TY - JOUR TI - Top-down fabrication of GaN-based nanorod LEDs and lasers AU - Wang, George T. AU - Li, Qiming AU - Wierer, Jonathan AU - Figiel, Jeffrey AU - Wright, Jeremy B. AU - Luk, Ting S. AU - Brener, Igal AU - Streubel, KP AU - Jeon, H AU - Tu, LW AU - Linder, N T2 - Light-Emitting Diodes: Materials, Devices, and Applications For Solid State Lighting Xvi AB - Although planar heterostructures dominate current optoelectronic architectures, 1D nanowires and nanorods have distinct and advantageous properties that may enable higher efficiency, longer wavelength, and cheaper devices. We have developed a top-down approach for fabricating ordered arrays of high quality GaN-based nanorods with controllable height, pitch and diameter. This approach avoids many of the limitations of bottom-up synthesis methods. In addition to GaN nanorods, the fabrication and characterization of both axial and radial-type GaN/InGaN nanorod LEDs have been achieved. The precise control over nanorod geometry achiveable by this technique also enables single-mode single nanowire lasing with linewidths of less than 0.1 nm and low lasing thresholds of ~250kW/cm2. DA - 2012/// PY - 2012/// DO - 10.1117/12.909377 VL - 8278 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000301055700017&KeyUID=WOS:000301055700017 ER - TY - JOUR TI - Influence of barrier thickness on the performance of InGaN/GaN multiple quantum well solar cells AU - Wierer, J. J., Jr. AU - Koleske, D. D. AU - Lee, S. R. T2 - Applied Physics Letters AB - The performance of InGaN/GaN multiple quantum well (MQW) solar cells containing 15 periods of 2.7 nm thick In0.21Ga0.79N wells and three different GaN barriers thicknesses of 3.0 nm, 6.3 nm, and 10.0 nm is investigated. Increasing barrier thickness results in absorption at lower energies, consistent with piezoelectric polarization induced electric fields tilting the energy bands of the MQW and changing the transition energy of well states. The internal quantum efficiency and leakage currents are additionally affected by GaN barrier thickness, resulting in the 6.3 nm barrier structure achieving the highest power conversion efficiency (1.66%, 1 sun AM1.5G). DA - 2012/// PY - 2012/// DO - 10.1063/1.3695170 VL - 100 IS - 11 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000302204900019&KeyUID=WOS:000302204900019 ER - TY - JOUR TI - III- nitride core-shell nanowire arrayed solar cells AU - Wierer, Jonathan J., Jr. AU - Li, Qiming AU - Koleske, Daniel D. AU - Lee, Stephen R. AU - Wang, George T. T2 - Nanotechnology AB - A solar cell based on a hybrid nanowire–film architecture consisting of a vertically aligned array of InGaN/GaN multi-quantum well core–shell nanowires which are electrically connected by a coalesced p-InGaN canopy layer is demonstrated. This unique hybrid structure allows for standard planar device processing, solving a key challenge with nanowire device integration, while enabling various advantages by the nanowire absorbing region such as higher indium composition InGaN layers by elastic strain relief, more efficient carrier collection in thinner layers, and enhanced light trapping from nano-scale optical index changes. This hybrid structure is fabricated into working solar cells exhibiting photoresponse out to 2.1 eV and short-circuit current densities of ∼1 mA cm−2 under 1 sun AM1.5G. This proof-of-concept nanowire-based device demonstrates a route forward for high-efficiency III-nitride solar cells. DA - 2012/// PY - 2012/// DO - 10.1088/0957-4484/23/19/194007 VL - 23 IS - 19 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000303534600008&KeyUID=WOS:000303534600008 ER - TY - JOUR TI - High-Efficiency, Microscale GaN Light-Emitting Diodes and Their Thermal Properties on Unusual Substrates AU - Kim, Tae-il AU - Jung, Yei Hwan AU - Song, Jizhou AU - Kim, Daegon AU - Li, Yuhang AU - Kim, Hoon-sik AU - Song, Il-Sun AU - Wierer, Jonathan J. AU - Pao, Hsuan An AU - Huang, Yonggang AU - Rogers, John A. T2 - Small AB - A method for forming efficient, ultrathin GaN light-emitting diodes (LEDs) and for their assembly onto foreign substances is reported. The LEDs have lateral dimensions ranging from ~1 mm × 1 mm to ~25 μm × 25 μm. Quantitative experimental and theoretical studies show the benefits of small device geometry on thermal management, for both continuous and pulsed-mode operation, the latter of which suggests the potential use of these technologies in bio-integrated contexts. DA - 2012/// PY - 2012/// DO - 10.1002/smll.201200382 VL - 8 IS - 11 SP - 1643-1649 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000304817700002&KeyUID=WOS:000304817700002 ER - TY - JOUR TI - Effect of interface grading and lateral thickness variation on x-ray diffraction by InGaN/GaN multiple quantum wells AU - Lee, S. R. AU - Koleske, D. D. AU - Crawford, M. H. AU - Wierer, J. J., Jr. T2 - Journal of Crystal Growth AB - We develop a method for simulating the effects of interface grading and lateral variation in layer thickness on x-ray diffraction by InGaN/GaN multiple quantum wells (MQWs). Using the resulting simulation scheme, we perform detailed fitting of symmetric (0002) ω/2θ scans measured for a selection of typical InGaN/GaN MQW heterostructures. We find that incorporation of the combined effects of interface grading and thickness variation substantially improves the goodness of fit relative to a conventional model that assumes ideal MQW structure. The improved simulations of experiments reveal that the examined InxGa1−xN/GaN MQWs (0.17≤x≤0.24) grown on the basal plane of GaN have graded heterointerface widths, w, in the range 0.5≤w≤1.1 nm concomitant with lateral variations in total MQW thickness of 0.7–6.3 nm rms. Atomic force microscopy of 10×10 μm2 areas of the as-grown MQWs finds surface roughnesses of 1.0–5.6 nm rms in agreement with corresponding rms thickness variations found by simulating the XRD measurements. For samples with smaller thickness variations, higher order MQW satellites are observed in high-dynamic-range diffraction experiments and best-fit simulations find evidence for asymmetric MQW interface widths. The lower interfaces are narrower than the upper interfaces in agreement with recent transmission electron microscopy and atom-probe studies of MQW interfaces by other groups. These under-recognized structural features—heterointerface grading and lateral film-thickness variation—will influence not only x-ray diffraction, but also polarization, bandstructure, and carrier localization within InGaN-based MQW heterostructures. DA - 2012/// PY - 2012/// DO - 10.1016/j.jcrysgro.2012.06.048 VL - 355 IS - 1 SP - 63-72 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000307121900011&KeyUID=WOS:000307121900011 ER - TY - CONF TI - Advanced Bus Bar System Design AU - Hopkins, Douglas C. T2 - IEEE Energy Conversion Congress and Exposition, ECCE C2 - 2012/9/10/ C3 - IEEE Energy Conversion Congress and Exposition, ECCE CY - Raleigh, N.C. DA - 2012/9/10/ PY - 2012/9/15/ ER - TY - CONF TI - Bus Bars – Slap Them Together and They Ought to Work AU - Hopkins, Douglas C. T2 - 27th Annual IEEE Applied Power Electronics Conference and Exposition (APEC) C2 - 2012/2/5/ C3 - 27th Annual IEEE Applied Power Electronics Conference and Exposition (APEC) CY - Orlando, FL DA - 2012/2/5/ PY - 2012/2/5/ PB - IEEE Applied Power Electronics Conf ER - TY - JOUR TI - Hybrid Resonant and PWM Converter With High Efficiency and Full Soft-Switching Range AU - Yu, Wensong AU - Lai, Jih-Sheng AU - Lai, Wei-Han AU - Wan, Hongmei T2 - IEEE Transactions on Power Electronics AB - A novel soft-switching converter combining resonant half-bridge and phase-shifted pulsewidth modulation (PWM) full-bridge configuration is proposed to ensure the switches in the leading-leg operating at zero-voltage switching from true zero-load to full-load, and the switches in the lagging leg working at zero-current switching with minimum duty cycle loss and circulating conduction loss by significantly reducing leakage or series inductance. Experimental results of a 3.4-kW hardware prototype show that the circuit achieves true full-range soft switching with 98% peak efficiency. The hybrid resonant and PWM converter is attractive for electrical vehicle battery charger application. DA - 2012/12// PY - 2012/12// DO - 10.1109/tpel.2012.2192293 VL - 27 IS - 12 SP - 4925-4933 J2 - IEEE Trans. Power Electron. OP - SN - 0885-8993 1941-0107 UR - http://dx.doi.org/10.1109/tpel.2012.2192293 DB - Crossref ER - TY - JOUR TI - Rationale for Further Medical and Health Research on High-Potency Sweeteners AU - Schiffman, Susan S. T2 - Chemical Senses AB - High-potency or artificial sweeteners have historically been considered inert compounds without physiological consequences other than taste sensations. However, recent data suggest that some of these sweeteners have biological effects that may impact human health. Furthermore, there are significant gaps in our current knowledge of the pharmacokinetics of these sweeteners, their potential for "sweetener-drug interactions" and their impact on appetite and body weight regulation. Nine research needs are described that address some of the major unknown issues associated with ingestion of high-potency sweeteners. DA - 2012/4/26/ PY - 2012/4/26/ DO - 10.1093/chemse/bjs053 VL - 37 IS - 8 SP - 671-679 LA - en OP - SN - 1464-3553 0379-864X UR - http://dx.doi.org/10.1093/chemse/bjs053 DB - Crossref ER - TY - JOUR TI - Sucralose revisited: Rebuttal of two papers about Splenda safety AU - Schiffman, Susan S. AU - Abou-Donia, Mohamed B. T2 - Regulatory Toxicology and Pharmacology AB - Sucralose is widely used as non-caloric intense artificial sweetener. It was previously considered to be thermally stable and safe. This was based on studies performed in the early 1990s. However, significant concerns have been raised more recently regarding the physicochemical stability of sucralose at high temperatures in the context of food processing. Over the last decades different independently performed studies indicated that sucralose is decomposed at high temperatures, e.g. through cooking. This – in turn – was considered to be associated with the formation of chlorinated potentially toxic compounds, such as chloropropanols and dioxins.In this review, the literature on thermal stability of sucralose and the generation of potentially toxic compounds was assessed and comparatively discussed. Considering the validity of published data, we conclude that sucralose can be degraded at high temperatures, e.g. during cooking or baking of sucralose-containing foods. As a consequence potentially toxic chlorinated compounds might be generated. DA - 2012/8// PY - 2012/8// DO - 10.1016/j.yrtph.2012.05.002 VL - 63 IS - 3 SP - 505-508 J2 - Regulatory Toxicology and Pharmacology LA - en OP - SN - 0273-2300 UR - http://dx.doi.org/10.1016/j.yrtph.2012.05.002 DB - Crossref ER - TY - JOUR TI - Experimental Realization of a Metamaterial Detector Focal Plane Array AU - Shrekenhamer, David AU - Xu, Wangren AU - Venkatesh, Suresh AU - Schurig, David AU - Sonkusale, Sameer AU - Padilla, Willie J. T2 - Phys. Rev. Lett. AB - We present a metamaterial absorber detector array that enables room-temperature, narrow-band detection of gigahertz (GHz) radiation in the $S$ band (2--4 GHz). The system is implemented in a commercial printed circuit board process and we characterize the detector sensitivity and angular dependence. A modified metamaterial absorber geometry allows for each unit cell to act as an isolated detector pixel and to collectively form a focal plane array . Each pixel can have a dedicated microwave receiver chain and functions together as a hybrid device tuned to maximize the efficiency of detected power. The demonstrated subwavelength pixel shows detected sensitivity of $\ensuremath{-}77\text{ }\text{ }\mathrm{dBm}$, corresponding to a radiation power density of $27\text{ }\text{ }\mathrm{nW}/{\mathrm{m}}^{2}$, with pixel to pixel coupling interference below $\ensuremath{-}14\text{ }\text{ }\mathrm{dB}$ at 2.5 GHz. DA - 2012/10// PY - 2012/10// DO - 10.1103/physrevlett.109.177401 VL - 109 IS - 17 ER - TY - CONF TI - Analysis of Extrinsic Losses in a Corrugated Photonic Crystal Waveguide AU - Lopez-Galmiche, G. AU - Vazquez-Guardado, A. AU - Romero-Antequera, D.L. AU - Murugkar, S. AU - Sanchez-Mondragon C2 - 2012/// C3 - Optics InfoBase Conference Papers DA - 2012/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85136245036&partnerID=MN8TOARS ER - TY - CONF TI - Slow Surface Plasmon-Polaritons in a Metal-Dielectric Structure Incorporating a Lorentzian Gain Medium AU - Vázquez-Guardado, Abraham AU - Lopez-Galmiche, Gisela AU - Arizpe, Israel De Leon AU - Paez-López, Rafael AU - Torres-Cisneros, Miguel AU - Sanchez-Mondragon, Jose Javier AB - Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text A. Vázquez-Guardado, G. López-Galmiche, I. De León, R. Paez-López, M. Torres-Cisneros, and J. J. Sánchez-Mondragón, "Slow Surface Plasmon-Polaritons in a Metal-Dielectric Structure Incorporating a Lorentzian Gain Medium," in Latin America Optics and Photonics Conference, OSA Technical Digest (online) (Optica Publishing Group, 2012), paper LM2A.27. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article C2 - 2012/// C3 - Latin America Optics and Photonics Conference DA - 2012/// DO - 10.1364/laop.2012.lm2a.27 PB - Optical Society of America (OSA) UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85136270475&partnerID=MN8TOARS ER - TY - CONF TI - Total internal reflection of photorefractive spatial solitons at a metallic interface AU - Cardenas-Ortiz, Gustavo AU - Vázquez-Guardado, Abraham AU - Ceballos, Daniel AU - Lopez-Galmiche, Gisela AU - May-Arrioja, Daniel A. AU - Sanchez-Mondragon, Jose J. AB - We study the reflection of spatial solitons with TM polarization at the interface between a photorefractive medium and a metal one. Depending of the incident angle and power, the reflected beam conserves its nondiffracting properties. C2 - 2012/// C3 - Frontiers in Optics, FIO 2012 DA - 2012/// DO - 10.1364/fio.2012.fw3a.24 PB - Optical Society of America (OSA) UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85088755302&partnerID=MN8TOARS ER - TY - CONF TI - Analysis of Gain Assisted Slow Surface Plasmon-Polaritons in a Symmetrically Cladded Metal Slab Structure AU - Vázquez-Guardado, Abraham AU - Lopez-Galmiche, Gisela AU - Leon, Israel De AU - Sanchez-Mondragon, Jose J. AU - Boyd, Robert W. AB - We investigate slow surface plasmon-polariton modes supported by a symmetrically cladded metal slab waveguide incorporating optical gain media. We show that the structure can support a group index as large as 800 when losses are compensated. C2 - 2012/// C3 - Frontiers in Optics 2012/Laser Science XXVIII DA - 2012/// DO - 10.1364/fio.2012.ftu3a.58 PB - Optical Society of America (OSA) UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84893144699&partnerID=MN8TOARS ER - TY - CONF TI - Analysis of Extrinsic Losses in a Corrugated Photonic Crystal Waveguide AU - Lopez-Galmiche, Gisela AU - Vázquez-Guardado, Abraham AU - Antequera, David L. Romero AU - Murugka, Sangeeta AU - Sanchez-Mondragon, Jose Javier AB - We analyzed the scattering produced by technological imperfections in a corrugated photonic crystal waveguide. Modeling and losses analysis of the slow-light structures were carried out by plane wave expansion method using the MPB software. C2 - 2012/// C3 - Latin America Optics and Photonics Conference DA - 2012/// DO - 10.1364/laop.2012.lm2a.29 PB - Optical Society of America (OSA) UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-85136245036&partnerID=MN8TOARS ER - TY - CONF TI - Finite Lorentzian-like gain in the analysis of gain assisted slow surface plasmon-polaritons AU - Vázquez-Guardado, A. AU - López-Galmiche, G. AU - De León, I. AU - Sánchez-Mondragón, J.J. AU - Boyd, R.W. C2 - 2012/// C3 - Frontiers in Optics, FIO 2012 DA - 2012/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84893043589&partnerID=MN8TOARS ER - TY - CONF TI - Analysis of gain assisted slow surface plasmon-polaritons in a symmetrically cladded metal slab structure AU - Vázquez-Guardado, A. AU - López-Galmiche, G. AU - De León, I. AU - Sánchez-Mondragón, J.J. AU - Boyd, R.W. C2 - 2012/// C3 - Frontiers in Optics, FIO 2012 DA - 2012/// UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84893144699&partnerID=MN8TOARS ER - TY - CONF TI - Finite Lorentzian-Like Gain in the Analysis of Gain Assisted Slow Surface Plasmon-Polaritons AU - Vázquez-Guardado, Abraham AU - Lopez-Galmiche, Gisela AU - Leon, Israel De AU - Sanchez-Mondragon, Jose J. AU - Boyd, Robert W. AB - We investigate slow surface plasmon-polariton in a metal/dielectric interface when a Lorentzian function is used to model the gain response in the dielectric medium. An increase in the well know group index of 1.86 to 10 is achieved. C2 - 2012/// C3 - Frontiers in Optics 2012/Laser Science XXVIII DA - 2012/// DO - 10.1364/fio.2012.ftu3a.53 PB - Optical Society of America (OSA) UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84893043589&partnerID=MN8TOARS ER - TY - CONF TI - Modeling Power Variability (from Small to Large AU - Davis, W.R. T2 - Silicon Integration Inititative (Si2) Conference C2 - 2012/10/9/ DA - 2012/10/9/ PY - 2012/10/9/ ER - TY - CONF TI - Modulated backscatter for ultra-low power uplinks from wearable and implantable devices AU - Thomas, Stewart J. AU - Besnoff, Jordan S. AU - Reynolds, Matthew S. AB - Wearable and implantable wireless biomedical devices are often constrained by the limited bandwidth and high power consumption of their communication links. The VHF or UHF transceivers (e.g. MICS radios) traditionally used for this communication function have relatively high power consumption, on the order of mW, due to the high bias currents required for the analog sections of the radio. To reduce overall power consumption, both the data rate and the duty cycle of the radio are usually minimized, because the lifetime of the device is limited by the energy density of available battery technologies. C2 - 2012/// C3 - Proceedings of the 2012 ACM workshop on Medical communication systems - MedCOMM '12 DA - 2012/// DO - 10.1145/2342536.2342538 PB - Association for Computing Machinery (ACM) ER - TY - CONF TI - Near field modulated backscatter for in vivo biotelemetry AU - Besnoff, Jordan S. AU - Reynolds, Matthew S. AB - Fully implantable wireless biotelemetry devices have traditionally used active VHF/UHF transmitters or load modulation at HF frequencies. HF systems tend to be bandwidth-limited due to low frequency magnetic induction, while active VHF/UHF transmitters generally consume a significant amount of power in DC bias current. We show in this paper that UHF near-field backscatter can be used to achieve higher data rates at lower implant power budgets. We present experimental path loss measurements in a saline proxy system using a segmented loop antenna designed for UHF near-field operation. We present experimental results from a modulated backscatter test circuit at bit rates of up to 30 Mbps and penetration depths of up to 6 cm. The main communication element, an RF switch, consumes about 164 μA at 3 V while operating at a data rate of 30 Mbps, which is equivalent to approximately 16.4 pJ/bit. C2 - 2012/4// C3 - 2012 IEEE International Conference on RFID (RFID) DA - 2012/4// DO - 10.1109/rfid.2012.6193041 PB - Institute of Electrical and Electronics Engineers (IEEE) ER - TY - JOUR TI - Erratum: Stamp transfer electrodes for electrochemical sensing on non-planar and oversized surfaces (Analyst (2012) 137 (1570-1575) DOI:10.1039/C2AN35041F) AU - Windmiller, J.R. AU - Bandodkar, A.J. AU - Parkhomovsky, S. AU - Wang, J. T2 - Analyst DA - 2012/// PY - 2012/// DO - 10.1039/c2an90108k VL - 137 IS - 24 SP - 5925 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870492918&partnerID=MN8TOARS ER - TY - CONF TI - Printable Packaging for High Power, High Temperature Power Module AU - Hopkins, D.C. T2 - IEEE Applied Power Electronics Conference C2 - 2012/// CY - Orlando, FL DA - 2012/// PY - 2012/2/5/ ER - TY - CONF TI - Point Source Thermal Management in Dense Power Modules and Systems AU - Hopkins, D.C. T2 - IEEE Applied Power Electronics Conference C2 - 2012/// CY - Orlando, FL DA - 2012/// PY - 2012/2/5/ ER - TY - CONF TI - Results for an Al/AlN composite 350°C SiC solid-state circuit breaker module AU - Bhat, Krishna P. AU - Guo, Yuan-Bo AU - Xu, Yang AU - Baltis, Theodore AU - Hazelmyer, Donald R. AU - Hopkins, Douglas C. T2 - 2012 IEEE Applied Power Electronics Conference and Exposition - APEC 2012 AB - This paper describes final results for the verification and testing of a SiC MOSFET-based solid-state circuit breaker power module for ultra-fast current interruption. The module exhibited a single-die (4.1mm × 4.1 mm) 48 A, 5 ms trip point from a 300 V bus with a di/dt of 2.1 kA/us (23 ns opening time). An internal snubber increased the response to 390 ns. The die absorbed ∼4.6 J causing a transient junction temperature increase of ∼245 °C. Ambient was set at 25 °C and 105 °C. Hence, maximum junction temperature was conservatively projected to reach 350 °C during the 5 ms pulse. An Aluminum composite structure was used for high temperature thermal management and high reliability. Testing of the final module surpassed 750 total cycles. Electrical, thermal and mechanical design and testing results are presented. C2 - 2012/2// C3 - 2012 Twenty-Seventh Annual IEEE Applied Power Electronics Conference and Exposition (APEC) CY - Orlando, FL DA - 2012/2// PY - 2012/2/5/ DO - 10.1109/apec.2012.6166172 PB - IEEE SN - 9781457712166 9781457712159 9781457712142 UR - http://dx.doi.org/10.1109/apec.2012.6166172 ER - TY - JOUR TI - Extreme Thermal Transient Stress Analysis with Pre-Stress in a Metal Matrix Composite Power Package AU - Hopkins, Douglas C. AU - Baltis, Theodore AU - Pitaress, James M AU - Hazelmyer, Donald R. T2 - Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) AB - This paper culminates several years of development of a SiC MOSFET-based solid-state circuit breaker power module designed and fabricated for aluminum-based composite metal-ceramic packaging. The aluminum composite structure was used for high temperature thermal management &gt;350°C and high reliability. Testing of the final module surpassed 750 total cycles. The module was optimized for four dies, 4.1mm × 4.1 mm each for SiC or GaN. The electrically loading per die was 48 A for 5 ms with a di/dt of 2.1 kA/us (23 ns opening time). An internal snubber increased the response to 390 ns. The die absorbed ∼4.6 J causing a transient junction temperature increase of ∼245 °C. Two ambient temperatures were used in testing and set at 25 °C and 105 °C. The maximum junction temperature was conservatively projected to reach 350 °C during the 5 ms pulse. Electrical, thermal and mechanical design and testing results are presented. DA - 2012/1/1/ PY - 2012/1/1/ DO - 10.4071/hitec-2012-tha25 VL - 2012 IS - HITEC SP - 000361-000372 LA - en OP - SN - 2380-4491 UR - http://dx.doi.org/10.4071/hitec-2012-tha25 DB - Crossref ER - TY - JOUR TI - Development of Printed Power Packaging for a High Voltage SiC Module AU - Ke, Haotao AU - Hopkins, Douglas C T2 - International Symposium on Microelectronics AB - Due to rapidly developing post silicon power devices, in particular SiC and GaN, three primary parameters in power packaging: temperature, voltage and current, are much more difficult to manage. The SiC devices are being developed for high voltage (&gt;15kV). The GaN devices will have extremely low internal resistance, operate at extreme current densities (≫10A/mm2), and can account for &lt;50% of the resistance in a power module. Both devices can operate at high temperatures (&gt;300°C) and &gt;10-times frequency compared to Si. The traditional power electronics packaging approaches need augmentation or replacement. Most technologies used in packaging of power electronic systems, or more generally Electronic Energy Systems, are ported from microelectronics. The recent development of printable 3D circuit techniques, e.g. jetting and dispensing, provide additional major approaches applicable to power packaging. Some printing techniques are already applied to solar cells and batteries. This paper explores the printable electronics technologies for application to power. DA - 2012/1/1/ PY - 2012/1/1/ DO - 10.4071/isom-2012-wp55 VL - 2012 IS - 1 SP - 000955-000960 LA - en OP - SN - 2380-4505 UR - http://dx.doi.org/10.4071/isom-2012-wp55 DB - Crossref ER - TY - CONF TI - Mean time to failure of SnAgCuNi solder joints under DC AU - Basaran, Cemal AU - Li, Shidong AU - Hopkins, Douglas C. AU - Yao, Wei T2 - 2012 13th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm) AB - Electromigration time to failure and electrical resistivity of 95.5%Sn-1.5%Ag-0.5%Cu-0.03W%Ni (SACN) microelectronics solder joints have been investigated experimentally. A Black's type electromigration time to failure equation is developed to describe the time to failure versus current density and temperature. The activation energy over the range of 83°C~174°C is measured to be 0.77±0.12eV, and the current density exponent is found to be (8.60±1.65). It is also shown that the most commonly used Black's electromigration time to failure equation cannot be used for solder joints. C2 - 2012/5// C3 - 13th InterSociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems DA - 2012/5// DO - 10.1109/itherm.2012.6231474 PB - IEEE SN - 9781424495320 9781424495337 9781424495313 UR - http://dx.doi.org/10.1109/itherm.2012.6231474 DB - Crossref ER - TY - CONF TI - Efficient and accurate data dependence profiling using software signatures AU - Vanka, Rajeshwar AU - Tuck, James C2 - 2012/// C3 - Proceedings of the Tenth International Symposium on Code Generation and Optimization DA - 2012/// SP - 186-195 ER - TY - CONF TI - Control-flow decoupling AU - Sheikh, Rami AU - Tuck, James AU - Rotenberg, Eric T2 - IEEE C2 - 2012/// C3 - 2012 45th Annual IEEE/ACM International Symposium on Microarchitecture DA - 2012/// SP - 329-340 ER - TY - CONF TI - HiRe: using hint & release to improve synchronization of speculative threads AU - Han, Liang AU - Jiang, Xiaowei AU - Liu, Wei AU - Wu, Youfeng AU - Tuck, James C2 - 2012/// C3 - Proceedings of the 26th ACM international conference on Supercomputing DA - 2012/// SP - 143-152 ER - TY - JOUR TI - Fundamental limits and improved algorithms for linear least-squares wireless position estimation AU - Guvenc, Ismail AU - Gezici, Sinan AU - Sahinoglu, Zafer T2 - Wireless Communications and Mobile Computing AB - ABSTRACT In this paper, theoretical lower bounds on performance of linear least‐squares (LLS) position estimators are obtained, and performance differences between LLS and nonlinear least‐squares (NLS) position estimators are quantified. In addition, two techniques are proposed in order to improve the performance of the LLS approach. First, a reference selection algorithm is proposed to optimally select the measurement that is used for linearizing the other measurements in an LLS estimator. Then, a maximum likelihood approach is proposed, which takes correlations between different measurements into account in order to reduce average position estimation errors. Simulations are performed to evaluate the theoretical limits and to compare performance of various LLS estimators. Copyright © 2010 John Wiley & Sons, Ltd. DA - 2012/8/25/ PY - 2012/8/25/ DO - 10.1002/wcm.1029 VL - 12 IS - 12 SP - 1037–1052 SN - 1530-8669 UR - http://dx.doi.org/10.1002/wcm.1029 KW - wireless positioning KW - time-of-arrival (TOA) KW - least-squares (LS) estimation KW - maximum likelihood (ML) KW - Cramer-Rao lower bound (CRLB) ER - TY - CHAP TI - Current opinion in tissue engineering microscopy techniques AU - Tayebi, L. AU - Nozari, A. AU - Vashaee, D. AU - Mozafari, M. T2 - Current microscopy contributions to advances in science and technology T3 - Current opinion in tissue engineering microscopy techniques PY - 2012/// VL - 5 PB - Formatex Research Center ER - TY - CONF TI - A detailed comparative analysis between two soft switching techniques used in PV applications AU - Anurag, Anup AU - Bal, Satarupa AU - Chitti Babu, B. T2 - 2012 Annual IEEE India Conference (INDICON) AB - This paper presents a detailed comparative study between two different soft switching techniques used in PV applications. An extended range ZVS active clamped current fed full-bridge isolated boost converter has been studied and the comparison has been done with a soft switching boost converter using an auxiliary resonant circuit. The former uses the energy stored in the leakage inductance of the transformer and its magnetizing inductance to perform the soft switching whereas the latter uses a resonant circuit in order to carry out the same. A typical 500 W converter is employed to investigate both the converters. Comparisons have been made on the basis of operating modes and range of operation. Detailed operation, analysis and simulation results for the designs have been presented. The systems are modeled and simulated in PSIM 64 bit version 9.0 Environment. C2 - 2012/12// C3 - 2012 Annual IEEE India Conference (INDICON) CY - Kochi, India DA - 2012/12// PY - 2012/12/7/ DO - 10.1109/indcon.2012.6420807 PB - IEEE SN - 9781467322720 9781467322706 9781467322713 UR - http://dx.doi.org/10.1109/indcon.2012.6420807 ER - TY - CONF TI - Welcome to ICCD 2012! AU - Tahar, S. AU - Byrd, G. AU - Schneider, K. AU - Bose, P. C2 - 2012/// C3 - Proceedings - IEEE International Conference on Computer Design: VLSI in Computers and Processors DA - 2012/// DO - 10.1109/ICCD.2012.6378605 SP - 11-20 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84872063468&partnerID=MN8TOARS ER - TY - CONF TI - Shared Memory Multiplexing: A Novel Way to Improve GPGPU Throughput AU - Yang, Y. AU - Xiang, P. AU - Mantor, M. AU - Rubin, N. AU - Zhou, H. T2 - 2012 21st International Conference on Parallel Architectures and Compilation Techniques (PACT) C2 - 2012/9// C3 - Proceedings of the 2012 21st International Conference on Parallel Architectures and Compilation Techniques (PACT) CY - Minneapolis, MN, USA DA - 2012/9// PY - 2012/9/19/ SN - 9781509066094 9781450311823 ER - TY - BOOK TI - Nile Green . Bombay Islam: The Religious Economy of the West Indian Ocean, 1840–1915 . New York: Cambridge University Press. 2011. Pp. xvi, 327. $90.00. AU - Gilmartin, David AU - Green, Nile AB - Nile Green's book on “Bombay Islam” is in many respects a pathbreaking work that will significantly influence scholarly interpretations of the relationship between Muslim religious thought and organization, and the new worlds of colonialism in the nineteenth century. Green's book focuses on Bombay as a rising center of communication, trade, travel, industry, and publishing in the nineteenth and early twentieth centuries. He argues that Bombay's central position as a “modern” node of trade, production, and print dramatically influenced what he calls the “religious economy” of the entire western Indian Ocean. Drawing on a range of previously untapped nineteenth‐century published works in Urdu, Persian, Arabic, and English, Green gives us a richly textured and physically grounded picture of the myriad forms of Muslim organization and ideas circulating and competing for support both among the emerging new classes of industrial Bombay and among transoceanic groups linked to Bombay, from Iran to South Africa. DA - 2012/4// PY - 2012/4// DO - 10.1086/ahr.117.2.508 VL - 117 PB - Oxford University Press (OUP) SE - 508–509 UR - http://dx.doi.org/10.1086/ahr.117.2.508 ER - TY - CHAP TI - Hierarchical Auctions for Network Resource Allocation AU - Tang, Wenyuan AU - Jain, Rahul T2 - Game Theory for Networks. GameNets 2011 A2 - Jain, R. A2 - Kannan, R. T3 - Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering PY - 2012/// DO - 10.1007/978-3-642-30373-9_2 SP - 11–26 PB - Springer SN - 9783642303722 9783642303739 SV - 75 UR - http://dx.doi.org/10.1007/978-3-642-30373-9_2 ER - TY - JOUR TI - “Swipe and Scan”: Integration of sampling and analysis of gunshot metal residues at screen-printed electrodes AU - O'Mahony, Aoife M. AU - Windmiller, Joshua R. AU - Samek, Izabela A. AU - Bandodkar, Amay Jairaj AU - Wang, Joseph T2 - Electrochemistry Communications AB - Increasing security needs require field-deployable, on-the-spot detection tools for the rapid and reliable identification of gunshot residue (GSR), and thus the collection of GSR samples is a crucial step in forensic analysis. In this work we demonstrate a novel protocol integrating GSR sampling and electroanalysis using microfabricated carbon sensor-strips. The new integrated sampling/detection methodology relies on abrasive stripping voltammetry (AbrSV) involving an initial mechanical transfer of trace amounts of surface-confined GSR from the hand of a suspect directly onto the electrode contingent of the sensor strip, which is immediately ready for electrochemical analysis. The integrated sampling/detection method holds much promise as a portable, rapid and inexpensive system to promptly identify a subject who has discharged a firearm in various forensic scenarios. DA - 2012/9// PY - 2012/9// DO - 10.1016/j.elecom.2012.07.004 VL - 23 IS - 1 SP - 52-55 J2 - Electrochemistry Communications LA - en OP - SN - 1388-2481 UR - http://dx.doi.org/10.1016/j.elecom.2012.07.004 DB - Crossref KW - Sensor strip KW - Abrasive stripping voltammetry KW - Gunshot residue KW - Sampling ER - TY - JOUR TI - Stamp transfer electrodes for electrochemical sensing on non-planar and oversized surfaces AU - Windmiller, Joshua Ray AU - Bandodkar, Amay Jairaj AU - Parkhomovsky, Serguey AU - Wang, Joseph T2 - The Analyst AB - This article describes a new alternative approach to the fabrication of printed electrochemical sensors and biosensors based on the transfer of electrode patterns comprising common conductive and insulating inks from elastomeric stamps to a wide variety of rigid and flexible substrates. This simple, low cost, yet robust methodology is demonstrated to be well-suited for the formation of electrochemical sensors on non-planar substrates and large objects/structures, which have traditionally been off-limits to conventional screen printing techniques. Furthermore, the stamped electrode devices are shown to exhibit electrochemical performance that rivals that of their screen printed counterparts and display resilience against severe mechanical deformation. The stamp transfer approach is further extended to the demonstration of epidermal electrochemical sensors through the transfer of the electrode patterns directly onto the skin. The resulting sensors demonstrate a wide range of usability, from the detection of various physiological analytes, including uric acid on the skin, to the identification of residues originating from the handling of munitions and explosives. The migration of printable electrochemical sensors to non-conventional (non-planar and/or oversized) surfaces provides new opportunities within the personal healthcare, fitness, forensics, homeland security, and environmental monitoring domains. DA - 2012/// PY - 2012/// DO - 10.1039/c2an35041f VL - 137 IS - 7 SP - 1570 J2 - Analyst LA - en OP - SN - 0003-2654 1364-5528 UR - http://dx.doi.org/10.1039/c2an35041f DB - Crossref ER - TY - JOUR TI - Electrochemical sensing based on printable temporary transfer tattoos AU - Windmiller, Joshua Ray AU - Bandodkar, Amay Jairaj AU - Valdés-Ramírez, Gabriela AU - Parkhomovsky, Serguey AU - Martinez, Alexandra Gabrielle AU - Wang, Joseph T2 - Chemical Communications AB - The realization of epidermal chemical sensing requires a fabrication methodology compatible with the non-planarity and irregularities of the human anatomy. This communication describes the development of printed temporary transfer tattoo (T3) electrochemical sensors for physiological and security monitoring of chemical constituents leading to the demonstration of 'electronic skin'. DA - 2012/// PY - 2012/// DO - 10.1039/c2cc32839a VL - 48 IS - 54 SP - 6794 J2 - Chem. Commun. LA - en OP - SN - 1359-7345 1364-548X UR - http://dx.doi.org/10.1039/c2cc32839a DB - Crossref ER - TY - JOUR TI - Fundamentals and application of ordered molecular assemblies to affinity biosensing AU - Matharu, Zimple AU - Bandodkar, Amay Jairaj AU - Gupta, Vinay AU - Malhotra, Bansi Dhar T2 - Chem. Soc. Rev. AB - Organization of biomolecules in two/three dimensional assemblies has recently aroused much interest in nanobiotechnology. In this context, the development of techniques for controlling spatial arrangement and orientation of the desired molecules to generate highly-ordered nanostructures in the form of a mono/multi layer is considered highly significant. The studies of monolayer films to date have focused on three distinct methods of preparation: (i) the Langmuir-Blodgett (LB) technique, involving the transfer of a monolayer assembled at the gas-liquid interface; (ii) self-assembly at the liquid-solid interface, based on spontaneous adsorption of desired molecules from a solution directly onto a solid surface; and (iii) Layer-by-layer (LBL) self-assembly at a liquid-solid interface, based on inter-layer electrostatic attractions for fabrication of multilayers. A variety of monolayers have been utilized to fabricate biomolecular electronic devices including biosensors. The composition of a monolayer based matrix has been found to influence the activity(ies) of biomolecule(s). We present comprehensive and critical analysis of ordered molecular assemblies formed by LB and self-assembly with potential applications to affinity biosensing. This critical review on fundamentals and application of ordered molecular assemblies to affinity biosensing is likely to benefit researchers working in this as well as related fields of research (401 references). DA - 2012/// PY - 2012/// DO - 10.1039/c1cs15145b VL - 41 IS - 3 SP - 1363-1402 J2 - Chem. Soc. Rev. LA - en OP - SN - 0306-0012 1460-4744 UR - http://dx.doi.org/10.1039/c1cs15145b DB - Crossref ER - TY - CONF TI - Design of universal multicoset sampling patterns for compressed sensing of multiband sparse signals AU - Domínguez-Jiménez, M.E. AU - González-Prelcic, N. AU - Vazquez-Vilar, G. AU - López-Valcarce, R. AB - Many problems in digital communications involve wideband radio signals. As the most recent example, the impressive advances in Cognitive Radio systems make even more necessary the development of sampling schemes for wideband radio signals with spectral holes. This is equivalent to considering a sparse multiband signal in the framework of Compressive Sampling theory. Starting from previous results on multicoset sampling and recent advances in compressive sampling, we analyze the matrix involved in the corresponding reconstruction equation and define a new method for the design of universal multicoset codes, that is, codes guaranteeing perfect reconstruction of the sparse multiband signal. C2 - 2012/// C3 - ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings DA - 2012/// DO - 10.1109/ICASSP.2012.6288630 SP - 3337-3340 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84867606886&partnerID=MN8TOARS ER - TY - CONF TI - Analysis and design of multirate synchronous sampling schemes for sparse multiband signals AU - Domínguez-Jitnénez, M.E. AU - González-Prelcic, N. C2 - 2012/// C3 - European Signal Processing Conference DA - 2012/// SP - 1184-1188 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84869776929&partnerID=MN8TOARS ER - TY - CONF TI - Intermetallic Formation in PZT for MEMS Structures AU - Sharma, K.P. AU - Oseroff, T. AU - Lunardi, L. C2 - 2012/// C3 - Materials Research Society Symposium Proceedings DA - 2012/// DO - 10.1557/opl.2012.1404 VL - 1427 SP - 56-61 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84879273166&partnerID=MN8TOARS ER - TY - CONF TI - An Improved Soft Switching DC-DC Converter for Low Power PV Applications AU - Bal, Satarupa AU - Anurag, Anup AU - Babu, B. Chitti T2 - 2012 International Symposium on Electronic System Design (ISED) AB - This paper presents the analysis of a soft switching boost converter for PV applications. The designed converter maintains Zero Voltage Switching (ZVS) turn on and turn off of the main switch and Zero Current Switching (ZCS) turn on and ZVS turn off of the auxiliary switch. Detailed operation, analysis and simulation results for the design have been presented. Switching and conduction losses across the switches and the diodes have also been calculated and analyzed. Some light has been thrown on the design of inductor for the practical implementation of the same. The Perturbation and Observation (P &O) method has been used in order to track the Maximum Power Point (MPP) from the PV panel. This soft switching technique can be used in telecom services where there is a necessity of high voltage with low DC power. The systems are modeled and simulated in PSIM 64 bit version 9.0 environment. C2 - 2012/12// C3 - 2012 International Symposium on Electronic System Design (ISED) DA - 2012/12// DO - 10.1109/ised.2012.34 PB - IEEE SN - 9781467347044 9780769549026 UR - http://dx.doi.org/10.1109/ised.2012.34 DB - Crossref KW - Zero Voltage Switching (ZVS) KW - Zero Current Switching (ZCS) KW - Soft Switching Techniques KW - Perturb and Observe Method KW - DC-DC boost converter ER - TY - CONF TI - Control of Grid Connected Inverter system for sinusoidal current injection with improved performance AU - Anurag, Anup AU - Babu, B. Chitti T2 - 2012 Students Conference on Engineering and Systems (SCES) AB - This paper presents a control strategy for a three-phase Grid Connected Inverter (GCI) under abnormal conditions of the grid like voltage sag, line to ground fault and presence of harmonics. This technique intends to overcome the hitches faced by the conventional controller working under abnormal conditions of the grid. The control strategy adopted here counterbalances the distortions in grid voltage by injecting sinusoidal current into the grid. In addition to this, active and reactive power control during the step changes of the load has also been studied. In order to study the dynamic performance of the system, the models are simulated and the results are analyzed. Simulation results exhibits improved performance under grid disturbances and the studied system is modeled and simulated in the MATLAB/Simulink environment. C2 - 2012/3// C3 - 2012 Students Conference on Engineering and Systems DA - 2012/3// DO - 10.1109/sces.2012.6199022 PB - IEEE SN - 9781467304559 9781467304566 9781467304542 UR - http://dx.doi.org/10.1109/sces.2012.6199022 DB - Crossref ER - TY - CONF TI - Comparative analysis of mathematical modeling of Photo-Voltaic (PV) array AU - Bal, Satarupa AU - Anurag, Anup AU - Babu, B. Chitti T2 - 2012 Annual IEEE India Conference (INDICON) AB - This paper presents a comparative study between various models of Photo-Voltaic (PV) array which have been formulated exclusively using the data sheet parameters. The models used for comparative study in this paper includes single diode model, the two diode model, the simplified single diode model and the improved single diode model. PV systems are generally integrated with specific control algorithms in order to extract the maximum possible power. Hence it is highly imperative that the Maximum Power Point (MPP) is achieved effectively and thus we need to design a model from which the MPPT algorithm can be realized in an efficient way. Also other parameters should be taken into account for finding the best model for the use in simulator. In this paper, comparisons have been made on basis of the MPP tracking, the RMSD from the experimental data. Further, the resemblance of the P-V and I-V curves as obtained on the basis of experimental data has also been included in this study. On the basis of all these, the best model that can be used for simulation purposes has been selected. It is envisaged that the work can be very useful for professionals who require simple and accurate PV simulators for their design. All the systems here are modeled and simulated in MATLAB/Simulink environment. C2 - 2012/12// C3 - 2012 Annual IEEE India Conference (INDICON) DA - 2012/12// DO - 10.1109/indcon.2012.6420627 PB - IEEE SN - 9781467322720 9781467322706 9781467322713 UR - http://dx.doi.org/10.1109/indcon.2012.6420627 DB - Crossref ER - TY - CONF TI - Video-aware MIMO precoding with packet prioritization and unequal modulation C2 - 2012/// C3 - European Signal Processing Conference DA - 2012/// SP - 1905-1909 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84869779012&partnerID=MN8TOARS ER - TY - CONF TI - Using random shape theory to model blockage in random cellular networks AB - Shadow fading is severe in downtown areas where buildings are densely located. This paper proposes a stochastic model to quantify blockages due to shadowing, using methods from random shape theory. Buildings inside a cell are modeled as line segments with random sizes and orientations, with locations from a spatial Poisson point process. Dense urban areas can be modeled by the parameters of the line process. Based on this construction, the distribution of the power loss caused by shadowing in a particular path is expressed in closed form. The distribution can be used to compute several performance metrics of interest in random systems. Simulations illustrate coverage and connectivity as a function of the metrics of blockages, such as the density and the average size of buildings. C2 - 2012/// C3 - 2012 International Conference on Signal Processing and Communications, SPCOM 2012 DA - 2012/// DO - 10.1109/SPCOM.2012.6290250 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84867706619&partnerID=MN8TOARS ER - TY - JOUR TI - User partitioning for less overhead in MIMO interference channels T2 - IEEE Transactions on Wireless Communications AB - This paper presents a study on multiple-antenna interference channels, accounting for general overhead as a function of the number of users and antennas in the network. The model includes both perfect and imperfect channel state information based on channel estimation in the presence of noise. Three low-complexity methods are proposed for reducing the impact of overhead in the sum network throughput by partitioning users into orthogonal groups. The first method allocates spectrum to the groups equally, creating an imbalance in the sum rate of each group. The second proposed method allocates spectrum unequally among the groups to provide rate fairness. Finally, geographic grouping is proposed for cases where some receivers do not observe significant interference from other transmitters. For each partitioning method, the optimal solution not only requires a brute force search over all possible partitions, but also requires full channel state information, thereby defeating the purpose of partitioning. We therefore propose greedy methods to solve the problems, requiring no instantaneous channel knowledge. Simulations show that the proposed greedy methods switch from time-division to interference alignment as the coherence time of the channel increases, and have a small loss relative to optimal partitioning only at moderate coherence times. DA - 2012/// PY - 2012/// DO - 10.1109/TWC.2011.122211.101188 VL - 11 IS - 2 SP - 592-603 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84857364288&partnerID=MN8TOARS KW - MIMO KW - multiaccess communication KW - interference alignment KW - ad hoc networks KW - multiple access interference ER - TY - JOUR TI - User arrival in MIMO interference alignment networks T2 - IEEE Transactions on Wireless Communications AB - In this paper we analyze a constant multiple-input multiple-output interference channel where a set of active users are cooperating through interference alignment while a set of secondary users desire access to the channel. We find the minimum number of secondary transmit antennas required so that a secondary user can use the channel without affecting the sum rate of the active users, under a zero-forcing equalization assumption. When the secondary users have enough antennas, we derive several secondary user precoders that approximately maximize the secondary users' sum rate without changing the sum rate of the active users. When the secondary users do not have enough antennas, we perform numerical optimization to find secondary user precoders that cause minimum degradation to the sum rate of the active users. Through simulations, we confirm that i) with enough antennas at the secondary users, gains equivalent to the case of all the users cooperating through interference alignment is obtainable, and ii) when the secondary users do not have enough antennas, large rate losses at the active users can be avoided.channels DA - 2012/// PY - 2012/// DO - 10.1109/TWC.2011.120511.111088 VL - 11 IS - 2 SP - 842-851 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84857368090&partnerID=MN8TOARS ER - TY - JOUR TI - Transmission capacity of Ad-hoc networks with multiple antennas using transmit stream adaptation and interference cancellation T2 - IEEE Transactions on Information Theory AB - The transmission capacity of an ad-hoc network is the maximum density of active transmitters per unit area, given an outage constraint at each receiver for a fixed rate of transmission. Assuming that the transmitter locations are distributed as a Poisson point process, this paper derives upper and lower bounds on the transmission capacity of an ad-hoc network when each node is equipped with multiple antennas. The transmitter either uses eigen multi-mode beamforming or a subset of its antennas without channel information to transmit multiple data streams, while the receiver uses partial zero forcing to cancel certain interferers using some of its spatial receive degrees of freedom (SRDOF). The receiver either cancels the nearest interferers or those interferers that maximize the post-cancellation signal-to-interference ratio. Using the obtained bounds, the optimal number of data streams to transmit, and the optimal SRDOF to use for interference cancellation are derived that provide the best scaling of the transmission capacity with the number of antennas. With beamforming, single data stream transmission together with using all but one SRDOF for interference cancellation is optimal, while without beamforming, single data stream transmission together with using a fraction of the total SRDOF for interference cancellation is optimal. DA - 2012/// PY - 2012/// DO - 10.1109/TIT.2011.2173712 VL - 58 IS - 2 SP - 780-792 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84856846185&partnerID=MN8TOARS KW - Ad hoc network KW - beamforming KW - multiple antennas KW - interference cancelation KW - spatial multiplexing KW - transmission capacity ER - TY - JOUR TI - Spatial interference cancellation for multiantenna mobile ad hoc networks T2 - IEEE Transactions on Information Theory AB - Interference between nodes is a critical impairment in mobile ad hoc networks. This paper studies the role of multiple antennas in mitigating such interference. Specifically, a network is studied in which receivers apply zero-forcing beamforming to cancel the strongest interferers. Assuming a network with Poisson-distributed transmitters and independent Rayleigh fading channels, the transmission capacity is derived, which gives the maximum number of successful transmissions per unit area. Mathematical tools from stochastic geometry are applied to obtain the asymptotic transmission capacity scaling and characterize the impact of inaccurate channel state information (CSI). It is shown that, if each node cancels interferers, the transmission capacity decreases as as the outage probability vanishes. For fixed , as grows, the transmission capacity increases as where is the path-loss exponent. Moreover, CSI inaccuracy is shown to have no effect on the transmission capacity scaling as vanishes, provided that the CSI training sequence has an appropriate length, which we derive. Numerical results suggest that canceling merely one interferer by each node may increase the transmission capacity by an order of magnitude or more, even when the CSI is imperfect. DA - 2012/// PY - 2012/// DO - 10.1109/TIT.2011.2178140 VL - 58 IS - 3 SP - 1660-1676 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84857719913&partnerID=MN8TOARS KW - Ad hoc networks KW - adaptive arrays KW - channel estimation KW - interference cancellation KW - multiple-input multiple-output (MIMO) KW - Rayleigh channels ER - TY - CONF TI - The capacity optimality of beam steering in large millimeter wave MIMO systems AB - Millimeter wave (mmWave) systems must overcome the heavy attenuation at high frequency to support high-throughput wireless communication. The small wavelength in mmWave systems enables beamforming using large antenna arrays to combat path loss with large array gain. Beamforming in traditional microwave systems is often done at baseband for maximum flexibility. Such baseband processing requires a dedicated transceiver chain per antenna element. The high cost of radio frequency (RF) chains in mmWave systems, however, makes supporting each antenna with a dedicated RF chain expensive. This mismatch between the number of antennas and transceiver chains makes baseband processing infeasible; thus mmWave systems typically rely on a traditional approach known as beam steering which can be done at RF using inexpensive phase shifters. Unlike baseband precoding, however, traditional beam steering is not explicitly designed to achieve the capacity of the mmWave channel. In this paper, we consider both beamforming and multi-stream precoding in single user systems with large mmWave antenna arrays at both transmitter and receiver. Using a realistic channel model, we show that the unconstrained capacity-achieving precoding solutions converge to simple beam steering solutions. Therefore, in large mmWave systems, no rate loss is incurred by adopting the traditional lower-complexity solution. C2 - 2012/// C3 - IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC DA - 2012/// DO - 10.1109/SPAWC.2012.6292865 SP - 100-104 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84868031081&partnerID=MN8TOARS ER - TY - CONF TI - Spectral efficiency limits in pilot-assisted cooperative communications AB - Cooperation in a large wireless network with pilotassisted coherent communication is shown to have certain fundamental limitations, namely that even perfect cooperation cannot in general change an interference-limited network to a noise-limited one. Specifically, we demonstrate the existence of a spectral efficiency upper bound that does not grow with the transmit power, when channels are estimated via pilot signals. This is because pilot-assisted channel estimation is only possible within finite cooperation clusters, resulting in out-of-cluster interference that scales with the transmit power. Making the clusters excessively large can actually worsen this effect, nor does sidestepping the pilot-assisted channel estimation via noncoherent demodulation provide an escape. Using a cellular system as an example, it is demonstrated that the spectral efficiency saturates at power levels of operational relevance, indicating that the lackluster gains from cooperation observed in practice may be based on fundamental information-theoretic limitations, rather than current technology imperfections. C2 - 2012/// C3 - IEEE International Symposium on Information Theory - Proceedings DA - 2012/// DO - 10.1109/ISIT.2012.6283030 SP - 1132-1136 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84867529979&partnerID=MN8TOARS ER - TY - JOUR TI - On the overhead of interference alignment: Training, feedback, and cooperation T2 - IEEE Transactions on Wireless Communications AB - Interference alignment (IA) is a cooperative transmission strategy that, under some conditions, achieves the interference channel's maximum number of degrees of freedom. Realizing IA gains, however, is contingent upon providing transmitters with sufficiently accurate channel knowledge. In this paper, we study the performance of IA in multiple-input multiple-output systems where channel knowledge is acquired through training and analog feedback. We design the training and feedback system to maximize IA's effective sum-rate: a non-asymptotic performance metric that accounts for estimation error, training and feedback overhead, and channel selectivity. We characterize effective sum-rate with overhead in relation to various parameters such as signal-to-noise ratio, Doppler spread, and feedback channel quality. A main insight from our analysis is that, by properly designing the CSI acquisition process, IA can provide good sum-rate performance in a very wide range of fading scenarios. Another observation from our work is that such overhead-aware analysis can help solve a number of practical network design problems. To demonstrate the concept of overhead-aware network design, we consider the example problem of finding the optimal number of cooperative IA users based on signal power and mobility. DA - 2012/// PY - 2012/// DO - 10.1109/TWC.2012.092412120588 VL - 11 IS - 11 SP - 4192-4203 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870494450&partnerID=MN8TOARS KW - MIMO KW - multiple access interference KW - interference channels KW - interference cancellation KW - interference alignment KW - channel estimation KW - channel state information (CSI) KW - analog feedback ER - TY - CONF TI - Prioritized multimode precoding for joint minimization of source-channel video distortions AU - Khalek, A.A. AU - Caramanis, C. AU - Heath, R.W. AB - Real-time video streaming over wireless channels suffers from channel-induced distortions due to losses and errors as well as source-induced distortions due to lossy compression. This paper proposes a cross-layer design for quality-driven packet prioritization at the physical layer combined with source and link rate adaptation to jointly minimize the source and channel distortions. With a MIMO physical layer, packet prioritization is achieved by mapping video packets to ordered spatial streams to maximize the throughput weighted by the per-packet loss visibility. The MIMO mode controls the number of priority levels and is dynamically optimized to provide the best tradeoff between high source rate and low channel distortion. Jointly with mode adaptation, source rate adaptation is driven by the client by estimating the end-to-end throughput based on the transmission rate. Results show that the proposed design enables composite video quality gains due to prioritized delivery and rate adaptation. C2 - 2012/// C3 - Conference Record - Asilomar Conference on Signals, Systems and Computers DA - 2012/// DO - 10.1109/ACSSC.2012.6489151 SP - 925-929 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84876271891&partnerID=MN8TOARS ER - TY - CONF TI - Pre- and post-FFT interference leakage minimization for MIMO OFDM networks AB - Interference alignment (IA) has been shown to achieve the maximum degrees of freedom in the multiple-input multiple-output (MIMO) K-user interference channel (IFC). In the presence of frequency-selective channels, orthogonal frequency-division multiplexing (OFDM) is typically used to deal with the multipath nature of the channel. While IA techniques can be applied in a per-subcarrier basis (post-FFT), the existence of symbol timing offsets (STOs) between the desired and the interfering OFDM symbols decreases the system performance dramatically. To solve this problem, we design pre-FFT precoders and decoders for single-beam MIMO IFCs for OFDM transmissions. Since the IA decoders operate before the FFT, they mitigate the interference before synchronization takes place. We show that our proposed scheme improves the system performance when STOs occur, in comparison with traditional post-FFT IA techniques. We provide simulation results to compare post and pre-FFT beamforming techniques and to illustrate the performance of the proposed method. C2 - 2012/// C3 - Proceedings of the International Symposium on Wireless Communication Systems