• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.34-37
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• 2009

본 논문에서는 원자적 계산(atomistic calculation)을 이용한 나노박막의 평형상태(self-equilibrium state)에 대한 해석기법을 제시한다. 두께가 얇은 나노박막은 표면 응력(surface stress)에 의한 영향으로 원자간 거리가 벌크상태의 거리보다 작아진다. 두께가 얇은 나노박막에서의 원자 사이의 거리는 표면 응력과 탄성계수들의 표현식으로 계산이 가능하며, 본 논문에서는 {100}, {111}, {110} 표면을 가지는 나노박막의 평형상태의 해석을 위한 해석적 방법을 제시한다. 원자 사이의 거리를 계산하기 위해서는 보다 정확한 표면 응력의 계산방법이 필요하다. 본 연구에서는 나노박막의 평형상태에 대한 해석을 위해 surface relaxation model을 제시하고, 이 모델을 이용하여 표면응력(surface stress)과 표면강성계수(surface stiffness tensor)와 같은 surface parameter의 계산을 수행한다. 본 논문에서 제시된 surface relaxation model을 검증하기 위하여 분자동역학 전산모사(molecular dynamics simulation)의 수치 결과를 제시하고, 본 연구에서 계산한 equilibrium strain과 비교 검증한다.

• Journal of Korean Port Research
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• v.11 no.1
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• pp.121-128
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• 1997

To analyze the ocean wave more efficiently, more fine grids are used with relatively less computer memory. Each element of free surface is discretized into more fine grids because the ocean waves are much influenced by the mesh used in the finite difference scheme. According to the flow analysis, remarkable improvements could be seen in the free surface generation. The multi grid is applied to confirm the validity of scheme. The Baldwin Lomax turbulence model is used for the analysis of S103 Inuid ship. Finally some discussion on experiments was made for the physical phenomena of the viscous

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.131-134
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• 2009

Krylov 부공간 모델차수축소법은 초기 유한요소모델과 축소모델의 전달함수의 계수인 모멘트를 일치시키는 방법을 이용하는 축소기법으로 이미 대형 유한요소모델의 주파수응답 해석의 효율적인 계산에 많이 사용되고 있는 방법 중의 하나이다. 본 논문에서는 Krylov 부공간 축소기법을 이용한 관심 주파수영역에 대한 주파수응답 해석 및 이를 통하여 계산된 주파수응답의 여러 가지 설계변수에 대한 설계민감도 해석방법을 제안하였다. 일반적으로 구조물의 주파수응답을 고려한 최적설계를 위해서는 설계변수에 대한 관심 주파수영역에서의 주파수응답 및 그의 민감도 정보가 요구되므로, 고려하는 유한요소모델이 대형일 경우에 관심 주파수영역에서의 반복적인 해석으로 인한 계산비용의 문제가 대두된다. 본 논문에서는 축소모델을 이용하여 주파수응답과 주파수응답의 설계민감도 해석을 수행하여 계산의 효율성을 극대화하였다. 민감도 계산에는 시간측면과 구현의 용이성 측면에서 장점이 있는 준해석적 방법을 이용하였다. 수치 예제를 통하여 축소기법을 이용한 주파수응답의 설계민감도 해석 결과를 유한차분법에 근거한 민감도 결과와 비교하였다. 본 논문에서 제안된 방법을 이용하는 경우, 주파수응답을 고려한 최적설계를 계산비용 측면에서 매우 효율적으로 수행할 수 있을 것이다.

• Fire Science and Engineering
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• v.31 no.3
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• pp.49-53
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• 2017

In the present study, the hydrodynamic force acting on the vertical wall of a portable water storage tank is examined. A Dispersion Relation Preserving (DRP) method, proposed by Jang, is applied for simulating lapping waves and their impact on the wall. A meaningful investigation has been observed, which may be applied to the strength design for the portable water storage tank.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.1
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• pp.14-28
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• 1992

For a planar curve-sided paned with constant or linear density distributions of source or doublet in the singularity methods, Cantaloube and Rehbach(1986) show that the surface integral can be transformed into contour integral by using Stokes' formulas. As an extension of their formulations, this paper deals with a planar polygonal panel for which we derive the closed-forms of the potentials and the velocities induced by the singularity distributions. Test calculations show that the analytical evaluation of the closed-forms is superior to numerical integration(suggested by Cantaloube and Rehbach) of the contour integral. The compact and explicit expressions may produce accurate values of matrix elements of simultaneous linear equations in the singularity methods with much reduced computer tiome.

