• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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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.

• Transactions of the Korean hydrogen and new energy society
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• v.35 no.2
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• pp.205-215
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• 2024

This study introduced a direct contact heat exchanger to enhance the efficiency of polymer electrolyte membrane fuel cells (PEMFCs) systems. According to previous research, 28% of the operating costs of fuel cell systems are attributed to heat exchanger devices, prompting the design of a direct contact heat exchanger to address this issue. Optimal configurations were determined through computational fluid dynamics analysis and experimental device fabrication, and the enhanced heat exchange performance of the heat exchanger was experimentally confirmed. Through this, the contribution of the direct contact heat exchanger to the heat management and efficiency enhancement of PEMFC systems was established.

• Journal of the Korean Magnetic Resonance Society
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• v.18 no.2
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• pp.58-62
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• 2014

Human transmembrane proteins (hTMPs) are closely related to transport, channel formation, signaling, cell to cell interaction, so they are the crucial target of modern medicinal drugs. In order to study the structure and function of these hTMPs, it is important to prepare reasonable amounts of proteins. However, their preparation is seriously difficult and time-consuming due to insufficient yields and low solubility of hTMPs. We tried to produce large amounts of Syndecan-4 transmembrane domain (Syd4-TM) that is related to the healing wounds and tumor for a long time. In this study, we performed the structure determination of Syd4-TM combining the Polarity Index at Slanted Angle (PISA) wheel pattern analysis based on $^{15}N-^1H$ 2D SAMPI-4 solid-state NMR of expressed Syd4-TM and Molecular Dynamics (MD) simulation using Discovery Studio 3.1.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.5
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• pp.386-392
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• 2013

Polymer electrolyte membrane (PEM) fuel cell stacks are constructed by stacking several to hundreds of unit cells depending on their power outputs required. Fuel and oxidant are distributed to each cell of a stack through so-called manifolds during its operation. In designing a stack, if the manifold sizes are too small, the fuel and oxidant would be maldistributed among the cells. On the contrary, the volume of the stack would be too large if the manifolds are oversized. In this study, we present a three-dimensional computational fluid dynamics (CFD) model with a geometrically simplified flow-field to optimize the size of the manifolds of a stack. The flow-field of the stack was simplified as a straight channel filled with porous media to reduce the number of computational meshes required for CFD simulations. Using the CFD model, we determined the size of the oxidant manifold of a 30 kW-class PEM fuel cell stack that comprises 99 cells. The stack with the optimal manifold size showed a quite uniform distribution of the cell voltages across the entire cells.

• BMB Reports
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• v.50 no.4
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• pp.214-219
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• 2017

Mitochondria play pivotal roles in the ATP production, apoptosis and generation of reactive oxygen species. Although dynamic regulation of mitochondria morphology is a critical step to maintain cellular homeostasis, the regulatory mechanisms are not yet fully elucidated. In this study, we identified miR-200a-3p as a novel regulator of mitochondrial dynamics by targeting mitochondrial fission factor (MFF). We demonstrated that the ectopic expression of miR-200a-3p enhanced mitochondrial elongation, mitochondrial ATP synthesis, mitochondrial membrane potential and oxygen consumption rate. These results indicate that miR-200a-3p positively regulates mitochondrial elongation by downregulating MFF expression.

• Bulletin of the Korean Chemical Society
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• v.30 no.3
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• pp.623-629
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• 2009

We have performed replica-exchange molecular dynamics simulations on 41 residue peptide mainly composed of NAC (non A$\beta$ component) sequence in $\alpha$-Synuclein. To investigate conformational characteristics of intrinsically unstructured peptides, we carried out structural analysis on the ‘representative structures’ for ensemble of structures occurring at different temperatures. The secondary structure profile obtained from our simulations suggests that the NAC region of $\alpha$-synuclein can be divided into roughly three helical-like segments. It is found that the overall helix-turn-helix like topology is conserved even though the conformational fluctuations grow as the temperature increases. The coordinate-based and the distance-based representative structures exhibit noticeable differences at higher temperatures while they are similar at lower temperatures. It is found that structural variations for the coordinate-based representative structures are much larger, suggesting that distance-based representative structures provide more reliable information concerning characteristic features of intrinsically unstructured proteins. The present analysis also indicates that the conformational features of representative structures at high temperatures might be related to those in membrane or low pH environment.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.1
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• pp.29-35
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• 2016

