• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.61.1-61.1
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• 2010

$CuIn_{1-x}-GaxSe_2$ based materials with direct bandgap and high absorption coefficient are promising materials for high efficiency hetero-junction solar cells. CIGS champion cell efficiency(19.9%, AM1.5G) is very close to polycrystalline silicon(20.3%, AM1.5G). A reduction in the price of CIGS module is required for competing with well matured silicon technology. Price reduction can be achieved by decreasing the manufacturing cost and by increasing module efficiency. Manufacturing cost is mostly dominated by capital cost. Device properties of CIGS are strongly dependent on doping, defect chemistry and structure which in turn are dependent on growth conditions. The complex chemistry of CIGS is not fully understood to optimize and scale processes. Control of the absorber grain size, structural quality, texture, composition profile in the growth direction is important to achieving reliable device performance. In the present work, CIS nanoparticles were prepared by a simple wet chemical synthesis method and their structural and optical properties were investigated. XRD patterns of as-grown nanopowders indicate CIS(Cubic), $CuSe_2$(orthorhombic) and excess selenium. Further, as-grown and annealed nanopowders were characterized by HRTEM and ICP-OES. Grain growth of the nanopowders was followed as a function of temperature using HT-XRD with overpressure of selenium. It was found that significant grain growth occurred between $300-400^{\circ}C$ accompanied by formation of ${\beta}-Cu_{2-x}Se$ at high temperature($500^{\circ}C$) consistent with Cu-Se phase diagram. The result suggests that grain growth follows VLS mechanism which would be very useful for low temperature, high quality and economic processing of CIGS based solar cells.

• 한국재료학회지
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• 제26권10호
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• pp.513-520
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• 2016

The effect of NaOH concentration on the properties of electrolytic plasma processing (EPP) coating formed on AZ61A Mg alloy is studied. Various types of EPP were employed on magnesium alloy AZ61A in a silicate bath with different concentrations of NaOH additive. Analysis of the composition and structure of the coating layers was carried out using an X-ray diffractometer (XRD) and a scanning electron microscope (SEM). The results showed that the oxide coating layer mainly consisted of MgO and $Mg_2SiO_4$; its porosity and thickness were highly dependent on the NaOH concentration. The Vickers hardness was over 900 HV for all the coatings. The oxide layer with 3 g/l of NaOH concentration exhibited the highest hardness value (1220 HV) and the lowest wear rate. Potentiodynamic testing of the 3 g/l NaOH concentration showed that this concentration had the highest corrosion resistance value of $2.04{\times}10^5{\Omega}cm^2$; however, the corrosion current density value of $5.80{\times}10^{-7}A/cm^2$ was the lowest such value.

• Journal of Magnetics
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• 제13권1호
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• pp.23-29
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• 2008

The magnetic and other physical characteristics of $Mn_xSi_{1-x}Te$ have been investigated by electron magnetic resonance (EMR), X-ray diffraction (XRD) and other experiments. $Mn_xSi_{1-x}Te$ is found to have corundum structure for manganese contents up to 10% and also to be ferromagnetic for temperatures below 80 K. While ferromagnetic resonance signal coexists with the usual paramagnetic resonance signal, invariance of the g-factor inferred from the electron paramagnetic resonance signals throughout all temperature ranges clearly confirms that the manganese ions are in the electronic 3d5 state. The temperature dependence of EMR line-width is the same as other diluted magnetic semiconductors. From the EMR signals relaxation times $T_2$ and $T_1$ of $Mn_xSi_{1-x}Te$ compounds are estimated to be about $4.4{\times}10^{-10}s$ and $9.3{\times}10^{-8}s$ respectively and are found to vary slightly with temperature or composition change. Exchange narrowing of the EMR line-width becomes dominant for the sample in which the substitution ratio, x = 30%. For one sample, in which x = 0.5%, spin glass-like behavior is indicated by EMR signals for temperatures lower than 60 K. This behavior may authentic for samples within a certain range of x.

• Nuclear Engineering and Technology
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• 제51권3호
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• pp.755-760
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• 2019

