.orgel.2010.08.020 VL - 11 IS - 12 SP - 1896-1900 SN - 1878-5530 KW - Organic solar cell KW - Encapsulation KW - Atomic layer deposition KW - Ozone ER - TY - JOUR TI - Demonstration of polarization grating imaging spectropolarimeter (PGIS) AU - Kim, Jihwan AU - Escuti, Michael J. T2 - POLARIZATION: MEASUREMENT, ANALYSIS, AND REMOTE SENSING IX AB - We have introduced the concept of a snapshot imaging spectropolarimeter based on anisotropic diffraction gratings known as Polarization Gratings (PGs). This instrument can acquire both spectral and polarization information of an object by using the unique optical properties of PGs, which create a diffraction pattern on a single focal plane array. In this paper we develop a system matrix for reconstructing the object information from this diffraction pattern. This matrix is extendable to various configurations containing several PGs. Moreover, we demonstrate an imaging spectropolarimeter based on this approach, that was used to reconstruct both screen generated scenes and outdoor objects. Reconstructed objects are sampled at 100 ×100 × 51 (x, y, λ) with 4 nm spectral resolution. DA - 2010/// PY - 2010/// DO - 10.1117/12.849758 VL - 7672 SP - SN - 0277-786X KW - Spectrometry KW - polarimetry KW - spectropolarimeter KW - imaging spectrometry KW - polarization grating KW - liquid crystals KW - reactive mesogens KW - remote sensing ER - TY - JOUR TI - An analytical model of source injection for N-type enhancement mode GaN-based Schottky Source/Drain MOSFET's with experimental demonstration AU - Park, Jaehoon AU - Ozbek, Ayse M. AU - Ma, Lei AU - Veety, Matthew T. AU - Morgensen, Michael P. AU - Barlage, Douglas W. AU - Wheeler, Virginia D. AU - Johnson, Mark A. L. T2 - SOLID-STATE ELECTRONICS AB - Abstract This study investigates the effect of the Gate-to-Source/Drain overlap structure of a GaN Schottky Source/Drain MOSFET. The Gate-to-Source overlap structure of the device allows the gate electric field to reduce the height of the Nickel(source)–GaN Schottky barrier near the SiO 2 –GaN interface at the source side, injecting more thermionically generated carriers over the partially reduced Schottky barrier. Based on this Schottky barrier lowering mechanism, an analytical model was developed. The analytical model shows that the reduction of the Schottky barrier height by 0.25 eV increases the on-state drain current by two orders of magnitude, which is in agreement of the previously reported TCAD simulation result in [6] . A specifically designed GaN Schottky Source/Drain MOSFET with the Gate-to-Source/Drain overlap structure was fabricated and characterized; the I D – V DS characteristic of the device shows that the on-state drain current of the device was increased by up to 160× compared to the same kind of device without the overlap structure (reported in Lei Ma (2007) [7] ), which is in agreement with the analytical model described herein. DA - 2010/12// PY - 2010/12// DO - 10.1016/j.sse.2010.06.013 VL - 54 IS - 12 SP - 1680-1685 SN - 0038-1101 KW - GaN KW - MOSFET KW - Schottky Source/Drain KW - Schottky barrier KW - Gate to Source overlap structure KW - Gate induced Schottky barrier lowering ER - TY - CONF TI - All-terminal network reliability optimization in fading environment via cross entropy method AU - Kharbash, S. AU - Wang, Wenye AB - This paper presents a new algorithm that can be readily applied to solve all-terminal network reliability optimization problem of a wireless network in a fading environment. The optimization problem solved considers finding the optimal topological layout of links at which the all-terminal network reliability is maximized by controlling the nodes' transmission powers. To that end, a link probabilistic model is developed to relate fading, attenuation, interference and nodes' transmission powers to link reliability. Then, the proposed algorithm utilized this probabilistic model to control nodes' transmission power to maximize links reliabilities and hence all-terminal network reliability. The proposed algorithm is based on two major steps that use a global stochastic optimization technique, Cross Entropy (CE) to generate the optimal network topology and control nodes transmission powers such that all-terminal network reliability is maximized. An illustrative example is used to illustrate the proposed algorithm. C2 - 2010/// C3 - 2010 ieee international conference on communications - ICC 2010 DA - 2010/// DO - 10.1109/icc.2010.5501918 ER - TY - CONF TI - A novel 4H-SiC IGBT structure with improved trade-off between short circuit capability and on-state voltage drop AU - Sung, W. AU - Huang, A. Q. AU - Baliga, B. J. C2 - 2010/// C3 - Proceedings of the international symposium on power semiconductor DA - 2010/// SP - 217-220 ER - TY - JOUR TI - Theory and applications of artificial immune systems AU - Gao, Xiao-Zhi AU - Chow, Mo-Yuen AU - Pelta, David AU - Timmis, Jon T2 - NEURAL COMPUTING & APPLICATIONS AB - For many years, biology has served as inspiration for the development of novel solutions to computer science and engineering problems. One of the more recent developments in this area is the use of the immune system as inspiration to solve such problems. The area of artificial immune systems (AIS) arose from the inter-disciplinary workings of immunologists and computer scientists to develop solutions to such problems as distributed control and computer security. The field has developed significantly over the recent years, with the development of solutions to a wide variety of problems ranging from document analysis, optimization, dynamic error detection, intrusion detection, robot control and bioinformatics. Within the AIS, there are common, well-understood algorithms, based on specific aspects of immunology. Clonal selection algorithms are the most widely employed and take their inspiration from how cells of the adaptive immune system (specifically, cells called B cell) interact with ‘antigen’ (something that causes an immune response) and then undergo a process of cloning, mutation and selection. This process has some similarities with the basic concept of evolution, and it is no surprise that the algorithms inspired by clonal selection have much in common with well-known evolutionary algorithms and have been applied in a similar manner. Negative selection algorithms, based on how immune cells (known as T cells) are matured in a gland called the thymus, are also very popular. This process allows for the filtering of non-reactive cells in the immune system and has been used as inspiration for building computer security systems, where there is some knowledge of what normal or self is. Finally, immune network algorithms are based on a theory regarding how immune cells (in this case B cells) are maintained as memory in the immune system over time. These B cells interact with each other in a stimulatory and inhibitory way to maintain the memory. This has been used as a metaphor to create dynamic learning algorithms and optimization methods. The special issue on the AIS is dedicated to the latest work in the theory and applications in this exciting area. Our aim is to provide several case studies of the AIS in solving typical real-world problems. After a detailed review process, a total of three papers were selected for this special issue. The first paper entitled ‘An immune-inspired multiobjective approach to the reconstruction of phylogenetic trees’ by Guilherme P. Coelho, Ana Estela A. da Silva, and Fernando J. Von Zuben proposes a new multi-objective optimization technique, namely omni-aiNet, in the reconstruction of phylogenetic trees. This work is based on the immune network metaphor. The phylogenetic trees are often used to represent the relationship among different species, whose construction can be considered as a difficult multi-objective optimization problem of simultaneously minimizing two criteria: minimum evolution and meansquared error. In this paper, the immune algorithm is X.-Z. Gao (&) Aalto University, Aalto, Finland e-mail: gao@cc.hut.fi DA - 2010/11// PY - 2010/11// DO - 10.1007/s00521-010-0388-2 VL - 19 IS - 8 SP - 1101-1102 SN - 0941-0643 ER - TY - JOUR TI - RaPTEX: Rapid Prototyping Tool for Embedded Communication Systems AU - Lim, Jun Bum AU - Jang, Beakcheol AU - Yoon, Suyoung AU - Sichitiu, Mihail L. AU - Dean, Alexander G. T2 - ACM TRANSACTIONS ON SENSOR NETWORKS AB - Advances in microprocessors, memory, and radio technology have enabled the emergence of embedded systems that rely on communication systems to exchange information and coordinate their activities in spatially distributed applications. However, developing embedded communication systems that satisfy specific application requirements is a challenge due to the many tradeoffs imposed by different choices of underlying protocols and their parameters. Furthermore, evaluating the correctness and performance of the design and implementation before deploying it is a nontrivial task due to the complexity of the resulting system. This article presents the design and implementation of RaPTEX, a rapid prototyping tool for embedded communication systems, especially well suited for wireless sensor networks (WSNs), consisting of three major subsystems: a toolbox, an analytical performance estimation framework, and an emulation environment. We use a hierarchical approach in the design of the toolbox to facilitate the composition of the network stack. For fast exploration of the tradeoff space at design time, we build an analytical performance estimation model for energy consumption, delay, and throughput. For realistic performance evaluation, we design and implement a hybrid, accurate, yet scalable, emulation environment. Through three use cases, we study the tradeoff space for different protocols and topologies, and highlight the benefits of using RaPTEX for designing and evaluating embedded communication systems for WSNs. DA - 2010/8// PY - 2010/8// DO - 10.1145/1806895.1806902 VL - 7 IS - 1 SP - SN - 1550-4859 KW - Design KW - Verification KW - Experimentation KW - Wireless sensor networks KW - rapid prototyping tool KW - analytical performance modeling KW - real code simulation KW - RaPTEX KW - TinyOS ER - TY - JOUR TI - Probing the Chain and Crystal Lattice Orientation in Polyethylene Thin Films by Near Edge X-ray Absorption Fine Structure (NEXAFS) Spectroscopy AU - Wang, Yantian AU - Zou, Ying AU - Araki, Tohru AU - Luening, Jan AU - Kilcoyne, A. L. D. AU - Sokolov, Jonathan AU - Ade, Harald AU - Rafailovich, Miriam T2 - MACROMOLECULES AB - The chain and the crystal unit cell orientation of linear low density polyethylene (LLDPE) were measured with near edge X-ray absorption fine structure (NEXAFS) spectroscopy. A strongly attractive substrate, silicon, and a weakly attractive substrate, mica, were used. For a 100 nm thick LLDPE film on the silicon substrate, the crystals exhibit an edge-on lamellar morphology, with the chains predominantly parallel to the substrate, and the orthorhombic unit cell ⟨a, b, c⟩ in the following approximate orientation: b and c are in the film plane with b along the crystal fibril direction and c perpendicular to the fibril direction and a perpendicular to the film plane. On the mica substrates, LLDPE films with thickness below 180 nm completely dewet the surface and form isolated droplets, while a film 366 nm thick crystallizes as spherulites with most of the chains perpendicular to the substrate before annealing and with a twisted lamellar structure after isothermal crystallization at 60 °C. The results demonstrate that the combination of electron yield NEXAFS and high spatial resolution transmission NEXAFS is a powerful tool to measure the crystal orientation in the polymer thin films on a small length scale. DA - 2010/10/12/ PY - 2010/10/12/ DO - 10.1021/ma101213h VL - 43 IS - 19 SP - 8153-8161 SN - 1520-5835 ER - TY - JOUR TI - Polarization-Insensitive Variable Optical Attenuator and Wavelength Blocker Using Liquid Crystal Polarization Gratings AU - Nicolescu, Elena AU - Mao, Chongchang AU - Fardad, Amir AU - Escuti, Michael T2 - JOURNAL OF LIGHTWAVE TECHNOLOGY AB - We demonstrate a variable optical attenuator (VOA) based on liquid crystal polarization gratings (LCPGs), which eliminates the need for complex polarization management found in competing LC technologies. We then configure the VOA as a multi-channel wavelength blocker resulting in a simple, compact architecture with high performance and low cost. Together with a dual fiber collimator, relay lenses, a diffraction grating, a quarter wave plate, and a mirror we achieve optical attenuation of ~50 dB with minimal polarization dependent loss (≤ 0.3 dB) and insertion loss ( ≤ 2.5 dB). The device also manifests competitive wavelength flatness (≤ 0.35 dB variation), response times ( ~ 40 ms), and temperature dependent loss (≥ 47 dB maximum attenuation up to 85°C). We describe the principle of operation, explain the fabrication process and optimization challenges, and finally present the system design and experimental results for a four-channel, 100 GHz wavelength blocker in the C-band. DA - 2010/11/1/ PY - 2010/11/1/ DO - 10.1109/jlt.2010.2078487 VL - 28 IS - 21 SP - 3121-3127 SN - 1558-2213 KW - Polarization grating KW - variable optical attenuator KW - wavelength blocker ER - TY - JOUR TI - PILOTING PHOTONICS CURRICULUM IN STAFF DEVELOPMENT AU - Gilchrist, Pamela O. AU - Conover, Brandon AU - Bowles, Tuere AU - deDeugd, Casey AU - Hilliard-Clark, Joyce T2 - OPTICS EDUCATION AND OUTREACH AB - The paper's goal is to inform outreach coordinators and scientists of strategies used to develop a Light Emitting Diode (LED) curriculum module for high school students. Field-testing the weeklong LED curriculum, teachers acquired new instructional strategies to develop students career and global workforce skills in STEM disciplines. The National Science Foundation (NSF) Innovative Technology Experiences for Students and Teachers (ITEST) funded program session will highlight initial findings of the developmental process, review data of the pilot study with middle and high school teachers participating in a teacher workshop and student program offered by The Science House of North Carolina State University. DA - 2010/// PY - 2010/// DO - 10.1117/12.861092 VL - 7783 SP - SN - 0277-786X KW - photonics investigations KW - curriculum development KW - teacher professional development KW - underrepresented minorities (URM) KW - informal science setting KW - science, technology engineering, and mathematics (STEM) compentencies KW - college preparatory skills ER - TY - JOUR TI - Linear amplification by time-multiplexed spectrum AU - Mazzaro, G. J. AU - Gard, K. G. AU - Steer, M. B. T2 - IET CIRCUITS DEVICES & SYSTEMS AB - A new waveform processing technique for reducing intermodulation distortion (IMD) generated by an amplitude-modulated signal is presented. The technique eliminates amplifier-generated IMD by time-multiplexing portions of the signal spectrum prior to amplification. The input signal is described as a sum of