“去福利化”解决城市停车问题

中国城市停车位普遍存在建设投入高和使用价格低之间的极端不对称,导致小汽车过度使用、停车矛盾不断加剧。首先对中国城市停车问题及停车收费定价体系进行分析。比较分析按公众心理承受能力和参考车位土地资源价值两种定价模式,指出因收费定价不合理导致的停车福利化现象是城市停车问题的根源所在。最后阐明,建立与基本国情相适应的停车经济技术支撑体系、实行去福利化的停车改革、推进停车产业化发展,是实现城市交通可持续发展的必然选择。     

基于混合遗传算法的船台装配优化研究

为了在船台装配作业中最小化船台周期、降低作业成本、均衡资源负荷,分析了船台装配作业的特点并对其进行了建模,设计了一种适于解决本优化问题的混合遗传算法,开发了对应的软件。将最小化船台周期的优化目标体现在解码的过程中,保证了解码的唯一性;同时将降低成本的优化目标体现在评价和选择的过程中。经本方法得出的船台装配日程计划为实际生产提供了很好的指导。最后,通过一个算例,验证了本方法的可行性和有效性。     

汽车覆盖件冲压工艺与成本分析研究

汽车开发过程中工艺人员如对产品设计的工艺性进行研究,以及应用冲压成形CAE技术对产品成本进行控制尤为重要.本文将结合公司某系列车型产品开发过程中的工作实际,阐述并行开发过程中如何对覆盖件冲压工艺进行分析、优化,降低汽车覆盖件的开发成本、零件的制造成本等方法.     

多类型旅客出行选择的客运专线运价优化模型

为制定客运专线的最优运价,按费用敏感程度将旅客分为3类,用随机用户平衡理论建立了不同运输方式弹性需求的中间层模型和不同铁路运输产品的下层模型.在此基础上,建立了以铁路企业收益最大化为目标的上层模型.用相继平均法求解中间层和下层模型,用粒子群算法求解整个三层规划模型.算例结果表明:取客运专线最优运价时,在运输方式铁路、公路和航空,以及铁路内部产品客运专线与既有线之间,客运专线承担了较大的客运量.     

A new look at the external pressure capacity of sandwich pipes

Sandwich Pipes (SPs) have been developed to overcome the required flow assurance and pressure capacity issues in deep and ultra-deep waters. This research aims at studying the influence of certain structural parameters on the pressure capacity (also referred to as the plastic buckling pressure) of Sandwich pipelines. The use of high grade steel pipes, as the internal or external pipes, has also been considered as one of the design parameters in this study. Moreover, a comprehensive parametric study, considering a practical range of the parameters that influence the response of SPs (and considering 3840 SP configurations) was conducted. The results from this large array of pipes were used to formulate a practical equation, capable of estimating the plastic buckling pressure of SPs. The accuracy of the proposed equation was evaluated by comparing the results with the experimental and numerical results available in the literature. The comparative results demonstrated that the proposed equation could predict the buckling capacity of such pipes with a reasonable accuracy. Furthermore, the proposed equation was used, along with a general optimization procedure, to establish the most optimum and cost-effective combination of structural parameters for SPs suitable for use in various water depths.     

Nonlinear pricing on private roads with congestion and toll collection costs

Nonlinear pricing (a form of second-degree price discrimination) is widely used in transportation and other industries but it has been largely overlooked in the road-pricing literature. This paper explores the incentives for a profit-maximizing toll-road operator to adopt some simple nonlinear pricing schemes when there is congestion and collecting tolls is costly. Users are assumed to differ in their demands to use the road. Regardless of the severity of congestion, an access fee is always profitable to implement either as part of a two-part tariff or as an alternative to paying a toll. Use of access fees for profit maximization can increase or decrease welfare relative to usage-only pricing for profit maximization. Hence a ban on access fees could reduce welfare.     

Modelling the effects of road pricing on traffic using ERP traffic data

Singapore’s Electronic Road Pricing (ERP) system involves time-variable charges which are intended to spread the morning traffic peak. The charges are revised every three months and thus induce regular motorists to re-think their travel decisions. ERP traffic data, captured by the system, provides a valuable source of information for studying motorists’ travel behaviour. This paper proposes a new modelling methodology for using these data to forecast short-term impacts of rate adjustment on peak period traffic volumes. Separate models are developed for different categories of vehicles which are segmented according to their demand elasticity with respect to road pricing. A method is proposed for estimating the maximum likelihood value of preferred arrival time (PAT) for each vehicle’s arrivals at a particular ERP gantry under different charging conditions. Iterative procedures are used in both model calibration and application. The proposed approach was tested using traffic datasets recorded in 2003 at a gantry located on Singapore’s Central Expressway (CTE). The model calibration and validation show satisfactory results.     

Managing network mobility with tradable credits

A system of tradable travel credits is explored in a general network with homogeneous travelers. A social planner is assumed to initially distribute a certain number of travel credits to all eligible travelers, and then there are link-specific charges to travelers using that link. Free trading of credits among travelers is assumed. For a given credit distribution and credit charging scheme, the existence of a unique equilibrium link flow pattern is demonstrated with either fixed or elastic demand. It can be obtained by solving a standard traffic equilibrium model subject to a total credit consumption constraint. The credit price at equilibrium in the trading market is also conditionally unique. The appropriate distribution of credits among travelers and correct selection of link-specific rates is shown to lead to the most desirable network flow patterns in a revenue-neutral manner. Social optimum, Pareto-improving and revenue-neutral, and side-constrained traffic flow patterns are investigated.     

拥挤收费下基于前景理论的出行者路径选择行为分析

出行者（特指私家车出行者）路径选择行为的研究对于城市的交通管理和交通组织都有着重要的意义,而且随着交通出行费用的不断增加,以及道路拥挤收费政策逐步实施,仅仅考虑距离最短、时间最短来对出行者路径选择行为模型进行研究,往往实用性欠佳。针对以往的研究中考虑因素单一、模型实用性不强这一问题,运用能有效描述出行者不确定性条件下决策行为的前景理论,综合考虑出行者的出行时间、出行费用以及出行者的个人偏好、出行经验等因素,建立一个更为贴合实际的出行者路径选择行为模型。以实际算例的形式对比分析了,不同收费标准对不同出行者人群、不同性质出行的路径选择行为的影响程度。结果表明：与拥挤收费政策实施前相比,收费3元时,高收入水平出行者购物出行时的路径发生变化,而对于通勤出行,当收费大于6元时出行路径才发生变化;对于中低收入水平出行者来说,因为其较高收入者对费用更为敏感,所以拥挤收费政策实施后他们的反应也不尽相同。     

不同市场经营机制下停车设施定价模型

基于网络均衡理论,在分析出行者交通方式、出行路径和停车设施选择均衡的基础上,建立了不同市场经营机制(包括垄断、寡头竞争和社会最优3种类型)下市区内的路外停车设施和市区边缘的停车换乘设施的定价模型;并对所提出模型进行了实际应用,同时比较了不同市场均衡解的效果。结果表明:垄断经营机制会导致最高的停车收费价格、最低的停车需求和社会福利及最高的总系统利润;社会最优与其相反,而寡头竞争介于二者之间。