• Composites Research
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• v.34 no.6
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• pp.406-411
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• 2021

PEM (proton exchange membrane) fuel cells generate only water as a by-product, and thus are in the spotlight as an eco-friendly energy source. Among the various components composing the stack of the fuel cell, research on the bipolar plate that determines the efficiency of the fuel cell is being actively conducted. The composite bipolar plate has high strength, rigidity and corrosion resistance, but has the disadvantage of having a relatively low electrical conductivity. In this study, to overcome these shortcomings, a gas diffusion layer (GDL)-composite bipolar plate assembly was developed and its performance was experimentally verified. The graphite foil coating method developed in the previous study was applied to reduce the contact resistance between the bipolar plate and the GDL. In addition, in order to improve electron path in the stack and minimize the contact resistance between the GDL and the bipolar plate, a GDL-bipolar plate assembly was fabricated using a thin metal foil. As a result of the experiment, it was confirmed that the developed GDL-bipolar plate assembly had 98% lower electrical resistance compared to the conventional composite bipolar plate.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.12
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• pp.1022-1030
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• 2009

Numerical analysis was carried out to investigate the effect of GDL (Gas diffusion layer) porosity on the performance of PEMFC (proton exchange membrane fuel cell). A complete three-dimensional model was chosen for single straight channel geometry including cooling channel. Main emphasis is placed on the heat and mass transfer through the GDL with different porosity. The present numerical results show that at high current densities, the cell voltage is influenced by the GDL porosity while the cell performance is nearly the same at low current densities. At high current densities, low value of GDL porosity results in decrease of the fuel cell performance since the diffusion of reactant gas through GDL becomes slow with decreasing porosity. On the other hand, for high GDL porosity, the effective thermal conductivity becomes low and the heat generated in the cell is not removed rapidly. This causes the temperature of fuel cell to increase and gives rise to dehydration of the membrane, and ultimately increase of the ohmic loss.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.132-132
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• 2009

To achieve the commercialization of PEM fuel cell, the durability problem must be solved. Recently, many researchers have focused on this durability problem and degradation studies about membrane and electrode have been reported. But durability characteristics of gas diffusion layer is not much reported yet. Durability of GDL is very important to maintain the performance of PEM fuel cell because the main function of GDL is a path of fuel and water and the GDL degradation causes the loss of the GDL function. In this study, the degradation of GDL, especially, the mechanical degradation process was investigated with the leaching test. The effect of water dissolution was observed through the test and the amount of GDL degradation was measured with various measurement methods such as weight measurement, static contact angle measurement, scanning electron microscope. After 2,000 hours test, the GDL showed structural damage and loss of hydrophobicity.

• Journal of the Korean Society of Food Science and Nutrition
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• v.23 no.1
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• pp.98-103
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• 1994

Some quality characteristics of tofu prepared with soyprotein isolate (SPI) were investigated to study the effects of various ratio of coagulants mixture and addition of oil, sucrose and dextrin. The tofu was prepared by addition of coagulants into the boiled SPI suspension and compression. The results showed that the mixed coagulants of CaCl $_2$-GDL(50 :50) and CaSO$_4$-GDL(25 :75) resulted the highest volume yield of 4.23g/g SPI among the various ratios of CaCl$_2$-CaSO$_4$, CaCl$_2$-GDL and CaSO$_4$-GDL. The water holding capacity(WHC) expressed as the area of water absorbed on filter paper was relatively high for those tofu coagulation with CaCl$_2$-GDL(75 : 25) and CaSO$_4$ -GDL(75 : 25). Addition of sucrose or oil-sucrose (1 : 1) decreased the yield wihle WHC was improved. Their addition also caused less hard and cohesive tofu which was coagulated by CaCl$_2$-GDL(75 : 25) and CaSO$_4$-GDL(75 : 25).

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.3114-3119
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• 2008

Relatively high convective flow exists in the under-rib regions of a gas diffusion layer (GDL) when serpentine flow fields are employed in a PEMFC. This under-rib convection is believed to be favorable for the performance of PEMFCs, by enabling more effective use of catalysts in the under-rib regions. From the fact that the under-rib convection in a GDL is directly proportional to the permeability of the GDL, computational fluid dynamics (CFD) simulations were performed to discover the relationship between the GDL permeability and the PEMFC performance. Single-, triple-, and quintuple-path parallel serpentine flow fields for $9\;cm^2$ active cell area were considered while changing the GDL permeability from $1{\times}10^{-12}$ to $5{\times}10^{-11}m^2$. The results showed that higher GDL permeability generally resulted in better performance of PEMFCs, but the degree of performance enhancement became smaller as the parallel path number increased. The effects of the permeability on the local variables were also discussed.

