• Title/Summary/Keyword: Single cell Performance

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Synthetic Aperture Radar Target Detection Using Multi-Cell Averaging CFAR Scheme (다중 셀 평균 기반 CFAR 검출을 이용한 SAR 영상 표적 탐지 기법)

  • Song, Woo-Young;Rho, Soo-Hyun;Jung, Chul-Ho;Kwag, Young-Kil
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.21 no.2
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    • pp.164-169
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    • 2010
  • Since the range and Doppler resolution of the synthetic aperture radar(SAR) image becomes very high, the target detection accuracy can be significantly increased, but the computational burden is also increased. The conventional single-cell based CFAR detector performs the target detection on every single cell basis, thus it causes the serious increment of the computational load. In this paper, the improved two-step MCA-CFAR detector is proposed for the improvement of the target detection as well as the reduction of computational load: the first step is to use the MCA-CFAR, and the second step is to use the single-cell based CFAR detection in the expected target area for final decision. The performance of the proposed algorithm is compared with the conventional single-cell based CFAR and MCA-CFAR on SAR images.

Lightweight Metallic Bipolar Plates of PEMFC for a Small Reconnaissance UAV (소형 정찰 UAV를 위한 고분자 전해질막 연료전지의 경량의 금속 분리판)

  • Kim, Ki-In;Lee, Jong-Kwang;Jang, Bo-Sun;Kwon, Se-Jin
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.38 no.10
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    • pp.1031-1037
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    • 2010
  • This paper proposed lightweight aluminum bipolar plates as an alternative for conventional graphite bipolar plates in fuel cell systems used as a power source for small reconnaissance UAVs. Since bipolar plates occupy more than 80% of the total weight of the fuel cell system, lightweight aluminum bipolar plates can improve the overall payload and flight time of the fuel cell UAV. The aluminum and graphite bipolar plates were fabricated to compare the performance of each of them. A 15% higher performance per weight was obtained from aluminum bipolar plates than the graphite bipolar plates. Also, the performance of a single cell using aluminum bipolar plates was evaluated under various operating conditions.

Performance of Fuel Cell with PEMFC Fabricated under Different Pressure (고분자 전해질 연료전지 성능에 미치는 MEA 가압제조 공정 조건의 영향)

  • Lee, Ki-Seong;Sim, Sooman;Kim, Dongmin
    • Transactions of the Korean hydrogen and new energy society
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    • v.24 no.1
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    • pp.70-75
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    • 2013
  • It has fabricated membrane electrode assemblies (MEA) for proton exchange membrane fuel cell by hot-pressing method. The hot-pressing was used for the fabrication of MEA which is composed of commercial platinum electrode on carbon paper. The performance of MEA was studied with different fabrication conditions of temperature, pressure and torque. As the temperature increased, the performance of MEA was increased. and started to decrease l after arrived at the maximum performance of MEA. This is related with good contact between electrode and polymer electrolyte membrane at high temperature and microstructural change at much higher temperature. Similarly, as the pressure increased, the performance of the MEA increased up to highest values and start to decrease. According to the our results, the maximal performance of the MEA was at the temperature of $140^{\circ}C$ and the pressure of $1.5{\times}10^3$ kPa. The optimal torque to assemble the single stack was 3.2 N m.

Performance Analysis of PEMFC Using Computational Flow Dynamics (CFD) (전산유체역학 (CFD)을 이용한 PEMFC의 성능분석)

  • Kim, Sunhoe
    • Journal of Digital Convergence
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    • v.11 no.8
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    • pp.199-204
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    • 2013
  • Computational fluid dynamics (CFD) is used to reduce number of experiments. The CFD tools are widely used for engine design and flow pattern analysis to reduce experiments. In this study the performance of a PEMFC single cell was analyzed by using STAR-CD, product of CD-ADAPCO. The effect of cell design and flow pattern on the performance of a PEMFC was analyzed with the 3-D simulation. As a result the performance of rectangular cell was the higher than that of square cell, while the flow direction scarcely affected on the performance of a PEMFC. Also the current density according to different excess ratio of air flow rate was compared and analyzed. The difference between maximum and minimum current density of flip-flow was lower than that of co-flow.

A Study on Thermal Cycle Characteristics of Solid Oxide Fuel Cell (고체 산화물 연료전지의 열사이클 따른 성능 열화 특성 연구)

  • Kim, Eung-Yong;Song, Rak-Hyun;Jeon, Kwang-Sun;Shin, Dong-Ryul;Kang, Thae-Khapp
    • Proceedings of the KIEE Conference
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    • 1998.07d
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    • pp.1312-1314
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    • 1998
  • SOFC system is often subject to thermal cycle condition during normal start/stop, shutdown, and emergence state. Under the thermal cycle condition of heating and cooling, the SOFC components expand or shrink, which produces thermal stress and thermal shock. The SOFC performance is degraded by the thermal factors. To protect SOFC system from the thermal degradation, the optimum thermal condition must be clarified. In this study, to examine the thermal cycle characteristics, we fabricated single cells of planar SOFC with an area of $5{\times}5cm$. The electrolyte and PEN were tested under thermal cycle conditions in the range of$ 2-8^{\circ}C/min$. After thermal cycle test. crack creation of the components were examined using ultraviolet apparatus. No crack in the electrolyte and PEN were observed. The single cell system with alumina frame were also tested under thermal cycle conditions of 2, 3, $4^{\circ}C/min$. The single cell was fractured at the thermal cycle of 3 and $4^{\circ}C/min$ and the optimum condition of the thermal cycle to be found below $2^{\circ}C/min$.

