• Journal of the Chungcheong Mathematical Society
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• v.22 no.1
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• pp.73-80
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• 2009

This paper aims to study local and global structure of holomorphic flows on $\mathbb{C}^1$. At a singular point of a holomorphic flow, we locally sector the flow into parabolic or elliptic types. By the local structure of holomorphic flows, we classify all the possible types of topologies of $\omega$-limit sets.

• Journal of the Korean Society of Marine Environment & Safety
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• v.1 no.2
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• pp.61-67
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• 1995

This study examines experimentally and theoretically, the wave deformation by two large cylindrical structure in relation to the case of one structure. The wave height around the structures varies, according to the changes of the incident wave angles, the number of the structure, and the distances between the two structures. The wave deformation around the large cylindrical structures is shown to be well predicted theoretically by the diffraction theory based on the singular point distribution method using a vertical line wave source Green's function.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.146-152
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• 2002

In this study, the singular thermal stresses induced during cooling down from high temperature to room temperature have been analyzed for the viscoelastic thin layer. The time domain boundary element method has been employed to investigate the behavor of stresses for the whole interface. Within the context of a linear viscoelastic theory, a stress singularity exists at the point where the interface between the elastic substrate and the viscoelastic thin layer intersects the free surface.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.3
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• pp.447-457
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• 1994

This paper presents a compensation method for discrete-time control systems with saturation nonlinearities to cope with the reset windup phenomena. The proposed ARW (Anti-Reset Windup) method is motivated by the concept of the equilibrium point. The design parameter of the ARW scheme is explicitly derived by minimizing a reasonable performance index. The resulting dynamics of the compensated controller exhibits the reduced model form of the unsaturated system which can be obtained by the singular perturbational model reduction method. An example is given to illustrate the effectiveness of the proposed method.

• Journal of the Korean Mathematical Society
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• v.58 no.5
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• pp.1059-1079
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• 2021

We show that given any chain transitive set of a C¹ generic diffeomorphism f, if a diffeomorphism f has the eventual shadowing property on the locally maximal chain transitive set, then it is hyperbolic. Moreover, given any chain transitive set of a C¹ generic vector field X, if a vector field X has the eventual shadowing property on the locally maximal chain transitive set, then the chain transitive set does not contain a singular point and it is hyperbolic. We apply our results to conservative systems (volume-preserving diffeomorphisms and divergence-free vector fields).

• Honam Mathematical Journal
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• v.43 no.2
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• pp.259-267
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• 2021

Given 𝛽 > 1, we consider real numbers whose 𝛽-expansions are Sturmian words. When the slope of Sturmian words varies, their behaviors have been well studied from analytical point of view. The regularity enables us to find the Fourier series expansion, while the singularity at rational slopes yields a new kind of trigonometric series representing 𝜋.

• Journal of the Korean Institute of Landscape Architecture
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• v.27 no.4
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• pp.59-64
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• 1999

This study is about gaining orientation through anchorage act of a group of ferryman. In addition, a point acquisition and character of landmark that is closely realated to a point acquisition would be clarified by studying the form of configuration of the earth and object which is used landmark for anchorage. There are 13 anchorage points in the north part of Pusan harbor. 12 anchorage points are used to anchor. A ferryman let a ship which is temporarily anchoring move safely and speedily at the anchorage point. At that time, he uses landmarks by a technique of Overlay View. Between landmarks and viewer would be formed exquisite location combination. A mountain peak, a peak of island, nature configuration of land such as intermitent rock and location, size and form of buildings or structures of a city were variously appeared as landscape elements which were used landmarks. Looking at conditions to be easily captured as a target object, 1. A particular point of a mountain ridge line which was not shield by buildings. 2. In case objects have similar form, the building which was located in the front or the highest. 3. In case of a singular object, whatever there is physical elements, that would be a target object. Through this study a configuration of the ground such as a mountain peak which is become the background of harbor landscape is very important element to find anchorage point in configuration of the ground and object. So, the continuous preservation of the contour line of mountain is needed to do safe and effective anchorage act.

• Korean Journal of Mathematics
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• v.24 no.3
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• pp.545-565
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• 2016

In this paper, we present some general results on the pointwise convergence of the non-convolution type nonlinear singular integral operators in the following form: $$T_{\lambda}(f;x)={\large\int_{\Omega}}K_{\lambda}(t,x,f(t))dt,\;x{\in}{\Psi},\;{\lambda}{\in}{\Lambda}$$, where ${\Psi}$ = and ${\Omega}$ = stand for arbitrary closed, semi-closed or open bounded intervals in ${\mathbb{R}}$ or these set notations denote $\mathbb{R}$, and ${\Lambda}$ is a set of non-negative numbers, to the function $f{\in}L_{p,{\omega}}({\Omega})$, where $L_{p,{\omega}}({\Omega})$ denotes the space of all measurable functions f for which $\|{\frac{f}{\omega}}\|^p$ (1 ${\leq}$ p < ${\infty}$) is integrable on ${\Omega}$, and ${\omega}:{\mathbb{R}}{\rightarrow}\mathbb{R}^+$ is a weight function satisfying some conditions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.1
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• pp.71-77
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• 2001

A flow visualization study using the oil film method and the smoke-laser light sheet arrangement is carried out to investigate the three-dimensional flow pattern around the free end surface region of a finite circular cylinder (aspect ratios of 1.25 and 4.25) mounted on a flat plate. The experiment is performed for the cases of two Reynolds numbers: 5.92${\times}$10$^3$and 1.48${\times}$10(sup)5. Various kinds of singular points on the free-end surface are disclosed from the oil surface flow visualization. The smoke-laser light sheet visualization, to aid in understanding the oil streak-line patterns, clearly demonstrates that a pair of tornado-like vortices marched along the downstream together with a pair of side tip vortices. A topological sketch to characterize the surface flow and the four vortices emanating from the top surface is included.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.496-500
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• 1997

This paper describes an automated system for analyzing the stress intensity factors(SIFs) of three-dimensional (3D) cracks. A geometry model, i.e.a solid containing one or several 3D cracks is defined. Several distributions of local node density are chosen, and then automatically superposed on one another over the geometry model by using the fuzzy knowledge processing. Nodes are generated by the bucketing method, and ten-noded quadratic tetrahedral solid elements are generated by the Delauuay triangulation techniques. The singular elements such that the mid-point nodes near crack fornt are shifted at the quarter-points are automatically placed along the 3D crack front. THe complete finite element (FE) model generated, i.e the mesh with material properties and boundary conditions is given to one of the commercial FE codes, and a stress analysis is performed. The SIFs are calculated using the displacement extrapolation method. To demonstrate practical performance of the present system, a semi- elliptical surface crack in a plate subjected to tension is solved.