Square-mean almost periodic solutions to some stochastic evolution equations

This paper concerns the square-mean almost periodic mild solutions to a class of abstract nonautonomous functional integro-differential stochastic evolution equations in a real separable Hilbert space. By using the so-called "Acquistapace–Terreni" conditions and the Banach fixed point theorem, we establish the existence, uniqueness and the asymptotical stability of square-mean almost periodic solutions to such nonautonomous stochastic differential equations. As an application, almost periodic solution to a concrete nonautonomous stochastic integro-differential equation is considered to illustrate the applicability of our abstract results.     

时滞细胞神经网络方程概周期解的存在唯一性

主要考虑了一类连续神经网络系统离散化情况.在一定条件下得到了这类方程概周期解的存在性和唯一性以及其全局吸引性.作为应用,最后给出一个例子.     

On the stability of two new two-step explicit methods for the numerical integration of second order initial value problem on a variable mesh

We present two novel two-step explicit methods for the numerical solution of the second order initial value problem on a variable mesh. In the case of a constant mesh the method is superstable in the sense of Chawla (1985). Numerical experimentation is provided to verify the stability analysis.     

Homology of Centralizers

Given a group Π, we study the group homology of centralizers Π _g , g ? Π, and of their central quotients Π _g /〈 g〉. This study is motivated by the structure of the Hochschild and the cyclic homology of group algebras, and is based on Quillen's approach to the cyclic homology of algebras via algebra extensions. A method of computing the de Rham complex of a group algebra by means of a Gruenberg resolution is also developed.     

具有概周期系数的三种群第Ⅱ类功能性反应的全局渐近稳定性

讨论了一类具有概周期系数的三种群第Ⅱ类功能性反应的模型，通过利用微分不等式及构造适当的李雅普诺夫函数获得了其存在全局渐近稳定性的概周期解的充分条件．     

On almost self-complementary graphs

A graph is called almost self-complementary if it is isomorphic to one of its almost complements X^c-I, where X^c denotes the complement of X and I a perfect matching (1-factor) in X^c. Almost self-complementary circulant graphs were first studied by Dobson and Šajna [Almost self-complementary circulant graphs, Discrete Math. 278 (2004) 23-44]. In this paper we investigate some of the properties and constructions of general almost self-complementary graphs. In particular, we give necessary and sufficient conditions on the order of an almost self-complementary regular graph, and construct infinite families of almost self-complementary regular graphs, almost self-complementary vertex-transitive graphs, and non-cyclically almost self-complementary circulant graphs.     

On the existence of f-local subgroups in a group

We prove the existence of infinite subgroups with nontrivial locally finite radicals and of locally finite subgroups in the groups with almost finite almost solvable elements of prime orders and in the groups with generally finite elements.     

Independence of almost periodicity upon the topology of the acting group

Answering a question first explicitly stated by de Vries in 1993, we observe that for an arbitrary topological dynamical system the property of being an almost periodic point does not depend on the topology of the acting group. In other words, the traditional distinction made between the notions of an almost periodic point and of a discretely almost periodic point is unnecessary.     

H—空间的覆盖性质及其应用

我们得到了Ｈ－空间闭（开）覆盖性质的几个定理，改进和推广了Ｓｐｅｒｎｅｒ，Ｋｌｅｅ，Ａｌｅｘａｎｄｒｏｆｆ－Ｐａｓｙｎｋｏｆｆ，Ｂｅｒｇｅ，Ｇｈｏｕｉｌａ－Ｈｏｕｒｉ，Ｄａｎｚｅｒ－Ｇｒｕｎｂａｕｍ－Ｋｌｅｅ，Ｋｙ Ｆａｎ，ｓｈｉｈ－Ｔａｎ，Ｈｏｒｖａｔｈ和Ｌａｓｓｏｎｄｅ等人的相应结果。作为应用，我们对ｌ．ｃ．－空间内的下半连续集值映象证明了一个几站不动点定理并且推广吉洪诺夫不动点定理到ｌ．ｃ．