Activity sequencing,location, and formation of individual non-mandatory tours: application to the activity-based models for Columbus,Cincinnati, and Cleveland,OH

Most of the earlier activity based models (ABMs) largely relied on a tour-based modeling paradigm which explicitly predicts tour frequency and then adds details including stop frequency, order, and location of stops within each tour. The current study is part of new tour formation design framework for an ABM in which the underlying tour structure and the stop frequency within tours emerge from temporal, sequencing, and locational preferences of activities that the traveler intends to participate during the day. In order to do this, the study developed a modified rank-ordered logit (ROL) framework that is capable of modeling sequence, locations, as well as the underlying tour structure of all activity episodes simultaneously in an integrated manner. Model estimation with the household survey data, provided several important behavioral insights into underlying choices that drive tour formation. Specifically, the study uncovered pairwise ordering preferences among episodes of different activity purposes, clustering tendencies among episodes of same activity purpose, the impact of supply side activity opportunities on the location and sequence choice dimensions, and impedance effects (including distance and mode and time-of-day logsums) on location and tour break dimensions. The developed models are incorporated in the operational ABM structure adopted for three major cities (Columbus, Cleveland, and Cincinnati) in Ohio.     

Incorporating features of autonomous vehicles in activity-based travel demand model for Columbus,OH

Transportation - Autonomous vehicles (AVs) could change travel patterns of the population significantly and with the rapid improvements in AV technology, transportation planners should address AV...     

基于拓扑优化的扭力梁式轿车后桥结构轻量化设计

在某轿车原扭力梁后桥的基础上，建立了扭力梁式后桥的结构力学模型，具体分析了原车后桥的模态及在静止、制动或启动及侧翻工况下的强度。在此基础上进行原车后桥的拓扑结构轻量化设计，通过在原后桥的基础上获得后桥空间设计域及非设计域，定义设计目标、设计函数、加载条件及响应，迭代计算获得了最佳的结构拓扑方案。根据结构拓扑优化的最终结果，通过CAD 重构获得了拓扑结构轻量化的后桥设计。模态及强度计算结果显示，优化后的后桥前三阶模态频率较原后桥有大幅减小，不同工况下后桥的应力分布更趋合理，在设计域内及安装位置不变的条件下，新后桥的质量由原后桥的19.06 kg 减少到17.67 kg，减重7.29%。