• Geotechnical Engineering
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• v.11 no.3
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• pp.139-162
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• 1995

The possibility of the development of gas driven hydrofractures at the Waste Isolation Pilot Plant(WIPP) is investigated through analytical and numerical calculations and through laboratory experiments. First, an investigation of the chemical reactions involved shows that a large volume of gas could potentially be generated through the oxidation of iron in the waste. Simple ground water'flow calculations then show that unless regions of high permeability has been created, this gas volume will build up the pressure high enough to cause tensile damage in the horizontal planes of weakness or in the halite itself. The analytical calculations were performed using the concepts of linear elastic fracture mechanics and the numerical calculations were done using the finite element method. Also, laboratory tests were conducted to illustrate possible failure mechanisms. It is possible that after growing horizontal crack in the weaker anhydride layer, the crack could break out of this layer and propagate upward into the halite and toward the ground surface at an inclined argle of around 53$^{\circ}$ above horizontal. To prevent this latter phenomenon the anhydrite must have a fracture toughness less than 0.5590 times than that of the halite. Through the tests, three types of crack(radial vertical cracks, horizontal circular cracks and cone -shaped cracks) were observed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.2
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• pp.157-163
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• 2010

Solid oxide fuel cells (SOFCs) are commonly composed of ceramic compartments, and it is known that the physical properties of the ceramic materials can be changed according to the operating temperature. Thus, the physical properties of the ceramic materials have to be properly predicted to develop a highly reliable simulation model. In this study, several physical properties that can affect the performance of SOFCs were selected, and simulation models for those physical properties were developed using our own code. The Gibbs free energy for the open circuit voltage, exchange current densities for the activation polarization, and electrical conductivity for the electrolyte were calculated. In addition, the diffusion coefficient-including the binary and Knudsen diffusion mechanisms-was calculated for mass transport analysis at the porous electrode. The physical property and electrochemical reaction models were then simulated simultaneously. The numerical results were compared with the experimental results and previous works studied by Chan et al. for code validation.

• Journal of Radiation Protection and Research
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• v.27 no.1
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• pp.67-75
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• 2002

The groundwater flow and contaminant transport numerical models have been established for understanding the movement of pollutants in surface soil environment. The numerical solutions were compared with the analytic solutions for the verification and the application of the models. The numerical solutions from the groundwater and transport models agreed welt with analytic solutions. Especially, the results of groundwater flow model were validated in one- and two-dimensional heterogeneous media. Therefore, it will represent well the characteristics of the heterogeneous media in the field applications. Also, the phenomena of the pollutant dispersion represented quite well by the advection and the hydrodynamic dispersion in the results of the transport model. The important input factor is the choice of complicated boundary conditions in operating the numerical models. The numerical results are influenced by the choice of the proper boundary conditions.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.1
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• pp.9-26
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• 2001

In this paper. the development of a pusher-barge hull form which enables the continuous transportation along the coast and canal is performed. For the design stage of the hull forms. these are developed for Kyungin canal which is will be drawn up as the next contribution project of the Korean government are adopted. The model tests for the designed ship are carried out in the Inha University Towing Tank and the numerical simulations are done with a finite difference method based on MAC scheme. At first, the experiments are performed with designed model ships from low speed to high speed including service speed(6knots) among the corresponding designed speed. Resistance characteristics of designed ships are compared with experimental results of other several pusher-barge hull shapes. Next, the numerical simulations are performed for three cases, that is pusher only, barge only and pusher-barge condition in the designed speed. Each calculations are carried out in deep and restricted water condition. The flow characteristics around hulls in the latter condition are compared with those in the former condition.

• Journal of Korean Association for Spatial Structures
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• v.6 no.3 s.21
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• pp.77-86
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• 2006

The stress analysis of cold-formed channel section steel beams under transverse load is presented. The local buckling as well as the lateral buckling effects are included in the analysis. The analytical model is developed based on the thin-walled beam theory, and a one-dimensional finite element model is formulated to solve the analytical model. Numerical results are compared with AISI code. It shows that the proposed model is appropriate for predicting of stress as well as deflection of the cold-formed channel section beam.