• 한국대기환경학회지
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• 제24권5호
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• pp.594-603
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• 2008

A single particle analytical technique, named low-Z particle electron probe X-ray microanalysis, was applied to characterize four samples collected at an underground shopping area connected to Dongdeamun subway station, in January and May 2006. Based on the analysis of their chemical compositions of the samples, many distinctive particle types are identified and the major chemical species are observed to be soil-derived particles, iron-containing particles. sulfates. nitrates, and carbonaceous particles. which are encountered both in coarse and fine fractions. Carbonaceous particles exist in carbon-rich and organic. Soil derived particles such as aluminosilicates, AlSi/C, $CaCO_3\;and\;SiO_2$ are more frequently encountered in spring samples than winter samples. Nitrate- and sulfate-con taming particles are more frequently encountered in winter samples, and those nitrate- and sulfate-containing particles mostly exist in the chemical forms of $Ca(CO_3,\;NO_3),\;Ca(NO_3,\;SO_4),\;(Na,\;Mg)NO_3\;and\;(Mg,\;Na)(NO_3,\;SO_4)$. Fe-containing particles which came from nearby subway platform are in the range of about 10% relative abundances for all the samples. It is observed that nitrate- and sulfate-containing particles and carbonaceous particles are much more frequently encountered in indoor aerosol samples than in outdoor aerosols, implying that $NO_x,\;SO_x$, and VOCs at the underground shopping area were more partitioned into aerosol phase.

• Archives of Plastic Surgery
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• 제40권1호
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• pp.11-18
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• 2013

Background To minimize the inflammatory reaction and improve healing, a new modified dermal substitute composed of an atelocollagen, chondroitin-6-sulfate, and amniotic membrane (AM) was applied to full-thickness skin defects in a pig. Atelocollagen was extracted from bovine skin, and two modified dermal substitutes were generated according to the cross-linking type. Methods The AM-collagen dermal substitutes were characterized and compared with currently used dermal substitutes in a pig skin defect model. There were five experimental groups: dehydrothermal (DHT) cross-linking atelocollagen with the AM on the top (AM-DHT), DHT and chemical cross-linking atelocollagen with the AM on the top (AM-DHT/chemical), Terudermis, Integra, and AlloDerm. After $3{\times}3cm$ full-thickness skin defects on the back of a pig were created, each dermal substitutes dermal substitutes was randomly grafted on the defects. Two weeks after grafting, autologous partial-thickness skin was over-grafted on the neodermis. The take rate of the dermal substitutes, skin, and histological sections were all assessed at 1, 2, and 4 weeks postoperatively. Results More rapid healing and a higher take rate were evident in the AM-DHT and Terudermis groups. Histological examination revealed fewer inflammatory cells and more fibroblast hyperplasia in these two groups. Four weeks after surgery, the amount of newly formed collagen was significantly more appropriate in the AM-DHT group. Conclusions These observations provide supporting evidence that a newly developed amniotic-collagen dermal substitute may inhibit inflammatory reactions and promote wound healing.

• Progress in Superconductivity
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• 제8권1호
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• pp.108-112
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• 2006

We fabricated Bi-2212/$SrSO_4$ bulk superconductors by the casting process and evaluated the effects of the powder mixing method and annealing temperature on the texture, microstructure, and critical current. In the process, the Bi-2212 powders were mixed with $SrSO_4$ by hand-mixing(HM) and planetary ball milling(PBM) method and then the powder mixtures were melted at $1100^{\circ}C{\sim}1200^{\circ}C$, solidified, and annealed. We observed that the rod made by the PBM had a more homogeneous microstructure and smaller $SrSO_4$ and second phases than that of the rod made by the HM, resulting in increased $I_c$. The $I_c$ of the rod also depended on the annealing temperature and the highest $I_c$ was obtained to be 200 A when prepared by HM at $1200^{\circ}C$ and annealed at $810^{\circ}C$ which is probably due to the moderate density and 2212 texture and the smaller and less second phase compared to that at higher temperature. The possible causes of the variations of $I_c$ with the powder mixing method and annealing temperature were related to the microstructural evolution based on the SEM, EPMA, and DTA analyses.

