• Journal of the Korean Mathematical Society
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• v.36 no.2
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• pp.345-354
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• 1999

In this paper, we obtain a matrix theorem which will be widely used in several theory and give it's applications. In particular, we present a further improvement of the improved Stile's theorem.

• Bulletin of the Korean Mathematical Society
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• v.35 no.2
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• pp.301-309
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• 1998

The purpose of this paper is to give a theorem of Liouvilletype for complete Riemannian manifolds as an extension of the Theorem of Nishikawa [6].

• Bulletin of the Korean Mathematical Society
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• v.40 no.2
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• pp.301-307
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• 2003

The purpose of this paper is to give a generalization of the quasi fixed-point theorem due to Lefebvre, and prove a new existence theorem of equilibrium in a generalized quasi-game.

• Journal of the Korean Mathematical Society
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• v.34 no.2
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• pp.285-291
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• 1997

In this paper, we obtain an abstract formulation of a fixed point theorem for nonexpansive mappings. Our theorem is a non-metric version of Kirk's original theorem.

• Honam Mathematical Journal
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• v.25 no.1
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• pp.75-82
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• 2003

In this note it is shown that if T satisfies ($G_{1}$)-condition with finite spectrum then Weyl's theorem holds for T. If T is totally *-paranormal then $T-{\lambda}$ has finite ascent for all ${\lambda}{\in}{\mathbb{C}},\;T$ is isoloid, and Weyl's theorem holds for T.

• Journal of the Chungcheong Mathematical Society
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• v.26 no.3
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• pp.533-539
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• 2013

In this paper, using the E-convexity, we introduce the generalized E-KKM map, and next prove the generalized E-KKM theorem which generalizes the KKM theorem due to Fan [4]. As an application, a fixed point theorem in E-convex sets is given.

• Bulletin of the Korean Mathematical Society
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• v.54 no.3
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• pp.715-729
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• 2017

In this paper, we investigate the existence and multiplicity of solutions for systems driven by two non-local integrodifferential operators with homogeneous Dirichlet boundary conditions. The main tools are the Saddle point theorem, Ekeland's variational principle and the Mountain pass theorem.

• Bulletin of the Korean Mathematical Society
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• v.56 no.6
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• pp.1577-1588
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• 2019

We show a multiple recurrence theorem for topological dynamical systems with countable directed partial semigroup actions, which generalizes the well-know IP-version of multiple recurrence theorem proved by Furstenberg and Weiss.

• Korean Journal of Mathematics
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• v.30 no.4
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• pp.615-628
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• 2022

In this paper, we will prove some extensions of the Eneström-Kakeya theorem to quaternionic polynomials which were already valid for the classical Eneström-Kakeya theorem to complex polynomials. Our kind of extensions have considerably improved the bounds by relaxing and weakening the hypothesis in some cases.

• Communications of the Korean Mathematical Society
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• v.38 no.2
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• pp.561-573
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• 2023

In this paper, we extend the medial triangle theorem and Varignon's theorem to generic two-dimensional polygons and highlight the role played by diagonals in this process. One of the results is a synthetic definition of the concept of median for an n-sided polygon.