共查询到20条相似文献,搜索用时 109 毫秒
1.
Chen Yangjun 《计算机科学技术学报》1998,13(4):300-316
In this paper,an optimal method to handle cyclic and acyclic data relations in the linear recursive queries is proposed.High efficiency is achieved by integrating graph traversal mechanisms into a top-down evaluation.In such a way,the subsumption checks and the identification of cyclic data can be done very efficiently.First,based on the subsumption checks,the search space can be reduced drastically by avoiding any redundant expansion operation.In fact,in the case of non-cyclic data,the proposed algorithm requires only linear time for evaluating a linear recursive query.On the other hand,in the case of cyclic data,by using the technique for isolaiting strongly connected components a lot of answers can be generatded directly in terms of the intermediate results and the relevant path information instead of evaluating them by performing algebraic operations.Since the cost of generating an answer in much less than that of evaluating an answer by algebraic operations,the bime consumption for cyclic data can be reduced by an order of magnitude or more. 相似文献
2.
The linear combination of certain partition of unity, subordinate to certain open covering of a compact set, is proved to be capable of approximating to a continuous function at arbitrarily precision. By using proper open covering and partition of unity, the robust nonlinear controllers and adaptive laws are designed for a class of nonlinear systems with uncertainties. The states and parameters of the closed-loop systems can be stabilized in the meaning of UUB (uniformly ultimately bounded) via the robus tnonlinear controllers and adaptive laws. Finally, an example shows the validity of method in this paper. 相似文献
3.
李勇 《计算机科学技术学报》2002,17(6):0-0
In this paper, the problem of checking a timed automaton for a Duration Calculus formula of the form Temporal Duration Property is addressed. It is shown that Temporal Duration Properties are in the class of discretisable real-time properties of Timed Automata, and an algorithm is given to solve the problem based on linear programming techniques and the depth-first search method in the integral region graph of the automaton. The complexity of the algorithm is in the same class as that of the solution of the reachability problem of timed automata. 相似文献
4.
Design of Nonlinear Decoupling Controller for Double-electromagnet Suspension System 总被引:1,自引:0,他引:1
Aiming at the coupling characteristic between the two groups of electromagnets embedded in the module of the maglev train, a nonlinear decoupling controller is designed. The module is modeled as a double-electromagnet system, and based on some reasonable assumptions its nonlinear mathematical model, a MIMO coupling system, is derived. To realize the linearization and decoupling
from the input to the output, the model is linearized exactly by means of feedback linearization, and an equivalent linear decoupling model is obtained. Based on the linear model, a nonlinear suspension
controller is designed using state feedback. Simulations and experiments show that the controller can effectually solve the coupling problem in double-electromagnet suspension system. 相似文献
5.
《中国科学F辑(英文版)》2008,(1)
A recursive algorithm is adopted for the computation of dyadic Green's functions in three-dimensional stratified uniaxial anisotropic media with arbitrary number of layers. Three linear equation groups for computing the coefficients of the Som- merfeld integrals are obtained according to the continuity condition of electric and magnetic fields across the interface between different layers, which are in corre- spondence with the TM wave produced by a vertical unit electric dipole and the TE or TM wave produced by a horizontal unit electric dipole, respectively. All the linear equation groups can be solved via the recursive algorithm. The dyadic Green's functions with source point and field point being in any layer can be conveniently obtained by merely changing the position of the elements within the source term of the linear equation groups. The problem of singularities occurring in the Sommer- feld integrals is efficiently solved by deforming the integration path in the complex plane. The expression of the dyadic Green's functions provided by this paper is terse in form and is easy to be programmed, and it does not overflow. Theoretical analysis and numerical examples show the accuracy and effectivity of the algo-rithm. 相似文献
6.
Lauro Cassio Martins de Paula Anderson da Silva Soares 《通讯和计算机》2014,(4):339-346
This paper presents a parallel implementation of the hybrid BiCGStab(2) (bi-conjugate gradient stabilized) iterative method in a GPU (graphics processing unit) for solution of large and sparse linear systems. This implementation uses the CUDA-Matlab integration, in which the method operations are performed in a GPU core using Matlab built-in functions. The goal is to show that the exploitation of parallelism by using this new technology can provide a significant computational performance. For the validation of the work, we compared the proposed implementation with a BiCGStab(2) sequential and parallelized implementation in the C and CUDA-C languages. The results showed that the proposed implementation is more efficient and can be viable for simulations being carried out with quality and in a timely manner. The gains in computational efficiency were 76x and 6x compared to the implementation in C and CUDA-C, respectively. 相似文献
7.
