The effects of added transportation capacity on travel: a review of theoretical and empirical results

(Added to the original text) A fundamental solution to the issue of congestion cannot be reached without addressing the question of life-style. This paper reviews the definitions of life-style found in the literature, and identifies variables that have been commonly associated with life-style. Using US consumer expenditure data, life-styles are analyzed longitudinally (examining trends during the 1953–1983 time frame) and cross-sectionally (comparing segments of the population stratified by income, life-cycle stage, and age), and likely relationships to travel behavior are noted. The usefulness of existing empirical findings to long-range forecasting is explored by speculating on shifts of behavioral units across life-style segments, and on shifts in the behavioral patterns within each life-style segment.     

道路路阻函数模型及适用性研究

交通诱导系统中两节点间最优路径的选择是目前的一个难点问题,其中路阻函数的确定是路径优化的核心内容.针对交通流由畅通状态到拥挤状态再到堵塞状态的过程,应用经典交通流理论和实际调查数据,构建交通流诱导系统分段路阻函数模型,以q=10veh/h为一个单位,对函数进行分段拟合,构建高速公路和城市快速路下的分段路阻函数,并对其适应性进行拟合分析.应用结果表明:在不同的流量范围内,高速公路和城市快速路分段路阻函数在自由流状态、高密度状态和低密度条件下适合不同的分段函数.     

基于Prescan 的信号灯路口跟停场景虚拟重构

为满足我国智能驾驶汽车测试场景库的搭建和ADAS(高级驾驶辅助系统)功能研发和验证的需求,设计了一种基于Prescan的交通信号灯路口车辆跟停场景虚拟重构方法,该方法由道路环境建设模块、初始条件设定模块和车辆控制模块组成。道路环境建设模块通过输入道路参数信息构建虚拟道路,初始条件设定模块通过输入本车和目标车的初始位置、初始速度信息确定零时刻车辆和道路的空间位置及状态信息,车辆控制模块依据车辆速度位置等信息,利用训练的神经网络控制本车加速度,实现跟停场景的虚拟重构。仿真结果表明,该方法可以实现交通信号灯路口车辆跟停场景的虚拟重构。     

Optical device for measuring the injectors opening in common rail systems

Since the needle displacement exerts a fundamental influence on the operation of Common Rail injection systems, accurate measurements of the control piston position can be crucial for a more thorough analysis of the behaviour of injectors, in particular when multiple injections are employed. Eddy current sensors have traditionally been used in lab activities to measure the control piston position inside injectors; apart from the high cost, the scientific literature clearly shows their inadequacy, which is mainly due to the presence of electromagnetic disturbance: the current pulse, which controls the opening of the injector, generates electromagnetic fields which strongly affect the acquisition of data. Many attempts have recently been made either to solve the interference occurring during such measurements or to propose alternative displacement transducers whose operation is not influenced by electromagnetic interference. In this paper, a new device for measuring the injector opening is proposed: it is an optical transducer characterized both by simple and very cheap construction and by a reliable physical principle for measuring the control piston lift. The reliability of the proposed sensor is assessed by a thorough experimental campaign and by comparing the experimental results with the numerical predictions achieved by a Common Rail injector model. Since the assembly of the optical sensor does not affect the injector operation, it can efficiently be used both for experimental tests and for on-board diagnosis and monitoring of the injector operation.     

Method of estimating human error probabilities in construction for structural reliability analysis based on analytic hierarchy process and failure likelihood index method

Partial safety factors must be evaluated precisely for the given target reliability index to ensure the certain level of structural reliability due to uncertain factors. The current studies of partial safety factors do not consider human error in construction for structural reliability. A mathematically model should be improved to simulate the partial safety coefficient concerned uncertainty factors which concern the effect of human error in construction. We employ the contaminated distribution to obtain the realistic mean value and standard variance of variable of structural parameters which coexist with random error human error. The reasonable partial safety coefficient can be calculated based on the realistic value of structural parameters concerned the effects of random error and gross error.     

