• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6B
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• pp.379-385
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• 2012

Recent development of computing power and theoretical advances in computational fluid dynamics have made possible numerical simulations of water waves with full Navier-Stokes equations. In this study, an internal wave maker using the mass source function approach was combined with the level set finite element method for generation of waves. The model is first applied to the two-dimensional linear wave generation and propagation. Then, it is applied to the three-dimensional simulation of the same problem. To effectively utilize computational resources and enhance the speed of execution, parallel algorithms are developed and applied for the three-dimensional problem. The results of numerical simulations are compared with theoretical values and good agreements are observed.

• 한국HCI학회:학술대회논문집
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• 2006.02a
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• pp.535-540
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• 2006

집적 영상(Integral Imaging) 시스템은 관찰자가 특수안경의 착용 없이 육안으로 3 차원 영상을 볼 수 있는 무안경식 양안시차 디스플레이 방식 중 하나로, 수직, 수평 시차와 총천연색의 영상을 제공한다. 집적영상 시스템은 3 차원 정보를 2 차원 엘리멘탈 이미지 (Elemental image)의 형태로 저장하는데, 엘리멘탈 이미지는 조금씩 다른 방향에서 제한된 크기로 촬영된 이미지이다. 엘리멘탈 이미지는 컴퓨터 그래픽으로 만들어질 수도 있는데, 이를 이용하는 집적 영상 방식을 CG 직접 영상 시스템이라 한다. 이와 같이 컴퓨터 계산에 의해 엘리멘탈 이미지를 얻는 과정을 이미지 매핑 (Image mapping)이라 부른다. 이제까지 제안된 이미지 매핑 방식에는 점대점 (Point to Point), MVR (Multi-Viewpoint Rendering), PGR (Parallel Group Rendering) 이 있다. 그러나 이런 방식들은 계산량이 많거나 렌즈 어레이 개수의 증가에 의해 속도에 영향을 받는 단점이 있어, 아직 가상현실 같은 실시간 CG 응용 분야에 사용하기 어려운 문제가 있다. 본 논문에서는 VVR (Viewpoint Vector Rendering)이라는 기존의 방법과 비교해 향상된 새로운 이미지 매핑 방법을 제안한다. 먼저 VVR 개념을 자세히 설명한 후 VVR 을 사용한 집적 영상 시스템을 구현하여 MVR 방법과 비교 분석한 실험결과와 개선되어야 할 방향을 제시한다.

• Journal of Radiation Protection and Research
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• v.10 no.1
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• pp.41-49
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• 1985

Neutron Streaming analysis in 1300 MWe pressurized water reactor cavity was performed. In this calculation, the discrete ordinates transport codes, ANISN and DOT 3.5, and the Monte Carlo code, TRIPOLI-02 were used with the coupling code, DOTTRI. In this study IBM 3033 type computer was used. The calculated neutron fluxes and dose rates were compared with the measured data in a 900MWe pressurized water reactor cavity to show a good agreement, although some deviations in the results for each energy group were noticed. These results will be applied in the radiation shielding design of high capacity nuclear power reactors and, to the means of radiation protection in case of the reactor maintenance and the access of the reactor cavity.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.216-219
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• 2009

3 차원 콘텐트를 이용한 물리기반 시뮬레이션은 최근 컴퓨터 그래픽스 분야에서 가장 활발히 연구되는 연구 중 하나이다. 이와 더불어 이러한 기술들과 사용자간의 몰입감을 증가시키는 상호작용 기술 역시 계속하여 증가하는 추세이다. 본 연구는 이러한 추세에 발맞추어 물리기반 형상변형 기술의 몰입감을 증가시키기 위한 상호작용 방법을 제안한다. 제안된 방법에서는 3 차원 객체와 사용자와의 효율적인 상호작용을 위해서 시스템을 증강현실 환경에서 구현하였다. 증강현실을 이용한 시스템의 제약조건은 실시간 계산이다. 때문에, 제안된 시스템은 RBF(Radial Basis Function) [1] 와 LSM (Lattice Shape Matching) [2, 3] 방법을 조합하여 물리기반 상호작용 기술을 완성 하였고 실험을 통해 실시간 계산을 확인하였다. 또한, 3 차원 객체가 충돌하여 변형이 일어날 때 감각형 객체 (Tangible object)에 진동을 주어 물리기반 형상변형의 사용자 상호작용에 관한 몰입감을 증가시켰다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2002.04a
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• pp.35-40
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• 2002

