• 한국환경보건학회지
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• 제33권4호
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• pp.276-282
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• 2007

The purpose of this study is to assess the accurate state of the following: total welding fumes versus welding fumes in the air, respirable particulate mass, and exposure of dockyard welders to heavy metals. In addition, this study provides basic data for proposing improvements to create efficient and appropriate welding environments and to prevent occupational diseases. The subjects of this study were 94 laborers who worked at the block construction sites of large-scale dockyards located in Gyeongnam Province from March 2005 to June 2005. In order to collect samples on total welding fumes in the air and respirable particulate mass from the welders, Methods 0500 and 0600, established by the National Institute for Occupational Safety and Health (NIOSH), were used. The metals within the welding fumes were also analyzed using Inductively Coupled Plasma (ICP) under Method 7300 from NIOSH. The results of this research are summarized below. The geometric mean concentration of total welding fumes and that of respirable particulate mass were $4.11\;mg/m^3\;and\;3.53\;mg/m^3$, respectively. As a result of comparing the two measurement methods, there were significant differences (p<0.05) between the two groups for Ca, Cu, Cr, and Ni; however, there were no differences in Fe, Mg, Zn, Mg, Pb, and Cd. As a result of the analysis, the correlation between Mn and the concentration of heavy metals in the total welding fumes and respirable particulate mass was found to be -0.29, a significant negative correlation. The correlation between other heavy metals, however, was low. Finally, in the same total welding fumes, the correlation of Fe and Mg was high.

• 한국산학기술학회논문지
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• 제20권11호
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• pp.416-424
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• 2019

우리나라에서 지하층 누름콘크리트는 주로 무근 콘크리트를 사용하고 있다. 이러한 시스템에서는 건조수축이나 불규칙한 온도 분포로 인하여 바닥콘크리트의 균열이 빈번히 발생되고 있다. 이러한 문제점을 해결하고자 과거에는 메탈라스, 섬유 등을 사용하였지만 균열을 제어하기에는 효과가 미비한 점이 있었다. 이에, 본 연구에서는 여러 가지 혼화 재료를 혼입한 지하층 누름콘크리트의 균열 저감 효과에 관하여 분석하였다. 혼화재료의 종류에 따른 균열저감 효과를 알아보기 위해 공기량 실험, 슬럼프 실험, 압축강도 실험, 소성수축 실험을 실시하였다. 공기량 실험결과, 혼화재료들을 혼입한 시편들은 Plain과 유사한 공기량(4.5±1.5%)을 나타내었으며, 슬럼프 실험에서는 고성능 감수제를 혼입한 시편들이 Plain에 비하여 가장 높게 나타내었지만, 폴리머를 혼입한 경우 Plain과 유사하게 나타났다. 압축강도 실험에서는 실리카 흄, 고성능 감수제 및 SBR을 혼입한 시편들이 Plain에 비하여 10-15% 높게 나타났다. 소성수축 실험결과 MC, 고성능 감수제, SBR를 혼입한 시편들이 Plain에 비하여 균열발생이 적었으며, 특히 MC섬유를 혼입한 시편은 균열이 발생하지 않았다.

• 한국산업보건학회지
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• 제11권1호
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• pp.1-8
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• 2001

This study was performed to evaluate a local exhaust ventilation system capability and welding fume concentration in welding laboratory at 5 technical high schools. Results of the study are as follows; 1. The personal exposure of welding fume in welding laboratory was measured. The geometric mean of 73 personal samples was $6.27mg/m^3$($3.85{\sim}9.88mg/m^3$), and 68.5% of these exceeded TLV of the Korea Ministry of Labor. 2. The geometric mean of welding fume at outside of booth was $2.27mg/m^3$($1.57{\sim}2.58mg/m^3$). All of measured concentrations were lower than TLV of the Korea Ministry of Labor. 3. Local exhaust ventilation system in welding laboratory could not remove hazardous substance effectively because of inappropriate canopy hood and absurd design. 4. The possibility of exposure risk was estimated to be high because of working point under breathing zone, misplacement of working table and insufficient supply of respiratory protector. 5. The mean values of capture velocity and transportation velocity of local exhaust ventilation system in welding laboratory were 0.38m/sec, 4.27m/sec respectively. These values were satisfied the guideline of the Korea Ministry of Labor. 6. The efficiency of performance of local ventilation system was anticipated to be decreased because of accumulated dust and alien substance on fan and duct.

