层焰系统奇点结构的研究

在一定的假设条件下,将气体燃烧的物理模型简化为层焰系统．借助于热力学理论和相关的守恒定律建立了层焰系统的数学模型并对其进行了深入地分析．利用常微分方程的定性理论和方法,结合燃烧的实际需要,对应于参数的不同取值,研究了位于瑞利线上奇点的个数和位置,确定了暴燃区和爆炸区内不同奇点的定性结构及其稳定性,给出了在反应速度-滞止焓平面及燃烧速度-滞止焓平面内层焰系统轨线的相图．     

一类平面奇次系统的全局结构

通过研究一类平面奇次系统的有限远奇点和无穷远奇点的类型,对其进行定性分析,得到系统的全局结构及其相图.     

平面五次微分系统高次奇点的拓扑分类

该文讨论了平面五次微分系统高次奇点的拓扑分类，并给出按右端多项式系数的判断准则．     

具有星形结点的一类平面四次系统的全局结构（Ⅰ）

该文，证明了前文中的Ⅰ－Ⅳ型区域同样适合于原点是星形结点和有五个无穷远奇点的一类平面四次系统．应用它得到上述系统的三十九种可能的全局结构．     

拟二次系统的广义焦点量与极限环分枝

本文给出了拟二次系统的前18个奇点量和可积性条件,由此统一解决了几类实平面微分自治系统的初奇点、高次奇点以及无穷远点的中心焦点判定与极限环分枝问题.     

一类平面系统的定性分析

利用平面系统的定性理论 ,提供系统的全局分析 ,讨论了一类平面系统奇点的稳定性和极限环问题 ,给出奇点稳定和极限环唯一的充分条件     

Z6等变系统所有可能的相图

简单介绍了 Z6 等变系统的背景 ,利用微分方程的定性理论及分枝理论 ,求出有限平面奇点及无穷远奇点 ;通过特征值方法判断奇点类型 ;根据系统等变性及解的唯一性讨论了在参数空间里所有可能的相图 ,给出了具体的形式 ,一共五类十六个相图 .     

一类带有三次项的平面五次微分系统的全局拓扑结构分析

一类带有三次项的平面五次微分系统在Poincare变换下可以讨论系统的无穷远奇点的性质,进而得到奇点附近轨线的拓扑结构,并利用判断函数给出极限环存在与否的条件,补充完善了五次系统的定性分析.     

平面时标线性自治系统的渐近行为

本文讨论了平面时标线性自治系统的渐近行为,得到一些在时标意义下类似于平面线性自治系统奇点分类的新准则,并指出该准则可以将连续和离散方程的渐近行为统一.     

一类双中心平面二次系统的Abel积分零点个数

利用Abel积分与第一、第二型完全椭圆积分,本文研究一类具有两个中心奇点的平面二次系统在n次小扰动下的Abel积分零点个数上界问题,得到了较小的上界估计．     

关于总体分布的矩确定

本文引进了局部分布、局部矩、局部矩法估计、样本局部矩和局部分布的矩确定等概念。从而为著名的经典矩量问题提供了新的研究途径与方法并获得了若干新结果。     

Necessary Optimality Conditions and New Optimization Methods for Cubic Polynomial Optimization Problems with Mixed Variables

Multivariate cubic polynomial optimization problems, as a special case of the general polynomial optimization, have a lot of practical applications in real world. In this paper, some necessary local optimality conditions and some necessary global optimality conditions for cubic polynomial optimization problems with mixed variables are established. Then some local optimization methods, including weakly local optimization methods for general problems with mixed variables and strongly local optimization methods for cubic polynomial optimization problems with mixed variables, are proposed by exploiting these necessary local optimality conditions and necessary global optimality conditions. A global optimization method is proposed for cubic polynomial optimization problems by combining these local optimization methods together with some auxiliary functions. Some numerical examples are also given to illustrate that these approaches are very efficient.     

Complexity of local search for the p-median problem

We study the complexity of finding local minima for the p-median problem. The relationship between Swap local optima, 0–1 local saddle points, and classical Karush–Kuhn–Tucker conditions is presented. It is shown that the local search problems with some neighborhoods are tight PLS-complete. Moreover, the standard local descent algorithm takes exponential number of iterations in the worst case regardless of the tie-breaking and pivoting rules used. To illustrate this property, we present a family of instances where some local minima may be hard to find. Computational results with different pivoting rules for random and Euclidean test instances are discussed. These empirical results show that the standard local descent algorithm is polynomial in average for some pivoting rules.     

B值渐近鞅的局部收敛性

Ｂ值渐近鞅是Ｂ值鞅的重要推广,它保持了鞅的一些是一性质,然后对Ｂ值渐近鞅的局部收敛性很少有文献论及。本文利用Ｂ值渐近鞅的Ｄｏｏｂ分解,对Ｂ值渐近鞅的局部收敛性作些探讨,得到了Ｂ值渐近鞅局部收敛性的几个结果,它们是鞅的有关结论的推广与改进。     

关于凸曲面的几个定义的关系

本文讨论了凸曲面的几种定义及其关系，发现有的定义是局部凸的定义，有的是整体凸的定义，有的则对于局部凸和整体凸都适合，最后给出了各种定义之间互推的证明，对于局部凸和整体凸定义之间不能推证的，则说明了原因．     

Local and Parallel Finite Element Algorithms Based on Two-Grid Discretizations for Nonlinear Problems

In this paper, some local and parallel discretizations and adaptive finite element algorithms are proposed and analyzed for nonlinear elliptic boundary value problems in both two and three dimensions. The main technique is to use a standard finite element discretization on a coarse grid to approximate low frequencies and then to apply some linearized discretization on a fine grid to correct the resulted residual (which contains mostly high frequencies) by some local/parallel procedures. The theoretical tools for analyzing these methods are some local a priori and a posteriori error estimates for finite element solutions on general shape-regular grids that are also obtained in this paper.     

On Some Brauer Subgroups Arising From Twists of Matrix Algebras

We study some relations between groups of continuous characters and subgroups of Brauer groups. Explicit determination of some subgroups of Brauer groups arising from this connection are done for some cases in the local fields via local class field theory.     

Minimaxness and finiteness properties of local homology and local cohomology modules

We prove some results concerning minimaxness and finiteness of local homology modules and by Matlis duality we extend some results for the minimaxness and finiteness of local cohomology modules. We introduce the concept of C-minimax R-modules, and we discuss the maximum and minimum integers such that local homology and local cohomology modules are C-minimax. As a consequence, we find minimum integers such that local homology and local cohomology modules are of finite length.     

Local and parallel finite element algorithms based on two-grid discretizations

A number of new local and parallel discretization and adaptive finite element algorithms are proposed and analyzed in this paper for elliptic boundary value problems. These algorithms are motivated by the observation that, for a solution to some elliptic problems, low frequency components can be approximated well by a relatively coarse grid and high frequency components can be computed on a fine grid by some local and parallel procedure. The theoretical tools for analyzing these methods are some local a priori and a posteriori estimates that are also obtained in this paper for finite element solutions on general shape-regular grids. Some numerical experiments are also presented to support the theory.

     

超空间2x的局部覆盖性质

本文讨论了超空间２^x的某些局部覆盖性质，并给出下面二个结果：定理１设Ｘ是Ｔ₂空间，则２^x紧当且仅当２^x是局部ｍｅｔａ－Ｌｉｎｄｅｌｏｆ空间．定理２₁设Ｘ是Ｔ¹空间，则２^xｍ－紧当且仅当２^x是局部ｍ－紧。