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Showing papers in "Kyungpook Mathematical Journal in 1996"


Journal Article
TL;DR: Using the Galois connection between submodules of Horn (M, N) and N, this paper proved that if M is quasi-projective right R-module, then corank, where A is the endomorphism ring of.
Abstract: Using the Galois connection between submodules of Horn (M, N) and N, we can prove that if M is quasi-projective right R-module, then corank , where A is the endomorphism ring of .

35 citations




Journal Article
TL;DR: In this article, by using regular g-closed sets, the authors obtained a characterization of normal spaces and used it to improve the preservation theorems of mildly normal spaces established in [1] and [8].
Abstract: In this paper, by using regular g-closed sets we obtain a characterization of mildly normal spaces and use it to improve the preservation theorems of mildly normal spaces established in [1] and [8].

21 citations





Journal Article
TL;DR: In this paper, the authors study an 3D Minkowski space and classify ruled surfaces satisfying the condition for the Lorentz version of the problem for 3D ruled surfaces.
Abstract: We study an 3-dimensional Minkowski space and classify ruled surfaces satisfying the condition for the Lorentz version.

11 citations


Journal Article

10 citations


Journal Article
TL;DR: In this article, weak forms of continuity and closure are introduced and used to strengthen several results in the literature concerning the preservation of g-closed sets, which are used in this paper.
Abstract: New weak forms of continuity and closure are introduced and used to strengthen several results in the literature concerning the preservation of g-closed sets.

8 citations


Journal Article
TL;DR: As a continuation to the study of fuzzy quasi-associative ideals in BCI-algebras, this work is devoted to investigating some further properties.
Abstract: As a continuation to the study of fuzzy quasi-associative ideals in BCI-algebras initiated by the present author, this work is devoted to investigating some further properties.

Journal Article
TL;DR: In this paper, a new technique to construct conformal CMC-1 surfaces in the hyperbolic 3-space has been proposed, which induces a conformal pseudometric of curvature 1 on the square torus with conical singularities of nonintegral order.
Abstract: We give a new technique to construct CMC-1 surfaces in the hyperbolic 3-space. Using the technique, we have a new example of conformal CMC-1 immersion of the square torus excluded two points. The example induces a conformal pseudometric of curvature 1 on the square torus with conical singularities of non-integral order.

Journal Article
TL;DR: In this paper, a necessary condition for the oscillation of all solutions of neutral differential equations of odd order is proved and some comparison results are derived along with a sufficient condition for all solutions.
Abstract: A necessary condition for the oscillation of all solutions of neutral differential equations of odd order is proved. A sufficient condition for the oscillation of all solutions is derived along with some comparison results.

Journal Article
TL;DR: In this article, the authors studied the convergence rate of modified Baskakov operators for function of bounded variation, using some results of probability theory, and showed that the convergence of these operators is bounded.
Abstract: In this paper, we study the rate of convergence of modified Baskakov operators for function of bounded variation, using some results of probability theory.

Journal Article
TL;DR: The boundary value problem for a partial differential equation of hyperbolic type with boundary conditions involving generalized fractional integrals and derivatives with the Gauss hypergeometric function in the kernel was studied in this paper.
Abstract: The paper deals with a boundary value problem for a partial differential equation of hyperbolic type with boundary conditions involving generalized fractional integrals and derivatives with the Gauss hypergeometric function in the kernel. By using the properties of the fractional calculus operators in spaces it is shown that this problem can be reduced to a singular integral equation with the Cauchy kernel, and its solvability conditions and a solution in a closed form are given.

Journal Article
TL;DR: In this paper, the notion of prime one-sided ideal was introduced, and it was shown that there is a one-to-one correspondence between the set of all prime right ideals of a semigroup and all prime left ideals of M where M is the left operator semigroup of the semigroup.
Abstract: In this paper we introduce the notion of prime one-sided ideal in S where is a and show that there is a one-to-one correspondence between the set of all prime right ideals of S and the set of all prime right ideals of M where M is the left operator semigroup of the . We also introduce the notions of right Noetherian on S where is a and Noetherian and study it. Lastly we show that a commutative with unities is Noetherian if and only if every prime ideal of S is finitely generated, thus extending a result of Cohen's Theorem [1] for semi group to .

Journal Article
TL;DR: In this paper, a complete classification of real hypersurfaces in complex hyperbolic space on which the sectional curvature of planes is constant is given; see Section 2.1.
Abstract: In this paper we give a complete classification of real hypersurfaces in complex hyperbolic space on which the sectional curvature of planes is constant.

Journal Article
TL;DR: In this paper, it was shown that compact submanifolds of finite type and finite type maps are characterized by a variational minimal principle, where the point of the area-functional is defined by a critical point of all deformations.
Abstract: Let be a class of deformations acting on a compact submanifold M in We say that M satisfies the variational minimal principle in the class if M is a critical point of the area-functional among all deformations of M given by . In this article, we show that compact submanifolds of finite type and finite type maps introduced by the first-named author (cf. [1]) are characterized by a variational minimal principle. Some related results will also be proved.

Journal Article
TL;DR: In this paper, the authors define a scattered Cantor set and investigate the value of its -dimensional Hausdorff measure, which is a special case of the set in the general case.
Abstract: We define a scattered Cantor set and investigate the value of its -dimensional Hausdorff measure.

