ON THE INSTABILITY OF GROUND STATES FOR A GENERALIZED DAVEY-STEWARTSON SYSTEM

In this paper, we give a simpler proof for Ohta's theorems [1995, Ann. Inst.Henri Poincare, 63, 111; 1995, Diff. Integral Eq., 8, 1775] on the strong instability of the ground states for a generalized Davey-Stewartson system. In addition, a sufficient condition is given to ensure the nonexistence of a minimizer for a variational problem, which is related to the stability of the standing waves of the Davey-Stewartson system. This result shows that the stability result of Ohta [Diff. Integral Eq., 8, 1775] is sharp.     

THE EXISTENCE AND STABILITY OF ALMOST PERIODIC SOLUTION

By using the ordinary dichotomy and theory of stability,we study the nonli- near differential equation and obtain some sufficient conditions which guarantee the existence and stability of almost periodic solution for the nonlinear diffe- rential equation.     

非线性波的指数衰减(I)

非线性波的指数衰减（Ｉ）盛其荣（新疆大学，乌鲁木齐市８３００４６）国家自然科学基金资助项目．１９９１年５月２２日收到，１９９１年１１月１１日收到修改稿．一、引言考虑下面问题：其中中的有界开集，边界且存在常数ｃ＞０使中的有界函数且在。内，（５）这里中非...     

变系数MDDEs系统的数值稳定性

１．引言考虑下列变系数ＭＤＤＥｓ系统其中　　是复Ｎ级连续矩阵函数,是光滑时滞函数, 是光滑初始函数．下文中,我们恒设（１．１）有唯一光滑解ｙ（ｔ）．对于系统（１．１）的一些子系统,如单滞量系统、多滞量常系数系统,其理论解与数值解的渐近稳定性已被广泛研究（参见［１－４］,特别是在研究数值解的渐近稳定性时, Ｐｍ－、 ＧＰｍ－稳定性概念被提出,其实质是指数值解｛ｙｎ｝以 ０为其吸引点, Ｌ．Ｔｏｒｅｌｌｉ［５,６］则针对单滞量标量线性系统及一般非线性单滞量系统分别提出了另一类稳定性概念,即 ＧＰＮ－稳定与…     

关于插值的稳定性

实际计算表明,高阶多项式插值是不稳定的,分片低阶多项式插值则有良好的稳定性.在[1]中对此有简要的说明,本文将对此进行较详尽的理论分析.     

THE STABILITY OF A CLASS OF FUNCTIONAL DIFFERENTIAL EQUATIONS WITH INFINITE DELAYS

1 IntroductionConsider the following functional differential equationX'(t) = A(t)x(t) [' C(t,s)x(s)ds, (1)icwhere x E m; A(t) = (ail(t))... is a n x n function matrix, which continuesin [0, co); C(t,s) = (qj(t,8))... is a n x n function matrix, which conti-nues when 0 5 s 5 t < co, and L oo IIC(u,t)lldu continues in [0, co).The problem on the stability for the zero solution of (1) has been studied bymany papers. But in the known results, the boundedness of j: IIC(t, s)lldsor L " IIC…     

R＆D和边干边学的混合模型的稳定性分析

本文研究了由R＆D和边千边学构成的混合模型的稳定性问题，利用二次Liapunov判别法．得出关于混合模型在确定和随机状态下的若干结论.     

算子方程离散格式判稳的充分条件

萨马斯基曾给出判稳的充分条件,但它涉及估计算子的模或特征值,这在一般情况下是困难的,不容易检验.本文给出一种易于检验的充分条件,即把稳定性与一代数方程组的Jacobi迭代法的迭代阵的最大特征值联系起来,从而可利用迭代法收敛的某些已知结果来判别稳定性,其中特别方便的是利用矩阵的对角占优条件.本方法的特点是适用于一般的非均匀有限元剖分.     

THE DIMENSIONS OF THE RANGE OF RANDOM WALKS IN TIME-RANDOM ENVIRONMENTS

Suppose {Xn} is a random walk in time-random environment with state space Zd,|Xn| approaches infinity, then under some reasonable conditions of stability, the upper bound of the discrete Packing dimension of the range of {Xn} is any stability index a. Moreover, if the environment is stationary, a similar result for the lower bound of the discrete Hausdorff dimension is derived. Thus, the range is a fractal set for almost every environment.     

ON THE EQUIVALENCE OF AUTONOMOUS AND NONAUTONOMOUS DIFFERENTIAL SYSTEMS

Using reflecting function of Mironenko we construct some nonautonomous differential systems which are equivalent to the given autonomous differential systems. The results are applied to discuss the existence and stability of periodic solution of these nonautonomous nonlinear differential systems.     

