• 한국환경보건학회지
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• 제28권2호
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• pp.109-116
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• 2002

The purpose of this study was to evaluate a new sampling and analytical method for the determination of airborne hexavalent chromium, Cr(Ⅵ), in a field plating operation. The procedures of this new method (Shin & Paik's Method) are as the following: Airborne hexavalent chromium is collected on polyvinyl chloride (PVC) filter according to the National Institute iota Occupational Safety and Health (NIOSH) Method 7600, and the filler sample is placed in a screw-capped vial and soaked with 2% NaOH/3% Na₂CO₃ solution immediately after sampling. The Cr(Ⅵ) sample is analyzed by ion chromatography/visible spectrophotometry (IC/VS) according to the U.S. Environmental Protection Agency (EPA) Method 218.6. The airborne Cr(Ⅵ) concentrations measured by this method were compared with those determined by three reference methods: One (NIOSH/EPA Method) consisted of sampling airborne Cr(Ⅵ) on PVC filters and storing the sample filters in strew-capped vials according to the NIOSH method, and analyzing Cr(Ⅵ) in samples using IC/VS according to the EPA method. The second method (Impinger Method/NaHCO₃) consisted of absorbing airborne Cr(Ⅵ) into 0.02 M NaHCO₃ solution in midget impinger, and analyzing the Cr(Ⅵ) in samples using IC/VS. The third method was the OSHA Method ID-215. Using these four different methods, lour replicates of air samples were collected at an electroplating process and analyzed simultaneously. Two-way ANOVA and paired t-test were used to test difference among values determined by the methods. There was no significant difference and a strong correlation (r²:0.99) between Cr(Ⅵ) concentrations measured by the Shin & Paik's Method and an impinger method (p>0.05). However, Cr(Ⅵ) concentrations determined by Shin & Paik's Method were significant1y different from those by the NIOSH/EPA Method (p<0.05) or the OSHA method (p<0.05). The Cr(Ⅵ) concentrations of Shin & Paik's Method were significantly higher than those of the NIOSH/EPA Method or the OSHA method. This result indicated that the Shin & Paik's Method may prevent Cr(Ⅵ) losses caused by reduction and give more reliable results of airborne Cr(Ⅵ) concentrations in work environments.

• 한국환경과학회지
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• 제9권3호
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• pp.253-259
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• 2000

The purpose of this study is to investigate the physicochemical characteristics of salinization of groundwater at the estern area of Cheju island. For this purpose, the major ions of groundwater, spring water are analyzed. The concentration of $Cl^-$ and Na^++K^+$/ contained in the groundwater at near the coastline are higher than those at inland area away from the coastline. The water quality components of groundwater observed at this area can be classified into 4 types such as Na-Cl, $HCO_3, Na-Cl-HCO_3$ and Ca-HCO$_3$. The concentration ratio of $SO_4^1 to Cl^- is 0.1354(R^2=0.972)$ at this area. This value is very similar with Dittomer's ratio of 0.13. For Na^+, K^+, and Mg^{2+}/ versus Cl^-$, their ratios also show a significant relationship between sea water and groundwater in this area. From the chloride-bicarbonate ratio, it can be estimated that the intrusion distance of seawater from coastline to inland area is 2.8km at Onpyung-Nansan, Sangdo and Pyungdae areas, and 5.4km at Kosung-Susan area. The mixing ratio between seawater and fresh water by the intrusion of seawater is decreased with the distance toward inland from coastline. This ratio(fresh water : seawater) is 80:20 in spring water adjacent the coastlines, Onpyung area and 99.8:0.2 in the well at No.3 of Susan located at inland away from the coastline. The concentration of $Na^+$ observed at field is 25~45% lower than that theoretically calculated by this mixing ratio. Based on the data of EC, the equipotential line of 500$\mu$mhos/cm is located at 4~5km poing at Kosung-Susan area and 2.5km point at the other area. The equation of correlation between $Cl^-$ concentration and EC values is $Cl^-$=0.1927EC-16.683 for the area lower than 500 $\mu$mhos/cm and $Cl^-$=0.2773EC for the area beyond 500 $\mu$mhos/cm.

• 자원리싸이클링
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• 제18권4호
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• pp.31-37
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• 2009

본 연구에서는 고로슬래그 미분말과 플라이애쉬 혼입률에 따른 3성분계 콘크리트의 역학적 특성과 내구성을 평가하였다. 이를 위해 플라이애쉬 혼입률 변화(0%, 10%)와 고로슬래그 혼입률 변화(0%, 10%, 20%, 30%)를 실험변수로 하였으며, OPC와 TBC의 특성분석을 위하여 압축강도, 휨강도 그리고 내약품성 시험을 실시하였다. 실험결과, 압축강도와 휨강도에서 플라이애쉬 및 고로슬래그 미분말 혼입이 장기재령에서 강도 증진효과를 나타내는 것으로 평가되었다. 특히 플라이애쉬 10%와 고로슬래그 30%의 3성분계 콘크리트 사용은 매우 타당한 것으로 나타났다. TBC의 특수저항성은 재령 90일에서 매우 낮은 등급으로 나타났다. 또한 OPC에 혼입되는 플라이애쉬 및 고로슬래그 미분말은 투수저항성 및 화학저항성의 향상을 가져오는 것으로 나타났다.

