沥青路面辙槽破坏分析及车辙试验改进

从沥青混凝土的物理力学性能以及面层厚度和结构类型等方面阐述了沥青路面辙槽破坏的影响因素及减小辙槽破坏的措施,并对我国车辙试验仪器和试验方法存在的不足提出了几点改进意见。     

熵对状态参量的偏弹性研究

给出熵对状态参量偏弹性的定义,研究熵对状态参量偏弹性的物理意义,并举例讨论.     

需求弹性理论在铁路运价调整中的应用

在市场经济条件下,合理调节和运用价格因素,是运输企业提升竞争优势,把握市场竞争力的关键,常用的定价方法主要以运输价值为理论依据,该理论较少考虑市场机制作用下运输需求变动对运价的影响,难以适应短期价格决策.根据经济学弹性理论,提出了运输价格调整过程中的调价方向、调价幅度的确定方法,并给出了具体算例.     

徐变引起的不同龄期混凝土组合截面的应力重分布

不同龄期混凝土组合而成的组合构件截面由于各组合部分徐变系数不同会引起截面应力重分布,从而导致截面内的附加应力.本文引入假想弹性模量的概念,提出了计算徐变引起的应力重分布的附加应力的方法,并通过算例说明考虑这一附加应力的重要性.     

Overview of missing physical commodity trade data and its imputation using data augmentation

The physical aspects of commodity trade are becoming increasingly important on a global scale for transportation planning, demand management for transportation facilities and services, energy use, and environmental concerns. Such aspects (for example, weight and volume) of commodities are vital for logistics industry to allow for medium-to-long term planning at the strategic level and identify commodity flow trends. However, incomplete physical commodity trade databases impede proper analysis of trade flow between various countries. The missing physical values could be due to many reasons such as, (1) non-compliance of reporter countries with the prescribed regulations by World Customs Organization (WCO) (2) confidentiality issues, (3) delays in processing of data, or (4) erroneous reporting. The traditional missing data imputation methods, such as the substitution by mean, substitution by linear interpolation/extrapolation using adjacent points, the substitution by regression, and the substitution by stochastic regression, have been proposed in the context of estimating physical aspects of commodity trade data. However, a major demerit of these single imputation methods is their failure to incorporate uncertainty associated with missing data. The use of computationally complex stochastic methods to improve the accuracy of imputed data has recently become possible with the advancement of computer technology. Therefore, this study proposes a sophisticated data augmentation algorithm in order to impute missing physical commodity trade data. The key advantage of the proposed approach lies in the fact that instead of using a point estimate as the imputed value, it simulates a distribution of missing data through multiple imputations to reflect uncertainty and to maintain variability in the data. This approach also provides the flexibility to include fundamental distributional property of the variables, such as physical quantity, monetary value, price elasticity of demand, price variation, and product differentiation, and their correlations to generate reasonable average estimates of statistical inferences. An overview and limitations of most commonly used data imputation approaches is presented, followed by the theoretical basis and imputation procedure of the proposed approach. Lastly, a case study is presented to demonstrate the merits of the proposed approach in comparison to traditional imputation methods.     

Complementarity formulations for the cell transmission model based dynamic user equilibrium with departure time choice, elastic demand and user heterogeneity

In this paper we formulate the dynamic user equilibrium problem with an embedded cell transmission model on a network with a single OD pair, multiple parallel paths, multiple user classes with elastic demand. The formulation is based on ideas from complementarity theory. The travel time is estimated based on two methods which have different transportation applications: (1) maximum travel time and (2) average travel time. These travel time functions result in linear and non-linear complementarity formulations respectively. Solution existence and the properties of the formulations are rigorously analyzed. Extensive computational experiments are conducted to demonstrate the benefits of the proposed formulations on various test networks.     

实桥预应力孔道压浆调查和钢丝性能分析

在某后张法预应力混凝土桥梁拆除过程中,调查了该桥的预应力孔道压浆情况。对该桥预应力钢丝试样进行一系列试验,得到了钢丝的腐蚀情况,以及弹性模量和极限强度等重要力学指标。分析这些经过约10年使用年限的钢丝的力学性能变化情况,为研究和评估类似预应力混凝土结构的耐久性和承载能力提供了参考。     

基于非集计模型的公交票价弹性研究

利用城市居民出行意愿调查数据,结合济南公交发展历史数据,通过构建非集计模型,分析得到济南公交票价弹性值.结果显示,济南公交票价弹性值为-0.234,略低于国内外相关研究结论.公交出行时间对公交出行需求的弹性要高于公交票价的弹性,通过缩短公交出行时间,提高公交服务水平来增加公交出行吸引力将更有效.     

利润弹性在工程项目评估中的应用分析

影响建筑企业工程项目利润值的主要变量有工程成本、追加价格、创优增量成本。工程成本包括直接费、其他直接费、现场经费、间接费和非生产费用支出;追加价格包括设计变更、施工索赔以及区域内滚动发展的其他项目投资;创优增量成本包括质量、安全、工期、环保、文明施工等增量成本。分别给出成本利润弹性、追加价格利润弹性、创优增量成本利润弹性的理论计算公式。分析提高利润弹性的途径。在工程项目中,目标利润分为正常利润和经济利润,分析工程成本利润弹性、追加价格利润弹性、创优增量成本利润弹性对经济利润的影响。认为事前速度、事中激励、事后评价是提高利润弹性的有效方法。     

盾尾密封刷实验平台的设计与研究

为判断盾尾刷的质量,从盾尾刷的耐磨性和弹性2个关键性能参数入手,运用液压原理、PLC及运算放大控制原理,通过对动力参数和控制系统的详细研究,设计出一台套用于检测盾尾刷耐磨性和弹性的实验平台,用于优选盾尾刷,提高施工安全性。