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윤병진(Byung Jin Yoon),김현욱(Hyun Uk Kim),박희정(Hee Jeoung Park),이재응(Jae Eung Lee) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
Coil springs are widely used in the industries of machinery, buildings, supplies and general well-rounded life by having a unique, superior efficiency and low-frequency vibration, but have the disadvantage of damping. In previous studies, to compensate for this disadvantage, a coil spring wrapped with the polymer film was evaluated for damping effect while maintaining the dynamic characteristics of system. Damping property of the polymer film was investigated base on the different film type, the magnitude of tension of the film, and number of layer of the film. The performance of the system is characterized by impact testing. In this paper, we evaluate the damping effect of the performance factor through simulation and determines the reliability as compared with experimental data. Also, we check the relative importance between the performance factor, and find the optimum value to maximize the damping effect through simulation.
주암호 외남천 유역 하천수의 질소농도와 동위원소비 분석을 이용한 오염원 평가
최유진 ( Yu Jin Choi ),정재운 ( Jae Woon Jung ),최우정 ( Woo Jung Choi ),윤광식 ( Kwang Sik Yoon ),최동호 ( Dong Ho Choi ),임상선 ( Sang Sun Lim ),정주홍 ( Ju Hong Jeong ),임병진 ( Byung Jin Lim ),장남익 ( Nam Ik Chang ) 한국물환경학회 2011 한국물환경학회지 Vol.27 No.4
In an effort to investigate water pollution characteristics of Juam lake, water samples were collected from three sites (Sites A, B, and C) of Oenam stream which is a typical tributary of rural watershed in the lake and analyzed for N concentration and the corresponding isotope ratio (δ15N) of NO3-. Concentrations of NO3- were not dramatically different among the sites; 0.8±0.2 mg N L-1 (range: 0.0~4.3 mg N L-1) for Site A, 1.1±0.2 mg N L-1 (0.0~4.3 mg N L-1) for Site B, and 1.1±0.1 mg N L-1 (0.1~2.6 mg N L-1) for Site C. Meanwhile, δ15N tended to decrease with river flow; it was highest for Site A (45.5±5.3‰) followed by Site B (19.7±2.0‰) and Site C (8.7±1.5‰). Such high δ15N values of NO3- in Site A suggested that NO3- derived from livestock feedlot (specifically livestock excrete of which δ15N is higher than 10‰) is the predominant pollution sources despite mountainous area occupied the most of land-use in the watershed. Using the two-sources isotope mixing model, it was estimated that the contribution of cropping activities (i.e. fertilization) became greater in down-stream area (Sites B and C) due to the higher agricultural land-use than the up-stream area (Site A). Particularly, during the active cropping season, the low contribution of organic pollution sources indicated that domestic sewage was not the predominant pollution source. Therefore, it was suggested that agricultural sources such as livestock farming and cropping rather than mountainous and residential are the dominant sources of water pollution in the study area. These results could be effectively utilized in elucidating water pollution sources in rural areas and selecting water management practices.