• Title/Summary/Keyword: OFF cell

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Simulation of Liquid Crystals Considering Flow Effect (흐름효과를 고려한 액정의 시뮬레이션)

  • Kim Hoon;Park Woo-Sang
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.19 no.3
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    • pp.260-266
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    • 2006
  • In this paper, We coupled fluid balance and director balance equation from Ericksen-Leslie's continuum theory and observed the motion of Liquid Crystal molecular. We simulated flow velocity and director distribution in which flow effect is considered in switching on and switching off state. We interpreted the dynamic response characteristic caused by the flow. As the result of the simulation, We could see the flow effect. In the case of Twisted Nematic(TN) cell, this flow caused abnormal twist temporarily in switching off state. We could prove that this abnormal twist is a direct cause of optical bounce phenomenon known well until now with the result of simulation. In addition, We analyzed the mechanism of the fast response due to flow in the case of Optically Compensated Bend(OCB) cell.

Study on the Feasibility of the Use of the Commercial WCDMA Network for CBTC (CBTC를 위한 상용 WCDMA망의 적용 가능성 연구)

  • Kim, Yong-Sang;Ko, Dong-Hwan;Eun, Chang-Soo;Kim, Back-Hyun;Yoon, Yong-Ki
    • Proceedings of the KSR Conference
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    • 2008.11b
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    • pp.1138-1144
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    • 2008
  • To study the feasibility of applying wireless communication technology to the control of train for the effective control of train and for the reduction of cost and time to construct the necessary infra structure, we investigate into the application of the existing commercial WCDMA network to CBTC (communication-based train control) to grasp the obstacles and propose the solutions to circumvent them. The obstacles can be categorized into the hand-off problem, the interference problem near the stations, and the problem of radio shadow areas. We propose, as solutions, the cell overlap method and multi-terminal approach for the hand-off problem, the cell sectoring method for the interference problem, and establishment of new base stations along the railroad both to provide the wireless train control and communication service to the customers on the train which was otherwise impossible because of the shadowing effect.

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Surface Flame Patterns and Stability Characteristics of Premixed Burner System for Fuel Reformers (개질기용 예혼합 버너의 화염형태 및 안정성 특성)

  • Lee, Pil-Hyong;Park, Bong-Il;Jo, Soon-Hye;Hwang, Sang-Soon
    • Journal of the Korean Society of Combustion
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    • v.15 no.3
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    • pp.8-14
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    • 2010
  • Fuel processing systems which convert fuel into rich gas (such as stream reforming, partial oxidation, autothermal reforming) need high temperature environment ($600{\sim}1,000^{\circ}$). Generally, anode-off gas or mixture of anode-off gas and LNG is used as input gas of fuel reformer. In order to make efficient and low emission burner system for fuel reformer, it is necessary to elucidate the combustion and emission characteristic of fuel reformer burner. The purpose of this study is to develop a porous premixed flat ceramic burner that can be used for 1~5 kW fuel cell reformer. Ceramic burner experiments using natural gas, hydrogen gas, anode off gas, mixture of natural gas & anode off gas were carried out respectively to investigate the flame characteristics by heating capacity and equivalence ratio. Results show that the stable flat flames can be established for natural gas, hydrogen gas, anode off gas and mixture of natural gas & anode off gas as reformer fuel in the porous ceramic burner. For all of fuels, their burning velocities become smaller as the equivalence ratio goes to the lean mixture ratio, and a lift-off occurs at lean limit. Flame length in hydrogen and anode off gas became longer with increasing the heat capacity. In particular, the blue surface flame is found to be very stable at a very lean equivalence ratio at heat capacity and different fuels. The exhausted NOx and CO measurement shows that the blue surface flame represents the lowest NOx and CO emissions since it remains very stable at a lean equivalence ratio.

