科创中国

依据故障树分析法(VIA)原理,对城市轨道交通车辆维修的安全故障因素进行了分析.城市轨道交通车辆维修的工艺过程存在着安全"风险累积"效应;维修后车辆的营运过程存在着"风险扩散"效应.在分析目前城市轨道交通车辆维修面临挑战的基础上,提出了风险应急和风险控制的相应对策.

随着石家庄市城市规模的扩大,越来越多的城市水文环境问题日益突出.在分析石家庄市目前水文环境的基础上,提出城市面临的水文问题:城市化进程的加快,对降水量、地下水位、灾害性天气、地表水环境、地下水水质等一系列水文参数产生影响,根据石家庄城市水文的特点,探讨其变化规律并采取相应的解决对策,对城市经济发展有重要意义.

通过对渠家大院院落空间的调查研究,将院落单元作为渠家大院空间形态的构成要素,探究渠家大院的空间形态.通过对该院落空间的平面、立面和微观营造模式进行研究,深入地分析了该院落空间的布局特点、空间意向与营造理念,最终为读者解读了渠家大院空间系统的成长规律,进而揭示了渠家大院院落空间组织的方式与机制,有助对晋中城市民居营造理念与发展趋势有更好的把握.

Thermal damage caused by frictional heat of rolling-sliding contact is one of the most important failure forms of wheel and rail.Many studies of wheel-rail frictional heating have been devoted to the temperature field,but few literatures focus on wheel-rail thermal stress caused by frictional heating.However,the wheel-rail creepage is one of important influencing factors of the thermal stress.In this paper,a thermo-mechanical coupling model of wheel-rail rolling-sliding contact is developed using thermo-elasto-plastic finite element method.The effect of the wheel-rail elastic creepage on the distribution of heat flux is investigated using the numerical model in which the temperature-dependent material properties are taken into consideration.The moving wheel-rail contact force and the frictional heating are used to simulate the wheel rolling on the rail.The effect of the creepage on the temperature rise,thermal strain,residual stress and residual strain under wheel-rail sliding-rolling contact are investigated.The investigation results show that the thermally affected zone exists mainly in a very thin layer of material near the rail contact surface during the rolling-sliding contact.Both the temperature and thermal strain of rail increase with increasing creepage.The residual stresses induced by the frictional heat in the surface layer of rail appear to be tensile.When the creepage is large,the frictional heat has a significant influence on the residual stresses and residual strains of rail.This paper develops a thermo-mechanical coupling model of wheel-rail rolling-sliding contact,and the obtained results can help to understand the mechanism of wheel/rail frictional thermal fatigue.

针对当前交叉口信号灯模糊控制器结构参数固定的缺陷,提出了一种新的分级模糊控制器用于交叉路口交通流的控制与优化,该控制器能有效地减少规则数,易于提取模糊规则,能够显著改善交叉路口的通行能力.仿真实验结果证明该模型是有效的.

关于我国农民工的福利与社会政策问题,已有的研究多专注于实际状况与问题,从一定的理论视角出发进行的研究并不多.综合考量以往研究成果以及我国农民工面临的问题后建立的农民工社会政策决定分析框架,有助于对我国进入新世纪以来国家关于农民工社会政策的转变进行分析.近年来,我国各级政府在农民工政策选择转向中发挥了较大作用,但中央政府责任承担过少,对于地方政府的激励、约束措施不足,导致政策实施效果差强人意.因此,今后农民工社会政策的实践效果与社会权利的平等获得,在很大程度上取决于中央政府的责任承担,包括在中央层面的组织机构、制度创新以及资源供给上作出适当安排.