sinusoidal signals. The peak-to-average ratio of the time-multiplexed amplifier input is lower than that of its non-multiplexed counterpart, but it contains spectral aliases at multiples of the switching frequency. Thus, the reduction in distortion of the desired amplified signal is achieved at the expense of momentarily widening the signal bandwidth. Following amplification, the desired signal is recovered using a bandpass filter which spreads the signal in time and narrows its bandwidth. An analytical expression for distortion reduction when amplifying two multiplexed carriers is developed along with measurements verifying the theory. Distortion reduction is demonstrated experimentally at 3.6 GHz for 2–20 multiplexed carriers, and linear recovery is demonstrated for four multiplexed carriers. The technique reduces third-order IMD by 8–22 dB in experimental measurements of three different amplifiers. The presented technique has the unique property of improving linearity without requiring feedback, feedforward cancellation or calibration. DA - 2010/9// PY - 2010/9// DO - 10.1049/iet-cds.2009.0263 VL - 4 IS - 5 SP - 392-402 SN - 1751-858X ER - TY - JOUR TI - Contact degradation in hot/cold operation of direct contact micro-switches AU - Yang, Z. AU - Lichtenwalner, D. AU - Morris, A. AU - Krim, J. AU - Kingon, A. I. T2 - JOURNAL OF MICROMECHANICS AND MICROENGINEERING AB - Degradation of gold contacts in micro-switches was studied under an extensive range of operation conditions including high-electric-field ac/dc hot switching, low-electric-field hot switching and cold switching. Tests were conducted in a unique experimental switching operation set-up. Gold micro-contacts were characterized by an atomic force microscope. It was found that a unique material transfer/distribution feature was correlated with specific switching operations. New insights into contact degradation mechanisms of micro-switches were achieved by analyzing contact degradation features under varied operation conditions. Our results indicate that for high-electric-field hot switching, gold atoms are transferred from the 'anode' contact to the 'cathode' contact via field evaporation; for low-electric-field hot switching, material transfer is induced by transient heat; and for cold switching, contact resistance can be jeopardized by surface contamination and surface roughness if contact force is low. DA - 2010/10// PY - 2010/10// DO - 10.1088/0960-1317/20/10/105028 VL - 20 IS - 10 SP - SN - 1361-6439 ER - TY - JOUR TI - Computation of Induced Current Densities in the Human Body at Low Frequencies Due to Contact Electrodes Using the ADI-FDTD Method AU - Singh, Vinit AU - Ajeet, Ajeet AU - Kwatra, Nitin AU - Cela, Carlos J. AU - Ziriax, John AU - D'Andrea, John AU - Lazzi, Gianluca T2 - IEEE TRANSACTIONS ON ELECTROMAGNETIC COMPATIBILITY AB - We report the use of the alternating direction implicit (ADI) finite-difference time-domain (FDTD) method in a D-H formulation to compute induced current densities and recruitment volumes in the human body due to contact electrodes for human electromuscular incapacitation devices at frequencies below 200 kHz. A computational model resolution of 1 mm has been used for most of the human body model, including regions proximal to the electrode contact points, while a progressively coarser resolution up to 5 mm is utilized, according to an expanding grid scheme for body regions distant from the source, such as the lower extremities. Using quasi-static assumptions, discrete Fourier transforms have been used to average the electric field values at the desired frequencies for times much shorter than their time periods. The field values induced in the human body were then obtained as ratios with respect to the source, which can be scaled depending on the magnitude. This study suggests that the ADI-FDTD method can be used for the solution of low-frequency large-scale bioelectromagnetic problems. It is shown that, when used with quasi-static assumptions, Fourier series decomposition, and expanding grid, the D-H ADI-FDTD can be an effective computational bioelectromagnetics tool. DA - 2010/8// PY - 2010/8// DO - 10.1109/temc.2009.2039482 VL - 52 IS - 3 SP - 537-544 SN - 1558-187X KW - D-H ADI-FDTD KW - HEMI devices KW - impedance method KW - low frequency computational bioelectromagnetics KW - neuron recruitment volume ER - TY - JOUR TI - An Optimizing Compiler for GPGPU Programs with Input-Data Sharing AU - Yang, Yi AU - Xiang, Ping AU - Kong, Jingfei AU - Zhou, Huiyang T2 - PPOPP 2010: PROCEEDINGS OF THE 2010 ACM SIGPLAN SYMPOSIUM ON PRINCIPLES AND PRACTICE OF PARALLEL PROGRAMMING AB - Developing high performance GPGPU programs is challenging for application developers since the performance is dependent upon how well the code leverages the hardware features of specific graphics processors. To solve this problem and relieve application developers of low-level hardware-specific optimizations, we introduce a novel compiler to optimize GPGPU programs. Our compiler takes a naive GPU kernel function, which is functionally correct but without any consideration for performance optimization. The compiler then analyzes the code, identifies memory access patterns, and generates optimized code. The proposed compiler optimizations target at one category of scientific and media processing algorithms, which has the characteristics of input-data sharing when computing neighboring output pixels/elements. Many commonly used algorithms, such as matrix multiplication, convolution, etc., share such characteristics. For these algorithms, novel approaches are proposed to enforce memory coalescing and achieve effective data reuse. Data prefetching and hardware-specific tuning are also performed automatically with our compiler framework. The experimental results based on a set of applications show that our compiler achieves very high performance, either superior or very close to the highly fine-tuned library, NVIDIA CUBLAS 2.1. DA - 2010/// PY - 2010/// DO - 10.1145/1693453.1693505 SP - 343-344 KW - GPGPU KW - Compiler ER - TY - CONF TI - 3D surface reconstruction using structured circular light patterns AU - Lee, D. AU - Krim, H. AB - Reconstructing a 3D surface in ℝ3 from a 2D image in ℝ2 has been a widely studied issue as well as one of the most important problems in image processing. In this paper, we propose a novel approach to reconstructing 3D coordinates of a surface from a 2D image taken by a camera using projected circular light patterns. Known information (i.e. intrinsic and extrinsic parameters of the camera, the structure of the circular patterns, a fixed optical center of the camera and the location of the reference plane of the surface) provides a mathematical model for surface reconstruction. The reconstruction is based on a geometrical relationship between a given pattern projected onto a 3D surface and a pattern captured in a 2D image plane from a viewpoint. This paper chiefly deals with a mathematical proof of concept for the reconstruction problem. C2 - 2010/// C3 - Advanced concepts for intelligent vision systems, pt i DA - 2010/// DO - 10.1007/978-3-642-17688-3_27 VL - 6474 SP - 279-289 ER - TY - JOUR TI - Voltage and Power Balance Control for a Cascaded Multilevel Solid State Transformer AU - Zhao, Tiefu AU - Wang, Gangyao AU - Zeng, Jie AU - Dutta, Sumit AU - Bhattacharya, Subhashish AU - Huang, Alex Q. T2 - 2010 TWENTY-FIFTH ANNUAL IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC) AB - In this paper, a 20 kVA Solid State Transformer (SST) based on 6.5 kV IGBT is proposed for interface with 7.2 kV distribution system voltage. The proposed SST consists of a cascaded multilevel AC/DC rectifier stage, a Dual Active Bridge (DAB) converter stage with high frequency transformers and a DC/AC inverter stage. Based on the single phase d-q vector control, a novel control strategy is proposed to balance the rectifier capacitor voltages and the real power through the DAB parallel modules. Furthermore, the power constraints of the voltage balance control are analyzed. The SST switching model simulation demonstrates the effectiveness of the proposed voltage and power balance controller. A 3 kW SST scale-down prototype is implemented. The experiment results verify the single phase d-q vector controller for the SST cascaded multilevel rectifier. DA - 2010/// PY - 2010/// DO - 10.1109/apec.2010.5433584 SP - 761-767 SN - 1048-2334 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77952178838&partnerID=MN8TOARS ER - TY - JOUR TI - Thermoelectric properties of graphene nanoribbons, junctions and superlattices AU - Chen, Y AU - Jayasekera, T AU - Calzolari, A AU - Kim, K W AU - Buongiorno Nardelli, M T2 - Journal of Physics: Condensed Matter AB - Using model interaction Hamiltonians for both electrons and phonons and Green's function formalism for ballistic transport, we have studied the thermal conductance and the thermoelectric properties of graphene nanoribbons (GNR), GNR junctions and periodic superlattices. Among our findings we have established the role that interfaces play in determining the thermoelectric response of GNR systems both across single junctions and in periodic superlattices. In general, increasing the number of interfaces in a single GNR system increases the peak ZT values that are thus maximized in a periodic superlattice. Moreover, we proved that the thermoelectric behavior is largely controlled by the width of the narrower component of the junction. Finally, we have demonstrated that chevron-type GNRs recently synthesized should display superior thermoelectric properties. DA - 2010/8/31/ PY - 2010/8/31/ DO - 10.1088/0953-8984/22/37/372202 VL - 22 IS - 37 SP - 372202 J2 - J. Phys.: Condens. Matter OP - SN - 0953-8984 1361-648X UR - http://dx.doi.org/10.1088/0953-8984/22/37/372202 DB - Crossref ER - TY - JOUR TI - Review of Non-isolated Bi-directional DC-DC Converters for Plug-in Hybrid Electric Vehicle Charge Station Application at Municipal Parking Decks AU - Du, Yu AU - Zhou, Xiaohu AU - Bai, Sanzhong AU - Lukic, Srdjan AU - Huang, Alex T2 - 2010 TWENTY-FIFTH ANNUAL IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC) AB - There is a growing interest on plug-in hybrid electric vehicles (PHEV's) due to energy security and green house gas emission issues, as well as the low electricity fuel cost. As battery capacity and all-electric range of PHEV's are improved, and potentially some PHEV's or EV's need fast charging, there is increased demand to build high power off-board charging infrastructures. A charge station architecture for municipal parking decks has been proposed, which has a DC microgrid to interface with multiple DC-DC chargers, distributed renewable power generations and energy storage, and provides functionalities of normal and rapid charging, grid support such as reactive and real power injection (including V2G), current harmonic filtering and load balance. Several non-isolated bidirectional DC-DC converters suited for charge station applications have been reviewed and compared, as the major focus of this paper. Half bridge converter is a good candidate but it is difficult to maintain high efficiency in wide battery pack voltage range. A variable frequency pulse width modulation (VFPWM) scheme is proposed to mitigate this issue. Finally three-level bi-directional DC-DC converter is suggested to be employed in this application. A 10kW prototype verifies that 95.1-97.9% full load efficiency can be achieved in charging mode with 180-360V battery pack voltage. In addition, the inductor size is only one third of the half bridge counterpart, which is a great advantage for high power converters. DA - 2010/// PY - 2010/// DO - 10.1109/apec.2010.5433359 SP - 1145-1151 SN - 1048-2334 ER - TY - JOUR TI - Optimal composition of europium gallium oxide thin films for device applications AU - Wellenius, P. AU - Smith, E. R. AU - LeBoeuf, S. M. AU - Everitt, H. O. AU - Muth, J. F. T2 - JOURNAL OF APPLIED PHYSICS AB - Europium gallium oxide (EuxGa1-x)2O3 thin films were deposited on sapphire substrates by pulsed laser deposition with varying Eu content from x=2.4 to 20 mol %. The optical and physical effects of high europium concentration on these thin films were studied using photoluminescence (PL) spectroscopy, x-ray diffraction (XRD), and Rutherford backscattering spectrometry. PL spectra demonstrate that emission due to the D50 to F7J transitions in Eu3+ grows linearly with Eu content up to 10 mol %. Time-resolved PL indicates decay parameters remain similar for films with up to 10 mol % Eu. At 20 mol %, however, PL intensity decreases substantially and PL decay accelerates, indicative of parasitic energy transfer processes. XRD shows films to be polycrystalline and beta-phase for low Eu compositions. Increasing Eu content beyond 5 mol % does not continue to modify the film structure and thus, changes in PL spectra and decay cannot be attributed to structural changes in the host. These data indicate the optimal doping for optoelectronic devices based on (EuxGa1-x)2O3 thin films is between 5 and 10 mol %. DA - 2010/5/15/ PY - 2010/5/15/ DO - 10.1063/1.3319670 VL - 107 IS - 10 SP - SN - 0021-8979 ER - TY - JOUR TI - Optimal Phase Changing Frequency Determination for Multiphase Voltage Regulator Modules AU - Ramamurthy, Anand AU - Bhattacharya, Subhashish AU - Thompson, Chris AU - Day, Jon T2 - 2010 TWENTY-FIFTH ANNUAL IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC) AB - Modern processers have the capability of indicating the power state of the processor to the Voltage Regulator (VR) PWM controller so that it can change its operating state to maximize efficiency at light loads and to flatten out its efficiency curve for idle power reduction. The CPU worst case assert and de-assert frequency can be very high for the PWM controller and for the VR to follow. Thus for the VR to take advantage of the low power state signal from the CPU, the signal has to be passed through an analog/digital low-pass filter. The optimum frequency for this filter design is determined in this paper. This filtered frequency with which the VR drops its phases optimizes the overall efficiency of the system. The experimental results are given for a four-phase VRM. It is also shown in this paper that the transient efficiency is as vital as the steady state efficiency considering the load profile of modern CPUs. DA - 2010/// PY - 2010/// DO - 10.1109/apec.2010.5433342 SP - 1243-1247 SN - 1048-2334 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77952193155&partnerID=MN8TOARS ER - TY - JOUR TI - NixPt1-xSi/n-Si contacts with sub-0.1 eV effective Schottky barrier heights obtained by sulfur segregation AU - Alptekin, Emre AU - Ozturk, Mehmet C. T2 - MICROELECTRONIC ENGINEERING AB - We demonstrate tuning of the Schottky barrier height, ϕB of nickel–platinum alloy silicide (NixPt1-xSi) contacts on n-type silicon by segregating sulfur at the silicide/Si interface. It is shown that while there is negligible effect of sulfur on the thermal stability and silicide