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김옥현,이희복,이민기,홍정희,곽용운,Kim, Ock-Hyun,Lee, Hee-Bok,Lee, Min-Ki,Hong, Jeong-Hui,Kwak, Yong-Woon 한국생산제조학회 2010 한국생산제조학회지 Vol.10 No.6
Magnetic fluid seal is characterized by its simple design, low friction and being dustless. Those advantages are deduced from the fact that the sealing element is not a solid such as rubber or plastic but it is a fluid. Those are critical for application to a rotating shaft which is inserted into a vacuum chamber where high level of vacuum and cleanness are required. For the reason the magnetic fluid seal has become a standard for vacuum chambers for semiconductor and LCD processing. It should be noted that its sealing performance is sensitive to temperature. If necessary, water cooling should be considered. Thus anticipation of the temperature distribution of the magnetic fluid seal is important before applying it. In this paper an FEM analysis of the heat transfer has been executed and compared with experimental results. An overall convective heat transfer coefficient has been adopted for the analysis, which results in satisfactory consistency of the theoretical and experimental results.
천연 소재 BF-7의 어린이 장ㆍ단기 기억력 향상 효과
김도희(Do-Hee Kim),김옥현(Ok-Hyeon Kim),여주홍(Joo-Hong Yeo),이광길(Kwang-Gill Lee),박금덕(Geum Duck Park),김대진(Dae-Jin Kim),정윤희(Yoon-Hee Chung),김경용(Kyung-Yong Kim),이원복(Won-Bok Lee),윤영철(Young Chul Youn),정윤화(Yoonhwa C 한국식품영양과학회 2010 한국식품영양과학회지 Vol.39 No.3
본 연구는 BF-7이 어린이의 장기 및 단기 기억을 현저하게 촉진시킴을 보여주었다. 기존 임상 시험 결과를 통해 입증된 바와 같이 천연 소재인 BF-7의 안전성을 고려할 때, BF-7은 어린이 장기 및 단기 기억력, 기억유지도 및 기억의 효과적 활용 등 전반적인 기억 수행 능력 향상에 도움을 주는 매우 안전하면서 효과가 탁월한 천연소재임을 확인하였다. It has been shown that BF-7 enhances short- and long-term memory and attention in normal person. BF-7 was addressed to clinical study for children if BF-7 is also effective to children, since accumulated verification of safety and effectiveness is needed for young ages, in special. We administered BF-7 and a placebo control to two different groups of children (7-12 years old, 9.78 on averages). Their memory enhancement was tested with Rey-Kim Memory Test for Children before and after the administration of BF-7 and a placebo, in a double blinded way. The results showed that long- and short-term memories were significantly improved by the administration of BF-7. Interestingly, the degree of memory preservation, the ability of memory application and awareness of complex thing were also significantly improved. These results indicate that BF-7 is a promising substance from natural resource improving learning and memory of children as well as cognitive function of adults
간호대학생의 KCUE-Q1(Korean College & University Education Questionnaire)에 따른 비인지적 학습성과
김옥현(Ok-Hyun Kim),최은주(Eun-Ju Choi) 한국콘텐츠학회 2014 한국콘텐츠학회논문지 Vol.14 No.10
본 연구의 목적은 대학의 특성을 반영하고 비용 면에서 경제적이며 간편한 KCUE-Q1을 활용하여 간호학생의 비인지적 학습성과 수준을 파악하기 위함이다. 본 연구는 2013년 12월 2일부터 12월 20일까지 4개교의 전문대학 졸업예정자인 3, 4학년 간호대학생 중 연구목적을 이해하고 참여에 동의한 424명을 연구대상으로 편의표집하였다. 연구 결과 간호대학생의 비인지적 학습성과 성취수준은 평균 2.69점이었으며, 대상자의 일반적 특성 중 성별, 학년, 소속 대학의 2주기 간호교육 인증평가 및 동아리 활동에 따라 통계적으로 유의한 차이가 있었다. 또한 학습열의가 높을수록 학습경험이 높아지고 교육성과도 높은 것으로 나타났다. 따라서 간호학 전공 학생들의 학습성과 향상을 위한 전략으로 교육과정과 비교과활동을 통합할 수 있는 프로그램 개발 및 운영이 필요하며, 이는 간호대학생의 간호학 학습성과 성취수준 향상에 기여할 수 있으리라 생각된다. The purpose of this study was to examine the affective outcome according to KCUE-Q1 in nursing students. The survey was performed with 424 nursing students of 3-year or 4-year that scheduled to graduate from college. Collected data was analyzed using descriptive statistics, t-test, one-way ANOVA and Pearsons correlation coefficient. The level of affective outcome was 2.69. The affective outcome was significantly different according to gender, grade, nursing education accreditation and club activity. Learning passion showed a positive correlation with learning experience and educational outcome. Learning experience showed a positive correlation with leaning passion and educational outcome. The findings of this study indicates a need to develop outcome-based nursing curriculum for nursing students. It is also necessary to evaluate affective outcome in undergraduate nursing students.
