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지하철 7호선 차륜의 구름 및 미끄럼 접촉으로 인한 피로손상 예측 연구
이희섭(Lee Hee-Sub),주세민(Joo Se-Min),김호경(Kim Ho-Kyung),권석진(Kwon Seok-Jin) 한국철도학회 2009 한국철도학회 학술발표대회논문집 Vol.2009 No.11월
Since the train wheel supports the whole weight of train carriage as an important mechanical component which moves on the rail, the damage to wheel surface occurs due to exfoliation, abrasion, depression and micro-cracking, while its interaction with rail eventually leads to wear during operation. The interaction between several parameters could be a reason for the damage. But, in this study, we tried to identify the economical and optimal period of rail re-profiling for operation by investigating the life span of the train wheel and estimate its safety through estimating fatigue damage on the train wheel surface in consideration of the effect of friction coefficient of rolling and sliding on the contact surface between the wheel and rail during operation. Therefore, a fatigue damage analysis model was embodied by applying stress which occurs during rolling contact with rail, using the material properties and the analysis of operating data, which were obtained through tensile tests on the sample extracted from a train wheel of Subway Line 7. It also has analyzed the effect of friction on fatigue damage in wheel during its rolling and sliding.
Revisiting the Cost of Business Cycles: A Demand Shock Channel
김형석(Hyung Seok Kim),주세민(Se Min Joo) 한국계량경제학회 2019 JOURNAL OF ECONOMIC THEORY AND ECONOMETRICS Vol.30 No.2
This paper estimates the welfare cost of the US business cycle episodes over the period 1964-2018. Under the restriction of a balanced growth path, the representative consumer in a frictionless, competitive business cycle world would reduce GDP by around 1.3 percent each year to eliminate business cycle risk; our estimates are comparable to the benefits of stabilization by Barro(2009). The key to these results is augmentation with investment-specific shocks `a la Fisher (2006) to a standard business cycle model.