• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.373-373
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• 2011

$Cu(In,Ga)Se_2$(CIGS) 박막 태양전지는 Chalcopyrite계 박막 태양전지로 Cu, In, Ga, Se 각 원소의 조성을 적절히 조절하여 박막을 성장시킨다. 성장시킨 CIGS 박막은 광흡수계수가 105cm-1로 다른 물질 보다 뛰어나고 직접 천이형 반도체로서 얇은 두께로도 고효율의 박막 제작이 가능하다. 얇은 두께로도 충분히 빛의 흡수가 가능하지만, cell 표면 반사에 의한 광 손실은 cell 효율을 떨어뜨리게 된다. 본 연구에서는 CIGS 박막 태양전지의 광 흡수 향상을 위해 굴절률이 1.86인 ITO 위에 ITO보다 굴절률이 작은 $MgF_2$ (n=1.377) [1]를 80, 100, 120, 140 nm로 증착하여 $MgF_2$/Al/Ni/ITO/i-ZnO/CdS/CIGS/Mo/SLG 시료를 제작하고, optical reflectance, Quantum Efficiency를 이용하여 분석하였다. optical reflectance 분석 결과, $MgF_2$ AR coating을 한 경우, 두께가 두꺼워짐에 따라 광 반사도가 감소하는 경향을 보였다. 또한 AR coating 두께가 커짐에 따라 fluctuation이 점점 커지며, 파형이 장파장 쪽으로 shift하는 것을 관찰 할 수 있었다. Quantum efficiency (QE)를 분석한 결과 $MgF_2$ AR coating 할 경우, 측정된 대부분의 파장에서 QE가 향상되는 것을 확인할 수 있었다. 하지만 AR coating 두께에 따른 변화는 뚜렷한 차이를 보이지 않았다. AR coating 결과, JSC가 증가하여 efficiency가 향상되는 것을 확인 할 수 있다. 그러나 $MgF_2$ AR coating 80~140 nm 범위에서 cell 효율 변화의 뚜렷한 차이는 관찰할 수 없었다.

• Proceedings of the Korean Reliability Society Conference
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• 2002.06a
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• pp.117-120
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• 2002

The addition of minor alloying elements such as Al, Si, Mg, Cr, Zr, and Sn changed the microstructure and the oxidation characteristics of the Cu-40%Zn alloys. Detailed microstructure, scale morphology and the oxidation mechanism were described.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1032-1032
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• 2006

• Journal of Environmental Science International
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• v.27 no.7
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• pp.543-554
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• 2018

From November 2013 to December 2016, ambient fine particulate matter ($PM_{2.5}$) was sampled in the downtown area of Jeju City, South Korea, which has seen rapid urbanization. The atmospheric concentrations of elements were measured in the $PM_{2.5}$ samples. This study focused on Cd, Cr, Cu, Mn, Ni, Pb, As, Sb, Sn, V, and Zn. The concentrations of Al, Na, K, Fe, Ca, Mg, Sr, and La were also obtained for reference. The objectives of this study were to examine the contributions of these elements to $PM_{2.5}$ concentrations in downtown Jeju City, and to investigate the inter-element relationships and the elemental sources by using enrichment factors and principal components analysis (PCA). A composition analysis showed that the 19 elements constituted 6.65 % of the $PM_{2.5}$ mass, and Na, K, Al, Fe, Ca, Mg, and Zn constituted 98 % of the total ion mass. Seasonal trend analysis for the sampling period indicated that the concentrations of the elements increased from November to April. However, no substantial seasonal variations were found in the concentrations of the elements. The composition ratios of some elements (Cu/Zn, Cu/Cd, Cu/Pb, V/Ni, and V/La) were found to be out of range when compared to the literature from other urban areas. The ratios between the elements and the PCA results showed that local contaminant sources in Jeju City rarely influence the composition of $PM_{2.5}$. This suggests that the major sources of $PM_{2.5}$ in Jeju City may include long-range transport of fine particulate matter produced in other areas.

• Journal of the Korean Society of Groundwater Environment
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• v.5 no.3
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• pp.148-154
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• 1998

Gubong gold-mine, previously one of the largest gold mines in Korea, is located at the mid-west of the South Korea. In the areas nearby the mine, the shallow groundwater was the major source for domestic and farming water-supply. Soil contamination by Cd, Cu, Pb and Zn was previously known in this area. This study is objected to identify quality of the shallow groundwater, possibly affected by the mine tailings. Samples were collected from a nearby stream, shallow groundwater and seepage from the tailings. Chemical analysis for the water quality includes major cations such as Na, K, Ca, and Mg, anions as F, Cl, NO$_3$, SO$_4$, HCO$_3$, and trace elements as Al, Cr, Mn, Fe, Ni, Cu, Zn, Cd, Pb, Se, As, Hg. Water types could be drawn into four groups from the plots of Piper, Stiff diagrams and cluster analysis. SAR-Conductivity plot indicates the water does not pose either alkalinity or salinity hazards for irrigation. Major contaminant in groundwater appeared to be arsenic, released from arsenopyrites in tailings by oxidation. Dredging of buried railing materials could stimulate the release of arsenic from the sediments to the groundwater.

