曹妃甸新区交通需求预测模型的思考

对于没有基础的交通量和经济社会发展状况等方面数据的未开发区域以及没有系统科学的交通量调查数据的曾经偏远落后的地区,很难用经典的交通需求预测模型来预测其远景年的交通量,可以考虑采用土地利用回归模型对该地区进行交通需求预测。     

A study of the relationship between Magic Formula coefficients and tyre design attributes through finite element analysis

Pacejka's Magic Formula Tyre Model is widely used to represent force and moment characteristics in vehicle simulation studies meant to improve handling behaviour during steady-state cornering. The experimental technique required to determine this tyre model parameters is fairly involved and highly sophisticated. Also, total test facilities are not available in most countries. As force and moment characteristics are affected by tyre design attributes and tread patterns, manufacturing of separate tyres for each design alternative affects tyre development cycle time and economics significantly. The objective of this work is to identify the interactions among various tyre design attributes-cum-operating conditions and the Magic Formula coefficients. This objective is achieved by eliminating actual prototyping of tyres for various design alternatives as well as total experimentation on each tyre through simulation using finite element analysis. Mixed Lagrangian–Eulerian finite element technique, a specialized technique in ABAQUS, is used to simulate the steady-state cornering behaviour; it is also efficient and cost-effective. Predicted force and moment characteristics are represented as Magic Formula Tyre Model parameters through non-linear least-squares fit using MATLAB. Issues involved in the Magic Formula Tyre Model representation are also discussed. A detailed analysis is made to understand the influence of various design attributes and operating conditions on the Magic Formula parameters. Tread pattern, tread material properties, belt angle, inflation pressure, frictional behaviour at the tyre–road contact interface and their interactions are found to significantly influence vehicle-handling characteristics.     

郑州市公交场站复合利用策略研究

公交场站是公共交通网络的关键节点,其复合利用模式可影响公交服务质量。本文从理论基础及应用策略两个层面对城市公交场站复合利用模式进行梳理,对公交场站复合利用的意义、模式及方法进行研究,建立集约高效的公交场站复合利用模式。以郑州市为例,验证了本文提出的公交场站复合利用模式能够适应这个时期的城市用地发展特征,提高公交场站服务能力,同时可减轻政府财政压力,发挥投资效益,可为政府部门制定公交场站复合利用模式提供参考。     

Multi-level condition-based maintenance planning for railway infrastructures – A scenario-based chance-constrained approach

This paper develops a multi-level decision making approach for the optimal planning of maintenance operations of railway infrastructures, which are composed of multiple components divided into basic units for maintenance. Scenario-based chance-constrained Model Predictive Control (MPC) is used at the high level to determine an optimal long-term component-wise intervention plan for a railway infrastructure, and the Time Instant Optimization (TIO) approach is applied to transform the MPC optimization problem with both continuous and integer decision variables into a nonlinear continuous optimization problem. The middle-level problem determines the allocation of time slots for the maintenance interventions suggested at the high level to optimize the trade-off between traffic disruption and the setup cost of maintenance slots. Based on the high-level intervention plan, the low-level problem determines the optimal clustering of the basic units to be treated by a maintenance agent, subject to the time limit imposed by the maintenance slots. The proposed approach is applied to the optimal treatment of squats, with real data from the Eindhoven-Weert line in the Dutch railway network.     

石灰桩融化岛状多年冻土的试验研究

针对岛状多年冻土区的新建工程和既有工程改扩建过程中面临的地基多年冻土稳定性问题,利用生石灰与水反应放热原理,采用预融技术对多年冻土地基进行处理,达到使冻土融化并固结沉降从而增强地基承载力的效果。在收集国内外工程中处理岛状多年冻土的主要方法和生石灰桩在处理地基的应用范围等相关资料的基础上,创新性开展石灰桩预融冻土地基室内模型试验研究,通过试验确定适用于融化高温岛状冻土且增强其地基承载力的石灰桩材料类型、材料配合比及施工工艺,并对其应用效果进行评价,形成在高温岛状冻土地区可以应用的一种新型成套石灰桩预融技术。     

Modelling minimum-time manoeuvering with global optimisation of local receding horizon control

In this paper, we explore the notion that a human driver uses a receding horizon model predictive control (MPC) scheme for minimum-time manoeuvering. However, MPC is an inherently sub-optimal control scheme because not all future information is incorporated into its finite preview horizon. In many practical applications, this sub-optimality is tolerated as the solution is sufficiently close to optimal. However, it is known that professional drivers have the ability to learn driving circuits and exploit its features to minimise their global manoeuvering time. In this paper, we will model their process with a cascaded optimisation structure. Therein, the inner-loop features a local MPC scheme tasked with finding the control inputs that achieve a blended objective of minimising time and maximising velocity in each preview horizon/distance. The outer loop of this cascaded structure computes the best set of weights for the two components of the local objectives in order to minimise the global manoeuvering time. The proposed cascaded optimisation and control approach is compared against a straight-forward fixed-cost time optimal MPC applied to minimum-time manoeuvering over two well-known race courses. The paper also includes an extended literature review and details of the computational formulation of the model approach.     

轨道交通接驳方式选择行为分析——以上海松江大学城为例

基于上海松江大学城站轨道衔接方式选择行为的调查数据,对城市轨道交通接驳方式选择行为进行研究,从大学城学生个体角度分析学生群体的出行特征和规律,合理有效地调整交通结构,进而优化城市轨道交通服务水平,增加城市轨道交通的吸引力.基于Nested Logit非集计模型,建立两种不同分组选择支的轨道交通衔接方式选择模型进行参数标定,对比模型的优比度、分支相关系数和命中率,择优选择精度较高的模型.根据建模结果,在调查数据分析的基础上,对不同接驳方式的分担率进行预测.预测结果为:公共汽车的分担率最高,为59.9％,即公共汽车仍为学生选择的主要接驳方式,出租车的分担率次之,自行车分担率最低.最后,对NL模型进行应用.研究发现,对于学生群体而言,提高出租车的起步价对出租车的分担率并无较大影响.综合比较性别、接驳时间、接驳费用等影响因素,发现性别对学生接驳方式的选择有较大影响.     

基于灰理论的成都市铁路旅客周转量预测

铁路旅客周转量是一个受多种因子制约的多层次的复杂关系量,将成都市2004—2008年铁路旅客周转量作为基础数据,运用灰理论所提出的灰系统模型预测法,建立GM（1,1）模型,预测2009--2011年的铁路旅客周转量。预测结果表明2009--2011年成都市铁路旅客周转量总体呈上升趋势。同时,GM（1,1）预测值经过检验,预测结果精度较高,说明预测方法的可靠性,预测结果对合理布局规划成都市铁路枢组具有重要的现实意义。     

远期城市交通模型的公交线网建立方法初探——以温州为例

公交线网是城市交通模型的重要组成部分,由于远期城市公交线网存在较大的不确定因素,本文针对远期城市交通模型提出了几种可能的公交线网建立方法,并对各种方法的优缺点和适用条件进行了评价,最后以温州城市交通模型为具体案例研究确定了公交线网的建立方法.