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Spin relaxation times of single-wall carbon nanotubes

Physical Review B 2013年第4期88卷 041401(R)-041401(R)页

作者： W. D. Rice R. T. Weber P. Nikolaev S. Arepalli V. Berka A.-L. Tsai J. Kono Department of Electrical and Computer Engineering Rice University Houston Texas 77005 USA Department of Physics and Astronomy Rice University Houston Texas 77005 USA Bruker BioSpin Corporation Billerica Massachusetts 01821 USA Air Force Research Lab Wright-Patterson Air Force Base Ohio 45433 USA National Institute of Aerospace 100 Exploration Way Hampton Virginia 23666 USA University of Texas Medical School Houston Texas 77005 USA

We have measured temperature (T)- and power-dependent electron spin resonance in bulk single-wall carbon nanotubes to determine both the spin-lattice and the spin-spin relaxation times, T1 and T2. We observe that T1−1 increases linearly with T from 4 K to 100 K, whereas T2−1 decreases by over a factor of two when T is increased from 3 K to 300 K. We interpret the T1−1∝T trend as spin-lattice relaxation via interaction with conduction electrons (Korringa law) and the decreasing T dependence of T2−1 as motional narrowing. By analyzing the latter, we find the spin hopping frequency to be 285 GHz. Last, we show that the Dysonian line shape asymmetry follows a three-dimensional variable-range hopping behavior from 3 K to 20 K; from this scaling relation, we extract a localization length of the hopping spins to be ∼100 nm.

关键词： TEMPERATURE measurements ELECTRON paramagnetic resonance CARBON nanotubes SPIN polarization ELECTRONS LATTICE field theory

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Fractional Order Controller for Pitch Loop Control of a VTOL UAV

Fractional Order Controller for Pitch Loop Control of a VTOL...

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International Conference on Unmanned Aircraft Systems

作者： Jinlu Han Long Di Calvin Coopmans YangQuan Chen Department of Electrical and Computer Engineering Utah State University Logan Utah 84322-4120 USA Charles L. Brown Department of Electrical and Computer Engineering University of Virginia Charlottesville Virginia 22904 USA MESA Lab and faculty of School of Engineering University of California Merced Merced CA 95343 USA

ISBN: (纸本)9781479908158

As the fundamental tuning step for vertical takeoff and landing (VTOL) unmanned aerial vehicles (UAVs), pitch loop control has significant impact on the flight. In this paper, an auto-regressive with exogenous input (ARX) model is acquired and converted to a first-order plus time delay (FOPTD) model for the pitch loop of a VTOL UAV. Based on the FOPTD model, a fractional order [proportional integral] (FO[PI]) controller is designed. An integer order PI controller based on the modified Ziegler-Nichols (MZNs) tuning rule and a general integer order proportional integral derivative (PID) controller are also designed for comparison following three design specifications. Simulation results have shown that the proposed fractional order controller outperforms both the MZNs PI controller and the integer order PID controller in terms of robustness and disturbance rejection.

关键词： Order Controller Pitch

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The Accuracy and Precision of Signal Source Localization with Tetrodes

The Accuracy and Precision of Signal Source Localization wit...

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

作者： Chang Won Lee Agnieszka A. Szymanska Yuji Ikegaya Zoran Nenadic Samsung Dallas Technology Lab Department of Biomedical Engineering University of California Laboratory of Chemical Pharmacology Graduate School of Pharmaceutical Sciences University of Tokyo Department of Biomedical Engineering and Department of Electrical Engineering and Computer Science University of California

ISBN: (纸本)9781457702150

Four-sensor microelectrodes, commonly referred to as tetrodes, have the ability to significantly increase the signal-to-noise ratio of neuronal extracellular recordings. They also provide spatio-temporal information about extracellular action potentials (EAP) which may be used to localize and resolve individual neuronal signal sources. Since the relative position of sensors and neurons whose EAPs are recorded is not known during in vivo experiments, the accuracy and precision of neuronal source localization algorithms remain untested. In this study, electrical signals generated by a stimulator were recorded simultaneously with four recording micropipettes immersed in artificial cerebrospinal fluid. The location of the source was estimated using the multiple signal classification algorithm, with an accuracy and precision of ～4 μm and ～7 μm, respectively. These results suggest that in vivo localization and resolution of individual neuronal sources is feasible.

