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구름요소의 Waviness 를 고려한 볼베어링 해석 이론
정성원,장건희 한국소음진동공학회 2001 한국소음진동공학회 논문집 Vol.11 No.7
The research presents an analytical theory to calculate the characteristics of the bal bearing with waviness in its rolling elements considering the centrifugal force and gyroscopic moment of bal. The effects of centrifugal force and gyroscopic moment are introduced to the kinematic constraints and force equilibrium equations. and the waviness of rolling elements is modeled by sinusoidal function to calculate the contact force at each ball. The numerical solutions of governing equation of berating due to waviness are calculated by using the Newton-Raphson method. The accuracy of the research is validated by comparing the contact force. contact angle in case of considering the centrifugal force and gyroscopic moment of bal and the contact force and vibration frequencies in cases of considering waviness with the prior researches respectively. It investigates the stiffness, contact force. displacement and vibration frequencies of the ball bearing considering not only the centrifugal force and gyroscopic moment of ball but also the waviness of the rolling elements.
Waviness가 있는 볼베어링으로 지지된 회전계의 동특성해석 (I) -진동 해석-
정성원,장건희,Jeong, Seong-Weon,Jang, Gun-Hee 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.12
This research presents an analytical model to investigate vibration due to ball bearing waviness in a rotating system supported by two or more ball bearings, taking account of the centrifugal force and gyroscopic moment of the ball. The waviness of rolling elements is modeled by the sinusoidal function, and it is incorporated into the position vectors of the race curvature center. The Hertzian con tact theory is applied to calculate the elastic deflection and nonlinear contact force while the rotor has translational and angular motions. Both the centrifugal force and gyroscopic moment of the ball and the waviness of the rolling elements are included in the kinematic constraints and force equilibrium equations of a ball to derive the nonlinear governing equations of the rotor, which are solved by using the Runge-Kutta-Fehlberg algorithm to determine the new position of the rotor. The proposed model is validated by the comparison of the results of the prior researchers. This research shows that the centrifugal force and gyroscopic moment of the ball plays the important role in determining the bearing frequencies, i.e. the principal frequencies, their harmonics and the sideband frequencies resulting from the waviness of the rolling elements of ball bearing. It also shows that the bearing vibration frequencies are generated by the waviness interaction not only between the rolling elements of one ball bearing but also between those of two or more ball bearings constrained by the rotor.
정성원,이준희,이경재 대한예방의학회 2019 예방의학회지 Vol.52 No.5
Objectives: Presenteeism is currently recognized as a significant global health issue that can potentially cause productivity losses. Hence, many studies have analyzed the relationships between workplace factors and presenteeism. However, few studies have considered non-occupational factors. This study examined the associations between presenteeism and activities outside work, including volunteering, self-development, leisure/sports, and gardening and house repair activities, in Korean wage workers. Methods: This study analyzed the fourth Korean Working Conditions Survey, in which a total of 19 294 wage workers participated. To identify relationships between presenteeism and activities outside work, multivariate logistic regression analysis was used after adjusting for general and occupational characteristics. Results: Self-development and leisure/sports activities significantly increased the odds ratio (OR) of presenteeism (OR, 1.166; 95% confidence interval [CI], 1.061 to 1.282 and OR, 1.276; 95% CI, 1.181 to 1.379, respectively). Conclusions: Certain activities outside work, such as self-development or leisure/sports, were related to presenteeism among Korean wage workers. Although many previous studies have emphasized the positive effects of those activities on health, this study documented negative effects of these activities outside work on health.
정성원 생화학분자생물학회 2018 Experimental and molecular medicine Vol.50 No.-
Obesity and type 2 diabetes (T2D) are two major conditions that are related to metabolic disorders and affect a large population. Although there have been significant efforts to identify their therapeutic targets, few benefits have come from comprehensive molecular profiling. This limited availability of comprehensive molecular profiling of obesity and T2D may be due to multiple challenges, as these conditions involve multiple organs and collecting tissue samples from subjects is more difficult in obesity and T2D than in other diseases, where surgical treatments are popular choices. While there is no repository of comprehensive molecular profiling data for obesity and T2D, multiple existing data resources can be utilized to cover various aspects of these conditions. This review presents studies with available genomic data resources for obesity and T2D and discusses genome-wide association studies (GWAS), a knockout (KO)- based phenotyping study, and gene expression profiles. These studies, based on their assessed coverage and characteristics, can provide insights into how such data can be utilized to identify therapeutic targets for obesity and T2D.
대학생의 피임 관련 지식 및 태도와 성적 자기주장간에 관계
정성원 한국모자보건학회 2017 한국모자보건학회 학술대회 연제집 Vol.2017 No.2
연구배경 및 목적 개방적 성문화의 급속한 확산과 무분별한 성적 정보 노출로 인해 대학생들은 ‘성’과 관련된 문제들을 직면하고 있음. 이들은 고등학생 때와는 달리 이성교제가 자유로워지면서 성경험을 할 수 있는데, 이들의 성 행위는 생식건강과 직결되기 때문에 예방적 차원의 피임은 매우 중요함. 본 연구는 대학생들의 피임 관련 지식 및 태도, 그리고 성적 자기주장의 수준이 어떠한지를 파악하고, 이들 변수간의 관련성이 있는지를 규명하고자 하는데 목적이 있음. 대상 및 방법 본 연구는 2016년 8월 15일부터 9월1일까지 연구목적을 이해하고 연구참여에 자발적으로 동의한 남학생 96명, 여학생 98명의 자료를 분석하였음. 분석방법으로는 PASW 22.0를 활용하여 t―test, AN0VA, Pearson’s correlation coefficient를 실시함. 연구결과 연구대상자 중 106명(54.6%)의 학생이 성경험이 있었으며, 주 피임법은 콘돔이었음(95명). 피임 관련 지식 수준은 15점 만점에 8.56점 이었고, ‘자궁내 장치’에 대한 질문의 정답률이 가장 낮았음. 성별에 따른 지식과 성적 자기주장 수준은 차이가 있었으나, 전공에 따른 차이는 없었음. 한편 피임 태도와 성적 자기주장은 양의 상관관계가 있었음(r=.573, p=.000). 결론 성에 대한 지식은 성적 자기주장과 관련이 있었으므로, 성적 자기주장 수준을 높일 수 있도록 대학생 대상으로 성별 맞춤형 교육프로그램의 개발 및 보급이 필요함. 향후 대학생의 피임에 대한 지식 및 태도 그리고 성적 자기주장에 영향하는 다양한 요인을 규명하는 후속 연구가 필요함.