It is important to uniformly supply the fuel gas into the reaction activity area in polymer electrolyte membrane fuel cell (PEMFC). Recent studies have shown that the cell performance can be significantly improved by employing metal foam gas distributor as compared with the conventional bipolar plate types. The metal foam gas distributor has been reported to be more efficient to fuel transport. In this study, three-dimensional computational fluid dynamics (CFD) simulations have been performed to examine the effects of metal foam flow field design on the fuel supply to the reaction site. Darcy's law is used for the flow in the porous media. By solving additional advection equation for fluid particle trajectory, the gas transport has been visualized and examined for various geometrical configuration of metal foam gas distributor.

• Prospectives of Industrial Chemistry
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• v.24 no.3
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• pp.14-27
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• 2021

수소 에너지는 환경 문제를 최소화하고 고갈되는 화석연료를 대체할 수 있는 에너지원으로 각광을 받고 있다. 수소연료전지는 이러한 수소를 에너지원으로 사용하고 수소를 전기에너지로 전환하여 그 부산물로 물을 만드는 대표적인 친환경 전기화학 장치이다. 고분자 전해질막 연료전지는 수소이온교환 특성을 갖는 고분자막을 전해질로 사용하는 연료전지로 막전극집합체의 전극층은 촉매가 포함된 고분자 전해질막 연료전지의 주요 요소 중의 하나이다. 소재개발 측면에서 고분자 전해질막 연료전지 전극층 핵심 소재의 물성 발현 원리 등을 이해하고 최적화된 소재 설계를 위해서는 원자레벨에서의 소재 설계 접근법이 필요하다. 따라서 실험적인 연구가 어려운 부분과 원자단위에서의 물질 현상에 대한 이해 그리고 연구 개발의 효율성 증진을 위해 전산재료과학(computational materials science) 기술이 광범위하게 활용될 수 있다. 본 기고문에서는 고분자 전해질막 연료전지에서의 전극층 소재에 대한 분자동역학 기반의 전산모사 활용과 연구동향에 대하여 소개하고자 한다.

• Applied Microscopy
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• v.23 no.1
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• pp.1-14
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• 1993

The present study was carried out to analyze the evidence of membrane recycling, and the regulation of cellular transport by dynamic changes in apical membrane area that functionally interacts with the number of cytoplasmic vesicles. Under scanning electron micrographs, turtle bladder mucosa contain three main type of cells; granular cells and carbonic anhydrase (CA)-rich cells, deviding into a and b type of epithelial cell. The granular cell is the majority cell type of the mucosa comprising 80% of the total cell number. The remaining 20% of the cells are characteristically rich in carbonic anhydrase. Uptake of HRP was detected in the most vacuoles or tubulovesicles in both type of CA-rich cells in the turtle bladder, indicating that the part of plasma membrane was internalized in the apical cytoplasmic vacuoles. It seems quite likely that CA-rich cells possess intracellular vesicles carrying proton pumps which are recycling back to the apical plasma membrane. In turtle bladder, the granular cells actively secrete large quantities of mucin and other proteins by an exocytotic mechanism in an apparently constitutive fashion. The possibility that bladder epithelial cells secrete mucin via a regulated secretory pathway has not been rigorously examined and much is still to be determined about these issues from this cell type.

• Journal of Aerospace System Engineering
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• v.10 no.4
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• pp.1-10
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• 2016

This study analyzes the fabric skin of a wind turbine blade. The fabric skin is a membrane structure that was analyzed using a static Fluid Structure Interaction (FSI) method. For this study the blade of large 5 MW wind turbine was selected. In order to examine the validity of the analysis, a variety of reference data were used. Before conducting static FSI analysis, a Computational Fluid Dynamics (CFD) analysis and modal analysis were done. Then interaction analysis was conducted. FSI analysis was done with imported Aerodynamic data that resulted from the CFD analysis. The resulting observations about the membrane structure, inherent tensions, deformation of the final structure, and aerodynamic forces caused by deformation are reported.