张量对称类上诱导算子的y-数值半径(英文)

本文研究了诱导矩阵K(A)的y-数值半径ry(K(A))、y-可分数值半径ryχ(K(A))与范数A2、广义矩阵函数dχG(A)之间的关系问题.利用ry(K(A))及ryχ(K(A))的概念,得到了ry(K(A))、ryχ(K(A))、‖A‖2、dGχ(A)它们之间的两个不等式.     

群逆的扰动界及其在奇异线性系统中的应用

本文建立了群逆的扰动界,此界基于矩阵A的Jordan标准形和P-范数,其中P是非异矩阵满足 是非异上双对角阵且 当矩阵A和A+E有相同的秩且 较小时,得到了 较好的估计.在相同的条件下,研究了相容的奇异线性系统Aχ=b的扰动,给出了χopt=A#b扰动的上界,其中A#是A的群逆,χopt是最小P-范数解.     

线性常微分方程系统的稳定性

本文用矩阵的Lozinskii测度的方法,得到了线性常微分方程系统的某些稳定性准则.导出了关于线性系统x'=A(t)x稳定性的充要条件.对于A是常数或周期矩阵的情形,我们的结果与从Jordan标准型和Floquet理论得到的经典结论相同.     

移动最小二乘法的近似稳定性

移动最小二乘近似法在无网格法中得到广泛应用,然而近似计算可能因A矩阵奇异或病态而产生不稳定问题.为了保证A矩阵非奇异,证明了支撑点集的必要几何条件.基于此,给出了判定A矩阵病态性的推论.为了克服A矩阵在特定条件下容易产生病态的问题,提出了采用核基的核近似法.研究结果为保证近似稳定性给出了简便的判别法则,为提高近似稳定性建议了有效的改进方法,为无网格法的合理数值实施提供了初步的理论依据.     

一般矩阵函数的变差

设Sn是n次对称群,G为Sn的子群,χ是G的次数为1的特征标.如果A是一个n阶复变矩阵,定义一般矩阵函数dχG为dχG(A)=∑σ∈Gχ(σ)∏ni=1aiσ(i).本文用lp-算子范数(1≤p≤∞)的性质证明了一般矩阵函数变差的两个不等式.     

EP矩阵与矩阵方程的解

证明了如下结论:设A∈C~(n×n)是群可逆矩阵,则(i)A为EP矩阵当且仅当矩阵方程A~HXA=XAA~H在χ_A至少有一个解;(ii)A为EP矩阵当且仅当矩阵方程A~HXA=AA~HX在χ_A至少有一个解,其中χ_A={A,A~#,A~+,A~H,(A~#)~H,(A~+)~H}.     

M类矩阵及差分格式稳定性条件

Householder 在[1]中详细讨论过 M 类矩阵.本文不用几何上的凸体概念,而用 Young所引入的 L 模来讨论 M 类矩阵,给出一个 M 类矩阵充分条件的较为简单的新证明.同时,若A 是 M 类矩阵,给出了一类具体的非奇异矩阵 L,使得‖A‖L=■(A).但我们未能找到使得‖A‖L=■(A)的通解 L.然后用 M 类矩阵来讨论差分格式稳定性问题,给出了一个比较一般的实用的稳定性充分条件.     

关于与给定矩阵可交换的矩阵的多项式表示

文[1]得到:若矩阵A的Jordan标准形中没有纯量矩阵的Jordan块,那么AB=BA的充要条件为B可以化为A的n-1次多项式.本文指出这个结论是错误的.在已有相关文献的基础上,得到了与给定矩阵A可交换的矩阵B是A的多项式的十个等价刻划.     

系数和常量的摄动对最小范数最小二乘解稳定性的影响

通过对在欧氏范数下系数矩阵和常数向量的摄动△A和△b对最小范数最小二乘解稳定性影响的大小的研究,得到了△x在欧氏范数下的上界.     

自共轭四元数循环矩阵的特征值问题

循环矩阵是一类应用广泛的特殊矩阵.设A是一个自共轭四元数循环矩阵,运用四元数矩阵的复表示,以及循环矩阵的特定结构形式,得到了矩阵A的特征值的计算公式.反之,对于任意给定的n个实数,证明了一定存在自共轭四元数循环矩阵A,使得A以这n个实数为它的特征值,同时给出了自共轭四元数循环矩阵A的计算方法.推广了复循环矩阵的相关理论结果.     

Stability radii of positive linear Volterra-Stieltjes equations

We study stability radii of linear Volterra-Stieltjes equations under multi-perturbations and affine perturbations. A lower and upper bound for the complex stability radius with respect to multi-perturbations are given. Furthermore, in some special cases concerning the structure matrices, the complex stability radius can precisely be computed via the associated transfer functions. Then, the class of positive linear Volterra-Stieltjes equations is studied in detail. It is shown that for this class, complex, real and positive stability radius under multi-perturbations or multi-affine perturbations coincide and can be computed by simple formulae expressed in terms of the system matrices. As direct consequences of the obtained results, we get some results on robust stability of positive linear integro-differential equations and of positive linear functional differential equations. To the best of our knowledge, most of the results of this paper are new.     

