• Bulletin of the Korean Mathematical Society
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• v.55 no.5
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• pp.1351-1370
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• 2018

In the first part of this paper we show that, under some conditions, a polynomially demicompact operator can be demicompact. An example involving the Caputo fractional derivative of order ${\alpha}$ is provided. Furthermore, we give a refinement of the left and the right Weyl essential spectra of a closed linear operator involving the class of demicompact ones. In the second part of this work we provide some sufficient conditions on the inputs of a closable block operator matrix, with domain consisting of vectors which satisfy certain conditions, to ensure the demicompactness of its closure. Moreover, we apply the obtained results to determine the essential spectra of this operator.

• Korean Journal of Mathematics
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• v.24 no.2
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• pp.139-168
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• 2016

In this work, we rst introduce a class of analytic functions involving the Dziok-Srivastava linear operator that generalizes the class of uniformly starlike functions with respect to symmetric points. We then establish the closure of certain well-known integral transforms under this analytic function class. This behaviour leads to various radius results for these integral transforms. Some of the interesting consequences of these results are outlined. Further, the lower bounds for the ratio between the functions f(z) in the class under discussion, their partial sums $f_m(z)$ and the corresponding derivative functions f'(z) and $f^{\prime}_m(z)$ are determined by using the coecient estimates.

• Journal of the Korean Mathematical Society
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• v.44 no.2
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• pp.261-273
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• 2007

In this paper, we introduce some new properties of a topological space which are respectively generalizations of $Fr\'{e}chet$-Urysohn property. We show that countably AP property is a sufficient condition for a space being countable tightness, sequential, weakly first countable and symmetrizable, to be ACP, $Fr\'{e}chet-Urysohn$, first countable and semimetrizable, respectively. We also prove that countable compactness is a sufficient condition for a countably AP space to be countably $Fr\'{e}chet-Urysohn$. We then show that a countably compact space satisfying one of the properties mentioned here is sequentially compact. And we show that a countably compact and countably AP space is maximal countably compact if and only if it is $Fr\'{e}chet-Urysohn$. We finally obtain a sufficient condition for the ACP closure operator $[{\cdot}]_{ACP}$ to be a Kuratowski topological closure operator and related results.

• The Pure and Applied Mathematics
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• v.11 no.3
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• pp.243-265
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• 2004

In this paper, we introduce the fundamental concepts of intuitionistic fuzzy Q-neighborhood, intuitionistic Q-first axiom of countability, intuitionistic first axiom of countability, intuitionistic fuzzy closure operator, intuitionistic fuzzy boundary point and intuitionistic fuzzy accumulation point and investigate some of their properties.

• Communications of the Korean Mathematical Society
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• v.25 no.2
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• pp.273-282
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• 2010

The concept of intuitionistic fuzzy $\theta$-interior operator is introduced and discussed in intuitionistic fuzzy topological spaces. As applications of this concept, intuitionistic fuzzy strongly $\theta$-continuous, intuitionistic fuzzy $\theta$-continuous, and intuitionistic fuzzy weakly continuous functions are characterized in terms of intuitionistic fuzzy $\theta$-interior operator.

• Bulletin of the Korean Mathematical Society
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• v.43 no.4
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• pp.671-677
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• 2006

Let $A, B{\in}B(H)$ be Hilbert space contractions, and let ${\Delta}_{AB}$ be the elementary operator ${\Delta}_{AB}:X{\rightarrow}AXB-X$. A number of conditions which are equivalent to '${\Delta}_{AB}$ has closed range' are proved.

• Korean Journal of Mathematics
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• v.27 no.4
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• pp.1109-1118
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• 2019

In this paper, we introduce the notion of residuated and Galois connections on adjoint triples and investigate their properties. Using the properties of residuated and Galois connections, we solve fuzzy relation equations and give their examples.

• The Pure and Applied Mathematics
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• v.12 no.1
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• pp.75-91
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• 2005

The main objective of this paper is to introduce the gradation of neigh-bourhoodness in L-fuzzy topology and to introduce the fuzziness in the concept of convergence of L-fuzzy nets.

• Journal of Internet Computing and Services
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• v.23 no.2
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• pp.19-28
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• 2022

In this paper, we propose an guidance system about closure using push notification of smart device. Restaurant operators can use the proposed application to schedule and modify the restaurant closures for a week from push notification and users can check the restaurant information and whether it is closed or not through the proposed application. The proposed method uses a server system to provide closed information, and the proposed application performs push notifications to the restaurant operator every morning to confirm the day's closed again. To verify the utility of the proposed system, we built a closure management application, user application, and server system to conduct experiments for restaurant closures guidance, resulting in 96% about checking opening hours. And we confirmed that the proposed method is better than the existing information service in comparison experiments. Thus, the proposed method will be a useful service system that could easily share closure information with restaurant operators and users.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.8 no.1
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• pp.6-10
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• 2008

In this paper, we introduce the concept of fuzzy (r, s)-adherence points, fuzzy (r, s)-accumulation points and fuzzy (r, s)-derived sets in double fuzzy topology. We investigate some of their properties. The relationship with double fuzzy closure operator was studied.