• Clean Technology
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• v.13 no.2
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• pp.99-103
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• 2007

Pt/Nafion self-humidifying membranes for Polymer Electrolyte Membrane Fuel Cell (PEMFC) were synthesized via a supercritical-impregnation method. The Nafion 112 membranes were impregnated with Pt(II) acetylacetonate from a supercritical carbon dioxide ($scCO_2$) solution at $80^{\circ}C$ and 19.8 MPa. After the impregnation, the Pt-impregnated Nafion membrane was converted Pt deposited Nafion(Pt/Nafion) membrane by reducing agent, sodium borohydride ($NaBH_4$) under $50^{\circ}C$ and 2 hours. The prepared Pt/Nafion membranes were investigated by SEM, EDS and EPMA. The performance of the Pt/Nafion membranes was examined in PEMFC as a self-humidifying membrane. The cell performance of the Pt/Nafion membrane at $65^{\circ}C$ is better than that of Nafion 112.

• Journal of the Korean Ceramic Society
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• v.39 no.6
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• pp.566-569
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• 2002

In general, Pb-based complex perovskite powders have not been directly prepared because pyrochlore that is secondary phase appears. In this study, we tried to prepare Pb(Fe$_{1}$2/Nb$_{1}$2/)O$_3$ which was used to the electronic multicomponent by supercitical fluid method in order to fabricate very active powder not through pyrochlore.

• Clean Technology
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• v.16 no.4
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• pp.239-244
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• 2010

The carboxylation of the fluorenyl epoxide with a spiro framework, 9,9'-Bis(4-oxiranylmethoxyphenyl) fluorine (2) was catalyzed by some onium salts such as quaternary ammonium and phosphonium salts to produce the corresponding five-membered cyclic carbonate (3) in an efficient and environmentally benign fashion. The coupling reactions depend greatly on the kind of the halide anions and alkyl chain length of the onium salts. While the reaction was sensitive to the reaction temperature, the reaction trends suggest that the catalytic efficiency of the quaternary ammonium halides may correlate strongly with the melting points of the halides. The reactions using a catalytic amount (2 mol %) of quaternary ammonium bromide with an n-butyl chain at 75.9 bar of $CO_2$ and 393 K give the highest yield of the cyclic carbonate (92%).

• Korean Chemical Engineering Research
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• v.50 no.6
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• pp.988-993
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• 2012

Energy and cost analysis of the preprocessing for carbon capture and storage transportation such as supercritical compression and liquefaction is done using chemical simulation model. Direct compression to supercritical phase (process 1-1), liquefaction and pumping (process 1-2), carbon dioxide compression and expansion as a refrigerant itself (process 2), usage of other refrigerant with compression and expansion (process 3-1), with absorption chiller (process 3-2), cascade refrigeration (process 3-2) have been simulated and evaluated. The specific cost is about 4 to 7 $/ton.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.2
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• pp.158-165
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• 2008

The carbon dioxide properties change sharply near the critical or pseudo-critical point in the heat transfer processes. The reduction in turbulent, convective heat transfer parameters observed in some supercritical data and in experiments with common gases can be due to property variation, acceleration, buoyancy or combinations of these phenomena, depending on the conditions of the applications. In this study, the measurement for the secondary flow driven by buoyancy was carried out on the supercritical carbon dioxide turbulent flows in the different boundary condition with the constant mass flow rate. The available measuring techniques were used to clarify the behaviour of any supercritical fluid. Laser Doppler Velocimeter (LDV) and a special device was used to measure the secondary velocity and turbulent characteristics of the supercritical flows.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.150-155
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• 2010

Liquid rocket injectors play crucial roles on propulsive performance, combustion stability, and heat transfer characteristics. Nevertheless, their developments have mainly relied on empirical methods and expensive hot-firing tests due to lack of fundamental understanding of high pressure combustion phenomena in the near-injector regions. The present study was motivated by recent efforts to develop reliable modeling of liquid rocket combustion. The turbulent combustion model based on the flamelet concept has been extended to take into account real-fluid behaviors occurred at supercritical pressures, and validated against measurements for a cryogenic nitrogen injection, a non-premixed turbulent jet flame at atmospheric pressure, and a LOx/$GH_2$ coaxial shear injector at a supercritical pressure.

• Journal of Engineering Education Research
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• v.13 no.6
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• pp.72-79
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• 2010

The purpose of this study was to explore good college instructional practice in the industrial teacher education in order to improve the quality of instruction. The study that what is the good instructional practice have been relatively more researched on elementary and middle school than colleges. Research methods used in this study were an individual interview and focus group interview. Research results and analyses were three directions in good instructional practice to be in teacher's college, engineering college and teacher's graduate school. Based on the result of the study, some recommendations for future researches were made as follows: First, good instructional practice in teacher's college were to be interested in students and be enthusiastic class and practical training. Second, good instructional practice in engineering colleges were class to be a faithful college program for teaching profession orientation and practical training. Third, good instructional practice in teacher's graduate school were class to allow for an academic standard and subjects of special study of each students.

