• 한국수소및신에너지학회논문집
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• 제24권4호
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• pp.311-319
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• 2013

A clear understanding on cell voltage-reversal behavior due to local hydrogen starvation in a stack is of paramount importance to operate the fuel cell vehicle (FCV) stably since it affects significantly the cell performance and durability. In the present study, a novel experimental method to simulate the local cell voltage-reversal behavior caused by local hydrogen starvation, which typically occurs only one or several cells out of several hundred cells in a stack of FCV, has been proposed. Contrary to the conventional method of overall fuel starvation, the present method of local hydrogen starvation caused the local cell voltage-reversal behavior in a stack very well. Degradation of both membrane electrode assembly (i.e., pin-hole formation) and gas diffusion layer due to an excessive exothermic heat under voltage-reversal condition was also observed clearly.

• 한국환경과학회지
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• 제5권3호
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• pp.387-398
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• 1996

Granular sludge formation and it's activity change are the most important factors in achieving successful start-up and operation of UASB reactor. Nevertheless, the detailed mechanism is still unknown. On the basic of the experiments in laboratory-scale UASB reactor, the effect of hydrogen partial pressure on sludge granulation was evaluated. Size distribution method and specific metabolic activity of the sludge with the operation time were used as a means for estimating the degree of the sludge granulation. At the constant hydrogen loading, the granulation increased as starvation periods in hydrogen supply increased, resulting in high organic removal efficiency. It was evidient that hydrogen play very important role in granulation and sludge granulation was achieved through mutual symbiosis between hydrogen utilizing bacteria and hydrogen producing bacteria under the hydrogen dificient conditions. Key words : granular sludge, UASB reactor, hydrogen partial pressure.

• 대한전기학회논문지
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• 제45권3호
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• pp.374-379
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• 1996

Effects of reactant gas flow rates and starvation on phosphoric acid fuel cell performance were studied. As the reactant gas flow rates increased, the cell performance increased and then the cell maintained constant performance. The optimum flow rates of hydrogen, oxygen and air under galvanostatic condition of 150 mA/cm$_{2}$ are found to be 5cc/min cm$_{2}$ 5cc/min cm$_{2}$ and 15cc/min cm$_{2}$ at room temperature and 1 atm, respectively. Also the open circuit voltage of single cell decreased with increasing oxygen flow rate due probably to the decreased probably to the decreased oxygen pressure in the cathode side. Hydrogen and oxygen starvation resulted in voltage loss of about 5mV and 0-2mV, respectively. The voltage loss was independent of starvation time. These results were discussed from point of view of electrochemical reaction of the cell. (author). 9 refs., 8 figs.

• 한국수소및신에너지학회논문집
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• 제17권2호
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• pp.133-140
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• 2006

The performance of proton exchange membrane fuel cell was decreased by reverse voltage using fuel starvation. Performance decrease in local area could be affected by duration and extent of reverse voltage. Hydrogen and air stoichiometic ratio was used to find the experimental condition of abrupt voltage decrease. LabVIEW was used to make control logic of automatic load off system in preset voltage. Reverse voltage experiment was done down to -1.2 V at constant current condition. When fuel cell voltage was reached to preset voltage, electronic load was disconnected to make open circuit voltage for 1 minute. Fuel cell performance was checked every 5 cycle and the degree of performance decrease and/or recovery was estimated. Ohmic resistance and charge transfer resistance were increased and platinum surface area was reduced 41% after reverse voltage experiment.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 B
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• pp.662-665
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• 1992

Effects of reactant gas flow rates and starvation on phosphoric acid fuel cell performance were studied. As the reactant gas flow rates increased, the cell performance increased and then the cell maintained constant performance. The optimum flow rates of hydrogen, oxygen and air under galvanostatic condition of 150 mA/$\textrm{cm}^2$ are found to be 3cc/min${\cdot}\textrm{cm}^2$, 4cc/min${\cdot}\textrm{cm}^2$, and 15cc/min${\cdot}\textrm{cm}^2$, respectively. Hydrogen and oxygen starvation resulted in voltage loss of about 5mV and 0-2mV, respectively. The voltage loss was independent of starvation time. These results were discussed from the point of view of electrochemical reaction of the cell.

• 미생물학회지
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• 제52권1호
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• pp.1-9
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• 2016

치오레독신 환원효소(TrxR)를 encoding하는 Schizosaccharomyces pombe의 유일한 $TrxR^+$ 유전자는 스트레스 반응 전사인자인 Pap1의 매개에 의하여 스트레스 유발 인자들에 의하여 양성적으로 조절됨이 발견되었다. 본 연구에서는, TrxR 과잉 발현 재조합 플라스미드 pHSM10을 사용하여 S. pombe TrxR의 방어적 역할들이 평가되었다. 과산화수소($H_2O_2$)와 superoxide anion을 생성하는 menadione (MD)의 존재 하에서, S. pombe TrxR은 세포성장과 총 글루타치온 (GSH) 수준을 증강시키나, 세포 내 활성산소종(ROS) 수준은 감소시켰다. $H_2O_2$와 MD에 의하여 크게 영향 받지 않는 일산화질소(NO) 수준에는 유의성 없는 효과를 보였다. S. pombe TrxR은 sodium nitroprusside(SNP)에 의하여 생성되는 NO를 소거할 수 있었으나, SNP에 노출된 세포들의 성장, ROS 수준이나 총 글루타치온 수준에는 영향을 보이지 않았다. S. pombe TrxR은 질소 결핍(nitrogen starvation)에 의하여 감소되는 세포 성장 및 총 글루타치온 수준을 증가시키며, 질소 결핍에 의하여 생성되는 ROS와 NO를 소거하였다. 요약하건대, S. pombe TrxR은 산화적, 일산화질소 및 영양 스트레스로부터 효모 세포를 보호하지만, 공통적인 기전에 의하지는 않는다.

