燃料电池电动汽车商业化存在的问题

综述了燃料电池电动汽车商业化存在的9个方面的问题,这些问题解决的程度和速度,关系到燃料电池电动汽车商业化的时间问题.这些问题可以分为两类:性能与成本问题和燃料供应与基础设施问题.介绍了解决这些问题的方法以及与此相关的研究方向和热点.     

电子商务企业物流配送最短线路问题探讨

对电子商务物流配送线路问题进行了介绍,提出了最短线路问题的解决方法,并对该问题进行了实证。     

电子警察的市场需求与发展趋势分析

本文通过总结电子警察系统的现状和需求，提出电子警察系统已进入了功能完善阶段，但是遇到了各种各样的问题，包括电子警察本身的问题，观念的问题和管理的问题等，并提出了电子警察系统的发展趋势。     

高速公路线形设计中有关问题的分析探讨

提出了高速公路线形设计中出现频率最高的3个问题,即同向曲线强扭成反向曲线问题、超高缓和段真实纵坡问题、S形曲线超高过渡问题,分析了这3个问题按常规处理方法可能产生的不良后果,并给出了相应的处理建议。     

市政道路排水管道安装质量浅析

该文重点阐述了市政道路排水管道安装过程中存在的各类质量问题,详细地分析了这些质量问题产生的原因,提出了解决这些质量问题的方法和预防措施。     

一类快速公交车辆调度问题算法设计与实现

该文提出了一类有发车间隔和总发车次数约束的快速公交(BRT)车辆调度问题,并建立了此数学模型。根据问题的特点设计了优化该问题的遗传算法。通过多次仿真运算,计算结果及分析表明用遗传算法优化此类调度问题是有效的。     

效益造价比在公路平面交叉口交通安全改善中的应用

为了改善我国公路平面交叉口的交通安全状况,研究了平面交叉口交通安全问题的诊断方法,给出了交通安全问题诊断流程.制定了交通安全问题显著性和严重性的评判标准,设计了交通安全问题诊断表.通过实地调查与分析,发现了我国公路平面交叉口存在的主要交通安全问题,并给出了相应的安全改善对策.介绍了效益造价比的概念及其排序模型,并对该模型进行了简化.利用简化的效益造价比排序模型对安全改善对策进行排序,得到工程上需要首先实施的安全改善对策.通过工程实例.验证了安全问题诊断方法和效益造价比排序模型能够找出公路平面交叉口存在的主要安全问题和效益造价比高的改善对策.     

兰州市水安全问题成因分析及防治对策

水安全问题是城市安全问题的重要组成部分。以水污染严重、水土流失加剧、洪涝灾害加重、突发水安全事件等为特征的城市水安全问题,成为制约城市社会、经济、生态可持续发展的重要因素之一。该文以兰州市为例,探讨了城市发展过程中存在的主要水安全问题,分析了产生这些问题的原因,提出了解决这些问题的对策。     

浅谈天津主城区停车问题的对策研究

在对国内外停车问题现状分析的基础上,描述了天津市主城区的停车问题,并给出了解决天津市主城区停车问题的对策。     

房屋建筑工程质量影响因素探究

近年来我国经济取得了较快发展,随之建筑行业也发展越来越快。在快速发展的同时,建筑行业也出现了许多问题,例如施工质量问题和施工安全问题。这些问题严重影响了建筑工程施工质量和建筑工程施工企业的品牌与形象,所以房屋建筑工程的质量问题十分重要。本文首先简单介绍了房屋建筑工程质量管理方式的发展,随后又详细分析了房屋建筑工程质量影响因素。     

风吹雪雪害地区公路路基高度的确定

通过对风吹雪雪害地区不同路基高度的风雪流场的观测与分析,初步掌握了公路路基高度与风雪流场的关系,建立了风吹雪雪害地区不易积雪的合理路基高度的数学模型,为风吹雪雪害地区公路路基高度的合理确定提供了有力的科学依据。     

On the interest of integrating vehicle dynamics for the ground propagation of vibrations: the case of urban railway traffic

This paper presents a complete numerical model for studying the vertical dynamics of the vehicle/track interaction and its impact on the surrounding soil, with the emphasis on vehicle modelling. A decoupling between the track and the soil is proposed, due to the difficulty of considering all the subsystem components. The train/track model is based on a multibody model (for the vehicle) and a finite element model (for the track). The soil is modelled using an infinite/finite element approach. Simulations of both models are carried out in the time domain, which is better able to simulate the propagation of the vibration waves and to take into account the possible nonlinearity of a component. The methodology is applied in the case of an urban tram track and validated with the available experimental data. Models for the tram, the track and the soil are described. Results from the complete model of the vehicle and a simple model, based on an axle load, are compared with experimental results and the benefits of a complete model in the simulation of the ground vibration propagation induced by railway vehicles are demonstrated. Moreover, a parametric study of the vehicle wheel type is conducted, which shows the advantage of a resilient wheel, for various rail defects.     

