An integrated analysis of workers’ physically active activity and active travel choice behavior

Using Texas add-on sample data from the 2009 National Household Travel Survey, this study examines adult workers’ daily active choice decisions in the context of physical activity and attendant health benefits. The study looked at workers’ two choice behaviors: active activity and active travel. The first choice behavior, active activity, is developed as an ordered-response model based on the number of physically active recreational activities pursued during the workday. The second choice behavior, active travel, is developed as a binary-response model that examines workers’ active travel choices—whether or not the worker used any active mode of travel during the same workday. The study improves the understanding and knowledge of observed factors influencing workers’ physically active activity-travel behavior. The study also provides several observations regarding the role (and constraints) of employment in individuals’ active choices. Using a flexible copula modeling methodology, we explore the true correlation (or dependence) between the two behavior choices that could occur due to the presence of unobserved factors, suggesting a simultaneously low or simultaneously high propensity for being physically active across workers. The study findings suggest that transportation and public health policy makers can mutually benefit from encouraging workers to be physically active (from an activity and/or travel perspective). Overall, the study draws attention to the integrated nature of the public health and transportation fields, thereby providing a distinct view of active/inactive choice behavior. To our knowledge, this is the first study exploring a rich variety of components for workers’ active activity-travel behavior through a robust copula approach.     

焊缝超声波探伤铁道行业标准与国际标准的对比分析

针对铁路行业应用较多的焊缝超声波探伤的行业标准TB/T 1558.2—2010和国际标准ISO 17640:2013及ISO 11666:2010,从标准组成、探头参数、扫查面准备及母材的检测、灵敏度和时基线的校准、检测等级、质量评定等方面对比2种标准在钢焊缝超声波探伤中检测技术及质量分级方面的差异。通过试验对比说明采用2种标准对同一缺陷进行质量评定时,结果可能完全不同,为现场探伤工作人员工作提供参考。     

基于遗传算法的盾构隧道管片接头刚度反演研究北大核心CSCD

梁-弹簧模型在管片衬砌结构计算中应用较广泛,目前接头刚度取值方法主要有模型试验法及经验取值法,模型试验法耗时长、成本高昂,而依据经验取值难免存在一定主观性。鉴于此,利用C++编程语言,基于遗传算法开发了盾构隧道管片结构位移反分析程序,首先通过弹性模量值反演算例,得出反演值与理论值误差为1.4%,验证了算法和程序的可行性。利用程序将反演接头刚度值与实际设计案例管片接头刚度值进行对比,反演计算结果表明:正弯矩下管片环向接头转动刚度值反演误差为2.6%,负弯矩下管片环向接头转动刚度值反演误差为4.3%。     

列车撞击作用下盾构隧道管片接头错动和张开分析

建立盾构隧道三维数值模型,在管片内侧施加特定速度和角度的列车脱轨撞击荷载,获取与被撞击块相连6颗螺栓所在位置的接头错动及张开量时程曲线。通过对比分析在撞击过程中不同位置接头的错动和张开量变化趋势以及出现的最大张开、错动量,揭示在列车小角度撞击作用下盾构隧道管片接头张开和错动特性。结果表明:在速度200 km/h列车斜向12.5°撞击作用下,各螺栓位置的管片接头均出现不同程度的张开和错动,在撞击过程中各位置接头出现的最大错动量均远远超过实际工程中的限值;相对于管片接头的错动,撞击作用所造成的各位置接头平均张开量相对较小,某些位置接头在整个撞击过程中始终未发生张开。研究所得结论对盾构隧道的结构防撞和防水设计具有一定的参考价值。     

路面基层平整度控制方案

对影响基层平整度的因素进行了简要分析,从拌和、运输、摊铺、碾压等环节提出改进措施,同时对落实平整度控制的保证措施提出合理建议。     

Joint inventory-location problem under the risk of probabilistic facility disruptions

This paper studies a reliable joint inventory-location problem that optimizes facility locations, customer allocations, and inventory management decisions when facilities are subject to disruption risks (e.g., due to natural or man-made hazards). When a facility fails, its customers may be reassigned to other operational facilities in order to avoid the high penalty costs associated with losing service. We propose an integer programming model that minimizes the sum of facility construction costs, expected inventory holding costs and expected customer costs under normal and failure scenarios. We develop a Lagrangian relaxation solution framework for this problem, including a polynomial-time exact algorithm for the relaxed nonlinear subproblems. Numerical experiment results show that this proposed model is capable of providing a near-optimum solution within a short computation time. Managerial insights on the optimal facility deployment, inventory control strategies, and the corresponding cost constitutions are drawn.     

动力作用下盾构隧道接头破坏行为研究

为揭示盾构隧道接头在高速列车动力撞击下的破坏行为,通过建立盾构隧道三维数值模型,对螺栓开裂与否两种工况下的管片接头破坏情况进行分析对比,同时捕捉管片接头与螺栓的动态开裂过程。研究结论:是否引入螺栓开裂对于管片纵向接头的开裂情况有较大影响,引入螺栓开裂后管片纵向接头部位不会出现完全破坏的单元,但其裂缝张开度总体上反而有所增大。撞击荷载下,管片纵向接头率先出现开裂的部位均为弯螺栓处,且环向弯螺栓呈环状断裂破坏,纵向直螺栓纵向剥离破坏。     

共同配送分形管理模式研究

共同配送涉及多个企业及环节,其管理具有复杂性。文章将复杂系统分形建模技术及分形企业的先进理念引入共同配送管理模式的建立中,分析了共同配送企业的自相似性、自组织性、动态、高效的信息交流等特性,给出了共同配送实施分形管理的结构组成和信息交流机制,改变了金字塔型企业繁琐的信息结构、复杂的计划方式和缺乏自主性的局面,为共同配送的实现提供了一种新的管理模式。     

水泥混凝土路面接缝养护技术研究

结合国内目前水泥混凝土路面接缝养护现状，消化吸收国外先进技术，研制开发出新材料、新机具、新工艺相互结合的完整配套技术，应用于水泥混凝土路面接缝的养护，改善水泥混凝土路面接缝养护施工人工作业的落后状况，使接缝养护施工步入小型机具作业的新水平。     

钛管焊接时接头的保护

钛管焊接过程中的污染将严重地影响接头的焊接质量，降低其机械性能。分析了钛管焊接过程中接头污染的主要形式，并有针对性地提出了防止这些污染的工艺措施。实践证明：通过采取控制焊接环境，加强焊前清理及焊接过程保护等措施，可有效地防止钛管焊接接头的污染。