• 공업화학
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• 제21권6호
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• pp.676-679
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• 2010

이송식 직류 열플라즈마를 이용하여 ZrVFe 합금모재로부터 복합 나노 입자를 제조하여 플라즈마 가스 유량이 제조된 입자의 특성에 미치는 영향을 분석하였다. 입자의 특성은 전계방출 주사전자 현미경(FE-SEM), 입도 분석기(PSA), X선 분광기(EDS), X선 회절계(XRD), Brunauer-Emmett-Teller (BET) 비표면적 측정기를 사용하여 분석하였다. 플라즈마 가스 유량을 20 L/min에서 40 L/min으로 증가시키면 평균입자크기가 91 nm에서 55 nm로 감소하며 입도분포의 기하학적 편차가 줄어들었고 비표면적은 $200m^2/g$에서 $255m^2/g$으로 증가하였으며 제조된 입자의 조성에는 큰 영향을 미치지 못했지만 결정성이 향상되었다.

• Journal of Welding and Joining
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• 제5권1호
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• pp.23-33
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• 1987

플라즈마 절단은 산업계에서 널리 사용되고 있으나 공정의 해석에 대한 연구는 매우 부족하다. 본 연구에서는 알미늄판재에 나타나는 온도분포를 해석함으로써 절달폭을 이론적으로 예측하고 자 하였다. 열유동을 해석하는데 있어서, 플라즈마 아아크의 강도가 폭방향으로는 정상분포 (Gaussian distribution)을 갖고 두께방향으로는 지수함수적으로 감소한다고 가정하였다. 측정된 아아크효율을 이용한 계산결과 이론적으로 예측된 절단부의 크기 및 형상이 실험치와 매우 잘 일치하였으며, 따라서 제안된 해석방법은 플라즈마 절달공정의 해석에 유용하게 적용될 수 있 었다.

• Journal of Astronomy and Space Sciences
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• 제30권2호
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• pp.95-100
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• 2013

In this paper we examine a total of 16 dipolarization events that were observed by THEMIS spacecraft in space close to geosynchronous orbit, r < ${\sim}7\;R_E$. For the identified events, we examine the characteristics of the plasma flows and associated bubbles as defined based on $pV^{5/3}$, where p is the plasma pressure and V the volume of unit magnetic flux. First, we find that the flow speed in the near-geosynchronous region is very low, mostly within a few tens of km/s, except for a very few events for which the flow can rise up to ~200 km/s but only very near the dipolarization onset time. Second, the bubble parameter, $pV^{5/3}$, decreases by a much smaller factor after the dipolarization onset than for the events in the farther out tail region. We suggest that the magnetic dipolarization in the near-geosynchronous region generates or is associated with only very weak plasma bubbles. Such bubbles in the near-geosynchronous region would penetrate earthward only by a small distance before they stop at an equilibrium position or drift around the Earth.

• 한국환경과학회지
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• 제24권7호
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• pp.947-954
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• 2015

Dielectric barrier discharge plasma is a new technique in water pollutant degradation, which that is characterized by the production of chemically active species such as hydroxyl radicals, ozone, hydrogen peroxide, etc. If dissolving of plasma gas generated in the plasma reaction has increased, it is possible to increase the contaminant removal capacity. In this study, the improvement on the dissolving performance of plasma gas was evaluated by the indirect method measuring the overall oxygen transfer coefficient. Experiments were conducted to examine the effects of nozzle type, distance from water surface, air supply rate and liquid circulation rate. The experimental results showed that the $K_{La}$ value of the 3-prong nozzle is 2.67 times higher than the diffuser. The order of $K_{La}$ value with nozzle type ranked in the following order: 3-prong nozzle (inner diameter, less 1 mm) > circular nozzle (inner diameter, 1.5 mm) > ellipse nozzle (short diameter 1 mm, long diameter 2.5 mm) > circular nozzle (inner diameter, 3 mm). Optimal liquid circulation rate was appeared to be 1.7 L/min, the value of $K_{La}$ was 0.510 1/min. The value of $K_{La}$ with increasing air supply rate was revealed in the form of an exponential such as $K_{La}=0.3581e^{0.2919^*air\;flow\;rate}$.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.365-368
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• 2002

The design of industrial arc plasma systems is still largely based on trial and error although the situation is rapidly improving because of the available computational power at a cost which is still fast coming down. The desire to predict the behavior of arc plasma system, thus reducing the development cost, has been the motivation of arc research. To interrupt fault current, the most enormous duty of a circuit breaker, is achieved by separating two contacts in a interruption medium, $SF_{6}$ gas or air etc., and arc plasma is inevitably established between the contacts. The arc must be controlled and interrupted at an appropriate current zero. In order to analyze arc behavior in $SF_{6}$ gas circuit breakers, a numerical calculation method combined with flow field and electromagnetic field has been developed. The method has been applied to model arc generated in the Aachen nozzle and compared the results with the experimental results. Next, we have simulated the unsteady flow characteristics to be induced by arcing of AC cycle, and conformed that the method can predict arc behavior in account of thermal transport to $SF_{6}$ gas around the arc, such as increase of arc voltage near current zero and dependency of arc radius on arc current to maintain constant arc current density.