• 한국분말재료학회지
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• 제23권2호
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• pp.136-142
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• 2016

As precursors of cathode materials for lithium ion batteries, $Ni_{1/3}Co_{1/3}Mn_{1/3}(OH)_2$ powders are prepared in a continuously stirred tank reactor via a co-precipitation reaction between aqueous metal sulfates and NaOH in the presence of $NH_4OH$ in air or nitrogen ambient. Calcination of the precursors with $Li_2CO_3$ for 8 h at $1,000^{\circ}C$ in air produces dense spherical cathode materials. The precursors and final powders are characterized by X-ray diffraction (XRD), scanning electron microscopy, particle size analysis, tap density measurement, and thermal gravimetric analysis. The precursor powders obtained in air or nitrogen ambient show XRD patterns identified as $Ni_{1/3}Co_{1/3}Mn_{1/3}(OH)_2$. Regardless of the atmosphere, the final powders exhibit the XRD patterns of $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ (NCM). The precursor powders obtained in air have larger particle size and lower tap density than those obtained in nitrogen ambient. NCM powders show similar tendencies in terms of particle size and tap density. Electrochemical characterization is performed after fabricating a coin cell using NCM as the cathode and Li metal as the anode. The NCM powders from the precursors obtained in air and those from the precursors obtained in nitrogen have similar initial charge/discharge capacities and cycle life. In conclusion, the powders co-precipitated in air can be utilized as precursor materials, replacing those synthesized in the presence of nitrogen injection, which is the usual industrial practice.

• 한국분말재료학회지
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• 제23권4호
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• pp.287-296
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• 2016

$Ni_{1/3}Co_{1/3}Mn_{1/3}(OH)_2$ powders have been synthesized in a continuously stirred tank reactor via a co-precipitation reaction between aqueous metal sulfates and NaOH using $NH_4OH$ as a chelating agent. The co-precipitation temperature is varied in the range of $30-80^{\circ}C$. Calcination of the prepared precursors with $Li_2CO_3$ for 8 h at $1000^{\circ}C$ in air results in Li $Ni_{1/3}Co_{1/3}Mn_{1/3}O_2$ powders. Two kinds of obtained powders have been characterized by X-ray diffraction (XRD), scanning electron microscopy, particle size analyzer, and tap density measurements. The co-precipitation temperature does not differentiate the XRD patterns of precursors as well as their final powders. Precursor powders are spherical and dense, consisting of numerous acicular or flaky primary particles. The precursors obtained at 70 and $80^{\circ}C$ possess bigger primary particles having more irregular shapes than those at lower temperatures. This is related to the lower tap density measured for the former. The final powders show a similar tendency in terms of primary particle shape and tap density. Electrochemical characterization shows that the initial charge/discharge capacities and cycle life of final powders from the precursors obtained at 70 and $80^{\circ}C$ are inferior to those at $50^{\circ}C$. It is concluded that the optimum co-precipitation temperature is around $50^{\circ}C$.

• 한국수산과학회지
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• 제35권5호
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• pp.524-528
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• 2002

국내에서 양식되는 가시파래의 당 결합 양식을 조사하기 위하여 가시파래의 수용성 산성 다당을 황산기 제거 및 우론산의 환원처리를 한 후 methylation하여 GC/MSD로 분석을 하였다. 가시파래의 수용성 산성 다당의 우론산은 대부분이 glucuronic acid 였으며, 주로 황산기를 함유한 rhamnose, xylose, glucuronic acid로 이루어진 다당이었다. 이 수용성 산성 다당을 화학적 수식한 후 GC/MSD로 분석시 황산기는 rhamnose의 C-3과 xylose의 C-2에 결합되어 있었으며, 주 결합구조는 C-3에 황산기가 결합한 1,4-, 1,2,4-결합된 rhamnose, C-2에 황산기가 결합한 1,4-결합된 xylose, 1,4-결합된 xylose, 그리고 1,4-결합된 glucuronic ac:김였다. 그리고 일부 미량의 1,4-결합된 rhamnose, 1,4,6-결합된 galactose도 분리되었다.

• 청정기술
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• 제17권4호
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• pp.353-362
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• 2011

빗물 활용은 건전한 물 순환 개념에서 중요하며, 신도시 개발 등으로 증가되는 불투수면의 증대에 따른 영향을 해소시키는 방법 중의 하나가 되므로 빗물 처리 시스템의 개선을 통한 수질 개선 방안을 연구하였다. 대전서남부지구의 개발 전 빗물 유출계수는 0.40이었으나 개발 후의 유출계수는 0.59로 산정되었다. 필터를 통과한 우수의 Cu, As, Cr, Fe, Mn 등 중금속 함량은 지하수의 중금속 함량보다 양호하였으며, 집수된 빗물의 수질은 경도, 과망간산칼륨소비량, 염소이온, 증발잔류물, 황산이온, 질산성질소 등의 항목에서는 지하수의 수질보다 양호한 것을 보여 주었으며, 중수도 수질기준을 충족시키는 것으로 확인되었다. 100일 이상 장기 저장 시에도 화장실 용수, 조경 용수 등으로 적합하였다. 종전의 빗물집수 시스템에 덮개가 있는 gutter 설치, 적합한 필터 사용 및 저장조의 지하설치 등으로 시스템을 개선하면 집수되는 수질을 100일 정도 양호하게 유지할 수 있는 것을 확인하였다.

