• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
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• pp.89-94
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• 1996

The purpose of this study is to investigate the workability and strength of concrete containing admixtures. For this purpose, four kinds of admixtures such as silica fume, fly ash, ground granulated blast-furnace, rice husk ash are selected and tested on the workability and strength according to the replacement ratio of them. As a result, considering their workability and strength, the optimum replacement ratio of them were obtained for each concrete containting admixtures.

• 한국독성학회:학술대회논문집
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• 한국독성학회 2005년도 춘계 국제심포지엄 및 학술대회
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• pp.109-109
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• 2005

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 가을 학술발표회 논문집
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• pp.140-147
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• 1996

This study was performed to investigate the characteristics of workability and strength of the concrete containing admixtures such as silica fume, fly ash, blast furnace slag, and rice husk ash. For this purpose, the workability and the strength of the concrete containing each admixture were tested and analyzed according to the unit weight of binder and the replacement ratio of each admixture.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1991년도 가을 학술발표회 논문집
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• pp.129-134
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• 1991

The effects of water-cement ratio, age, and admixture such as fly ash, silica fume on the bond strength between aggregate and mortar were investigated. As the result, with increasing of water-cement ratio, the bond strength was slightly decreased while the compressive strengths of mortar and concrete were seriously decreased. The rate of strength gain of bond strength was not decreased with increasing of water-cement ratio while that of compressive strength was gradually decreased.

• Advances in materials Research
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• 제2권4호
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• pp.195-208
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• 2013

A comprehensive theory of the spin coating technique has been reviewed and the basic principles and parameters controlling the process are clearly highlighted, which include spin speed, spin time, acceleration and fume exhaust. The process generally involves four stages: a dispense stage, substrate acceleration stage, a stage of substrate spinning at a constant rate and fluid viscous forces dominate fluid thinning behaviour and a stage of substrate spinning at a constant rate and solvent evaporation dominates the coating thinning behaviour. The study also considered some common thin film defects associated with this technique, which include comet, striation, chucks marks environmental sensitivity and edge effect and possible remedies.

• 한국산업보건학회지
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• 제10권1호
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• pp.32-44
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• 2000

The practice of welding stainless steel is known to produce various valance states of chromium. $CO_2$ flux cored arc welding on stainless was performed in fume collection chamber. Content of total chromium and hexavalent chromium in fumes, content of hexavalent chromium in total chromium, solubility of hexavalent chromium were investigated. Content of total chromium in fumes increases from 2~3% to 7~9% as a function of input energy, but hexavalent chromium, less than 1.2% in fumes, is not related to input energy. Hexavalent chromium in fumes exists as solubles up to 90%. Content of total chromium in flux cored arc welding fumes and solubility of hexavalent chromium are similar to shielded metal arc welding fumes, but content of hexavalent chromium is similar to metal inert gas welding fumes. These characteristics are relevant to flux of wires and $CO_2$ shielding gas.

• 한국건설순환자원학회논문집
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• 제6권4호
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• pp.127-133
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• 2012

본 연구에서는 양생온도가 혼화재 치환 고강도 모르타르의 자기수축에 미치는 영향에 대하여 실험적으로 고찰하였다. 혼화재료는 실리카흄, 고로슬래그, 플라이애시의 3종류로서 치환률은 10, 20, 30%의 3수준으로 하였고 양생온도는 5, 20 및 $35^{\circ}C$의 3수준으로 계획하였다. 연구결과 양생온도가 높아질수록 혼화재 치환률이 감소할수록 응결시간은 단축되는 것으로 나타났으며, 양생온도에 따른 자기수축의 경우 양생온도가 증가할수록 수화반응속도 증가에 의해 자기수축이 커지는 것으로 나타났다. 또한 SF나 BS를 사용한 경우 자기수축이 플레인보다 증가하는 것으로 나타났고, FA의 경우는 플레인과 큰차이가 없거나 약간 감소하는 경향을 보였다. 또한 적산온도에 의한 자기수축 평가결과 동일한 적산온도에서 양생온도별 자기수축량의 차이가 크게 나타나 온도민감도를 보다 정확하게 고려할 수 있는 방법이 요구되었다.

