• Journal of the Korean Mathematical Society
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• v.56 no.6
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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.

• Journal of the Chungcheong Mathematical Society
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• v.33 no.4
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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.

• Bulletin of the Korean Mathematical Society
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• v.59 no.4
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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.

• Bulletin of the Korean Mathematical Society
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• v.60 no.5
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• pp.1201-1219
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• 2023

We characterize the boundedness and compactness of differences of weighted composition operators acting from weighted Bergman spaces A^p_ω to Lebesgue spaces L^q(dµ) for all 0 < p, q < ∞, where ω is a radial weight on the unit disk admitting a two-sided doubling condition.

• East Asian mathematical journal
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• v.25 no.1
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• pp.45-53
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• 2009

In this paper, by using the technique of the resolvent operators, we study the behaviour and sensitivity analysis of the solutions set for a class of parametric completely generalized nonlinear variational inclusions with set-valued mappings.

• Bulletin of the Korean Mathematical Society
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• v.60 no.3
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• pp.845-848
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• 2023

Erratum/Addendum to the paper "Biisometric operators and biorthogonal sequences" [Bull. Korean Math. Soc. 56 (2019), No. 3, pp. 585-596].

• Bulletin of the Korean Mathematical Society
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• v.60 no.4
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• pp.1061-1070
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• 2023

In this paper, we study products of composition, multiplication and differentiation acting on the fractional Cauchy spaces and mapping into the Zygmund space. Characterizations are provided for boundedness and compactness of these operators.

• Journal of the Korean Mathematical Society
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• v.39 no.1
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• pp.51-60
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• 2002

Some random fixed point theorems for nonexpansive and *-nonexpansive random operators defined on convex and star-shaped sets in a Frechet space are proved. Our work extends recent results of Beg and Shahzad and Tan and Yaun to noncontinuous multivalued random operators, sets analogue to an earlier result of Itoh and provides a random version of a deterministic fixed point theorem due to Singh and Chen.

• Journal of the Korean Mathematical Society
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• v.46 no.3
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• pp.577-588
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• 2009

In this paper, the author studies the k-th commutators of oscillatory singular integral operators with a BMO function and phases more general than polynomials. For 1 < p < $\infty$, the $L^p$-boundedness of such operators are obtained provided their kernels belong to the spaces $L(log+L)^{k+1}(S^{n-1})$. The results of the corresponding maximal operators are also established.

• Bulletin of the Korean Mathematical Society
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• v.59 no.1
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• pp.1-13
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• 2022

The main aim of the article is to introduce new generalizations of Fredholm and Browder classes of spectra when the underlying Hilbert space is not necessarily separable and study their properties. To achieve the goal the notions of 𝛼-Browder operators, 𝛼-B-Fredholm operators, 𝛼-B-Browder operators and 𝛼-Drazin invertibility have been introduced. The relation of these classes of operators with their corresponding weighted spectra has been investigated. An equivalence of 𝛼-Drazin invertible operators with 𝛼-Browder operators and 𝛼-B-Browder operators has also been established. The weighted Browder spectrum of the sum of two bounded linear operators has been characterised in the case when the Hilbert space (not necessarily separable) is a direct sum of its closed invariant subspaces.