• 한국자동차공학회논문집
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• 제18권4호
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• pp.140-146
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• 2010

An experimental study was carried out to investigate the emission characteristics for various alternative fuels in a 2.0 liter 4-cylinder turbo-charged diesel engine. The conventional diesel fuel, neat GTL (Gas to Liquid), blends of diesel and biodiesel(BD20), and blends of GTL and biodiesel(G+BD20 and G+BD40) were applied, and their emission characteristics were compared at various steady-state engine operating conditions. A noticeable reduction of exhaust emissions compared to conventional diesel fuel, except for NOx emission, was observed for G+BD40, where there is a maximum 30% averaged reduction for gaseous emissions (THC and CO) and 70% for PM mass concentrations. When comparing PM size distributions for biodiesel blended fuels, the PM number concentration in accumulation mode, where the diameter of PM is greater than 50 nm, decreased due to additional oxygen content in the biodiesel fuel; in nucleation mode, where the diameter of PM is less than 50nm, there was a slight increase or decrease in the PM number concentration depending on the amount of oxygen available in the combustion chamber.

• 대한기계학회논문집B
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• 제31권7호
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• pp.588-595
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• 2007

The water transport inside a polymer electrolyte fuel cell (PEFC) varied according to the anodic supply mode. The performance characteristics of a PEFC which can be affected by the water transport were observed with the anodic supply mode. In the flow-through and recirculation mode the performance showed no reduction with time because the flow in the anode was not stagnated. In the dead-end mode, without any discharged gas, the water remains inside of the anode, which caused the reduction of the performance with the lapse of time. However, even in the dead-end mode, little reduction of the performance with time was shown when only the anode was humidified externally. It means that the back-diffusion was the major factor to the accumulation of water in the anode rather than external humidification.

• 전자공학회논문지
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• 제53권9호
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• pp.49-53
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• 2016

RF 채널 분포효과를 위한 전압 종속 외부 게이트 커패시턴스가 사용된 High resistivity(HR) silicon-on-insulator(SOI) RF accumulation-mode MOS 버랙터의 대신호 모델이 새롭게 개발되었다. 이 모델의 전압 종속 파라미터들은 정확한 S-파라미터 optimization을 사용하여 추출되었고, 이를 피팅하여 empirical 모델 방정식을 구축하였다. 이러한 새로운 대신호 RF 모델은 넓은 전압영역에서 측정된 Y11-파라미터 데이터와 20 GHz까지 잘 일치함으로써 정확도가 검증되었다.

• 한국환경과학회지
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• 제2권4호
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• pp.317-324
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• 1993

Effluent recycling effect on UASB reactor performances is known as an important operational factor. In the present study, the possibility of intermittent recycle in UASB process for saving the power consumption was examined at different organic loading and various operational modes in recycle time period. The organic removal efficiencies of the reactors operated with the intermittent effluent recycle were considerably higher compared to those without the effluent recycle. In the intermittent recycle mode, the organic removal efficiencies slightly decreased as the non-recycle time period in the operational mode increased. Proper ratio of recycle and non-recycle time period in the mode seemed to be required to prevent the produced biogas from accumulation in the sludge bed, which caused dead zone in the reactor and sludge loss when the gas was escaped from the bed at the certain pressure.

• JSTS:Journal of Semiconductor Technology and Science
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• 제13권4호
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• pp.361-366
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• 2013

A full-range analytic drain current model for depletion-mode long-channel surrounding-gate nanowire field-effect transistor (SGNWFET) is proposed. The model is derived from the solution of the 1-D cylindrical Poisson equation which includes dopant and mobile charges, by using the Pao-Sah gradual channel approximation and the full-depletion approximation. The proposed model captures the phenomenon of the bulk conduction mechanism in all regions of device operation (subthreshold, linear, and saturation regions). It has been shown that the continuous model is in complete agreement with the numerical simulations.

• 한국수소및신에너지학회논문집
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• 제24권2호
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• pp.99-106
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• 2013

The variations of performance and metabolites at an early stage were investigated for the successful start-up technology in continuous fermentative hydrogen production. Unsuccessful start-up was observed when the operation mode was changed from batch to continuous mode after the yield was reached to 0.5 mol $H_2$/mol $hexose_{added}$ by batch mode. $H_2$ production continued till 12 hours accompanied by butyrate production, but did not last with propionate production increase. It was suspected that the failure was due to the regrowth of propionic acid bacteria during batch mode which were inhibited by heat-shock but not completely killed. Thus, successful start-up was tried by early switchover from batch to continuous operation; continuous operation was started after the $H_2$ yield was reached to 0.2 mol $H_2$/mol $hexose_{added}$ by batch mode. Although $H_2$ production rate decreased at an early stage, stable $H_2$ yield of 0.8 mol $H_2$/mol $hexose_{added}$ was achieved after 10 days by lowering down propionate production. And it was also concluded that the reason for $H_2$ production decrease at an early stage was due to alcohol production by self detoxification mechanism against VFAs accumulation.