resistance, extremely small barrier height values of 0.05–0.07 eV at the silicide/Si interface can be achieved by sulfur segregation. DA - 2010/11// PY - 2010/11// DO - 10.1016/j.mee.2010.04.008 VL - 87 IS - 11 SP - 2358-2360 SN - 1873-5568 KW - Schottky barrier height KW - Contact resistivity KW - Nickel KW - Platinum KW - Silicide KW - NiSi KW - PtSi KW - NixPt1-xSi KW - Sulfur ER - TY - CONF TI - Low-dropout (LDO) regulator output impedance analysis and transient performance enhancement circuit AU - Lim, S. AU - Huang, A. Q. AB - This paper presents a low-dropout regulator with a transient performance enhancement circuit. The transient performance enhancement circuit improves the transient response time by sinking a remaining current in a power delivery path. Due to the limited control bandwidth, traditional LDO could not respond rapidly to the load transients. As a result, a large output voltage spike can be occurred and the output voltage settling time is long during the load transients. In this paper, the stability conditions and the output impedance of LDO are discussed, and the output voltage spike and current distributions in the power delivery path are analyzed. The theoretical analysis will be confirmed by the cadence simulation results. C2 - 2010/// C3 - Annual ieee conference on applied power electronics conference and DA - 2010/// DO - 10.1109/apec.2010.5433489 SP - 1875-1878 ER - TY - JOUR TI - Digital Controller Development for Grid-Tied Photovoltaic Inverter with Model Based Technique AU - Liang, Zhigang AU - Alesi, Larry AU - Zhou, Xiaohu AU - Huang, Alex Q. T2 - 2010 TWENTY-FIFTH ANNUAL IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC) AB - The main objective for a grid-tied photovoltaic (PV) inverter is to feed the harvested energy from PV panels to the grid with high efficiency and high power quality. A digital controller is the ¿heart¿ of the PV system: it calculates the maximum power point (MPP) and regulates the output current to meet the utility inter-connection standards. This paper introduced a new approach ¿model based design¿ to develop current controller for PV inverter. This design methodology filled the gap between computer simulation and hardware implementation of the digital controller and made an easy way for the implementation of complex and high level algorithm in a digital signal processor (DSP). The inverter's small signal model in D-Q rotating frame is derived and a double loop current controller is designed. The performance of the developed controller has been verified by both of the simulation in MATLAB and experimental results from a 2 kW single phase PV inverter prototype. DA - 2010/// PY - 2010/// DO - 10.1109/apec.2010.5433570 SP - 849-853 SN - 1048-2334 ER - TY - JOUR TI - Design and Development of Generation-I Silicon based Solid State Transformer AU - Bhattacharya, Subhashish AU - Zhao, Tiefu AU - Wang, Gangyao AU - Dutta, Sumit AU - Baek, Seunghun AU - Du, Yu AU - Parkhideh, Babak AU - Zhou, Xiaohu AU - Huang, Alex Q. T2 - 2010 TWENTY-FIFTH ANNUAL IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC) AB - The Solid State Transformer (SST) is one of the key elements proposed in the National Science Foundation (NSF) Generation-III Engineering Research Center (ERC) ¿Future Renewable Electric Energy Delivery and Management¿ (FREEDM) Systems Center. The SST is used to enable active management of distributed renewable energy resources, energy storage devices and loads. In this paper, the Generation-I SST single-phase 20 kVA, based on 6.5 kV Si-IGBT is proposed for interface with 12 kV distribution system voltage. The SST system design parameters, overall system efficiency, high frequency transformer design, dual active bridge converter, auxiliary power supply and gate drives are investigated. Design considerations and experimental results of the prototype SST are reported. DA - 2010/// PY - 2010/// DO - 10.1109/apec.2010.5433455 SP - 1666-1673 SN - 1048-2334 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77952195486&partnerID=MN8TOARS KW - Solid state transformer KW - FREEDM system ER - TY - JOUR TI - Automated Broadband High-Dynamic-Range Nonlinear Distortion Measurement System AU - Wilkerson, Jonathan R. AU - Gard, Kevin G. AU - Steer, Michael B. T2 - IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES AB - This paper presents an intermodulation distortion measurement system based on automated feedforward cancellation that achieves 113 dB of broadband spurious-free dynamic range for discrete tone separations down to 100 Hz. For 1-Hz tone separation, the dynamic range is 106 dB, limited by carrier phase noise. A single-tone cancellation formula is developed requiring only the power of the probing signal and the power of the combined probe and cancellation signal so that the phase shift required for cancellation can be predicted. The technique is applied to a two-path feedforward cancellation system in a bridge configuration. The effects of reflected signals and of group delay on system performance is discussed. Spurious frequency content and interchannel coupling are analyzed with respect to system linearity. Feedforward cancellation and consideration of electromagnetic radiation coupling and reverse-wave isolation effects extends the dynamic range of spectrum and vector analyzers by at least 40 dB. Application of the technique to the measurement of correlated and uncorrelated nonlinear distortion of an amplified wideband code-division multiple-access signal is presented. DA - 2010/5// PY - 2010/5// DO - 10.1109/tmtt.2010.2045525 VL - 58 IS - 5 SP - 1273-1282 SN - 1557-9670 KW - Broadband KW - dynamic range KW - measurement KW - nonlinear vector signal analyzer KW - passive intermodulation distortion (PIM) ER - TY - JOUR TI - Application of Active NPC Converter on Generator Side for MW Direct-driven Wind Turbine AU - Li, Jun AU - Huang, Alex Q. AU - Bhattacharya, Subhashish AU - Jing, Wei T2 - 2010 TWENTY-FIFTH ANNUAL IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC) AB - 3L-NPC topology is usually used in MW wind turbine (WT) systems with full-scale converter configuration. However, due to its drawback of unequal device loss distribution, the converter rated power, and thus the WT unit capacity is limited. Moreover, in cased of device failure in generator converter, in order to protect the WT system, the converter has to shut down to disconnect the WT. This paper presents the application of active NPC (ANPC) converter on generator side. Loss-balancing schemes are discussed, and thermal performance of NPC and ANPC generator converters are compared. Also, the control scheme of generator converter under single device failure condition is proposed to maintain the WT in service and continue to provide real power, which brings benefits in the reliable and economic aspects to the WT system. Simulation results are provided to validate the proposed control methods. DA - 2010/// PY - 2010/// DO - 10.1109/apec.2010.5433381 SP - 1010-1017 SN - 1048-2334 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-77952213746&partnerID=MN8TOARS ER - TY - CONF TI - An adaptive external ramp control of the peak current controlled buck converters for high control bandwidth and wide operation range AU - Yang, L. Y. AU - Park, J. AU - Huang, A. Q. C2 - 2010/// C3 - Annual ieee conference on applied power electronics conference and DA - 2010/// SP - 2181-2188 ER - TY - JOUR TI - A New Resonant Gate Driver for Switching Loss Reduction of High Side Switch in Buck Converter AU - Zhou, Xin AU - Liang, Zhigang AU - Huang, Alex T2 - 2010 TWENTY-FIFTH ANNUAL IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC) AB - In this paper, a new resonant gate driver circuits is proposed to reduce the switching loss of high side switch in buck converter. Hard switching causes major parts of the power loss in high side switch and limits high switching frequency application of DC-DC converter. The proposed resonant gate driver behaves more like the ideal current source driver which can fast turn-on/turn-off power switch to reduce switching loss. In addition, with proposed resonant gate driver, impact of parasitic gate resistance on switching speed of power switch can be greatly reduced. Test results show that, for buck converter with 12 V input voltage, 1.3 V output voltage, 10 A load current and 5.5 ¿ gate resistance, comparing to conventional driver, with the proposed resonant gate driver for high side switch, total efficiency of buck converter can be improved by more than 3.5%. DA - 2010/// PY - 2010/// DO - 10.1109/apec.2010.5433425 SP - 1477-1481 SN - 1048-2334 ER - TY - JOUR TI - A High Efficiency Regulated Charge Pump over Wide Input and Load Range AU - Guo, Rong AU - Yang, Liyu AU - Huang, Alex AU - Endredy, John T2 - 2010 TWENTY-FIFTH ANNUAL IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION (APEC) AB - A multi-modes regulated charge pump with improved efficiency over wide input and load range is proposed in this paper. The output voltage is regulated to 5 V when input is 4.5-2.7 V. By alternating the switch network, it can realize 2x, 1.5x, and 1.33x conversion modes, which improves the efficiency over wide input range. During each mode, the output voltage is regulated by a controlled current source. The regulated charge pump is designed for a very wide load range (10 mA to 500 mA). A hybrid control scheme is proposed and analyzed to achieve a high efficiency over desired load range. Both of the simulation and test results are provided to verify the control scheme. The results show that the total loss at light load can be reduced by 56% to 83%. DA - 2010/// PY - 2010/// DO - 10.1109/apec.2010.5433355 SP - 1172-1176 SN - 1048-2334 ER - TY - JOUR TI - Robust reduced-order modelling of distributed linear networks AU - Saunders, C. S. AU - Mazzaro, G. J. AU - Steer, M. B. T2 - IET MICROWAVES ANTENNAS & PROPAGATION AB - Foster's canonical form provides a causal bridge between the transfer function representation of the characteristics of a distributed structure and both time-domain and frequency-domain non-linear circuit simulation. It is particularly advantageous in modelling bandpass-like characteristics. In the modelling procedure, a transfer function having Foster's canonical form is fitted to measured or simulated data which may not have an inherent pole-zero description. Even if there is a good transfer function representation, the number of poles required for a reasonable fit is not known a priori which can lead to poor models that may cause convergence problems during either fitting or simulation. In this study, an extension of Foster's model is developed and a robust procedure for fitting the transfer function to data without a priori knowledge of the number of poles is presented. A robust stamp for implementation of the model in a transient circuit simulator is developed. DA - 2010/7// PY - 2010/7// DO - 10.1049/iet-map.2009.0554 VL - 4 IS - 7 SP - 962-973 SN - 1751-8733 ER - TY - JOUR TI - Polarization-independent tunable optical filters using bilayer polarization gratings AU - Nicolescu, Elena AU - Escuti, Michael J. T2 - APPLIED OPTICS AB - We demonstrate a polarization-independent tunable optical filter based on switchable polarization gratings (PGs) formed using reactive and nonreactive liquid crystals (LCs). PGs are anisotropic diffraction gratings that exhibit unique properties, including a zero-order transmittance that is independent of incident polarization and that can vary from approximately 0% to approximately 100%, depending on wavelength and applied voltage. A stack of several PGs of varying thicknesses combined with an elemental angle filter yields polarization-independent bandpass tuning with minimal loss. We introduce a novel hybrid PG consisting of both reactive and nonreactive LC layers, which allows very thick gratings to be created with thin active LC layers. We demonstrate a tunable optical filter with a peak transmittance of 84% of unpolarized light, a minimum full width at half-maximum of 64 nm, and a maximum tuning range of 140 nm. DA - 2010/7/10/ PY - 2010/7/10/ DO - 10.1364/ao.49.003900 VL - 49 IS - 20 SP - 3900-3904 SN - 2155-3165 ER - TY - JOUR TI - Plasmonic Nanoparticles and Nanowires: Design, Fabrication and Application in Sensing AU - Vo-Dinh, Tuan AU - Dhawan, Anuj AU - Norton, Stephen J. AU - Khoury, Christopher G. AU - Wang, Hsin-Neng AU - Misra, Veena AU - Gerhold, Michael D. T2 - JOURNAL OF PHYSICAL CHEMISTRY C AB - This study involves two aspects of our investigations of plasmonics-active systems: (i) theoretical and simulation studies and (ii) experimental fabrication of plasmonics-active nanostructures. Two types of nanostructures are selected as the model systems for their unique plasmonics properties: (1) nanoparticles and (2) nanowires on substrate. Special focus is devoted to regions where the electromagnetic field is strongly concentrated by the metallic nanostructures or between nanostructures. The theoretical investigations deal with dimers of nanoparticles and nanoshells using a semi-analytical method based on a multipole expansion (ME) and the finite-element method (FEM) in order to determine the electromagnetic enhancement, especially at the interface areas of two adjacent nanoparticles. The experimental study involves the design of plasmonics-active nanowire arrays on substrates that can provide efficient electromagnetic enhancement in regions around and between the nanostructures. Fabrication of these nanowire structures over large chip-scale areas (from a few millimeters to a few centimeters) as well as FDTD simulations to estimate the EM fields between the nanowires are described. The application of these nanowire chips using surface-enhanced Raman scattering (SERS) for detection of chemicals and labeled DNA molecules is described to illustrate the potential of the plasmonics chips for sensing. DA - 2010/4/29/ PY - 2010/4/29/ DO - 10.1021/jp911355q VL - 114 IS - 16 SP - 7480-7488 SN - 1932-7455 ER - TY - JOUR TI - On the Performance of Content Delivery under Competition in a Stochastic Unstructured Peer-to-Peer Network AU - Chiu, Yuh-Ming AU - Eun, Do Young T2 - IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS AB - Peer-to-peer (P2P) network is widely used for transferring large files nowadays. Measurement results show that most downloading peers are patient as the average download session is usually very long. It is sometimes even longer than downloading from a dedicated server using a modem. Existing results in the literature indicate that the stochastic fluctuation and the heterogeneity in the service capacity of each peer are two of the major reasons that make the average download time far longer than expected. In those studies, it has been often assumed that there is only one downloading peer in the network, ignoring the interaction and competition among peers. In this paper, we investigate the impact of the interaction and competition among peers on downloading performance under stochastic, heterogeneous, and unstructured P2P settings, thereby