• Journal of the Korean Applied Science and Technology
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• v.30 no.1
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• pp.146-151
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• 2013

This paper reveals the performance decrease and recovery of PEMFC when the contaminated fuel gas and air source with sulfur impurities such as hydrogen sulfide and sulfur dioxide were simultaneously introduced to anode and cathode, respectively. Three different GDLs were fabricated with different carbon black and activated carbon to prevent an introduction of sulfur compound impurities into MEA. components. The severity of $SO_2$ and $H_2S$ poisoning was depended on concentrations(3 ppm - 10 ppm) of sulfur impurities. Especially, cell performance degradation rate was rapid when MEA fabricated with CN-2 GDL because it had little porosity on GDL surface. Moreover, the cell performance can be recovered up to 90%-95% only with neat hydrogen and fresh air feeding.. Conclusively, MEA fabricated with porous CN-1 GDL showed the best cell performance and recovery efficiency during exposure to poisoning condition by simultaneous sulfur impurities.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.2
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• pp.244-251
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• 2011

Pipe rolling process using the planetary rolling mill for AISI 304 stainless steel has been studied by using finite element method. Mannesmann method using three-roll is applied to this rolling process. Commonly, rolling process has started from the cold working and finished to the hot working. This rolling process has more advantage that make reduction of process and cost than existing extrusion process. This process includes various and complex process parameters. Each of the process parameters affects forming result. Therefore, all of the process parameters should be considered in FEA. In this study, possibility and productivity of forming pipe for AISI 304 stainless steel had been investigated. Also, preheating process and variations of rotation velocity and product thickness were considered in FEA. Rolling process for AISI 304 stainless steel pipe was successfully simulated and it should be useful to determine optimal rolling condition.

• Korean Chemical Engineering Research
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• v.51 no.5
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• pp.540-544
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• 2013

During start up and shut down of a proton exchange membrane fuel cells (PEMFC), the performance and lifetime of PEMFC were reduced. In this study, effect of startup and shutdown were investigated in dead-end type PEMFC using oxygen as a cathode gas with polarization curve, impedance spectroscopy (EIS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Dummy load which eliminates residual hydrogen and oxygen during startup and shutdown operation should be applied to mitigated the degradation of PEMFC performance. At 50% relative humidity (RH) under the repetitive on/off cycling, the cell performance decayed faster than at 100% RH because of corrosion of the cathode carbon support. Water suppling into cell reduced the degradation rate of dead-end type PEMFC during start up and shut down cycling at 50% RH.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.995-1000
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• 2001

Distributions of the parameters in proton exchange membrane fuel cell (PEMFC) has been analyzed numerically under steady-state and isothermal conditions. The distributions of the crucial parameters (e.g., temperature and pressure) in a PEMFC have a major impact on its safe and efficient operation. This paper predicts the performance of the model electrode plates by calculating the pressure and temperature distributions of working fluid. The calculated results of pressure and temperature at exit condition shows good agreement to experiments and gives details of flow pattern inside of electrode plates.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.583-586
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• 1991

This paper presents a comprehensive study on the stability of several control schemes for the induction motor driven by current source inverters. A stator voltage-controlled current source inverter drive system without a speed sensor is investigated in order to find appropriate control schemes, which are primarily based on direct or, alternatively, indirect frequency control scheme. The overall control systems with either voltage control loop or current and voltage control loops provided in addition to each frequency control scheme are analyzed by utilizing the root locus method and simulated by computer to illustrate the validity of this analysis.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.3
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• pp.311-319
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• 1998

DC Motors have been widely used in industry as driving power motors for electrical vehicles cranes and winches due to their strong starting torques and as servo-motors for position and speed control systems due to their convenience of speed control etc. Generally in the speed control systems of motors speed sensors are required and this fact results in he increased price and operating cost and in the limitted applications. This paper presents a new speed control method for sensorless DC motors. In this scheme the speed signal is estimatd by the measurement values of the armature voltage and current. A Fuzzy feedback controller instead of the conventional PID controller. Through simulations the effectiveness and usefullness of the proposed method are illustrated.