DA - 2012/// DO - 10.1109/ISWCS.2012.6328429 SP - 556-560 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84871289770&partnerID=MN8TOARS ER - TY - CONF TI - Online learning for quality-driven unequal protection of scalable video AU - Khalek, A.A. AU - Caramanis, C. AU - Heath, R.W. AB - Video packet losses affect perceived video quality non-uniformly due to several factors related to video encoding such as inter-frame coding and motion compensation as well as due to psycho-visual perception of natural scenes with unequal motion. This motivates protecting video packets unequally based on their loss visibility. This paper proposes an adaptive online algorithm for unequal error protection driven by two key motivations: On one hand, for real-time video, where a video sequence is not pre-encoded, an offline approach is infeasible and determining the unequal protection levels to maintain a target video quality level must be performed online. On the other hand, an online approach enables adapting to scene changes as well as changes in video temporal and spatial characteristics. The proposed online algorithm uses local linear regression to learn the mapping between packet losses from each scalable video layer and quality degradation without assuming an underlying statistical model. The notion of locality captures the similarity in video scene characteristics as well as proximity in time. The algorithm provably guarantees an average target video quality level and converges rapidly to a stable solution. Furthermore, it provides a bias/variance tradeoff between factual estimation of loss visibility and fine adaptation to the changing video temporal characteristics. C2 - 2012/// C3 - IEEE International Workshop on Machine Learning for Signal Processing, MLSP DA - 2012/// DO - 10.1109/MLSP.2012.6349781 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870688150&partnerID=MN8TOARS ER - TY - CONF TI - On the limitations of cooperation in wireless networks AU - Lozano, A. AU - Andrews, J.G. AU - Heath, R.W. AB - Cooperation in a large wireless network (such as a cellular system) is shown to have certain fundamental limitations: namely, even perfect cooperation cannot in general change an interference-limited network to a noise-limited one. In contrast to existing literature that routinely assumes that the spectral efficiency scales with log P as the transmit power P grows large, we show the existence of a spectral efficiency upper bound that does not grow with P. The result uses well-accepted principles of information theory to reach the conclusion that it is not possible (or even helpful) to fully coordinate a large wireless network. Rather than simply low- and high-power regimes, there are three distinct network operating regimes: low-power; a DoF regime, where the log P scaling holds; and a saturation regime where the spectral efficiency hits a ceiling that is independent of P. Using a cellular system example, it is demonstrated that the transition to the saturation regime is operationally relevant and perhaps explains the lackluster gains from cooperation observed in practice. C2 - 2012/// C3 - 2012 Information Theory and Applications Workshop, ITA 2012 - Conference Proceedings DA - 2012/// DO - 10.1109/ITA.2012.6181813 SP - 123-130 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84860456235&partnerID=MN8TOARS ER - TY - JOUR TI - Link adaptation with position/motion information in vehicle-to-vehicle networks T2 - IEEE Transactions on Wireless Communications AB - Wireless communication networks use link adaptation to select physical layer parameters that optimize the transmission strategy as a function of the wireless channel realization. In the vehicle-to-vehicle (V2V) networks considered in this letter, the short coherence time of the wireless channel makes link adaptation based on the impulse response challenging. Consequently, link adaptation in V2V wireless networks may instead exploit the large-scale characteristics of the wireless channel (i.e. path loss) since they evolve slowly and enable less frequent feedback. Large-scale channel information may be captured through channel or position/motion measurements. We show, through the definition of new large-scale coherence expressions, that channel measurements render large-scale coherence as a function of time-change while the position/motion measurements render coherence as a function of velocity-change. This letter is concluded with highway simulations of modeled and measured channels to demonstrate the advantage of position/motion information for feedback reduction in V2V link adaptation. DA - 2012/// PY - 2012/// DO - 10.1109/TWC.2011.121911.110086 VL - 11 IS - 2 SP - 505-509 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84857370598&partnerID=MN8TOARS KW - Adaptive modulation and coding KW - GPS KW - link adaptation KW - PNT KW - vehicular communication KW - wireless fingerprinting ER - TY - JOUR TI - Introduction to the issue on signal processing in heterogeneous networks for future broadband wireless systems T2 - IEEE Journal on Selected Topics in Signal Processing AB - The six papers in this special issue focus on signal processing in heterogeneous networks for future broadband wireless systems. DA - 2012/// PY - 2012/// DO - 10.1109/JSTSP.2012.2190541 VL - 6 IS - 3 SP - 213-215 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84861199727&partnerID=MN8TOARS ER - TY - BOOK TI - Multicell handoff in MIMO cellular systems AB - This paper is concerned with handoff mechanisms in wireless cellular networks that employ MIMO technology. To achieve optimal performance during handoff, the mobile receiver can be linked to antennas from both the base stations of the adjacent cells. Then the handoff is termed multicell handoff. The basic idea is that in a region know as the multicell handoff region, the mobile terminal communicates simultaneously with multiple base stations. The simulation results demonstrate that the multicell handoff provides an improvement of average throughput in the high spatial correlation case. DA - 2012/// PY - 2012/// DO - 10.1007/978-3-642-27552-4_117 VL - 133 AISC SE - 893-898 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84862067601&partnerID=MN8TOARS ER - TY - CONF TI - Multi-cell coordination: A stochastic geometry approach AB - Partial base station coordination is analyzed on the downlink of a cellular system with randomly deployed base stations. In contrast with existing work, a stochastic geometry framework is considered for both base station deployment and base station clustering. The cluster-cells form a Poisson tessellation of the plane generated by Poisson distributed cluster base stations. Inter-cell interference nulling is applied to coordinate interference inside each cluster-cell. Both perfect and limited channel state information (CSI) sharing among coordinating base stations are considered. The average achievable rate with perfect CSI and the mean loss in rate due to limited CSI feedback are derived for a typical user inside the cell. Numerical results show that the average achievable rate with interference coordination as well as the mean loss in rate with equal-bit partitioning increase with increasing average cluster size and increasing number of antennas at the transmitter. C2 - 2012/// C3 - IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC DA - 2012/// DO - 10.1109/SPAWC.2012.6292881 SP - 16-20 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84868020373&partnerID=MN8TOARS ER - TY - CONF TI - Modeling heterogeneous network interference AB - Cellular systems are becoming more heterogeneous with the introduction of low power nodes including femtocells, relays, and distributed antennas. Unfortunately, the resulting interference environment is also becoming more complex, making evaluation of different communication strategies for cellular systems more challenging in both analysis and simulation. This paper suggests a simplified interference model for heterogeneous network. Leveraging recent applications of stochastic geometry to analyze cellular systems, this paper propose to analyze performance in a fixed-size typical cell surrounded by an interference field consisted of superposition of marked Poisson point processes outside a guard region. The proposed model simplifies the simulation of cellular systems and may provide analytical insights for certain signaling strategies. C2 - 2012/// C3 - 2012 Information Theory and Applications Workshop, ITA 2012 - Conference Proceedings DA - 2012/// DO - 10.1109/ITA.2012.6181825 SP - 17-22 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84860433126&partnerID=MN8TOARS ER - TY - CONF TI - Interference-free relay transmission without CSI-S for the MIMO two-hop interference channel C2 - 2012/// C3 - 2012 19th International Conference on Systems, Signals and Image Processing, IWSSIP 2012 DA - 2012/// SP - 217-221 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84863895761&partnerID=MN8TOARS ER - TY - CONF TI - Not too delayed CSIT achieves the optimal degrees of freedom AU - Lee, N. AU - Heath, R.W. AB - Channel state information at the transmitter (CSIT) aids interference management in many communication systems. Due to channel state information (CSI) feedback delay and time-variation in the wireless channel, perfect CSIT is not realistic. In this paper, the CSI feedback delay-DoF gain trade-off is characterized for the multi-user vector broadcast channel. A major insight is that it is possible to achieve the optimal degrees of freedom (DoF) gain if the delay is less than a certain fraction of the channel coherence time. This precisely characterizes the intuition that a small delay should be negligeable. To show this, a new transmission method called space-time interference alignment is proposed, which actively exploits both the current and past CSI. C2 - 2012/// C3 - 2012 50th Annual Allerton Conference on Communication, Control, and Computing, Allerton 2012 DA - 2012/// DO - 10.1109/Allerton.2012.6483363 SP - 1262-1269 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84875750403&partnerID=MN8TOARS ER - TY - CONF TI - Multiuser MIMO in distributed antenna systems with limited feedback AU - Schwarz, S. AU - Heath, R.W. AU - Rupp, M. AB - Augmenting the central antennas of a cellular base station with remote radio units (RRUs) has the potential of providing more uniform coverage of the area served by the base station. In distributed antenna systems (DASs) these RRUs are connected to the base station via high bandwidth and low latency links, enabling coherent transmission from potentially all available antennas at the same time. Prior work has identified multiuser transmission over the entire distributed antenna array as a promising technique. In this work, we demonstrate the viability of zero forcing multiuser MIMO DASs with perfect channel state information (CSI) at the transmitter (CSIT) in an LTE simulation framework. Furthermore, the impact of imperfect CSIT, obtained via limited feedback, on the achievable transmission rates is investigated. Specifically, we modify previously derived feedback algorithms to exploit the large scale fading differences inherently existing in DASs. C2 - 2012/// C3 - 2012 IEEE Globecom Workshops, GC Wkshps 2012 DA - 2012/// DO - 10.1109/GLOCOMW.2012.6477632 SP - 546-551 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84875641046&partnerID=MN8TOARS ER - TY - CONF TI - Low complexity precoding for large millimeter wave MIMO systems AU - Ayach, O.E. AU - Heath, R.W. AU - Abu-Surra, S. AU - Rajagopal, S. AU - Pi, Z. AB - Millimeter wave (mmWave) systems must overcome heavy signal attenuation to support high-throughput wireless communication links. The small wavelength in mmWave systems enables beamforming using large antenna arrays to combat path loss with directional transmission. Beamforming with multiple data streams, known as precoding, can be used to achieve even higher performance. Both beamforming and precoding are done at baseband in traditional microwave systems. In mmWave systems, however, the high cost of mixed-signal and radio frequency chains (RF) makes operating in the passband and analog domains attractive. This hardware limitation places additional constraints on precoder design. In this paper, we consider single user beamforming and precoding in mmWave systems with large arrays. We exploit the structure of mmWave channels to formulate the precoder design problem as a sparsity constrained least squares problem. Using the principle of basis pursuit, we develop a precoding algorithm that approximates the optimal unconstrained precoder using a low dimensional basis representation that can be efficiently implemented in RF hardware. We present numerical results on the performance of the proposed algorithm and show that it allows mmWave systems to approach waterfilling capacity. C2 - 2012/// C3 - IEEE International Conference on Communications DA - 2012/// DO - 10.1109/ICC.2012.6363634 SP - 3724-3729 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84871956153&partnerID=MN8TOARS ER - TY - JOUR TI - Interference aware-coordinated beamforming in a multi-cell system T2 - IEEE Transactions on Wireless Communications AB - In this paper, we propose jointly optimized linear transceiver algorithms called interference aware-coordinated beamforming (IA-CBF) for a two-cell system where each base station is equipped with multiple transmit antennas. To generalize IA-CBF to more than two-cell scenarios, a new beam-switching mechanism combined with IA-CBF is proposed. For a two-cell system, we derive a minimum-mean-square-error-type IA-CBF algorithm based on a lower bound on the achievable sum rate. We propose optimal (under an assumption of zero other-cell interference) and suboptimal transmit/receive beamforming vectors through zero-forcing IA-CBF algorithms. We also investigate the optimality of the proposed IA-CBF algorithms with respect to the number of receive antennas. Numerical results confirm that the proposed system with two transmit/receive antennas achieves the full degrees of freedom (a.k.a. multiplexing gain) of the two-cell multiple-input multiple-output channel while showing a better sum rate performance than competitive solutions such as non-cooperative eigen-beamforming and interference nulling. A three-dimensional ray tracing tool is also used to evaluate the proposed multi-cell IA-CBF algorithm. DA - 2012/// PY - 2012/// DO - 10.1109/TWC.2012.081312.112119 VL - 11 IS - 10 SP - 3692-3703 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84867897247&partnerID=MN8TOARS KW - MIMO system KW - multiuser system KW - multi-cell system KW - interference alignment KW - interference suppression KW - coordinated beamforming ER - TY - JOUR TI - Interference alignment with analog channel state feedback T2 - IEEE Transactions on Wireless Communications AB - Interference alignment (IA) is a multiplexing gain optimal transmission strategy for the interference channel. While the achieved sum rate with IA is much higher than previously thought possible, the improvement comes at the cost of requiring network channel state information at the transmitters. This can be achieved by explicit feedback, a flexible yet potentially costly approach that incurs large overhead. In this paper we propose analog feedback as an alternative to limited feedback or reciprocity based alignment. We show that the full multiplexing gain observed with perfect channel knowledge is preserved by analog feedback and that the mean loss in sum rate is bounded by a constant when signal-to-noise ratio is comparable in both forward and feedback channels. When signal-to-noise ratios are not quite symmetric, a fraction of the multiplexing gain is achieved. We consider the overhead of training and feedback and use this framework to numerically optimize the system's effective throughput. We present simulation results to demonstrate the performance of IA with analog feedback, verify our theoretical analysis, and extend our conclusions on optimal training and feedback length. DA - 2012/// PY - 2012/// DO - 10.1109/TWC.2011.122211.101814 VL - 11 IS - 2 SP - 626-636 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84857366485&partnerID=MN8TOARS KW - Interference alignment KW - interference channel KW - multiple antennas KW - MIMO KW - analog feedback KW - limited feedback ER - TY - JOUR TI - A cross-layer design for perceptual optimization of H.264/SVC with unequal error protection T2 - IEEE Journal on Selected Areas in Communications AB - Delivering high perceptual quality video over wireless channels is challenging due to the changing channel quality and the variations in the importance of one source packet to the next for the end-user's perceptual experience. Leveraging perceptual metrics in concert with link adaptation to maximize perceptual quality and satisfy real-time delay constraints is largely unexplored. We introduce an APP/MAC/PHY cross-layer architecture that enables optimizing perceptual quality for delay-constrained scalable video transmission. We propose an online QoS-to-QoE mapping technique to quantify the loss visibility of packets from each video layer using the ACK history and perceptual metrics. At the PHY layer, we develop a link adaptation technique that uses the QoS-to-QoE mapping to provide perceptually-optimized unequal error protection per layer according to packet loss visibility. At the APP layer, the source rate is adapted by selecting the set of temporal and quality layers to be transmitted based on the channel statistics, source rates, and playback buffer state. The proposed cross-layer optimization framework allows the channel to adapt at a faster time scale than the video codec. Furthermore, it provides a tradeoff between playback buffer occupancy and perceptual quality. We show that the proposed architecture prevents playback buffer starvation, provides immunity against short-term channel fluctuations, regulates the buffer size, and achieves a 30% increase in video capacity versus throughput-optimal link adaptation. DA - 2012/// PY - 2012/// DO - 10.1109/JSAC.2012.120802 VL - 30 IS - 7 SP - 1157-1171 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84864623707&partnerID=MN8TOARS KW - Scalable video coding (SVC) KW - unequal error protection (UEP) KW - cross-layer design KW - link adaptation KW - QoS-to-QoE mapping ER - TY - CONF TI - Interference leakage minimization for convolutive MIMO interference channels AB - An alternating optimization algorithm was recently proposed for the K-user multiple-input multiple-output (MIMO) interference channel. For flat-fading channels and feasible problems, this algorithm successfully aligns the interfering signals exploiting the spatial dimensions. In this paper, we consider the case in which all pairwise MIMO channels are frequency-selective (convolutive), and the users transmit broadband signals using a single-carrier scheme. Unlike the flat-fading case, for frequency-selective channels it is necessary to add a spectral mask in the frequency response of the precoders and decoders to avoid trivial solutions. We show in the paper that each step of the alternating minimization algorithm can be reformulated as a convex optimization problem in which the autocorrelation function of the precoders or decoders is obtained. Upon convergence, a final spectral factorization stage must be applied to obtain the precoders and decoders from their autocorrelation functions. Simulation results are provided to illustrate the performance of the proposed algorithm. C2 - 2012/// C3 - ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings DA - 2012/// DO - 10.1109/ICASSP.2012.6288506 SP - 2829-2832 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84867602257&partnerID=MN8TOARS ER - TY - CONF TI - Data sharing coordination and blind interference alignment for cellular networks AU - Akoum, S. AU - Chen, C.S. AU - Debbah, M. AU - Heath, R.W. AB - We consider coordination in a multi-user multiple input single output cellular system. In contrast with existing base station cooperation methods that rely on sharing CSI with or without user data to manage interference, we propose to share user data only. We consider a system where blind interference alignment (BIA) is applied to serve multiple users in each cell. We apply interference coordination through data sharing to mitigate other-cell interference at the cell-edge users. While BIA mitigates intra-cell interference in MU-MISO systems, it does not address the problem of inter-cell interference. We apply interference coordination through data sharing to mitigate inter-cell interference at the cell-edge users. We propose a new cooperative BIA scheme that takes into account the users whose data is being shared between adjacent base stations. We derive the achievable sum rate with interference mitigation and we compare it to achievable rates with the original BIA strategy. Numerical results show that the achievable sum rate of the cell-edge users with data sharing decreases with increasing number of served users in each cell and increasing number of antennas at the base stations. C2 - 2012/// C3 - GLOBECOM - IEEE Global Telecommunications Conference DA - 2012/// DO - 10.1109/GLOCOM.2012.6503789 SP - 4273-4277 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84877671225&partnerID=MN8TOARS ER - TY - CONF TI - Coverage and capacity in mmWave cellular systems AU - Akoum, S. AU - El Ayach, O. AU - Heath, R.W. AB - Millimeter wave (mmWave) communication has recently been proposed for use in commercial cellular systems as a solution to the microwave spectrum gridlock. MmWave spectrum is (potentially) available around the globe and recent hardware advances make mass market deployments feasible. In this paper, we study the coverage and capacity of mmWave cellular systems with a special focus on their key differentiating factors such as the limited scattering nature of mmWave channels, and the use of RF beamforming strategies such as beam steering to provide highly directional transmission with limited hardware complexity.We show that, in general, coverage in mmWave systems can rival or even exceed coverage in microwave systems assuming that the link budgets promised by existing mmWave system designs are in fact achieved. This comparable coverage translates into a superior average rate performance for mmWave systems as a result of the larger bandwidth available for transmission. C2 - 2012/// C3 - Conference Record - Asilomar Conference on Signals, Systems and Computers DA - 2012/// DO - 10.1109/ACSSC.2012.6489099 SP - 688-692 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84876261829&partnerID=MN8TOARS ER - TY - CONF TI - Interference alignment with limited feedback for two-cell interfering MIMO-MAC AB - In this paper, we consider a two-cell interfering multiple-input multiple-output multiple access channel (MIMO-MAC). We first investigate the multiplexing gain of such channel when users have perfect channel state information at the transmitter (CSIT) by exploiting an interference alignment scheme. In addition, we propose a quantized transmit beamforming vector feedback method for the interference alignment in the limited feedback system. On the basis of the proposed feedback framework, we analyze the rate gap loss and it is shown that in order to keep the same multiplexing gain with the case of perfect CSIT, the number of feedback bits per receiver should be increased linearly with the SNR in dB scale. Throughout the simulation results, it is shown that the sum-rate performance coincides with the derived results. C2 - 2012/// C3 - Proceedings of the International Symposium on Wireless Communication Systems DA - 2012/// DO - 10.1109/ISWCS.2012.6328431 SP - 566-570 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84871287378&partnerID=MN8TOARS ER - TY - CONF TI - Implementation of a real-time wireless interference alignment network AU - Massey, J.W. AU - Starr, J. AU - Lee, S. AU - Lee, D. AU - Gerstlauer, A. AU - Heath, R.W. AB - Interference alignment (IA) is a cooperative transmission technique for the interference channel. This paper describes two testbeds that implement real-time Multiple-input multiple-output (MIMO) IA for a network with three 2-antenna user pairs using software defined radio techniques: a PC-based testbed for rapid prototyping of potential IA protocols and an embedded testbed for evaluating IA under real-world computational constraints. The IA implementations rely on a wired backbone to share global channel state information (CSI) and a shared clock for frequency and timing synchronization. The testbeds are used to demonstrate the viability of IA, and to compare its robustness with several alternative transmission strategies, such as 2 × 2 MIMO TDMA, in terms of sum-rates. Results show that we are able to successfully achieve over-the-air IA in our three-user 2×2 MIMO testbed. The paper highlights key challenges with the practical realization of IA that are encountered while developing the testbed and identifies areas for future research. C2 - 2012/// C3 - Conference Record - Asilomar Conference on Signals, Systems and Computers DA - 2012/// DO - 10.1109/ACSSC.2012.6488968 SP - 104-108 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84876213212&partnerID=MN8TOARS ER - TY - JOUR TI - Grassmannian differential limited feedback for interference alignment AU - El Ayach, O. AU - Heath, R.W. T2 - IEEE Transactions on Signal Processing AB - Channel state information (CSI) in the interference channel can be used to reduce the dimension of received interference and helps achieve the channel's maximum multiplexing gain through what is known as interference alignment (IA). Most interference alignment algorithms require knowledge of all the interfering channels to compute the alignment precoders. CSI, considered available at the receivers, can be shared with the transmitters via limited feedback. When IA is done by coding over frequency extensions in a single antenna system, the required CSI lies on the Grassmannian manifold and its structure can be exploited in feedback. Unfortunately, the number of channels to be shared grows with the square of the number of users, creating too much overhead with conventional feedback methods. This paper proposes Grassmannian differential feedback to reduce feedback overhead by exploiting both the channel's temporal correlation and Grassmannian structure. The performance of the proposed algorithm is characterized both analytically and numerically as a function of channel length, mobility, and the number of feedback bits. The main conclusions are that the proposed feedback strategy allows IA to perform well over a wide range of Doppler spreads, and to approach perfect CSI performance in slowly varying channels. Numerical results highlight the trade-off between the frequency of feedback and the accuracy of individual feedback updates. DA - 2012/// PY - 2012/// DO - 10.1109/TSP.2012.2218238 VL - 60 IS - 12 SP - 6481-6494 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870493187&partnerID=MN8TOARS KW - Channel state information (CSI) KW - differential feedback KW - Grassmann manifold KW - interference alignment KW - interference cancellation KW - interference channels KW - limited feedback KW - multiple access interference KW - OFDM ER - TY - CONF TI - CSI feedback delay and degrees of freedom gain trade-off for the MISO interference channel AU - Lee, N. AU - Heath, R.W. AB - Channel state information at the transmitter (CSIT) plays a significant role in managing interference for the multiple-input-single-output (MISO) interference channel. Because of channel state information (CSI) feedback delay and time-variation in the wireless channel, perfect CSIT may be difficult to obtain, which results in the system performance degradation. In this paper, a CSI feedback delay-DoF gain trade-off is characterized for the MISO interference by using space-time interference alignment that exploits current and outdated CSI jointly. From this trade-off characterization, insight is provided the interplay between CSI feedback delay and DoF gain in the MISO interference channel. C2 - 2012/// C3 - Conference Record - Asilomar Conference on Signals, Systems and Computers DA - 2012/// DO - 10.1109/ACSSC.2012.6489357 SP - 1851-1854 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84876257405&partnerID=MN8TOARS ER - TY - JOUR TI - Ultrasound-Induced Currents in Planar Lipid Blayers: Origins and Potential Physiological Significance AU - Prieto, Martin L. AU - Oralkan, Omer AU - Khuri-Yakub, Butrus T. AU - Maduke, Merritt C. T2 - Biophysical Journal AB - Low-intensity focused ultrasound shows great promise for non-invasive, spatially resolved modulation of neural activity in vivo. To determine the mechanisms involved in ultrasonic modulation of neural activity and guide the development of this technology, we have been investigating the effects of ultrasound on protein-free planar lipid bilayers. Previously, we reported that ultrasound causes decaying current oscillations in planar bilayers at the onset and offset of the stimulus. These on and off responses are of opposite polarity but otherwise identical. Here, we report that if the rise time of the ultrasound pulse is prolonged, the on response is resolved into two distinct components: a sigmoidal component during the rise time and a damped oscillating component once the pulse reaches its final value. This result suggests that changes in ultrasound intensity during the rise time of the pulse may be important in determining the response to ultrasound in vivo, and is consistent with the observation that pulsed ultrasound is more effective than continuous ultrasound in modulating neural activity. To investigate further the origins of the on/off behavior, we used an optical interferometer to measure the velocity of the ultrasound-induced movement (acoustic streaming) in the solution surrounding the bilayer. We find that the time course of the ultrasound-induced current matches the time course of the streaming velocity, with a ratio of 162 pA/(mm/s). This acoustic streaming is probably due to the action of ultrasonic radiation force. To explore the potential physiological relevance of these effects, and to obtain further mechanistic insight, we are investigating the response of planar bilayers to ultrasound under current-clamp. In preliminary experiments, we find that ultrasound pulses with intensity comparable to those used in vivo produce voltage changes that would be sufficient to initiate an action potential. DA - 2012/1// PY - 2012/1// DO - 10.1016/j.bpj.2011.11.212 VL - 102 IS - 3 SP - 34a J2 - Biophysical Journal LA - en OP - SN - 0006-3495 UR - http://dx.doi.org/10.1016/j.bpj.2011.11.212 DB - Crossref ER - TY - JOUR TI - Deviation from exponential decay for spin waves excited with a coplanar waveguide antenna AU - Birt, Daniel R. AU - An, Kyongmo AU - Tsoi, Maxim AU - Tamaru, Shingo AU - Ricketts, David AU - Wong, Kin L. AU - Khalili Amiri, Pedram AU - Wang, Kang L. AU - Li, Xiaoqin T2 - Applied Physics Letters AB - We have investigated the propagation of surface spin waves in a Permalloy thin film excited by an asymmetric coplanar antenna. A surprising oscillatory behavior superimposed on the exponential decay is observed in the spin wave intensity mapped with the micro-Brillouin light scattering technique. The oscillations can be modeled as the interference between a propagating spin wave and a background magnetization with spatially uniform phase. We use a simple closed-form equation that includes both contributions to fit our experimental results. From the fit results, we extract the spin wave propagation length and the spin wave vector in a frequency range limited by the antenna bandwidth. DA - 2012/12/17/ PY - 2012/12/17/ DO - 10.1063/1.4772798 VL - 101 IS - 25 SP - 252409 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.4772798 DB - Crossref ER - TY - JOUR TI - In situ quantification of electrical isolation in STM-fabricated TiOx nanostructures AU - Hu, W. AU - Bain, J.A. AU - Ricketts, D.S. T2 - Micro & Nano Letters AB - In this Letter, a combination of conductive atomic force microscopy (AFM) and scanning tunnelling microscopy (STM) with a compliant cantilever is used to electrically probe oxidised TiO2−x nanostructures in situ. In STM mode, both the written width and the effective resistivity of material in the written line increase with write bias. At low writing voltages (∼3.5 V), the STM written lines are narrow (30 nm), but they are not resistive enough to allow patterns with a 1–2 µm perimeter to provide electrical isolation above 10 MΩ. Raising the bias to 8.5 V during writing allows similar structures to provide isolation of better than 250 MΩ. The resistivity in the lines written at the latter with high bias is 28 Ω m. From electrical estimates, the oxidation appears to go through the thickness at all voltages, but is more chemically incomplete (larger value of x) at low voltage. The data are not consistent, with a small amount of metallic Ti remaining under the written mark, that is, partial penetration of the oxidation. The thickness of this Ti layer would have to be unphysically small (1 million times smaller than an atomic layer thickness) to allow this interpretation. DA - 2012/// PY - 2012/// DO - 10.1049/mnl.2011.0678 VL - 7 IS - 4 SP - 334 J2 - Micro Nano Lett. LA - en OP - SN - 1750-0443 UR - http://dx.doi.org/10.1049/mnl.2011.0678 DB - Crossref ER - TY - JOUR TI - Fish scale terrace GaInN/GaN light-emitting diodes with enhanced light extraction AU - Stark, Christoph J. M. AU - Detchprohm, Theeradetch AU - Zhao, Liang AU - Paskova, Tanya AU - Preble, Edward A. AU - Wetzel, Christian T2 - Applied Physics Letters AB - Non-planar GaInN/GaN light-emitting diodes were epitaxially grown to exhibit steps for enhanced light emission. By means of a large off-cut of the epitaxial growth plane from the c-plane (0.06° to 2.24°), surface morphologies of steps and inclined terraces that resemble fish scale patterns could controllably be achieved. These patterns penetrate the active region without deteriorating the electrical device performance. We find conditions leading to a large increase in light-output power over the virtually on-axis device and over planar sapphire references. The process is found suitable to enhance light extraction even without post-growth processing. DA - 2012/12/3/ PY - 2012/12/3/ DO - 10.1063/1.4769442 VL - 101 IS - 23 SP - 232106 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.4769442 DB - Crossref ER - TY - JOUR TI - Below band-gap optical absorption and photoluminescence excitation spectroscopy at room temperature in low-defect-density bulk GaN:Fe AU - Gladkov, P. AU - Hulicius, E. AU - Paskova, T. AU - Preble, E. AU - Evans, K. R. T2 - Applied Physics Letters AB - We present a detailed study of the below band-gap optical absorption at room temperature in bulk semi-insulating GaN:Fe versus the Fe-doping. It was established that the 1.24 eV photoluminescence band at 300 K consists of only vibrational replicas of the Fe3+ 4T1(G)→6A1(S) internal transition. We also studied the below band-gap photoluminescence excitation of the 1.24 eV band. The identical exponential rise of the photoluminescence excitation and the optical absorption coefficient identify the Fe3+/2+ charge-transfer as the main contributor to the 300 K optical absorption in the range 400-500 nm. Practical implications of these results for Fe-doping determination are discussed. DA - 2012/1/16/ PY - 2012/1/16/ DO - 10.1063/1.3678195 VL - 100 IS - 3 SP - 031908 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.3678195 DB - Crossref ER - TY - JOUR TI - Anisotropy of free-carrier absorption and diffusivity in m-plane GaN AU - Ščajev, P. AU - Jarašiūnas, K. AU - Özgür, Ü. AU - Morkoç, H. AU - Leach, J. AU - Paskova, T. T2 - Applied Physics Letters AB - Polarization-dependent free-carrier absorption (FCA) in bulk m-plane GaN at 1053 nm revealed approximately 6 times stronger hole-related absorption for E⊥c than for E||c probe polarization both at low and high carrier injection levels. In contrast, FCA at 527 nm was found isotropic at low injection levels due to electron resonant transitions between the upper and lower conduction bands, whereas the anisotropic impact of holes was present only at high injection levels by temporarily blocking electron transitions. Carrier transport was also found to be anisotropic under two-photon excitation, with a ratio of 1.17 for diffusivity perpendicular and parallel to the c-axis. DA - 2012/1/9/ PY - 2012/1/9/ DO - 10.1063/1.3674306 VL - 100 IS - 2 SP - 022112 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.3674306 DB - Crossref ER - TY - JOUR TI - Quantitative low-energy electron diffraction analysis of the GaN (1×1) reconstruction AU - Romanyuk, O. AU - Jiricek, P. AU - Paskova, T. T2 - Surface Science AB - Abstract The atomic structure of the GaN ( 000 1 ¯ ) (1 × 1) reconstruction was investigated by quantitative low-energy electron diffraction (LEED). The GaN ( 000 1 ¯ ) surface was annealed in an NH3 atmosphere and cooled down without any NH3 flux. LEED patterns with 6-fold symmetry were measured after annealing. The diffraction symmetry was explained by the presence of two domains on the GaN surface. LEED intensity–voltage (I–V) curves were acquired up to 500 eV and calculated in the framework of the dynamical theory of electron scattering. Good agreement between the experimental and theoretical curves was achieved for the bare GaN ( 000 1 ¯ ) (1 × 1) surface. Relaxation of the surface atomic layers decreased Pendry's R-factor to 0.21 ± 0.03. The plane relaxations derived from the LEED analysis were found to be in qualitative agreement with ab initio calculations. By using previously suggested models with adlayers on the bare GaN ( 000 1 ¯ ) (1 × 1) surface, much worse R-factors were obtained. It was concluded that the measured LEED I–V curves could be used to determine the bare GaN polarity. DA - 2012/4// PY - 2012/4// DO - 10.1016/j.susc.2012.01.002 VL - 606 IS - 7-8 SP - 740-743 J2 - Surface Science LA - en OP - SN - 0039-6028 UR - http://dx.doi.org/10.1016/j.susc.2012.01.002 DB - Crossref KW - Gallium nitride GaN (000(1)over-bar) KW - Semiconductor surfaces KW - Quantitative low-energy electron diffraction LEED KW - Dynamical theory of scattering KW - Surface reconstruction ER - TY - JOUR TI - Microstructure of epitaxial GaN films grown on chemomechanically polished GaN(0001) substrates AU - Huang, Li AU - Liu, Fang AU - Zhu, Jingxi AU - Kamaladasa, Ranga AU - Preble, Edward A. AU - Paskova, Tanya AU - Evans, Keith AU - Porter, Lisa AU - Picard, Yoosuf N. AU - Davis, Robert F. T2 - Journal of Crystal Growth AB - An organometallic vapor phase epitaxy-based process route has been developed to achieve homoepitaxial deposition of GaN(0001) films via step-flow growth on substrates having <1° off-cut. Atomic force microscopy of the surfaces of 0, 1, 2, 5 and 10 nm thick films revealed steps and terraces as the only features; three-dimensional GaN islands were not observed. Film–substrate interfaces were not present in cross-sectional samples using high-resolution TEM. This indicated that continuous film growth occurred from steps on the substrate without re-nucleation and defect formation on the terraces. This process route also mitigated the generation of additional dislocations, as validated by the exact matches of the density and positions of dislocations that reached the substrate surface and those observed in a subsequently grown 600 nm film. The influence of grain boundaries in the interior of the GaN substrates was manifest in variations in terrace width and step orientation across the substrates and the films. A grain orientation map generated across a representative substrate revealed highly disoriented grains on the periphery. The disorientation angles between these adjacent grains were centered around ∼35°, ∼70° and ∼90°. DA - 2012/5// PY - 2012/5// DO - 10.1016/j.jcrysgro.2012.03.002 VL - 347 IS - 1 SP - 88-94 J2 - Journal of Crystal Growth LA - en OP - SN - 0022-0248 UR - http://dx.doi.org/10.1016/j.jcrysgro.2012.03.002 DB - Crossref KW - Grain boundary KW - Substrate KW - Terrace/step KW - Threading dislocations KW - Homoepitaxy KW - GaN ER - TY - JOUR TI - Cathodoluminescence imaging for the determination of dislocation density in differently doped HVPE GaN AU - Meissner, E. AU - Schweigard, S. AU - Friedrich, J. AU - Paskova, T. AU - Udwary, K. AU - Leibiger, G. AU - Habel, F. T2 - Journal of Crystal Growth AB - In this study we report the potential and limitations of the cathodoluminescence dark spot (DS) counting as a method for the determination of dislocation density and distribution in GaN, produced by the hydride vapour phase epitaxy (HVPE). Different GaN sample series (s.i. GaN:Fe and n-type GaN:Si) were used, in order to study the dependence of the results of the DS-counting on the dopant type and concentration. By the direct comparison of these results to classical defect selective etching, the DS-measurements were validated. It could be shown that each of the both methods have their particular restrictions, which must be considered in their application. DA - 2012/2// PY - 2012/2// DO - 10.1016/j.jcrysgro.2011.12.043 VL - 340 IS - 1 SP - 78-82 J2 - Journal of Crystal Growth LA - en OP - SN - 0022-0248 UR - http://dx.doi.org/10.1016/j.jcrysgro.2011.12.043 DB - Crossref ER - TY - JOUR TI - Near-Infrared Absorption in Lattice-Matched AlInN/GaN and Strained AlGaN/GaN Heterostructures Grown by MBE on Low-Defect GaN Substrates AU - Edmunds, C. AU - Tang, L. AU - Li, D. AU - Cervantes, M. AU - Gardner, G. AU - Paskova, T. AU - Manfra, M. J. AU - Malis, O. T2 - Journal of Electronic Materials DA - 2012/2/1/ PY - 2012/2/1/ DO - 10.1007/S11664-011-1881-9 VL - 41 IS - 5 SP - 881-886 J2 - Journal of Elec Materi LA - en OP - SN - 0361-5235 1543-186X UR - http://dx.doi.org/10.1007/S11664-011-1881-9 DB - Crossref KW - Intersubband absorption KW - near infrared KW - quantum well infrared photodetector KW - electromodulation KW - III-nitride semiconductors KW - molecular-beam epitaxy ER - TY - JOUR TI - Electrical and optical properties of bulk GaN substrates studied by Kelvin probe and photoluminescence AU - McNamara, J. D. AU - Foussekis, M. A. AU - Baski, A. A. AU - Li, X. AU - Avrutin, V. AU - Morkoç, H. AU - Leach, J. H. AU - Paskova, T. AU - Udwary, K. AU - Preble, E. AU - Reshchikov, M. A. T2 - physica status solidi (c) AB - Abstract We have investigated the N‐ and Ga‐polar faces of bulk GaN substrates with photoluminescence (PL) and the surface photovoltage (SPV) technique using a Kelvin probe attached to an optical cryostat. Experiments were conducted in vacuum. Some of the surfaces were mechanically polished (MP), while others were epi‐ready after a chemical‐mechanical polish (CMP). From the SPV measurements, the band bending in a sample having both surfaces treated with the CMP method was calculated to be about 0.83 and 0.70 eV for the Ga‐ and N‐polar surfaces, respectively. The restoration of the SPV after ceasing the UV illumination showed that the SPV from CMP‐treated surfaces behaved as predicted by a thermionic model, whereas the SPV from MP‐treated surfaces restored with a much faster‐than‐predicted rate. This result can be interpreted by the hopping of charge carriers in the highly‐defective near‐surface layer of the MP‐treated samples. Remarkably, removing the top 700 nm defective layer by dry etching restored the quality of the electrical and optical properties of GaN. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) DA - 2012/12/21/ PY - 2012/12/21/ DO - 10.1002/pssc.201200662 VL - 10 IS - 3 SP - 536-539 J2 - Phys. Status Solidi C LA - en OP - SN - 1862-6351 UR - http://dx.doi.org/10.1002/pssc.201200662 DB - Crossref KW - photoluminescence KW - Kelvin probe KW - GaN KW - surface ER - TY - JOUR TI - Enzyme Recognition: Substrate-Baited Nanoparticles: A Catch and Release Strategy for Enzyme Recognition and Harvesting (Small 13/2012) AU - Daniele, Michael A. AU - Bandera, Yuriy P. AU - Sharma, Deepti AU - Rungta, Parul AU - Roeder, Ryan AU - Sehorn, Michael G. AU - Foulger, Stephen H. T2 - Small AB - The cover image illustrates a universal model for concentrating and extracting protein–substrate pairs via substrate-baited nanoparticles, which can be an invaluable tool in recognizing unknown protein–substrate affinities. The isolation of a single type of protein from a complex mixture is vital for the characterization of the function, structure, and interactions of the protein of interest and is typically the most laborious aspect of the protein purification process. Enzyme trapping and recycling is illustrated with the carbazole 1,9a-dioxygenase (CARDO) system, an enzyme important in bioremediation and natural product synthesis. The enzymes are baited by carbazolyl-moieties attached to nanoparticles through a click transformation. The single-step procedure for attracting the enzymes to the particles is capable of concentrating the protein from raw lysate and sequestering all required components of the protein to maintain bioactivity. For more information, please read the Full Paper “Substrate-Baited Nanoparticles: A Catch and Release Strategy for Enzyme Recognition and Harvesting” by S. H. Foulger, and co-workers, beginning on page 2083. DA - 2012/7/4/ PY - 2012/7/4/ DO - 10.1002/smll.201290072 VL - 8 IS - 13 SP - 1961-1961 J2 - Small LA - en OP - SN - 1613-6810 UR - http://dx.doi.org/10.1002/smll.201290072 DB - Crossref ER - TY - JOUR TI - Substrate-Baited Nanoparticles: A Catch and Release Strategy for Enzyme Recognition and Harvesting AU - Daniele, Michael A. AU - Bandera, Yuriy P. AU - Sharma, Deepti AU - Rungta, Parul AU - Roeder, Ryan AU - Sehorn, Michael G. AU - Foulger, Stephen H. T2 - Small AB - The isolation of a single type of protein from a complex mixture is vital for the characterization of the function, structure, and interactions of the protein of interest and is typically the most laborious aspect of the protein purification process. In this work, a model system is utilized to show the efficacy of synthesizing a “baited” nanoparticle to capture and recycle enzymes (proteins that catalyze chemical reactions) from crude cell lysate. Enzyme trapping and recycling is illustrated with the carbazole 1,9a-dioxygenase (CARDO) system, an enzyme important in bioremediation and natural product synthesis. The enzymes are baited with azide-modified carbazolyl moieties attached to poly(propargyl acrylate) nanoparticles through a click transformation. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis indicates the single-step procedure to immobilize the enzymes on the particles is capable of significantly concentrating the protein from raw lysate and sequestering all required components of the protein to maintain bioactivity. These results establish a universal model applicable to concentrating and extracting known substrate–protein pairs, but it can be an invaluable tool in recognizing unknown protein–ligand affinities. DA - 2012/4/24/ PY - 2012/4/24/ DO - 10.1002/smll.201200013 VL - 8 IS - 13 SP - 2083-2090 J2 - Small LA - en OP - SN - 1613-6810 UR - http://dx.doi.org/10.1002/smll.201200013 DB - Crossref KW - nanoparticles KW - biological activity KW - enzyme-substrates KW - click chemistry KW - protein purification ER - TY - JOUR TI - Rapid and Continuous Hydrodynamically Controlled Fabrication of Biohybrid Microfibers AU - Daniele, Michael A. AU - North, Stella H. AU - Naciri, Jawad AU - Howell, Peter B. AU - Foulger, Stephen H. AU - Ligler, Frances S. AU - Adams, André A. T2 - Advanced Functional Materials AB - Abstract Cell encapsulation is critical for many biotechnology applications including environmental remediation, bioreactors, and regenerative medicine. Here, the development of biohybrid microfibers comprised of encapsulated bacteria in hydrogel matrices produced on‐chip using microfluidics is reported. The fiber production process utilizes hydrodynamic shaping of a cell‐laden core fluid by a miscible sheath fluid. Production of the fibers containing viable bacteria was continuous in contrast to the more typical methods in which cells infiltrated or were attached to prepared fibers. The biohybrid fibers were composed of poly (ethylene glycol dimethacrylate) matrices and individually both E. coli and B. cereus were explored as model cellular payloads. Post processing growth curves (24 h) of bacteria within fibers were in excellent agreement with that of controls suggesting minimal impact. Finally, the biohybrid fibers showed even distribution of encapsulated cells and >90% cell viability. DA - 2012/9/11/ PY - 2012/9/11/ DO - 10.1002/adfm.201202258 VL - 23 IS - 6 SP - 698-704 J2 - Adv. Funct. Mater. LA - en OP - SN - 1616-301X UR - http://dx.doi.org/10.1002/adfm.201202258 DB - Crossref KW - cell encapsulation KW - microfiber extrusion KW - hydrogel KW - microfabrication KW - hydrodynamic focusing ER - TY - JOUR TI - Planar defects in thin films of InGaN AU - Liliental-Weber, Z. AU - Yu, K.M. AU - Zakharov, D. AU - Bedair, S. T2 - Microscopy and Microanalysis AB - Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012. DA - 2012/7// PY - 2012/7// DO - 10.1017/S1431927612009282 VL - 18 IS - S2 SP - 1486-1487 J2 - Microsc Microanal LA - en OP - SN - 1431-9276 1435-8115 UR - http://dx.doi.org/10.1017/S1431927612009282 DB - Crossref ER - TY - JOUR TI - Parallel-connected shunt hybrid active power filters operating at different switching frequencies for improved performance AU - Bhattacharya, A. AU - Chakraborty, C. AU - Bhattacharya, S. T2 - IEEE Transactions on Industrial Electronics AB - This paper proposes a combination of low- and high-frequency hybrid active power filter (APF) to operate in parallel for better performance. The individual hybrid APF is a series combination of L-C filter with the corresponding voltage source inverter. The dc links of both the inverters are connected in parallel, and the voltage of the dc link is maintained by the low-frequency inverter (LFI). The low- and high-frequency inverters eliminate lower order and higher order harmonics, respectively. In addition, it is possible to design the LFI such that it can also compensate the reactive power of the load. The individual L-C filter of the hybrid topology is designed to take care of specific order of harmonics that are predominant in the load. A combination of feedforward and feedback controller is designed for the proposed conditioner. The performances of the proposed topology and the controller are first examined by MATLAB/SIMULINK-based simulation. An experimental prototype is also designed to confirm the usefulness of the proposed system. DA - 2012/// PY - 2012/// DO - 10.1109/TIE.2011.2173893 VL - 59 IS - 11 SP - 4007-4019 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84862999144&partnerID=MN8TOARS KW - Active power filter (APF) KW - harmonics KW - passive filter KW - reduced switch topology ER - TY - CONF TI - Practical operation range improvement of Voltage-Sourced Converter based STATCOM AB - Voltage-Sourced Converter (VSC) based STATCOM is used for voltage regulation in transmission and distribution systems. In order to lower the STATCOM losses and total system loss, switching devices in “angle controlled” STATCOM are fired once with the line frequency (50/60 Hz). Despite the superior features on voltage waveform quality and efficiency, the practical angle controlled STATCOMs suffer from the over current and possible saturation of the interfacing transformers caused by negative sequence generated by system faults and disturbances. In this paper, the current control scheme and Instantaneous Phase-Locked Loop (IPLL) for an “angle controlled” STATCOM are presented. From power electronic point of view, IPLL prevents over-current in the VSC under system faults and bus voltage distortions. The current control can further improve STATCOM operation with higher percentages of negative sequence voltage. In addition to improved system performance under fault, the system can be installed with regular transformers, not custom-designed or over-rated transformers. RTDS (Real Time Digital Simulator) results verify the applicability of the proposed IPLL based control methods. C2 - 2012/// C3 - Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC DA - 2012/// DO - 10.1109/APEC.2012.6165822 SP - 211-217 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84860158421&partnerID=MN8TOARS ER - TY - CONF TI - Solid state transformer specification via feeder modeling and simulation AU - Wang, Z. AU - Xu, J. AU - Hatua, K. AU - Madhusoodhanan, S. AU - Bhattacharya, S. AB - This paper discusses the design specification method of a 1MVA, 13.8kV/480V solid state transformer (SST, also called a Transformerless Intelligent Power Substation - TIPS). A simplified IEEE 34 bus test feeder was used in the study and a dynamic model of the TIPS was developed and incorporated into the feeder model. Feeder circuit stability issues when TIPS connects at a weak system point were observed and mitigation method studied. The overloading capability of TIPS and the overvoltage protection requirements of TIPS were also investigated. C2 - 2012/// C3 - IEEE Power and Energy Society General Meeting DA - 2012/// DO - 10.1109/PESGM.2012.6345403 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870598630&partnerID=MN8TOARS ER - TY - CHAP TI - Smart vehicles in the smart grid: Challenges, trends, and application to the design of charging stations AU - Bayram, I.S. AU - Michailidis, G. AU - Devetsikiotis, M. AU - Granelli, F. AU - Bhattacharya, S. T2 - Control and Optimization Methods for Electric Smart Grids PY - 2012/// DO - 10.1007/978-1-4614-1605-6 SP - 133-145 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84957378317&partnerID=MN8TOARS ER - TY - CONF TI - Numerical investigation of electronic liquid cooling based on the thermomagnetic effect AU - Karimi-Moghaddam, G. AU - Gould, R.D. AU - Bhattacharya, S. AB - Liquid cooling for thermal management has been widely applied in high power electronic systems. Use of pumps may often introduce reliability and mechanical limitations such as vibration of moving parts, noise problems, leakage problems, and considerable power consumption. This paper presents a theoretical design of circulating a liquid coolant using magnetic and thermal fields which surround high power electronic systems by means of thermomagnetic effects of temperature sensitive magnetic fluids. Numerical simulation models of the heat transfer process from a magnetic liquid contained in a closed flow loop in the presence of an external magnetic field have been developed. These models include the coupling of three fundamental phenomena, i.e. magnetic, thermal, and fluid dynamic features. In this cooling device, the thermomagnetic convection is generated by a non-uniform magnetic field from a solenoid, which is placed close to the fluid loop. The device cooling load is calculated in the region near the solenoid. No energy is needed, other than the heat load (i.e. waste heat from actual electrical device), to drive the cooling system, and as such, the device can be considered completely self-powered. In effect, the heat added to the ferrofluid in the presence of a magnetic field is converted into useful flow work. In this numerical study, the effects of different factors such as input heat load, magnetic field strength and magnetic distribution (based on solenoid dimensions and the applied electrical current) along the loop, on the performance of the cooling system are analyzed and discussed. Finally, the variation of the local Nusselt number along the heated and cooled regions of the flow loop are calculated and compared with laminar entry length analytical solutions. C2 - 2012/// C3 - ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) DA - 2012/// DO - 10.1115/IMECE2012-87764 VL - 7 SP - 1441-1447 M1 - PARTS A, B, C, D UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84887279923&partnerID=MN8TOARS ER - TY - CONF TI - Inductive power transfer for electric vehicles: Potential benefits for the distribution grid AU - Mohagheghi, S. AU - Parkhideh, B. AU - Bhattacharya, S. AB - It is believed that the latest advances in battery and converter technology, along with government mandates on energy independence and resilience, will pave the way for higher deployment of electric vehicles in the transportation fleet. These vehicles, when equipped with bidirectional energy transfer capabilities, can function as mobile energy resources and be utilized in a vehicle-to-grid (V2G) scheme to temporarily inject energy back into the power grid. The forecasted increase in the number of these vehicles can turn them into a considerable energy resource to be used by the utilities as ancillary services or even for long-term integration with the grid. The energy injection into the power system by electric vehicles has been investigated in the literature for charging stations or single residential charging devices. The need for the vehicle to be stationary during the transfer, and the possible drive and/or change in the driving route in order to go the station are some of the hurdles that may lead to inconvenience and hence lower V2G participation by the vehicle drivers. Moreover, the need for an electrical connection between the vehicle and the station makes implementing remote supervisory control schemes difficult, if not impractical. However, with the advent of inductive charging systems for contactless transfer of energy, new horizons have been opened for seamless integration of these resources of energy into the distribution grid. This paper focuses on the applications of inductive power transfer systems for V2G purposes in the modern distribution grid. It will be shown here that such a scheme could potentially allow for supervisory control and management of the mobile energy resources with the ultimate goal of improving the reliability and security of the power grid without the need for capacity expansion. C2 - 2012/// C3 - 2012 IEEE International Electric Vehicle Conference, IEVC 2012 DA - 2012/// DO - 10.1109/IEVC.2012.6183266 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84860788026&partnerID=MN8TOARS ER - TY - CONF TI - High performance, ultra high voltage 4H-SiC IGBTs AU - Ryu, S.-H. AU - Capell, C. AU - Cheng, L. AU - Jonas, C. AU - Gupta, A. AU - Donofrio, M. AU - Clayton, J. AU - O’Loughlin, M. AU - Burk, A. AU - Grider, D. AU - Agarwal, A. AU - Palmour, J. AU - Hefner, A. AU - Bhattacharya, S. AB - We present our latest developments in ultra high voltage 4H-SiC IGBTs. A 4H-SiC P-IGBT, with a chip size of 6.7 mm × 6.7 mm and an active area of 0.16 cm 2 exhibited a record high blocking voltage of 15 kV, while showing a room temperature differential specific on-resistance of 24 mΩ-cm 2 with a gate bias of -20 V. A 4H-SiC N-IGBT with the same area showed a blocking voltage of 12.5 kV, and demonstrated a room temperature differential specific on-resistance of 5.3 mΩ-cm 2 with a gate bias of 20 V. Buffer layer design, which includes controlling the doping concentration and the thickness of the field-stop buffer layers, was used to control the charge injection from the backside. Effects on buffer layer design on static characteristics and switching behavior are reported. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012 DA - 2012/// DO - 10.1109/ECCE.2012.6342311 SP - 3603-3608 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870861131&partnerID=MN8TOARS ER - TY - CONF TI - Design considerations of a three phase dual active bridge based on reactive power flow AU - Boillat, D. AU - Roy, S. AU - Tripathi, A. AU - Bhattacharya, S. AB - This paper discusses about the reactive power flow calculation in a dual-active-bridge (DAB) following the CP (conservative power) and PQ (instantaneous reactive power) theories. Based on the results from reactive power calculation, the optimal virtual turns ratio is determined so as to draw equal reactive power from the primary and secondary sides of the DAB-transformer. The equal sharing of the reactive power makes the DAB system more efficient. This paper also discusses about the computation of active and reactive power flow based on experimental data. As an example, a three winding transformer is selected for the experimentation and the better turns ratio is pointed out which can provide better efficiency. