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IEEE Aerospace Conference

作者： Lahcene Hadj Abderrahmane Peter Garner Centre of Space Techniques 1Bd de la Palestine BP13 Arzew Oran ALGERIA Surrey Satellite Technology Limited Guildford Surrey GU2 7XH UNITED KINGDOM

ISBN: (纸本)9781457705564

In this paper, an earth observation Microsatellite communication system is proposed. The spacecraft will revolve in a sun-synchronous retrograde circular orbit. Therefore, it is equipped with two banks of cameras giving a total of 600km field of view at 30 meters spatial resolution in three spectral bands, the Red, Green and Near Infra-Red. The communication sub-system is designed to support the mission and the telemetry /telecommand data. The imaging system allows windowing and it is supported by a total storage capacity of 0.5 Gbytes of data, which could be downloaded to a ground station at 8 Mbps within 10 min. The downlink and the uplink, both operate in S band at 8 Mbps in normal operation and 38.4 kbps during commissioning for the downlink and at 9.6 kbps for the uplink. This paper describes the different modules constituting the communication system.

关键词： Space applications COMMUNICATION SYSTEMS up link Communication Research total storage capacity Land station multiprogramming Spacecraft normal operation COMMISSIONING Cameras Downlink telecommand

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Reduced-Complexity SFBC-OFDM for Vehicular Channels with High Mobility

Reduced-Complexity SFBC-OFDM for Vehicular Channels with Hig...

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IEEE Vehicular Technology Conference

作者： Ahmed A. Abotabl Amr El-Keyi Yahya Mohasseb Tamer ElBatt Wireless Intelligent Networks Center (WINC) Nile University

ISBN: (纸本)9781467318808

Space frequency block coding with orthogonal frequency division multiplexing (SFBC-OFDM) suffers from the effect of inter-carrier interference (ICI) in doubly-selective communication channels. In this paper;a scheme is proposed in which windowing is applied to the received signal to reduce the effect of ICI to a limited number of neighboring sub-carriers. The sub-carriers holding the SFBC components of each codeword are separated by a number of sub-carriers larger than the ICI range, and hence, they do not interfere with each other. In order to preserve the structure of the SFBC, the separation between the codeword components is also selected within the coherence bandwidth of the channel. As a result, the diversity gain of the SFBC is preserved. A decision feedback equalizer is proposed to estimate the transmitted data symbols with low complexity. Simulation results are presented showing the ability of the proposed scheme to significantly improve the performance of SFBC-OFDM and preserve its diversity gain.

关键词： coherence bandwidth space-frequency block coding Diversity methods decision feedback equalisers codeword ICI multiprogramming Preserves received signal Orthogonal frequency division multiplexing

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Frequency-domain weighted non-linear least-squares estimation of continuous-time, time-varying systems

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IET CONTROL THEORY AND APPLICATIONS 2011年第7期5卷 923-933页

作者： Lataire, J. Pintelon, R. Vrije Univ Brussel Dept ELEC Fundamental Elect & Instrumentat B-1050 Brussels Belgium

A frequency-domain least-squares estimator is presented for identifying linear, continuous-time, time-varying dynamical systems. The model considered is a linear, ordinary differential equation whose coefficients vary as polynomials in time. A frequency-domain approach is used, thus allowing the user to determine easily the frequency band(s) of interest. It is shown that the bias errors because of windowing and sampling the continuous-time signals can be modelled by a polynomial function of the frequency. The regression matrices of the estimators are shown to be very efficiently computed using the fast Fourier transform algorithm and its inverse. The total least-squares, generalised total least-squares and weighted, non-linear least-squares estimators are constructed. The latter two are shown to be consistent. The estimators are illustrated on simulation and measurement data.

关键词： Frequency function Estimators time-varying systems FFT algorithm Frequency bands Ordinary differential equation measurement data Polynomial multiprogramming least-squares estimator

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Waste Not, Want Not Resource-based Garbage Collection in a Shared Environment 11

Waste Not, Want Not Resource-based Garbage Collection in a S...

