• Bulletin of the Korean Mathematical Society
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• v.47 no.2
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• pp.307-317
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• 2010

In this paper we find necessary and sufficient conditions for weak amenability of the convolution Banach algebras A(K) and $L^2(K)$ for a compact hypergroup K, together with their applications to convolution Banach algebras $L^p(K)$ ($2\;{\leq}\;p\;<\;{\infty}$). It will further be shown that the convolution Banach algebra A(G) for a compact group G is weakly amenable if and only if G has a closed abelian subgroup of finite index.

• Journal of the Korean Mathematical Society
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• v.36 no.1
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• pp.97-107
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• 1999

Given a C-dynamical system (A, G, $\alpha$) with a locally compact group G, two kinds of C-algebras are made from it, called the full C-crossed product and the reduced C-crossed product. In this paper, we extend the theory of the classical C-crossed product to the C-dynamical system (A, G, $\alpha$) with a left-cancellative semigroup M with unit. We construct a new C-algebra A $\alpha$rM, the reduced crossed product of A by the semigroup M under the action $\alpha$ and investigate some properties of A $\alpha$rM.

• Communications of Mathematical Education
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• v.18 no.2 s.19
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• pp.133-142
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• 2004

선형대수 교육과정 연구 단체(LACSG, The Linear Algebra Curriculum Study Group)는 1990년 그의 결성과 함께 선형대수 교육과정에서 중점적으로 고려해야할 다섯 가지 추천 목록을 발표하였다. 그 중 가장 두드러진 특징은 기존의 형식적이고 엄밀한 벡터공간 중심의 선형대수 교육과정을 보다 실용적인 행렬중심으로 바꿀 것을 주장하고 있다. 본 연구에서는 벡터 공간 중심의 교육과정과 행렬 중심에 기반한 교육과정의 역사적 흐름에서 행렬 중심의 교육과정이 우위를 차지하게 된 배경을 살핀다. 또한 이러한 교육과정과 맥을 같이한 선형대수 교과서의 변천과, 행렬의 곱의 전개를 중심으로 두 중심사이의 차이를 논한다.

• Journal of the Korean Mathematical Society
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• v.37 no.4
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• pp.645-655
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• 2000

We calculate the R(G)-algebra structure on the reduced equivariant K-groups of two-dimensional spheres on which a compact Lie group G acts as a reflection. In particular, the reduced equivariant K-groups are trivial if G is abelian, which shows that the previous Y. Yang's calculation in [8] is incorrect.

• Bulletin of the Korean Mathematical Society
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• v.37 no.2
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• pp.249-254
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• 2000

We give an easy proof of the fact that every noncommutative torus $A_{\omega}$ is stably isomorphic to the noncommutative torus $C(\widehat{S\omega}){\;}\bigotimes{\;}A_p$ which hasa trivial bundle structure. It is well known that stable isomorphism of two separable $C^{*}-algebras$ is equibalent to the existence of eqivalence bimodule between the two stably isomorphic $C^{*}-algebras{\;}A_{\omega}$ and $C(\widehat{S\omega}){\;}\bigotimes{\;}A_p$.

• Journal for History of Mathematics
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• v.10 no.2
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• pp.24-29
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• 1997

Derivation은 Lie group, Lie ring 그리고 Lie Algebra에서 정의되어 사용되며 발전하였으며 ring에서 일반화 되었다. 역시 prime ring에서 연구되어지는 derivation의 성질들은 prime near-ring에서 일반화 시키려고 하고 있다. 1957년 E. Posner는 prime ring에서 두 개의 derivation의 곱(함수합성)이 derivation이면 이들중 하나의 derivation이 0임을 밝혔다. 본 논문에서는 prime ring에서 derivation이 연구된 역사적인 배경을 소개하고 몇가지 성질을 찾는다. 즉, D. F를 prime ring R의 derivation들이라 할 때 정수 $n{\ge}1$에 대하여 $DF^n$=0이면 D=0이거나 또는 $F^{3n-1}$=0이고, $D^nF$=0이면 $D^{9n-7}$=0 이거나 또는 $F^2$=0 이다.

• Journal of the Chungcheong Mathematical Society
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• v.5 no.1
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• pp.75-85
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• 1992

Let R be an associative ring and let G be a finite group of Jordan automorphisms of R. Let $R^G$ be the set of elements in R fixed by all $g{\in}G$. In this paper we will study the relationship between the Levitzki radical of $R^G$ and R as that a Jordan ring. We also show that if R is a P.I. algebra, then the algebraicity of $R^G$ implies the algebraicity of R.

• The Pure and Applied Mathematics
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• v.12 no.1
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• pp.1-15
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• 2005

We study continuous fields and K-groups of crossed products of C＊-algebras. It is shown under a reasonable assumption that there exist continuous fields of C＊ -algebras between crossed products of C＊ -algebras by amenable locally compact groups and tensor products of C＊ -algebras with their group C＊ -algebras, and their K-groups are the same under the additional assumptions.

• Bulletin of the Korean Mathematical Society
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• v.56 no.2
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• pp.391-397
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• 2019

In this paper, we give a simple proof of the improved Johnson bound for A(n, d), the maximum number of codewords in a binary code of length n and minimum distance d, given by Mounits, Etzion and Litsyn.

• Journal of the Korean Mathematical Society
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• v.58 no.6
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• pp.1407-1419
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• 2021

The Iwasawa decomposition NAK of the Lie group G = SO₀(2, 1) with a left invariant metric produces Riemannian submersions G → N\G, G → A\G, G → K\G, and G → NA\G. For each of these, we calculate the curvature of the base space and the lifting of a simple closed curve to the total space G. Especially in the first case, the base space has a constant curvature 0; the holonomy displacement along a (null-homotopic) simple closed curve in the base space is determined only by the Euclidean area of the region surrounded by the curve.