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Pacific Rim International Symposium on Dependable Computing

作者： Meng-lai Yin Bruce Orenstein Department of Electrical and Computer Engineering Cal Poly Pomona USA Network Centric Systems Raytheon Advanced Device Center USA

This paper addresses the conditional probability for undetectable burst errors when using two CRC (cyclic redundancy check) codes in tandem, given that non-guaranteed-detectable burst errors have occurred. Three distinctive cases are discussed based on the error positions and the conditional probability of undetectable errors under each case is derived. Because this probability depends on the exact CRC polynomials selected, an upper-bound assessment is provided to address general cases

关键词： Cyclic redundancy check Polynomials computer errors Decoding Cyclic redundancy check codes Communication channels Degradation Guidelines Performance analysis Arm

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RF Isolated Real-Time Multipath Testbed for Performance Analysis of WLANs

RF Isolated Real-Time Multipath Testbed for Performance Anal...

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Annual Conference on Information Sciences and Systems (CISS)

作者： Leon T. Metreaud Kaveh Pahlavan Center for Wireless Information Network Studies (CWINS) Electrical and Computer Engineering Department Worcester Polytechnic Institute Worcester MA USA

Real-time performance evaluation of WLANs is an extremely challenging topic. The major drawback of real-time performance analysis in actual network installations is a lack of repeatability due to uncontrollable interference and propagation complexities, which are caused by unpredictable variations in the propagation channel. This stresses a need for an RF test system that provides isolation from interfering sources while simulating a real-time channel, thereby creating a realistic and controllable radio propagation test environment. In this paper we introduce a novel testbed for real-time laboratory performance evaluation of WLANs utilizing an RF isolated test system (Azimuthtrade Systems 801W) for isolation from interference and a real-time multipath channel simulator (Elektrobit PROPSimtradeC8) for channel emulation. A software protocol analyzer (WildPackets Airopeek NX) is used to capture data packets in the testbed. The relationship between the throughput and received power, under controlled propagation and interference conditions, is analyzed. We present practical models describing the throughput/power relationship for multirate IEEE 802.11b/g devices in different propagation conditions.

关键词： Radio frequency Performance analysis System testing Real time systems Interference Throughput Stress control Radio control Radio propagation Laboratories

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Incorporating network Connectivity Analysis in Maintenance Planning

Incorporating Network Connectivity Analysis in Maintenance P...

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Pacific Rim International Symposium on Dependable Computing

作者： Meng-lai Yin Rafael R. Arellano Department of Electrical and Computer Engineering Cal Poly Pomona USA Network Centric Systems Raytheon Advanced Device Center USA

This study is motivated by the unexpected failure of a network-based system during the performance of corrective maintenance. This incident highlights the importance of incorporating network connectivity analysis in maintenance planning. This study shows that it is crucial to consider network connectivity when planning maintenance. Procedures to conduct maintenance planning with network connectivity consideration is proposed and discussed

关键词： Satellite broadcasting Spine network topology Degradation Redundancy Failure analysis Performance analysis Availability Fault tolerant systems Large-scale systems

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Application of Agent Negotiation in Supporting Adaptive Learning

Application of Agent Negotiation in Supporting Adaptive Lear...

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International Conference on Advanced Learning Technologies (ICALT)

作者： K.R. Lai Chung Hsien Lan Chen Chung Liu Department of Computer Science and Engineering Yuan-Ze University Taiwan Institute of Network Learning Technology National Central University Taiwan

This study presents a negotiation-based e-learning framework to promote learning motive and enhance the interaction between learners and instructors. In terms of learning communication, a fuzzy constraint-based agent negotiation mechanism is proposed as a flexible model to suggest pedagogies or learning strategies. Examples are provided to illustrate the proposed framework for constructive and collaborative learning

关键词： Electronic learning Collaboration computer science Collaborative work Space technology Education Feedback Switches Application software Intelligent networks

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Track and vehicle condition monitoring during normal operation using reduced sensor sets

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HKIE Transactions Hong Kong Institution of Engineers 2006年第1期13卷 47-53页