Recursive algorithm and accurate computation of dyadic Green’s functions for stratified uniaxial anisotropic media 总被引:1,自引:0,他引:1
A recursive algorithm is adopted for the computation of dyadic Green's functions in three-dimensional stratified uniaxial anisotropic media with arbitrary number of layers. Three linear equation groups for computing the coefficients of the Sommerfeld integrals are obtained according to the continuity condition of electric and magnetic fields across the interface between different layers, which are in correspondence with the TM wave produced by a vertical unit electric dipole and the TE or TM wave produced by a horizontal unit electric dipole, respectively. All the linear equation groups can be solved via the recursive algorithm. The dyadic Green's functions with source point and field point being in any layer can be conveniently obtained by merely changing the position of the elements within the source term of the linear equation groups. The problem of singularities occurring in the Sommerfeld integrals is efficiently solved by deforming the integration path in the complex plane. The expression of the dyadic Green's functions provided by this paper is terse in form and is easy to be programmed, and it does not overflow. Theoretical analysis and numerical examples show the accuracy and effectivity of the algorithm. 相似文献
8.
The problem of delay-dependent stability and passivity for linear neutral systems is discussed. By constructing a novel type Lyapunov-krasovskii functional, a new delay-dependent passivity criterion is presented in terms of linear matrix inequalities (LMIs). Model transformation, bounding for cross terms and selecting free weighting matrices [12-14] are not required in the arguments. Numerical examples show that the proposed criteria are available and less conservative than existing results . 相似文献
9.
Stabilization of switched linear systems with bounded disturbances and unobservable switchings 总被引:2,自引:0,他引:2
LIU Feng School of Electronics Information Engineeing Beijing Jiaotong University Beijing China 《中国科学F辑(英文版)》2007,50(5):711-718
This paper studies the stabilization problem of switched linear systems with bounded disturbances. It is assumed that the system switches among an infinite set of uniformly controllable linear systems, and that the switching signals are not observable, but the switching duration has a lower bound. It will be shown that by combining on-line adaptive estimation and control in the controller design, a feedback control law can be constructed which makes the switched linear system globally stable. 相似文献
10.
A necessary and sufficient condition of the quadratic D-stability for a class of uncertain linear systems is presented in terms of linear matrix inequality (LMI) technology. Finally, the validity and less conservatism of the obtained results in this paper are illustrated by a benchmark example. 相似文献
11.
直线电机的发展及应用概况 总被引:5,自引:0,他引:5
介绍了直线电机的分类及特点,直线电机是一种将电能直接转换成直线运动,而不需要通过任何中间转换机构的新颖电机.阐述了直线电机理论分析和优化设计的研究手段和最新研究成果,分析了直线电机核心控制部件、外围输出通道、控制理论和控制技术发展状况,简要叙述了直线电机在工业、办公设备、交通、家庭自动化、军事装备等领域的的应用现状和动态.根据直线电机应用研究的发展趋势,指出在利用计算机提高直线电机的控制精度和依据新原理研制新型直线电机的新技术推动下,直线电机具有广阔的应用和发展前景. 相似文献
12.
非线性模型下的摄像机自标定 总被引:7,自引:0,他引:7
摄像机标定是从二维图像获取三维信息必不可少的步骤,线性(小孔)模型摄像机自标定,目前已成为计算机视觉领域的研究热点之一,对于非线性模型下摄像机的自标定,目前还未见到相关的研究报道,用于线性模型一般不能准确地描述真实像机的几何成像关系,因此对非线性模型摄像机自标定的研究具有十分重要的实际意义,该文主要探索非线性模型摄像机的自标定方法,基本原理是将非线性模型视为线性模型和畸变项的叠加,然后利用线性模型的基本矩阵或单应矩阵,给出非线性模型参数的约束方程,从而实现非线性模型摄像机的自标定,模拟和真实图像实验均表明该文所给的方法是可行的,具有一定的实用价值。 相似文献
13.
