检索结果-南通市图书馆

Journal of Systems engineering and electronics 1994年第1期5卷 44-52页

作者： Xu Yanhou Wu Guangyu(Department of Modern Mechanics,university of science & Technology of china, Hefei, 230026)Gong Guanghui(Graduate school of USTC, beijing, 100039)Yang Xueshi(P.O.Box 142-206, beijing, 100854) Department of Modern Mechanics University of Science & Technology of China Hefei 230026 Graduate school of USTC Beijing 100039 P.O. Box 142-206 Beijing 100854

This problem is a nonlinear control system with variable-domain distributed parameter. In this paper, the numerical simulation of the dynamic functions has been carried out by transforming this problem to a fixed-domain initial-boundary value problem, and the numerical results are obtained: (1) Thedistribution of temperature rises, the ablation amount and velocity of the thermal shield vary with the time; (2) The maximum ablating velocity, the time of the ablation beginning and ending related to thetranspiration quantity. This method succeeds in overcoming the difficulty brought up by variable *** the other hand, the critical transpiration quantity for the surface to start ablating, the maximum ablating velocity and time of the ablation ending are obtained theoretically.

关键词： Ablation,Transpiration cooling Variable domain Distributed parameter control NumericalSimulation

Molecular Computations of the Maximal Clique Problem Using DNA Self-assembly

在线全文

学校读者我要写书评

暂无评论

Molecular Computations of the Maximal Clique Problem Using D...

A NOVEL SUPER-RESOLUTION BEAMFORMING ALGORITHM

2009 Fourth International Conference on Bio-Inspired Computing:Theories and Applications(BIC-TA2009)

作者： Yang Jing1 Zhang Cheng2 Xu Jin3 Institute of Software school of electronics engineering and computer science peking university Key laboratory of High Confidence Software Technologies Ministry of Education beijing 100871

In recent years,DNA self-assembly has widely developed in the fields of DNA computing and *** to now,many kinds of DNA self-assembly structures have been applied to solve some computational *** this paper,a novel molecular computing model based on DNA self-assembly is developed to solve a maximal clique problem（MCP） with *** assembled hairpin structure plays a key role in searching for the maximal *** model has some significant advantages such as easy detecting,controllable automation and low algorithm *** a graph with n-vertices,using our model,the time complexity is O（m+n）,where m is the number of edges of the complementary ***,this work demonstrates clear evidence of the ability of DNA computing to solve NP-complete problems.

关键词：

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Journal of electronics(china) 2007年第3期24卷 406-411页

作者： Guo Li Guo Yan Li Ning school of Information engineering Beijing University of Posts and Telecommunications Beijing 100876 China Institute of science PLA University of Science and Technology Nanjing 210007 China

A novel simply-structured hybrid smart antenna system suitable to be used in ad-hoc network terminals is proposed in this letter. The super-resolution beamforming algorithm is also pre-sented based on the system using DOA estimation results. The algorithm can switch the beamforming to the direction of the expected signal and get the best transmitting performance after the pre-beamforming of the Butler matrix. The shifting value formulas are presented to obtain the best SNR when there is no interfering signal and to acquire the highest Signal to Interference Ratio (SIR) as there is one interfering signal. When there are more than one interfering signals,the pre-beamforming feature of the Butler matrix can also suppress the interfering signals. Simulation results verified the algorithm.

关键词： Smart antennas Beamforming Direction-Of-Arrival (DOA) Iteration method

一类具有随机离去策略的排队系统及其在Internet拥塞控制中的应用

在线全文

学校读者我要写书评

暂无评论

计算机科学 2007年第12期34卷 37-40页

作者：汪浩李晓明严伟北京大学信息科学技术学院网络实验室北京大学信息科学技术学院网络实验室北京100871

当顾客到达一个排队系统时,可以根据当前队列的长度,按照一定的概率选择加入排队系统等待队列,或选择离开排队系统且不再返回。这样的排队系统称为'具有随机离去策略的排队系统'。我们利用输入流稀疏化(Thinning of recurrent flows)和... 详细信息

