Are young Americans carless across the United States? A spatial analysis

This study uses the National Household Travel Survey (NHTS) data to investigate the most recent correlates of vehicle ownership among young Americans. This study performs a spatial analysis to examine the potentially non-stationary relationships between sociodemographic factors and vehicle ownership. Consistent with previous studies, modeling results from this study showed that young Americans are more likely to be carless than older adults. The spatial analysis answers the research question – in which regions(s) young Americans are even less likely to have a car. The results highlighted the Northeast states for the young American’s extra-lower vehicle ownership if the influences of all other factors are held constant. The cost of living and availability of transportation alternatives are possible reasons. Further, this study built separate models for young adults (25–34 years old) and three older age groups. The vehicle ownership correlates within the young adults are found to be generally consistent with the correlates among all adults. Among young adults, vehicle ownership is still significantly related to their gender, educational attainment, employment status, household characteristics, and travel demand. However, young adults’ vehicle ownership seems to be less sensitive to household income than mid-age adults’ (35–44 years old), perhaps because young people may not perceive financial stress such as child support and mortgage. This study contributes by using a spatial analysis approach to reveal the non-stationary correlates of vehicle ownership. This approach is useful for future travel behavior research and transportation policy considering the spatial heterogeneity.     

基于两性一度的《汽车服务工程》教学改革研究

随着金课的提出,线上线下混合式教学模式逐渐成为高等教育教学模式改革的突破口。《汽车服务工程》课程基于两性一度,首先进行可行性分析,其次提出改革思路;最后展示典型的混合式教学案例。     

车身焊接修复过程中影响焊接质量的因素

随着科技日益发展,人们的生活水平越来越好。汽车逐步成为家庭的出行的必备工具。我们中国是人口大国,汽车的保有量逐年上升,伴随车辆的不断增多,汽车发生的碰撞事故也随之增多。而对于严重碰撞损伤的车辆,车身修复过程中的焊接质量,直接影响着维修后车辆的安全系数。     

基于联合调度优化模型的共享汽车分析

共享汽车行业曾在几年前广为繁荣,但由于其所具有的重模式、高成本、难以盈利等弊端,造成企业难以持续融资,行业难以持续繁荣的困境。如今,随着汽车车型更新换代日益迅速,加之疫情影响经济发展,消费者更倾向于轻便的用车模式,使得具有“分时租赁”特点的共享汽车获得很大发展机遇。本文综合利用Excel、Python软件,先以经纬度为横纵目标对附件数据进行离群值剔除与可视化展示,并将其在空间上划分成25个区域,从而更准确地研究其空间特征;其次,使用Matlab软件构建DBSCAN聚类算法模型,将不同区域共享汽车的实际密度情况以热力图形式在地图上可视展现,得出共享汽车分布主要集中在经度34.78377、纬度32.0556等区域附近,这些区域大多集中位于城市中心,人口密度相对高,共享汽车使用频率高的结论,同时编程得出不同型号车辆在整体区域信息的出现频率次数表,进行不同维度变化分析,得到共享汽车使用集中在早午晚高峰期,该时间段内人流量大,用车需求量高,汽车使用频率高的结论。     

无砟轨道板精调车结构可靠性分析及优化

为提高无砟轨道板精调车结构的设计水平,考虑精调车荷载、几何尺寸和材料弹性模量等设计变量的随机性,对精调车结构进行可靠性分析、可靠性灵敏度分析和可靠性优化。首先,分析并得到精调车结构在串联失效模式下的结构功能函数;然后,运用响应面法和重要抽样方法,分析得到基于确定性优化的精调车结构的失效概率和可靠性灵敏度结果。最后,根据可靠性灵敏度分析结果,对该结构进行可靠性优化。分析精调车结构在可靠性优化前后的差异,结果表明,与确定性优化结果相比,可靠性优化使精调车结构自重增加了3.55%,但可靠度提高为0.999 999 987 7,说明设计变量的随机性对结构性能的干扰大幅减小。     

Human resources in the mixed ownership reform of Chinese ports: the mediating effects of organizational commitment

In the process of the change to mixed ownership of Chinese ports, the allocation of human resources has become increasingly important because of the workforce’s growing concerns regarding losses of benefits. The mediating effect of organizational commitment in the relationship between person-organization fit and organizational citizenship behavior (OCB) can provide a significant reference for port managers and regulators, i.e., the government, regarding the framework of human resource systems. The data examined in this study were collected from three Chinese ports (Qingdao Port, Yantai Port and Rizhao Port) that are in the process of changing to mixed ownership. Structural equation modeling was applied to test the hypotheses. The results show that it is extremely difficult for groups with vested interests in Chinese ports to achieve consistency fit in the short term and to accept potential losses. Moreover, it is imperative to adopt a scientific and efficient person-organization fit mechanism and personnel system to achieve a higher level of fit.     

中国乘用车工况构建

依托“中国工况”项目，对我国乘用车行驶工况进行深入研究. 在全国41 个城市采集乘用车共计1 600 万km的行驶数据，收集各城市交通量大数据用于权重因子开发；利用权重因子对采集数据进行加权，获取代表我国驾驶特征的、统一的速度-加速度分布，以其为基准，使用卡方检验选择最优短片段组合作为我国乘用车行驶工况(CLTC). 对比CLTC工况特征与其他典型工况及实测数据GIS加权结果，CLTC工况更符合我国实际.     

重载货车摩擦缓冲器阻抗特性的数值模拟

为预测摩擦缓冲器的实际工作状态,从几何特征和作用原理的角度,建立详细的MT-2型缓冲器理论模型。首先,通过对缓冲器内部各摩擦元件的运动学和静力学分析,推导出缓冲器在准静态下的阻抗特性;其次,引入附加摩擦系数量化各摩擦元件之间动静态摩擦过渡时的黏滞补偿,并模拟出缓冲器在动态下的阻抗特性;最后,利用C80型货车冲击试验数据对该缓冲器的理论模型进行验证。验证结果表明:总体上,数值模拟和现场试验下的缓冲器示功曲线基本吻合,说明模型的正确性;局部上数值模拟中缓冲器从加载Ⅰ阶段过渡至加载Ⅱ阶段的突变现象在冲击试验中表现的并不明显,还有待进一步完善。     

驾驶人“感知-决策-操控”行为模型

为准确模拟驾驶人跟车行为，提出基于隐马尔可夫模型(Hidden Markov Model，HMM)的驾驶人“感知-决策-操控”行为模型。建立描述驾驶意愿的HMM模型，模拟驾驶人感知过程，获得期望的车间距；预测模块模拟驾驶人根据交通环境和自身生理、心理状态预测车辆未来轨迹，即决策过程；优化模块描述驾驶人为使预测的车辆轨迹跟踪上期望的车辆间距而采取的操控汽车的执行动作，即操控过程。上述3个模块的滚动过程实现了对驾驶人跟车行为的模拟。利用自然驾驶数据进行算例分析，结果表明，本文模型预测车间距平均误差仅为1.47%，证明了所建模型的有效性及准确性。本文为驾驶行为建模方法的理论研究和应用拓宽了思路。     

后疫情时代国内纯电动乘用车市场发展现状

2020年国内纯电动乘用车市场在新冠肺炎、补贴退坡、各地促销政策陆续出台等多方面因素影响下先抑后扬、市场回暖,呈现出厂商竞争加剧、销售区域转变、私户占比增加、车型趋向高端化等特征。在我国碳达峰、碳中和的宏伟目标下,随着消费者环保认知的不断提升,纯电动乘用车市场将稳步发展并进一步向智能化、自动化方向转变。