• Communications of the Korean Mathematical Society
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• v.29 no.1
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• pp.195-204
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• 2014

We consider a functional difference equation and use fixed point theory to analyze the stability of its zero solution. In particular, our study focuses on the nonlinear delay functional difference equation x(t + 1) = a(t)g(x(t - r)).

• Bulletin of the Korean Mathematical Society
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• v.51 no.2
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• pp.539-545
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• 2014

We show that roots of log-concave Alexander knot polynomials are dense in C. This in particular implies that the log-concavity and Hoste's conjecture on the Alexander polynomial of alternating knots are (essentially) independent.

• Korean Journal of Mathematics
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• v.10 no.1
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• pp.25-28
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• 2002

We introduce the notion of $s{\gamma}$-sets, and we investigate some properties of $s{\gamma}$-sets. In particular, we characterize the $s{\gamma}$-closure by terms of supra-convergence of filters.

• Korean Journal of Mathematics
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• v.7 no.1
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• pp.11-25
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• 1999

We will define a smooth fuzzy closure space and a subspace of it. We will investigate relationships between smooth fuzzy closure spaces and smooth fuzzy topological spaces. In particular, we will show that a subspace of a smooth fuzzy topological space can be obtained by the subspace of the smooth fuzzy closure space induced by it.

• Communications of the Korean Mathematical Society
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• v.10 no.1
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• pp.187-194
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• 1995

We are to present some properties of binary relations by means of categorical method. The concept of semi-topogenous structures is due to Cs$\acute{a}$sz$\acute{a}$r. Using this, we give a new definition of a $\sigma$-topogenous structure as a particular type of semi-topogenous structure.

• Communications of the Korean Mathematical Society
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• v.11 no.2
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• pp.407-413
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• 1996

The $(\alpha, \beta)$-metric is a Finsler metric which is constructed from a Riemannian metric $\alpha$ and a differential 1-form $\Beta$; it has been sometimes treat in theoretical physics. In particular, the projective flatness of Finsler space with a metric $L^2 = 2\alpha\beta$ is considered in detail.

• Journal of the Korean Mathematical Society
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• v.48 no.4
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• pp.703-725
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• 2011

In this paper, we establish the vector-valued inequalities for the commutators of singular integrals with rough kernels. In particular, our results can essentially improve some well-known results.

• Bulletin of the Korean Mathematical Society
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• v.51 no.4
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• pp.1211-1216
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• 2014

In this paper, we study the structure of m-quasi Einstein manifolds when there exists another distinct solution to the (${\lambda}$, n + m)-Einstein equation. In particular, we derive sufficient conditions for the non-existence of such solutions.

• Communications of the Korean Mathematical Society
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• v.33 no.3
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• pp.1001-1011
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• 2018

We introduce some variants of the finite Ramsey theorem. The variants are based on a refinement of homogeneity. In particular, they cover homogeneity, minimal homogeneity, end-homogeneity as special cases. We also show how to obtain upper bounds for the corresponding Ramsey numbers.

• Korean Journal of Mathematics
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• v.4 no.1
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• pp.77-82
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• 1996

We introduce the concepts of fuzzy $s$-continuous functions. And we investigate several properties of the fuzzy $s$-continuous function. In particular, we study the relation between fuzzy continuous functions and fuzzy $s$-continuous functions.