透明计算系统端计算机间的数据传送方法

提出一种透明计算系统中端计算机间的数据传送方法,该方法通过将数据传送的控制信息和传送的数据分离,省去数据在网络上的传送过程,从而提高对传送请求的处理速度,减少对相关资源的占用,通过优化服务器对传送请求的调度处理,改善系统整体的响应速度和性能。在基于龙芯平台的透明计算原型系统中实现了上述方法,并作了性能测试和分析,验证了该方法的有效性。     

A software design technique for client–server applications

Software design is the process of mapping software functional requirements into a set of modules for implementation. In this paper, a new design technique called the concurrent software design technique (CSDT) is proposed. CSDT extends software design techniques, which are based on structured analysis and design, by identifying independent concurrent tasks for implementation in multiprocessing, multitasking and the C/S environment. A case study on re-engineering a large legacy system, implemented on mainframes as a sequential system, to a C/S environment is presented next in order to highlight the benefits of the CSDT. Finally, this paper concludes with a comparison of CSDT with other existing approaches and the lessons learned from the experience with this technique. © 1999 John Wiley & Sons, Ltd.     

Transient analysis of structural members by the CSDT riccati transfer matrix method

A method for the direct integration of the dynamic governing partial differential equations of motion for structural members is developed. This technique is called the continuous-space discrete-time (CSDT) Riccati transfer matrix method. This formulation transforms a boundary value problem of governing partial differential equations of motion into a boundary value problem of ordinary differential equations. First, a standard procedure such as finite differences is employed to discretize the time derivatives. Then, a line solution technique such as the Riccati transfer matrix method is utilized to integrate the spatial derivatives. The stability and accuracy of the CSDT Riccati transfer matrix method using the Newmark generalized acceleration formulation for time discretization is studied. For a particular class of governing equations, it is shown that the method is unconditionally stable without amplitude decay error for particular parameter values in the Newmark formulation. The method, however, exhibits period elongation error as a function of the time step. Numerical results for bar and beam example problems indicate that this may well be a viable method for calculating the dynamic response of linear structural members.     

Solving parabolic PDE's by a decomposition method

The paper deals with the application of the hybrid method of decomposition for the solution of two-dimensional parabolic partial differential equations with constant coefficients. The convergence and accuracy of the CSDT method are analysed, deriving the form of the relationship between ‘eigenvalues’ and the time step. Theoretical problems of this method of decomposition are mentioned. Also, the expression for computing the coefficients for various types of boundary problems has been derived. Practical applications of the method are presented. The cubic spline function interpolation is used for the continuous signal reproduction in the hybrid system. Some results obtained are presented at the end.     

Stability of linear multistep methods for delay integro-differential equations

This paper is concerned with the numerical solution of delay integro-differential equations. The adaptation of linear multistep methods is considered. The emphasis is on the linear stability of numerical methods. It is shown that every A-stable, strongly 0-stable linear multistep method of Pouzet type can preserve the delay-independent stability of the underlying linear systems. In addition, some delay-dependent stability conditions for the stability of numerical methods are also given.     

Adams-type methods with increased ranges of stability

Nonlinear optimization and root-finding procedures were used to locate Adams-type methods with increased ranges of stability. PE(CE)^m and P(EC)^m methods, where P is an Adams—Bashforth predictor and C is an Adams-type corrector, with order of up to 20 for relative stability and up to 12 for absolute stability are given. The methods were obtained from one-parameter families of Adams methods by numerically maximizing the size of the largest real stability interval with the right end-point as origin. The results given indicate that the stability of the usual Adams methods can be improved significantly from this point of view without sacrificing their other computational advantages.     

Asymptotic stability of block boundary value methods for delay differential-algebraic equations

Block boundary value methods are applied to solve a class of delay differential-algebraic equations. We focus on the asymptotic stability of the numerical methods for linear delay differential-algebraic equations with multiple delays. It is shown that A-stable block boundary value methods satisfying a restrictive condition can preserve the asymptotic stability of the analytical solution. Numerical experiments further confirm the effectiveness and stability of the methods.     

New results on relationships between multipoint Padé approximation and stability preserving methods in model reduction

Three well-known stability preserving methods of reduction are shown to be special forms of the multipoint pade approximation. Two of the methods—the modified forms of the Schwarz approximation and the stability equation method—are consequently shown to be closely related. Previously observed properties of the methods are explained by treating them as multipoint approximants, and the significance of using expansion points on the imaginary axis is shown to be central to stability preservation.     

Asymptotic stability of general linear methods for systems of linear neutral delay differential-algebraic equations

This paper is concerned with numerical stability of general linear methods (GLMs) for a system of linear neutral delay differential-algebraic equations. A sufficient and necessary condition for asymptotic stability of GLMs solving such system is derived. Based on this main result, we further investigate the asymptotic stability of linear multistep methods, Runge–Kutta methods, and block θ-methods, respectively. Numerical experiments confirm our theoretical result.     

Temporal stability in predictive process monitoring

Predictive process monitoring is concerned with the analysis of events produced during the execution of a business process in order to predict as early as possible the final outcome of an ongoing case. Traditionally, predictive process monitoring methods are optimized with respect to accuracy. However, in environments where users make decisions and take actions in response to the predictions they receive, it is equally important to optimize the stability of the successive predictions made for each case. To this end, this paper defines a notion of temporal stability for binary classification tasks in predictive process monitoring and evaluates existing methods with respect to both temporal stability and accuracy. We find that methods based on XGBoost and LSTM neural networks exhibit the highest temporal stability. We then show that temporal stability can be enhanced by hyperparameter-optimizing random forests and XGBoost classifiers with respect to inter-run stability. Finally, we show that time series smoothing techniques can further enhance temporal stability at the expense of slightly lower accuracy.     

