• Communications of the Korean Mathematical Society
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• v.11 no.4
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• pp.975-981
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• 1996

Let $D \subset C^2$ be a bounded convex domain with real analytic boundary. We get some Lipschitz regularity of the Cauchy transform on the convex domain D.

• Bulletin of the Korean Mathematical Society
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• v.33 no.1
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• pp.17-28
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• 1996

• Bulletin of the Korean Mathematical Society
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• v.55 no.5
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• pp.1419-1431
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• 2018

Let $f=h+{\bar{g}}$ be a harmonic mapping of the unit disk ${\mathbb{D}}$ with the holomorphic part h satisfying that h is injective and $h({\mathbb{D}})$ is an M-linearly connected domain. In this paper, we obtain the sufficient and necessary conditions for f to be bi-Lipschitz, which is in particular, quasiconformal. Moreover, some distortion theorems are also obtained.

• East Asian mathematical journal
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• v.29 no.1
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• pp.91-99
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• 2013

In this paper, we prove that the BMO norm and the Garsia norm are equivalent on a bounded domain in $\mathbb{R}^N$. Also, we investigate the equivalent relation between the Lipschitz norm and the Garsia-type norm for harmonic functions.

• Bulletin of the Korean Mathematical Society
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• v.58 no.3
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• pp.745-765
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• 2021

Let Ω be a proper open subset of ℝⁿ and p(·) : Ω → (0, ∞) be a variable exponent function satisfying the globally log-Hölder continuous condition. In this article, the author introduces the "geometrical" variable Hardy spaces H^p(·)_r (Ω) and H^p(·)_z (Ω) on Ω, and then obtains the grand maximal function characterizations of H^p(·)_r (Ω) and H^p(·)_z (Ω) when Ω is a strongly Lipschitz domain of ℝⁿ. Moreover, the author further introduces the "geometrical" variable local Hardy spaces h^p(·)_r (Ω), and then establishes the atomic characterization of h^p(·)_r (Ω) when Ω is a bounded Lipschitz domain of ℝⁿ.

• Bulletin of the Korean Mathematical Society
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• v.35 no.2
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• pp.269-278
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• 1998

Let ($G,\;{\upsilon}$) be a bounded smooth domain and reflection vector field on $\partial$G, which points uniformly into G. Under the condition that locally for some coordinate system, ${\mid}{\upsilon^i}{\mid}\;i\;=\;1,{\cdot},{\cdot}$,d - 1, where is constant depending on the Lipschitz constant of G, we have tightness for reflected diffusion with jump on G with reflection $\upsilon$ depending only on c. From this, we obtain some properties of L-harmonic function where L is a sum of Laplacian and integro one.

• Bulletin of the Korean Mathematical Society
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• v.50 no.3
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• pp.753-760
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• 2013

We consider the global existence of strong solutions of the 3D incompressible Navier-Stokes equations in a bounded Lipschitz do-main under Dirichlet boundary condition. We present by a very simple argument that a strong solution exists globally when the product of $L^2$ norms of the initial velocity and the gradient of the initial velocity and $L^{p,2}$, $p{\geq}4$ norm of the forcing function are small enough. Our condition is scale invariant and implies many typical known global existence results for small initial data including the sharp dependence of the bound on the volumn of the domain and viscosity. We also present a similar result in the whole domain with slightly stronger condition for the forcing.

• East Asian mathematical journal
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• v.19 no.2
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• pp.291-303
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• 2003

A result of Hardy and Littlewood relates Holder continuity of analytic functions in the unit disk with a bound on the derivative. Gehring and Martio extended this result to the class of uniform domains. In this paper we obtain a similar result to the class of uniformly John domains in terms of the inner diameter metric. We give several properties of a domain with the property. Also we show some results on the Holder continuity of conjugate harmonic functions in the above domains.

• East Asian mathematical journal
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• v.24 no.3
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• pp.289-293
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• 2008

We recently showed in [5] a semilocal convergence theorem that guarantees convergence of Newton's method to a locally unique solution of a nonlinear equation under hypotheses weaker than those of the Newton-Kantorovich theorem [7]. Here, we first weaken Miranda's theorem [1], [9], [10], which is a generalization of the intermediate value theorem. Then, we show that operators satisfying the weakened Newton-Kantorovich conditions satisfy those of the weakened Miranda’s theorem.

• Journal of the Korean Mathematical Society
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• v.56 no.2
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• pp.311-327
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• 2019

The aim of this paper is to extend the applicability of Gauss-Newton method for solving underdetermined nonlinear least squares problems in cases not covered before. The novelty of the paper is the introduction of a restricted convergence domain. We find a more precise location where the Gauss-Newton iterates lie than in earlier studies. Consequently the Lipschitz constants are at least as small as the ones used before. This way and under the same computational cost, we extend the local as well the semilocal convergence of Gauss-Newton method. The new developmentes are obtained under the same computational cost as in earlier studies, since the new Lipschitz constants are special cases of the constants used before. Numerical examples further justify the theoretical results.