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이중 에너지 X선 흡수계측법을 이용하여 폐경기간에 따른 골밀도 변화의 상관관계 연구
정승훈(Seung Hun Jeong),이태희(Tae Hui Lee),김동우(Dong Woo Kim) 대한방사선과학회(구 대한방사선기술학회) 2018 방사선기술과학 Vol.41 No.1
To evaluate the applicability of osteoporosis management by statistical analysis of the correlation between bone mineral density (BMD) changes after menopause by dividing the T-score of bone mineral density measured by dual energy X-ray absorptiometry do. Between January 1, 2016 and July 31, 2017, women who visited the medical center of W Medical Center were enrolled in this study. The postmenopausal period was divided into 5 groups, There were 18 patients within 5 years, 44 patients in 6~10 years, 134 patients in 11~15 years, 109 patients in 16~20 years and 21 patients in 21 years or older. And postmenopausal women. Bone mineral density (BMD) of the lumbar spine and femur was measured using a dual energy X-ray absorptiometry. The lowest value among lumbar spine 1, 2, 3 and 4 and the lowest value among the femoral neck, greater trochanter, total femur, and ward Values were measured. The statistical significance was analyzed by using bivariate correlation coefficient method and one – way ANOVA. In 326 patients who underwent BMD, the correlation between bone mineral density and postmenopausal BMD showed a negative correlation (-.159, p<. 01) with BMD of femur and BMD of lumbar spine The correlation between the meno- . . pausal period and negative (-.208, p< 01) was shown There was a significant difference (p<.012) between the postmenopausal femur bone density and the mean value of the lumbar spine BMD (p<.000). The relationship between bone mineral density (BMD) and postmenopausal women s postmenopausal status can be estimated by estimating the bone mineral density and using it as a basic data for osteoporosis management.
AZ31 마그네슘 합금의 인장 특성에 미치는 변형속도의 영향
정승훈 ( Seung Hun Jeong ),박지연 ( Ji Youn Park ),최일동 ( Il Dong Choi ),박성혁 ( Sung Hyuk Park ) 대한금속재료학회(구 대한금속학회) 2013 대한금속·재료학회지 Vol.51 No.10
The effect of the strain rate at a range of 10?4 ~ 3 × 102 s?1 on the tensile characteristics of a olled AZ31 magnesium alloy was studied. The normal tensile specimens were tested using a high rate hydraulic testing machine. Specimens were machined from four sheets with different thicknesses, 1, 1.5, 2 and 3 mm, along three directions, 0˚, 45˚, and 90˚to the rolling direction. The results revealed that all the specimens had a positive strain rate sensitivity of strength, that is, the strength increased with increasing strain rate. This is the same tendency as other automotive steels have. Our results suggest that the AZ31 magnesium alloy has better collision characteristics at high strain rates because of improved strength with an increasing strain rate. Ductility decreased with an increasing strain rate with a strain rate under 1 s?1, but it increased with an increasing strain rate over 1 s?1. The mechanical properties of the AZ31 magnesium alloy depend on the different microstructures according to the thickness. Two and 3 mm thickness specimens with a coarse and non-uniform grain structure exhibited worse mechanical properties while the 1.5 mm thickness specimens with a fine and uniform grain structure had better mechanical properties. Specimens machined at 0˚ and 45˚to the rolling direction had higher absorbed energy than that of the 90˚specimen. Thus, we demonstrate it is necessary to choose materials with proper thickness and machining direction for use in automotive applications. (Received December 28, 2012)
압축공기 공급압력 능동서보제어 시스템 개발과 작동성능 검증
정승훈(Seung Hun Jeong),조현우(Hyun Woo Joe),장인배(In Bae Chang) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.5
Compressed air is widely used as the primary energy source of automated production facilities. However, most compressed air supply systems have been operated without any consideration about the energy efficiency. Especially, rapidly changing the demand for pneumatic pressure causes pressure fluctuation and waste of energy. Therefore, we developed the supply pressure control system of compressed air by using PID control algorithms to stabilize the supply pressure. The developed system was successfully commercialized by the brand name of Flow Master. In this paper, the performance of the Flow Master' was verified in the field tests and the results show that the performance of supply pressure stabilization were below ± 1psi even the worst cases.