• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.157-160
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• 2007

The catalyst layer of a proton exchange membrane (PEM) fuel cell is a mixture of polymer, carbon, and platinum. The characteristics of the catalyst layer play critical role in determining the performance of the PEM fuel cell. This research investigates the role of catalyst layer composition using a Central Composite Design (CCD) experiment with two factors which are Nafion content and carbon loading while the platinum catalyst surface area is held constant. For each catalyst layer composition， polarization curves are measured to evaluate cell performance at common operating conditions, Electrochemical Impedance Spectroscopy (EIS), and Cyclic Voltammetry (CV) are then applied to investigate the cause of the observed variations in performance. The results show that both Nafion and carbon content significantly affect MEA performance. The ohmic resistance and active catalyst area of the cell do not correlate with catalyst layer composition, and observed variations in the cell resistance and active catalyst area produced changes in performance that were not significant relative to compositions of catalyst layers.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.1
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• pp.133-137
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• 2006

Ion permeability characteristics in nano-polymer membrane structures are performed to investigate the chemical composition and characteristics of MEA(Membrane Electrolyte Assembly) which is one of the most important parts to decide the performance in PEMFC(Polymer Electrolyte Membrane Fuel Cell) system. Subsequently, the MEA manufacturing process is presented for the uniformed MEA product. In the meantime, the analysis of SEM(Scanning Electron Microscope) is carried out in order to investigate the joint aspect and chemical composition of MEA. As a result of SEM analysis, it is found that the bonded catalyst and carbon composition contain the reasonable amount to get unit cell output. It is also found that the humidification gives the better performance result slightly.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.6
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• pp.32-41
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• 1999

Natural gas is an attractive fuel in view of environment benefits due to its flow carbon-to-hydrogen ratio. However, its compositions and properties are varied depending upon production regional groups. Therefore, study on the combustion characteristics of natural gas engines with a variety of compositions has been demanded for the efficient application of gas engines. This study aims to investigate the effects of gas composition on engine combustion characteristics. It was found that , by controlling an engine with fixed fuel nozzle area, power and heat release were subject to Wobbe Index. And at fixed excess air ratios, power and heat release were subject to low heating value of unit mixture . In addition, in case of constant nozzle area, combustion duration was found to be inversely proportional to CP(Combustion Potential), and the condition of fixed excess air ratios showed no change in combustion duration, regardless of CP.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.4
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• pp.266-274
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• 2008

The need for more fuel-efficient and lower-emission vehicles has driven the technical development of alternative fuels such as Liquefied Petroleum Gas(LPG) which is able to meet the limits of better emission levels without many modifications to current engine design. LPG has a high vapor pressure and lower viscosity and surface tension than diesel and gasoline fuels. These different fuel characteristics make it difficult to apply it for the conventional gasoline or diesel fuel pump directly. In this study, experiments are performed to get performance and efficiency of the fuel pump at different condition as temperature, rotating speeds, composition of fuel. The characteristics of fuel pump is affected by cavitation due to the variation of temperature and composition.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.15 no.3
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• pp.273-282
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• 1986

The purpose of this research was to study the characteristics of heat transfer in Heat Pipe which used the composition wick of screened groove - metallic mesh by ADI method and experimental results. As the results, the more than number of metallic mesh screen layers in a heat pipe increased, the fewer the effect of heat recovery decreased. In case of 1 - layer metallic mesh screen wick, the response of the effect in heat recovery was more rapidly showed than in case of other layers and in spite of high load, the evaporation section of Heat pipe with 1 - layer metallic mesh screen wick showed the stable response and did not show excessive super heat. There was a interrelation between thermal resistance and the variable layers, between thermal resistance and the variable gaps of metallic meshes, the heat transfer characteristics of Heat pipe were depended on the thermal resistance of composition wick.

• Korean Institute of Interior Design Journal
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• v.21 no.3
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• pp.95-102
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• 2012

The purpose of this study is to analyze characteristics of residential architecture designed by Gwathmey Siegel in terms of their way of composing spaces and forms. Charles Gwathmey, one of the founders of Gwathmey Siegel, is a worldly famous architect who actively developed Neo-Modernistic architecture in his career. For this study, 15 major houses designed by Gwathmey Siegel were selected and analyzed in terms of their approaches on how to compose various spaces and forms, and how these approaches evolved as time passed. The analysis was mainly based on the drawings and photos of the houses published. The main characteristics found in this study can be summarized as follows: elevated LDK level, split-level composition, use of framing structure, layered space, and linear galleries as a spine of circulation with collaged volumes attached. It turned out these characteristics appeared, faded away, or evolved affecting each other. In early days, Gwathmey often elevated LDK level from ground level for providing privacy, views, and also for separating private rooms. Soon they composed spaces by splitting levels. It not only helped provide privacy where needed effectively, but made space composition more interesting. As sizes of the houses they designed grew, Gwathmey came up with the framing idea for expressing his original architectural language in larger scale. With the split-level composition, the framing method represented Gwathmey's in 70's. This framing introduced layers of interior spaces, and the layers started to break down the monumental framing into individual volumes by bringing in linear spine of circulation. These characteristics helped Gwathmey Siegel develop their own architectural language.

