• 전자공학회논문지CI
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• 제49권4호
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• pp.71-81
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• 2012

다양한 사용자들이 증강 현실을 쉽게 제작하기 위하여 3차원 물체의 추적 및 인식이 가능하도록 하기 위한 물체 등록과정이 직관적이고 간단하여야 한다. 물체 등록에 활용될 수 있는 다양한 3차원 재구성 방법이 개발되었지만, 아직은 실험적인 단계에 있다. 본 논문은 증강 현실 저작 시 다양한 사용자들에게 다양한 환경에서 직관적으로 활용될 수 있도록 하기 위한 3차원 재구성 방법으로써 마커를 활용하는 마커 기반 탠저블 인터페이스를 제안한다. 본 논문에서 제안하는 인터페이스를 이용하여 사용자가 물체의 표면을 직접 접촉함으로써 물체 여러 표면의 3차원 기하학 정보를 획득한다. 이 인터페이스를 이용하여 단순히 그래픽적인 모델링을 위한 3차원 재구성을 하는 것이 아니라 물체의 특징점 정보를 제공함으로써 증강현실에 활용할 수 있도록 한다. 최종적으로 제안하는 방법을 통하여 증강 현실 응용을 보임으로써 제안하는 방법의 효용성을 확인한다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1995년도 추계 학술대회논문집
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• pp.43-48
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• 1995

A numerical computation is carried out to analyse characteristics of flow fields around Air Supported Ships having arbitrary form. The computations are performed in a rectangular grid system with MAC(Marker And Cell) method. The governing equations are represented in a Finite Difference form by forward differencing in time and centered differencing in space except for convection terms. For validation of this numerical analysis method, the computation of flow fields around Catamaran and ACV(Air Cushion Vehicle) with pressure distribution on free surface are done, and that around Surface Effect Ship is also carried out. The results of the computations are compared with the those of existed numerical computation and experimental results with the same condition.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 추계학술대회논문집
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• pp.1-1
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• 2009

In this presentation, I talk about various fluid simulation methods that have been developed for computer graphics special effects since 1996. They are all based on CFD but sacrifice physical reality for visual plausability and time. But as the speed of computer increases rapidly and the capability of GPU (graphics processing unit) improves, methods for more physical realism have been tried. In this talk, I will focus on four aspects of fluid simulation methods for computer graphics: (1) particle level-set methods, (2) particle-based simulation, (3) methods for exact satisfaction of incompressibility constraint, and (4) GPU-based simulation. (1) Particle level-set methods evolve the surface of fluid by means of the zero-level set and a band of massless marker particles on both sides of it. The evolution of the zero-level set captures the surface in an approximate manner and the evolution of marker particles captures the fine details of the surface, and the zero-level set is modified based on the particle positions in each step of evolution. (2) Recently the particle-based Lagrangian approach to fluid simulation gains some popularity, because it automatically respects mass conservation and the difficulty of tracking the surface geometry has been somewhat addressed. (3) Until recently fluid simulation algorithm was dominated by approximate fractional step methods. They split the Navier-Stoke equation into two, so that the first one solves the equation without considering the incompressibility constraint and the second finds the pressure which satisfies the constraint. In this approach, the first step introduces error inevitably, producing numerical diffusion in solution. But recently exact fractional step methods without error have been developed by fluid mechanics scholars), and another method was introduced which satisfies the incompressibility constraint by formulating fluid in terms of vorticity field rather than velocity field (by computer graphics scholars). (4) Finally, I want to mention GPU implementation of fluid simulation, which takes advantage of the fact that discrete fluid equations can be solved in parallel.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2000년도 Proceeding of CIN-KIN Joint Symposium 2000 on M.E.T. Under STCW 78/95 and SINO-KOREA MARITIME CONTACT IN MID-CENTURIES
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• pp.107-114
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• 2000

Marine analysis was made to investigate the hydrodynamic effects of a Wing in Ground (WIG) by means of finite difference techniques. The air flow field around WIG is analyzed by the Marker & Cell (MAC) based method, and the interaction between WIG and the free surface are studied by showing pressure distributions above the free surface. In the latter part, computations are extended to make clear the flow characteristics of a high speed catamaran in the rang of Froude numbers 0.2 to 1.0 with a separation to length ratios of 0.2, 0.3 and 0.5. The Navier-Stokes solver is invoked in which the nonlinear free-surface boundary condition is applied. For the validation, computational results are compared with the experiments.

• Journal of Computational Design and Engineering
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• 제1권1호
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• pp.1-12
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• 2014

In this paper, we propose a new method of reconstructing the hand models for individuals, which include the link structure models, the homologous skin surface models and the homologous tetrahedral mesh models in a reference posture. As for the link structure model, the local coordinate system related to each link consists of the joint rotation center and the axes of joint rotation, which can be estimated based on the trajectories of optimal markers on the relative skin surface region of the subject obtained from the motion capture system. The skin surface model is defined as a three-dimensional triangular mesh, obtained by deforming a template mesh so as to fit the landmark vertices to the relative marker positions obtained motion capture system. In this process, anatomical dimensions for the subject, manually measured by a caliper, are also used as the deformation constraints.

