• 한국지능시스템학회논문지
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• 제15권4호
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• pp.514-519
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• 2005

We define extensional spaces. Moreover, we investigate the relations among T-upper-approximation spaces, T-quasi -equivalence relations and extensional spaces.

• 충청수학회지
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• 제29권1호
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• pp.177-186
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• 2016

For a map $f:A{\rightarrow}X$, there are concepts of $H^f$-spaces, $T^f$-spaces, which are generalized ones of H-spaces [17,18]. In general, Any H-space is an $H^f$-space, any $H^f$-space is a $T^f$-space. For a principal fibration $E_k{\rightarrow}X$ induced by $k:X{\rightarrow}X^{\prime}$ from ${\epsilon}:PX^{\prime}{\rightarrow}X^{\prime}$, we obtain some sufficient conditions to having liftings $H^{\bar{f}}$-structures and $T^{\bar{f}}$-structures on $E_k$ of $H^f$-structures and $T^f$-structures on X respectively. We can also obtain some results about $H^f$-spaces and $T^f$-spaces in Postnikov systems for spaces, which are generalizations of Kahn's result about H-spaces.

• 대한수학회논문집
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• 제14권2호
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• pp.393-403
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• 1999

Some fuzzy T\ulcorner-axioms are characterized in terms of the notion of fuzzy closure and the relationship between those fuzzy T\ulcorner-axioms are obtained. Also, finite fuzzy topological spaces satisfying one of those axioms are studied.

• 충청수학회지
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• 제30권1호
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• pp.129-139
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• 2017

For a map $p:X{\rightarrow}A$, there are concepts of co-$H^p$-spaces, co-$T^p$-spaces, which are generalized ones of co-H-spaces [17,18]. For a principal cofibration $i_r:X{\rightarrow}C_r$ induced by $r:X^{\prime}{\rightarrow}X$ from $\imath:X^{\prime}{\rightarrow}cX^{\prime}$, we obtain some sufficient conditions to having extensions co-$H^{\bar{p}}$-structures and co-$T^{\bar{p}}$-structures on $C_r$ of co-$H^p$-spaces and co-$T^p$-structures on X respectively. We can also obtain some results about co-$H^p$-spaces and co-$T^p$-spaces in homology decompositions for spaces, which are generalizations of Golasinski and Klein's result about co-H-spaces.

• Korean Journal of Mathematics
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• 제31권4호
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• pp.479-484
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• 2023

In this paper, we introduce the concept of a generalized derived set in generalized topological spaces and we investigate its properties. Using these, we study T_D-spaces in generalized topological spaces.

• Korean Journal of Mathematics
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• 제26권4호
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• pp.709-727
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• 2018

Here we have studied the ideas of $g^*$-closed sets, $g{\bigwedge}_{{\tau}^-}$ sets and ${\lambda}^*$-closed sets and investigate some of their properties in the spaces of A. D. Alexandroff [1]. We have also studied some separation axioms like $T_{\frac{\omega}{4}}$, $T_{\frac{3\omega}{8}}$, $T_{\omega}$ in Alexandroff spaces and also have introduced a new separation axiom namely $T_{\frac{5\omega}{8}}$ axiom in this space.

• 호남수학학술지
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• 제29권1호
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• pp.41-54
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• 2007

In this paper, we introduce the notion of $g{\cdot}{\gamma}$-closed sets and study its basic properties. Also we introduce the notion of ${\gamma}-T_*$ spaces and investigate relationships among these spaces and ${\gamma}-T_i$ spaces (i = 0,1/2,1) due to Ogata [5].

• 대한수학회보
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• 제35권2호
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• pp.311-317
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• 1998

For Hilbert spaces H, K, a compact operator T: H $\rightarrow$ K, and column, row, operator Hilbert spaces $H_c,\;K_c,\;H_r,\;K_r,\;H_o, K_o$,we show that ${\parallel}T_{co}{\parallel}_{cb}={\parallel}T_{ro}{\parallel}_{cb}={\parallel}T_{oc}{\parallel}_{cb}={\parallel}T_{or}{\parallel}_{cb}={\parallel}T{\parallel}_4$.

• Korean Journal of Mathematics
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• 제6권2호
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• pp.155-164
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• 1998

In this paper, the fuzzy $T_2$-axioms due to Hutton and Reilly, Ganguly and Saha and Sinha are characterized by using the notion of fuzzy closure. As consequences, we study the relation between the fuzzy $T_2$-axioms and give some examples which show that the axiom of fuzzy compactness, due to Ganguly and Saha, is not compatible with the fuzzy $T_2$-axioms.

• 호남수학학술지
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• 제27권1호
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• pp.101-113
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• 2005

We define and study a concept of $T_A$-space which is closely related to the generalized Gottlieb group. We know that X is a $T_A$-space if and only if there is a map $r:L(A,\;X){\rightarrow}L_0(A,\;X)$ called a $T_A$-structure such that $ri{\sim}1_{L_0(A,\;X)}$. The concepts of $T_{{\Sigma}B}$-spaces are preserved by retraction and product. We also introduce and study a dual concept of $T_A$-space.