• 한국수소및신에너지학회논문집
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• 제22권2호
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• pp.257-264
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• 2011

This study discribes performance of DEFC (Direct Ethanol Fuel Cell) utilized bio-ethanol based on fruit wastes. To produce the bio-ethanol, fruit wastes were treated at temperature $120^{\circ}C$ and 90minutes in acid pre-treatment. After pre-treatment was done, alcohol fermentation process was running. Initial alcohol concentration was 5%. Using the multi coloumn distillation system, more than 95% ethanol was distilled and each component of bio-ethanol was analyzed. In DEFC performance test, it was revealed that cell performance was much higher than that of ethanol. Comparing ethanol with mixed fuel (bio-ethanol (10%) + ethanol (90%)), the performance of ethanol was higher than that of mixed fuel. Even though the bio-ethanol from the fruit wastes is corresponded with transport ethanol standards, it thought that organic matter in bio-ethanol could be negative effect on fuel cell.

• 한국수소및신에너지학회논문집
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• 제24권4호
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• pp.320-325
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• 2013

TUnitized reversible fuel cells (URFC) combine the functionality of a fuel cell and electrolyzer in one unitized device. For a URFC with proton exchange membrane, a titanium (Ti)-felt is applied to the gas diffusion layer (GDL) substrate at the oxygen electrode, and additionally titanium (Ti)-powders and TiN-powders are loaded in the GDL substrate as a micro porous layer (MPL). Double porous layer with TiN MPL was not acceptable for the URFC because both of fuel cell performance and electrolysis performance are degraded. The double porous layer with Ti-powder loading in the Ti-felt substrate influence rearly for the electrolysis performance. In contrast, the change of pore-size distribution brings a significant improvement of fuel cell performance under fully humidification conditions. This fact indicates that the hydrophobic meso-pores in the GDL play an important role for mass transport.

• 대한기계학회논문집B
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• 제24권12호
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• pp.1596-1607
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• 2000

The optimal design of auto-catalyst needs a good compromise between the pressure drop and flow uniformity in the substrate. One of the effective methods to achieve this goal is to use the concept of radially variable cell density. But this method has not been examined its usefulness in terms of chemical behavior and conversion performance. In this work, two-dimensional performance prediction of catalyst coupled with turbulent reacting flow simulation has been used to evaluated the benefits of this method n the flow uniformity and conversion efficiency. The results showed that two cell combination of 93cpsc and 62 cpsc was the most effective for improved pressure drop and conversion efficiency due to balanced space velocity and efficient usage of geometric surface area of channels. It was also found that large temperature difference between the bricks in case that the edge of the frontal face of brick has too much lower cell density(less than 67% of cell density of the center of the brick). This study has also demonstrated that the present computational results show the better prediction accuracy in terms of CO, HC and NO conversion efficiencies compared to those of conventional 1-D adiabatic model by comparison with experimental results.

• 한국통신학회논문지
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• 제19권12호
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• pp.2328-2339
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• 1994

ATM 전송 기술에 있어 PBS 방법은 혼재된 트래픽 환경하에서 각각의 트래픽이 서로 다른 서비스 품질을 요구할 경우, 체증 상태의 망 관리를 효율적으로 하기 위한 제시된 셀 준위의 우선 순위 제어방식이다. 이 논문에서는 시간 지연과 셀 손실에 민감한 두 트래픽에 대한 처리를 PBS 방법을 적용시켜 셀 손실에 대한 분포를 분석하고자 한다. 특히, 실시간 트래픽의 주요한 성능 척도인 연속적 셀 손실 확률을 정확하게 구하기 위한 셀 손실 간의 독립성을 가정하지 않은 재귀적 알고리듬을 사용한다. 이 방법에 의해 유도된 셀 손실에 대한 분포의 결과는 독립을 가정한 경우보다 더 심각하게 나타난다. 그리고, 실시간 트래픽에 대한 PBS 방법의 제한성과 주어진 서비스 품질 기준에 따른 허용 부하를 증가시킬 수 있음을 보여준다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.83.1-83.1
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• 2010

A Dead-end mode operation is one of the best way to maximize the gas usage rate. But, some components of fuel cell stack like gas diffusion layer(GDL) or membrane can be damaged in dead-end mode operation. In this study, a Large Scale Polymer electrolyte membrane fuel cell(PEMFC) for a dead-end operation has been developed. The stack is composed with 4 cells which has over 400cm2 of active area. Hydrogen is used as a fuel, and oxygen is used as a oxidant. The dead-end operation performance was evaluated by a long-term dead-end mode operation. The fuel cell stack is operated over 1,500 hours in dead-end mode operating fuel cell test station. And the performance change of the fuel cell stack was investigated.

