• 대한수학회보
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• 제51권2호
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• pp.501-510
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• 2014

We characterize hypergeneralized k-projectors (i.e., $A^k=A^{\dag}$). Also, some representation for the Moore-Penrose inverse of a linear combination of hypergeneralized k-projectors is found and the invertibility for some linear combinations of commuting hypergeneralized k-projectors is considered.

• East Asian mathematical journal
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• 제22권2호
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• pp.151-162
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• 2006

In this paper two coincidence point theorems in complete metric spaces for two pairs of single and multi-valued mappings have been established.

• 대한수학회보
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• 제29권2호
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• pp.221-226
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• 1992

The involutions in a left Artinian ring A with identity are investigated. Those left Artinian rings A for which 2 is a unit in A and the set of involutions in A forms a finite abelian group are characterized by the number of involutions in A.

• 대한교통학회:학술대회논문집
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• 대한교통학회 2007년도 제56회 학술발표회논문집
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• pp.118-127
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• 2007

• 충청수학회지
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• 제14권1호
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• pp.105-111
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• 2001

The purpose of this paper is to give a new generalization of the well-known common fixed point theorem due to Markov-Kakutani in general settings.

• 대한수학회논문집
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• 제16권2호
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• pp.235-241
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• 2001

In this paper we study some properties of he joint Weyl and Browder spectra for the slightly larger classes containing doubly commuting n-tuples of hyponormal operators.

• 대한수학회보
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• 제37권1호
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• pp.53-62
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• 2000

In this paper we explore relations between joint Weyl and Browder spectra. Also, we give a spectral characterization of the Taylor-Browder spectrum for special classes of doubly commuting n-tuples of operators and then give a partial answer to Duggal's question.

• 대한수학회지
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• 제44권4호
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• pp.855-861
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• 2007

Let A and B be commuting bounded linear operators on a Hilbert space. In this paper, we study spectral area estimates for norms of $A^*B-BA^*$ when A is subnormal or p-hyponormal.

• 대한수학회논문집
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• 제34권2호
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• pp.533-542
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• 2019

We study commutants of Toeplitz operators acting on the Dirichlet space of the unit disk and prove that an operator in the Toeplitz algebra commuting with a Toeplitz operator with a nonconstant polynomial symbol must be a Toeplitz operator with an analytic symbol.

• 대한수학회논문집
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• 제34권4호
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• pp.1099-1104
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• 2019

In [1], Ali and Dar proved the ${\ast}$-version of classical theorem due to Posner [15, Theorem] with involution of the second kind. The main objective of this paper is to improve the above mentioned result without the condition of the second kind involution. Moreover, a related result has been discussed.