• KSBB Journal
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• v.11 no.1
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• pp.100-106
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• 1996

The extraction of taxol and baccatin III from the ground needles of Taxus cuspidata were carried out by using supercritical carbon dioxide with and without cosolvents such as ethylacetate and methanol at 300 bar and 313K. Taxol is a promising anticancer agent and baccatin III is a precursor of semisysthesis of taxol. The taxol and baccatin III contents in the extracts were determined by a HPLC. The highest yields of taxol and baccatin III could be obtained by the supercritical extraction with 3wt% methanol and ethylacetate, respectively, as cosolvents. It was also found that the selectivity of taxol and baccatin III were 0.117 and 1.245wt%, respectively, with 0.7wt% ethylacetate, which demonstrated that the selectivity of taxol and baccatin III were increased about 1.8 and 19 times than those of conventional organic solvent extraction.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.251.1-251.1
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• 2010

바이오디젤은 동식물성 기름과 메탄올의 트랜스에스테르화 반응에 의해 생산되는 지방산메틸에스테르(FAME, fatty acid methyl esters)로서, 트랜스에스테르화 공정에는 KOH, NaOH, $NaOCH_3$등의 균질계 화학촉매를 이용한 방법, 무촉매 공정인 초임계 메탄올 이용 방법, 그리고 효소촉매를 이용한 방법이 있다. 초임계 공정은 에너지 소비와 장치비가 커서 경제성이 떨어지는 것으로 보고되며 화학촉매 공정은 반응 효율이 높다는 장점을 가지고 있지만, 반응 및 정제단계가 복잡하고 정제과정에 폐수를 발생시키는 문제점을 가지고 있다. 고정화 효소를 사용하는 효소 공정은 에너지 비용의 절감, 후 처리 공정의 단순화, 고 순도의 글리세롤을 얻을 수 있는 장점이 있지만, 반응 속도가 느리고 효소 가격이 비싸다는 단점이 있어 현재까지 상업화되지 못하고 있다. 반응속도가 높고 재사용이 가능한 효소 촉매 공정 개발을 위해 본 연구에서는 Candida rugosa, Rizhopus oryzae 2종을 실리카에 동시 고정화하였다. 고정화 Lipase의 제조는 실리카겔을 과산화수소를 이용하여 전처리를 하고 Acetone과 3-APTES의 혼합용액을 첨가한 후 실리카겔과 (silanization)을 진행 하였다. 그리고 glutaraldehyde를 첨가 하여 공유 결합을 형성 한 후에 증류수를 사용하여 실리카겔을 회수하여 lipase(Rizhopus oryzae, Candida rugosa 10% 용액)를 고정화 하였다. 고정화 효소의 효소 활성을 측정한 결과 3000-3500 Unit(${\mu}mol/g{\cdot}min$)으로 측정되었다. 제조된 고정화 효소를 이용하여 Canola Oil을 바이오디젤로 전환하는 실험을 진행하였으며 생성물로부터 고정화 효소를 분리한 후에 상층의 에스테르층을 취하여 수세한 뒤 원심분리하여 FAME 함량을 측정한 결과 83%의 바이오디젤을 얻을 수 있었다. 그리고 효소 촉매 트랜스에스테르화 반응의 Enzyme, Water, Methanol 투입량의 반응 변수들에 대하여 반응표면분석법(Response Surface Methodology)을 적용하여 최적 반응조건을 도출하는 연구를 수행하였다.

• Korean Chemical Engineering Research
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• v.47 no.4
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• pp.453-458
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• 2009

Recently, new methods to synthesize and process polymers without toxic organic solvents are needed in order to solve environmental problems. The use of supercritical carbon dioxide as a solvent for the polymer synthesis is attractive since it is non-toxic, non-flammable, naturally abundant, and the product may be easily separated from the solvent. In this study, we developed the method using super critical $CO_2$ to prepare P(MAA-co-EGMA) hydrogel nanoparticles as an intelligent drug delivery carrier. The effects of concentrations of PtBuMA-PEO as a dispersion stabilizer and AIBN as an initiator on the particle synthesis were investigated. When PtBuMA-PEO concentration increased, the particle size decreased. However, there was no significant difference in the particle size according to the AIBN concentration. There was a drastic change of the equilibrium weight swelling ratio of P(MAA-co-EGMA) hydrogel nanoparticles at a pH of around 5, which is the $pK_a$ of PMAA. At a pH below 5, the hydrogels were in a relatively collapsed state but at a pH higher than 5, the hydrogels swelled to a high degree. In release experiments using Rh-B as a model solute, the P(MAA-co-EGMA) hydrogel nanoparticles showed a pH-sensitive release behavior. At low pH(pH 4.0) a small amount of Rh-B was released while at high pH(pH 6.0) a relatively large amount of Rh-B was released from the hydrogels.