The cost saving potential of carsharing in a US context

Carsharing is a vehicle sharing service for those with occasional need of private transportation. Transportation planners are beginning to see great potential for carsharing in helping to create a more diversified and sustainable transport system. While it has grown quickly in the US in recent years, it is still far from the level where it can deliver significant aggregate benefits. A key element to the potential growth of carsharing is its ability to provide cost savings to those who adopt it in favor of vehicle ownership. This research seeks to quantify these potential cost savings. The costs of carsharing and vehicle ownership are compared based on actual vehicle usage patterns from a large survey of San Francisco Bay Area residents. The results of this analysis show that a significant minority of Bay Area households own a vehicle with a usage pattern that carsharing could accommodate at a lower cost. Further research is required to indentify how these cost savings translate to the adoption of carsharing.     

Characteristics of premium transit services that affect mode choice

This research seeks to improve the understanding of the full range of determinants for mode choice behavior and to offer practical solutions to practitioners on representing and distinguishing these characteristics in travel demand forecasting models. The principal findings were that the representation of awareness of transit services is significantly different than the underlying assumption of mode choice and forecasting models that there is perfect awareness and consideration of all modes. Furthermore, inclusion of non-traditional transit attributes and attitudes can improve mode choice models and reduce bias constants. Additional methods and analyses are necessary to bring these results into practice. The work is being conducted in two phases. This paper documents the results of Phase I, which included data collection for one case study city (Salt Lake City), research and analysis of non-traditional transit attributes in mode choice models, awareness of transit services, and recommendations for bringing these analyses into practice. Phase II will include data collection for two additional case study cities (Chicago and Charlotte) with minor modifications based on limitations identified in Phase I, additional analyses where Phase I results indicated a need, and a demonstration of the research in practice for at least one case study city.     

半柔性路面材料级配设计与性能研究

以体积法设计母体沥青混合料矿料级配,结合马歇尔、谢伦堡析漏和肯塔堡飞散试验确定混合料沥青用量。通过室内试验(车辙试验、浸水马歇尔试验)以及实验段现场性能检测(抗滑性能试验、渗水性能试验)评价其综合路用性能。结果表明,半柔性路面材料具有优良的高温稳定性、水稳定性和抗渗水性,但其抗滑性能稍显不足。     

Optimal traffic assignment to urban streets with air pollution consideration

Traffic assignment is usually determined solely on the basis of minimum travel time through the network. The present study on traffic assignment has taken into account not only traffic performance but also air quality over the street. A simple model of highway air pollution is developed by considering macroscopic material balance of polluted air mass over a segment of a highway that passes through an urban area, A new traffic assignment scheme has been developed based on the air pollution model. The optimal traffic assignment obtained by the new scheme is affected significantly by meteorological conditions.     

现代有轨电车车辆段检修作业安全管控系统

现代有轨电车属于城市中的重要公共交通工具,通过车辆段检修,能够使有轨电车在运行时的技术性能和安全性能获得保证。传统模式下,有轨电车在车辆段进行检修作业时,主要运用制度约束以及人工监督方式保障安全,在作业中难免存有安全隐患,而且各作业环节处于独立与分散状态,关联互动性不强,难以对检修作业展开整体性安全管控。检修作业安全管控系统的运用,使有轨电车在检修作业时的安全性得到极大保证。     

高等职业院校学生素质结构分析

开办高等职业教育以来,高职教育事业取得了迅猛的发展。各高职院校针对其办学特点,在培养学生应用技能等方面都做出了探索和努力,并取得了一定的成果。我们针对当前高职学生基本素质状况,在进行大量采集的基础上,进行了科学分析,力求更加全面地掌握高职学生特点,有的放矢地发展高等职业教育。     

山区高墩大跨连续刚构桥施工阶段稳定性影响参数分析

以某连续刚构桥为工程背景,利用大型通用有限元软件ANSYS建立数值模型,研究结构初始缺陷、荷载因素和结构设计参数对山区高墩大跨连续刚构桥施工阶段稳定性的影响程度,得出不同参数对高墩大跨连续刚构桥施工过程稳定性影响的规律及原因。结果表明:结构初始几何缺陷、初始材料缺陷、风荷载、温度荷载、施工不平衡荷载和结构材料强度对结构施工阶段的稳定性影响较大,应采取适当的控制措施,保证结构在施工阶段的稳定性和安全性。     

Efficient calculation of slamming pressures on ships in irregular seas

An efficient method for calculation of the slamming pressures on ship hulls in irregular waves is presented and validated for a 290-m cruise ship. Nonlinear strip theory was used to calculate the ship–wave relative motions. The relative vertical and roll velocities for a slamming event were input to the slamming calculation program, which used a two-dimensional boundary element method (BEM) based on the generalized 2D Wagner formulation presented by Zhao et al. To improve the calculation efficiency, the method was divided into two separate steps. In the first step, the velocity potentials were calculated for unit relative velocities between the section and the water. In the next step, these precalculated velocity potentials were used together with the real relative velocities experienced in a seaway to calculate the slamming pressure and total slamming force on the section. This saved considerable computer time for slamming calculations in irregular waves, without significant loss of accuracy. The calculated slamming pressures on the bow flare of the cruise ship agreed quite well with the measured values, at least for time windows in which the calculated and experimental ship motions agreed well. A simplified method for calculation of the instantaneous peak pressure on each ship section in irregular waves is also presented. The method was used to identify slamming events to be analyzed with the more refined 2D BEM method, but comparisons with measured values indicate that the method may also be used for a quick quantitative assessment of the maximum slamming pressures.     

Parametric rolling prediction in irregular seas using combination of deterministic ship dynamics and probabilistic wave theory

In recent years there have been reports of serious accidents of parametric rolling for modern container ships and car carriers. For avoiding such accidents, a prediction method of parametric rolling in irregular seas is required. Since parametric rolling is practically non-ergodic, repetitions of numerical simulations or experiments could be not feasible to ascertain the behaviour. Therefore, in this paper, a method combining a stochastic approach with a deterministic approach in order to estimate the probabilistic index without such simple repetitions is developed. The ship's response in regular seas is estimated by solving an averaged system of the original 1-DoF roll model, and random waves necessary for occurrence of parametric rolling is achieved by using Longuet-Higgins’s or Kimura’s wave group theory. As a result, a fast and robust computation method of the probabilistic index is established. Finally, it is concluded that the proposed method is considered to be one of the useful tools for discussing the new IMO Intact Stability Code.     

基于行波原理的接触网故障测距的分析

根据接触网特点,分析了基于行波故障测距原理的接触网行波故障测距技术,并研制测距精度高、性能可靠、运行稳定的牵引网行波故障测距系统。