Accessibility and transport infrastructure improvement assessment: The role of borders and multilateral resistance

The market potential indicator is a commonly used tool in transport planning for evaluating the potential economic effects derived from improvements in transport infrastructures. The general assumption is that exports from a given region will rise with increased accessibility, thus benefiting economic activities. However, the specification of the market potential model is typically very simple and ignores both the impact of competing rivals and the role of international borders, which leads to unrealistic results. Spatial interaction models on bilateral trade have already proved that international trade is affected by multilateral resistance, borders, adjacency, language or currency. Nevertheless, apart from some recent analyses that simply calibrate the distance decay parameter from trade datasets, these variables have hardly been integrated into research on market potential. This paper sets out to demonstrate that more realistic results are obtained by calibrating the distance-decay parameter and introducing the impact of competing rivals and border effects into the market potential formulation. The proposed model is then applied to the assessment of the accessibility impacts of new road transport infrastructure in the European Union between 2001 and 2012, which shows that the greatest improvements in accessibility were experienced by peripheral countries with high road infrastructure investment.     

基于HLA的智能交通信息试验平台研究

从智能交通信息平台的概念出发,研究利用已有的智能交通系统资源建立智能交通信息试验平台。首先对比分析了已有的平台体系结构开发方法,即面向过程的开发方法和面向对象的开发方法,两者都已不能适应复杂大系统的开发需求。通过引入计算机建模与仿真领域的HLA（高层体系结构）技术,创造性地提出了基于HLA的体系结构开发方法,结合信息试验平台需求分析,设计了智能交通信息试验平台的逻辑结构。平台分4层来组织,分别是基础数据层、数据库层、应用服务层和用户主体层,在若干接口程序的衔接下,各类联邦成员协同作用以实现信息平台的功能。结合现有的技术设备条件,实现了信息平台的物理连接。平台搭建后运营正常,已接入信息平台的ITS系统包括车载导航系统和城市商用车辆调度系统,并为其他子系统的接入预留了接口。     

智能车辆安全辅助驾驶技术研究近况

论述了安全辅助驾驶技术的研究现状、研究的必要性以及研究进展。安全辅助驾驶技术包括车道偏离预警与保持、前方车辆探测及安全车距保持、行人检测、驾驶员行为监测、车辆运动控制与通讯等。分析了各种传感器的优缺点及其在实际应用过程中存在的问题,基于单一传感器不能很好地解决安全辅助驾驶技术可靠性和环境适应能力的要求,应结合激光雷达技术解决图像模糊问题,利用红外传感器增强机器视觉识别的可靠性,未来的安全辅助驾驶技术应该采取多种传感器融合的技术,结合毫米波雷达和激光雷达系统具有深度测量精确的特点,将极大的推动汽车安全辅助驾驶系统的应用和推广。     

多尺度图像边缘检测技术在车辆识别中的应用

指出了图像边缘检测的定义及现有算法的不足,并对Canny边缘检测离散准则及该准则下的最优线性滤波器进行了论述。根据边缘检测离散准则,利用数值方法求出该准则下边缘检测的最优线性滤波器及对应的平滑算子,将其与Canny边缘检测技术相结合进行边缘检测,检测出不同尺度下多幅边缘图像,并根据小尺度下图像边缘细节信息丰富、边缘定位精度高,大尺度下图像边缘稳定、抗噪性好等特点,将检测到的多尺度边缘进行融合,得到抗噪性好的精确的单像素宽边缘;同时将该方法应用于汽车特征提取,检测到完整连续的汽车边缘图像,为车型识别提供条件。试验结果表明:该方法不仅能准确检测出图像边缘,而且能有效地抑制噪声,是边缘检测的实用方法。     

基于Q-learning和BP神经元网络的交叉口信号灯控制

解决单交叉口信号灯最优控制问题。提出了基于强化学习的信号灯控制系统结构,应用强化学习中Q学习,将信号灯最优控制问题转变成是否切换运行相位的决策问题,提出了采用BP神经元网络实现Q学习的信号灯控制系统。应用微观交通仿真软件PARAMICS进行仿真分析,结果表明该系统能够感知交通流变化,并能够自适应地调整信号灯切换策略,以达到最优的控制效果,该方法是可行的,与定时控制相比具有明显的优势。     

Nonlinear three-dimensional wagon-track model for the investigation of rail corrugation initiation on curved track

A nonlinear wagon-track model on curved track has been developed to characterize rail corrugation formation due to self-excitation of the wheel-rail stick-slip process. In this model, wagon movements were described using up to 78 degrees of freedom (DOFs) to model a three-piece freight bogie. Innovatively, the wheelset movements are described using nine DOFs, including torsional and bending modes about the longitudinal and vertical directions. The track modelling is considered as a one-layer structure (two rail beams on discrete spring and damper elements). The wheel sliding after creepage saturation is considered in the wheel-rail interface modelling. Simulation of a case study shows that the frequencies of the wheel stick-slip process are composed of the basic frequency, which might come from the combined effect of sleeper-passing frequency and one-third of the combined torsional and bending frequency of the wheelset, and the double and triple basic frequencies, which form the wavelengths of rail corrugation at different situations.     

小型运输船船型经济性论证分析

文章根据大连湾老铁山水道的情况,考虑变吃水的运输方式,以船长、船宽、吃水及航速作为变量来进行船型方案的组合。选用净现值、内部收益率、投资回收期、必要运费率和综合经济指标作为衡量船型方案的标准,通过分析计算得出最佳的船型方案,为小型渔货船型选择提供参考。     

辗压混凝土机械化施工的体会

本文以交通部第二公路工程局1990年在安徽省312国道进行辗压混凝土施工中,如何解决诸如辗压混凝土路面结构、路面平整度、摊铺厚度、混合料级配、离析的影响以及自卸车倒料、压实、运输与摊铺等问题,并参考有关资料,进一步探讨了辗压混凝土施工工艺及施工机械的合理配套.     

公路客运班车报停制度研究

公路客运峰谷现象明显,在运能、运力有限的情况下,如何才能更好地满足客运高峰期(如春运)的交通需求是政府和企业的一项重要课题。现有的政策并没有使有限的客运资源得到最合理的利用,给能源和环境都带来了一定的影响。文章较系统地从企业和政府两个角度论述了建立班车报停制度的必要性和可行性,通过对客运线路的调查,对公路客运班车报停制度的社会经济效益作了定性和定量分析。     

Modelling of wheels and rail discontinuities in dynamic wheel-rail contact analysis

A classification of wheel-rail contact is given. Difference is made between modelling of a running wheel with continuous single-point-contact, as is common practice in wheel-rail contact analysis, and a wheel with transient double- or multi-point-contact, which may occur for rail irregularities with curvatures larger than that of the wheel circumference. It is shown that application of the first model for these irregularities will strongly underestimate the contact forces as it does not describe occurring mechanisms correctly. Further, it is shown that in principle it is not possible to describe the second type of contact fully correct with a lumped wheel model. Both wheel models are formulated mathematically for some basic contact cases. Afterwards, results are applied to a linear track model. Analytical closed-form solutions are found in the frequency domain for arbitrary type of contact and numerically transformed to the time domain. Finally, the necessity is shown to avoid situations where transient multiple-point-contact may occur (like rail joints) in practice.