An efficient and exact event-based algorithm for solving simplified first order dynamic network loading problems in continuous time

In this paper a novel solution algorithm is proposed for exactly solving simplified first order dynamic network loading (DNL) problems for any generalised network. This DNL solution algorithm, termed eLTM (event-based Link Transmission Model), is based on the seminal Lighthill–Witham–Richards (LWR) model, adopts a triangular fundamental diagram and includes a generalised first order node model formulation. Unlike virtually all DNL solution algorithms, eLTM does not rely on time discretisation, but instead adopts an event based approach. The main advantage of this approach is the possibility of yielding exact results. Furthermore, an approximate version of the same algorithm is introduced. The user can configure an a-priori threshold that dictates the approximation error (measurable a-posteriori). Using this approximation the computational effort required decreases significantly, making it especially suitable for large scale applications. The computational complexity is investigated and results are demonstrated via theoretical and real world case studies. Fixed periods of stationary demands are included adopting a matrix demand profile to mimic basic departure time demand fluctuations. Finally, the information loss of the approximate solution is assessed under different configurations.     

Indicators of reliability and vulnerability: Similarities and differences in ranking links of a complex road system

This article investigates two performance attributes of road networks, reliability and vulnerability, analyzing their similarities as well as the differences that justify distinct definitions, based on consolidation of recent studies. We also discuss the indicators found in the literature for these two performance attributes. Since various authors treat vulnerability as an aspect of reliability instead of a specific attribute, we carried out an application to a complex road network representative of the city of Rio de Janeiro to check the suitability of this approach. The results show that the vulnerability indicators are more strongly affected by the characteristics of alternative routes while the reliability metrics are more sensitive to the congestion level. The conclusion is that reliability and vulnerability should be treated distinctly for evaluating the performance of road network links.     

基于复杂网络的机场群航线网络动态特征分析

随着航空运输和区域经济一体化的快速发展,我国已形成京津冀、长三角和珠三角三大典型机场群。文章以三大典型机场群为研究对象,构建基于滑动时间窗的航线网络拓扑结构,运用复杂网络理论分析机场群航线网络动态特征和同构性。研究结果表明,机场群航线网络具有无标度和小世界网络特征,并表现出显著的波峰和波谷动态性,并且长三角机场群的航班集中度分布明显高于其他两大机场群。文章首次从航线网络视角,运用Dice相似系数衡量了机场群内部各机场之间航线网络同构性程度。     

客运专线铁路隧道高陡坡洞口开裂整治技术研究

以宝兰客运专线塔稍村隧道为依托,分析隧道进口边坡及洞内裂缝的成因,评价边坡的稳定性,并提出具体的处理措施。对该隧道地层岩性、构造属性、围岩等级等进行阐述,针对该边坡建立系统的地表及洞内变形监测网并进行钻孔内位移测量工作,结合详细的地质调查,查明隧道进口处边坡、洞口挡墙、隧道内二衬裂缝的成因和基本特征,结合区段的工程地质特征,提出合理的工程处理措施,为类似工程的调查与处理提供参考。     

碱矿渣胶凝材料的开裂性能研究

碱矿渣胶凝材料是具有高强、高耐久性的胶凝材料,但其收缩大,易开裂,是阻碍其广泛应用的主要原因.通过圆环法研究了MgO膨胀剂、聚丙烯纤维和减缩剂单掺或复掺对碱矿渣胶凝材料开裂性能的影响.研究结果表明:单掺MgO膨胀剂对碱胶凝体系抗裂不利,减缩剂和聚丙烯纤维的掺入能够有效延缓裂缝的形成,减小开裂面积.     

美国市场汽车准入制度研究

美国的汽车认证制度作为全球车辆产品主要认证制度之一,在汽车产品认证制度中具有典型的代表性,并引领了全球的认证制度发展和进步。本文通过对美国汽车市场准入制度介绍,使中国车企能够了解进入美国市场需要注意和准备的事项。     

物流网络优化中路径问题的研究

在深入分析物流系统化和网络化的基础上,对物流网络优化中物流路径问题进行研究,通过分析物流结构模型和数学模型,提出了最短路径和关键路径物流策略的分析方法,给出了具体的计算方法,并举实例加以说明,为解决现代物流结构中存在的系统设计和运作等问题提供了理论依据和技术方法。     

基于文化粒子群网络优化算法的医学图像研究

文章提出了基于文化粒子群的网络优化算法的医学图像方法，通过在50例唇裂矫正术中运用BP神经网络进行学习．对唇部进行解剖观察和美学分析，在矫正修复手术中不断学习和调整来接近期望输出，并通过实验仿真及客观的图像提出了评估准则。实验结果表明，在美学研究基础上的基于文化粒子群BP神经网络的医学图像研究，适用于唇裂的矫正修复。     

混合不确定条件下绿色多式联运路径优化

主要研究了当运输时间、中转时间、客户需求和中转集拼货运量四重混合不确定因素服从随机分布时的绿色多式联运路径优化问题，运用随机优化理论，以运输成本、碳排放成本和时间惩罚成本为目标，建立混合不确定条件下绿色多式联运路径优化模型.通过对各子目标函数权重进行赋值，得出考虑不同成本因素的多式联运路径优化方案.探讨时间、需求和网络服务能力对多式联运路径优化结果的灵敏度分析，发现各成本随时间变动而变化的规律和边际运输成本最小时的服务时间；当货运量形成规模效应后可降低边际运输成本；不同网络服务规模的运输路径优化结果，以及满足客户不确定需求的最小网络配置.