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012 DA - 2012/// DO - 10.1109/ECCE.2012.6342790 SP - 424-430 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870919073&partnerID=MN8TOARS ER - TY - CONF TI - Analysis of 48-pulse based STATCOM and UPFC performance under balanced and fault conditions AU - Babaei, S. AU - Parkhideh, B. AU - Bhattacharya, S. AB - Convertible Static Compensator (CSC) which is a versatile Flexible AC Transmission System (FACTS) technology has been installed on Marcy 345 kV substation and increases power transfer capability, operational functionality, and power flow controllability of the New York Power Authority (NYPA) transmission system. This paper presents a comprehensive description of CSC inverter 48-pulse wave construction along with introduction of control strategy deployed in CSC when it is operating as a STATCOM and UPFC. STATCOM and UPFC steady state and dynamic operation PSCAD simulation results under different testing conditions including unbalanced condition and faults are presented. This paper also provides comprehensive analysis of the STATCOM response to negative sequence and harmonic voltage components on the transmission line during fault conditions. The amounts of DC-link capacitance that lead to maximum and minimum of fundamental negative sequence current on the tie line and 120 Hz oscillation on the DC-link voltage are calculated. Simulation results of STATCOM performance with different DC-link capacitance during fault condition will be shown. At the end of the paper, one exiting problem regarding to UPFC operation of NYPA CSC has been addressed and illustrated with precise simulation results. C2 - 2012/// C3 - IECON Proceedings (Industrial Electronics Conference) DA - 2012/// DO - 10.1109/IECON.2012.6388598 SP - 1211-1216 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84872923067&partnerID=MN8TOARS ER - TY - CONF TI - Architecture of solid state transformer-based energy router and models of energy traffic AU - Zhang, J. AU - Wang, W. AU - Bhattacharya, S. AB - Recently, a large number of renewable energy resources and DC loads spur the research spotlight of the future power grid, which is also referred to as Energy Internet. In order to achieve such a fundamental innovation to the novel energy paradigm, many devices are to be designed, manufactured, and evaluated. In this paper, we describe the solid state transformer-based energy router in which incoming energy traffic can be converted and routed to an outgoing energy traffic. In particular, we focus on the architecture design of such a router and models of energy storage devices, generators, and loads, for Energy Local Area Network (ELAN). The proposed energy router features plug-and-play Multiple-Input Multiple-Output (MIMO), and customized operating system, that providing a system level modeling for the optimal design and performance analysis of energy routers. C2 - 2012/// C3 - 2012 IEEE PES Innovative Smart Grid Technologies, ISGT 2012 DA - 2012/// DO - 10.1109/ISGT.2012.6175637 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84860849112&partnerID=MN8TOARS ER - TY - CONF TI - A comparative study of three-phase dual active bridge topologies and their suitability for D-Q mode control AU - Tripathi, A.K. AU - Hatua, K. AU - Bhattacharya, S. AB - A comparative evaluation of three different three-phase Dual Active Bridge (DAB) topologies with a 15-kV Si-IGBT based three-level converter at the high-voltage side and 1200-V SiC-MOSFET based converters in three different arrangements at the low-voltage side are compared. The proposed DABs are an integral part of a solid state transformer which connects a 13.8-kV distribution grid and a 480-V utility grid. The three-level converters connected at the high-voltage side in each topology with 30° zero-enforcing and proposed arrangements at low-voltage side of the high frequency-link transformer help to reduce dominant harmonic currents. Thus harmonic-free currents in the high frequency link transformer are achieved without pulse-width modulation which can be utilized for D-Q Mode smooth-control. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012 DA - 2012/// DO - 10.1109/ECCE.2012.6342605 SP - 1719-1724 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870924513&partnerID=MN8TOARS ER - TY - CONF TI - A fast acting DC solid state fault isolation device (FID) with Si and SiC devices for MVDC distribution system AU - Juvekar, S. AU - Compton, B. AU - Bhattacharya, S. AB - This paper presents a low voltage (400V) hardware prototype of a fast acting medium voltage DC circuit breaker. Simulation results obtained using PLECS software and hardware testing results are also presented for the same prototype. The prototype serves as a proof of concept showing implementation of firmware logic capable of interrupting DC fault current within 4.042 micro-seconds from the instant an overcurrent condition occurs. The authors propose that the same concept can be extended to medium voltage DC level and present a performance comparison of real 6.5kV silicon (Si) and 10kV silicon carbide (SiC) devices as solid state fault isolation devices (SSFID) in a medium voltage DC (MVDC) distribution system using SPICE simulations. The MVDC SSFID described in this paper finds an application in MVDC distribution system described by Next Generation Integrated Power System (NGIPS) roadmap [1] proposed by Electric Ship Office (ESO) of Office of Naval Research (ONR). Other applications include large scale grid connected solar and wind farm at MVDC level. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012 DA - 2012/// DO - 10.1109/ECCE.2012.6342566 SP - 2005-2010 PB - IEEE UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870869018&partnerID=MN8TOARS ER - TY - CONF TI - A single phase PSCad electric arc furnace model AU - White, L.W. AU - Bhattacharya, S. AB - Electric Arc Furnaces (EAFs) are among the larger loads imposed upon the electrical grid. The size of these loads, when combined with the stochastic nature of the electric arc, and the poor reaction of the grid to such loads, makes the EAF worthy of study in general and modeling in particular. The present work develops a model of an EAF that is designed as a custom component for use with the PSCad modeling software but can be used equally well in real-time simulation systems. The model is single-phase, allowing multiple instances to be connected in any configuration so that unbalanced situations can be easily simulated. The model is completely documented so that it can be duplicated with no additional information. C2 - 2012/// C3 - IECON Proceedings (Industrial Electronics Conference) DA - 2012/// DO - 10.1109/IECON.2012.6389532 SP - 5352-5356 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84872908679&partnerID=MN8TOARS ER - TY - BOOK TI - Flame detection for video-based early fire warning for the protection of cultural heritage AU - Dimitropoulos, K. AU - Gunay, O. AU - Kose, K. AU - Erden, F. AU - Chaabene, F. AU - Tsalakanidou, F. AU - Grammalidis, N. AU - Cetin, E. AB - Cultural heritage and archaeological sites are exposed to the risk of fire and early warning is the only way to avoid losses and damages. The use of terrestrial systems, typically based on video cameras, is currently the most promising solution for advanced automatic wildfire surveillance and monitoring. Video cameras are sensitive in visible spectra and can be used either for flame or smoke detection. This paper presents and compares three video-based flame detection techniques, which were developed within the FIRESENSE EU research project. DA - 2012/// PY - 2012/// DO - 10.1007/978-3-642-34234-9_38 VL - 7616 LNCS SE - 378-387 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84868030366&partnerID=MN8TOARS ER - TY - JOUR TI - Wavelet based flame detection using differential PIR sensors AU - Erden, F. AU - Toreyin, B.U. AU - Soyer, E.B. AU - Inac, I. AU - Gunay, O. AU - Kose, K. AU - Cetin, A.E. T2 - 2012 20th Signal Processing and Communications Applications Conference (SIU) AB - In this paper, a flame detection system using a differential Pyro-electric Infrared (PIR) sensor is proposed. A differential PIR sensor is only sensitive to sudden temperature variations within its viewing range and it produces a time-varying signal. The wavelet transform of the differential PIR sensor signal is used for feature extraction and feature vectors are fed to Markov models trained with uncontrolled fire flames and walking person. The model yielding the highest probability is chosen. Results suggest that the system can be used in spacious rooms for uncontrolled fire flame detection. DA - 2012/4// PY - 2012/4// DO - 10.1109/siu.2012.6204529 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84863434890&partnerID=MN8TOARS ER - TY - CONF TI - An Intra-cavity bottom emitting 1325 nm VCSEL using GaInAs / GaInP MQWs and AlGaInAs / InP DBRs for epitaxial fabrication AB - In this paper, a bottom emitting Ga 0.586 In 0.414 As / Ga 0.252 In 0.748 P MQW Intra-cavity Vertical Cavity Surface Emitting Laser (VCSEL) capable of emitting light output at 1325 nm has been designed. After a number of computations of the material gain and band gap energy it has been found that the ternary compound of Ga 0.586 In 0.414 As as the quantum well material and the lattice matched ternary compound material Ga 0.252 In 0.748 P as the barrier material are suitable for operating at 1325 nm. Ga 0.252 In 0.748 P has been used for the 2 SCH layers which is also lattice matched. Si doped Al 0.6 In 0.4 As has been used as the lattice matched p-cladding material and C doped Al 0.5 In 0.5 As has been used as the n-cladding material. The design has been based on building the laser on an InP substrate which is lattice matched with the bottom DBR layers made of lattice matched Al 0.26 Ga 0.21 In 0.53 As / InP (48 pairs). The top DBR structure has been designed using Al 0.26 Ga 0.21 In 0.53 As / InP (80 pairs) which is also lattice matched with the p-cladding material and the active region material. This design is aimed at fabricating the VCSEL using the widely used epitaxial technologies. The performance characteristics of the designed VCSEL show expected performance. C2 - 2012/// C3 - IEEE International Conference on Electron Devices and Solid-State Circuits (EDSSC) DA - 2012/// DO - 10.1109/EDSSC.2012.6482771 UR - https://publons.com/publon/30967579/ ER - TY - CHAP TI - System Identification: 3D Measurement Using Structured Light System AU - Lee, Deokwoo AU - Krim, Hamid T2 - Advanced Concepts for Intelligent Vision Systems AB - The problem of 3D reconstruction from 2D captured images is solved using a set of cocentric circular light patterns. Once the number of light sources and cameras, their location and the orientations, and the sampling density (the number of circular patterns) are determined, we propose a novel approach to representation of the reconstruction problem as system identification. Akin to system identification using the relationship between input and output, to develop an efficient 3D functional camera system, we identify the reconstruction system by choosing / defining input and output signals appropriately. One algorithm states that an input and an output are defined as projected circular patterns and 2D captured image (overlaid with deformed circular patterns) respectively. Another one is that a 3D target and the captured 2D image are defined as the input and the output respectively, leading to a problem of input estimation by demodulating an output (received) signal. The former approach identifies the system from the ratio of output to input, and is akin to a modulation-demodulation theory, the latter identifies the reconstruction system by estimating the input signal. This paper proposes the approach to identification of reconstruction system, and also substantiates the algorithm by showing results using inexpensive and simple experimental setup. PY - 2012/// DO - 10.1007/978-3-642-33140-4_1 SP - 1-11 OP - PB - Springer Berlin Heidelberg SN - 9783642331398 9783642331404 UR - http://dx.doi.org/10.1007/978-3-642-33140-4_1 DB - Crossref ER - TY - JOUR TI - Dynamic electrothermal simulation of three-dimensional integrated circuits using standard cell macromodels AU - Priyadarshi, S. AU - Harris, T.R. AU - Melamed, S. AU - Otero, C. AU - Kriplani, N.M. AU - Christoffersen, C.E. AU - Manohar, R. AU - Dooley, S.R. AU - Davis, W.R. AU - Franzon, P.D. AU - Steer, M.B. T2 - IET Circuits, Devices & Systems AB - Physics-based compact electrothermal macromodels of standard cells are developed for fast dynamic simulation of three-dimensional integrated circuits (3DICs). Such circuits can have high thermal densities and thermal effects often limit their performance. The macromodels developed here use fewer state-variables than a discrete transistor-level implementation while retaining transistor-level accuracy. This results in significant speed-up over transistor-level simulation for large-scale circuits. The macromodel-based methodology enables robust and significantly faster dynamic electrothermal simulation over the long times required for thermal transients to subside. Consequently, transient junction temperature can be examined in the design phase. Simulated junction and measured surface thermal transients are compared. DA - 2012/// PY - 2012/// DO - 10.1049/iet-cds.2011.0061 VL - 6 IS - 1 SP - 35 J2 - IET Circuits Devices Syst. LA - en OP - SN - 1751-858X UR - http://dx.doi.org/10.1049/iet-cds.2011.0061 DB - Crossref ER - TY - JOUR TI - Perimeter detection in wireless sensor networks AU - Luthy, Kyle AU - Grant, Edward AU - Deshpande, Nikhil AU - Henderson, Thomas C. T2 - Robotics and Autonomous Systems AB - For a mobile robotic agent to bridge the gaps between disconnected networks, it is beneficial for the robot to first determine the network coverage boundary. Several techniques have been introduced to determine the boundary nodes of a network, but the correctness of these techniques is often ill-defined. We present a technique for obtaining boundary node ground truth from region adjacency analysis of a model-based image created from a network graph. The resulting ground truth baseline is then used for quantitative comparison of several boundary detection methods including a local application of the image region adjacency analysis and the computation of the local convex hull with the addition of a perturbation value to overcome small boundary concavities in the node location point set. Given our proposed metrics of the techniques evaluated, the perturbed convex hull technique demonstrates a high success rate for boundary node identification, particularly when the convex hull is formed using two-hop neighborhoods. This technique was successfully implemented on a physical 25-node network, and the performance of this network implementation is evaluated. DA - 2012/2// PY - 2012/2// DO - 10.1016/j.robot.2011.10.004 VL - 60 IS - 2 SP - 266-277 J2 - Robotics and Autonomous Systems LA - en OP - SN - 0921-8890 UR - http://dx.doi.org/10.1016/j.robot.2011.10.004 DB - Crossref KW - Wireless sensor networks KW - Boundary detection KW - Coverage hole KW - Convex hull KW - Robotic repair ER - TY - CONF TI - Fixing Performance Bugs: An Empirical Study of Open-Source GPGPU Programs AU - Yang, Yi AU - Xiang, Ping AU - Mantor, Mike AU - Zhou, Huiyang T2 - 2012 41st International Conference on Parallel Processing (ICPP) AB - Given the extraordinary computational power of modern graphics processing units (GPUs), general purpose computation on GPUs (GPGPU) has become an increasingly important platform for high performance computing. To better understand how well the GPU resource has been utilized by application developers and then to facilitate them to develop high performance GPGPU code, we conduct an empirical study on GPGPU programs from ten open-source projects. These projects span a wide range of disciplines and many are designed as high performance libraries. Among these projects, we found various performance 'bugs', i.e., code segments leading to inefficient use of GPU hardware. We characterize these performance bugs, and propose the bug fixes. Our experiments confirm both significant performance gains and energy savings from our fixes and reveal interesting insights on different GPUs. C2 - 2012/9// C3 - 2012 41st International Conference on Parallel Processing DA - 2012/9// DO - 10.1109/icpp.2012.30 PB - IEEE SN - 9781467325080 9780769547961 UR - http://dx.doi.org/10.1109/icpp.2012.30 DB - Crossref ER - TY - JOUR TI - Wavelet based flickering flame detector using differential PIR sensors AU - Erden, Fatih AU - Toreyin, B. Ugur AU - Soyer, E. Birey AU - Inac, Ihsan AU - Gunay, Osman AU - Kose, Kivanc AU - Cetin, A. Enis T2 - Fire Safety Journal AB - A Pyro-electric Infrared (PIR) sensor based flame detection system is proposed using a Markovian decision algorithm. A differential PIR sensor is only sensitive to sudden temperature variations within its viewing range and it produces a time-varying signal. The wavelet transform of the PIR sensor signal is used for feature extraction from sensor signal and wavelet parameters are fed to a set of Markov models corresponding to the flame flicker process of an uncontrolled fire, ordinary activity of human beings and other objects. The final decision is reached based on the model yielding the highest probability among others. Comparative results show that the system can be used for fire detection in large rooms. DA - 2012/// PY - 2012/// DO - 10.1016/j.firesaf.2012.06.006 VL - 53 SP - 13-18 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000309029500002&KeyUID=WOS:000309029500002 KW - Flame detection KW - Pyro-electric Infrared (PIR) sensor KW - Wavelet transform KW - Markov models ER - TY - JOUR TI - Jamming-Resistant Collaborative Broadcast Using Uncoordinated Frequency Hopping AU - Xiao, Liang AU - Dai, Huaiyu AU - Ning, Peng T2 - IEEE Transactions on Information Forensics and Security AB - We propose a jamming-resistant collaborative broadcast scheme for wireless networks, which utilizes the Un coordinated Frequency Hopping (UFH) technique to counteract jamming without preshared keys, and exploits node cooperation to achieve higher communication efficiency and stronger jamming resistance. In this scheme, nodes that already obtain the broadcast message serve as relays to help forward it to other nodes. Relying on the sheer number of relay nodes, our scheme provides a new angle for jamming countermeasure, which not only significantly enhances the performance of jamming-resistant broadcast, but can readily be combined with other existing or emerging antijamming approaches in various applications. We present the collaborative broadcast protocol, and analyze its successful packet reception rate and the corresponding cooperation gain for both synchronous and asynchronous relays for a snapshot scenario. We also investigate the full broadcast process based on a Markov chain model and derive a closed-form expression of the average broadcast delay. Simulation results in both single-hop and multihop networks indicate that our scheme is a promising antijamming technique in wireless networks. DA - 2012/2// PY - 2012/2// DO - 10.1109/tifs.2011.2165948 VL - 7 IS - 1 SP - 297-309 J2 - IEEE Trans.Inform.Forensic Secur. OP - SN - 1556-6013 1556-6021 UR - http://dx.doi.org/10.1109/tifs.2011.2165948 DB - Crossref KW - Antijamming communication KW - collaborative broadcast KW - frequency hopping KW - wireless networks ER - TY - JOUR TI - Communication Efficiency of Anti-Jamming Broadcast in Large-Scale Multi-Channel Wireless Networks AU - Li, Chengzhi AU - Dai, Huaiyu AU - Xiao, Liang AU - Ning, Peng T2 - IEEE Transactions on Signal Processing AB - Uncoordinated Frequency Hopping (UFH) and Collaborative UFH (CUFH) are viable countermeasures for jamming attacks without dependency on pre-shared secret keys. In this work we analytically evaluate their communication efficiency in large-scale networks, where the number of nodes n is large and may even exceed the number of channels C . Such a large-system analysis is pertinent to emerging complex networks and systems, and helps us reveal the scaling behavior of the system performance with respect to the network size and other important system parameters. In particular, we show that the average network broadcast delay incurred by UFH scales as O ( C ln n ) , while that incurred by CUFH scales as O (ln n ) when C = o (ln n ). This demonstrates a significant improvement achieved by cooperative relays and the feasibility of UFH-based schemes in large-scale networks. In large-scale networks, the number of relays in CUFH needs to be carefully controlled for best performance. In this study the optimal number of relays in CUFH is derived such that the packet reception rate is maximized, and the optimal cooperation gain achieved by CUFH over UFH is quantified. To facilitate the implementation of CUFH, a suboptimal protocol, CUFH-p, is proposed, which achieves the optimal cooperation gain asymptotically. As an intermediate step, we also study an ideal cooperative network, whose results may be of independent interest. Our analytical results are well substantiated by simulations, and our analytical methodology applies largely to general anti-jamming broadcast in multi-channel networks. DA - 2012/10// PY - 2012/10// DO - 10.1109/tsp.2012.2206589 VL - 60 IS - 10 SP - 5281-5292 J2 - IEEE Trans. Signal Process. OP - SN - 1053-587X 1941-0476 UR - http://dx.doi.org/10.1109/tsp.2012.2206589 DB - Crossref KW - Anti-jamming communication KW - collaborative broadcast KW - frequency hopping KW - multi-channel wireless networks ER - TY - JOUR TI - MAC Design of Uncoordinated FH-Based Collaborative Broadcast AU - Xiao, Liang AU - Dai, Huaiyu AU - Ning, Peng T2 - IEEE Wireless Communications Letters AB - Uncoordinated Frequency Hopping (UFH) techniques are promising to address jamming attacks in wireless networks without requiring pre-shared secret keys, and its communication efficiency in the broadcast scenario can be significantly improved through node cooperation. In this letter, we take a first step to investigate efficient Media Access Control (MAC) strategies for the UFH-based collaborative broadcast, and derive closed-form expressions of the channel access probabilities for time-slotted systems to minimize the broadcast delay and to significantly reduce the energy cost. Numerical and simulation results are provided to verify our analysis and reveal some insights. DA - 2012/6// PY - 2012/6// DO - 10.1109/wcl.2012.041012.120162 VL - 1 IS - 3 SP - 261-264 J2 - IEEE Wireless Commun. Lett. OP - SN - 2162-2337 2162-2345 UR - http://dx.doi.org/10.1109/wcl.2012.041012.120162 DB - Crossref KW - Collaborative broadcast KW - frequency hopping KW - MAC KW - jamming KW - wireless networks ER - TY - JOUR TI - Hierarchical Auction Mechanisms for Network Resource Allocation AU - Tang, Wenyuan AU - Jain, Rahul T2 - IEEE Journal on Selected Areas in Communications AB - Motivated by allocation of bandwidth, wireless spectrum and cloud computing services in secondary network markets, we introduce a hierarchical auction model for network resource allocation. A Tier 1 provider owns a homogeneous network resource and holds an auction to allocate this resource among Tier 2 operators, who in turn allocate the acquired resource among Tier 3 entities. The Tier 2 operators play the role of middlemen, since their utilities for the resource depend on the revenues gained from resale. We first consider static hierarchical auction mechanisms for indivisible resources. We study a class of mechanisms wherein each sub-mechanism is either a first-price or VCG auction, and show that incentive compatibility and efficiency cannot be simultaneously achieved. We also briefly discuss sequential auctions as well as the incomplete information setting. We then propose two VCG-type hierarchical mechanisms for divisible resources. The first one is composed of single-sided auctions at each tier, while the second one employs double-sided auctions at all tiers except Tier 1. Both mechanisms induce an efficient Nash equilibrium. DA - 2012/12// PY - 2012/12// DO - 10.1109/jsac.2012.121204 VL - 30 IS - 11 SP - 2117-2125 J2 - IEEE J. Select. Areas Commun. OP - SN - 0733-8716 UR - http://dx.doi.org/10.1109/jsac.2012.121204 DB - Crossref KW - Network economics KW - mechanism design KW - auctions KW - hierarchical models KW - resource allocation ER - TY - JOUR TI - A Massively Parallel, Energy Efficient Programmable Accelerator for Learning and Classification AU - Majumdar, Abhinandan AU - Cadambi, Srihari AU - Becchi, Michela AU - Chakradhar, Srimat T. AU - Graf, Hans Peter T2 - ACM Transactions on Architecture and Code Optimization AB - Applications that use learning and classification algorithms operate on large amounts of unstructured data, and have stringent performance constraints. For such applications, the performance of general purpose processors scales poorly with data size because of their limited support for fine-grained parallelism and absence of software-managed caches. The large intermediate data in these applications also limits achievable performance on many-core processors such as GPUs. To accelerate such learning applications, we present a programmable accelerator that can execute multiple learning and classification algorithms. To architect such an accelerator, we profile five representative workloads, and find that their computationally intensive portions can be formulated as matrix or vector operations generating large amounts of intermediate data, which are then reduced by a secondary operation such as array ranking, finding max/min and aggregation. Our proposed accelerator, called MAPLE, has hundreds of simple processing elements (PEs) laid out in a two-dimensional grid, with two key features. First, it uses dynamic in-memory processing where on-chip memory blocks perform the secondary reduction operations. Second, MAPLE uses banked off-chip memory, and organizes its PEs into independent groups each with its own off-chip memory bank. These two features allow MAPLE to scale its performance with data size. We also present an Atom based energy-efficient heterogeneous system with MAPLE as the accelerator that satisfies the application’s performance requirements at a lower system power. This article describes the MAPLE architecture, explores its design space with a simulator, illustrates how to automatically map application kernels to the hardware, and presents its performance improvement and energy benefits over classic server-based implementations. We implement a 512-PE FPGA prototype of MAPLE and find that it is 1.5-10x faster than a 2.5 GHz quad-core Xeon processor despite running at a modest 125 MHz clock rate. With MAPLE connected to a 1.6GHz dual-core Atom, we show an energy improvement of 38-84% over the Xeon server coupled to a 1.3 GHz 240 core Tesla GPU. DA - 2012/3/1/ PY - 2012/3/1/ DO - 10.1145/2133382.2133388 VL - 9 IS - 1 SP - 1-30 J2 - TACO LA - en OP - SN - 1544-3566 UR - http://dx.doi.org/10.1145/2133382.2133388 DB - Crossref KW - Design KW - Performance KW - Accelerator-based computing KW - parallel computing KW - heterogeneous computing KW - machine learning KW - architecture ER - TY - JOUR TI - Accelerating large-scale protein structure alignments with graphics processing units AU - Pang, Bin AU - Zhao, Nan AU - Becchi, Michela AU - Korkin, Dmitry AU - Shyu, Chi-Ren T2 - BMC Research Notes AB - Abstract Background Large-scale protein structure alignment, an indispensable tool to structural bioinformatics, poses a tremendous challenge on computational resources. To ensure structure alignment accuracy and efficiency, efforts have been made to parallelize traditional alignment algorithms in grid environments. However, these solutions are costly and of limited accessibility. Others trade alignment quality for speedup by using high-level characteristics of structure fragments for structure comparisons. Findings We present ppsAlign , a p arallel p rotein s tructure Align ment framework designed and optimized to exploit the parallelism of Graphics Processing Units (GPUs). As a general-purpose GPU platform, ppsAlign could take many concurrent methods, such as TM-align and Fr-TM-align, into the parallelized algorithm design. We evaluated ppsAlign on an NVIDIA Tesla C2050 GPU card, and compared it with existing software solutions running on an AMD dual-core CPU. We observed a 36-fold speedup over TM-align, a 65-fold speedup over Fr-TM-align, and a 40-fold speedup over MAMMOTH. Conclusions ppsAlign is a high-performance protein structure alignment tool designed to tackle the computational complexity issues from protein structural data. The solution presented in this paper allows large-scale structure comparisons to be performed using massive parallel computing power of GPU. DA - 2012/// PY - 2012/// DO - 10.1186/1756-0500-5-116 VL - 5 IS - 1 SP - 116 J2 - BMC Research Notes LA - en OP - SN - 1756-0500 UR - http://dx.doi.org/10.1186/1756-0500-5-116 DB - Crossref ER - TY - CONF TI - Research for Transporting Alpha ISA and Adopting Multi-processor to FabScalar AU - Nakabayashi, T. AU - Sasaki, T. AU - Rotenberg, E. AU - Ohno, K. AU - Kondo, T. C2 - 2012/5// C3 - Proceedings of the Symposium on Advanced Computing Systems and Infrastructures 2012 (SACSIS 2012) DA - 2012/5// SP - 374–381 ER - TY - JOUR TI - Micro-Grid Tie-line Power Smoothing using Demand Response Program AU - Wang, Chenshan AU - Liu, Mengxuan AU - Lu, N. T2 - Proceedings of the CSEE DA - 2012/// PY - 2012/// VL - 25 IS - 32 SP - 36–43 ER - TY - CHAP TI - Electroconductive Nanocomposite Scaffolds: A New Strategy Into Tissue Engineering and Regenerative Medicine AU - Mozafari, Masoud AU - Mehraien, Mehrnoush AU - Vashaee, Daryoosh AU - Tayebi, Lobat T2 - Nanocomposites - New Trends and Developments PY - 2012/9/27/ DO - 10.5772/51058 OP - PB - InTech SN - 9789535107620 UR - http://dx.doi.org/10.5772/51058 DB - Crossref ER - TY - JOUR TI - Effects of heat treatment on physical, microstructural and optical characteristics of PbS luminescent nanocrystals AU - Mozafari, Masoud AU - Moztarzadeh, Fathollah AU - Vashaee, Dayoosh AU - Tayebi, Lobat T2 - Physica E: Low-dimensional Systems and Nanostructures AB - Abstract The oxidation of lead sulfide (PbS) luminescent nanocrystals (NCs) considerably changes their luminescence characteristics. Hence, an understanding of the oxidation mechanism, the structure and properties of oxidized moieties is important. In this research, well-defined spherical PbS NCs were synthesized via a simple, effective and surfactant-free method and characterized. Then, the effects of heat treatment (at 250, 350, 450 and 550 °C) on the PbS NCs were investigated. The transmission electron microscope (TEM) micrographs of the synthesized PbS NCs revealed that they had a well-defined spherical morphology. In addition, the average crystallite size using Scherrer's formula was about 13 nm and the calculated lattice constant using Bragg's equation was 0.5950 nm, which was very close to the value in the standard card (JCPDS No. 5-592). Furthermore, the X-ray diffraction (XRD) revealed that the heat treatment of samples at temperatures of 250, 350,450 and 550 °C in air results in the formation of oxide sulfate phase of the compositions PbSO4 and PbO·PbSO4. The lattice parameter, crystallite size, average internal stress, micro-strain and optical properties of PbS NCs were calculated and correlated with the heat-treatment temperature. DA - 2012/4// PY - 2012/4// DO - 10.1016/j.physe.2012.03.006 VL - 44 IS - 7-8 SP - 1429-1435 J2 - Physica E: Low-dimensional Systems and Nanostructures LA - en OP - SN - 1386-9477 UR - http://dx.doi.org/10.1016/j.physe.2012.03.006 DB - Crossref ER - TY - JOUR TI - Structural Configuration of Myelin Figures Using Fluorescence Microscopy AU - Tayebi, Lobat AU - Mozafari, Masoud AU - Vashaee, Daryoosh AU - Parikh, Atul N. T2 - International Journal of Photoenergy AB - Using epifluorescence microscopy, the configuration of myelin figures that are formed upon hydration of lipid stack was studied qualitatively. Little knowledge is currently available for conditions that determine the diameter of myelin figures and their degree of multilamellarity. Examining more than 300 samples, we realized that there are distinct populations of myelin figures protruding from discrete regions of lipid stack. Each population contains myelin figures with similar diameters. This indicates a direct relationship between local characteristics of parent lipid stack and the diameter of myelin figures. Evidenced by fluorescent images, we classified all the observed myelin figures into three major groups of (1) solid tubes, (2) thin tethers, and (3) hollow tubes. Solid tubes are the most common structure of myelin figures which appeared as dense shiny cylinders. Thin tethers, with long hair-shaped structure, were observed protruding from part of lipid plaque which is likely to be under tension. Hollow tubes were protruded from the parts that are unpinned from the substrate and possibly under low or no tension. The abrupt change in the configuration of myelin figures from solid tubes to hollow ones was described in a reproducible experiment where the pinned region of the parent stack became unpinned. Our observations can indicate a relation between the membrane tension of the source material and the diameter of the myelin figures. DA - 2012/// PY - 2012/// DO - 10.1155/2012/685617 VL - 2012 SP - 1-7 J2 - International Journal of Photoenergy LA - en OP - SN - 1110-662X 1687-529X UR - http://dx.doi.org/10.1155/2012/685617 DB - Crossref ER - TY - JOUR TI - A critical stress model for cell motility AU - Mehrayin, Mehrnush AU - Farmanzad, Farhad AU - Mozafari, Masoud AU - Vashaee, Daryoosh AU - Tayebi, Lobat T2 - Theoretical Biology and Medical Modelling AB - Abstract A detailed theoretical model that combines the conventional viscoelastic continuum description of cell motion with a dynamic active stress is presented. The model describes the ameboid cells movement comprising of protrusion and adhesion of the front edge followed by detachment and movement of the tail. Unlike the previous viscoelastic descriptions in which the cell movement is steady, the presented model describes the “walking” of the cell in response to specific active stress components acting separately on the front and rear of the cell. In this locomotive model first the tail of the cell is attached to the substrate and active stress is applied to the front of the cell. Consequently, the stress in the tail increases. When the stress in the tail exceeds a critical value, namely critical stress, the conditions are updated so that the front is fixed and the tail of the cell is detached from the substrate and moves towards the front. Consequently, the stress in the tail decreases. When the stress goes to zero, the starting conditions become active and the process continues. At start the cell is stretched and its length is increased as the front of cell migrates more than the rear. However, after several steps the front and rear move equally and the cell length stays constant during the movement. In this manuscript we analyzed such cell dynamics including the length variation and moving velocity. Finally, by considering this fact that at the single-cell level, interactions with the extracellular environment occur on a nanometer length scale, the value of critical stress was estimated. DA - 2012/// PY - 2012/// DO - 10.1186/1742-4682-9-49 VL - 9 IS - 1 SP - 49 J2 - Theor Biol Med Model LA - en OP - SN - 1742-4682 UR - http://dx.doi.org/10.1186/1742-4682-9-49 DB - Crossref KW - Finite difference KW - Cell motility KW - Continuum model KW - Critical stress ER - TY - JOUR TI - Aqueous sol–gel synthesis of zirconium titanate (ZrTiO4) nanoparticles using chloride precursors AU - Salahinejad, E. AU - Hadianfard, M.J. AU - Macdonald, D.D. AU - Karimi, I. AU - Vashaee, D. AU - Tayebi, L. T2 - Ceramics International AB - Zirconium titanate powders were synthesized by a straightforward sol–gel method using zirconium and titanium chlorides as metal precursors, deionized water as solvent and oxygen donor, and a NaOH solution for adjusting pH to 7. According to transmission electron microscopy, amorphous particles of nearly 5 nm in size with a relatively spherical morphology were prepared. Thermogravimetry and differential scanning calorimetery analyses on the xerogel at a heating rate of 10 °C/min indicated a crystallization temperature of 690 °C, which is comparable with previous reports. Furthermore, via differential scanning calorimetery studies using the Kissinger's equation, the activation energy for ZrTiO4 crystallization was determined to be 850 kJ/mol. Structural evaluations in the isothermal regime, using X-ray diffraction experiments, implied the onset of ZrTiO4 crystallization at 550 °C. DA - 2012/12// PY - 2012/12// DO - 10.1016/j.ceramint.2012.04.064 VL - 38 IS - 8 SP - 6145-6149 J2 - Ceramics International LA - en OP - SN - 0272-8842 UR - http://dx.doi.org/10.1016/j.ceramint.2012.04.064 DB - Crossref KW - Sol-gel processes KW - X-ray methods KW - Thermal properties ER - TY - JOUR TI - Zirconium titanate thin film prepared by an aqueous particulate sol–gel spin coating process using carboxymethyl cellulose as dispersant AU - Salahinejad, E. AU - Hadianfard, M.J. AU - Macdonald, D.D. AU - Mozafari, M. AU - Vashaee, D. AU - Tayebi, L. T2 - Materials Letters AB - This paper deals with the preparation of ZrTiO4 thin film by a novel aqueous particulate sol–gel deposition method using carboxymethyl cellulose as dispersant. The structural characterization was performed by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. According to the results, the amorphous xerogel crystallizes to polycrystalline ZrTiO4 nanoparticles due to structural ordering conducted by calcination at 700 °C. A well-covering, crack-free, and homogeneous ZrTiO4 thin film was processed, which is attributable to the efficient role of the dispersing agent in the aqueous sol. It was also found that the outermost layer of the coating surface consists of nanoparticles with 20 nm in size. DA - 2012/12// PY - 2012/12// DO - 10.1016/j.matlet.2012.08.013 VL - 88 SP - 5-8 J2 - Materials Letters LA - en OP - SN - 0167-577X UR - http://dx.doi.org/10.1016/j.matlet.2012.08.013 DB - Crossref KW - Nanoparticles KW - Ceramics KW - Sol-gel preparation KW - Thin films ER - TY - JOUR TI - Modeling of Thermoelectric Properties of Magnesium Silicide (Mg2Si) AU - Satyala, Nikhil AU - Vashaee, Daryoosh T2 - Journal of Electronic Materials DA - 2012/3/27/ PY - 2012/3/27/ DO - 10.1007/s11664-012-2024-7 VL - 41 IS - 6 SP - 1785-1791 J2 - Journal of Elec Materi LA - en OP - SN - 0361-5235 1543-186X UR - http://dx.doi.org/10.1007/s11664-012-2024-7 DB - Crossref KW - Magnesium silicide KW - thermoelectric KW - modeling KW - Boltzmann equation KW - Debye model ER - TY - JOUR TI - Enhancement in thermoelectric power factor of polycrystalline Bi0.5Sb1.5Te3by crystallite alignment AU - Dehkordi, Arash Mehdizadeh AU - Vashaee, Daryoosh T2 - physica status solidi (a) AB - Abstract It is known that the random orientation of crystallites in polycrystalline Bi 0.5 Sb 1.5 Te 3 reduces its thermoelectric power factor. An efficient method for growing ordered bulk polycrystalline Bi 0.5 Sb 1.5 Te 3 was used and the enhancement of thermoelectric power factor was demonstrated. For comparison, samples with randomly and preferentially oriented crystallites were sintered from similar powder of Bi 0.5 Sb 1.5 Te 3 . A press process similar to extrusion was used to align the crystallites during the hot press. The crystallites alignment was verified by X‐ray diffraction (XRD) and scanning electron microscopy (SEM). The dominant orientation in the aligned sample was in c ‐plane (0,0,15). The aligned sample demonstrated significant increase in electrical conductivity while the Seebeck coefficient remained unchanged. As a result, the thermoelectric power factor of the aligned sample was improved by ∼50%. DA - 2012/7/25/ PY - 2012/7/25/ DO - 10.1002/pssa.201228147 VL - 209 IS - 11 SP - 2131-2134 J2 - Phys. Status Solidi A LA - en OP - SN - 1862-6300 UR - http://dx.doi.org/10.1002/pssa.201228147 DB - Crossref KW - bismuth antimony telluride KW - polycrystalline materials KW - thermoelectric power factor KW - thermoelectric properties ER - TY - JOUR TI - An Investigation of Electrical Contacts for Higher Manganese Silicide AU - Shi, Xinghua AU - Zamanipour, Zahra AU - Krasinski, Jerzy S. AU - Tree, Alan AU - Vashaee, Daryoosh T2 - Journal of Electronic Materials DA - 2012/6/27/ PY - 2012/6/27/ DO - 10.1007/s11664-012-2149-8 VL - 41 IS - 9 SP - 2331-2337 J2 - Journal of Elec Materi LA - en OP - SN - 0361-5235 1543-186X UR - http://dx.doi.org/10.1007/s11664-012-2149-8 DB - Crossref KW - Electrical contact KW - thermoelectric device KW - higher manganese silicide KW - MnSi KW - TiSi2 KW - thermal stability ER - TY - JOUR TI - The effect of synthesis parameters on transport properties of nanostructured bulk thermoelectric p-type silicon germanium alloy AU - Zamanipour, Zahra AU - Shi, Xinghua AU - Dehkordi, Arash M. AU - Krasinski, Jerzy S. AU - Vashaee, Daryoosh T2 - physica status solidi (a) AB - Abstract Nanostructured silicon germanium thermoelectric materials prepared by mechanical alloying and sintering method have recently shown large enhancement in figure‐of‐merit, ZT . The fabrication of these structures often involves many parameters whose understanding and precise control is required to attain large ZT . In order to find the optimum parameters for further enhancing the ZT of this material, we have grown and studied both experimentally and theoretically different nanostructured p‐type SiGe alloys. The effect of various parameters of milling process and sintering conditions on the thermoelectric properties of the grown samples were studied. The electrical and thermal properties were calculated using Boltzmann transport equation and were compared with the data of nanostructured and crystalline SiGe. It was found that the thermal conductivity not only depends on the average crystallite size in the bulk material, but also it is a strong function of alloying, porosity, and doping concentration. The Seebeck coefficient showed weak dependency on average crystallite size. The electrical conductivity changed strongly with synthesis parameters. Therefore, depending on the synthesis parameters the figure‐of‐merit reduced or increased by ∼60% compared with that of the crystalline SiGe. The model calculation showed that the lattice part of thermal conductivity in the nanostructured sample makes ∼80% of the total thermal conductivity. In addition, the model calculation showed that while the room temperature hole mean free path (MFP) in the nanostructured sample is dominated by the crystallite boundary scattering, at high temperature the MFP is dominated by acoustic phonon scattering. Therefore, the thermal conductivity can be further reduced by smaller crystallite size without significantly affecting the electrical conductivity in order to further enhance ZT . DA - 2012/6/26/ PY - 2012/6/26/ DO - 10.1002/pssa.201228102 VL - 209 IS - 10 SP - 2049-2058 J2 - Phys. Status Solidi A LA - en OP - SN - 1862-6300 UR - http://dx.doi.org/10.1002/pssa.201228102 DB - Crossref KW - synthesis parameters KW - thermal and electrical transport KW - thermoelectrics ER - TY - JOUR TI - Detrimental influence of nanostructuring on the thermoelectric properties of magnesium silicide AU - Satyala, Nikhil AU - Vashaee, Daryoosh T2 - Journal of Applied Physics AB - Nanostructuring techniques have steered the performance of many thermoelectric (TE) compounds towards significant improvement in performance in the last two decades. In this paper, we present a comprehensive study on the effect of bulk nanostructuring in magnesium silicide (Mg2Si) through simulation of thermoelectric properties using a multi-band semi-classical approach. It is shown that the magnitude of reduction in lattice thermal conductivity in nanostructured Mg2Si is comparable to that of reduction in charge carrier mobility for any chosen range of the grain sizes. The results are justified through a comparison with experimental data for both n-type and p-type Mg2Si characteristics versus temperature as well as doping concentration. In order to understand the underlying reasons for the detrimental effect of nanostructuring in Mg2Si, analogous calculations were performed on the well-known TE system of nanostructured Si0.8Ge0.2 and the results are compared. Model calculations show that in nanostructured Mg2Si a grain size of 20 nm results in approximately 40% reduction in lattice thermal conductivity, whereas the reduction in electrical conductivity is nearly 50% of its value in crystalline structures. For the case of nanostructured Si0.8Ge0.2, the loss in electrical conductivity was found to be a mere 20% of its magnitude in crystalline structures. The differential electrical and thermal conductivities versus charge carrier and phonon energies were calculated, respectively, and it was shown that the enhancement in Seebeck coefficient due to the energy filtering effect is also marginal. Therefore, it is conclusively shown that bulk nanostructuring in Mg2Si is not an efficient method to enhance ZT. DA - 2012/11// PY - 2012/11// DO - 10.1063/1.4764872 VL - 112 IS - 9 SP - 093716 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.4764872 DB - Crossref ER - TY - JOUR TI - Comparison of thermoelectric properties of p-type nanostructured bulk Si0.8Ge0.2 alloy with Si0.8Ge0.2 composites embedded with CrSi2 nano-inclusisons AU - Zamanipour, Zahra AU - Vashaee, Daryoosh T2 - Journal of Applied Physics AB - P-type nanostructured bulk Si0.8Ge0.2 and Si0.8Ge0.2 composites with CrSi2 nano-crystallite inclusions were synthesized via sintering approach. The composite structure showed power factor enhancement compared with nanostructured Si0.8Ge0.2 alloy. The experimental data for both structures were modeled with solving the multiband Boltzmann transport equation in the relaxation time approximation for charge carriers and phonons. The Si0.8Ge0.2 crystallite boundary scattering was modeled by a cylindrical potential barrier at the interfaces and the effects of CrSi2 nano-inclusions were modeled by spherical potential barriers in the Si0.8Ge0.2 lattice. The model calculations revealed that the enhancement in power factor is not an effect of hot carrier energy filtering, but it is due to the enhancement in charge carrier mobility in the composite structure. The analysis of charge carrier mobility components showed that while in nanostructured Si0.8Ge0.2 the ionize impurities and acoustic phonons are dominant scatterers, in the composite structure the scattering by CrSi2 nano-inclusions and acoustic phonons are dominant. The optimum size of the CrSi2 nano-inclusions for enhancing ZT was predicted with the characteristic that ZT drops rapidly when the crystallite size decreases, but it changes slowly as it is increased above its optimum value. DA - 2012/11// PY - 2012/11// DO - 10.1063/1.4764919 VL - 112 IS - 9 SP - 093714 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.4764919 DB - Crossref ER - TY - JOUR TI - The effect of crystallite size on thermoelectric properties of bulk nanostructured magnesium silicide (Mg2Si) compounds AU - Satyala, Nikhil AU - Vashaee, Daryoosh T2 - Applied Physics Letters AB - In nanostructured bulk materials, the additional interfaces in the material enhance phonon scattering and reduce the thermal conductivity. However, interfaces also scatter electrons and deteriorate charge carrier transport. In order to benefit from the interfacial effects, the crystallite size in the material must be small compared with phonon mean free path (PMFP) and large compared with the charge carrier mean free path (CMFP). In this paper, we solve the Boltzmann transport equation for charge carriers and phonons. We show that bulk nanostructuring of Mg2Si is not an efficient method to enhance the figure-of-merit as the PMFP and CMFP are in the same range. DA - 2012/2/13/ PY - 2012/2/13/ DO - 10.1063/1.3684615 VL - 100 IS - 7 SP - 073107 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.3684615 DB - Crossref ER - TY - JOUR TI - The effect of nanostructuring on thermoelectric transport properties of p-type higher manganese silicide MnSi1.73 AU - Norouzzadeh, Payam AU - Zamanipour, Zahra AU - Krasinski, Jerzy S. AU - Vashaee, Daryoosh T2 - Journal of Applied Physics AB - Higher manganese silicide (HMS) alloys have a complex band structure with multiple valleys close to the conduction and valence band edges, which complicates the analysis of their electronic transport properties. We present a semi-classical two-band model that can describe the charge carrier and phonon transport properties of p-type HMS in crystalline and bulk nanostructured forms. The effect of grain boundaries is modeled with an interface potential scattering for charge carriers and diffusive and refractive scattering for phonons. A unique set of effective masses and acoustic phonon deformation potentials are introduced that can explain both electrical and thermal transport properties versus temperature. The acoustic phonon and ionized impurity scatterings for charge carriers and phonon-phonon, point defect, and electronphonon scattering mechanisms for phonons are included in the model. The simplicity of the presented model would be valuable especially for practical purposes. The thermoelectric transport properties of nanostructured HMS were calculated versus grain size and it was shown that even though bulk nanostructuring of HMS enhances thermoelectric performance, it is not sufficient to enhance considerably the figure-of-merit. DA - 2012/12/15/ PY - 2012/12/15/ DO - 10.1063/1.4769884 VL - 112 IS - 12 SP - 124308 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.4769884 DB - Crossref ER - TY - JOUR TI - Long-range interlayer alignment of intralayer domains in stacked lipid bilayers AU - Tayebi, Lobat AU - Ma, Yicong AU - Vashaee, Daryoosh AU - Chen, Gang AU - Sinha, Sunil K. AU - Parikh, Atul N. T2 - Nature Materials DA - 2012/10/21/ PY - 2012/10/21/ DO - 10.1038/NMAT3451 VL - 11 IS - 12 SP - 1074-1080 J2 - Nature Mater LA - en OP - SN - 1476-1122 1476-4660 UR - http://dx.doi.org/10.1038/NMAT3451 DB - Crossref ER - TY - CONF TI - FPGA modeling of diverse superscalar processors AU - Dwiel, Brandon H. AU - Choudhary, Niket K. AU - Rotenberg, Eric T2 - 2012 IEEE International Symposium on Performance Analysis of Systems & Software (ISPASS) AB - There is increasing interest in using Field Programmable Gate Arrays (FPGAs) as platforms for computer architecture simulation. This paper is concerned with modeling superscalar processors with FPGAs. To be transformative, the FPGA modeling framework should meet three criteria. (1) Configurable: The framework should be able to model diverse superscalar processors, like a software model. In particular, it should be possible to vary superscalar parameters such as fetch, issue, and retire widths, depths of pipeline stages, queue sizes, etc. (2) Automatic: The framework should be able to automatically and efficiently map any one of its superscalar processor configurations to the FPGA. (3) Realistic: The framework should model a modern superscalar microarchitecture in detail, ideally with prototype quality, to enable a new era and depth of microarchitecture research. A framework that meets these three criteria will enjoy the convenience of a software model, the speed of an FPGA model, and the experience of a prototype. This paper describes FPGA-Sim, a configurable, automatically FPGA-synthesizable, and register-transfer-level (RTL) model of an out-of-order superscalar processor. FPGA-Sim enables FPGA modeling of diverse superscalar processors out-of-the-box. Moreover, its direct RTL implementation yields the fidelity of a hardware prototype. C2 - 2012/4// C3 - 2012 IEEE International Symposium on Performance Analysis of Systems & Software DA - 2012/4// DO - 10.1109/ispass.2012.6189225 PB - IEEE SN - 9781467311465 9781467311434 9781467311458 UR - http://dx.doi.org/10.1109/ispass.2012.6189225 DB - Crossref ER - TY - CONF TI - A physical design study of fabscalar-generated superscalar cores AU - Choudhary, Niket K. AU - Dwiel, Brandon H. AU - Rotenberg, Eric T2 - 2012 IEEE/IFIP 20th International Conference on VLSI and System-on-Chip (VLSI-SoC) AB - FabScalar is a recently published tool for automatically generating superscalar cores, of different pipeline widths, depths and sizes. The output of FabScalar is a synthesizable register-transfer-level (RTL) description of the desired core. While this capability makes sophisticated cores more accessible to designers and researchers, meaningful applications require reducing RTL descriptions to physical designs. This paper presents the first systematic physical design study of FabScalar-generated superscalar cores. C2 - 2012/10// C3 - 2012 IEEE/IFIP 20th International Conference on VLSI and System-on-Chip (VLSI-SoC) DA - 2012/10// DO - 10.1109/vlsi-soc.2012.7332095 PB - IEEE SN - 9781467326582 UR - http://dx.doi.org/10.1109/vlsi-soc.2012.7332095 DB - Crossref ER - TY - JOUR TI - Computational intelligence-based energy management for a large-scale PHEV/PEV enabled municipal parking deck AU - Su, Wencong AU - Chow, Mo-Yuen T2 - Applied Energy AB - There is a growing need to address the potential problems caused by the emergence of Plug-in Hybrid Electric Vehicles (PHEVs) and Plug-in Electric Vehicles (PEVs) within the next 10 years. In the near future, a large number of PHEVs/PEVs in our society will add a large-scale energy load to our power grids, as well as add substantial energy resources that can be utilized. The large penetration of these vehicles into the marketplace poses a potential threat to the existing power grid. The existing parking infrastructure is not ready for the large penetration of plug-in vehicles and the high demand of electricity. Nowadays, the advanced computational intelligence methods can be applied to solve large-scale optimization problems in a Smart Grid environment. In this paper, authors propose and implement a suite of computational intelligence-based algorithms (e.g., Estimation of Distribution Algorithm, Particle Swarm Optimization) for optimally managing a large number of PHEVs/PEVs charging at a municipal parking station. Authors characterize the performance of the proposed methods using a Matlab simulation, and compare it with other optimization techniques. DA - 2012/8// PY - 2012/8// DO - 10.1016/j.apenergy.2011.11.088 VL - 96 SP - 171-182 J2 - Applied Energy LA - en OP - SN - 0306-2619 UR - http://dx.doi.org/10.1016/j.apenergy.2011.11.088 DB - Crossref KW - Plug-in Hybrid Electric Vehicle (PHEV) KW - Plug-in Electric Vehicle (PEV) KW - Electric Vehicle (EV) KW - Smart Grid KW - Estimation of Distribution Algorithm (EDA) KW - Particle Swarm Optimization (PSO) ER - TY - JOUR TI - Optimal Tradeoff Between Performance and Security in Networked Control Systems Based on Coevolutionary Algorithms AU - Zeng, Wente AU - Chow, Mo-Yuen T2 - IEEE Transactions on Industrial Electronics AB - Networked control systems (NCS) have to be well protected with security mechanisms from malicious attackers on the network (e.g., Internet). However, the additional security mechanism might sacrifice the performance of the NCS due to limited system resources. This paper addresses the issue of the tradeoff between NCS security and the NCS real-time performance. Using a networked DC motor system as an example, a tradeoff model for performance and security on NCS is presented. This paper also presents a framework of performance-security tradeoff optimization based on coevolutionary genetic algorithm (CGA) for the networked DC motor system. Experiments show that CGA is highly efficient in finding the Nash equilibrium for the tradeoff model on NCS. The framework presented in this paper is also demonstrated to be an effective approach for performance-security tradeoff analysis and optimization on NCS. DA - 2012/7// PY - 2012/7// DO - 10.1109/tie.2011.2178216 VL - 59 IS - 7 SP - 3016-3025 J2 - IEEE Trans. Ind. Electron. OP - SN - 0278-0046 1557-9948 UR - http://dx.doi.org/10.1109/tie.2011.2178216 DB - Crossref KW - Coevolutionary genetic algorithm (CGA) KW - networked control systems (NCS) KW - networked DC motor system ER - TY - RPRT TI - Final Project Report Load Modeling Transmission Research AU - Lesieutre, Bernard AU - Bravo, Richard AU - Yinger, Robert AU - Chassin, Dave AU - Huang, Henry AU - Lu, Ning AU - Hiskens, Ian AU - Venkataramanan, Giri A3 - Office of Scientific and Technical Information (OSTI) AB - The research presented in this report primarily focuses on improving power system load models to better represent their impact on system behavior. The previous standard load model fails to capture the delayed voltage recovery events that are observed in the Southwest and elsewhere. These events are attributed to stalled air conditioner units after a fault. To gain a better understanding of their role in these events and to guide modeling efforts, typical air conditioner units were testing in laboratories. Using data obtained from these extensive tests, new load models were developed to match air conditioner behavior. An air conditioner model is incorporated in the new WECC composite load model. These models are used in dynamic studies of the West and can impact power transfer limits for California. Unit-level and systemlevel solutions are proposed as potential solutions to the delayed voltage recovery problem. DA - 2012/3/31/ PY - 2012/3/31/ DO - 10.2172/1183173 PB - Office of Scientific and Technical Information (OSTI) UR - http://dx.doi.org/10.2172/1183173 DB - Crossref ER - TY - BOOK TI - appliance commitment for household load scheduling AU - Du, Pengwei AU - Lu, Ning AU - Ieee, P. E. S. DA - 2012/// PY - 2012/// PB - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000317001100061&KeyUID=WOS:000317001100061 ER - TY - CHAP TI - The Potential of Thermostatically Controlled Appliances for Intra-hour Energy Storage Applicationst AU - Lu, Ning AU - Du, Pengwei AU - Makarov, Yuri V. AU - Ieee T2 - 2012 Ieee Power and Energy Society General Meeting PY - 2012/// SP - PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000312493703097&KeyUID=WOS:000312493703097 ER - TY - BOOK TI - Smart Meter Data Analysis AU - Lu, Ning AU - Du, Pengwei AU - Guo, Xinxin AU - Greitzer, Frank L. AU - Ieee, P. E. S. DA - 2012/// PY - 2012/// PB - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000317001100198&KeyUID=WOS:000317001100198 ER - TY - CHAP TI - Improving Performance of Power Systems with Large-scale Variable Generation Additions AU - Makarov, Yuri V. AU - Etingov, Pavel V. AU - Samaan, Nader A. AU - Lu, Ning AU - Ma, Jian AU - Subbarao, Krishnappa AU - Du, Pengwei AU - Kannberg, Landis D. AU - Ieee T2 - 2012 Ieee Power and Energy Society General Meeting PY - 2012/// SP - PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000312493705101&KeyUID=WOS:000312493705101 ER - TY - JOUR TI - An Evaluation of the HVAC Load Potential for Providing Load Balancing Service AU - Lu, Ning T2 - Ieee Transactions on Smart Grid AB - This paper investigates the potential of providing intra-hour load balancing services using aggregated heating, ventilating, and air-conditioning (HVAC) loads. A directload control algorithm is presented. A temperature-priority-list method is used to dispatch the HVAC loads optimally to maintain customer-desired indoor temperatures and load diversity. Realistic intra-hour load balancing signals are used to evaluate the operational characteristics of the HVAC load under different outdoor