Compound samples based on the mineral-like magnesium potassium phosphate matrix $MgKPO_4{\times}6H_2O$ were synthesized by solidification of high level waste surrogate. Phase composition and structure of synthesized samples were studied by XRD and SEM methods. Compressive strength of the compounds is $12{\pm}3MPa$. Coefficient of thermal expansion of the samples in the range $250-550^{\circ}C$ is $(11.6{\pm}0.3){\times}10^{-6}1/^{\circ}C$, and coefficient of thermal conductivity in the range $20-500^{\circ}C$ is $0.5W/(m{\times}K)$. Differential leaching rate of elements from the compound, $g/(cm^2{\times}day)$: $Mg-6.7{\times}10^{-6}$, $K-3.0{\times}10^{-4}$, $P-1.2{\times}10^{-4}$, $^{137}Cs-4.6{\times}10^{-7}$; $^{90}Sr-9.6{\times}10^{-7}$; $^{239}Pu-3.7{\times}10^{-9}$, $^{241}Am-9.6{\times}10^{-10}$. Leaching mechanism of radionuclides from the samples at the first 1-2 weeks of the leaching test is determined by dissolution ($^{137}Cs$), wash off ($^{90}Sr$) or diffusion ($^{239}Pu$ and $^{241}Am$) from the compound surface, and when the tests continue to 90-91 days - by surface layer depletion of compound. Since the composition and physico-chemical properties of the compound after irradiation with an electron beam (absorbed dose of 1 MGy) are constant the radiation resistance of compound was established.

• 한국식품영양과학회지
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• 제19권1호
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• pp.1-12
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• 1990

To investigate effects of ethanol and dietary fat on growth and bichemical indices of liver tissue and blood in rats 40 male rats of Sprague-Dawley wtrain weighing about 160g were divided into 5 groups (low-fat diet group ethanol-administered low-fat diet group high-fat diet group ethanol-administered high-fat diet group and commercial diet group) and fed expe-rimental diets for 8 weeks. Ethanol-administered groups consumed ethanol corresponding to 22 cal% which was considered as moderate drinking. Neither the ethanol intake nor the dietary fat level affected calorie intake. Nonetheless the low-fat diet group with ethanol had the lowest growth rate and 2-fold increase in the concentration of plasma triglyceride. There was no effect of ethanol and dietary fat level on contents of protein lipid and lipid composition of liver tissue. The level of lipid peroxide of liver tissue tended to be increased by ethanol intake but the increase was statistically insignificatnt. The low-fat ethanol group had lowered hepatic mitochondrial respiration rate and deformed structure of mitochondria of hepatocytes.

• 한국표면공학회지
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• 제48권2호
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• pp.56-61
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• 2015

In this study, the wear performance of manganese phosphate coating on SM45C with addition agent of Tartaric acid and Citric acid were investigated. The Surface morphology of manganese phosphate coating was examined by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray spectroscopy (EDS). It is found that Mn, P, Fe, O and C. The crystal structure and thee composition was analysis and determined by using XRD. The XRD results indicated that manganese phosphate coatings are mainly composed of $(Mn,Fe)_5H_2(PO_4)_44H_2O$ and consists of a lot of close packed lump crystalline. Based on the time dependence of morphology and the weight of manganese phosphate coating, it shows that the phosphating process mainly includes three stages: corrosion of the substrate, creation and growth of phosphate crystal nucleus and thickening of manganese phosphate coating. The wear tests were performed in a ball on disc apparatus as per ASTM G-99 Standard. It was showed that the initial wear was quite high followed by low sludge.

• 한국환경복원기술학회지
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• 제13권5호
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• pp.146-153
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• 2010

Urban development typically results in many species being confined to small, isolated and degraded habitat fragments. Fragment size and isolation underpin many studies of modified landscape to prevent biodiversity loss. However, habitat characteristics such as vegetation structure and edge effects are less frequently incorporated in planning. The relative influence of biogeographic (e.g. size, isolation) and vegetation parameters on assemblages is poorly understood, but critical for conservation management. In this study, the relative importance of biogeographic and vegetation parameters in explaining the diversity of forest-interior dwelling birds in forest fragments in Chungcheong Province Area. Fragment size and vegetation characteristics were consistently important predictors of bird diversity. Forestinterior bird richness was influenced by fragment size (0.437), wood age (0.332), wood diameter (0.068), and patch shape (-0.079). To preserve bird diversity of Chungcheong Province Area, it is important to consider differing responses of bird diversity to landscape change, move beyond a focus primarily on spatial attributes (size, isolation) to recognize that landscape change also has profound effects on habitat composition and quality. The result is very useful for long-term aspect of biodiversity conservation plan in regional scale.

• 한국세라믹학회지
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• 제36권5호
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• pp.504-512
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• 1999

The high-quality carbon nanofibers were prepared by chemical vapor deposition of gas mixtures of CO-H2 and C3H8-H2 over Fe-Cu and Ni-Cu bimetallic catalysts. The yield and structure of carbon nanofiber produced were altered by the change of catalyst composition and reaction temperature. The high yields were obtained around 500$^{\circ}C$ with e-Cu catalyst and around 700-750$^{\circ}C$ with Ni-Cu catalyst and the relatively higher yields were obtained with the bimetallic catalyst containing 50-90% of Ni and Fe respectively in comparison with the pure metals. The carbon nanofibers produced over the Fe-Cu catalyst at around 500$^{\circ}C$ with the maximum yields had the highest surface ares of 160-200 m2/g around 650$^{\circ}C$ which was slightly lower than the temperature for maximum yields. In order to examine the characteristics of carbon nanofibers as catalyst support Ni and Co metals were supporte on the carbon nanofibers and CO hydrogenation reaction was performed with the catalysts. The particle size distribution of Ni and Co supported over the carbon nanofibers were 6-15 nm and the CO hydrogenation reaction rate with the carbon-nanofiber supported catalysts was much higher than that over the other supports.