• Journal of environmental and Sanitary engineering
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• v.9 no.2
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• pp.8-23
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• 1994

During the period from Mar., 1991 to Feb., 1992 66 tSP samples were collected by Hi volume air sampler at 1 sampling site in Seoul and the amount of concentration of 21 components(SO$_{4}$$^{2-}$, NO$_{3}$$^{-}$, NH$_{4}$$^{+}$, Cl$^{-}$, Al, Ba, Ca, Cd, Cr, Cu, Fe, It Mg, Mn, Na, Ni, Pt Si, Ti, Zn, Zr ) were measured. And monthly and seasonal variation were surveyed and the principal component analysis( PCA ) were carried out with respect to these amount of pollutants, minimum of visibility and radiation on a horizontal surface. The total amount of soluble ion in water was high in order o(SO$_{4}$$^{2-}$> NO$_{3}$$^{-}$> N%'>Cl$^{-}$ and metal ion was high in order of Na> Ca>Si> Fe> Al> K> Mg> Zn> Pb> Cu>Ti> Mn > Ba> Cr> Zr> Ni> Cd. There was Seasonal variation in concentration for SO$_{4}$$^{2-}$, NH$_{4}$$^{+}$, Cl$^{-}$, Na, Al, Ca, Bt Mg, Fe and Si. It was assumed that the components of the highest concentration on April were depend on yellow sand and the frequency of wind velocity and direction. As the results of PCA, the amount of pollution components was able to characterized with two principal components(Z$_{1}$, Z$_{2}$ ). The first principal components Z$_{1}$ was considered to be a factor indicating the pollutants originated from natural generation and The second principal components Z$_{2}$ was considered to be a factor indicating the pollutants originated from human work. The monthly concentration of pollutants in ISP, minimum of visibility and radiation on a horizontal surface was possible to evaluate by the use of these two principal components Z$_{1}$ and Z$_{2}$ .

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.10
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• pp.96-100
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• 1990

The cordierite ($2MgO,2Al_{2}O_{3},5SiO_{2}$) is of great interest for packaging substrates of multilayer IC. The Cu layer was fabricated on the cordierite substrate by the screen printing method and the adhesion properties of the interfaces at the different cosintering conditions were studied. When cosinted in the $Ar+H_{2}O$atmosphere good adhesion was obtained and the heating was found out to be an important factor for the adhesion.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.10
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• pp.1686-1694
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• 2003

The foam-filled tube beams can be used for the front rail and firewall structures to absorb impact energy during frontal or side collision of vehicles. In the case of side collision where bending is involved in the crushing mechanism, the foam filler would be effective in maintaining progressive crushing of the thin-walled structures so that much impact energy could be absorbed. In this study, bending behaviors of the closed-cell-aluminum-alloy-foam-filled stainless steel tube were investigated. The various foam-filled specimens including piecewise fillers were prepared and tested. The aluminum-alloy-foam filling offered the significant increase of bending resistance. Their suppression of the inward fold formation at the compression flange as well as the multiple propagating folds led to the increase of load carrying capacity of specimens. Moreover, the piecewise foams would provide the easier way to fill the thin-walled shell structures without the drawback of strength.

• Analytical Science and Technology
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• v.15 no.4
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• pp.321-328
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• 2002

From May 1999 to July 2000, concentration of 17 metals (Al, Ba, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, Pb, Sr, V, Zn), 4 ions (${NH_4}^+$, $Cl^-$, ${NO_3}^-$, ${SO_4}^{2-}$) and pH in rainwater were investigated. The volume-weighted mean concentrations (VWM) of ${NO_3}^-$ and ${SO_4}^{2-}$ were 16.0 and $17.0{\mu}mol\;L^{-1}$. The average pH was 4.53, which ranged from 3.83 to 6.06. The characteristic variations of these species were investigated in terms of the source of these species by principal component analysis (PCA) and interelement correlation coefficients. The elements were classified into three categories: anthropogenic source (Cd, Cu, Fe, Ni, Pb, V, Zn, ${NH_4}^+$, ${NO_3}^-$, ${SO_4}^{2-}$ and $H^+$), soil and crust dust (Al, Ba, Ca, Fe, Mn) and sea salts (Mg, Na, $Cl^-$). In addition, we compared the concentrations in rainwater, which were taken on the same day in three sites (Higashi-Hiroshima, an urban-facing area and a mountain-facing area of Mt. Gokurakuji) in order to examine the regional effect against the concentrations in them. At the urban-facing area of Mt. Gokurakuji, the concentrations of chemical compositions were higher than other areas.

• Journal of Environmental Science International
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• v.9 no.4
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• pp.325-330
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• 2000

The hydroxyapatite (HAp) for the present study was prepared by precipitation method in semiconductor fabrication and the crystallized at ambient to 95$0^{\circ}C$ for 30min in electric furnace. The ion-exchange characteristics of HAp for various heavy metal ions such as $Cd^{2+}, Cu^{2+}, Mn^{2+}, Zn^{2+}, Fe^{2+}, Pb^{2+}, Al^{3+}, and Cr^{6+}$ in aqueous solution has been investigated. The removal ratio of various metal ions for HAp were investigated with regard to reaction time, concentration of standard solution, amount of HAp and pH of solution. The order of the ions exchanged amount was as follws: $Pb^{2+}, Fe^{3+}>Cu^{2+}>Zn^{2+}>Al^{3+}>Cd^{2+}>Mn^{2+}>Cr^{6+}. The Pb^{2+}$ ion was readily removed by the Hap, even in the strongly acidic region. The maximum amount of the ion-exchange equilibrium for $Pb^{2+}$ ion was about 45 mg/gram of HAp. The HAp would seem to be possible agent for the removal of heavy metal ions in waste water by recycling of waste sludge in semiconductor fabrication.