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Theoretical and Experimental Study of Barium Zinc-Cadmium Tantalate-based Microwave Dielectrics

MRS Online Proceedings Library (OPL) 2011年第1期783卷 B4.7-B4.7页

作者： Shaojun Liu Mark Van Schilfgaarde Jian Sun Louisa Badd David Smith Novak S. Petrovixc R. Taylor N. Newman Chemical and Materials Engineering Department Science and Engineering of Materials Program Center for Solid State Science Arizona State University Tempe AZ 85287–6006 Electrical and Computer Engineering Department Queens land University Paddington Australia 4064

Single-phase Ba(Cd1/3Ta2/3)O3 ceramics have been produced using conventional powder processing methods. In our initial investigations, 2wt% ZnO powder was added to act as a sintering aid since a high-density ceramic was not formed from solid-state diffusion alone. The resulting Ba(Cd0.327Zn0.006Ta2/3)O3 material sintered at 1550° C exhibits a dielectric constant of ∼33 and loss tangent of <5×10−5 at 2 GHz. In our more recent work, we have used boron as a sintering aid to facilitate sintering at temperatures as low as 1300° C, enhance the structural quality and improve the microwave properties of Ba(Cd1/3Ta2/3)O3 dielectrics. TEM results indicate that the liquid sintering mechanism is an important factor for boron concentrations exceeding 0.5wt%, while a point defect mechanism plays the dominant role at lower boron concentrations. The presence of superstructure peaks and splitting of the (220) and (214) peaks in X-ray diffraction spectra are direct evidence for the distortion from cubic symmetry as a result of Cd and Ta ordering on the ***-initio electronic structure calculations within the local density functional approximation have been used to give insight into the unusual properties of this class of materials. In both Ba(Zn1/3Ta2/3)O3 and Ba(Cd/3Ta2/3)O3, the conduction band maximum and valence band minimum are composed of mostly weakly itinerant Ta 5d-and Zn-3d/Cd-4d levels, respectively. The covalent nature of the directional d-electron bonding in these high-Z oxides plays an important role in producing a more rigid lattice with higher melting points and enhanced phonon energies, and possibly inherently lower intrinsic microwave loss than comparable ionic materials.

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Synthesis and Second-Order Nonlinear Optical Properties of New Coumaromethacrylate-Methylmethacrylate Copolymers

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MRS Online Proceedings Library 2011年第1期173卷 601-606页

作者： R. A. Henry J. M. Hoover A. Knoesen S. T. Kowel G. A. Lindsay M. A. Mortazavi Research Department Chemistry Division China Lake USA Department of Electrical Engineering and Computer Science Organized Research Program on Polymeric Ultrathin Film Systems University of California Davis USA

The synthesis and second-order nonlinear optical (NLO) properties of a new family of optically nonlinear coumarin dye-containing polymers is reported. Polymerizable coumaromethacrylate (CMA) monomers having various alkyl spacers (C2 to C5) between the polymerizable group and the chromophore were prepared and copolymerized with methylmethacrylate (MMA) and other vinyl monomers. The CMA copolymers had high chromophoric content (up to 18 × 1020) and glass transitions as high as 132°C. Spin cast films were prepared on BK7 substrates and oriented by corona-onset poling at elevated temperatures (COPET). The poled CMA copolymer films were characterized for spectroscopic absorption and second harmonic properties. A comparison of the nonlinear optical properties of poled CMA-MMA copolymers to poled guest-host systems is made. Relative to guest/host systems, CMA-MMA copolymer films exhibit larger and much more stable second-order nonlinear optical properties.

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282

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Cytokine 2013年第3期63卷 310-310页

