Optimal congestion taxes in a time allocation model

The purpose of this paper is to study optimal congestion taxes in a time-allocation framework. This makes it possible to distinguish taxes on inputs in the production of car trips and taxes on transport as an activity. Moreover, the model allows us to consider the implications of treating transport as a demand, derived from other activities. We extend several well known tax rules from the public finance literature and carefully interpret the implications for the optimal tax treatment of passenger transport services. The main findings of the paper are the following. First, if governments are limited to taxing market inputs into transport trip production, the time-allocation framework: (i) provides an argument for taxing congestion below marginal external cost, (ii) implies a favourable tax treatment for time-saving devices such as GPS, and (iii) provides a previously unnoticed argument for public transport subsidies. Second, if the government has access to perfect road pricing that directly taxes transport as an activity, all previous results disappear. Third, in the absence of perfect road pricing, the activity-specific congestion attracted by employment centres, by shopping centres or by large sports and cultural events should be corrected via higher taxes on market inputs in these activities (e.g., entry tickets, parking fees, etc.).     

海洋平台T型管节点应力集中系数研究

以具有代表性的海洋平台形管接头为例,采用有限元方法,研究接头处的应力集中系数分布.分析支管6个自由度的约束条件和受载方式,基于ABAQUS计算管节点在各种载荷下的应力分布,尤其关注几何学上的最危险地带——管筒十字交叉点处的应力集中系数,并根据6种基本情况下T形管节点的有限元计算结果,得到管节点所受到的应力最大、结构强度...     

磁罗经自差半自动测校装置

提出一种磁罗经自差半自动测校方法，并从旋回法测定自差原理计算自差系数，安放磁棒位置和软铁数量，所用磁场传感器基本原理，罗经涡动误差的影响，半自动测校装置组成等方面，论证了研制磁罗经自差半自动测校装置的可能性。     

基于循环分辨分析的湍流特征参数计算法

采用不同的孔板结构和不同的驱动电机转速在定容燃烧弹内生成具有不同的湍流特性参数的气流 ,并用热线风速仪进行了测量。在循环分辨分析的基础上 ,计算分析了它们各自的湍流强度、积分时间尺度和时频谱密度。结果表明 ,电机转速越大 ,孔板总通孔面积越小 ,则湍流越强 ,积分时间尺度越小 ;对于不同的孔板结构和电机转速 ,湍流能量分布明显不同。     

The History of the Transport Future—Evaluating Dutch Transport Scenarios of the Past

Abstract

This paper examines 42 business‐as‐usual (BAU) scenarios for future transport and traffic development in the Netherlands from the period 1970 to 2000. An important aspect of these scenarios is that they indicate the potential future state of the transport system if the policies in place at the time continue unchanged, thus raising issues which may require a policy response. This paper shows that in most of the important BAU transport scenario results of the past in the Netherlands, such as future car use and transport emissions, the policy makers were not misled. The prognoses for traffic congestion are an important exception as they underestimated the congestion problems that would arise. This paper shows that, based on the research it examines, BAU transport forecasting is an inaccurate practice. It is recommended that the BAU scenario designer communicates this high inaccuracy, enabling the policy maker to include the inherent future uncertainty in their decision‐making.     

Understanding individual travel decisions: results from a commuters survey in Geneva

In this paper, we present the results of an extended traveler behavior survey conducted in Geneva (Switzerland) in March 1994. In this survey, commuters were asked about the impact of various factors, related to individual or household characteristics and situational, contextual and environmental constraints on their basic travel decisions. In particular, the issues of mode, route and departure time choice were investigated, together with the diversion from normal patterns in response to adverse weather conditions. Some cross cultural comparisons are discussed with respect to the results of a similar survey conducted in Brussels (Belgium) in 1992 (Khattak & de Palma 1995, 1997).     

交通目标综合防护系统实施方案探讨

在分析交通目标面临的威胁和现有防护方法局限性的基础上,认为交通目标的防护重点在于干扰敌精确制导武器的末端制导,降低其命中概率,提出了建立交通目标综合防护系统的设想,形成一个集威胁告警、有源干扰和无源干扰的一体化光电对抗系统,并针对不同交通目标的防护特点和实际可能受到精确制导武器打击的威胁状况,设计出相应的具体实施方案,为我军在高技术条件下切实做好军事运输保障工作提供借鉴。     

船舶纵向下水曲线直接计算法

提出一种船舶纵向下水曲线的直接计算法。将船体外表面假设为刚性面,利用商用有限元软件ABAQUS/AQUA模块对纵向下水曲线进行直接计算。针对一艘方形驳船,将直接计算获得的6条下水曲线与传统邦戎曲线方法的结果进行比较,两者吻合很好;通过针对一艘型线变化较大驳船的计算,发现该方法对网格尺寸不敏感,验证了所提方法的准确性和便捷性。将该方法进一步应用于Wigley船型和油船,验证了其可行性和普适性。算例表明,所提出的直接计算法具有潜在的工程应用价值。     

V型无压载水船舱口角隅疲劳寿命计算新方法

提出一种计算V型无压载水船这种特殊船型结构疲劳寿命的新方法,该方法不受船型、航区航线及分析部位的限制,具有通用性。通过结合综合海洋决策支持系统(Integrated marine decision support system)提供的海浪数据,采用Matlab编程,得到只属于所计算船的特定的散布图和营运特性表。然后,通过SESAM软件计算在该营运特性表下的载荷,采用ABAQUS建模计算热点应力。最后,计算结构的疲劳寿命。结果表明,经过舱口优化后,无压载水船舱口角隅的疲劳寿命要高于母型船。     

预应力混凝土斜拉桥悬臂施工的拉索式长挂篮新构思

在预应力混凝土斜拉桥主梁的悬臂施工中 ,经常遇到在浇注混凝土过程中发现标高误差无法调整这一难题 ,介绍了拉索式长挂篮的新构思 ,即将挂篮设计成简支受力结构。拉索式长挂篮由贝雷桁架片、万能杆件以及非标构件组合在一起 ,利用贝雷片用销子连接存在间隙的特点 ,实现上述构思。该挂篮经过一大跨预应力混凝土斜拉桥的施工应用 ,取得了良好的效果 ,主要介绍这一挂篮的结构设计与使用情况。