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DQDB-ATM MAN:一种新的局域网-ATM网互连方案 被引量:1
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作者 汪小涓 续敏 《计算机工程与应用》 CSCD 北大核心 2002年第4期174-176,185,共4页
文章提出了一种新的局域网-ATM互连方案(分布式队列双总线子网)和相应的流量控制算法,这里称为“基于信用的流量控制”。该算法既能够在保持数据优先级的前提下按照传输请求的时序进行网络传输,又有效地防止了ATM缓冲区溢出。
关键词 局域网 ATM网 网络互连 DQDB 异步传输模式
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Efficient Channel Estimation Techniques for MIMO Systems with 1-Bit ADC 被引量:5
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作者 Hany SHussein Shaimaa Hussein Ehab Mahmoud Mohamed 《China Communications》 SCIE CSCD 2020年第5期50-64,共15页
With a low resolution 1-bit ADC on its receiver(RX) side, MIMO with 1-bit ADC took a considerable step in the fulfillment of the hardware complexity constrains of the internet of things(IoT) PHY layer design. However,... With a low resolution 1-bit ADC on its receiver(RX) side, MIMO with 1-bit ADC took a considerable step in the fulfillment of the hardware complexity constrains of the internet of things(IoT) PHY layer design. However, applying 1-bit ADC at MIMO RX results in severe nonlinear quantization error. By which, almost all received signal amplitude information is completely distorted. Thus, MIMO channel estimation is considered as a major barrier towards practical realization of 1-bit ADC MIMO system. In this paper, two efficient sparsity-based channel estimation techniques are proposed for 1-bit ADC MIMO systems, namely the low complexity sparsity-based channel estimation(LCSCE), and the iterative adaptive sparsity channel estimation(IASCE). In these techniques, the sparsity of the 1-bit ADC MIMO channel is exploited to propose a new adaptive and iterative compressive sensing(CS) recovery algorithm to handle the 1-bit ADC quantization effect. The proposed algorithms are tested with the state-of-the-art 1-bit ADC MIMO constant envelope modulation(MIMO-CEM). The 1-bit ADC MIMO-CEM system is chosen as it fulfills both energy and hardware complexity constraints of the IoT PHY layer. Simulation results reveal the high effectiveness of the proposed algorithms in terms of spectral efficiency(SE) and computational complexity. The proposed LCSCE reduces the computational complexity of the 1-bit ADC MIMO-CEM channel estimation by 86%, while the IASCE reduces it by 96% compared to the recent techniques of MIMO-CEM channel estimation. Moreover, the proposed LCSCE and IASCE improve the spectrum efficiency by 76 % and 73 %, respectively, compared to the recent techniques. 展开更多
关键词 channel estimation 1-bit ADC MIMO sparsity recovery compressive sensing Internet of things
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计算机系统结构研究的新方向 被引量:2
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作者 汪小涓 续敏 《重庆邮电学院学报(自然科学版)》 2001年第4期1-6,共6页
以 RISC技术和分层存贮器为主要特征的计算机系统在科学计算与交易处理领域获得了成功 ,但是新的应用需求和技术困难使得这种现有的体系结构不能适应未来的计算需要。分析了现有的体系结构与以多媒体处理和个人移动计算为主要内容的应... 以 RISC技术和分层存贮器为主要特征的计算机系统在科学计算与交易处理领域获得了成功 ,但是新的应用需求和技术困难使得这种现有的体系结构不能适应未来的计算需要。分析了现有的体系结构与以多媒体处理和个人移动计算为主要内容的应用趋势的不协调性 ,并介绍一种新的计算机系统结构Vector IRAM,为计算机系统结构研究提供参考。 展开更多
关键词 RISC 分层存储器 计算机 系统结构
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PERFORMANCE COMPARISON OF A LINEARLY COMBINED ORDERED-STATISTIC DETECTORS UNDER POSTDETECTION INTEGRATION AND NONHOMOGENEOUS SITUATIONS 被引量:2
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作者 Mohamed Bakry El_Mashade 《Journal of Electronics(China)》 2006年第5期698-707,共10页
Several Constant False Alarm Rate (CFAR) architectures, where radar systems often employ them to automatically adapt the detection threshold to the local background noise or clutter power in an attempt to maintain a... Several Constant False Alarm Rate (CFAR) architectures, where radar systems often employ them to automatically adapt the detection threshold to the local background noise or clutter power in an attempt to maintain an approximately constant rate of false alarm, have been recently proposed to estimate the unknown noise power level. Since the Ordered-Statistics (OS) based algorithm has some advantages over the Cell-Averaging (CA) technique, we are concerned here with this type of CFAR detectors. The Linearly Combined Ordered-Statistic (LCOS) processor, which sets threshold by processing a weighted ordered range samples within finite moving window, may actually perform somewhat better than the conventional OS detector. Our objective in this paper is to analyze the LCOS processor along with the conventional OS scheme for the case where the radar receiver incorporates a postdetection integrator amongst its contents and where the operating environments contain a number of secondary interfering targets along with the primary target of concern and the two target types fluctuate in accordance with the Swerling Ⅱ fluctuation model and to compare their performances under various operating conditions. 展开更多