当顾客到达一个排队系统时,可以根据当前队列的长度,按照一定的概率选择加入排队系统等待队列,或选择离开排队系统且不再返回。这样的排队系统称为'具有随机离去策略的排队系统'。我们利用输入流稀疏化(Thinning of recurrent flows)和输入流阻行(Balking)两种方法分别扩充了GI/M/1/N和GIX/M/1/N两个排队系统,建立了3个具有随机离去策略的排队系统,给出了这类排队系统的顾客丢失率、系统利用率、队列长度的均值/方差、平均等待时间等性能指标。最后,讨论了这类排队系统在Internet拥塞控制中的应用。

关键词：排队系统输入流稀疏化输入流阻行 GI/M/1/N GIX/M/1/N Internet 拥塞控制

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

强激光束在等离子体通道中传输的变分法研究

物理学报 2004年第5期53卷 1419-1424页

作者：刘明伟郭弘邓冬梅张宇陈徐宗华南师范大学传输光学实验室广州510631 北京大学信息科学技术学院量子信息与测量教育部重点实验室北京100871

给出了低密度等离子体中包含高阶相对论效应的激光场传输方程 .用变分法研究了强激光束在等离子体通道中传输时包括真空衍射、等离子体通道和低阶与高阶相对论效应对传输的影响 .在傍轴近似下 ,激光束宽依然有“势阱”方程 .当激光强度... 详细信息

给出了低密度等离子体中包含高阶相对论效应的激光场传输方程 .用变分法研究了强激光束在等离子体通道中传输时包括真空衍射、等离子体通道和低阶与高阶相对论效应对传输的影响 .在傍轴近似下 ,激光束宽依然有“势阱”方程 .当激光强度较大时 ,高阶相对论效应变得重要 :它一方面减小激光束宽的振荡幅度 ,另一方面又加快激光束宽的振荡速度 .当激光功率大于 (等于 )相对论临界功率时 ,高阶相对论效应避免了激光强度随传输距离出现无穷大的奇异性 .同时 ,给出了考虑高阶相对论效应后激光束宽平衡解的存在条件 .

关键词：等离子体通道变分法高阶相对论激光束真空衍射傍轴近似

Improved Error Estimate for Extraordinary Catmull-Clark Subdivision Surface Patches

在线全文

学校读者我要写书评

暂无评论

Improved Error Estimate for Extraordinary Catmull-Clark Subd...

Analysis and modeling of multi-rate networked control systems with long time delay

2007 10th IEEE International Conferences on computer Aided Design and computer Graphics(CAD/Graphics 2007)

作者： Zhangjin Huang 1,2,Guoping Wang 1,2 1 school of Electronic engineering and computer science,peking university,beijing 100871,P.R.china 2 Key Laboratory of High Confidence Software Technologies (peking university),Ministry of Education,P.R.china

Based on an optimal estimate of the convergence rate of the second order norm,an improved error estimate for extraordinary Catmull-Clark subdivision surface (CCSS) patches is *** the valence of the extraordinary vertex of an extraordinary CCSS patch is even,a tighter error bound and,consequently,a more precise subdivision depth for a given error tolerance,can be ***,examples of adaptive subdivision illustrate the practicability of the error estimation approach.

关键词： Clark Improved Error Estimate for Extraordinary Catmull-Clark Subdivision Surface Patches

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Analysis and modeling of multi-rate networked control system...

A Numerical Scheme to Obtain the RCS of Serrated Targets Using CG-FFT

第24届中国控制与决策会议

作者： Qixin Zhu 1,2 , Guangming Xie 1,2 1. The Center for System and Control, Department of Mechanics and engineering science, peking university, 100871, beijing2. school of Electrical &electronics engineering, East china Jiaotong university, 330013, Nanchang

By multi-rate networked control systems, we mean the sampling periods of the sensor, the controller and the actuator in networked control systems are not the same, that is to say there are more than one sampling rates in networked control systems. The models of multi-rate networked control systems with no network-induced delay and long time delay are proposed respectively in this paper. It is stated that the multi-rate networked control systems with long time delay can be formulated as a discrete-time switched stochastic system. Especially the multi-rate networked control systems with long time delay can be formulated as a discrete-time switched deterministic system when the actuator is clock driven and the state noise is not considered. An example is given in the end.

