• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1307-1311
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• 2007

Three-dimensional transient keyhole profile is numerically analyzed for the case of stationary laser keyhole welding. Volume of fluid (VOF) method is adopted to track the free surface of molten metal based on the three governing equations which are continuity, momentum and energy equations. Multiple reflections of laser beam at the keyhole walls are also included in analysis through a real-time ray tracing technique. In this simulation, especially, polarization of laser is considered as an energy absorption mechanism following the Fresnel reflection theory. Both cases of linearly and circularly polarized beam are simulated and compared. The results show that the theoretically generated keyhole is asymmetrically stretched along the direction of polarization which is already observed experimentally before.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.3
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• pp.205-212
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• 2002

The catalytic combustion of benzene, toluene and xylene over Pt-based catalyst was investigated in a fixed bed flow reactor system with atmospheric pressure to recycle the waste industrial catalyst for the processes of removing volatile organic compounds. According to the pretreatment condition, the properties of the waste Pt-based catalyst were characterized by XRD (X-ray diffraction) and BET (Brunauer-Emmett-Toller). In the carte of air pretreatment, 20$0^{\circ}C$ was found to be optimal, and increasing pretreatment temperature resulted in the reduction of the catalytic activity. When Pt-based catalyst pretreated at 20$0^{\circ}C$ by alto was retreated by hydrogen, the catalytic activity increased by increasing treatment temperature. In the case of HNO$_3$aqueous solution pretreatment, the catalytic activity decreased by increasing the concentration of HNO$_3$aqueous solution. The catalytic activity was seen to observe the following sequence : benzene > toluene > xylene.

• Journal of Korean Society for Atmospheric Environment
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• v.13 no.4
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• pp.307-317
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• 1997

Samples of fine particle $(d_P<2.5 \mum)$ were taken in Chongju area using a dichotomous sampler. The data set was collected on fifty-eight different days with 24 hour sampling period from October 27, 1995 through August 25, 1996. The samples were analyzed using a proton induced x-ray emission (PIXE) for Na, Mg, Al, Si, S, Cl, K, Ca, Ti, V, Cr, M, Fe, Ni, Cu, Zn, Br and Pb. Values of Fe, Ca, Si, Cu, K and Cl exhibit marked seasonal variations. Mean concentrations for this study had the following order S > Cl > Si > K > Al > Fe on fine particle. Concentrations of Ca, Si and Fe were higher during the spring season compared with any other season. These phenomena may be attributable to soil dust. Cl and K were higher in the winter, which may be explained by combustion of fossil fuel. Higher values for Cu and Zn in the Winter may be due to the combustion and incineration.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.694-698
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• 2002

Ti films were deposited onto $100{\times}100$ mm alumina substrates using dc magnetron sputtering under the following conditions; substrate temperature of R.T. ${\sim}400^{\circ}C$, annealing temperature of $100{\sim}400^{\circ}C$ and sputtering gas pressure of $1.3{\sim}3.0{\times}10^{-2}$ Torr. And the films were examined by X-ray diffraction analysis (XRD), scanning electron microscopy(SEM) and 4-point measurement system. The best electrical and structural properties obtained by substrate temperature of ${\sim}200^{\circ}C$, target-substrate distance of ~14 cm and sputtering pressure of $1.3{\sim}1.7{\times}10^{-2}$ Torr. Also at that condition the most excellent adhesion was observed.

• Journal of radiological science and technology
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• v.12 no.1
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• pp.25-29
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• 1989

This paper investigated on influence on the distinguishability of renal stone in the accordance with thickness of object, x-ray tube voltage and base density. In the relationship between object and renal stone shadow, object and tube voltage, the obtained results can be summarized as the following. 1. When thickness of object was thin, the distinguishability increased in base density $2.0{\sim}2.5$, but for adults was best shown in base density 1.5. 2. In the relationship between object and tube voltage, the distinguishability increased at lower tube voltages ($50{\sim}60\;kVp$), using grid. As mentioned above, it was thought that this method was very effective in describing the phenomena of renal stone in film density 1.5, tube voltages 60 kVp.

