• International Journal of Naval Architecture and Ocean Engineering
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• 제6권2호
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• pp.219-235
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• 2014

With the development of the technology of underwater moving bodies, the need for developing the knowledge of surface effect interaction of free surface and underwater moving bodies is increased. Hence, the two-phase flow is a subject which is interesting for many researchers all around the world. In this paper, the non-linear free surface deformations which occur during the water-exit of a circular cylinder due to its buoyancy are solved using finite volume discretization based code, and using Volume of Fluid (VOF) scheme for solving two phase flow. Dynamic mesh model is used to simulate dynamic motion of the cylinder. In addition, the effect of cylinder mass in presence of an external force is studied. Moreover, the oblique exit and entry of a circular cylinder with two exit angles is simulated. At last, water-exit of a circular cylinder in six degrees of freedom is simulated in 3D using parallel processing. The simulation errors of present work (using VOF method) for maximum velocity and height of a circular cylinder are less than the corresponding errors of level set method reported by previous researchers. Oblique exit shows interesting results; formation of waves caused by exit of the cylinder, wave motion in horizontal direction and the air trapped between the waves are observable. In 3D simulation the visualization of water motion on the top surface of the cylinder and the free surface breaking on the front and back faces of the 3D cylinder at the exit phase are observed which cannot be seen in 2D simulation. Comparing the results, 3D simulation shows better agreement with experimental data, specially in the maximum height position of the cylinder.

• 지구물리와물리탐사
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• 제10권4호
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• pp.275-284
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• 2007

MT 탐사 자료의 정확한 해석에 있어 중요한 지형효과를 연구하기 위해서, 언덕과 골짜기가 있는 3차원 모형에 대한 겉보기 비저항, 위상, 티퍼, induction vector, 임피던스 극도표 등을 분석하였다. 지형에 의해 왜곡되는 MT 반응을 계산하기 위해서 변유한요소법에 기초한 3차원 알고리듬을 이용하였다. 겉보기 비저항과 위상에서 지형효과는 전류의 왜곡이 주 원인이다. 티퍼의 크기는 언덕과 골짜기에서 동일하지만, 방향은 언덕에서는 중앙으로 골짜기에서는 바깥쪽으로 향했다. Induction vector의 실수성분은 언덕에서는 중앙부로 골짜기에서는 바깥쪽으로 향했으나 허수성분은 이와 반대이다.

• 한국측량학회지
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• 제40권5호
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• pp.403-412
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• 2022

최근 4차 산업혁명이 본격화되고 차세대 ICT 융합 기술이 개발됨에 따라 건설분야 역시 기술변화에 대응하기 위해 다양한 스마트 건설기술이 건설 단계별로 빠르게 도입되고 있다. 특히, 건설현장의 경우 부지설계를 위한 토공량 산출 공정이 설계비용에 큰 부분을 차지하고 있어 공정의 효율화와 정확한 토공량 산출을 위한 관련 연구가 활발히 진행되고 있다. 본 연구는 건설현장의 지형을 3차원으로 신속하게 구축하고 이를 이용하여 효율적으로 토공량을 산출할 수 있는 방법을 제시하고자 한 것이다. 이를 위해 무인비행체로부터 획득한 대축척의 항공사진을 이용하여 건설현장을 3차원 실사모델로 구축하였다. 이때, 구축한 3차원 실사모델은 체적 산출이 불가한 surface 모델 구조를 가짐에 따라 체적 산출이 가능하도록 3차원의 solid 모델로 구조 변환을 수행하였다. 그리고 변환된 solid 모델을 이용하여 CAD 기반으로 토공량을 산출할 수 있는 방법론을 구상하였다. 정립한 방법론을 적용한 solid 모델로부터 토공량을 자동 산출한 결과, 기존의 현황측량 결과로부터 산출한 토공량과 1.52%의 상대적 편차를 확인할 수 있었다. 추가적으로 방법별 공정 소요시간을 비교분석한 결과 60%의 소요시간 절감을 확인할 수 있었다. 이로부터 본 연구에서 제시한 기법은 토공량 산출을 위한 비용절감은 물론 건설공사 전 공정에서 주기적인 현장의 모니터링 등 스마트 건설관리를 위한 기술로써 활용이 기대된다.

• 한국측량학회지
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• 제29권4호
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• pp.429-438
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• 2011

LiDAR technology is a combination of laser ranging, satellite positioning technology and digital image technology for study and determination with high accuracy of the true earth surface features in 3 D. Laser scanning data is typically a points cloud on the ground, including coordinates, altitude and intensity of laser from the object on the ground to the sensor (Wehr & Lohr, 1999). Data from laser scanning can produce products such as digital elevation model (DEM), digital surface model (DSM) and the intensity data. In Vietnam, the LiDAR technology has been applied since 2005. However, the application of LiDAR in Vietnam is mostly for topological mapping and DEM establishment using point cloud 3D coordinate. In this study, another application of LiDAR data are present. The study use the intensity image combine with some other data sets (elevation data, Panchromatic image, RGB image) in Bacgiang City to perform land cover classification using neural network method. The results show that it is possible to obtain land cover classes from LiDAR data. However, the highest accurate classification can be obtained using LiDAR data with other data set and the neural network classification is more appropriate approach to conventional method such as maximum likelyhood classification.