作者： Weston, P.F. Li, P. Ling, C.S. Goodman, C.J. Goodall, R.M. Roberts, C. Department of Electronic Electrical and Computer Engineering University of Birmingham United Kingdom Department of Engineering University of Leicester United Kingdom Department of Electronic and Electrical Engineering Loughborough University United Kingdom Rail Research UK University of Birmingham Department of Electronic Electrical and Computer Engineering United Kingdom Department of Engineering University of Leicester United Kingdom Department of Mechanical Engineering University of Bristol United Kingdom Traction Systems Denmark Rail Research UK Universities Centre for Rail Systems Research United Kingdom IEE United Kingdom Railway Engineering Professional Network Management Team United Kingdom

The Enhanced Rail Contribution by Increased Reliability (ERCIR) project aimed to enhance availability by condition monitoring of the track and vehicle suspension from in-service trains. In this project, the possibility of instrumenting an inservice train is explored, with emphasis on using a minimal sensor set for the detection and diagnosis of track and vehicle faults. The use of a bogie-mounted pitch rate gyro to observe mean vertical track geometry is novel, as is using a bogie-mounted yaw rate gyro to observe mean lateral alignment as well as the more usual longer wavelength track curvature. Mathematical algorithms are developed to detect vehicle suspension faults and track irregularities. The suspension faults considered are changes in secondary lateral and anti-yaw dampers, and changes in effective conicity. Sudden changes are detected and diagnosed using a Kalman filter-based innovation approach;gradual changes in damping coefficients and effective conicity are detected by parameter estimation using a Rao-Blackwellised particle filter. Observable track geometry irregularities include mean vertical and lateral alignment irregularities, as well as crosslevel and twist faults. This paper finally describes the results of trials carried out on two different railway vehicles, using the data obtained to assess the validity of the fault detection algorithms.

关键词： Railroad tracks

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Cloud microphysical properties retrieved from MODIS sub-sampling radiance dataset over the extended GAME region

Cloud microphysical properties retrieved from MODIS sub-samp...

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Remote Sensing of the Atmosphere and Clouds

作者： Nakajima, Takashi Y. Suzuki, Kentaroh Nakajima, Teruyuki School of Information and Design Department of Network and Computer Engineering Tokai University 2-28-4 Tomigaya Shibuya-ku Tokyo 151-0063 Japan Center for Climate System Research University of Tokyo 5-1-5 Kashiwanoha Kashiwa Chiba 277-8568 Japan

The cloud microphysical properties retrieved from MODIS sub-sampling radiance dataset (MOD02SSH) over the extended GAME region are shown in this paper. The spatial distributions and temporal variations of the cloud optical thickness (τc) and effective particle radius (re), are important observation targets to understand the role of clouds in the radiation budget estimations, especially in the cloud-aerosol interaction studies, because they will have information of cloud growth process. Thus, the wide-area and relatively high-temporal observations of the cloud properties are necessary. The most passed researches that retrieved near-global distributions of the cloud properties, used the reduced data volume satellite radiance subset, such as the globally map-projected radiances dataset at the discretized degrees in latitude and longitude (e.g. 0.5 degrees) or narrow-swath (around nadir) radiance subset. In fact, these subsets reduced the computing time but unexpectedly reduced the observation samplings. In this study, we used MODIS 5-km subsampling radiance subsets (MOD02SSH) for the retrievals. The MOD02SSH conserves scene texture with moderately reduced data volume of 1/25 from original MODIS scene, so that they will be suitable for the more precise estimations of τc and re over synoptic to global scale. We retrieved τc and re from one-month MOD02SSH over the extended GAME region (60E-180E longitude and 20S to 60N latitude) in July 2004. In the obtained τc versus re scatter plots, we found interesting features that will be explained as the cloud properties under the pristine and polluted environments in the region. The non-hydrostatic spectral microphysics cloud model simulates these phenomena well. In the presentation, we will discuss about the MODIS radiance dataset for the cloud analysis, retrieval algorithm, then show the typical and interesting features appeared in observed τc-re scatter plots over the extended GAME regions.

