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Dynamic analysis of a pulley-belt system with different pulley radii and support stiffness
김민성,정진태 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.12
Herein we present a new model to describe a pulley-belt system with various ratios of spring constants supporting the two pulleys and various ratios of pulley radii. The main object of this paper is to analyze the effects of differences between the radii of the two pulleys and the two spring constants on the dynamic characteristics of the pulley-belt system. To this end, five equations of motion and eight boundary conditions are derived using Hamilton's principle, and the governing equations are discretized using Galerkin's method. The natural frequencies and the mode shapes corresponding to the various radius ratios of the two pulleys and ratios of the two spring constants are obtained, and the responses are calculated to verify the dynamic characteristics of the pulley-belt system. This study shows the exact cause of the coupling between the rigid-body motions and belt deflection motions, and the difference between natural frequency veering and crossing phenomena is analyzed by confirming the mode shapes near each phenomenon. In addition, we confirm the influences of the radius ratio of the two pulleys and the ratio of the two spring constants on the changes of the natural frequencies according to the moving velocity of the belt.
H.264 기반의 PIP(Picture-In-Picture)를 위한 비디오 트랜스코더 설계
김민성,전도영,조병국,유홍연,홍성훈 전남대학교 전자통신기술연구소 2008 전자통신기술논문지 Vol.11 No.1
최근 들어 멀티미디어 서비스가 확산되면서 비디오 및 오디오의 비중이 더욱 커지고 있다. 또한 기존의 아날로그 서비스로투버 디지털 방식으로의 전환도 활발하다. 디지털 비디오나 오디오는 저장매체나 전송매체의 용량에 비해 데이터 량이 지나치게 많다는 것은 잘 알려진 사실이다. 따라서 대표적인 압축 방식인 H.264 및 MPEG 등의 기술을 이용해 디지털 원 신호(source)를 압축하고 있다. 더 나아가 원 신호를 그대로 보관하기 보다는 압축된 상태의 비트스트림을 보관하고 있다가 재활용하는 시도가 활발해지고 있다. 현재 디지털 비디오 서비스를 하려면 디지털 원 신호를 MPEG 등과 같은 부호화기에 입력시켜 압축을 한 후 전송하는 것이 보통이다. 스튜디오에서는 나중에 사용하기 위해 원 신호를 그대로 보관하고 있다. 하지만 원 신호 대신 비트스트림을 저장하고 있다면 저장 공간을 수십 배 절약할 수 있다. 스튜디오에서 신호를 압축된 비트스트림의 상태로 저장하기 위해서는 비디오 검색, 화면내화면(picture-in-picture), 비디오 합성, 비디오 편집, 전송 비트율 변환 등의 다양한 응용이 가능해야만 한다. 따라서 최근에 원 신호를 사용하지 않고 이 비트스트림을 그대로 활용하고자 하는 연구가 활발하다. 본 논문에서는 앞에 언급한 응용 가운데 다중의 영상 비트스트림을 합성하여 단일의 H.264/AVC 비트스트림으로 출력하는 화면 내 화면을 가지는 변환 방법에 대해서 논하고자 한다. 이 변환 부호기는 단순한 복호기에서 부호기로 연결된 형태이지만 실제로는 압축된 비트스트림 내의 여러 정보(헤더정보 및 모션벡터)를 이용하고 복호기와 부호화기의 중복 부분을 제거하므로 단순화되는 형태이다.
한국 육종터봇(Scophthalmus maximus)의 성장률 비교 분석
김민성,김태환,한재용,조현경,곽주리,박지빈,서종표,이우재 한국수산과학회 2020 한국수산과학회지 Vol.53 No.4
Turbot Scophthalmus maximus can be cultured at a higher density and has a faster growth rate than olive flounder Paralichthys olivaceus, making it an attractive alternative for flounder farmers in Korea. As it is a relatively new species to Korean farming environments, there is no general farming protocol, which takes multiple generations to develop, for turbot in Korea. Nevertheless, we applied breeding technology to develop a stock, which we considered first-generation turbot. Then we compared its growth rate (an important economic trait) to different populations (the original stock of Korean turbot, French turbot, and Chinese turbot). The four different populations were grown in similar culture conditions. First-generation Korean turbots grew about 28% faster than all others. We will continue to select for important traits such as color, disease resistance, and heat tolerance in this turbot broodstock; we believe that with the appropriate selection process, Korean turbot should become competitive in the markets, and will become a major farming species in the Korean aquaculture industry.
Development of noise pattern map for predicting refrigerant-induced noise in refrigerators
김민성,정의봉,한형석 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.9
In refrigeration systems, flow state in evaporators is two-phase. Acoustic characteristics of noise generated in pipes with two-phaseflow depend on flow patterns and instantaneous cycle conditions. Refrigerant-induced noises are irregular and have a band frequency. Therefore, it is difficult to predict the occurrence conditions of refrigerant-induced noise in evaporators. Hence, the development of adesign guide that anticipates the occurrence of refrigerant-induced noise is important. Flow pattern maps have been proposed by Baker,Hewitt, Taitel-Dukler, etc. However, these do not consider the acoustic viewpoint and cannot predict refrigerant-induced noise basedsolely on the estimated flow patterns. Therefore, in this study, we suggest a noise pattern map for directly anticipating refrigerant-inducednoise from various flow patterns. We performed experiments using R600a refrigerant and refrigerant-supply equipment designed for flowvisualization and flow regime transition. Based on experimental data, we suggest a noise pattern map for determining the level of refrigerant-induced noise.
참옻 추출물의 MCF-7 인체 유방암 세포에서 증식 억제효과
김민성,안원근,이장천,Kim, Min Sung,An, Won Gun,Lee, Jang Cheon 대한한의학방제학회 2016 大韓韓醫學方劑學會誌 Vol.24 No.4
Objectives : The purpose of this study was to investigate the anti-cancer effects of extract of Rhus verniciflua Stokes (RVS) in human breast cancer cell lines. Methods : In cultured human breast cancer MCF-7 cells, we investigated growth inhibitory effect of RVS. MCF-7 cells were cultured with various concentrations (0, 200, 300, and 400 ug/ml) of RVS at $37^{\circ}C$ for 24 h. We performed CCK-8 assay and flow cytometry for detection of Annexin V-PI staining. Results : As a result, RVS inhibits the cell growth and induction of apoptosis in dose dependent manner in MCF-7 breast cancer cells. Conclusion : RVS has anti-cancer activities and induced apoptosis in human breast cancer MCF-7 cells. Therefore we suggest that RVS can use as a novel class of anti-cancer drugs.
WAGE DIFFERENTIAL BY EMPLOYMENT TYPE AND CONTRACT LENGTH
김민성,류성현 한국경제학회 2010 The Korean Economic Review Vol.26 No.1
We estimate wage differentials by employment type and contract length using Oaxaca decomposition. In the Economically Active Population Survey of Korea from 2004 through 2008, we find that regular workers receive slightly higher wage rates than non-regular workers after controlling for a standard list of individual attributes. This coincides with the findings in Lee and Kim (2009) and Nam (2007) that wage discrimination explains a very small part of the observed wage differential between regular and nonregular workers. On the other hand, the wage gap between regular and nonregular workers within a subgroup of similar contract lengths can be quite significant. Among workers with longer contracts, regular workers receive significantly higher wage rates than non-regular workers. This result is in line with the findings in Kim and Park (2006) that wage discrimination between regular and non-regular workers is significant after controlling for establishment characteristics.