作者： Elia D. Tait Wojno Mario Noti Brian S. Kim Mark C. Siracusa Paul R. Giacomin Meera G. Nair Alain J. Benitez Kathryn R. Ruymann Amanda B. Muir David A. Hill Kudakwashe R. Chikwava Amin E. Moghaddam Quentin J. Sattentau Aneesh Alex Chao Zhou Paul Menard-Katcher Masato Kubo Kazushige Obata-Ninomiya Hajime Karasuyama Michael R. Comeau David Artis Department of Microbiology University of Pennsylvania Philadelphia PA USA Institute for Immunology Perelman School of Medicine University of Pennsylvania Philadelphia PA USA Queensland Tropical Health Alliance and School of Public Health and Tropical Medicine James Cook University Cairns Australia Division of Gastroenterology Hepatology and Nutrition Children’s Hospital of Philadelphia Philadelphia PA USA Department of Pediatrics Division of Allergy and Immunology Children’s Hospital of Philadelphia Philadelphia PA USA Department of Pathology and Laboratory Medicine Children’s Hospital of Philadelphia Philadelphia PA USA The Sir William Dunn School of Pathology The University of Oxford Oxford UK Department of Electrical and Computer Engineering Lehigh University Bethlehem PA USA Center for Photonics and Nanoelectronics Lehigh University BethlehemPA USA Bioengineering Program Lehigh University Bethlehem PA USA Division of Gastroenterology Hospital of the University of Pennsylvania Philadelphia PA USA Laboratory for Signal Network Research Center for Allergy and Immunology RIKEN Yokohama Institute Yokohama Japan Division of Molecular Pathology Research Institute for Biological Science Tokyo University of Science Chiba Japan Department of Immune Regulation Tokyo Medical and Dental University Graduate School Tokyo Japan JST CREST Tokyo Medical and Dental University Graduate School Tokyo Japan Inflammation Research Amgen Inc. Seattle WA USA Department of Pathobiology School of Veterinary Medicine University of Pennsylvania Philadelphia PA USA

Eosinophilic esophagitis (EoE) is a food allergy-associated disease characterized by esophageal eosinophilia and associated inflammation. EoE has become increasingly common in industrialized countries. However, current management strategies, such as treatment with swallowed steroids and dietary restrictions, are nonspecific or negatively impact the quality of life of EoE patients. In addition, use of more specific therapies that target immunoglobulin E (IgE) and interleukin (IL)-5 have been largely unsuccessful in ameliorating EoE. Thus, there is an urgent need to identify novel, specific immunological pathways that underlie the pathogenesis of EoE that could be targeted to treat this disease. Recently, a genome-wide association study identified that EoE is associated with a gain-of-function polymorphism in the gene that encodes thymic stromal lymphopoietin (TSLP). TSLP is an IL-7 family member cytokine that promotes allergic inflammation by eliciting T helper type 2 cytokine responses, IgE production, and the expansion of a distinct population of basophils . However, whether TSLP directly promotes allergic inflammation in the esophagus and the mechanisms by which TSLP might contribute to the pathogenesis of EoE remain unknown. Here, we describe a new murine model of experimental EoE-like disease that was used to investigate the role of TSLP in allergic inflammation of the esophagus. Murine experimental EoE-like disease developed independently of IgE but was dependent on TSLP-elicited basophils. Critically, therapeutic antibody-mediated neutralization of TSLP or depletion of basophil populations ameliorated established EoE-like disease in mice. Finally, elevated TSLP levels and exaggerated basophil responses were observed in esophageal biopsies from EoE patients, and a gain-of-function polymorphism in TSLP correlated with increased basophil responses in patients with EoE. Together, these data indicate that TSLP-elicited basophil responses may play a key role in medi

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Handling failures of static sensor nodes in wireless sensor network by use of mobile sensors

Handling failures of static sensor nodes in wireless sensor ...

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25th IEEE International Conference on Advanced Information Networking and Applications Workshops, WAINA 2011

作者： Pignaton De Freitas, Edison Heimfarth, Tales Netto, Ivayr Farah Pereira, Carlos Eduardo Ferreira, Armando Morado Wagner, Flávio Rech Larsson, Tony IDE Halmstad University Halmstad Sweden Institute of Informatics Federal University of Rio Grande Do Sul Porto Alegre Brazil Computer Science Department Federal University of Lavras Lavras Brazil Electrical Engineering Department Federal University of Rio Grande Do Sul Porto Alegre Brazil Defense Engineering Graduate Program Military Institute of Engineering Rio de Janeiro Brazil

ISBN: (纸本)9780769543383

Node failures in Wireless Sensor Networks composed by static sensor nodes are common due to the nature of the sensor devices and the usually harsh environments in which they are deployed. Node failures can diminish the performance of the network as a whole, thus affecting its functionality in delivering the desired services. For instance, significant regions can become uncovered due to failure of several nearby nodes. This paper reports a study about the use of mobile sensor nodes acting in cooperation with static ones in order to fill gaps created by faulty static nodes. The proposed fault handling mechanism presents alternative policies with pros and cons, depending on the user priorities imposed to the system and the occurrence of failures. A discussion about this topic is presented based on results obtained by simulation of the proposed mechanisms. © 2011 IEEE.

