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주기적 물림강성 변화와 백래쉬에 의한 기어구동계의 비선형 동특성
조윤수(Cho, Yun-Su),최연선(Choi, Yeon-Sun) 한국소음진동공학회 2002 한국소음진동공학회 논문집 Vol.12 No.12
Main sources of the nitration of a gear-pair system are backlash and transmission error, the difference between required and actual rotation during gear meshing. This paper presents the nonlinear dynamic characteristics of gear motions due to the existence of backlash and periodic variation of meshing stiffness, which is assumed as a one-term harmonic component. Gear motions are classified as three types with the consideration of backlash. Each response is calculated using the harmonic balance method and confirmed by numerical integration. The responses with the increase of the rotating speed show abrupt changes in its magnitude for the variation of the preload, exciting force, and damping coefficient. The result also shows that there is a chaotic motion with some specific design parameters and operating conditions In gear diving system. Consequently the design of gear driving system with low nitration and noise requires the study on the effects of nonlinear dynamic characteristics due to stiffness variation and backlash.
손종렬(Jong-Ryeul Sohn),변상훈(Sang-Hoon Byeon),김영환(Young-Whan Kim),김종혁(Jong-Hyeok Kim),조윤수(Yun-Su Cho),이재영(Jae-young Lee),박윤주(Youn-Ju Park) 대한환경위생공학회 2003 대한환경위생공학회지 Vol.18 No.3
Recently, Indoor air quality(IAQ) in workplace, residential environments and schools has been concern of people, scientists and related the public. And so in Seoul has recognized the healthy effect related to IAQ in schools. Therefore, the objective of this study reported in this article were to measure and compare the perception of IAQ of selected air pollutants at three different schools in Seoul. We performed a questionnaire survey of 400 students about their awareness for the importance of IAQ in our school. And we measured the IAQ of 3 schools considering as site region, construction year and studying level. The indoor air pollutants and parameters such as temperature, relative humidity, respirable particulate matter(PM10). formaldehyde(HCHO), total bacteria counts(TBC), carbon dioxide(C0₂), and noise were monitored in indoors. In results, all most response of occupant has recognized the awareness of IAQ at schools. The PM10. TBC and Noise level of all schools were higher than the standard of the public 150㎍/m³ and 500 CFU/rn³, the level formaldehyde(HCHO) was below 0.1 ppm of the healthy guideline of Korea And the concentration of CO₂ were investigated below 1,000 ppm of the standard implying ventilation in 2 schools except for 1 school(c school). Finally. the control of most important pollutants of IAQ in school were PM 10. TBC and Noise. Therefore, it can be concluded that the indoor air quality of selected 3 schools studied was perceived as acceptable. it is recommended that the government related IAQ was suggested the guideline and control of lAQ problems in schools. and all member relating school need to be effort to reduce the exposure of sources to undesirable indoor pollutants such as Particlate and Noise.