The role of children’s independent mobility and social media use for face-to-face social interaction with friends

Transportation - Social interaction with friends is an important contributor to children’s well-being, but how transport affects this is rarely studied. For two or more children (not of the...     

The impact of planned disruptions on rail passenger demand

Transportation - Disruptions to rail journeys are experienced by rail passengers on a daily basis throughout the world, with the impacts on passengers ranging from minimal to major. Such...     

���зֲ�����Ϣ��ģ��

熵最大化方法被广泛应用于交通规划，为交通需求预测模型提供了理论依据.本文使用信息论中的熵概念描述居民出行分布，并根据最大信息熵理论提出了基于原点矩典型特征量约束条件下的出行分布模型，详细阐述了模型中各个参数的实际含义，该模型是一个普适性模型，其具体形式决定于最高阶原点矩阶数的取值，此值对模型精度及参数标定难易程度有重要影响.为确定模型参数，提出了实用的参数标定方法.由于模型中原点矩的最高阶数对模型精度有较大影响，为找到两者之间的关系，利用长春市出行调查数据研究了四种出行方式分别时应于五种原点矩最高阶数的模型拟合情况.因文中所建立的模型是一系列模型，为比较其描述问题的优劣差异，按照最大信息熵原理给出了确定系统分布的熵方法，并运用该方法对前述模型进行了比较.调查数据的验证结果表明，出行分布的信息熵模型可以正确地描述出行分布规律，熵方法可以简单有效地评价不同模型对同一问题描述的优劣差异.本文提出的熵模型和熵方法对城市交通规划具有指导意义.     

层状边坡渐进破裂与失稳过程数值模拟探讨

运用岩石破裂与失稳过程分析RFPA^2D系统，以含层理弱层边坡的渐进破裂与失稳分析为例，通过对边坡渐进破裂与失稳发生孕育机制及其锚固控制规律的数值模拟，数值模拟再现了含层理弱层和锚固边坡渐进破坏与失稳的发生、发展过程，模拟结果表明，复杂结构边坡的渐进破坏与失稳现象是一些简单机理的演化结果。     

列车运行与优化系统的设计

随着世界能源消耗的逐年增长,燃油的节省技术越来越受到重视。本文就GE公司运输系统集团的新一代节油产品列车运行与优化系统设计展开讨论,针对软件模块功能进行介绍,也汇总了在全球应用的现状,最后展望了在中国应用的未来。     

Dual objective active suspension system based on a novel nonlinear disturbance compensator

This paper proposes an active suspension system to fulfil the dual objective of improving ride comfort while trying to keep the suspension deflection within the limits of the rattle space. The scheme is based on a novel nonlinear disturbance compensator which employs a nonlinear function of the suspension deflection. The scheme is analysed and validated by simulation and experimentation on a laboratory setup. The performance is compared with a passive suspension system for a variety of road profiles.     

Practicability study on the suitability of artificial,neural networks for the approximation of unknown steering torques

For steer-by-wire systems, the steering feedback must be generated artificially due to the system characteristics. Classical control concepts require operating-point driven optimisations as well as increased calibration efforts in order to adequately simulate the steering torque in all driving states. Artificial neural networks (ANNs) are an innovative control concept; they are capable of learning arbitrary non-linear correlations without complex knowledge of physical dependencies. The present study investigates the suitability of neural networks for approximating unknown steering torques. To ensure robust processing of arbitrary data, network training with a sufficient volume of training data is required, that represents the relation between the input and target values in a wide range. The data were recorded in the course of various test drives. In this research, a variety of network topologies were trained, analysed and evaluated. Though the fundamental suitability of ANNs for the present control task was demonstrated.     

Clamping performance of fastener in windshield wiper assembly using theoretical and experimental methods

Improper clamping of wiper arms can cause problems in the operation of the wiper. An excessive clamping force can cause damage to the wiper arm head. On the other hand, an insufficient clamping force can cause self-loosening of the nut. Given the lack of direct research on the clamping force of the fastener in wiper assembly, this study verifies the existing clamping performance of the fastener in windshield wiper assembly by theoretical and experimental methods. The theoretical calculation results show that all the clamping performance are satisfied under the general snow load condition. However, under the critical load condition, maximum assembly preload and safety margin against slipping are in disagreement with the standard values. This problem is solved by increasing the strength grade of the bolt. The experimental results show a reducing tendency of the clamping force during the snow durability test. However, this reducing clamping force during the 60,000 test cycles is acceptable. In the case of nut reusing more than two times possibly cause a problem of its loosening because of insufficient clamping force. Therefore, it is recommended that the nut should not be reused more than two times.     

Application of a modified thermostatic control strategy to parallel mild HEV for improving fuel economy in urban driving conditions

A modified thermostatic control strategy is applied to the powertrain control of a parallel mild hybrid electric vehicle (HEV) to improve fuel economy. This strategy can improve the fuel economy of a parallel mild HEV by operating internal combustion engine (ICE) in a high-efficiency region. Thus, in this study, experiments of a parallel mild HEV were conducted to analyze the characteristics of the hybrid electric powertrain and a numerical model is developed for the vehicle. Based on the results, the thermostatic control strategy was modified and applied to the vehicle model. Also, battery protection logic by using electrochemical battery model is applied because the active usage of battery by thermostatic control strategy can damage the battery. The simulation results of the vehicle under urban driving conditions show that the thermostatic control strategy can improve the vehicle’s fuel economy by 3.7 % compared with that of the conventional strategy. The results also suggest that the trade-off between the fuel economy improvement by efficient ICE operation and the battery life reduction by active battery usage should be carefully investigated when a thermostatic control strategy is applied to a parallel mild HEV.     

Automobile aerodynamics influenced by airfoil-shaped rear wing

Computational model is developed to analyze aerodynamic loads and flow characteristics for an automobile, when the rear wing is placed above the trunk of the vehicle. The focus is on effects of the rear wing height that is investigated in four different positions. The relative wind incidence angle of the rear wing is equal in all configurations. Hence, the discrepancies in the results are only due to an influence of the rear wing position. Computations are performed by using the Reynolds-averaged Navier-Stokes equations along with the standard k-ε turbulence model and standard wall functions assuming the steady viscous fluid flow. While the lift force is positive (upforce) for the automobile without the rear wing, negative lift force (downforce) is obtained for all configurations with the rear wing in place. At the same time, the rear wing increases the automobile drag that is not favorable with respect to the automobile fuel consumption. However, this drawback is not that significant, as the rear wing considerably benefits the automobile traction and stability. An optimal automobile downforce-to-drag ratio is obtained for the rear wing placed at 39 % of the height between the upper surface of the automobile trunk and the automobile roof. Two characteristic large vortices develop in the automobile wake in configuration without the rear wing. They vanish with the rear wing placed close to the trunk, while they gradually restore with an increase in the wing mounting height.