• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.3
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• pp.1-8
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• 2008

We present a model for simulating high energy laser heating of metal for ignition of energetic materials. The model considers effect of ablation of steel plate with long laser pulses and continuous lasers of several kilowatts and the thermal response of well-characterized high explosives for ignition. Since there is enough time for the thermal wave to propagate into the target and to create a region of hot spot in the high explosives, electron thermal diffusion of ultra-short (femto- and pico-second) lasing is ignored; instead, heat diffusion of absorbed laser energy in the solid target is modeled with thermal decomposition kinetic models of high explosives. Numerically simulated pulsed-laser heating of solid target and thermal explosion of RDX, TATB, and HMX are compared to experimental results. The experimental and numerical results are in good agreement.

• Journal of Technologic Dentistry
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• v.19 no.1
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• pp.37-42
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• 1997

The interfacial bond strengh and microstructural analysis of pre-heat treated porcelain-fusedmetal(PFM) were investigated using a mechanical three-point bending tester and scanning electron microscope(SEM). Four kinds of heat treated samples were prepared as follows ; A: Heating $1200^{\circ}F{\to}1600^{\circ}F$, holding 1min, reheating ${\to}1850^{\circ}F$, hold 3min under vacuum, B: heating $1200^{\circ}F{\to}1600^{\circ}F$, holding 1min, reheating${\to}1850^{\circ}F$ under vacuum conditon, C: heating $1200^{\circ}F{\to}1600^{\circ}F$, holding 1min, reheating${\to}1850^{\circ}F$, holding 3min in the air, repeat same heat treatment process under vacuum condition, D: heating $1200^{\circ}F{\to}1600^{\circ}F$, holding 1min, reheating${\to}1850^{\circ}F$, holding 1min in the air. The three-point bening test result shows that the interfacial bond strength of specimen B and C were higher than that of A and D. The SEM study indicate that Specimen C shows the highest surface density.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.422-426
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• 2003

Cu thin films of $6000{\AA}$ thickness were deposited by Electron Beam Evaporation(EBE) method on the glass. The resistivity properties and adhesion of Cu thin films were investigated by various annealing and substrate temperature. Cu thin films were annealed in the air and vacuum condition for 10 min after the deposition. The resistivity and adhesion(the force required to separate films from substrates) was measured by 4-point probe and scratch testing. The resistivity of non-annealing Cu thin films was distinguished more substrate temperature loot than substrate temperature R.T, $200^{\circ}C$. In the case of air condition annealing, as heating temperature was increased, the resistivity was decreased. In the case of vacuum condition annealing, the resistivity was increased at heating temperature $200^{\circ}C$. The best resistivity($1.72\;{\mu}{\Omega}{\cdot}cm$) of Cu thin films was obtained by the air condition heating temperature $200^{\circ}C$ at the substrate heating temperature $100^{\circ}C$. As a result of scratch testing, adhesion was increased by annealing. And maximum adhesion had 600 gf.

• Journal of Powder Materials
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• v.4 no.4
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• pp.298-303
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• 1997

The activated sintering behavior of $MoSi_2$ powder compacts with addition of 0.5 and 1.0 wt.%Ni during the sintering under As atmosphere was studied. The shrinkage was measured and the microstructures were observed by SEM (scanning electron microscopy) and BEI (backscattered electron image) along with the phase analysis by EDS during heating up to 155$0^{\circ}C$ and holding for various time at 155$0^{\circ}C$. The most of shrinkage occurred upon heating and 92% of theoretical density was attained after sintering for 1 hr at 155$0^{\circ}C$. However, little shrinkage ensued even for prolonged sintering over 1 hr at 155$0^{\circ}C$. A liquid film formed at about 135$0^{\circ}C$ along necks and grain boundaries. The polyhedral grain structure composed of $(Mo,Ni)_5Si_3$and $Ni_2Si$ across the $MoSi_2$ grain boundary developed at 155$0^{\circ}C$. It was concluded that the activated sintering of $MoSi_2$ powder by Ni led to the diffusion of Si into Ni decreasing the liquidus temperature and the enhanced diffusion of Mo and Si through such a liquid phase and/or interboundary of $(Mo,Ni)_5Si_3$.