关键词： Clouds

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Finding hierarchical frequent items in data streams

Finding hierarchical frequent items in data streams

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6th World Congress on Intelligent Control and Automation, WCICA 2006

作者： Wenfeng, Feng Qiao, Guo Zhibin, Zhang Network Information Center Beijing Institute of Technology Beijing 100081 Department of Computer Science and Engineering Henan University of Technology Jiaozuo 454000

ISBN: (纸本)1424403324

A Hierarchical Sketch was implemented to summarize the hierarchical structure in stream data. The sketch used a XOR-based pair-wise independent family of hash functions on the hierarchical domain to map stream data items to a three dimensional array of counters of size L×D×W. Of the counter array, L was the layers in hierarchy, D was the number of uniformly and randomly chosen hash functions, and W was the range of hash functions. Based on the sketch, an algorithm that identified and evaluated the hierarchical frequent items over data streams approximately was implemented. This algorithm has sub-linear time and space costs and is almost exact in statistic meaning. © 2006 IEEE.

关键词： Data structures

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Finding Hierarchical Frequent Items in Data Streams

Finding Hierarchical Frequent Items in Data Streams

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World Congress on Intelligent Control and Automation (WCICA)

作者： Wenfeng Feng Qiao Guo Zhibin Zhang Network Information Center Beijing Institute of Technology Beijing China Department of Computer Science and Engineering Henan University of Technology Jiaozuo China

A hierarchical sketch was implemented to summarize the hierarchical structure in stream data. The sketch used a XOR-based pair-wise independent family of hash functions on the hierarchical domain to map stream data items to a three dimensional array of counters of size LtimesDtimesW. Of the counter array, L was the layers in hierarchy, D was the number of uniformly and randomly chosen hash functions, and W was the range of hash functions. Based on the sketch, an algorithm that identified and evaluated the hierarchical frequent items over data streams approximately was implemented. This algorithm has sub-linear time and space costs and is almost exact in statistic meaning

关键词： Electronic mail Counting circuits Intelligent networks computer science Data engineering Costs Statistics Data structures Gold Intelligent control

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Impedance analysis of overhead medium voltage power lines for broadband PLC

Impedance analysis of overhead medium voltage power lines fo...

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IEEE International Symposium on Electromagnetic Compatibility (EMC)

作者： Dong-wan Chun Chull-chai Shin Young-jin Park Kwan-ho Kim Young-song Cho Gi-deok Yang Young-chul Rhee Department of electrical and computer engineering Ajou University Suwon South Korea Korea Electrotechnology Research Institute KERI Electrical telecommunication network group Euiwang South Korea Department of information and communication engineering Chodang University South Korea Department of electrical and computer engineering Ansan Technical College South Korea Department of information and communication engineering Kyungnam University South Korea

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Analysis of the IEEE 802.11e EDCA Under Statistical Traffic

Analysis of the IEEE 802.11e EDCA Under Statistical Traffic

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IEEE International Conference on Communications (ICC)

作者： Juki Wirawan Tantra Chuan Heng Foh Ilenia Tinnirello Giuseppe Bianchi Centre for Multimedia and Network Technology School of Computer Engineering Nanyang Technological University Singapore Department of Electrical Engineering Università di Palermo Palermo Italy Department of Electrical Engineering Università degli Studi di Roma Tor Vergata Rome Italy

Many models have been proposed to analyze the performance of the IEEE 802.11 distributed coordination function (DCF) and the IEEE 802.11e enhanced distributed coordination function (EDCA) under saturation condition. To analyze DCF under statistical traffic, Foh and Zukerman introduce a model that uses Markovian Framework to compute the throughput and delay performance. In this paper, we analyze the protocol service time of EDCA mechanism and introduce a model to analyze EDCA under statistical traffic using Markovian Framework. Using this model, we analyze the throughput and delay performance of EDCA mechanism under statistical traffic.

关键词： Performance analysis Throughput Delay Traffic control Telecommunication traffic Wireless LAN Quality of service Multiaccess communication Media Access Protocol Access protocols

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