关键词 Constant False Alarm Rate (CFAR) detectors Clutter edges Extraneous targets Postdetection integration Ordered-statistic algorithm
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PERFORMANCE EVALUATION OF THE DOUBLE-THRESHOLD CFAR DETECTOR IN MULTIPLE-TARGET SITUATIONS 被引量:2
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作者 Mohamed B. El Mashade 《Journal of Electronics(China)》 2006年第2期204-210,共7页
In radar systems of automatic detection, an estimate of background clutter power is used to set the detection threshold. An interference saturated environment is frequently encountered in these systems (multiple targe... In radar systems of automatic detection, an estimate of background clutter power is used to set the detection threshold. An interference saturated environment is frequently encountered in these systems (multiple target situations). Therefore, the detection of signals in such an environment becomes one of the most important problems to be solved. The double-threshold algorithm is one of the more interesting detectors used in these situations. While the first threshold operation ensures that the calculation of the detection (second) threshold is based on a set of samples which is free of strong interferers and is therefore much more representative of the noise level, the second threshold is used to declare the presence or the absence of the radar target. The object of the present paper is to analyze the performance of such type of CFAR schemes when the radar receiver contains a noncoherent integrator amongst its basic elements. It is found that the processor detectabil ity loss is very low and the performance degradation, caused by interferers is quite small even if the number of outlying targets is large, given that the first threshold is properly chosen. 展开更多
关键词 Double-threshold CFAR detector Noncoherent integration Multitarget environments Swerling target fluctuation model
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EXACT ANALYSIS OF OS MODIFIED VERSIONS WITH NONCOHERENT INTEGRATION 被引量:2
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作者 Mohamed B.El Mashade 《Journal of Electronics(China)》 2004年第4期265-277,共13页
This paper deals with the exact detection analysis of the Ordered-Statistic(OS) processor along with OS Greatest Of(OSGO) and OS Smallest Of(OSSO) modified versions, for M postdetection integrated pulses when the oper... This paper deals with the exact detection analysis of the Ordered-Statistic(OS) processor along with OS Greatest Of(OSGO) and OS Smallest Of(OSSO) modified versions, for M postdetection integrated pulses when the operating environment is nonhomogeneous. Analytical results are presented in multiple-target case as well as in regions of clutter power transitions. The primary and the secondary interfering targets are assumed to be fluctuating in accordance with the SWII target fluctuation model. As the number of noncoherently integrated pulses increases,lower threshold values and consequently better detection performances are obtained in both homogeneous and multiple target background models. However, the false alarm rate performance of OSSO-CFAR(Constant False Alarm Rate) scheme at clutter edges is worsen with increasing the postdetection integrated pulses. As predicted, the OSGO-CFAR detector accommodates the presence of spurious targets in the reference window, given that their number is within its allowable range in each local window, and controls the rate of false alarm when the contents of the reference cells have clutter boundaries. 展开更多
关键词 Adaptive radar detectors Ordered-Statistic(OS) modified versions Interfering targets Clutter boundaries Postdetection integration
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Fuzzy PID Controllers Using FPGA Technique for Real Time DC Motor Speed Control 被引量:4
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作者 Basil Hamed Moayed Almobaied 《Intelligent Control and Automation》 2011年第3期233-240,共8页
The design of intelligent control systems has become an area of intense research interest. The development of an effective methodology for the design of such control systems undoubtedly requires the synthesis of many ... The design of intelligent control systems has become an area of intense research interest. The development of an effective methodology for the design of such control systems undoubtedly requires the synthesis of many concepts from artificial intelligence. The most commonly used controller in the industry field is the proportional-plus-integral-plus-derivative (PID) controller. Fuzzy logic controller (FLC) provides an alternative to PID controller, especially when the available system models are inexact or