铝合金耐压结构设计分析与试验验证

根据水下潜器总体性能要求,按照最小重量原则,结合规范和有限元方法设计工作潜深为500m的铝合金带加强筋形式的圆柱耐压舱,并通过压力筒加压试验,对Ansys有限元静力分析的精确度进行了验证,为耐压结构设计与校核提供重要参考.     

Historic vehicles: an overview from a transport policy perspective

Historic vehicles (HVs) are the heritage of road transport that have surprisingly received little attention in the academic literature. This study presents an overview of the literature on HVs, focusing on the three topics that dominate the policy debate on transport: environmental, safety and congestion impacts. We observed that polluting emissions of HVs are per kilometre much higher (often a factor 5 or more) than those of moderns vehicles. The annual average mileage per vehicle per year of HVs is much lower than other vehicles. The lower active and passive safety levels of HVs are compensated by the way these vehicles are driven, resulting in the risk factors per kilometre being roughly equal or lower than other vehicles. The contribution of HVs to congestion is negligible. However, the transport policy discourse is divided on the topic of HVs. More comprehensive and effective laws and regulation are needed to protect this aspect of the heritage of road transport whilst concurrently avoiding or limiting the problems caused by them.     

Shared autonomous electric vehicle (SAEV) operations across the Austin,Texas network with charging infrastructure decisions

Shared autonomous vehicles, or SAVs, have attracted significant public and private interest because of their opportunity to simplify vehicle access, avoid parking costs, reduce fleet size, and, ultimately, save many travelers time and money. One way to extend these benefits is through an electric vehicle (EV) fleet. EVs are especially suited for this heavy usage due to their lower energy costs and reduced maintenance needs. As the price of EV batteries continues to fall, charging facilities become more convenient, and renewable energy sources grow in market share, EVs will become more economically and environmentally competitive with conventionally fueled vehicles. EVs are limited by their distance range and charge times, so these are important factors when considering operations of a large, electric SAV (SAEV) fleet.This study simulated performance characteristics of SAEV fleets serving travelers across the Austin, Texas 6-county region. The simulation works in sync with the agent-based simulator MATSim, with SAEV modeling as a new mode. Charging stations are placed, as needed, to serve all trips requested (under 75 km or 47 miles in length) over 30 days of initial model runs. Simulation of distinctive fleet sizes requiring different charge times and exhibiting different ranges, suggests that the number of station locations depends almost wholly on vehicle range. Reducing charge times does lower fleet response times (to trip requests), but increasing fleet size improves response times the most. Increasing range above 175 km (109 miles) does not appear to improve response times for this region and trips originating in the urban core are served the quickest. Unoccupied travel accounted for 19.6% of SAEV mileage on average, with driving to charging stations accounting for 31.5% of this empty-vehicle mileage. This study found that there appears to be a limit on how much response time can be improved through decreasing charge times or increasing vehicle range.     

The effect of crowding on public transit user travel behavior in a large-scale public transportation system through modeling daily variations

In this paper, the crowding effect in a transit vehicle is modeled in a time-expanded network that considers the daily variation in passenger flows. The study models the daily variation of in-vehicle crowding in a real large-scale transit system. A transit assignment for this real network is modeled and implemented by constructing a crowding cost function that follows the valuation of crowding and by using the reliable shortest path finding method. The direct application of the crowding model to a real network for the Utah Transit Authority indicates that crowd modeling with multi-user classes could influence public transportation system planning and affect the revenues of transit agencies. Moreover, the addition of the disutility factor, crowding, does not always appear to cause an increase in disutility for transit users.     

Innovative strategies for urban car-sharing systems and a simulator to assess their performance

In this paper, three innovative car-sharing systems for urban areas are proposed, based on fleets of individual intelligent vehicles with three service characteristics: instant access, open-ended reservations and one-way trips. These features provide high flexibility but create an uneven distribution of vehicles among stations. Therefore, relocation of vehicles must be performed. Three different system procedures are proposed: in the first system, relocations are performed by users; in the other two, vehicles relocate automatically, thanks to their automation. In the first two systems, vehicles are accessible only at stations, whereas in the third they are also accessible along roads. In order to provide transport managers with a tool to test systems in different realities, an object-oriented simulator is developed. The simulation provides outputs of system performance, in terms of user waiting times and system efficiency. The proposed systems are simulated for the city of Genoa, in Italy, and a comparative analysis is presented.     

Instantaneous communication throughputs of vehicular ad hoc networks

Vehicular ad hoc networks (VANETs) formed by connected vehicles in a traffic stream could be applied to improve safety, mobility, and environmental impacts of a transportation system. In this paper, we present analytical models for the instantaneous communication throughputs of VANETs to measure the efficiency of information propagation under various traffic conditions at a time instant. In particular, we define broadcast and unicast communication throughputs by the wireless channel bandwith multiplied by the average probabilities that one vehicle is a successful receiver and sender in a VAENT, respectively. With a protocol communication model, we derive formulas to determine the probabilities for an equipped vehicle to be a successful broadcast receiver and a successful unicast receiver/sender, and obtain broadcast and unicast throughputs along discrete and continuous traffic streams. We further examine the impacts on communication throughputs of the transmission range and the interference range of dedicated short range communication devices as well as the market penetration rate of equipped vehicles and the percentage of senders. Finally, we investigate the influence of shock waves on communication throughputs.     

液化天然气(LNG)汽车日常检查方法及维护技术综述

天然气是一种优质的替代燃料,具有污染小、安全系数高、运行费用低等优点。天然气已经成为城市公共交通领域应用最为成功和广泛的车辆替代燃料技术,为推动交通运输行业的节能减排做出了显著的贡献。液化天然气汽车,作为天然气汽车的一种类型,与传统汽柴油车相比,液化天然气汽车安装了包括液化天然气气瓶、气管路及各种控制阀门和仪表在内的专用装置,在对液化天然气汽车进行日常检查时需要针对液化天然气汽车的专用装置进行重点检查。本文则针对液化天然气汽车的特点,对液化天然气汽车的正确使用方法、日常检查方法及维护技术要求、以及相关注意事项三个方面进行了解读,为指导液化天然气汽车进行日常检查与定期维护提供了技术参考。     

汽车排放污染及净化对策研究

阐述汽车排放污染物的成分及其危害,介绍新排放法规Ⅰ型、Ⅲ型、Ⅳ型试验限值,重点分析汽车的5项排放影响因素及其净化措施。     

地铁列车逻辑控制电路安全服役技术应用研究

为克服传统地铁列车继电器控制电路高故障率和无记录功能等诸多缺陷,提出了基于新型二乘二取二技术的无触点逻辑控制方案.完成了系统架构设计包括热备冗余、网络通信、故障诊断、日志分析等功能.针对既有地铁列车进行了控制电路技术方案设计和施工改造,首先在分析原有控制回路原理的基础上,完成无触点逻辑控制单元替代继电器点位设计;然后综...     

军运保障中高原和山区对汽车性能的影响及对策

从高原和山区的海拔高度及地理环境等对汽车的动力和制动性的影响入手,分析了高原和山区汽车运输的特点,并根据部队的使用经验和试验结论,提出了改善发动机性能和改进汽车制动系的措施,为高原和山区的车辆装备综合管理及技术保障提供了科学的依据。