• Journal of Environmental Science International
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• v.30 no.8
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• pp.703-708
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• 2021

To improve the environmental management and resources, in this study, we aimed to investigate the effect of adding oyster shell powder to Hanwoo manure on its characteristics and microbial composition during the storage period. Additives were deposited on top of the manure surface at the rate of 0, 0.5, and 1% of oyster shell powder per 200 g of Hanwoo manure in a plastic container with three replicates; however, untreated manure litter served as the control. Manure characteristics (dry matter, organic matter and crude ash) and microbial composition (lactic acid bacteria, yeast, Bacillus subtilis, Salmonella, and E.coli) were evaluated at day 0, 2, 4, and 8. Manure characteristics exhibited an effect on dry matter, organic matter, and crude ash at day 2 and 8 (p<0.05), and not for day 0 and 4 (p>0.05). With the exception of yeast content at day 4 of storage, lactic acid bacteria, yeast, Bacillus subtilis, Salmonella, and E.coli exhibited no significant differences in all conditions during the storage period. Conclusively, addition of 1% oyster shell powder to Hanwoo manure resulted in slightly better manure characteristics; however, its microbial composition remained unchanged.

• Asian-Australasian Journal of Animal Sciences
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• v.21 no.3
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• pp.426-433
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• 2008

Heat stress is major welfare problem in the poultry industry. Huge economic losses occur every year because of mortality and decreased production due to high environmental temperatures. This experiment was conducted to determine the effects of level of inclusion of ascorbic acid supplementation to the diet on performance, carcass composition and bone characteristics of male turkeys during high summer temperature. A total of 120 day-old turkey chicks were wing banded at hatch and randomly distributed into 3 treatment groups. Three diets were formulated to provide a similar nutrient profile with the exception of using three graded levels of ascorbic acid, namely 0, 150 and 300 mg/kg of the diet. The experimental diets were used from 0 to 18 weeks of age. Body weights, feed intake and feed conversion ratio, slaughter weight, carcass yield, portions, composition and thigh and breast pigmentation of the turkeys were not affected by ascorbic acid (p>0.05). Also, shank and tibia bone characteristics were not affected by ascorbic acid (p>0.05).

• Journal of the Korean Institute of Rural Architecture
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• v.19 no.1
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• pp.1-9
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• 2017

The purpose of this study is to clarify the actual condition of the multicultural family support center in Gyeongnam area in order to provide more faithful services for the multicultural family members. As a research method, the social characteristics of multicultural families were examined through literature review, and the installation and operation standard of the support center was reviewed. In addition, 15 multicultural family support centers set up and operated in Gyeongnam area were identified and the characteristics of the plan composition of the detailed case facilities were identified. As a result, the characteristics of multicultural family support center area size, composition type, and operation type were revealed. Through analysis of the spatial areas of the regional support centers of cities and counties, it was revealed that 42.1% of the education area, 40.7% of the administrative area, 12.0% of the consultation area and 5.2% of the exchange area were analyzed. In addition, when the dedicated area of the multicultural family support center is a small-scale facility, it has been found that the space for administration, counseling, and education is secured.

• Journal of the Semiconductor & Display Technology
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• v.4 no.4 s.13
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• pp.1-4
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• 2005

The chemical composition and uniaxial compressive stress are varied to observe their effect on the current-voltage characteristics of ZnO based ceramics. The variation of chemical composition produces two kinds of ceramics showing ohmic and nonohmic current-voltage characteristics. The current at a fixed voltage increased with the increase of the compressive stress for both ohmic and nonohmic ceramics. Ceramics showing nonohmic behavior exhibit better reversible return of current-voltage curve when the applied compressive stress is removed from the ceramics than those showing ohmic behavior do. We found an appropriate chemical composition showing linear relation between current and stress at a fixed voltage. The ceramic materials with an appropriate chemical composition can be used as a potential sensing material in pressure sensors.