• 한국소음진동공학회논문집
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• 제14권8호
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• pp.661-667
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• 2004

The characteristics of noise and vibration by a heavy impact source was studied. The triggering method was used for increasing the reliability and stability to measure the level of sound pressure. sound intensity and vibration acceleration. A simple finite element model and a rigid body analysis method were suggested to calculate the natural frequencies of the multi-layer floor system. The results show that the resilient materials decrease the natural frequency of the reinforced concrete slab, make a resonance with dominant driving frequency in the low frequency region, and increase the vibration and noise level. A simple finite element model and rigid body models was suggested to calculate the natural frequencies of the floor systems.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제20권4호
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• pp.309-332
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• 2016

Finite element method has been applied to solve the fundamental governing equations of natural convective, electrically conducting, incompressible fluid flow past an infinite vertical plate surrounded by porous medium in presence of thermal radiation, viscous dissipation, Soret and Dufour effects. In this research work, the results of coupled partial differential equations are found numerically by applying finite element technique. The sway of significant parameters such as Soret number, Dufour number, Grashof number for heat and mass transfer, Magnetic field parameter, Thermal radiation parameter, Permeability parameter on velocity, temperature and concentration evaluations in the boundary layer region are examined in detail and the results are shown in graphically. Furthermore, the effect of these parameters on local skin friction coefficient, local Nusselt number and Sherwood numbers is also investigated. A very good agreement is noticed between the present results and previous published works in some limiting cases.

• 한국전자파학회논문지
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• 제13권2호
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• pp.170-175
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• 2002

등각사상이 결합된 변분적 유한요소법을 이용하여 대칭 스트립 전송선의 고차모드 차단주파수를 계산한다. 등각사상은 스트립 전송선의 무한영역을 적절한 유한영역으로 변환하는데 사용된다. 변환된 유한영역에 대한 변분 방정식을 유도하고 유한요소법으로 그 해를 구하여 차단주파수를 계산한다. 다른 해석법에 의한 결과와 비교하여 이 해석법이 무한영역이 포함된 전송선의 고차모드 차단주파수 계산에 적합함을 확인한다.

• 한국해양공학회지
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• 제18권2호
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• pp.10-17
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• 2004

In this research, a numerical simulation for the acoustic sounds around a two-dimensional circular cylinder in a uniform flaw was developed, using the finite difference lattice Boltzmann model. We examine the boundary condition, which is determined by the distribution function concerning density, velocity, and internal energy at the boundary node. Pressure variation, due to the emission of the acoustic waves, is very small, but we can detect this periodic variation in the region far from the cylinder. Daple-like emission of acoustic waves is seen, and these waves travel with the speed of sound, and are synchronized with the frequency of the lift on the cylinder, due to the Karman vortex street. It is also apparent that the size of the sound pressure is proportional to the central distance to the circular cylinder. The lattice BGK model for compressible fluids is shown to be a powerful tool for the simulation of gas flaws.

• 한국농공학회지
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• 제36권3호
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• pp.144-154
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• 1994

An efficient tidal model, TIDE which is an iterative type, nonlinear finite element model has developed for the analysis of the tidal movement in the coastal area which is characterized by irregular boundaries and bottom topography. Traditional time domain finite element models have been in difficulties with requirement for high eddy viscosity coefficients and small time steps to insure numerical instability. These problems are overcome by operating in the frequency domain with an elaborate grid system by combining the triangular and quadrilateral shape grids. Furthermore, in order to handle non-linearity which will be more significant in the shallow region, an iterative scheme with least square error minimization algorithm has been implemented in the model. The results of TIDE model are agreed with the analytical solutions in a rectangular channel under the condition of tidal waves entering the channel closed at one end.

• International Journal of Automotive Technology
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• 제6권5호
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• pp.513-517
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• 2005

A full-bead of multi-layer-steel engine head gasket, taking charge of the dynamic sealing of combustion chamber, is susceptible to fatigue failure. The fatigue durability of full-bead was assessed with the finite element analysis results and the high-cycle multi-axial fatigue theory. The assessment aimed to reveal the effects of the forming parameters and dimensions of full-bead. The results show that the selection of embossing parameters producing less deformation of bead plate is beneficial for the improvement of durability while the flatting has marginal influence. The fatigue durability also improves with the increase in the width of full-bead and the radial length of bore-side flat region. However, the dimensional effects are limited due to the occurrence of snap-through.

• 연구논문집
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• 통권24호
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• pp.81-96
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• 1994

To investigate failure mechanisms observed in carbon-phenolic thermal insulators, differential equations which govern the decomposition process in a deformable anisotropic porous solid are derived for three-dimensional axisymmetric constructions. The governing equations not only couple the material deformation with pore pressure, but also couple pressure and temperature, which means that heat convected by the pyrolysis gases is properly accounted for. Then the Bubnov-Galerkin finite element method is applied to these equations to transform them into a semidescrete finite element system. A thermal insulation liner in the cowl region under typical operating conditions is analyzed to find a mechanism for plylift. The results from the structural analysis show across-ply failure in the cowl zone. The mechanism for plylift is hypothesized as a sequential procedure : 1) the across-ply failure which is the precursor to plylift and 2) the local fiber buckling caused by generation of excessive in-plane compressive stress. To prevent plylift, the across-ply stress can be reduced by using appropriate material ply angles in cowl zone design.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부A
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• pp.22-24
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• 1998

The current distribution in the source coil region is analyzed using the two dimensional finite element method. The variables in the FEM are the magnetic vector potentials and the source current density. The boundary condition for the source current density is that the total current is the sum of the eddy current and the source current and is known quantity from measurement. The simulation results are compared with the analytical solution. It is found that the method can analyze the current distribution in the source conductors very accurately.

• 소성∙가공
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• 제14권6호
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• pp.547-552
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• 2005

In general, the sheet metal and die are described by finite elements for the simulation of the metal forming processes. Because the characteristics as continuum of the sheet metal are represented with triangles and rectangles, the errors occur inevitably in finite element analysis. Many contact schemes to describe the deformation modes exactly have been introduced in order to decrease these errors. In this study, a scheme for continuous contact treatment is proposed in order to consider the realistic behavior of contact phenomena during the forming process. The discrete mesh causes stepwise propagation of contact nodes of the sheet even though the contact region of the real forming process is altered very smoothly. It gives rise to convergence problem in case that the process, for example bending process, is sensitive to the contact between the sheet and the tools. The analysis of the unconstrained cylindrical bending process without blank holder is also presented in order to investigate the effect of the proposed algorithm.

• 소성∙가공
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• 제12권7호
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• pp.631-639
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• 2003

Ring rolling process is simulated by using the general-purpose commercial finite element analysis software, MSC.Superform. Because the deforming region is restricted to the vicinity of the roll gap, only a ring segment spanning the roll gap is analyzed in order to save computation time and cost. First, a plain ring rolling of rectangular cross-section is simulated. Comparisons between computation and experiment show good agreement in the cross-sectional configuration of the deformed ring. Then, a profile ring with an external round groove is analyzed. The rolls with and without groove have been analyzed to compare the amount of side spread. It is found that the grooves in the rolls are effective in reducing the amount of side spread.