• Proceedings of the Korea Air Pollution Research Association Conference
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• 2008.10a
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• pp.303-304
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• 2008

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2009.10a
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• pp.377-378
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• 2009

• Proceedings of the Korean Environmental Health Society Conference
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• 2006.06a
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• pp.73-89
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• 2006

• Proceedings of the IEEK Conference
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• 2001.06b
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• pp.237-240
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• 2001

In this paper, we have presented processing technique about wet etching for silicon membrane construction formation. In order to make selective etching of backside silicon wafer, we used Si$_3$N$_4$ layer by PECVD(Plasma Enhanced Chemical Vapor Deposition). We have measured the surface thickness in backside silicon wafer after anisortropic wet etching with KOH:distilled water solutions. Through this experiment, we acquired the etching rate for 1.29${\mu}{\textrm}{m}$/min. The average rough of Si-membrane frontside and backside was 0.26${\mu}{\textrm}{m}$, 0.90${\mu}{\textrm}{m}$, respectively.

• Nuclear Engineering and Technology
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• v.50 no.6
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• pp.849-853
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• 2018

Mechanistic calculations for wet scrubbing of aerosol/vapor from gas bubble rising in liquid pool are essential to safety of sodium-cooled fast reactor. Hence, scrubbing of volatile fission product from mixed gas bubble rising in sodium pool is presented in this study. To understand this phenomenon, a theoretical model has been setup based on classical theories of aerosol/vapor removal from bubble rising through liquid pools. The model simulates pool scrubbing of sodium iodide aerosol and cesium vapor from a rising mixed gas bubble containing xenon as the inert species. The scrubbing of aerosol and vapor are modeled based on deposition mechanisms and Fick's law of diffusion, respectively. Studies were performed to determine the effect of various key parameters on wet scrubbing. It is observed that for higher vapor diffusion coefficient in gas bubble, the scrubbing efficiency is higher. For aerosols, the cut-off size above which the scrubbing efficiency becomes significant was also determined. The study evaluates the retention capability of liquid sodium used in sodium-cooled fast reactor for its safe operation.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.146.2-146.2
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• 2010

PEMFC를 구성하는 여러 부품 중 핵심부품은 MEA(Membrane Electrode Assembly)으로서 실제 연료전지 반응이 일어나며 연료전지의 성능을 결정하는 부품이다. 그러나 PEMFC의 특성 상 촉매로 귀금속인 Pt가 사용됨에 따라 경제성이 확보된 MEA의 성능을 얻기 위해선 현재 Pt 담지량을 0.3mg/$cm^2$ 이하로 크게 감소시키면서 Pt촉매의 고분산화와 미반응 사이트의 감소가 필요하다. 본 연구에서는 Pt 촉매의 미반응 사이트를 줄이고자 전기영동법에 의해 카본전극(carbon black + GDL) 상에 Pt 나노입자를 직접 석출시켜 Pt/C 촉매 전극을 제조 하였다. 본 실험에서는 가장 좋은 Pt 나노입자의 석출거동을 나타낸 30mA/$cm^2$, pH 2, duty cycle 25% 조건을 기준으로 하여 electro-deposition time을 통한 석출량 제어와 carbon paper의 wet proofing 정도에 따른 Pt의 석출거동을 조사하였으며, 종래의 방법으로 제조한 Pt/C 촉매전극의 전기화학적 특성과 비교 분석하였다. 전기영동 석출법에 사용된 Pt나노입자는 $H_2PtCl_6{\cdot}6H_2O$로부터 화학적 환원법으로 합성한 2~3nm 입경을 갖는 Pt콜로이드를 사용하였으며, magnetic stirring과 항온 ($20^{\circ}C$)을 유지하여 실험하였다. 전기영동 석출량 제어는 electro-deposition time을 5~25분까지 5분 간격으로 나누어 실험하였고 카본전극을 구성하는 carbon paper의 wet proofing 정도가 Pt 나노입자 석출거동에 미치는 영향을 조사하기 위하여 20, 40, 60%의 서로 다른 wet proofing 값을 갖는 carbon paper를 사용하여 Pt/C 촉매 전극을 제조하였다. 전기영동법으로 석출된 카본블랙 전극 상 Pt나노입자의 분산도와 담지량는 각각 FE-SEM과 TGA 장비를 사용하여 측정하였고, 제조된 Pt/C 촉매 전극의 전기화학적 촉매 특성은 cyclic voltammetry(CV)법으로 측정하였다.