• 한국광물학회지
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• 제23권4호
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• pp.395-402
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• 2010

고씨동굴 내에 퇴적되어 있는 박쥐배설물을 대상으로 박쥐배설물 퇴적층에 생성된 인산염 및 황산염광물상들의 동정과 광물학적 특성연구를 통해 이들 광물상들의 지화학적 생성환경을 규명하고자 하였다. 박쥐배설물 내 및 하부에 침전된 물질들은 대부분 인산염 및 황산염광물로 확인되었다. 인산염광물로는 francoanellite, taranakite, ardealite, brushite, monetite가 관찰되었으며, 황산염광물로는 석고와 중정석이 관찰되었다. 인산염 광물은 하부로 갈수록 상대적으로 taranakite ${\rightarrow}$ francoanellite ${\rightarrow}$ ardealite ${\rightarrow}$ brushite ${\rightarrow}$ monetite의 변화양상을 보이는 반면 황산염광물 석고는 단면 전반에 걸쳐 확인되며, 특히 침전물 층 상부에 농집되어 나타난다. 중정석은 박쥐배설물 내에 소량 산재되어 나타난다. 인산염광물들의 침전과 이들의 수직적 광물상 변화양상은 박쥐배설물로부터 이들이 생성된 지화학적 조건이 산성환경이며, 하부로 갈수록 수분함량이 낮아지는 상대적인 건조한 환경이었음을 지시한다.

• 한국전기전자재료학회논문지
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• 제19권6호
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• pp.579-585
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• 2006

We fabricated BSCCO-2212 (2212) rod by the melt casting process (MCP) and evaluated the effect of the melt flowing on the critical current ($I_c$) by using vertical and tilt casting. It was observed that the $2212-SrSO_4$ rod processed by the tilt casting method with homogeneous pre-heating temperature of the mold had a higher $I_c$ than that processed by the vertical casting method. We also evaluated the influence of the strontium sulfates ($SrSO_4$) addition on the texture, microstructure, critical current and temperature, and mechanical hardness of the $2212-SrSO_4$ rods. It was observed that the addition of $SrSO_4$ improved the critical current ($I_c$) and mechanical hardness of the 2212. The $I_c$ of the 2212 increased as the $SrSO_4$ content increased and reached a peak value (260 A at 77 K) at an $SrSO_4$ content of 6 wt.%. In addition, the addition of $SrSO_4$ had a beneficial effect on the mechanical hardness of the 2212. We studied the possible cause of the variation in the $I_c$ with the melt flowing and the $SrSO_4$ content based on the XRD, EPMA analysis and the microstructural observation.

• 공업화학
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• 제19권3호
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• pp.259-263
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• 2008

소각로에서 발생한 다이옥신 및 질소산화물 제거용 폐탈질 촉매($V_2O_5/TiO_2$)의 비활성화 원인을 규명하고자 반응 활성 실험 및 물리 화학적 특성 분석을 수행하였으며, 다양한 재생방법을 통한 폐탈질 촉매의 재생효율을 연구하였다. 고정층 실험 결과 $260^{\circ}C$를 기준으로 약 60% 정도 질소산화물 제거 활성 차이를 보였으며, 허니컴 실험의 경우 1, 2-Dichlorobenzen (1, 2-DCB) 분해효율이 $200^{\circ}C$에서 약 14% 정도 차이가 나타났다. 또한 촉매의 비활성화 원인을 연구하기 위해서 신촉매와 폐촉매에 대하여 XRD, TGA, 그리고 ICP의 특성 분석을 실시한 결과 황산 암모늄염, 중금속(Pb, As 등), 전이금속(Fe 등), 알칼리 금속(Ca), 그리고 상전이가 촉매의 비활성화 원인으로 조사되었다. 또한, 폐촉매의 재생을 위해 다양한 방법으로 처리한 결과 수세과정을 배제한 공기분위기에서 열처리한 경우 우수한 재생효과를 나타내었다.