• 제목/요약/키워드: Two-cell

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자동차용 고분자 연료전지 수소 재순환 시스템의 이상 유동해석 (Two-Phase Flow Analysis of The Hydrogen Recirculation System for Automotive Pem Fuel Cell)

  • 곽현주;정진택;김재춘;김용찬;오형석
    • 대한기계학회논문집B
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    • 제32권6호
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    • pp.446-454
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    • 2008
  • The purpose of this paper is to analyze two-phase flows of the hydrogen recirculation system. Two-phase flow modeling is one of the great challenges in the classical sciences. As with most problems in engineering, the interest in two-phase flow is due to its extreme importance in various industrial applications. In hydrogen recirculation systems of fuel cell, the changes in pressure and temperature affect the phase change of mixture. Therefore, two-phase flow analysis of the hydrogen recirculation system is very important. Two-phase computation fluid dynamics (CFD) calculations, using a commercial CFD package FLUENT 6.2, were employed to calculate the gas-liquid flow. A two-phase flow calculation was conducted to solve continuity, momentum, energy equation for each phase. Then, the mass transfer between water vapor and liquid water was calculated. Through an experiment to measure production of liquid water with change of pressure, the analysis model was verified. The predictions of rate of condensed liquid water with change of pressure were within an average error of about 5%. A comparison of experimental and computed data was found to be in good agreement. The variations of performance, properties, mass fraction and two-phase flow characteristic of mixture with resepct to the fuel cell power were investigated.

이동 통신망에 있어서 새로운 셀 체류시간 모형화에 따른 최적 이동성 관리 (Optimal Mobility Management of PCNs Using Two Types of Cell Residence Time)

  • 홍정식;장인갑;이창훈
    • 한국경영과학회지
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    • 제27권3호
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    • pp.59-74
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    • 2002
  • This study investigates two basic operations of mobility management of PCNs (Personal Communication Networks), i.e., the location update and the paging of the mobile terminal. From the realistic consideration that a user either moves through several cells consecutively or stays in a cell with long time, we model the mobility pattern by introducing two types of CRT (Cell Residence Time). Mobility patterns of the mobile terminal are classified Into various ways by using the ratios of two types of CRT. Cost analysis is performed for distance-based and movement-based location update schemes combined with blanket polling paging and selective paging scheme. It is demonstrated that in a certain condition of mobility pattern and call arrival pattern, 2-state CRT model produces different optimal threshold and so, is more effective than IID ( Independently-Identically-Distributed) CRT model. An analytical model for the new CRT model is compact and easily extendable to the other location update schemes.

Hydroxy Aromatic Polyimide계 광폴리머 표면을 이용한 광배향 TN 셀의 전기광학 특성 (Electro-optic Characteristics on Photoaligned TN Cell using Photopolymer Based Hydroxy Aromatic Polyimide)

  • 이휘원;황정연;최성호;서동학;서대식
    • 한국전기전자재료학회논문지
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    • 제18권10호
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    • pp.924-928
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    • 2005
  • We synthesized the two types of photoalignment material of high thermal resistance with hydroxyl aromatic polyimide, and studied the liquid crystal (LC) aligning capabilities on the photopolymer layers. Also, electro-optical (EO) performances for the twisted-nematic (TN)-liquid crystal display (LCD) photoaligned with linearly polarized UV exposure were investigated. A good LC alignment with UV exposure on the two types of photopolymer surface can be obtained. The Voltage-transmittance (V-T) curve in the photoaligned TN cell with UV exposure was different from two type. The response time of photoaligned TN cell was measured about 21 ms in two alkyl chain and about 15 ms in four alkyl chain.

타겟간 거리 변화에 따른 OLED용 ITO 박막의 제작 (Preparation of ITO Thin Film with Distance of Between Two Targets)

  • 김현웅;금민종;김경환
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2005년도 추계학술대회 논문집 전기물성,응용부문
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    • pp.62-64
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    • 2005
  • Indium Tim Oxide(ITO) thin film was prepared for TOLEDs by Facing Targets Sputtering(FTS) apparatus which can suppress the damage of organic layer due to the collisions of high energetic particles. In particular, ITO thin film was prepared with changing the distance between two targets for reduced the bombardment by high energetic particles such as ${\gamma}-electron$ or negative oxygen ions. The electrical and optical properties of ITO thin films as a function of distance of between two targets were measured. Additionally, the ITO thin films were prepared on the cell (cell : MgAg/LiF/EML/HTL/ bottom electrode) with distance of between two targets. And the I-V characteristics of ITO/cell was investigated.