• 생명과학회지
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• 제27권12호
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• pp.1479-1485
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• 2017

일반적으로 노화, 영양부족 및 다양한 만성질환에 의하여 유발되는 근위축은 근육 단백질 합성 억제 및 분해증가를 통하여 근섬유 및 근육의 밀도를 감소시키는 것으로 알려져 있다. 본 연구에서는 근위축과 관련된 in vitro 실험을 위한 C2C12 근아세포에서 근관세포로의 분화과정을 확립하고, 분화가 유발된 C2C12 근관세포를 대상으로 dexamethasone 및 hydrogen peroxide에 의한 근위축 유발 및 관련 단백질들의 발현 변화를 조사하였다. 먼저 C2C12 근아세포에 분화배지를 처리하였을 경우 근관세포로 분화가 유발되었으며, 분화와 관련된 단백질인 myogenin 및 myoD의 발현이 증가하는 것으로 나타났다. 분화가 유발된 C2C12 근관세포에 세포독성이 없는 조건의 dexamethasone 및 hydrogen peroxide를 처리하였을 경우 근관의 지름이 감소하였으며, 이러한 현상은 musclespecific ubiquitin ligases인 MAFbx/atrogin-1 및 MuRF1의 발현 증가와 함께 muscle-specific transcription factor인 myogenin 및 MyoD의 발현 감소와 관련이 있다는 것을 확인하였다. 본 연구 결과는 근위축과 관련된 in vitro 실험 모델의 구축을 위한 최적의 분화조건 확립과 함께 dexamethasone 및 hydrogen peroxide를 근위축 유도제로 사용할 수 있는 가능성 을 제시하는 것이다.

• 한국수소및신에너지학회논문집
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• 제17권3호
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• pp.279-285
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• 2006

Recirculation for the unreacted fuel is necessary to improve the overall efficiency of the fuel cell system and to prevent fuel starvation since the fuel cell for a vehicle application is a closed system. In case of the automotive fuel cell, the ejector which does not require any parasitic power is good for the performance improvement and easy operation. It is essential to design the customized ejector due to the lack of the commercial ejector corresponding to the operating conditions of the fuel cell systems. In this study, the design methodology for the ejector customized to an automotive fuel cell is proposed. The model based sensitivity analysis prevents the time-consuming redesign and reduces the cost of developing ejector. As a result, the customized ejector to meet the desired performance within overall operating range has developed for the PEMFC automotive system.

• 공업화학
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• 제10권8호
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• pp.1210-1215
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• 1999

Pd/C촉매가 부유되어 있는 3상 슬러리 반응기에서 원료 p-nitroaniline(PNA)를 수소 첨가시켜 고순도의 p-phenylenediamine(PPD)를 합성하는 최적 반응조건을 구하였다. 수소첨가 반응시 활성점에서 수소부족을 줄이고 불순물의 생성을 감소시킬 수 있도록, 기체-액체, 액체-촉매사이의 물질전달 저항을 최소화하고 표면반응속도가 율속할 수 있게 반응조건을 설정하였다. 이 반응조건은 온도 $60^{\circ}C$, 압력 60~70 psig, 촉매농도 1~2 g-cat/L일 때가 최적이었으며, 반응속도는 PNA 농도에 0차, 수소 반응압력에 1차를 각각 보여주었으며, 총괄반응속도식은 $R_A=6.44{\times}10^6{\cdot}H{\cdot}P{\cdot}m{\cdot}$exp(-4659/T)로 나타났다.

• 조명전기설비학회논문지
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• 제25권3호
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• pp.50-64
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• 2011

In this paper, a DC-coupled photovoltaic (PV), fuel cell (FC) and ultracapacitor hybrid power system is studied for building microgrid. In this proposed system, the PV system provides electric energy to the electrolyzer to produce hydrogen for future use and transfer to the load side, if possible. Whenever the PV system cannot completely meet load demands, the FC system provides power to meet the remaining load. The main weak point of the FC system is slow dynamics, because the power slope is limited to prevent fuel starvation problems, improve performance and increase lifetime. A power management and control algorithm is proposed for the hybrid power system by taking into account the characteristics of each power source. The main works of this paper are hybridization of alternate energy sources with FC systems using long and short storage strategies to build an autonomous system with pragmatic design, and a dynamic model proposed for a PV/FC/UC bank hybrid power generation system. A simulation model for the hybrid power system has been developed using Matlab/Simulink, SimPowerSystems and Matlab/Stateflow. The system performance under the different scenarios has been verified by carrying out simulation studies using a practical load demand profile, hybrid power management and control, and real weather data.