• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.86.2-86.2
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• 2010

In order to improve polymer electrolyte membrane fuel cell (PEMFC) durability, the durability of membrane electrode assemblies (MEA), in which the electrochemical reactions actually occur, is one of the vital issues. Many articles have dealt with catalyst layer degradation of the durability-related factors on MEAs in relation to loss of catalyst surface area caused by agglomeration, dissolution, migration, formation of metal complexes and oxides, and/or instability of the carbon support. Degradation of catalyst layer during long-term operation includes cracking or delamination of the layer which result either from change in the catalyst microstructure or loss of electronic or ionic contact with the active surface, can result in apparent activity loss in the catalyst layer. Membrane degradation of the durability-related factors on MEAs can be caused by mechanical or thermal stress resulting in formation of pinholes and tears and/or by chemical attack of hydrogen peroxide radicals formed during the electrochemical reactions. All of these effects, the mechanical damage of membrane and degradation of catalyst layers are more facilitated by uneven stress or improper MEA fabrication process. In order to improve the PEMFC durability, therefore, it is most important to minimize the uneven stress or improper MEA fabrication process in the course of the fabrication of MEA. We analyzed the effects of the MEA fabrication condition on the PEMFC durability with MEA produced using CCM (catalyst coated membrane) method. This paper also investigated the effects of MEA fabrication condition on the PEMFC durability by adding additional treatment process, hot pressing and pressing, on the MEA produced using CCM method.

• 한국재료학회지
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• 제22권8호
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• pp.426-432
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• 2012

This study involves using nickel chloride solution as a raw material to produce nano-sized nickel oxide powder with average particle size below 50 nm by the spray pyrolysis reaction. The influence of the inflow speed of raw material solution on the properties of the produced powder is examined. When the inflow speed of the raw material solution is at 2 ml/min., the average particle size of the powder is 15~25 nm and the particle size distribution is relatively uniform. When the inflow speed of the solution increases to 10 ml/min., the average particle size of the powder increases to about 25 nm and the particle size distribution becomes much more uneven. When the inflow speed of the solution increases to 20 ml/min., the average particle size of the powder increases in comparison to the case in which the inflow speed of the solution was 10 ml/min. However, the particle size distribution is very uneven, showing various particle size distributions ranging from 10 nm to 70 nm. When the inflow speed of solution increases to 50 ml/min., the average particle size of the powder decreases in comparison to the case in which the inflow speed was 20 ml/min., and the particle size distribution shows more evenness. As the inflow speed of the solution increases from 2 ml/min. to 20 ml/min., the XRD peak intensities gradually increase, while the specific surface area decreases. When the inflow speed of solution increases to 50 ml/min., the XRD peak intensities rather decrease, while the specific surface area increases.

• 대한인간공학회지
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• 제25권4호
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• pp.115-119
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• 2006

To investigate the effects of independent suspension technology(IST) of hiking boot on the stability and load of foot, eight participants performed medial and lateral drop landing from 33.4cm height and 85cm distance to uneven surface while wearing normal & IST hiking boots. For the stability of foot during the drop landing, the balance angle & suspension angle and rearfoot angle was analyzed using high-speed video analysis. Also kinetic analysis using the force plate and insole pressure measurement was conducted to analyze vertical & breaking ground reaction force and pressure distribution. Not only the balance angle & suspension angle but also rearfoot angle was improved with IST boots for lateral drop landing. These results indicate the IST boots may have the suspension function which keeps the foot to be stable during landing. However the IST boots did not show any effect for medial landing. This might be related to the hardness of medial part of outsole. Therefore the softer outsole of medial part could be recommended. Furthermore the impact force & breaking force and insole pressure were reduced with IST boot. These results means that IST boot has not only cushioning effect but also good grip effect. Therefore the hiking boots applied the independent suspension function may help to reduce fatigue and prevent injury such as ankle sprain in hiking on uneven surface.

• 생물환경조절학회지
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• 제19권2호
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• pp.93-96
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• 2010

Breaker 단계 토마토의 저온장해 증상은 착색불량과 호흡률 증가 등으로 알려져 있다. 본 실험은 이러한 저온 장해 증상과 맞물려 나타나는 이산화탄소 발생 증가와의 관계를 분석하고, 나아가 저장 중 원예산물 저온장해의 판단기준으로 이용할 수 있는 기초 자료를 만들고자 실시하였다. Breaker 단계로 선별된 토마토는 $2^{\circ}C$에서 1차로 0, 3, 6, 9일간 2차로 0, 1, 2, 3, 10일간 저장 후 상온으로 옮겨 3, 6, 9, 12, 24, 36, 48시간마다 호흡률을 측정하였다. 저온장해로 인한 토마토 과실의 호흡률은 1일 저장 처리구부터 증가하였으며 저온 저장기간이 길어질수록 발생량 증가폭도 커졌다. Breaker 단계 토마토의 과피색은 $a^*$ 값으로 나타내었는데 각 기간별로 저온저장 후 상온으로 옮겨 10일째에 측정하였는데 Breaker 단계 토마토는 2일 저장 처리구부터 $a^*$ 값이 증가가 둔화되면서 착색불량이 나타났다. 저온저장 기간에 증가함에 따라 증가한 호흡률과 반대로 감소한 $a^*$ 값의 상관계수(r)는 0.9716로 1%의 유의성을 나타내었다 이상의 결과로 보아 Breaker 단계 토마토의 경우 저온 저장후 상온으로 옮긴 직후 이산화탄소 발생 양상으로 저온장해를 미리 진단할 수 있었으며, 그 발생량 증가폭으로 저온장해 정도도 파악할 수 있을 것으로 생각된다.