• Journal of Pharmaceutical Investigation
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• 제30권1호
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• pp.51-54
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• 2000

A column-switching high performance liquid chromatographic method has been developed for the determination of a fluconazole in human plasma. Each plasma sample was centrifuged for 10 min at 5000 g. After an aliqout of the supernatant was taken to nylon microcentrifuge filter, these samples were centrifuged for 10 min at 5000 g. An aliqout of the supernatant was injected directly onto the HPLC column. Deionized water was run for 2 min at a flow rate of 1.0 ml/min to retain fluconazole in an extration column, while proteins and endogenous interferences were eluted to the waste. The analyte was then back-flushed onto an analytical column, $C_{18}$ reversed-phase column. The mobile phase for analytical column, 0.01 M sodium acetate (pH 5.0)-methanol (65:35, v/v), was run at a flow rate of 1.0 ml/min. The column effluent was monitored by ultraviolet detection at 261 nm. The retention time for fluconazole was 11.76 min in human plasma. The detection limit for fluconazole in human plasma was $0.2\;{\mu}g/ml$. No interference from endogenous substances was observed.

• 전기학회논문지
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• 제60권3호
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• pp.669-673
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• 2011

This study explores the numerical analysis method of fluid dynamics in the reaction section to improve the gas processing efficiency in the hazardous gas removal by atmospheric thermal plasma. This study also intends to contribute in technology advance to improve the processing efficiency and make the process more stable. Numerical analysis of temperature distribution in the reaction section dependent on the change in flow velocity of Ar and plasma temperature change, which are major control variables in the cracking process of HFC-23 using arc plasma, was done. The characteristic of incoming oxygen by temperature suggested that when temperature increased to 1600K, 1700K, 1800K respectively, the range of cracking temperature 1500K increased to 75.0%, 83.3%, 90.2% respectively. The temperature change of Ar by velocity change was widest in the area higher than 1500K when the velocity was 2.5m/s; however, since there was no big difference when the velocity was 2m/s, it is believed that 2 m/s would be most proper.

• 한국정밀공학회지
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• 제16권1호통권94호
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• pp.238-245
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• 1999

For the optimal design of plasma facing components of a fusion reactor, thorough understanding of thermal behavior of high heat. nux components are required. The purpose of this research is to investigate the characteristics of heat flow and thermal stress in divertors which are exposed to high heat load varing with time and space-Numerical simulations of heat now and thermal stress for three types of diverter are performed using finite volume method and finite element method. Respectly, commercial FLUENT code are used in the heat flow simulation, and maximum surface temperature, temperature distribution and cooling rate are calculated. Commercial ABQUS code are used for calculating temperature distribution. thermal stress, strain and displacement. Through this computer simulation. design data for cooling system and Structural provided.

• Bulletin of the Korean Chemical Society
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• 제16권11호
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• pp.1023-1027
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• 1995

A comparative study of different torches in the Microwave Induced Plasma is reported. Three types of torches that have been used in this area are characterized and compared with each other. Especially, recently developed laminar flow torches have been optimized in design and analytical performances. The ratio of inner to outer tubes is found to be the most important parameter. As inner tube size increases, recirculating region also increases and consequently, sensitivity becomes better. An optimized laminar flow torch has been coupled to a gas chromatography and examined for halogen compounds. Detection limits are 25 pg s-1 for Cl and 12 pg s-1 for Br. These values are improved over the conventional laminar flow torch.

• 한국레이저가공학회지
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• 제5권1호
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• pp.33-42
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• 2002

In order to investigate the characteristics of the plasma induced by lap-joint CO$_2$ laser welding of automotive steel sheets, the effects of welding speed, shield gas flow rate, gap size, and laser beam defocus to plasma intensity emitted from keyhole have been investigated. The plasma light is measured by fiber and photodiode. Also, the plasma images were captured by the high speed digital camera in 1000frames/sec in order to correlate the plasma light signal with plasma pattern. From the results, it is observed that the difference of the plasma intensity for between the deep penetration and partial penetration exists from 1.2 to 2 times. The plasma light intensity decreased in case of the deep penetration Is observed due to the exhausting of the plasma gas under the sheet. On the other hand, under the conditions of the deep penetration, the plasma intensity is significantly increased by controling the conditions decreasing the penetration depth. It was specially founded that the effect of 0.3mm gap size at partial penetration condition is approximately similar to deep penetration in 0mm gap. It is concluded that the plasma intensity is able to evaluate the penetration depth in lap-joint welding and appears to offer the most straightforward correlation to the welding process.