Stability radius of linear parameter-varying systems and applications

In this paper, we present a unifying approach to the problems of computing of stability radii of positive linear systems. First, we study stability radii of linear time-invariant parameter-varying differential systems. A formula for the complex stability radius under multi perturbations is given. Then, under hypotheses of positivity of the system matrices, we prove that the complex, real and positive stability radii of the system under multi perturbations (or affine perturbations) coincide and they are computed via simple formulae. As applications, we consider problems of computing of (strong) stability radii of linear time-invariant time-delay differential systems and computing of stability radii of positive linear functional differential equations under multi perturbations and affine perturbations. We show that for a class of positive linear time-delay differential systems, the stability radii of the system under multi perturbations (or affine perturbations) are equal to the strong stability radii. Next, we prove that the stability radii of a positive linear functional differential equation under multi perturbations (or affine perturbations) are equal to those of the associated linear time-invariant parameter-varying differential system. In particular, we get back some explicit formulas for these stability radii which are given recently in [P.H.A. Ngoc, Strong stability radii of positive linear time-delay systems, Internat. J. Robust Nonlinear Control 15 (2005) 459-472; P.H.A. Ngoc, N.K. Son, Stability radii of positive linear functional differential equations under multi perturbations, SIAM J. Control Optim. 43 (2005) 2278-2295]. Finally, we give two examples to illustrate the obtained results.     

Linear stability of general linear methods for systems of neutral delay differential equations

This paper is concerned with the numerical solution of delay differential equations (DDEs). We focus on the stability of general linear methods for systems of neutral DDEs with multiple delays. A type of interpolation procedure is considered for general linear methods. Linear stability properties of general linear methods with this interpolation procedure are investigated. Many extant results are unified.     

Stability radii of higher order linear difference systems under multi-perturbations

We study stability radii of higher order linear difference systems under multi-perturbations. A formula for complex stability radius of higher order linear difference systems under multi-perturbations is given. Then, for the class of positive systems, we prove that the complex stability radius and real stability radius of the system under multi-perturbations coincide and they are computed via a simple formula. These are extensions of corresponding results of Hinrichsen and Son, Hinrichsen et al., Ngoc and Son, and Pappas and Hinrichsen. An example is given to illustrate the obtained results.     

Finite-time stability analysis of fractional order time-delay systems: Gronwall’s approach

In this paper, a stability test procedure is proposed for linear nonhomogeneous fractional order systems with a pure time delay. Some basic results from the area of finite time and practical stability are extended to linear, continuous, fractional order time-delay systems given in state-space form. Sufficient conditions of this kind of stability are derived for particular class of fractional time-delay systems. A numerical example is given to illustrate the validity of the proposed procedure.     

Volterra泛函微分方程一般线性方法的稳定性

本文研究Volterra泛函微分方程(k,p,q)-代数稳定的一般线性方法的稳定性,获得了该类方法的一系列新的稳定性结果.     

Robust asymptotic stability for BAM neural networks with time-varying delays via LMI approach

Several novel stability conditions for BAM neural networks with time-varying delays are studied.Based on Lyapunov-Krasovskii functional combined with linear matrix inequality approach,the delay-dependent linear matrix inequality（LMI） conditions are established to guarantee robust asymptotic stability for given delayed BAM neural networks.These criteria can be easily verified by utilizing the recently developed algorithms for solving LMIs.A numerical example is provided to demonstrate the effectiveness and less conservatism of the main results.     

Stability of implicit-explicit linear multistep methods for ordinary and delay differential equations

Stability properties of implicit-explicit (IMEX) linear multistep methods for ordinary and delay differential equations are analyzed on the basis of stability regions defined by using scalar test equations. The analysis is closely related to the stability analysis of the standard linear multistep methods for delay differential equations. A new second-order IMEX method which has approximately the same stability region as that of the IMEX Euler method, the simplest IMEX method of order 1, is proposed. Some numerical results are also presented which show superiority of the new method.      

On positivity and stability of a class of time-delay systems

In this paper, the properties of positivity and stability dependent on and independent of the delays as well as the closed-loop stabilization under linear feedback of continuous-time linear time-invariant multi-input multi-output dynamic systems subject to point constant delays are discussed. A main attention is paid to provide joint stability and positivity results which are shown to be conflictive objectives in the general case. Links with positive realness are given for the single-input single-output case. Illustrative examples are also given.     

关于辛算法稳定性的若干注记

我们讨论辛算法的线性稳定性和非线性稳定性,从动力系统和计算的角度论述了研究辛算法的这两类稳定性问题的重要性,分析总结了相关重要结果.我们给出了解析方法的明确定义,证明了稳定函数是亚纯函数的解析辛方法是绝对线性稳定的.绝对线性稳定的辛方法既有解析方法（如Runge-Kutta辛方法）,也有非解析方法（如基于常数变易公式对线性部分进行指数积分而对非线性部分使用其它数值积分的方法）.我们特别回顾并讨论了R.I.McLachlan,S.K.Gray和S.Blanes,F.Casas,A.Murua等关于分裂算法的线性稳定性结果,如通过选取适当的稳定多项式函数构造具有最优线性稳定性的任意高阶分裂辛算法和高效共轭校正辛算法,这类经优化后的方法应用于诸如高振荡系统和波动方程等线性方程或者线性主导的弱非线性方程具有良好的数值稳定性.我们通过分析辛算法在保持椭圆平衡点的稳定性,能量面的指数长时间慢扩散和KAM不变环面的保持等三个方面阐述了辛算法的非线性稳定性,总结了相关已有结果.最后在向后误差分析基础上,基于一个自由度的非线性振子和同宿轨分析法讨论了辛算法的非线性稳定性,提出了一个新的非线性稳定性概念,目的是为辛算法提供一个实际可用的非线性稳定性判别法.