• JOURNAL OF ELECTRICAL WORLD
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• s.305
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• pp.69-74
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• 2002

최근 승강기의 현대화 사업에서는 단공기(短工期)$\cdot$저가격으로 특히 신뢰성 향상을 기대할 수 있는 제어개수(制御改修:전기기기를 일신하는 개수방법)가 주류를 이루고 있다. 그래서 미쓰비시(삼릉)전기에서는 납품한지 20년 이상 경과한 직류-기어리스(DC-GL)고속엘리베이터를 대상으로 하는 제어개수전용의 구동방식을 개발하여 동사 본사빌딩에 납품하였다. 새로운 구동방식은 현재 널리 적용되고 있는 고속엘리베이터의 인버터제어기술을 응용하여 개발한 초퍼회로방식이다. 제어회로에서는 동사의 최신 엘리베이터와 같은 마이컴시스템을 채용하여 고성능화와 부품의 공용화를 도모하였다. 또한 주회로에는 고조파대책, EMI(Eletro-magnetic Interference) 대책 및 누설전류대책을 시행하였다. 특히 직류전동기의 계자제어에서는 엘리베이터의 운전상태에 따라 계자전류를 가변하는 가변계자전류제어를 적용하였다. 이번에 개발한 제어방식은 다음의 특징을 갖고 있다. (1)고조파전류를 억제하였기 때문에 빌딩측에서의 고조파대책이 불필요하다. (2)동사 제작의 워드레오나드방식과 비교하여 약 $40\%$정도 소비전력을 감소시킬 수 있다. (3)동사 제품인 최신 엘리베이터 수준의 성능(승차감, 착상정도 등)을 실현하였다. (4)최신 엘리베이터와 동등한 풍부한 옵션에 대응할 수 있다. 당분간은 속도 $120\~$360m/min, 용량 1,600kg 이하의 고속엘리베이터에 적용하고 점차적으로 적용영역을 확대해 나갈 예정이다.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.120.2-120.2
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• 2012

천리안위성은 2010년 6월 발사되어 지구적도상공 약36,000km, 동경 128.2도에 위치하고 지구 자전 방향으로 지구와 같은 속도로 회전하며 24시간 한반도를 관측하는 정지궤도위성이다. 정지궤도위성은 높은 고도로 인하여 태양활동 변화에 따른 태양풍, 고에너지 전자 등에 의한 영향을 직접적으로 받는 환경에 놓여있다. 과거 사례들로부터 정지궤도위성의 오작동은 태양활동에 의해 다양한 현상으로 발생될 수 있다는 사실도 밝혀졌다. 본 연구에서는 2013년 태양활동 극대기를 대비하여 태양활동 변화가 천리안위성의 탑재체에 끼치는 영향에 대해 조사되었다. 천리안위성은 기상 해양관측을 위한 광학탑재체와 통신서비스를 위한 통신탑재체로 이루어져있다. 이 중 우리는 2011년에 발생된 X등급의 태양폭발 규모에 따라서 기상관측을 수행하는 기상탑재체 상태가 태양폭발이 없는 기간의 상태와 어느 정도 차이를 보이는지 분석하였다. 2011년에 발생된 경보는 3단계 10회, 4단계 2회로 발생빈도가 증가하는 추세이다. 4단계 경보의 태양폭발에도 천리안위성은 모든 부분에서 정상운영을 유지하고 있다. 이번연구를 통해 태양폭발 규모에 따른 기상탑재체의 영향 정도를 가시화하여 앞으로 발생 가능한 문제를 예측하고 대비함으로서 안정적인 위성운영을 도모하고자 한다.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.81-84
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• 2006

To investigate the characteristics of water droplet on the gas diffusion layer from both upper-view and side-view of flow channel, a rig test apparatus was designed and fabricated with L-shape acryl plate in a $1mm{\times}1mm$ micro-channel. This experimental device is used to simulate the single droplet growth and its transport process under fuel cell operating condition. As a first step, we investigated the growth and transport of single water droplet with working temperature and air flow velocity. The contact angle and its hysteresis of water droplet at departing moment are measured and analyzed. It is expected that this study can provide the basic understanding of liquid water droplet behavior in gas flow channel and GDL interface during the PEM fuel cell operation.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.13 no.3
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• pp.10-24
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• 2014

Bicycle is a useful transportation mode that is healthy, emission-free, and environmentally compatible. Although large efforts have been made to promote the use of bicycling to date, there still exist various hurdles and limitations. One of the key issues to increase bicycling is how to gather bicycle-related data from the field and to generate valuable information for both users and operations agencies. This study proposes a method to process bicycle trajectory data which is obtained from tracing global positioning systems(GPS) equipped bicycle, which is defined as the probe bicycle. The proposed method is based on the concept of statistical quality control of data. In addition, a data collection and processing scenario in support of public bicycle system is presented. The outcomes of this study would be valuable fundamentals for developing bicycle traffic information systems that is a part of future intelligent transportation systems(ITS).