How does air pollution influence cycling behaviour? Evidence from Beijing

It is widely believed air pollution is an obstacle to cycling as it has negative effects on cyclists’ health outcomes and deteriorates their cycling experiences. However, the empirical studies investigating the impact of air pollution on cycling behaviour remains scarce. The aim of this paper is to fill the gap by looking at Beijing as a case study. The authors conducted a survey of 307 cyclists on the days with different levels of air quality in terms of concentration of PM_2.5 in 2015. The results show that in the polluted weather, those who persist in cycling are more likely to be male, over 30 years old, lower income or those who travel short distances. Specifically, female cyclists have a higher tendency to shift from cycling to public transit than the males and medium and high-income earners are more likely to shift to using a car than low income earners. The residents’ subjective perceptions of safety and comfort have major effects on their cycling behaviour. A higher perception of comfort and safety is related to a higher possibility of continuing cycling when air quality became polluted. Cycling for commuting trips is less likely to be replaced by other modes than cycling for non-commuting trips, such as shopping. Results of this study reveal that improving air quality in a metropolitan area such as Beijing has co-benefits of cycling renaissance. The huge investments into cycling infrastructure should be integrated with policies designed to create an attractive environment for cycling.     

后背门气弹簧布置与撑力计算

气弹簧助力式开启机构是目前高档汽车特别是轿车上经常采用的一种结构。以后背门为例,详细介绍了后背门气弹簧的布置与撑力计算的设计过程。从力学和运动学角度着重分析了后背门在开启过程中所受到各种力和力矩之间的关系,根据分析结果,用C语言编制程序,用Matlab进行计算,实现了气弹簧的优化布置。并通过选择合适的气弹簧,便可以实现后背门的平稳开启,人手助力轻松。     

Determinants of the willingness-to-pay for reducing the environmental impacts of road transportation

This paper examines the willingness-to-pay of people living in a number of villages in Navarre, in the Spanish Pyrenees to reduce noise and air pollution. Several models are used for estimation based on contingent valuation, noting that those living near roads are willing to pay more to reduce air and noise pollution. In addition, younger people, the better educated, and the more environmentally aware individuals are also willing to pay more to reduce those externalities.     

宇通客车气压ABS原理及检测

介绍宇通客车气压ABS的组成,每个元件的功能、测试方法以及ABS的闪码诊断程序和故障码含义.     

基于LabVIEW的空气流量传感器性能检测系统

本文简述了传统空气流量传感器检测系统的弊端,提出了一种基于LabVIEW软件的空气流量传感器测试系统的设计方案。本系统运用LabVIEW灵活性和多输入多输出的特点,能够很好地实现对测试数据实时绘图,方便操作。同时,给出了详细的硬件和软件设计方案。     

A numerical study of the derailment caused by collision of a rail vehicle using a virtual testing model

This study investigated the wheel-lift and roll-over derailment mechanisms caused by train collisions using a precise virtual testing model (VTM) of a Korean high-speed train. The VTM was a complex, nonlinear finite element model composed of the shell, beam, solid, spring, and surface contact elements for the car body, bogies, suspensions, and wheel–rail interfaces. The VTM was validated by checking the errors in the total energy and the dynamic responses of the spring elements. To achieve a quick, dynamic relaxation of the dead weight of the VTM before the collision analysis, the artificial damping method and the artificial force method were introduced and numerically evaluated. The surface-to-surface contact model from commercial software, Ls-Dyna, was applied to the VTM in order to simulate the derailment mechanisms caused by collision accidents. The numerical analyses of the VTM colliding with a large deformable obstacle or a rigid wall revealed for the first time that a mixed slip/roll-over-type derailment mechanism generally occurs. Furthermore, the simulation results were consistent with the results from a simplified theoretical derailment model of a wheel set.     

A contact-area model for rail-pads connections in 2-D simulations: sensitivity analysis of train-induced vibrations

A numerical model to predict train-induced vibrations is presented. The dynamic computation considers mutual interactions in vehicle/track coupled systems by means of a finite and discrete elements method. The rail defects and the case of out-of-round wheels are considered. The dynamic interaction between the wheel-sets and the rail is accomplished by using the non-linear Hertzian model with hysteresis damping. A sensitivity analysis is done to evaluate the variables affecting more the maintenance costs. The rail–sleeper contact is assumed extended to an area-defined contact zone, rather than a single-point assumption which fits better real case studies. Experimental validations show how prediction fits well experimental data.     

饱和器热力过程数学模型

建立了饱和器湿空气涡轮循环中的关键部件的一维传热传质均匀模型,得出了热,质交换沿高度分布的理论曲线;给出了水气交换界面的含湿曲线,从而解释了饱和器内的传热传质量与高度的关系及原因;还考虑了水气界水膜热阻对饱和器性能的影响,并提供了水膜热阻的计算方法。     

电源屏输入空开跳闸的原因分析及解决方案

通过对电源屏转换电路的分析,找出电源屏输入空开跳闸的原因,研究解决问题的方法,减少外电网波动冲击带来的电源屏故障。     

青岛地铁工程建设隐患排查治理体系研究

依据地铁工程建设隐患排查治理体系构建要求,结合近年来青岛地铁工程建设隐患排查治理体系构建情况,着重阐述如何建立合理的政府监管方式和三级管控管理模式,如何推行全员、全方位、全过程的隐患管控制度;如何将隐患排查依据、排查人员、排查过程及监督考核标准化管理;详细介绍隐患排查治理信息系统研发目标、功能及其创新点。本研究可为新建城市、多模式建设城市和其他行业工程建设的隐患排查治理体系的构建提供借鉴。