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볼 베어링에 의해 발생하는 HDD 회전축계 NRRO의 온도 상승에 따른 변화
김동균(Kim, D.K.),장건희(Jang, G.H.) 한국소음진동공학회 2004 한국소음진동공학회 논문집 Vol.14 No.9
This research investigates the non-repeatable runout (NRRO) of a HDD spindle system at elevated temperature by analyzing the characteristics of a ball bearing and the natural vibration characteristics of a HDD spindle system due to the effect of elevated temperature. It shows that the elevated temperature results in the increase of the contact angle and the decrease of the deformation of the ball bearing in a HDD spindle system. The variation of bearing frequencies, which are dependent on the cosine function of contact angle, is almost negligible at elevated temperature. However, the decrease of bearing deformation at elevated temperature reduces the stiffness of the ball bearing and the natural frequencies of a HDD spindle system consequently. The latter has a significant effect on the amplitude and the frequency distribution of NRRO at elevated temperature.
녹용분말 급여가 성장기별 흰쥐의 성장 및 장기발육에 미치는 효과
성하균,김동균,신형태 한국동물자원과학회 2003 한국축산학회지 Vol.45 No.5
The velvet antler of Korean sika deer has been used to the important resources for human health care with ginseng in Korea and Chinese. For studying on biological function of deer velvet being recorded in many ancient literatures, this experiment was conducted to evaluate the effects of powdered velvet antler on growth, feed intake, feed efficiency and intestinal organ development in growing and adult Sprague-Dawley Rats. Experiments were designed by adding amount of powdered velvet antler such as control (non-supplementation), powdered velvet antler Ⅰ (PVA Ⅰ, recommended dos) and powdered velvet antler Ⅱ (PVA Ⅱ, thrice recommended dose). The recommended dose of powdered velvet in this experiment was calculated with metabolic body weight of rats, which based on the recommended amounts for 70㎏ of human. The growths of growing and adult rats generally appeared advantage in PVA supplementation. The final body weight of control, PVA Ⅰ and Ⅱ were respectively 470±39.00g, 478±3033g and 475±22.72g in growing rats, and 485±38.50g, 521±38.67g and 508±34.44g in adult rats. The average daily feed intake were not significantly influenced but the feed efficiency ratios (feed/gain) were improved by PVA supplementation. The feed/gain ratios of control, PVA Ⅰ and Ⅱ were respectively 5.99, 5.47 and 5.54 in growing rats, and 9.04m 7.73 and 8.18 in adult rats. In case of developments of liver, heart, kidney and stomach, we obtained favorable results in both PAC Ⅰ and Ⅱ, but their results were not significantly different according to amount of PVA supplementation. Because liver and heart are important organs in the circulation of blood, their favorable effects suggest that velvet antler may have factors contributing hematopoiesis. Conclusively, supplementation of that velvet antler may have factors contributing hematopoiesis. Conclusively, supplementation of powdered velvet antler resulted in an improved growth, feed efficiency and development of some intestinal organs in growing and adult rat. Even if further investigation of dose in human health care are should be performed, this experiment appeared the best desirable results in PVA Ⅰ, recommended dose of powdered velvet antler.