• Journal of the Korean Mathematical Society
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• v.44 no.6
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• pp.1197-1211
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• 2007

In this article, we characterize the quasi-isomorphism classes of bracket groups in terms of vertices using vertex-switches. In particular, if two bracket groups are quasi-isomorphic, then there is a sequence of vertex-switches transforming a collection of vertices of a group to a collection of vertices of the other group.

• Bulletin of the Korean Mathematical Society
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• v.45 no.1
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• pp.111-118
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• 2008

Using the Hyers-Ulam-Rassias stability method, we investigate isomorphisms in quasi-Banach algebras and derivations on quasi-Banach algebras associated with the Cauchy-Jensen functional equation $$2f(\frac{x+y}{2}+z)$$=f(x)+f(y)+2f(z), which was introduced and investigated in [2, 17]. The concept of Hyers-Ulam-Rassias stability originated from the Th. M. Rassias' stability theorem that appeared in the paper: On the stability of the linear mapping in Banach spaces, Proc. Amer. Math. Soc. 72 (1978), 297-300. Furthermore, isometries and isometric isomorphisms in quasi-Banach algebras are studied.

• Communications of the Korean Mathematical Society
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• v.14 no.1
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• pp.135-146
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• 1999

In this paper, we introduce the (4k-1)-diagonal algebra $Alg{\iota}(\array{4k-1\\\infty}\)$ and investigate the necessary and sufficient condition that isomorphisms of $Alg{\iota}(\array{4k-1\\\infty}\)$ are quasi-spatial.

• Journal of the Korean Mathematical Society
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• v.49 no.3
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• pp.493-502
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• 2012

In this article, we give a characterization theorem for a class of corank-1 Butler groups of the form $\mathcal{G}$($A_1$, ${\ldots}$, $A_n$). In particular, two groups $G$ and $H$ are quasi-isomorphic if and only if there is a label-preserving bijection ${\phi}$ from the edges of $T$ to the edges of $U$ such that $S$ is a circuit in T if and only if ${\phi}(S)$ is a circuit in $U$, where $T$, $U$ are quasi-representing graphs for $G$, $H$ respectively.