• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.1 no.2
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• pp.128-137
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• 1989

Numerical solutions for two-dimensional, steady, free convection are presented for a cylinder filled with saturated porous media. An annulus is bounded by inner wall with constant heat flux and two adiabatic horizontal walls with outer wall isothermally cooled. Governing equations are numerically solved for the range of Aspect Ratio 1 to 20, Radius Ratio, 1 to 20, and Rayleigh number, 50 to $10^4$ by Finite Difference method utilizing upwind scheme. Results are presented in terms of stream lines and isotherms, temperature distributions and local Nusselt numbers at the heated wall. Average Nusselt numbers are also presented for the comparisons.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.8
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• pp.175-184
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• 2003

A method of the shape design sensitivity analysis based on the boundary integral equation formulation is presented for two-dimensional inhomogeneous thermal conducting solids with multiple domains. Shape variation of the external and interface boundary is considered. A sensitivity formula of a general performance functional is derived by taking the material derivative to the boundary integral identity and by introducing an adjoint system. In numerical analysis, state variables of the primal and adjoint systems are solved by the boundary element method using quadratic elements. Two numerical examples of a compound cylinder and a thermal diffuser are taken to show implementation of the shape design sensitivity analysis. Accuracy of the present method is verified by comparing analyzed sensitivities with those by the finite difference. As application to the shape optimization, an optimal shape of the thermal diffuser is found by incorporating the sensitivity analysis algorithm in an optimization program.

• Proceedings of the KIEE Conference
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• 2000.11b
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• pp.309-311
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• 2000

An advanced angular position detector (APD) for the SMART CEDM (control element drive mechanism) was designed. The APD is required to be small size with high resolution for angular displacement of rotary step motor. Unfortunately the proximity sensors can not be adopted to SMART CEDM because the motor shaft is located in the pressure boundary cylinder filled with the primary coolant under high temperature and pressure. This paper describes the electromagnetic finite element analysis for the design of advanced angular position detector for the SMART CEDM. The electromagnetic properties obtained will be used as Input for the optimization analysis of the APD.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.323-326
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• 1996

Dental implant is increasingly used to recover the mastication function of tooth. Several types of implant were designed to give an optimal stress distribution in surrounding bony regions. In this study, six types of implant were investigated using finite element method and it was studied i) how the variation of cortical bone thickness affects the stress distribution in surrounding bony regions depending upon implant types, ii) which type gives the best characteristics in the sence of stress distribution and stability. The hybrid-type implant with cylinder and screw gave the optimum properties in view of stability and response to the variation of cortical bone thickness.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.9
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• pp.938-945
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• 2012

To design and estimate material failures of Type III pressure vessels, which have excellent stability and performance, various modeling techniques have been introduced. This paper provided a hybrid modeling technique composed of ply-based modeling for a cylinder part and laminate-base modeling technique for a dome part for enhancing modeling efficiency. The ply-based modeling technique provided accurate ply stresses directly for predicting material failure, on the other hand, additional manipulations in stress calculations, which may cause some errors, were needed for the case of the laminate-based modeling technique. The ply stresses in fiber, transverse and in-plane shear directions were compared with the corresponding material strengths to predict material failure.

• International Journal of Naval Architecture and Ocean Engineering
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• v.1 no.1
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• pp.20-28
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• 2009

In thus paper we validate a numerical model for wave-structure interaction by comparing numerical results with laboratory data. The numerical model is based on the Navier-Stokes (N-S) equations for an incompressible fluid. The N-S equations are solved by a two-step projection finite volume scheme and the free surface displacements are tracked by the volume of fluid (VOF) method The numerical model is used to simulate solitary waves and their interaction with a group of slender vertical piles. Numerical results are compared with the laboratory data and very good agreement is observed for the time history of free surface displacement, fluid particle velocity and wave force. The agreement for dynamic pressure on the cylinder is less satisfactory, which is primarily caused by instrument errors.

• Elastomers and Composites
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• v.30 no.3
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• pp.235-246
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• 1995

When an O-ring is installed in a high fluid pressure device, a section of the O-ring is extruded into the piston-cylinder clearance gap. Any tendency towards extrusion will induce wear in dynamic applications, leading to premature failure of the seal. In this study, the mechanism of initial extrusion of the O-ring was studied, 1.e., how much amount of the O-ring will be extruded into the clearance gap at a certain pressure. The relationship between extrusion depth and a clearance gap or fluid pressure were studied by finite element analysis (FEA). After that, Salita's experimental data were analyzed. The result is that Initial extrusion depth for an O-ring into a clearance gap was 1.11 times the product of dimensionless pressure difference $(p-p_1)/E$ and clearance gap c. The required pressure $p_1$ for zero extrusion depth was found to decrease logarithmically with increasing clearance gap.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.14 no.2
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• pp.118-124
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• 1985

The motion of a fluid in the closed annular cavity formed by two concentric vertical cylinders with externally finned tube has been analysed by a numerical solutions of the equation of momentum and energy. For the calculation procedure, the fluid is assumed to have constant thermo-dynamic and transporties except for the density, which is temperature-dependent in the buoyancy term of the vertical momentum equation (Boussinesq approximation). The govern ins equations for velocity and temperature are solved by a finite difference technique which incoorporates a scheme for treating the coupled variables. Results are presented for a range of the Rayleigh number and for various values of the fin height and the number of fins.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.9 no.3
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• pp.161-169
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• 1980

In order to enhance the thermal energy storage capacity of cement mortar and to improve the effective thermal conductivity of paraffin waxes, cement- sand- paraffin wax mixture was investigated. By means of finite difference method, the transient temperature distribution in a hollow cylinder with phase change using average composite properties was obtained, and compared with experimental results. It was shown that the heat absorbed by mixture with $25\%$ paraffin fraction was as much as $50\%$ more than either a concrete mortar or pure paraffin wax in the case of ${\Delta}T=\;18.25^{\circ}C$.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.3
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• pp.313-319
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• 2017

Cylindrical shells are often used in ship structures at deck plating with a camber, side shell plating at fore and aft parts, and bilge structure part. It has been believed that such curved shells can be modelled fundamentally by a part of a cylinder under axial compression. From the estimations with the usage of cylinder models, it is known that, in general, curvature increases the buckling strength of a curved shell subjected to axial compression, and that curvature is also expected to increase the ultimate strength. We conduct series of elasto-plastic large deflection analyses in order to clarify the fundamentals in buckling and plastic collapse behaviour of cylindrical shells under axial compression. From the numerical results, we derive design formula for predicting the ultimate strength of cylindrical shell, based on a series of the nonlinear finite element calculations for all edges, simply supporting plating, varying the slenderness ratio, curvature and aspect ratio, as well as the following design formulae for predicting the ultimate strength of cylindrical shell. From a number of analysis results, fitting curve can be developed to use parameter of slenderness ratio with implementation of the method of least squares. The accuracy of design formulae for evaluating ultimate strength has been confirmed by comparing the calculated results with the FE-analysis results and it has a good agreement to predict their ultimate strength.