关键词： Precision tetrodes signal sources signal to noise ratios Extensible Authentication Protocol Position measurement Stimulators position sensor

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Person localization through ground vibrations using a sand-scorpion inspired spiking neural network

Person localization through ground vibrations using a sand-s...

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Annual Conference on Information Sciences and Systems (CISS)

作者： Guillaume Garreau Eleni Proxenou Andreas G. Andreou Julius Georgiou Holistic Electronics Research Lab University of Cyprus Nicosia Cyprus Department of Electrical and Computer Engineering Johns Hopkins University Baltimore MD USA

Sand-scorpions can locate a prey using the vibration it creates in the ground when moving. We introduce a spiking neural model of the sand-scorpion and a successful implementation of this model with data collected wit... 详细信息

关键词： Sensors Data acquisition Portable computers Legged locomotion Concrete Rubber

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A spiking neural network architecture for visual motion estimation

A spiking neural network architecture for visual motion esti...

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IEEE Biomedical Circuits and Systems (BIOCAS)

作者： Garrick Orchard Ryad Benosman Ralph Etienne-Cummings Nitish V. Thakor Singapore Institute for Neurotechnology (SINAPSE) National University of Singapore Singapore Vision Institute University Pierre and Marie Curie Paris France Department of Electrical and Computer Engineering Johns Hopkins University Baltimore MD USA

Current interest in neuromorphic computing continues to drive development of sensors and hardware for spike-based computation. Here we describe a hierarchical architecture for visual motion estimation which uses a spiking neural network to exploit the sparse high temporal resolution data provided by neuromorphic vision sensors. Although spike-based computation differs from traditional computer vision approaches, our architecture is similar in principle to the canonical Lucas-Kanade algorithm. Output spikes from the architecture represent the direction of motion to the nearest 45 degrees, and the speed within a factor of √2 over the range 0.02 to 0.27 pixels/ms.

关键词： Neurons Sensors Delays Visualization computer architecture Motion estimation Cameras

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A novel paradigm for context-aware content pre-fetching in mobile networks

A novel paradigm for context-aware content pre-fetching in m...

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IEEE Conference on Wireless Communications and Networking

作者： Pavan Kamaraju Pietro Lungaro Zary Segall Department of Computer Science and Electrical Engineering University of Maryland Baltimore County USA Mobile Service Lab Royal Institute of Technology Kista Sweden

ISBN: (纸本)9781467359382

The current content provision methods and associated pricing and business models are challenged by the traffic requirements anticipated for future “data intensive” services. In order to deliver substantially higher peak rates operators will need to deploy a much denser infrastructure and/or acquire more spectrum, thus significantly increasing their CAPEX and OPEX and reducing revenues. To improve the utilization of available network resources this paper presents ActiveCast, a disruptive content delivery paradigm that supports opportunistic content pre-fetching by introducing semantic and context awareness in the currently “agnostic” networking paradigm. The experimental investigations presented in the paper focus on mobile video provision and a content provider, integrated with Facebook and YouTube, has been developed and used to identify socially relevant content for a set of test users. Part of the studies presented in the paper aim at experimentally understanding the structure of the energy costs associated with pre-fetching and on defining a delivery strategy that allows controlling the amount of energy invested. A comparison between a centralized implementation, in which pre-fetching is coordinated by the mobile operators, and an Over-The-Top (OTT) implementation of ActiveCast are also presented. The results show that complementing the context information available at individual user terminals with traffic information, shared by mobile operators through the ActiveCast API, can substantially reduce the energy costs of content delivery, as compared with “on demand” video streaming. Additionally, opportunistically exploiting connections with WiFi APs can amplify the gains already achievable by prefetching on wide area networks.

关键词： Mobile communication Streaming media Context Servers YouTube IEEE 802.11 Standards Monitoring

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A distributed collapse of a network's dimensionality

A distributed collapse of a network's dimensionality

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IEEE Global Conference on Signal and Information Processing (GlobalSIP)

作者： Adam C. Wilkerson Harish Chintakunta Hamid Krim Terrence J. Moore Ananthram Swami Department of Electrical and Computer Engineering North Carolina State University Raleigh North Carolina USA Army Research Lab Adelphi Maryland USA

Algebraic topology has been successfully applied to detect and localize sensor network coverage holes with minimal assumptions on sensor locations. These methods all use a computation of topological invariants called homology spaces. We develop a distributed algorithm for collapsing a sensor network, hence simplifying its analysis. We prove that the collapse is equivalent to a previously developed strong collapse in that it preserves coverage hole locations. In this way, the collapse simplifies the network without losing crucial information about the coverage region. We show that the algorithm requires only one-hop information in a communication network, making it faster than clique-finding algorithms that increase the number of computations necessary for hole localization. This makes it an effective pre-processing step to finding network coverage holes.

