• Journal of Mechanical Science and Technology
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• v.16 no.9
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• pp.1121-1136
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• 2002

The flow characteristics of film coolant issuing into turbulent boundary layer developing on a convex surface have been investigated by means of flow visualization and three-dimensional velocity measurement. The Schlieren optical system with a spark light source was adopted to visualize the jet trajectory injected at 35° and 90° inclination angles. A five-hole directional pressure probe was used to measure three-dimensional mean velocity components at the injection angle of 35°. Flow visualization shows that at the 90° injection, the jet flow is greatly changed near the jet exit due to strong interaction with the crossflow. On the other hand, the balance between radial pressure gradient and centrifugal force plays an important role to govern the jet flow at the 35° injection. The velocity measurement shows that at a velocity ratio of 0.5, the curvature stabilizes downstream flow, which results in weakening of the bound vortex structure. However, the injectant flow is separated from the convex wall gradually, and the bound vortex maintains its structure far downstream at a velocity ratio of 1.98 with two pairs of counter rotating vortices.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.2
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• pp.302-312
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• 1992

Three dimensional velocity measurements of a 35.deg. inclined jet issuing into turbulent boundary layer on both concave and convex surfaces have been conducted. To investigate solely the effect of each curvature on the flow field, streamwise pressure variations are minimized by adjusting the shape of the opposite wall in the curved region. From the measured velocity components, streamwise mean vorticities are calculated to determine jet-crossflow interface. The results on convex surface show that the injected jet is separated from the wall and the bound vortex maintains its structure far downstream. On concave surface, the secondary flow in the jet cross-sections are enhanced and in some downstream region from the jet exit, the flow on the concave surface has been developed to Taylor-Gortler vortices

• Journal of the Korean Mathematical Society
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• v.55 no.3
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• pp.695-704
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• 2018

In this paper we derive some basic inequalities connecting the Minkowski measure of symmetry, the Minkowski symmetral and the Banach-Mazur distance. We then explore the geometric contents of these inequalities and shed light on the structure of the quotient 𝔅/Aff of the space of convex bodies modulo the affine transformations.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.4
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• pp.916-925
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• 1988

The Navier-Stokes equations of the vorticity-stream-function form are solved numerically for the flow past a semicircular arc for Reynolds numbers in the range 0.1

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.3
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• pp.305-312
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• 2012

This paper aims at improving the accuracy and computational efficiency in reconstructing building boundaries from airborne Lidar points. We proposed an adaptive convex hull algorithm, which is a modified version of local convex hull algorithm in three ways. The candidate points for boundary are first selected to improve efficiency depending on their local density. Second, a searching-space is adjusted adaptively, based on raw data structure, to extract boundary points more robustly. Third, distance between two points and their IDs are utilized in detecting the seed points of inner boundary to distinguish between inner yards and inner holes due to errors or occlusions. The practicability of the approach were evaluated on two urban areas where various buildings exist. The proposed method showed less shape-dissimilarity(8.5%) and proved to be two times more efficient than the other method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.436-439
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• 2005

Dynamic contact of a cantilever beam with Sap at the end is discussed. The gap in a structure induces dynamic contact, and the contact problem is always accompanied by inequality constraints which mean that the solution of the structure with contact condition should satisfy variational inequality. Inequality, but, can be reduced to equality condition considering convex penalty function. In this paper, formulation of a beam with contact is derived using quasi convex penalty function. General coordinate solution which is needed to increase computational efficiency is applied. Nonlinear behavior of a beam with rigid and elastic contact condition was discussed.

• Journal of the Korean Operations Research and Management Science Society
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• v.10 no.1
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• pp.9-13
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• 1985

This paper develops a decomposition method for stochastic programming with a block diagonal structure. Here we assume that the right-hand side random vector of each subproblem is differente each other. We first, transform this problem into a master problem, and subproblems in a similar way to Dantizig-Wolfe's Decomposition Princeple, and then solve this master problem by solving subproblems. When we solve a subproblem, we first transform this subproblem to a Deterministic Equivalent Programming (DEF). The form of DEF depends on the type of the random vector of the subproblem. We found the subproblem with finite discrete random vector can be transformed into alinear programming, that with continuous random vector into a convex quadratic programming, and that with random vector of unknown distribution and known mean and variance into a convex nonlinear programming, but the master problem is always a linear programming.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.500-500
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• 2012

플라즈마 디스플레이 패널(PDP)는 미소체적의 dielectric barrier discharge (DBD)를 이용한 한 예로 볼 수 있다. PDP 셀은 실험을 통하여 방전 특성을 분석하기에 아주 작은 크기이기 때문에 시뮬레이션을 이용하는 것이 방전 특성을 분석하기에 유용하다. 시뮬레이션 방법 중 유체 시뮬레이션은 높은 압력에서 기체 방전을 분석하기에 아주 유용한 방법이다. PDP 전극 각도를 바꿈으로써 발광 효율을 높일 수 있음이 논문으로 발표 되었다. 이 발표에서는 2차원 유체 시뮬레이션을 사용하여 전극의 각도 변화뿐만 아니라 전극 간격과 압력 변화에 따른 방전 특성 변화를 연구하였다. 평판 전극의 각도 변화에 따라 전기장 세기, 방전 공간 내 전하 및 여기된 입자수 및 분포, 방전 개시 전압 등의 진단을 통하여 결과를 분석하였다. 전극 간격이 길어질수록 convex 구조의 효율 증가가 크게 나타났으며 압력이 커질수록 concave 구조의 효율 증가가 크게 나타났다.

• Bulletin of the Korean Mathematical Society
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• v.34 no.3
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• pp.385-394
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• 1997

In this paper, we prove in p-uniforlmy convex space a fixed point theorem for a class of mappings T satsfying: for each x, y in the domain and for n = 1, 2, 3, $\cdots$, $$ \left\$\mid$ T^n x - T^n y \right\$\mid$ \leq a \cdot \left\$\mid$ x - y \right\$\mid$ + b(\left\$\mid$ x - T^n x \right\$\mid$ + \left\$\mid$ y - T^n y \right\$\mid$) + c(\left\$\mid$ c - T^n y \right\$\mid$ + \left\$\mid$ y - T^n x \right\$\mid$, $$ where a, b, c are nonnegative constants satisfying certain conditions. Further we establish some fixed point theorems for these mappings in a Hilbert space, in $L^p$ spaces, in Hardy spaces $H^p$ and in Sobolev spaces $H^{p,k}$ for 1 < p < $\infty$ and k $\leq$ 0. As a consequence of our main result, we also the results of Goebel and Kirk [7], Lim [8], Lifshitz [12], Xu [20] and others.

• Journal of the Korean Society of Safety
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• v.28 no.4
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• pp.66-71
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• 2013

There is a critically structural problem of scaffolding system when one of scaffold columns is remove to be used as a gangway for their temporary office in the structure before finishing all such as an apartment or office building. This is not used to checking to structurally checking at a construction site. This study is to find out which system at a site will be more effective and low-cost-high effectiveness of aluminum ladder, timber ladder, ${\phi}$1/2 inch steel pipe truss with a type of concave, convex warren truss ladders. Theses are structurally tested with horizontal set as a truss type with 1.8 meter long. Concentrated load has been loaded at the upper center of the system and checked its strain at the bottom center, using aluminum-use strain gage and steel-use gauge have been attached concave warren truss with diameter 1/2 inch has 14% stronger than convex truss. Convex truss has almost same strength as an aluminum ladder truss, it is found out.