• 대한환경공학회지
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• 제35권6호
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• pp.436-441
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• 2013

복류수와 천변여과지 그리고 점차 여과거리가 짧아지고 있는 우리나라의 강변/하상여과 등이 가지는 미량오염물에 대한 저항능력을 평가하기 위하여 5 m 길이의 모래칼럼을 이용한 실험을 수행하였다. 실험결과 우리나라 하상의 토양은 유기물 함량이 상당하여 염소이온의 토양표면 흡착이 비교적 활발함 알 수 있었다. 페놀은 칼럼의 여과수에서 검출되지 않았고, 1,4-다이옥산과 다이아지논은 하상토양과 흡착반응을 일으키면서 이동하며, 2.5 m의 이동과정에서 1,4-다이옥산의 첨두농도는 유입농도의 약 40%로 그 농도가 감소하였고, 다이아지논의 첨두농도는 약 60%로 감소하는 것으로 나타났다. 실규모 설비에서는 여과거리가 5 m 보다 더 길기 때문에 첨두농도의 감소효과는 상당히 클 것으로 기대되었다.

• 한국물환경학회지
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• 제18권3호
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• pp.253-260
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• 2002

The purpose of this research was to describe the mechanisms and prevention of initial degradation in turbidity of the sand filter effluent. The method used was by adding a coagulant (PAC) to the sand filter after backwashing as a means of reducing turbidity. It was found that adding 80 mg/L of PAC solution to the sand filter was very effective in improving the initial effluent turbidity. A turbidity removal efficiency of 99 % was observed in the initial term period as compared to a 70% efficiency without PAC addition. The PAC solution added to the sand filter resulted in high aluminum concentration at the upper layer as compared with the bottom layer of the sand filter column. A change in the zeta potential to a strong positive-ions at upper layer was observed at this time but only a small change was obtained at the bottom. This result showed that the zeta potential of the sand was changed to positive with PAC coating. The effect of pH on zeta potential with PAC addition was also investigated. Zeta potential was greatly changed to positive-ion at pH 4~6. A series of experiments was then conducted in this study to optimize the pH of the PAC solution to be added to the sand filter after backwashing. The removal efficiency of turbidity was found to be highest at pH 5. This result suggested that hydrolyzed aluminium species attached to the surface of the sand enhanced the removal of turbidity of the effluent.

• 펄프종이기술
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• 제29권1호
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• pp.52-61
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• 1997

This study was aimed to decrease AOX(Adsorbed Organic Halide Compounds) by applying bleaching methods of A(HNO$_3$ ＋ NaNO$_2$) and $D^{(H/L)}$(dual pH chlorine dioxide bleaching) to conventional OCEDED bleaching stages. And so we investigate the effects of NSA treatment and the influence of production rate of ion species in chlorine dioxide and pulp mixtures according to various pH as well as dual pH on pulp bleaching. Finally the effects of AOC_DED^{(H/L)}ED^{(H/L)}$ bleaching stage were investigated by measuring AOX, brightness, kappa number and viscosity of pulps. A stage was treated by using 4% $HNO_3$ and 0.05~2.0% $NaNO_2$ on pulp and $D^{(H/L)}$ stage was like that pulp mixed with chlorine dioxide solution was adjusted at pH 7.0 and reacted in pulp cosistency 3%, S~20min, $70^{\circ}C$, and then successively for 160~175min at pH 4.0. It was found that suitable $NaNO_2$ addition rate was at 0.6% where the brigtness of pulp was most higher and pulp viscosity was not decreased much. Chlorate ($CIO_3$) was decreased according to pH increase but chlorite($CIO_2$) was highly decreased according to pH increase. And chloride was slightly increased with pH increase. The applying of A and D^{(H/L)}$ bleaching stages to some various multiple bleaching stages ($AOC_DED^{(H/L)}/EopD^{(H/L)} etc.$) had good results that brightness was increased more 2~3% ISO than conventional method(OCEDEopD), but viscosity was dropped by only 1~2cps.