• 한국환경과학회지
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• 제14권12호
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• pp.1093-1102
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• 2005

Effects of abscisic acid(ABA) and temperature on the anthocyanin accumulation and phenylalanine ammonia Iyase(PAL) activity were investigated in seedlings of Arabidopsis thaliana. In time course study, exogenous application of ABA $(50-1000\;{\mu}M)$ led to a noticeable increase in anthocyanin pigments which persisted over the following 5 days. Anthocyanins increased in concert with the chlorophyll loss. The activity of PAL, a key enzyme in the phenylpropanoid pathway, increased on exposure to ABA and reached maximum on the 4th day, This result shows that anthocyanin synthesis and PAL activity have a close physiological relationships. In the effects of temperatures ($10^{\circ}C,\;17^{\circ}C,\;25^{\circ}C$and $30^{\circ}C$) on anthocyanin accumulation and PAL activity in seedlings, a moderate-low temperatures ($17^{\circ}C$) enhanced both anthocyanin content and PAL activity, whereas elevated temperatures ($30^{\circ}C$) showed low levels of anthocyanin and PAL activity, suggesting a correlation between temperature-induced anthocyanin synthesis and the accumulation of PAL mRNA. Simultaneous application of ABA with temperatures Induced higher anthocyanin synthesis and PAL activity in seedlings than ABA or temperature stress alone. Moderate-low temperature with ABA exposure elicited the maximal induction of anthocyanin synthesis and PAL activity. Therefore, ABA treatment significantly increased thermotolerance in .A. thalinan seedlings. Ethephon and ABA showed similar mode of action in physiological effects on anthocyanin accumulation and PAL activity. Our data support that anthocyanins may be protective in preventing damage caused by environmental stresses and play an important role in the acquisition of freezing tolerance.

• 분석과학
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• 제10권2호
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• pp.114-118
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• 1997

히드록실아민 존재하에서 오스뮴(IV)의 벗김 전압전류법적 정량법을 연구하였다. 가장 좋은 조건은 다음과 같다: 히드록실아민 0.05M, pH 1.8, 누적전위 -0.65V, 누적시간 60초, 주사속도 10mV/s. 이 조건에서 검출한계는 $6.3{\times}10^{-8}M$이었으며, 검량선의 직선성이 성립하는 오스뮴의 농도 범위는 $10^{-4}{\sim}10^{-7}M$이었다. 유사한 매질에서 같은 족인 루테늄이 촉매 수소파를 주는데 비해 오스뮴은 촉매성이 전혀 없는 확산 지배성 전류를 주었다.

• ALGAE
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• 제39권3호
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• pp.187-205
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• 2024

Chlorella species of microalgae are utilized in the crop and food industries. The aim of this research was to investigate the metabolite profiles of Chlorella fusca for the first time and evaluate its biological properties. The two ion modes of UPLC-Q-TOF-MS/MS were used to identify a total of 62 components in the methanol extract of C. fusca, with 26 in the negative and 36 in the positive ion mode, including 10 identical ingredients. Fatty acids (negative mode) and combinations of chlorophyll and fatty acids (positive mode) were the most prevalent chemical structures, constituting over 80 and 70% of the total metabolites, respectively, followed by chlorophyll, polar lipids, carotenoids, and fatty alcohols. Moreover, this extract exhibited potent antioxidant and anti-aging benefits in decreasing order of potency at a concentration of 200 ㎍ mL^-1: tyrosinase inhibition (100%), ABTS radical scavenging (90%), elastase inhibition (88%), and DPPH radical scavenging (34%). Notably, this extract protected the mobility of DNA fragments up to 5 ㎍ mL^-1 (26%), with potential effects (> 60% at 200 ㎍ mL^-1). These findings suggest that C. fusca may be a promising candidate for applications related to its biological functions, owing to the high accumulation of fatty acids and chlorophyll derivatives.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.485-489
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• 2007

Knowledge-based economy is the economy or economic structure based on production, accumulation and utilization of knowledge. With the emergence of knowledge-based economy, the importance to the corporate competitiveness of IP and IP-related activities has increased. This paper discuss the issues related to the mode of IP-related activities, including the comparison of SMEs and large firms. Especially, I focus on the role and impact of IP-related activities on innovation and growth of firm in machinery industry. The result of this study can help to set up strategy for supporting firm's technology innovation.