Optimal Strong-Stability-Preserving Runge–Kutta Time Discretizations for Discontinuous Galerkin Methods

Discontinuous Galerkin (DG) spatial discretizations are often used in a method-of-lines approach with explicit strong-stability-preserving (SSP) Runge–Kutta (RK) time steppers for the numerical solution of hyperbolic conservation laws. The time steps that are employed in this type of approach must satisfy Courant–Friedrichs–Lewy stability constraints that are dependent on both the region of absolute stability and the SSP coefficient of the RK method. While existing SSPRK methods have been optimized with respect to the latter, it is in fact the former that gives rise to stricter constraints on the time step in the case of RKDG stability. Therefore, in this work, we present the development of new “DG-optimized” SSPRK methods with stability regions that have been specifically designed to maximize the stable time step size for RKDG methods of a given order in one space dimension. These new methods represent the best available RKDG methods in terms of computational efficiency, with significant improvements over methods using existing SSPRK time steppers that have been optimized with respect to SSP coefficients. Second-, third-, and fourth-order methods with up to eight stages are presented, and their stability properties are verified through application to numerical test cases.     

非最小相位控制系统的智能设计方法

提出了两种非最小相位控制系统的智能设计方法，并以此设计了控制系统，证实了设计方法能同时满足系统的稳定性、鲁棒性、静态动态性能，以及控制器的简单性和控制器本身的稳定性等方面的要求。     

Über die Integration von Differentialgleichungssystemen 1. Ordnung mit exponentiell angepaßten numerischen Methoden

A general theoretical basis for the design of exponentially fitted numerical integration methods will be derived for obtaining methods which, from accuracy and stability, allow large discretization intervals even for systems with large eigenvalues. The technique of transforming existing numerical methods to an exponentially fitted version will be exemplified and the influence of exponential fitting on discretization error and stability for one-step methods will be discussed.     

Direct method for transient stability studies in power system analysis

This paper deals with recent advances in developing direct methods for studying the transient stability problem of single-machine and multimachine power systems. The paper starts out with the construction of the mathematical model that is usually employed in the analyis of power system transient stability. Computer simulation methods are then briefly discussed, and it is indicated why accurate direct methods for transient stability investigations would be most welcome. It is shown that the classical direct methods, which are based on energy considerations, can be derived and generalized by means of Lyapunov's second method. The main purpose of the paper is to give an exposition of the interesting results that have been obtained by applying Lyapunov's second method to the transient stability problem of single-machine and multimachine power systems. In the final portion of the paper some areas for further research are discussed.     

模糊系统稳定性

简要综述了模糊控制系统的稳定性分析方法,详细介绍了这些方法的概念和原理,分析总结了每种方法的适用对象及优缺点,最后展望了这一领域今后的研究方向.     

Numerical methods for elastic structural stability analysis

The Gauss-Seidel, the successive overrelaxation, the conjugate gradient, the Cholesky's square root and the Cholesky's decomposition methods for solving systems of linear algebraic equations encountered in structural analysis are considered. Theorems for these methods establishing necessary and sufficient conditions for the matrix of the coefficients to be positive definite are converted into criteria for elastic structural stability. Numerical procedures, by using these methods in conjunction with their corresponding stability criteria, for checking the elastic stability and determining the elastic critical load of a structure are proposed. Application of these procedures to the stability analysis of plane frameworks leads to the conclusion that the proposed direct schemes are more efficient than the iterative ones.     

Delay-dependent robust stability of uncertain networked control systems with multiple state time-delays

In this paper, delay-dependent robust stability for a class of uncertain networked control systems （NCSs） with multiple state time-delays is investigated. Modeling of multi-input and multi-output （MIMO） NCSs with networkinduced delays and uncertainties through new methods are proposed. Some new stability criteria in terms of LMIs are derived by using Lyapunov stability theory combined with linear matrix inequalities （LMIs） techniques. We analyze the delay-dependent asymptotic stability and obtain maximum allowable delay bound （MADB） for the NCSs with the proposed methods. Compared with the reported results, the proposed results obtain a much less conservative MADB which are more general. Numerical example and simulation is used to illustrate the effectiveness of the proposed methods.     

多输入多输出线性定常系统稳定裕度的分析与改进

针对多输入多输出(MIMO)控制系统的稳定裕度求解问题,首先分析了现有的回差阵奇异值法这一计算方法,并得到其解决单输入单输出(SISO)系统的稳定裕度结论,在此基础上,提出两种基于系统回差阵的稳定裕度改进方法;一种是在有限条件下利用矩阵的特征值代替奇异值来建立与稳定裕度关系的策略,另一种是利用系统逆回差阵的行列式,通过求其奇异值来计算系统稳定裕度;最后结合工程实例,通过数值仿真验证两种稳定裕度计算方法相比原方法都有不同程度的改进,而且三种方法可以结合起来进行分析,最大化的减小系统稳定裕度结果的保守性.     

Convergence and stability of the balanced methods for stochastic differential equations with jumps

This paper deals with the balanced methods which are implicit methods for stochastic differential equations with Poisson-driven jumps. It is shown that the balanced methods give a strong convergence rate of at least 1/2 and can preserve the linear mean-square stability with the sufficiently small stepsize. Weak variants are also considered and their mean-square stability analysed. Some numerical experiments are given to demonstrate the conclusions.