• Proceedings of the KAIS Fall Conference
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• 2000.04a
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• pp.15-15
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• 2000

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.4
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• pp.93-99
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• 2022

Analytical solutions for regular waves generated by bottom wave makers in a 3-dimensional wave basin were derived in this study. Bottom wave makers which have triangular, rectangular and combination of two shapes were adopted. The 3-dimensional velocity potential was derived based on the linear wave theory with the bottom moving boundary condition, kinematic and dynamic free surface boundary conditions in a wave basin. Then, analytical solutions of 3-dimensional particle velocities and free surface displacement were derived from the velocity potential. The solutions showed physically valid results for regular waves generated by bottom wave makers in a wave basin. The analytical solution for obliquely propagating wave generation from bottom wave maker which works like a snake was also derived. Numerical results of the solution agree well with theoretically predicted results.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.88-91
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• 2012

본 연구에서는 다양한 형상의 수중방파제를 이용하여 고립파(지진해일)에 대한 파랑의 제어기능을 검토하였다. 먼저, 연구를 수행하기 위하여 Navier-Stokes 방정식에 기초한 RANS 모형을 사용하였다. RANS 모형에서는 VOF기법을 이용하여 자유수면을 해석하였고, 또한 조밀한 격자간격을 사용하여 수치실험을 실시하였다. 수중방파제의 형상에는 삼각형, 반타원형, 직사각형 및 사다리꼴형을 사용하여 각각의 수중방파제 위를 통과하는 고립파를 해석하였다. 고립파의 파고와 여러 가지 형태를 갖는 각각의 수중방파제의 높이를 조절하면서 수중방파제를 지나는 고립파의 투과율을 해석하였다.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.3
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• pp.21-32
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• 1992

Numerical solutions are presented for solving the free surface flow created by a three-dimensional body moving beneath the free surface with constant velocity at an angle of attack. The solution is obtained using a panel method based on the perturbation potential, which employs Havelock sources and normal dipoles distributed on the body surface and Havelock normal dipoles in the wake downstream of the trailing edge. A pressure Kutta condition with an iterative solution procedure is implemented to satisfy equal pressure condition on the upper and lower surfaces at the trailing edge. Numerical calculation examples in the present paper include an ellipsoid at zero angle of attack, a rectangular planform wing at a small angle of attack in the limit of zero Froude number and then free surface flows and hydrodynamic forces acting on the submerged spheroid and parabolic strut are calculated. Discussions are made about the validity of the present method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.6 no.1
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• pp.61-68
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• 1986

A set of the shape functions which perfectly satisfy the homogeneous Euler Equations has been proposed for deep beam problems. A finite element beam model using the proposed shape functions has been derived by the Galerkin weighted residual method and used to analyze the numerical examples without reduced shear integration, to show the accuracy and efficiency of the proposed shape functions. The result shows that the finite element model using the proposed shape functions gives very accurate solutions for both static and free vibration analyses. The concept of the proposed shape functions is thought to be applied for the finite element analysis of the elasto-static problems.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.4
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• pp.475-484
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• 2000

In this paper, new additional nonconforming modes for the improvement of bending behavior in the distorted 8 node hexahedral element and their effective modification method are studied. The rotational degrees of freedom are introduced by using a functional in which the rotations are independent variables. In an element formulation, the same interpolations are used in displacement and rotation fields, but nonconforming modes we applied only in displacement fields. To verify the developed element various numerical tests are carried out and test results show good behavior.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.1
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• pp.63-70
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• 1994

The three-dimensional incompressible clavier-Stokes equations are solved to simulate the flow field around a Wigley model with free-surface. The IAF(Implicit Approximate Factorization) method is used to show a good success in reducing the computing time. The CPU time is almost an half of that if the IAF method were used. The present method adopts the local linearization and Euler implicit scheme without the pressure-gradient terms for the artificial viscosity. Calculations are carried out at the Reynolds number of $10^6$ and the Froude numbers are 0.25, 0.289 and 0.316. For the approximations of turbulence, the Baldwin-Lomax model is used. The resulting free-surface wave configurations and the velocity vectors are compared with those by the explicit method and experiments.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1992.04b
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• pp.545-554
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• 1992

본 논문에서는 복합형상의 금형을 가공하기 위하여 필요한 공구와 가공경로를 자동으로 생성해 주는 자동공정계획(CAPP)방법을 제시한다. 금형곡면은 일반적으로 복잡한 형상의 자유곡면들의 조합으로 이루어 지는데 육면체 형상의 소재로부터 원하는 금형곡면을 가공하는데는 수십시간의 기계가공 시간이 소요되며 또한 NC Code를 준비하는데도 같은정도의 시간이 소요된다. 금형곡면의 NC가공에 있어서 또다른 어려움은 공구의 과부하와 공구간섭이 빈번하게 발생할 수 있다는 점이다. 제안하는 자동공정계획방법은 전처리, 공정계획, 공구경로 생성의 3단계로 구성된다. 자동공정계획시스템의 입력정보는 1) 생성될 곡면형상 2) 가공할 소재형상 3) 가공공구 셀(드릴, 볼 엔드밀, 플렛 엔드밀), 절삭성 데이타등이다. 전처리 단계에서는 곡면모델러로부터 생성된 입력 형상을 Z-map이라 부르는 자료구조로 변환한다. 두번째 단계에서는 절삭 가공작업의 순서가 사용되는 공구와 함께 후방순환법에 의하여 결정된다. 그리고 실제 가공될 NC공구경로가 마지막 세번째 단계에서 생성된다.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.3
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• pp.1-14
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• 1992

Using form parameters representing geometric characteristics of the form, this paper attempts the generation of 3-D free surface given in terms of B-spline surface equation. This is achieved by coupling the form parameter decision, Coons surface of the form parameters, and B-spline. To check the validing of the present method, a analogous surface to the bulbous bow was generated.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.42 no.1
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• pp.1-11
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• 2005

Several Solid Freeform Fabrication Systems(SFFS) are commercialized in a few companies for rapid prototyping. However, they have many technical problems including the limitation of applicable materials. A new method of agile prototyping is required for the recent manufacturing environments of multi-item and small quantity production. The objectives of this paper include the development of a novel method of SFFS, the CAFL/sup VM/(Computer Aided Fabrication of Lamination for Various Material), and the manufacture of the various material samples for the certification of the proposed system and the creation of new application areas. For these objectives, the technologies for a highly accurate robot path control, the optimization of support structure, CAD modeling, adaptive slicing was implemented. However, there is an important problem with the conventional 2D lamination method. That is the inaccuracy of 3D model surface, which is caused by the stair-type surface generated in virtue of vertical 2D cutting. In this paper, We design the new control algorithm that guarantees the constant speed, precise positioning and tangential cutting on the 5DOF SFFS. We develop the tangential cutting algorithm to be controlled with constant speed and successfully implemented in the 5DOF CAFL/sup VM/ system developed in this paper. Finally, this paper confirms its high-performance through the experimental results from the application into CAFL/sup VM/ system.