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오광제(Kwang-Je Oh),김경호(Gyungho Khim),박천홍(Chun-Hong Park),정성종(Sung-Chong Chung) 대한기계학회 2016 大韓機械學會論文集A Vol.40 No.2
LM 볼가이드는 구름접촉을 갖는 이송시스템의 핵심요소로서 공작기계, 반도체 장비, 로봇 등 정밀기계에 널리 사용된다. 그러나 LM 볼가이드에서 발생하는 마찰력은 마찰열을 유발하여 위치 정도를 저하시키고 강성과 예압 변화를 야기한다. 이런 영향을 정확하게 분석하여 정밀 기계설계에 응용하기 위해서는 마찰력 모델의 정식화가 요구된다. 본 논문에서는 구름마찰, 점성마찰, 슬립마찰을 고려한 LM 볼가이드의 정확한 마찰력 모델을 유도한다. 그리고 다양한 조립, 부하 및 속도 조건에서 실험을 수행하여 마찰력 모델의 신뢰성을 검증하고, 마찰력 모델로부터 마찰 성분의 영향력을 분석한다. Linear motion (LM) ball guides with rolling contact are core units of feed-drive systems. They are widely applied for precision machinery such as machine tools, semiconductor fabrication machines and robots. However, the friction force induced from LM ball guides generates heat, which deteriorates positioning accuracy and incurs changes of stiffness and preload. To accurately analyze the effects and apply the results to precision machine design, mathematical modeling of the friction force is required. In this paper, accurate formulation of the friction force due to rolling, viscous, and slip frictions is conducted for LM ball guides. To verify the reliability of the developed friction model, experiments are performed under various assembly, load and velocity conditions. Effects of frictional components are analyzed through the formulated friction model.
박봉수,오광제,변동일,김형길,방규태,박찬근,최낙현,최웅승,정동균,심강섭 대한내과학회 1993 대한내과학회지 Vol.45 No.5
Ulcers of the small bowel distal to the duodenum are not common, and some ulcers are unexplaned by any specific mechanism and have been termed $quot;nonspecific$quot; or $quot;idiopathic$quot; small bowel ulcer. In Korea, nonspecific ulcer of the small bowel is quite rare, comparison of the western contury. Recently we experienced a patient with nonspecific ulcer of ileum. A 50-year-old male patient was admitted to the hospital because of intestinal obstruction and perforation. By laparotomy, perforation and numerous stenosis were identified in the 55 cm from ileocecal valve, segmental resection has been done. The histologic findings identical to the peptic ulcer suggested the feature of nonspecific ulcer of small bowel. We present this case with the review of literature.