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Vol.15 No.3

Jin, Dae-Ho pp.209-215
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Abstract

The purpose of this paper is to study the geometry of null Bertrand curves in a Lorentz manifold.

Jun, Sook-Heui pp.217-220
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Abstract

In this paper, we investigate the harmonic mappings that arise in connection with Scherk's surface and helicoid.

Min, Won-Keun pp.221-227
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Abstract

We introduce and study the new concepts of interior and closure operators on strong generalized neighborhood spaces. Also we introduce and investigate the concept of sgn-continuity on SGNS.

Choi, Su-Jeong pp.229-243
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Abstract

This paper is intended to clarify and verify two representation algorithms computing representations of elements of free groups generated by two linear fractional transformations. Moreover in practice some parts of the two algorithms are modified for computational efficiency. In particular the justification of the algorithms has been rigorously done by showing how both algorithms work correctly and efficiently according to inputs with some properties of the two linear fractional transformations.

Kwun, Young-Chel ; Park, So-Hyun ; Park, Dong-Gun ; Park, Jong-Seo pp.245-257
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Abstract

In this paper, we find the sufficient conditions of controllability of semi-linear neutral functional differential evolution equations with non local conditions using by fractional power of operators and Sadovskii's fixed point theorem.

Kim, Byung-Do pp.259-296
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Abstract

Let A be a noncommutative Banach algebra. Suppose there exists a continuous linear Jordan derivation D : A <TEX>$\rightarrow$</TEX> A such that <TEX>$D(x)^2$</TEX>[D(x),x] <TEX>$\in$</TEX> rad(A) or [D(x),x]<TEX>$D(x)^2$</TEX> <TEX>$\in$</TEX> rad(A) for all x <TEX>$\in$</TEX> A. In this case, we have D(A) <TEX>$\subseteq$</TEX> rad(A).

Lee, Kyoung-Ja ; So, Keum-Sook ; Bang, Keum-Seong pp.297-308
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Abstract

The notions of vague BCK/BCI-algebras and vague ideals are introduced, and their properties are investigated. Conditions for a vague set to be a vague ideal are provided. Characterizations of a vague ideal are established.

Jun, Young-Bae ; Park, Chul-Hwan pp.309-313
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Abstract

The notion of central Hilbert algebras and central deductive systems is introduced, and related properties are investigated. We show that the central part of a Hilbert algebra is a deductive system. Conditions for a subset of a Hilbert algebra to be a deductive system are given. Conditions for a subalgebra of a Hilbert algebra to be a deductive system are provided.

Park, Chun-Kee ; Oh, Mee-Na pp.315-327
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Abstract

In this paper we introduce the concepts of <TEX>$Denjoy_*$</TEX>-Stieltjes-Dunford, <TEX>$Denjoy_*$</TEX>-Stieltjes-Pettis, <TEX>$Denjoy_*$</TEX>-Stieltjes-Bochner and <TEX>$Denjoy_*$</TEX>-McShane-Stieltjes integrals of Banach-valued functions using the <TEX>$Denjoy_*$</TEX>-Stieltjes integral of real-valued functions and investigate their properties.

Shin, Seong-A pp.329-342
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Abstract

There have been many experimental and observational evidences which indicate the predator response to prey density needs not always monotone increasing as in the classical predator-prey models in population dynamics. Holling type functional response depicts situations in which sufficiently large number of the prey species increases their ability to defend or disguise themselves from the predator. In this paper we investigated the stability and instability property for a Holling type predator-prey system of a generalized form. Hopf type bifurcation properties of the non-diffusive system and the diffusion effects on instability and bifurcation values are studied.

Park, Jae-Myung ; Kim, Byung-Moo ; Kim, Young-Kuk pp.343-351
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Abstract

In this paper, we define the Denjoy and ap-Denjoy integrals of Banach-valued functions, and we investigate some properties of these two integrals. In particular, we show that a Denjoy integrable function is ap-Denjoy integrable.

Journal of the Korean Society of Mathematical Education Series B: The Pure and Applied Mathematics