• 한국산업보건학회지
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• 제11권1호
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• pp.42-47
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• 2001

The purpose of this study was to investigate for filtration efficiency of several dust masks, comparing with filtration efficiency certified by KOSHA(Korea Occupational Safety & Health Agency), and to require of the right use of protective respirators. Using a welding fume generator and chamber, several dust masks, which were widely used in the workplaces in korea, were tested for their filtering efficiency for stainless steel arc welding fume. The filtration efficiency testing system consisted of a welding fume generator, a chamber and a filtration unit. The filtration unit was made of a mask which was inserted into the sampling cassette and another sampling cassette, which contained mixed cellulose ester filter paper. These two cassettes were connected with tubing. Stainless steel arc welding fume generator was delivered into an chamber. The welding fume in the chamber was passed into the filtration unit with flow rate of 30 liter/min. The welding fume filtration efficiency was evaluated by gravimetric measurement. Metal concentrations in the welding fume before and after filtration were measured with inductive coupling plasma analyzer. Following results were obtained: Filtration efficiency of welding fume for common hygienic mask was 63.82% and the average efficiencies for A, B, C, D, E, F and G masks were 94.62%, 96.58%, 83.20%, 82.76%, 77.25%, 86.55% and 93.22%, respectively. Our results indicate that dust masks used widely in the welding workplaces in korea are not proper for protecting worker's health and then the use of fume mask should be required.

• 한국산업보건학회지
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• 제24권2호
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• pp.229-237
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• 2014

Objectives: This study intends to determine the current status of management of personal protective equipment fume hoods in university laboratories. Methods: A walk-through survey of 402 labs in Gyeongbuk Province and Daegu Metropolitan City were carried out between May 2009 and July 2010. Respectively, 348 and 54 laboratories were examined in Gyeongbuk Province and Daegu. Results: In size, labs serving over 15,000 student made up the majority with 276(66.4%). In terms of major, engineering labs were the highest in number with 100(24.9%). As to personal protective equipment, a gas mask and a dust mask were available in 17.8% and 14.3% of the labs, respectively, but 68.9% of labs were equipped with protective goggles. Meanwhile, only 12.7% of labs had separate protective equipment storage boxes. About 60% of the labs had installed a fume hood, of which the average capture velocity was 0.37 m/sec. Conclusions: For toxic substances, the labs are obliged to provide personal protective equipment in in accordance with the Occupational Safety and Health Act. In addition, the capture velocity of fume hoods must be in strict compliance in order to prevent occupational diseases due to toxic chemicals.

• 한국방재학회 논문집
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• 제3권4호
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• pp.119-129
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• 2003

콘크리트와 철은 건설에서 필수적인 구조 재료이다. 그러나, 철과 달리 콘크리트는 하나의 재료가 아니라 많은 물질들로 구성된 복합재료이며, 구성 재료, 현장 환경, 그리고 기술자의 숙련도 등에 의해 많은 영향을 받는다. 그리고 유동성과 공기량 등 즉시 알 수 있는 물성도 있지만 강도나 내구성 같이 시간이 지나야 알 수 있는 특성도 존재하므로 콘크리트의 배합은 전문가의 경험에 많이 의존해 왔다. 하지만, 콘크리트도 고성능화 되는 시점에서 첨가 재료도 늘어나고 기존의 자료도 부족하기 때문에 새로운 기법이 필요한 때이다. 신경망은 복잡한 비선형 문제를 처리하는 인간의 두뇌를 모방한 모델로 패턴 인식 및 분류, 예측 등의 분야에서 많이 사용되고 있다 여기서는 그 중에서 역전파 알고리즘과 광선형 기저 함수망 모형이 사용되었다. 여덟가지 재료(물, 시멘트, 잔골재, 굵은 골재, 플라이 애쉬, 실리카 흄, 유동화제, 그리고 공기연행제)가 배합에 사용되었으며, 압축강도와 슬럼프, 공기량을 물성으로 사용하였다. 결과적으로 신경망은 고성능 콘크리트치 배합 및 물성 예측 등 활용에 유용하게 사용될 수 있음을 알 수 있었다.