greatly extending the existing results on stochastic P2P networks made only under a single downloading peer in the network. To analyze the average download time in a P2P network with multiple competing downloading peers, we first introduce the notion of system utilization tailored to a P2P network. We investigate the relationship among the average download time, system utilization, and the level of competition among downloading peers in a stochastic P2P network. We then derive an achievable lower bound on the average download time and propose algorithms to give the peers the minimum average download time. Our result can much improve the download performance compared to earlier results in the literature. The performance of the different algorithms is compared under NS-2 simulations. Our results also provide theoretical explanation to the inconsistency of performance improvement by using parallel connections (parallel connections sometimes do not outperform a single connection) observed in some measurement studies. DA - 2010/10// PY - 2010/10// DO - 10.1109/tpds.2010.15 VL - 21 IS - 10 SP - 1487-1500 SN - 1558-2183 KW - Computer network performance KW - P2P networks ER - TY - JOUR TI - Nutrient removal capability of a constructed wetland receiving groundwater contaminated by swine lagoon seepage AU - Hathaway, J. M. AU - Cook, M. J. AU - Evans, R. O. T2 - Transactions of the ASABE AB - Seepage from waste lagoons has the potential to leach into underlying groundwater systems. Groundwater flow can transport this nutrient-rich lagoon seepage to surrounding surface waters where water quality degradation may occur. Groundwater contaminated by lagoon seepage can be removed from the shallow aquifer by pumping, but the pumped water must still be treated before discharge into surface waters. Constructed wetlands have been successfully implemented to attenuate nitrogen and phosphorus in wastewaters. A constructed wetland receiving groundwater contaminated by swine lagoon seepage was monitored for four years during this study. Wetland effluent concentrations were variable but were on average substantially lower than influent concentrations. During the four-year study, the wetland assimilated between 76% and 84% of the influent total nitrogen and between 22% and 42% of the influent total phosphorus, or 520 to 575 kg of total nitrogen per hectare per year and 83 to 158 kg of total phosphorus per hectare per year. Residence time likely played a major role in nutrient assimilation within the wetland. DA - 2010/// PY - 2010/// DO - 10.13031/2013.30079 VL - 53 IS - 3 SP - 741-749 ER - TY - JOUR TI - Modeling of tunnel junctions for high efficiency solar cells AU - Hauser, John R. AU - Carlin, Zach AU - Bedair, S. M. T2 - APPLIED PHYSICS LETTERS AB - Ultrahigh efficiency, in the range of 40%, can be achieved in multijunction solar cells operating at high solar concentrations, larger than 100 suns. Critical to this approach are high band gap tunnel junctions that serve as electrically low loss interconnections between the cells. The purpose of this work is to theoretically model such wide band gap tunnel junctions and to explore the advantages of a staggered band line up for improving the peak tunnel current. Theoretical results are calculated for heterojunction diodes made of n+-InGaP/p+-AlGaAs over a range of doping levels. The results illustrate the advantage of a conduction band discontinuity in achieving low interconnect resistance for multijunction solar cells. DA - 2010/7/26/ PY - 2010/7/26/ DO - 10.1063/1.3469942 VL - 97 IS - 4 SP - SN - 1077-3118 KW - aluminium compounds KW - conduction bands KW - gallium arsenide KW - gallium compounds KW - indium compounds KW - semiconductor diodes KW - semiconductor heterojunctions KW - solar cells KW - tunnelling ER - TY - JOUR TI - MULTI-LEVEL OPTIMIZATION OF NEGATIVE SELECTION ALGORITHM DETECTORS WITH APPLICATION IN MOTOR FAULT DETECTION AU - Gao, X. Z. AU - Ovaska, S. J. AU - Wang, X. AU - Chow, M. -Y. T2 - INTELLIGENT AUTOMATION AND SOFT COMPUTING AB - Abstract This paper proposes amulti-level optimization strategy for the Negative Selection Algorithm (NSA) detectors, based on both the Genetic Algorithms (GA) and clonal selection principle. The NSA is a natural immune response-inspired pattern discrimination method In our hierazchical optimization scheme, the NSA detectors are fast optimized by the GA to occupy the maximal coverage of the nonself space. Next, these detectors are further fine-tuned and optimized using the Clonal Selection Algorithm (CSA) so as to achieve the best fault detection performance. This novel NSA detectors optimization approach is also examined with artificial data and a practical motor fault detection example. DA - 2010/// PY - 2010/// DO - 10.1080/10798587.2010.10643086 VL - 16 IS - 3 SP - 353-375 SN - 2326-005X KW - Artificial Immune Systems (AIS) KW - Negative Selection Algorithm (NSA) KW - Genetic Algorithms (GA) KW - Clonal Selection Algorithm (CSA) KW - optimization KW - anomaly detection KW - motor fault detection ER - TY - CONF TI - Growth and optical spectroscopy of Ho-doped KPb2Cl5 for infrared solid-state lasers AU - Oyebola, O. AU - Hommerich, U. AU - Brown, E. AU - Trivedi, S. B. AU - Bluiett, A. G. AU - Zavada, J. M. C2 - 2010/// C3 - Journal of Crystal Growth DA - 2010/// VL - 312 SP - 1154-1156 M1 - 8 ER - TY - JOUR TI - Feasibility of optimally assigning channels by exhaustive search in commercial multi-radio wireless mesh networks AU - Xie, Wei AU - Zhang, Ying Jun AU - Sichitiu, Mihail L. AU - Fu, Liqun AU - Yao, Yan T2 - TELECOMMUNICATION SYSTEMS DA - 2010/6// PY - 2010/6// DO - 10.1007/s11235-009-9216-3 VL - 44 IS - 1-2 SP - 171-178 SN - 1018-4864 KW - Wireless mesh networks KW - Channel assignment KW - Exhaustive search KW - Combinatorics ER - TY - JOUR TI - Effect of scattering albedo on attenuation and polarization of light underwater AU - Cochenour, Brandon AU - Mullen, Linda AU - Muth, John T2 - OPTICS LETTERS AB - Recent work on underwater laser communication links uses polarization discrimination to improve system performance [Appl. Opt.48, 328 (2009)] [in Proceedings of IEEE Oceans 2009 (IEEE, 2009), pp. 1–4]. In the laboratory, Maalox antacid is commonly used as a scattering agent. While its scattering function closely mimics that of natural seawaters, its scattering albedo can be much higher, as Maalox particles tend to be less absorbing. We present a series of experiments where Nigrosin dye is added to Maalox in order to more accurately recreate real-world absorption and scattering properties. We consider the effect that scattering albedo has on received power and the degree of depolarization of forward-scattered light in the context of underwater laser communication links. DA - 2010/6/15/ PY - 2010/6/15/ DO - 10.1364/ol.35.002088 VL - 35 IS - 12 SP - 2088-2090 SN - 0146-9592 ER - TY - JOUR TI - Effect of oxygen pressure on the structure and luminescence of Eu-doped Gd2O3 thin films AU - Wellenius, Patrick AU - Smith, Eric R. AU - Wu, Pae C. AU - Everitt, Henry O. AU - Muth, John F. T2 - PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE AB - Abstract Europium‐doped gadolinium oxide (Gd 2 O 3 ) thin films were deposited on sapphire substrates by pulsed laser deposition (PLD). The effect of oxygen pressure during deposition on the structure of the thin films, investigated by transmission electron microscopy (TEM) and X‐ray diffraction (XRD), was correlated to photoluminescence spectra. The polycrystalline films, like the one deposited in 5 mTorr oxygen environment, were primarily monoclinic phase; however the rarer cubic phase was achieved at 50 mTorr pressure. Time‐integrated and time‐resolved photoluminescence (TIPL and TRPL) spectra of the bright 5 D 0 to 7 F 2 radiative transition revealed how the differing host material phases altered the local environment of the Eu dopants. DA - 2010/8// PY - 2010/8// DO - 10.1002/pssa.201026071 VL - 207 IS - 8 SP - 1949-1953 SN - 1862-6300 KW - gadolinium oxide KW - photoluminescence KW - pulsed laser deposition ER - TY - JOUR TI - A GPGPU Compiler for Memory Optimization and Parallelism Management AU - Yang, Yi AU - Xiang, Ping AU - Kong, Jingfei AU - Zhou, Huiyang T2 - ACM SIGPLAN NOTICES AB - This paper presents a novel optimizing compiler for general purpose computation on graphics processing units (GPGPU). It addresses two major challenges of developing high performance GPGPU programs: effective utilization of GPU memory hierarchy and judicious management of parallelism. The input to our compiler is a naïve GPU kernel function, which is functionally correct but without any consideration for performance optimization. The compiler analyzes the code, identifies its memory access patterns, and generates both the optimized kernel and the kernel invocation parameters. Our optimization process includes vectorization and memory coalescing for memory bandwidth enhancement, tiling and unrolling for data reuse and parallelism management, and thread block remapping or address-offset insertion for partition-camping elimination. The experiments on a set of scientific and media processing algorithms show that our optimized code achieves very high performance, either superior or very close to the highly fine-tuned library, NVIDIA CUBLAS 2.2, and up to 128 times speedups over the naive versions. Another distinguishing feature of our compiler is the understandability of the optimized code, which is useful for performance analysis and algorithm refinement. DA - 2010/6// PY - 2010/6// DO - 10.1145/1809028.1806606 VL - 45 IS - 6 SP - 86-97 SN - 0362-1340 KW - Performance KW - Experimentation KW - Languages KW - GPGPU KW - Compiler ER - TY - JOUR TI - Ultrahigh Vacuum Chemical Vapor Deposition of Doped and Intrinsic Si1-xCx Epitaxy from Disilane, Trimethylsilane, and Phosphine AU - Alptekin, Emre AU - Ozturk, Mehmet C. T2 - JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB - Epitaxial alloys grown in recessed source/drain junctions of n-channel MOSFETs are of interest to induce uniaxial tensile strain in the channel for electron mobility enhancement. In this work, we have studied chemical vapor deposition of intrinsic and heavily phosphorus-doped epitaxial layers on silicon using disilane, trimethylsilane, phosphine, and hydrogen as the gaseous precursors. The results show that phosphorus segregation to the growth surface can be fully suppressed by growing the layers at or below . The best films were obtained at this temperature yielding a growth rate of 4 nm/min. A maximum phosphorus concentration of was obtained with a minimum resistivity of and a substitutional carbon concentration of 1.0%. DA - 2010/// PY - 2010/// DO - 10.1149/1.3414167 VL - 157 IS - 6 SP - H699-H704 SN - 1945-7111 ER - TY - JOUR TI - Time division multiplexing front-ends for multiantenna integrated wireless receivers AU - Krishnamurthy, G. AU - Gard, K. G. T2 - IEEE Transactions on Circuits and Systems. I, Regular Papers DA - 2010/// PY - 2010/// VL - 57 IS - 6 SP - 1231-1243 ER - TY - JOUR TI - The importance of fuel dissociation and propargyl plus allyl association for the formation of benzene in a fuel-rich 1-hexene flame AU - Hansen, N. AU - Li, W. AU - Law, M. E. AU - Kasper, T. AU - Westmoreland, P. R. AU - Yang, B. AU - Cool, T. A. AU - Lucassen, A. T2 - Physical Chemistry Chemical Physics DA - 2010/// PY - 2010/// VL - 12 IS - 38 SP - 12112-12122 ER - TY - JOUR TI - Platinum Nanoparticles Grown by Atomic Layer Deposition for Charge Storage Memory Applications AU - Novak, Steven AU - Lee, Bongmook AU - Yang, Xiangyu AU - Misra, Veena T2 - JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB - This paper explores platinum nanoparticle formation during the early stages of growth by atomic layer deposition. Particle size and distribution can be controlled by altering growth parameters. The particles show excellent temperature stability up to as examined by transmission electron microscopy and in situ heating. Capacitance–voltage and charge retention measurements demonstrate the memory effect in metal-oxide-semiconductor capacitors with embedded nanoparticles. The size, density, charge storage, and temperature stability of the platinum nanoparticles make them attractive for use as charge storage layers for nonvolatile memory devices. DA - 2010/// PY - 2010/// DO - 10.1149/1.3365031 VL - 157 IS - 6 SP - H589-H592 SN - 1945-7111 ER - TY - JOUR TI - On the Survivability of Wireless Ad Hoc Networks with Node Misbehaviors and Failures AU - Xing, Fei AU - Wang, Wenye T2 - IEEE TRANSACTIONS ON DEPENDABLE AND SECURE COMPUTING AB - Network survivability is the ability of a network to stay connected under failures and attacks, which is a fundamental issue to the design and performance evaluation of wireless ad hoc networks. In this paper, we focus on the analysis of network survivability in the presence of node misbehaviors and failures. First, we propose a novel semi-Markov process model to characterize the evolution of node behaviors. As an immediate application of the proposed model, we investigate the problem of node isolation where the effects of denial-of-service (DoS) attacks are considered. Then, we present the derivation of network survivability and obtain the lower and upper bounds on the topological survivability for k-connected networks. We find that the network survivability degrades very quickly with the increasing likelihood of node misbehaviors, depending on the requirements of disjoint outgoing paths or network connectivity. Moreover, DoS attacks have a significant impact on the network survivability, especially in dense networks. Finally, we validate the proposed model and analytical result by simulations and numerical analysis, showing the effects of node misbehaviors on both topological survivability and network performance. DA - 2010/// PY - 2010/// DO - 10.1109/tdsc.2008.71 VL - 7 IS - 3 SP - 284-299 SN - 1941-0018 KW - Network survivability KW - node misbehaviors KW - semi-Markov process KW - node behavior modeling KW - node isolation problem KW - k-connectivity KW - wireless ad hoc networks ER - TY - JOUR TI - Magnetoconcentration effect in intrinsic graphene ribbons AU - Sokolov, V. N. AU - Kochelap, V. A. AU - Kim, K. W. T2 - Applied Physics Letters AB - We consider transverse redistributions of the electrons and holes in intrinsic graphene ribbons under the influence of crossed electric and magnetic fields, i.e., the magnetoconcentration effect. The electron and hole transport is described from the Boltzmann kinetic equation assuming the local quasiequilibrium distributions of the carriers over energy states. The effective control of the carriers is achieved from deep depletion to accumulation modes depending on the properties of the ribbon edges, provided electron-hole recombination/generation rates at the edges are different from those inside the ribbon. The current-voltage characteristics reflect the behavior of the carrier redistributions across the ribbon. The obtained results suggest that interesting effects such as the