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HVDC適用을 考慮한 高密度폴리에틸렌에틸렌비닐아세테이트 混合 絶緣物의 內部電界 및 電位分布에 關한 考察
유종철,이흥규 忠州大學校 2007 한국교통대학교 논문집 Vol.42 No.-
Recently, many attention has been paid to blended polymer power cable for HVDC. The electric field in an insulation system is decided by its conductivity or space charge for DC. Also, the conductivity or space charge is very sensitive to additives, impurities, or physical structure of insulating polymer. In this study, we tried to overcome the defects by mixing HDPE and EVA has good miscibility with the ratios of 80:20, 70:30, 60:40, 50:50 respectively. The basic properties such as FE-SEM and XRD analysis, FT-IR analysis are discussed. In the internal electric field and potential distribution analysis, we investigated tendency with applied voltage variation, also applied time dependency of internal electric field and potential distribution calculated from space charge density distribution according to blend ratio each specimen. Through this experiment, we present mixture ratio with optimal insulation performance for HVDC transmission and distribution cable.
채경연,유양자,경규항,박세원,김연순 한국조리과학회 2002 한국식품조리과학회지 Vol.18 No.1
Effect of copper ions (Cu^+ and Cu^2+) on the fermentation of kimchi, especially on their effect on the prevention of over-acidification of kimchi, was investigated. The effect of Cu^2+ ion on the growth of individual lactic acid bacterium originally isolated from kimchi was also investigated. The addition of Cu^+(≥4.0mM) or Cu^2+(≥3.0mM) ions in kimchi effectively inhibited growth of lactic acid bacteria and maintained a titratable acidity of less than 1.0% for a periods of 14 days. Leuconostoc mesenteroides significantly decreased at the 10th day of fermentation in control kimchi, whereas the group with Cu^+ and Cu^2+ showed 10^5-10^6 CFU/㎖ at the 14th day of fermentation. This indicates that the addition of Cu^+ and Cu^2+ inhibited the production of excessive acids by inhibiting lactic acid bacteria, and allowed Leu. mesenteroides stay alive longer. Fe^2+ and SO_4^2- ions did not have any effect on the fermentation of kimchi. Cu^2+ inhibited growth of all lactic acid bacteria tested, such as Leu. mesenteroides 6, Streptococcus faecalis 12, Lactobacillus plantarum 14, Lac. brevis 15, Leu. mesenteroides LA 10, and Lac. plantarum LA 97.
Effects of van der Waals Bonding on the Collisional Dissociation of a Highly Excited Chemical Bond
Yoo Hang Kim,Hyung Kyu Shin Korean Chemical Society 1991 Bulletin of the Korean Chemical Society Vol.12 No.4
Dissociation of a highly excited diatomic molecule in the Ar + Ar…$O_2$ and Ar + $O_2$ collisions is studied using trajectory dynamics procedures in the collision energy range of 0.050 to 1.0 eV. Between 0.050 and 0.2 eV, dissociation probabilities are very large for the complexed system compared to the uncomplexed system. This efficient dissociation of $O_2$ in Ar…$O_2$ is attributed to the ready flow of energy from the incident atom to the large-amplitude vibrational motion of the excited O2 via the van der Waals bond. Thermal-averaged dissociation probabilites of $O_2$ in Ar + Ar…$O_2$ near room temperature are nearly two orders of magnitude larger than those of $O_2$ in Ar + $O_2$.
유양자,경규항,이민정 한국조리과학회 1990 한국식품조리과학회지 Vol.6 No.2
냉장 온도에서 보리차를 저장하는 동안에 보리알을 그대로 둔 상태에서는 보리차의 산도가 증가되고 pH는 감소하는 경향이 뚜렷이 나타나나 보리알이 제거된 상태에서는 산도나 pH의 변동이 없어 보리차를 저장하는 동안 볶은 보리로부터 산성물질이 용출된다는 사실이 밝혀졌다. 보리차의 저장온도를 높여 20∼35℃에 저장하였을때에는 온도가 상승함에 따라 세균이 출현하는 빈도가 증가하였으며 모든 시료에서 산도가 저장 일주일 정도까지 증가하다가 그 이후 약간씩 감소하기 시작하는 때부터 증가하기 시작하여 산도와 pH는 적절한 관계를 나타냄이 관찰되었다. 변패되어 혼탁해진 시료로부터 미생물을 분리하여 이 세균들의 형태학적 생리학적 성질을 조사하여 본 결과 분리세균 모두가 Bacillus속에 속하는 포자형성 세균으로 동정되어 분리된 세균은 Bacillus licheniformis, Bacillus coagulans, Badillus cirulans, Badillus stearothermophilus Bacillus brevis이었다. 이 세균들이 보리차에 번식하게 된 원인은 이들이 내열성 포자를 만들기 때문에 보리를 볶는 과정이나 볶은 보리를 물에 넣고 끓이는 가열 과정에서도 견딜 수 있었다고 판단된다. 변패되고 있는 보리차의 유기산 분석 결과로 휘발성 유기산으로는 acetic acid가 현저히 검출되었고 유기산은 아니지만 많은 양의 ethanel이 검출되었다. 비휘발성 유기산으로는 lactic acid와 succinic acid의 검출빈도가 가장 놓았고 양적으로도 많은 결과가 나타났으며 보리차의 관능적인 면에서 볼 때 변패되는 보리차는 주로 acetic acid와 ethanol이 변패취의 주요물질인 것으로 생각된다. 보리차의 보리알을 제거하고 저장하였을 때에는 보리알을 그대로 두고 저장하였을 때보다 미생물에 의한 변패 빈도나 정도가 약하게 나타났는데 그원인은 보리알에 부착되어 있는 미생물 포자를 보리알과 동시에 제거함은 물론 보리알로부터 용출되어 나올 영양소를 제거하였기 때문이라고 생각되나 세균수의 증감이 일률적이지 못한점이 아직 의문으로 남는다. 그러므로 보리차를 끓인 후에는 보리알을 제거하고 될 수 있으면 20℃이하의 낮은 온도에 저장하는 것이 미생물의 성장을 억제할 뿐 아니라 보리차의 산패 및 혼탁 방지에 유리하다고 할 수 있다. Quality deterioration of barley drink during storage was examined by measuring viable count, titratable acidity (TA), turbidity and pH of barley drinks with or without barley particles stored at temperatures of 20, 25, 30, and 35℃. Qualitative analysis of organic acids in spoiled barley drink was also performed. TA of barley drink during storage increased to 0.009, 0.0095, 0.0097 and 0.020% at 20, 25, 30 and 35℃, restectively. TA reached the mixima between 7 and 10 days of storage and reduced from then on. pH values followed the exactly reverse trend of TA. The rate of bacterial spoilage of barley drinks was faster when it was stored at higher temperatures. The numbers of bacteria were in the range between 9.0×10^6-8.0×10^8 cells/ml depending on the storage temperatures and the different brands. Those samples with higher bacterial growths showed higher optical densities. Volatile organic acids such as acetic, formic, propionic, isobutyric, isovaleric acids were detected in addition to ethyl alcohol. Non-volatile organic acids such as pyruvic, lactic, oxalacetic, succinic, fumaric acids were detected. Among them, acetic and lactic acids were most important in their quantities. Five different kinds of spoilage bacteria were isolated and identified as Bacillus licheniformis, Bacillus coagulans, Badillus cirulans, Badillus stearothermophilus and Bacillus brevis, all of which were found to form endospores.