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解析CRT彩色电视机消磁电路产生的干扰
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作者 朱式庆 《安庆师范学院学报(自然科学版)》 2007年第3期100-101,共2页
CRT彩色电视接收机的消磁电路的剩电流对扫描电子束和偏转磁场在一定条件下进行误调制,使光栅出现多种干扰,可以采用多种方案减小或消除消磁电路的干扰。
关键词 消磁电路 干扰 剩电流 光栅 误调制
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DIGITAL PWM OF AC-AC MATRIX CONVERTER BASED ON OUTPUT-VOLTAGE ERROR FUNCTION 被引量:1
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作者 葛红娟 穆新华 +1 位作者 张绍 周波 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2005年第4期307-311,共5页
Based on the output-voltage error function, a novel time discrete modulation technique is proposed for matrix converters (MCs) and time-discrete difference equations of a MC circuit are derived. Switch states of MC ... Based on the output-voltage error function, a novel time discrete modulation technique is proposed for matrix converters (MCs) and time-discrete difference equations of a MC circuit are derived. Switch states of MC are obtained when the output voltage error function is minimized, thus the optimum combination of switch states is derived for the closed-loop control of MC. Meanwhile, advantages of the least calculation workload, the simple process, and the convenient for implementation are brought while switch states are described as space vectors in the α-β coordination system. Simulation and experimental results demonstrate the validity of the time-discrete modulation technique and the feasibility of the control approach. 展开更多
关键词 matrix converter time-discrete modulation error function switch state
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介绍QAM的测量
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《广播与电视技术》 北大核心 2003年第8期138-138,共1页
关键词 QAM 相位差振幅调制 码率 误调制 星座图 HFC网络
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Effect of phase noise in an OFDM/OQAM system
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作者 陈琦帆 吴炳洋 程时昕 《Journal of Southeast University(English Edition)》 EI CAS 2003年第2期108-113,共6页
The performance of an OFDM/OQAM system under phase noise is analyzed. The analysis helps to direct the design of low cost tuners through specifying the required phase noise characteristics. Discrete time formulation o... The performance of an OFDM/OQAM system under phase noise is analyzed. The analysis helps to direct the design of low cost tuners through specifying the required phase noise characteristics. Discrete time formulation of OFDM/OQAM is first derived with the square root raised cosine (SRRC) filter as the pulse-shaping filter. Then the effect of multiplicative phase noise is equivalently represented as additive white Gaussian noise (AWGN), the variance of which is given analytically. We can observe that the same result as OFDM/QAM system is derived. Lastly, all the analytical results are verified by the bit error rate (BER) degradation through Monte Carlo simulation. 展开更多
关键词 OFDM/OQAM OFDM/QAM phase noise BER performance
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PRECISE LEVELING OF THE VERY LONG QINLING MOUNTAIN TUNNEL 被引量:1
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作者 ZHANG Zhenglu YANG Zhentao XU Shaoquan ZHANG Xiangduo 《Geo-Spatial Information Science》 2000年第1期57-61,共5页
The Qinling tunnel with length of 18. 488km is located on the railway line from Xi’ an (Shanxi Province) to Ankan (Sichuan Province) in the middle of Qinling moun- tain. It is the longest double track railway tunnel ... The Qinling tunnel with length of 18. 488km is located on the railway line from Xi’ an (Shanxi Province) to Ankan (Sichuan Province) in the middle of Qinling moun- tain. It is the longest double track railway tunnel in China and takes the third place in the world. According to the design, the break-through error in vertical direction caused by the al- timetric control surveying is limited to 18mm for the case of one piercing face. Because the leveling route reaches over 120km in length and must go over two mountains in 2 800m height, the first-order precise leveling and precise gravity measurement should be carried out in the construction stage. In this paper the field leveling approach, the application of new technology,some experience as well as the office calculation with final results analysis are in- troduced. By meticulous planning, organization and observation, the final accuracy of vertical difference between two tunnel end points is only 8mm, and it provides reliable surveying guarantee for this great tunnel engineering. Finally it is pointed out that this vertical differ- ence distinguishes obviously from the primary measurement result as high as 114mm. It means that the primary result is not accurate enough. 展开更多
