• Journal of applied mathematics & informatics
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• v.31 no.3_4
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• pp.559-564
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• 2013

In this paper we investigate necessary conditions for the mirror algebra $(M(X),{\bigoplus},(0,0))$ to be a $d$-algebra (having the condition (D5), resp.) when (X, *, 0) is a d-algebra (having the condition (D5), resp.). Moreover, we obtain the necessary conditions for M(X) of a $d^*$-algebra X to be a $d^*$-algebra.

• Journal of the Korean Mathematical Society
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• v.43 no.5
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• pp.931-950
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• 2006

We study the identification problems of constant parameters appearing in the perturbed sine-Gordon equation with the Neumann boundary condition. The existence of optimal parameters is proved, and necessary conditions are established for several types of observations by utilizing quadratic optimal control theory due to Lions [13].

• Korean Journal of Mathematics
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• v.25 no.4
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• pp.587-606
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• 2017

This paper is a continuation of study semi-potentness endomorphism rings of module. We give some other characterizations of endomorphism ring to be semi-potent. New results are obtained including necessary and sufficient conditions for the endomorphism ring of semi(injective) projective module to be semi-potent. Finally, we characterize a module M whose endomorphism ring it is semi-potent via direct(injective) projective modules. Several properties of the endomorphism ring of a semi(injective) projective module are obtained. Besides to that, many necessary and sufficient conditions are obtained for semi-projective, semi-injective modules to be semi-potent and co-semi-potent modules.

• Journal of the Korean Mathematical Society
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• v.46 no.3
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• pp.621-642
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• 2009

In this paper we give necessary and sufficient conditions that two Toeplitz operators with monomial symbols acting on the weighted Bergman space commute. We also present necessary and sufficient conditions for the hyponormality of Toeplitz operators with some special symbols on the weighted Bergman space. All the results are stated in terms of the Mellin transform of the symbol.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.947-951
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• 1989

A Class of nonlinear distributed parameter control problems is first stated in a partial differential equation form in multi-index notion and then converted into an integral equation form. Necessary conditions for optimality in the form of maximum principle are then derived in Sobolev space W$^{l}$, p/(1 leq. p .leq. .inf.)..

• Journal of applied mathematics & informatics
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• v.8 no.3
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• pp.1027-1033
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• 2001

In this paper we obtain the necessary and sufficient conditions for convergence concerning the Mann iterative sequences with errors for the class of continuous accretive operators in smooth Banach spaces.

• Journal of applied mathematics & informatics
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• v.32 no.3_4
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• pp.447-454
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• 2014

Two necessary and sufficient conditions for the oscillation of the bounded solutions of the second-order nonlinear delay differential equation $$(a(t)x^{\prime}(t))^{\prime}+q(t)f(x[{\tau}(t)])=0$$ are obtained by constructing the sequence of functions and using inequality technique.

• Communications of the Korean Mathematical Society
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• v.35 no.4
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• pp.1329-1352
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• 2020

In this paper we consider a class of nonlinear evolution equations on infinite dimensional Banach spaces driven by vector measures. We prove existence and uniqueness of solutions and continuous dependence of solutions on the control measures. Using these results we prove existence of optimal controls for Bolza problems. Based on this result we present necessary conditions of optimality.

• Communications of the Korean Mathematical Society
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• v.24 no.1
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• pp.145-152
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• 2009

In this paper, we introduce a new property of a topological space which is weaker than sequential compactness and give some necessary and sufficient conditions for a $Fr{\acute{e}}chet$-Urysohn space with the property to be sequentially compact.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1875-1877
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• 2002

There exist several forms of transfer function descriptions for multivariable LTI systems. We treat transfer function matrix with characteristic polynomial as its common denominator named Characteristic Transfer-function Matrices (CTM). First, we clarify necessary and sufficient conditions of CTM, then, we show some related lemmas. These interpretations not only offer deeper explanations but they also provide ways for calculations of all possible transfer matrices, system zeros, and inverse polynomial matrices.