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International Symposium on Memory Management (ISMM 11)

作者： Hertz, Matthew Kane, Stephen Keudel, Elizabeth Bai, Tongxin Ding, Chen Gu, Xiaoming Bard, Jonathan E. Canisius Coll Dept Comp Sci Buffalo NY 14208 USA Univ Rochester Dept Comp Sci Rochester NY 14627 USA SUNY Buffalo NYS Ctr Excellence Bioinformat & Life Sci Buffalo NY 14203 USA

ISBN: (纸本)9781450302630

To achieve optimal performance, garbage-collected applications must balance the sizes of their heaps dynamically. Sizing the heap too small can reduce throughput by increasing the number of garbage collections that must be performed. Too large a heap, however, can cause the system to page and drag down the overall throughput. In today's multicore, multiprocessor machines, multiple garbage-collected applications may run simultaneously. As a result, each virtual machine (VM) must adjust its memory demands to reflect not only the behavior of the application it is running, but also the behavior of the peer applications running on the system. We present a memory management system that enables VMs to react to memory demands dynamically. Our approach allows the applications' heaps to remain small enough to avoid the negative impacts of paging, while still taking advantage of any memory that is available within the system. This memory manager, which we call Poor Richard's Memory Manager, focuses on optimizing overall system performance by allowing applications to share data and make system-wide decisions. We describe the design of our memory management system, show how it can be added to existing VMs with little effort, and document that it has almost no impact on performance when memory is plentiful. Using both homogenous and heterogenous Java workloads, we then show that Poor Richard's memory manager improves average performance by up to a factor 5.5 when the system is paging. We further show that this result is not specific to any garbage collection algorithm, but that this improvement is observed for every garbage collector on which we test it. We finally demonstrate the versatility of our memory manager by using it to improve the performance of a conservative whole-heap garbage collector used in executing. Net applications.

关键词： Experimentation Measurement Performance poor richard's memory manager garbage collection multiprogramming throughput paging

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Model Checking Multitask Applications for OSEK Compliant Real-Time Operating Systems

Model Checking Multitask Applications for OSEK Compliant Rea...

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17th IEEE Pacific Rim International Symposium on Dependable Computing (PRDC)

作者： McKelvin, Mark L., Jr. Gamble, Edward B., Jr. Holzmann, Gerard J. CALTECH Jet Prop Lab Lab Reliable Software Pasadena CA 91109 USA

ISBN: (纸本)9780769545905

In the verification of multitask software in real-time embedded systems, general purpose model checkers do not inherently consider characteristics of the real-time operating system, such as priority-based scheduling, priority inversion, and protocols for protecting shared memory resources. Since explicit state model checkers generally explore all possible execution paths and task interleaving, this could potentially lead to exploring execution paths that are redundant, unnecessarily increasing verification complexity and hampering tractability. Based on this premise, in this work we investigate how one can improve the performance of explicit state model checkers, such as SPIN, for the verification of multitask applications that target real-time operating systems.

关键词： Computational modeling Computer science Embedded systems Object oriented modeling Real time systems SPIN automated verification compliant real-time operating system characteristics embedded systems execution paths explicit state model checker model checking multiprogramming multitask application multitask applications multitask software verification operating systems (computers) program verification real time embedded system real-time operating systems shared memory resources shared memory systems task interleaving

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Multi-task Beta Process Sparse Kernel Machines

Multi-task Beta Process Sparse Kernel Machines

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International Joint Conference on Neural Networks (IJCNN)

作者： Gao, Junbin Charles Sturt Univ Sch Comp & Math Bathurst NSW 2795 Australia

ISBN: (纸本)9781424496365

In this paper we propose a nonparametric extension to the sparse kernel machine using a beta process prior. The extended beta process sparse kernel machine (BPSKM) allows for a sparse model to be constructed from a set of training data. The recent research on beta process reveals elegant property of Bayesian conjugate prior which is utilized to derive a variational Bayes inference algorithm. The performance of the proposed algorithm has been investigated on both synthetic and real-life data sets.

关键词： Bayes methods Bayesian conjugate prior Bayesian methods Data models Kernel Machine learning Sparse matrices Training Training data inference mechanisms learning (artificial intelligence) multiprogramming multitask beta process sparse kernel machine nonparametric extension real-life data set sparse matrices variational Bayes inference algorithm

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Wavelet As A Diagnostic Tool For Fault Classification And Identification In Underground Power Cable

Wavelet As A Diagnostic Tool For Fault Classification And Id...

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Conference on Electrical Insulation and Dielectric Phenomena (CEIDP)

作者： Pandey, Abhishek Younan, Nicolas Mississippi State Univ Dept Elect & Comp Engn Mississippi State MS 39762 USA

ISBN: (纸本)9781457709869

In this paper, a diagnostic technique based on the wavelet transform (WT) for identifying and classifying different fault types is developed. In general, the wavelet transform provides multiresolution type analysis with variable window size;thus better suited for such analysis. Variable window sizes provide good resolution in the time and frequency domains;thus helping not only in identifying the fault, but also in localizing it. Three types of cables are used in this study;a normal cable, a shorted cable, and a cable with holes. Wavelet transformation is then applied to the impedance in each case, with various windowing to eliminate possible interference. The identification is then carried out by examining the resulting impedance magnitude. This study reveals that the wavelet transform is a better tool for fault identification and classification.