A numerical analysis based on two-dimensional and three-dimensional incompressible Navier-Stokes equations has been carried out for double-circular-arc compressor cascades and the results are compared with available experimental data at various incidence angles. The 2-D and 3-D computational codes based on SIMPLE algorithm adopt pressure weighted interpolation method for non-staggered grid and hybrid scheme for the convertive terms. Turbulence modeling is very important for prediction of cascade flows, which are extremely complex with separation and reattachment by adverse pressure gradient. In this paper k-$\varepsilon$ turbulence model with wall function is used to increase efficiency of computation times.

• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.3
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• pp.29-36
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• 2002

A numerical analysis based on two-dimensional and three-dimensional incompressible Wavier-Stokes equations has been carried out for double-circular-arc compressor cascades and the results are compared with available experimental data at various incidence angles. The 2-D and 3-D computational codes based on SIMPLE algorithm adopt pressure weighted interpolation method for non-staggered grid and hybrid scheme for the convective terms. Turbulence modeling is very important for prediction of cascade flows, which are extremely complex with separation and reattachment by adverse pressure gradient. Considering computation times, $\kappa$-$\varepsilon$ turbulence model with wall function is used.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.11
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• pp.165-170
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• 2013

When we build up a 3D model from the given 2D images, linear algorithms are often used to reduce computational cost or for initialization of nonlinear algorithms. However, contemporary linear algorithms have apparently linear structures, but virtually they are implemented using SVD. The SVD is also implemented using numerical analysis algorithms that need initialization. Moreover, solutions using SVD are more difficult to analyze than closed-form solutions. To avoid from such inconvenient numerical analysis algorithms of the contemporary methods and for convenient analysis of solutions, this paper proposes a convenient linear method that produces a closed-form solution.

• Journal of Korea Multimedia Society
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• v.1 no.2
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• pp.194-203
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• 1998

In this paper, a new DCT-VQ method is proposed which can solve the problems of VQ such as the degradation of edge and enormous calculations. VQ is carried in DCT domain but spatial domain in order to protect the degradation of edge. DCT makes high correlated image data decorrelated and the energy concentrated on a few coefficients. In DCT domain, the DC coefficient is quantized with 8 bits uniform scalar quantizer and the AC coefficients are divided to three regions and coded with vector qiantizer for considering edge components. For the decrease of the calculation and memory, the vectors for three region have small dimension of $1{\times}7$ and use the same codebook. Thus, the proposed method can fully express the edge components by considering AC coefficients in DCT domain and decrease the calculation and memory be reducing the dimension of vectors.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.1
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• pp.39-48
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• 2013

This paper develops a 2-D moving least squares(MLS) difference method for Stefan problem by extending the 1-D version of the conventional method. Unlike to 1-D interfacial modeling, the complex topology change in 2-D domain due to arbitrarily moving boundary is successfully modelled. The MLS derivative approximation that drives the kinetics of moving boundary is derived while the strong merit of MLS Difference Method that utilizes only nodal computation is effectively conserved. The governing equations are differentiated by an implicit scheme for achieving numerical stability and the moving boundary is updated by an explicit scheme for maximizing numerical efficiency. Numerical experiments prove that the MLS Difference Method shows very good accuracy and efficiency in solving complex 2-D Stefan problems.

• Journal of the Korea Computer Industry Society
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• v.3 no.3
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• pp.321-330
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• 2002

A 2-D median filter has many applications in various image and video signal processing areas. The rapid development in VLSI technology makes it possible to implement a real-time or near real-time 2-D median filter with reasonable cost. For the efficient VLSI implementation, the algorithm should have characteristics such as small memory requirements, regular computations, and local data transfers. This paper presents an architecture of the real-time two-dimensional separable median filter which has appropriate characteristics for the VLSI implementation. For the efficient two-dimensional median filter, a separable two-dimensional median filtering structure and a bit-sliced pipelined median searching algorithm are used. A behavioral simulator is implemented with C language and used for the analysis of the presented architecture.