population inversion in certain ranges of energies and the induced transparency are possible, which make them attractive for various optoelectronics applications in the terahertz spectral range. DA - 2010/9/13/ PY - 2010/9/13/ DO - 10.1063/1.3486124 VL - 97 IS - 11 SP - 112112 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.3486124 DB - Crossref KW - Boltzmann equation KW - electrical conductivity KW - electron mobility KW - electron-hole recombination KW - energy states KW - graphene KW - hole mobility KW - spin Hall effect KW - transparency ER - TY - JOUR TI - M-ary PPM for Transmitted Reference Ultra-Wideband Communications AU - Li, Liping AU - Townsend, J. Keith T2 - IEEE TRANSACTIONS ON COMMUNICATIONS AB - In this paper, we investigate the multiple-access (MA) performance of transmitted reference (TR) ultra-wideband (UWB) systems employing M-ary PPM in multipath environments. Because we assume there is no power control in the network, interfering power levels from users can vary over many 10's of dB. We categorize the interfering users into two groups with respect to power levels. A new method for deriving the variance of the Gaussian random variable resulting from multiple-access interference (MAI) is developed using the power delay profile (PDP) of the channel. This makes the theoretical analysis tractable and enables us to predict the system-level performance such as the supported number of users, the achievable data rate, and the required bit-energy-to-noise ratio. Chip discrimination is applied and shown to mitigate the effect of high-power users. Performance is quantified due to the combined effects of equal-power and high-power users. DA - 2010/7// PY - 2010/7// DO - 10.1109/tcomm.2010.07.080675 VL - 58 IS - 7 SP - 1912-1917 SN - 1558-0857 KW - Ultra-wideband KW - M-ary PPM KW - transmitted reference KW - multiple-access interference KW - chip discrimination ER - TY - JOUR TI - Intermodulation distortion in narrowband amplifier circuits AU - Mazzaro, G. J. AU - Steer, M. B. AU - Gard, K. G. T2 - IET MICROWAVES ANTENNAS & PROPAGATION AB - The contribution of bandpass filter memory to intermodulation distortion in narrowband amplifier circuits is examined. A method for generating multisines from filtered switched tones is presented, and techniques for measuring an amplifier's IP3 and extracting a filter's passband using these multisines are developed. It is shown that amplified filtered pulses produce intermodulation distortion in frequency-hopping communication systems. In the experimental study, 465 and 900-MHz Chebyshev bandpass filters are considered. DA - 2010/9// PY - 2010/9// DO - 10.1049/iet-map.2009.0281 VL - 4 IS - 9 SP - 1149-1156 SN - 1751-8733 ER - TY - JOUR TI - Influence of Environment on Terahertz Spectra of Biological Molecules AU - Bykhovski, Alexei AU - Gelmont, Boris T2 - JOURNAL OF PHYSICAL CHEMISTRY B AB - The variability of molecular vibrations and low terahertz spectra of biological molecules depending on the three-dimensional structure of molecular clusters, chemical bonding, and molecular concentration in the surrounding media is studied using computer simulations. The resonant terahertz spectra of biological molecules and their associations are described within the framework of molecular mechanics using an all-atom molecular mechanical force field for proteins and nucleic acids. Both the absolute values of absorption coefficients and their spectral properties are considered for murein-lipoprotein and thioredoxin of E. coli and models of bacterial DNAs using energy minimization and molecular dynamics. The obtained results indicate that structural changes introduced by chemical reactions and molecule associations can strongly affect terahertz spectra, causing significant changes in absorption peak intensities and shifts in peak positions. Terahertz light absorption intensities of studied proteins are predicted to be strongly affected by solvents. DA - 2010/9/30/ PY - 2010/9/30/ DO - 10.1021/jp101510k VL - 114 IS - 38 SP - 12349-12357 SN - 1520-5207 ER - TY - JOUR TI - Fault-Tolerant Design and Control Strategy for Cascaded H-Bridge Multilevel Converter-Based STATCOM AU - Song, Wenchao AU - Huang, Alex Q. T2 - IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS AB - Cascaded H-bridge multilevel converter (CHMC) is a promising topology for flexible ac transmission systems such as static synchronous compensator (STATCOM) applications. Attention was drawn to the issue of converter reliability due to the large number of power devices used in CHMC applications. This paper proposed an effective fault-tolerant strategy by using H-bridge building block (HBBB) redundancy in CHMC-based STATCOM. The operating principle and the control strategy of the fault tolerance are proposed and discussed. The controller design consideration for the fault-tolerant STATCOM is presented. The proposed fault-tolerant control strategy is implemented on a seven-level CHMC-based STATCOM simulation platform and a five-level CHMC-based STATCOM hardware prototype. Simulation and experimental results are illustrated to verify the feasibility of the proposed fault-tolerant design with the HBBB redundancy. DA - 2010/8// PY - 2010/8// DO - 10.1109/tie.2009.2036019 VL - 57 IS - 8 SP - 2700-2708 SN - 1557-9948 KW - Cascaded H-bridge multilevel converter (CHMC) KW - fault tolerance KW - flexible ac transmission systems (FACTS) KW - H-bridge building block (HBBB) and redundancy KW - static synchronous compensator (STATCOM) ER - TY - JOUR TI - Simulation accuracy of the built-in PSCAD and an owner-defined synchronous machine model AU - Abdulahovic, T. AU - Teleke, S. AU - Thiringer, T. AU - Svensson, J. T2 - Compel DA - 2010/// PY - 2010/// VL - 29 IS - 3 SP - 840-855 ER - TY - JOUR TI - Networked Control System: Overview and Research Trends AU - Gupta, Rachana Ashok AU - Chow, Mo-Yuen T2 - IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS AB - Networked control systems (NCSs) have been one of the main research focuses in academia as well as in industry for many decades and have become a multidisciplinary area. With these growing research trends, it is important to consolidate the latest knowledge and information to keep up with the research needs. In this paper, the NCS and its different forms are introduced and discussed. The beginning of this paper discusses the history and evolution of NCSs. The next part of this paper focuses on different fields and research arenas such as networking technology, network delay, network resource allocation, scheduling, network security in real-time NCSs, integration of components on a network, fault tolerance, etc. A brief literature survey and possible future direction concerning each topic is included. DA - 2010/7// PY - 2010/7// DO - 10.1109/tie.2009.2035462 VL - 57 IS - 7 SP - 2527-2535 SN - 1557-9948 KW - Networked control system (NCS) KW - overview KW - research trends KW - survey ER - TY - JOUR TI - Multiphase Joint Segmentation-Registration and Object Tracking for Layered Images AU - Chen, Ping-Feng AU - Krim, Hamid AU - Mendoza, Olga L. T2 - IEEE TRANSACTIONS ON IMAGE PROCESSING AB - In this paper we propose to jointly segment and register objects of interest in layered images. Layered imaging refers to imageries taken from different perspectives and possibly by different sensors. Registration and segmentation are therefore the two main tasks which contribute to the bottom level, data alignment, of the multisensor data fusion hierarchical structures. Most exploitations of two layered images assumed that scanners are at very high altitudes and that only one transformation ties the two images. Our data are however taken at mid-range and therefore requires segmentation to assist us examining different object regions in a divide-and-conquer fashion. Our approach is a combination of multiphase active contour method with a joint segmentation-registration technique (which we called MPJSR) carried out in a local moving window prior to a global optimization. To further address layered video sequences and tracking objects in frames, we propose a simple adaptation of optical flow calculations along the active contours in a pair of layered image sequences. The experimental results show that the whole integrated algorithm is able to delineate the objects of interest, align them for a pair of layered frames and keep track of the objects over time. DA - 2010/7// PY - 2010/7// DO - 10.1109/tip.2010.2045164 VL - 19 IS - 7 SP - 1706-1719 SN - 1941-0042 KW - Active contour KW - joint segmentation registration KW - layered sensing KW - multiphase active contour KW - optical flow KW - visual motion ER - TY - JOUR TI - Introduction to the Special Section on Electronic and Ionic Interfaces to Biomolecules and Cells AU - Bartic, Carmen AU - Chan, Mansun AU - Fromherz, Peter AU - Judy, Jack W. AU - Kan, Edwin C. AU - Leburton, Jean-Pierre AU - Li, Jun AU - Misra, Veena AU - Reed, Mark A. AU - Timp, Greg L. T2 - IEEE TRANSACTIONS ON NANOTECHNOLOGY AB - The six articles in this special section focus on electronic and ionic interfaces to biomolecules and cells. The section includes discussions on the current status of experimental and modeling efforts on such topics as ion channels, nanowires, and patch clamps. DA - 2010/5// PY - 2010/5// DO - 10.1109/tnano.2010.2049699 VL - 9 IS - 3 SP - 268-268 SN - 1536-125X ER - TY - JOUR TI - Graphene spin capacitor for magnetic field sensing AU - Semenov, Y. G. AU - Zavada, J. M. AU - Kim, K. W. T2 - Applied Physics Letters AB - An analysis of a magnetic field sensor based on a graphene spin capacitor is presented. The proposed device consists of graphene nanoribbons on top of an insulator material connected to a ferromagnetic source/drain. The time evolution of spin polarized electrons injected into the capacitor can be used for an accurate determination at room temperature of external magnetic fields. Assuming a spin relaxation time of 100 ns, magnetic fields on the order of ∼10 mOe may be detected at room temperature. The observational accuracy of this device depends on the density of magnetic defects and spin relaxation time that can be achieved. DA - 2010/7/5/ PY - 2010/7/5/ DO - 10.1063/1.3462297 VL - 97 IS - 1 SP - 013106 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.3462297 DB - Crossref KW - capacitors KW - ferromagnetic materials KW - graphene KW - magnetic field measurement KW - magnetic sensors KW - nanosensors KW - spin polarised transport ER - TY - JOUR TI - An Optimizing Compiler for GPGPU Programs with Input-Data Sharing AU - Yang, Yi AU - Xiang, Ping AU - Kong, Jingfei AU - Zhou, Huiyang T2 - ACM SIGPLAN NOTICES AB - Developing high performance GPGPU programs is challenging for application developers since the performance is dependent upon how well the code leverages the hardware features of specific graphics processors. To solve this problem and relieve application developers of low-level hardware-specific optimizations, we introduce a novel compiler to optimize GPGPU programs. Our compiler takes a naive GPU kernel function, which is functionally correct but without any consideration for performance optimization. The compiler then analyzes the code, identifies memory access patterns, and generates optimized code. The proposed compiler optimizations target at one category of scientific and media processing algorithms, which has the characteristics of input-data sharing when computing neighboring output pixels/elements. Many commonly used algorithms, such as matrix multiplication, convolution, etc., share such characteristics. For these algorithms, novel approaches are proposed to enforce memory coalescing and achieve effective data reuse. Data prefetching and hardware-specific tuning are also performed automatically with our compiler framework. The experimental results based on a set of applications show that our compiler achieves very high performance, either superior or very close to the highly fine-tuned library, NVIDIA CUBLAS 2.1. DA - 2010/5// PY - 2010/5// DO - 10.1145/1837853.1693505 VL - 45 IS - 5 SP - 343-344 SN - 1558-1160 KW - Performance KW - Experimentation KW - Languages KW - GPGPU KW - Compiler ER - TY - JOUR TI - A High-Dynamic Range Current Source Gate Driver for Switching-Loss Reduction of High-Side Switch in Buck Converter AU - Zhou, Xin AU - Liang, Zhigang AU - Huang, Alex T2 - IEEE TRANSACTIONS ON POWER ELECTRONICS AB - In this letter, a high-dynamic range current source gate driver (HD-CSD) circuit is proposed to reduce the switching loss of the high-side switch in buck converter with wide variation of the gate resistance. Hard switching loss is the major loss in high-side switch and limits the high switching-frequency application of dc-dc converter. Comparing with conventional voltage source gate driver (VSD) and the reported four switches CSD (4S-CSD), the proposed HD-CSD behaves more like the ideal current source driver which can realize the fast switching of power switches to reduce the switching loss. In addition, with proposed HD-CSD, impact of gate resistance that limits the switching speed of the power switch can be greatly reduced. Experimental results are presented to show the power efficiency improvement of buck converter with HD-CSD high-side driver comparing with VSD and 4S-CSD high-side drivers at switching frequency of 1 MHz. DA - 2010/6// PY - 2010/6// DO - 10.1109/tpel.2009.2039649 VL - 25 IS - 6 SP - 1439-1443 SN - 1941-0107 KW - Current source gate driver (CSD) KW - gate driver KW - power MOSFET KW - switching loss ER - TY - JOUR TI - Viscous flow over a shrinking sheet with a second order slip flow model AU - Fang, Tiegang AU - Yao, Shanshan AU - Zhang, Ji AU - Aziz, Abdul T2 - COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION AB - In this paper, viscous flow over a shrinking sheet is solved analytically using a newly proposed second order slip flow model. The closed solution is an exact solution of the full governing Navier–Stokes equations. The solution has two branches in a certain range of the parameters. The effects of the two slip parameters and the mass suction parameter on the velocity distribution are presented graphically and discussed. For certain combinations of the slip parameters, the wall drag force can decrease with the increase of mass suction. These results clearly show that the second order slip flow model is necessary to predict the flow characteristics accurately. DA - 2010/7// PY - 2010/7// DO - 10.1016/j.cnsns.2009.07.017 VL - 15 IS - 7 SP - 1831-1842 SN - 1878-7274 KW - Similarity solution KW - Stretching surface KW - Shrinking sheet KW - Navier-Stokes equations KW - Analytical solution KW - Exact solution KW - Slip flow ER - TY - JOUR TI - Squigraphs for Fine and Compact Modeling of 3-D Shapes AU - Aouada, Djamila AU - Krim, Hamid T2 - IEEE TRANSACTIONS ON IMAGE PROCESSING AB - We propose to superpose global topological and local geometric 3-D shape descriptors in order to define one compact and discriminative representation for a 3-D object. While a number of available 3-D shape modeling