temperature profiles and different indoor temperature settings. The number of HVAC units needed is also investigated. Modeling results suggest that the number of HVAC units needed to provide a ±1-MW load balancing service 24 hours a day varies significantly with baseline settings, high and low temperature settings, and outdoor temperatures. The results demonstrate that the intra-hour load balancing service provided by HVAC loads meets the performance requirements and can become a major source of revenue for load-serving entities where the two-way communication smart grid infrastructure enables direct load control over the HVAC loads. DA - 2012/// PY - 2012/// DO - 10.1109/tsg.2012.2183649 VL - 3 IS - 3 SP - 1263-1270 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000325484500020&KeyUID=WOS:000325484500020 KW - Air conditioning KW - ancillary service KW - demand response KW - direct load control KW - HVAC KW - load balancing KW - load following KW - regulation service KW - renewable integration KW - smart grid KW - thermostatically controlled appliances ER - TY - CHAP TI - A Multi-layer, Data-driven Advanced Reasoning Tool for Intelligent Data Mining and Analysis for Smart Grids AU - Lu, Ning AU - Du, Pengwei AU - Greitzer, Frank L. AU - Guo, Xinxin AU - Hohimer, Ryan E. AU - Pomiak, Yekaterina G. AU - Ieee T2 - 2012 Ieee Power and Energy Society General Meeting PY - 2012/// SP - PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000312493704028&KeyUID=WOS:000312493704028 ER - TY - CONF TI - Wide-Area Damping Control of Power Systems Using Inversion Techniques: A TCSC-Based Model Reference Approach AU - Chakrabortty, A. C2 - 2012/// C3 - Proceedings of IEEE PES General Meeting CY - San Diego, CA DA - 2012/// ER - TY - CONF TI - Power efficient power amplifiers for 60GHz phased array transmitters AU - Sarkar, A. AU - Floyd, B. C2 - 2012/9// C3 - Proceedings SRC Techcon Conference DA - 2012/9// ER - TY - CONF TI - Pathfinder 3D: A flow for system-level design space exploration AU - Priyadarshi, S. AU - Hu, J. AU - Choi, W.H. AU - Melamed, S. AU - Chen, X. AU - Davis, W.R. AU - Franzon, P.D. T2 - 2011 IEEE International 3D Systems Integration Conference (3DIC) AB - Three dimensional integration technology has the potential to provide enhanced performance and device density gains beyond that available from technology scaling alone. However, it provides plethora of design choices for system designers. The full exploitation of the benefits of 3D integration requires a system-level exploration flow which can facilitate in finding an optimal 3D design by comparing possible early design choices. In this paper we present a flow for fast system-level exploration useful for path finding studies. The flow enables users to explore the tradeoff between different stacking and partitioning schemes in terms of performance, power, and temperature. We also present a free open source design kit compiler, FreePDK3D45 and a tool for fast floorplan evaluation of TSV-based digital architectures, Pathfinder3D. The open source design kit and architecture evaluator can help the community to research, learn and explore the various aspects of 3D integration. Using the proposed flow and design kit, we present a case study of 3D integration of a Network on Chip. This case study demonstrates system-level comparisons of the performance, power and temperature of different homogenously partitioned stacking schemes. C2 - 2012/1// C3 - 2011 IEEE International 3D Systems Integration Conference (3DIC), 2011 IEEE International CY - Osaka, Japan DA - 2012/1// PY - 2011/1/31/ DO - 10.1109/3dic.2012.6262961 PB - IEEE SN - 9781467321907 9781467321891 9781467321884 UR - http://dx.doi.org/10.1109/3dic.2012.6262961 DB - Crossref ER - TY - CONF TI - A novel double floating-gate unified memory device AU - Di Spigna, Neil AU - Schinke, Daniel AU - Jayanti, Srikant AU - Misra, Veena AU - Franzon, Paul T2 - 2012 IEEE/IFIP 20th International Conference on VLSI and System-on-Chip (VLSI-SoC) AB - A novel double floating-gate unified memory device is experimentally demonstrated for the first time. The device can be used to store both volatile and nonvolatile memory states simultaneously. Simulations of scaled devices show that the device offers several advantages compared to conventional memory devices. Such a device could have a dramatic impact on next generation memory architectures. C2 - 2012/10// C3 - 2012 IEEE/IFIP 20th International Conference on VLSI and System-on-Chip (VLSI-SoC) DA - 2012/10// DO - 10.1109/vlsi-soc.2012.7332076 PB - IEEE SN - 9781467326582 UR - http://dx.doi.org/10.1109/vlsi-soc.2012.7332076 DB - Crossref ER - TY - CONF TI - Coordinating 3D designs: Interface IP, standards or free form? AU - Franzon, P. D. AU - Davis, W. R. AU - Zhou, Zheng AU - Priyadarshi, S. AU - Hogan, M. AU - Karnik, T. AU - Srinavas, G. T2 - 2011 IEEE International 3D Systems Integration Conference (3DIC) AB - Three dimensional integration technology introduces new complexities to design and particularly codesign. Additional complexity is added when one considers that the design needs to be “future-proof”. How do you ensure that the 3D chip stack will work for future chips within the stack, whose parameters are yet to be fully anticipated. This paper proposes that this be managed through an Interface IP approach Design blocks with associated properties that not only supports signaling and power delivery but also constraints that must be managed between chips both during design but also in-situ and as part of physical verification. C2 - 2012/1// C3 - 2011 IEEE International 3D Systems Integration Conference (3DIC), 2011 IEEE International DA - 2012/1// DO - 10.1109/3dic.2012.6262960 PB - IEEE SN - 9781467321907 9781467321891 9781467321884 UR - http://dx.doi.org/10.1109/3dic.2012.6262960 DB - Crossref ER - TY - CONF TI - Photoacoustic imaging using a 9F microLinear CMUT ICE catheter AU - Nikoozadeh, Amin AU - Choe, Jung Woo AU - Kothapalli, Sri-Rajasekhar AU - Moini, Azadeh AU - Sanjani, Sahinaz S. AU - Kamaya, Aya AU - Oralkan, Omer AU - Gambhir, Sanjiv S. AU - Khuri-Yakub, Pierre T. T2 - 2012 IEEE International Ultrasonics Symposium AB - This work presents our preliminary results on developing a multi-modality imaging catheter enabling combined ultrasound and photoacoustic imaging. We have developed an optical fiber ring catheter for use with our previously demonstrated 9F, real-time, forward-looking intracardiac ultrasound imaging catheter. Our custom software provides realtime ultrasound and photoacoustic imaging on a PC-based imaging platform. The promising phantom and in vivo imaging results presented here demonstrate the utility of a fully integrated catheter that provides both anatomical and functional information through co-registered ultrasound and photoacoustic imaging capabilities. C2 - 2012/10// C3 - 2012 IEEE International Ultrasonics Symposium DA - 2012/10// DO - 10.1109/ultsym.2012.0007 PB - IEEE SN - 9781467345620 9781467345613 9781467345606 UR - http://dx.doi.org/10.1109/ultsym.2012.0007 DB - Crossref KW - photoacoustic KW - ultrasound KW - catheter KW - real-time KW - intracardiac echocardiography KW - forward-looking KW - capacitive micromachined ultrasonic transducers KW - CMUT ER - TY - CONF TI - Providing statistical QoS guarantees in large cognitive machine-to-machine networks AU - Lin, Shih-Chun AU - Gu, Lei AU - Chen, Kwang-Cheng T2 - 2012 IEEE Globecom Workshops (GC Wkshps) AB - Promising machine-to-machine (M2M) communication emerges to achieve ubiquitous communications among objects and the surrounding environment in everyday life. For a large M2M network to support scrupulous connections among abundant devices, sharing radio resource efficiently with the existing wireless networks while maintaining sufficient quality-of-service (QoS) for reliable communications becomes an essential and challenging requirement. Via social network analysis, we provide mathematical examination on network connectivity and network diameter. Upon such connected M2M networks, an opportunistic transmission protocol is proposed for spectrum-efficient communications by leveraging cognitive radio technology with cooperative communication. Specifically, the cognitive machines can autonomously sense the radio resource usage to mitigate interference and exploit opportunistic relay selection with lower link delay for packet transmissions. Under this protocol, analytical bound of end-to-end delay is derived and the corresponding QoS guaranteed throughput is examined for practical applications. Simulation results confirm that the proposed protocol successfully accommodates statistical QoS guarantees, to facilitate a new paradigm for dependable data transportation in large M2M communication networks. C2 - 2012/12// C3 - 2012 IEEE Globecom Workshops DA - 2012/12// DO - 10.1109/glocomw.2012.6477841 PB - IEEE SN - 9781467349413 9781467349420 9781467349406 UR - http://dx.doi.org/10.1109/glocomw.2012.6477841 DB - Crossref ER - TY - CONF TI - Wide-area damping control of power systems using clustering and FACTS-based redesigns AU - Chakrabortty, A. T2 - 2012 American Control Conference - ACC 2012 AB - In this paper we present a FACTS (Flexible AC Transmission Systems)-based control design for electromechanical oscillation damping in large power systems, facilitated by aggregate models that can be constructed using Synchronized phasor measurements. Our approach consists of three steps, namely - 1. Model Reduction, where Synchrophasors are used to identify second-order models of the oscillation clusters of the power system retaining the inter-ties on which FACTS devices such as Thyristor Controlled Series Compensators (TCSC) are installed, 2. Aggregate Control, where feedback controllers are designed to achieve a desired closed-loop transient response between every pair of clusters, and finally 3. Control Inversion, where the aggregate control design is distributed and tuned to actual TCSC controllers in the full-order model until its inter-area responses match the respective inter-machine responses of the reduced-order system. It is shown that the inversion problem can be posed equivalently as decomposing the swing dynamics into fast and slow states, and designing the controllers such that the slow dynamics can optimally track a desired closed-loop signal designed for the aggregate model. C2 - 2012/6// C3 - 2012 American Control Conference (ACC) DA - 2012/6// DO - 10.1109/acc.2012.6315533 PB - IEEE SN - 9781457710964 9781457710957 9781457710940 9781467321020 UR - http://dx.doi.org/10.1109/acc.2012.6315533 DB - Crossref ER - TY - CONF TI - Impact of wind farm placement on inter-area oscillations in large power systems AU - Gayme, D. F. AU - Chakrabortty, A. T2 - 2012 American Control Conference - ACC 2012 AB - This paper presents an analytical method for evaluating how the placement of wind farms in a large, geographically dispersed power system may affect its inter-area oscillation dynamics. We consider a continuum representation of the electro-mechanical swing dynamics for the power system leading to a linear hyperbolic wave equation for the rotor phase angle across the transfer path. The wind power is modeled as the output of a dynamic system entering the wave equation as a point source in space located at a certain electrical distance from one end of the path. We then derive the spectrum of the line power flow for this forced system using a Fourier analysis, and show how its frequency response, especially for the inter-area or low-frequency modes, is parameterized by this distance variable. We finally pose this parametric dependence as a planning problem in light of finding the optimal distance for placing the wind farm such that a specified set of inter-area modes are damped. We illustrate our results using simulations based on a two-area power system model inspired by US west coast transfer paths such as the Pacific AC Inter-tie. C2 - 2012/6// C3 - 2012 American Control Conference (ACC) DA - 2012/6// DO - 10.1109/acc.2012.6315617 PB - IEEE SN - 9781457710964 9781457710957 9781457710940 9781467321020 UR - http://dx.doi.org/10.1109/acc.2012.6315617 DB - Crossref ER - TY - CONF TI - Shaping power system inter-area oscillations through control loops of grid integrated wind farms AU - Gayme, Dennice F. AU - Chakrabortty, Aranya T2 - 2012 IEEE 51st Annual Conference on Decision and Control (CDC) AB - This paper presents a control design for shaping the inter-area oscillation spectrum of a large wind-integrated power system. The power system is modeled using a continuum representation of the electro-mechanical swing dynamics with the wind power entering as a spatial point source at a specific electrical distance along the transfer path. The frequency response, particularly that of inter-area oscillations, has previously been shown to be highly sensitive to this location. However, in many situations, it may not be possible to site a wind farm at the location with the most desirable frequency response. Here, we show that one can design a wind farm controller to shape the frequency response of the power system with a wind farm at an arbitrary location to closely resemble that of a system with a more favorable wind injection site. The results are illustrated using simulations based on power system models inspired by US west coast transfer paths such as the Pacific AC Inter-tie. C2 - 2012/12// C3 - 2012 IEEE 51st IEEE Conference on Decision and Control (CDC) DA - 2012/12// DO - 10.1109/cdc.2012.6426125 PB - IEEE SN - 9781467320665 9781467320658 9781467320634 9781467320641 UR - http://dx.doi.org/10.1109/cdc.2012.6426125 DB - Crossref ER - TY - CONF TI - Graph-theoretic model reduction of oscillation propagation in spatially distributed power system networks AU - Chakrabortty, Aranya AU - Khan, Taufiquar R. T2 - 2012 IEEE 51st Annual Conference on Decision and Control (CDC) AB - In this paper we consider continuum models of large distributed power systems defined over dynamic equivalent clusters, and derive a model reduction method to illustrate how oscillations can propagate from one cluster to another in the form of equivalent frequency waves depending on the topology of their interconnections. Previous results in [1], [2] have modeled such electromechanical waves mostly for two-area radial transfer paths (or, equivalently for a two-node line graph) by representing the swing dynamics in terms of partial differential equations (PDEs). Our results extend this approach to a network of areas connected by equivalent transfer paths, and defines an equivalent Sturm-Liouville eigenvalue equation for the entire network. We show that depending on the network topology the solutions of this eigenvalue problem can be significantly different from those for the individual paths. Simulation results for several representative power system network structures confirm our hypothesis. C2 - 2012/12// C3 - 2012 IEEE 51st IEEE Conference on Decision and Control (CDC) DA - 2012/12// DO - 10.1109/cdc.2012.6426348 PB - IEEE SN - 9781467320665 9781467320658 9781467320634 9781467320641 UR - http://dx.doi.org/10.1109/cdc.2012.6426348 DB - Crossref ER - TY - JOUR TI - Electronic and Structural Properties of Turbostratic Epitaxial Graphene on the 6H-SiC (000-1) Surface AU - Jayasekera, Thushari AU - Kim, K.W. AU - Nardelli, M. Buongiorno T2 - Materials Science Forum AB - We propose an atomistic model to study the interface properties of mis-oriented (turbostratic) epitaxial graphene on SiC (000-1) surface. Using calculations from first principles, we compare the energetics, and structural/electronic properties of AB and turbostratic stacking sequences within a model based on the Si adatom surface reconstruction. Our calculations show that the systems with AB and turbostratic sequences are very close in energy, demonstrating the possibility of the observation of Moire patterns in epitaxial graphene on the C-face of SiC. The two-dimensional electron gas behavior is preserved in the epitaxial turbostratic graphene systems. However, there are deviations from the ideal turbostratic epitaxial graphene. DA - 2012/5// PY - 2012/5// DO - 10.4028/www.scientific.net/MSF.717-720.595 VL - 717-720 SP - 595-600 J2 - MSF OP - SN - 1662-9752 UR - http://dx.doi.org/10.4028/www.scientific.net/MSF.717-720.595 DB - Crossref KW - epitaxial graphene KW - turbostratic KW - Moire patterns KW - SiC C-face ER - TY - JOUR TI - Ab initiothermal transport properties of nanostructures from density functional perturbation theory AU - Calzolari, Arrigo AU - Jayasekera, Thushari AU - Kim, Ki Wook AU - Nardelli, Marco Buongiorno T2 - Journal of Physics: Condensed Matter AB - We present a comprehensive first-principles study of the thermal transport properties of low-dimensional nanostructures such as polymers and nanowires. An approach is introduced where the phonon quantum conductance is computed from the combination of accurate plane-wave density functional theory electronic structure calculations, the evaluation of the interatomic force constants through density functional perturbation theory for lattice dynamics, and the calculation of transport properties by a real-space Green's function method based on the Landauer formalism. This approach is computationally very efficient, can be straightforwardly implemented as a post-processing step in a standard electronic structure calculation (Quantum ESPRESSO and WanT in the present implementation), and allows us to directly link the thermal transport properties of a device to the coupling, dimensionality, and atomistic structure of the system. It provides invaluable insight into the mechanisms that govern heat flow at the nanoscale and paves the way to the fundamental understanding of phonon engineering in nanostructures. DA - 2012/11/20/ PY - 2012/11/20/ DO - 10.1088/0953-8984/24/49/492204 VL - 24 IS - 49 SP - 492204 J2 - J. Phys.: Condens. Matter OP - SN - 0953-8984 1361-648X UR - http://dx.doi.org/10.1088/0953-8984/24/49/492204 DB - Crossref ER - TY - JOUR TI - Publisher’s Note: “Charge transfer equilibria in ambient-exposed epitaxial graphene on (0001¯) 6 H-SiC” [J. Appl. Phys. 111, 113706 (2012)] AU - Sidorov, Anton N. AU - Gaskill, Kurt AU - Buongiorno Nardelli, Marco AU - Tedesco, Joseph L. AU - Myers-Ward, Rachel L. AU - Eddy, Charles R., Jr. AU - Jayasekera, Thushari AU - Wook Kim, Ki AU - Jayasingha, Ruwantha AU - Sherehiy, Andriy AU - Stallard, Robert AU - Sumanasekera, Gamini U. T2 - Journal of Applied Physics AB - First Page DA - 2012/7/15/ PY - 2012/7/15/ DO - 10.1063/1.4742134 VL - 112 IS - 2 SP - 029908 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.4742134 DB - Crossref ER - TY - CONF TI - Performance assessment Of CMUTs in dual modality imaging/HIFU applications AU - Meynier, Cyril AU - Yanamer, Yalcin AU - Canney, Michael AU - Nguyen-Dinh, An AU - Carpentier, Alexandre AU - Chapelon, Jean-Yves T2 - 2012 IEEE International Ultrasonics Symposium AB - In this paper, multi-element arrays based on cMUT and piezoelectric technologies, using the same geometry, have been realized. The first part of the paper is focused on comparing both in terms of imaging performances. The CMUT is shown to be lower in sensivity but better in terms of bandwidth and resolution. The second part of the paper investigates the ability of the CMUT array for HIFU applications. The dual imaging-HIFU capability of the cMUT array is demonstrated. This is a new feature of the CMUT technology, as piezoelectric transducers are designed with a trade-off between bandwidth and transduction efficiency. C2 - 2012/10// C3 - 2012 IEEE International Ultrasonics Symposium DA - 2012/10// DO - 10.1109/ultsym.2012.0020 PB - IEEE SN - 9781467345620 9781467345613 9781467345606 UR - http://dx.doi.org/10.1109/ultsym.2012.0020 DB - Crossref KW - cMUT KW - transducer KW - HIFU KW - ultrasound imaging ER - TY - JOUR TI - High-power CMUTs: design and experimental verification AU - Yamaner, F. Yalcin AU - Olcum, Selim AU - Oguz, H. Kagan AU - Bozkurt, Ayhan AU - Koymen, Hayrettin AU - Atalar, Abdullah T2 - IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control AB - Capacitive micromachined ultrasonic transducers (CMUTs) have great potential to compete with piezoelectric transducers in high-power applications. As the output pressures increase, nonlinearity of CMUT must be reconsidered and optimization is required to reduce harmonic distortions. In this paper, we describe a design approach in which uncollapsed CMUT array elements are sized so as to operate at the maximum radiation impedance and have gap heights such that the generated electrostatic force can sustain a plate displacement with full swing at the given drive amplitude. The proposed design enables high output pressures and low harmonic distortions at the output. An equivalent circuit model of the array is used that accurately simulates the uncollapsed mode of operation. The model facilities the design of CMUT parameters for high-pressure output, without the intensive need for computationally involved FEM tools. The optimized design requires a relatively thick plate compared with a conventional CMUT plate. Thus, we used a silicon wafer as the CMUT plate. The fabrication process involves an anodic bonding process for bonding the silicon plate with the glass substrate. To eliminate the bias voltage, which may cause charging problems, the CMUT array is driven with large continuous wave signals at half of the resonant frequency. The fabricated arrays are tested in an oil tank by applying a 125-V peak 5-cycle burst sinusoidal signal at 1.44 MHz. The applied voltage is increased until the plate is about to touch the bottom electrode to get the maximum peak displacement. The observed pressure is about 1.8 MPa with-28 dBc second harmonic at the surface of the array. DA - 2012/6// PY - 2012/6// DO - 10.1109/tuffc.2012.2318 VL - 59 IS - 6 SP - 1276-1284 J2 - IEEE Trans. Ultrason., Ferroelect., Freq. Contr. OP - SN - 0885-3010 UR - http://dx.doi.org/10.1109/tuffc.2012.2318 DB - Crossref ER - TY - JOUR TI - Demystifying Surrogate Modeling for Circuits and Systems AU - Yelten, M. B. AU - Zhu, Ting AU - Koziel, S. AU - Franzon, P. D. AU - Steer, M. B. T2 - IEEE Circuits and Systems Magazine AB - In this article, grey-box and black-box surrogate modeling are described, with some key findings. The important point is that surrogate modeling has a solid mathematical basis leading to what has become a dramatic increase in our ability to develop engineering models and to engineer systems. In Section 2, a systematic approach to constructing surrogate models is provided. Each step is explained using published methods. Section 3 presents surrogate modeling examples from the domain of circuits and systems. DA - 2012/// PY - 2012/// DO - 10.1109/mcas.2011.2181095 VL - 12 IS - 1 SP - 45-63 J2 - IEEE Circuits Syst. Mag. OP - SN - 1531-636X UR - http://dx.doi.org/10.1109/mcas.2011.2181095 DB - Crossref ER - TY - JOUR TI - First In Vivo Use of a Capacitive Micromachined Ultrasound Transducer Array-Based Imaging and Ablation Catheter AU - Stephens, Douglas N. AU - Truong, Uyen T. AU - Nikoozadeh, Amin AU - Oralkan, Ömer AU - Seo, Chi Hyung AU - Cannata, Jonathan AU - Dentinger, Aaron AU - Thomenius, Kai AU - de la Rama, Alan AU - Nguyen, Tho AU - Lin, Feng AU - Khuri-Yakub, Pierre AU - Mahajan, Aman AU - Shivkumar, Kalyanam AU - O'Donnell, Matt AU - Sahn, David J. T2 - Journal of Ultrasound in Medicine AB - Objectives The primary objective was to test in vivo for the first time the general operation of a new multifunctional intracardiac echocardiography (ICE) catheter constructed with a microlinear capacitive micromachined ultrasound transducer (ML‐CMUT) imaging array. Secondarily, we examined the compatibility of this catheter with electroanatomic mapping (EAM) guidance and also as a radiofrequency ablation (RFA) catheter. Preliminary thermal strain imaging (TSI)‐derived temperature data were obtained from within the endocardium simultaneously during RFA to show the feasibility of direct ablation guidance procedures. Methods The new 9F forward‐looking ICE catheter was constructed with 3 complementary technologies: a CMUT imaging array with a custom electronic array buffer, catheter surface electrodes for EAM guidance, and a special ablation tip, that permits simultaneous TSI and RFA. In vivo imaging studies of 5 anesthetized porcine models with 5 CMUT catheters were performed. Results The ML‐CMUT ICE catheter provided high‐resolution real‐time wideband 2‐dimensional (2D) images at greater than 8 MHz and is capable of both RFA and EAM guidance. Although the 24‐element array aperture dimension is only 1.5 mm, the imaging depth of penetration is greater than 30 mm. The specially designed ultrasound‐compatible metalized plastic tip allowed simultaneous imaging during ablation and direct acquisition of TSI data for tissue ablation temperatures. Postprocessing analysis showed a first‐order correlation between TSI and temperature, permitting early development temperature‐time relationships at specific myocardial ablation sites. Conclusions Multifunctional forward‐looking ML‐CMUT ICE catheters, with simultaneous intracardiac guidance, ultrasound imaging, and RFA, may offer a new means to improve interventional ablation procedures. DA - 2012/2// PY - 2012/2// DO - 10.7863/jum.2012.31.2.247 VL - 31 IS - 2 SP - 247-256 LA - en OP - SN - 0278-4297 UR - http://dx.doi.org/10.7863/jum.2012.31.2.247 DB - Crossref KW - ablation KW - capacitive micromachined ultrasound transducer KW - electroanatomic mapping KW - electrophysiology KW - intracardiac echocardiography KW - intracardiac imaging KW - microelectromechanical system KW - thermal strain ER - TY - JOUR TI - Deep Tissue Photoacoustic Imaging Using a Miniaturized 2-D Capacitive Micromachined Ultrasonic Transducer Array AU - Kothapalli, S. AU - Ma, Te-Jen AU - Vaithilingam, S. AU - Oralkan, O. AU - Khuri-Yakub, B. T. AU - Gambhir, S. S. T2 - IEEE Transactions on Biomedical Engineering AB - In this paper, we demonstrate 3-D photoacoustic imaging (PAI) of light absorbing objects embedded as deep as 5 cm inside strong optically scattering phantoms using a miniaturized (4 mm × 4 mm × 500 μm), 2-D capacitive micromachined ultrasonic transducer (CMUT) array of 16 × 16 elements with a center frequency of 5.5 MHz. Two-dimensional tomographic images and 3-D volumetric images of the objects placed at different depths are presented. In addition, we studied the sensitivity of CMUT-based PAI to the concentration of indocyanine green dye at 5 cm depth inside the phantom. Under optimized experimental conditions, the objects at 5 cm depth can be imaged with SNR of about 35 dB and a spatial resolution of approximately 500 μm. Results demonstrate that CMUTs with integrated front-end amplifier circuits are an attractive choice for achieving relatively high depth sensitivity for PAI. DA - 2012/5// PY - 2012/5// DO - 10.1109/tbme.2012.2183593 VL - 59 IS - 5 SP - 1199-1204 J2 - IEEE Trans. Biomed. Eng. OP - SN - 0018-9294 1558-2531 UR - http://dx.doi.org/10.1109/tbme.2012.2183593 DB - Crossref KW - Capacitive micromachined ultrasound transducer (CMUT) array KW - deep tissue imaging KW - optoacoustic KW - photoacoustic ER - TY - JOUR TI - Volumetric real-time imaging using a CMUT ring array AU - Choe, Jung Woo AU - Oralkan, Omer AU - Nikoozadeh, Amin AU - Gencel, Mustafa AU - Stephens, Douglas N. AU - O'Donnell, Matthew AU - Sahn, David J. AU - Khuri-Yakub, Butrus T. T2 - IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control AB - A ring array provides a very suitable geometry for forward-looking volumetric intracardiac and intravascular ultrasound imaging. We fabricated an annular 64-element capacitive micromachined ultrasonic transducer (CMUT) array featuring a 10-MHz operating frequency and a 1.27-mm outer radius. A custom software suite was developed to run on a PC-based imaging system for real-time imaging using this device. This paper presents simulated and experimental imaging results for the described CMUT ring array. Three different imaging methods--flash, classic phased array (CPA), and synthetic phased array (SPA)--were used in the study. For SPA imaging, two techniques to improve the image quality--Hadamard coding and aperture weighting--were also applied. The results show that SPA with Hadamard coding and aperture weighting is a good option for ring-array imaging. Compared with CPA, it achieves better image resolution and comparable signal-to-noise ratio at a much faster image acquisition rate. Using this method, a fast frame rate of up to 463 volumes per second is achievable if limited only by the ultrasound time of flight; with the described system we reconstructed three cross-sectional images in real-time at 10 frames per second, which was limited by the computation time in synthetic beamforming. DA - 2012/6// PY - 2012/6// DO - 10.1109/tuffc.2012.2310 VL - 59 IS - 6 SP - 1201-1211 J2 - IEEE Trans. Ultrason., Ferroelect., Freq. Contr. OP - SN - 0885-3010 UR - http://dx.doi.org/10.1109/tuffc.2012.2310 DB - Crossref ER - TY - JOUR TI - Wide-Area Damping Control of Power Systems Using Dynamic Clustering and TCSC-Based Redesigns AU - Chakrabortty, Aranya T2 - IEEE Transactions on Smart Grid AB - In this paper we present a FACTS (Flexible AC Transmission Systems)-based control design for electromechanical oscillation damping in large power systems, facilitated by aggregate models that can be constructed using Synchronized phasor measurements. Our approach consists of three steps, namely-1. Model Reduction, where Synchrophasors are used to identify second-order models of the oscillation clusters of the power system retaining the inter-ties on which FACTS devices such as Thyristor Controlled Series Compensators (TCSC) are installed, 2. Aggregate Control, where feedback controllers are designed to achieve a desired closed-loop transient response between every pair of clusters, and finally 3. Control Inversion, where the aggregate control design is distributed and tuned to actual TCSC controllers in the full-order model until its inter-area responses match the respective inter-machine responses of the reduced-order system. It is shown that the inversion problem can be posed equivalently as decomposing the swing dynamics into fast and slow states, and designing the controllers such that the slow dynamics can optimally track a desired closed-loop signal designed for the aggregate model. Application of the approach to two-area power systems is demonstrated through topological examples inspired by the US west coast grid. DA - 2012/9// PY - 2012/9// DO - 10.1109/tsg.2012.2197029 VL - 3 IS - 3 SP - 1503-1514 J2 - IEEE Trans. Smart Grid OP - SN - 1949-3053 1949-3061 UR - http://dx.doi.org/10.1109/tsg.2012.2197029 DB - Crossref KW - Damping control KW - model reduction KW - model reference control KW - power systems KW - swing equation ER - TY - CONF TI - Small-signal analysis and modeling of the Dual Active Half Bridge converter AU - Wang, Mengqi AU - Du, Yu AU - Lukic, Srdjan AU - Huang, Alex Q T2 - IEEE C2 - 2012/// C3 - 2012 Twenty-Seventh Annual IEEE Applied Power Electronics Conference and Exposition (APEC) DA - 2012/// SP - 1833-1837 ER - TY - JOUR TI - Single-Phase Electronics-Modulation Technique to Reverse Power Flow for the Isolated Series Resonant DC-DC CorTverter With Clamped Capacitor Voltage AU - Du, Y AU - Lukic, SM AU - Jacobson, BS AU - Huang, AQ T2 - IEEE Transactions on Industrial Electronics DA - 2012/// PY - 2012/// VL - 59 IS - 12 SP - 4617 ER - TY - JOUR TI - On integration of solid-state transformer with zonal DC microgrid AU - She, Xu AU - Huang, Alex Q AU - Lukic, Srdjan AU - Baran, Mesut E T2 - IEEE Transactions on Smart Grid DA - 2012/// PY - 2012/// VL - 3 IS - 2 SP - 975-985 ER - TY - JOUR TI - Framework and topology for active tuning of parallel compensated receivers in power transfer systems AU - Pantic, Zeljko AU - Lukic, Srdjan M T2 - IEEE Transactions on Power Electronics DA - 2012/// PY - 2012/// VL - 27 IS - 11 SP - 4503-4513 ER - TY - CONF TI - Dynamic programming technique in hybrid electric vehicle optimization AU - Wang, Rui AU - Lukic, Srdjan M T2 - IEEE C2 - 2012/// C3 - 2012 IEEE International Electric Vehicle Conference DA - 2012/// SP - 1-8 ER - TY - CONF TI - Control strategy of fuel cell hybrid electric vehicle based on driving cycle recognition AU - Ravey, Alexandre AU - Blunier, Benjamin AU - Lukic, Srdjan AU - Miraoui, Abdellatif T2 - IEEE C2 - 2012/// C3 - 2012 IEEE Transportation Electrification Conference and Expo (ITEC) DA - 2012/// SP - 1-5 ER - TY - CONF TI - Reducing Migration-induced Cache Misses AU - Reza, Sajjid AU - Byrd, Gregory T. AB - In a large multiprocessor server platform, using multicore chips, the scheduler often migrates a scheduling entity, i.e. a thread or process or virtual machine, in order to achieve better load balancing or ensure fairness. The migration impact is likely to be more severe in virtualized environments, where high over-subscription of logical CPUs is very common for server consolidation workloads or virtual desktop infrastructure deployment. We demonstrate the performance benefit of saving and restoring cached data during migration. In particular, we measure the efficiency (benefit per cache block) of saving various subsets of the cached data, in order to balance implementation cost and complexity with improvements in cycle time. We also describe an implementation that moves cached data when a thread migrates, and we show the benefits in terms of reduced misses and reduced processor cycles. C2 - 2012/5// C3 - 2012 IEEE 26th International Parallel and Distributed Processing Symposium Workshops & PhD Forum DA - 2012/5// DO - 10.1109/ipdpsw.2012.215 SP - 1732-1741 PB - IEEE UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84867430979&partnerID=MN8TOARS KW - caches KW - multiprocessors KW - process migration ER - TY - CONF TI - Wireless orientation sensing using magnetoquasistatic fields and complex image theory AU - Arumugam, D.D. AU - Griffin, J.D. AU - Stancil, D.D. AU - Ricketts, D.S. AB - In this paper we report on a magnetoquasistatic orientation sensor that uses the magnetoquasistatic coupling between an electrically small emitting loop (magnetic dipole) and seven vertical receiving loops located on a circle of radius 12.19 m to determine the orientation of an object. By inverting the theoretical expression for the coupling between the emitter and receivers and using complex image theory, we are able to estimate the azimuthal orientation, φ, and inclination orientation, θ, of the emitter from the received fields. We achieved an average error of 5.93° and 10.66°, respectively, and a median error of 4.08° and 8.68°, respectively. C2 - 2012/// C3 - RWW 2012 - Proceedings: IEEE Radio and Wireless Symposium, RWS 2012 DA - 2012/// DO - 10.1109/RWS.2012.6175362 SP - 251-254 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84860659293&partnerID=MN8TOARS ER - TY - CONF TI - Experimental study on the effects of groups of people on magnetoquasistatic positioning accuracy AU - Arumugam, D.D. AU - Griffin, J.D. AU - Stancil, D.D. AU - Ricketts, D.S. AB - Position and orientation measurements have been demonstrated, recently, using low-frequency magnetoquasistatic fields and complex image theory for distances up to 50 m [1]. The key motivation for using magnetoquasistatic fields is to enable accurate estimation of an object's position and orientation when near weakly conducting dielectric obstacles, e.g., groups of people. An example application is tracking an American football during game-play [1]. In this paper, we present measurements using the magnetoquasistatic technique to show that the presence of a large group of 25 people introduces a peak distance error of less than 4.5 cm for an emitter-receiver distance of 10 m. C2 - 2012/// C3 - IEEE Antennas and Propagation Society, AP-S International Symposium (Digest) DA - 2012/// DO - 10.1109/APS.2012.6349385 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870566632&partnerID=MN8TOARS ER - TY - JOUR TI - Demonstration of communication using neutrinos AU - Stancil, D.D. AU - Adamson, P. AU - Alania, M. AU - Aliaga, L. AU - Andrews, M. AU - Del Castillo, C.A. AU - Bagby, L. AU - Bazo Alba, J.L. AU - Bodek, A. AU - Boehnlein, D. AU - Bradford, R. AU - Brooks, W.K. AU - Budd, H. AU - Butkevich, A. AU - Caicedo, D.A.M. AU - Capista, D.P. AU - Castromonte, C.M. AU - Chamorro, A. AU - Charlton, E. AU - Christy, M.E. AU - Chvojka, J. AU - Conrow, P.D. AU - Danko, I. AU - Day, M. AU - Devan, J. AU - Downey, J.M. AU - Dytman, S.A. AU - Eberly, B. AU - Fein, J.R. AU - Felix, J. AU - Fields, L. AU - Fiorentini, G.A. AU - Gago, A.M. AU - Gallagher, H. AU - Gran, R. AU - Grange, J. AU - Griffin, J. AU - Griffin, T. AU - Hahn, E. AU - Harris, D.A. AU - Higuera, A. AU - Hobbs, J.A. AU - Hoffman, C.M. AU - Hughes, B.L. AU - Hurtado, K. AU - Judd, A. AU - Kafka, T. AU - Kephart, K. AU - Kilmer, J. AU - Kordosky, M. AU - Kulagin, S.A. AU - Kuznetsov, V.A. AU - Lanari, M. AU - Le, T. AU - Lee, H. AU - Loiacono, L. AU - Maggi, G. AU - Maher, E. AU - Manly, S. AU - Mann, W.A. AU - Marshall, C.M. AU - McFarland, K.S. AU - Mislivec, A. AU - McGowan, A.M. AU - Morfín, J.G. AU - Da Motta, H. AU - Mousseau, J. AU - Nelson, J.K. AU - Niemiec-Gielata, J.A. AU - Ochoa, N. AU - Osmanov, B. AU - Osta, J. AU - Palomino, J.L. AU - Paradis, J.S. AU - Paolone, V. AU - Park, J. AU - PeÑa, C. AU - Perdue, G. AU - Pérez Lara, C.E. AU - Peterman, A.M. AU - Pla-Dalmau, A. AU - Pollock, B. AU - Prokoshin, F. AU - Ransome, R.D. AU - Ray, H. AU - Reyhan, M. AU - Rubinov, P. AU - Ruggiero, D. AU - Sands, O.S. AU - Schellman, H. AU - Schmitz, D.W. AU - Schulte, E.C. AU - Simon, C. AU - Solano Salinas, C.J. AU - Stefanski, R. AU - Stevens, R.G. AU - Tagg, N. AU - Takhistov, V. AU - Tice, B.G. AU - Tilden, R.N. AU - Vel?squez, J.P. AU - Vergalosova, I. AU - Voirin, J. AU - Walding, J. AU - Walker, B.J. AU - Walton, T. AU - Wolcott, J. AU - Wytock, T.P. AU - Zavala, G. AU - Zhang, D. AU - Zhu, L.Y. AU - Ziemer, B.P. T2 - Modern Physics Letters A AB - Beams of neutrinos have been proposed as a vehicle for communications under unusual circumstances, such as direct point-to-point global communication, communication with submarines, secure communications and interstellar communication. We report on the performance of a low-rate communications link established using the NuMI beam line and the MINERvA detector at Fermilab. The link achieved a decoded data rate of 0.1 bits/sec with a bit error rate of 1% over a distance of 1.035 km, including 240 m of earth. DA - 2012/// PY - 2012/// DO - 10.1142/S0217732312500770 VL - 27 IS - 12 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84859365414&partnerID=MN8TOARS KW - Neutrino KW - communication ER - TY - JOUR TI - Active negative inductor based on magnetic flux AU - Stancil, D.D. T2 - Progress In Electromagnetics Research C DA - 2012/// PY - 2012/// VL - 32 SP - 259-269 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84867155570&partnerID=MN8TOARS ER - TY - BOOK TI - Creating fast, responsive and energy-efficient embedded systems using the Renesas RL78 microcontroller AU - Dean, A. G. AU - Conrad, J. M. DA - 2012/// PY - 2012/// PB - Weston, Florida: Micrium Press ER - TY - BOOK TI - Control and Optimization Methods for Electric Smart Grids AU - Libraries, NC State University AB - Control and Optimization Methods for Electric Smart Grids brings together leading experts in power, control and communication systems, and consolidates some of the most promising recent research in sm DA - 2012/// PY - 2012/// DO - 10.1007/978-1-4614-1605-0 PB - New York: Springer SE - 1-371 ER - TY - CONF TI - Projects with a practical purpose: Creating successful team projects in a virtual environment AU - Pittman, B. C. C2 - 2012/// C3 - Inted2012: international technology, education and development conference DA - 2012/// SP - 3724-3727 ER - TY - CONF TI - The latency of gaining -reliability for message dissemination in vehicle-to-vehicle networks AU - Li, Y. J. AU - Wang, Wenye AU - Duel-Hallen, A. AB - In many Vehicular Ad-hoc Network applications, such as hazard warning and traffic coordination, the message dissemination in unreliable and highly mobile network environment is a key challenge. In order to understand the relationship between dissemination latency and reliability, we analyze the latency of gaining α-reliability that a node correctly receives a message with probability larger than α (0 < α< 1). Under a 1-Dimensional (1-D) network scenario with unreliable channel and constrained vehicle mobility, we derive the minimum latency of gaining almost sure α-reliability, denoted as t min (α). Besides dissemination reliability requirement α, t min (α) also depends on node's original distance from the source, node mobility, channel reliability, and traffic flow. Numerical analysis discloses several interesting insights that 1) t min (α) is dominated by the first attempt to send the message to a destination, 2) node mobility has little impact on t min (α) in emergency information dissemination, and 3) transmission range and node density greatly affect dissemination latency and reliability. C2 - 2012/// C3 - GLOBECOM 2012 - 2012 IEEE Global Communications Conference CY - Piscataway, NJ, USA DA - 2012/// DO - 10.1109/glocom.2012.6504004 SP - 5550 - 5 UR - http://dx.doi.org/10.1109/GLOCOM.2012.6504004 ER - TY - CONF TI - A decentralized ID algorithm for detecting slow-fast oscillations in power systems from overwhelming volumes of phasor data AU - Chakrabortty, Aranya AU - Michailidis, G. AU - Xin, Y. F. AB - As the number of sensors, namely Phasor Measurement Units or PMUs, in the US power transmission grid scales up into the thousands within the next few years, the current state-of-the-art centralized data processing architecture will no longer be sustainable, and decentralized algorithms must be developed instead. In this paper we propose such an algorithm for one of the most critical applications in power system monitoring- namely, modal decomposition of swing dynamics for detecting slow and fast oscillation modes in the system with evaluation of their respective damping factors. Given a multiple set of coherent generation clusters in the system, we first use data from all PMU sources to calculate the oscillatory modes, their damping and participation in a centralized fashion. Next, we categorize the PMUs into several disjoint sets, and use the data from each of these sets to evaluate the modal frequencies for the entire system individually, assuming that the network has a connected topology guaranteeing system observability. A global estimate for any specific eigenvalue of interest is then computed from the geometric mean of those obtained from the disjoint estimation, and analytical expressions are derived to indicate how this geometric mean, representing the `fused distributed solution' compares to the centralized solution. A discussion on how the output nodes in the network should be chosen appropriately contingent on the topological structure of the network, in order to minimize the error between the two estimates is also presented. We illustrate our results with prototype power system network models inspired by two well-known transfer paths in the US west coast grid. C2 - 2012/// C3 - 2012 ieee 51st annual conference on decision and control (cdc) DA - 2012/// DO - 10.1109/cdc.2012.6426669 SP - 5010–5015 ER - TY - CONF TI - Optimal volt/var control strategy for distribution system with multiple voltage regulating devices AU - Shen, Z. AU - Wang, Z. AU - Baran, Mesut AB - This paper studies the volt/var control strategy for smart distribution system by formulating and solving system optimization problems. In the study, solid state transformers (SST) are used for continuous var compensation, while voltage regulators (VR) are for voltage regulation. The objectives are to minimize total system power loss while maintaining voltages along the feeder within acceptable limits. A two step optimization volt/var control method for multiple, discrete/continuous mixed regulating device is introduced in this paper. Simulation results demonstrate that the proposed technique is able to achieve the objective efficiently. C2 - 2012/// C3 - 2012 ieee pes transmission and distribution conference and exposition (t&d) DA - 2012/// DO - 10.1109/tdc.2012.6281479 ER - TY - CONF TI - Graph-theoretic algorithms for PMU placement in power systems under measurement observability constraints AU - Anderson, J. E. AU - Chakrabortty, Aranya AB - In this paper we develop two graph-theoretic PMU placement algorithms for multi-area power system networks with the objective of identifying a dynamic equivalent model for the system. We first show that to derive the equivalent line parameters connecting the different areas we must have PMUs placed at the minimum vertex cover of the bipartite graphs formed between every pair of node-sets arising out of the boundary buses of the areas. Considering further that the number of tie-lines observable from any given PMU is constrained by an upper limit, we derive an algorithm to compute the sub-optimal minimum cover, first for a bipartite graph and then for any general topology. We illustrate our results using a IEEE 34-bus model. C2 - 2012/// C3 - 2012 IEEE Third International Conference on Smart Grid Communications (SmartGridComm) DA - 2012/// DO - 10.1109/smartgridcomm.2012.6486054 SP - 617–622 ER - TY - CONF TI - Evaluating the computation times of real-time algorithms for power system modeling and state prediction AU - Felder, J. AU - Chakrabortty, Aranya AB - This paper presents a comparative study of three real-time algorithms for power system model identification, parameter estimation and state prediction using real-time Phasor Measurement (PMU) data available from various selected nodes in a power system. Current modeling and state estimation algorithms in power control centers only use limited amount of data, leading to local observability. Our approach, on the other hand, is to use data from wide regions in the grid to gain insight on the global health of the system. The two main challenges for our approach are, therefore, the large size of the system and the large amount of measured data. Three specific algorithms, namely the Eigenvalue Realization Algorithm, linear least squares and state observer method, are used for this purpose. The first algorithm identifies the global system dynamics from PMU data in real-time, the second relaxes the identification problem as a parameter estimation problem, while the third generates estimate of the global state and, thereafter, computes the impulse response of a selected oscillation mode depending on the participation of that mode on the chosen output. The performance of these three methods is then compared in terms of their computational time delays and accuracy of prediction. C2 - 2012/// C3 - 2012 IEEE Third International Conference on Smart Grid Communications (SmartGridComm) DA - 2012/// DO - 10.1109/smartgridcomm.2012.6485956 SP - 37–42 ER - TY - CONF TI - Development of distributed grid intelligence platform for solid state transformer AU - Wang, F. AU - Lu, X. AU - Wang, Wenye AU - Huang, A. AB - This paper introduces the development of a platform intended as a distributed controller for grid intelligence (DGI) system at FREEDM Systems Center. This platform serves as both a hard real-time local converter controller and a communication node for distributed deployment of energy management schemes. One of the converter devices it controls is the solid state transformer (SST), one of the key elements to interface renewable energy sources into distribution system in FREEDM Center. Both the hardware design and software structure for SST control are presented in this paper. For the communication part, the Distributed Network Protocol (DNP) 3.0 is adopted to congregate multiple SSTs to balance local generation and demands in a coordinated manner. Experiment results are presented to show that this distributed platform has good performance. C2 - 2012/// C3 - 2012 IEEE Third International Conference on Smart Grid Communications (SmartGridComm) DA - 2012/// DO - 10.1109/smartgridcomm.2012.6486031 SP - 481–485 ER - TY - CONF TI - The dominance of poisson noise in color digital cameras AU - Trussell, H. J. AU - Zhang, R. C2 - 2012/// C3 - 2012 IEEE international conference on image processing (ICIP 2012) DA - 2012/// SP - 329-332 ER - TY - CONF TI - Novel power electronics overload and temperature rise and time interval prediction based on dynamic thermal modeling AU - Dutta, S. AU - Moghaddam, G. K. AU - Bhattacharya, S. AU - Gould, R. AB - In this digest an overload predicting algorithm is proposed based on the converter operating point and the thermal model of a 6.5 KV Silicon IGBT module. This algorithm can predict both the overload and the time interval for overload and hence can be used for thermal cycle performance evaluation for converters. C2 - 2012/// C3 - Proceedings of the ASME International Mechanical Engineering Congress and Exposition, 2011, vol 11 DA - 2012/// DO - 10.1115/imece2011-64048 SP - 809-813 ER - TY - CONF TI - Investigation of high performance heat sink characteristics in forced convection cooling of power electronic systems AU - Karimi-Moghaddam, G. AU - Rende, C. AU - Gould, R. D. AU - Bhattacharya, S. AB - This study presents the experimental performance of a high fin density heat sink for semiconductor power modules — such as IGBTs. As a case study a commercially available extruded heat sink has been chosen. By analyzing the steady-state maximum temperatures as well as various geometric orientations, Nusselt number correlations were found experimentally, which can be used to predict the performance of the heat sink. It was found that the experimental Nusselt number correlations can predict the performance of the heat sink to within a 10%. Furthermore, steady-state maximum temperature results showed that for low fan speeds (2 m/s–3 m/s), the device junction temperatures achieved a value no higher than 80°C, which is well below the junction temperature limit for 125°C for silicon power semiconductor devices. Furthermore, it was shown that for two heat sinks in series forced convection tests, gap spacing between the devices has a minimal effect on the overall performance. Also, a numerical simulation study using COMSOL Multiphysics simulation software to study flow and temperature fields has been conducted. These modeling results the thermal behavior of heat sink are validated by experimental measurements. C2 - 2012/// C3 - Proceedings of the ASME International Mechanical Engineering Congress and Exposition, 2011, vol 11 DA - 2012/// DO - 10.1115/imece2011-64318 SP - 815-821 ER - TY - CONF TI - S-parameter based multimode signaling AU - Yan, Z. AU - Won, C. Y. AU - Franzon, Paul AU - Aygun, K. AU - Braunisch, H. AB - As the demands for higher density of interconnects and denser packages are increasing, crosstalk is becoming more important in input/output (I/O) design. Multimode signaling has been investigated for crosstalk cancellation. This paper presents a new scattering parameter (S-parameter) based methodology for multimode signaling. The set of coder/decoder coefficients (CODEC) is obtained from the S-parameters of the whole channel, which makes the scheme more applicable for practical systems. The derived CODEC shows a 20 dB improvement in signal-to-noise ratio and 45% reduction of root mean square (RMS) jitter compared with single-ended signaling for a practical benchmark problem. C2 - 2012/// C3 - Ieee conference on electrical performance of electronic packaging and DA - 2012/// DO - 10.1109/epeps.2012.6457832 SP - 11–14 ER - TY - CONF TI - Near threshold RF-only analog to digital converter AU - Gadfort, P. AU - Franzon, Paul AB - This paper describes an analog-to-digital converter (ADC) capable of operating in a RF-only circuit topology. A major limitation to direct RF-powered sensors are the lack of analog circuits. The proposed architecture is comprised of a cross-coupled pair of inverters, which act as the comparator for the ADC. This setup has been simulated in IBMs 0.13 μm bulk CMOS process for a 3 bit analog-to-digital converter (ADC). At a RF supply voltage of 300 mV RMS and frequency 13.57 MHz, the ADC has a resolution of 20 mV and can resolve voltages ranging from -80 mV to 80 mV, and at a frequency of 915 MHz the ADC can resolve voltages ranging from -140 mV to 140 mV. In order to optimize the ADC operation, the sampling time has been adjusted to one-third of the evaluation time, to give the comparator enough time to complete the amplification. C2 - 2012/// C3 - 2012 IEEE subthreshold microelectronics conference (SUBVT) DA - 2012/// DO - 10.1109/subvt.2012.6404321 ER - TY - JOUR TI - Control-Flow Decoupling AU - Sheikh, Rami AU - Tuck, James AU - Rotenberg, Eric T2 - 2012 IEEE/ACM 45TH INTERNATIONAL SYMPOSIUM ON MICROARCHITECTURE (MICRO-45) AB - Mobile and PC/server class processor companies continue to roll out flagship core micro architectures that are faster than their predecessors. Meanwhile placing more cores on a chip coupled with constant supply voltage puts per-core energy consumption at a premium. Hence, the challenge is to find future micro architecture optimizations that not only increase performance but also conserve energy. Eliminating branch mispredictions -- which waste both time and energy -- is valuable in this respect. We first explore the control-flow landscape by characterizing mispredictions in four benchmark suites. We find that a third of mispredictions-per-1K-instructions (MPKI) come from what we call separable branches: branches with large control-dependent regions (not suitable for if-conversion), whose backward slices do not depend on their control-dependent instructions or have only a short dependence. We propose control-flow decoupling (CFD) to eradicate mispredictions of separable branches. The idea is to separate the loop containing the branch into two loops: the first contains only the branch's predicate computation and the second contains the branch and its control-dependent instructions. The first loop communicates branch outcomes to the second loop through an architectural queue. Micro architecturally, the queue resides in the fetch unit to drive timely, non-speculative fetching or skipping of successive dynamic instances of the control-dependent region. Either the programmer or compiler can transform a loop for CFD, and we evaluate both. On a micro architecture configured similar to Intel's Sandy Bridge core, CFD increases performance by up to 43%, and reduces energy consumption by up to 41%. Moreover, for some applications, CFD is a necessary catalyst for future complexity-effective large-window architectures to tolerate memory latency. DA - 2012/// PY - 2012/// DO - 10.1109/micro.2012.38 SP - 329-340 SN - 1072-4451 ER - TY - CONF TI - Comparison of TSV-based PDN-design effects using various stacking topology methods AU - Charles, G. AU - Franzon, Paul AB - In this study, we estimate, compare and analyze the PDN effects of four chip-stacking topologies. The chip-stacking topologies are: (1) F2B; (2) F2F; (3) B2F; and (4) B2B. The arrangement of various on-chip interconnect elements based on the chip-stacking topologies specific to the design of 3D IC-PDN, varies in impedance properties. To reduce the impedance effects NMOS decap unit cells are integrated into PDN system to suppress 3D-SSN. Conclusively, the results of the case study indicate B2F and F2B die stacking topologies results in lower impedance effects relative to F2F topology. C2 - 2012/// C3 - Ieee conference on electrical performance of electronic packaging and DA - 2012/// DO - 10.1109/epeps.2012.6457848 SP - 83–86 ER - TY - CONF TI - An analysis of subthreshold SRAM bitcells for operation in low power RF-only technologies AU - Ledford, J. AU - Gadfort, P. AU - Franzon, Paul AB - Current RFID systems rely on the RF transciever to transmit information and convert RF power to DC to operate any integrated digital circuits. Research investigating the application of RF signals directly on digital CMOS circuits without RF-DC conversion is an emerging area for RFID technologies. One crucial digital circuit for most RFID systems is memory, needed for storing operational instructions and sampled data. An in-depth study and comparison of subthreshold SRAM bitcells has been conducted to analyze how such memories will function in a subthreshold RF-only regime without the need for RF-DC conversion. Several SRAM cells were chosen for conversion into the RF-only family and measured against several metrics, including highest performance at lowest operating voltage, power consumption, and static noise margins (SNM). Including RF supply transistors, an 18-T subthreshold RF-only bitcell is proposed, capable of operating at a data rate of 100 kHz at VRF of 200mVRMS. C2 - 2012/// C3 - 2012 IEEE subthreshold microelectronics conference (SUBVT) DA - 2012/// DO - 10.1109/subvt.2012.6404316 ER - TY - JOUR TI - Surrogate Model-Based Self-Calibrated Design for Process and Temperature Compensation in Analog/RF Circuits AU - Zhu, T. AU - Steer, M. B. AU - Franzon, P. D. T2 - IEEE Design Test of Computers AB - Analog circuits designed in submicrometer nodes suffer from process variations, typically requiring calibration in order to center their performance parameters and to recover yield loss. This article presents a design flow to find appropriate tuning knob settings to compensate for different process variation scenarios. DA - 2012/12// PY - 2012/12// DO - 10.1109/mdt.2012.2220332 VL - 29 IS - 6 SP - 74-83 SN - 0740-7475 DB - IEEE Xplore ER - TY - CONF TI - Power management strategy for plug and play DC microgrid AU - Yu, X. W. AU - Wang, F. AU - Huang, A. Q. AB - DC microgrid is getting more and more attention as an effective and efficient solution to integrate different kinds of renewable energy storage and energy resources with DC loads. A typical DC microgrid envisioned for future DC powered residential homes is investigated in this paper, including distributed power management strategy design, plug and play function implementation, communication ports to monitor the system performance. In this power management strategy, each module in the system is in the distributed control and can be plugged and unplugged into the system without affecting the system performance. Furthermore, the communication ports guarantee all modules information can be sent to the control center to monitor the whole system information. C2 - 2012/// C3 - 2012 3rd ieee pes innovative smart grid technologies europe (isgt europe) DA - 2012/// DO - 10.1109/isgteurope.2012.6465882 ER - TY - JOUR TI - Comprehensive control framework for ensuring loading margin of power systems considering demand-side participation AU - Rabiee, A. AU - Parvania, M. AU - Vanouni, M. AU - Parniani, M. AU - Fotuhi-Firuzabad, M. T2 - IET GENERATION TRANSMISSION & DISTRIBUTION AB - This study presents a comprehensive control framework to ensure desired loading margin (LM) while minimising the corresponding control cost. The proposed framework is divided into corrective control (CC) and preventive control (PC) subproblems. The CC subproblem deals with the condition that a power system encounters voltage instability as a result of severe contingencies. This control is merely devised to restore system stability. The PC subproblem is brought up when the system operates in a stable region but its LM is insufficient. In this manner, the system-operating point is changed such that the desired LM is achieved. One of the features of the proposed methodology is to consider participation of demand-side resources as an effective control facility that reduces control costs considerably. Active and reactive redispatch of generating units and involuntary load curtailment (ILC) are employed along with voluntary demand-side participation as control facilities in CC and PC subproblems. The proposed control framework is examined through case studies conducted on the IEEE 14-bus and the IEEE 118-bus test systems. The results presented demonstrate the effectiveness and efficiency of the proposed framework. DA - 2012/12// PY - 2012/12// DO - 10.1049/iet-gtd.2011.0683 VL - 6 IS - 12 SP - 1189-1201 SN - 1751-8695 ER - TY - CONF TI - communication theory perspective on antenna selection for compact transceivers AU - Taluja, P. S. AU - Hughes, B. L. AB - Traditional antenna selection applied to MIMO systems ignores the presence of unselected (or inactive) antennas. However, compact arrays offer a unique advantage in that mutual coupling can be exploited to improve the system performance. Previous studies on selection with coupling have not considered the effects of the inactive-antenna terminations and lack detailed transceiver modeling. In this work, we present a communication-theoretic analysis and design of antenna selection systems for compact transceivers. We also propose a simple parasitic antenna selection technique that can significantly outperform traditional selection when coupling is present. C2 - 2012/// C3 - 2012 ieee international conference on communications (icc) DA - 2012/// DO - 10.1109/icc.2012.6364251 ER - TY - CONF TI - ZVS range extension of 10A 15kV SiC MOSFET based 20kW dual active half bridge (DHB) DC-DC converter AU - Wang, G. Y. AU - Huang, A. AU - Li, C. S. AB - SiC MOSFET is favorable for high voltage applications due to its fast switching speed, low loss and high voltage rating compared with silicon power devices. This paper presents the switching performance of 10A 15kV SiC MOSFET and analyzes its switching loss when considering the impact of parasitic capacitance. A 20 kHz 20 kW Dual Active Half Bridge (DHB) dc-dc converter based on this new device is designed with full ZVS range. Simulation and experiment results are given to validate the analysis. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// DO - 10.1109/ecce.2012.6342631 SP - 1533-1539 ER - TY - CONF TI - Ultra fast protection of radial and looped electric power grid using a novel solid-state protection device AU - Rezaei, M. A. AU - Huang, A. AB - Exploiting the fast operation of solid-state Fault Isolation Devices (FIDs), this paper presents a novel over-current protection scheme for radial and looped electric power distribution systems. The main feature of the proposed protection scheme is that it ensures the maximum restoration of the system in less than a quarter of the electric cycle. Due to the inherent characteristics of the solid-state devices, the FID is also able to limit the fault current to the maximum allowable fault current level of the system, thus reducing the thermal and mechanical stress on transformers and other power system equipments. Using the inherent characteristics of the solid state devices, a novel fault detection criteria is also proposed that eliminates the necessity of the current sensor or transformer (CT) for detecting the over-current fault. These advantages are all achieved without requiring communication between FIDs. Performance of the FID with the proposed protection scheme is demonstrated based on an all-analog logic-level grid-voltage scale experimental setup. The experiments demonstrate the capability of the proposed protection scheme to fulfill the demands of highly inter-connected electric power distribution systems. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// DO - 10.1109/ecce.2012.6342765 SP - 610-614 ER - TY - CONF TI - Thermal design considerations for 12kV SiC n-IGBT based 3L NPC converter AU - Karimi-Moghaddam, G. AU - Gould, R.D. AU - Madhusoodhanan, S. AU - Hatua, K. AU - Bhattacharya, S. AU - Leslie, S. AU - Ryu, S.-H. AU - Das, M. AU - Agarwal, A. AU - Grider, D. AB - Transformer less Intelligent Power Substation (TIPS) is a solid state replacement for the conventional bulky distribution transformers used for 13.8kV and 480V grid interconnectivity. A 100kVA 3L NPC converter is being built using 12kV SiC n-IGBT for the high voltage grid interface. In this paper, detailed thermal behavior of this converter is studied for optimum thermal design. The thermal profile at the die level at different power factor of operation is studied. This study helps the optimum component placement in the converter. Also it shows that the operating modes of the converter play a key role in optimum thermal design. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012 DA - 2012/// DO - 10.1109/ECCE.2012.6342445 SP - 2180-2186 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870903069&partnerID=MN8TOARS ER - TY - CONF TI - Statistical classification of social networks AU - Wang, T. AU - Krim, H. AB - This paper proposes a new social network classification method by comparing statistics of their centralities and clustering coefficients. Specifically, the proposed method uses the statistics of Degree Centralities and clustering coefficients of networks as a classification criterion. A theoretical justification to this method is also given. In relation to the widely held belief that a social network graph is solely defined by its degree distribution, the novelty of this paper consists in revealing the strong dependence of social networks on Degree Centralities and clustering coefficients, and in using them as minimal information to classify social networks. In addition, experimental classification demonstrates a very good performance of the proposed method on real social network data, and validates the hypothesis that Degree Centralities and clustering coefficients are the only two viable independent properties of a social network. C2 - 2012/// C3 - 2012 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) DA - 2012/// DO - 10.1109/icassp.2012.6288789 SP - 3977-3980 ER - TY - CONF TI - Solid state transformer interfaced wind energy system with integrated active power transfer, reactive power compensation and voltage conversion functions AU - She, X. AU - Wang, F. AU - Burgos, R. AU - Huang, A. Q. AB - As the power of wind energy system increases, the control of their active and reactive power becomes increasingly more important from a system standpoint given that these are typical frequency and voltage control parameters. In this paper a family of wind energy systems with integrated active power transfer, reactive power compensation and voltage-conversion functionality is proposed. The proposed wind energy systems using solid state transformer (SST) can effectively suppress the voltage fluctuation caused by the transient nature of wind energy without additional reactive power compensator and as such may enable the large penetration of wind farm (WF) into the distribution system. To this end, a simulation study for WF driven by squirrel-cage induction generators is presented to verify the effectiveness of the proposed system. In addition, a modular type high voltage and high power three-phase SST topology is presented for the proposed system, and its basic building block, which is a single-phase SST, is analyzed. The function of SST in the presented wind energy system is verified in a single-phase laboratory prototype with scaled down experiments. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// DO - 10.1109/ecce.2012.6342508 SP - 3140-3147 ER - TY - CONF TI - Self-power emitter turn-off thyristor (SPETO) based circuit breaker for power distribution system AU - Chen, Q. AU - Tan, K. AU - Huang, A. Q. AB - Compared to mechanical solution, solid-state circuit breaker (SSCB) offers enormous advantages in terms of switching speed and maintenance. With fast switching performance, high current turn-off capability, self-power and built-in sensor functions, SPETO is a very promising high power switching device for the application of SSCB in power distribution system. The experimental results show that the SPETO based SSCB can turn off current quickly and works well with self-power function, and therefore is suitable for SSCB in power distribution system. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// DO - 10.1109/ecce.2012.6342564 SP - 2017-2021 ER - TY - CONF TI - Review of solid state transformer in the distribution system: From components to field application AU - She, X. AU - Burgos, R. AU - Wang, G. Y. AU - Wang, F. AU - Huang, A. Q. AB - The emergence of high power converters makes the modern power grid more active than it was before. One of the research directions in this area is the solid state transformer, which aims at replacing the traditional 50/60 Hz power transformer by means of high frequency isolated AC/AC solid state conversion techniques. This paper presents a systematical technology review essential for the development of solid state transformer in the distribution system, especially focusing on the following four areas: high voltage and high frequency power devices, high power and high frequency transformers, AC/AC converter topologies, and applications of solid state transformer in the distribution system. For each category, the state-of-art technologies are reviewed and possible research directions are presented. It is concluded that the solid state transformer is an emerging technology for the modernization of the future smart grid. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// DO - 10.1109/ecce.2012.6342269 SP - 4077-4084 ER - TY - CONF TI - Reliability of 4H-SiC SBD/JBS diodes under repetitive surge current stress AU - Huang, X. AU - Wang, G. Y. AU - Lee, M. C. AU - Huang, A. Q. AB - The reliability of power diode under surge current stress is crucial to the applications like motor drives. In this paper, the single and repetitive surge reliability of the 4H-SiC Schottky Barrier Diodes (SBDs) and Junction Barrier Schottky (JBS) diodes have been tested and the corresponding failure mechanisms studied. The single surge test results of two SBDs and three JBS didoes suggest a 450W/mm 2 constant power line of the safe operation area for single surge current with a half sinusoidal pulse width of 8.3ms. The stress tests show no degradation of SBDs up to 10,000 cycles of surge current below 34.9A/mm 2 . The JBS diodes show V F degradation after surge stress at different current levels, which might be dependent on the hole injection levels. The aluminum metallization and bipolar degradation are the main limits for the reliability of SiC diodes under surge conditions. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// DO - 10.1109/ecce.2012.6342436 SP - 2245-2248 ER - TY - CONF TI - Posture estimation for a canine machine interface based training system AU - Brugarolas, R. AU - Roberts, D. AU - Sherman, B. AU - Bozkurt, A. AB - Dogs and humans have worked in partnership throughout history thanks to dogs' unique capability of detecting signals in human voices or gestures and learning from human inputs. Traditional canine training methods rely solely on subjective visual observations made by trainers. We propose a canine body-area-network (cBAN) to incorporate context-aware sensing with objective detection algorithms to augment the sensitivity and specificity of human trainer's awareness of the dogs they are training. As an initial effort, we developed a Bluetooth-based wireless infrastructure and tested inertial measurement units as cBAN sensor nodes to electronically assess the posture of the dogs. As a result, we were able to optimize the sensor locations and distinguish different postures using the distinct patterns in the measured angles. C2 - 2012/// C3 - 2012 annual international conference of the ieee engineering in medicine and biology society (embc) DA - 2012/// DO - 10.1109/embc.2012.6346964 SP - 4489-4492 ER - TY - CONF TI - Parallel operation of solid state transformer AU - Wang, F. AU - She, X. AU - Wang, G. Y. AU - Huang, A. AU - Burgos, R. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// SP - 1433-1438 ER - TY - CONF TI - On the connectivity of large multi-channel cognitive radio networks AU - Sun, L. AU - Wang, Wenye AB - Cognitive Radio Networks (CRNs) have become promising network components to improve spectrum utilization efficiency, where secondary (unlicensed) users exploit spectrum opportunistically without interfering with the coexisting primary users. A challenging yet open question is how to ensure that information can be disseminated to the entire CRN, which is a prerequisite to applications of wireless networks. In this paper, we address the connectivity of large multi-channel CRNs. Particularly, we study full connectivity and percolation of secondary networks. The former is the existence of a communication path between any two nodes and the latter is the existence of a large component of secondary users. We find that the sufficient and necessary condition to achieve full connectivity is λ = Θ(log n/πr 2 P s ), where λ is the density, n is the number and r is the transmission range of secondary users respectively, and P s is the probability that any two secondary users can communicate with each other without interfering with primary users. We further show that the required density for percolation is a constant, and identify an upper bound on λ, above which the network is percolated and a lower bound on λ below which the network is not percolated. Our results provide a theoretical understanding of connectivity in large multi-channel cognitive radio networks. C2 - 2012/// C3 - 2012 ieee international conference on communications (icc) DA - 2012/// DO - 10.1109/icc.2012.6363893 SP - 1854–1858 ER - TY - CONF TI - Ocean energy power take-off using oscillating paddle AU - Hazra, S. AU - Bhattacharya, Subhashish AU - Uppalapati, K.K. AU - Bird, J. AB - This paper presents an ocean energy power take-off system using paddle like wave energy converter (WEC), magnetic gear and efficient power converter architecture. As the WEC oscillates at a low speed of about 5-25 rpm, the direct drive generator is not an efficient design. To increase the generator speed a cost effective flux focusing magnetic gear is proposed. Power converter architecture is discussed and integration of energy storage in the system to smooth the power output is elaborated. Super-capacitor is chosen as energy storage for its better oscillatory power absorbing capability than battery. WEC is emulated in hardware using motor generator set-up and energy storage integration in the system is demonstrated. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012 DA - 2012/// DO - 10.1109/ecce.2012.6342793 SP - 407-413 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870926635&partnerID=MN8TOARS ER - TY - CONF TI - Modeling and analysis of battery hysteresis effects AU - Eichi, H. R. AU - Chow, M. Y. AB - Battery state estimation is an essential step in providing an optimal management system for the battery. With an accurate relaxation-effect model, the battery's open circuit voltage (VOC) can be obtained from direct measurements of the terminal voltage and load current. The battery's state-of-charge (SOC), thereby, can be accurately estimated if a precise model for the VOC-SOC relationship with hysteresis effect is considered. This paper proposes a novel battery hysteresis effect dynamics model that provides a compact and accurate description of a family of the battery VOC-SOC trajectories over a large operating range and charging/discharging control strategies such as those used in Plug-in Hybrid Electric Vehicles (PHEVs). The battery hysteresis loops are modeled as responses to a Linear Time-Invariant (LTI) four-state system with various initial conditions. Experimental validations demonstrate that the proposed model can provide accurate descriptions of the battery hysteresis loops. The proposed hysteresis effect modeling method can be used as the basis for the VOC-based battery SOC estimation. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// DO - 10.1109/ecce.2012.6342212 SP - 4479-4486 ER - TY - CONF TI - Magnetic link optimization for wireless power transfer applications: modeling and experimental validation for resonant tubular coils AU - Pantic, Zeljko AU - Heacock, Benjamin AU - Lukic, Srdjan T2 - IEEE C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// SP - 3825-3832 ER - TY - CONF TI - Line following terrestrial insect biobots AU - Latif, T. AU - Bozkurt, A. AB - The present day technology falls short in offering centimeter scale mobile robots that can function effectively under unknown and dynamic environmental conditions. Insects, on the other hand, exhibit an unmatched ability to navigate through a wide variety of environments and overcome perturbations by successfully maintaining control and stability. In this study, we use neural stimulation systems to wirelessly navigate cockroaches to follow lines to enable terrestrial insect biobots. We also propose a system-on-chip based ZigBee enabled wireless neurostimulation backpack system with on-board tissue-electrode bioelectrical coupling verification. Such a capability ensures an electrochemically safe stimulation and avoids irreversible damage to the interface which is often misinterpreted as habituation of the insect to the applied stimulation. C2 - 2012/// C3 - 2012 annual international conference of the ieee engineering in medicine and biology society (embc) DA - 2012/// DO - 10.1109/embc.2012.6346095 SP - 972-975 ER - TY - CONF TI - LCL filter utilized in battery charging applications to achieve compact size and low ripple charging AU - Zhou, Xiaohu AU - Yu, Xunwei AU - Lukic, Srdjan AU - Huang, Alex T2 - IEEE AB - In this paper, an LCL filter is proposed to replace L-type filter in a dc/dc converter for battery charging applications. The merits of using an LCL filter are compact size, and extremely low ripple of charging current. The ripple free charging can reduce the heat generated by the ripple of the charging current and improve the battery lifetime. Filter based controller is proposed to solve the control loop instability issue caused by LCL filter. Low-pass filter and notch filter based controllers are designed and compared. The controller robustness to the variation of the filter parameters is investigated. The proposed system and control methods are verified by simulation and experiment. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// DO - 10.1109/ecce.2012.6342758 SP - 660-665 ER - TY - CONF TI - Investigation of the electrical system design concept and grid connection of ocean energy devices to an offshore compressed energy storage system AU - Agamloh, E. B. AU - Husain, I. AU - Safayet, A. AB - One of the biggest challenges of ocean wave and wind energy systems is the mitigation of the intermittency effects, in order to allow for their integration into the electric grid. Energy extraction using an ocean based compressed air energy storage system (OCAES) is proposed to enhance the economic dispatch of these energy sources onto the grid. There are land based compressed air energy systems storage systems. The ocean based version is a relatively new concept that is not proven and has not been studied in detail, yet it has significant advantages over the land based systems. The focus of the paper is on the power transmission and grid control utilizing the OCAES. System design concepts are discussed and simulation results are provided. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// DO - 10.1109/ecce.2012.6342377 SP - 2819-2826 ER - TY - CONF TI - Integrated electric motor drive and power electronics for bidirectional power flow between electric vehicle and DC or AC grid AU - Khan, M. A. AU - Husain, I. AU - Sozer, Y. AB - This paper presents an integrated traction machine and converter topology that has bidirectional power flow capability between an electric vehicle and the DC or AC supply or grid. The inductances of the traction motor windings are used for bi-directional converter operation to transfer power eliminating the need for extra inductors for the charger and vehicle-to-grid (V2G) converter operation. The electric powertrain system size and weight can be minimized with this approach. The concept has been analyzed with finite element coupled simulation with dynamic analysis software. Experimental results are also provided with an electric machine. The interleaving technique has been used with the inductors to share the current and reduce the converter switching stresses. The proposed integrated converter can operate in the traction mode and in the bidirectional power flow mode when energy can be transferred between the vehicle and the DC or single phase AC supply. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// DO - 10.1109/ecce.2012.6342328 SP - 3403-3410 ER - TY - CONF TI - High frequency GaN device-enabled CubeSat EPS with real-time scheduling AU - Shah, M. AU - Juneja, A. AU - Bhattacharya, Subhashish AU - Dean, A.G. AB - This paper describes the hardware and software architectures and experimental results of a flexible and scalable electric power system (EPS) for CubeSat applications. The EPS has the three flexible battery charging modules (FBCM) to charge the battery and the four flexible digital point of load (FDPOL) converters to drive loads. It uses the maximum power point tracking (MPPT) algorithm to maximize output power from the solar arrays along with the battery state of health and state of charge determination algorithms to determine the health of the Li-ion batteries. This paper also evaluates converter performance with GaN devices driven at high frequencies in order to reduce the size of the filter components and provide better control of the converters. Analysis of a sample load's transients and its voltage regulation, using a real-time operating system (RTOS), is also discussed briefly in this paper. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012 DA - 2012/// DO - 10.1109/ecce.2012.6342522 SP - 2934-2941 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870948186&partnerID=MN8TOARS ER - TY - CONF TI - Geo-dissemination in vehicular ad hoc networks AU - Li, Y. J. AU - Wang, Wenye AB - Vehicular Adhoc Networks (VANETs) aim to improve road safety and convenience through vehicle-to-vehicle and vehicle-to-roadside communications. Traffic information and accident warnings are often disseminated to vehicles in certain areas where driving could be affected by hazardous situations. Such message dissemination with destinations confined in specific geographic regions is referred to as Geo-Dissemination. In this paper, we analyze how far a geo-dissemination can possibly reach over a period of time t (denoted as dissemination distance D(t)), and what is the latency for a message to reach locations that are d distance far from the source (denoted as the stopping time τ). Simulations results of two dissemination methods (stateless opportunistic forwarding and GPS-based message broadcasting) are compared with our analytic results. C2 - 2012/// C3 - 2012 ieee international conference on communications (icc) DA - 2012/// DO - 10.1109/icc.2012.6364456 ER - TY - CONF TI - Four-quadrant torque ripple minimization of switched reluctance machine through current profiling with mitigation of rotor eccentricity problem and sensor errors AU - Mikail, R. AU - Husain, I. AU - Sozer, Y. AU - Islam, M. AU - Sebastian, T. AB - The paper presents a method of profiling the phase currents to minimize the torque ripple of switched reluctance machines (SRM) operating in four quadrant mode over the entire speed range of operation. A single quadrant current profiling presented in [1] is extended to be applicable in the four quadrant mode of operation. The method is based on machine and controller design through coupled simulation of the finite element based machine model and the dynamic controller model. The coupled simulation considers the magnetic nonlinearities, electrical and magnetic losses, and mutual coupling. The research quantifies the effect of position sensor error and manufacturing build variations on the level of torque ripple minimization. The mitigation processes to account for those issues in mass production are also presented. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// DO - 10.1109/ecce.2012.6342732 SP - 838-842 ER - TY - CONF TI - Field Programmable Analog Array (FPAA) based Shunt Active Filter controller AU - Kumar, M. AU - Green, E. AU - De, A. AU - Roy, S. AU - Bhattacharya, Subhashish AB - The presence of multiple harmonics in the power line due to various non-linear loads like adjustable speed drives, computers, fax machine, PLC's, etc. requires high frequency switching of an active filter inverter so as to reduce the harmonic content at the point of common coupling (PCC) to be typically lower than 5% as specified by IEEE 519 harmonic standards. In this paper, the Field Programmable Analog Array (FPAA) based analog controller has been used to implement a Synchronous Reference Frame (SRF) controller algorithm for harmonic current extraction for Shunt Active Filter controller and the results are compared with the conventional digital implementation on Field Programmable Gate Array (FPGA). The FPAA based analog controller implementation proves to be faster than the digital FPGA implementation and can be a potential to replace analog controllers used for active filters. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012 DA - 2012/// DO - 10.1109/ecce.2012.6342708 SP - 1011-1016 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870904185&partnerID=MN8TOARS ER - TY - CONF TI - Equivalent complex permeability and conductivity of litz wire in wireless power transfer systems AU - Etemadrezaei, Mohammad AU - Lukic, Srdjan M T2 - IEEE AB - In this paper the skin and proximity effect losses for Litz wire winding used in wireless power transfer system is calculated using exact 2-D method. Based on those losses the equivalent complex permeability and conductivity are calculated for each strand in the bundle. Due to specific properties of Litz wire, the whole bundle is homogenized using isotropic complex permeability and conductivity and is simulated numerically in Finite Element (FE) verifying the analytical and experimental results. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// DO - 10.1109/ecce.2012.6342286 SP - 3833-3840 ER - TY - CONF TI - Efficiency Comparison of AC-Link and TIPS (SST) Topologies based on accurate device models AU - De, A. AU - Roy, S. AU - Bhattacharya, Subhashish AB - In this paper, a comparative study on AC-Link™ Topology and a conventional solid state transformer (TIPS) has been shown. Alongside, as a building block, a comparative device level design study has been shown for 6.5kV Si-IGBT/SiC JBS diode, 6.5kV Si-IGBT/Si-PiN Diode and 10kV SiC-MOSFET/SiC-JBS Diode for a zero voltage/current transition and hard switched condition for medium voltage application. It is shown that soft switching yields a considerable reduction of losses for all devices. A low voltage hardware device test prototype has been built and tested. The main motive of the paper is to make a fair judgment on the two topologies with accurate device testing. This is further extended to the maximum attainable frequency analysis, corresponding efficiency comparison, frequency transfer capability and various other topology based comparisons. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012 DA - 2012/// DO - 10.1109/ecce.2012.6342282 SP - 3862-3868 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870894365&partnerID=MN8TOARS ER - TY - CONF TI - Dual-GCT design criteria and voltage scaling AU - Van Brunt, E. AU - Huang, A. Q. AU - Butschen, T. AU - De Doncker, R. W. AB - Global optimization has been performed to derive optimal Dual-GCT structures for 3.3 kV, 5 kV, and 6.5 kV class devices by using numerical simulation results. A treatment of all relevant physical concepts for both standard- and Dual-GCTs are taken into account in the optimization process, providing an insight into the effect of design parameters such as minority carrier lifetime, buffer region design, and device geometry. The results indicate that within the scope of a Dual Active Bridge power converter application, the Dual-GCT can provide more than 54 % improvement in the current density when compared to equivalent conventional devices for each of the device ratings examined, which verifies the scalability of the Dual-GCT concept. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// DO - 10.1109/ecce.2012.6342394 SP - 2596-2603 ER - TY - CONF TI - Design of experiments to address manufacturing tolerances and process variation influencing cogging torque and back EMF in the mass production of the permanent magnet synchronous motors AU - Khan, M. A. AU - Husain, I. AU - Islam, R. AU - Klass, J. AB - A number of manufacturing challenges exist in creating a robust permanent magnet synchronous motor (PMSM) design to meet critical requirements for cogging torque and torque ripple in specific applications. In addition, reduction of back EMF harmonics that lead to torque ripple is also required during design. Due to manufacturing tolerances, maintaining capability with these requirements is very difficult especially for mass production of units. A design of experiments (DOE) that combines manufacturing tolerances with assembly process variations is proposed here to address the sensitivity of cogging torque and harmonics. The limits for the parts and the process variations are extracted from an actual production environment. The DOE is laid out according to one of the robust engineering matrices chosen from Taguchi's method. The findings of the DOE are then utilized to set the tolerance limits for manufacturing the rotor magnets and to set the allowance for the rotor assembly process variation. The method helps limit the cogging torque and harmonics within predefined bands and make the motor design robust. This paper also investigates the capability of maintaining the tolerances of magnets for a surface mounted PMSM. The analysis is done using finite-element method and verified with experimental results. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// DO - 10.1109/ecce.2012.6342359 SP - 3032-3039 ER - TY - CONF TI - Design issues in a medium-voltage DC amplifier with a multi-pulse thyristor bridge front-end AU - Mirzaee, H. AU - Bhattachary, S. AU - Bala, S. AB - In this paper the design issues of a medium-voltage DC amplifier with a multi-pulse thyristor bridge front-end are presented. A medium voltage dc amplifier is needed in de-risking new technologies coming onboard future electric ships. Based on the required system dynamic specifications, an initial design reveals the problems with a multi-pulse thyristor front-end, and then provides a novel solution to meet the requirements, are presented. The proposed system solution is validated through both simulation and experimental results. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012 DA - 2012/// DO - 10.1109/ecce.2012.6342766 SP - 603-609 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870881833&partnerID=MN8TOARS ER - TY - CONF TI - Design considerations in development of Active Mobile Substations AU - Parkhideh, B. AU - Yousefpoor, N. AU - Babaei, S. AU - Bhattacharya, Subhashish AB - While conventional mobile substations are used to bypass the whole substation in case of loss or maintenance of power transformers, Active Mobile Substations (AMS) can be used in normal conditions as a power router and contingencies as a recovery transformer. The AMS is a mobile substation with integrated power electronics and by controlling its throughput power can be connected across different transformers of the grid. The AMS is expected to be at least 20MVA with 230kV and 69kV outputs. This paper proposes transmission-level active mobile substations that provide back-up in case of power transformer failure or forced reduced operation scenarios in addition to power flow control for seasonal renewable energy transmission. These functions altogether have been aggregated not only because of the technical merits but also to address the economic concerns regarding the cost of the power electronics for transmission applications. In this paper, design considerations in development of the AMS will be provided in terms of power electronics building blocks, converter system control and its effects, and required supervisory control. Throughout the paper, theoretical analyses and relevant results are presented. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012 DA - 2012/// DO - 10.1109/ecce.2012.6342767 SP - 595-602 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870944060&partnerID=MN8TOARS ER - TY - CONF TI - Current sharing control for cascaded H-bridge applied to secondary use batteries in Community Energy Storage systems AU - Lomaskin, Mark AU - Bai, Sanzhong AU - Lukic, Srdjan T2 - IEEE AB - This paper presents a cascaded H-bridge inverter topology for the application of secondary-use batteries as grid-connected energy storage. The proposed control strategy allows a degree of control over individual battery currents while the total system follows an arbitrary current command. This enables the aggregation and optimal use of battery packs with different capacities and states of health, overcoming a significant drawback of existing implementations. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// DO - 10.1109/ecce.2012.6342455 SP - 2107-2111 ER - TY - CONF TI - Control of cascaded multi-level STATCOM using line voltage total harmonic distortion minimization technique AU - Yousefpoor, N. AU - Parkhideh, B. AU - Babaei, S. AU - Bhattacharya, Subhashish AB - In this paper, a new switching strategy is proposed for a multi-level STATCOM system. An efficient approach in reducing the harmonic contents of the inverter's output voltage is total harmonic distortion (THD) minimization. In multilevel inverters with fundamental frequency switching strategy (each switch turning on and off once per output cycle), the switching angles can be selected such that the output THD is minimized. In three phase multilevel inverters, the optimization algorithm is commonly applied to the phase voltage of the inverter. This results in the minimum THD in phase voltage, but not necessarily in the line to line minimum THD. In this paper, THD minimization process is directly applied to the line to line voltage of the inverter, and a new control strategy of multilevel STATCOM is proposed. The proposed method will be implemented, in RTDS and the closed loop operation of multi-level STATCOM will be explored. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012 DA - 2012/// DO - 10.1109/ecce.2012.6342596 SP - 1782-1787 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870890532&partnerID=MN8TOARS ER - TY - CONF TI - Comparison study of 12kV n-type SiC IGBT with 10kV SiC MOSFET and 6.5kV Si IGBT based on 3L-NPC VSC applications AU - Madhusoodhanan, S. AU - Hatua, K. AU - Bhattacharya, Subhashish AU - Leslie, S. AU - Ryu, S.-H. AU - Das, M. AU - Agarwal, A. AU - Grider, D. AB - Silicon Carbide (SiC) devices and modules have been developed with high blocking voltages for Medium Voltage power electronics applications. Silicon devices do not exhibit higher blocking voltage capability due to its relatively low band gap energy compared to SiC counterparts. For the first time, 12kV SiC IGBTs have been fabricated. These devices exhibit excellent switching and static characteristics. A Three-level Neutral Point Clamped Voltage Source Converter (3L-NPC VSC) has been simulated with newly developed SiC IGBTs. This 3L-NPC Converter is used as a 7.2kV grid interface for the solid state transformer and STATCOM operation. Also a comparative study is carried out with 3L-NPC VSC simulated with 10kV SiC MOSFET and 6.5kV Silicon IGBT device data. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012 DA - 2012/// DO - 10.1109/ecce.2012.6342807 SP - 310-317 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870947926&partnerID=MN8TOARS ER - TY - CONF TI - Chunk and object level deduplication for web optimization: A hybrid approach AU - Papapanagiotou, I. AU - Callaway, R. D. AU - Devetsikiotis, M. AB - Proxy caches or Redundancy Elimination (RE) systems have been used to remove redundant bytes in WAN links. However, they come with some inherited deficiencies. Proxy caches provide less savings than RE systems, and RE systems have limitations related to speed, memory and storage overhead. In this paper we advocate the use of a hybrid approach, in which each type of cache acts as a module in a system with shared memory and storage space. A static scheduler precedes the cache modules and determines what types of traffic should be forwarded to which module. We also propose several optimizations for each of the modules, such that the storage and memory overhead are minimized. We evaluate the proposed system by performing a trace driven emulation. Our results indicate that a hybrid system is able to provide better savings than a proxy cache, or a standalone RE system. The hybrid system requires less memory, less disk space and provides a speed-up ratio equal to three compared to an RE system. C2 - 2012/// C3 - 2012 ieee international conference on communications (icc) DA - 2012/// DO - 10.1109/icc.2012.6363843 ER - TY - CONF TI - Black start control of a solid state transformer for emergency power restoration AU - Parks, N. AU - Dutta, S. AU - Ramachandram, V. AU - Hatua, K. AU - Bhattacharya, Subhashish AB - This paper demonstrates the black start capabilities of a single phase 20kVA solid state transformer (SST), specifically for microgrid power restoration during islanding. SST's have many benefits including better management of renewable energy resources and more intelligent control than the classical transformer which acts only as a passive device. An additional benefit of the SST that is demonstrated in this paper is the ability to use these renewable energy resources directly connected to the SST to restore microgrid load power during an islanding event. During the black start procedure the SST can switch the control operation of its three cascaded power converter stages, AC/DC rectifier, Dual Active Bridge, and DC/AC inverter, in order to restore the microgrid load. The benefits of using the SST for black start restoration are also discussed and compared with other traditional methods. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012 DA - 2012/// DO - 10.1109/ecce.2012.6342824 SP - 188-195 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870862926&partnerID=MN8TOARS ER - TY - CONF TI - Balancing network connectivity and the life-time of sensors through percolation and consensus AU - Ban, D. AU - Devetsikiotis, M. AB - Due to replacement infeasibility, methods to extend the life-time of sensors have been an issue in Wireless Sensor Networks (WSNs) and these should consider network connectivity simultaneously. Controlling the sleep/awake of sensors is one simple way to reduce their energy consumption. However, this causes a network connectivity degradation by varying network connection topology. For this reason, we propose a simple and autonomous sensor sleep/awake method to achieve their balance. The size of clusters can be a metric to measure network connectivity in that a path exists among any cluster node. From percolation theory, we observe that a cluster size suffers a sharp transition based on edge connection patterns. This allows us to design a sensor sleep/awake algorithm which has an immense simplicity, but still requires global topology information. In many cases, sensors are not aware of the global topology. Further, managing the information becomes challenging under physical topology changes such as sensor add/drop. We show that the global knowledge requirement can be resolved by using a consensus algorithm. Through several graph tests, we show that our method achieves a network balancing between connectivity and life-time with preserving its simplicity. Also, the balancing is autonomous even under physical topology variations. C2 - 2012/// C3 - 2012 ieee international conference on communications (icc) DA - 2012/// DO - 10.1109/icc.2012.6364130 ER - TY - CONF TI - Average delay SLAs in cloud computing AU - Saovapakhiran, B. AU - Devetsikiotis, M. AU - Michailidis, G. AU - Viniotis, Y. AB - In this paper, we conduct feasibility studies on the average delay space for Cloud computing, and we propose a heuristic method to control the vector of average delays, subject to predefined delay constraints. Our work is strongly motivated by the fact that delay control plays a critical role to improve Service Level Agreements (SLA) between users and Cloud service providers, which is necessary for empowering online business. Specifically, our main contributions are two-fold: First, the feasible regions of various routing algorithms for the system's dispatcher are investigated in depth. Second, a simple heuristic algorithm is designed, to move the average delay point along the feasible direction until achieving the delay constraints. Average delay is dependent on multiple factors such as job size, inter-arrival time, flow rate, and the dispatching rules of the system. Therefore, we vary their distribution, parameters and routing rules to examine how the feasible regions move or change. After establishing the feasible delay space, then by moving along the feasible directions, we show that a simple heuristic algorithm can achieve the delay constraints for a two queue system. C2 - 2012/// C3 - 2012 ieee international conference on communications (icc) DA - 2012/// DO - 10.1109/icc.2012.6364548 ER - TY - CONF TI - Auxiliary power supply for Solid State Transformers AU - Kadavelugu, A. AU - Wang, G. AU - Bhattacharya, Subhashish AU - Huang, A. AB - In contrast to traditional 60 Hz transformer, solid state transformer (SST) offers power flow control, integration of renewables and maintaining grid stability in high renewable penetration scenario. Like a typical power converter, SST requires low voltage (24 V dc) power for its control and sensing circuits. In running condition, this power is derived from its low voltage dc bus at 400 V. But it is challenging to derive it during start-up, because the only source available during start-up is the distribution grid at 7.2 kV, 60 Hz. Due to high input voltage (7.2 kV, 60 Hz), deriving a control supply of about 150 W, even for just start-up duration of about 200 ms, presents a novel power electronics problem. In this paper, two solutions have been proposed to address this issue, by taking a 20 kVA, 6.5 kV Si IGBT and 15 kV SiC MOSFET based SSTs as the reference converters. The first solution is generic and is based on storing the required start-up energy in a dc capacitance. This is based on developing a cost-effective high voltage switch using low voltage IGBTs with self-driven functionality. The second solution, applicable only to SST topologies with high voltage ac capacitive filter, is to tap the energy from the capacitor itself. The fundamental constraints considered for both the solutions are practical feasibility at high voltage (7.2 kV ac or over 10 kV dc), power loss, size, weight and cost-effectiveness. Experimental validation of extracting continuous power for the IGBT gate driver ICs from the snubber is presented with 200 V input. And, the results of the auxiliary power derivation from the filter capacitor are shown with 5.7 kV ac input. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012 DA - 2012/// DO - 10.1109/ecce.2012.6342647 SP - 1426-1432 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870892973&partnerID=MN8TOARS ER - TY - CONF TI - Auction-based energy management system of a large-scale PHEV municipal parking deck AU - Rahimi-Eichi, H. AU - Chow, M. Y. AB - The Plug-in Hybrid Electric Vehicle (PHEV) is becoming the most significant component of the future advanced transportation system and an important part of the smart grid. The energy management issue of charging a large number of PHEVs parked in a municipal parking lot with a limited amount of power available from the grid can be formulated as an optimization problem. Since the problem is basically a scalable resource allocation problem, a proportional allocation mechanism in auction theory is used to address the issue as a market-based tool. Also, a decentralized algorithm based on auction theory is developed that furnishes an updating rule to the vehicles as bidders to make the optimal decision about their next bid. This decision considers their previous bids and the price they have received from the market manager as a feedback. In this paper, considering PHEVs as price-taker bidders, we apply the auction theory method to solve the PHEV parking lot optimization problem for 10 vehicles, as a small example, and then for a large number of vehicles. The results are presented for both cases and compared to the Particle Swarm Optimization (PSO) as a well-known population-based optimization method. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// DO - 10.1109/ecce.2012.6342592 SP - 1811-1818 ER - TY - CONF TI - An energy management system for a community energy storage system AU - Huq, K. M. M. AU - Baran, Mesut AU - Lukic, Srdjan AU - Nare, O. E. T2 - IEEE AB - This paper considers the operational issues related to community level micro-grids which uses PV systems as the main local power generation. To facilitate the operation of such systems, the paper investigates the use of local storage, and proposes an Energy Management System (EMS) for this purpose. The paper shows that the proposed EMS can address the main operational issues, such as reducing energy consumption during peak loading conditions and limiting excess reverse power flow back to the utility. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// DO - 10.1109/ecce.2012.6342532 SP - 2759–2763 ER - TY - CONF TI - An approach to regulating Dual Series Static Compensator (DSSC) AU - Yousefpoor, N. AU - Parkhideh, B. AU - Bhattacharya, Subhashish AB - For power flow control with specific attention to renewable energy resources based transmission in a meshed network, less complex coordinated control can be obtained with the proposed convertible static transmission controller (CSTC) concept which is connected across the substation power transformer and can be reconfigured to the required modes of operation. Dual Series Static Compensator (DSSC) mode or series-series mode available in the CSTC provides superior performance in terms of operating characteristics compared to conventional power flow controllers. In this paper, detailed steady-state and dynamic performance of DSSC will be investigated, and the control structure of DSSC will be proposed to control active and reactive power independently. This paper specifically explores the challenges of the proposed control method. In particular, the proposed control structure is based on line current PLL. The dynamic performance of DSSC is further investigated in PSCAD/EMTDC environment. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012 DA - 2012/// DO - 10.1109/ecce.2012.6342176 SP - 4732-4737 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870923153&partnerID=MN8TOARS ER - TY - CONF TI - An algorithm for joint guidance and power control for electric vehicles in the smart grid AU - Saovapakhiran, B. AU - Michailidis, G. AU - Devetsikiotis, M. AB - A massive amount of energy consumption currently stems from the transportation sector. Therefore, improvements in power usage by commuting vehicles are being studied and becoming an increasingly popular research topic. In particular, there is a growing need to model the envisioned smart infrastructure, including charging stations, some of which might include energy storage devices and swappable, pre-charged batteries. For such new stations, power management is indeed crucial for operation costs, driver convenience, and overall smart grid efficiency. Information technology, communications and vehicle intelligence need to play a crucial role in this process. In this paper, we describe a quantitative model and propose a guiding and control system for the charging of PHEVs in a future smart infrastructure. Specifically, we describe an algorithm that can be used for the joint guidance and power control of smarter electric vehicles in the smart grid. We envision it as part of a larger Smart Guide for the Smart Grid (SGSG) system. Its function is to guide PHEV drivers, directing them to the appropriate charging station, while attempting to achieve an optimization goal at the same time. Our algorithm aims at a joint guiding and power control, in order to heuristically maximize the weighted sum of the average of throughput and energy cost consumption from multiple vehicle charging stations, while satisfying a cost constraint at each station, as well as system stability. C2 - 2012/// C3 - 2012 ieee international conference on communications (icc) DA - 2012/// DO - 10.1109/icc.2012.6364112 ER - TY - CONF TI - An accurate prediction of two-dimensional carrier density profile in IGBT and its significances on steady-state and transient analysis AU - Lee, M. C. AU - Huang, X. AU - Huang, A. Q. AB - This work presents a piecewise two-dimensional steady-state analytical model for insulated gate bipolar transistor (IGBT). The proposed model can accurately describes the dependence of carrier density profile on the ratio of accumulation gate width (L g ) to the half cell width (L cell ) without ignoring the recombination in the drift region. The drift region of IGBT is divided into four regions in this model. By determining the boundary that separates one- and two-dimensional regions, the carrier density profiles in the four regions can be derived with proper boundary conditions. The model is originally developed for, but not limited to, 4H-SiC p-IGBT. The results of proposed model are in good agreement with the simulation results at varied current densities and with different values of L g /L cell . The I-V curves in the linear region generated by the proposed model match well with the simulated results. The error of the amount of stored charge generated by one-dimensional model will also be examined. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// DO - 10.1109/ecce.2012.6342637 SP - 1496-1502 ER - TY - CONF TI - Accurate equivalent circuit modeling of a medium-voltage and high-frequency coaxial winding DC-link transformer for solid state transformer applications AU - Baek, S.S. AU - Bhattacharya, Subhashish AU - Cougo, B. AU - Ortiz, G. AB - The 12kV–400V dc-dc stage of a distribution level solid state transformers (SST) has been under research and development. Development of a 15kV SiC Mosfet allows a single stage of the dc-dc converter to operate at medium voltage at an operating frequency of over 20kHz. Nonetheless, the high rising and falling time during pulse switching in the dual active bridge operation is another significant obstacle to realize this technology. In order to understand and predict the frequency response with pulse switching and consider common-mode response via circuit analysis accurately, lumped-element equivalent circuit model has been developed for broadband coaxial winding transformer (CWT) with analytic expressions. The simple lumped-element equivalent circuit introduced in this paper has been verified by measurement results from a prototype for a medium-voltage (MV) and high frequency (HF) coaxial winding power transformer up to the frequency where the length of the coaxial body is a quarter of a wavelength and further study up to 30MHz has been described. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012 DA - 2012/// DO - 10.1109/ecce.2012.6342645 SP - 1439-1446 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870918183&partnerID=MN8TOARS ER - TY - CONF TI - A novel predictive phase shift controller for bidirectional isolated dc to dc converter for high power applications AU - Dutta, S. AU - Bhattacharya, Subhashish AU - Chandorkar, M. AB - In this paper a novel predictive algorithm has been proposed for bi-directional dc-dc converters with high frequency transformer isolation. The converter is a dual active bridge converter. The proposed algorithm is a faster alternative to the classical PI based phase shift controller. This mode of control can remove dc bias in the isolation transformer within several switching cycles hence preventing transformer saturation. Aspects of the proposed algorithm have been implemented on a hardware test bed and verified. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012 DA - 2012/// DO - 10.1109/ecce.2012.6342791 SP - 418-423 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870872317&partnerID=MN8TOARS ER - TY - CONF TI - A fixed switching frequency predictive current control method for switched reluctance machines AU - Mikail, R. AU - Husain, I. AU - Sozer, Y. AU - Islam, M. AU - Sebastian, T. AB - The paper presents a novel fixed switching frequency predictive current control method for switched reluctance machines (SRM). The proposed deadbeat predictive current controller accurately predicts the required amount of on-time for the PWM pulse for a given reference current in each digital time step over the entire speed range of operation. The required pulse width depends on the operating conditions, machine parameters and the rotor position. The controller utilizes the machine inductance profile as a function of current and rotor position to accurately predict the required voltage. The control method is studied through computer simulation and followed by experimental validation. The method is suitable for torque ripple sensitive applications requiring accurate tracking of a given current profile and mitigating the audible noise due to the switching of the inverter. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// DO - 10.1109/ecce.2012.6342731 SP - 843-847 ER - TY - CONF TI - A New nonisolated three-port DC-DC converter with high step-up/down ratio AU - Chen, Y. M. AU - Yu, X. W. AU - Huang, A. Q. AB - A new nonisolated three-port dc-dc converter integrating PV and battery power is proposed in this paper. The topology includes two coupled inductors and two active-clamp circuits. The coupled inductors are used to achieve high step up/down gain and to reduce the voltage stress on both primary and auxiliary switches. Two sets of active-clamp circuits in the proposed converter are used to recycle the energy stored in the leakage inductors. Therefore, the system efficiency can be improved. Charging/discharging transition of the battery is autonomous while tracking the maximum power of PV source and regulating the output voltage simultaneously. When the charging voltage is too high, the control loop of PV port will be switched from maximum power point tracking (MPPT) to battery voltage regulation. Experimental results of a 200W laboratory prototype are presented to verify the performance of the proposed three-port converter. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// DO - 10.1109/ecce.2012.6342633 SP - 1520-1526 ER - TY - CONF TI - A 12-pulse diode rectifier with energy storage integration and high power quality on both ac and dc side AU - Bai, Sanzhong AU - Lukic, Srdjan T2 - IEEE AB - The 12-pulse diode rectifier has been widely used in high power applications. Although the dominant 5th and 7th harmonics of the input current are canceled out, the total harmonic distortion is still well above 5%. Therefore additional filtering is required to meet the pertinent standards. In this paper, several methods that deal with the input current harmonics are reviewed. The fundamentals behind these methods are discussed. By utilizing the concept of virtual resistor, a new approach is proposed in this paper to, not only eliminate the AC input current harmonics, but also eliminate DC output voltage harmonics. Moreover, the energy storage integration is possible with the proposed method. We analyze the control and operation of the proposed method. Simulation and experiment results verify the analysis. C2 - 2012/// C3 - 2012 IEEE Energy Conversion Congress and Exposition (ECCE) DA - 2012/// DO - 10.1109/ecce.2012.6342274 SP - 4042-4048 ER - TY - CONF TI - Set membership state and parameter estimation for nonlinear differential equations with sparse discrete measurements AU - Marvel, S. W. AU - Williams, Cranos AB - This paper presents a method to perform parameter and state estimation in a bounded-error context for nonlinear continuous-time systems with sparse, discrete measurements. Direct application of a guaranteed parameter estimation method can be fruitless when few data measurements are available. This lack of measurements results in what we term “phantom” sets of parameter values that cannot be correctly discarded due to instability in the estimation method caused by the lack of information. Preprocessing the measurements through the addition of application specific stabilizing bounds vastly improves bounded parameter and state estimations. Comparisons between applying guaranteed estimation methods to raw and preprocessed data measurements are illustrated with an example application. C2 - 2012/// C3 - Ieee international conference on systems man and cybernetics conference DA - 2012/// DO - 10.1109/icsmc.2012.6377679 SP - 72–77 ER - TY - CONF TI - Region of attraction estimation of biological continuous Boolean models AU - Matthews, M. L. AU - Williams, Cranos AB - Quantitative analysis of biological systems has become an increasingly important research field as scientists look to solve current day health and environmental problems. The development of modeling and model analysis approaches that are specifically geared toward biological processes is a rapidly growing research area. Continuous approximations of Boolean models, for example, have been identified as a viable method for modeling such systems. This is because they are capable of generating dynamic models of biochemical pathways using inferred dependency relationships between components. The resulting nonlinear equations and therefore nonlinear dynamics, however, can present a challenge for most system analysis approaches such as region of attraction (ROA) estimation. Continued progress in the area of biosystems modeling will require that computational techniques used to analyze simple nonlinear systems can still be applied to nonlinear equations typically used to model the dynamics associated with biological processes. In this paper, we assess the applicability of a state of the art ROA estimation technique based on interval arithmetic to a subnetwork of the Rb-E2F signaling pathway modeled using continuous Boolean functions. We show that this method can successfully be used to provide an estimate of the ROA for dynamic models described using Hillcube continuous Boolean approximations. C2 - 2012/// C3 - Ieee international conference on systems man and cybernetics conference DA - 2012/// DO - 10.1109/icsmc.2012.6377982 SP - 1700–1705 ER - TY - CONF TI - Fundamental capacity limits on compact MIMO-OFDM systems AU - Taluja, P. S. AU - Hughes, B. L. AB - We undertake an information-theoretic approach to characterize the optimal design of a broadband multi-antenna system in the presence of mutual coupling. It was shown recently that mutual coupling effectively decomposes otherwise spectrally-identical spatial modes of an antenna array into spectrally non-identical eigen-modes. We shall use Shannon's information theory and Fano's broadband matching theory to develop optimal transceiver designs for a compact broadband MIMO system. It will be shown that in the presence of channel state information, optimal transmit power allocation and matching characteristic follow a mutual space-frequency water-pouring solution. C2 - 2012/// C3 - 2012 ieee international conference on communications (icc) DA - 2012/// DO - 10.1109/icc.2012.6363765 SP - 2547-2552 ER - TY - CONF TI - Enabling adaptive rate and relay selection for 802.11 mobile ad hoc networks AU - Mehta, N. AU - Duel-Hallen, A. AU - Wang, Wenye AB - Mobile ad hoc networks (MANETs) are self-configuring wireless networks that lack permanent infrastructure and are formed among mobile nodes on demand. Rapid node mobility results in dramatic channel variation, or fading, that degrades MANET performance. Employing channel state information (CSI) at the transmitter can improve the throughput of routing and medium access control (MAC) protocols for mobile ad hoc networks. Several routing algorithms in the literature explicitly incorporate the fading signal strength into the routing metric, thus selecting the routes with strong channel conditions. While these studies show that adaptation to the time-variant channel gain is beneficial in MANETs, they do not address the effect of the outdated fading CSI at the transmitter. For realistic mobile node speeds, the channel gain is rapidly varying, and becomes quickly outdated due the feedback delay. We analyze the link throughput of joint rate adaptation and adaptive relay selection in the presence of imperfect CSI. Moreover, for an 802.11 network that employs geographic opportunistic routing with adaptive rate and relay selection, we propose a novel method to reduce the effect of the feedback delay at the MAC layer in the presence of Rayleigh fading. This method exploits channel reciprocity and fading prediction and does not require significant modification to the existing 802.11 frame structure. Extensive network simulations demonstrate that the proposed approach significantly improves the throughput, delay, and packet delivery ratio for high mobile velocities relative to previously proposed approaches that employ outdated CSI at the transmitter. C2 - 2012/// C3 - IEEE International Conference on Communications (ICC 2012) CY - Piscataway, NJ, USA DA - 2012/// DO - 10.1109/icc.2012.6363785 SP - 4150 - 4 UR - http://dx.doi.org/10.1109/ICC.2012.6363785 ER - TY - JOUR TI - Channel-aware adaptive resource allocation for multicast and unicast services in orthogonal frequency division multiplexing systems AU - Zhang, H. AU - Wang, X. AU - Li, F. AU - Dai, H. T2 - IET COMMUNICATIONS AB - To support the multicast and unicast services in the orthogonal frequency division multiplexing system simultaneously, a channel-aware adaptive resource allocation algorithm is proposed to maximise the total throughput of the unicast service while guaranteeing the required quality of service (QoS) for the multicast service. The two-step optimisation scheme is developed to solve the problem based on the perfect channel state information at the base station: first, subcarriers are allocated to the multicast and the unicast services under the assumption that power is divided equally to every subcarrier. Especially, the noisy chaotic neural network with a new parameter set is applied to allocate the subcarriers to the unicast service by elaborately constructing the energy function to fully exploit the multiuser diversity gain, the optimal solution is found successfully through its rich neurodynamics; Secondy, the power averagely allocated to the unicast service is reallocated quickly in a linear water-filling fashion. Compared with existing algorithms the proposed algorithm achieves higher spectrum efficiency and better bit-error rate for the multicast service, also higher throughput for the unicast service. DA - 2012/11/27/ PY - 2012/11/27/ DO - 10.1049/iet-com.2012.0111 VL - 6 IS - 17 SP - 3006-3014 SN - 1751-8636 ER - TY - CONF TI - Short time power smoothing of a low power wave energy system AU - Hazra, S. AU - Bhattacharya, Subhashish AB - This paper presents smoothing of oscillatory power generated by a wave energy converter (WEC) from sea wave. WEC oscillates in sea wave and an electrical generator connected to it generates oscillatory power of typical period of oscillation of 6 to 10 seconds. This power can not be directly fed to a load or grid and hence an energy storage device is required to filter out the oscillation. Super-capacitor (SC) is a better choice over battery as an energy storage device due to its low maintenance requirement and better power capacity. A WEC is emulated in hardware using induction motor (IM) and a permanent magnet synchronous machine (PMSM) is used as the generator. Power generation from WEC is controlled by controlling PMSM current. Power flow to and from SC is controlled to smooth the power output. The overall control system is implemented in hardware and smoothing of the oscillatory power using SC is demonstrated. C2 - 2012/// C3 - IECON Proceedings (Industrial Electronics Conference) DA - 2012/// DO - 10.1109/iecon.2012.6389128 SP - 5846-5851 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84872982349&partnerID=MN8TOARS ER - TY - CONF TI - Sampling Rate Selection Influences on Incremental Cost Consensus Algorithm in Decentralized Economic Dispatch AU - Ying, X. C. AU - Chow, M. Y. AB - In a smart grid, distributed control algorithms can be embedded in the distributed controllers of generators to solve energy management problems without the presence of a central controller. Incremental Cost Consensus (ICC) algorithm is such a distributed algorithm that solves the economic dispatch problem (EDP) in a distributed manner. This paper considers the sampling rate selection of a system that consists of the ICC algorithm and generator dynamics. The mathematical formulation of the hybrid system is presented and the selection of a proper sampling rate is discussed. In addition, the results of the case studies are presented to show the convergence performance of a hybrid system under different sampling rate choices. C2 - 2012/// C3 - 38th annual conference on ieee industrial electronics society (iecon 2012) DA - 2012/// DO - 10.1109/iecon.2012.6388566 SP - 1410-1415 ER - TY - CONF TI - Large-signal FET Models and a New AlGaN/GaN HFET model for power amplifier design AU - Trew, R. J. AU - Hou, D. AU - Schimizzi, R. AU - Goswami, A. AU - Bilbro, G. L. AB - A historical review of large-signal compact FET models is presented. Device models used in circuit design typically are based upon equivalent circuit techniques. However, it is possible to develop physics-based compact models. In this work, a new physics-based model for AlGaN/GaN HFETs that can be integrated into the commercial simulators is described. The new model has demonstrated good agreement between measured and simulated data for communications band power amplifiers. C2 - 2012/// C3 - 2012 IEEE International Conference on Wireless Information Technology and Systems (ICWITS) DA - 2012/// DO - 10.1109/icwits.2012.6417696 ER - TY - CONF TI - Framework for Investigating the Impact of PHEV Charging on Power Distribution System and Transportation Network AU - Su, W. C. AU - Wang, J. H. AU - Zhang, K. L. AU - Chow, M. Y. AB - Plug-in hybrid electric vehicles (PHEVs) and plug-in electric vehicles (PEVs) have received increasing attention because of their low pollution emissions, petroleum independence, and high fuel economy. The large market penetration of these vehicles is dramatically changing the view of the power distribution system. Unlike other power loads, these vehicles can be connected to power grids anywhere and anytime, which brings more spatial and temporal diversity and uncertainty. There is an urgent need to investigate the impact of PHEV/PEV charging on the power distribution system considering multidisciplinary complexities (e.g., driving behavior, route and departure time choice, charging station location, engineering, policy, economic, environment, technology, and social impact). This paper consolidates the modeling and simulation of power distribution system and transportation network in order to assess the emerging electric vehicle technologies. Moreover, this paper proposes a comprehensive co-modeling/simulation framework for investigating the impact of the electrification of transportation in the real world. C2 - 2012/// C3 - 38th annual conference on ieee industrial electronics society (iecon 2012) DA - 2012/// DO - 10.1109/iecon.2012.6389482 SP - 4735-4740 ER - TY - CONF TI - Circulating Current Control of Double-Star Chopper-Cell Modular Multilevel Converter for HVDC System AU - She, X. AU - Huang, A. AB - Modular multilevel converter is regarded as a promising technology in high voltage application, such as off-shore wind farm system. This paper proposes control technique for modular multilevel converters, aiming at suppressing the AC components in the circulating current. Specifically, an additional proportional-resonant control loop is designed to regulate the AC component of the circulating current to zero. The proposed method can effectively suppress the AC circulating current even in the unbalanced/fault condition. Simulation results for a 10MVA, 25KV DC system are provided to demonstrate the feasibility of the proposed method. C2 - 2012/// C3 - 38th annual conference on ieee industrial electronics society (iecon 2012) DA - 2012/// DO - 10.1109/iecon.2012.6388594 SP - 1234-1239 ER - TY - CONF TI - Adaptive Parameter Identification and State-of-Charge Estimation of Lithium-Ion Batteries AU - Rahimi-Eichi, H. AU - Chow, M. Y. AB - Estimation of the State of Charge (SOC) is a fundamental need for the battery, which is the most important energy storage in Electric Vehicles (EVs) and the Smart Grid. Regarding those applications, the SOC estimation algorithm is expected to be accurate and easy to implement. In this paper, after considering a resistor-capacitor (RC) circuit-equivalent model for the battery, the nonlinear relationship between the Open Circuit Voltage (V OC ) and the SOC is described in a lookup table obtained from experimental tests. Assuming piecewise linearity for the V OC -SOC curve in small time steps, a parameter identification technique is applied to the real current and voltage data to estimate and update the parameters of the battery at each step. Subsequently, a reduced-order linear observer is designed for this continuously updating model to estimate the SOC as one of the states of the battery system. In designing the observer, a mixture of Coulomb counting and VOC algorithm is combined with the adaptive parameter-updating approach and increases the accuracy to less than 5% error. This paper also investigates the correlation between the SOC estimation error and the observability criterion for the battery model, which is directly related to the slope of the V OC - SOC curve. C2 - 2012/// C3 - 38th annual conference on ieee industrial electronics society (iecon 2012) DA - 2012/// DO - 10.1109/iecon.2012.6389248 SP - 4012-4017 ER - TY - CONF TI - AC Circulating Currents Suppression in Modular Multilevel Converter AU - She, X. AU - Huang, A. AU - Ni, X. J. AU - Burgos, R. AB - Modular multilevel converter is a next generation multilevel converters for medium to high voltage conversion applications, such as medium voltage motor drive and high voltage direct current transmission. One potential issue of this type of converter is the AC circulating current, which increases the current stress and brings additional conduction loss to the system. This paper proposes modified control architecture for modular multilevel converters, aiming at suppressing the AC components in the circulating current. Specifically, a proportional-resonant type minor loop is incorporated to regulate the most AC components of the circulating current to zero in addition to the DC regulation loop. The proposed minor loop can also be applied to single phase MMC, which is not available in previous methods. Simulation results for a three-phase MMC operating as an inverter are provided to demonstrate the feasibility of the proposed method. C2 - 2012/// C3 - 38th annual conference on ieee industrial electronics society (iecon 2012) DA - 2012/// DO - 10.1109/iecon.2012.6388809 SP - 191-196 ER - TY - JOUR TI - Standoff Acoustic Modulation of Radio Frequency Signals in a Log-Periodic Dipole Array Antenna AU - Wetherington, Joshua M. AU - Steer, Michael B. T2 - IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS AB - An acoustic tone isonifying an antenna is shown to produce radio frequency (RF) distortion in a log-periodic dipole array. This distortion is capable of interfering with a sensitive receiver. The passive distortion produces two sidebands, the powers of which have a 1:1 relationship with both the RF and acoustic tone, but have nonmonotonic behavior with respect to RF and acoustic frequency. DA - 2012/// PY - 2012/// DO - 10.1109/lawp.2012.2210692 VL - 11 SP - 885-888 SN - 1536-1225 KW - Acousto-electromagnetic coupling KW - antenna distortion KW - co-site interference KW - passive intermodulation distortion ER - TY - JOUR TI - Set membership experimental design for biological systems AU - Marvel, Skylar W. AU - Williams, Cranos M. T2 - BMC SYSTEMS BIOLOGY AB - Experimental design approaches for biological systems are needed to help conserve the limited resources that are allocated for performing experiments. The assumptions used when assigning probability density functions to characterize uncertainty in biological systems are unwarranted when only a small number of measurements can be obtained. In these situations, the uncertainty in biological systems is more appropriately characterized in a bounded-error context. Additionally, effort must be made to improve the connection between modelers and experimentalists by relating design metrics to biologically relevant information. Bounded-error experimental design approaches that can assess the impact of additional measurements on model uncertainty are needed to identify the most appropriate balance between the collection of data and the availability of resources. In this work we develop a bounded-error experimental design framework for nonlinear continuous-time systems when few data measurements are available. This approach leverages many of the recent advances in bounded-error parameter and state estimation methods that use interval analysis to generate parameter sets and state bounds consistent with uncertain data measurements. We devise a novel approach using set-based uncertainty propagation to estimate measurement ranges at candidate time points. We then use these estimated measurements at the candidate time points to evaluate which candidate measurements furthest reduce model uncertainty. A method for quickly combining multiple candidate time points is presented and allows for determining the effect of adding multiple measurements. Biologically relevant metrics are developed and used to predict when new data measurements should be acquired, which system components should be measured and how many additional measurements should be obtained. The practicability of our approach is illustrated with a case study. This study shows that our approach is able to 1) identify candidate measurement time points that maximize information corresponding to biologically relevant metrics and 2) determine the number at which additional measurements begin to provide insignificant information. This framework can be used to balance the availability of resources with the addition of one or more measurement time points to improve the predictability of resulting models. DA - 2012/3/21/ PY - 2012/3/21/ DO - 10.1186/1752-0509-6-21 VL - 6 SP - SN - 1752-0509 ER - TY - JOUR TI - Parallel Transient Simulation of Multiphysics Circuits Using Delay-Based Partitioning AU - Priyadarshi, Shivam AU - Saunders, Christopher S. AU - Kriplani, Nikhil M. AU - Demircioglu, Harun AU - Davis, W. Rhett AU - Franzon, Paul D. AU - Steer, Michael B. T2 - IEEE TRANSACTIONS ON COMPUTER-AIDED DESIGN OF INTEGRATED CIRCUITS AND SYSTEMS AB - A parallel transient simulation technique for multiphysics circuits is presented. The technique develops partitions utilizing the inherent delay present within a circuit and between physical domains. A state-variable-based circuit delay element is presented, which implements the coupling between two spatially or temporally isolated circuit partitions. A parallel delay-based iterative approach for interfacing delay-partitioned subcircuits is applied, which achieves the reasonable accuracy of nonparallel circuit simulation if both incorporate the same interblock delay. The partitioned subcircuits are distributed to different cores of a shared-memory multicore processor and solved in parallel. A multithreaded implementation of the methodology using OpenMP is presented. Examples showing superlinear speedup compared to unpartitioned single-core simulation using the direct method are presented. This paper also discusses the impact of load balancing and absolute delay on simulation speedup. DA - 2012/10// PY - 2012/10// DO - 10.1109/tcad.2012.2201156 VL - 31 IS - 10 SP - 1522-1535 SN - 1937-4151 KW - Delay element KW - electrothermal simulation KW - multicore KW - multiphysics KW - parallel simulation KW - parallelization KW - transient simulation ER - TY - JOUR TI - Overgrowth of GaN on GaN nanowires produced by mask-less etching AU - Frajtag, P. AU - Hosalli, A. M. AU - Samberg, J. P. AU - Colter, P. C. AU - Paskova, T. AU - El-Masry, N. A. AU - Bedair, S. M. T2 - JOURNAL OF CRYSTAL GROWTH AB - We report on the generation of GaN nanowires (NWs) using mask-less reactive ion etching (RIE). The NWs are believed to be the result of a high etching rate in regions where a high dislocation density is present in the GaN films grown on sapphire substrates. We have studied the effect of defect densities in the original GaN films and its relation to the generation of these NWs. We show that defect reduction in the overgrown GaN is related to the presence of a network of embedded voids generated between these nanowires during the regrowth on the etched nanowires. We show that further reduction in dislocation density can be achieved by repeating the process of nanowire generation and overgrowth. Also we report on the residual strain and curvature in GaN after the first and second embedded voids approach (EVA). DA - 2012/8/1/ PY - 2012/8/1/ DO - 10.1016/j.jcrysgro.2011.12.055 VL - 352 IS - 1 SP - 203-208 SN - 0022-0248 KW - Defects KW - Etching KW - GaN nanowires KW - X-ray diffraction KW - Lateral overgrowth KW - Nitrides ER - TY - JOUR TI - Optimal scheduling in multi-server queues with random connectivity and retransmissions AU - Al-Zubaidy, Hussein AU - Lambadaris, Ioannis AU - Viniotis, Yannis T2 - COMPUTER COMMUNICATIONS AB - We investigate an optimal scheduling problem in a discrete-time, multiserver system of parallel queues. The servers are connected to the queues in a random fashion and scheduled packets complete service successfully with a given probability. This model is suitable for the study of dynamic packet scheduling problems in wireless systems. We study first a two-server system of two infinite-capacity queues with homogeneous arrival, service and connectivity assumptions. We use coupling arguments to prove that a “Most Balancing” scheduling policy is optimal, in a stochastic ordering sense, for this system. We then consider a finite-capacity, non-homogeneous, multi-server and multi-queue system. We develop a dynamic programming model to determine numerically the scheduling policy that optimizes a range of cost functions, including average total queue sizes. We also compare the performance of the optimal policy to that of a few other policies via simulations. DA - 2012/7/15/ PY - 2012/7/15/ DO - 10.1016/j.comcom.2012.05.007 VL - 35 IS - 13 SP - 1626-1638 SN - 1873-703X KW - Optimal scheduling KW - Stochastic coupling arguments KW - Stochastic dominance KW - Most Balancing algorithms KW - Random connectivity ER - TY - CONF TI - Optimal estimation with arbitrary error metrics in compressed sensing AU - Tan, J. AU - Carmon, D. AU - Baron, Dror AB - Noisy compressed sensing deals with the estimation of a system input from its noise-corrupted linear measurements. The performance of the estimation is usually quantified by some standard error metric such as squared error or support error. In this paper, we consider a noisy compressed sensing problem with any arbitrary error metric. We propose a simple, fast, and general algorithm that estimates the original signal by minimizing an arbitrary error metric defined by the user. We verify that, owing to the decoupling principle, our algorithm is optimal, and we describe a general method to compute the fundamental information-theoretic performance limit for any well-defined error metric. We provide an example where the metric is absolute error and give the theoretical performance limit for it. The experimental results show that our algorithm outperforms methods such as relaxed belief propagation, and reaches the suggested theoretical limit for our example error metric. C2 - 2012/// C3 - 2012 IEEE Statistical Signal Processing Workshop (ssp) DA - 2012/// DO - 10.1109/ssp.2012.6319767 SP - 588–591 ER - TY - JOUR TI - Modulation Technique to Reverse Power Flow for the Isolated Series Resonant DC-DC Converter With Clamped Capacitor Voltage AU - Du, Yu AU - Lukic, Srdjan M. AU - Jacobson, Boris S. AU - Huang, Alex Q. T2 - IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS AB - The series resonant dc-dc converter with clamped capacitor voltage exhibits excellent characteristics in forward operating mode, including simple control, high reliability, soft switching, high power density, and inherently limited load fault current. However, the conventional single angle phase-shift modulation that works well in the forward mode cannot reverse the power flow. In this paper, we propose a modulation strategy for reverse-mode operation by utilizing three phase-shift angles afforded by the two active full bridges of the circuit. We identify the optimal modulation trajectories in 3-D modulation space and implement a lookup-table-based modulator for power flow control. A high-fidelity simulation model of a 35-kW 750-V input, 300-600-V output, and 50-kHz insulated-gate bipolar-transistor-based converter was used for verification. The proposed modulation scheme and efficiency calculations were validated on a scaled-down (15-kW) prototype. The power loss distribution was analyzed for further converter efficiency optimization. DA - 2012/12// PY - 2012/12// DO - 10.1109/tie.2011.2175669 VL - 59 IS - 12 SP - 4617-4628 SN - 1557-9948 KW - Bidirectional dc-dc power converters KW - energy storage KW - lookup table (LUT) KW - phase modulation KW - resonant converters ER - TY - JOUR TI - Magnetic domain wall transfer via graphene mediated electrostatic control AU - Duan, X. AU - Stephanovich, V. A. AU - Semenov, Y. G. AU - Kim, K. W. T2 - Applied Physics Letters AB - A mechanism that enables electrically controlled magnetic domain wall transfer in a ferromagnetic insulator (FMI) is investigated theoretically by utilizing graphene as a crucial mediating material. The concept is grounded on the variability of the exchange interaction energy between a ferromagnetic insulator and a proximate graphene layer with an inhomogeneous carrier density. A memory device prototype is proposed based on the effect that does not require an active current for its intrinsic function. Our analysis illustrates the highly efficient device operation, with an estimated switching energy of 10−16 J for one binary bit of nonvolatile information. DA - 2012/7/2/ PY - 2012/7/2/ DO - 10.1063/1.4732794 VL - 101 IS - 1 SP - 013103 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.4732794 DB - Crossref KW - carrier density KW - exchange interactions (electron) KW - ferromagnetic materials KW - graphene KW - magnetic domain walls KW - MRAM devices ER - TY - JOUR TI - Leakage Power Contributor Modeling AU - Dhanwada, Nagu AU - Hathaway, David AU - Frenkil, Jerry AU - Davis, W. Rhett AU - Demircioglu, Harun T2 - IEEE DESIGN & TEST OF COMPUTERS AB - Low-power or power-aware design is one of the greatest challenges facing the semiconductor industry. The fidelity of low power design is dependent on the accuracy of power modeling across a wide range of PVT values. This paper describes an alternative “power contributor”based approach to cell leakage characterization that exploits inherent separability of power consumption for different portions of a cell. An experimental use of this approach is also presented that demonstrates how the effort to characterize leakage power can be greatly reduced with only a marginal impact on accuracy. DA - 2012/// PY - 2012/// DO - 10.1109/mdt.2012.2183573 VL - 29 IS - 2 SP - 71-78 SN - 0740-7475 ER - TY - CONF TI - Human activity modeling as Brownian motion on shape manifold AU - Yi, S. AU - Krim, H. AU - Norris, L. K. AB - In this paper we propose a stochastic modeling of human activity on a shape manifold. From a video sequence, human activity is extracted as a sequence of shape. Such a sequence is considered as one realization of a random process on shape manifold. Then Different activities are modeled by manifold valued random processes with different distributions. To solve the problem of stochastic modeling on a manifold, we first regress a manifold values process to a Euclidean process. The resulted process then could be modeled by linear models such as a stationary incremental process and a piecewise stationary incremental process. The mapping from manifold to Euclidean space is known as a stochastic development. The idea is to parallelly transport the tangent along curve on manifold to a single tangent space. The advantage of such technique is the one to one correspondence between the process in Euclidean space and the one on manifold. The proposed algorithm is tested on database [5] and compared with the related work in [5]. The result demonstrate the high accuracy of our modeling in characterizing different activities. C2 - 2012/// C3 - Scale space and variational methods in computer vision DA - 2012/// DO - 10.1007/978-3-642-24785-9_53 VL - 6667 SP - 628-639 ER - TY - JOUR TI - Front-End Design for Compact MIMO Receivers: A Communication Theory Perspective AU - Domizioli, Carlo P. AU - Hughes, Brian L. T2 - IEEE TRANSACTIONS ON COMMUNICATIONS AB - The front-end is a crucial component in modern wireless communication systems. For SISO systems minimizing the front-end noise factor is optimal, and this also applies to MIMO systems with i.i.d. noise. However, for compact MIMO receivers that may exhibit spatially correlated noise, e.g., through antenna mutual coupling, the optimal design procedure is not clear. In this paper we develop MIMO low-noise design principles from a communication theory perspective by deriving generalizations of SNR and noise factor from various MIMO communication schemes. As one result, we are able to derive optimal matching networks for a bank of uncoupled amplifiers. DA - 2012/10// PY - 2012/10// DO - 10.1109/tcomm.2012.072612.110541 VL - 60 IS - 10 SP - 2938-2949 SN - 1558-0857 KW - MIMO KW - antenna arrays KW - noise figure KW - receivers KW - channel capacity ER - TY - JOUR TI - Efficient and monolithic polarization conversion system based on a polarization grating AU - Kim, Jihwan AU - Komanduri, Ravi K. AU - Lawler, Kristopher F. AU - Kekas, D. Jason AU - Escuti, Michael J. T2 - APPLIED OPTICS AB - We introduce a new polarization conversion system (PCS) based on a liquid-crystal polarization grating (PG) and louvered wave plate. A simple arrangement of these elements laminated between two microlens arrays results in a compact and monolithic element, with the ability to nearly completely convert unpolarized input into linearly polarized output across most of the visible bandwidth. In our first prototypes, this PG-PCS approach manifests nearly 90% conversion efficiency of unpolarized to polarized for ±11° input light divergence, leading to an energy efficient picoprojector that presents high efficacy (12  lm/W) with good color uniformity. DA - 2012/7/10/ PY - 2012/7/10/ DO - 10.1364/ao.51.004852 VL - 51 IS - 20 SP - 4852-4857 SN - 2155-3165 ER - TY - JOUR TI - An MCMC Approach to Universal Lossy Compression of Analog Sources AU - Baron, Dror AU - Weissman, Tsachy T2 - IEEE TRANSACTIONS ON SIGNAL PROCESSING AB - Motivated by the Markov chain Monte Carlo (MCMC) approach to the compression of discrete sources developed by Jalali and Weissman, we propose a lossy compression algorithm for analog sources that relies on a finite reproduction alphabet, which grows with the input length. The algorithm achieves, in an appropriate asymptotic sense, the optimum Shannon theoretic tradeoff between rate and distortion, universally for stationary ergodic continuous amplitude sources. We further propose an MCMC-based algorithm that resorts to a reduced reproduction alphabet when such reduction does not prevent achieving the Shannon limit. The latter algorithm is advantageous due to its reduced complexity and improved rates of convergence when employed on sources with a finite and small optimum reproduction alphabet. DA - 2012/10// PY - 2012/10// DO - 10.1109/tsp.2012.2206585 VL - 60 IS - 10 SP - 5230-5240 SN - 1941-0476 KW - Compression algorithms KW - rate distortion KW - simulated annealing ER - TY - JOUR TI - Adaptive Bit-Interleaved Coded Modulation Based on the Expurgated Bound for Mobile Radio OFDM Systems Aided by Fading Prediction AU - Jia, Tao AU - Duel-Hallen, Alexandra T2 - IEEE TRANSACTIONS ON COMMUNICATIONS AB - Adaptive bit-interleaved coded modulation (ABICM) is attractive for rapidly varying mobile radio channels due to its robustness to imperfect channel state information (CSI). A novel ABICM method that exploits the expurgated bound to maintain the target bit error rate (BER) for diverse CSI conditions is proposed and evaluated for an adaptive mobile radio orthogonal frequency division-multiplex (OFDM) system aided by the long-range fading prediction. It is demonstrated that ABICM is much less sensitive to prediction errors than adaptive modulation techniques that do not employ interleaving. However, reliable fading prediction is still necessary for ABICM to achieve high spectral efficiency for practical channel conditions. DA - 2012/8// PY - 2012/8// DO - 10.1109/tcomm.2012.062512.110022 VL - 60 IS - 8 SP - 2059-2064 SN - 0090-6778 UR - http://dx.doi.org/10.1109/TCOMM.2012.062512.110022 KW - Adaptive modulation KW - fading channels KW - interleaved coding KW - frequency division multiplexing KW - resource management ER - TY - CONF TI - A sampling theorem for a 2D surface AU - Lee, D. AU - Krim, H. AB - The sampling rate for signal reconstruction has been and remains an important and central criterion in numerous applications. We propose, in this paper, a new approach to determining an optimal sampling rate for a 2D-surface reconstruction using the so-called Two-Thirds Power Law. This paper first introduces an algorithm of a 2D surface reconstruction from a 2D image of circular light patterns projected on the surface. Upon defining the Two-Thirds Power Law we show how the extracted spectral information helps define an optimal sampling rate of the surface, reflected in the number of projected circular patterns required for its reconstruction. This result is of interest in a number of applications such as 3D face recognition and development of new efficient 3D cameras. Substantive examples are provided. C2 - 2012/// C3 - Scale space and variational methods in computer vision DA - 2012/// DO - 10.1007/978-3-642-24785-9_47 VL - 6667 SP - 556-567 ER - TY - JOUR TI - A cascaded second-order approach to computing third-order scattering of noncollinear acoustic beams AU - Garner, Glenwood AU - Steer, Michael B. T2 - APPLIED ACOUSTICS AB - A theoretical development of the third-order nonlinear scattering of sound from two noncollinear ultrasonic beams produced by baffled piston sources is presented. The third-order intermodulation (IM3) frequency components are derived by exploiting cascaded second-order nonlinear effects where the quadratic nonlinear interaction of second-order frequency components with first-order (primary) frequency components is considered. It is shown that cascaded second-order interactions generate intermodulation frequency components that are equivalent to those generated by cubic nonlinear effects. Comparison of measured and modeled amplitude sweeps demonstrate the three-to-one gain in decibels of the amplitudes of the third-order intermodulation frequency components to that of the primary frequency components. Measurements are also presented for the farfield interaction of distantly spaced sources, which results in a highly focused ultrasonic parametric array. Also considered are the nearfield interaction of closely spaced sources, which results in scattering, with good agreement to the theory. DA - 2012/12// PY - 2012/12// DO - 10.1016/j.apacoust.2011.12.013 VL - 73 IS - 12 SP - 1220-1230 SN - 1872-910X KW - Nonlinear acoustics KW - Intermodulation distortion KW - Acoustic sensors KW - Focused sound KW - Ultrasound KW - Parametric array ER - TY - CONF TI - Why it is so hard to find small radio frequency signals in the presence of large signals AU - Steer, M. B. AU - Wilkerson, J. R. AU - Kriplani, N. M. AU - Wetherington, J. M. AB - The essence of radar, radio and wireless sensor engineering is extracting small information-bearing signals. This is notoriously difficult and engineers compensate by transmitting high power signals, reducing range, and spacing wireless systems in frequency and time. New understandings of passive intermodulation distortion, thermal effects, time-frequency effects, and noise are presented. It is seen that the familiar frequency-domain-based abstractions have missed important underlying physics. Through greater understanding, RF engineers can develop microwave systems with far lower levels of distortion and noise. C2 - 2012/// C3 - 2012 Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits (INMMIC) DA - 2012/// DO - 10.1109/inmmic.2012.6331916 ER - TY - JOUR TI - Variable Length Compression of Codeword Indices for Lossy Compression AU - Baron, Dror AU - Jacob, Theju T2 - IEEE SIGNAL PROCESSING LETTERS AB - Many problems in information theory feature an index into a random codebook being encoded with a fixed length scheme. We propose to purposefully select the index in a manner that skews its distribution, thus making variable length entropy coding of the index more attractive. In an application to lossy compression of a Bernoulli source, we illustrate that variable length coding yields a reduction in the rate over fixed length coding, and allows to reach a requisite rate distortion performance level using a smaller codebook. DA - 2012/12// PY - 2012/12// DO - 10.1109/lsp.2012.2223462 VL - 19 IS - 12 SP - 849-852 SN - 1070-9908 KW - Entropy coding KW - lossy compression KW - rate distortion KW - variable length coding ER - TY - JOUR TI - Transition Control Strategy Between Standalone and Grid-Connected Operations of Voltage-Source Inverters AU - Arafat, Md. Nayeem AU - Palle, Sreeshailam AU - Sozer, Yilmaz AU - Husain, Iqbal T2 - IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS AB - This paper proposes a smooth transition control strategy for voltage-source inverters between standalone (SA) and grid-connected (GC) modes of operation. In the GC mode, the amount of power exchanged with the utility grid is controlled by regulating the phase currents. In the SA mode, the load voltage is regulated by the inverter with its phase dictated by the inverter control. The transition between SA and GC operations that will ensure continuous power delivery to the load requires continuation in the phase of the system voltage. The proportional-integral, trapezoidal, sinusoidal, and staircase frequency variation techniques have been analyzed to find the best approach for minimizing the total harmonic distortion (THD). A smooth frequency variation technique has been developed, which provides lower THD on the voltage waveforms compared with the other techniques. The new algorithm has been implemented on a 5-kW single-phase utility interactive inverter having the SA operation capability. The simulation and experimental results show that the proposed technique provides seamless transition between the inverter modes of operation with minimal distortion at the inverter output voltage. DA - 2012/// PY - 2012/// DO - 10.1109/tia.2012.2210013 VL - 48 IS - 5 SP - 1516-1525 SN - 1939-9367 KW - AC-DC power converters KW - distributed power generation KW - uninterruptible power systems ER - TY - JOUR TI - Switched Reluctance Generator Controls for Optimal Power Generation and Battery Charging AU - Narla, Sandeep AU - Sozer, Yilmaz AU - Husain, Iqbal T2 - IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS AB - This paper presents the control strategy for varying the turn-on and turn-off angles of three-phase switched reluctance generators (SRGs) to maximize the efficiency as well as to reduce the dc-link ripple current resulting from the commutation of the phases at high speeds. The behavior of the commutation angles is analyzed first through the offline measurement of dc-link current and voltage, generator speed, and phase currents. The analysis of the collected data has shown that the commutation angles providing the minimum ripple on the dc-link current achieve the maximum generating efficiencies. A novel control technique, developed based on the finding, achieves the desired generating set point with maximum efficiency and minimum ripple on the charging current. The control algorithm actively searches the turn-off angles to reduce the amount of normalized ripple on the dc-link current, which also ensures the generation with the maximum efficiency. The turn-on angle is controlled through a proportional-integral controller to generate a desired power level. The algorithm is implemented successfully on a 1-kW three-phase SRG charging a NiMH battery pack. DA - 2012/// PY - 2012/// DO - 10.1109/tia.2012.2209850 VL - 48 IS - 5 SP - 1452-1459 SN - 1939-9367 KW - Commutation angle KW - generator control KW - SRG control KW - switched reluctance generators (SRGs) ER - TY - JOUR TI - Functional redundancy of the two 5-hydroxylases in monolignol biosynthesis of Populus trichocarpa: LC-MS/MS based protein quantification and metabolic flux analysis AU - Wang, Jack P. AU - Shuford, Christopher M. AU - Li, Quanzi AU - Song, Jina AU - Lin, Ying-Chung AU - Sun, Ying-Hsuan AU - Chen, Hsi-Chuan AU - Williams, Cranos M. AU - Muddiman, David C. AU - Sederoff, Ronald R. AU - Chiang, Vincent L. T2 - PLANTA DA - 2012/9// PY - 2012/9// DO - 10.1007/s00425-012-1663-5 VL - 236 IS - 3 SP - 795-808 SN - 1432-2048 KW - Lignin KW - Syringyl lignin KW - Angiosperm KW - Kinetics KW - Subcellular localization ER - TY - CONF TI - Design, modeling, and fabrication of mm(3) three-dimensional integrated antennas AU - Gadfort, P. AU - Franzon, Paul AB - This paper describes the design, modeling, and fabrication methods of a new method to build three-dimensional integrated antenna arrays. The goal is to create a mm-scale sensor for implantation in the human body. Since the orientation of the sensor is not known in advance the antenna must work equally well in all directions. The best way to do this is to build antennas on each side of a cubic structure. The antenna is intended for near field power harvesting. By utilizing the edge antenna the power transfer efficiency can be increased by 18.9 dB at even the worst orientations for the sensors. Another application would be to create an omnidirectional antenna for high frequency mobile devices. C2 - 2012/// C3 - 2012 IEEE 62nd Electronic Components and Technology Conference (ECTC) DA - 2012/// DO - 10.1109/ectc.2012.6249081 SP - 1794–1799 ER - TY - JOUR TI - Charge transfer equilibria in ambient-exposed epitaxial graphene on (0001¯) 6 H-SiC AU - Sidorov, Anton N. AU - Gaskill, Kurt AU - Buongiorno Nardelli, Marco AU - Tedesco, Joseph L. AU - Myers-Ward, Rachel L. AU - Eddy, Charles R., Jr. AU - Jayasekera, Thushari AU - Kim, Ki Wook AU - Jayasingha, Ruwantha AU - Sherehiy, Andriy AU - Stallard, Robert AU - Sumanasekera, Gamini U. T2 - Journal of Applied Physics AB - The transport properties of electronic materials have been long interpreted independently from both the underlying bulk-like behavior of the substrate or the influence of ambient gases. This is no longer the case for ultra-thin graphene whose properties are dominated by the interfaces between the active material and its surroundings. Here, we show that the graphene interactions with its environments are critical for the electrostatic and electrochemical equilibrium of the active device layers and their transport properties. Based on the prototypical case of epitaxial graphene on (0001¯) 6 H-SiC and using a combination of in-situ thermoelectric power and resistance measurements and simulations from first principles, we demonstrate that the cooperative occurrence of an electrochemically mediated charge transfer from the graphene to air, combined with the peculiar electronic structure of the graphene/SiC interface, explains the wide variation of measured conductivity and charge carrier type found in prior reports. DA - 2012/6// PY - 2012/6// DO - 10.1063/1.4725413 VL - 111 IS - 11 SP - 113706 J2 - Journal of Applied Physics LA - en OP - SN - 0021-8979 1089-7550 UR - http://dx.doi.org/10.1063/1.4725413 DB - Crossref ER - TY - CONF TI - Characterization of the dynamic range of a single aperture communications system AU - Wetherington, J. M. AU - Steer, M. B. AB - A resonant antenna displays passive intermodulation related to antenna vibrations at levels that impact communications systems. A non-resonant antenna was immune to structure vibrations. Both antennas were of solid construction with thick metalization and did not exhibit electro-thermal passive intermodulation distortion previously observed with microstrip structures. The ultimate dynamic ranges of two antennas are explored using a measurement system with a dynamic range of 98 dB at one hertz offset from a 30 dBm, 500 MHz transmit signal. This increased to 140 dB when the separation increased to 100 Hz. C2 - 2012/// C3 - 2012 Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits (INMMIC) DA - 2012/// DO - 10.1109/inmmic.2012.6331945 ER - TY - JOUR TI - Tunable photogalvanic effect on topological insulator surfaces via proximity interactions AU - Semenov, Yuriy G. AU - Li, Xiaodong AU - Kim, Ki Wook T2 - Physical Review B AB - An unusual photo-galvanic effect is predicted on the topological insulator surface when its semi-metallic electronic spectrum is modified by an adjacent ferromagnet. The effect is correlated with light absorption in a wide frequency range (from a few to hundreds of meV) and produces a pronounced response that is not only resonant to the photon energy but also tunable by an external electrical bias. The exceptionally strong peak photocurrent of the order of $\mu$A/cm may be achieved at elevated temperatures with the illumination power of 1 W/cm$^2$ in the THz range on Bi$_2$Se$_3$. These advantages could enable room-temperature detection of far-infrared radiation. DA - 2012/11/1/ PY - 2012/11/1/ DO - 10.1103/physrevb.86.201401 VL - 86 IS - 20 SP - J2 - Phys. Rev. B LA - en OP - SN - 1098-0121 1550-235X UR - http://dx.doi.org/10.1103/PhysRevB.86.201401 DB - Crossref ER - TY - JOUR TI - Research Funding and the PROCEEDINGS OF THE IEEE Centennial AU - Trew, Robert J. T2 - PROCEEDINGS OF THE IEEE DA - 2012/5// PY - 2012/5// DO - 10.1109/jproc.2012.2190682 VL - 100 SP - 1273-1277 SN - 0018-9219 ER - TY - JOUR TI - Overview for Reflections and Reviews of Past Predictions AU - Trusell, H. Joel T2 - PROCEEDINGS OF THE IEEE DA - 2012/5// PY - 2012/5// DO - 10.1109/jproc.2012.2190166 VL - 100 SP - 1255-1260 SN - 0018-9219 ER - TY - JOUR TI - Drainage water management AU - Skaggs, R. Wayne AU - Fausey, Norman R. AU - Evans, Robert O. T2 - JOURNAL OF SOIL AND WATER CONSERVATION AB - This article introduces a series of papers that report results of field studies to determine the effectiveness of drainage water management (DWM) on conserving drainage water and reducing losses of nitrogen (N) to surface waters. The series is focused on the performance of the DWM (also called controlled drainage [CD]) practice in the US Midwest, where N leached from millions of acres of cropland contributes to surface water quality problems on both local and national scales. Results of these new studies are consistent with those from previous research reported in the literature that DWM can be used to reduce N losses (primarily in the nitrate nitrogen [NO3-N] form) from subsurface drained fields. The measured impact varied over a wide range (18% to more than 75% reduction in N loss to surface waters), depending on drainage system design, location, soil, and site conditions. Crop yields were increased by DWM on some sites and not on others, with the year-to-year impacts of DWM on yields dependent on weather conditions, as well as the above factors. Papers reporting advances in the development of datasets and models to predict the impact of drainage intensity and DWM on hydrology and water quality at watershed and… DA - 2012/// PY - 2012/// DO - 10.2489/jswc.67.6.167a VL - 67 IS - 6 SP - 167A-172A SN - 1941-3300 ER - TY - JOUR TI - Atomic Layer Deposition of SiO2 for AlGaN/GaN MOS-HFETs AU - Kirkpatrick, Casey J. AU - Lee, Bongmook AU - Suri, Rahul AU - Yang, Xiangyu AU - Misra, Veena T2 - IEEE ELECTRON DEVICE LETTERS AB - This letter investigates the electrical properties of SiO 2 gate dielectric on GaN heterostructures deposited by atomic layer deposition (ALD). ALD SiO 2 has a dielectric constant of 3.9 and a bandgap of 8.8 eV. ALD SiO 2 provides a good interface to GaN and minimizes the interfacial layer growth. The threshold voltage of metal-oxide-semiconductor heterojunction field-effect transistors with ALD SiO 2 dielectric is -1.5 V, owing to a fixed charge concentration of -1.6 × 10 12 cm -2 . It was also found that devices with ALD SiO 2 dielectric exhibit three orders of magnitude reduction in gate leakage current compared to conventional Schottky gate HFETs. DA - 2012/9// PY - 2012/9// DO - 10.1109/led.2012.2203782 VL - 33 IS - 9 SP - 1240-1242 SN - 1558-0563 KW - Atomic layer deposition (ALD) KW - GaN KW - heterostructure field-effect transistor (HFET) KW - metal-oxide-semiconductor heterojunction field-effect transistor (MOS-HFET) KW - SiO2 ER - TY - JOUR TI - A Comparative Study of Gate Structures for 9.4-kV4H-SiC Normally On Vertical JFETs AU - Sung, Woongje AU - Van Brunt, Edward AU - Baliga, B. Jayant AU - Huang, Alex Q. T2 - IEEE TRANSACTIONS ON ELECTRON DEVICES AB - This paper reports the development of 9.4-kV 4H-SiC normally on lateral-channel vertical JFETs. The developed JFETs utilize a buried layer to create a lateral conduction channel, shielding the source from the effects of drain bias. The lowest measured $R_{\rm on, sp}$ was 127 $\hbox{m}\Omega\cdot\hbox{cm}^{2}$ . Measurements indicate that the channel resistivity can be further reduced by channel optimization. The fabricated JFETs exhibit pentode-like $I_{D}$$V_{\rm DS}$ characteristics with a high forward direct-current blocking gain of over 500. This paper provides a comparative study of gate structures in order to achieve the lowest on -state switching losses and to provide stable forward blocking characteristics for a normally on JFET. DA - 2012/9// PY - 2012/9// DO - 10.1109/ted.2012.2203337 VL - 59 IS - 9 SP - 2417-2423 SN - 0018-9383 KW - High voltage KW - JFET KW - normally on KW - silicon carbide KW - 4H-SiC ER - TY - JOUR TI - Two dimensional crystal tunneling devices for THz operation AU - Kong, B. D. AU - Zeng, C. AU - Gaskill, D. K. AU - Wang, K. L. AU - Kim, K. W. T2 - Applied Physics Letters AB - Two dimensional (2D) crystal heterostructures are shown to possess a unique opportunity for novel THz nonlinear devices. In contrast to the oxide tunneling barrier, the uniformity of 2D insulators in the thickness control provides an ideal condition for tunneling barriers in the atomic scale. Numerical calculations based on a first principles method clearly indicate the feasibility of diode operation with barriers as thin as two monolayers of hexagonal boron nitride or molybdenum disulfide when placed between graphene-metal asymmetric electrodes. Further analysis predicts the cut-off frequencies of the proposed device over 10 THz while maintaining strong nonlinearity for zero-bias rectification. Application of the tunneling structure to hot electron transistors is also investigated, illustrating the THz operation with superior power performance. The proposed concept provides an excellent opportunity for realizing active nonlinear devices in the frequency range inaccessible thus far. DA - 2012/12/24/ PY - 2012/12/24/ DO - 10.1063/1.4773514 VL - 101 IS - 26 SP - 263112 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.4773514 DB - Crossref ER - TY - CONF TI - Target-directed navigation using wireless sensor networks and implicit surface interpolation AU - Deshpande, N. AU - Grant, E. AU - Henderson, T. C. AB - This paper extends the novel research for event localization and target-directed navigation using a deployed wireless sensor network (WSN) [4]. The goal is to have an autonomous mobile robot (AMR) navigate to a target-location by: (i) producing an artificial magnitude distribution within the WSN-covered region, and (ii) having the AMR use the pseudo-gradient from the interpolated distribution in its neighborhood, as it moves towards the target location. Implicit surfaces are used to interpolate the artificial distribution. This scheme only uses the topology of the WSN and received signal strength (RSS) to estimate an efficient navigation path for the AMR. Here, the AMR does not require global coordinates for the region, as it relies on local, neighborhood information alone to navigate. The performance of the scheme is analyzed with hardware experiments and in simulation, using a variety of node-densities and with increasing levels of noise to ensure robustness. C2 - 2012/// C3 - 2012 IEEE International Conference on Robotics and Automation (ICRA) DA - 2012/// DO - 10.1109/icra.2012.6224997 SP - 457-462 ER - TY - JOUR TI - Spatial heterodyne interferometry with polarization gratings AU - Kudenov, Michael W. AU - Miskiewicz, Matthew N. AU - Escuti, Michael J. AU - Dereniak, Eustace L. T2 - OPTICS LETTERS AB - The implementation of a polarization-based spatial heterodyne interferometer (SHI) is described. While a conventional SHI uses a Michelson interferometer and diffraction gratings, our SHI exploits mechanically robust Wollaston prisms and polarization gratings. A theoretical model for the polarization SHI is provided and validated with data from our proof of concept experiments. This device is expected to provide a compact monolithic sensor for subangstrom resolution spectroscopy in remote sensing, biomedical imaging, and machine vision applications. DA - 2012/11/1/ PY - 2012/11/1/ DO - 10.1364/ol.37.004413 VL - 37 IS - 21 SP - 4413-4415 SN - 1539-4794 ER - TY - CONF TI - Secure distributed control in unreliable D-NCS AU - Zeng, W. T. AU - Chow, M. Y. AU - Ning, P. AB - Distributed Networked Control Systems (D-NCS), such as the electric power system, the transportation system, or almost any large-scale network, are vulnerable to cyber attacks. The compromised nodes in the D-NCS can affect it and cause the distributed control algorithms (e.g., consensus algorithm) to fail. This paper is concerned with the problem of designing a secure distributed control methodology that is capable of performing a secure consensus computation in a D-NCS in the presence of misbehaving nodes. We consider the case of formation control in a multi-robot system using the linear consensus algorithm, and we model the malicious attack as an exogenous input that compromises the behavior of a single robot in this multi-robot system. The proposed secure distributed control methodology includes four phases: (1) Detect the neighbors' misbehaviors relying only on each robot's local observations; (2) Adjust the consensus computation weights according to the neighbors' reputation values; (3) Identify and isolate the compromised robot; and (4) Update the reference state using the adjusted consensus computation weights to ensure the convergence of well-behaving robots. A Simulink-based testbed for multi-robot formation control is used to illustrate the effectiveness of the proposed method. C2 - 2012/// C3 - 2012 IEEE International Symposium on Industrial Electronics (ISIE) DA - 2012/// DO - 10.1109/isie.2012.6237375 SP - 1858-1863 ER - TY - JOUR TI - Phonon engineering in nanostructures: Controlling interfacial thermal resistance in multilayer-graphene/dielectric heterojunctions AU - Mao, R. AU - Kong, B. D. AU - Kim, K. W. AU - Jayasekera, T. AU - Calzolari, A. AU - Buongiorno Nardelli, M. T2 - Applied Physics Letters AB - Using calculations from first principles and the Landauer approach for phonon transport, we study the Kapitza resistance in selected multilayer graphene/dielectric heterojunctions (hexagonal BN and wurtzite SiC) and demonstrate (i) the resistance variability (∼50−700×10−10 m2K/W) induced by vertical coupling, dimensionality, and atomistic structure of the system and (ii) the ability of understanding the intensity of the thermal transmittance in terms of the phonon distribution at the interface. Our results pave the way to the fundamental understanding of active phonon engineering by microscopic geometry design. DA - 2012/9/10/ PY - 2012/9/10/ DO - 10.1063/1.4752437 VL - 101 IS - 11 SP - 113111 J2 - Appl. Phys. Lett. LA - en OP - SN - 0003-6951 1077-3118 UR - http://dx.doi.org/10.1063/1.4752437 DB - Crossref ER - TY - JOUR TI - Orthogonal Positive-Bevel Termination for Chip-Size SiC Reverse Blocking Devices AU - Huang, Xing AU - Van Brunt, Edward AU - Baliga, B. Jayant AU - Huang, Alex Q. T2 - IEEE ELECTRON DEVICE LETTERS AB - Symmetric blocking power semiconductor switches require positive-bevel edge terminations for the reverse blocking p-n junction. This technique has been extensively applied to silicon wafer-size devices with high current ratings. In this letter, we propose and experimentally demonstrate, for the first time, that an orthogonal positive-bevel termination can be used for the reverse blocking junction of chip-size SiC devices. The edge termination was formed by sawing the SiC wafer with a V-shaped dicing blade. For proof of concept, our experiment was done on a SiC wafer with a 15.8-μm 6.1 × 10 15 cm -3 p-type epitaxial layer grown on an N + substrate. The positive-bevel termination resulted in a breakdown voltage of over 1000 V as limited by reach-through breakdown even without removal of damage from the sawing. The leakage current was found to be reduced by two orders of magnitude after reactive ion etching of the SiC bevel surface to remove the sawing damage. DA - 2012/11// PY - 2012/11// DO - 10.1109/led.2012.2215003 VL - 33 IS - 11 SP - 1592-1594 SN - 1558-0563 KW - Edge termination KW - fault interruption device (FID) KW - positive bevel KW - reverse blocking KW - symmetric blocking KW - 4H-SiC ER - TY - JOUR TI - Opportunistic Decode-and-Forward Relaying With Beamforming in Two-Wave With Diffuse Power Fading AU - Lu, Yao AU - Yang, Nan AU - Dai, Huaiyu AU - Wang, Xiaoxiang T2 - IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY AB - In this paper, we propose new opportunistic decode-and-forward (DF) relaying with beamforming for multirelay networks, where an N s -antenna source communicates with an N d -antenna destination with the aid of N parallel single-antenna relays. Among these relays, only one relay that correctly decodes the signal from the source and has the highest instantaneous signal-to-noise ratio (SNR) to the destination is selected for transmission. The source employs maximum ratio transmission (MRT) to transmit, whereas the destination performs maximum ratio combining (MRC) to the received signals. To examine the benefits of the proposed scheme, we first derive the exact outage probability for independently but non-identically distributed (i.n.i.d.) two-wave with diffuse power (TWDP) fading channels. We then derive an easy-to-compute expression for the exact outage probability to reduce computational cost. Our results encompass Rayleigh and Rician fading as special cases. We further derive a compact expression for the asymptotic outage probability, which characterizes two factors governing the network performance at high SNRs, i.e., the diversity order and the array gain. We demonstrate that our scheme preserves the maximum diversity order of N × min {N s , N d }. Additionally, we derive the optimal power allocation factor, which provides a practical design rule to optimally distribute the total transmission power between the source and the selected relay to minimize the outage probability. DA - 2012/9// PY - 2012/9// DO - 10.1109/tvt.2012.2205028 VL - 61 IS - 7 SP - 3050-3060 SN - 1939-9359 KW - Decode and forward (DF) KW - multiple-input multiple-output KW - opportunistic relaying KW - optimal power allocation KW - two-wave with diffuse power (TWDP) fading ER - TY - CONF TI - Modeling and online parameter identification of Li-polymer battery cells for SOC estimation AU - Rahimi-Eichi, H. AU - Baronti, F. AU - Chow, M. Y. AB - Finding an accurate and easily to implement model of batteries is an essential step in properly estimating the state of charge (SOC) of the battery in real-time. In this paper, an equivalent circuit based battery model with nonlinear relationship between the open circuit voltage (V OC ) and the SOC is projected into several piece-wise linear functions. Moving window Least Squares (LS) parameter identification technique is then utilized to estimate and update the parameters of the battery model in each sampling time. The continuously updated parameters are fed to a linear observer to estimate the SOC of the battery. The effectiveness of the proposed modeling and estimation approach are verified experimentally on Lithium Polymer batteries. C2 - 2012/// C3 - 2012 IEEE International Symposium on Industrial Electronics (ISIE) DA - 2012/// DO - 10.1109/isie.2012.6237284 SP - 1336-1341 ER - TY - CONF TI - Gene library for real-time monitoring of large scale time-sensitive systems AU - Ojha, U. AU - Asr, N. R. AU - Chow, M. Y. AB - For time-sensitive applications with hard real-time constraint, the utility of a decision goes to zero if the deadline is missed thus it is very important to use methodologies that can deliver solutions within their time limit. For large scale monitoring and prediction systems with small time periods this problem renders conservative optimization techniques to be useless especially because of the time they take to calculate optimal values. In order to make real-time decisions, we need to introduce methods that are computationally light and can still maintain accuracy that is close to results given by optimization methods. A gene library was formulated that stored (i) the regulatory proteins in order to select the relevant features that determined the system behavior and (ii) computationally simple mappings that mapped these relevant features to the desired system state. The proposed method was implemented in an Intelligent Transportation System scenario to determine the rollover risk. A gene library was created that eliminated the need to perform heavy computations (solving second order differential equation) while still maintaining the accuracy of prediction to +/− 4% of the actual value in the normal operating range. C2 - 2012/// C3 - 2012 IEEE International Symposium on Industrial Electronics (ISIE) DA - 2012/// DO - 10.1109/isie.2012.6237319 SP - 1535-1540 ER - TY - JOUR TI - Error Reduction in Magnetoquasistatic Positioning Using Orthogonal Emitter Measurements AU - Arumugam, Darmindra D. AU - Griffin, Joshua D. AU - Stancil, Daniel D. AU - Ricketts, David S. T2 - IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS AB - Measurements of the emitted magnetoquasistatic fields generated by a vertical emitting loop and detected at the terminals of seven fixed vertical receiving loops, all located above earth, are used to solve for position and orientation of the emitter. The coupling between the mobile emitting and fixed receiving loops was measured over a 3 × 3 emitter grid spanning an 18 ×18-m 2 area and for azimuthal orientations between 0 ° and 330 ° at 30 ° increments. Inverting the theoretical coupling expressions for two-dimensional position and azimuthal orientation resulted in a mean position and