• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.11
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• pp.529-535
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• 2018

The range extender vehicle runs on a mechanism that allows the small power generation engine to start in the most efficient specific operating range to charge the battery and extend the mileage. In this study, we developed a step motor type intake air supply system that replaces existing throttle body system to develop a simple low cost control logic system. The system was applied to the existing base engine, and in order to improve the performance by increasing the amount of intake air, the effect of changing the length of the intake and exhaust manifold was experimentally examined. As a result, the Type B intake air control actuator operated by one step motor showed higher performance than the Type A in all the operation region, but the performance was lower than that of the base engine due to the increase of flow resistance. To improve this, it was confirmed that the engine performance was improved at both speeds of 2200rpm and 4300rpm when the 140mm adapter was installed in the intake manifold and when the newly designed 70mm exhaust manifold was applied. Through this process, high - precision operation control was realized by connecting the generator load to the optimized engine for the range extender electric vehicle. Experimental results showed that the speed change rate was within ${\pm}2.5%$ at 2200rpm in 1st stage and 4300rpm in 2nd stage and the speed follow-up result of 610 rpm/s was obtained when the speed was increased from 2200rpm to 4300rpm.

• Korean Chemical Engineering Research
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• v.61 no.4
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• pp.517-522
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• 2023

A chemical/mechanical durability test of polymer membrane evaluation method is used in which air and hydrogen are supplied to the proton exchange membrane fuel cell (PEMFC) and wet/dry is repeated in the open circuit voltage (OCV) state. In this protocol, when wet/dry is repeated, voltage increase/decrease is repeated, resulting in electrode degradation. When the membrane durability is excellent, the number of voltage changes increases and the evaluation is terminated due to electrode degradation, which may cause a problem that the original purpose of membrane durability evaluation cannot be performed. In this study, the same protocol as the department of energy (DOE) was used, but oxygen was used instead of air as the cathode gas, and the wet/dry time and flow rate were also increased to increase the chemical/mechanical degradation rate of the membrane, thereby shortening the durability evaluation time of the membrane to improve these problems. The durability test of the Nafion 211 membrane electrode assembly (MEA) was completed after 2,300 cycles by increasing the acceleration by 2.6 times using oxygen instead of air. This protocol also accelerated degradation of the membrane and accelerated degradation of the electrode catalyst, which also had the advantage of simultaneously evaluating the durability of the membrane and the electrode.

• 한국연소학회:학술대회논문집
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• 2006.10a
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• pp.137-144
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• 2006

Oil-fired power plants usually use several burners and the combustion air is supplied to each burner through the complicated duct which is called windbox. A windbox should be designed to supply combustion air to each burner evenly but, due to the complicated duct shape, flow distribution in the windbox is unbalanced and uneven supplies of combustion air to each burner are induced by these unbalanced flow distribution in the windbox. These flow patterns tend to make flame unstable, increase the formation of pollutants and lower the overall combustion efficiency. To prevent these disadvantages, flow patterns in the windbox should be investigated for the uniform flow distribution. In this study, computational simulation method was used to investigate the flow distribution in the windbox and measured the velocities at the exit of burners in the real windbox to compare with CFD results. The results show two significant flow patterns. One is that the flow rates of each burner are different from each other and this means that all burners operate in different conditions of air to fuel ratio. The other is that the flow distribution at the exit of each burner is not axi-symmetric although the burner shape is axi-symmetric and this increases the pollutant products like CO.

• Journal of the Korean Electrochemical Society
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• v.16 no.1
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• pp.9-18
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• 2013

Components of zinc-air battery and their problems are explained. Energy density of zinc air battery is superior to other commercial ones including Li-ion batteries. Cycle life of the zinc air batteries is poor because of irreversible redox reactions on both electrodes. In order to improve the performance of the zinc air battery, catalysts, passivation, and the new structure of electrodes should be developed to optimize several reactions in an electrode. Multidisciplinary efforts, such as mechanics, corrosion science, composite materials are necessary from the beginning of the research to obtain a meaningful product.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.182.1-182.1
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• 2010

현재 전 세계적으로 가장 널리 개발하고 보급되어지고 있는 풍력산업의 시장 규모는 매년 확대되고 있다. 특히 소형 풍력발전 시스템은 낙도 등의 전력 공급이 어려운 지역에 경제성 있는 전력 보급을 가능하게 한다. 국내의 미전화 지역과 일반 가정에서 풍력 에너지 자원을 적극 활용 개발하기 위해서 보다 우수한 성능의 풍력발전기용 블레이드를 설계하고자, 공기역학적인 최적설계에 대해 연구함으로써 추후 보급형 풍력발전 시스템의 개발에 필요한 설계 기술을 확립하고자한다. 본 연구는 설계된 블레이드의 유동해석 및 성능예측을 위하여 경제적으로 많은 지원이 필요한 대규모 풍동실험이 아닌 상용 CFD를 사용하여 보다 효율적으로 우수한 성능을 가지는 풍력 터빈을 설계함에 있다. Reynolds Averaged Navier-Stokes 방정식에 기반을 둔 CFD의 경우 이론적으로 명확한 해석이 가능하고, 실제 터빈의 운전 환경과 동일한 다양한 물리적 변수를 입력 데이터로서 활용할 수 있는 장점이 있기 때문에 풍력 터빈의 설계 과정에서 반영된 미소한 블레이드 형상변화 및 운전 조건의 변화에 따른 유동장의 변화 및 풍력터빈 성능을 정확히 예측할 수 있는 장점을 가지고 있다.

