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81.
The timing and duration of an activity episode are two important temporal aspects of activity-travel behavior. Understanding the causal relationship between these two variables would be useful in the development of activity-based travel demand modeling systems. This paper investigates the relationship between these two variables by considering two different causal structures – one structure in which time-of-day choice is determined first and influences duration and a second structure in which activity duration is determined first and affects time-of-day choice. These two structures are estimated within a discrete-continuous simultaneous equations framework employing a full-information maximum likelihood methodology that allows error covariance. The estimation is performed separately for commuter and non-commuter samples drawn from a 1996 household travel survey data set from the Tampa Bay area in Florida. The results of the model estimation effort show that the causal structure in which activity duration precedes or affects activity timing (time of day choice) performs better for the non-commuter sample. For the commuter sample, the findings were less conclusive with both causal structures offering equally good statistical measures of fit. In addition, for the commuter sample, all error correlations were found to be zero. These two findings suggest that time of day choice and activity episode duration are only loosely related for the commuter sample, possibly due to the relatively non-discretionary and inflexible work activity and travel. 相似文献
82.
列车运行图可调整度评价系统研究 总被引:1,自引:0,他引:1
彭其渊 《西南交通大学学报》1998,33(4):367-371
在详细分析了列车运行图缓冲时间的大小及其分布规律对列车晚点传播影响的基础上,通过建立列车运行图调整系统,对给定晚点程度的列车进行模拟调整,从而计算出列车晚点恢复率,晚点传播区大小,连带晚点时间和关键列车运行线等。指标来达到对列车运行图可高速程度优劣评判的目的。 相似文献
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大跨度钢管混凝土拱桥地震反应分析 总被引:6,自引:5,他引:6
利用有限元法分析大跨度钢管混凝土拱桥的地震反应,考虑了剪切变形的影响,用子空间迭代法分析了其振动规律和动力特性,应用反应谱法和时程分析法分析了该拱桥的地震反应,得出了一些有价值的结论。 相似文献
85.
公共交通系统营运可靠性研究 总被引:5,自引:2,他引:5
优先发展公共交通是大城市解决交通拥堵,实现城市交通可持续发展的一项重要措施,然而,公交营运水平的低下制约着公交的发展。本文借鉴可靠性理论对公共交通营运可靠性进行定义,并对公交营运时间和乘客服务可靠性分别进行了描述,据此建立起公交系统营运可靠性模型,然后采用随机模拟技术(即Monte Carlo模拟)进行求解,通过算例说明模型的可行性,最后通过分析可靠性模型得出大型活动期间改善公交营运的途径。 相似文献
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超深振捣对混凝土成品质量有害无益,研究超深振捣引起模板侧压力增大的规律,可为规避其害提供依据。为此设计4个混凝土墙体试件,实测在浇筑过程中模板侧压力的变化情况。基于振捣液化和液体压力平衡理论,建立了超深振捣情况下混凝土模板侧压力计算模型,推导了计算公式,并与实验数据进行对比验证。研究结果表明,振捣深度是影响混凝土墙体模板侧压力的重要因素,本文提出的计算模型能很好地预测墙体结构超深振捣位置的模板侧压力。 相似文献
90.
Multi-state supernetworks have been advanced recently for modeling individual activity-travel scheduling decisions. The main advantage is that multi-dimensional choice facets are modeled simultaneously within an integral framework, supporting systematic assessments of a large spectrum of policies and emerging modalities. However, duration choice of activities and home-stay has not been incorporated in this formalism yet. This study models duration choice in the state-of-the-art multi-state supernetworks. An activity link with flexible duration is transformed into a time-expanded bipartite network; a home location is transformed into multiple time-expanded locations. Along with these extensions, multi-state supernetworks can also be coherently expanded in space–time. The derived properties are that any path through a space–time supernetwork still represents a consistent activity-travel pattern, duration choice are explicitly associated with activity timing, duration and chain, and home-based tours are generated endogenously. A forward recursive formulation is proposed to find the optimal patterns with the optimal worst-case run-time complexity. Consequently, the trade-off between travel and time allocation to activities and home-stay can be systematically captured. 相似文献