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教师指导学生板演应注意的问题与策略 被引量:1
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作者 陈翠云 《教育教学论坛》 2014年第7期47-48,共2页
数学课堂教学中,学生板演是一个重要环节,教师作为施教者,要注意把握板演的时间、机会,同时要明确板演目的,精选习题,注意课堂纪律组织与未板演学生的学习情况,这样才能使板演这一手段起到很好的效果。
关键词 数学板演 课堂组织 题目选择 效果监测
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Calculus of the Railway Vertical Stiffness Depending on the Base Plate Stiffness and the Ballast for High Speed Railways
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作者 Ramon Miralbes Luis Castejon 《Journal of Mechanics Engineering and Automation》 2011年第6期450-454,共5页
The study aims to determine a mathematical formula that correlates the vertical stiffness of the principal elements of a high speed railway. To do this, beginning on the traditional formulations, a new mathematical mo... The study aims to determine a mathematical formula that correlates the vertical stiffness of the principal elements of a high speed railway. To do this, beginning on the traditional formulations, a new mathematical model has been proposed, and has been verified and confirmed with the real information of high speed railways. Finally, there has been obtained a simple expression that correlates simply the vertical stiffness of the railway with the vertical stiffness of the elements that compound it, essentially with the base plate and the ballast system set. On the other hand, also the accuracy of the model has been verified to select the stiffness of the base plate and the ballast system depending on one of this stiffness and the total vertical stiffness that it is wanted. With this simplified formula, it is possible to optimize the vertical stiffness of the railway to obtain the best behavior in each zone and to reduce the final cost of the use of the via, taking in consideration the energy needed to move the trains, the maintenance cost, the useful life, etc.. The process to optimize the railway stiffness in each point depends on the vertical stiffness of the ballast and the sub-ballast, and it is possible to use different plate bases with different stiffness to obtain the optimal stiffness that has been previously obtained with a cost and maintenance analysis. 展开更多
关键词 RAILWAY WAY STIFFNESS BALLAST PLATFORM base plate.
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