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Comparison Study on Power Output Characteristics of Power Management Methods for a Hybrid-electric UAV with Solar Cell/Fuel Cell/Battery

  • Lee, Bohwa;Kwon, Sejin
    • International Journal of Aeronautical and Space Sciences
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    • 제17권4호
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    • pp.631-640
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    • 2016
  • A dual-mode power management for a hybrid-electric UAV with a cruise power of 200W is proposed and empirically verified. The subject vehicle is a low-speed long-endurance UAV powered by a solar cell, a fuel cell, and a battery pack, which operate in the same voltage bounds. These power sources of different operational characteristics can be managed in two different methods: passive management and active management. This study proposes a new power management system named PMS2, which employs a bypass circuit to control the individual power sources. The PMS2 normally operates in active mode, and the bypass circuit converts the system into passive mode when necessary. The output characteristics of the hybrid system with the PMS2 are investigated under simulated failures in the power sources and the conversion of the power management methods. The investigation also provides quantitative comparisons of efficiencies of the system under the two distinct power management modes. In the case of the solar cell, the efficiency difference between the active and the passive management is shown to be 0.34% when the SOC of the battery is between 25-65%. However, if the SOC is out of this given range, i.e. when the SOC is at 90%, using active management displays an improved efficiency of 6.9%. In the case of the fuel cell, the efficiency of 55% is shown for both active and passive managements, indicating negligible differences.

Berberine Production by Cell Suspension Cultures of Cork Tree (Phellodendron amurense Rupr)

  • Choi, Myung-Suk;Shin, Dong-Ill;Park, Young-Goo
    • 생약학회지
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    • 제27권1호
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    • pp.32-36
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    • 1996
  • Various culture conditions for cell growth and berberine production in cork tree (Phellodendron amurense Rupr.) were investigated. Callus was induced from cambium tissue of cork tree, and cultured on LS liquid medium supplemented with 0.5 mg/1 2,4-D, 0.1mg/1 BA, and 3% sucrose. Several factors enhancing berberine production and cell growth in cork tree cell cultures were found. Some of them enhanced both cell growth and berberine production, but others resulted in a decoupling of cell growth and berberine production with significant in the specific levels. High level of nitrate (80mM), high level of phosphate (8.98mM), and sucrose (7%), 1.0mg/l IAA were effective in berberine production, whereas low level of nitrate (40mM), and phosphate (2.25mM), and high level of sucrose (7%) in the medium were effective in cell growth. Two stage culture(first stage for cell growth, and second stage for berberine production) increased berberine production almost twice (5.06mg/g dry weight) as much as single stage cultures in berberine production.

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자궁목 반지세포암종의 세포학적 소견 -2예 보고- (Cytologic Features of Signet Ring Cell Carcinoma of the Uterine Cervix - A Report of Two Cases -)

  • 조현이;하승연;정재걸;오영하;정동해;김나래;이종민;이의돈
    • 대한세포병리학회지
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    • 제14권2호
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    • pp.66-70
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    • 2003
  • Signet ring cell carcinoma is a rare type of mucinous adenocarcinoma of the uterine cervix. To the best of our knowledge, there is no report on cytologlc findings of primary signet ring cell carcinoma of the uterine cervix in the literature. Recently, we experienced two cases of signet ring cell carcinoma of the uterine cervix. The finding of characteristic signet ring cells on cervicovaginal smear led to the diagnosis of signet ring cell carcinoma. However, primary signet ring cell carcinoma could not be cytologically distinguished from more common metastatic tumor. Therefore, diagnosis rests upon the recognition of signet ring cells and the absence of signet ring cell carcinoma elsewhere.

생쥐초기배아 세포기가 동결보존 및 융해후 생존에 미치는 영향 (Effect of Cell Stage on Development of Mice Embryo After Cryopreservation and Thawing)

  • 한혁동;김영대;손성욱;권장연;이영진;정인배;차동수
    • Clinical and Experimental Reproductive Medicine
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    • 제20권2호
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    • pp.161-164
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    • 1993
  • To forsee appropriate developmental cell stage in human embryos for cryopreservation, we observed blastocyst development in culture medium after cryopreservatlon and thawing of one cell, two cell, four cell stage of mice embryos. According to our results, development of the blastocyst of cryopreserved two cell mice embryos was significantly higher than that of cryopreserved one cell mice zygotes or four cell mice embryos.

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