orientation error of 0.62 m and 2.86 ° , respectively. Calculations including orthogonal-emitter configurations resulted in a mean position and orientation error of 0.21 m and 1.12 ° , respectively, which represents a 66.1% and 60.8% reduction in error, respectively. DA - 2012/// PY - 2012/// DO - 10.1109/lawp.2012.2229958 VL - 11 SP - 1462-1465 SN - 1536-1225 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84871829678&partnerID=MN8TOARS KW - Electromagnetic fields KW - magnetoquasistatics KW - radio position measurement KW - radio tracking ER - TY - JOUR TI - Enabling Code Diversity for Mobile Radio Channels using Long-Range Fading Prediction AU - Wu, Yiyue AU - Jia, Tao AU - Calderbank, Robert AU - Duel-Hallen, Alexandra AU - Hallen, Hans T2 - IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS AB - Code diversity integrates space-time coding with beamforming by using a small number of feedback bits to select from a family of space-time codes. Different codes lead to different induced channels at the receiver, where Channel State Information (CSI) is used to instruct the transmitter how to choose the code. Feedback can be combined with sub-optimal low complexity decoding of the component codes to match Maximum-Likelihood (ML) decoding performance of any individual code in the family. It can also be combined with ML decoding of the component codes to improve performance beyond ML decoding performance of any individual code. Prior analysis of code diversity did not take into account the effect of the mobile speed and the delay in the feedback channel. This paper demonstrates the practicality of code diversity in space-time coded systems by showing that performance gains based on instantaneous feedback are largely preserved when long-range prediction of time-varying correlated fading channels is employed to compensate for the effect of the feedback delay. To maintain prediction accuracy for realistic SNR, noise reduction that employs oversampled pilots is used prior to fading prediction. We also propose a robust low pilot rate method that utilizes interleaving to improve the spectral efficiency. Simulations are presented for two channel models: the conventional Jakes model and a realistic physical channel model where the parameters associated with the reflectors vary in time and the arrival rays have different strengths and asymmetric arrival angles. DA - 2012/12// PY - 2012/12// DO - 10.1109/twc.2012.101712.111884 VL - 11 IS - 12 SP - 4362-4371 SN - 1558-2248 UR - http://dx.doi.org/10.1109/TWC.2012.101712.111884 KW - Fading channels KW - space-time codes KW - code diversity KW - long-range channel prediction KW - feedback delay KW - channel state information ER - TY - JOUR TI - Electrically controlled magnetization in ferromagnet-topological insulator heterostructures AU - Semenov, Yuriy G. AU - Duan, Xiaopeng AU - Kim, Ki Wook T2 - Physical Review B AB - Electrostatic control of magnetic anisotropy is proposed by utilizing a hybrid structure of a topological insulator (TI) and insulating ferromagnet. The concept relies on the exchange interaction at the interface and the subsequent change in the free energy of the combined system. Calculations illustrate that the spin-momentum interlocked nature of TI surface electrons can induce the out-of-plane magnetic anisotropy of the system. Moreover, it is shown that modulation of its strength via surface chemical potential can achieve magnetization rotation between the in-plane and out-of-plane directions with a characteristic time of nanoseconds. A deterministic 180${}^{\ensuremath{\circ}}$ turn is further hypothesized with the aid of a small TI surface current with natural spin polarization. DA - 2012/10/15/ PY - 2012/10/15/ DO - 10.1103/physrevb.86.161406 VL - 86 IS - 16 SP - J2 - Phys. Rev. B LA - en OP - SN - 1098-0121 1550-235X UR - http://dx.doi.org/10.1103/PhysRevB.86.161406 DB - Crossref ER - TY - JOUR TI - Convergence Analysis of the Incremental Cost Consensus Algorithm Under Different Communication Network Topologies in a Smart Grid AU - Zhang, Ziang AU - Chow, Mo-Yuen T2 - IEEE TRANSACTIONS ON POWER SYSTEMS AB - In a smart grid, effective distributed control algorithms could be embedded in distributed controllers to properly allocate electrical power among connected buses autonomously. By selecting the incremental cost of each generation unit as the consensus variable, the incremental cost consensus (ICC) algorithm is able to solve the conventional centralized economic dispatch problem in a distributed manner. The mathematical formulation of the algorithm has been presented in this paper. The results of several case studies have also been presented to show that the difference between network topologies will influence the convergence rate of the ICC algorithm. DA - 2012/11// PY - 2012/11// DO - 10.1109/tpwrs.2012.2188912 VL - 27 IS - 4 SP - 1761-1768 SN - 1558-0679 KW - Distributed control KW - economic dispatch KW - leader-follower consensus KW - multi-agent system KW - smart grid ER - TY - CONF TI - CGA based performance-security trade-off optimization in a networked DC motor system AU - Zeng, W. T. AU - Chow, M. Y. AB - There are increasing concerns about the protection of the Networked Control Systems (NCS) security because of the growing threats of cyber attacks. However, security requirements often conflict with other performance requirements, like realtime dynamic performance due to limited system resources. We investigate the problem of the trade-off between NCS security and the NCS real-time performance in this paper. We first present a trade-off model for performance and security on NCS using a networked DC Motor system as an example. Then, a framework of performance-security trade-off optimization based on Coevolutionary Genetic Algorithm (CGA) for this networked DC motor system is proposed. Finally, simulation results show that the proposed CGA framework is an effective approach for performance-security trade-off analysis and optimization on NCS. C2 - 2012/// C3 - 2012 IEEE International Symposium on Industrial Electronics (ISIE) DA - 2012/// DO - 10.1109/isie.2012.6237371 SP - 1834-1839 ER - TY - CONF TI - AntiLiar: Defending against cheating attacks in mesh based streaming AU - So, J. K. AU - Reeves, D. S. AB - Peer-to-peer (P2P) mesh based streaming systems have gained widespread use for multicasting of audio and video. In approaches based on BitTorrent, members of the swarm share their content availability through gossiping, and redistribute file pieces cached locally. However, such systems are vulnerable to cheating attacks such as fake reporting, selective omission, fake block attack, and neighbor selection attack. These attacks will severely impact quality of service, waste resources, and discourage cooperation among participants. A defense mechanism, called AntiLiar, is proposed for defending against cheating attacks in mesh based streaming. AntiLiar uses a secure progress log that consists of commitments and one-time signatures, and maintains consistency for an expanded neighbor view. Experimental results demonstrate that AntiLiar minimizes required costs, and improves service quality over alternatives in the face of cheating attacks. C2 - 2012/// C3 - 2012 IEEE 12th international conference on peer-to-peer computing (p2p) DA - 2012/// DO - 10.1109/p2p.2012.6335791 SP - 115-125 ER - TY - JOUR TI - A Simplified Physical Model of RF Channel Breakdown in AlGaN/GaN HFETs AU - Schimizzi, Ryan D. AU - Trew, Robert J. AU - Bilbro, Griff L. T2 - IEEE TRANSACTIONS ON ELECTRON DEVICES AB - A temperature-dependent impact-ionization-initiated RF breakdown model in the 2DEG channel of AlGaN/GaN HFETs is reported. When operating these devices in RF power amplifier circuits, impact ionization in the channel has a significant effect upon gain saturation, power-added efficiency, and output power. An analytical physics-based model of channel breakdown is formulated based on TCAD investigations of the internal device behavior. This model is integrated with an existing physics-based HFET compact model and accurately predicts large-signal device performance. Values of thermal resistance and the breakdown temperature coefficient were extracted from simulations of an industrial HFET and are in agreement with the literature, thus validating that the model captures the dominant breakdown mechanism. DA - 2012/11// PY - 2012/11// DO - 10.1109/ted.2012.2211360 VL - 59 IS - 11 SP - 2973-2978 SN - 1557-9646 KW - Avalanche breakdown KW - impact ionization KW - microwave FET amplifiers KW - semiconductor device modeling ER - TY - JOUR TI - A Novel 4H-SiC Fault Isolation Device with Improved Trade-off between On-state Voltage Drop and Short Circuit SOA AU - Sung, Woongje AU - Baliga, B. J. AU - Huang, Alex Q. T2 - SILICON CARBIDE AND RELATED MATERIALS 2011, PTS 1 AND 2 AB - This paper aims to introduce a solid-state fault isolation device (FID) for the short circuit protection application in the power distribution systems. The key performance of a FID is to have a low on-state loss and a strong short circuit safe operating area (SCSOA). As a FID, a novel 15kV 4H-SiC field controlled diode (FCD) with a p+buried layer is proposed to provide an improved trade-off between the on-state forward voltage drop and the saturation current. Dynamic response to the fault and the application example of the proposed FCD are described in this paper. DA - 2012/// PY - 2012/// DO - 10.4028/www.scientific.net/msf.717-720.1045 VL - 717-720 SP - 1045-1048 SN - 0255-5476 KW - 4H-SiC KW - fault isolation device KW - power distribution system KW - field controlled diode KW - field controlled thyristor KW - gating technique KW - cascode circuit KW - short circuit safe operating area ER - TY - CONF TI - A 10.35 mW/GFlop Stacked SAR DSP unit using fine-grain partitioned 3D integration AU - Thorolfsson, T. AU - Lipa, S. AU - Franzon, Paul AB - In this paper we present a technique for implementing a fine-grain partitioned three-dimensional SAR DSP system using 3D placement of standard cells where only one of the 3D tiers is clocked to reduce clock power. We show how this technique was used to build the first fine-grain partitioned 3D integrated system to be demonstrated with silicon measurements in the literature, which is an ultra efficient floating-point synthetic aperture radar (SAR) DSP processing unit. The processing unit was fabricated in two tiers of GlobalFoundries, 1.5 V 130nm process that were 3D stacked face-to-face by Tezzaron. After fabrication the test chip was measured to consume 4.14 mW of power while running at 40 MHz operating for an operating efficiency of 10.35 mW/GFlop. C2 - 2012/// C3 - 2012 ieee custom integrated circuits conference (cicc) DA - 2012/// DO - 10.1109/cicc.2012.6330589 ER - TY - CONF TI - WEST: Cloning data cache behavior using stochastic traces AU - Balakrishnan, G. AU - Solihin, Y. AB - Cache designers need an in-depth understanding of end user workloads, but certain end users are apprehensive about sharing code or traces due to the proprietary or confidential nature of code and data. To bridge this gap, cache designers use a reduced representation of the code (a clone). A promising cloning approach is the black box approach, where workloads are profiled to obtain key statistics, and a clone is automatically generated. Despite its potential, currently there are no highly accurate black box cloning methods for replicating data cache behavior. We propose Workload Emulation using Stochastic Traces (WEST), a highly accurate black box cloning technique for replicating data cache behavior of arbitrary programs. First, we analyze what profiling statistics are necessary and sufficient to capture a workload. Then, we generate a clone stochastically that produces statistics identical to the proprietary workload. WEST clones can be used in lieu of the workload for exploring cache sizes, associativities, write policies, replacement policies, cache hierarchies and co-scheduling, at a significantly reduced simulation time. We use a simple IPC model to control the rate of accesses to the cache hierarchy. We evaluated WEST using CPU2006 and BioBench suites over a wide cache design space for single core and dual core CMPs. The clones achieve an average error in miss ratio of only 0.4% across 1394 single core cache configurations. For co-scheduled mixes, WEST achieves an average error in miss ratio of only 3.1% for over 600 configurations. C2 - 2012/// C3 - International symposium on high-performance computer DA - 2012/// DO - 10.1109/hpca.2012.6169042 SP - 387-398 ER - TY - CONF TI - Vector analysis and performance evaluation of Modular Transformer Converter (MTC) based Convertible Static Transmission Controller AU - Parkhideh, B. AU - Yousefpoor, N. AU - Fardanesh, B. AU - Bhattacharya, Subhashish AB - Modular Transformer Converter (MTC) is the building block to realize a versatile and transportable transmission controller which can perform several functions including power flow control for renewable resources transmission and transformer back-up for disaster management or life extension purposes. This structure has several advantages in comparison with conventional FACTS controllers. Modularity for manufacturers and utilities using standard high power electronic systems is one of the advantages of this structure. Different connecting configuration options (shunt-shunt, series-shunt, and series-series) can be obtained in the transmission controller with the MTC structures. These features allow them to be deployed dispersedly or aggregated to meet power, voltage, VAR and other power systems contingency requirements. In this paper, vector analysis of each mode to determine the operating characteristics of the proposed transmission controller is presented and compared to conventional FACTS controllers. The dynamic performance of the MTC system is further investigated in three different connecting configurations in PSCAD/EMTDC environment. C2 - 2012/// C3 - IEEE Power and Energy Society General Meeting DA - 2012/// DO - 10.1109/pesgm.2012.6344967 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870580518&partnerID=MN8TOARS ER - TY - CONF TI - Understanding the tempo-spatial limits of information dissemination in multi-channel cognitive radio networks AU - Sun, L. AU - Wang, Wenye AB - Cognitive Radio Networks (CRNs) have emerged to become promising network components for exploiting spectrum opportunistically in order that information can be delivered in circumstances otherwise impossible. Challenging yet open questions are how fast and how far a packet can be delivered in such networks, in temporal and spatial domains, respectively. The answers to these questions offer a straightforward interpretation of the potentials of CRNs for time-sensitive applications. To tackle these questions, we define two metrics, dissemination radius ∥ℒ(t)∥ and propagation speed S(d). The former is the maximum Euclidean distance that a packet can reach in time t, and the latter is the speed that a packet transmits between a source and destination at Euclidean distance d apart, which can be used to measure the transmission delay. Further, we determine the sufficient and necessary conditions under which there exist spatial and temporal limits of information dissemination in CRNs. We find that when information cannot be disseminated to the entire network, the limiting dissemination radius is statistically dominated by an exponential distribution, while the limiting information propagation speed approaches to zero. Otherwise, the dissemination radius approaches to infinity and the propagation speed S(d) is no lower than some constant k for large d. The results are validated through simulations. C2 - 2012/// C3 - 2012 Proceedings IEEE infocom DA - 2012/// DO - 10.1109/infcom.2012.6195489 SP - 1278–1286 ER - TY - JOUR TI - Threshold voltage stability comparison in AlGaN/GaN FLASH MOS-HFETs utilizing charge trap or floating gate charge storage AU - Kirkpatrick, Casey AU - Lee, Bongmook AU - Choi, YoungHwan AU - Huang, Alex AU - Misra, Veena T2 - PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 9, NO 3-4 AB - Abstract Enhancement mode operation of AlGaN/GaN devices with breakdown voltage over 700 V is achieved by threshold shifting in a FLASH metal oxide semiconductor heterojunction field effect transistor. Charge stored during a programming step in either a charge trap or metal floating gate charge storage layer is responsible for this shift. Threshold stability for charge trap and floating gate memories is compared with charge trap devices losing <10% of initial threshold voltage shift after 10 4 seconds. Charge trap and floating gate devices maintain enhancement mode operation after 4 × 10 4 s. Threshold voltage as a function of drain bias for each storage method is compared. The most stable threshold voltage is observed when utilizing charge trap storage due to the discrete nature of the traps. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) DA - 2012/// PY - 2012/// DO - 10.1002/pssc.201100421 VL - 9 IS - 3-4 SP - 864-867 SN - 1862-6351 KW - GaN KW - MOS-HFET KW - ALD KW - enhancement mode ER - TY - CONF TI - Ruggedness analysis of 600V 4H-SiC JBS diodes under repetitive avalanche conditions AU - Huang, X. AU - Wang, G. Y. AU - Jiang, L. AU - Huang, A. Q. AB - The repetitive avalanche reliability of power rectifiers is crucial to the safe operation of the hard switching power converters under extreme conditions as well as transient voltage suppression (TVS) applications. In this paper, the ruggedness of two state-of-art 4H-SiC Junction Barrier Schottky (JBS) diodes under repetitive avalanche stresses has been studied. Two different post-stress behaviors have been observed: V F degradation and BV drifting for the two different JBS diodes. The V F degradation could happen to the device that avalanches in the active area. However, for the device that avalanches in the edge termination, the repetitive avalanche stress greatly increases the breakdown voltage for about 100V. These results bring new concerns for SiC devices that are expected to be operated in avalanche conditions. C2 - 2012/// C3 - 2012 twenty-seventh annual ieee applied power electronics conference and exposition (apec) DA - 2012/// DO - 10.1109/apec.2012.6166048 SP - 1688-1691 ER - TY - JOUR TI - Reconfigurable liquid metal circuits by Laplace pressure shaping AU - Cumby, Brad L. AU - Hayes, Gerard J. AU - Dickey, Michael D. AU - Justice, Ryan S. AU - Tabor, Christopher E. AU - Heikenfeld, Jason C. T2 - APPLIED PHYSICS LETTERS AB - We report reconfigurable circuits formed by liquid metal shaping with &lt;10 pounds per square inch (psi) Laplace and vacuum pressures. Laplace pressure drives liquid metals into microreplicated trenches, and upon release of vacuum, the liquid metal dewets into droplets that are compacted to 10–100× less area than when in the channel. Experimental validation includes measurements of actuation speeds exceeding 30 cm/s, simple erasable resistive networks, and switchable 4.5 GHz antennas. Such capability may be of value for next generation of simple electronic switches, tunable antennas, adaptive reflectors, and switchable metamaterials. DA - 2012/10/22/ PY - 2012/10/22/ DO - 10.1063/1.4764020 VL - 101 IS - 17 SP - SN - 1077-3118 ER - TY - CONF TI - Process mismatch analysis based on reduced-order models AU - Yelten, M. B. AU - Franzon, Paul AU - Steer, M. B. AB - This paper describes a methodology based on reduced-order models to investigate the effects of process mismatch in analog circuits in the presence of reliability degradation. Neural network-based reduced-order models for the DC drain current, I ds , of 65 nm n- and p-channel transistors have been generated in terms of six process parameters, temperature, and device age. The models identify the contribution of process parameters to the mismatch of n- and p-channel transistors as they age. Hot carrier injection (HCI) is considered as the main reliability degradation for n-channel devices and negative bias temperature instability (NBTI) is considered for p-channel devices. It is demonstrated that the variations of the effective channel length and intrinsic threshold voltage are major contributors to device mismatch in the absence of aging. Finally, a beta multiplier current reference is analyzed using the developed models for the impact of process mismatch with and without the aging effects. It is shown that in a cascode current mirror the variability of the reference current can be reduced by ensuring that the same rail transistors experience similar variations. C2 - 2012/// C3 - 2012 13th international symposium on quality electronic design (isqed) DA - 2012/// DO - 10.1109/isqed.2012.6187561 SP - 648–655 ER - TY - CONF TI - Practical operation range improvement of voltage-sourced converter based STATCOM C2 - 2012/// C3 - 2012 twenty-seventh annual ieee applied power electronics conference and exposition (apec) DA - 2012/// SP - 211-217 ER - TY - CONF TI - Power management strategies for the green hub AU - Shen, Z. AU - Liu, Z. N. AU - Baran, Mesut AB - In this study power management strategies for a novel distribution level microgrid which is being developed at FREEDM center - Green Hub- are investigated. The Green Hub is a 12 kV distribution circuit with high level PV penetration. A large scale dispatchable distributed energy storage device (DERD) has also been added to this system to provide the additional power that is needed during islanding conditions. The high level penetration of photovoltaic (PV) units potentially necessitates new controls for both islanded and grid-connected X operation modes and smooth transition between the two modes to enable the best utilization of the microgrid resources. In this paper, state-of-the-art power management strategies have been investigated for this purpose. The Green Hub has been simulated using simpower/simulink of MATLAB, and it is used to assess the performance of the centralized control scheme considered. C2 - 2012/// C3 - 2012 IEEE Power and Energy Society General Meeting DA - 2012/// DO - 10.1109/pesgm.2012.6345698 ER - TY - CONF TI - On latency distribution and scaling: From finite to large cognitive radio networks under general mobility AU - Sun, L. AU - Wang, Wenye AB - Cognitive Radio Networks (CRNs), as a phenomenal technique to improve spectrum efficiency for opportunistic communications, become an integral component in the future communication regime. In this paper, we study the end-to-end latency in CRNs because many CRN applications, such as military networks and emergency networks, are either time-sensitive or dependent on delay performance. In particular, we consider a general mobility framework that captures most characteristics of the existing models and accounts for spatial heterogeneity resulting from the scenario that some locations are more likely to be visited by mobile nodes (these can be home in the case of people, or garage in the case of vehicles). By assuming that secondary users are mobile under this general framework, we find that there exists a cutoff point on the mobility radius #, which indicates how far a mobile node can reach in the spatial domain, below which the latency has a heavy-tailed distribution and above which the tail distribution is bounded by some Gamma (light-tailed) distribution. A heavy tail of the latency implies a significant probability that it takes long time to disseminate a message from the source to the destination and thus a light-tailed latency is crucial for time-critical applications. Moreover, as the network grows large, we notice that the latency is asymptotically scalable (linear) with the dissemination distance (e.g., the number of hops or Euclidean distance). Another interesting observation is that although the density of primary users adversely impacts the expected latency, it makes no influence on the dichotomy of the tail distribution of the latency in finite networks and the linearity of latency in large networks. Our results encourage the CRN deployment for real-time and large applications, when the mobility radius of secondary users is large enough. C2 - 2012/// C3 - 2012 Proceedings IEEE infocom DA - 2012/// DO - 10.1109/infcom.2012.6195491 SP - 1287–1295 ER - TY - JOUR TI - Normally-off AlGaN/GaN MOSHFET using ALD SiO2 tunnel dielectric and ALD HfO2 charge storage layer for power device application AU - Lee, Bongmook AU - Kirkpatrick, Casey AU - Choi, Young-hwan AU - Yang, Xiangyu AU - Huang, Alex Q. AU - Misra, Veena T2 - PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 9, NO 3-4 AB - Abstract 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 characteristics within a high‐ k layer. By combining ALD SiO 2 tunnel dielectric and HfO 2 charge trapping layer, up to 7 V of threshold voltage (V T ) shift depending on the applied gate pulse amplitude (corresponding ∼ 1.2 × 10 13 charges/cm 2 stored within the charge storage layer) is obtained. Electrical characteristics such as gate leakage current, transconductance, and off‐state breakdown after programming are similar to the initial device. Retention characteristics show about 20% of charge loss after 20000 s. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) DA - 2012/// PY - 2012/// DO - 10.1002/pssc.201100422 VL - 9 IS - 3-4 SP - 868-870 SN - 1862-6351 KW - enhancement mode KW - GaN-MOSHFET KW - normally-off KW - atomic layer deposition ER - TY - JOUR TI - Modeling and Analyzing Key Performance Factors of Shared Memory MapReduce AU - Tiwari, Devesh AU - Solihin, Yan T2 - 2012 IEEE 26TH INTERNATIONAL PARALLEL AND DISTRIBUTED PROCESSING SYMPOSIUM (IPDPS) AB - MapReduce parallel programming model has seen wide adoption in data center applications. Recently, lightweight, fast, in-memory MapReduce runtime systems have been proposed for shared memory systems. However, what factors affect performance and what performance bottlenecks exist for a given program, are not well understood. This paper builds an analytical model to capture key performance factors of shared memory MapReduce and investigates important performance trends and behavior. Our study discovers several important findings and implications for system designers, performance tuners, and programmers. Our model quantifies relative contribution of different key performance factors for both map and reduce phases, and shows that performance of MapReduce programs are highly input-content dependent. Our model reveals that performance is heavily affected by the order in which distinct keys are encountered during the Map phase, and the frequency of these distinct keys. Our model points out cases in which reduce phase time dominates the total execution time. We also show that data-structure and algorithm design choices affect map and reduce phases differently and sometimes affecting map phase positively while affecting reduce phase negatively. Finally, we propose an application classification framework that can be used to reason about performance bottlenecks for a given application. DA - 2012/// PY - 2012/// DO - 10.1109/ipdps.2012.119 SP - 1306-1317 SN - 1530-2075 ER - TY - JOUR TI - Low ContentionMapping of Real-Time Tasks onto a TilePro 64 Core Processor AU - Zimmer, Christopher AU - Mueller, Frank T2 - 2012 IEEE 18TH REAL-TIME AND EMBEDDED TECHNOLOGY AND APPLICATIONS SYMPOSIUM (RTAS) AB - Predictability of task execution is paramount for real-time systems so that upper bounds of execution times can be determined via static timing analysis. Static timing analysis on network-on-chip (NoC) processors may result in unsafe underestimations when the underlying communication paths are not considered. This stems from contention on the underlying network when data from multiple sources share parts of a routing path in the NoC. Contention analysis must be performed to provide safe and reliable bounds. In addition, the overhead incurred by contention due to inter-process communication (IPC) can be reduced by mapping tasks to cores in such a way that contention is minimized. This paper makes several contributions to increase pre-predictability of real-time tasks on NoC architectures. First, we contribute a constraint solver that exhaustively maps real-time tasks onto cores to minimize contention and improve predictability. Second, we develop a novel TDMA-like approach to map communication traces into time frames to ensure separation of analysis for temporally disjoint communication. Third, we contribute a novel multi-heuristic approximation, H Solver, for rapid discovery of low contention solutions. H Solver reduces contention by up to 70% when compared with naive and constrained exhaustive solutions. We evaluate our experiments using a micro-benchmark of task system IPC on the TilePro64, a real, physical NoC processor with 64 cores. To the best of our knowledge, this is the first work to consider IPC for worst-case time frames to simplify analysis and to measure the impact on actual hardware for NoC-based real-time multi core systems. DA - 2012/// PY - 2012/// DO - 10.1109/rtas.2012.36 SP - 131-140 SN - 1545-3421 ER - TY - CONF TI - Locality principle revisited: A probability-based quantitative approach AU - Gupta, S. AU - Xiang, P. AU - Yang, Y. AU - Huiyang AB - This paper revisits the fundamental concept of the locality of references and proposes to quantify it as a conditional probability: in an address stream, given the condition that an address is accessed, how likely the same address (temporal locality) or an address within its neighborhood (spatial locality) will be accessed in the near future. Based on this definition, spatial locality is a function of two parameters, the neighborhood size and the scope of near future, and can be visualized with a 3D mesh. Temporal locality becomes a special case of spatial locality with the neighborhood size being zero byte. Previous works on locality analysis use stack/reuse distances to compute distance histograms as a measure of temporal locality. For spatial locality, some ad-hoc metrics have been proposed as a quantitative measure. In contrast, our conditional probability-based locality measure has a clear mathematical meaning, offers justification for distance histograms, and provides a theoretically sound and unified way to quantify both temporal and spatial locality. The proposed locality measure clearly exhibits the inherent application characteristics, from which we can easily derive information such as the sizes of the working data sets and how locality can be exploited. We showcase that our quantified locality visualized in 3D-meshes can be used to evaluate compiler optimizations, to analyze the locality at different levels of memory hierarchy, to optimize the cache architecture to effectively leverage the locality, and to examine the effect of data prefetching mechanisms. A GPU-based parallel algorithm is also presented to accelerate the locality computation for large address traces. C2 - 2012/// C3 - 2012 ieee 26th international parallel and distributed processing symposium (ipdps) DA - 2012/// DO - 10.1109/ipdps.2012.93 SP - 995–1009 ER - TY - JOUR TI - Leveraging both Data Cache and Scratchpad Memory through Synergetic Data Allocation AU - Kang, Sangyeol AU - Dean, Alexander G. T2 - 2012 IEEE 18TH REAL-TIME AND EMBEDDED TECHNOLOGY AND APPLICATIONS SYMPOSIUM (RTAS) AB - Although a data cache provides fast access latency, it degrades the timing predictability of real-time embedded systems due to misses which are difficult to predict. Scratch pad memory is accessed as fast as a data cache, but does not suffer from unpredicted misses thanks to its software-controlled mechanism. This study presents how scratch pad memory reduces data cache pollution and misses for preemptive real-time embedded systems, so that both of the fast memory subsystems can work together with synergy. First, by classifying data cache misses into intrinsic misses and interference misses we reveal previously hidden characteristics of the interactions between data in the cache. Second, we suggest a heuristic method of data allocation to scratch pad memory using the new perspective, which reduces the cache pollution and finally improve the cache performance. Third, we examine these concepts with several tasks running on a real hardware platform and a preemptive real-time operating system. In addition, we perform a supplementary case study which shows how sensitive the data cache is to small changes of data memory layout and its dynamic contents. Our proposed scheme guides us through the synergetic process by using scratch pad memory beyond the sensitive data cache. In our experiments, the proposed data allocation scheme significantly reduces inter-task cache pollution as well as the intrinsic cache misses of the tasks themselves. DA - 2012/// PY - 2012/// DO - 10.1109/rtas.2012.22 SP - 119-128 SN - 1545-3421 KW - Scratchpad Memory KW - Data Cache KW - Data Allocation KW - Inter-task Cache Pollution ER - TY - CONF TI - Hybrid front end converters for large multi-motor applications integrated with energy storage AU - Parkhideh, B. AU - Mirzaee, H. AU - Bhattacharya, Subhashish AB - To supply the AC drive systems several Active Front Ends (AFE) with DC choppers are used to insure a reliable and acceptable harmonic current spectrum operation. Recently, energy storage system integration with the mining equipment has received industry attention, especially for peak load shaving and smarter energy management of the mine. Currently, the regenerative energy is often burnt into the choppers and is not fed back to the grid. The industry is motivated to capture this regenerative power since it can be as high as 60% of the motoring power and as high as 24 MW. Therefore, there is a possibility of large cost reduction and component downsizing. However, present status of development seems not to be very promising mainly because energy storage systems, (such as ultracapacitors) are still considered as an add-on part to existing products. In this paper, we investigate the operation of the current state-of-the-art front end converter systems for multi-motor applications. In particular, we propose power conversion configurations and methodology to determine the suitable energy storage technology for development of the multi-motor mobile mining equipment that has encouraging incentives for both the manufacturer and the mine operator. C2 - 2012/// C3 - Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC DA - 2012/// DO - 10.1109/apec.2012.6165881 SP - 607-614 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84860116590&partnerID=MN8TOARS ER - TY - JOUR TI - Human Activity as a Manifold-Valued Random Process AU - Yi, Sheng AU - Krim, Hamid AU - Norris, Larry K. T2 - IEEE TRANSACTIONS ON IMAGE PROCESSING AB - Most of the previous shape-based human activity models are built with either a linear assumption or an extrinsic interpretation of the nonlinear geometry of the shape space, both of which proved to be problematic on account of the nonlinear intrinsic geometry of the associated shape spaces. In this paper, we propose an intrinsic stochastic modeling of human activity on a shape manifold. More importantly, within an elegant and theoretically sound framework, our work effectively bridges the nonlinear modeling of human activity on a nonlinear space, with the classic stochastic modeling in a Euclidean space, and thereby provides a foundation for a more effective and accurate analysis of the nonlinear feature space of activity models. From a video sequence, human activity is extracted as a sequence of shapes. Such a sequence is considered as one realization of a random process on a shape manifold. Different activities are then modeled as manifold valued random processes with different distributions. To address the problem of stochastic modeling on a manifold, we first construct a nonlinear invertible map of a manifold valued process to a Euclidean process. The resulting process is then modeled as a global or piecewise Brownian motion. The mapping from a manifold to a Euclidean space is known as a stochastic development. The advantage of such a technique is that it yields a one-one correspondence, and the resulting Euclidean process intrinsically captures the curvature on the original manifold. The proposed algorithm is validated on two activity databases and compared with the related works on each of these. The substantiating results demonstrate the viability and high-accuracy of our modeling technique in characterizing and classifying different activities. DA - 2012/8// PY - 2012/8// DO - 10.1109/tip.2012.2197008 VL - 21 IS - 8 SP - 3416-3428 SN - 1941-0042 KW - Activity recognition KW - parallel transport KW - shape manifold KW - stationary incremental process KW - stochastic development ER - TY - CONF TI - High efficiency switched capacitor buck-boost converter for PV application AU - Liang, Z. G. AU - Huang, A. Q. AU - Guo, R. AB - A switched capacitor buck-boost DC/DC converter is proposed for the parallel connected distributed photovoltaic (PV) power generation application: an uncontrolled switched capacitor resonant converter is in parallel connection with a buck-boost converter where their outputs are summed to support the load. The switched capacitor converter is operated with a fixed conversion gain whereas the buck-boost converter is controlled to do the MPPT regulation and only a small portion of energy flows through it. In order to obtain ZVS for switched capacitor circuit in the full load range, an auxiliary inductor is added. The converter's performance has been evaluated on a 240W experimental prototype. The test results show that 92.5% efficiency is achieved to generate 200V high output voltage from a 60 cells crystalline PV module with V mpp =30V. C2 - 2012/// C3 - 2012 twenty-seventh annual ieee applied power electronics conference and exposition (apec) DA - 2012/// DO - 10.1109/apec.2012.6166090 SP - 1951-1958 ER - TY - CONF TI - Hiding traffic with camouflage: Minimizing message delay in the smart grid under jamming AU - Lu, Z. AU - Wang, Wenye AU - Wang, C. AB - The smart grid is an emerging cyber-physical system that integrates power infrastructures with information technologies. In the smart grid, wireless networks have been proposed for efficient communications. However, the jamming attack that broadcasts radio interference is a primary security threat to prevent the deployment of wireless networks. Hence, spread spectrum systems with jamming resilience must be adapted to the smart grid to secure wireless communications. There have been extensive works on designing spread spectrum schemes to achieve feasible communication under jamming attacks. Nevertheless, an open question in the smart grid is how to minimize message delay for timely communication in power applications. In this paper, we address this problem in a wireless network with spread spectrum systems for the smart grid. By defining a generic jamming process that characterizes a wide range of existing jamming models, we show that the worst-case message delay is a U-shaped function of network traffic load. This indicates that, interestingly, increasing a fair amount of redundant traffic, called camouflage, can improve the worst-case delay performance. We demonstrate via experiments that transmitting camouflage traffic can decrease the probability that a message is not delivered on time in order of magnitude for smart grid applications. C2 - 2012/// C3 - 2012 Proceedings IEEE infocom DA - 2012/// DO - 10.1109/infcom.2012.6195760 SP - 3066–3070 ER - TY - CONF TI - Feed-forward control of solid state transformer AU - Wang, F. AU - Huang, A. AU - Wang, G. Y. AU - She, X. AU - Burgos, R. AB - The solid state transformer (SST) can be viewed as an energy router for electricity in an analogous way to what network routers are for information. The SST impact on the system can be hence paramount, especially in terms of stability since it is essentially an active closed-loop regulated power converter. Within the SST itself however, with its different ac-dc, dc-dc and dc-ac stages, stability is also crucial, as it is well understood that for cascaded converter systems the interaction between stages is the cause of instability from a small-signal perspective. This paper represents an initial quest into the SST stability study, exploring two feed-forward control schemes for the ac-dc and dc-dc converter stages. Simulation and experimental results with a 7.2 kV ac 400 V dc, 20 kW laboratory prototype are presented for validation purposes. C2 - 2012/// C3 - 2012 twenty-seventh annual ieee applied power electronics conference and exposition (apec) DA - 2012/// DO - 10.1109/apec.2012.6165964 SP - 1153-1158 ER - TY - JOUR TI - Effects of a High-k Dielectric on the Performance of III-V Ballistic Deflection Transistors AU - Kaushal, Vikas AU - Iniguez-de-la-Torre, Ignacio AU - Gonzalez, Tomas AU - Mateos, Javier AU - Lee, Bongmook AU - Misra, Veena AU - Margala, Martin T2 - IEEE ELECTRON DEVICE LETTERS AB - This letter presents a first successful integration of a high-k dielectric, i.e., Al 2 O 3 , with III-V semiconductors in ballistic deflection transistors (BDTs). The Al 2 O 3 is deposited using atomic layer deposition, which allows the formation of uniform layers along the walls of etched trenches. The BDT transfer characteristic shows strong dependence on the dielectric permittivity of the material filling the etched trenches. When Al 2 O 3 is deposited in the trenches, the transconductance of the BDT is enhanced and shifted to lower gate bias. Moreover, the ratio between output and leakage currents was also enhanced. DA - 2012/8// PY - 2012/8// DO - 10.1109/led.2012.2197669 VL - 33 IS - 8 SP - 1120-1122 SN - 1558-0563 KW - High-k dielectric KW - III-V semiconductors KW - nanodevices ER - TY - CONF TI - Development of a predictive observer thermal model for power semiconductor devices for overload monitoring in high power high frequency converters AU - Dutta, S. AU - Parkhideh, B. AU - Bhattacharya, Subhashish AU - Moghaddam, G.K. AU - Gould, R. AB - In this paper a predictive observer model for power semiconductor devices is developed and integrated in the digital controller. The Model is simulated in Mat lab Simulink and tested with a power converter in hardware for the accuracy of modeling. C2 - 2012/// C3 - Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC DA - 2012/// DO - 10.1109/apec.2012.6166144 SP - 2305-2310 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84860126119&partnerID=MN8TOARS ER - TY - CONF TI - Convertible static compensator (CSC) performance under system fault AU - Babaei, S. AU - Parkhideh, B. AU - Fardanesh, B. AU - Bhattacharya, Subhashish AB - Convertible Static Compensator (CSC) which is a versatile FACTS technology has been installed on Marcy 345 kV substation and increases power transfer capability, operational functionality, and power flow controllability of the New York Power Authority (NYPA) transmission system. This paper presents a detailed description of CSC inverter operation and PSCAD simulation results of the CSC when it is operating as a STATCOM. The STATCOM steady state and dynamic operation simulation results under different conditions including unbalanced condition and faults is discussed. For fault condition analysis, attention is focused to Double L-G (LLG) fault at three different locations, one very close and two others electrically far from STATCOM terminals. This paper also demonstrates the effectiveness of the emergency PWM (EPWM) strategy a solution for limiting the poles current and preventing STATCOM over current tripping during fault conditions. C2 - 2012/// C3 - IEEE Power and Energy Society General Meeting DA - 2012/// DO - 10.1109/pesgm.2012.6345705 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84870604089&partnerID=MN8TOARS ER - TY - JOUR TI - Compact snapshot birefringent imaging Fourier transform spectrometer for remote sensing and endoscopy AU - Kudenov, Michael W. AU - Banerjee, Bhaskar AU - Chan, Victoria C. AU - Dereniak, Eustace L. T2 - ELECTRO-OPTICAL REMOTE SENSING, PHOTONIC TECHNOLOGIES, AND APPLICATIONS VI AB - The design and implementation of a compact multiple-image Fourier transform spectrometer (FTS) is presented. Based on the multiple-image FTS originally developed by A. Hirai, the presented device offers significant advantages over his original implementation. Namely, its birefringent nature results in a common-path interferometer which makes the spectrometer insensitive to vibration. Furthermore, it enables the potential of making the instrument ultra-compact, thereby improving the portability of the sensor. The theory of the birefringent FTS is provided, followed by details of its specific embodiment. A laboratory proof of concept of the sensor, designed and developed at the Optical Detection Lab, is also presented. Spectral measurements of laboratory sources are provided, including measurements of light-emitting diodes and gas-discharge lamps. These spectra are verified against a calibrated Ocean Optics USB2000 spectrometer. Other data were collected outdoors and of a rat esophagus, demonstrating the sensor’s ability to resolve spectral signatures in both standard outdoor lighting and environmental conditions, as well as in fluorescence spectroscopy. DA - 2012/// PY - 2012/// DO - 10.1117/12.945873 VL - 8542 SP - SN - 0277-786X KW - Spectral imaging KW - multiple image KW - Fourier transform spectrometer KW - birefringent interferometer KW - snapshot ER - TY - JOUR TI - Charge transfer in semi-insulating Fe-doped GaN AU - Dashdorj, J. AU - Zvanut, M. E. AU - Harrison, J. G. AU - Udwary, K. AU - Paskova, T. T2 - JOURNAL OF APPLIED PHYSICS AB - Charge transfer kinetics is studied in free-standing Fe-doped GaN using photo-induced electron paramagnetic resonance (EPR). Samples with Fe concentrations of 1017 cm−3 reveal an increase in Fe3+ during exposure with photon energy greater than 0.8 eV, while samples with higher Fe concentrations exhibit a decrease in the Fe3+ under the same conditions. Steady-state photo-EPR measurements of the most lightly doped sample imply the existence of an Fe2+/3+ defect level within 0.8 eV of the conduction band edge consistent with earlier work, but time-dependent measurements of more heavily doped crystals indicate a multi-step charge transfer process. Analysis of time-dependent photo-EPR data reveals that charge exchange may be separated into two processes, one that is temperature independent and one that depends monotonically on temperature. While a physical model for the charge transfer is not apparent, likely scenarios involve charge trapping at extended defects and phonon interactions. DA - 2012/7/1/ PY - 2012/7/1/ DO - 10.1063/1.4732352 VL - 112 IS - 1 SP - SN - 1089-7550 ER - TY - CONF TI - CPU-assisted GPGPU on fused CPU-GPU architectures AU - Yang, Y. AU - Xiang, P. AU - Mantor, M. AU - Zhou, H. Y. C2 - 2012/// C3 - International symposium on high-performance computer DA - 2012/// SP - 103-114 ER - TY - CONF TI - A three-phase three winding topology for dual active bridge and its D-Q mode control AU - Tripathi, A.K. AU - Hatua, K. AU - Mirzaee, H. AU - Bhattacharya, Subhashish AB - A new Dual Active Bridge (DAB) topology is proposed with a 15-kV SiC-IGBT based three-level inverter at the high-voltage side and 1200-V SiC-MOSFET based paralleled two-level inverter at the low-voltage side. The proposed DAB is an integral part of a solid state transformer which connects a 13.8-kV distribution grid and a 480-V utility grid. The three-level inverter connected at the high-voltage side and a pair of two-level inverters connected at the low-voltage sides (in Y/Δ) of the high frequency link transformer help to reduce dominant harmonic currents. Thus harmonic-free currents in the high frequency link transformer are achieved without pulse-width modulation. A simple control is proposed and validated with simulation results. C2 - 2012/// C3 - Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC DA - 2012/// DO - 10.1109/apec.2012.6165998 SP - 1368-1372 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84860132779&partnerID=MN8TOARS ER - TY - CONF TI - A novel high step-up ratio bi-directional DC-DC converter AU - Du, Yu AU - Huang, Alex Q AU - Wang, Mengqi AU - Lukic, Srdjan M T2 - IEEE AB - High step-up ratio bi-directional DC-DC converter is attractive in energy storage systems for renewable energy generation and in electric vehicle applications. A novel high step-up ratio bi-directional DC-DC converter and its alternative topology which can achieve soft switching in full load range and wide voltage range are proposed. The operation principle of the converter is analyzed in this paper. The modulation strategy and the optimum operation region are presented. A 400kHz 14.4V to 360V prototype was built to verify the analysis and the operation of the proposed converter. Zero voltage switching of all the switches was verified by experimental waveforms. The tested converter efficiency at 450W is 94.1%. C2 - 2012/// C3 - 2012 Twenty-Seventh Annual IEEE Applied Power Electronics Conference and Exposition (APEC) DA - 2012/// DO - 10.1109/apec.2012.6165870 SP - 524-531 ER - TY - CONF TI - A novel cost function for parameters estimation in oscillatory biochemical systems AU - Nabavi, S. AU - Williams, Cranos AB - Oscillatory pathways are among the most important classes of biochemical systems with examples ranging from circadian rhythms and cell cycle maintenance. Mathematical modeling of these highly interconnected biochemical networks is needed to meet numerous objectives such as investigating, predicting and controlling the dynamics of these systems. Identifying the kinetic rate parameters is essential for fully modeling these and other biological processes. These kinetic parameters, however, cannot be measured directly and most of them have to be estimated using parameter fitting techniques. One of the issues with estimating kinetic parameters in oscillatory systems is the irregularities in the Least Square (LS) cost function surface used to estimate these parameters, which is caused by the periodicity of the measurements. These irregularities result in numerous local minima, which limit the performance of even some of the most robust global optimization algorithms. We proposed a cost function to address these issues by integrating temporal information with periodic information embedded in the measurements. This new cost function has better surface properties leading to fewer local minima and better performance of global optimization algorithms. We verified for two oscillatory biochemical systems that our method results in an increased ability to estimate accurate kinetic parameters as compared to the traditional LS cost function. This will eventually lead to biochemical models that are more precise, predictable and controllable. C2 - 2012/// C3 - 2012 Proceedings of IEEE Southeastcon DA - 2012/// DO - 10.1109/secon.2012.6196978 ER - TY - CONF TI - A minimum cover algorithm for PMU placement in power system networks under line observability constraints AU - Anderson, J. E. AU - Chakrabortty, Aranya AB - In this paper we develop a graph-theoretic PMU placement algorithm for multi-area power system networks with the objective of identifying a dynamic equivalent model for the system. The system is considered to be divided into clusters or areas of synchronous generators, with each area connected to other sets of areas through designated transmission networks. The buses in the system are accordingly divided into two types, namely - boundary buses of the areas and boundary buses of the transmission networks. We first show that in order to derive the equivalent line parameters connecting the different areas we must have PMUs placed at the minimum vertex cover of the bipartite graphs formed between every pair of node-sets arising out of the boundary buses of the areas and those of the corresponding transmission networks they are connected to. Considering further that the number of tie-lines observable from any given PMU is constrained by an upper limit, we derive an algorithm to compute the sub-optimal minimum cover for the multi-area system. The method is illustrated via a 4-6 bipartite network, as well as with two small examples from the WECC system. Statistical analyses of the algorithm are also presented describing how the final set of chosen PMU locations as well as the computational time needed to run the algorithm are dependent on the size, complexity and measurement constraints of the network. C2 - 2012/// C3 - 2012 IEEE Power and Energy Society General Meeting DA - 2012/// DO - 10.1109/pesgm.2012.6345002 ER - TY - CONF TI - A high fidelity wide bandwidth (HFWB) buck converter with switching ripple cancellation for wireless communication application AU - Lin, P. C. AU - Huang, A. Q. AU - Fan, J. W. AB - This paper presents a ripple based fixed on time control scheme for a novel high efficiency linear transmitter. To support FCC power emission mask, this control scheme needs to have a wide bandwidth and to achieve high fidelity. Moreover, in order to improve linearity at far band due to extreme stringent emission mask regulation of the FCC, an auxiliary cancellation branch is adopted. The theoretical derivation in frequency domain is given to prove the system stability and high control bandwidth. Detailed large and small signals analyses of the modulator design are also presented in this paper. The simulation results are provided to verify the proposed design. C2 - 2012/// C3 - 2012 twenty-seventh annual ieee applied power electronics conference and exposition (apec) DA - 2012/// DO - 10.1109/apec.2012.6165980 SP - 1258-1265 ER - TY - JOUR TI - A Low-Loss Gate Drive for Emitter Turn-Off Thyristor (ETO) AU - Chen, Qian AU - Huang, Alex Q. T2 - IEEE TRANSACTIONS ON POWER ELECTRONICS AB - This letter introduces a new and energy-efficient gate drive circuit for emitter turn-off thyristor (ETO). The proposed circuit is a buck converter with two controllers that obtains power from gate current when the ETO gate voltage is negative, thus reducing power dissipation of the ETO gate drive and significantly mitigating a limitation of current ETO self-power designs. Various on-state gate current circuits are discussed and simulated. Experimental results verify the proposed circuit's operation and low-power consumption performance. The proposed circuit can be used in integrated gate-commutated thyristor and gate-commutated thyristor as well. DA - 2012/12// PY - 2012/12// DO - 10.1109/tpel.2012.2203146 VL - 27 IS - 12 SP - 4827-4831 SN - 1941-0107 KW - Emitter turn-off thyristor (ETO) KW - gate-commutated thyristor (GCT) KW - gate drive KW - integrated gate-commutated thyristor (IGCT) KW - self-power ER - TY - JOUR TI - A Highly Linear and Efficient CMOS RF Power Amplifier With a 2-D Circuit Synthesis Technique AU - Ding, Miaofu AU - Gard, Kevin G. AU - Steer, Michael B. T2 - IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES AB - A 2-D circuit synthesis technique (2DCST) is introduced that simultaneously linearizes the AM–AM and AM–PM distortions of CMOS RF power amplifiers (PAs). A class-AB nMOS RF PA fabricated in a ${0.18-}\mu{\hbox {m}}$ CMOS process is reported. With a WCDMA signal, the amplifier achieved 41.6% power-added efficiency (PAE) with $-{\hbox{33-dBc}}$ single-adjacent channel power ratio (ACPR1) and 38.5% PAE with $-{\hbox{40-dBc}}$ ACPR1 at output powers of 24.9 and 24.0 dBm, respectively. This state-of-the-art linearity and efficiency performance is comparable to that of GaAs HBT linear RF PAs. The 2DCST is applicable to a broad range of analog circuits and other semiconductor technologies. DA - 2012/9// PY - 2012/9// DO - 10.1109/tmtt.2012.2206824 VL - 60 IS - 9 SP - 2851-2862 SN - 1557-9670 KW - Circuit synthesis KW - CMOS KW - linearization KW - power amplifier (PA) KW - RF ER - TY - JOUR TI - A Dataflow Framework for DSP Algorithm Refinement AU - Kim, Youngsoo AU - Alexander, Winser E. AU - Edmonson, William W. T2 - 2012 IEEE COMPUTER SOCIETY ANNUAL SYMPOSIUM ON VLSI (ISVLSI) AB - Current video compression algorithms are increasingly complicated and difficult to analyze and profile. Design tools and system level languages often prove to be inefficient and incapable of providing complexity analysis as a first step directed toward at the implementation of video compression algorithms. This paper proposes framework that will help to develop a methodology that facilitates the derivation of analytical dataflow models. The framework proposes dataflow models for quantifying the underlying algorithm's memory complexity, related timing considerations, and verification of the correctness of the video compression algorithm. DA - 2012/// PY - 2012/// DO - 10.1109/isvlsi.2012.74 SP - 1-+ KW - refinement KW - DSP KW - dataflow KW - framework ER - TY - CONF TI - A Byzantine attack defender: The Conditional Frequency Check AU - He, X. F. AU - Dai, H. Y. AU - Ning, P. AB - Collaborative spectrum sensing is vulnerable to the Byzantine attack. Existing reputation based countermeasures will become incapable when malicious users dominate the network. Also, there is a scarcity of methods that fully explore the Markov property of the spectrum states to restrain sensors' statistical misbehaviors. In this paper, a new malicious user detection method based on two proposed Conditional Frequency Check (CFC) statistics is developed with a Markovian spectrum model. With the assistance of one trusted sensor, the proposed method can achieve high malicious user detection accuracy in the presence of arbitrary percentage of malicious users, and thus significantly improves collaborative spectrum sensing performance. C2 - 2012/// C3 - 2012 ieee international symposium on information theory proceedings (isit) DA - 2012/// DO - 10.1109/isit.2012.6284709 ER - TY - JOUR TI - Transparent IGZO-Based Logic Gates AU - Luo, Haojun AU - Wellenius, Patrick AU - Lunardi, Leda AU - Muth, John F. T2 - IEEE ELECTRON DEVICE LETTERS AB - Optically transparent indium-gallium-zinc-oxide-based nand and nor gates and inverters were fabricated and characterized using transistors deposited at room temperature with 5-, 10-, and 20-μm gate lengths and beta ratio between 2.5 and 40. The nand and nor gates' operation frequencies were measured up to 5 kHz. The individual transistors were measured to have saturation mobility of 14 cm 2 /V ·s, subthreshold swing of 190 mV/dec, and current on/off ratios in excess of 10 8 . Logic operations were satisfactorily demonstrated for bias voltage between 1 and 20 V. These results indicate that viable digital logic can be applied particularly where optical transparency or the use of novel flexible substrates is more important than the operating speeds. DA - 2012/5// PY - 2012/5// DO - 10.1109/led.2012.2186784 VL - 33 IS - 5 SP - 673-675 SN - 1558-0563 UR - http://dx.doi.org/10.1109/led.2012.2186784 KW - Indium-gallium-zinc-oxide (IGZO) KW - logic gate KW - NAND gate KW - NOR gate KW - thin-film transistors (TFTs) KW - transparent circuits ER - TY - JOUR TI - Optimal reactive power dispatch for improving voltage stability margin using a local voltage stability index AU - Rabiee, Abbas AU - Vanouni, Maziar AU - Parniani, Mostafa T2 - ENERGY CONVERSION AND MANAGEMENT AB - Management of reactive power resources is vital for stable and secure operation of power systems in the view point of voltage stability. This paper deals with the management of on-load tap changers (OLTCs) and dynamic VAR sources (including synchronous generators, synchronous condensers, and shunt reactive power compensators) to improve voltage stability margin (VSM) of power systems. This problem is usually called optimal reactive power dispatch (ORD) in the literature. The main contribution of the paper is to introduce a new objective function for the ORD problem. The proposed objective function is derived based on a local voltage stability index, called DSY, and has a strong correlation with VSM. This strong correlation makes the objective function effective for improving VSM, which is the main purpose of ORD. The proposed objective