• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.99.1-99.1
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• 2012

Hapke의 양방향 분포 함수를 균일하게 입힌 실 크기 3차원 달표면 BRDF 모델을 이용한 달의 조도 수치모사 와 Big Bear Solar Observatory(BBSO)의 달빛 조도 관측 결과를 비교하였다. 1999년 9월 5일 UT9:30에서 UT12:30까지 지구상의 $34^{\circ}$ 15'30.04"N $116^{\circ}$ 55'16.49"W 위치에서 계산된 달의 조도가 관측된 조도와 1% 이내의 차이를 보이는 것을 확인하였다. 이후 검증된 달의 BRDF 모델과 램버시안 산란 지구 모델을 이용해 시간별 전 지구 알베도 추이를 광선 추적 수치 모사한 결과와 실제 BBSO에서의 측정결과 간 1% 이내의 차이를 보이는 것을 확인하여, .BRDF 모델과 광선추적 수치모사 기법의 타당성을 검증하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.10
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• pp.788-793
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• 2017

This paper presents the verification of accuracies of theoretical models for calculating the microwave reflections from rough sea surfaces. First of all, the Pierson-Moskowitz ocean spectrum was used to generate the rough sea surfaces. Then the relationship between the significant wave heights, root-mean-square(RMS) heights and wind speed was derived by estimating the significant wave heights and RMS heights of the generated sea surfaces according to various wind speeds, and compared the derived relationship with other measurement data sets. The reflection coefficients of the sea surfaces were calculated by using a numerical method(the moment method). Then, the numerical results were compared with Ament model, PO(Physical Optics) model, GO(Geometrical Optics) model and B-M(Brown-Miller) model for various roughness conditions(wind speed) and incidence angles. It was found that the Ament model is not accurate except for a very low roughness conditions($kh_{rms}$<0.4, k is wavenumber and $h_{rms}$ is RMS height). It was also found that at incidence angles lower than $70^{\circ}$, the PO and the GO models agree well with the numerical results, while the B-M model agrees well with the numerical analysis results at incidence angles higher than $80^{\circ}$ for very rough sea surfaces with $kh_{rms}$>10.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.1
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• pp.58-69
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• 1995

The present paper is devoted to constructing a numerical algorithm for solving un steady problems on generation, propagation and interaction of nonlinear waves at a surface of ideal fluid, within the framework of the potential-flow model. The numerical scheme is implicit. with non-linearity iteration at every step of time. the finite-difference method with boundary-fitted coordinates are presented in favor for validity and high efficiency of the numerical model developed. Among these arguments, there are the results of calculations of two test problems-on stretching of a liquid ellipse and on wave generation by lifting a portion of a bottom.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.7
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• pp.721-730
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• 2012

The present paper presents a numerical study on multiphase flows induced by wall adhesion. The continuum surface force (CSF) model with the wall adhesion boundary condition model is used for calculating the surface tension force; this model is implemented in an in-house solution code (PowerCFD). The present method (code) employs an unstructured cell-centered method based on a conservative pressure-based finite-volume method with a volume capturing method (CICSAM) in a volume of fluid (VOF) scheme for phase interface capturing. The effects of wall adhesion are then numerically simulated by using the present method for a shallow pool of water located at the bottom of a cylindrical tank with no external forces such as gravity. Two different cases are computed, one in which the water wets the wall and one in which the water does not wet the wall. It is found that the present method efficiently simulates the surface tension-dominant multiphase flows induced by wall adhesion.

• Journal of Korean Society for Geospatial Information Science
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• v.14 no.4 s.38
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• pp.61-70
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• 2006

This paper presents photogrammetric processing to generate digital elevation models using SPOT-5 HRG stereo images and deals with the accuracy potential of HRG (High Resolution Geometry) supermode imagery for DEM generation. After bundle adjustment was preformed for sensor modelling, digital surface models were generated through the procedures of Epipolar image resampling and image matching. The DEM extracted from HRG imagery was compared along several test sections with the the refernce DEM which was obtained from the digital topographic maps of a scale of 1 to 5000. The ratio of the zone with DEM errors less than 5m to the whole zone was 53.8%, and about 2.5m RMSE was showed when assuming that the zones larger than 5m were affected by clouds, water bodies and buildings and excluding those zones from accuracy evaluation. In addition, the three-dimensional bird's eye view model and 3D building model were producted based on the DSM which was extracted from SPOT-5 HRG data.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.249-249
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• 2014

