• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.311-317
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• 2005

It has been the most progressive interruption technique to use the ablation gas from the surface of PTFE nozzle driven by arc plasma during switching process in $SF_6$ gas circuit breakers. This advanced interruption technique can reduce the required mechanical energy to compress and blow the gas for extinguishing the arc plasma between the electrodes due to using the ablation effect instead. In order to consider the phenomena during calculation of switching process, it is required to confirm the principles of ablation from PTFE nozzle as well as of arc plasma during switching process. In this study, we have calculated the switching process considered the ablation of PTFE nozzle driven by arc plasma using multidisciplinary simulation technique and compared the results with the data without the ablation effect. More $50\%$ difference of pressure rise inside expansion chamber has been found from the results and it should be indispensable for this type of computational work to consider and include the ablation effect of PTFE nozzle. Further study on turbulence and radiation will be followed.

• Journal of Chest Surgery
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• v.29 no.8
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• pp.883-888
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• 1996

Expanded polytertrafluoroethylene (expanded PTFE) graft fistulas are widely used as secondary vascu- lar access for patients receiving long-term hemodialysis treatment. We implanted 48 grafts in )5 patients during the period from August 1990 to August 1995. Forty-three grafts in 32 patients were followed for 1 to 46 months. We performed forearm straight grafts in 36 grafts and upperarm straight grafts in 7 grafts. We experienced 3 operative failures, 22 early and late complications(15 graft thrombosis). Cumulative patency for all grafts at 12 months was 63%, at 24 months 32%, at 36 months 32% Forearm graft survival at 12 months was 55%, at 24 months 30%, at )6 months 30%. Upperarm graft survival at 12 months was 8)oyo and 24 months 41%. After reviewing our experience, we think that expanded-PTFE grart as secondary vascular access still have many complications and low survival than autogenous a teriovenous fistula. And so utilization of the expanded PTFE fistula requires better techniques, close observation and maintenance to keep it functional.

• Journal of the Korean Electrochemical Society
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• v.5 no.1
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• pp.7-12
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• 2002

The gas diffusion electrodes as oxygen cathodes f3r the brine electrolysis process were investigated. The gas diffusion electrode consists of a reaction layer, a gas diffusion layer, and a current distributor. The reaction layer was made from hydrophilic carbon black, hydrophobic carbon black, PTFE(polyterafluoroethylene), and Ag catalyst loaded by the silver mirror reaction or impregnation method. The gas diffusion layer was made from hydrophobic carbon black and PTFE, and Ni mesh was used as the current distributor in the reaction layer. The result that the gas diffusion electrode $(10wt\%\;Ag\;catalyst\;and\;20wt\%\;binder)$ manufactured by applying impregnation method to the carbon black f3r reaction layer showed the better performance was obtained from experiments. From the half-cell test, the measured overpotential of this oxygen cathode was about 700mV, And through the electrolysis experiment under the condition of $80^{\circ}C,\;32wt\%$ NaOH, and $300mA/cm^2$, the electrolysis voltage of this electrode was about 2.2 V, The gas diffusion electrodes manufactured in the present research were capable of continuous operations for three months.