• International Journal of Concrete Structures and Materials
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• 제11권1호
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• pp.29-43
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• 2017

This study investigates the blast resistance of fiber-reinforced cementitious composite (FRCC) panels, with fiber volume fractions of 2%, subjected to contact explosions using an emulsion explosive. A number of FRCC panels with five different fiber mixtures (i.e., micro polyvinyl alcohol fiber, micro polyethylene fiber, macro hooked-end steel fiber, micro polyvinyl alcohol fiber with macro hooked-end steel fiber, and micro polyethylene fiber with macro hooked-end steel fiber) were fabricated and tested. In addition, the blast resistance of plain panels (i.e., non-fiber-reinforced high strength concrete, and non-fiber-reinforced cementitious composites) were examined for comparison with those of the FRCC panels. The resistance of the panels to spall failure improved with the addition of micro synthetic fibers and/or macro hooked-end steel fibers as compared to those of the plain panels. The fracture energy of the FRCC panels was significantly higher than that of the plain panels, which reduced the local damage experienced by the FRCCs. The cracks on the back side of the micro synthetic fiber-reinforced panel due to contact explosions were greatly controlled compared to the macro hooked-end steel fiber-reinforced panel. However, the blast resistance of the macro hooked-end steel fiber-reinforced panel was improved by hybrid with micro synthetic fibers.

• 전기학회논문지
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• 제65권6호
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• pp.1026-1031
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• 2016

Neat Epoxy, nano alumina composites, micro alumina composites and multi-nano alumina composites were prepared and experiment were performed to measure their partial discharge resistant characteristics. The partial discharge resistance obtained for the microcomposites, nanocomposites and multi-nanocomposites are compared with those of unfilled epoxy and with GDE amount for surface modifier. It was observed that compare multi-nano alumina composites to micro alumina composites, the partial discharge resistance to degradation gets improved considerably. The improvement in the degradation resistance is attributed to the interface intension between the nano alumina composites and GDE, micro alumina and epoxy neat.

• Corrosion Science and Technology
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• 제17권3호
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• pp.129-137
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• 2018

The resistance to corrosion of additive manufactured (3D printing) Ti-6Al-4V alloys was investigated using micro-electrochemical tests. In terms of corrosion resistance, the acicular martensitic ${\alpha}^{\prime}$ phase in such additive manufactured Ti-6Al-4V was the focus of attention, and its behavior was distinct from that of conventional subtractive manufactured Ti-6Al-4V. To order to identify ${\alpha}^{\prime}$ phase, XRD tests were performed and micro Vickers hardness was measured for different grains (bright and dark grains) in the additive manufactured Ti-6Al-4V alloy. Micro-electrochemical tests were performed to measure corrosion resistance of bright and dark grains in the additive manufactured Ti-6Al-4V alloy with specially designed electrochemical micro-droplet cell. Critical pitting temperature (CPT) measurement was performed to evaluate the resistance to pitting corrosion of additive manufactured Ti-6Al-4V alloys with different volumes of ${\alpha}^{\prime}$ phase and subtractive manufactured Ti-6Al-4V alloy. The dark grains of the laminated Ti-6Al-4V alloy distributed broader than the bright grains measured with low microhardness. The dark grains of the Ti-6Al-4V alloy, which was rich in martensite ${\alpha}^{\prime}$, had lower general corrosion and pitting resistance than bright grains. As the fraction of martensite ${\alpha}^{\prime}$ phase increased, the resistance to the pitting corrosion decreased.

• 신재생에너지
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• 제6권1호
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• pp.38-45
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• 2010

Abstract Under the physical stress on photovoltaic (PV) module, it will be warped according to elongation of the front glass and then micro-crack will be occurred in the thermally sealed solar cell. This micro-crack leads to drop of short circuit current of the PV module. This is because of increase of resistance component by micro-crack. Micro-crack at specific solar cell in the module lessens the durability of PV module with reduced output, hot-spot caused by solar cell output mismatch and increased resistance component. This study shows the relation between electrical characteristics and micro- cracks due to mechanical stress on PV module.

• 대한기계학회논문집B
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• 제32권10호
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• pp.776-783
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• 2008

The object of this paper is to study on the thermal performance of a micro channel water block for computer CPU cooling. The effects of liquid flow rate, micro channel width and height on the thermal performances of water block are investigated experimentally. The water block was fabricated Al and machined with a micro milling. The water block consisted of rectangular micro channels 0.5 to 0.9 mm width and 1.5 to 4.5 mm height. The experiments were conducted using deionized water, over a liquid flow rate ranging from 0.2 to 2.0 kg/min. The base temperature and thermal resistance decrease with increasing of liquid flow rate. The increase of a channel height is more effective on the thermal resistance than the decrease of a channel width. At the flow rate of 0.7 kg/min, input power of 100 W, the base temperature and thermal resistance of sample 6 is $33^{\circ}C$ and $0.13\;^{\circ}C/W$ respectively.