unavailable. Also rapid advances in digital technologies have given designers the option of implementing controllers using Field Programmable Gate Array (FPGA) which depends on parallel programming. This method has many advantages over classical microprocessors. In this research, A model of the fuzzy PID control system is implemented in real time with a Xilinx FPGA (Spartan-3A, Xilinx Company, 2007). It is introduced to maintain a constant speed to when the load varies.,The model of a DC motor is considered as a second order system with load variation as a an example for complex model systems. For comparison purpose, two widely used controllers “PID and Fuzzy” have been implemented in the same FPGA card to examine the performance of the proposed system. These controllers have been tested using Matlab/Simulink program under speed and load variation conditions. The controllers were implemented to run the motor as real time application under speed and load variation conditions and showed the superiority of Fuzzy-PID. 展开更多
关键词 DC MOTOR Fuzzy LOGIC Control PID CONTROLLER REAL Time FPGA
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Experimental Study on Triggering Characteristics of a Surface Flashover Triggered Vacuum Switch 被引量:1
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作者 姚学玲 陈景亮 孙伟 《Plasma Science and Technology》 SCIE EI CAS CSCD 2010年第6期734-737,共4页
Triggering characteristics of triggered vacuum switch (TVS), including the discharge delay time, delay jitter, range of operational voltage and peak of pulsed current, are investigated. Both structure and experiment... Triggering characteristics of triggered vacuum switch (TVS), including the discharge delay time, delay jitter, range of operational voltage and peak of pulsed current, are investigated. Both structure and experimental circuit of TVS are presented. The results indicate that TVS, as a surface flashover triggering device with high dielectric permittivity material, is with excellent triggering characteristics. When the hold-off voltage reaches 120 kV, the minimum operational voltage is 1.3 kV, and the minimum discharge delay time and jitter are 100 ns and ±10 ns, respectively. The peak current is up to 240 kA when the operational voltage reaches 100 kV. TVS can well satisfy the main demands of high voltage and current applications, and can also be used under a multi-crowbar circuit. 展开更多
关键词 surface flashover dielectric material TVS(triggered vacuum switch) discharge delay time delay jitter
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ANALYSIS OF CELL-AVERAGING BASED DETECTORS FOR χ^2 FLUCTUATING TARGETS IN MULTITARGET ENVIRONMENTS 被引量:1
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作者 Mohamed B. El_Mashade 《Journal of Electronics(China)》 2006年第6期853-863,共11页
The χ^2 family of signal fluctuation distributions represents the main fluctuation models which most radar targets follow it in their reflections. This family can be categorized as fluctuation distribution with two d... The χ^2 family of signal fluctuation distributions represents the main fluctuation models which most radar targets follow it in their reflections. This family can be categorized as fluctuation distribution with two degrees of freedom and those with four degrees of freedom. The first category represents all important class of fluctuation models which when illuminated by a coherent pulse train, return a train of fully correlated pulses (Swerling Ⅰ model) or fully decorrelated pulses (Swerling Ⅱ model). The detection of this type of fluctuating targets is therefore of great importance. This paper is devoted to the analysis of Cell-Averaging (CA) based detectors for the case where the radar receiver noncoherently integrates M square-law detected pulses and the signal fluctuation obeys 2 statistics with two degrees of freedom. These detectors include the Mean-Of (MO), the Greatest-Of (GO) and the Smallest-Of(SO) schemes. In these processors, the estimation of the noise power levels from the leading and the trailing reference windows is based on the CA technique. Exact formulas for the detection probabilities are derived, in the absence as well as in the presence of spurious targets. The primary and the secondary interfering targets are assumed to be fluctuating in accordance with the χ^2 fluctuation model with two degrees of freedom (SWI & SWII). The numerical results show that the MO version has the best homogeneous performance, the SO scheme has the best multiple-target performance, while the GO procedure does not offer any merits, neither in the absence nor in the presence of outlying targets. 展开更多
关键词 Adaptive detectors Cell-averaging processors Noncoherent integration χ^2 fluctuating targets Target multiplicity environments