关键词 TUNNEL break-through error vertical control surveying gravity measurement
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Continuous rotation north-finding algorithm based on constrained adaptive Kalman filter 被引量:2
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作者 GUO Fengzhi LI Xingfei LI Jingxian 《Journal of Measurement Science and Instrumentation》 CAS CSCD 2021年第2期133-145,共13页
As an orientation measurement system,north-finder has been playing a significant role in both military and civilian fields of orientation and control.In this paper,to deal with drawbacks in the conventional north-find... As an orientation measurement system,north-finder has been playing a significant role in both military and civilian fields of orientation and control.In this paper,to deal with drawbacks in the conventional north-finding systems,a dynamic strategy based on continuous rotation modulation to measure the rotational angular velocity of the earth is proposed.By modeling the dynamic error,optimizing the process constraint and estimating dynamic noise,a method combining delay compensation and hardware adjustment,and a constrained adaptive Kalman filter(CAKF)algorithm are designed for the north-finding strategy.According to simulation and experiments,the proposed algorithm can achieve the high-precision north-finding with robust and anti-noise performance. 展开更多
关键词 north-finding constrained adaptive Kalman filter(CAKF) continuous rotation modulation dynamic error tilted base
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Analysis of error performance on Turbo coded FDPIM
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作者 ZHU Yin-bing WANG Hong-Xing ZHANG Tie-Ying 《Optoelectronics Letters》 EI 2008年第4期287-291,共5页
Due to variable symbol length of digital pulse interval modulation(DPIM),it is difficult to analyze the error performances of Turbo coded DPIM.To solve this problem,a fixed-length digital pulse interval modulation(FDP... Due to variable symbol length of digital pulse interval modulation(DPIM),it is difficult to analyze the error performances of Turbo coded DPIM.To solve this problem,a fixed-length digital pulse interval modulation(FDPIM) method is provided.The FDPIM modulation structure is introduced.The packet error rates of uncoded FDPIM are analyzed and compared with that of DPIM.Bit error rates of Turbo coded FDPIM are simulated based on three kinds of analytical models under weak turbulence channel.The results show that packet error rate of uncoded FDPIM is inferior to that of uncoded DPIM.However,FDPIM is easy to be implemented and easy to be combined.with Turbo code for soft-decision because of its fixed length.Besides,the introduction of Turbo code in this modulation can decrease the average power about 10 dBm,which means that it can improve the error performance of the system effectively. 展开更多
关键词 TURBO码 通信系统 数字脉冲间隔调制
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Pairwise codeword error probability for coded atmospheric optical communication systems
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作者 HAN Jia-jia RONG Jian ZHONG Xiao-chun 《Optoelectronics Letters》 EI 2006年第3期203-205,共3页
To study the performance of various error-control coding schemes,exact expressions and upper bounds on the pairwise codeword error probability(PEP)for several modulation schemes(OOK,SC-BPSK,BPPM)used in atmospheric op... To study the performance of various error-control coding schemes,exact expressions and upper bounds on the pairwise codeword error probability(PEP)for several modulation schemes(OOK,SC-BPSK,BPPM)used in atmospheric optical communication systems are derived.To simplify the computation,this research was under the assumption of weak turbulence.Moreover,by simulation of expressions,the performances of PEP in different modulation schemes are compared and the best one of them is given. 展开更多
关键词 编码理论 差概率 大气光通信系统 调制系统
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Error Control Strategy in Ultrasonic Body Area Networks
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作者 Wenbin Liu Yongjian Yang +1 位作者 Fan Wang En Wang 《China Communications》 SCIE CSCD 2016年第11期244-259,共16页
