• 한국경영과학회지
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• 제19권1호
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• pp.189-199
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• 1994

This paper considers the covering network design problem (CNDP). In the CNDP, an undirected graph is given where nodes correspond to potential facility sites and arcs to potential links connecting facilities. The objective of the CNDP is to identify the least cost connected subgraph whose nodes cover the given demand points. The problem difines a demand point to be covered if some node in the selected graph is present within an appropriate distance from the demand point. We present an integer programming formulation for the problem and develop a dual-based solution procedure. The computational results for randomly generated test problems are also shown.

• 한국생활과학회지
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• 제16권2호
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• pp.227-235
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• 2007

This study investigated 4- and 5-year-olds' social knowledge and interpersonal problem solving strategies according to their sex, age, and hypothetical situation, and the relationships among them. Subjects were 116 preschoolers (73 boys and 43 girls; 68 four and 48 five-year-olds). Results showed that preschoolers had the higher scores of freindliness in potential entry situations than in support situations. Also, 4-year-old children were higher in forceful problem solving strategies than 5-year-olds. Furthermore, children's social knowledge assertiveness scores were positively related to their relevant problem solving strategies in conflict situations, while children's social knowledge friendliness scores were negatively related to their forceful problem solving strategies in conflict and potential entry situations.

• International Journal of Ocean System Engineering
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• 제2권1호
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• pp.32-36
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• 2012

This paper presents a comparison of potential and viscous computational codes for the water entry problem. A po-tential code was developed which adopted the boundary element method to solve the problem. A nonlinear free surface boundary condition was integrated to find new locations of free surface. The dynamic boundary condition was simplified by taking constant potential values for every time steps. The simplified dynamic boundary condition was applied in the new position of the free surface not at the mean level, which is the usual practice for linearized theory. The commercial code FLUENT was used to solve the water entry problem from the viscosity point of view. The movement of the air-liquid interface is traced by distribution of the volume fraction of water in a computational cell. The pressure coefficients were compared with each other, while experimental results published by other researchers were also examined. The characteristics of each method were discussed to clarify merits and limitations when they were applied to the water entry problems.

• 대한지리학회지
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• 제46권3호
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• pp.366-381
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• 2011

일반적으로 이산적 입지 공간에서 경쟁적 입지 문제는 입지 후보지에 따라 수많은 조합의 경우가 발생하는 의사결정 문제이기 때문에, 수리적으로 계산하기가 쉽지 않다. 따라서 본 연구에서는 결정적 배분 형태를 가정한 이산적 입지 공간의 경쟁적 입지 문제를 보다 효율적으로 해결하기 위한 대안적 방법에 대해 논의한다. 제안된 방법론의 핵심은 입지 문제의 크기와 관련되는 잠재적 입지후보지의 개수를 기하학적 개념을 이용하여 줄이는 것이다. 사례 분석으로 경쟁이 가열화되고 있는 초고속 인터넷 시장을 대상으로 제안된 방법론을 적용하였는데 두 가지 다른 크기의 문제, 즉 연구 지역 전체에 대해 정의된 잠재적 입지 후보지와 GIS 기반의 기하학적 알고리즘에 의해 추출된 보다 적은 수의 잠재적 입지 후보지에 대해 계산 결과와 공간적 배열을 비교하였다. 사례 분석 결과, 두 문제 모두 고객 유치를 최대화시키는 동일한 최적 입지를 보여주는 한편, 적은 수의 잠재적 입지 후보지를 가진 경쟁적 입지 모델이 보다 효율적으로 해결될 수 있었다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2008년도 하계학술대회 논문집
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• pp.385-387
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• 2008

Three-level Diode Clamped Multilevel Inverter, generally known as Neutral-Point-Clamped(NPC) inverter, has an inherent problem causing Neutral Point(NP) potential variation. Until now, in many literatures NP potential problem has been investigated and lots of solutions have also been proposed. However, in the case of NP potential variation was rarely published from the standpoint of reliability. In this paper, NP potential is analytically investigated both normal and fault conditions under carrier based PWM. Subsequently, relation between fault detection time and size of capacitor is analyzed. This information is explored by simulation results, which contribute to enhance the reliability of the NPC inverter system.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.373-376
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• 2002

