• 충청수학회지
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• 제21권2호
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• pp.287-292
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• 2008

We introduce jointly weak subnormal operators. It is shown that if $T=(T_1,T_2)$ is subnormal then T is weakly subnormal and if f $T=(T_1,T_2)$ is weakly subnormal then T is hyponormal. We discuss the flatness of weak subnormal operators.

• Journal of applied mathematics & informatics
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• 제28권5_6호
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• pp.1101-1116
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• 2010

The aim of this paper is to give some simultaneous approximation properties as well as differential properties, Voronovskaya type theorem, several asymptotic formulae for the partial derivative and the degree of approximation for two dimensional Lupas type operators.

• Kyungpook Mathematical Journal
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• 제46권4호
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• pp.497-502
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• 2006

An asymmetric Fuglede-Putnam theorem for $p$-hyponormal operators and class ($\mathcal{Y}$) is proved, as a consequence of this result, we obtain that the range of the generalized derivation induced by the above classes of operators is orthogonal to its kernel.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제21권3호
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• pp.183-194
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• 2014

In this paper, we investigate the properties of Alexandrov fuzzy topologies and meet-join approximation operators. We study fuzzy preorder, Alexandrov topologies and meet-join approximation operators induced by Alexandrov fuzzy topologies. We give their examples.

• 대한수학회보
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• 제36권2호
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• pp.351-355
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• 1999

If ($H_1$, $H_2$) is a doubly commuting pair of hyponormal operators on a Hilbert spaces H, then there exists a commuting pair ($T_1$,$T_1$) of contractions on H such that $H_i$=$H_i^*$$T_i$ for each i=1,2.

• 대한수학회논문집
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• 제36권4호
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• pp.651-669
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• 2021

In this paper, we investigate some basic results on the slice regular Besov spaces of hyperholomorphic functions on the unit ball 𝔹. We also characterize the boundedness, compactness and find the essential norm estimates for composition operators between these spaces.

• 대한수학회지
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• 제56권6호
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• pp.1489-1502
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• 2019

This paper describes when a partial isometry satisfies several weak normal properties. Topics treated include quasi-normality, subnormality, hyponormality, p-hyponormality (p > 0), w-hyponormality, paranormality, normaloidity, spectraloidity, the von Neumann property and Weyl's theorem.

• Nonlinear Functional Analysis and Applications
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• 제26권1호
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• pp.105-115
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• 2021

Generalized pseudo-differential operators (PDO) involving fractional Fourier transform associate with the symbol a(x, y) whose derivatives satisfy certain growth condition is defined. The product of two generalized pseudo-differential operators is shown to be a generalized pseudo-differential operator.

• 충청수학회지
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• 제33권4호
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• pp.489-495
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• 2020

We define new integral operators on the Haydy space similar to Szegö projection. We consider a relationship between these Szegö type operators and the partial sum of Taylor series on the Hardy space.

• 대한수학회보
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• 제59권4호
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• pp.905-915
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• 2022

This paper studies the boundedness of integral operators on the Cesàro function spaces. As applications of the main result, we obtain the Hilbert inequalities, the boundedness of the Erdélyi-Kober fractional integrals and the Mellin fractional integrals on the Cesàro function spaces.