techniques yield satisfactory object classification rates, there is still a need for a refined and efficient identification/recognition of objects among the same class. In this paper, we use Morse theory in a two-phase approach. To ensure the invariance of the final representation to isometric transforms, we choose the Morse function to be a simple and intrinsic global geodesic function defined on the surface of a 3-D object. The first phase is a coarse representation through a reduced topological Reeb graph. We use it for a meaningful decomposition of shapes into primitives. During the second phase, we add detailed geometric information by tracking the evolution of Morse function's level curves along each primitive. We then embed the manifold of these curves into ¿ 3 , and obtain a single curve. By combining phase one and two, we build new graphs rich in topological and geometric information that we refer to as squigraphs. Our experiments show that squigraphs are more general than existing techniques. They achieve similar classification rates to those achieved by classical shape descriptors. Their performance, however, becomes clearly superior when finer classification and identification operations are targeted. Indeed, while other techniques see their performances dropping, squigraphs maintain a performance rate of the order of 97%. DA - 2010/2// PY - 2010/2// DO - 10.1109/TIP.2009.2034693 VL - 19 IS - 2 SP - 306-321 SN - 1941-0042 KW - Iso-geodesic curves KW - object matching KW - Reeb graph KW - shape geometry KW - topo-geometric modeling KW - Whitney embedding ER - TY - JOUR TI - Noise Correlation in Compact Diversity Receivers AU - Domizioli, Carlo P. AU - Hughes, Brian L. AU - Gard, Kevin G. AU - Lazzi, Gianluca T2 - IEEE TRANSACTIONS ON COMMUNICATIONS AB - The impact of antenna mutual coupling on signal correlation in multi-antenna receivers has been studied in great detail. By contrast, there has been little work on how mutual coupling affects noise. In this paper we present a noise model for a diversity receiver that includes noise generated by the antennas, front-end amplifiers, and other receiver components. This model shows that noise in a compact diversity receiver may be spatially correlated. Expressions relating noise correlation to properties of the antennas and amplifiers are derived and its impact on the outage probability of an optimal diversity combiner is studied. Examples illustrating the relationship between mutual coupling and noise correlation demonstrate how different noise sources may impact performance in profoundly different ways. DA - 2010/5// PY - 2010/5// DO - 10.1109/tcomm.2010.05.080601 VL - 58 IS - 5 SP - 1426-1436 SN - 1558-0857 KW - Antenna arrays KW - mutual coupling KW - noise KW - receivers KW - diversity methods ER - TY - JOUR TI - High-resolution land cover change detection based on fuzzy uncertainty analysis and change reasoning AU - Hester, D. B. AU - Nelson, S. A. C. AU - Cakir, H. I. AU - Khorram, S. AU - Cheshire, H. T2 - INTERNATIONAL JOURNAL OF REMOTE SENSING AB - Land cover change detection is an important research and application area for analysts of remote sensing data. The primary objective of the research described here was to develop a change detection method capable of accommodating spatial and classification uncertainty in generating an accurate map of land cover change using high resolution satellite imagery. As a secondary objective, this method was designed to facilitate the mapping of particular types and locations of change based on specific study goals. Urban land cover change pertinent to surface water quality in Raleigh, North Carolina, was assessed using land cover classifications derived from pan-sharpened, 0.61 m QuickBird images from 2002 and 2005. Post-classification map errors were evaluated using a fuzzy logic approach. First, a ‘change index’ representing a quantitative gradient along which land cover change is characterized by both certainty and relevance, was created. The result was a continuous representation of change, a product type that retains more information and flexibility than discrete maps of change. Finally, fuzzy logic and change reasoning results were integrated into a binary change/no change map that quantified the most certain, likely, and relevant change regions within the study area. A ‘from-to’ change map was developed from this binary map inserting the type of change identified in the raw post-classification map. A from-to change map had an overall accuracy of 78.9% (κ = 0.747) and effectively mapped land cover changes posing a threat to water quality, including increases in impervious surface. This work presents an efficient fuzzy framework for transforming map uncertainty into accurate and practical change analysis. DA - 2010/// PY - 2010/// DO - 10.1080/01431160902893493 VL - 31 IS - 2 SP - 455-475 SN - 1366-5901 ER - TY - JOUR TI - High-Throughput Continuous Beam Steering Using Rotating Polarization Gratings AU - Oh, Chulwoo AU - Kim, Jihwan AU - Muth, John AU - Serati, Steve AU - Escuti, Michael J. T2 - IEEE PHOTONICS TECHNOLOGY LETTERS AB - A new beam steering concept comprising independently rotating, inline polarization gratings (PGs) is experimentally demonstrated. The approach, which we term Risley gratings, achieves high steering throughput within a large field-of-regard (FOR) in a fashion similar to Risley prisms, composed of wedged prisms. However, because PGs are patterned in thin liquid crystal layers, they enable a system with far less thickness, weight, and beam walk-off. Furthermore, large apertures are feasible and wavelengths from visible to infrared can be chosen. Any direction within a solid angle defined by twice the diffraction angle of each PG can be addressed mechanically. Here we demonstrate a Risley grating system with a 62° FOR and 89%-92% transmittance at 1550-nm wavelength, using two PGs with 6-¿m grating period. DA - 2010/2/15/ PY - 2010/2/15/ DO - 10.1109/LPT.2009.2037155 VL - 22 IS - 4 SP - 200-202 SN - 1041-1135 KW - Beam steering KW - diffraction KW - polarization grating (PG) KW - Risley prism ER - TY - JOUR TI - Electrical and magnetic properties of GaN codoped with Eu and Si AU - Wang, R. AU - Steckl, A. J. AU - Nepal, N. AU - Zavada, J. M. T2 - Journal of Applied Physics DA - 2010/// PY - 2010/// VL - 107 IS - 1 ER - TY - JOUR TI - Constrained Dimensionality Reduction Using a Mixed-Norm Penalty Function with Neural Networks AU - Zeng, Huiwen AU - Trussell, H. Joel T2 - IEEE TRANSACTIONS ON KNOWLEDGE AND DATA ENGINEERING AB - Reducing the dimensionality of a classification problem produces a more computationally-efficient system. Since the dimensionality of a classification problem is equivalent to the number of neurons in the first hidden layer of a network, this work shows how to eliminate neurons on that layer and simplify the problem. In the cases where the dimensionality cannot be reduced without some degradation in classification performance, we formulate and solve a constrained optimization problem that allows a trade-off between dimensionality and performance. We introduce a novel penalty function and combine it with bilevel optimization to solve the constrained problem. The performance of our method on synthetic and applied problems is superior to other known penalty functions such as weight decay, weight elimination, and Hoyer's function. An example of dimensionality reduction for hyperspectral image classification demonstrates the practicality of the new method. Finally, we show how the method can be extended to multilayer and multiclass neural network problems. DA - 2010/3// PY - 2010/3// DO - 10.1109/TKDE.2009.107 VL - 22 IS - 3 SP - 365-380 SN - 1558-2191 KW - Pruning KW - neural networks KW - penalty function KW - mixed-norm penalty ER - TY - JOUR TI - Analysis of Process-Dependent Maximal Switching Frequency, Choke Effect, and Its Relaxed Solution in High-Resolution DPWM AU - Wang, Xiaopeng AU - Zhou, Xin AU - Park, Jinseok AU - Guo, Rong AU - Huang, Alex Q. T2 - IEEE TRANSACTIONS ON POWER ELECTRONICS AB - This letter uses the fanout-of-4 (FO4) metric to analyze the semiconductor process (SP) dependent maximal switching frequency (MSF) of a digital pulsewidth modulator (DPWM). After discussing the choke effect in a self-oscillating hybrid (SOH) DPWM and its impact on MSF, this letter further shows that separating the voltage-controlled oscillator (VCO) and the delay mux line is an effective way to relax the choke effect so that the MSF in the SOH could be almost doubled, together with 10%-20% power saving. Taking a low-cost AMI06 SP and 9-bit-resolution specification as an example, this letter predicts that 8 MHz switching frequency could be achieved with the proposed SOH. The SOH chip was custom-designed and fabricated in a 0.703 mm 2 die via the metal oxide semiconductor implementation service (MOSIS) educational program. The chip test demonstrated that the MSF is 7.4 MHz with 1.07 mA power consumption, and the adjustable switching frequency range is from 1.8 to 7.4 MHz. DA - 2010/1// PY - 2010/1// DO - 10.1109/tpel.2009.2025272 VL - 25 IS - 1 SP - 152-157 SN - 1941-0107 KW - Delay estimation KW - digital integrated circuits KW - phase-locked loops (PLL) KW - pulsewidth modulation (PWM) KW - voltage-controlled oscillators (VCOs) ER - TY - JOUR TI - A Delay-Tolerant Potential-Field-Based Network Implementation of an Integrated Navigation System AU - Gupta, Rachana Ashok AU - Masoud, Ahmad A. AU - Chow, Mo-Yuen T2 - IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS AB - Network controllers (NCs) are devices that are capable of converting dynamic, spatially extended, and functionally specialized modules into a taskable goal-oriented group called networked control system. This paper examines the practical aspects of designing and building an NC that uses the Internet as a communication medium. It focuses on finding compatible controller components that can be integrated via a host structure in a manner that makes it possible to network, in real-time, a webcam, an unmanned ground vehicle (UGV), and a remote computer server along with the necessary operator software interface. The aim is to deskill the UGV navigation process and yet maintain a robust performance. The structure of the suggested controller, its components, and the manner in which they are interfaced are described. Thorough experimental results along with performance assessment and comparisons to a previously implemented NC are provided. DA - 2010/2// PY - 2010/2// DO - 10.1109/TIE.2009.2026764 VL - 57 IS - 2 SP - 769-783 SN - 1557-9948 UR - http://dx.doi.org/10.1109/tie.2009.2026764 KW - Harmonic potential field (HPF) KW - intelligent space (iSpace) KW - network-based integrated navigation system ER - TY - JOUR TI - Vibrational characteristics of genetic codons: 5 '-GGX-3 ' and 5 '-XGG-3 ' (X = A C, and T) AU - Zhao, P. J. AU - Woolard, B. N. T2 - IEEE Sensors Journal DA - 2010/// PY - 2010/// VL - 10 IS - 3 SP - 630-638 ER - TY - JOUR TI - Technique to improve performance of Al2O3 interpoly dielectric using a La2O3 interface scavenging layer for floating gate memory structures AU - Jayanti, Srikant AU - Yang, Xiangyu AU - Lichtenwalner, Daniel J. AU - Misra, Veena T2 - APPLIED PHYSICS LETTERS AB - A technique of scavenging the SiO2 interfacial layer (IL) to improve the electrical performance of Al2O3 as the interpoly dielectric for flash memories has been studied. Scavenging was performed by the reaction of a thin La2O3 layer with the native oxide to form a high-κ lanthanum silicate. Significant improvement in the charge trapping and leakage characteristics were obtained. Transmission electron microscopy analysis was done to corroborate the electrical results. Results show that seven orders of magnitude leakage reduction was achieved by the replacement of the SiO2 IL with a higher-κ dielectric LaSiO at the Si interface. DA - 2010/3/1/ PY - 2010/3/1/ DO - 10.1063/1.3355547 VL - 96 IS - 9 SP - SN - 0003-6951 KW - aluminium compounds KW - dielectric materials KW - flash memories KW - lanthanum compounds KW - silicon compounds KW - transmission electron microscopy ER - TY - JOUR TI - Speech Enhancement Using Harmonic Emphasis and Adaptive Comb Filtering AU - Jin, Wen AU - Liu, Xin AU - Scordilis, Michael S. AU - Han, Lu T2 - IEEE TRANSACTIONS ON AUDIO SPEECH AND LANGUAGE PROCESSING AB - An enhancement method for single-channel speech degraded by additive noise is proposed. A spectral weighting function is derived by constrained optimization to suppress noise in the frequency domain. Two design parameters are included in the suppression gain, namely, the frequency-dependent noise-flooring parameter (FDNFP) and the gain factor. The FDNFP controls the level of admissible residual noise in the enhanced speech. Enhanced harmonic structures are incorporated into the FDNFP by time-domain processing of the linear prediction residuals of voiced speech. Further enhancement of the harmonics is achieved by adaptive comb filtering derived using the gain factor with a peak-picking algorithm. The performance of the enhancement method was evaluated by the modified bark spectral distance (MBSD), ITU-Perceptual Evaluation of Speech Quality (PESQ) scores, composite objective measures and listening tests. Experimental results indicate that the proposed method outperforms spectral subtraction; a main signal subspace method applicable to both white and colored noise conditions and a perceptually based enhancement method with a constant noise-flooring parameter, particularly at lower signal-to-noise ratio conditions. Our listening test indicated that 16 listeners on average preferred the proposed approach over any of the other three approaches about 73% of the time. DA - 2010/2// PY - 2010/2// DO - 10.1109/TASL.2009.2028916 VL - 18 IS - 2 SP - 356-368 SN - 1558-7924 KW - Constrained optimization KW - harmonic enhancement KW - speech enhancement ER - TY - JOUR TI - Special Issue on Enhancement Algorithms, Methodologies and Technology for Spectral Sensing AU - Jensen, James O. AU - Trew, Robert J. AU - Woolard, Dwight L. AU - Gupta, Neelam AU - Theriault, Jean-Marc AU - Hayat, Majeed M. AU - Li, Yanqiu AU - Gillespie, Patti T2 - IEEE SENSORS JOURNAL AB - The paper is an editorial issue on enhancement algorithms, methodologies and technology for spectral sensing and serves as a valuable and useful reference for researchers and technologists interested in the evolving state-of-the-art and/or the emerging science and technology base associated with spectral-based sensing and monitoring problem. This issue is particularly relevant to those seeking new and improved solutions for detecting chemical, biological, radiological and explosive threats on the land, sea, and in the air. DA - 2010/3// PY - 2010/3// DO - 10.1109/jsen.2010.2041385 VL - 10 IS - 3 SP - 373-378 SN - 1530-437X ER - TY - JOUR TI - Rule of Law, Rule of Life: Caste, Democracy, and the Courts in India AU - Gilmartin, David T2 - AMERICAN HISTORICAL REVIEW DA - 2010/4// PY - 2010/4// DO - 10.1086/ahr.115.2.406 