武汉新区道路网规划研究

通过对城市新区道路网规划理念的分析,结合武汉新区道路网的现状,讨论了武汉新区对外、对内、慢行等道路交通系统的规划策略。     

机动车冷启动排放试验研究

在底盘测功机上,采用NEDC循环,对汽油车和柴油车分别在常温和低温环境下冷启动排放进行试验,研究车辆冷启动的排放情况。试验结果表明:常温冷启动状态下,催化器激活之前的排放在整个排放测试循环中所占的比重比较大,其中汽油车的冷启动排放占到整个循环排放量的50%以上,柴油车也达到了20%以上。汽油车低温冷启动下,催化器激活之前排放所占比重超过90%。     

A new method for the solution of the normal contact problem in the dynamic simulation of railway vehicles

Due to requirements related to computational efficiency, in the majority of railway dynamic simulators the Hertz theory is used for solving the normal problem in wheel/rail contact. This theory is based on a large number of assumptions. Particularly noteworthy is the assumed simplification that the undeformed distance between the bodies in contact can be assimilated by a quadratic function. There are many situations in which the undeformed distance cannot be represented by this kind of function. As such, the results obtained with Hertz theory in these cases are not accurate.

In this paper, a new method for solving the normal problem that overcomes the above-mentioned limitation is presented. First, the exactness of the new method is tested with Hertzian cases. The results obtained are almost exact. Second, the results calculated with the new method in more general cases are compared with the ones obtained with the variational method of Kalker (more exact but computationally less efficient).     

汉字字高与笔划宽度对标志静态视认距离影响的实验研究

实验测定9名被试对不同字高和笔划宽度汉字的静态视认距离,对实验数据进行描述性统计和方差分析,结果表明字高和笔划宽度对于汉字视认性的影响均显著,两者的交互作用也显著。字高越高,汉字视认性越好;相同字高下,1/14h笔划宽度的汉字视认性最佳。研究为道路交通标志汉字的设置提供了理论依据,并为以后研究的开展提供了参考。     

利用机器人检查斜拉索初探

针对目前迫切需要斜拉桥缆索检测自动化而设计的一种轻型缆索检测机器人,该款机器人已在广州番禺西丽大桥斜拉索检测现场试验成功,取得满意效果。主要介绍该款机器人的驱动系统、摄像系统以及扩展功能,对斜拉索检测机器人的应用、推广具有一定意义。     

兵团垦区软土路基工后差异沉降控制标准研究

针对新疆建设兵团垦区软土地区的公路工程特点,运用有限元软件,建立计算模型来研究路基发生不均匀沉降时路面结构的受力特性,从控制路面结构的容许弯拉应力的角度,分析了影响软土地基的工后容许差异沉降量的因素,包括公路等级、路基宽度、交通量、路堤填土高度等;提出了垦区软土地区公路路基顶面的工后差异沉降控制标准的计算思路,并总结了计算流程.在此基础上,通过计算,提出了垦区软土地区二,三,四级公路路基顶面的工后差异沉降控制标准,并根据路基顶面的差异沉降率控制标准,反算出软土地基的工后容许差异沉降量控制标准.     

Effects of the throttle opening ratio and the injection timing of CNG on the combustion characteristics of a DI engine

We investigated the effects of the fuel injection timing — both for early and late injection — in conjunction with the throttle opening ratio on the fuel-air mixing characteristics, engine power, combustion stability and emission characteristics of a DI CNG spark engine and control system that had been modified and designed according to the author’s original idea. We verified that the combustion characteristics were affected by the fuel injection timing and that the engine conditions were affected by the throttle opening ratios and the rpm. The combustion characteristics were greatly improved for a complete open throttle ratio with an early injection timing and for a partial throttle ratio with a late injection timing. The combustion duration was governed by the duration of flame propagation in late injection timing scenarios and by the duration of early flame development in cases of early injection timing. As the result, the combustion duration is shortened, the lean limit is improved, the air-fuel mixing conditions are controlled, and the emissions are reduced through control of the fuel injection timing and vary according to ratio of the throttle opening.     

山区公路风化岩地质边坡滑塌的治理设计

从勘察山区公路的地质条件入手,对风化岩体的稳定性、边坡的稳定性、边坡的变形机理与发展趋势进行了评价,并提出对滑塌边坡岩体的治理方法。