关键词： Sensor nodes

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Design and performance evaluation of a digital wideband receiver on a hybrid computing platform

Design and performance evaluation of a digital wideband rece...

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IEEE Instrumentation and Measurement Technology Conference

作者： Kiran George Chien-In Henry Chen Computer Engineering Program California State University Fullerton CA USA Department of Electrical Engineering Wright State University Dayton OH USA

Design and implementation of a modern radar receiver that is capable of rapidly searching a large frequency range with maximum sensitivity in real time presents a challenge. Such a receiver not only has stringent operational requirements like high instantaneous dynamic range (IDR), multiple signal detection capability, wider bandwidth and also high frequency resolution. Currently, operating speeds of digital processors are not on par with state-of-the-art ADCs. To overcome this impediment, researchers are exploring methods of offloading the computational intensive tasks to specialized hardware accelerators. A 3 giga-sample-per-second (GSPS) wideband digital receiver system implemented on a unique hybrid computing platform, which is composed of two Tesla C2050 GPUs and a Xilinx Virtex-5 FPGA, is presented. Drastically improving its performance over its predecessors, the proposed receiver system detects five simultaneous signals in 1.25 GHz bandwidth (125-1375 MHz) with a maximum IDR of 42.5 dB and a frequency resolution of 0.5 MHz. The proposed receiver architecture performs a high-resolution spectral estimation and employs a hardware efficient platform for detecting multiple signals before the next set of buffered data arrives for processing.

关键词： Receivers Graphics processing unit Signal detection Field programmable gate arrays Signal resolution Wideband

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Exploring Time-Scales of Closed-Loop Decoder Adaptation in Brain-Machine Interfaces

Exploring Time-Scales of Closed-Loop Decoder Adaptation in B...

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Annual International Conference of the IEEE engineering in Medicine and Biology Society

作者： Amy L. Orsborn Siddharth Dangi Helene G. Moorman Jose M. Carmena Berkeley - Unviversity of California Department of Electrical Engineering and Computer Sciences University of California Helen Wills Neuroscience Institute University of California Department of Electrical Engineering and Computer Sciences Helen Wills Neuroscience Institute and Program in Cognitive Science University of California

ISBN: (纸本)9781424441211

Performing closed-loop modifications of a brain-machine interface (BMI) decoder is a technique that shows great promise for improving performance. We compare two algorithms for implementing adaptations that update decoder parameters on different time-scales (discrete batches vs. online), and present experimental results of a non-human primate performing a standard center-out BMI task. To ensure that our experimental training models are representative of a broad range of paralyzed patients, our decoders were initially trained using neural activity recorded during subject observation of cursor movement. We find that both closed-loop adaptation algorithms can be used to boost BMI performance from 20-30% to 80%, yielding movement kinematics similar to natural arm movements. Based on insights derived from the performance of each algorithm, we propose that a hybrid of batch and online decoder adaptation may be the best approach.

关键词： Decoding Kinematics Training Educational institutions Adaptation models Kalman filters USA Councils

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Online correction of orientation estimates using spatial memory in a neuromorphic head direction system

Online correction of orientation estimates using spatial mem...

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IEEE International Symposium on Circuits and Systems (ISCAS)

作者： Tarek M. Massoud Timothy K. Horiuchi Electrical and Computer Engineering Department Institute of Systems Research University of Maryland College Park MD USA Electrical and Computer Engineering Department Institute of Systems Research Neuroscience and Cognitive Science Program University of Maryland College Park MD USA

Many animals are known to maintain an internal estimate of their orientation in the environment. In the absence of external sensory cues, this estimate inevitably exhibits drift. When sensory information is available, associations between sensory landmarks and the internal estimate can be used to correct for drift. In this paper we present a neuromorphic system to model such associations between sensory landmarks in the environment (as provided by sonar) and the activity of a hardware-based head direction cell system (HDS) that continuously integrates angular velocity signals to maintain an estimate of the orientation. These associations are shown to correct for drift errors that are encountered in the HDS.

关键词： High definition video Robot sensing systems Neurons Navigation Sonar detection Neuromorphics

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EEG Analysis for Estimation of Duration and Inter-Event Intervals of Seizure-Like Events Recorded in vivo From Mice

EEG Analysis for Estimation of Duration and Inter-Event Inte...

