• Proceedings of the KSME Conference
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• 2001.06d
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• pp.726-731
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• 2001

A thermal design software is developed for the heat recovery steam generator(HRSG) of combined cogeneration systems. The heat transfer is calculated by using the element method to account for the varying thermal properties across the heat transfer elements. The circulation balance is computed for the evaporator to accurately estimate the steam generation rate and to check the proper circulation of the boiler water through the tubes. The software developed can be used to simulate HRSG systems with various combinations of auxiliary burner, wall superheater, superheater, reheater, evaporator, and economizer. Systems with several different combinations of the system components are successfully tested. And it is concluded that the developed software can be used for the design of heat recovery steam generators with various combinations of heat transfer components.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.55-58
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• 2002

Parallel finite element code has been recently developed for the analysis of the incompressible Wavier-Stokes equations using domain decomposition method. Metis and MPI libraries are used for the domain partitioning of an unstructured mesh and the data communication between sub-domains, respectively. For unsteady computation of the incompressible Navier-Stokes equations, 4-step splitting method is combined with P1P1 finite element formulation. Smagorinsky and dynamic model are implemented for the simulation of turbulent flows. For the validation performance-estimation of the developed parallel code, three-dimensional Laplace equation has been solved. It has been found that the speed-up of 40 has been obtained from the present parallel code fir the bench mark problem. Lastly, the turbulent flows around the MIRA model and Tiburon model have been solved using 32 processors on IBM SMP cluster and unstructured mesh. The computed drag coefficient agrees better with the existing experiment as the mesh resolution of the region increases, where the variation of pressure is severe.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.3
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• pp.232-240
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• 1984

The plane elastostatic boundary value problem with the sharp V-notched singularity is formulated by a contour integral method for determining numerically the stress intensity factors. The integral formula is based on Somigliana type of reciprocal work in terms of displacement and traction vectors on the plate boundary. The characteristic singular solutions can be identified on the basis of traction free boundary conditions of two radial notch edges. Two numerical example examples are treated in detail; a symmetric mode-I type of notched plate with various interior angles and a mixed mode type of cantilever subjected to end shear.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.4
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• pp.401-410
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• 2008

The natural frequency of a beam plays an important role in not only vibration analysis but also understanding its dynamic characteristics. It is complicated to analyse the natural frequency of a stepped beam with discontinuously varying section. Approximate analysis methods such as Rayleigh-Ritz method, FEM, etc. are frequently used for the vibration analysis of stepped beams. In such a case, accuracy of these methods depends upon the number of partitioned elements, the number of the iterations in calculation and the assumed mode shape. This study presents an approximate analysis method for the fundamental natural frequency analysis of stepped cantilever beam, using equivalent beam transformation technique. Validity and usefulness are verified by comparing the proposed method with FEM for several example problems.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.935-937
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• 1993

This paper presents a three dimensional automatic mesh generation scheme for the boundary element method, and this scheme can be applicable to practical problems of complex shape. The geometry of the problem is expressed as an assemblage of linear Coon's surfaces, and each surface is made up of four edge curves which are defined in the form of a parametric function. Curves are automatically segmented according to their characteristics. With these segments of curves, interior points and triangular mesh elements are generated in the parametric plane using Lindholm's method, and then their projection on the real surface forms the initial mesh. The refinement of initial mesh is performed so that the discrete triangular planes are close to the real continuous surfaces. The bisection method is used for the refinement. Finally, interior points in the refined mesh are rearranged so as to make each element be close with an equilateral triangle. An attempt has been made to apply the proposed method to a DY(Deflection Yoke) model.

• The Journal of the Acoustical Society of Korea
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• v.18 no.3
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• pp.73-78
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• 1999

The paper describes a theoretical study on the flexural vibration of an elastic flat bar with periodically nonuniform material properties. The approximate solution of the natura1 frequency and mode shape has been obtained using the perturbation technique for sinusoidal modulation of the flexural rigidify and mass density. The numerical solution obtained by using the finite element method verifies the trend of the approximate solution. It appears that distributed vibrations exist in the low modes, and this approach can be extended to the vibration analysis of the p1ate in the flat panel speaker.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.357-364
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• 2006

The meshfree method is extended by the local partition of unity method to model the cohesive cracks in two dimensional continuum The shape function of a particle whose domain of influence is completely cut by a crack is enriched by the step enrichment function. If the domain of influence contains a crack tip inside, it is enriched by the branch enrichment function without the stress singularity. It is found that this method is more accurate and converges faster than the meshless methods for LEFM cracks based on the visibility concept Several staic and dynamic examples are solved to verify the method.

• Journal of the Korean Society of Industry Convergence
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• v.2 no.2
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• pp.3-10
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• 1999

Recently, It is proceeding the project of offshore structures in the many contury. A hybrid boundary-integral method is developed for computing wave forces on floating bodies. In this method, using the cylindric boundary for deviding elements, it is convenient to analysis but is difficult to apply to the rectangular or slender bodies. Thus, in this paper, I propose the new method by using the fictitious vertical cylinder of arbitary cross-section and shows results of the numerical analysis for testing.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.828-829
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• 2007

전력산업의 구조를 기존의 독점적 구조에서, 분할을 통한 경쟁체제로 변환하려는 움직임이 현재 진행 중이다. 전력산업에 경쟁을 도입함으로써 효율성을 최대화하기 위함이다. 향후 형성될 도매경쟁시장에서 발생될 시장참여자의 여러 가지 행태에 대한 예상과 분석은 시장의 불안정 요소를 미리 찾아내고, 이를 사전에 예방할 수 있는 규제수단을 개발하기 위해 아주 중요하다. 본 논문에서, 우리는 에이전트 기반모델을 활용해서 전력 시장의 주요 논제를 평가할 수 있는 지표를 정의하여 제시할 것이다. 그 지표에는 시장운영지표, 시장수급지표, 시장예측지표가 있다. 그리고 에이전트 기반 모델 접근법은 전력시장의 개편으로 인해 더욱 복잡해진 시장 환경을 반영하여서, 기존의 게임이론의 한계를 넘어서 실제적인 값들을 지표에 반영시켜줄 것이다

• Archives of design research
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• v.13
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• pp.55-64
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• 1996

Garment is not only a part of formative art that establishes a live shape by wearer but also space modeling which features the solidity based on human body. Hence, beyond the simple meaning of 'wearing clothes', modeling which makes a cubic shape in accordance with human body's movement, is an important element in garment design. This study examined puli-over-typed garment design that owns abundant space sense, taking complex shapes of geometrical diagrams with brief and simple features as a motive. The study aims at seeking after the combination of plane and cubic forms, and exploring formative garments which are further modern and different variance by approaching the natural section of geomentrical facets with tightfitting idea and composition of delicate colors and forms when plane pattern was put on human body.