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Kyungpook mathematical journal
Journal Basic Information
pISSN :
1225-6951
eISSN :
0454-8124
Journal DOI :
10.5666/KMJ
Frequency :
Others
Publisher:
Department of Mathematics, Kyungpook National University
Editor in Chief :
Sang-Dong Kim
Volume & Issues
Volume 47, Issue 4 - Dec 2007
Volume 47, Issue 3 - Sep 2007
Volume 47, Issue 2 - Jun 2007
Volume 47, Issue 1 - Mar 2007
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1
Oscillation and Nonoscillation of Nonlinear Neutral Delay Differential Equations with Several Positive and Negative Coefficients
Elabbasy, Elmetwally M. ; Hassan, Taher S. ; Saker, Samir H. ;
Kyungpook mathematical journal, volume 47, issue 1, 2007, Pages 1~20
Abstract
In this paper, oscillation and nonoscillation criteria are established for nonlinear neutral delay differential equations with several positive and negative coefficients
. Our criteria improve and extend many results known in the literature. In addition we prove that under appropriate hypotheses, if every solution of the associated linear equation with constant coefficients,
, oscillates, then every solution of the nonlinear equation also oscillates.
2
On Semicommutative Modules and Rings
Agayev, Nazim ; Harmanci, Abdullah ;
Kyungpook mathematical journal, volume 47, issue 1, 2007, Pages 21~30
Abstract
We say a module
a semicommutative module if for any
and any
,
implies
. This paper gives various properties of reduced, Armendariz, Baer, Quasi-Baer, p.p. and p.q.-Baer rings to extend to modules. In addition we also prove, for a p.p.-ring R, R is semicommutative iff R is Armendariz. Let R be an abelian ring and
be a p.p.-module, then
is a semicommutative module iff
is an Armendariz module. For any ring R, R is semicommutative iff A(R,
) is semicommutative. Let R be a reduced ring, it is shown that for number
and
,
is semicommutative ring but
is not.
3
Stability and Optimal Harvesting in Lotka-Volterra Competition Model for Two-species with Stage Structure
Al-Omari, J.F.M. ;
Kyungpook mathematical journal, volume 47, issue 1, 2007, Pages 31~56
Abstract
In this paper, we consider a delay differential equation model of two competing species with harvesting of the mature and immature members of each species. The time delay in the model represents the time from birth to maturity of that species, which appears in the adults recruitment terms. We study the dynamics of our model analytically and we present results on positivity and boundedness of the solution, conditions for the existence and globally asymptotically stable of equilibria, a threshold of harvesting, and the optimal harvesting of the mature populations of each species.
4
Meromorphic Functions with Weighted Sharing of One Set
Alzahary, Thamir C. ;
Kyungpook mathematical journal, volume 47, issue 1, 2007, Pages 57~68
Abstract
In this article, we investigate the problem of uniqueness of meromorphic functions sharing one set and having deficient values, and obtain a result which improves some earlier results.
5
On the Stability of Orthogonally Cubic Functional Equations
Baak, Choonkil ; Moslehian, Mohammad Sal ;
Kyungpook mathematical journal, volume 47, issue 1, 2007, Pages 69~76
Abstract
Let
denote a mapping from an orthogonality space (
,
) into a real Banach space
. In this paper, we prove the Hyers-Ulam-Rassias stability of the orthogonally cubic functional equations
and
, where
,
,
.
6
A Note on the Spectral Mapping Theorem
Jung, Il Bong ; Ko, Eungil ; Pearcy, Carl ;
Kyungpook mathematical journal, volume 47, issue 1, 2007, Pages 77~79
Abstract
In this note we point out how a theorem of Gamelin and Garnett from function theory can be used to establish a spectral mapping theorem for an arbitrary contraction and an associated class of
-functions.
7
Stability of Iterative Sequences Approximating Common Fixed Point for a System of Asymptotically Quasi-nonexpansive Type Mappings
Li, Jun ; Huang, Nan-Jing ; Cho, Yeol Je ;
Kyungpook mathematical journal, volume 47, issue 1, 2007, Pages 81~89
Abstract
In this paper, we introduce the concept of a system of asymptotically quasinonexpansive type mappings. Furthermore, we define a
-step iterative sequence approximating common fixed point for a system of asymptotically quasi-nonexpansive type mappings and study its stability in real Banach spaces.
8
A Generalization of the Hyers-Ulam-Rassias Stability of the Pexiderized Quadratic Equations, II
Jun, Kil-Woung ; Lee, Yang-Hi ;
Kyungpook mathematical journal, volume 47, issue 1, 2007, Pages 91~103
Abstract
In this paper we prove the Hyers-Ulam-Rassias stability by considering the cases that the approximate remainder
is defined by
,
, where (G, *) is a group, X is a real or complex Hausdorff topological vector space and f, g, h, k are functions from G into X.
9
New Two-Weight Imbedding Inequalities for
-Harmonic Tensors
Gao, Hongya ; Chen, Yanmin ; Chu, Yuming ;
Kyungpook mathematical journal, volume 47, issue 1, 2007, Pages 105~118
Abstract
In this paper, we first define a new kind of two-weight-
-weight, and then prove the imbedding inequalities for
-harmonic tensors. These results can be used to study the weighted norms of the homotopy operator T from the Banach space
to the Sobolev space
,
, and to establish the basic weighted
-estimates for
-harmonic tensors.
10
Linear Derivations Satisfying a Functional Equation on Semisimple Banach Algebras
Jung, Yong-Soo ; Chang, Ick-Soon ;
Kyungpook mathematical journal, volume 47, issue 1, 2007, Pages 119~125
Abstract
In this paper, we investigate the following: Let A be a semisimple Banach algebra. Suppose that there exists a linear derivation
such that the functional equation
<
>
holds for all
. Then we have
on A.
11
PF-rings of Generalized Power Series
Kim, Hwankoo ; Kwon, Tae In ;
Kyungpook mathematical journal, volume 47, issue 1, 2007, Pages 127~132
Abstract
In this paper, we show that if R is a commutative ring with identity and (S,
) is a strictly totally ordered monoid, then the ring [[
]] of generalized power series is a PF-ring if and only if for any two S-indexed subsets A and B of R such that
, there exists
such that
for all
, and that for a Noetherian ring R,
]] is a PP ring if and only if R is a PP ring.
12
Metric and Spectral Geometric Means on Symmetric Cones
Lee, Hosoo ; Lim, Yongdo ;
Kyungpook mathematical journal, volume 47, issue 1, 2007, Pages 133~150
Abstract
In a development of efficient primal-dual interior-points algorithms for self-scaled convex programming problems, one of the important properties of such cones is the existence and uniqueness of "scaling points". In this paper through the identification of scaling points with the notion of "(metric) geometric means" on symmetric cones, we extend several well-known matrix inequalities (the classical L
wner-Heinz inequality, Ando inequality, Jensen inequality, Furuta inequality) to symmetric cones. We also develop a theory of spectral geometric means on symmetric cones which has recently appeared in matrix theory and in the linear monotone complementarity problem for domains associated to symmetric cones. We derive Nesterov-Todd inequality using the spectral property of spectral geometric means on symmetric cones.
13
Note on σ-derivations in Near-rings and Reduced Near-rings
Asokkumar, Arjunan ;
Kyungpook mathematical journal, volume 47, issue 1, 2007, Pages 151~154
Abstract
We study
-derivations on reduced near-rings and extend certain results on derivations to
-derivations with some conditions.