대면적 사각형 기판의 플라즈마 표면처리를 위한 유도 결합 플라즈마 발생 시스템의 수치 계산을 유체 모델을 이용하여 진행하였다. 연산 자원이 많이 요구되는 3차원 모델임을 감안하여 준중성 조건을 이용한 간략화 알고리즘을 사용하였다. Poisson 방정식을 풀지 않고 준중성 조건에 의한 양극성 전기장을 계산하여 이용한다. 쉬스는 모델을 이용하여 처리하였다. 1차적으로 사각 spiral 형태의 안테나를 가정하여 LCD 3세대 급의 기판을 대상으로 작성하였다. 다중 분할을 하지 않고 4개의 가지를 갖는 single spiral을 적용하였고 1.125 turn의 low impedance 구조에 대해서 계산하였다. Ar을 이용한 sputter etching 공정을 타겟으로 하여 기판에서의 Ar 이온 밀도 분포의 균일도가 어떤 설계 변수에 의해서 영향을 받는지를 중점적으로 계산하였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2013.05a
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• pp.65-66
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• 2013

최근 개발된 수치해석 알고리즘 및 RF sheath 모델을 적용하여 반도체 식각 공정용 공간 평균 시뮬레이터를 개발하였다. 개발된 시뮬레이터는 전자가열 모듈, 수송 모듈, 그리고 RF sheath 모듈로 구성된다. 유도결합 플라즈마원에 대한 전자가열모듈은 비충돌 과정인 anomalous skin effect가 포함된 Yoon의 모델을 적용하였고, 축전결합 플라즈마원에 대해서는 RF sheath 모델을 수치적으로 풀어 흡수된 파워를 결정하고 수송 모듈과 일관성을 잃지 않게 결합되었다. RF sheath 모듈에서는 Dai의 collisonless sheath 모듈을 적용하였고 RF 펄싱이 적용될 수 있도록 확장하였다. 특히, 식각 공정에 사용되는 fluorocarbon 플라즈마에 대한 데이터베이스를 개발하였고, 또한 진단 데이터와의 비교를 통해 데이터베이스를 최적화하였다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.2
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• pp.148-155
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• 1995

For an accurate prediction of the temperature Held induced by surface discharge of heated water into an ambient cross-flow field. a three-dimensional near-field numerical model using k-$\varepsilon$ turbulence clousure is developed Rather restricted as it is, the numerical results of the model agree well with the experimental data. The developed model simulates quite adequately the stratification, gravitational lateral spreading, and upward entrainment of thermal jet which cannot be simulated by a depth-integrated two-dimensional numerical model, as well as the interaction with cross-flow.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.6
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• pp.1257-1268
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• 1989

본 연구에서는 이에 천이와 난류모델을 첨가하여 층류 경계층이 천이를 거쳐 난류 경계층으로 발달해가는 전과정을 해석하려고 한다. 또, 이러한 부분 면파의 특성을 needle contact법에 의하여 측정 포물형이나 완전 Navier-Stokes 방정식을 사용함에 있어서 표면곡률항의 중요성을 보이며, 익형의 선단등 표면곡률이 중요한 영역에서도 적용가능한 수치적 방법을 제시한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.464-469
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• 2017

This study evaluated the displacements of a Cu bar in the Y-direction and the relationship between swaging pressures and total contact forces to increase the productivity of the rotor core swaging process. Elastic-plastic numerical analyses of four different Cu bar shapes were performed with a constant swaging pressure to evaluate the displacements of the Cu bar in the Y-direction and the contact force distributions at the contact surfaces during the swaging process. Based on the numerical analysis results, the following conclusions were obtained. First, a simplified 2-dimensional cyclic symmetric analysis model was developed for the numerical analysis of the rotor core swaging process. Second, the final displacements of the Cu bar in the Y-direction were nearly the same as the change of the Cu bar size at a constant swaging pressure. Third, a linear relationship between the swaging pressures and the total contact forces, the so called resistance forces, was suggested.