• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 C
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• pp.1430-1432
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• 1997

A solar cell conversion effiency was degraded by grain boundary effect in polycrystalline silicon. To reduce these effects of the grain boundaries, we investigated various influencing factors such as preferential chemical etching of grain boundaries, grid design, transparent conductive thin film, and top metallization along grain boundaries. Pretreatment in $N_2$ atmosphere and gettering by $POCl_3$ and Al were performed to obtain polycrystalline silicon of the reduced defect density. Structural, electrical, and optical properties of solar cells were characterized. Improved conversion efficiencies of solar cell were obtained by a combination of Al diffusion into grain boundaries on rear side, fine grid finger, top Yb metal grid on Cr thin film of $200{\AA}$ and buried contact metallization along grain boundaries.

• 대한전자공학회논문지
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• 제27권9호
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• pp.1402-1408
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• 1990

We studied the electrical, optical and structural properties of microcrystalline silicon thin films prepared by a new chemical vapour deposition technique, called filament assisted(FA)-CVD. The microcrystalline silicon is sucessfully deposited when the hydrogen dilution ratio exceeds 30. The Raman peak at 520 cm-1 and the X-ray diffraction peak at 27.7\ulcorner0.2\ulcornerbecome sharper with increasing hydrogen dilution ratio. We obtain high quality microcrystalline Si by FA-CVD with optical gap of \ulcorner2.2eV and hydrogen content of \ulcorner3 at %.

• 한국세라믹학회지
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• 제43권12호
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• pp.833-838
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• 2006

Graphite is suitable for high temperature structural materials because of chemical stability as well as unique crystal structure. Especially, graphite can be used as a part of a nuclear reactor due to high tolerance at the extreme conditions of high temperature and neutron irradiations. Although study of oxidation properties or behaviors of graphite are very important and essential for the life and stability of the nuclear reactor, most of studies treat this theme lightly. This work focuses on the oxidation characteristics of several grade isotropic graphite of the nuclear reactor.

• 한국결정성장학회지
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• 제22권6호
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• pp.269-273
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• 2012

Ammonia decomposition over titanium carbides were investigated using eight different samples which have been synthesized by TPR (temperature-programmed reduction) method of titanium oxide ($TiO_2$) with pure $CH_4$. The resulting materials which were synthesized using wo different heating rates and space velocity exhibited the different surface areas. These results indicated that the structural properties of these materials have been related to heating rates and space velocity employed. The titanium carbides prepared in this study proved to be active for ammonia decomposition, and the activity changed with the particle size/surface area. These showed the relationship between ammonia decomposition activity and the different active species. Compared to molybdenum carbide, the titanium carbides were one order of magnitude less active, suggesting the correlation between the activity difference and the degree of electron transfer between metals and carbon in metal carbides.

• Smart Structures and Systems
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• 제7권1호
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• pp.27-40
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• 2011

Geopolymer concrete is finding a growing number of niche applications in the field of civil engineering due to its high compressive strength and strength gain rate, retainage of structural properties in elevated temperature environments, chemical stability in highly acidic conditions and environmental benefits. Combining the above mentioned characteristics with induced electrical conductivity, could enable geopolymer cement to serve as a smart and sustainable cementitious material suitable for health monitoring of civil structures. Carbon fibers were added to fresh geopolymer and OPC (ordinary Portland cement) mixes to enhance their electrical conductivities. AC-impedance spectroscopy analysis was performed on the specimens with fiber fraction ranging from 0.008 to 0.8 with respect to the weight of cementitious binder, to measure their electrical resistivity values and to determine the maximum beneficial fiber content required to attain electrical percolation. Experimental observations suggest that CFR-geopolymer cement exhibits superior performance to CFR-OPC in terms of conducting electrical current.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.165-168
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• 2006

Carbon fiber reinforced polymer(CFRP) have superior mechanical and chemical properties in comparison with conventional materials. And post-tensioning method has been used for structural reinforcement of RC structures due to easy installation and good effect of resisting capacity of structures. But the higher cost of CFRP and the loss of prestressing force with time are considered the major problems to use it. In this study, CFRP Strips and external post tensioning for rehabilitation of old concrete structures were adapted and optimal combination of these methods is considered. A total of 17 concrete members were made and tested. The types and numbers of CFRP strips and post-tensioning types were selected as major test variables. From test results, it is shown that the concrete members that post tensioned and bonded CFRP strips has a pronounced effect on the strength and deformational behavior. This present study indicates that external temporally post tensioning can reduce the amount of CFRP strips required and the combination of temporally post tensioning and CFRP strips may meet the strength and ductility requirements of old structures.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.767-770
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• 2000

This study was investigated for searching a cause of flashover failure of polymer insulator and preparing countermeasures. Hydrophobicity, microstructure and chemical structural change of polymer weathershed were studied by polymer characterization methods. In addition, the electrical properties such as power frequency dry flashover voltage/impulse voltage tests, contamination characteristics were carried out. The hydrophobicity of polymer weathershed was decreased significantly and cracks were observed on the surface. Also, the electrical characteristics did not satisfy the KEPCO specification. The failed polymer insulators showed the more leakage current than 4 years service-aged ones. From the result, it can be concluded that the flashover failure of polymer insulator was attributed to the surface aging and severe contamination.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1365-1366
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• 2007

Cobalt oxide was composite with MWNT to attain cycle stable by chemical method. We have been considered CoOx is the ideal material for high energy density electrochemical capacitor due to pseudo capacitor reaction. In this study we found that decrease in resistance due to composite MWNT. Also CoOx/MWNT composite material have resulted larger capacitance and exhibits better electrochemical behavior. The structural feature was investigated by using SEM. The CoOx/MWNT composite is not only a promising ultracapacitor material for energy storages but also has a good possibility because of its great capacitive properties, simple preparation and low cost.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.276-279
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• 2004

CdS thin films on polymer substrates such as polycarbonate(PC) and polyethylene terephthalat(PET) have many merits such as light weight, small volume and can make the obtained devices folded, easily carried. In present work, CdS thin films on glass, PC, and PET substrates have been prepared by chemical bath deposition. The structural and optical propertied of the films depending on substrate types have been investigated.

• 한국표면공학회지
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• 제48권5호
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• pp.185-193
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• 2015

Anodization of die-casted AZ91D magnesium alloy was carried out using silicate based electrolyte solution instead of fluoride based solution to improve biocompatibility of oxidized layers. The anodic layer obtained from silicate based solution has smaller size of pore and smoother surface, resulting in lower corrosion rate in simulate body solution (SBF). Effect of enhanced structural and chemical properties in oxidized layer on biocompatibility was carefully considered.