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Analysis of activation, ohmic, and concentration losses in hydrogen fuelled PEM fuel cell

  • Rohan Kumar;K.A Subramanian
    • Advances in Energy Research
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    • v.8 no.4
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    • pp.253-264
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    • 2022
  • This paper deals with the effects of design (active area, current density, membrane conductivity) and operating parameters (temperature, relative humidity) on the performance of hydrogen-fuelled proton exchange membrane (PEM) fuel cell. The design parameter of a PEM fuel cell with the active area of the single cell considered in this study is 25 cm2 (5 × 5). The operating voltage and current density of the fuel cell were 0.7 V and 0.5 A/cm2 respectively. The variations of activation voltage, ohmic voltage, and concentration voltage with respect to current density are analyzed in detail. The membrane conductivity with variable relative humidity is also analyzed. The results show that the maximum activation overpotential of the fuel cell was 0.4358 V at 0.21 A/cm2 due to slow reaction kinetics. The calculated ohmic and concentrated overpotential in the fuel cell was 0.01395 V at 0.76 A/cm2 and 0.027 V at 1.46 A/cm2 respectively.

Operating Characteristics of Direct Methanol Fuel Cell Based on Pt-Ru/C Anode Catalyst (Pt-Ru/C 촉매를 이용한 직접메탄을 연료전지 운전 특성)

  • Jung, D.H.;Lee, C.H.;Kim, C.S.;Chun, Y.G.;Shin, D.R.
    • Proceedings of the KIEE Conference
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    • 1997.07d
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    • pp.1252-1254
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    • 1997
  • Direct methanol fuel cell based on a proton-exchange membrane electrolyte was investigated. 60% Pt-Ru/C and 60%Pt/C catalysts were employed for methanol oxidation and oxygen reduction, respectively. Morphologies of the catalysts were investigated by x-ray power diffraction, energy dispersive x-ray spectroscopy, and transmission microscopy. Electrochemical characteristics of the catalysts were tested by using cyclic voltametry technique. I-V characteristics of the fuel cell were tested by changing methanol concentration, temperature, and Nafion type as a proton-exchange membrane electrolyte. AC impedance technique was used to investigate the electrochemical performance of the fuel cell. The performance of single cell was enhance with increasing cell temperature. High operation temperature attributed to the combined effects of the reduction of ohmic resistance and polarization. High cell voltage was obtained from the concentration of 205M methanol. With Nafion 112, a current density of $230mA/cm^2$ at 0.55V was obtained from the concentration of 2.5M methanol.

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Location-Aware Hybrid SLC/MLC Management for Compressed Phase-Change Memory Systems (압축 기반 상변화 메모리 시스템에서 저장 위치를 고려한 하이브리드 SLC/MLC 관리 기법)

  • Park, Jaehyun;Lee, Hyung Gyu
    • IEMEK Journal of Embedded Systems and Applications
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    • v.11 no.2
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    • pp.107-116
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    • 2016
  • Density of Phase-Change Memory (PCM) devices has been doubled through the employment of multi-level cell (MLC) technology. However, this doubled-capacity comes in the expense of severe performance degradation, as compared to the conventional single-level cell (SLC) PCM. This negative effect on the performance of the MLC PCM detracts from the potential benefits of the MLC PCM. This paper introduces an efficient way of minimizing the performance degradation while maximizing the capacity benefits of the MLC PCM. To this end, we propose a location-aware hybrid management of SLC and MLC in compressed PCM main memory systems. Our trace-driven simulations using real application workloads demonstrate that the proposed technique enhances the performance and energy consumption by 45.1% and 46.5%, respectively, on the average, over the conventional technique that only uses a MLC PCM.

A Study on Performance Improvement in PEMFC (소면적 PEM연료전지 성능개선 연구)

  • Chon, Kwang Wu;Park, Chang Kwon;Lee, Ho Yeol;Oh, Byeong Soo
    • Transactions of the Korean hydrogen and new energy society
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    • v.15 no.4
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    • pp.291-300
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    • 2004
  • Performance of PEMFC is affected by many factors such as that of MEA, configuration of flow field, operating conditions, humidification, cooling and so on. In this study, in order to improve the performance of fuel cell, a small area fuel cell stack was made and its performance was tested under various operating conditions. Stack consists of 3 single PEM fuel cells. Channel is serpentine type and the active area of the electrode is $50cm^2$. The test results show that the peak power is 60W at $70^\circ{C}$ of stack temperature with humidification condition.

The Performance Evaluation of Metallic Bipolar Plates of Fuel Cells for a Small Reconnaissance UAV (소형 정찰 UAV를 위한 연료전지 금속 분리판의 성능 평가)

  • Kim, Ki-In;Lee, Jong-Kwang;Kwon, Se-Jin
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2009.11a
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    • pp.278-281
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    • 2009
  • The performance of aluminum bipolar plates was evaluated for the lightweight fuel cell system as a power source for a small reconnaissance UAV. Higher performance per weight was obtained from aluminum bipolar plates than the graphite bipolar plates. To check the influence of operating temperature, the performance of a single cell using aluminum bipolar plates was evaluated at 40 / 50 / $60^{\circ}C$. When dry hydrogen and air were used, the finest performance was obtained at $40^{\circ}C$, a lower operating temperature compared with usual operating temperatures.

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