• Journal of the Korean institute of surface engineering
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• v.25 no.5
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• pp.215-221
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• 1992

This research is aimed at developing(110) preferred TiS2 cathode films and glass typed solid electro-lytes which have high ionic migrations and low electron conductivities for thin secondary solid batteries. To obtain preferred oriented TiS2 thin films on a substrate by CVD method using TiCl4 and H2S gases three factors of heating temperature, inner pressure of furnace and TiCl4/H2S gas mole fraction were ex-amined systematically. To obtain solid films of Li2O-B2O3-SiO2 electrolytes by r.f. sputtering for thin proto-type batteries of Li/Li2O-B2O3-SiO2TiS2, sputtering conditions were examined. TiS2 cathode films showed columnar structure, namely c axis oriented parallely. At low pressure of reaction chamber and low heating temperature, surface of smooth TiS2 films couldd be obtained. Ionic conductivity of Li2O-B2O3-SiO2 films manufactured by r.f. magnetron sputtering were 3$\times$10-7$\Omega$-1cm-1 and electron conductivities were 10-11$\Omega$-1cm-1. Open cell voltage of thin lithium batteries were 2.32V with a designed prototype cell.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.149-150
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• 2022

In Korea, there is no clearly established technology for diagnosing and evaluating the damage depth of concrete structures created by fire. There have been cases of repairing, reinforcing, and demolishing degraded structures without diagnosing the damage depth. The commonly used phenolphthalein-based carbonate thickness measurement does not satisfy the complete disappearance condition of Ca(OH)₂ in the interval where the relatively stationary flow declines after exposure to high temperatures. Even a small amount of Portlandite[Ca(OH)₂] reacts with a red color, and the damage depth is misjudged. It was confirmed by X-ray diffraction and scanning electron microscope that Ca(OH)₂ existed from 300℃ to 500℃ where the residual compressive strength decreased.

• Proceedings of the KWS Conference
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• v.43
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• pp.76-78
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• 2004

The phenomenon of weld shrinkage mainly occurs owing to residual stress by heating, which largely effects on welding quality, Actually as the shrinkage rate depends on the weld deposit amount, so it is desired that the sectional area of weld joint shall be reduced. In this respect the Electron beam welding has more profitable position compare to Narrow-gap TIG welding which is even superior to other arc welding processes. In case of thick austenitic stainless steel the shrinkage rate of Electron beam welding has about $10\%$ of Narrow-gap TIG welding's, which means that residual stress is a lot less than that of Narrow-gap TIG welding. And heat input and welded section area also indicate large difference between two processes.

• Applied Science and Convergence Technology
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• v.23 no.2
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• pp.83-89
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• 2014

Adsorption of residual gas molecules damped the emission current of a W (310) field electron emission (FE) emitter. The damping speed was linearly proportional to the pressure gauge readings at pressure ranging from ${\sim}10^{-8}Pa$ to ${\sim}10^{-9}Pa$, and the proportionality constant was employed to measure pressure in the $10^{-10}Pa$ range. A time plot of FE current revealed the existence of an "initial stable region" after the flash heating of W(310) FE, during which the FE current damps very slowly. The presence of non-hydrogen gas removed this region from the plot, supplying a means of qualitatively analysing the gas species.

• Bulletin of the Korean Chemical Society
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• v.6 no.5
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• pp.304-308
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• 1985

Morphological structure of tin oxide thin films was examined by transmission electron microscopy. TEM samples were prepared by chemical etching in hydrogen fluoride solution: firstly floating for 2-3 minutes in acid solution, then suspending on water found to be useful for the preparation of TEM samples. Electron micrographs showed the size of grains of the tin oxide crystal was dependent upon the temperature of the film preparation. Dopant concentration and heating time also influence the grain size. The resistivity of tin oxide material was explained by grain size and grain boundaries in a limited temperature and dopant concentration ranges.

• Korean Journal of Materials Research
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• v.20 no.12
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• pp.636-639
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• 2010

ZnO thin films were prepared on a glass substrate by radio frequency (RF) magnetron sputtering without intentional substrate heating and then surfaces of the ZnO films were irradiated with intense electrons in vacuum condition to investigate the effect of electron bombardment on crystallization, surface roughness, morphology and hydrogen gas sensitivity. In XRD pattern, as deposited ZnO films show a higher ZnO (002) peak intensity. However, the peak intensity for ZnO (002) is decreased with increase of electron bombarding energy. Atomic force microscope images show that surface morphology is also dependent on electron bombarding energy. The surface roughness increases due to intense electron bombardment as high as 2.7 nm. The observed optical transmittance means that the films irradiated with intense electron beams at 900 eV show lower transmittance than the others due to their rough surfaces. In addition, ZnO films irradiated by the electron beam at 900 eV show higher hydrogen gas sensitivity than the films that were electron beam irradiated at 450 eV. From XRD pattern and atomic force microscope observations, it is supposed that intense electron bombardment promotes a rough surface due to the intense bombardments and increased gas sensitivity of ZnO films for hydrogen gas. These results suggest that ZnO films irradiated with intense electron beams are promising for practical high performance hydrogen gas sensors.