• 한국표면공학회지
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• 제22권1호
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• pp.26-42
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• 1989

It has between investigated that the optimum spaying conditions, such as, spraying distance, fusing temperature and fusing time, ect, in a Ni-cr base self fluxing alloy sprayed on the mild steel substrate by oxygen-acetylenc flame spraying. Sprayed specimens on various conditions were fuused in a vacuum furnace and the results were as follows. The optimum spraying condition for excellent coating layer are obtained under spraying distances, fusing temperature and fusing and time ; 180~240mm,1050~110$0^{\circ}C$and 15~30min, respectively. The adhesive strength and surface hurface hardness of the as sprayed specimens were very low by mechanical bonding becaus of the diffusion layer during process. The carbides and borides and formed in the sprayed coating layer and densification of the layer was resulted from the elimination of pores and oxides. The hardness of sprayed coating layer, particularly in the high temperature, was superior to ordinary tool steels.

• Journal of Radiation Protection and Research
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• 제36권4호
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• pp.190-194
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• 2011

After the first report that electrons with sub-ionization energy of DNA could cause single strand breaks or double strand breaks to DNA, there have been various studies to investigate the mechanisms of DNA damage by low-energy electrons. In this paper, we examined the possibility of using X-ray photoelectron spectroscopy (XPS) to analyze the dissociation patterns of the molecular bonds by electron irradiation on DNA thin films and tried to establish the method as a general tool for studying the radiation damage of biomolecules by low energ yelectrons. For the experiment, pBR322 plasmid DNA solution was formed into the films on tantalum plates by lyophilization and was irradiated by 5-eV electrons. Un-irradiated and irradiated DNA films were compared and analyzed using the XPS technique.

• Steel and Composite Structures
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• 제1권1호
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• pp.75-96
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• 2001

Actual buckling curves are always characterised by the erosion of ideal buckling curves. In case of compact sections this erosion is due to the imperfections, while for thin-walled members, a supplementary erosion is induced by the phenomenon of coupled instabilities. The ECBL approach- Erosion of Critical Bifurcation Load - represents a practical and convenient tool to characterise the instability behaviour of thin-walled members. The present state-of-art paper describes the theoretical background of this method and the applications to cold-formed steel sections in compression and bending. Special attention is paid to the evaluation methods of erosion coefficient and to their validation. The ECBL approach can be also used to the plastic-elastic interactive buckling of thin-walled members, and the paper provides significant results on this line.

• 대한기계학회논문집
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• 제18권12호
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• pp.3118-3126
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• 1994

This paper describes the use of the concept of (relative) entropy for effective characterization of the amplitude and the frequency distributions of the surface profile formed in machining operation. For this purpose, a theoretical model for surface texture formation in turning operation is developed first. Then, the concept of (relative) entropy is reviewed and its effectiveness is examined based on the simulation and experimental results. The results also suggest that under random tool vibration the effect of the geometrical factors on the surface texture formation can be successfully decomposed and therefore, identified by applying the concept of (relative) entropy.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1102-1103
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• 2006

The pretreatment for substrate was carried out in change of gun pressure of $0.5\sim3.5$ bar using wet blasting. The size of $Al_2O_3$ powder was about $50{\sim}150{\mu}m$. As the results, the surface roughness of cemented carbide substrate was improved with increment of gun pressure of wet blasting. A new surface layer was formed and Co particles were uniformly distributed over the entire surface after pretreatment. The adhesion of the pretreated substrate in same PVD-TiAlN film was improved and in approximately $Ra=90\sim120\;nm$ shown the best adhesion value.

• 한국초전도ㆍ저온공학회논문지
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• 제21권4호
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• pp.6-8
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• 2019

Iron-based superconductors (IBSs) possess nematic phases in which rotational symmetry of the electronic structure is spontaneously broken. This novel phase has attracted much attention as it is believed to be closely linked to the superconductivity. However, observation of the symmetry broken phase by using a macroscopic experimental tool is a hard task because of naturally formed twin domains. Here, we report on a novel detwinning method by using a magnetic field on FeTe single crystal. Detwinning effect was measured by resistivity anisotropy using the Montgomery method. Our results show that FeTe was detwinned at 2T, which is a relatively weak field compared to the previously reported result. Furthermore, detwinning effect is retained even when the field is turned off after field cooling, making it an external stimulation-free detwinning method.

• Bulletin of the Korean Chemical Society
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• 제26권6호
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• pp.966-970
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• 2005

To measure the thickness of liquid films from 10 to 60 ${\mu}m$, we used photochromic dye activation. And we used silicone oil with 10 centi-Stokes and commercial photochromic dyes. To make films with exact and known thicknesses, we used two glass wafers. A film formed between two wafers after placing a drop of liquid of known volume on one wafer and covering the other. The film thickness could be estimated from the diameter of wafer and the dropped liquid volume. To quantitatively evaluate the result, captured the images using digital camera then analyzed the images using the image tool. The gray scale intensity using the captured images of activated dye with these thicknesses showed the repeatability below ${\pm}$ 1.0% when measured with a silicone oil solution containing 0.1% SO and SO-ANTH dyes. And we showed that photochromic dye activation method could be used to measure our liquid film thickness ranges.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 춘계학술대회 논문집
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• pp.134-140
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• 1999

The side mirrors play an important role in driver's safety and convenience. People drive safely based on the side mirrors and room mirror through observation of environment. However, the drivers can not completely confront environments because of the dead angle of the side mirrors. In this research, based on geometric optics and geometric modeling, aspheric surfaces of the side mirror mold with dead angle free has been designed and machined in CNC machining center, Surface roughness of the mold was evaluated by using surface shaping system. The analysis on the shape of formed mirrors shows the mirrors have been reduced the dead angle comparing with the original mold.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1996년도 춘계학술대회 논문집
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• pp.108-113
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• 1996

Conventionally, grinding of stainless steel, aluminium alloy, copper alloy, and titanum alloy is difficult due to the mechanical properties such as low hardness, high toughness which result in the loading of wheel and the poor surface finish. In order to grind this sort of materials easily, discontinuous grinding wheel with multi-porous grooves was newly developed. The multi-porous grooves were formed during wheel production. This discontinuous grinding wheel drastically increases the grinding performance. It is desirable to use the discontinuous grinding wheel when grinding materials with high efficiency and accuracy which is impossible by conventional wheels. In this paper, the construction and manufacturing method of grinding wheel with multi-porous grooves are explained. The grinding charateristics of discontinuous grinding wheel was also illustrated.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 추계학술대회 논문집
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• pp.440-445
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• 2002

The characteristic equation for regenerative chatter loop including a delay element replaced by a rational function is presented by a linear differential-difference equation, accounting for the dynamics of the AMB controllers, the uncut chip thickness equation and the cutting process as well as the rigid spindle dynamics itself. The chatter stability analysis of a rigid milling spindle suspended by 5-axes active magnetic bearings(AMBs) is also performed to investigate the influences of the damping and stiffness coefficients of AMBs on the chatter free cutting conditions, as they are allowed to vary within the stable region formed by the AMB control gains. Several cutting tests varying the derivative gains of the AMB were performed to investigate the regenerative chatter vibrations, and it was concluded that the theoretical analysis results are in good consistency with the test results.