• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 봄 학술발표회 논문집
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• pp.577-584
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• 2001

For construction and design of tunnels, groundwater flow models are used to find the influence of groundwater to the stability of tunnels considering the geological condition around the tunnels and the materials used in tunnel linings. For the analysis of tunnel flow, some commercial programs, e.g. MODFLOW, SEEP/W etc., are used. These programs have limitations that MODFLOW could not define curved surface smoothly in three dimensional flow media and SEEP/W is the 2-dimensional flow model. In this paper, the ability of a finite element program developed for analyzing 3-dimensional groundwater flow is examined. Confined steady state groundwater flow solution in non-homogeneous media is obtained using isoparametric element with eight trilinear hexahedron nodes and is compared with the result of MODFLOW. It was found that the solution yielded a good result with the three dimensional flow studied.

• 대한조선학회논문집
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• 제47권3호
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• pp.291-305
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• 2010

A three-dimensional time-domain calculation method is of crucial importance in prediction of the motions and wave loads of a ship advancing in a severe irregular sea. The exact solution of the free surface wave-ship interaction problem is very complicated because of the essentially nonlinear boundary conditions. In this paper, an approximate body nonlinear approach based on the three-dimensional time-domain forward-speed free-surface Green function has been presented. The Froude-Krylov force and the hydrostatic restoring force are calculated over the instantaneous wetted surface of the ship while the forces due to the radiation and scattering potentials over the mean wetted surface. The time-domain radiation and scattering potentials have been obtained from a time invariant kernel of integral equations for the potentials which are discretized according to the second-order boundary element method (Hong and Hong 2008). The diffraction impulse-response functions of the Wigley seakeeping model advancing in transient head waves at various Froude numbers have been presented. A simulation of coupled heave-pitch motion of a long rectangular barge advancing in regular head waves of large amplitude has been carried out. Comparisons between the linear and the approximate body nonlinear numerical results of motions and wave loads of the barge at a nonzero Froude number have been made.

• Coupled systems mechanics
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• 제8권4호
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• pp.339-350
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• 2019

A numerical simulation of the incompressible multiphase hydraulic jump flow was performed to compare the interface prediction through the use of the three RANS turbulence models: $k-{\varepsilon}$, $RNGk-{\varepsilon}$ and SST $k-{\omega}$. A three dimensional no submerged hydraulic jump and a two dimensional submerged hydraulic jump were modeled. Both the geometry and the mesh were created using the open source Gmsh code. The project's geometry consists of a rectangular channel with length and height differences between the two dimensional and three dimensional simulations. Uniform hexahedral cells were used for the mesh. Three refining meshes were constructed to allow to verify simulation convergence. The Volume of Fluid (abbr. VOF) method was used for treatment of the air-water surface. The turbulence models were evaluated in three distinct set up configurations to provide a greater accuracy in the flow representation. In the two-dimensional analysis of a submerged hydraulic jump simulation, the turbulence model RNG RNG $k-{\varepsilon}$ provided a better interface adjust with the experimental results than the model $k-{\varepsilon}$ and SST $k-{\omega}$. In the three-dimensional simulation of a no-submerged hydraulic jump the k-# showed better results than the SST $k-{\omega}$ and RNG $k-{\varepsilon}$ capturing the height and length of the ledge with a better fit with the experimental results.

• 한국수산과학회지
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• 제47권2호
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• pp.168-173
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• 2014

The effect of critical minimum depth in the coastal region on storm surges was examined using a three-dimensional primitive equation model (POM). Case studies using numerical experiments in a small coastal bay in the southern sea of Korea (Hanam Bay) have examined the 'critical depth' (CD) that stabilizes the numerical calculations. Dependence of the CD of typhoon tracks and tidal components such as M2, S2, O1, and K1 were examined. The model results clearly demonstrated that the numerically unstable state of the calculation was caused by the coarse resolution of sea surface elevation.

• Bulletin of the Korean Chemical Society
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• 제21권11호
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• pp.1095-1100
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• 2000

we have proposed a three-dimensional GLE approach to gas-surface reactive scattering, model H + H $${\rightarrow}$H_2/Si(100)-(2$ ${\times}$1) system, and the implementation of 3D GLE method on the hydrogen on silicon surface has been presented. The formalism and algori thm of the 3D GLE are worked properly in the reactive scattering system. The calculated normal mode frequencies of surface vibrations were almost identical to previous harmonic slab calculations. The reaction probabilities were calculated for two energies. The calculations show that a very large amount of energy is transferred in surface in low energy scattering. Three different types of reaction mechanisms has been observed, which can not be shown in flat and rigid surface models. Further work on the reaction mechanisms and calculations of the vibrational and rotation distributions of products is in progress. The results will be reported elsewhere soon.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 B
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• pp.828-830
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• 2000

This paper describes BIEM(Boundary Integral Equation Method) for computation of three dimensional electric field distribution and numerical method that an equivalent charge density is unknown variable. After computing numerically the surface charge distribution. the distribution of both potential and electric field are obtained. Finally, this numerical method is applied to the concentric sphere and the coaxial cylindrical model and numerical result is compared to the analytic solution.