VL - 115 IS - 2 SP - 406-427 SN - 1937-5239 ER - TY - JOUR TI - Quasi-Coherent Thermal Emission in the Terahertz by Doped Semiconductors AU - Kong, B. D. AU - Sokolov, V. N. AU - Kim, K. W. AU - Trew, R. J. T2 - IEEE Sensors Journal AB - We investigate thermal emission characteristics mediated by surface plasmon polaritons (SPPs) resonantly excited at a semiconductor-vacuum interface. The characteristic plasma and SPP resonant frequencies in the interval from 0.3 to 10 THz can be controlled with conventional doping densities. All of the cases under consideration (n-doped GaAs, GaN, and Si) demonstrate the spectral energy density in the near field that is several orders of magnitude larger than the blackbody radiation. The strongly resonant SPPs are also shown to enhance drastically the radiative heat transfer between two semi-infinite surfaces separated by nanometric distances. The possibility of extending spatially coherent emission through 1-D binary grating is examined based on a rigorous coupled-wave analysis. Our calculation results clearly indicate that n -doped semiconductors with properly designed surface grating can achieve efficient directional thermal emission in the THz frequency range for potential use in a number of applications including sensing. DA - 2010/3// PY - 2010/3// DO - 10.1109/jsen.2009.2038133 VL - 10 IS - 3 SP - 443-450 J2 - IEEE Sensors J. OP - SN - 1530-437X 1558-1748 UR - http://dx.doi.org/10.1109/JSEN.2009.2038133 DB - Crossref KW - 1-D grating KW - radiative heat transfer KW - surface plasmon polaritons (SPPs) KW - terahertz radiation KW - thermal emission ER - TY - JOUR TI - Object Recognition Through Topo-Geometric Shape Models Using Error-Tolerant Subgraph Isomorphisms AU - Baloch, Sajjad AU - Krim, Hamid T2 - IEEE TRANSACTIONS ON IMAGE PROCESSING AB - We propose a method for 3-D shape recognition based on inexact subgraph isomorphisms, by extracting topological and geometric properties of a shape in the form of a shape model, referred to as topo-geometric shape model (TGSM). In a nutshell, TGSM captures topological information through a rigid transformation invariant skeletal graph that is constructed in a Morse theoretic framework with distance function as the Morse function. Geometric information is then retained by analyzing the geometric profile as viewed through the distance function. Modeling the geometric profile through elastic yields a weighted skeletal representation, which leads to a complete shape signature. Shape recognition is carried out through inexact subgraph isomorphisms by determining a sequence of graph edit operations on model graphs to establish subgraph isomorphisms with a test graph. Test graph is recognized as a shape that yields the largest subgraph isomorphism with minimal cost of edit operations. In this paper, we propose various cost assignments for graph edit operations for error correction that takes into account any shape variations arising from noise and measurement errors. DA - 2010/5// PY - 2010/5// DO - 10.1109/tip.2009.2039372 VL - 19 IS - 5 SP - 1191-1200 SN - 1941-0042 KW - Morse theory KW - Reeb graph KW - shape recognition KW - skeletal graph KW - 3-D shape modeling ER - TY - JOUR TI - Methodologies for Developing Surface-Enhanced Raman Scattering (SERS) Substrates for Detection of Chemical and Biological Molecules AU - Dhawan, Anuj AU - Du, Yan AU - Yan, Fei AU - Gerhold, Michael D. AU - Misra, Veena AU - Vo-Dinh, Tuan T2 - IEEE SENSORS JOURNAL AB - This paper describes methodologies for developing efficient surface-enhanced Raman scattering (SERS) substrates such as annealing thin gold films for developing gold nanoislands, fabrication of nanopillars arrays and roughened films by employing focused ion beam (FIB) milling of gold films, as well as overcoating deep-UV-fabricated silicon nanowires with a layer of gold film. Excitation of surface plasmons in these gold nanostructures leads to substantial enhancement in the Raman scattering signal obtained from molecules lying in the vicinity of the nanostructure surface. In this paper, we perform comparative studies of SERS signals from molecules such as p-mercaptobenzoic acid and cresyl fast violet attached to or adsorbed on various gold SERS substrates. It was observed that gold-coated silicon nanowire substrates and annealed gold island substrates provided considerably higher SERS signals as compared to those from the FIB patterned substrates and planar gold films. The SERS substrates developed by the different processes were employed for detection of biological molecules such as dipicolinic acid, an excellent marker for spores of bacteria such as Anthrax. DA - 2010/3// PY - 2010/3// DO - 10.1109/jsen.2009.2038634 VL - 10 IS - 3 SP - 608-616 SN - 1558-1748 KW - Annealing KW - focused ion beam KW - nanoislands KW - nanopillars KW - nanowires KW - surface-enhanced Raman scattering (SERS) KW - surface plasmons ER - TY - JOUR TI - Large-Signal Analysis of Terahertz Generation in Submicrometer GaN Diodes AU - Barry, E. A. AU - Sokolov, V. N. AU - Kim, K. W. AU - Trew, R. J. T2 - IEEE Sensors Journal AB - The conditions for microwave power generation in a submicrometer GaN diode, with a relatively lightly doped active channel, coupled to an external resonant circuit are investigated. Applying a high-field electron transport model based on the local quasi-static approximation, we show that oscillations in group III-nitride diodes can be supported in the terahertz-frequency range near the limited space-charge accumulation regime. The shape of the diode voltage and electronic current waveforms are examined in terms of the circuit parameters and operating frequencies over the bandwidth of active generation. Based on a Fourier series analysis of the diode voltage and current, the generated power and dc-to-RF conversion efficiency at the fundamental and the second or higher order harmonic frequencies are estimated. The calculation results clearly indicate that submicrometer GaN diodes (channel doping of 1 × 10 17 cm -3 ) can achieve large output powers (> 1 W) in the absence of Gunn domain formation, over a wide range of frequencies, near 0.5 THz. DA - 2010/3// PY - 2010/3// DO - 10.1109/jsen.2009.2038132 VL - 10 IS - 3 SP - 765-771 J2 - IEEE Sensors J. OP - SN - 1530-437X 1558-1748 UR - http://dx.doi.org/10.1109/JSEN.2009.2038132 DB - Crossref KW - Harmonic power and efficiency analysis KW - negative differential mobility KW - resonant circuit KW - submicrometer GaN diode KW - terahertz oscillator ER - TY - JOUR TI - First Principle Study of the Terahertz and Far-Infrared Spectral Signatures in DNA Bonded to Silicon Nanodots AU - Bykhovski, Alexei AU - Zhao, Peiji AU - Woolard, Dwight T2 - IEEE SENSORS JOURNAL AB - The first principle study of hydrogen-terminated silicon (111) with deoxyguanosine (dG) residues chemically bonded to a silicon surface via carbon linkers is performed to reveal new insights into the spectral signatures of constrained DNA chains. Silicon surface structure models are generated to accommodate one or two dG residues. In particular, structural models for two dG residues bonded onto silicon nanodots and that formed a single strand of DNA in the lateral direction (along the surface) were developed. First principle simulations with valence electron basis and effective core potentials are conducted. These studies utilized all-atom geometric optimizations to determine the final conformations and normal mode analyses to derive the spectral absorption information. Stable dG conformations on silicon are obtained for varying types of DNA chain length and Nanodot size/shape. These results show that optically active modes lying within the terahertz spectrum typically arise out of joint coupling between the DNA's vibrational behavior and that of the substrate. However, the dominant absorption line below 6 THz is predicted to most strongly represent the DNA dynamics and effects of sodium, but it is only weakly influenced by the nanodot vibrations. In this study, the phonon-induced light absorption spectra of the DNA chains were analyzed in the context of nanodot influence (e.g., edge effects). These results suggest that DNA strands can be chemically bonded to arbitrary nanosized features on silicon surfaces without perturbing some of the key spectral signatures in the THz regime, and this suggests active THz illumination strategies for DNA identification and characterization. DA - 2010/3// PY - 2010/3// DO - 10.1109/jsen.2009.2038442 VL - 10 IS - 3 SP - 585-598 SN - 1530-437X KW - Ab initio KW - DNA KW - nano KW - terahertz ER - TY - JOUR TI - Fabrication of Nanoshell Arrays Using Directed Assembly of Nanospheres AU - Lou, Yi AU - Lunardi, Leda M. AU - Muth, John F. T2 - IEEE SENSORS JOURNAL AB - Extraordinary transmission of light has been observed when light is incident on periodic nanostructures patterned metal films, which results from the interaction between the incident photons and the excited surface plasmon polaritons with wavenumbers constrained by the geometry and periodicity of the surface structure. Usually, the surface patterns are fabricated by Focused Ion Beam (FIB) milling, which is expensive and has low throughput. We employ the nanosphere lithography method to fabricate periodic nanoshell arrays on a gold film as an alternative to FIB milling. In this process, polystyrene nanospheres are deposited on glass substrates as a template for subsequent gold deposition. This results in the close-packed hexagonal nanoshell arrays patterned gold surface. The transmission spectra of the patterned surfaces show strong enhanced transmission in the red and IR wavelength regions, and the peak enhanced transmission wavelengths vary with the chemical environments above the surface. DA - 2010/3// PY - 2010/3// DO - 10.1109/jsen.2009.2038586 VL - 10 IS - 3 SP - 617-620 SN - 1558-1748 UR - http://dx.doi.org/10.1109/jsen.2009.2038586 KW - Hexagonal nanoshell arrays KW - nanosphere lithography KW - surface plasmon enhanced transmission ER - TY - JOUR TI - Classification of Curves in 2D and 3D via Affine Integral Signatures AU - Feng, Shuo AU - Kogan, Irina AU - Krim, Hamid T2 - ACTA APPLICANDAE MATHEMATICAE AB - We propose new robust classification algorithms for planar and spatial curves subjected to affine transformations. Our motivation comes from the problems in computer image recognition. To each planar or spatial curve, we assign a planar signature curve. Curves, equivalent under an affine transformation, have the same signature. The signatures are based on integral invariants, which are significantly less sensitive to small perturbations of curves and noise than classically known differential invariants. Affine invariants are derived in terms of Euclidean invariants. We present two types of signatures: the global and the local signature. Both signatures are independent of curve parameterization. The global signature depends on a choice of the initial point and, therefore, cannot be used for local comparison. The local signature, albeit being slightly more sensitive to noise, is independent of the choice of the initial point and can be used to solve local equivalence problem. An experiment that illustrates robustness of the proposed signatures is presented. DA - 2010/3// PY - 2010/3// DO - 10.1007/s10440-008-9353-9 VL - 109 IS - 3 SP - 903-937 SN - 1572-9036 KW - Euclidean and affine transformations KW - Equivalence problem for curves KW - Integral invariants KW - Signatures KW - Image recognition ER - TY - JOUR TI - Band Engineering and Magnetic Doping of Epitaxial Graphene on SiC (0001) AU - Jayasekera, Thushari AU - Kong, B. D. AU - Kim, K. W. AU - Buongiorno Nardelli, M. T2 - Physical Review Letters AB - Using calculations from first principles we show how specific interface modifications can lead to a fine-tuning of the doping and band alignment in epitaxial graphene on SiC. Upon different choices of dopants, we demonstrate that one can achieve a variation of the valence band offset between the graphene Dirac point and the valence band edge of SiC up to 1.5 eV. Finally, via appropriate magnetic doping one can induce a half-metallic behavior in the first graphene monolayer. These results clearly establish the potential for graphene utilization in innovative electronic and spintronic devices. DA - 2010/4/5/ PY - 2010/4/5/ DO - 10.1103/physrevlett.104.146801 VL - 104 IS - 14 SP - J2 - Phys. Rev. Lett. LA - en OP - SN - 0031-9007 1079-7114 UR - http://dx.doi.org/10.1103/PhysRevLett.104.146801 DB - Crossref ER - TY - JOUR TI - A Sample-Data Model for Double Edge Current Programmed Mode Control (DECPM) in High-Frequency and Wide-Range DC-DC Converters AU - Park, Jinseok AU - Fan, Jiwei AU - Wang, Xiaopeng AU - Huang, Alex T2 - IEEE TRANSACTIONS ON POWER ELECTRONICS AB - This paper focuses on a sample-data model for double edge current programmed mode control (DECPM) and its application to high-frequency and wide-range dc-dc converters. Steady-state conditions and subharmonic oscillation issues for DECPM are addressed. By combining the conventional peak and valley current programmed mode control, a sample-data model for DECPM is proposed. A small signal model for DECPM is developed by deriving the modulation gains (F m ) and the sampling gains (H e ) for DECPM from the proposed sample-data model. The sampling frequency dependence on the duty ratio and a large current loop gain at high frequency for DECPM are emphasized. The analytical results are verified by the simulation. Finally, DECPM is proposed as a method to control the high-frequency and wide-range dc-dc converters. A 10-MHz four-switch buck boost converter is implemented with DECPM to verify the viability of its application to high-frequency and wide-range converters. DA - 2010/4// PY - 2010/4// DO - 10.1109/tpel.2009.2036618 VL - 25 IS - 4 SP - 1023-1033 SN - 1941-0107 KW - Double edge current programmed mode control (DECPM) KW - four-switch buck boost converter (4SBBC) KW - high-frequency and wide-range converter KW - sample-data modeling ER - TY - JOUR TI - Superdiffusive Behavior of Mobile Nodes and Its Impact on Routing Protocol Performance AU - Kim, Sungwon AU - Lee, Chul-Ho AU - Eun, Do Young T2 - IEEE TRANSACTIONS ON MOBILE COMPUTING AB - Mobility is the most important component in mobile ad hoc networks (MANETs) and delay-tolerant networks (DTNs). In this paper, we first investigate numerous GPS mobility traces of human mobile nodes and observe superdiffusive behavior in all GPS traces, which is characterized by a ¿faster-than-linear¿ growth rate of the mean square displacement (MSD) of a mobile node. We then investigate a large amount of access point (AP) based traces, and develop a theoretical framework built upon continuous time random walk (CTRW) formalism, in which one can identify the degree of diffusive behavior of mobile nodes even under possibly heavy-tailed pause time distribution, as in the case of reality. We study existing synthetic models and trace-based models in terms of the capability of producing various degrees of diffusive