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Research on resolution between multi-component LFM signals in the fractional Fourier domain

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Science china(Information Sciences) 2012年第6期55卷 1301-1312页

作者： LIU Feng 1,XU HuiFa 1,2.TAO Ran 3 & WANG Yue 3 1 department of Electronic and Information Engineering,Naval Aeronautical Engineering institute,Yantai 2.4001,{2. 2.The 94362.th Unit of People's Liberation Army,Qingdao 2.6111,{2. 3 School of Information Science and technology,beijing institute of technology,beijing 100081,{2. 1. department of Electronic and Information Engineering Naval Aeronautical Engineering Institute Yantai 264001 China2. The 94362th Unit of People’s Liberation Army Qingdao 266111 China3. School of Information Science and Technology Beijing Institute of Technology Beijing 100081 China

When the initial frequencies and chirp rates of multi-component linear frequency modulation (LFM or chirp) signals are close,the signals may not be distinguished in the fractional Fourier domain (FRFD).Consequently,some signals cannot be *** this paper,first,the spectral distribution characteristics of a continuous LFM signal in the FRFD are analyzed,and then the spectral distribution characteristics of a LFM signal in the discrete FRFD are ***,the critical resolution distance between the peaks of two LFM signals in the FRFD is deduced,and the relationship between the dimensional normalization parameter and the distance between two LFM signals in the FRFD is also *** is discovered that selecting a proper dimensional normalization parameter can increase the ***,a method to select the parameter is proposed,which can improve the resolution ability of the fractional Fourier transform (FRFT).Its effectiveness is verified by simulation results.

关键词： fractional Fourier transform LFM signal signal resolution

Reconfigurable design and implementation of the MD6 Hash function

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The Journal of china Universities of Posts and Telecommunications 2010年第2期17卷 109-115页

作者： GAO Xian-wei department of Electronic and Information Engineering,beijing Electronic Science and {2. institute,beijing 100070,china [a] department of Electronic Information Engineering Beijing Electronic Science technology institute Beijing 100070 China

Efficient reconfigurable field programmable gate array （FPGA） architectures for the MD6-2.4/2.6/384/512.Hash algorithm are proposed in this article. The basic iterative compact design requires 92. ALMs and achieves a throughput ranging from 2.5 Mbit/s to 394 Mbit/s at a maximum frequency of 198 MHz. The 32.step-urtrolled high-throughput design requires 7 090 ALMs and achieves a throughput ranges from 5 776 Mbit/s to 9 490 Mbit/s at a maximum frequency of 173 MHz. The simulation results show that high flexibility and efficient FPGA implementation of the MD6 Hash function is achieved.

关键词： SHA-3 MD6 reconfigurable iterative loop-unrolling

Time-varying sliding mode control for a class of uncertain MIMO nonlinear system subject to control input constraint

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Science china(Information Sciences) 2010年第1期53卷 89-100页

作者： JIN YongQiang1,2. LIU XiangDong1, QIU Wei2.& HOU ChaoZhen1 1department of Automatic Control, beijing {2. of technology, beijing 100081, china 2.erospace System Engineering Shanghai, Shanghai 2.1108, china 1. department of Automatic Control Beijing Institute of Technology Beijing 100081 China2. Aerospace System Engineering Shanghai Shanghai 201108 China

To solve the regulator problem of a class of uncertain MIMO nonlinear systems subject to control input constraint, three types of time-varying sliding mode control laws are proposed. The sliding surfaces pass the initial value of the system at the initial time, and are shifted/rotated towards the predetermined ones. The controller parameters are optimized by genetic algorithm (GA). Lyapunov method is adopted to prove the stability and robustness to the parameter uncertainties and external disturbance. By mean of time-varying sliding mode control law, the reaching phase in the conventional sliding mode control is eliminated, and the system is guaranteed to have robustness from the very beginning. Taking the control of two-link manipulator and attitude tracking of rigid spacecraft as two examples, we illustrate the features of the time-varying sliding mode control. The simulation results show the validity of the control law to a class of uncertain MIMO systems. Better robustness against the uncertainties and external disturbance could be achieved by time-varying sliding mode control without violating the constraint on control input.

关键词： time-varying sliding surface sliding mode control MIMO nonlinear system uncertain control input constraints

A user-space file system for on-demand legacy desktop software

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Science china(Information Sciences) 2011年第6期54卷 1142-1150页

作者： ZHANG YouHui 1,2., SU GeLin 1,2.& ZHENG WeiMin 1,2.1 department of computer Science and {2., Tsinghua University, beijing 100084, china 2.Tsinghua National Laboratory for Information Science and {2., Tsinghua University, beijing 100084, china 1. department of computer Science and {2. Tsinghua University Beijing 100084 China2. Tsinghua National Laboratory for Information Science and Technology Tsinghua University Beijing 100084 China

Some user-level virtualization technologies have been used to convert legacy software (like the existing Windows desktop applications) into the on-demand software without any modification. To give the client a friendly and compatible method to access on-demand legacy software across the Internet, this paper presents a clientend file system for this usage case. It is a Windows user-space file system based on the cloud storage (where the on-demand software is stored), which converts the local file system accesses into remote visits. Quite a few optimizations are adopted and adjusted to suit the file-access-pattern of on-demand software, including the local cache, metadata/data/software prefetch and content-addressable storage (CAS), to decrease the number of remote visits and/or to overlap IO (input/output) operations with software execution. Detailed access-pattern analyses are also presented. This file system has been implemented and tests show that it is practical for much daily-used software-a local cache of limited size can provide up to 80% hit ratio and the corresponding overhead of running-time is about 37%. Owing to this method, on any compatible and networked computer, a user can use his/her personalized software conveniently although it does not exist on the local host.