• Computers and Concrete
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• 제21권2호
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• pp.199-207
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• 2018

With the development of concrete technology, producing concrete products that have the ability to flow under their own weights and do not need internal or external vibrations is an important achievement. In this study, assessments are made on using travertine, marble and limestone rock flours in self-compacting lightweight concrete (SCLC). In fact, the effects of these powders on plastic and hardened phases of SCLC are studied. To address this issue, concrete mixtures with water to cementitious materials ratios of 0.42 and 0.45 were used. These mixtures were made with 0 and 10% silica fume (SF) replacement levels by cement weight. To achieve lightweight concrete, lightweight expanded clay aggregate (Leca) with the bulk density of about $520kg/m^3 $was utilized. Also two kinds of water were consumed involving tap water and magnetic water (MW) for investigating the possible interaction of MW and rock flour type. In this study, 12 mixtures were studied, and their specific weights were in the range of $1660-1692kg/m^3$. To study the mixtures in plastic phase, tests such as slump flow, J-ring, V-funnel and U-box were performed. By using marble and travertine powders instead of limestone flour, the plastic viscosities and rheology were not changed considerably and they remained in the range of regulations. Moreover, SCLC showed better compressive strength with travertine, and then with marble rock flours compared to limestone powders. According to the results of the conducted study, MW showed better performance in both fresh and hardened phases in all the mixes, and there was no interaction between MW and rock flour type.

• 콘크리트학회논문집
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• 제19권6호
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• pp.701-706
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• 2007

본 연구는 장기간 숏크리트의 강도를 유지할 수 있는 영구지보재로서 알칼리 프리계 및 시멘트 광물계 급결제를 사용한 적정 배합비의 고성능 숏크리트의 내구성을 평가하였다. 내구성 실험은 염소이온 투과 시험, 동결융해 반복 시험, 촉진 중성화 시험 및 숏크리트에 염해의 영향 실험을 실시하였다. 실험 결과 실리카퓸을 사용한 모든 배합이 낮은 투과성을 나타내었다. 실험 결과 실리카퓸을 사용한 모든 배합이 모두 낮은 투과성을 나타내었다. 또한 동결융해 300회 반복 후에 상대동탄성계수가 85% 이상을 초과하는 우수한 동결융해 저항성을 보였다. 촉진 중성화 시험 결과 급결제에 따른 영향은 나타나지 않았으며 실리카퓸을 사용한 배합에서 중성화 깊이가 약간 깊게 나타났다. 염해 환경에서는 어떠한 영향도 없었다. 따라서 본 연구에서의 고성능 숏크리트 배합은 우수한 내구 성능을 보여주었다.

• 대한임상검사과학회지
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• 제40권2호
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• pp.147-152
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• 2008

Due to the development and expansion of industries and medical standards, the number of workers who handle organic solvents within hospitals is increasing. The authors in this study intended to investigate the actual conditions of the handling of the solvents and to encourage the recognition that the exposure to such solvents may be possible because of insensitivity to safety. In order to investigate the actual conditions of exposure of workers within hospitals, the experimental group included the three sections (Pathology department, Central Supply Room, and Operating Room), which handle organic solvents most frequently. Meanwhile, university interns were selected to be the control group. This study was conducted between May 1 to May 30, 2007, and urine was taken as samples. Hippuric acid, mandelic acid, methylhippuric acid, and phenylglyoxylic acid were analyzed through gas chromatography, and a total of 52 subjects of the experimental and the control groups were performed of the analysis. As for the results of the analysis of the experimental group, the exposure to benzene was $42.27{\pm}3.70mg/g$ creatinine, that of xylene was $1.30{\pm}0.18g/g$ creatinine, and that of toluene was $2.36{\pm}0.24g/g$ creatinine. Meanwhile, the results of the analysis of the control group showed that the exposure to benzene was $15.54{\pm}2.85mg/g$ creatinine, that of xylene was $0.52{\pm}0.02g/g$ creatinine, and that of toluene was $0.85{\pm}0.20g/g$ creatinine. The amount of exposure to benzene, xylene, and toluene was shown to be under the maximum permitted level, but as for Pathology department, it was required to educate on working conditions, to educate workers on prevention management about their health, and to install fume hood and exhaust system to improve the environments.