behavior, and use a set of Levy walk models due to its simplicity and flexibility. In addition, we show that diffusive properties make a huge impact on contact-based metrics and the performance of routing protocols in various scenarios, and that existing models such as random waypoint, random direction model, or Brownian motion lead to overly optimistic or pessimistic results when diffusive properties are not properly captured. Our work in this paper, thus, suggests that the diffusive behavior of mobile nodes should be correctly captured and taken into account for the design and comparison study of network protocols. DA - 2010/2// PY - 2010/2// DO - 10.1109/TMC.2009.124 VL - 9 IS - 2 SP - 288-304 SN - 1558-0660 KW - Mobility models KW - trace-based models KW - superdiffusion KW - mobile ad hoc networks KW - routing protocols ER - TY - JOUR TI - Interfacial self cleaning during atomic layer deposition and annealing of HfO2 films on native (100)-GaAs substrates AU - Suri, Rahul AU - Lichtenwalner, Daniel J. AU - Misra, Veena T2 - APPLIED PHYSICS LETTERS AB - The reduction in native oxides on GaAs surface during atomic layer deposition (ALD) of HfO2 using tetrakis-dimethylamino-hafnium precursor was investigated using x-ray photoelectron spectroscopy. The role of the ALD growth temperature on the reaction between surface oxides and precursor was studied. Interfacial oxide reduction was found to be insignificant for ALD at 200 °C, while nearly complete for growth at 300 °C. During postdeposition annealing at 400 °C, any arsenic oxides present were found to decompose, resulting in an increase in the interfacial gallium oxides. Thus, control of the ALD process plays a large role in determining interface properties. DA - 2010/3/15/ PY - 2010/3/15/ DO - 10.1063/1.3357422 VL - 96 IS - 11 SP - SN - 0003-6951 KW - annealing KW - atomic layer deposition KW - gallium arsenide KW - high-k dielectric thin films KW - III-V semiconductors KW - interface phenomena KW - surface cleaning KW - X-ray photoelectron spectra ER - TY - JOUR TI - Global registration of overlapping images using accumulative image features AU - Krish, Karthik AU - Heinrich, Stuart AU - Snyder, Wesley E. AU - Cakir, Halil AU - Khorram, Siamak T2 - PATTERN RECOGNITION LETTERS AB - This paper introduces a new feature-based image registration technique which registers images by finding rotation- and scale-invariant features and matching them using a novel feature matching algorithm based on an evidence accumulation process reminiscent of the generalized Hough transform. Once feature correspondence has been established, the transformation parameters are then estimated using non-linear least squares (NLLS) and the standard RANSAC (random sample consensus) algorithm. The technique is evaluated under similarity transforms – translation, rotation and scale (zoom) and also under illumination changes. DA - 2010/1/15/ PY - 2010/1/15/ DO - 10.1016/j.patrec.2009.09.016 VL - 31 IS - 2 SP - 112-118 SN - 1872-7344 KW - Image registration KW - Feature matching KW - Accumulator-based methods KW - Feature correspondence KW - Evidence accumulation ER - TY - JOUR TI - Fast All-Transparent Integrated Circuits Based on Indium Gallium Zinc Oxide Thin-Film Transistors AU - Suresh, Arun AU - Wellenius, Patrick AU - Baliga, Vinay AU - Luo, Haojun AU - Lunardi, Leda M. AU - Muth, John F. T2 - IEEE ELECTRON DEVICE LETTERS AB - We describe the fabrication and characterization of visible transparent small-scale indium gallium zinc oxide (IGZO) integrated circuits. The IGZO channel and indium tin oxide (ITO) contacts and interconnects were pulsed laser deposited at room temperature. Low-temperature (200 ° C ) atomic-layer-deposited Al 2 O 3 was used as the gate dielectric in bottom-gated thin-film transistors with field-effect mobility near 15 cm 2 /V·s. Logic inverters and ring oscillators were fabricated and characterized, with operations at frequencies as high as 2.1 MHz, corresponding to a propagation delay of less than 48 ns/stage with a supply voltage of 25 V. To the best of our knowledge, these are the fastest all-transparent oxide semiconductor circuits reported to date. DA - 2010/4// PY - 2010/4// DO - 10.1109/led.2010.2041525 VL - 31 IS - 4 SP - 317-319 SN - 1558-0563 UR - http://dx.doi.org/10.1109/led.2010.2041525 KW - Indium gallium zinc oxide (IGZO) KW - oxide semiconductors KW - ring oscillators (ROs) KW - thin-film transistors (TFTs) KW - transparent circuits ER - TY - JOUR TI - A Discrete MatlabSimulink Flickermeter Model for Power Quality Studies AU - White, Leonard W. AU - Bhattacharya, Subhashish T2 - IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT AB - A discrete model of the IEC 61000-4-15 flickermeter is developed for use with the Matlab-Simulink simulation software package. The discrete model is a faithful reproduction of a flickermeter defined by the IEC Standard; it duplicates the functional blocks described by the standard and operates in the same way as the standardized instrument to assure complete fidelity of results. The model is intended to be used within larger simulations that contain discrete model blocks, either alone or in combination with the Simulink SimPowerSystems blockset, to provide direct quantification of flicker. The model is fully developed, and all model parameters are provided for use with 60-Hz systems. A discrete calibrator is described that duplicates the test waveforms described by the IEC Standard. DA - 2010/3// PY - 2010/3// DO - 10.1109/tim.2009.2023121 VL - 59 IS - 3 SP - 527-533 SN - 1557-9662 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-76849100178&partnerID=MN8TOARS KW - Lighting KW - measurement KW - modeling KW - power quality KW - standards ER - TY - JOUR TI - Special issue on light-emitting diodes AU - Kumar, M. J. AU - Lunardi, L. AU - Meneghesso, G. AU - Pearton, S. J. AU - Schubert, E. F. T2 - IEEE Transactions on Electron Devices DA - 2010/// PY - 2010/// VL - 57 IS - 1 SP - 7-11 ER - TY - PAT TI - Molecular memory devices including solid-state dielectric layers and related methods AU - Misra, V. AU - Shrivastava, R. AU - Chen, Z. AU - Mathur, G. C2 - 2010/// DA - 2010/// PY - 2010/// ER - TY - JOUR TI - First-principles analysis of electron-phonon interactions in graphene AU - Borysenko, K. M. AU - Mullen, J. T. AU - Barry, E. A. AU - Paul, S. AU - Semenov, Y. G. AU - Zavada, J. M. AU - Nardelli, M. Buongiorno AU - Kim, K. W. T2 - Physical Review B AB - The electron-phonon interaction in monolayer graphene is investigated using density-functional perturbation theory. The results indicate that the electron-phonon interaction strength is of comparable magnitude for all four in-plane phonon branches and must be considered simultaneously. Moreover, the calculated scattering rates suggest an acoustic-phonon contribution that is much weaker than previously thought, revealing an important role of optical phonons even at low energies. Accordingly it is predicted, in good agreement with a recent measurement, that the intrinsic mobility of graphene may be more than an order of magnitude larger than the already high values reported in suspended samples. DA - 2010/3/16/ PY - 2010/3/16/ DO - 10.1103/physrevb.81.121412 VL - 81 IS - 12 SP - J2 - Phys. Rev. B LA - en OP - SN - 1098-0121 1550-235X UR - http://dx.doi.org/10.1103/PhysRevB.81.121412 DB - Crossref ER - TY - JOUR TI - Enhancing erbium emission by strain engineering in GaN heteroepitaxial layers AU - Feng, I. W. AU - Li, J. AU - Sedhain, A. AU - Lin, J. Y. AU - Jiang, H. X. AU - Zavada, J. T2 - Applied Physics Letters DA - 2010/// PY - 2010/// VL - 96 IS - 3 ER - TY - JOUR TI - Energy-band alignment of Al2O3 and HfAlO gate dielectrics deposited by atomic layer deposition on 4H–SiC AU - Suri, Rahul AU - Kirkpatrick, Casey J. AU - Lichtenwalner, Daniel J. AU - Misra, Veena T2 - Applied Physics Letters AB - Energy band alignment and band gap of Al2O3 and HfAlO films grown by atomic layer deposition on 4H–SiC were determined using x-ray photoelectron spectroscopy. Al2O3 exhibited a symmetric band profile with a conduction band offset (ΔEC) of 1.88 eV and a valence band offset (ΔEV) of 1.87 eV. HfAlO yielded a smaller ΔEC of 1.16 eV and ΔEV of 1.59 eV. The higher dielectric constant and higher effective breakdown field of HfAlO compared to Al2O3, coupled with sufficient electron and hole barrier heights, makes it a potential dielectric for use on 4H–SiC, and provokes interest in further investigation of HfAlO/4H–SiC properties. DA - 2010/1/25/ PY - 2010/1/25/ DO - 10.1063/1.3291620 VL - 96 IS - 4 SP - 042903 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.3291620 DB - Crossref KW - alumina KW - atomic layer deposition KW - conduction bands KW - electric breakdown KW - energy gap KW - hafnium compounds KW - high-k dielectric thin films KW - permittivity KW - semiconductor-insulator boundaries KW - valence bands KW - X-ray photoelectron spectra ER - TY - JOUR TI - Electrically controlled magnetic switching based on graphene-magnet composite structures AU - Semenov, Y. G. AU - Zavada, J. M. AU - Kim, K. W. T2 - Journal of Applied Physics AB - A nonvolatile magnetic switch is proposed by utilizing the unique properties of graphene-ferromagnet composite structures. The basic mechanism relies on the role of graphene in mediating and modulating the effective exchange bias between adjacent magnetic layers, which can lead to electrically controlled rotation of magnetic bits. Readout of magnetization states is also achieved electrically through the magnetoresistance effect in the graphene channel. The proposed switch can be used to realize both the memory and programmable logic elements. Theoretical estimates illustrate the feasibility of the concept as well as its potential advantage of low power consumption (∼10−19 J) for the intrinsic switching operation. DA - 2010/3/15/ PY - 2010/3/15/ DO - 10.1063/1.3354066 VL - 107 IS - 6 SP - 064507 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.3354066 DB - Crossref KW - composite materials KW - ferromagnetic materials KW - graphene KW - magnetic switching KW - magnetisation ER - TY - JOUR TI - Effect of m-plane GaN substrate miscut on InGaN/GaN quantum well growth AU - Lai, K. Y. AU - Paskova, T. AU - Wheeler, V. D. AU - Grenko, J. A. AU - Johnson, M. A. L. AU - Udwary, K. AU - Preble, E. A. AU - Evans, K. R. T2 - JOURNAL OF CRYSTAL GROWTH AB - The effect of m-plane GaN substrate miscut on the growth of InGaN/GaN quantum wells (QWs) was investigated. It was found that the miscut toward [0 0 0 1] c+-axis resulted in an increase of In incorporation efficiency and in a green-shift of the QW emission, while the miscut toward [1 1 2 0] a-axis resulted in even higher In compositions but it also led to an increased epitaxial surface roughness and deterioration of the QW structures. The results indicated that miscut toward a-axis is undesirable while miscut toward c+-axis is beneficial for achieving longer wavelength emission in QWs grown on m-plane GaN substrates. DA - 2010/3/15/ PY - 2010/3/15/ DO - 10.1016/j.jcrysgro.2010.01.020 VL - 312 IS - 7 SP - 902-905 SN - 1873-5002 KW - Metalorganic chemical vapor deposition KW - Nitrides KW - Semiconducting III-V materials KW - Light emitting diodes ER - TY - JOUR TI - A functional unit and register binding algorithm for interconnect reduction AU - Kim, T. AU - Liu, X. T2 - IEEE Transactions on Computer-aided Design of Integrated Circuits and Systems DA - 2010/// PY - 2010/// VL - 29 IS - 4 SP - 641-646 ER - TY - JOUR TI - Intelligent method for sensor subset selection for machine olfaction AU - Phaisangittisagul, Ekachai AU - Nagle, H. Troy AU - Areekul, Vutipong T2 - SENSORS AND ACTUATORS B-CHEMICAL AB - A fundamental design concept for an array of sensors used in machine olfaction devices, electronic noses (e-noses), is that each sensor should maximize the overall sensitivity and provides different selectivity profiles over the range of target odor application. Ideally, each sensor should produce a different response to a given odor so that a unique odor pattern is created. Since this is rarely the case, sensor selection or reduction is needed when classification performance, cost, and technology limitations are issues of concern. The first step in the selection/reduction process is to generate features from each sensor's output waveform. In practice, some of the features obtained from an array of sensors are redundant and irrelevant due to cross-sensitivity and odor characteristics. As a result, inappropriate features or a poor configuration of features can lead to a deterioration of classification performance, or a more complex classification algorithm may be required. Hence, sensor selection for e-nose systems is of great important. In this study, a novel computationally efficient method is introduced by selecting the first few critical sensors based on a maximum margin criterion among different odor classes. Then, a stochastic search algorithm, a genetic algorithm (GA), uses those features as an initial step to optimize our sensor selection problem. The advantages of the proposed method are not only to avoid any initial misstep starting the search, but also to reduce the searching space for the optimal sensor array. From the experimental results on coffee and soda data sets, the number of selected sensors is significantly reduced (up to 90%) and classification performance is near 100%. DA - 2010/3/4/ PY - 2010/3/4/ DO - 10.1016/j.snb.2009.12.063 VL - 145 IS - 1 SP - 507-515 SN - 0925-4005 KW - Electronic noses (e-noses) KW - Feature subset selection KW - Genetic algorithm (GA) KW - Sensor subset selection KW - Transient feature extraction ER - TY - JOUR TI - An Overview of Technologies Related to Care for Venous Leg Ulcers AU - Hegarty, Meghan Sarah AU - Grant, Edward AU - Reid, Lawrence, Jr. T2 - IEEE TRANSACTIONS ON INFORMATION TECHNOLOGY IN BIOMEDICINE AB - Venous leg ulcers remain a major problem in the United States, with spending reaching more than $1 billion annually. Current treatment options for this condition center around the use of compression therapy delivered by bandages, medical-grade stockings, or pneumatic compression devices. While these forms of therapy can produce dramatic improvements, cost and patient compliance remain an issue. In parallel with this need, wearable, wireless health monitoring systems have recently emerged as a low-cost solution for management of chronic health conditions. To this end, researchers at the Center for Robotics and Intelligent Machines (North Carolina State University) and the Carolon Company (Rural Hall, NC) have proposed an integrated sensing and therapeutic compression module. This article will review technologies related to the design of such a device, as well as provide direction for future research. DA - 2010/3// PY - 2010/3// DO - 10.1109/titb.2009.2036009 VL - 14 IS - 2 SP - 387-393 SN - 1558-0032 KW - Ambulatory monitoring KW - biological control system KW - biological system modeling KW - compression therapy KW - medical diagnosis KW - wearable sensors ER -