• Structural Engineering and Mechanics
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• v.86 no.3
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• pp.349-359
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• 2023

This paper presents a technique for determining the optimal number of elements in stochastic finite element analysis based on reliability analysis. Using the change-of-variable perturbation stochastic finite element approach, the probability density function of the dynamic responses of stochastic structures is explicitly determined. This method combines the perturbation stochastic finite element method with the change-of-variable technique into a united model. To further examine the relationships between the random fields, discretization of the random field parameters, such as the variance function and the scale of fluctuation, is also performed. Accordingly, the reliability index is calculated based on the explicit probability density function of responses with Gaussian or non-Gaussian random fields in any number of elements corresponding to the random field discretization. The numerical examples illustrate the effectiveness of the proposed method for a one-dimensional cantilever reinforced concrete column and a two-dimensional steel plate shear wall. The benefit of this method is that the probability density function of responses can be obtained explicitly without the use simulation techniques. Any type of random variable with any statistical distribution can be incorporated into the calculations, regardless of the restrictions imposed by the type of statistical distribution of random variables. Consequently, this method can be utilized as a suitable guideline for the efficient implementation of stochastic finite element analysis of structures, regardless of the statistical distribution of random variables.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.8
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• pp.224-232
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• 1999

Topology optimization has evolved into a very efficient concept design tool and has been incorporated into design engineering processes in many industrial sectors. In recent years, topology optimization has become the focus of structural design community and has been researched and applied widely both in academia and industry. There are mainly tow approaches for topology optimization of continuum structures ; homogenization and density methods. The homogenization method is to compute is to compute an optimal distribution of microstructures in a given design domain. The sizes of the micro-calvities are treated as design variables for the topology optimization problem. the density method is to compute an optimal distribution of an isotropic material, where the material densities are treated as design variables. In this paper, the density method is used to formulate the topology optimization problem. This optimization problem is solved by using an optimality criteria method. Several example problems are solved to show the usefulness of the present approach.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.449-453
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• 2005

Electrochemical systems find widespread technical application. Industrial electrolytic process include electroplating, electroforming, and electropolishing. Electroforming and electroplating is widely used in the manufacture of metal parts. This paper based on the basic equations of electrics and electrochemical kinetics, was employed for a theoretical explanation of the current density distribution on electroforming process. We calculated current density distribution and potential distribution on cathode. Also, calculated current density distribution of vertical direction. It was shown that current density is related with distance of between anode and cathode and mass transfer process. And make an experiment on its relation and electroformed thickness. It shows that it is useful method using FEM with multi-physics to estimate electroformed thickness.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.277-280
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• 2002

It is well known that the critical current of a HTS tape has anisotropic characteristic in magnetic field. We are interested in critical current density distribution of a HTS tape. We assumed the experimentally obtained Ic-B curves do represent the local properties of HTS tapes and calculated the critical current density distribution of HTS tapes using numerical method. Also we predicted the critical current of the tapes.

• Proceedings of the KSR Conference
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• 1999.05a
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• pp.226-231
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• 1999

A composition brake shoe composed of iron, graphite, kevlar, barium sulphate, etc. was developed for Diesel locomotives. The density distribution of the shoe depends on groove shapes of the shoe (or punch shape). In this study, we investigated the influence of the punch shape on the density distribution, stresses, etc. The inclination of the groove exerts more influence on the density distribution than the groove filet radius.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.40 no.7
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• pp.643-655
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• 1991

The analysis method on air gap permeance distribution, air gap MMF distribution, air gap flux density distribution, cogging torque and BEMF about the skewed stator slots or the skewed rotor magnet segments for BLDCM, respectively, is studied as a function of the skew ratio. The proposed method describes the differences between the skewed stator slots and teh skewed rotor magnet segments for the air gap permeance distribution, air gap MMF distribution and air gap flux density distribution. The reliability of the method is also confirmed by the waveform of the cogging torque and BEMF through experiments. And the result shows that the effects on the cogging torque and BEMF due to the skewed stator slots or the skewed rotor magnet segments are the same. In case of the skewed stator slots, the effects of the variations of the winding resistance and inductance are also studied.

• Journal of the Korean Solar Energy Society
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• v.24 no.4
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• pp.11-18
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• 2004

A solar concentrator, named KIERDISH II, was built at KIER in order to investigate the feasibility of high temperature solar energy application system. The constructed concentrator is a dish type solar concentrator with a focal length of 4.68m and a diameter of 7.9m. To successfully operate KIERDISH II, optimal design of the absorber is very important and flux density distribution has to be known. The focal flux density distribution on the receiver was measured. We have observed the shape and size of flux images and evaluated percent power within radius. Flux density distribution is usually measured by a CCD(charge coupled device) camera and a radiometer. In this paper we present a flux mapping method to estimate the characteristic features of the flux density distribution in the focal region of solar concentrator. The minimum radius of receiver is found to be 0.15m and approximately 90% of the incident radiation is intercepted by receiver aperture.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.12
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• pp.2962-2969
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• 1993

Recently, a study on the mirror-like surface grinding of brittle materials is active and as branch of these study, new dressing method for superabrasive wheel, electrolytic inprocess dressing(Elid) was developed. Using Elid, the mirror-like surface of brittle material can be generated without polishing or lapping process. In the future, Elid grinding will take important place in industry. But so far the analysis on Elid grinding was not quantitative but qualitative. In this study, The purpose is the quantitative analysis on Elid grinding by computer simulation, For computer simulation, the mean and the variance of the abrasive distribution were measured by tracing of the grinding wheel with stylus in transverse direction in the case of respective dressing current condition. This measurement result in a density distribution of abrasive by mathematical formulation using statistical method. The prediction of the surface roughness in Elid grinding was based on this density distribution.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.3
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• pp.506-513
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• 2007

This paper proposes a rotary magnetic position sensor which has a sinusoidally magnetized permanent magnet with a small number of poles. To make the sinusoidal magnetic flux density distribution from the permanent magnet, a magnetizing future is optimized by the DOE(Design of Experiments) method. The magnetization process is analyzed using the Preisach model and 2 dimensional finite element method. The magnetic flux density distribution from the magnetized permanent magnet is very similar to ideal sine wave. The simulation result of the magnetic flux density distribution is compared with the experimental one. Also the availability of the proposed rotary type magnetic position sensor is confirmed by position calculation technique.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.5
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• pp.49-58
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• 2013

Appropriate random variables and probability density functions based on statistical analysis should be defined to execute reliability analysis. Most studies have focused on only normal distributions or assumed that the variables showing non-normal characteristics follow the normal distributions. In this study, the reliability problem with non-normal probability distribution was dealt with using the convolution method in the case that the integration domains of variables are limited to a finite range. The results were compared with the traditional method (linear transformation of normal distribution) and Monte Carlo simulation method to verify that the application was in good agreement with the characteristics of probability density functions with peak shapes. However it was observed that the reproducibility was slightly reduced down in the tail parts of density function.