• Journal of Hydrogen and New Energy
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• v.20 no.6
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• pp.499-504
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• 2009

The effect of gas diffusion layer (GDL) compression caused by different stack clamping pressures on fuel cell performance was experimentally studied in a miniature 5-cell proton exchange membrane fuel cell (PEMFC) stack. Three stacks with different GDL compressions, 15%, 35% and 50%, were prepared using SGL 10BC carbon fiber felt GDL and Gore 57 series MEA. The PEMFC stack performance and the stack stability were enhanced with increasing stack clamping pressure resulting in the best performance and stability for the stack with higher GDL compressions up to 50%. The excellent performance of the stack with high GDL compression was mainly due to the reduced contact resistance between GDL and bipolar plate in the stack, while reduced gas permeability of the excessively compressed GDL in the stack hardly affected the stack performance. The high stack clamping pressure also resulted in excessive GDL compression under the rib areas of bipolar plate and large GDL intrusion into the channels of the plate, which reduced the by-pass flow in the channels and increase gas pressure drop in the stack. It seems that these phenomena in the highly compressed stack enhance the water management in the stack and lead to the high stack stability.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.50 no.3
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• pp.279-288
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• 2024

This study investigates the efficacy of anti-acne cosmetics containing lactonic hydroxy acid, specifically gluconodeltalactone (GDL), in improving acne skin treatment. In sebaceous cells induced by linoleic acid, GDL at concentrations of 1.0 mg/mL or higher demonstrated a concentration-dependent inhibition of lipid synthesis. Antibacterial activity of GDL against Cutibacterium acnes (C. acnes) was confirmed through minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays. Based on these in vitro results, a clinical test was conducted involving 65 participants to evaluate the effects of a anti-acne cosmetic formulation containing 3% GDL over an eight-week period. The results indicated a statistically significant improvement (p < 0.05) in both inflammatory acne lesions (papules, pustules, and nodules) and non-inflammatory lesions (comedones) from as early as two weeks of application, without any reported skin irritation. The results confirm that cosmetics with GDL can be used effectively and safely without long-term skin irritation, even for consumers with sensitive acne-prone skin.

• Korean Journal of Food Science and Technology
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• v.26 no.1
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• pp.26-30
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• 1994

The purpose of this study was to investigate the effects of heating times of soy protein isolate(SPI) and mixing ratio of coagulants mixture on water holding capacity(WHC) and oil absorption capacity (OAC) of SPI, texture properties and yield of tofu. The effect of heating at $100^{\circ}C$ on the amounts of coagulants required for coagulation showed that the amounts of $CaCl_{2},\;MgCl_{2}$ and GDL decreased as the heating time extended to $6{\sim}9$ minutes while $CaSO_{2}$ was changed little. The tofu yield showed maximum for the tofu prepared by 6 minutes boiling and coagulation with $CaSO_{4}$. The WHC of SPI was significantly reduced by heating at $100^{\circ}C$ while OAC was rather increased until 9 minutes of heating. The textural properties of SPI tofu coagulated with mixed coagulants$(CaSO_{4}-GDL,\;CaSO_{4}-CaCl_{2},\;CaCl_2-GDL)$ showed that softer tofu was obtained as the ratio of $CaSO_{2}$ increased and harder tofu as the ratio of $CaCl_{2}$ and GDL increased. The maximum and minimum tofu yields were prepared from 100% of $CaSO_{2}$ and 100% of GDL, respectively. Organoleptic properties showed that more uniform and tender tofu were obtained with higher portion of $CaSO_{2}$ in the mixed coagulants and higher intensity of sourness and bitterness were scored as the GDL and $CaCl_{2}$ added more.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.8
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• pp.767-773
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• 2013

This study suggested the variations of porosity and gas permeability of gas diffusion layers (GDLs), which are easily deformed among the components of a highly compressed PEMFC stack. The volume change owing to compression was measured experimentally, and the variations in the porosity and gas permeability were estimated using correlations published in previous literature. The effect of polytetrafluoroethylene (PTFE) which is added to the GDLs to enhance water discharge was investigated on the variations of porosity and gas permeability. The gas permeability which strongly affects the mass transport through GDL, decreases sharply with increasing compression when the GDL has high PTFE loading. As a result, the mass transport through the pore network of GDL can be changed considerably according to the PTFE loading even with the same clamping force. The accuracy of modeling of transport phenomena through GDL can be improved due to the enhanced correlations developed based on the results of this study.

• Journal of Hydrogen and New Energy
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• v.24 no.3
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• pp.216-222
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• 2013

Durability characteristics of Gas Diffusion Layer(GDL) is one of the important issues for accomplishing commercialization of Proton Exchange Membrane Fuel Cell(PEMFC). It is strongly related to the performances of PEMFC because one of the main functions of GDL is to work as a path of fuel, air and water. When the GDL does not work on their proposed functions due to the degradation of durability, mass transfer in PEMFC is disturbed and it might cause the flooding phenomenon. Thus, investigating the durability of GDL is important and understanding the GDL degradation process is needed. In this study, electrochemical degradation with carbon corrosion is introduced. The carbon corrosion experiment is carried out with GDLs which have different MPL penetration thicknesses. After the experiment, the amount of degradation of GDL is measured with various properties of GDL such as weight, thickness and performance of the PEMFC. The degraded GDL shows loss of their properties.