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Dive into the research topics where Nam Jip Koo is active.

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Featured researches published by Nam Jip Koo.


Computers & Mathematics With Applications | 2003

Asymptotic equivalence between two difference systems

Sung Kyu Choi; Nam Jip Koo; Hyun Sook Ryu

Abstract In this paper, we study the asymptotic equivalence between the linear system Δx ( n ) = A ( n ) x ( n ) and its perturbation Δy ( n ) = A ( n ) y ( n )+ g ( n , y ( n )) by using the comparison principle and supplementary projections. Furthermore, we establish some asymptotic properties for the nonlinear system Δx ( n ) = f ( n , x ( n )).


Computers & Mathematics With Applications | 2004

Asymptotic equivalence between two linear volterra difference systems

Sung Kyu Choi; Nam Jip Koo

Abstract We study asymptotic equivalence between the solutions of linear Volterra difference system x(n+1)=A(n)x(n)+ ∑ s=n 0 n B(n,s)x(s) and its perturbed system y(n+1)=A(n)y(n)+ ∑ s=n 0 n B(n,s)y(s)+F(n)


Applied Mathematics Letters | 2005

Asymptotic property in variation for nonlinear differential systems

Sung Kyu Choi; Nam Jip Koo; S. Dontha

For nonlinear differential systems, we investigate that the two concepts of the asymptotic equivalence and asymptotic equivalence in variation are equivalent under the conditions of strong stability and t∞-similarity, and give some examples.


Computers & Mathematics With Applications | 2001

The oscillation of partial difference equations with continuous arguments

Sung Kyu Choi; Nam Jip Koo; Binggen Zhang

Abstract For the partial difference equations and we shall obtain sufficient conditions for the oscillation of all solutions of these equations.


Bulletin of The Korean Mathematical Society | 2007

ASYMPTOTIC BEHAVIOR OF NONLINEAR VOLTERRA DIFFERENCE SYSTEMS

Sung Kyu Choi; Yoon Hoe Goo; Nam Jip Koo

We study the asymptotic behavior of nonlinear Volterra difference system x(n + 1) = f(n, x(n)) + n ∑ s=n0 g(n, s, x(s)), x(n0) = x0 by using the resolvent matrix R(n, m) of the corresponding linear Volterra system and the comparison principle.


Bulletin of The Korean Mathematical Society | 2005

ASYMPTOTIC EQUIVALENCE BETWEEN LINEAR DIFFERENTIAL SYSTEMS

Sung Kyu Choi; Nam Jip Koo; Dong Man Im

We study the strong stability for linear difierential sys- tems in connection with t1-similarity, and investigate the asymp- totic equivalence between linear difierential systems.


Bulletin of The Korean Mathematical Society | 2002

h-STABILITY OF PERTURBED VOLTERRA DIFFERENCE SYSTEMS

Sung Kyu Choi; Nam Jip Koo; Yoon Hoe Goo

We discuss the h-stability of perturbed Volterra dif- ference systems by means of the resolvent matrix and discrete in- equalities.


Journal of Mathematical Analysis and Applications | 2000

Variationally Stable Difference Systems by n∞-Similarity☆☆☆

Sung Kyu Choi; Nam Jip Koo


Journal of Mathematical Analysis and Applications | 2001

Variationally stable difference systems

Sung Kyu Choi; Nam Jip Koo; Yoon Hoe Goo


Journal of Mathematical Analysis and Applications | 2006

Asymptotic property of linear Volterra difference systems

Sung Kyu Choi; Nam Jip Koo

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Sung Kyu Choi

Chungnam National University

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Hyun Sook Ryu

Chungnam National University

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S. Dontha

Florida Institute of Technology

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