function is tested on the New England 39-bus test system and its performance is compared with some of the most common objective functions used in ORD. The obtained results show that solving ORD problem using the proposed objective function yields considerable increase in VSM. DA - 2012/7// PY - 2012/7// DO - 10.1016/j.enconman.2012.02.017 VL - 59 SP - 66-73 SN - 1879-2227 KW - Optimal power flow (OPF) KW - Optimal reactive dispatch (ORD) KW - Voltage stability index KW - Voltage stability margin (VSM) ER - TY - JOUR TI - Multiple coexisting intercalation structures of sodium in epitaxial graphene-SiC interfaces AU - Sandin, Andreas AU - Jayasekera, Thushari AU - Rowe, J. E. AU - Kim, Ki Wook AU - Buongiorno Nardelli, M. AU - Dougherty, Daniel B. T2 - Physical Review B AB - We show using scanning tunneling microscopy, spectroscopy, and ab initio calculations that two intercalation structures coexist for Na in epitaxial graphene on SiC(0001). Intercalation takes place at room temperature, and Na electron dopes the graphene. It inserts in between single-layer graphene and the interfacial layer and also penetrates beneath the interfacial layer and decouples it to form a second graphene layer. Decoupling is accelerated by annealing and is verified by Na deposition onto the interface layer combined with computational modeling of the two new decoupled buffer layer structures. DA - 2012/3/9/ PY - 2012/3/9/ DO - 10.1103/physrevb.85.125410 VL - 85 IS - 12 SP - J2 - Phys. Rev. B LA - en OP - SN - 1098-0121 1550-235X UR - http://dx.doi.org/10.1103/PhysRevB.85.125410 DB - Crossref ER - TY - JOUR TI - Multi-twist retarders for broadband polarization transformation AU - Komanduri, Ravi K. AU - Kim, Jihwan AU - Lawler, Kristopher F. AU - Escuti, Michael J. T2 - EMERGING LIQUID CRYSTAL TECHNOLOGIES VII AB - We introduce a family of broadband retarders, comprised of a low number of twisted nematic liquid crystal layers, that accomplishes well-controlled polarization transformation for nearly any bandwidth desired. For example, we show that broadband linear to circular polarization conversion can be achieved with only two twist layers where the performance matches the popular three-waveplate approach by Pancharatnam. Using liquid crystal polymers on a single substrate, we show how these multi-twist retarders are embodied as a monolithic birefringent plate with excellent performance and potentially very low cost. DA - 2012/// PY - 2012/// DO - 10.1117/12.913795 VL - 8279 SP - SN - 0277-786X KW - achromatic KW - broadband KW - twist KW - quarter-wave KW - chiral KW - liquid crystal ER - TY - JOUR TI - Flexible Liquid Metal Alloy (EGaIn) Microstrip Patch Antenna AU - Hayes, Gerard J. AU - So, Ju-Hee AU - Qusba, Amit AU - Dickey, Michael D. AU - Lazzi, Gianluca T2 - IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION AB - This paper describes a flexible microstrip patch antenna that incorporates a novel multi-layer construction consisting of a liquid metal (eutectic gallium indium) encased in an elastomer. The combined properties of the fluid and the elastomeric substrate result in a flexible and durable antenna that is well suited for conformal antenna applications. Injecting the metal into microfluidic channels provides a simple way to define the shape of the liquid, which is stabilized mechanically by a thin oxide skin that forms spontaneously on its surface. This approach has proven sufficient for forming simple, single layer antenna geometries, such as dipoles. More complex fluidic antennas, particularly those featuring large, co-planar sheet-like geometries, require additional design considerations to achieve the desired shape of the metal. Here, a multi-layer patch antenna is fabricated using specially designed serpentine channels that take advantage of the unique rheological properties of the liquid metal alloy. The flexibility of the resulting antennas is demonstrated and the antenna parameters are characterized through simulation and measurement in both the relaxed and flexed states. DA - 2012/5// PY - 2012/5// DO - 10.1109/tap.2012.2189698 VL - 60 IS - 5 SP - 2151-2156 SN - 0018-926X KW - EGaIn antenna KW - flexible microstrip patch antenna KW - liquid metal antenna KW - multi-layer KW - polydimethylsiloxane (PDMS) ER - TY - JOUR TI - Coupling Effect Reduction of a Voltage-Balancing Controller in Single-Phase Cascaded Multilevel Converters AU - She, Xu AU - Huang, Alex Q. AU - Zhao, Tiefu AU - Wang, Gangyao T2 - IEEE TRANSACTIONS ON POWER ELECTRONICS AB - This paper presents a new voltage-balancing controller for cascaded multilevel converters, especially for single-phase cascaded multilevel converters. It proposes a control algorithm that devotes itself not only to balancing the floating dc capacitors but also to eliminating the coupling effect between the voltage-balancing controller and the original system controller (controller without additional voltage-balancing controllers). Specifically, the average model in the d-q coordinate frame is derived and the control law is established. Then, the coupling effect between the voltage-balancing controller and the original system controller is identified and a new expression for duty cycle modification is proposed thus to eliminate the effect. Furthermore, this paper gives the design considerations of the pro- posed method, including the derivation of key transfer functions and effective voltage-balancing area, for the completeness of the discussion. Moreover, the reference generation techniques of the voltage-balancing controller are also discussed. This paper investigates the voltage imbalance in the soft-start process caused by an unsuitable reference, and presents a simple modified reference generation solution. Finally, both simulation and experimental results verify the performance of the proposed control system. DA - 2012/8// PY - 2012/8// DO - 10.1109/tpel.2012.2186615 VL - 27 IS - 8 SP - 3530-3543 SN - 1941-0107 KW - Cascaded multilevel converter KW - decoupling control KW - single-phase d-q control KW - voltage balance ER - TY - JOUR TI - Bombay Islam: The religious economy of the West Indian Ocean, 1840-1915. AU - Gilmartin, D. T2 - American Historical Review DA - 2012/// PY - 2012/// VL - 117 IS - 2 SP - 508-509 ER - TY - JOUR TI - Analog Negative-Bias-Temperature-Instability Monitoring Circuit AU - Yelten, Mustafa Berke AU - Franzon, Paul D. AU - Steer, Michael B. T2 - IEEE TRANSACTIONS ON DEVICE AND MATERIALS RELIABILITY AB - A negative-bias-temperature-instability (NBTI) monitor subcircuit is presented and implemented in 65-nm CMOS technology. The subcircuit can be incorporated in various analog circuit blocks subject to different variability, stress, and aging histories. For an amplifier block, the NBTI monitor is a linear sensor, and sensing is provided as variation of the amplifier gain in response to NBTI-induced bias variation. The monitor sensitivity in this configuration is 3.15 V -1 and is demonstrated through electrothermal stress on the amplifier circuit. DA - 2012/3// PY - 2012/3// DO - 10.1109/tdmr.2011.2178096 VL - 12 IS - 1 SP - 177-179 SN - 1558-2574 KW - Amplifier KW - analog circuits KW - negative-bias temperature instability (NBTI) KW - reliability KW - sensor ER - TY - JOUR TI - A compact dielectric elastomer tubular actuator for refreshable Braille displays AU - Chakraborti, P. AU - Toprakci, H. A. Karahan AU - Yang, P. AU - Di Spigna, N. AU - Franzon, P. AU - Ghosh, T. T2 - SENSORS AND ACTUATORS A-PHYSICAL AB - Electroactive polymer actuators stimulated by appropriate levels of electric field are particularly attractive for human-assist devices such as Braille. The development of a full page refreshable Braille display is very important for the integration of the visually impaired into the new era of communication. In this paper, development of a compact dielectric elastomer actuator suitable for Braille application is reported. The actuators are fabricated from commercially available silicone tubes. The tube has been rendered mechanically anisotropic through asymmetric levels of applied pretension in circumferential and axial directions in order to direct the actuation strain in the axial direction of the actuator. Key performance parameters, such as displacement, force, and response time of the actuator are investigated. The test results demonstrate the potential of the compact, lightweight, and low cost dielectric elastomer as actuators for a refreshable full page Braille display. DA - 2012/6// PY - 2012/6// DO - 10.1016/j.sna.2012.02.004 VL - 179 SP - 151-157 SN - 0924-4247 KW - Electroactive polymers KW - Dielectric elastomer actuator KW - Braille display actuators KW - Refreshable Braille display ER - TY - JOUR TI - Work function extraction of metal gates with alternate channel materials AU - Coan, Mary AU - Johnson, Derek AU - Woo, Jung Hwan AU - Biswas, Nivedita AU - Misra, Veena AU - Majhi, Prashant AU - Harris, H. Rusty T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B AB - The effects of a heterojunction on the effective work function in a metal/high κ gate stack are studied and a new structure developed for the extraction of the work function. It is found that when a Ge/Si heterostructure on silicon is low doped and sufficiently thin, then the work function can be extracted in a manner similar to that on a simple silicon substrate. Modifications to the terraced oxide structure are proposed to remove oxidation effects of the alternate channel materials. The extracted work function of thickness variation of TiN is found to be in agreement with that of TiN on a silicon substrate. DA - 2012/3// PY - 2012/3// DO - 10.1116/1.3679412 VL - 30 IS - 2 SP - SN - 2166-2746 ER - TY - JOUR TI - RESOURCE-FOCUSED TOOLCHAIN FOR RAPID PROTOTYPING OF EMBEDDED SYSTEMS AU - Peng, Shaolin AU - Parsons, Gregory AU - Dean, Alexander G. T2 - JOURNAL OF CIRCUITS SYSTEMS AND COMPUTERS AB - This paper introduces the RaPTEX toolchain and its use for rapid prototyping and evaluation of embedded communication systems. This toolchain is unique for several reasons. First, by using static code analysis techniques, it is able to predict both the typical case and bounds for resource usage, such as computational, memory (both static and dynamic), and energy requirements. Second, it provides a graphical user interface with configurable software building blocks which allows easy creation and customization of protocol stacks. Third, it targets low-cost, low-energy hardware, allowing the creation of low-cost systems. We demonstrate the RaPTEX toolchain by evaluating different design options for an experimental ultrasonic communication system for biotelemetry in extremely shallow waters. The power, size, mass, and cost constraints of this application make it critical to pack as much processing into the available resources as possible. The RaPTEX toolchain analyzes resource use, enabling the system to safely operate closer to the edge of the resource envelope. The toolchain also helps users with the rapid prototyping of communication protocols by providing users with quick feedback on resource requirements. We demonstrate the use and output of the toolchain. We compare the accuracy of its predictions against measurements of the real hardware. DA - 2012/4// PY - 2012/4// DO - 10.1142/s0218126612400038 VL - 21 IS - 2 SP - SN - 1793-6454 KW - RaPTEX KW - static timing analysis KW - code generation KW - optimization ER - TY - JOUR TI - Optimal Antenna Selection Designs for Coupled MIMO Systems AU - Taluja, Pawandeep S. AU - Hughes, Brian L. T2 - INTERNATIONAL JOURNAL OF ANTENNAS AND PROPAGATION AB - We consider the impact of antenna mutual coupling on receive antenna selection systems. Prior work on selection with mutual coupling has not considered the effects of the inactive (i.e., unselected) antenna terminations and spatial noise correlation. In this work, we show that the presence of inactive antennas can profoundly alter system performance when the antennas are strongly coupled. We also propose a new antenna selection technique that seeks to exploit coupling to improve performance. Simulations suggest that the new technique can significantly outperform traditional selection when coupling is present. DA - 2012/// PY - 2012/// DO - 10.1155/2012/694627 VL - 2012 SP - SN - 1687-5877 ER - TY - JOUR TI - Interval-based flow watermarking for tracing interactive traffic AU - Pyun, Young June AU - Park, Younghee AU - Reeves, Douglas S. AU - Wang, Xinyuan AU - Ning, Peng T2 - COMPUTER NETWORKS AB - Tracing interactive attack traffic that traverses stepping stones (i.e., intermediate hosts) is challenging, as the packet headers, lengths, and contents can all be changed by the stepping stones. The traffic timing (delays between packets) has therefore been studied as a means of tracing traffic. One such technique uses traffic timing as a side channel into which a watermark, or identifying tag, can be embedded to aid with tracing. The effectiveness of such techniques is greatly reduced when the packet count of the traffic is changed at the stepping stone. Such transformations may occur as a result of either active countermeasures (e.g. chaff packets, flow splitting) by an adversary attempting to defeat tracing, or by incidental repacketization of the traffic by network interfaces. This paper presents a new method of embedding a watermark in traffic timing, for purposes of tracing the traffic in the presence of flow splitting, chaff packets, timing perturbation, and repacketization. This method uses an invariant characteristic of two connection flows which are part of the same stepping stone chain, namely, the elapsed time of the flows. The duration of each flow is sliced into short fixed-length intervals. Packet timing is adjusted to manipulate the packet count in specific intervals (without adding or deleting any packets), for purposes of embedding the watermark. The method is self-synchronizing and does not require clock synchronization between the watermark encoder and decoder. A statistical analysis of the method, with no assumptions or limitations concerning the distribution of packet times, proves the effectiveness of the method given a sufficient number of packets, despite natural and/or deliberate repacketization and countermeasures by an adversary. The method has been implemented and tested on a large number of SSH traffic flows. The results demonstrate that 100% detection rates and very low false positive rates are achieved under conditions of multiple countermeasures, and using only a few hundred packets. DA - 2012/3/30/ PY - 2012/3/30/ DO - 10.1016/j.comnet.2012.01.017 VL - 56 IS - 5 SP - 1646-1665 SN - 1872-7069 KW - Intrusion tracing KW - Stepping stones KW - Flow watermarking KW - Flow correlation ER - TY - JOUR TI - Factors affecting uniformity of irrigation-type manure application systems AU - Liu, Z. AU - Grabow, G. L. AU - Huffman, R. L. AU - Osborne, J. AU - Evans, R. O. T2 - Applied Engineering in Agriculture AB - Liquid manure is usually treated through application to agricultural land using irrigation systems. Land application of liquid manure needs to follow established guidelines in order to achieve economic goals as well as to protect the environment. Guidance at the time of this study in North Carolina suggested calibration of land application equipment be performed once every three years by the catch can method, a time- and labor-consuming method. The goals of this project were to investigate the relationship between liquid manure application uniformity by using data from historical uniformity assessment trials and from additional trials conducted during the study, and to use the results to provide guidance in developing a simplified field method for uniformity assessment. Trials were performed to test the liquid manure application uniformity for different irrigation system types, sprinkler types and models, nozzle types, nozzle diameters, and nozzle pressures. Wind speed during the trials was monitored. Different sprinkler overlaps were achieved by superposition, thereby allowing for assessment of multiple sprinkler spacings for each trial. Regression models were constructed using historic and study-period trial data and a process of main effect selection, collinearity checking, interaction term and quadratic term selection, parameter estimation, and normality testing of model residuals. The model for stationary systems performed well with an adjusted R2 of 0.72 and predicted application uniformity showed the expected tendencies with changes in predictive factors. The model for traveling gun systems did not perform as well as that for stationary systems; the adjusted R2 was only 0.33. The results of this study were used to amend uniformity assessment requirements to a simple procedure requiring measurement of sprinkler nozzle pressure, wetted diameter, and sprinkler spacing. DA - 2012/// PY - 2012/// DO - 10.13031/2013.41285 VL - 28 IS - 1 SP - 43-56 ER - TY - JOUR TI - Analytical solutions of laminar swirl decay in a straight pipe AU - Yao, Shanshan AU - Fang, Tiegang T2 - COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION AB - Abstract In this work, the laminar swirl flow in a straight pipe is revisited and solved analytically by using prescribed axial flow velocity profiles. Based on two axial velocity profiles, namely a slug flow and a developed parabolic velocity profiles, the swirl velocity equation is solved by the separation of variable technique for a rather general inlet swirl velocity distribution, which includes a forced vortex in the core and a free vortex near the wall. The solutions are expressed by the Bessel function for the slug flow and by the generalized Laguerre function for the developed parabolic velocity. Numerical examples are calculated and plotted for different combinations of influential parameters. The effects of the Reynolds number, the pipe axial distance, and the inlet swirl profiles on the swirl velocity distribution and the swirl decay are analyzed. The current results offer analytical equations to estimate the decay rate and the outlet swirl intensity and velocity distribution for the design of swirl flow devices. DA - 2012/8// PY - 2012/8// DO - 10.1016/j.cnsns.2011.11.038 VL - 17 IS - 8 SP - 3235-3246 SN - 1007-5704 KW - Laminar swirl flow KW - Pipe flow KW - Swirl nozzle KW - Analytical solutions KW - Developed flow ER - TY - JOUR TI - A compact holographic recording setup for tuning pitch using polarizing prisms AU - Kim, Jihwan AU - Komanduri, Ravi K. AU - Escuti, Michael J. T2 - PRACTICAL HOLOGRAPHY XXVI: MATERIALS AND APPLICATIONS AB - We introduce and demonstrate a new holographic recording technique based on birefringent prisms for creating polarization gratings (PGs). Conventional holographic arrangements for creating PGs consist of several polarization and collimating optics that are carefully aligned with each other, and often require substantial physical space. Both the size and the relative distance between these optics increase for large exposure areas, that limit the range of grating period achievable. Moreover, the cost and complexity associated with the mounting of the several elements also increases, and therefore such approaches are not viable for large area PGs and large volume manufacturing. To overcome the above limitations, we propose new approach using multiple polarizing prisms to record PGs that is compact, scalable for large areas, and enables easy tuning of the grating period by simple rotation of at most two elements. DA - 2012/// PY - 2012/// DO - 10.1117/12.913952 VL - 8281 SP - SN - 0277-786X KW - Polarization holography KW - holographic elements KW - polarization gratings KW - proximity lithography KW - liquid crystals KW - birefringent prism ER - TY - JOUR TI - A Transient Electrothermal Analysis of Three-Dimensional Integrated Circuits AU - Harris, T.R. AU - Priyadarshi, S. AU - Melamed, S. AU - Ortega, C. AU - Manohar, R. AU - Dooley, S.R. AU - Kriplani, N.M. AU - Davis, W.R. AU - Franzon, Paul AU - Steer, M.B. AU - al. T2 - IEEE TRANSACTIONS ON COMPONENTS PACKAGING AND MANUFACTURING TECHNOLOGY AB - A transient electrothermal simulation of a 3-D integrated circuit (3DIC) is reported that uses dynamic modeling of the thermal network and hierarchical electrothermal simulation. This is a practical alternative to full transistor electrothermal simulations that are computationally prohibitive. Simulations are compared to measurements for a token-generating asynchronous 3DIC clocking at a maximum frequency of 1 GHz. The electrical network is based on computationally efficient electrothermal macromodels of standard and custom cells. These are linked in a physically consistent manner with a detailed thermal network extracted from an OpenAccess layout file. Coupled with model-order reduction techniques, hierarchical dynamic electrothermal simulation of large 3DICs is shown to be tractable, yielding spatial and temporal selected transistor-level thermal profiles. DA - 2012/4// PY - 2012/4// DO - 10.1109/tcpmt.2011.2178414 VL - 2 IS - 4 SP - 660-667 SN - 2156-3985 KW - 3DIC KW - electrothermal effects KW - thermal management KW - transient analysis ER - TY - JOUR TI - Third-Order Parametric Array Generated by Distantly Spaced Primary Ultrasonic Tones AU - Garner, Glenwood AU - Steer, Michael B. T2 - IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL AB - Traditional parametric arrays are produced by a second-order nonlinear interaction between two primary ultrasonic tones that are close in frequency, resulting in a difference tone that is in the audio band. This article presents a parametric array produced by a third-order nonlinear interaction between two primary ultrasonic tones that are distantly spaced in frequency such that one tone is approximately the second harmonic of the other. The result is a third-order lower intermodulation (IM3) tone in the audio band with greater directivity and lower side lobe amplitude than comparable second-order fields. Measurements are presented that compare the directivity of 1-, 2-, and 4-kHz difference tones to that of 1-, 2-, and 4-kHz IM3 lower tones. Furthermore, a cascaded second-order approach for N-element transducer arrays is used to model third-order scattering with good agreement between measurement and theory. DA - 2012/4// PY - 2012/4// DO - 10.1109/tuffc.2012.2255 VL - 59 IS - 4 SP - 776-784 SN - 1525-8955 ER - TY - JOUR TI - Snapshot imaging Mueller matrix polarimeter using polarization gratings AU - Kudenov, Michael W. AU - Escuti, Michael J. AU - Hagen, Nathan AU - Dereniak, Eustace L. AU - Oka, Kazuhiko T2 - OPTICS LETTERS AB - A snapshot imaging Mueller matrix polarimeter (SIMMP) is theoretically described and empirically demonstrated through simulation. Spatial polarization fringes are localized onto a sample by incorporating polarization gratings (PGs) into a polarization generator module. These fringes modulate the Mueller matrix (MM) components of the sample, which are subsequently isolated with PGs in an analyzer module. The MM components are amplitude modulated onto spatial carrier frequencies which, due to the PGs, maintain high visibility in spectrally broadband illumination. An interference model of the SIMMP is provided, followed by methods of reconstruction and calibration. Lastly, a numerical simulation is used to demonstrate the system’s performance in the presence of noise. DA - 2012/4/15/ PY - 2012/4/15/ DO - 10.1364/ol.37.001367 VL - 37 IS - 8 SP - 1367-1369 SN - 1539-4794 ER - TY - JOUR TI - Robust Analog Canceller for High-Dynamic-Range Radio Frequency Measurement AU - Wetherington, Joshua M. AU - Steer, Michael B. T2 - IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES AB - An automated analog canceller is presented that uses feedforward cancellation in a bridge configuration. A minimum of 70 dB of analog cancellation is obtained. The canceller is used to construct an intermodulation distortion measurement system achieving up to 120 dBc of intermodulation dynamic range in two-port transmission testing and 140 dBc of intermodulation dynamic range in one-port reflection testing for frequency separations of at least 1 kHz. At a two-tone frequency separation of 1 Hz, the respective dynamic ranges are at least 94 and 111 dBc. The relationship of cancellation performance and dynamic range is examined in terms of application-specific definitions of dynamic range. The system is then used to measure passive intermodulation distortion using a two-tone test with a tone frequency separation from 1 Hz to 100 MHz. DA - 2012/6// PY - 2012/6// DO - 10.1109/tmtt.2012.2189230 VL - 60 IS - 6 SP - 1709-1719 SN - 0018-9480 KW - Broadband KW - cancellation system KW - dynamic range KW - nonlinear measurement KW - passive intermodulation distortion (PIM) KW - reverse power canceller KW - reverse power cancellers (RPC) ER - TY - JOUR TI - Indium incorporation in InGaN/GaN quantum wells grown on m-plane GaN substrate and c-plane sapphire AU - Lai, K. Y. AU - Paskova, T. AU - Wheeler, V. D. AU - Chung, T. Y. AU - Grenko, J. A. AU - Johnson, M. A. L. AU - Udwary, K. AU - Preble, E. A. AU - Evans, K. R. T2 - PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE AB - InGaN/GaN quantum wells (QWs) grown at identical conditions on m-plane GaN and c-plane sapphire substrates were characterized by several techniques, aiming to clarify the reason for different emission wavelengths often observed in similar LED structures with m- and c-plane surface orientations. Cathodoluminescence (CL) spectra of m-plane QWs revealed shorter wavelength and no blueshift with increasing CL probe current in accordance with previous reports. Relative indium compositions were estimated by high-resolution X-ray diffraction to be 5.1 and 13.9% for m-plane and c-plane QWs, respectively. Cross-sectional transmission electron microscopy images revealed that the well widths of the m-plane QWs were noticeably thicker than those of the c-plane QWs. The lower indium compositions and thicker well widths of the m-plane QWs indicated that different indium incorporation and diffusion occurred in the structures grown on the GaN substrate, which is attributed to its surface off-cut toward [0001] and the higher thermal conductivity with respect to that of sapphire. DA - 2012/3// PY - 2012/3// DO - 10.1002/pssa.201127345 VL - 209 IS - 3 SP - 559-564 SN - 1862-6319 KW - cathodoluminescence KW - MOCVD KW - quantum wells KW - TEM KW - RSM ER - TY - JOUR TI - IEEE 802.11 Saturation Throughput Analysis in the Presence of Hidden Terminals AU - Jang, Beakcheol AU - Sichitiu, Mihail L. T2 - IEEE-ACM TRANSACTIONS ON NETWORKING AB - Due to its usefulness and wide deployment, IEEE 802.11 has been the subject of numerous studies, but still lacks a complete analytical model. Hidden terminals are common in IEEE 802.11 and cause the degradation of throughput. Despite the importance of the hidden terminal problem, there have been a relatively small number of studies that consider the effect of hidden terminals on IEEE 802.11 throughput, and many are not accurate for a wide range of conditions. In this paper, we present an accurate new analytical saturation throughput model for the infrastructure case of IEEE 802.11 in the presence of hidden terminals. Simulation results show that our model is accurate in a wide variety of cases. DA - 2012/4// PY - 2012/4// DO - 10.1109/tnet.2011.2165322 VL - 20 IS - 2 SP - 557-570 SN - 1558-2566 KW - CSMA/CA KW - hidden terminal KW - IEEE 802.11 KW - infrastructure case KW - RTC/CTS KW - saturation throughput ER - TY - JOUR TI - FABSCALAR: AUTOMATING SUPERSCALAR CORE DESIGN AU - Choudhary, Niket K. AU - Wadhavkar, Salil V. AU - Shah, Tanmay A. AU - Mayukh, Hiran AU - Gandhi, Jayneel AU - Dwiel, Brandon H. AU - Navada, Sandeep AU - Najaf-Abadi, Hashem H. AU - Rotenberg, Eric T2 - IEEE MICRO AB - Providing multiple superscalar core types on a chip, each tailored to different classes of instruction-level behavior, is an exciting direction for increasing processor performance and energy efficiency. Unfortunately, processor design and verification effort increases with each additional core type, limiting the microarchitectural diversity that can be practically implemented. FabScalar aims to automate superscalar core design, opening up processor design to microarchitectural diversity and its many opportunities. DA - 2012/// PY - 2012/// DO - 10.1109/mm.2012.23 VL - 32 IS - 3 SP - 48-59 SN - 1937-4143 ER - TY - JOUR TI - Efficient 3D FDTD analysis of arbitrary birefringent and dichroic media with obliquely incident sources AU - Miskiewicz, Matthew N. AU - Bowen, Patrick T. AU - Escuti, Michael J. T2 - PHYSICS AND SIMULATION OF OPTOELECTRONIC DEVICES XX AB - We have developed a 3D Finite Difference Time Domain (FDTD) algorithm to model obliquely incident waves through arbitrary birefringent and dichroic media with transverse periodic boundaries. Beginning with arbitrary conductivity and permittivity tensors, we employed the split-field method (SFM) to enable broadband sources with oblique incidence. We terminate our boundaries with a uniaxial perfectly matched layer (UPML) in one dimension and periodic boundaries in the other two dimensions. The algorithm is validated via several case studies: a polarizer pair, a twisted nematic liquid crystal, and an array of conducting particles. Using this approach, we simulate for the first time polarization gratings with light obliquely incident in directions orthogonal to the grating vector (i.e., at oblique angles outside the normal diffraction plane). DA - 2012/// PY - 2012/// DO - 10.1117/12.913628 VL - 8255 SP - SN - 1996-756X KW - FDTD KW - 3D KW - oblique incidence KW - birefringence KW - dichroism KW - split-field ER - TY - JOUR TI - Area-Efficient Antenna-Scalable MIMO Detector for K-best Sphere Decoding AU - Moezzi-Madani, Nariman AU - Thorolfsson, Thorlindur AU - Chiang, Patrick AU - Davis, William Rhett T2 - JOURNAL OF SIGNAL PROCESSING SYSTEMS FOR SIGNAL IMAGE AND VIDEO TECHNOLOGY DA - 2012/8// PY - 2012/8// DO - 10.1007/s11265-011-0595-9 VL - 68 IS - 2 SP - 171-182 SN - 1939-8115 KW - MIMO KW - K-best KW - Sphere decoder KW - VLSI ER - TY - JOUR TI - Progress on large-area polarization grating fabrication AU - Miskiewicz, Matthew N. AU - Kim, Jihwan AU - Li, Yanming AU - Komanduri, Ravi K. AU - Escuti, Michael J. T2 - ACQUISITION, TRACKING, POINTING, AND LASER SYSTEMS TECHNOLOGIES XXVI AB - Over the last several years, we have pioneered liquid crystal polarization gratings (PGs), in both switchable and polymer versions. We have also introduced their use in many applications, including mechanical/non-mechanical laser beam steering and polarization imaging/sensing. Until now, conventional holographic congurations were used to create PGs where the diameter of the active area was limited to 1-2 inches. In this paper, we discuss a new holography setup to fabricate large area PGs using spherical waves as the diverging coherent beams. Various design parameters of this setup are examined for impact on the quality of the recorded PG profile. Using this setup, we demonstrate a large area polymer PG with approximately 66 inch square area, and present detailed characterization. DA - 2012/// PY - 2012/// DO - 10.1117/12.921572 VL - 8395 SP - SN - 0277-786X KW - polarization gratings KW - holography KW - liquid crystal KW - polymer KW - diffraction ER - TY - JOUR TI - High-Performance Solenoidal RF Transformers on High-Resistivity Silicon Substrates for 3D Integrated Circuits AU - Feng, Zhiping AU - Lueck, Matthew R. AU - Temple, Dorota S. AU - Steer, Michael B. T2 - IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES AB - Soleniod-like transformers based on a traveling-wave design and using advanced through silicon via process technology are reported for operation at frequencies from 1 to 14 GHz. The symmetrical 1:1 transformers are designed as compact slow-wave transmission-line structures with well-defined signal return paths. One-, two-, three-, and four-turn transformers have 1-dB bandwidths ranging from 6 to 9.2 GHz, and midband insertion losses from 0.24 to 0.37 dB. The measured intrinsic loss is 0.46 dB or less up to 10 GHz, and 0.97 dB up to 14 GHz. Relatively simple and scalable physically based lumped-element circuit models accurately predict the performance of these low parasitic transformers. DA - 2012/7// PY - 2012/7// DO - 10.1109/tmtt.2012.2195026 VL - 60 IS - 7 SP - 2066-2072 SN - 1557-9670 KW - Heterogeneous integration KW - RF transformer KW - slow-wave structure KW - 3D integrated circuit (3DIC) KW - through silicon via (TSV) ER - TY - JOUR TI - Effect of viscosities on structure and instability of sprays from a swirl atomizer AU - Yao, Shanshan AU - Zhang, Ji AU - Fang, Tiegang T2 - EXPERIMENTAL THERMAL AND FLUID SCIENCE AB - The breakup phenomena of liquid spray sheets and jets are encountered in daily life as well as in various industrial applications. The onset of instability has a direct impact on the downstream spray development, and thus it is necessary to investigate the effect of liquid physical properties on this instability. The present paper focuses on the effects of liquid viscosity on the spray characteristics and instability during the transient operation of a swirl atomizer in a trigger sprayer via experiments. In the experiments, water–glycerol mixtures were used to simulate fluids with a wide range of viscosities. The transient displacement of the dispensing piston was measured. A high-speed digital video camera was used to visualize the near-nozzle spray structure. The digital images of the sprays were further processed in order to analyze the spray angle and the surface waves on the spray cone. By using the spatiotemporal diagrams, the surface wave temporal frequency was also analyzed for fluids with different viscosities. From the experimental results, it is seen that the fluid viscosity plays a critical role in controlling the liquid sheet breakup and atomization. More viscous fluids result in smaller average spray cone angles. The spray cone developed very fast during the early stage for less viscous fluids, while for the most viscous liquid, a very small cone angle with little breakup and atomization was observed. As the liquid viscosity increases, the cone collapses earlier with larger droplets in the end stage. In addition to the spray cone angles, the surface wave temporal frequency was also calculated from the recorded images. The results show that the surface wave temporal frequency depends on the dispensing time and the fluid viscosity, and is almost independent of the location in the near nozzle liquid cone. The results also indicate that the surface wave temporal frequency decreases with time. DA - 2012/5// PY - 2012/5// DO - 10.1016/j.expthermflusci.2012.01.020 VL - 39 SP - 158-166 SN - 1879-2286 KW - Swirl atomizer KW - Spray KW - Liquid breakup KW - Flow instability KW - Fluid viscosity ER - TY - JOUR TI - Demonstration of communication using neutrinos AU - Stancil, D. D. AU - Adamson, P. AU - Alania, M. AU - Aliaga, L. AU - Andrews, M. AU - Del Castillo, C. A. AU - Bagby, L. AU - Alba, J. L. B. AU - Bodek, A. AU - Boehnlein, D. AU - Bradford, R. AU - Brooks, W. K. AU - Budd, H. AU - Butkevich, A. AU - Caicedo, D. A. M. AU - Capista, D. P. AU - Castromonte, C. M. T2 - Modern Physics Letters A DA - 2012/// PY - 2012/// VL - 27 IS - 12 ER - TY - JOUR TI - Comparison of modeling techniques in circuit variability analysis AU - Yelten, Mustafa Berke AU - Franzon, Paul D. AU - Steer, Michael B. T2 - INTERNATIONAL JOURNAL OF NUMERICAL MODELLING-ELECTRONIC NETWORKS DEVICES AND FIELDS AB - SUMMARY Three nonlinear reduced‐order modeling approaches are compared in a case study of circuit variability analysis for deep submicron complementary metal‐oxide‐semiconductor technologies where variability of the electrical characteristics of a transistor can be significantly detrimental to circuit performance. The drain currents of 65 nm N‐type metal‐oxide‐semiconductor and P‐type metal‐oxide‐semiconductor transistors are modeled in terms of a few process parameters, terminal voltages, and temperature using Kriging‐based surrogate models, neural network‐based models, and support vector machine‐based models. The models are analyzed with respect to their accuracy, establishment time, size, and evaluation time. It is shown that Kriging‐based surrogate models and neural network‐based models can be generated with sufficient accuracy that they can be used in circuit variability analysis. Numerical experiments demonstrate that for smaller circuits, Kriging‐based surrogate modeling yields results faster than the neural network‐based models for the same accuracy whereas for larger circuits, neural network‐based models are preferred as, in all metrics, better performance is obtained. Within‐die variations for an XOR circuit are analyzed, and it is shown that the nonlinear reduced‐order models developed can more effectively capture the within‐die variations than the traditional process corner analysis. Copyright © 2011 John Wiley & Sons, Ltd. DA - 2012/// PY - 2012/// DO - 10.1002/jnm.836 VL - 25 IS - 3 SP - 288-302 SN - 1099-1204 KW - artificial neural network KW - digital circuit KW - drain current KW - Kriging KW - least-squares support vector machine KW - surrogate modeling KW - variability Analysis KW - XOR ER - TY - JOUR TI - Comparing Through-Silicon-Via (TSV) Void/Pinhole Defect Self-Test Methods AU - Lou, Yi AU - Yan, Zhuo AU - Zhang, Fan AU - Franzon, Paul D. T2 - JOURNAL OF ELECTRONIC TESTING-THEORY AND APPLICATIONS DA - 2012/2// PY - 2012/2// DO - 10.1007/s10836-011-5261-4 VL - 28 IS - 1 SP - 27-38 SN - 1573-0727 KW - TSV KW - 3D stacking yield KW - On-chip capacitor bridge KW - Test-before-stacking ER - TY - JOUR TI - The Evolution of Optical Networking AU - Tomkos, Ioannis AU - Mukherjee, Biswanath AU - Korotky, Steven K. AU - Tucker, Rodney S. AU - Lunardi, Leda T2 - PROCEEDINGS OF THE IEEE DA - 2012/5// PY - 2012/5// DO - 10.1109/jproc.2012.2187363 VL - 100 IS - 5 SP - 1017-1022 SN - 0018-9219 UR - http://dx.doi.org/10.1109/jproc.2012.2187363 ER - TY - JOUR TI - Junction-level thermal analysis of 3-D integrated circuits using high definition power blurring AU - Melamed, S. AU - Thorolfsson, T. AU - Harris, T. R. AU - Priyadarshi, S. AU - Franzon, Paul AU - Steer, M. B. AU - Davis, W. R. T2 - IEEE Transactions on Computer-aided Design of Integrated Circuits and Systems AB - The degraded thermal path of 3-D integrated circuits (3DICs) makes thermal analysis at the chip-scale an essential part of the design process. Performing an appropriate thermal analysis on such circuits requires a model with junction-level fidelity; however, the computational burden imposed by such a model is tremendous. In this paper, we present enhancements to two thermal modeling techniques for integrated circuits to make them applicable to 3DICs. First, we present a resistive mesh-based approach that improves on the fidelity of prior approaches by constructing a thermal model of the full structure of 3DICs, including the interconnect. Second, we introduce a method for dividing the thermal response caused by a heat load into a high fidelity “near response” and a lower fidelity “far response” in order to implement Power Blurring high definition (HD), a hierarchical thermal simulation approach based on Power Blurring that incorporates the resistive mesh-based models and allows for junction-level accuracy at the full-chip scale. The Power Blurring HD technique yields approximately three orders of magnitude of improvement in memory usage and up to six orders of magnitude of improvement in runtime for a three-tier synthetic aperture radar circuit, as compared to using a full-chip junction-scale resistive mesh-based model. Finally, measurement results are presented showing that Power Blurring high definition (HD) accurately determines the shape of the thermal profile of the 3DIC surface after a correction factor is added to adjust for a discrepancy in the absolute temperature values. DA - 2012/// PY - 2012/// DO - 10.1109/tcad.2011.2180384 VL - 31 IS - 5 SP - 676–689 ER - TY - JOUR TI - A Unified Optimizing Compiler Framework for Different GPGPU Architectures AU - Yang, Yi AU - Xiang, Ping AU - Kong, Jingfei AU - Mantor, Mike AU - Zhou, Huiyang T2 - ACM TRANSACTIONS ON ARCHITECTURE AND CODE OPTIMIZATION AB - This article 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 generates two kernels, one optimized for global memories and the other for texture memories. The proposed compilation process is effective for both AMD/ATI and NVIDIA GPUs. The experiments show that our optimized code achieves very high performance, either superior or very close to highly fine-tuned libraries. DA - 2012/6// PY - 2012/6// DO - 10.1145/2207222.2207225 VL - 9 IS - 2 SP - SN - 1544-3973 KW - Performance KW - Experimentation KW - Languages KW - GPGPU KW - OpenCL KW - CUDA KW - CUBLAS KW - GPU Computing ER - TY - JOUR TI - THD minimization applied directly on the line-to-line voltage of multilevel inverters AU - Yousefpoor, N. AU - Fathi, S. H. AU - Farokhnia, N. AU - Abyaneh, H. A. T2 - IEEE Transactions on Industrial Electronics DA - 2012/// PY - 2012/// VL - 59 IS - 1 SP - 373-380 ER - TY - JOUR TI - Scaling Issues in Ferroelectric Barium Strontium Titanate Tunable Planar Capacitors AU - Lam, Peter G. AU - Haridasan, Vrinda AU - Feng, Zhiping AU - Steer, Michael B. AU - Kingon, Angus I. AU - Maria, Jon-Paul T2 - IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL AB - We report on the geometric limits associated with tunability of interdigitated capacitors, specifically regarding the impact of a parasitic non-tunable component that necessarily accompanies a ferroelectric surface capacitor, and can dominate the voltage-dependent response as capacitor dimensions are reduced to achieve the small capacitance values required for impedance matching in the X band. We present a case study of simple gap capacitors prepared and characterized as a function of gap width (i.e., the distance between electrodes) and gap length (i.e., the edge-to-edge gap distance). Our series of measurements reveals that for gap widths in the micrometer range, as gap lengths are reduced to meet sub-picofarad capacitance values, the non-tunable parasitic elements limit the effective tunability. These experimental measurements are supported by a companion set of microwave models that clarify the existence of parallel parasitic elements. DA - 2012/2// PY - 2012/2// DO - 10.1109/tuffc.2012.2179 VL - 59 IS - 2 SP - 198-204 SN - 1525-8955 KW - Capacitance KW - Capacitors KW - Barium KW - Strontium KW - Titanium compounds KW - Electrodes KW - Substrates ER - TY - JOUR TI - Performance of the 802.11p Physical Layer in Vehicle-to-Vehicle Environments AU - Fernandez, Joseph A. AU - Borries, Kevin AU - Cheng, Lin AU - Kumar, B. V. K. Vijaya AU - Stancil, Daniel D. AU - Bai, Fan T2 - IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY AB - A reliable robust wireless network of connected vehicles is desired to enable a number of future telematics and infotainment applications in the vehicular domain. To achieve this objective, vehicle-to-vehicle (V2V) communication is standardized by the IEEE 802.11p Dedicated Short Range Communications (DSRC) standard. Providing reliable communication performance in a highly dynamic time-varying V2V channel is a challenging task. To tackle this challenge, we propose a dynamic equalization scheme, on top of the existing DSRC technology, that significantly improves the packet error rate (PER) of data transmissions without changing the DSRC standard. We also show a hardware implementation of this scheme based on a field-programmable gate array (FPGA) to demonstrate its implementation feasibility. Furthermore, we extend our improved equalization scheme to various data rate options available in the DSRC standard, showing that the proposed scheme is sufficiently generic to support different types of V2V communication. Finally, we report the results of investigating the dependence of wireless communication performance (in terms of PER and throughput) on various design parameters such as packet length, payload size, and data rate. DA - 2012/1// PY - 2012/1// DO - 10.1109/tvt.2011.2164428 VL - 61 IS - 1 SP - 3-14 SN - 1939-9359 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84856196012&partnerID=MN8TOARS KW - Dedicated Short Range Communications (DSRC) KW - equalization KW - IEEE 802.11p KW - orthogonal frequency-division multiplexing (OFDM) KW - vehicle to vehicle (V2V) ER - TY - JOUR TI - Passivity Enforcement for Admittance Models of Distributed Networks Using an Inverse Eigenvalue Method AU - Saunders, Christopher S. AU - Steer, Michael B. T2 - IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES AB - Most transient circuit simulators are based on admittance representations of the constituent circuit elements. It is therefore natural to use admittance parameter descriptions of linear networks, preferably in the form of rational transfer functions that can be directly implemented in the analysis. A problem arises when the measured or calculated frequency-domain response of a linear distributed network must be derived from data that has inherent error, is of limited bandwidth, or is not in the appropriate rational form. A reduced-order rational model that is causal, stable, and passive must be developed. Previous methods of deriving rational functions for the admittance parameters of a network do guarantee stability and causality, but passivity of the model must be assured through subsequent post-processing. Enforcing passivity requires modification of the state-space parameters of the model with consequent introduction of errors. This paper reports on a procedure to simultaneously achieve passivity, accuracy, causality, and stability in the development of an admittance macromodel described using a matrix of rational functions. An iterative inverse eigenvalue algorithm enforces passivity, and is applied by conjoining sets of eigenvalue and admittance constraints. These constraints form a monolithic projection matrix, which simultaneously addresses both passivity and accuracy of the model. DA - 2012/1// PY - 2012/1// DO - 10.1109/tmtt.2011.2171500 VL - 60 IS - 1 SP - 8-20 SN - 0018-9480 KW - Circuit-field interactions KW - inverse eigenvalue problem KW - linear device modeling KW - passive models KW - passive reduced-order modeling KW - transient nonlinear circuit simulation ER - TY - JOUR TI - Momentum and heat transfer of the Falkner-Skan flow with algebraic decay: An analytical solution AU - Fang, Tiegang AU - Yao, Shanshan AU - Zhang, Ji AU - Zhong, Yongfang AU - Tao, Hua T2 - COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION AB - In this paper, an analytical solution of the Falkner–Skan equation with mass transfer and wall movement is obtained for a special case, namely a velocity power index of −1/3, with an algebraically decaying velocity profile. The solution is given in a closed form. Under different values of the mass transfer parameter, the wall can be fixed, moving in the same direction as the free stream, or opposite to the free stream (reversal flow near the wall). The thermal boundary layer solution is also presented with a closed form for a prescribed power-law wall temperature, which is expressed by the confluent hypergeometric function of the second kind. The temperature profiles and the wall temperature gradients are plotted. Interesting but complicated variation trends for certain combinations of controlling parameters are observed. Under certain parameter combinations, there exist singular points or poles for the wall temperature gradients, namely wall heat flux. With poles, the temperature profiles can cross the zero temperature line and become negative. From the results, it is also found empirically that under certain given values of the Prandtl number (Pr) and flow controlling parameter (b), the number of times for the temperature profiles crossing the zero line is the same as the number of poles when the wall temperature power index varies between zero and a given value n. The current result provides a new analytical solution for the Falkner–Skan equation with algebraic decay and greatly enriches the understanding of this important equation as well as the heat transfer characteristics for this flow. DA - 2012/6// PY - 2012/6// DO - 10.1016/j.cnsns.2011.10.021 VL - 17 IS - 6 SP - 2476-2488 SN - 1878-7274 KW - Similarity solution KW - Falkner-Skan equation KW - Algebraic decay KW - Analytical solution KW - Boundary layer flow ER - TY - JOUR TI - Active damping of output LC filter resonance for vector-controlled VSI-fed AC motor drives AU - Hatua, K. AU - Jain, A. K. AU - Banerjee, D. AU - Ranganathan, V. T. T2 - IEEE Transactions on Industrial Electronics DA - 2012/// PY - 2012/// VL - 59 IS - 1 SP - 334-342 ER - TY - JOUR TI - A Survey on the Electrification of Transportation in a Smart Grid Environment AU - Su, Wencong AU - Rahimi-Eichi, Habiballah AU - Zeng, Wente AU - Chow, Mo-Yuen T2 - IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS AB - Economics and environmental incentives, as well as advances in technology, are reshaping the traditional view of industrial systems. The anticipation of a large penetration of plug-in hybrid electric vehicles (PHEVs) and plug-in electric vehicles (PEVs) into the market brings up many technical problems that are highly related to industrial information technologies within the next ten years. There is a need for an in-depth understanding of the electrification of transportation in the industrial environment. It is important to consolidate the practical and the conceptual knowledge of industrial informatics in order to support the emerging electric vehicle (EV) technologies. This paper presents a comprehensive overview of the electrification of transportation in an industrial environment. In addition, it provides a comprehensive survey of the EVs in the field of industrial informatics systems, namely: 1) charging infrastructure and PHEV/PEV batteries; 2) intelligent energy management; 3) vehicle-to-grid; and 4) communication requirements. Moreover, this paper presents a future perspective of industrial information technologies to accelerate the market introduction and penetration of advanced electric drive vehicles. DA - 2012/2// PY - 2012/2// DO - 10.1109/tii.2011.2172454 VL - 8 IS - 1 SP - 1-10 SN - 1941-0050 KW - Battery KW - charging infrastructure KW - communication KW - electric vehicle (EV) KW - energy management KW - plug-in electric vehicle (PEV) KW - plug-in hybrid electric vehicle (PHEV) KW - smart grid KW - vehicle-to-grid (V2G) ER - TY - JOUR TI - Winnowing: Protecting P2P systems against pollution through cooperative index filtering AU - Shin, Kyuyong AU - Reeves, Douglas S. T2 - JOURNAL OF NETWORK AND COMPUTER APPLICATIONS AB - Pollution (i.e., sharing of corrupted files, or contaminating index information with bogus index records) is a de facto problem in many file sharing peer-to-peer (P2P) systems in use today. Pollution squanders network resources and frustrates users with unprofitable downloads (due to corrupted files) and unproductive download trials (due to bogus index records). In this paper, we propose a novel distributed hash table (DHT)-based anti-pollution scheme called winnowing. Winnowing aims to reduce or eliminate decoy index records (pointing to nonexisting or corrupted files) held by DHT (i.e., index) nodes in the system, so that download attempts based on the remaining (clean) index records are more likely to yield satisfactory results. To achieve this goal, two techniques are used: (1) publish verification is performed by index nodes to counteract index pollution and (2) privacy-preserving object reputation is integrated into the DHT to reduce the impact of content and metadata pollution. By integrating these techniques, winnowing converges quickly to a near-optimal solution. Winnowing has the added benefit that it does not reveal a peer's download history to other downloading peers. The publish verification of winnowing has been implemented on top of the latest eMule client, and extensive data has been collected from the Kad network using this modified client. The measurement results are summarized, and the findings from the measurement study are incorporated into an analytical model. The model demonstrates the robustness of the privacy-preserving object reputation of winnowing to a variety of pollution attacks, and to attacks on winnowing itself. The results of analysis are confirmed by means of event-driven simulations. DA - 2012/1// PY - 2012/1// DO - 10.1016/j.jnca.2011.02.015 VL - 35 IS - 1 SP - 72-84 SN - 1084-8045 KW - Peer-to-peer KW - Pollution KW - Distributed hash table (DHT) KW - Reputation KW - Filtering ER - TY - JOUR TI - Efficiently Exploiting Memory Level Parallelism on Asymmetric Coupled Cores in the Dark Silicon Era AU - Patsilaras, George AU - Choudhary, Niket K. AU - Tuck, James T2 - ACM TRANSACTIONS ON ARCHITECTURE AND CODE OPTIMIZATION AB - Extracting high memory-level parallelism (MLP) is essential for speeding up single-threaded applications which are memory bound. At the same time, the projected amount of dark silicon (the fraction of the chip powered off) on a chip is growing. Hence, Asymmetric Multicore Processors (AMP) offer a unique opportunity to integrate many types of cores, each powered at different times, in order to optimize for different regions of execution. In this work, we quantify the potential for exploiting core customization to speedup programs during regions of high MLP. Based on a careful design space exploration, we discover that an AMP that includes a narrow and fast specialized core has the potential to efficiently exploit MLP. Using the results of our analysis, we design an AMP with both an MLP and ILP specialized core, and we propose a hardware-level, application steering mechanism called Symbiotic Core Execution (SCE). SCE detects MLP phases by monitoring the L2 miss rate of the application, and it uses that information to steer the application to the best core. Interestingly, we show that L2 miss rates are important for deciding when an MLP region begins and when it ends. As a program runs, its execution migrates to a core customized for MLP during regions of high MLP; when the region ends, it is re-scheduled on the core that fits the application characteristics. Compared to a monolithic core optimized for both modes of operation, our AMP design provides a harmonic mean performance improvement of 5.3% and 6.6% for SPEC2000 and SPEC2006, respectively, with a maximum speedup of 14.5%. For the same study, it achieves a 18.3% and 21.1% energy delay 2 reduction for SPEC2000 and SPEC2006, respectively. Our findings yield an important message for designing AMPs with specialized cores: core customization enables efficient exploitation of MLP, and application steering mechanisms for MLP are simple to implement and effective. DA - 2012/1// PY - 2012/1// DO - 10.1145/2086696.2086707 VL - 8 IS - 4 SP - SN - 1544-3566 KW - Design KW - Performance KW - Memory level parallelism KW - multicore KW - asymmetric multicore processor KW - dark silicon ER - TY - JOUR TI - Analysis and Design of Active NPC (ANPC) Inverters for Fault-Tolerant Operation of High-Power Electrical Drives AU - Li, Jun AU - Huang, Alex Q. AU - Liang, Zhigang AU - Bhattacharya, Subhashish T2 - IEEE TRANSACTIONS ON POWER ELECTRONICS AB - Compared with neutral-point-clamped (NPC) inverters, active NPC (ANPC) inverters enable a substantially increased output power and an improved performance at zero speed for high-power electrical drives. This paper analyzes the operation of three-level (3L) ANPC inverters under device failure conditions, and proposes the fault-tolerant strategies to enable continuous operating of the inverters and drive systems under single and multiple device open- and short-failure conditions. Therefore, the reliability and robustness of the electrical drives are greatly improved. Moreover, the proposed solution adds no additional components to standard 3L-ANPC inverters; thus, the cost for robust operation of drives is lower. Simulation and experiment results are provided for verification. Furthermore, a comprehensive comparison for the reliability function of 3L-ANPC and 3L-NPC inverters is presented. The results show that 3L-ANPC inverters have higher reliability than 3L-NPC inverters when a derating is allowed for the drive system under fault-tolerant operation. If a derated operation is not allowed, the two inverters have similar reliability for device open failure, while 3L-NPC inverters have higher reliability than 3L-ANPC inverters for device short failure. DA - 2012/2// PY - 2012/2// DO - 10.1109/tpel.2011.2143430 VL - 27 IS - 2 SP - SN - 1941-0107 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-84855387046&partnerID=MN8TOARS KW - Active NPC (ANPC) KW - electrical drives KW - fault tolerant KW - high power KW - multilevel inverter KW - reliability ER - TY - JOUR TI - Thermal Properties of AlGaN/GaN HFETs on Bulk GaN Substrates AU - Killat, N. AU - Montes, M. AU - Pomeroy, J. W. AU - Paskova, T. AU - Evans, K. R. AU - Leach, J. AU - Li, X. AU - Oezguer, Ue AU - Morkoc, H. AU - Chabak, K. D. AU - Crespo, A. AU - Gillespie, J. K. AU - Fitch, R. AU - Kossler, M. AU - Walker, D. E. AU - Trejo, M. AU - Via, G. D. AU - Blevins, J. D. AU - Kuball, M. T2 - IEEE ELECTRON DEVICE LETTERS AB - Micro-Raman thermography, microphotoluminescence spectroscopy, and thermal simulation were used to study the thermal properties of AlGaN/GaN heterostructure field-effect transistors grown on semi-insulating bulk GaN substrates. A bulk GaN thermal conductivity of 260 $\hbox{W}\cdot\hbox{m}^{-1} \cdot\hbox{K}^{-1}$ was determined from temperature measurements on operating devices in combination with finite-difference thermal simulations. This is significantly higher than typical thin GaN epilayer thermal conductivities, due to a lower dislocation density in bulk GaN. Despite the thermal conductivity of bulk GaN being lower than that of SiC, transistors on bulk GaN exhibited a similar thermal resistance as GaN-on-SiC devices, attributed to the absence of a thermal boundary resistance between the device epilayers and substrate for GaN-on-GaN devices. DA - 2012/3// PY - 2012/3// DO - 10.1109/led.2011.2179972 VL - 33 IS - 3 SP - 366-368 SN - 1558-0563 KW - AlGaN/GaN heterostructure field-effect transistor (HFET) KW - bulk GaN thermal conductivity KW - Raman thermography KW - thermal boundary resistance ER - TY - JOUR TI - Metalorganic vapor phase epitaxy and characterizations of nearly-lattice-matched AlInN alloys on GaN/sapphire templates and free-standing GaN substrates AU - Liu, Guangyu AU - Zhang, Jing AU - Li, Xiao-Hang AU - Huang, G. S. AU - Paskova, Tanya AU - Evans, Keith R. AU - Zhao, Hongping AU - Tansu, Nelson T2 - JOURNAL OF CRYSTAL GROWTH AB - The epitaxy optimization studies of high-quality n-type AlInN alloys with different indium contents grown on two types of substrates by metalorganic vapor phase epitaxy (MOVPE) were carried out. The effect of growth pressure and V/III molar ratio on growth rate, indium content, and surface morphology of these MOVPE-grown AlInN thin films were examined. The surface morphologies of the samples were characterized by scanning electron microscopy and atomic force microscopy. By varying the growth temperatures from 860 °C to 750 °C, the indium contents in AlInN alloys were increased from 0.37% up to 21.4% as determined by X-ray diffraction (XRD) measurements. The optimization studies on the growth conditions for achieving nearly-lattice-matched AlInN on GaN templates residing on sapphire and free-standing GaN substrates were performed, and the results were analyzed in a comparative way. Several applications of AlInN alloy for thermoelectric and light-emitting diodes are also discussed. DA - 2012/2/1/ PY - 2012/2/1/ DO - 10.1016/j.jcrysgro.2011.12.037 VL - 340 IS - 1 SP - 66-73 SN - 0022-0248 KW - Metalorganic vapor phase epitaxy KW - Nitrides KW - Semiconducting III-V materials KW - Light emitting diodes ER -