Journal Article
TL;DR: In this paper, the authors introduce three types of functions called: strongly, strongly-open and strongly closed, and investigate the fundamental properties and effects of strongly on some topological spaces. But their characterizations are estabilished similarities and dissimilarities.
Abstract: Functions between spaces are impotent tools for studing their properties and for constructing new spaces from previously exiting ones. So, several authors have been interested in this subject and hence more sorts of continuous, open and closed functions arise as one goes further in mathematics. Therefore, this paper devoted to introduce three types of functions called: strongly , strongly-open and strongly closed. Some of their characterizations are estabilished similarities and dissimilarities between these new types of functions and other corresponding ones are studied. The fundamental properties and effects of strongly on some topological spaces are investigated.

Journal Article
TL;DR: In this paper, a complete classification of null 2-type surfaces in pseudo-Euclidean 4-space with null mean curvature vector has been given, and a classification of the null 2 -type surfaces with mean curvatures is given.
Abstract: We study null 2-type surfaces in pseudo-Euclidean 4-space and give a complete classification of null 2-type surfaces in with null mean curvature vector

Journal Article
TL;DR: In this article, a notion of 2-compactibility for noncommuting mappings in Menger space to obtain fixed point results is introduced, and a result on best approximation is obtained as application of the above notion.
Abstract: A notion os 2-compactibility is introduced for noncommuting mappings in Menger space to obtain fixed point results. Further a result in random normed space and a result on best approximation is obtained as application of the above notion.

Journal Article
TL;DR: In this paper, the authors studied submanifolds in hypersphere and hyperbolic space with mean curvature vector as an eigenvector of the Laplace operator defined on the sub manifolds.
Abstract: In this article, we study submanifolds in hypersphere and hyperbolic space with mean curvature vector as an eigenvector of the Laplace operator defined on the submanifolds. We characterize null 2-type spacelike surfaces in the de Sitter space-time and the antide Sitter space-time and we prove that there exist no null 2-type submanifolds in hypersphere and hyperbolic space.


Journal Article
TL;DR: A ring R is right complement bounded (strongly right bounded) if every nonzero right complement (right ideal) contains a nonzero two-sided ideal as discussed by the authors, and the right singular ideal and its closure are completely prime.
Abstract: A ring R is right complement bounded (strongly right bounded) if every nonzero right complement (right ideal) contains a nonzero two-sided ideal. For these rings we discuss the set of nilpotent elements and show that the right singular ideal and its closure are completely prime. Furthermore the inessential prime ideals and the inessential maximal right ideals are described. A decomposition of a right continuous strongly right bounded ring with unity and no infinite sets of orthogonal central idempotents is given.

Journal Article
TL;DR: Yen as mentioned in this paper showed that if R is a semiprime ring with 1, then it is not commutative or anticommutative, and he also showed that R need not be a ring with l. He also conjectured in this paper that R can be replaced by $'R^2=R'$ in the above conjecture.
Abstract: Let R be a ring, not necessarily with 1. Call potent (strongly potent) if for some natural (even natural number) n>1. The well known Jacobson's Commutavity Theorem [3] states : If every element x of a ring is potent, then R is commutative. Herstein [2, Theorem 3.13, pages 74] improved this: If, for every x, y in R, xy - yx is potent then R is commutative. Recently Machale [4] showed : If, for every x, y in R, xy+yx is strongly potent, then R is anticommutative. Yen [5] showed : If, for every x, y in R, either xy-yx is potent or xy+yx is strongly potent, then R is either commutative or anticommutative. Yen [6], also see [1], showed : If R is a semiprime ring and, for every x, y in R, xy+yx is potent, then R is commutative. The first author [1] showed : If R has 1 and, for every x, y in R, xy+yx is potent, then R is commutative. He also gave an example to show that in general if, for every x, y in R, xy+yx is potent, then R need not be commutative. Yen [7], proved : If R is a semiprime ring such that for every x, y in R, either xy+yx or xy-yx is potent then R is commutative. He conjectured in this paper : If R is a ring with 1 such that for every x, y in R either xy-yx is potent or xy+yx is potent, then R is commutative. Here we prove this conjecture. He also asked the following stronger question in a personal communication : Can we replace 'R with l' by $'R^2=R'$ in the above conjecture? Here we answer this question also as an application of the above result.

Journal Article
TL;DR: In this paper, a simple proof for this inequality is given, for subsets of a set such that the number of SDR's of the set is at most 2, if > 0.
Abstract: Let be subsets of a set such that . For the configuration , let denote the number of SDR's of . Ostrand[Os] proved that if > 0, then . In this note we give a simple proof for this inequality.

Journal Article
TL;DR: In this article, the class of functions, analytic and p-valent in the unit disc and satisfying for z in unit disc, under the assumption that $-1{\leq}\;B\;\;-p$$ for the class.
Abstract: Let be the class of functions , analytic and p-valent in the unit disc and satisfying for z in the unit disc and where $-1{\leq}\;B\; under the assumption that $-1{\leq}\;B\;\;-p$$ for the class .

Journal Article
TL;DR: In this article, the authors considered an M/G/1 retrial queueing system under the threshold control policy whose motivation comes from a telephone exchange system and found a necessary and sufficient condition for the model to be stable and derived the limiting distribution of the number of customers in the system at the moment of service completion.
Abstract: We consider an M/G/1 retrial queueing system under the threshold control policy whose motivation comes from a telephone exchange system. We find a necessary and sufficient condition for the model to be stable and derive the limiting distribution of the number of customers in the system at the moment of service completion. Special cases are treated and some numerical examples are also presented.

Journal Article
TL;DR: In this article, the best approximation theorems for set-valued maps in large chasses are deduced based on new fixed point theorem due to the author, and the results properly extend and improve a number of known results.
Abstract: Based on new fixed point theorems due to the author, best approximation theorems for set-valued maps in large chasses are deduced. Our results properly extend and improve a numbers of known results.