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Annual International Conference of the IEEE engineering in Medicine and Biology Society

作者： Sinisa Colic Rob Wither James H. Eubanks Liang Zhang Berj L. Bardakjian Department of Electrical and Computer Engineering University of Toronto Department of Physiology University of Toronto Division of Genetics and Development Department of Surgery and University of Toronto Epilepsy Research Program University of Toronto Division of Fundamental Neurology Department of Medicine and University of Toronto Epilepsy Research Program University of Toronto Department of Electrical and Computer Engineering and Institute of Biomaterials and Biomedical Engineering University of Toronto

ISBN: (纸本)9781424441211

Rett syndrome is a neurodevelopmental disorder of the brain that affects females more often than males. Its cause is linked to the mutations within the gene encoding methyl CpG-binding protein 2 (MeCP2). Presently, there is little information regarding how the loss of MeCP2 affects brain activity. It has been documented that during awake but immobile state, the MeCP2 deficient mice exhibit spontaneous, rhythmic electroencephalogram (EEG) seizure-like events (SLEs) in the range of 6-9 Hz. In this study, we analyze the cortical EEG activity in female MeCP2-deficient mice over 24 hour recordings. Characterizing the SLE and inter-SLE durations by fitting to a gamma distribution we show similarity to previous in vivo epilepsy studies. These results suggest that the SLE and inter-SLE dynamics differ. More precisely, the SLE terminations appear to be a result of time-dependent mechanisms, whereas the inter-SLEs are a result of a random process.

关键词： Methyl-CpG-Binding Protein 2 Electroencephalography Systemic Lupus Erythematosus Gamma Distribution Mus Seizures Neurodevelopmental Disorders Stochastic Processes Brain Diseases Rett Syndrome awake Mouse brain activity CXXC1 gene

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Optimal sensor placement for intruder detection: New design principles

Optimal sensor placement for intruder detection: New design ...

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Annual Allerton Conference on Communication, Control, and Computing

作者： Waseem A. Malik Nuno C. Martins Ananthram Swami Army Research Laboratory (STEP program) and the Department of Electrical and Computer Engineering University of Maryland College Park USA Department of Electrical and Computer Engineering University of Maryland College Park MD USA Army Research Laboratory Adelphi MD USA

ISBN: (纸本)9781457718175

We consider the centralized detection of an intruder, whose location is modeled as uniform across a specified set of points, using an optimally placed team of sensors. These sensors make conditionally independent observations. The local detectors at the sensors are also assumed to be identical, with detection probability (P D ) and false alarm probability (P F ). We formulate the problem as an N-ary hypothesis testing problem, jointly optimizing the sensor placement and detection policies at the fusion center. We prove that uniform sensor placement is never strictly optimal when the number of sensors (M) equals the number of placement points (N). We prove that for N 2 >; N 1 >; M, where N 1 , N 2 are number of placement points, the framework utilizing M sensors and N 1 placement points has the same optimal placement structure as the one utilizing M sensors and N 2 placement points. For M ≤ 6 and for fixed P D (or P F ), increasing P F (or P D ) leads to optimal placements that are higher in the majorization-based partial order. For M >; 6, this result does not necessarily hold and we provide a simple counterexample. It is conjectured that the set of optimal placements for a given (M, N) can always be placed on a majorization-based partial order.

关键词： Vectors Equations Educational institutions Joints Random variables Testing

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Adaptive Kalman filtering for closed-loop Brain-Machine Interface systems

Adaptive Kalman filtering for closed-loop Brain-Machine Inte...

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International IEEE/EMBS Conference on Neural engineering, CNE

作者： Siddharth Dangi Suraj Gowda Rodolphe Héliot Jose M. Carmena Department of Electrical Engineering and Computer Sciences University of California Berkeley CA USA CEA-LETI France Department of Electrical Engineering and Computer Sciences Helen Wills Neuroscience Institute and Program in Cognitive Science University of California Berkeley CA USA

Brain-Machine Interface (BMI) decoding algorithms are often trained offline, but this paradigm ignores both the non-stationarity of neural signals and the feedback that exists in online, closed-loop control. To address these problems, we have developed an Adaptive Kalman Filter (AKF), a Kalman filter variant that adaptively updates its model parameters during training. For a Kalman filter decoder, batch retraining methods require completely re-estimating the parameter matrices from sufficient data to perform regression accurately, even if only small changes are necessary. Conversely, the AKF is designed to update the decoder parameters continuously and more intelligently. We simulated a population of 41 neurons learning to control a 2D computer cursor. The AKF yielded significantly faster skill acquisition and better robustness to perturbation and neuron loss than a standard Kalman filter with periodic batch retraining.

关键词： Decoding Kalman filters Mathematical model Equations Kinematics Neurons Training

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