In reality, virtually every process is a nonlinear system. Nevertheless, linear controller design methods have proved to be adequate in many applications. In practice, the linear controller design is usually done disregarding a possible nonlinear plant/linear model mismatch. In this work we introduce a general framework for the development of linear controllers for nonlinear systems based on nonlinearity measures. Nonlinearity measures are tools to assess the extent of a system’s inherent nonlinearity instead of just recognizing a system as being linear or nonlinear. Recent work shows that nonlinearity measures characterize the magnitude of the modeling error when an optimal linear model is used for the nonlinear system. The best linear model can then be used to design a linear controller that robustly stabilizes the linear system in presence of the nonlinear modeling error. A crucial point is that both, the best linear model and the modeling error, are determined for a specified region of operation, thus significantly increasing the class of applicable nonlinear systems. Examples demonstrate the (necessity and) effectiveness of the proposed approach. 相似文献
14.
城市线性景观是景观设计学中的一个综合概念,可以理解为人类活动与生态环境相互叠加形成的具有线性特征的复合生态系统。文章以城市线性景观为主要研究对象,结合北方地区的实际情况,对如何构建城市线性景观进行探索研究,总结线性景观对于景观设计学的影响,并在线性景观构建的基础上探讨其在城市中的发展方向与趋势。 相似文献
15.
综合线性复杂度,k错线性复杂度、k错线性复杂度曲线和最小错误minerror(S)的概念,提出m紧错线性复杂度的概念.序列S的m紧错线性复杂度是一个二元组(km,LCm).序列S的k错线性复杂度曲线的第m个跃变点对应的km值和对应km错线性复杂度LCm,称为序列S的m紧错线性复杂度.通过使用简洁的cost二维结构,给出... 相似文献
16.
一种SPN线性层的设计方法 总被引:1,自引:0,他引:1
提出了线性码理论用于SPN分组密码线性层(或称扩散层)设计,并给出了过线性码设计最优扩散线性层的方法,从而为密码结构中的线性变换的没计提供了理论基础。利用该方法进行了实例设计与分析,并对其扩散特性进行了仿真。 相似文献
17.
18.
Fuzzy controller design includes both linear and non-linear dynamic analysis. The knowledge base parameters associated within the fuzzy rule base influence the non-linear control dynamics while the linear parameters associated within the fuzzy output signal influence the overall control dynamics. For distinct identification of tuning levels, an equivalent linear controller output and a normalized non-linear controller output are defined. A linear proportional-integral-derivative (PID) controller analogy is used for determining the linear tuning parameters. Non-linear tuning is derived from the locally defined control properties in the non-linear fuzzy output. The non-linearity in the fuzzy output is then represented in a graphical form for achieving the necessary non-linear tuning. Three different tuning strategies are evaluated. The first strategy uses a genetic algorithm to simultaneously tune both linear and non-linear parameters. In the second strategy the non-linear parameters are initially selected on the basis of some desired non-linear control characteristics and the linear tuning is then performed using a trial and error approach. In the third method the linear tuning is initially performed off-line using an existing linear PID law and an adaptive non-linear tuning is then performed online in a hierarchical fashion. The control performance of each design is compared against its corresponding linear PID system. The controllers based on the first two design methods show superior performance when they are implemented on the estimated process system. However, in the presence of process uncertainties and external disturbances these controllers fail to perform any better than linear controllers. In the hierarchical control architecture, the non-linear fuzzy control method adapts to process uncertainties and disturbances to produce superior performance. 相似文献
19.
P. Z. Wang R. Östermark R. Alex S. H. Tan 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2001,5(3):208-214
In [15], we introduced the concepts of fuzzy bases, fuzzy linear interpolation and fuzzy polygon of four-component fuzzy
linear bases. In [16], these concepts were used in the maximal profile of the set of polygons generated from a set of break
points for each variable dimension. Theconcept was operationalized in a fuzzy linear basis algorithm (FLBA) for nonlinear
separable programming problems involving no more than a finite number of discontinuities. The FLBA provides a powerful platform
forparallel processing of the fuzzy linear sub-problems included in the finite FLB-chain. In this paper we extend the theory
of fuzzy linear bases from the set of polygons toapolyhedral representation of four-component fuzzy linear bases defined on
a closed subset of the real line. 相似文献
20.
We consider the problem of semi-global stabilization of a class of partially linear composite systems. We show, by explicit construction of the control laws, that a cascade of linear stabilizable and nonlinear asymptotically stable subsystems is semi-globally stabilizable by a dynamic feedback of the state of the linear subsystem if (a) the linear subsystem is right invertible and has all its invariant zeros in the closed left half s-plane, and (b) the only linear variables entering the nonlinear subsystem are the output of the linear subsystem. Our work generalizes previous results by C.I. Byrnes and A. Isidori (1991), H.J. Sussmann and P.V. Kokotovic (1991), and A.R. Teel (1992). 相似文献