一类脉冲微分方程零解的稳定性

本文研究了一类在非固定时刻的脉冲微分方程。利用Lyapunov第二方法,建立了零解为稳定,渐近稳定及不稳定的判别准则。结果表明脉冲可能影响甚至改变相应的无脉冲时的微分方程的稳定性。文中还给出一例说明所得主要结果的应用。     

结构摄动下多项式的鲁棒稳定性

本文对与Ｋｈａｒｉｔｏｎｏｖ多项多族相对偶的菱形族式项式的一类结构摄动下的鲁棒稳定性进行了详细的研究，提出了在此结构摄动下，菱形族形族多项式稳定当且仅当检验有限个顶点多项式或有限个边多项式的稳定性定理，而菱形族定量只是本定理的推论，另外，对低阶多项式族进行了讨论。     

关于扰动微分方程组零解部分变元的稳定性

本文讨论未被扰动运动关于部分变元的稳定性，一致稳定性和全局渐近稳定性，给出了一种判定，改进了文［１］中的相应定理。     

Volterra 积分微分大系统的稳定性

近20年来大系统理论已得到了较大的发展,对其稳定性的研究已引起了人们的足够重视,出版的大量论文与专著中已涉及到微分方程、积分方程、泛函微分方程、随机与抽象微分方程、偏微与复微分方程以及差分方程所定义的大系统.虽然近年来对积分微分方程的研究也引起了不少学者的注意,但很少涉及到此类方程所定义的大系统.本文     

直接法的数值稳定性

到目前为止,数值线代数方面最重要的进展是五十年代末Wilkinson提出的向后误差分析方法。但他给出的数值稳定性定义太严格,把不少实际上工作得很好的算法排斥在外。1975年Miller发现了这一问题。他举了Z(d)=d_1 d_2 d_1d_2这样很简单的问题说明Wilkinson的定义不够恰当,并给出了改进的数值稳定性定义。 设X是n维Euclid空间,Y是m维Euclid空间。I X,φ Y。一个数值计算问题P是三元组{I,φ,F},F是I到φ的一个映照,即对x∈J,存在唯一的y∈φ,使F(x)=y。问题P可有若干个算法求解。譬如用算法A来解。显然A是一个数值计算     

DYNAMIC BEHAVIORS OF A DISCRETE COMMENSALISM SYSTEM

A two species discrete commensalism system is proposed and studied.By the Jury's conditions for the stability of second order discrete system,the local stability property of positive equilibrium is investigated;after that,sufficient conditions which ensure the global asymptotic stability of the interior equilibrium are obtained.An example together with its numeric simulation is given to illustrate the feasibility of the main result.     

预估-校正方法的绝对稳定性讨论

预估-校正方法,即PECE方法,常被用于求解常微分方程的初值问题.而一般文献中常只讨论了单个线性多步法公式的稳定性问题,很少涉及由一个显式公式和一个隐式公式组合而成的PECE方法的稳定性.本文应用根轨迹法和对分法讨论了常用的PECE方法的稳定性,求出了一些常用PECE方法的组合公式的绝对稳定区间和绝对稳定区域,并用数值...     

ON THE ALMOST PERIODIC SOLUTIONS OF HIGHER DIMENSIONAL NONAUTONOMOUS SYSTEMS

By means of the properties of almost periodic system and Lyapunov function, we give some criteria which guarantee the existence and uniqueness and stability of almost periodic solutions of higher dimensional nonautonomous system. The result is more convenient and effective than the related result in[1].     

TO DETERMINE THAT ALL THE ROOTS OF A TRANSCENDENTAL POLYNOMIAL HAVE NEGATIVE REAL PARTS

ＴＯＤＥＴＥＲＭＩＮＥＴＨＡＴＡＬＬＴＨＥＲＯＯＴＳＯＦＡＴＲＡＮＳＣＥＮＤＥＮＴＡＬＰＯＬＹＮＯＭＩＡＬＨＡＶＥＮＥＧＡＴＩＶＥＲＥＡＬＰＡＲＴＳＨｕＢｏＭａｎｕｓｃｒｉｐｔｒｅｃｅｉｖｅｄＮｏｖｅｍｂｅｒ２，１９９４．ＲｅｖｉｓｅｄＭａｙ３...     

GAMMA-MINIMAX ESTIMATORS FOR THE MEAN VECTOR OF A MULTIVARIATE NORMAL DISTRIBUTION

Γ-minimax estimators are determined for the mean vector of a multivariate normaldistribution under arbitrary squared error loss.Thereby the set Γ consists of all priorswhose vector of first moments and matrix of second moments satisfy some given restric-tions.Necessary and sufficient conditions are derived which ensure a prior being leastfavourable in Γ and the unique Bayes estimator with respect to this prior being Γ-minimax.By applying these results the Γ-minimax estimator is explicitly found in some special casesor can be computed by solving a system of non-linear equations or by minimizing a quad-ratic form on a compact and convex set.