局部紧度量空间的闭映象

借助弱紧k网络,获得了局部紧度量空间闭映象内部特征一个新的刻画,即空间X是局部紧度量空间的闭映象当且仅当X是具有点可数的弱紧k网络的Fr(e)chet空间.     

城市道路与地下工程综合测量方法

综合采用井上、井下导线测量和高程水准测量方法,结合隧道断面测量和地质雷达探测结果,对某城市次干道与主干道相交处西南侧电缆隧道及隧道外电缆线进行测量,并综合测量结果,确定了该次干道原设计匝道与主干道下方电缆隧道及其附属设施的具体位置和顶板标高,以及110 kV电缆的平面位置、标高和与隧道的连接位置,获取了修改原设计方案的资料.     

铲装机械手全关节动力学及其解析

目前,铲装机械手的动力学解析主要针对主动关节进行,对从动关节的动力学问题还很少进行过研究.在铲装机械手阻力检测系统设计时,有时需要在从动关节处安装力传感器,并对传感器的输出进行动力项、静力项的分离.为此,本文以铲装机械手主动关节动力学解析为基础,对连杆的受力进行了全面分析,推导出了从动关节的动力学计算式.在对主动关节和从动关节动力学解析进行综合的基础上,提出了全关节动力学的概念,并给出了铲装机械手全关节动力学方程式.     

建设大学校园文化塑造大学生健全人格

大学是教书育人的场所，它不仅要向大学生传授知识、培养大学生的能力，而且要使大学生形成良好的道德素养和健全的人格。大学校园文化以其独特的表现形式在塑造大学生健全人格中的重要作用越来越明显。因此，重视对大学校园文化的研究，建设适合提升大学生健全人格素质的大学校园文化，是当前大学建设和发展中所要面临的重要任务。     

复合地层顶管机刀盘中心驱动液压系统的设计与分析

常规刀盘电机驱动顶管机在特定复合地层条件下经常出现超转矩、掘不动的情况。针对这种情况,设计采用刀盘中心驱动的变量泵-变量马达闭式液压系统。根据复合地层的要求,在理论计算的基础上,针对性地匹配变量泵-变量马达的运行参数,再利用AMESim软件对液压系统进行建模,对刀盘在低速、高速和脱困3种模式进行仿真分析。理论计算和仿真分析结果表明所采用的闭式液压系统能够较好地适应复合地层对掘进的要求。     

Variation in predicting pantograph–catenary interaction contact forces,numerical simulations and field measurements

The contact force between the pantograph and the contact wire ensures energy transfer between the two. Too small of a force leads to arching and unstable energy transfer, while too large of a force leads to unnecessary wear on both parts. Thus, obtaining the correct contact force is important for both field measurements and estimates using numerical analysis. The field contact force time series is derived from measurements performed by a self-propelled diagnostic vehicle containing overhead line recording equipment. The measurements are not sampled at the actual contact surface of the interaction but by force transducers beneath the collector strips. Methods exist for obtaining more realistic measurements by adding inertia and aerodynamic effects to the measurements. The variation in predicting the pantograph–catenary interaction contact force is studied in this paper by evaluating the effect of the force sampling location and the effects of signal processing such as filtering. A numerical model validated by field measurements is used to study these effects. First, this paper shows that the numerical model can reproduce a train passage with high accuracy. Second, this study introduces three different options for contact force predictions from numerical simulations. Third, this paper demonstrates that the standard deviation and the maximum and minimum values of the contact force are sensitive to a low-pass filter. For a specific case, an 80?Hz cut-off frequency is compared to a 20?Hz cut-off frequency, as required by EN 50317:2012; the results show an 11% increase in standard deviation, a 36% increase in the maximum value and a 19% decrease in the minimum value.     

Resilience in transportation systems: a systematic review and future directions

ABSTRACT

The Belt and Road (B&R) initiative was introduced by the Chinese government to promote the worldwide economic development and multilateral cooperation between China and the associated countries. As a crucial part of global supply chains, transportation plays a key role to ensure the implementation of the B&R. Safety is one of the issues with great importance in transportation research. However, its foci have been expanded from traditional risk through security to resilience and sustainability. Resilience has attracted considerable interests from both researchers and practitioners across different research domains in recent years. Various studies have been conducted on transportation resilience from different perspectives. Consequently, different definitions have been developed to define and describe resilience. This paper presents a systematic review on transportation resilience with emphasis on its definitions, characteristics, and research methods applied in different transportation systems/contexts. It aims to figure out what transportation resilience is and what kind of essential characters it usually has. More importantly, research challenges are analysed and a future research agenda on the resilience of transportation systems is proposed. This paper will provide comprehensive insights into understanding the transportation resilience, as well as establish new horizons for relevant research topics within the context of the B&R.     

A study on the determinants of private car ownership in China: Findings from the panel data

This study examines the determinants of private car ownership in China. The target cities are 32 provincial capital cities and the target period is from 2001 to 2011. In order to capture the individual effects (heterogeneity), the fixed and random effect models are adopted and compared, in which 8 explanatory variables are selected to include economic characteristics, urban characteristics, and transportation characteristics. Moreover, double natural logarithm model is employed to measure the elastic relationship between the private car ownership and regressors. The estimated results show that the fixed effect model performs better than pooled regression model and the random effect model. In addition, there are variations of private car ownership among cities and regions. Finally, the influence of factors responsible for these variations is also presented and discussed in this paper.     

基于模块化神经网络的第三方逆向物流评价方法研究

在电子商务环境下,第三方逆向物流模式是最适合现有条件下,我国企业对逆向物流的迫切要求的、本文构建了对第三方逆向物流提供商的评价指标体系,通过模块化神经网络这一强有力的工具,可以对第三方逆向物流企业进行科学客观的评价。     

长江江苏段汽渡船舶AIS系统研究

从分析汽渡船舶安装AIS系统的必要性入手,借用管理学S．W．O．T．分析方法,对长江江苏段汽渡船舶安装AIS系统进行具体研究,提出相关策略。