• Kyungpook Mathematical Journal
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• v.32 no.1
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• pp.31-43
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• 1992

• Kyungpook Mathematical Journal
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• v.27 no.2
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• pp.127-134
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• 1987

The purpose of this paper is to introduce a topological space named an F-closed space. This space is properly contained between an S-closed space [17] and a quasi H-closed space [14], and between a nearly compact space [15] and a quasi H-closed space. We will investigate properties of F-closed spaces, and improve some results in [2], [7] and [17].

• Bulletin of the Korean Mathematical Society
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• v.20 no.2
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• pp.95-97
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• 1983

In this paper, we show a necessary and sufficient condition for QHC spaces to be S-closed. T. Thomson introduced S-closed spaces in [2]. A topological space X is said to be S-closed if every semi-open cover of X admits a finite subfamily such that the closures of whose members cover the space, where a set A is semi-open if and only if there exists an open set U such that U.contnd.A.contnd.Cl U. A topological space X is quasi-H-closed (denote QHC) if every open cover has a finite subfamily whose closures cover the space. If a topological space X is Hausdorff and QHC, then X is H-closed. It is obvious that every S-closed space is QHC but the converse is not true [2]. In [1], Cameron proved that an extremally disconnected QHC space is S-closed. But S-closed spaces are not necessarily extremally disconnected. Therefore we want to find a necessary and sufficient condition for QHC spaces to be S-closed. A topological space X is said to be semi-locally S-closed if each point of X has a S-closed open neighborhood. Of course, a locally S-closed space is semi-locally S-closed.

• Journal of the Chungcheong Mathematical Society
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• v.1 no.1
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• pp.55-64
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• 1988

We introduce the concept of a w-Lindel$\ddot{o}$f space which is a more general concept than that of a Lindel$\ddot{o}$f spaces. We obtain some characterization about H-closed sapces and w-Lindel$\ddot{o}$f spaces. Also, we investigate their invariance properties.

• Journal of applied mathematics & informatics
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• v.11 no.1_2
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• pp.379-384
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• 2003

In this paper, we obtain a topology $\tau\delta$ on X. From this topology, we obtain some characterizations of if-closed spaces.

• Bulletin of the Korean Mathematical Society
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• v.23 no.2
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• pp.91-102
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• 1986

A topological space (X,.tau.) is called invertible [7] if for each proper open set U in (X,.tau.) there exists a homoemorphsim h:(X,.tau.).rarw.(X,.tau.) such that h(X-U).contnd.U. Doyle and Hocking [7] and Levine [13], as well as others have investigated properties of invertible spaces. Recently, Crosseley and Hildebrand [5] have introduced the concept of semi-invertibility, which is weaker than that of invertibility, by replacing "homemorphism" in the definition of invertibility with "semihomemorphism", A space (X,.tau.) is said to be semi-invertible if for each proper semi-open set U in (X,.tau.) there exists a semihomemorphism h:(X,.tau.).rarw.(X,.tau.) such that h(X-U).contnd.U. The purpose of the present article is to introduce the class of almost-invertible spaces containing the class of semi-invertible spaces and to investigate its properties. One of the primary concerns will be to determine when a given local property in an almost-invertible space is also a global property. We point out that many of the results obtained can be applied in the cases of semi-invertible spaces and invertible spaces. For example, it is shown that if an invertible space (X,.tau.) has a nonempty open subset U which is, as a subspace, H-closed (resp. lightly compact, pseudocompact, S-closed, Urysohn, Urysohn-closed, extremally disconnected), then so is (X,.tau.).hen so is (X,.tau.).

• The Mathematical Education
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• v.14 no.1
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• pp.11-12
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• 1975

L. Herrington과 P.E. Long이 서술한 H-closed Space에 대해서 성질 즉 H-closed Space의 연속이고 전사인 상은 H-closed Space가 된다는 사실과 그외 몇가지 성질을 조사 했다.

• Communications of the Korean Mathematical Society
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• v.10 no.2
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• pp.325-330
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• 1995

In this paper we obtain some fixed point theorems on H-spaces by using H-KKM theorems.

• Journal of the Korean Institute of Intelligent Systems
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• v.11 no.3
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• pp.280-285
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• 2001

We introduce the new concepts of some fuzzy continuous and closed mappings and study their properties. Also we investigate the properties of fuzzy mildly normal spaces.

• Journal of the Korean Institute of Intelligent Systems
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• v.3 no.3
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• pp.19-26
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• 1993

In this paper, we introduce the notion of H-fuzzy esmitopogenous spaces. In section 1, we give the preliminary definitions and some basic results. In section 2, we show that category HFS of H-fuzzy semitiopogenous spaces and continuous maps between them is topological and cotopological. Using ordinary operations, we characterize coreflective subcatgories and then show that each of Top, Prox, Qunif, and Unig is isomorphic with some coreflective subcategory of HFS. Moreover, we show that sa-HFS is closed under the formation of initial sources in a-HFS, whewe a is a symmetrical elementary operation.