• 한국치위생학회지
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• 제10권5호
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• pp.947-953
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• 2010

Objectives : The purpose of this investigation was to evaluate the remineralization and acid resistance in fluoride varnish by Micro-computed tomography (micro CT). Methods : Specimens of bovine teeth enamel were embedded in resin, polished and randomly divided into 3 groups (a control group, a NaF solution group, a fluoride varnish group). Each group has 3 specimens that was standardized according to Vickers hardness number (VHN). Specimens were immersed in demineralization solution for 72 hours. The control group had no treatment, the NaF solution group was treated by a 5% NaF solution for 4 minutes, and the fluoride varnish group was treated by a fluoride varnish for one hour. All specimens were subjected to a chemical pH cycling method for 14 days. After a chemical pH cycling method, the density were measured using micro CT. Then, specimens were immersed in each demineralization solution for 72 hours. After demineralization processed, the density were measured using micro CT. Results : 1. The density was significantly higher in the fluoride varnish and 5% NaF solution group than that of the control group after 14 days cycling (p<0.05). And the density value of the fluoride varnish group was higher than that of the 5% NaF solution, with no significant difference. 2. The differences of density after acid resistance treatment were statistically significant among 3 groups(p<0.05). Conclusions : It is suggested that fluoride varnish showed the remineralizing effect and acid resistance effect on the enamel, and micro CT could be used to evaluate the change of enamel lesion.

• 한국식품저장유통학회지
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• 제15권5호
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• pp.731-735
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• 2008

본 연구는 벌꿀의 내포되어 있을 수 있는 미생물의 포자의 제균에 관한 연구로 선행연구로 일반세균, 대장균군, 살모넬라균, 포도상구균을 분석하였으며, 벌꿀 음료 제조 후 유통 중에 문제시 되어지고 있는 내열호산성균의 제균에 관한 연구결과이다. 분석을 위한 내열호산성균 실험법은 진공감압기를 이용하여 $0.45\;{\mu}m$ micro filter를 이용한 막분리 배양법을 이용하였다. 미생물 실험 결과 일반세균, 대장균군, 살모넬라균, 포도상구균은 모두 음성으로 나타났으며, 내열호산성균 제균을 위하여 식품의 일반 살균법을 적용한 결과 농도별 전해수 살균, 오존수 살균, 자외선살균, 일반 마이크로 필터 처리, 고온 가열 살균, microwave 살균 등 모든 제균 방법에서 균이 제어 되지 않는 것으로나타났다. 또한 마이크로 필터를 이용한 제균 처리에서도 일반 (nominal type) 필터를 사용하였을 경우 $44.8{\sim}64.5%$ 제균 효과를 나타낸 반면 absolute type의 필터를 사용하였을 경우 0.45, $0.8\;{\mu}m$ 마이크로 필터의 사용 시 모든 처리구에서 음성으로 나타나 제균 효과가 다른 살균법에 비해우수한 것으로 나타났다.

• 펄프종이기술
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• 제39권2호
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• pp.45-53
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• 2007

When micro flute corrugated paperboards are used for food packaging, they necessarily need to meet the requirements for the distribution, transportation, and storage of food. The requirements could vary ac-cording to the contents in the packaging boxes. Microflute corrugated packaging paperboard for hot foods such as just-made coffee and hamburger requires to have a decent resistance property against high temperature. Along with a recent trend for small-quantity-multi-item upgraded packaging, semiconductor products and consumer-electronic appliances become to be packed using the environmental friendly micro flute corrugated paperboard. In this case, the electric resistance property of the microflute corrugated paperboard becomes important. This study was carried out to investigate on the thermal conductivity and electric resistance properties of micro flute corrugated paperboard.

• 전기학회논문지
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• 제67권9호
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• pp.1189-1196
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• 2018

7 type composites (40, 45, 50, 55, 60, 65, and 70 wt.%)were prepared for the environmentally friendly GIS Spacer. Five kinds of samples were prepared for optimization of the filler content ratio (MS: MA = 1: 9, 3: 7, 5: 5, 7: 3, 9: 1) of epoxy / microsilica and microalumina. As a result of evaluation of the partial discharge resistance characteristic, surface erosion is generally slowed down as the fill amount of micro silica is increased. Also, partial discharge resistance characteristics for the development of insulating materials with optimal mixing ratios of heterologous showed a higher partial resistance of discharge and a decrease in erosion, as the filler content ratio of micro silica was larger. In the future, various researches such as electrical, mechanical, and thermal studies will be needed to develop insulating materials that can commercialize power devices in environmentally friendly insulating gas.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.918-921
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• 2000

Micro-machining, one of the non-traditional machining techniques, can achieve a wanted shape of the surface using metal dissolution with electrochemical reaction and can be applied to the metal such as high tension, heat resistance and hardened steel. The workpiece dissolves when it is positioned close to the tool electrode in electrolyte and the current is applied. Traditional machining has been used in the industries such as cutting, deburring, drilling and shaping. The aim of this work is to develop Micro-machining techniques for micro shape by establishing appropriate machining parameters of micro-machining