• Bulletin of the Korean Chemical Society
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• v.24 no.3
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• pp.363-368
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• 2003

The major ionic components of precipitation collected at the 1100 Site of Mt. Halla and Jeju city have been determined. The reliability of the analytical data was verified by the comparison of ion balances, electric conductivities and acid fractions; all of their correlation coefficients were above 0.94. Ionic strengths lower than $10^{-4}$ M were found in 53% of the 1100 Site samples and 28% of the Jeju city samples. Compared with other inland areas, the wet deposition of $Na^+,\;Cl^-\;and\;Mg^{2+}$ was relatively larger, but that of $NH_4^+,\;nss-SO_4^{2-}$(non-sea salt sulfate) and $NO_3^-$ was lower. Especially the wet deposition increase of $Ca^{2+}$ in the spring season supports the possibility of the Asian Dust effect. The acidification of precipitation was caused mostly by $SO_4^{2-}\;and\;NO_3^-$ in the Jeju area, and the organic acids have contributed only about 7% to the acidity. The neutralization factors by NH₃were 0.47 and 0.48, and that of CaCO₃was 0.31 and 0.25 at the 1100 Site and Jeju city, respectively. Investigation into major influencing sources on precipitation components by factor analysis showed that the precipitation at the 1100 Site had been influenced mostly by an anthropogenic source, followed by soil and seawater sources. The precipitation at Jeju city was mainly influenced by oceanic sources, followed by anthropogenic and soil sources.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.6
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• pp.1465-1468
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• 2010

The wet etching is a process using chemical solution and occurring chemical reaction on substrate surface. when we do wet etching process, we have to consider stoichiometry, etching time and temperature of etchant for good resolution. In this experiment, we used Cr, Al andIndium-tin-oxide (ITO) metal and we deposited them with DC sputtering machine. The Cr thin film metal thickness is about $1300{\AA}$, ITO films show a low electrical resistance and high transmittance in the visible range of an optical spectrum and Ai film is used for signal line. We measured and analysed wet etching properties on the metal thin films.

• Journal of Korea Water Resources Association
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• v.37 no.11
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• pp.959-967
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• 2004

The concentrations and loads of total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD) in wet deposition were investigated at Chungbuk National University in Cheongju, Chungbuk. Event based precipitation samples were collected during 1998 to 2003. The precipitation-weighted mean concentrations of pollutants were 0.60 mg/L for TN, 0.014 mg/L for TP, and 4.8 mg/L for COD, which were smaller than its arithmetic mean concentrations by 26% for TN, 18% for TP, and 14% for COD. The concentrations of TN, TP, and COD significantly decreased with precipitation. Mean concentrations of pollutants in spring (March-May) were higher than in other seasons likely due to dust caused by wind erosion and sand-dust storms, pollen etc. Significant relationships were determined between TN and TP, and TN and COD. Annual loads of wet deposition averaged 7.9 kg/ha$\cdot$yr for TN, 0.19 kg/ha$\cdot$yr for TP, and 63.9 kg/ha$\cdot$yr for COD, which are almost identical to the values of TN and TP but slightly higher than COD value reported in Japan.

• Journal of Korean Society for Atmospheric Environment
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• v.12 no.1
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• pp.101-112
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• 1996

Dry and wet deposition is an impertant removal mechanism of the amobient aerosol in the atmospheric environment. Since the deposition flut provides adverse impacts on various encironmental media including aquatic and ecological system as well as human health, it is essential to quantitatively estimate the removal fluxes of many air pollutants. Thus, the purposes of this experimental study are to investigate seasonal deposition flux variations of the total dustfall and various inorganic elements in the local ambient air and then to finally estimate their dry deposition velocities. To perform the study, the total of 90 dustfall samples were collected from January, 1994 thru February, 1995 in 5 different cities of Korea including Seoul, Suwon, Daejon, Kwangju, and Kangrung. Each sample was analyzed by an AAS and an ICP to determine the quantities of the 11 inorganic elements, such as Zn, Cd, Cr, K, Na, Pb, Ca, Fe, Mn, Mi, and Cu. As results, deposition fluxes, soluble/insoluble fractions, and deposition velocities for each element were extensively investigated. The resulting dry deposition velocities of some elements in Suwon were estimated by ranges of 0.57 .sim. 0.87 cm/sec for Zn, 0.35 .sim. 0.45 cm/sec for Pb, 1.25 .sim. 3.52 cm/sec for Ca, 0.21 .sim. 0.48 cm/sec for Fe, 0.95 .sim. 9.31 cm/sec for Mn, and 2.08 cm/sec for Cu.