Recently,ultrasonic waves had been introduced as the transmission medium in Body Area Networks(BANs) to reduce the incalculable damage caused by radio waves. However,the communications based on ultrasonic waves suffer... Recently,ultrasonic waves had been introduced as the transmission medium in Body Area Networks(BANs) to reduce the incalculable damage caused by radio waves. However,the communications based on ultrasonic waves suffer from poor propagation of signals in air and consume too much energy. To address these limitations,firstly,we make the theoretical analysis to ensure ultrasonic waves could be used in BANs(UBANs). Then,we propose an error control strategy in UBANs to dynamically adjust the error control scheme and the Max-Retries based on the current channel state,which is called UECS. The UECS is based on IEEE 802.15.6 standards and considering the characteristics of ultrasonic waves in BANs. Simulation results show that UECS achieves better performance in terms of packet delivery ratio and energy consumption compared with the traditional strategies. 展开更多
关键词 body area networks ULTRASONIC error control ultrasonic transducer
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MAKING FULL USE OF OUTDATED CHANNEL ESTIMATES FOR BLOCK BY BLOCK ADAPTIVE MODULATIONS
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作者 Shan Xiaohong Bi Guangguo 《Journal of Electronics(China)》 2007年第1期54-59,共6页
This paper explores the potential to use accurate but outdated channel estimates for adaptive modulation. The work is novel in that the research is conditioned on block by block adaptation. First,we define a new quant... This paper explores the potential to use accurate but outdated channel estimates for adaptive modulation. The work is novel in that the research is conditioned on block by block adaptation. First,we define a new quantity,the Tolerable Average Use Delay (TAUD),which can indicate the ability of an adaptation scheme to tolerate the delay of channel estimation results. We find that for the variable-power schemes,TAUD is a constant and dependent on the target Bit Error Rate (BER),average power and Doppler frequency; while for the constant-power schemes,it depends on the ad-aptation block length as well. At last,we investigate the relation between the delay tolerating per-formance and the spectral efficiency and give the system design criterion. The delay tolerating per-formance is improved at the price of lower data rate. 展开更多
关键词 Adaptive modulation Block by block adaptation Channel estimation Spectral efficiency
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Low Complexity Minimum Mean Square Error Channel Estimation for Adaptive Coding and Modulation Systems 被引量:2
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作者 GUO Shuxia SONG Yang +1 位作者 GAO Ying HAN Qianjin 《China Communications》 SCIE CSCD 2014年第1期126-137,共12页
Performance of the Adaptive Coding and Modulation(ACM) strongly depends on the retrieved Channel State Information(CSI),which can be obtained using the channel estimation techniques relying on pilot symbol transmissio... Performance of the Adaptive Coding and Modulation(ACM) strongly depends on the retrieved Channel State Information(CSI),which can be obtained using the channel estimation techniques relying on pilot symbol transmission.Earlier analysis of methods of pilot-aided channel estimation for ACM systems were relatively little.In this paper,we investigate the performance of CSI prediction using the Minimum Mean Square Error(MMSE)channel estimator for an ACM system.To solve the two problems of MMSE:high computational operations and oversimplified assumption,we then propose the Low-Complexity schemes(LC-MMSE and Recursion LC-MMSE(R-LC-MMSE)).Computational complexity and Mean Square Error(MSE) are presented to evaluate the efficiency of the proposed algorithm.Both analysis and numerical results show that LC-MMSE performs close to the wellknown MMSE estimator with much lower complexity and R-LC-MMSE improves the application of MMSE estimation to specific circumstances. 展开更多
关键词 adaptive coding and modulation channel estimation minimum mean square error low-complexity minimum mean square error
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The twoscale asymptotic error analysis for piezoelectric problems in the quasi-periodic structure 被引量:1
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作者 FENG YongPing DENG MingXiang GUAN XiaoFei 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2013年第10期1844-1853,共10页
Applications for piezoelectric effect have grown rapidly, and piezoelectric materials play important roles in countless areas of modem life. By means of twoscale method and coupled boundary layer, some new kinds of tw... Applications for piezoelectric effect have grown rapidly, and piezoelectric materials play important roles in countless areas of modem life. By means of twoscale method and coupled boundary layer, some new kinds of twoscale asymptotic expansions for solutions to the electrical potential and the displacement in quasi-periodic structure under coupled piezoelectric effect are derived, and the homogenization constants of piezoelectric materials are presented. The coupled twoscale relation between the electrical potential and the displacement is set up, and some improved asymptotic error estimates are analyzed. 展开更多