• 대한산업공학회지
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• 제19권3호
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• pp.91-102
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• 1993

This paper suggests an approach to quantitative evaluation of a manufacturing flexibility in automated manufacturing systems. The flexibility of a cell is newly defined and evaluated in use of the environmental change factors which may influence flexibility for satisfying a manufacturing performance objective. The number of machines, the number of operations, machine breakdowns and processing times are considered for this cell flexibility measure. The cell flexibility measures the extent that the cell utilizes the processes to acquire high throughput. Simulation program written in SLAM System was used to help measure cell flexibility. The proposed cell flexibility measure provides a prediction of the influence of the factors on throughput performance, and applies in case of comparison of existing system and a new system, changes in operation conditions of a cell, and comparison of rival machines. Therefore it can be used as decision making criteria for system justification.

• 한국컴퓨터정보학회논문지
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• 제3권2호
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• pp.169-175
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• 1998

ATM스위치에서 셀을 전송하기 위한 버퍼방식으로 HOL 블록킹을 방지하는 공유다중버퍼 방식이 있다. 그러나, 이러한 방식에서도 셀 손실이 발생하여 스위치의 성능을 저하시킨다. 따라서, 본 논문에서는 기존의 비충돌 공유 다중 버퍼 구조에서 발생하는 셀 손실을 방지하는 방안을 제안하였다. 셀 손실을 방지하는 방안으로 한 슬롯 타임동안에 손실되는 셀을 다음 슬롯 타임에 전송할 수 있도록 특정한 임시메모리에 저장할 수 있는 구조를 사용하였다. 이러한 구조를 시뮬레이션을 통해 성능평가를 한 결과 셀 손실율과 처리율면에서 기존의 시스템보다 우수함을 검증하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.460-465
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• 2003

The modeling of PEM (Proton Exchange Membrane) fuel cell system consisting of fuel cell stack and BOP (Balance of Plant) is presented in this paper. The effects of temperature, pressure (air, hydrogen), and humidity on the fuel cell system performance were mainly investigated using thermo-dynamical and electro-chemical equations. To understand the power distribution characteristics of fuel cell system, the effects of operating temperature and air pressure on maximum power and system power were also demonstrated. Through this study, we can get the basic insight into the fuel cell stack and BOP component sizing and it can be used effectively for the optimization of the practical fuel cell systems in purpose.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.759-764
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• 2005

In this paper, numerical analysis of hydrogen recycle system has been conducted in order to enhance the efficiency of automotive fuel cell. Generally, the excess hydrogen is provided in the automotive fuel cell. Since the non-reaction hydrogen reduces automotive fuel cell efficiency, reuse of the non-reaction hydrogen can be helpful to improve the fuel cell performance. In case of PEM FC, the water vapor is provided to hydrogen from the cathode so that the mixture experiences phase change depending on the changes of pressure and temperature. The internal flow of the mixture in the hydrogen recirculation system of fuel cell was investigated for real flow conditions. The variation of performance, properties and mass fractions of mixture, hydrogen and water-vapor were investigated. This study was performed based on 80KW level automotive fuel cell's recycling system.

• 한국시뮬레이션학회논문지
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• 제8권1호
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• pp.51-61
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• 1999

A cell scheduling method of Queue for the ATM switch is proposed and simulated. In this paper, we present the cell scheduling method proper to the proposed queue and the improved queue with Queue Sharing(QS) structure for CBR, VBR, ABR traffic. The proposed QS structure minimizes the CLS(Cell Loss Ratio) of ABR traffic and decreases the CLR of bursty VBR traffic. Also we propose a cell scheduling method using VRR(Variable Round Robin) scheme proper to the high-speed(ATM) switch. The VRR scheme provides a fairness in terms of service chance for the queues in the ATM switch as well as QOS of their cell delay characteristic of CBR and VBR traffic, QOS of ABR CLR. The simulation results show the proposed method achieves excellent CLR and average cell delay performance for the various ATM traffic services in the Queue Sharing structure.