• Journal of radiological science and technology
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• v.21 no.2
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• pp.19-25
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• 1998

By analyzing each part of expsure condition and the status of an entrance dose which is exposed to patients, this study reached the following conclusion. Since there is no standard in setting up an exposure condition, the technology practiced in each facility varies tremendously, and the entrance dose increased especially due to the improper selection of screen and grid and the shortage of a total amount of filtration in leaching the standard filtration amount. Entrance dose was, generally, turned out to be $2{\sim}3$ times as much as that of advanced countries, and there was big difference between facilities ; approximately 52 times inlateral of cervical vertebrae, 35 times in A-P of femur, 33 times in chest A-P, and 11 times in lumber A-P. Therefore, to minimize the entrance dose of a patient with thegreatest amount of image information, acquirement of technological know-how necessary for standardization of exposure condition for each part can be an important research task.

• Proceedings of the KWS Conference
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• 2006.10a
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• pp.199-201
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• 2006

The wetting balance test was carried out to compare the wettability of Sn-Xwt%Cu($0{\sim}3$wt%) solders. And, IMCs which were formed at interface between solders and substrates were investigated by using XRD(x-ray diffractometer), SEM(scanning electron microscope) and EDS(energy dispersive spectroscope). The value of ${\gamma}_[fl}$ and(${\gamma}_{fs}-{\gamma}_{ls}$) had a tendency to increase with increasing wetting temperature. The activation energy that was calculated between the bare Cu substrate and flux was increased in the following order Sn-0.7wt%Cu(68.42 kJ/mol);Sn-3.0wt%Cu(72.66 kJ/mol);100wt%Sn solder(94.53 kJ/mol).

• Tuberculosis and Respiratory Diseases
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• v.69 no.5
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• pp.389-391
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• 2010

Spinal epidural emphysema is rare and has been described secondary to following medical intervention, such as lumbar puncture and epidural analgesia, pneumothorax or pneumomediastinum, degenerative disk disease, epidural abscess, and trauma. Rarely, it occurs after chest tube placement. We report a case of spinal epidural emphysema incidentally noted on HRCT after chest tube placement.

• Journal of the Korean Ceramic Society
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• v.30 no.7
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• pp.557-562
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• 1993

Following conclusions are made from the detalied research on the relation between the phase change of the petroleum raw cokes after ball milling and the preheat treatment temperature. The petroleum raw cokes species are preheated in the temperature range of 350~45$0^{\circ}C$. At the preheat treatment temperature of 40$0^{\circ}C$ the particles of petroleum raw cokes from ball milling become spheically shape with the almost uniform particle size distribution of 1~5${\mu}{\textrm}{m}$. At the same temperature, they became low-graphitized with the d0.02 X-ray diffraction index of 3.41$\AA$. The carbon material made from the petroleum raw cokes at 40$0^{\circ}C$ turned out to have the good modulus of rupture about 600kg/$\textrm{cm}^2$, with the bulk density around 1.8g/㎤ and the appearent porosity around 8%.

• Journal of the Korean Ceramic Society
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• v.18 no.1
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• pp.41-47
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• 1981

The sintering characteristics of the SiC-Clay-Kaolin chamotte system were studied by addition of $Al_2O_3$ for the manufacture of silicate-bonded silicon carbide refractories at $1350^{\circ}C$. The sinterbilit of SiC-Binder mixture was measured by apparent porosity and compressive strength. And its mineral compositions were identified with X-ray diffractometer. The following results were obtained; 1) Optimum amount of mixed clay ($\textrm{Al}_2\textrm{O}_3$ 40 wt% mixed) as a binder was about 25wt% 2) Appropriate mixing ratio of mixed Kaolin chamotte ($\textrm{Al}_2\textrm{O}_3$ 40wt% mixed) was about 30wt% in the clay Kaolin chamotte binder. 3) Variation of apparent porosity and compressive strength of sintered SiC-binder mixture fired at $1350^{\circ}C$ were due to the sinterbility of clay.