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941.
为研究碾压温度对沥青混合料压实特性的影响,采用数值方法建立了松铺和密实2种状态下沥青混合料碾压温度场的分析模型.研究了不同环境因素、摊铺层厚度以及初始温度下沥青混合料碾压温度随时间的变化规律.计算了沥青混合料的最短有效压实时间和最长有效压实时间,建立了有效压实时间的多元回归模型,并通过实体工程进行了验证.结果表明:温度随着时间的增加而不断降低,降温速率随着风速的降低,大气温度、太阳辐射热量或摊铺层厚度的增加而降低,而松铺沥青混合料的降温速度快于密实沥青混合料,其有效压实时间更短.经验证,有效压实时间计算模型合理可靠,可为今后工程实践提供参考依据. 相似文献
942.
Travel time variability (i.e., random variations in travel time) leads to a travel time distribution for a repeated trip from a fixed origin to destination (e.g., from home to work). To represent travel time variability, a series of possible travel times per alternative (departure time, route or mode) are often used in stated choice experiments. In the traditional models, the probabilities associated with different travel scenarios (e.g., arriving early, on time and late) shown in the experiments are directly used as weights. However, evidence from psychology suggests that the shown probabilities may be transformed (underweighted or overweighted) by respondents. To account for this transformation of probabilities, this study incorporates perceptual conditioning through a non-linear probability weighting function into a utility maximisation framework, within which the empirical estimate of the value of expected travel time savings is estimated. The key advantage of this framework is that the estimated willingness to pay value can be directly linked to the source of utility (i.e., the probability distribution of travel time), while taking into account the perceptual transformation of probabilities. 相似文献
943.
944.
与其他优化问题相比,多式联运网络路径优化问题面临着变量较多且其结构、关系复杂的困扰.然而,现有的多式联运网络只能对网络属性逐一计算,难免重复冗余,效率偏低,只适用于小型网络.提出了不规则棱柱网络模型.采用相对编码设计,通过搜索判断余子式进行网络初始化,将网络中不同类别的弧线解释成满足某种约束条件的量,通过设计底边判断函数和侧棱判断函数,实现了网络中弧线的智能分类.该模型取消了运输网络阶段划分的限制;其节点与现实运输的地理坐标相对应;分类判断可以对网络进行群体修建与更新.通过对比各网络的时间频度,说明在多属性变量复杂且多样性的大规模多式联运网络中,该网络能够极大地提升网络构建和更新效率. 相似文献
945.
946.
耙吸式挖泥船溢流施工作为疏浚施工重要的方法之一,其施工效率的提高与装舱时间有关.确定最佳装舱时间及生产模式,需要对施工区土质、装舱时间、装舱效率、施工区域漂流出的土方量等要素进行分析计算,并加以工程实践验证.依据确定的最佳装舱时间组织生产施工,可以提高施工效率和经济效益. 相似文献
947.
在海域深厚层淤泥(>28 m)条件下,对定向滑移爆炸挤淤悬浮式防波堤施工技术,从堤头抛石加载、爆炸挤淤爆破参数选择、循环进尺控制、两侧爆夯等方面进行阐述.在施工过程中采用“体积平衡法,沉降观测,钻孔勘探”等检测手段进行监控,保证爆炸挤淤悬浮式防波堤地基质量,工期短、费用低、沉降小,值得在类似工程中推广应用. 相似文献
948.
949.
Xiaoning Zhang 《运输规划与技术》2013,36(3):267-286
This paper explores the effects of queue spillover in transportation networks, in the context of dynamic traffic assignment. A model of spatial queue is defined to characterize dynamic traffic flow and queuing formation in network links. Network users simultaneously choose departure time and travel route to minimize the travel cost including journey time and unpunctuality penalty. Using some necessary conditions of the dynamic user equilibrium, dynamic network flows are obtained exactly on some networks with typical structure. Various effects of queue spillover are discussed based on the results of these networks, and some new paradoxes of link capacity expansion have been found as a result of such effects. Analytical and exact results in these typical networks show that ignoring queuing length may generate biased solutions, and the link storage capacity is a very important factor concerning the performance of networks. 相似文献
950.
Jin-Su Mun 《运输规划与技术》2013,36(3):261-288
Abstract This paper investigates some features of non-linear travel time models for dynamic traffic assignment (DTA) that adopt traffic on the link as the sole determinant for the calculation of travel time and have explicit relationships between travel time and traffic on the link. Analytical proofs and numerical examples are provided to show first-in-first-out (FIFO) violation and the behaviour of decreasing outflow with increasing traffic in non-linear travel time models. It is analytically shown that any non-linear travel time model could violate FIFO in some circumstances, especially when inflow drops sharply, and some convex non-linear travel time models could show behaviour with outflow decreasing as traffic increases. It is also shown that the linear travel time model does not show these behaviours. A non-linear travel time model in general form was used for analytical proofs and several existing non-linear travel time models were adopted for numerical examples. Considering the features addressed in this study, non-linear travel time models seem to have limitations for use in DTA in practical terms and care should be taken when they are used for modelling time-varying transportation networks. 相似文献