• 한국정밀공학회지
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• 제28권7호
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• pp.834-850
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• 2011

In this paper, a novel tissue engineering scaffold design method based on triply periodic minimal surface (TPMS) is proposed. After generating the hexahedral elements for a 3D anatomical shape using the distance field algorithm, the unit cell libraries composed of triply periodic minimal surfaces are mapped into the subdivided hexahedral elements using the shape function widely used in the finite element method. In addition, a heterogeneous implicit solid representation method is introduced to design a 3D (Three-dimensional) bio-mimetic scaffold for tissue engineering from a sequence of computed tomography (CT) medical image data. CT image of a human spine bone is used as the case study for designing a 3D bio-mimetic scaffold model from CT image data.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1997년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Fall 1997
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• pp.107-114
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• 1997

A dynamic fluid-structure-soil interaction analysis method is developed to investigate the effects of rocking motion on the seismic response of the 3-D flexible rectangular liquid storage tanks founded on the deformable ground. The governing equation of 3-D rectangular tanks subjected to the translational and rocking motions is obtained by Rayleigh-Ritz method. The dynamic stiffness matrix of the rigid surface foundation resting on the surface of a stratum are calculated by hyperelement method. The seismic responses of a 3-D flexible tank model founded on the deformable ground is calculated by combining the governing equation of the structural motion with the dynamic stiffness matrix of the rigid surface foundation.

• International Journal of Ocean System Engineering
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• 제3권2호
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• pp.68-76
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• 2013

In this study, a 3D numerical model was used to predict nonlinear wave forces on a cylindrical pile installed in a shallow water region. The model was based on solving the viscous and incompressible Navier-Stokes equations for a two-phase flow (water and air) model and the volume of fluid method for treating the free surface of water. A new application was developed based on the cut-cell method to allow easy installation of complicated obstacles (e.g., bottom geometry and cylindrical pile) in a computational domain. Free-surface elevation, water particle velocities, and inline wave forces were calculated, and the results show good agreement with experimental data obtained by the Danish Hydraulic Institute. The simulation results revealed that the proposed model can, without the use of empirical formulas (i.e., Morison equation) and additional wave analysis models, reliably predict non-linear wave forces on an offshore wind turbine foundation installed in a shallow water region.

• 대한조선학회논문집
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• 제41권1호
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• pp.75-81
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• 2004

In this study surface modeling .method with 3D curve net is proposed. For surface modeling, ship hull was divided into several parts, Generated surface was loaded general purpose CAD program through IGES file format, and the quality of generated surface model was checked by CATIA's internal function. Lastly it is tried to find a method for improving the accuracy of surface connection by using the blending method in CATIA and the result was discussed.

• 한국콘텐츠학회논문지
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• 제11권6호
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• pp.106-115
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• 2011

본 논문에서는 기존에 제시된 쉐이딩 알고리즘들이 음영 표현을 통해 3차원 물체의 형태를 효과적으로 전달하는지 평가하고 검증한다. 8가지 스타일로 쉐이딩된 10개의 3차원 물체 중의 한 개의 이미지를 사람들에게 보여주고 물체 표면의 여러 곳의 위치에서 곡면의 법선 벡터와 일치하도록 측정기(gauge)의 방향을 조정하도록 요청하는 스터디를 수행한다. 이 실험에서 수집한 법선 벡터 추정치가 사람들 간에 서로 일치하는지 비교하고 또한 실제 3차원 곡면 모델의 법선 벡터와 일치하는지도 비교한다. 본 논문의 실험을 통하여 물체의 음영을 표현하는 방법에 따라서 사람들이 물체의 형태를 다르게 해석한다는 사실을 보인다. 또한, 기존의 쉐이딩 알고리즘들 중에서 음영 톤의 단계수가 많고 톤 단계가 전반적으로 균일하게 분포되어 있는 특성을 가지는 알고리즘이 물체의 형태를 보다 효과적으로 표현하는 것으로 나타났다. 본 논문에서 수집한 실험 데이터 및 분석 결과는 물체의 형태를 효과적으로 전달하는 것을 목적으로 하는 새로운 CG 쉐이딩 알고리즘을 설계하는데 활용 가능할 것으로 기대된다.

• 한국해양공학회지
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• 제15권4호
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• pp.28-37
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• 2001

The water quality in Yongil Bay is getting worse due to the sewage and the waste water from the surrounding industrial complex. The study aims to simulate the current system that is necessary to build ecosystem model for the optium water quality control and clarify the correlation of current system characteristics with water quality in Yongil Bay. To clarify the characteristics of coastal water movement system and verify the applicability of the 3-D model, the current system was simulated using 3-D model baroclinic model which considers tidal current and density effects. As the results of numerical experiments, it is proved the 3-D model is the most applicable on appearing the current system of the stratificated Yongil Bay difference of density. Form the results of simulation considered tidal current only, it can be clarified that the water body flows in the inner bay through the bottom layer and flows out the outer bay through the surface layer in Yongil Bay. And the fresh water from the Hyongsan river and the thermal discharge form POSCO have a little effect on the current system in Yongil Bay, but the diffusion of heat and salt has an important effect upon the formation of the density stratification of the water quality distribution is closely related with the current structure characteristics as well as the tidal residual current system in Yongil Bay.