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Trimethylolpropane triacrylate의 합성
김동국,박보현 漢陽大學校 工學技術硏究所 2001 工學技術論文集 Vol.10 No.-
환경오염을 야기시키지 않으므로 소비가 급격히 증가되고 있는 U.V. 경화형 도료의 원료로 사용되고 있는 아크릴계 다량체인 trimethylolpropane triacrylate를 다양한 반응조건에서 합성하고 분리하여 최적의 합성조건을 선정하였다. Trimethylolpropane triacrylate의 합성에서 trimethylolpropane : acrylic acid를 1 : 4로 하고 반응용매로 ethylbengene을, 촉매로 황산을, 중함 금지제로 2,6-di-tert-butyl-4-methylphenol과 Cu-powder 또는 zinc-sulfate를 함께 사용하는 반응 조건이 최적조건이었다. Trimethylolpropane triacrylate that is used for the composition of environmental-friendly UV curable coating materials wase synthesized in order to investigate the optimized reaction condition, The opitmal reaction condition was as follows : ratio of trimethlolpropane / acrylic acid : 1 / 4, solvent : ethylbenzene, catalyst : sulfuric acid, inhibitors : 2,6-di-tert-butyl-4-methylphenol / zinc-sulfate / Cu-powder.
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외국인 학습자를 위한 한국어 관용표현의 교육방안 연구 - 동물명이 포함된 관용표현을 중심으로 -
김동국,이상률 한국언어과학회 2015 언어과학 Vol.22 No.1
The purpose of this study is to investigate Korean idiomatic expressions with an animal name and to suggest the educational measures of Korean idiomatic expressions for the foreign learners of Korean language. After reviewing the previous studies on this subject we, first, classify the idioms into 4 types based on the two unique criteria, namely the degree of an idiomatic usuage and of the understanding the meaning of the idiom’s constituents. We also propose two types of educational measures-meaning-related and meaning-inferred educational measures and apply them to teach the idioms to the foreign students at Youngsan University. The results of this experiment say that the proposal gives us a more desirable outcome than the previous one. Hopefully, this study helps to understand and recognize the meaning of an idiom and will be expected to be referred to teach the Korean language and Korean culture, too.
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張瑛郁,金容眞,金東國 漢陽大學校 基礎科學硏究所 1995 基礎科學論文集 Vol.14 No.-
다양한 에스터 중합용 금속 촉매중에서 ε- caprolactone을 중합하는데는 tin octoate가 가장 우수한 촉매활성을 나타내었다. 괴상중합에서 촉매농도가 증가하면 분자량이 감소하였고 반응온도가 높아지면 분자량과 수율이 증가하였으며 중합온도 180℃, 촉매 0.036㏖%, 중합시간 50분에서 분자량이 41,000인 polycaprolactone을 얻었다. 용액 중합에서도 유사한 경향을 보였다. Lipase가 용해되어 있는 pH 7.4인 완충용액에서 30일간 침지한 polycaprolactone은 분자량이 높을수록 분해가 느려지는 현상을 파단신율의 측정으로 알 수 있었다. The investigation of effective catalyst system for the polymerization of ε- caprolactone showed that tin octoate, among the various catalysts used for polycondensation, was exhibited as having the high catalyst activity. In bulk polymerization the molecular weight of resulting polycaprolactone was decreased with increasing the concentration of tin octcate, while yields and molecular weight were increased with increasing of reaction temperature. The polymerization of ε- caprolactone was carried out using 0.036㏖% catalyst at 140℃ for 50min to give polycaprolactone with a molecular weight of 41,000. The solution polymerization underwent in the same manner as the bulk polymerization. The prepared polycaprolactone was hydrolysed with lipase in pH. 7.4 buffer solution for 30days and its lose of elongation at breaking point determined revealed that polycaprolactone with high molecular weight was degradated slower than that with low molecular weight.
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박판주조법으로 제조한 Al-8Zn-2.5Mg-xCu 합금 판재의 미세조직에 미치는 Cu의 영향
김동국,조용희,이윤수,김용유,김형욱,김정기 대한금속·재료학회 2022 대한금속·재료학회지 Vol.60 No.4
The effect of Cu content on the microstructure and mechanical properties of Al-8.0Zn-2.5Mg-xCu (x: 0, 1, 2, 3) aluminum alloys manufactured by the twin-roll casting process was investigated. The Al-8.0Zn- 2.5Mg-xCu alloy showed an increase in surface defects with increasing Cu content. This is because the amount of residual liquid in the final solidification region increased from 9.6 wt.% to 18.3 wt.% as the Cu content increased from 0Cu to 3 Cu alloy. For the 3Cu alloy, as the amount of residual liquid in the final solidification region exceeded the critical point, a large number of surface defects and internal shrinkage defect were observed. The main secondary phases of the four alloys were the T(Mg32(Al, Zn)49) and η(MgZn2) phases, and their fraction increased with Cu content. These secondary phases mainly existed in the center segregation band, and a fine η(MgZn2) phase was additionally observed. In terms of mechanical properties, as the Cu content increased, the hardness of the center matrix, secondary phase, and overall hardness increased respectively. Although the yield strength increased, the tensile strength and elongation decreased because the center segregation band was widened from 684 μm to 790 μm with increasing Cu content.
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