• 한국광물학회지
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• 제16권1호
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• pp.19-31
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• 2003

보석으로 사용되고 있는 파이로프-알만딘 계열의 보석을 대상으로 하여 이들의 화학성분, 결정구조, 굴절율, 비중, 색, 광택 등의 광물학적 성질을 알아보았다. 또한 위 고용체의 광물학적 성질이 화학성분의 치환 정도에 따라 점이적인 변화 양상이 나타나는지에 대해서도 연구하였고, 발색소에 대한 연구를 실시하였다. 특별히 보석업계에서 관행적으로 분류 기준으로 삼아 온 굴절율과 비중 값이 광물학적으로 오류가 없는 것인지를 검증하는 것 등도 주요 연구목적에 포함되었다 적색석류석 시료 중 화학성분에 따른 분류기준에 의하면 17개가 파이로프이며, 6개가 알만딘임을 알 수있다. 파이로프의 굴절율은 1.77까지이며, 알만딘은 그 이상임을 알 수 있으며, 비중은 파이로프인 경우 3.88까지의 범위이며, 파이로프는 적어도 4.11이상임을 알 수 있었다. 따라서 보석업계에서 파이로프와 알만딘을 구분하여 온 굴절율 기준(R.I. 1.75)은 오류이며, 비중값 기준(S.G. 3.88)은 무난한 것으로 밝혀졌다. 단결정 X-선회절분석 결과에 따르면, 파이로프-알만딘 석류석이 모두 등축정계의 Ia3d 공간군에 속하며, 화학성분의 변화에 따른 단위포의 크기는 변화를 느낄 정도의 차이는 없었다. 또한 굴절율과 비중은 파이로프-알만딘 고용체에 있어 특히 FeO 함량에 따라 일정한 변화양상을 나타내는데, FeO의 함량이 증가할수록 굴절율과 비중이 증가함을 알 수 있다. 화학분석 자료에 의하면, 적색 및 보라색은 $Fe^{＋2}$, 황색은 $Mn^{＋2}$ 함량에 따라 크게 좌우됨을 알 수 있다. 적색 석류석내에 들어있는 결정 내포물은 주로 저어콘과 금홍석이었다.

• Applied Biological Chemistry
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• 제48권4호
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• pp.364-369
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• 2005

Trichoderma harzianum이 생산하는 ${\beta}-mannanase$의 최적 사면배지조성은 2.0% malt extract, 2.0% glucose, 0.1% peptone, 2.0% agar로, 효소생산 배지조성은 3.0% cellulose, 3.0% C.S.L, 1% $KH_2PO_4$, 0.2% $(NH_4){_2}SO_4$로 결정되어 $28^{\circ}C$, 130 rpm, 진탕배양법으로 조효소액을 생산하였다. ${\beta}-mannanase$의 최적 pH와 최적온도는 pH 4.5, $60^{\circ}C$에서 최대 상대활성을 나타내었다. Locust bean gum에 대한 효소적 가수분해 pattern을 TLC에 의해 검토한 결과 반응초기부터 반응말기까지 주요 생성물은 단당류, 중합도 4와 7의 올리고당으로 확인되었다. 중합도별 올리고당을 조제하기 위하여 activated carbon column chromatography에 250 ml/hr유속으로 tube당 20 ml씩 ethanol $0{\sim}50%$의 gradient법으로 분리 회수하였고, 분리된 각각의 올리고당 중 중합도4는 TLC $R_f$ value상으로 ${\beta}-1,4-mannotetraose$로, 중합도 7은 Methylation method에 의해 M-M-M-M-M 구조로 //G-G 동정되었다. (G-와 M-은 각각 ${\alpha}-1,6-D-galactosidic,\;{\beta}-1,4-mannosidic$ 결합을 나타냄). Bifidobacterium longum에 대한 생육활성을 기존의 MRS media와 탄소원으로 중합도 4와 7의 올리고당으로 대체하였을때 3.4배, 4.3배의 생육활성이 증가하였고, Bifidobacterium bifidum에 대해서는 1.2배, 1.1배의 낮은 활성을 나타내었다.