• 박물관보존과학
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• 제22권
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• pp.15-26
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• 2019

이 연구에서는 표면형상 취득에 최적화되어 있는 광학식 정밀스캐닝과 내부 형상획득에 사용되는 X-선 CT스캐닝 결과를 이용하여 삼총통의 내·외부 형상을 다각적으로 분석할 수 있는 3차원(이하 3D) 융합 모델을 제작하였다. 먼저 두 스캐닝 결과를 호환 가능한 확장자로 변환 한 다음 상호간의 정합성을 검증하고자 3D 편차분석을 수행하였다. 이 결과, 두 스캐닝 모델은 대부분(56.98%) ±0.1mm 이내의 편차를 보였으며, 이 수치는 ICP 알고리즘 기반의 정합 및 병합에 큰 영향을 주지 않았다. 병합된 데이터는 총통의 외부 표면색 및 미세형상, 내부 두께 및 구조를 잘 표현하였다. 광학식 표면스캐닝과 X-선 CT스캐닝의 3D 융합 모델은 문화유산의 디지털기록화뿐만 아니라 제작기법 해석에 유용하게 사용되었다. 향후 박물관 전시 영역에서 전시품의 과학적 조사 정보를 보다 쉽게 관람객에게 전달하는 효과를 발휘 할 것으로 기대된다.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.318-321
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• 2002

As a part of the next generation PET project, we have developed a depth of interaction detector which is consist of three-dimensional arrays of GSO crystal elements sized 2.9mm ${\times}$ 2.9mm ${\times}$ 7.5mm. The basic structure of a detector block is 4-stages in depth, one stage is composed of 2 by 2 array of the crystal elements. The blocks are optically coupled to a position sensitive photomultiplier tube. Each crystal element can be in different conditions; rough or chemical etching for the crystal surface. The effect of the difference of crystal surface condition on the detector performance was analyzed in one-dimensional crystal array as a basic study for the three-dimensional detector by a simple model which is considered only probabilities of transmission, reflect and absorption of photons are in a crystal. As the next step, we investigated the effect of different crystal surface condition in a "U shaped detector" which is an array of stacked crystals bending at the center.

• 한국지구과학회지
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• 제39권1호
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• pp.46-52
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• 2018

이 논문은 자체 개발된 드론을 이용하여 사진측량기술을 적용하여 3차원 수치지표면모델(DSM)개발 연구를 수행하였다. 이 DSM을 개발하기 위하여 제주도 지역을 선정하여 24장의 사진을 개발된 드론으로 직접 촬영을 수행하였다. 촬영된 사진의 정확한 3차원 좌표를 부여하기 위하여, 10개의 지표기준점(GCP)점을 선정하여 상대측위 지구위치시스템(DGPS)측량을 실시하였다. 사진의 정확도를 평가하기 위하여 3개의 GCP점을 선정하여 사진상의 좌표와 지상점의 좌표의 정확도를 비교하였다. 사진좌표계과 지상좌표계의 정확도를 평가한 결과 수평오차는 8.8-14.7 cm로 나타났으며, 연직오차는 12.4 cm로 나타났다. 이 정확도는 국토지리정보원(NGII)이 인정하는 1/1,000 수치지도의 정확도를 가지는 측량결과이다. 이 연구를 통하여 본 연구에서 개발된 드론과 사진측량기법이 제주지역에서 우리가 원하는 DSM자료를 얻는데 유용한 기술임을 알 수 있었다.

• 대한치과기공학회지
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• 제29권1호
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• pp.93-101
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• 2007

The purpose of this study is to evaluate the effect of three different oblique mechanical loading to occlusal surfaces of posterior implant partial dentures on the stress distributions in surrounding bone, using 3-dimensional finite element method. A 3-dimensional finite element model of a posterior implant partial dentures composed of three unit implants, simplified 3 gold alloy crown and supporting bone was developed according to the design of AVANA self tapping implant for this study. Three kinds of surface distributed oblique loads(300 N) are applied to following occlusal surfaces in the three crowns; 1) All occlusal surfaces in the three crown(load of 300 N was shared to three crown), 2) Occlusal surface of centered crown (load of 300 N was applied to a centered crown), 3) Occlusal surface of proximal crown(load of 300 N was applied to a distal proximal crown). In the results, 141 MPa of maximum von Mises stress was calculated at third loading condition and 98 MPa of minimum von Mises stress was calculated at first loading condition. From the results, location and type of occlusive loading conditions are important for the safety of supporting bone.