• 대한화학회지
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• 제40권1호
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• pp.50-58
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• 1996

일정한 pH에서 Co(II), Ni(II), Sr(II), Cu(II), Fe(III) 및 U(VI) 등의 금속이온농도가 증가할 수록 흄산의 침적율이 증가하였으며, Sr

• 콘크리트학회논문집
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• 제18권5호
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• pp.703-708
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• 2006

역학적 특성이 개선되고 고성능 건설 재료로 가장 주목받고 있는 슬러리 충전 섬유 콘크리트(SIFCON)의 역학적 특성을 분석하기 위해서 양단 훅크형의 강섬유를 $4{\sim}10%$의 체적비로 혼입하여 시험체를 제작한 후, 압축강도시험과 직접인장시험을 실시하였다. 물-시멘트 비는 0.4, 슬러리의 워커빌리티를 향상시키기 위해 실리카 흄과 유동화제를 각각 시멘트 중량의 10%, 0.5%를 혼입하였다. SIFCON의 강섬유 혼입률별 시험에서 나타난 압축강도는 강섬유가 혼입되지 않은 시멘트 페이스트와 비교 하였을 때 약 $1.59{\sim}2.68$배 증가하였으며, 인장강도는 약 $2.51{\sim}8.77$ 증가하였다. 또한 강섬유의 혼입률이 증가함에 따라 인성과 연성도 크게 향상되는 것을 확인할 수 있었다.

• 한국환경보건학회:학술대회논문집
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• 한국환경보건학회 2002년도 춘계 국제 학술대회
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• pp.37-39
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• 2002

Geometric mean of airborne welding fume concentration at technical high schools was 4.80mg/㎥(N.D∼35.39mg/㎥) and the percentage of samples exceeded TLV of the Korean ministry of labor was 43.6％, Geometric mean of airborne Mn concentration was 0.06mg/㎥(N.D∼0.42mg/㎥) and the percentage of samples exceeded TLV of ACGIH was 15.4％. In case of airborne Mn concentration, there is a significant difference among schools (P＜0.05). Mn concentrations in blood of the exposed and control groups were 1.84$\mu\textrm{g}$/㎗ and 1.91$\mu\textrm{g}$/㎗, respectively. Mn concentrations in urine of the exposed and control groups were 1.36$\mu\textrm{g}$/$\ell$ and 0.57$\mu\textrm{g}$/$\ell$, respectively. In case of Mn concentrations in urine, there is a significant difference between both groups(P＜0.001) and among schools(P＜0.05). Mn concentrations in blood and urine of exposed group were not over BEIs of the Korean ministry of labor. Mn levels in blood and urine were not significantly affected by smoking, drinking and residence. There was no correlation between Mn concentration in air and blood, but there was a statistically significant correlation between Mn concentration in air and urine(r=0.323). There was no a Statistically significant correlation between Mn concentration in blood and urine.

• 한국산업보건학회지
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• 제19권4호
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• pp.328-334
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• 2009

There are various methods for welding fume control. These methods can be divided into local exhaust system, general ventilation system and integrated control system. With the general ventilation system, we should have a good prediction tool for testing various appropriate control options. But, until now there are not many studies about how to predict the welding fume concentrations. Especially, the prediction of welding fume concentration is not a very easy task because welding fume is the particulate matters. In this study, we tried to measure $CO_2$ concentrations and welding fume concentrations in a small single room with a small ventilation opening. Using commercially available CFD (Computational Fluid Dynamics) software, we tried to predict $CO_2$ concentrations under the exactly same conditions. Then, we tried to compare the numerical $CO_2concentrations$ with the experimental results to know whether we could predict $CO_2$ concentrations. Then we tried to compare $CO_2$ concentrations with experimental welding fume concentrations to know whether we can use the numerical $CO_2concentrations$ to predict the welding fume concentration indirectly.