纳米TiO2含量对汽车尾气因子降解效能影响试验研究

研制汽车尾气降解材料测试室,测试以超声波分散法制备的不同含量的5种纳米TiO2光催化材料,对汽车尾气因子的降解效能。选用车辆处于怠速工况下所排出的汽车尾气为试验样本,依据纳米光催化材料降解率计算公式,计算出不同含量的纳米TiO2光催化材料对汽车尾气中有害因子NOx、HC、CO的平均降解率。测试结果表明:纳米TiO2光催化材料对汽车尾气中NOx、HC、CO等因子具有一定的影响效能,且降解趋势一致。不同含量的纳米TiO2光催化材料,对汽车尾气中各因子的影响效能随时间的变化降解率不同;对应于汽车尾气因子NOx、HC、CO具有最佳降解效能的纳米TiO2光催化材料的含量分别为4%、2%、4%。     

水泥混凝土路面板下脱空的路面雷达电磁波模拟

建立了路面雷达电磁波在水泥混凝土路面结构中传播的二维时域有限差分(2D-FDTD)方程,并针对空气耦合式天线雷达进行了水泥混凝土路面板下存在脱空病害的路面雷达电磁波模拟。进一步分析了水泥混凝土板下脱空出现水充空洞及气充空洞两种情况的路面雷达回波特性,本文的研究对路面雷达技术应用于水泥混凝土路面脱空病害检测实施具有重要的理论参考意义。     

石笼挡墙支挡结构在巫十路的工程应用

分析了地质条件差、地形复杂和建筑原材料匮乏等问题给高大支挡结构物的设计和施工带来的困难。以地形地质条件复杂、地基承载力低的巫十路K17 300~K17 350段为试验段,从施工前的准备和施工控制两方面详细论述了石笼挡墙在施工过程中应把握的技术要点及处理方法。并以建成的石笼挡墙为例,采用有限差分法和强度折减法分别分析了石笼挡墙在施工过程中的变形特点及其稳定性。数值分析显示,石笼挡墙的变形量较小及变形主要集中在墙身中部,自身稳定性较好,达到了设计要求,满足工程的需要。同时石笼挡墙作为一种新的山区公路支挡结构,与传统的高大支挡结构物相比具有较大优势,能有效地降低山区支挡结构物的工程造价。     

深圳地铁2号线制动电阻设置浅析

结合深圳地铁2号线工程实践,从车辆、环控、变电所、土建等方面,分别对车载设置方案、地下变电所设置方案、地面变电所设置方案进行了较为详细的分析比较,得出推荐方案.为当前及今后地铁工程中制动电阻设置提供了参考和借鉴.     

南京大胜关大桥项目信息查询系统的设计与实现

研究和设计一个基于J2EE平台的信息查询系统在南京大胜关长江大桥项目中的运用.包括系统的开发及运行环境,系统的总体设计方案、关键技术、以及系统功能模块的实现等.     

Impacts of an emission based private car taxation policy - First year ex-post analysis

This paper assesses the impacts of a targeted policy designed to influence car purchasing trends towards lower CO₂ emitting vehicles. Vehicle registration tax and annual motor tax rates in Ireland changed in July 2008 from being based on engine size to emissions performance of cars. This paper provides a one year ex-post analysis of the first year of the tax change, tracking the change in purchasing trends arising from the measure related to specific CO₂ emissions, engine size and fuel, and the implications for car prices, CO₂ emissions abatement, and revenue gathered. While engine efficiency improvements had been offset by purchasing trends towards larger and generally less efficient cars in the past, with the average MJ/km remaining constant from 2000 to 2007, this analysis shows that in the first year of the new taxation system the average specific emissions of new cars fell by 13% to 145 g/km. This was brought about, not by a reduction in engine size, but rather through a significant shift to diesel cars. Despite an unexpected reduction in car sales due to a recession in 2008, the policy measure has had a larger than anticipated impact on CO₂ emissions, calculated to be 5.9 ktCO₂ in the first year of the measure. The strong price signal did however result in a 33% reduction in tax revenue from VRT, in financial terms amounting to a drop of €166 million compared to a baseline situation.     

Well-to-wheel analysis for electric, diesel and hydrogen traction for railways

This paper derives the energy efficiencies and CO₂ emissions for electric, diesel and hydrogen traction for railway vehicles on a well-to-wheel basis, using the low heating value and high heating value of the enthalpy of oxidation of the fuel. The tank-to-wheel and well-to-tank efficiency are determined. Gaseous hydrogen has a WTW efficiency of 25% low heating value, if produced from methane and used in a fuel cell. This efficiency is similar to diesel and electric traction in the UK, US, and California. A reduction of about 19% in CO₂ is achieved when hydrogen gas is used in a fuel cell compared to diesel traction, and a 3% reduction compared to US electricity.     

Scalable stability analysis on large connected vehicle systems subject to stochastic communication delays

In this paper large connected vehicle systems are analyzed where vehicles utilize vehicle-to-vehicle (V2V) communication to control their longitudinal motion. It is shown that packet drops in communication channels introduce stochastic delay variations in the feedback loops. Scalable methods are developed to evaluate stability and disturbance attenuation while utilizing the mean, second moment, and covariance dynamics in open chain and closed ring configurations. The stability results are summarized using stability diagrams in the plane of the control parameters while varying the packet delivery ratio and the number of vehicles. Also, the relationship between the stability of different configurations is characterized. The results emphasize the feasibility of V2V communication-based control in improving traffic flow.     

Modeling the information flow propagation wave under vehicle-to-vehicle communications

Vehicle-to-vehicle (V2V) communications under the connected vehicle context have the potential to provide new paradigms to enhance the safety, mobility and environmental sustainability of surface transportation. Understanding the information propagation characteristics in space and time is a key enabler for V2V-based traffic systems. Most existing analytical models assume instantaneous propagation of information flow through multi-hop communications. Such an assumption ignores the spatiotemporal relationships between the traffic flow dynamics and V2V communication constraints. This study proposes a macroscopic two-layer model to characterize the information flow propagation wave (IFPW). The traffic flow propagation is formulated in the lower layer as a system of partial differential equations based on the Lighthill-Whitham-Richards model. Due to their conceptual similarities, the upper layer adapts and modifies a spatial Susceptible-Infected epidemic model to describe information dissemination between V2V-equipped vehicles using integro-differential equations. A closed-form solution is derived for the IFPW speed under homogeneous conditions. The IFPW speed is numerically determined for heterogeneous conditions. Numerical experiments illustrate the impact of traffic density and market penetration of V2V-equipped vehicles on the IFPW speed. The proposed model can capture the spatiotemporal relationships between the traffic and V2V communication layers, and aid in the design of novel information propagation strategies to manage traffic conditions under V2V-based traffic systems.     

C-V2X应用场景的算法建模及评价模型综述

V2X利用无线信息交互技术,实现车与其他实体之间的信息交互,将人、车、路、云交通参与要素有机地联系在一起,构建一个智慧的交通体系。算法的评价基于算法建模,通过建模梳理算法的逻辑思路,输出算法相关的标定参数,进而使算法性能达到更优。基于C-V2X应用场景的算法评价模型,旨在研究如何评判不同应用场景的实现优劣,用于设计出标准的指标参数衡量算法的性能,重点从算法计算效率和算法有效性2个维度考虑,构建起评估算法功能及性能的立体模型,多角度权衡并分析,从而对应用场景的实现给予评估反馈。