김옥현(Ock Hyun Kim),이규호(Kyu Ho Lee) 한국생산제조학회 2012 한국생산제조학회지 Vol.21 No.3
Air bearing is characterized by its extremely low friction and cleanliness such that it is widely used especially for spindles with ultra-high rotational speed at several tens of thousands rpm. This paper contributes to design of a static radial air bearing suggesting numerical analysis to anticipate its performances. The numerical analysis is an iteration method based on finite difference formulation of the Reynolds equation. A prototype air bearing has been designed and manufactured. Its load capacity has been measured and compared with the numerical solutions. The result shows good consistency between the experiment and theory, which informs that the numerical analysis can be used as an useful tool to anticipate the performances. Effects of design variables on the bearing performance have been examined by Taguchis experimental methods using orthogonal array. Number of holes for supplying pressurized air, clearance between shaft and bearing, the hole diameter and bearing length are chosen for the design variables. The result shows that the clearance and the bearing length are the most influential variables while the others can be considered as almost negligible.
김옥현(Ock-Hyun Kim),이민기(Min-Ki Lee) 한국기계가공학회 2011 한국기계가공학회지 Vol.10 No.2
Magnetic seal uses a magnetic fluid to seal a gap between a rotating shaft and housing. It is distinguished from other kinds of seals from the fact that solid contact does not occur in the seal. This implies that it is free from solid rubbing thus dustless and provides a clean circumstance. That is the reason why the magnetic seal is used exclusively for most of vacuum chambers in semiconductor process where dustless clean circumstance is critical. A magnetic seal has been developed of which design parameters are determined based on published data, and an air pressure test has been done to examine its sealing capability. Effects of some design parameters have been studied through FEM analysis. The results show some notable aspects of design parameters and provide suggestions for developing the seals. Regarding the sealing capacity of the magnetic seal the factor to match the theoretical value with the actual one was found to be 0.4~0.7, which means still there is some discrepancy between theory and actual.
김옥현 ( Ock Hyun Kim ) 충북대학교 산업과학기술연구소 2016 산업과학기술연구 논문집 Vol.30 No.2
Suppression of vibrations of a car is important for driving safety and comfort. To suppress the vibrations, suspension systems are provided for most of cars. The suspensions have been concerned with only the up-down motion(vertical motion) of cars and the back-forth motion of cars has been ignored. Actually the back-forth motion would be ignored when a car is running. But just after a car stops with deceleration, the back-forth motion is activated and the driver feels more discomfort by the back-forth motion because of its higher frequency. In this study a vibrational model of a car has been suggested to consider the back-forth motion and the model parameters have been estimated by some experiments. Vibrational motions of a car when it stops with some constant decelerations have been simulated. Through the study it is verified that when a car stops with deceleration the back-forth motion occurs much larger than other up-down motion, which may raise necessity of a suspension device to suppress the back-forth motion.
마찰판의 마모 영향을 고려한 건식 클러치의 성능 모델에 대한 연구
김옥현(Okhyun Kim),김상국(Sangkook Kim),임원식(Wonsik Lim) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11
This study is analyzed a operation principal of dry-type clutch for development of prediction model of clamp and release operation point. And it is studied factors of dry-type clutch operation point decision, and travel characteristic of operation point with considering the wear. Then, the characteristic change of clamp load-travel and release load-travel are considered. Also, it is developed the performance prediction model of an assembly clutch is equipped with diaphram spring, cushion spring, and so on. The change factor of pressure plate contact point for improvement of clutch control performance of AMT is studied. Finally, it is studied decision process of actuator"s operation force and travel of release system in AMT.