• KDI Journal of Economic Policy
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• v.16 no.2
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• pp.111-139
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• 1994

최근 우리 정부는 공기업(公企業)의 민영화(民營化)를 적극 추전하고 있는바, 우리보다 앞서 민영화정책(民營化政策)을 성공적으로 추진한 경험이 있는 영국(英國)의 경우를 살펴봄으로써 앞으로 계속될 민영화(民營化) 정책수행(政策遂行)에 도움이 될 정책적(政策的) 시사점(示唆點)을 얻을 수 있을 것으로 판단된다. 특히 본고에서는 민영화기업(民營化企業)의 최초공모주(最初公募株) 가격결정(價格決定), 민영화기업 주식(株式)의 투자성과(投資成果) 및 민영화가 주식대중화(株式大衆化)에 미친 영향의 분석에 초점을 두고 있다. 민영화 기업의 최초공모주(最初公募株)는 일반기업의 최초공모주에 비해 현저히 저평가되어 발행되고 있음이 조사되었는데, 이는 정보비소유(情報非所有) 투자자(投資者)에게 최소한의 수익률 즉 무위험수익율(無危險收益率)은 보장해 주어야 한다는 Rock(1986)의 winner's curse 모형의 관점에서 설명되고 있다. 민영화기업의 최초공모주는 장기적으로 정(正)의 초과수익율(超過收益率)을 시현하고 있는데 이는 일반기업의 최초공모주의 주가(株價)와는 대조적인 것이다. 영국(英國) 민영화기업의 주식공급(株式供給)은 개별주주수의 증가를 가져와 주식대중화(株式大衆化)에는 상당한 영향을 미친 것으로 분석되었으나 많은 사람들이 단기간내에 주식(株式)을 매각하고 있어 장기보유유도(長期保有誘導)에는 미흡했던 것으로 밝혀졌다. 이러한 분석결과는 앞으로 우리나라의 공기업민영화(公企業民營化) 추진과정에서 주요 쟁점이 될 것으로 예상되는 주가결정(株價決定)에 대한 시사점을 제공할 수 있으며, 또한 일반투자자(一般投資者)의 민영화주식에 대한 투자전략을 수립하는데 도움을 줄 수 있을 것이다.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.1-4
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• 2008

Fuel cells have the potential of providing several times higher energy storage densities than those possible using current state-of-the-art lithium-ion batteries, but current energy density of fuel cell system is not better than that of lithium-ion batteries. To achieve the high energy density, volume and weight of fuel cell system need to be reduced by miniaturizing system components such as stack, fuel tank, and balance-of-plant. In this paper, the thin flexible PCB (Printed circuit board) is used as a current collector to reduce the stack volume. Two end plates are made from light weight aluminum alloy plate. The plate surface is wholly oxidized through the anodizing treatment for electrical insulation. The opening rate of cathode plate hole is optimized through unit cell performance measurement of various opening rates. The performances are measured at room temperature and ambient pressure condition without any repulsive air supply. The active area of MEA is 10.08 $cm^2$ and active area per a unit cell is 1.68 $cm^2$. The peak power density is about 210 mW/$cm^2$ and the air-breathing planar stack of 2 Wis achieved as a small volume of 18 cc.

• Fire Science and Engineering
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• v.16 no.2
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• pp.14-21
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• 2002

The several floor finishing materials that widely used in entertainment service industry buildings were evaluated according to the method of NES 713. Also, toxic gases of floor finishing materials in combustion without air flow rate were checked as concentration of fire gases variation according to time using gas analyzer. We had estimated the smoke hazard of floor finishing materials in fire. As results of gas analyses using the method of NES 713, toxic index of samples was estimated range of 2～9.7. Therefore, a large amount of toxic gases will release from a floor finishing materials fire and connoted great smoke hazard in fire.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.5
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• pp.735-742
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• 2010

This paper reviewed the diving standards for underwater work in hostile environment and analyzed applied Navy diving technique, diving equipments and procedure for rescue operation of Navy ship Cheonan's missing crew occurred near Bak Ryung Do in March 2010. The operation was done beyond the international standards and safety practice, and by considering the nature of the mission, urgency and effectiveness as well as the detailed facts such as duration and depth of the dive, type of work to be performed, environmental conditions, time constraints of early rescue operation, it is analyzed that using air scuba diving system was adequate.

• Microbiology and Biotechnology Letters
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• v.10 no.2
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• pp.155-162
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• 1982

A cell-recycled continuous fermentation process was studied to produce ethanol from molasses using Sacchoromyces uvarum ATCC26602 at 35 $^{\circ}C$. The fermentation system was divided into two stages in order to reduce the inhibitions of ethanol and substrate for cell growth and fermentation rate. The first reactor was aerated at the rate of 0.12 vvm whilst the second was kept anaerobic. In medium composition studies, it was revealed that inorganic nutrient supplement to the diluted molasses with 14% fermentable sugar was not needed for the fermentation, however, phosphate limitation was observed when cell propagation was contemplated. By using the cell-recycled continuous fermentation system, 14.5 hour was required to produce 8.4-9.0% (v/v) of ethanol from diluted molasses containing 14% of fermentable sugar. The ethanol productivity was 6.2g/$\ell$hr with the yield of 88.1-94.4% to the theoretical value.