关键词： cable Fault class wavelet transforms wavelets diagnostic tool Underground cables failure recognition multiprogramming Window Size impedance underground

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Exploring Energy-Efficient DRAM Array Organizations

Exploring Energy-Efficient DRAM Array Organizations

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54th IEEE International Midwest Symposium on Circuits and Systems (MWSCAS)

作者： O, Seongil Choo, Sungwoo Ahn, Jung Ho Seoul Natl Univ Grad Sch Convergence Sci & Technol Seoul South Korea

ISBN: (纸本)9781612848570

DRAM is widely used as main-memory storage in contemporary computer systems. As VLSI process technology advances, more transistors can be integrated in a single die leading to higher storage capacity and communication throughput per DRAM chip. New DRAM standards are created in order to keep up with these trends, and many factors such as performance, energy efficiency, reliability, and fabrication/testing cost are considered when a new DRAM architecture is designed. However, there are few studies on DRAM array organizations that consider both performance and energy efficiency of entire computer systems using the organizations. In this paper, we explore the design space of contemporary DRAM array organizations by varying the number of pages that can be concurrently accessed and the size of the pages. We compare various main-memory DRAM array organizations using multithreaded and multiprogrammed workloads on a chip-multiprocessor system with die-stacked DRAM memory in search of energy-efficient array configurations.

关键词： Arrays DRAM architecture DRAM chips DRAM chips Energy efficiency Organizations Timing VLSI VLSI process technology Wires chip-multiprocessor system communication throughput contemporary computer system design space die-stacked DRAM memory energy efficiency energy-efficient DRAM array organization energy-efficient array configuration fabrication cost main-memory storage microprocessor chips multi-threading multiprogrammed workload multiprogramming multithreaded workload reliability storage capacity testing cost transistor

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PACMan: Prefetch-aware cache management for high performance caching 44

PACMan: Prefetch-aware cache management for high performance...

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44th Annual IEEE/ACM Symposium on Microarchitecture, MICRO 44

作者： Wu, Carole-Jean Jaleel, Aamer Martonosi, Margaret Steely Jr., Simon C. Emer, Joel Princeton University Princeton NJ United States Intel Corporation VSSAD Hudson MA United States Massachusetts Institute of Technology Cambridge MA United States

ISBN: (纸本)9781450310536

Hardware prefetching and last-level cache (LLC) management are two independent mechanisms to mitigate the growing latency to memory. However, the interaction between LLC management and hardware prefetching has received very little attention. This paper characterizes the performance of state-of-the-art LLC management policies in the presence and absence of hardware prefetching. Although prefetching improves performance by fetching useful data in advance, it can interact with LLC management policies to introduce application performance variability. This variability stems from the fact that current replacement policies treat prefetch and demand requests identically. In order to provide better and more predictable performance, we propose Prefetch-Aware Cache Management (PACMan). PACMan dynamically estimates and mitigates the degree of prefetch-induced cache interference by modifying the cache insertion and hit promotion policies to treat demand and prefetch requests differently. Across a variety of emerging workloads, we show that PACMan eliminates the performance variability in state-of-the-art replacement policies under the influence of prefetching. In fact, PACMan improves performance consistently across multimedia, games, server, and SPEC CPU2006 workloads by an average of 21.9% over the baseline LRU policy. For multiprogrammed workloads, on a 4-core CMP, PACMan improves performance by 21.5% on average. © 2011 ACM.

关键词： multiprogramming

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A generalization of blocking and windowing algorithms for duplicate detection

A generalization of blocking and windowing algorithms for du...

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2nd International Conference on Data and Knowledge Engineering, ICDKE 2011

作者： Draisbach, Uwe Naumann, Felix Hasso Plattner Institute 14482 Potsdam Germany

ISBN: (纸本)9781457708640

Duplicate detection is the process of finding multiple records in a dataset that represent the same real-world entity. Due to the enormous costs of an exhaustive comparison, typical algorithms select only promising record pairs for comparison. Two competing approaches are blocking and windowing. Blocking methods partition records into disjoint subsets, while windowing methods, in particular the Sorted Neighborhood Method, slide a window over the sorted records and compare records only within the window. We present a new algorithm called Sorted Blocks in several variants, which generalizes both approaches. To evaluate Sorted Blocks, we have conducted extensive experiments with different datasets. These show that our new algorithm needs fewer comparisons to find the same number of duplicates. © 2011 IEEE.

关键词： duplicate detection multiprogramming BLOCKING windows window Dataset numerical invariant Records as Topic

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