• Korean Journal of Mathematics
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• 제30권3호
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• pp.513-524
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• 2022

In this paper, we introduce the notion of tensor product in groups and prove its existence and uniqueness. Next, we provide the Isbell's zigzag theorem for dominions in commutative groups. We then show that in the category of commutative groups dominions are trivial. This enables us to deduce a well known result epis are surjective in the category of commutative groups.

• Kyungpook Mathematical Journal
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• 제46권2호
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• pp.231-233
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• 2006

We characterize those commutative semigroups S such that every non-isomorphic homomorphic image of S has smaller cardinality than S. We also characterize commutative groups with the same property.

• 호남수학학술지
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• 제45권3호
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• pp.410-417
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• 2023

Suppose that there are 8 abelian varieties defined over a number field K which satisfy a commutative diagram. We show that if we know that three out of four short exact sequences satisfy the rate formula of Tate-Shafarevich groups, then the unknown short exact sequence satisfies the rate formula of Tate-Shafarevich groups, too.

• 대한수학회보
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• 제52권1호
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• pp.239-246
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• 2015

If for every elements x and y of an associative algebraic structure (S, ${\cdot}$) there exists a positive integer r such that $ab=b^ra$, then S is called quasi-commutative. Evidently, every abelian group or commutative semigroup is quasi-commutative. Also every finite Hamiltonian group that may be considered as a semigroup, is quasi-commutative however, there are quasi-commutative semigroups which are non-group and non commutative. In this paper, we provide three finitely presented non-commutative semigroups which are quasi-commutative. These are the first given concrete examples of finite semigroups of this type.

• Kyungpook Mathematical Journal
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• 제46권2호
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• pp.285-295
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• 2006

We present a concept of negative definite functions on a commutative normal hypercomplex system $L_1$(Q, $m$) with basis unity. Negative definite functions were studied in [5] and [4] for commutative groups and semigroups respectively. The definition of such functions on Q is a natural generalization of that defined on a commutative hypergroups.

• 대한수학회보
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• 제51권6호
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• pp.1689-1696
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• 2014

Recently, it was proved that every p-Schur ring over an abelian group of order $p^3$ is Schurian. In this paper, we prove that every commutative p-Schur ring over a non-abelian group of order $p^3$ is Schurian.

• 대한수학회보
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• 제52권5호
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• pp.1549-1557
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• 2015

Characterizations of closed subgroups in abelian groups have been generalized to modules in essentially dierent ways; they are in general inequivalent. Here we consider the relations between these generalizations over commutative rings, and we characterize the commutative rings over which they coincide. These are exactly the commutative noetherian distributive rings. We also give a characterization of c-injective modules over commutative noetherian distributive rings. For a noetherian distributive ring R, we prove that, (1) direct product of simple R-modules is c-injective; (2) an R-module D is c-injective if and only if it is isomorphic to a direct summand of a direct product of simple R-modules and injective R-modules.

• Kyungpook Mathematical Journal
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• 제3권2호
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• pp.43-48
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• 1960

• 한국초등수학교육학회지
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• 제18권1호
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• pp.1-17
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• 2014

초등학교에서 곱셈의 교환법칙의 지도는 $3{\times}4=12$, $4{\times}3=12$와 같이 $a{\times}b$와 $b{\times}a$ 의 값을 계산하고 실제로 그 값이 같은지를 확인하는 활동을 바탕으로 하는 것이 보통이다. 이 논문에서는 첫째로, 순수이성비판에 나타난 수학적 지식에 관한 칸트의 견해를 바탕으로, 곱셈의 교환법칙의 취급 방법을 비판적으로 고찰한다. 칸트에 의하면, 수학적 지식은 선험성과 도식성이라는 특징을 지니고 있다. 두 곱셈의 계산 결과를 비교하는 방법은 선험성과 도식성이라는 수학적 지식의 특성을 충족하지 못한다. 칸트의 관점에서 볼 때, $a{\times}b$를 $b{\times}a$ 로 변환하는 필연적이고 일반적인 도식이 드러나게 교환법칙을 취급하는 것이 적절하다. 둘째로, 곱셈의 교환법칙의 도식과 관련된 기본구성단위로의 분배 전략은 (자연수)${\times}$(10의 거듭제곱), 몫 분수 맥락에서 분수의 복합적 의미, 분수의 곱셈과 같은 학습 내용을 관통하는 일반적인 성격의 것임을 논한다. 끝으로, 이상의 두 논의를 바탕으로 초등 수학교과서에서 곱셈의 교환법칙이 다루어지는 방식을 비판적으로 고찰한다.

• 대한수학회지
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• 제34권2호
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• pp.383-393
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• 1997

In this paper, we study the dependence of corestriction (or transfer) map on the choice of transversals. We also study transfer theorems with respect to some commutative subgroups.