基于时间地理学的居民活动空间测度方法研究

活动空间能够反映居民受到的时空制约以及移动自由度，对分析居民出行行为有重要研究意义.本文基于时间地理学理论，强调时间维度对个体活动空间的重要塑造作用，引入活动持续时间作为权重因子，构建了活动空间的时空重心测度模型，提出“偏移度”“扩展度”两个概念来量化个体活动空间，并与传统空间中心测度方法进行对比分析，最后，以昆明市居民调查数据进行实例验证.结果表明，活动空间是由时间和空间两大要素共同决定，当存在出行距离大于4 km以上，偏移度对空间测度的修正程度约为5%~15%，时间要素对活动空间的影响程度变得较为敏感.     

A finite mixture model of vehicle-to-vehicle and day-to-day variability of traffic network travel times

This study proposes an approach to modeling the effects of daily roadway conditions on travel time variability using a finite mixture model based on the Gamma–Gamma (GG) distribution. The GG distribution is a compound distribution derived from the product of two Gamma random variates, which represent vehicle-to-vehicle and day-to-day variability, respectively. It provides a systematic way of investigating different variability dimensions reflected in travel time data. To identify the underlying distribution of each type of variability, this study first decomposes a mixture of Gamma–Gamma models into two separate Gamma mixture modeling problems and estimates the respective parameters using the Expectation–Maximization (EM) algorithm. The proposed methodology is demonstrated using simulated vehicle trajectories produced under daily scenarios constructed from historical weather and accident data. The parameter estimation results suggest that day-to-day variability exhibits clear heterogeneity under different weather conditions: clear versus rainy or snowy days, whereas the same weather conditions have little impact on vehicle-to-vehicle variability. Next, a two-component Gamma–Gamma mixture model is specified. The results of the distribution fitting show that the mixture model provides better fits to travel delay observations than the standard (one-component) Gamma–Gamma model. The proposed method, the application of the compound Gamma distribution combined with a mixture modeling approach, provides a powerful and flexible tool to capture not only different types of variability—vehicle-to-vehicle and day-to-day variability—but also the unobserved heterogeneity within these variability types, thereby allowing the modeling of the underlying distributions of individual travel delays across different days with varying roadway disruption levels in a more effective and systematic way.     

Forecasting demand for high speed rail

It is sometimes argued that standard state-of-practice logit-based models cannot forecast the demand for substantially reduced travel times, for instance due to High Speed Rail (HSR). The present paper investigates this issue by reviewing the literature on travel time elasticities for long distance rail travel and comparing these with elasticities observed when new HSR lines have opened. This paper also validates the Swedish long distance model, Sampers, and its forecast demand for a proposed new HSR, using aggregate data revealing how the air–rail modal split varies with the difference in generalized travel time between rail and air. The Sampers long distance model is also compared to a newly developed model applying Box–Cox transformations. The paper contributes to the empirical literature on long distance travel, long distance elasticities and HSR passenger demand forecasts. Results indicate that the Sampers model is indeed able to predict the demand for HSR reasonably well. The new non-linear model has even better model fit and also slightly higher elasticities.     

Time-varying effects of influential factors on incident clearance time using a non-proportional hazard-based model

Incident clearance time is a major performance measure of the traffic emergency management. A clear understanding of the contributing factors and their effects on incident clearance time is essential for optimal incident management resource allocations. Most previous studies simply considered the average effects of the influential factors. Although the time-varying effects are also important for incident management agencies, they were not sufficiently investigated. To fill up the gap, this study develops a non-proportional hazard-based duration model for analyzing the time-varying effects of influential factors on incident clearance time. This study follows a systematic approach incorporating the following three procedures: proportionality test, model development/estimation, and effectiveness test. Applying the proposed model to the 2009 Washington State Incident Tracking System data, five factors were found to have significant but constant (or time independent) effects on the clearance time, which is similar to the findings from previous studies. However, our model also discovered thirteen variables that have significant time-varying impacts on clearance hazard. These factors cannot be identified through the conventional methods used in most previous studies. The influential factors are investigated from both macroscopic and microscopic perspectives. The population average effect evaluation provides the macroscopic insight and benefits long-term incident management, and the time-dependent pattern identification offers microscopic and time-sequential insight and benefits the specific incident clearance process.     

基于地铁-货车联运的物流配送路径优化

为应对配送车辆引起道路拥堵和环境污染问题，提出地铁与货车联合运输. 在不改变地铁运行方案的前提下，利用地铁非高峰时段开展货物配送；考虑地铁剩余运能、货车容量、最大行驶距离、客户服务时间窗等限制条件，以配送距离最短为优化目标，构建基于地铁-货车联运的物流配送路径优化模型. 通过地铁配送路径设计不规则二维矩阵编码结构，使用改进自适应遗传算法求解. 以某市地铁货物运输为例，验证模型和算法的实用性、有效性. 结果表明，地铁-货车联合配送距离短，在客户时间窗范围内送达比例高，有效提高客户满意度.     

基于分类决策树的城市内部迁居人群通勤时间预测模型

针对迁居个体长距离、长时间的通勤现象，以南京迁居人群通勤出行多源数据为基础，综合考虑迁居人群个人家庭属性、迁居属性、建成环境属性及通勤属性，建立迁居人群通勤时间多元线性回归模型，分析各属性对通勤时间的影响. 结合多元线性回归和Logistic 回归确定决策树模型入选变量和通勤时间离散值，利用C4.5 算法建立迁居人群通勤时间决策树，以决策树结构揭示不同背景下迁居个体通勤时间模式特征. 结果显示，相较于个人家庭属性，职住同区、通勤出发时刻、住房类型、通勤距离、通勤方式及社区至主干道的便捷程度对迁居个体通勤时长的影响更为显著，侧面反映社区微观建成环境优化政策更利于提升迁居个体通勤效率.     

考虑时间效应下新旧桥基础差异沉降研究

在桥梁拓宽改造工程中,必然涉及新建桥梁和原有桥梁基础差异沉降及桥面板的开裂等问题。考虑沉降与时间的关系下,对桥梁基础沉降量计算方法进行了研究,计算出了旧桥的总沉降量及工后沉降结果,结合新建桥的实际情况提出相应处理办法。     

Stability and performance analysis of a full-train system with inerters

This paper discusses the use of inerters to improve the stability and performance of a full-train system. First, we construct a 28 degree-of-freedom train model in AutoSim, and obtain a linearised model for analysis in Matlab. Then, the benefits of inerters are investigated by the critical speed, settling time and passenger comfort. In addition, we apply a new mechatronic network for further performance improvement, and synthesise the optimal electrical circuit for experimental verification. From the results, inerters are shown to be effective in improving the stability and performance of train systems.     

铁路工程制存梁场设计及投资估算

在铁路设计中，制存梁场属于临时工程，其设计合理与否对于施工组织设计和投资控制至关重要。此文以巴新线地方铁路为例，介绍如何采用公式方法确定制、存梁台座的数量，从而对大型制存梁场进行设计和投资控制。实践证明，采用公式法设计制存梁场非常有效，能为超长铁路制存梁场的设计提供参考。