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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
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.
낙상 예방 프로그램이 농촌지역주민의 낙상 효능감과 활동 특이적 균형 자신감에 미치는 효과
김옥현(Kim, Ok Hyun),이은경(Lee, Eun Kyun),김은미(Kim, Eun Mi) 한국보건간호학회 2011 韓國保健看護學會誌 Vol.25 No.2
Purpose: The study evaluated the effects of a fall prevention program in a Korean rural area. Methods: A single pretest-posttest design group was studied. Thirty nine residents in the same rural area participated in a program comprised of education and exercise. The 5-week fall prevention program was performed for 60 minutes, once a week. Results: Fall Efficacy Scale (FES) score and Activities-specific of Balance Confidence Scale (ABC) score were significantly increased after the program, but the pre-and posttest FES and ABS scores were not significantly different between the fall experience group and non-fall experience group. Conclusion: The fall prevention program can improve rural residents’ FES and ABS, and is recommended as a fall prevention intervention.
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.
김옥현 ( Ock Hyun Kim ),이규호 ( Kyu Ho Lee ) 충북대학교 산업과학기술연구소 2011 산업과학기술연구 논문집 Vol.25 No.2
This paper contributes to design of a static air bearing. Performance of the air bearing is characterized by its load capacity and consumed air flow rate. Performance of the air bearing has been estimated theoreticallyby a numerical analysis based on the Reynolds equation. For the numerical analysis finite difference formulation of the Reynolds equation has been provided. A prototype air bearing has been designed and fabricated. Its performance of load capacity has been tested and compared with the numerical solutions. The result matches well with each other, which convinces that the numerical approach can be used as an efficient tool to anticipate air bearing performances. Effects of design parameters on the bearing performance have been analyzed by Taguchi’s experimental methods. It is shown that the clearance is the most influential parameter and the next is the number of holes.
체질량지수에 따른 여대생의 식이섭취 실태와 혈액성상에 관한 연구
김옥현(Ok Hyun Kim),김정희(Jung Hee Kim) 대한지역사회영양학회 2006 대한지역사회영양학회지 Vol.11 No.3
This study was conducted to investigate the relationships among body composition, dietary intake, and clinical blood indices in college students by body mass index (BMI). Their body compositions were determined by means of BIA (Bioelectrical Impedance Analysis) method. Their dietary intake was determined using a 3-day record method and their hematological indices were determined by semi-automated microcell counter (Sysmex F-520). Their serum lipid levels were measured using biochemical analyzer (Spotchem). Subjects were classified as underweight, normal or overweight groups according to their BMI. The subjects were 69 healthy college students aged 20 to 26 years. The average age, height, weight, and BMI was 21.3 years, 162.6 cm, 54.4 kg, and 20.6 cm/m2, respectively. Their average consumption of energy was 1693 kcal, 84.7% of RDA and their mean ratio of carbohydrate: protein: fat were 54.5 : 16.4 : 29.0. There was no significant difference in nutrient intake among the groups except β-carotene and vitamin C. The β-carotene intake was significantly higher in the underweight group. Vitamin C intake was significantly higher in the overweight group. The mean intakes of Ca, Fe, Zn and folate of subjects were 74.8% to 83.2% of RDA. Especially, intakes of Ca, Fe, Zn and folate were lower in the abnormal weight groups. The overall mean values of the hematological indices in female college students were within the normal range and there was no significant difference among the groups. However, anemic subjects with hemoglobin (<12g/dl) and hematocrit (<36g/dl) accounted for about 11% of the subjects. The overall mean values of the serum lipid levels were within the normal range and there was no significant difference among the groups. But serum HDL-cholesterol level of the overweight group was lower than that of the other groups. LDL-/HDL-cholesterol ratio and AI index were significantly higher in the overweight group compared to the other groups. Based upon this study, it is necessary for college women to be educated regarding consuming more Ca, Fe, Zn, folate and less fat and cholesterol in order to have better health promotion. (Korean J Community Nutrition 11(3) : 307~316, 2006)
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.