A Study on Bow of Silicon Solar Cell by Soldering Different Thickness of Ribbon (리본 두께에 따른 태양전지 Bowing현상 연구)

  • Yoon, Na-Ri;Jung, Tae-Hee;Shin, Jun-Oh;Kang, Ki-Hwan;Ahn, Hyeung-Ken;Han, Deuk-Young
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2010.06a
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    • pp.68-68
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    • 2010
  • To reduce PV manufacturing costs, the thickness of solar cell is getting thinner. Bow is shown after cooling down the temperature of solder cell. It happens because of different thermal expansion coefficients of different metals. Bowed cell can make micro crack while module processing and it can drop off efficiency of PV module. As thinner solar cell is produced, the thickness of ribbon should be concerned to prevent extra bow. In this paper we investigate the contrast of deflection when we solder different thickness of ribbons on same solar cell. This approach would help to find out the optical thickness of ribbon for particular thickness of solar cell later on.

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The Ejector Design and Test for 125 kW Class Molten Carbonate Fuel Cell System (125 kW급 용융탄산염 연료전지 시스템의 이젝터 설계 및 시험)

  • KIM, BEOMJOO;PARK, SOO-MAN;SONG, OH-SEOP
    • Transactions of the Korean hydrogen and new energy society
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    • v.29 no.2
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    • pp.139-147
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    • 2018
  • Korea Electric Power Research Institute (KEPCO RI) had developed molten carbonate fuel cell (MCFC) system since 1993. Finally, KEPCO RI developed and operated a 125 kW MCFC system in 2010. To make MCFC system compact, it is indispensable to install an ejector in this system where the anode off gas, the cathode off gas, and fresh air are mixed before flowing to the catalytic burner. KEPCO RI had developed various ejectors for MCFC system since 2006. The 125 kW MCFC system built with the developed ejector was operated successfully in Boryeong Thermal Power Plant in 2010. This 125 kW MCFC ejector was designed on the basis of the experimental results of 5 kW and 75 kW MCFC ejectors. The main goal of ejector design in our MCFC system is to maintain the entrainment ratio and the pressure between fuel cell stack and catalytic burner within the operating range. In this paper, the design results of the ejector are presented based on the 125 kW MCFC system operating conditions. In addition, a designed ejector was manufactured and installed in the MCFC system. As the fuel cell is under load operation, the pressure surrounding the ejector was measured to ensure that the fuel cell system is operating smoothly.

An Effective Training Pattern Processing Method for ATM Connection Admission Control Using the Neural Network (신경회로망을 이용한 ATM 연결 수락 제어를 위한 효율적인 학습패턴 처리 기법)

  • Kwon, Oh-Jun;Jeon, Hyoung-Goo;Kwon, Soon-Kak;Kim, Tai-Suk;Lee, Jeong-Bae
    • The KIPS Transactions:PartB
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    • v.9B no.2
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    • pp.173-180
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    • 2002
  • The virtual cell loss rate was introduced for the training pattern of the neural network in the VOB(Virtual Output Buffer) model. The VOB model shows that the neural network can find the connection admission boundary without the real cell loss rate. But the VOB model tends to overestimate the cell loss rate, so the utilization of network is low. In this paper, we uses the reference curve of the cell loss rate, which contains the information about the cell loss rate at the connection admission boundary. We process the patterns of the virtual cell loss rate using the reference curve, We performed the simulation with two major ATM traffic classes. One is On-Off traffic class that has the traffic characteristic of LAN data and other is Auto-Regressive traffic class that has the traffic characteristic of a video image communication.

Dynamic Channel Allocation Algorithm for Co-channel Interference Avoidance in Multi-cell OFDMA Systems (OFDMA 다중 셀 환경에서 동일 채널 간섭을 피하기 위한 동적 자원 할당 알고리즘)

  • Lee, Je-Min;Seo, Woo-Hyun;Wang, Hano;Hong, Dae-Sik
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.44 no.5
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    • pp.92-98
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    • 2007
  • We propose the schemes for the dynamic channel allocation (DCA) in multi-cell OFDMA systems to avoid co-channel interference (CCI) without the additional complexity. The allocatable subcarriers areas, which is designed to avoid CCI among cells, are determined for each cell. Each cell allocates the subcarriers within the allocatable subcarriers area of the cell independently. We consider the trade off between the reduced frequency selection diversity and the amount of CCI on a subcarrier by the determination of allocatable subcarriers area. Hence, the equal allocation bound scheme for the high selectivity channel and the flexible allocation bound scheme for the low selectivity channel are proposed. Through the numerical results, it is confirmed that the proposed schemes have better performance in the aspects of the number of overlapping allocated subcarriers, the capacity and the outage probability compared to the case which does not determined the allocatable subcarriers area.

