• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.9
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• pp.1137-1143
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• 2010

This paper presents a fatigue design method for plug- and ring-type gas-welded joints, which takes into account the effects of welding residual stress. To develop this method, we simulated the gas-welding process by performing nonlinear finite element analysis (FEA) To validate the FEA results, numerically calculated residual stresses in the gas welds were then compared with experimental results obtained by the hole-drilling method. To evaluate the fatigue strength of plug- and ring-type gas-welded joints influenced by welding residual stresses, the use of stress amplitude $(\sigma_a)_R$, which includes the welding residual stress in gas welds, is proposed $(\sigma_a)_R$ on the basis of a modified Goodman equation that includes the residual stress effects. Using the stress amplitude $(\sigma_a)_R$ at the hot spot point of gas weld, the relations obtained as the fatigue test results for plug and ring type gas welded joints having various dimensions and shapes were systematically rearranged to obtain the $(\sigma_a)_R-N_f$ relationship. It was found that more systematic and accurate evaluation of the fatigue strength of plug- and ring-type gas-welded joints can be achieved by using $(\sigma_a)_R$.

• Journal of the Korean Society of Radiology
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• v.13 no.2
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• pp.261-270
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• 2019

The separation permeation characteristics of $N_2-O_2$ gas in air at cell membrane model of skin which irradiated by high energy electron(linac 6 MeV) were investigated. The cell membrane model of skin used in this experiment was a sulfonated polydimethyl siloxane(PDMS) non-porous membrane. The pressure range of $N_2$ and $O_2$ gas were appeared from $1kg_f/cm^2$ to $6kg_f/cm^2$. In this experiment(temperature $36.5^{\circ}C$), the permeation change of $N_2$ and $O_2$ gas in non-porous membrane by non-irradiation were found to be $1.19{\times}10^{-4}-2.43{\times}10^{-4}$, $1.72{\times}10^{-4}-2.6{\times}10^{-4}cm^3(STP)/cm^2{\cdot}sec{\cdot}cmHg$, respectively. That of $N_2$ and $O_2$ gas in non-porous membrane by irradiation were found to be $0.19{\times}10^{-4}-0.56{\times}10^{-4}$, $0.41{\times}10^{-4}-0.76{\times}10^{-4}cm^3(STP)/cm^2{\cdot}sec{\cdot}cmHg$, respectively. The irradiated membrane was significantly decreased about 4-10 times than membrane which was not irradiated. And ideal separation factor of $N_2$ and $O_2$ gas by non-irradiation was found to be from 1.32 to 0.42 and that of $N_2$ and $O_2$ gas by irradiation was found to be from 0.237 to 0.125. The irradiated membrane was significantly decreased about 4-5 times than membrane which was not irradiated. When the operation change(cut) and pressure ratio(Pr) by non-irradiation were about 0, One was increased to the oxygen enrichment and the other was decreased to the oxygen enrichment. The irradiated membrane was significantly decreased about 4-19 times than membrane which was not irradiated. As the pressure of $N_2$ and $O_2$ gas was increased, the selectivity was decreased. As separation permeation characteristics of $N_2-O_2$ gas in cell membrane model of skin were abnormal, cell damages were appeared at cell.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.12
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• pp.1255-1265
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• 2001

A numerical study has been conducted to characterize the transient flow in a utility gas turbine burning natural gas. The solution domain encompasses the supply gas pressure regulator to the combustor of the gas turbine that employs multi-nozzle fuel injectors. Some results produced for verification in the present study agree suite well with the experimental ones. It is found that the total gas flow may decrease noticeably during its combustion mode change, which would be the reason of momentary combustion upset, when a reference case of opening ratios of control valves in the system is applied. Several parameters are then varied in order to make the total gas flow stable over that period of time. Results of this study may be useful to understand the unsteady behavior of combustion system burning natural gas.

• Journal of Life Science
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• v.9 no.6
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• pp.684-691
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• 1999

Gamdutang aqua-acupuncture solution (GAS), Gamdutang water-extracted solution (GWS) and Dae-Gamdutang aqua-acupuncture solution (DGAS) were prepared and tested for chemopreventive potentials. GAS was potent inducer of quinone reductase (QR) activity in Heapa1c1c7 murine hepatoma cells in culture, whereas GWS is less potent. GAS, GWS and DGAS were significantly induced QR activity in cultured rat normal liver cell, Ac2F. Glutathione (GSH) levels were increased about 1.8, 1.0 and 1.1 fold with GAS, GWS and DGAS in Hepa1c1c7 cells, respectively. In addition glutathione S-transferase (GST) activity was increased with GAS, GWS and DGAS. The effects of GAS, GWS and DGAS on the growth of Acanthamoeba castellanii were tested. Proliferation of A. castellanii was inhibited by GAS, GWS and DGAS at concentrations of 1 $\times$ and 5$\times$. These results suggest that GAS has chemopreventive potential by inducing QR and GST activities, increasing GSH levels and inhibition of polyamine metabolism.

• Journal of the Korean Society of Hazard Mitigation
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• v.5 no.4 s.19
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• pp.79-84
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• 2005

When polymeric materials are exposed to fire condition, a lot of heat and toxic gases evolved and cause damage to property and human being. Especially toxic gases are major hazard to life safety. This study FTIR(Fourier Transform Infrared) spectrometer analysis was performaed to etermine the gas analysis and the concentration of gases evolved from PVC, FRP, SMC and Ureathane foam using ASTM E 1678 fire model. And FED toxicity index calculated from FTIR data also presented. By the comparison of animal test adopted in KS F 2271 and FTIR gas analysis method, FTIR gas analysis method can replace current animal toxicity test and produce precise and quantitative combustion gas data.

• Journal of the Korean Institute of Gas
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• v.2 no.3
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• pp.60-69
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• 1998

Methane, the major constituent of natural gas, had been converted to higher hydrocarbons by microwave and radio-frequency plasma in vacuum condition. Methane had been activated to plasma by suppling high energy then converted to ethane, ethylene, acetylene. The direct conversion process of methane had produced few by-products and demanded low-energy. The plasma sources were microwave and radio-frequency. Two types of reactor had been used to activate methane. One is common single tubular-type reactor and the other is series coil-type reactor which used for the first time in this study. To produce more C2 products, methane had been converted by a plasma and catalyst. The results of this study could be used to study mechanism of plasma reaction of methane, design the plant-scale reactor.

• Proceedings of the SAREK Conference
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• 2004.11a
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• pp.27-27
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• 2004

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2006.04a
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• pp.125-126
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• 2006

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2005.11a
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• pp.170-170
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• 2005

• Proceedings of the Materials Research Society of Korea Conference
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• 2006.05a
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• pp.27.2-27.2
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• 2006