• 한국구조물진단유지관리공학회 논문집
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• 제22권5호
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• pp.31-38
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• 2018

이 본 연구에서는 메타카올린을 혼입한 초속경 폴리머 시멘트 콘크리트의 압축, 휨, 부착강도, 수밀성, 염화물 이온 침투 저항성,탄산화 깊이 및 동결융해 저항성에 미치는 폴리머-결합재비 및 메타카올린 첨가량의 영향에 대하여 검토하였다. 그 결과, 초속경 폴리머 시멘트 콘크리트의 휨, 압축 및 부착강도는 폴리머-결합재비의 증가에 따라 증가하는 경향을 보였다. 폴리머-결합재비에 관계없이, 초속경 폴리머 시멘트 콘크리트의 강도는 메타카올린 첨가량의 증가에 따라 증가하였으며, 메타카올린 첨가량 5%에서 최고 값을 나타내었다. 초속경 폴리머 시멘트 콘크리트의 흡수율, 탄산화 깊이 및 염화물이온 침투저항성은 폴리머-결합재비의 증가에 따라 감소하는 경향을 보였다. 초속경 폴리머 시멘트 콘크리트의 동결융해 저항성의 개선은 폴리머 에멀젼의 혼입에 의해 시멘트 수화물과 골재간의 접착성이 개선되기 때문이라 판단된다.

• 센서학회지
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• 제27권1호
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• pp.55-58
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• 2018

Low-cost and large-scale fabrication method of nanohole array, which comprises nanoscale voids separated by a few tens to a few hundreds of nanometers, has opened up new possibilities in biomolecular sensing as well as novel frontier optical devices. One of the key aspects of the nanohole array research is how to control the hole size following each specific needs of the hole structure. Here, we report the extensive study on the fine control of the hole size within the range of 500-2500 nm via surface-catalyzed chemical deposition. The initial hole structures were prepared via conventional photo-lithography, and the hole size was decreased to a designed value through the surface-catalyzed chemical reduction of the gold ion on the predefined hole surfaces, by simple dipping of the hole array device into the aqueous solution of gold chloride and hydroxylamine. The final hole size was controlled by adjusting reaction time, and the optimal experimental condition was obtained by doing a series of characterization experiments. The characterization of size-controlled hole array was systematically examined on the image results of optical microscopy, field emission scanning electron microscopy(FESEM), atomic-force microscopy(AFM), and total internal reflection microscopy.

• 한국표면공학회지
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• 제36권3호
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• pp.256-262
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• 2003

The current efficiency and the composition of Zn-Cr and Zn-Cr-X (X : Co, Mn) alloy electrodeposits were investigated by using chloride bath with EDTA auditive and flow cell plating system. The current efficiency of Zn-Cr alloy decreased with increasing current density, while it increased with the content of Co and Mn of the Zn-Cr-X alloy bath in high current density region. The Cr content in Zn-Cr alloy increased from 1.4-2.7 to $28wt\%$ with increasing current density and the phase structure of the alloys changed from $\eta-Zn$ through $\eta-Zn+\gamma'-ZnCr\;to\;\gamma'-ZnCr$ with Increasing Cr content of the alloys. The Co content in Zn-Cr-Co alloys increased with Co content of the bath, while Cr content of the alloy increased or decreased in low current density region $(10-75A/dm^2)$ or high current density region $(75-100A/dm^2)$, respectively. $\gamma-ZnCo$ phase was formed in the Zn-Cr-Co alloy with above $9.0wt\%$ Co. The content of Mn and Cr in Zn-Cr-Mn alloys increased or decreased with the increase of current density in high current density region, respectively while Cr content of the alloy decreased noticeably with the increase of Mn content in the bath. Two phases of $\delta_1-ZnMn$ and $\gamma'-ZnCr$ were formed in the Zn-Cr-Mn alloy with above $8.6wt\%$ Mn.

• 한국건축시공학회지
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• 제11권6호
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• pp.627-633
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• 2011

철근 콘크리트 구조물의 염해 내구수명 산정을 위해서는 비래염분량 평가가 필수적이다. 현재까지 국내에서도 국외에서 개발된 포집기를 주로 사용해 왔으나 포집기 자체의 결함으로 포집 정확도에 문제가 있다는 지적이 일어왔었다. 본 연구 결과 기존의 포집기는 후풍의 영향을 배제할 수 없어 실제 포집기를 통과하면서 거즈에 부착된 비래염분은 후풍의 영향에 의해 이탈되어 포집량이 낮게 평가됨과 동시에 방향성, 즉 남쪽에서 불어오는 비래염분도 북향하고 있는 포집기에 포집되어 방향에 대한 구분이 없어지는 현상을 해석적, 실험적으로 규명하고, 문제해결형 개량형 포집기를 개발하였다. 또 해안지역에서 실측에 사용하여 높이별 비래염분량 측정과 동시에 포집기의 성능검증을 실시하였다.