关键词 twoscale method PIEZOELECTRICITY quasi-periodic structure homogenization constants
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OpenMP-based parallel transient stability simulation for large-scale power systems 被引量:3
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作者 JIANG QuanYuan JIANG Han 《Science China(Technological Sciences)》 SCIE EI CAS 2012年第10期2837-2846,共10页
This paper provides an OpenMP-based parallel Very Dishonest Newton(VDHN) algorithm with variable step size,running transient stability simulations(TSA) on multi-core computers.Under the framework of simultaneous solut... This paper provides an OpenMP-based parallel Very Dishonest Newton(VDHN) algorithm with variable step size,running transient stability simulations(TSA) on multi-core computers.Under the framework of simultaneous solution method of TSA,the step-size control strategy is used according to the local truncation error theory firstly.Then,computation of the generation units,which is the most time-consuming part of the simulation,is dynamically dispatched to several cores using an α dynamic scheduling scheme to obtain workload balancing based on OpenMP.Due to the convergence of Newton-type iterations,an adaptive Jacobian update control strategy is applied to reduce the sequential part of the simulation and the overhead generated by OpenMP.Several large scale test cases verify the validity and practicability of the proposed parallel algorithm,showing that the proposed approach achieves high speed-up and a considerable reduction in parallel overheads. 展开更多
关键词 transient stability parallel compute OPENMP Very Dishonest Newton(VDHN) step-size control scheduling scheme adaptive Jacobian update control
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New decoding scheme for product accumulate code over an optical PPM channel
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作者 郭建中 艾勇 +2 位作者 谭莹 左涛 黄海波 《Optoelectronics Letters》 EI 2011年第2期147-150,共4页
A new decoding scheme for product accumulate (PA) code over a space optical Poisson/ pulse-position modulation (PPM) channel is investigated. In this scheme, the PPM and the accumulator of the PA code are taken as a s... A new decoding scheme for product accumulate (PA) code over a space optical Poisson/ pulse-position modulation (PPM) channel is investigated. In this scheme, the PPM and the accumulator of the PA code are taken as a single inner code, decoded with an iterative demodulating-decoding technique based on Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm, rather than belief propagation (BP) algorithm in the original scheme. Simulation results show that this scheme provides much better bit error rate (BER) performance. At a BER of 10-5, the new scheme has a gain of 1.8 dB more than the original one. In addition, extrinsic information transfer (EXIT) charts are employed to analyze and compare the performance. The results indicate that the new scheme has not only better BER performance, but also lower error floor. 展开更多
关键词 ALGORITHMS Bit error rate DEMODULATION
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Performance analyses of subcarrier BPSK modulation over M turbulence channels with pointing errors
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作者 马爽 李亚添 +2 位作者 吴佳彬 耿天文 吴志勇 《Optoelectronics Letters》 EI 2016年第3期221-225,共5页
An aggregated channel model is achieved by fitting the Weibull distribution, which includes the effects of atmospheric attenuation, M distributed atmospheric turbulence and nonzero boresight pointing errors. With this... An aggregated channel model is achieved by fitting the Weibull distribution, which includes the effects of atmospheric attenuation, M distributed atmospheric turbulence and nonzero boresight pointing errors. With this approximate channel model, the bit error rate (BER) and the ergodic capacity of free-space optical (FSO) communication systems utilizing sub- cartier binary phase-shift keying (BPSK) modulation are analyzed, respectively. A closed-form expression of BER is de- rived by using the generalized Gauss-Lagueree quadrature rule, and the bounds of ergodic capacity are discussed. Monte Carlo simulation is provided to confirm the validity of the BER expressions and the bounds of ergodic capacity. 展开更多
关键词 BPSK调制 信道模型 指向 大气湍流 性能分析 副载波 自由空间光通信 蒙特卡罗模拟
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