The drift force acting on a floating OWC chamber in waves is studied taking account of fluctuating air pressure in the air chamber. A velocity potential in the water due to the free surface oscillating pressure patch is added to the conventional radiation-diffraction potential problem. The potential problem inside the chamber is formulated by making use of the Green integral equation associated with the Rankine Green function while the outer problem with the Kelvin Green function. The drift forces as well as the chamber motions are calculated taking account of the air pressure in the chamber.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1999년도 춘계 학술대회논문집
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• pp.113-123
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• 1999

본 연구에서는 3차원, 비압축성 유동에 적용 가능한 순수 벡터 포텐셜 방법 (Pure Vector Potential Method, PVPM for short)의 정식화를 수행하였고, 2차원의 경우에 적용 가능한 수치적 방법과 경계조건의 부여법을 상세히 설명하였다. 이 방법의 타당성을 검증하기 위하여 급작스럽게 출발하는 벽구동 웅덩이 내부 유동과 엄밀해가 존재하는 Stokes의 제 1문제를 수치해석하였다. 계산 결과들은 이 두 유동의 중요한 거동을 매우 잘 묘사하였다.

• 대한수학회보
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• 제50권2호
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• pp.499-506
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• 2013

The half-inverse spectral problem for an impulsive Sturm-Liouville operator consists in reconstruction of this operator from its spectrum and half of the potential. In this study, the spectrum of the impulsive Sturm-Liouville problem is given and by using the Hochstadt and Lieberman's method we show that if $q(x)$ is prescribed on (0, ${\frac{\pi}{2}}$), then only one spectrum is sufficient to determine $q(x)$ on the interval (0, ${\pi}$) for this problem.

• 대한기계학회논문집A
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• 제28권9호
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• pp.1320-1327
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• 2004

An efficient boundary-based technique is developed for addressing shape design sensitivity analysis in supercavitating flow problem. An analytical sensitivity formula in the form of a boundary integral is derived based on the continuum formulation for a general functional defined in potential flow problems. The formula, which is expressed in terms of the boundary solutions and shape variation vectors, can be conveniently used for gradient computation in a variety of shape design in potential flow problems. While the sensitivity can be calculated independent of the analysis means, such as the finite element method (FEM) or the boundary element method (BEM), the FEM is used for the analysis in this study because of its popularity and easy-to-use features. The advantage of using a boundary-based method is that the shape variation vectors are needed only on the boundary, not over the whole domain. The boundary shape variation vectors are conveniently computed by using finite perturbations of the shape geometry instead of complex analytical differentiation of the geometry functions. The supercavitating flow problem is chosen to illustrate the efficiency of the proposed methodology. Implementation issues for the sensitivity analysis and optimization procedure are also addressed in this flow problem.

• Journal of Ship and Ocean Technology
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• 제10권1호
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• pp.10-26
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• 2006

The radiation problem for oscillating bodies on the free surface has been formulated by the over-determined Green integral equation, where the boundary condition on the free surface is satisfied by adopting the Kelvin-type Green function and the irregular frequencies are removed by placing additional control points on the free surface surrounded by the body. The B-Spline based higher order panel method is then applied to solve the problem numerically. Because both the body geometry and the potential on the body surface are represented by the B-Splines, that is in polynomials of space parameters, the unknown potential can be determined accurately to the order desired above the constant value. In addition, the potential expressed in B-Spline can be differentiated analytically to get the velocity on the surface without introducing any numerical error. Sample computations are performed for a semispherical body and a rectangular box floating on the free surface for six-degrees of freedom motions. The added mass and damping coefficients are compared with those by the already-validated constant panel method of the same formulation showing strikingly good agreements.