Fréchet拟基与度量空间的闭映象

本文利用林寿引入的Frechet拟基的概念,获得了度量空间的确定闭映象和局部可度量空间的确定闭映象的一些新的刻画,     

局部可分度量空间的序列覆盖局部可数象

本文给出了局部可分度量空间的序列复盖局部可数象的刻画。     

一致覆盖和度量空间的紧映象

本文利用一致覆盖的概念,讨论了度量空间的序列覆盖紧映象的结构.主要结果有: (1)空间X是局部可分度量空间的序列覆盖紧映象当且仅当X具有由cosmic子空间构成的一致sn网; (2)空间X是局部可分度量空间的序列覆盖,商紧映象当且仅当X是度量空间的序列覆盖,商紧映象且是局部cosmic空间.     

Paracompact locally Lindelöf spaces and <Emphasis Type=”Italic”>L</Emphasis>-systems

Summary We establish relationships between paracompact locally Lindel&ouml;f spaces and all kinds of spaces with L-systems by means of closed mappings, weakly perfect mappings and quotient mappings. In particular, we obtain some characterizations of paracompact locally Lindel&ouml;f spaces. Interestingly, they are also characterized as weakly perfect inverse images of locally separable metric spaces.     

关于点可数覆盖

本文证明了（１）具有点可数基空间的商ｓ－像Ｘ有点可数基的充要条件是Ｘ是ｑ－空间；（２）度量空间的伪开ｓ－像若满足条件（＊），则它在伪开ｓ－映射下是保持的，（３）给出反例否定地回答了［１］和［２］中的问题．     

k-COVERS AND CERTAIN QUOTIENT IMAGES OF PARACOMPACT LOCALLY COMPACT SPACES

We continue to discuss some properties of certain k-covers. As applications, we give some characterizations of certain quotient images of paracompact locally compact spaces.     

关于序列覆盖π映射

本文利用点星网的概念,讨论了度量空间的π映象的性质,建立了度量空间的序列商π映象和度量空间的序列覆盖π映象的内在特征,分别推广了 Kofner J、A.和 Tanaka Y.的一些结果.     

局部可分度量空间的伪序列覆盖映射

指出了文[1]中的一个问题,并给出了局部可分度量空间的伪序列覆盖s映象和局部可分度量空间的伪序列覆盖紧映象的刻划。     

k-systems, k-networks and k-covers

The concepts of k-systems, k-networks and k-covers were defined by A. Arhangel’skii in 1964, P. O’Meara in 1971 and R. McCoy, I. Ntantu in 1985, respectively. In this paper the relationships among k-systems, k-networks and k-covers are further discussed and are established by mk-systems. As applications, some new characterizations of quotients or closed images of locally compact metric spaces are given by means of mk-systems.     

A Note On g-Metrizable Spaces

In this paper, the relationships between metric spaces and g-metrizable spaces are established in terms of certain quotient mappings, which is an answer to Alexandroff's problems.