新冠肺炎疫情对铁路货运的影响及对策探讨

2020年初的新冠肺炎疫情对供应链上下游企业影响的波及,导致全社会货运量均受到不同程度的影响.在分析疫情对铁路货运量的影响基础上,针对货运总体需求下降、运输组织效率有待提高、营销激励机制有待加强等问题,通过畅通信息渠道、快速应对市场需求变化、建立"互利共赢"合作机制促进企业复工复产,通过加强运输组织、优化货运产品结构提...     

Robust Wardrop’s user equilibrium assignment under stochastic demand and supply: Expected residual minimization approach

Various models of traffic assignment under stochastic environment have been proposed recently, mainly by assuming different travelers’ behavior against uncertainties. This paper focuses on the expected residual minimization (ERM) model to provide a robust traffic assignment with an emphasis on the planner’s perspective. The model is further extended to obtain a stochastic prediction of the traffic volumes by the technique of path choice approach. We show theoretically the existence and the robustness of the ERM solution. In addition, we employ an improved solution algorithm for solving the ERM model. Numerical experiments are carried out to illustrate the characteristics of the proposed model, by comparing with other existing models.     

The use of the bicycle

The rediscovery of the bicycle by the public, by politicians and by professional urban transportation planners as a mode of transport which is perfectly in harmony with the goals of environmental protection, energy saving and personal fitness has stimulated this empirical study on the actual use of the bicycle by various population groups for obligatory and discretionary trip purposes. The influence on bicycle usage of such factors as age, education, car availability, residential density and town size, topography and time of year is analysed in this paper for selected population groups. For housewives from motorized households logit‐models were designed and calibrated to model their modal choice for shopping trips with special references to the bicycle. From the empirical results, the groups with the largest potentials for cycling are identified and the extent to which the potentials could be activated by specific policies is discussed. The research is based on a large sample held to be representative for the Federal Republic of Germany in 1976 and is supplemented by more recent surveys in selected German cities conducted by SOCIALDATA Munich.     

Robust optimization for emergency logistics planning: Risk mitigation in humanitarian relief supply chains

This paper proposes a methodology to generate a robust logistics plan that can mitigate demand uncertainty in humanitarian relief supply chains. More specifically, we apply robust optimization (RO) for dynamically assigning emergency response and evacuation traffic flow problems with time dependent demand uncertainty. This paper studies a Cell Transmission Model (CTM) based system optimum dynamic traffic assignment model. We adopt a min–max criterion and apply an extension of the RO method adjusted to dynamic optimization problems, an affinely adjustable robust counterpart (AARC) approach. Simulation experiments show that the AARC solution provides excellent results when compared to deterministic solution and sampling based stochastic programming solution. General insights of RO and transportation that may have wider applicability in humanitarian relief supply chains are provided.     

指数平滑法在路面使用性能预测中的应用

文章分析了路面使用性能的发展规律及其特点,指出了传统预测方法的不足,介绍采用指数平滑法来提高预测精度,可解决我国路面使用性能预测模型,预测精度不高的问题。     

回归分析方法在VTS预测研究中的应用

该文将数理统计中的回归分析方法应用到ＶＴＳ预测研究中，其预测结果有较高的精度，是基础理论应用于工程实际的有益实践，为ＶＴＳ规划研究提供了一种实用的预测方法。     

Forecast verification of a 3D model of the Mediterranean Sea. The use of discrete wavelet transforms and EOFs in the skill assessment of spatial forecasts

The quality assessment of a nested model system of the Mediterranean Sea is realised. The model has two zooms in the Provençal Basin and in the Ligurian Sea, realised with a two-way nesting approach. The experiment lasts for nine weeks, and at each week sea surface temperature (SST) and sea level anomaly are assimilated. The quality assessment of the surface temperature is done in a spatio-temporal approach, to take into account the high complexity of the SST distribution. We focus on the multi-scale nature of oceanic processes using two powerful tools for spatio-temporal analysis, wavelets and Empirical Orthogonal Functions (EOFs). We apply two-dimensional wavelets to decompose the high-resolution model and observed SST into different spatial scales. The Ligurian Sea model results are compared to observations at each of those spatial scales, with special attention on how the assimilation affects the model behaviour. We also use EOFs to assess the similarities between the Mediterranean Sea model and the observed SST. The results show that the assimilation mainly affects the model large-scale features, whereas the small scales show little or no improvement and sometimes, even a decrease in their skill. The multiresolution analysis reveals the connection between large- and small-scale errors, and how the choice of the maximum correlation length of the assimilation scheme affects the distribution of the model error among the different spatial scales.     

考虑外包因素的供应链生产柔性决策研究

研究需求不确定条件下考虑外包因素时供应链的生产柔性决策问题,建立模型,设计求解过程,通过算例来说明制造商生产量均值、OEM生产量与生产能力的关系。进而提出建议:为应对需求的不确定性,制造商应合理确定自身的生产柔性水平,保持一定的生产能力富余。     

基于ARIMAX模型的交通事故宏观预测

针对现有道路交通事故预测方法的不足,采用逐步回归法从众多宏观影响因素当中筛选出主要影响因素,并将动态回归ARIMAX模型应用于预测。前者保证了模型应用的准确性,后者则兼有回归与时间序列预测方法两方面的优点。根据1983年—2005年间相关数据,建立起道路交通死亡人数同人口总数、运输线质量里程数、客运量、驾驶员人数、人均GDP、公路运输汽车拥有量的相关关系,进一步应用ARIMAX模型进行预测,拟合结果显示,误差较小、预测情况良好,在交通事故宏观预测方面有很好的应用前景。     

跨国公司—当今国际海运市场需求的主要来源

当今以国际贸易来调剂或弥补国与国间各自资源稀缺状况的手段已不能完全适应世界经济发展的需要，对外直接投资及其组织形态——跨国公司能使资源在全世界范围内得到有效配置。跨国公司生产和经营特性决定了其对国际运输，特别对国际海运的作用，也决定了国际贸易的构成。本文在此认识上，分析了国际海运与国际贸易、跨国公司之间的关系；论述了跨国公司对国际海运需求的主要来源，归纳了由此需求而产生的对国际海运发展模式和趋势的影响。