A Characterization Theorem for the Canonical Basis of a Closure Operator

The purpose of this paper is to provide a characterization result for the canonical basis of an arbitrary closure operator. This theorem strengthens the result of Burosch, Demetrovics and Katona, who propose a characterization of the generating system of a closure operator defined by the quasi-closed sets of the closure operator.     

Graphs with Branchwidth at Most Three

In this paper we investigate both the structure of graphs with branchwidth at most three, as well as algorithms to recognise such graphs. We show that a graph has branchwidth at most three if and only if it has treewidth at most three and does not contain the three-dimensional binary cube graph as a minor. A set of four graphs is shown to be the obstruction set for the class of graphs with branchwidth at most three. Moreover, we give a safe and complete set of reduction rules for the graphs with branchwidth at most three. Using this set, a linear time algorithm is given that verifies if a given graph has branchwidth at most three, and, if so, outputs a minimum width branch decomposition.     

N指标d维广义Wiener过程的极性

本文讨论了N指标d维广义Wiener过程的极性,并得到了一个集合为极集的充分必要条件．     

Dulac函数的构造及其应用(Ⅰ)

本文研究（Ⅰ）和（Ⅱ）类系统Dulac函数的构造问题,作为应用,讨论此两类系统的极限环的不存在性问题,得到了一些新结果．     

A Technique for Stochastic Control Problems with Unbounded Control Set

We describe a change of time technique for stochastic control problems with unbounded control set. We demonstrate the technique on a class of maximization problems that do not have optimal controls. Given such a problem, we introduce an extended problem which has the same value function as the original problem and for which there exist optimal controls that are expressible in simple terms. This device yields a natural sequence of suboptimal controls for the original problem. By this we mean a sequence of controls for which the payoff functions approach the value function.     

Strong Cardinals and Sets of Reals in Lω1(ℝ)

We generalize results of [3] and [1] to hyperprojective sets of reals, viz. to more than finitely many strong cardinals being involved. We show, for example, that if every set of reals in L_ω (?) is weakly homogeneously Souslin, then there is an inner model with an inaccessible limit of strong cardinals.     

On a Class of Recursively Enumerable Sets

We define a class of so-called ∑(n)-sets as a natural closure of recursively enumerable sets W_n under the relation “∈” and study its properties.     

软代数的表示定理

本文研究了集对代数,证明了集对代数是Ｆｕｚｙ格。通过引入强素理想与强素滤的概念,证明了软代数的表示定理：定义了至多只有一个不动点的复原映射的格为软代数的充要条件是它具有同构集对表示。由表示定理可得任一软代数都具有集对表示     

非紧域上集值映象的重合点与不动点

在赋范线性空间的非空非紧凸集上建立了集值映象对的一个重合点定理,然后用这一定理改进了文献［１］中的集值映象内向集定理与外向集定理,并得到几个集值映象不动点定理．     

盒维数的一个等价定义及其应用

给出了盒维数的一个等价定义．该定义与盒维数的现有定义相比,从理论上更容易验证,在应用中更适合于数值计算．据此给出了计算盒维数的一个数值算法．