• Journal of the Korean Ceramic Society
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• v.41 no.10 s.269
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• pp.749-755
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• 2004

Fluosilicic acid ($H_2SiF_6$) is recovered as aqueous solution which absorbs $SiF_4$ produced from the manufacturing of industrial-graded $H_3PO_4$ or HF. Generally, fluosilicate salts prepared by the reaction between $H_2SiF_6$ and metal salts. Addition of fluosilicate salts to cement endows odd properties through unique chemical reaction with the fresh and hardened cement. In this study, two-component fluosilicate salt based chemical admixtures (MZ) of $4\%,\;6\%$, and $8\%$ concentration were prepared by the reaction of $H_2SiF_6$ ($25\pm2\%$) and metal salts. The effect of concentration of MZ at a constant adding ratio on the hydration and watertightness of cement were investigated respectively. In a cement containing MZ, metal fluorides such as $CaF_2$ and soluble silica by hydrolysis were newly formed during hydration. The total porosity of the hardened cement was lower in the presence of U because of packing role of metal fluoride and pozzolanic reaction of soluble $SiO_2$. Consequently, the watertightness of the hardened paste containing MZ was more improved than non-added (plain) due to an odd hydration between cement and MZ.

• Journal of the Korean Institute of Gas
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• v.22 no.4
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• pp.32-38
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• 2018

The purpose of this study is to assess quantitatively the amount of leaks and the extent of dispersion in case of a leak at a hydrogen fluoride tank container unloading station, and to suggest a safety improvement plan to prevent recurrence of similar accidents. In 2012, Company H leaks 8 tonnes of tank containers with a maximum storage capacity of 18 Ton, causing it to become a social issue. As a result of calculation using Gaussian plume model, the concentration was estimated to be more than 20ppm from the leak point to 1,321 m radius. The leakage of hydrogen fluoride from the company R in 2014 was estimated to be 11.02 kg, of which 2.9 kg was treated by the scrubber. As a result of calculation using Gaussian plum model, the damage range with a concentration of 20ppm or more from the leak source was estimated to be 69 m in radius. As a result of comparing the above two accidents, it was found that the leakage amount was about 987 times different and the damaged site was more than 19 times different. Therefore, it was concluded that it was necessary to control the wearing of the protective equipment, the enclosure of the unloading site, the installation of the scrubber, and the emergency training to avoid the accidental leakage of a hydrogen fluoride from the unloading site.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.5
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• pp.326-334
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• 2012

To determine the concentrations and the mass flow of selected 10 perfluorinated compounds (PFCs), a field study was conducted in a wastewater treatment plant. Raw influent, primary influent, primary effluent, aeration tank effluent, secondary effluent, final effluent, dehydration liquor, primary sludge, thickened sludge, final sludge were collected over 3 days in the summer and the winter respectively. Collected samples were equally mixed and then served as an analytical sample. Total 10 compounds were analyzed. In terms of treated water, the concentration of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) were in range of N.D.~26.29 ng/L and N.D.~38.15 ng/L respectively. Perfluorononanoate (PFNA) and perfluorohexanesulfonate (PFHxS) were ranged from N.D. to 36.79 ng/L and from N.D. to 24.36 ng/L. In terms of sludges, a concentration of PFOS, PFOA, and perfluorodecanesulfonate (PFDS) were detected from 6.82 to 59.37 ng/g, from 0.13 to 0.37 ng/g, from N.D. to 0.83 ng/g respectively. Mass loading for PFCs increased during wastewater treatment except for PFNA. The observed increase in mass flow of PFCs may have resulted from biodegradation of precursor compounds.

• Journal of Ethics
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• no.80
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• pp.1-30
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• 2011

Confucianism and Buddhism were compatible in the period of Goryeo Dynasty. And then, the rulers worshiped Confucianism and repressed the religious activity of the Buddhist monk in the early years of the Joseon Dynasty. But King Sejong planed to bring reconciliation between Confucianism and Buddhism. Especially on the ceremonies of mourning and sacrificial rituals, he always performed the two religious style. The reason of sticking to his amicable consciousness is as follows. Firstly, he thinks that both the theory of Confucianism and the religious spirit of Buddhism are very important for the building up the foundation of his Dynasty. Secondly, his mind has been of a same faith cure on the incurable disease. Therefor, when the Royal family is taken ill he must pray to Buddha for recovery from the first stage. Thirdly, he regards social conditions to be the most important and respect for man's life and dignity for the purpose of beneficent administration. But Joseon's government line was the anti-Buddhist policy. So, the policy came in the wake of a debate among King Sejong and Confucian government officials. However his harmonious mind was unchanged between Confucianism and Buddhism. After all, in the last phase of his life he was deeply religious on Buddhism. I think that King Sejong's amicable consciousness could make a contribution to overcome religious conflicts and to create a new political cultural form in the modern society

• Proceedings of the Materials Research Society of Korea Conference
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• 2002.05a
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• pp.32-32
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• 2002

• The Korean Publising Journal, Monthly
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• s.116
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• pp.4-5
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• 1992

• The Journal of the Korean dental association
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• v.1 no.1
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• pp.130-132
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• 1954

• KOMUNHWA
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• no.18
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• pp.2-12
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• 1980

• Proceedings of the Korean Nuclear Society Conference
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• 2001.05a
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• pp.371.1-371
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• 2001

• KOMUNHWA
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• no.10
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• pp.3-15
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• 1972