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Stability and Robustness Analysis of an Adaptive Algorithm for Quasi-periodic Disturbances Rejection
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作者 徐昱琳 张五一 杨向萍 《Journal of Donghua University(English Edition)》 EI CAS 2004年第6期49-53,共5页
Winding and web transport systems are subjected to quasi-periodic disturbances of the web tension due to the eccentricity and the non-circularity of the reel and rolls. The disturbances induced by the non-circularity ... Winding and web transport systems are subjected to quasi-periodic disturbances of the web tension due to the eccentricity and the non-circularity of the reel and rolls. The disturbances induced by the non-circularity and eccentricity of the rolls are quasi-periodic with a frequency that varies with their rotation speed. An adaptive method of rejection of these disturbances is proposed in this paper. It is based on a phase-locked loop structure that estimates simutaneously the phase and magnitude of the perturbation and then cancels it. This algorithm can be plugged in an existing industrial controller. The stability and robustness of the algorithm are also discussed. The ability of the algorithm to reject quasi-periodic disturbances with slowly varying frequencies is shown through simulation results. 展开更多
关键词 QUASI-PERIODIC DISTURBANCE rejection web WINDING systems adaptive algorithm phase-locked loop STABILITY and robustness analysis
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Performance Comparison of PIN and APD based FSO Satellite Systems for various Pulse Modulation Schemes in Atmospheric Turbulence
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作者 Pooja Gopal V. K. Jain Subrat Kar 《Communications and Network》 2013年第3期200-203,共4页
In this paper, the performance of various Pulse Position Modulation (PPM) schemes has been analysed for PIN and APD receivers in the presence of atmospheric turbulence. It is observed that the performance of the APD r... In this paper, the performance of various Pulse Position Modulation (PPM) schemes has been analysed for PIN and APD receivers in the presence of atmospheric turbulence. It is observed that the performance of the APD receiver is always better than that of the PIN receiver as expected. Among the various modulation schemes, the performance of Differential Amplitude PPM (DAPPM) scheme with more number of amplitude levels is better than that of the other schemes for the same single level peak amplitude. Further, the optimum gain of APD receiver does not change substantially for different modulation schemes and turbulent conditions. 展开更多
关键词 Free Space OPTICS Pulse Modulation Ground-to-satellite COMMUNICATIONS
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Efficient Fast Multiplication Free Integer Transformation for the 1-D DCT of the H.265 Standard
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作者 Mohamed Nasr Haggag Mohamed El-Sharkawy +1 位作者 Gamal Fahmy Maher Rizkalla 《Journal of Software Engineering and Applications》 2010年第8期784-795,共12页
In this paper, efficient one-dimensional (1-D) fast integer transform algorithms of the DCT matrix for the H.265 stan-dard is proposed. Based on the symmetric property of the integer transform matrix and the matrix op... In this paper, efficient one-dimensional (1-D) fast integer transform algorithms of the DCT matrix for the H.265 stan-dard is proposed. Based on the symmetric property of the integer transform matrix and the matrix operations, which denote the row/column permutations and the matrix decompositions, along with using the dyadic symmetry modification on the standard matrix, the efficient fast 1-D integer transform algorithms are developed. Therefore, the computational complexities of the proposed fast integer transform are smaller than those of the direct method. In addition to computational complexity reduction one of the proposed algorithms provides transformation quality improvement, while the other provides more computational complexity reduction while maintaining almost the same transformation quality. With lower complexity and better transformation quality, the first proposed fast algorithm is suitable to accelerate the quality-demanding video coding computations. On the other hand, with the significant lower complexity, the second proposed fast algorithm is suitable to accelerate the video coding computations. 展开更多
关键词 FAST Algorithm HDTV H.265 ICT Order-16 TRANSFORM Video Coding
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Particle Swarm Optimization and Its Application in Transmission Network Expansion Planning
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作者 Jin Yixiong Cheng Haozhong +1 位作者 Yan Jianyong Zhang Li 《Electricity》 2005年第3期32-36,共5页