关键词： on-demand software software as a service user-space file system cloud storage

Periodic Solutions of the Differential Delay Equation (?)(t)=-f(x(t-1))

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Acta Mathematica Sinica,English Series 1996年第2期12卷 113-121页

作者： Ge Weigao Ge Weigao department of Applied Mathematics beijing {2. of technology beijing,100081 china

For an odd function f(x)defined only on a finite interval,this paper deals with the existence of periodic solutions and the number of simple periodic solutions of the differential delay equation(DDE)(?)(t)=-f(x(t-1)).By use of the method of qualitative analysis combined with the constructing of special solutions a series of interesting results are obtained on these problems.

关键词： Odd function Periodic solution Differential delay equation

Fuzzy controllers based on some fuzzy implication operators and their response functions

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Progress in Natural Science:Materials International 2004年第1期14卷 16-21页

作者： LI Hongxing 1*, YOU Fei 1 and PENG Jiayin 2.1. department of Mathematics, beijing Normal University, beijing 100875, china 2. department of Mathematics, Neijiang Teacher's College, Neijiang 641112. china) beijing Normal Univ Dept Math Beijing 100875 Peoples R China

The fuzzy controllers constructed by 2. fuzzy implication operators based on CRI algorithm and their response functions are discussed. The conclusions show that the fuzzy controllers constructed by 9 fuzzy implication operators are universal approximators to continuous functions and can be used in practical fuzzy control systems. And these 9 fuzzy implication operators except for Einstein operator intersection are all the adjoint pairs of some fuzzy implication operators. Besides, there are 3 other fuzzy controllers formed by fuzzy implication operators being regarded approximately as fitted functions.

关键词： fuzzy implication operators CRI algorithm fuzzy controllers response functions universal approximators

Structure and kinematic analysis of a novel 2.DOF translational parallel robot

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Progress in Natural Science:Materials International 2007年第10期17卷 1213-1219页

作者： Chen Tao1, Wu Chao2.and Liu Xinjun2.1. School of Application Science and technology, Harbin University of Science and technology, Harbin 150080,{2. 2. department of Precision Instruments, Tsinghua University, beijing 100084,{2.) School of Application Science and technology Harbin University of Science and Technology Harbin 150080 China department of Precision Instruments Tsinghua University Beijing 100084 China

This paper addresses the analysis of a novel parallel robot with 2.translational degrees of freedom (DOFs). The robot can position a rigid body in a plane with constant orientation. The kinematic structure of the robot is first described in detail. Some kinematic problems, such as the inverse and forward kinematics, velocity, and singularity are then analyzed. The working and assembly modes are discussed. Since it is the most important index to design a robot, the workspace of the robot is studied systematically in this paper. Based on the analysis of reachable workspace and singularity, a kind of workspace concept characterizing the region that the end-effector of the robot can reach in practice is defined. The results of this paper will be very useful for the design and application of the robot.

关键词： parallel robot degree of freedom kinematics workspace.

On the tribological characteristics of dynamically loaded journal bearing with micropolar fluids

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Science china(Physics,Mechanics & Astronomy) 2004年第z1期47卷 45-50页

作者： WANG Xiaoli, WANG Kongying & ZHU KeqinSchool of Mechanical and Vehicular Engineering, beijing institute of {2., beijing 100081, china department of Engineering Mechanics, Tsinghua University, beijing 100084, china beijing Inst Technol Sch Mech & Vehicular Engn Beijing 100081 Peoples R China Tsing Hua Univ Dept Engn Mech Beijing 100084 Peoples R China

The addition of the additives to the lubricant oil to enhance the characteristics of the lubricant will influence the performance of the bearings. Based on the theory of micropolar fluids, the tribological characteristics of a dynamically-loaded journal bearing are numerically studied. Comparisons are made between the Newtonian fluids and the micropolar fluids. It is shown that for a dynamically-loaded journal bearing, the micropolar fluids yield an increase not only in the friction force, but also in the friction coefficient. In addition, the oil film pressure and the oil film thickness are obviously higher than that of Newtonian fluids.

关键词： micropolar fluids, dynamic loads journal bearing tribological characteristics.

TREE DECOMPOSITIONS OF MULTIGRAPHS

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Systems Science and Mathematical Sciences 1999年第3期12卷 231-237页

作者： SHI Minyong(department of computer Science and {2.,beijing Broadcasting institute, beijing 10002., china) 北京广播学院计算机系北京 100024

For a graph G, if E(G) can be partitioned into several pairwise disjoint sets as{E1 , E2....,El } such that the subgraph induced by Ei is a tree of order ki ) (i = 1, 2.... , l),then G is said to have a {k1, k2. ..., kl }-tree-decomposition, denoted by { k1, k2.,..., Kl } *** k 1 and l 0, a collection (k,l) is the set of multigraphs such that G e Q(k,l)if and only if e(G) = k(G - 1) - l and (H) max{(k - 1)(H - 1),k(H -1) -l}for any subgraph H of G. We Prove that (1) If k 2.0 l 3 and G Q(k,l) oforder + 1, then {n,n,...,n -- l} E G. (2. If 2.and G (k,2. of ordern 3, then {n,n, ...,n,n-- 2. E G and {n,n,.. -1,n - 1} G. (3) If 3 andG g(k,3) of order n 4, then {n, n,... n,n-- 3} G ) {n,n,.., n,n-- 1,n -- 2. Gand {n,n,... n,n -- 1,n -- 1,n -- 1} G.

关键词： Tree decomposition (k l) graphs Pk-graph maximal planar bipartitegraph maximal planar graph