Effects of Shut-down Process on Degradation of Polymer Electrolyte Membrane Fuel Cells I. Effects of Hydrogen Removal on the Degradation (운전 정지 시 보관방법이 고분자 전해질 연료전지의 열화에 미치는 영향 I. 잔류 수소 제거 방법의 영향)

  • Lim, Sang-Jin;Cho, Eun-Ae;Lee, Sang-Yeop;Kim, Hyoung-Juhn;Lim, Tae-Hoon;Lee, Kwan-Young
    • Journal of the Korean Electrochemical Society
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    • v.9 no.3
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    • pp.118-123
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    • 2006
  • Degradation of polymer electrolyte membrane fuel cell (PEMFC) that is facilitated by on/off cycles is one of the most important issues for commercialization of fuel cell vehicles. When a PEMFC stack is shut down, residual hydrogen and induce high voltage equivalent to open circuit voltage to the cathode side that might cause sintering of Pt catalyst and facilitate formation of hydrogen peroxide at the anode side that might decompose $Nafionc\'{A}$ membrane. In this study, degradation of PEMFC exposed to repetitive on/off cycles was investigated by measuring i-V characteristics, ac impedance, cyclic voltammograms, gas leak, cross-sectional SEM images, and TEM images. To prevent degradation of PEMFC caused by the residual gases, hydrogen was removed from anode gas channel by gas-purging and by using a dummy resistance, that were found to be a very effective method.

Dynamic Simulation of Molten Carbonate Fuel Cell and Mechanical Balance of Plant (용융탄산염연료전지 및 주변기기의 동적시뮬레이션)

  • Sung, Taehong;Kim, Kyung Chun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.38 no.2
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    • pp.121-128
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    • 2014
  • This study aims to develop a simulation bed for the mechanical balance of plants of high temperature fuel cells such as molten carbonate fuel cells. For using fuel cells in transportation, the optimization of the balance of plants should be considered. In this study, the dynamic model of a molten carbonate fuel cell and the model's responses to inlet gas composition, pressure, flow rate, and stack temperature were analyzed. On/off simulation was performed for testing the dynamic model's feasibility. The simulation results are in reasonable agreement with the experimental results from published literatures.

Clinical use of Centrifugal Biomedicus Pump (Centrifugal biomedicus pump의 임상 응용)

  • 강면식
    • Journal of Chest Surgery
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    • v.25 no.12
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    • pp.1550-1555
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    • 1992
  • From June 1989 to July 1992, we used centrifugal Biomedicus pump[CBP] in 20 patients In 9 cases, CBP was used as ventricular assistance after heart surgery for those who could not be weaned off bypass even with intra-aortic balloon counter-pulsation and with maximal inotropic support In 8 patients, CBP was used as partial left heart bypass during repair of aortic aneurysms or congenital aortic anomalies. And in 3 patients, CBP was used as vena caval bypass during resection of renal cell carcinoma with tumor extension into the inferior vena cava. In 2 of 9 patients with ventricular assistance, they were weaned off the device successfully after 16 hours and 7 days respectively. But the patients died of intracranial hemorrhage and sepsis, 7 and 29 days after weaning from cardiac support, respectively. In all the patients who underwent aortic of vena caval surgery using CBP as shunt, there were no complications such as postoperative bleeding necessitating reoperation, renal failure or neurologic sequelae. In conclusion, the centrifugal type of ventricular assistance may be potentially life saving treatment modality in patients with severe postoperative low cardiac output syndrome. The CBP can be safely employed for resection of renal cell carcinoma with vena caval tumor extension and for repair of aortic aneurysms.

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