• 열처리공학회지
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• 제18권2호
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• pp.105-111
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• 2005

In sheet metal forming, drawbeads are often used to control uneven material flow, which may cause defects such as wrinkles, fractures, surface distortion and springback. Appropriate setting and adjusting of the drawbead force is one of the most important parameters in sheet forming process control. Therefore in this study, drawbead test was performed at various bead surface treatment conditions to clarify the frictional characteristics between sheet and drawbead. Furthermore, the differences in drawing force between circular and rectangular shape beads have also been measured to estimate the effectiveness of bead shape on the material flow control. The results show that drawing and friction characteristic were strongly influenced by surface treatments of bead and bead shapes.

• 한국염색가공학회지
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• 제16권5호
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• pp.28-34
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• 2004

The polarizing film application exploits the unique physicochemical properties between PVA(Poly vinyl alcohol) film and CTA(Cellulose triacetate) film. However, hardly any research was aimed at improving the adhesion characteristics of the CTA film by radio frequency(RF) plasma treatment at argon(Ar) gaseous state. In this report, we deal with surface treatment technology for protective CTA film developed specifically for high adhesion applications. After Ar plasma, surface of the films is analyzed by atomic force microscopy(AFM), roughness parameter and peel strength. Furthermore, the wetting properties of the CTA film were studied by contact angle analysis. Results obtained for CTA films treated with a glow discharge showed that this technique is sensitive to newly created physical functions. The roughness and peel strength value increased with an increase in treatment time for initial treatment, but showed decreasing trend for continuous treatment time. The result of contact angle measurement refer that the hydrophilicity of surface was increased. AFM studies indicated that no considerable change of surface morphology occurred up to 3 minutes of treatment time, but a considerable uneven of surface structure resulted from treating time after 5 minutes.

• 한국의류산업학회지
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• 제10권1호
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• pp.101-105
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• 2008

This study was concerned with the influence of reaction conditions on the surface friction properties of Syrene-Butadiene Rubber(SBR) sheet when it was chlorinated by chemical treatment method using the sodium hypochlorite and sulfuric acid. The results of this study were as follows. SEM photographs of chlorinated SBR surface showed uneven etching caused by the chlorination. In the FTIR spectra, the intensity of C=C peak of SBR was decreased with increasing the concentration of sodium hypochlorite. Otherwise there was no trace of C=C peak in spectrum of SBR treated with 5 wt% NaOCl with pH 0.1 for 90 seconds. EDX spectra showed that relative content of chlorine of SBR was increased with increasing the amount of sodium hypochlorite, and also affected with pH condition of acid solution. Friction angle and friction coefficient of SBR were influenced with concentration of sodium hypochlorite, but were not with pH condition of acid solution.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권7호
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• pp.346-350
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• 2001

We present a surface-micromachined polysilicon capacitive accelerometer using unevenly distributed comb electrodes. The unique features of the accelerometer include a perforated proof-mass and the inner and outer comb electrodes with uneven electrode gaps. The perforated proof-mass reduces stiction between the structure and the substrate and the unevenly distributed electrodes shorten the electrode length required for a given sensitivity. The polysilicon accelerometer has been fabricated by the conventional 6-mask surface-micromachining process and showes a sensitivity of 1.03mV/g with a hybrid detection circuitry.

• 한국염색가공학회지
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• 제15권5호
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• pp.327-332
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• 2003

In this study, the polyurethane microcapsules for non-aqueous dyeing containing iron oxide and disperse dyes were prepared by in-situ polymerization method using hexamethylene diisocyanate(HDI) with ethylene glycol(EG). And the size, shape, and particle size distribution of microcapsules prepared were investigated. The size and shape of microcapsule were observed by optical microscope and scanning elecron microscope. The particle size distribution was analyzed by particle size analyzer. The microcapsule size and its distribution were largely effected by the existance of surface active agent in the system. When a surfactant did not exist in the system, the size distribution of microcapsules prepared was much uneven. By adding a surfactant, this phenomenon was disappeared. And the size of microcapsule was also effeced by the hydrophobicity of core material(disperse dye). It was considered due to the difference of dispersity of core materials. And the size of microcapsule prepared was inversely proportional to the stirring speed.

• Transactions on Electrical and Electronic Materials
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• 제8권2호
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• pp.97-102
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• 2007

The charging/discharging characteristics of electric double layer capacitors (EDLCs) for an electric power storage device application were investigated. The specific area of the carbonaceous electrode surface by the BET method was in the range of $1800{\sim}2000\;m^2/g$. The charge distributions during charging and discharging were measured by means of a pulsed-electro-acoustic (PEA) method, and the voltage characteristics of EDLCs connected to solar cells were evaluated. The results showed that the distributions of positive and negative charges were spatially uneven, which was due to the mobility of the positive and negative charges in the carbonaceous electrode surface of the EDLCs. The charge accumulation region concentrated on central part of the carbonaceous electrode and the required times for charging and discharging were almost same.