The author introduced particle swarm optimization as a new method for power transmission network expansion planning. A new discrete method for particle swarm optimization was developed,which is suitable for power tran... The author introduced particle swarm optimization as a new method for power transmission network expansion planning. A new discrete method for particle swarm optimization was developed,which is suitable for power transmission network expansion planning, and requires less computer s memory.The optimization fitness function construction, parameter selection, convergence judgement, and their characters were analyzod.Numerical simulation demonstrated the effectiveness and correctness or the method. This paper provides an academic and practical basis of particle swarm optimization in application of transmission network expansion planning for further investigation. 展开更多
关键词 transmission network particle swarm optimization discrete method integer planning
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Adaptive Hybrid Bivariate Double Density Discrete and Complex Wavelet for Image Denoising
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作者 Gamal Fahmy Mamdouh F. Fahmy Omar Fahmy 《Journal of Computer and Communications》 2023年第2期39-56,共18页
Image denoising is an important step in eliminating any noise impact in any image transmission process. Recently we presented two approaches for Bivariate based image denoising. They were Double Density Discrete Wavel... Image denoising is an important step in eliminating any noise impact in any image transmission process. Recently we presented two approaches for Bivariate based image denoising. They were Double Density Discrete Wavelet Transform (DD DWT) and Double Density Dual Tree Complex Wavelet Transform (DD CWT). In both techniques we decomposed noisy images with either DD DWT or DD CWT decompositions and then applied the Bivariate based denoising technique for noise removal. In this paper we propose an adaptive hybrid technique for Bivariate based image denoising that is based on the synthesis of DD-DWT bands or DD-CWT bands but with different weights, to deliver enhanced image features with less denoising impact especially around image edges, which is the most effected by noisy transmission channels. This proposed technique has been also enhanced by edge sharpening and Eigen analysis, as two separate stages. Simulation result comparisons have been performed between the proposed hybrid band adaptive DD-DWT and DD-CWT technique and the two primary techniques DD-DWT, DD- CWT, as well as other superior literature techniques such the original bivariate denoising technique with both original Complex Wavelet Transform and Double Density decompositions. This work in specific compares between Double Density DWT and Double Density CWT decompositions, proposes new filter design that suits each of them and proposes a hybrid technique between as will be shown. 展开更多
关键词 Complex Wavelet Image Deniosing Double Density Wavelets
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Assessment of dielectric strength and partial discharges patterns in nanocomposites insulation of single-core power cables
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作者 Ahmed Thabet M.Fouad 《Journal of Advanced Dielectrics》 CAS 2021年第4期64-73,共10页
Nanoparticles succeeded to enhance the dielectric properties of industrial insulation but the presence of voids inside the power cable insulation still leads to formation high electrical stress inside power cable insu... Nanoparticles succeeded to enhance the dielectric properties of industrial insulation but the presence of voids inside the power cable insulation still leads to formation high electrical stress inside power cable insulation material and collapse.In this paper,the dielectric strength of new design nanocomposites has been deduced as experimental work done to clarify the benefit of filling nanoparticles with different patterns inside dielectrics.Also,it has been studied the effect of electrical stress distribution in presence of air,water and copper impurities with different shapes(cylinder,sphere and ellipse)inside insulation of single core.In simulation model,it has been used finite element method(FEM)for estimating the electrostatic field distribution in power cable insulation.It has been applied new strategies of nanotechnology techniques for designing innovative polyvinyl chloride insula-tion materials by using nanocomposites and multi-nanocomposites.Finally,this research succeeded to remedy different partial discharges(PD)patterns according to using certain types and concentrations of nanoparticles. 展开更多
关键词 Partial discharges dielectric strength single core cables FEM NANOCOMPOSITES NANOPARTICLES
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