关键词： multi-rate networked control system modeling long time delay time-driven

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Journal of Systems engineering and electronics 1997年第2期8卷 24-32页

作者： Wang Baofa & Guan Dexin(Dept. of Electrical engineering and computer science,beijing university of Aeronautics and Astronautics, 100083, P. R. china) Dept. of Electrical engineering and computer science beijing university of Aeronautics and Astronautics 100083 P. R. China

A numerical scheme to obtain the radar cross section (RCS) of scattering bodies of resonant size with serrated structure is described. The RCS is obtained by solving the electric field integral equation (EFIE) using the conjugate gradientfast Fourier transform method (CGFFT). With this combination, the computational time required to solve scattering problems of resonant size bodies is much less than the time required by the ordinary conjugate gradient method and the method of moments. On the other hand, since the spatial derivatives are replaced with simple multilocations in the transformed domain. Some of the computational difficulties present in the ordinary conjugate gradient method and the method of moments do not exist here. The choice of a suitable set of basis and testing functions to discretize the EFIE leads to obtain a very accurate efficient CGFFT procedure. Finally, since the method is iterative, it is possible to know the accuracy in a problem solution.The numerical results also show that conducting serrated structure can be applied to reduce the RCS values of straight wedge so long as the shape and size are selected properly.

关键词： Radar cross section Conjugate gradient Fast Fourier transform.

Robust fault diagnosis for non-Gaussian stochastic systems based on the rational square-root approximation model

在线全文

学校读者我要写书评

暂无评论

science in china(Series F) 2008年第9期51卷 1281-1290页

作者： YAO LiNa1 & WANG Hong2,3 1 school of Electrical engineering,Zhengzhou university,Zhengzhou 450001,china 2 Control Systems Centre,university of Manchester,Manchester M60 1QD,UK 3 Institute of Automation,Chinese Academy of sciences,beijing 100080,china school of Electrical engineering Zhengzhou University Control Systems Centre University of Manchester Institute of Automation Chinese Academy of Sciences

The task of robust fault detection and diagnosis of stochastic distribution control （SDC） systems with uncertainties is to use the measured input and the system output PDFs to still obtain possible faults information of the system. Using the rational square-root B-spline model to represent the dynamics between the output PDF and the input, in this paper, a robust nonlinear adaptive observer-based fault diagnosis algorithm is presented to diagnose the fault in the dynamic part of such systems with model uncertainties. When certain conditions are satisfied, the weight vector of the rational square-root B-spline model proves to be bounded. Conver- gency analysis is performed for the error dynamic system raised from robust fault detection and fault diagnosis phase. computer simulations are given to demon- strate the effectiveness of the proposed algorithm.

关键词： SDC systems output probability density functions(PDFs) robust fault detection and diagnosis rational square-root B-spline functions

基于表面等离子激元的自由空间广角接收机研究

在线全文

学校读者我要写书评

暂无评论

china Communications 2009年第3期6卷 53-59,76页

作者：蔡琳李光元徐安士区域光纤通信网与新型光通信系统国家重点实验室信息科学技术学院电子学系北京大学北京100871

广角光接收机能够接收来自空间各个方向的信号光,大大降低了自由空间光通信系统对准、跟踪和捕获的复杂度,在未来无线光通信系统中有着广阔的应用前景。然而,当它采用传统光器件来实现时,其视场角会受到各种制约而很难扩展。本文提出采... 详细信息

广角光接收机能够接收来自空间各个方向的信号光,大大降低了自由空间光通信系统对准、跟踪和捕获的复杂度,在未来无线光通信系统中有着广阔的应用前景。然而,当它采用传统光器件来实现时,其视场角会受到各种制约而很难扩展。本文提出采用表面等离子激元的方法来实现空间光的广角接收,并提出了一种等离激元波纹喇叭结构,它能突破衍射极限,打破传统器件的种种制约,并且能在相对较宽的角度范围内获得较强的增益。我们对相关的原理和设计方法都做了详细的讨论。

关键词：广角空间光接收机表面等离子激元

同方期刊数据库