• Structural Engineering and Mechanics
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• v.2 no.3
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• pp.257-267
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• 1994

Motions of an unsymmetric rigid body on a rigid floor subjected to earthquake excitations with special attention to coefficient of friction are investigated. Motions of a body in a plane are classified (Ishiyama 1980) into six types, i.e. (1) rest, (2) slide, (3) rotation, (4) slide rotation, (5) translation jump, (6) rotation jump. Based upon the theoretical and experimental research work special attention is paid to the sliding of a body. The equations of motions and the behavior of coefficient of friction in the time of floor excitation are studied. One of the features of this investigation is the introduction and estimation of the "time dependent" coefficient of friction. It has been established that the constant kinetic coefficient of friction $${\mu}(kin){\sim_\sim}0.8{\mu}(stat)$$ does not give the appropriate results. The method for the estimation of the friction coefficient variation during the time is given.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.222-225
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• 2006

The effect of lubrication on the development of textures and Microstructure was studied by different lubricating condition during hot rolling of AA1050 aluminum alloy. Hot rolling without lubrication led to the evolution of the pronounced through-thickness texture gradients, whereas hot rolling with lubrication gave rise to the formation of uniform rolling texture in the whole thickness layer. The variation of texture and microstructure according to hot rolling condition are investigated by X-ray diffractometer (XRD) and Electron Back-Scattered Diffraction (EBSD). The experimental results were discussed base on the finite element method (FEM) simulation. FEM calculation reveals that a larger friction between roll and sheet causes the deviated strain state from a plane strain leading to the formation of shear textures in the thickness layers close to the surface.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.10
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• pp.604-614
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• 2005

Color segmentation takes great attentions since a color is an effective and robust visual cue for characterizing one object from other objects. Color segmentation is, however, suffered from color variation induced from irregular illumination changes. This paper proposes a reliable color modeling approach in HSI (Hue-Saturation-Intensity) rotor space considering intensity information by adopting B-spline curve fitting to make a mathematical model for statistical characteristics of a color with respect to brightness. It is based on the fact that color distribution of a single-colored object is not invariant with respect to brightness variations even in HS (Hue-Saturation) plane. The proposed approach is applied for the segmentation of human skin areas successfully under various illumination conditions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.748-751
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• 2000

Microlens made by laser radiation method have advantages in the easiness of their fabrication. The process is based on the projection of a chromium-on-quartz reticle on to the Polymer using a pulsed 248nm KrF excimer laser. Fabrication process is a fluence-dependent rate and density. The lens shape is defined by a rotationally symmetric sluence distribution with smooth radial variation in the image plane of the reticle. A typical lens of 50㎛ diameter was fabricated by irradiating 2000 laser pulses within 40 seconds. The experimental results show microlens fabrication by UV laser is possible and well worth studying further.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.955-962
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• 2006

This paper has the objects of deciding dynamic instability regions of thick plates on Pasternak foundation by finite element method and providing kinematic design data for mats and slabs of building structures. In this paper, dynamic stability analysis of tapered opening thick plate is done by use of Serendipity finite element with 8 nodes considering shearing strain of plate. To verify this finite element method, buckling stress and natural frequencies of thick pate with or without in-plane stress are compared with existing solutions. The results are as follow that this finite element solutions with 4x4 meshes are shown the error of maximum 0.56% about existing solutions, and obtained dynamic instability graph according with variation of opening positions.

• Journal of the Korean Ceramic Society
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• v.32 no.10
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• pp.1117-1122
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• 1995

The effect of grain boundary structure on zigzag migrtion has been studied. Five kinds of a(2110)-m(1010) diffusion couples with different twist angles by 30$^{\circ}$from a [0001] common direction of each plane were prepared. When chromia (Cr2O3) was added to the diffusion couples by a vapor phase, zigzag migration of the grain boundary occurred. The fraction of zigzag migration did not essentially vary with the twist angle, but the magnitude and migration distance of individual migrating segment varied. The variation of CIGM morphology thus appears to result from the change in grain boundary mobility due to microscopic deviation of grain boundary structure out of a macroscopic grain boundary orientation.

• Structural Engineering and Mechanics
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• v.22 no.5
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• pp.599-611
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• 2006

The theory with hierarchical warping functions had been used to analyze composite thin-walled structure, laminated beam and had good results. In the present paper, a series of hierarchical warping functions are developed to analyze the cylindrical bending problems of composite lamina. These warping functions which refine through-the-thickness variation of displacements were composed of basic and corrective functions by taking into account of anisotropic, material discontinues, and transverse shear and normal strain. Then the hierarchical finite element method was used to form a numerical algorithm. The distribution of the displacements, in-plane stresses, transverse shear stresses and transverse normal stress for composite laminate were analyzed with the present model. The results show that the present model has precise mechanical response compared with the first deformation transverse theory and the corrective order affects the accuracy of result.

• Structural Engineering and Mechanics
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• v.39 no.4
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• pp.541-558
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• 2011

This paper presents an analysis of stochastic eigenvalue problem of plane bar structures. Particular attention is paid to the effect of spatial variations of the flexural properties of the structure on the first four eigenvalues. The problem of spatial variations of the structure properties and their effect on the first four eigenvalues is analyzed in detail. The stochastic eigenvalue problem was solved independently by stochastic finite element method (stochastic FEM) and Monte Carlo techniques. It was revealed that the spatial variations of the structural parameters along the structure may substantially affect the eigenvalues with quite wide gap between the two extreme cases of zero- and full-correlation. This is particularly evident for the multi-segment structures for which technology may dictate natural bounds of zero- and full-correlation cases.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1580-1582
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• 1994

In this study, when AC voltage is applied to block type treeing specimen which is fabricated with polyethylene which dielectric characteristics is excellent, from initial tree to final breakdown, Using acoustic emission method. we take statistically on parameter, which is skewness. We experimented on quenching condition and illustrated skewness locus plane so that studied interrelation of life expectation and parameter.

• ETRI Journal
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• v.32 no.1
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• pp.62-67
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• 2010

In this paper, an ultra-wideband internal antenna for use in mobile applications is proposed. The proposed antenna has symmetrical bi-arm structures printed on the top and bottom of the substrate, and it occupies a compact area of 10 mm ${\times}$ 10 mm ${\times}$ 1 mm. The designed antenna has an impedance bandwidth from 3 GHz to 12 GHz and near omnidirectional radiation patterns over the frequency band of interest. The group delay between two antennas fabricated using the proposed design is less than 0.8 ns, and the maximum gain variation is about 3.16 dB.