Public sector comparators for UK PFI roads: inside the black box

A public sector comparator (PSC) represents the hypothetical, risk-adjusted cost of a project—such as a road scheme—when that project is financed, owned and implemented by government. A PSC is commonly used in public procurement decision-making as a yardstick against which private investment proposals are evaluated. Using original material released by the UK Highways Agency for the first time, the author recreated the PSCs used for the evaluation of the first eight road projects to be promoted under the UK’s private finance initiative (PFI). Alternative assumptions regarding project risks were modelled using different levels of optimism-bias uplift, and the impact on value-for-money of using different discount rates was evaluated. Public sector comparators have attracted considerable attention in the literature as they retain a pivotal role in the policy decision to use—or not use—private finance. However the fact that their detail is usually kept confidential by public sector procuring agencies—because of commercial sensitivities—has restricted informed discussion and open debate. Now the architecture of these comparators is laid bare for critical examination. It has generally been assumed that any reduction in the discount rate used in PSC calculations will favour conventional procurement over PFI-type contracting arrangements. The research reported in this paper demonstrates that the relationship between the discount rate and the attractiveness of using private finance is not as simple as has been assumed, and the outcome in terms of value-for-money is not as predictable as has previously been reported.     

河南省三淅高速公路施工期能源消耗总量分析研究

文章采用填报能耗统计表格的方式,调查了河南省三淅高速卢氏至寺湾段施工期能源消耗总量情况。统计结果显示,三淅高速公路卢氏至寺湾段施工期能源消耗总量折合标准煤为129 959.92 t,平均每公里能耗折合标准煤1 067.75 t,每万元投资能耗折合标准煤95.93 kg。     

水污染防治问题的数学模型研究

文章从数学建模的角度出发,使用微分方程等建模方法,给出了水污染防治问题的数学模型,得到了污染物扩散浓度所满足的微分方程,进而用差分法求出其数值解,最后对计算结果进行分析,获得了相关的结论。     

Aerodynamic characteristics of airship Zhiyuan-1

An airship named ＂Zhiyuan-l＂ was designed/fabricated/flied as a technical demonstration for stratospheric airship during 2007--2009 by Shanghai Jiaotong University. The calculation method and procedure of aerodynamic parameters were introduced, and the optimized configuration of the hull and the aerodynamic layout were given in this paper. Wind tunnel tests with different configurations, different pitch angles and different yaw angles were performed to study the wind load characteristics of the rigid model of the airship ＂Zhiyuan-1＂ in the φ3.2 m wind tunnel at China Aerodynamics Research ＆ Development Center. Also the numerical calculation about the test model was carried out to investigate the aerodynamic behavior. According to the results of wind test and numerical calculation, the excellent hull configuration of the airship ＂Zhiyuan-1＂ with lower drag characteristic was confirmed, which is based on optimism of the Michel transition law. And the phenomena of pressure coefficient distribution were discussed according to the results of wind tunnel test and numerical calculation at different flight attitudes.     

Gain-scheduled EGR control algorithm for light-duty diesel engines with static-gain parameter modeling

This paper presents a model-based gain scheduling algorithm of a PI-based EGR controller for light-duty diesel engines. In order to capture nonlinear characteristic of the EGR system, we have proposed a new scheduling variable to illustrate the static-gain of the plant model as a linear function. The proposed scheduling variable is composed of the air-tofuel ratio of the exhaust gas and the pressure ratio between the exhaust and intake manifolds. Using the scheduling variable, a static-gain model achieved 0.94 of the R-squared value with 810 of steady-state measurements which include key engine operating conditions. Based on the model of the static-gain parameter, the gains of the PI controller are decided by Skogestad internal model control (SIMC) tuning rule in real-time. Through various scenarios of engine experiments, the proposed gain scheduling algorithm represented that the PI gains were successfully adapted according to the changes of the engine operating conditions.