• 대한수학회보
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• 제59권5호
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• pp.1305-1315
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• 2022

Let u be a function on a connected finite graph G = (V, E). We consider the mean field equation (1) $-{\Delta}u={\rho}\({\frac{he^u}{\int_Vhe^ud{\mu}}}-{\frac{1}{{\mid}V{\mid}}}\),$ where ∆ is 𝜇-Laplacian on the graph, 𝜌 ∈ ℝ\{0}, h : V → ℝ⁺ is a function satisfying min_x∈V h(x) > 0. Following Sun and Wang [15], we use the method of Brouwer degree to prove the existence of solutions to the mean field equation (1). Firstly, we prove the compactness result and conclude that every solution to the equation (1) is uniformly bounded. Then the Brouwer degree can be well defined. Secondly, we calculate the Brouwer degree for the equation (1), say $$d_{{\rho},h}=\{{-1,\;{\rho}>0, \atop 1,\;{\rho}<0.}$$ Consequently, the equation (1) has at least one solution due to the Brouwer degree d_𝜌,h ≠ 0.

• 대한수학회보
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• 제34권3호
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• pp.491-493
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• 1997

This is to clarify that Taskovic's extension of the Brouwer fixed point theorem is incorrectly stated.

• 대한수학회보
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• 제40권2호
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• pp.215-221
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• 2003

There seems to be a love-hate relationship between Brouwer's fixed point theorem and the fundamental theorem of algebra; in this note we offer one more tweak at it, and give a version of Rouches theorem.

• 한국수학사학회지
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• 제24권4호
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• pp.45-59
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• 2011

20세기 초반에 등장한 수학기초론의 주류 세 학파 (직관주의 논리주의 형식주의)는 상호 대립관계를 보인다. 큰 틀에서 볼 때, 논리주의는 프레게를 계승하는 입장이다. 이와 대립관계의 기초론 중 하나인 직관주의는 구성주의 수학철학의 주축으로 평가된다. 그리고 직관주의가 터를 닦은 구성주의 수학철학을 후속 개진시킨 주역은 의미론적 반실 재론을 주창한 마이클 더밋이다. 따라서 외형상으로는 더밋이 직관주의를 계승하는 후계세대처럼 여겨질 수 있지만 그의 철학적 기반은 분명 프레게이다. 더밋이 논리주의가 아닌 직관주의 계열에 합류한 사실의 속내는 구성주의 내부의 두 입장 (즉, 직관주의와 반실재론) 이 보이는 배중률을 둘러싼 태도의 드러난 일치뿐만 아니라 가려진 차이까지 헤아려질 때 해명될 수 있다고 본다. 본고는 이런 해명을 통해 구성주의 수학철학에 대한 이해도 한층 더할 수 있다는 판단에 따른 제안적 노력이다.

• 대한수학회지
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• 제35권2호
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• pp.491-502
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• 1998

We obtain new fixed point theorems on maps defined on "locally G-convex" subsets of a generalized convex spaces. Our first theorem is a Schauder-Tychonoff type generalization of the Brouwer fixed point theorem for a G-convex space, and the second main result is a fixed point theorem for the Kakutani maps. Our results extend many known generalizations of the Brouwer theorem, and are based on the Knaster-Kuratowski-Mazurkiewicz theorem. From these results, we deduce new results on collectively fixed points, intersection theorems for sets with convex sections and quasi-equilibrium theorems.

• 한국수학사학회지
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• 제12권1호
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• pp.32-44
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• 1999

This paper is a sequel to [8]. Development of modern logic was initiated by Boole and Morgan. Boolean logic is one of their completed works. Cantor created the set theory along with cardinal and ordinal numbers. His theory on infinite sets brought about a remarkable development on modern mathematical theory, but generated many paradoxes (e.g. Russell Paradox) that in turn motivated mathematicians to solve them. Further, mathematicians attempted to construct sound foundations for Mathematics. As a result three important schools of thought were formed in relation to fundamentals of mathematics for the resolution of paradoxes of set theory, namely logicism developed by Russell and Whitehead, intuitionism lead by Brouwer and formalism contended by Hilbert and Bernays. In this paper, we examine the logic for intuitionism which is originated by Brouwer in 1908 and study Heyting algebra.

• Journal of applied mathematics & informatics
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• 제7권1호
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• pp.1-28
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• 2000

In the present paper, we introduce fundamental results in the KKM theory for G-convex spaces which are equivalent to the Brouwer theorem, the Sperner lemma, and the KKM theorem. Those results are all abstract versions of known corresponding ones for convex subsets of topological vector spaces. Some earlier applications of those results are indicated. Finally, We give a new proof of the Himmelberg fixed point theorem and G-convex space versions of the von Neumann type minimax theorem and the Nash equilibrium theorem as typical examples of applications of our theory.

• 대한수학회보
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• 제30권1호
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• pp.83-89
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• 1993

Applications of the classical Knaster-Kuratowski-Mazurkiewicz theorem [KKM] and the fixed point theory of multifunctions defined on convex subsets of topological vector spaces have been greatly improved by adopting the concept of convex spaces due to Lassonde[L]. Recently, this concept has been extended to pseudo-convex spaces, contractible spaces, or spaces having certain families of contractible subsets by Horvath[H1-4]. In the present paper we give a far-reaching generalization of the best approximation theorem of Ky Fan[F1, 2] to pseudo-metric spaces and improved versions of the well-known fixed point theorems due to Brouwer [B] and Schauder [S] for spaces having certain families of contractible subsets. Our basic tool is a generalized Fan-Browder type fixed point theorem in our previous works [P3, 4].

• 한국수학사학회지
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• 제10권2호
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• pp.82-88
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• 1997

수학 기초의 위기에 대한 직관주의적 대안은 파격적인 것이었다. 수학을 지나치게 축소시켰다고 비난을 받기도 하지만 역리의 제거라는 측면만 본다면 직관주의는 성공적이라고 할 수 있었다. 본고는 직관주의를 개관하고 직관주의가 가지는 보다 철학적이고 본질적인 측면을 직관주의의 창시자인 Brouwer의 수학관과 세계관에서 찾는다.

• 대한임상약리학회:학술대회논문집
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• 대한임상약리학회 2004년도 추계 학술대회
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• pp.19-20
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• 2004