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991.
《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(11):1535-1554
The coupled vehicle/track dynamic model with the flexible wheel set was developed to investigate the effects of polygonal wear on the dynamic stresses of the wheel set axle. In the model, the railway vehicle was modelled by the rigid multibody dynamics. The wheel set was established by the finite element method to analyse the high-frequency oscillation and dynamic stress of wheel set axle induced by the polygonal wear based on the modal stress recovery method. The slab track model was taken into account in which the rail was described by the Timoshenko beam and the three-dimensional solid finite element was employed to establish the concrete slab. Furthermore, the modal superposition method was adopted to calculate the dynamic response of the track. The wheel/rail normal forces and the tangent forces were, respectively, determined by the Hertz nonlinear contact theory and the Shen–Hedrick–Elkins model. Using the coupled vehicle/track dynamic model, the dynamic stresses of wheel set axle with consideration of the ideal polygonal wear and measured polygonal wear were investigated. The results show that the amplitude of wheel/rail normal forces and the dynamic stress of wheel set axle increase as the vehicle speeds rise. Moreover, the impact loads induced by the polygonal wear could excite the resonance of wheel set axle. In the resonance region, the amplitude of the dynamic stress for the wheel set axle would increase considerably comparing with the normal conditions. 相似文献
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This paper extends the work on Pareto-improving hybrid rationing and pricing policy for general road networks by considering heterogeneous users with different values of time. Mathematical programming models are proposed to find a multiclass Pareto-improving pure road space rationing scheme (MPI-PR) and multiclass hybrid rationing and pricing schemes (MHPI and MHPI-S). A numerical example with a multimodal network is provided for comparing both the efficiency and equity of the three proposed policies. We discover that MHPI-S can achieve the largest reduction in total system delay, MHPI can induce the least spatial inequity and MHPI-S is a progressive policy which is appealing to policy makers. Furthermore, numerical results reveal that different classes of users react differently to the same hybrid policies and multiclass Pareto-improving hybrid schemes yield less delay reduction when compared to their single-class counterparts. 相似文献
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丁自华 《武汉船舶职业技术学院学报》2010,9(2):120-123
随着中国加入WTO,中国日益深入国际社会,对外交流日益频繁,特别是从事航海运输工作的海员英语综合运用能力显得尤为重要。本文主要针对航海类高职院校英语教学中普遍出现的几个主要问题进行分析研究,然后根据现状,提出相应的对策,以便能更好的有针对性的进行教学,提高教学质量。 相似文献
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针对三峡库区复杂工程地质与水位条件下的港口高边坡稳定性与生态防护技术进行了深入研究,在国内外库区岸坡防护技术的基础上进行了优化比选,提出了采用香根草护面加筋边坡这一新型结构体系对三峡库岸边坡进行防护,并采用有限元仿真模拟计算与工程试验相结合的方法进行了论证。实践表明,该防护技术满足三峡库岸边坡防护的安全经济、环保性要求,是一种新型有效的库区港口边坡生态防护技术。 相似文献
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