• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.99-102
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• 2006

Optimal flow-field design of bipolar-plates for a commercial class PEM(polymer electrolyte membrane) fuel cell stack was carried out on the basis of three-dimensional computational fluid dynamics(CFD) simulation. A three-dimensional CFD model originally developed by Shimpalee et al., has been utilized for performing large-scale simulation of a single fuel cell consisting of bipolar-plates gas diffusion layers, and a membrane-electrode-assembly(MEA). The CFD model is able to predict the current density, pressure drops, gas velocities, vapor and liquid water contents, temperature distributions, etc. inside a single fuel cell. Depending on simulation results from the CFD modeling of a PEM fuel cell, several flow-fields of bipolar-plates were designed and verified. The final design of the bipolar-plate has been chosen from the simulations and experimental tests and showed the best performance as expected from the simulation results under a normal operating condition. Thus, the CFD simulation approach to design the optimal flow-field of the bipolar-plates was successful. The final design was adopted as the best flow-field to build a commercial scale PEM fuel cell stack, the performance of which shows about 42% higher than that of the older bipolar-plate design.

• 응용통계연구
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• 제20권3호
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• pp.449-458
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• 2007

양극성 장애 (bipolar disorder)는 조증 삽화 (manic episode)와 우울증 삽화 (depression episode)를 반복적으로 경험하는 기분장애이다. 양극성 장애환자에게 우울증은 조증보다 심각한 결과를 가져오며, 치료의 효과를 측정하기도 어렵다고 알려져 있다. 본 연구의 목적은 우울증(depression) 상태에 있는 환자들을 대상으로 항우울제를 사용하여 정상 (normal) 상태로 전환했을 때, 약물의 장기 사용으로 일어날 수 있는 조증 (mania)과 같은 부작용을 통제하고자 한다. 이를 위해 정상 상태에서 조증으로 전환하는데 소요되는 시간의 분포를 추정한다. 본 연구에서는 세 가지 방법, 모수적, 비모수적 그리고 준모수적 방법을 차례대로 적용하였다. 특히 기분 전환의 흐름을 파악하기 위해 3단계 모형을 사용하였다. 예를 들어, Illness-Death 모형하에서 기분 전환의 발생시점에 대한 분포를 추정하기 위해 계수 과정에 의해 기분 전환에 대한 과정을 모형화하였다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제14권3호
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• pp.268-273
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• 2014

The forming, reset and set operation of bipolar resistive random access memory (RRAM) have been predicted by using a finite element (FE) model which includes interface effects. To the best of our knowledge, our bipolar RRAM model is applicable to realistic cell structure optimization because our model is based on the FE method (FEM) unlike precedent models.

• 전기화학회지
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• 제2권1호
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• pp.13-16
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• 1999

복극성 전극반응기에서 복잡반응이 일어날 때 반응기 모델링하여 농도경시변화로 부터 전류값을 계산하였다. 이를 실험한 전류와 비교한 결과 잘 일치하였다. 본 논문에서 제안된 모델링이 파이로트 장치 설계에 유용하게 운용될 것이다.

• ETRI Journal
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• 제31권5호
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• pp.604-606
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• 2009

The primary dose effects on an insulated gate bipolar transistor (IGBT) irradiated with a $^{60}Co$ gamma-ray source are found in both of the components of the threshold shifting due to oxide charge trapping in the MOS and the reduction of current gain in the bipolar transistor. In this letter, the IGBT macro-model incorporating irradiation is implemented, and the electrical characteristics are analyzed by SPICE simulation and experiments. In addition, the collector current characteristics as a function of gate emitter voltage, VGE, are compared with the model considering the radiation damage of different doses under positive biases.

• 대한전자공학회논문지
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• 제26권10호
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• pp.1591-1597
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• 1989

Through the matematical alaysis of EX-NOR logic relation between the input vector and the memory matrix, we propose a new method for optical implementation of the bipolar Hopfield neural network model based on the optical vector-matrix multiplier.

• 전자공학회논문지A
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• 제30A권3호
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• pp.88-94
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• 1993

In this paper, a simple Ebers-Moll Model for the heterojunction bipolar transistor is presented. Using the model structure for the npn type HBT, the current-voltage characteristics was analyzed. And from the obtained terminal currents, the Ebers-Moll equations were derived. Then substituting the physical parameters for heterojunction to those for homojunction, this model would be used to analyze the characteristics of single and/or duble heterojunction HBT's. And directly relating model parameters to device parameters, it would be also used to optimize the characteristics of HBT's. The simulated results using this model were in good agreement with experimental data.

• 신재생에너지
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• 제3권3호
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• pp.14-19
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• 2007

A flow channel model of a bipolar plate with varying cross-sectional area was newly designed for improving performance and efficiency of a PEM fuel cell stack. As a result, the varying cross-sectional area model showed poor uniformity in velocity distribution, however, maximum velocity in the flow path is about 30% faster than that of the uniform cross-sectional area model. The proposed varying cross-sectional area model is expected to diffuse operating fluids more easily into diffusion layer because it has relatively higher values in pressure distribution compared with other flow channel models. It is expected that the implementation of the varying cross-sectional area model can reduce not only the mass transport loss but also the activation loss in a PEM fuel cell, and open circuit voltage of a fuel cell can thus be increased slightly.

• Journal of Power Electronics
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• 제18권6호
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• pp.1901-1911
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• 2018

This study presents a circuit model for simulating the switching transients of insulated-gate bipolar transistors (IGBTs) with inductive load switching. The modeling approach used in this study considers the behavior of IGBTs and freewheeling diodes during the transient process and ignores the complex semiconductor physics-based relationships and parameters. The proposed circuit model can accurately simulate the switching behavior due to the detailed consideration of device-circuit interactions and the nonlinear nature of model parameters, such as internal capacitances. The developed model is incorporated in an IGBT loss calculation module of an electromagnetic transient simulation program to enable the estimation of switching losses in voltage source converters embedded in large power systems.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.389-391
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• 2009

The performance loss as pressurized by inside components like GDL and bipolar plate happened when assembling the PEMFC stack with clamping force. Numerical analysis of Gasket was carried out to analyze distribution of clamping pressure about the inside components. In case of the gasket, Mooney-Rivlin model which is the Strain Energy Function was used for numerical analysis. This result made the stress distribution of bipolar plate to expect.