• 대한방사선치료학회지
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• 제33권
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• pp.99-108
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• 2021

목 적: 사이버나이프를 이용한 정위적 부분유방방사선치료(Stereotactic Partial Breast Irradiation) 시 기존의 침습적인 위치표지자(Fiducial Marker) 삽입 방식이 아닌 비침습방식에 대한 유용성을 평가 하고자 한다. 대상 및 방법: 본 연구를 위한 영상 중심(Imaging Center)의 일치도는 2D모의치료기와 사이버나이프의 양사방향(Both oblique, 45 °, 315 °) 영상 획득 후 다이스 유사 계수를 통해 정량적으로 평가하였다. 표면위치표지자의 위치 재현성은 본원 프로토콜을 기반으로 ATOM Phantom 표면에 금 재질의 위치표지자 8개를 부착하고 2D모의치료와 치료계획, 사이버나이프 영상을 분석하여 평가 하였다. 결 과: 영상 중심의 일치도 평가결과는 양사방향(45 °, 315 °)에서 각각 0.87, 0.9 였다. 표면위치표지자의 재현성 평가 결과 좌측 유방은 수평수직방향 Superior/Inferior 0.3 mm, Left/Right -0.3 mm, Anterior/Posterior 0.4 mm, 회전 방향 Roll 0.3 °, Pitch 0.2 °, Yaw 0.4 ° 로 나타났다. 우측 유방은 수평수직방향 Superior/Inferior -0.1 mm, Left/Right -0.1 mm, Anterior/Posterior -0.1 mm 회전 방향 Roll 0.2 °, Pitch 0.1 °, Yaw 0.1 ° 로 나타났다. 결 론: 사이버나이프를 이용한 정위적 부분유방암방사선치료 시 표면위치표지자의 비침습 트로토콜을 기반으로 통증 및 감염 등의 예방과 전처치 시간을 줄이고 환자의 경제적 부담을 경감 할 수 있었으며, 영상 중심의 높은 일치도 및 위치표지자의 재현성을 바탕으로 치료에 유용할 것으로 사료된다.

• 한국전기전자재료학회논문지
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• 제26권6호
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• pp.425-428
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• 2013

In this paper, we present a novel hydrophilic coating material (Wellture Finetech, Korea) which can be utilized as a coating layer for anti-contamination for electrical and electronic system. The coating material was deposited on 4 inch silicon wafer with several different film thickness. The film thickness was controlled by spin coating speed. After curing of the film, we have scratched by permanent marker to check self-cleaning property of the film. Also we have executed several mechanical tests of the films. As the spin coating speed is increased, the film thickness was thinned from 230 nm to 125 nm. Contact angle of the film was lowered from $30^{\circ}$ to $12^{\circ}$ as the spin coating speed is increased from 700 to 2,500 rpm. On permanent marker scratched film surface coated at 1,000 rpm, we have poured regular city water to investigate self cleaning property of the film. The scratches were gradually separated from the film surface due to super-hydrophilicity of the film. Hardness of spin coated film was 9H measured by ASTM D3363 method. and adhesion of all film was 5B tested by ASTM D3359 method. Also, to get exact hardness value of the film, we have utilized a nano-indenter. As spin speed is increased, the hardness of film was increased from 3 GPa to 5 GPa.

• 대한조선학회논문집
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• 제56권4호
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• pp.308-315
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• 2019

In this study, numerical simulations of slamming impact pressure acting on the flat plate and wedge type models using the cartesian-grid system and Modified Marker-Density Method (MMD method) were performed and the results were examined. The flat plate and wedge type models were selected as target objects, the turbulence characteristics were considered by applying the Sub-Grid Scale (SGS) turbulence model. Through this study, how the pressure acting on the target objects according to the incident angle influences the slamming impact pressure was examined and the results were compared with the flow characteristics of other experimental results. Also, the degree of slamming impact pressure is evaluated with respect to the cartesian-grid system and MMD method, which is easy to use and has a high degree of calculation for free surface.

• Journal of Mechanical Science and Technology
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• 제15권4호
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• pp.465-472
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• 2001

A numerical study is carried out to clarify the characteristics of flow fields and breaking phenomena around a high speed catamaran hull advancing on calm water. Computations are carried out for Froude numbers between 0.2 and 1.0 and for ratios of the distance between hulls to the catamaran length varying between 0.2 and 0.5 for a mathematically defined Wigley hull. A Navier-Stokes solver which includes the nonlinearities of free surface conditions is employed. Computations are performed in a rectangular grid system based on the Marker & Cell method. For validation, present computation results are compared with existing experimental results. As an application, the results of the displacement catamaran are used for the breaking analysis.

• 한국해양공학회지
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• 제11권2호
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• pp.70-76
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• 1997

수치격자의 크기제한에 의한 자유표면 유동해석 문제를 효율적으로 다루기 위하여 자유표면의 모든 격자를 x 방향으로 4,8,12개로 등분할 하고, y 방향으로는 4개로 잘라서 계산하였다. 이중격자 또는 삼중격자로 Navier-Stokes 방정식의 각항에 크기가 다른 격자를 사용해 효율을 향상시키는 계산방법의 연장으로, 본 논문에서는 자유표면 방정식에 보다 세분화된 격자를 적용해, Marker Particle 이동 및 자유수면 형성에 효율향상을 줄수 있는 수치방법을 도입하였다. 계산결과에 의하면 초기사용 격자가 coarse한 경우가 본방법의 효과가 커짐을 알 수 있고 대상물로는 층류유동에서 Wigley모형과 낭류유동의 S103 모형이다.