• Journal of applied mathematics & informatics
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• v.9 no.2
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• pp.531-542
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• 2002

In this paper we deal with a sequence of positive linear operators ${{R_n}}^{[$\beta$]}$ approximating functions on the unbounded interval [0, $\infty$] which were firstly used by K. balazs and J. Szabados. We give pointwise estimates in the framework of polynomial weighted function spaces. Also we establish a Voronovskaja type theorem in the same weighted spaces for ${{K_n}}^{[$\beta$]}$ operators, representing the integral generalization in Kantorovich sense of the ${{R_n}}^{[$\beta$]}$.

• Proceedings of the Korea Multimedia Society Conference
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• 2002.11b
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• pp.716-719
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• 2002

이 연구의 목적은 근래에 초등학교 수학과 교육과정의 도형영역에 새로이 도입된 '공간감각'을 기르기 위한 웹 코스웨어를 개발하여 단순히 교과서에만 제시된 구체물 조작만으로는 기르기 힘든 공간감각을 기르는데 있다. 개발된 코스웨어는 학습내용을 수준별로 구성하고 있어 바로 학습 현장에 투입하여 수준별 학습, 개별화 학습을 실현할 수 있도록 하였다. 또한 초등학교 저학년에게 구체물로서는 조작할 수 없는 것들을 다양한 애니메이션 기법을 통하여 직접 조작해 볼 수 있도록 하고, 재미있는 놀이를 학습에 적절히 활용함으로써 학습 흥미도를 높이고자 하였다.

• Communications of the Korean Mathematical Society
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• v.27 no.3
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• pp.523-535
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• 2012

In this paper, we investigate a fuzzy version of stability for the functional equation $$2f(x+y)+f(x-y)+f(y-x)-3f(x)-f(-x)-3f(y)-f(-y)=0$$ in the sense of M. Mirmostafaee and M. S. Moslehian.

• Journal of the Korean Institute of Intelligent Systems
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• v.16 no.1
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• pp.108-112
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• 2006

In this paper, we investigate some characterizing theorems for fuzzy (r,s)-semicontinuous, (r,s)-semiopen and (r,s)-semiclosed mappings on the intuitionistic fuzzy topological space in $\eseck{S}ostak's$ sense.

• Publications of The Korean Astronomical Society
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• v.8 no.1
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• pp.199-206
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• 1993

We review recent systematic investigation of the X-ray spectra of early type galaxies by using the Einstein data base and present new results by the ROSAT observations. The Einstein data suggested that the galaxies with low X-ray to optical luminosity ratio may have another very soft component. ROSAT observations confirm its presence and call for further study to understand the nature of this very soft emission. The X-ray bright galaxies have emission temperature of ${\sim}\;0.8\;keV$ and show radial gradients in the sense that X-ray emission is softer and more absorbed in the inner region.

• Journal of applied mathematics & informatics
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• v.29 no.3_4
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• pp.713-719
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• 2011

The problem of approximation from a set of scattered data arises in a wide range of applied mathematics and scientific applications. In this study, we present a quasi-interpolatory approximation scheme for scattered data approximation problem, which reproduces a certain space of polynomials. The proposed scheme is local in the sense that for an evaluation point, the contribution of a data value to the approximating value is decreasing rapidly as the distance between two data points is increasing.

• Journal of the Korean Mathematical Society
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• v.47 no.1
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• pp.41-62
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• 2010

In this article, we discuss a Grobner basis algorithm related to the stability of algebraic varieties in the sense of Geometric Invariant Theory. We implement the algorithm with Macaulay 2 and use it to prove the stability of certain curves that play an important role in the log minimal model program for the moduli space of curves.

• The Journal of the Acoustical Society of Korea
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• v.17 no.4E
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• pp.22-27
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• 1998

A modified perturbation method is proposed to optimize the beam pattern of thinned microphone arrays. Both microphone spacing and array weight are iteratively adjusted via successive perturbation to achieve an optimum beam pattern in a Dolph Chebyshev sense. To improve the sidelobe performance, an alternative perturbation with respect to microphone spacing and array weight is implemented. Also, a linear space-tapering is employed in the perturbation process. It is demonstrated that the proposed approaches successfully yield sidelobe performances comparable to that of a normal array. Computer simulation results are presented.

• Bulletin of the Korean Mathematical Society
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• v.28 no.2
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• pp.243-254
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• 1991

For a given function f.mem.F and a set of functions J.subeq.F, the problem of isotonic optimization is to determine an element in the set nearest to f in some sense. Specifically, let X be a partially ordered finite set with a partial order << and, let F"=F(X) be the linear space of all bounded real valued functions on X. A function g.mem.F is said to be an isotonic function if g(x).leq.g(y) whenever x,y.mem.X and x << y.<< y.

• Bulletin of the Korean Mathematical Society
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• v.55 no.5
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• pp.1599-1619
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• 2018

In this paper we study the initial value problem of the non-relativistic Vlasov-Darwin system with generalized variables (VDG). We first prove local existence and uniqueness of a nonnegative classical solution to VDG in three space variables, and establish the blow-up criterion. Then we show that it converges to the well-known Vlasov-Poisson system when the light velocity c tends to infinity in a pointwise sense.