Showing papers in "Kyungpook Mathematical Journal in 1999"

A contact version of B.-Y. Chen's inequality and its applications to slant immersions

Abstract: where n denotes the dimension of M and H is the mean curvature vector. On the other hand, it was remarked in [8] that the exact proof of (1.2) given in [4] yields the same inequality for totally real submanifolds in a complex-space-form M̃(4c) with constant holomorphic sectional curvature 4c. Later, Chen generalized the above situation by establishing an inequality for an arbitrary submanifold of dimension greater than 2 in a complex-space-form [6]. By

An n-dimensional Version of Ostrowski's Inequality for Mappings of the $H\ddot{o}lder$ Type

Abstract: Generalizations for multiple integrals and mappings of the Holder type, of the celebrated Ostrowski's inequality which extend Milovanovic result from 1975, are given.

Congruences and Idealas in Hilbert Algebras

Abstract: The concept of ideal for Hilbert algebras is introduced. It is presented a construction of a congruence having given ideal as its class. Moreover, it is shown that every congruence on a Hilbert algebra has this form.

Oscillations of Neutral Difference Equations

Abstract: In this paper, we establish some sufficient conditions for the oscillations of all solutions of the neutral difference equation with positive and negative coefficients. Our results improve the known results in the literature.

Linear Operators Strongly Preserving Multivariate Majorization with T(I) = I

Abstract: In this paper, we will investigate the set of linear operators that strongly preserve multivariate majorization with some additional conditions. We determine the linear operators that strongly preserve multivariate majorization with T(I) = I and which map nonnegative matrices to nonnegative matrices.

Oscillation of Nonlinear Delay Differential Equations with Several Positive and Negative Coefficients

Abstract: Some sufficient conditions for oscillation of all solutions of the nonlinear delay deferential equation of the form are obtained. In addition we prove that under appropriate hypotheses, if every solution of the associated liner equation with constant coefficients, oscillates, then every solution of the nonlinear equation also oscillates.

Some New Inequalities for the Average Number of Guesses

Abstract: Using some new analytic inequalities for real numbers we point out here some new lower bounds for the average number of guesses which complement in a natural sense the recent results obtained by E. Arikan in [2].

Some Inequalities for Random Variables whose Probability Density Functions are Bounded Using a Pre-Gruss Inequality

Abstract: Using the pre-Gruss inequality considered by Matic-Pecaric-Ujevic in a recent paper [1] and some related results, we point out some inequalities for random variables whose p.d.f.'s are bounded above and below by the assumed known constants γ and O.

A Common Fixed Point Theorem for a Pair of Coincidentally Commuting Mappings in Metric Spaces

Abstract: In this paper two common fixed point theorems are proved for a pair of coincidentally commuting mappings on a metric space satisfying generalized contractive condition which in turn include the fixed point theorems of Dhage [1] as the special cases in metric spaces.

Icm-Products of Number-theoretic Functions Revisited

Abstract: A representation is derived for the function of Lehmer which was used in his type inversion for the lcm-product. A few lcm-inverses are computed, from which additional inversion formulas result, two of which are symmetric. The representation formula is generalized, which provides a convenient formula for computing certain lcm-product powers. A list is included of some lcm-products to supplement the few that are available in the literature.

Argument Estimates of Meromorphically Multivalent Functions

Abstract: In the present paper, we obtain some argument properties of meromorphically multivalent functions in the punctured open unit disk. We also give some conditions for meromorphically close-to-convex functions. Furthermore, the integral preserving properties in a sector are considered.

A Note on Biregular Rings

Abstract: In this note, b-injectivity is introduced to study biregular rings. Von Neuman regular rings and strongly regular rings are also considered.

Existence of Periodic Solutions of Nonlinear Systems of a Generalized Lienard Type

Abstract: We obtain sufficient conditions for a generalized Lienard type system to have periodic solutions in given regions.

Global Stability of the Solutions of Impulsive Functional Differential Equations

Abstract: In the present paper the global stability is studied for the solutions of impulsive functional-differential equations with fixed moments of impulse effect. By means of piecewise continuous functions, which are generalizations of the classical Lyapunov functions, sufficient conditions are obtained for global stability of the zero solution of these equations.

Nonoscillatory Solutions of a Class of Impulsive Differential Equations of n-th Order with Retarded Argument

Abstract: Some asymptotic properties of the unbounded, nonoscillatory solutions of impulsive differential equations of n-th order with deviating argument and fixed moments of impulse effect are investigated.

Oscillatory and Asymptotic Properties of Solutions of Nonlinear Impulsive Differential Equations of Third Order with Retarded Argument

Abstract: Sufficient conditions are found for oscillation of the bounded solutions and for existence of bounded nonoscillatory solutions to a class of nonlinear impulsive differential equations of third order with retarded argument.

On Differential Subordinations Connected with Convex Functions Related to a Sector

Abstract: be fixed. In this paper the author calculates the constant such that the differential subordination of the form , implies .

On Integrability Conditions of Almost Generalized Hopf Structures

Abstract: An almost generalized Hopf structure is an almost Hermitian structure whose metric is locally conformal to an almost one. In this paper, we discuss integrability conditions of its almost complex structure: An integrability condition is obtained and it is applied to some classes of almost generalized Hopf manifolds.

Application of Fractional Calculus Operators to a Class of Univalent Functions with Negative Coefficients

Abstract: The object of present paper is to obtain distortion theorem using fractional calculus techniques for a class which consists of analytic and univalent functions with negative coefficients in the unit disc, and further same type of result we have obtained for fractional operator.

Asymptotic and Oscillatory Behavior of Higher Order Nonlinear Neutral Difference Equations

Abstract: The purpose of this paper is to study oscillation and asymptotic behavior of the higher order nonlinear forced neutral difference equations. We obtain a series of sufficient conditions for the oscillation and the asymptotic behavior of solutions of higher order neutral difference equations.

Ruled Surfaces of Finite Type Gauss Map in $S^3$

Abstract: In this paper we showed that ruled surfaces of finte type Gauss map in are totally geodesic or products of two plane circles.

Cyclic Inequalities Related to Hardy Type

Abstract: The aim of this paper is to establish some cyclic integral inequalities which related to the well-known Hardy's integral inequality. The method which we used to obtain our results is based on the idea used by Levinson to obtain the generalizations of Hardy's integral inequality.

Uniqueness Theorems for Meromorphic Functions with Two Deficient Values

Abstract: This paper discusses the problem of uniqueness of meromorphic functions, ignoring value-points of high multiplicity. The authors prove that if f is a nonconstant meromorphic function with $4{\delta}(0)+3(k+2){\circleddash}(\infty)>3k+9$, then f can be determined uniquely by either the sets , where are finite nonzero complex numbers such that . This improve some theorems given by K. L. Hiong, L. Yang, H. C. Xie, H. X. Yi and other authors. Examples are provided to show that the results in this paper are sharp.