• The Journal of Engineering Geology
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• v.5 no.3
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• pp.301-308
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• 1995

In this study, a stochastic finite element method is proposed with a view to consider rock property variations in the analysis of structural behavior on underground caverns. Here, the Monte carlo simulation technique, which has been widely used in probabilistic applications in many engineering fields, is applied for the analysis of the effect rock property distribution. Using the newly developed computer program based on the above - mentioned method, the underground opening in biaxial stress field is analyzed considering the effect of material property variation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.3
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• pp.236-241
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• 2008

The effect of organic solvent mixture ratio on the rheology property of slurry and thickness control of ceramic green sheet was investigated. For selecting a suitable dispersant multiple light scattering method was used to evaluate the particle migration velocity and variation of clarification layer thickness. Using the selected dispersant the dispersion property of solution according to solvent mixture ratio was investigated. Binder and plasticizers were added to formulate slurries and their viscosity was evaluated according to solvent mixture ratio. Ceramic green sheets with average thickness of 30, 50 urn were fabricated via tape casting and their thickness tolerances measured. As a result according to solvent mixture ratio the solution and slurry properties varied and for the mixture ratio of ethanol/toluene of 80/20 the ceramic green sheet with the lowest thickness tolerance was obtained.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1-6
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• 2008

Due to the self-similarity of Berkovich and conical indenters, different materials may show the same loaddepth curve for single indentation. In this study, we first compare the load-depth characteristics of conical and Berkovich indenters via finite element method. We also analyze the variation of load-depth curves with angle of Berkovich indenter, indentation parameters, and material properties. With numerical regressions of obtained data, we then propose dual-Berkovich indentation formulae for material property evaluation. The proposed approach provides the values of elastic modulus, yield strength and strain-hardening exponent and corresponding stress-strain curve with an average error of less than 3%. The method is valid for any elastic indenters made of tungsten carbide and diamond for instance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05c
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• pp.88-91
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• 2001

The mechanical properties and surface luminous intensities of copper foil have been studied with variation of the amount of additives into the electrolyte. Especially, organic compound of HEC was added from 0.1 to 10ppm for the propose of increasing the mechanical property and the surface state. The total thickness of electrodeposited copper foil was decreased with increasing the amount of organic compounds. There was not so much significant effect of the current density. It has been observed that mechanical property and surface luminous intensity increase with increasing concentration of organic compounds.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1998.11a
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• pp.9-11
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• 1998

A phenomenon of electroluminescent radiate as electric field applied in the phosphor, in this paper, we produced the Powder Electroluminescent Device(PELD) which was changing the structure and the thickness of phosphor and insulator for realization of the PELD with high brightness. We made PELD with structure that is WK-1(ITO film/Phosphor/Insulator/Electrode), WK-2(ITO film/Phosphor/Insulator/Electro de), WK-3(ITO film/Phosphor/Insulator/Electrode), WK-4(ITO film/Phosphor+Insulator/ Electrode). The property of the produced PELD are analyzed by measuring the spectrum which electrical and optical property, the brightness and the transferred charge density. In this result, the structure of WK-4 have good luminescence property than others, it's effective thickness is 60${\mu}{\textrm}{m}$. At 100V 400Hz, High brightness of 2700cd/m2 was performed.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.228-233
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• 2016

Auxetic material is a material which has negative Poisson's ratio(NPR). Auxetic material shows some distinctive property like high energy absorbing property and high shear modulus. Among these, synclastic curvature is very interesting characteristic. When synclastic-curvature-material bends, it changes its shape like dome, contrary to non-auxetic material which changes its shape like saddle(anticlastic). This distinctive property could make it easy to manufacture curved structure like nose cone or wing panel in aerospace engineering. In this study, we studied a quantitative analysis about synclastic curvature of re-entrant panel with finite element model. We suggested a concept 'Degree of Synclasticity(DOS)', which means a ratio of curvature of load-direction and load-orthogonal direction. We studied the variation of DOS with two factor, unit cell inner angle(${\theta}$) and load position angle(${\phi}$). DOS decreases as ${\theta}$ increases because the unit cell goes out of auxetic-shape. As ${\phi}$ varies, DOS changes in a large range. So proper optimization of ${\phi}$ would be needed for application.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.607-608
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• 2008

• Journal of applied mathematics & informatics
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• v.33 no.5_6
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• pp.687-697
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• 2015

This paper shows that the solutions to the perturbed nonlinear functional differential system

• Proceedings of the Optical Society of Korea Conference
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• 2004.07a
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• pp.228-229
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• 2004

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.11
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• pp.1048-1055
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• 2005

The formula to calculate a variation of optical path length of single crystal by the electric field was derived by this study. The formula was applied to $Bi_{12}SiO_{20}$ single crystal. The results are as follows. In case of the applied electric field in the body diagonal direction and the passing light along the same direction, the variation of optical path length had the largest value. The symmetry of the space distribution of optical path length satisfied $E3C_2\;8C_3$, the set of elements of the symmetry of $Bi_{12}SiO_{20}$ single crystal. The property which gave the largest influence to the variation of optical path length is the strain of length by the Inverse piezoelectric effect. The second influence, is the variation of the refractive index by the electro-optic effect. The variation of optical path length by the inverse piezoelectric effect and by the electro-optic effect have a reverse sign each other.