关键词： Topology Network topology Complexity theory Distributed algorithms Face Educational institutions Algorithm design and analysis

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InAs/GaSb Type-II Superlattice Detectors

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Advances in Electronics 2014年第1期2014卷

作者： Elena A. Plis Center for High Technology Materials Department of Electrical and Computer Engineering University of New Mexico Albuquerque NM USAunm.edu Skinfrared LLC Lobo Venture Lab 801 University Boulevard Suite 10 Albuquerque NM 87106 USA

InAs/(In,Ga)Sb type-II strained layer superlattices (T2SLs) have made significant progress since they were first proposed as an infrared (IR) sensing material more than three decades ago. Numerous theoretically predicted advantages that T2SL offers over present-day detection technologies, heterojunction engineering capabilities, and technological preferences make T2SL technology promising candidate for the realization of high performance IR imagers. Despite concentrated efforts of many research groups, the T2SLs have not revealed full potential yet. This paper attempts to provide a comprehensive review of the current status of T2SL detectors and discusses origins of T2SL device performance degradation, in particular, surface and bulk dark-current components. Various approaches of dark current reduction with their pros and cons are presented.

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Security and privacy of electric vehicles in the smart grid context: Problem and solution

Security and privacy of electric vehicles in the smart grid ...

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3rd ACM Int. Symp. on Design and Analysis of Intelligent Vehicular Networks and Applications, DIVANet 2013, Held in Conjunction with the 16th ACM Int. Conf. on Modeling, Analysis and Simulation of Wireless and Mobile Systems, MSWiM 2013

作者： Nicanfar, Hasen TalebiFard, Peyman Hosseininezhad, Seyedali Leung, Victor C.M. Damm, Mark WiNMoS Lab. Department of Electrical and Computer Engineering University of British Columbia Vancouver BC V6T 1Z4 Canada Fuseforward Solution Group Ltd. Vancouver BC V6K 2G8 Canada

ISBN: (纸本)9781450323581

The technology, security and privacy requirements of the electric vehicle (EV) in the smart grid (SG) context, especially when the EV acts as mobile power storage, have gained much attention from the research community and market recently. This role of the EV is motivated by the increase in capacity of the power storages in the EV. In this paper, first we present different situations that an EV can be in the SG context and their privacy issues. Then, we provide two authentication schemes, first one between the EV and a trusted SG server directly, and second one via a non-trusted third party entity with a robust privacy-preserving agenda. Our analysis shows that our mechanisms are secure and robust enough to make sure the privacy of the customers is fully preserved, and at the same time, are efficient since they consume very limited resources. © 2013 ACM.

关键词： Electric vehicles

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Bangla text processing and recognition based on Fuzzy unsupervised Feature Extraction and SVM

Bangla text processing and recognition based on Fuzzy unsupe...

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International Conference on Machine Learning and Cybernetics (ICMLC)

作者： M. A. Haque Monil MD. S. Q. Zulkar Nine Bruce Poon M. Ashraful Amini Hong Yan Computer Vision and Cybernetics Research Independent University Bangladesh School of Electrical & Information Engineering University of Sydney NSW Australia Chittagong Independent University Chittagong BD Department of Electronic Engineering City University of Hong Kong Hong Kong China

Optical character recognition (OCR) is a widely used technology to convert text images to editable text. Researchers already proposed many machine learning algorithms to address this problem. However, Bangla text recognition is highly challenging job for its complicated writing style, compound characters and highly diversified fonts. To address the segmentation problem we have proposed an algorithm namely Blob-labeled character Segmentation (BLCS) that initiates with an extensive preprocessing to extract the characters from text. Our novel character segmentation procedure extracts characters maintaining 97.5% accuracy. Unsupervised feature learning becomes a powerful tool in machine learning nowadays. To increase the recognition rate of the characters, we have introduced a fuzzy unsupervised feature learning algorithm to learn features of individual characters. We then use Artificial Neural Network (ANN) and Support Vector Machine (SVM) to classify the characters. The SVM provides 99.4% accuracy which outperforms all other approaches.

关键词： Optical imaging Artificial neural networks Image segmentation Support vector machines Abstracts Three-dimensional displays Histograms

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