热推弯头加工工艺参数的确定

中频加热推制无缝弯头是目前中、低压弯头制作中普通采用的加工工艺，其工艺参数直接影响产品的质量，成本，效益等。本文对芯棒后接管径，推制用管规格，管坯长度等工艺参数结合生产实际进行了较为详细的论述。     

浅谈无缝急弯弯的热推制

介绍了无缝急弯弯头的热推制原理及工艺过程。还重点叙述了牛角芯棒的设计及推制中选用的中频感应加热方法及加热温度的选择。     

热推弯头的可靠性与管坯直径的关系

讨论了管坯直径对热推弯头壁厚的影响，根据对弯头受内压时应力分布状况和试验结果的分析，提出了选择热推弯头管坯直径的原则。     

热推Φ558.8弯头芯棒设计与工艺分析

介绍了热推制弯头成形机理，芯棒设计，影响弯头成形因素。给出了采用感应加热方法时，成形弯头各部位度分布。     

单缝推制弯头工艺试验

哈夫弯头在内弧和外弧存在两条焊缝,为了减少内弧的一条焊缝,优化弯头的结构设计,采用两种不同焊材的卷管进行了热推制工艺试验,得到了单缝弯头推制工艺关键参数:焊缝置于弯头外弧偏侧弧约10°的位置能够满足推制工艺的要求,不会产生焊缝缺陷。对推制弯头进行取样分析,分析结果表明:R307和R407两种不同焊材的焊缝,推制后其性能均满足相关标准的要求,但R307焊材的抗拉强度余量较小。     

波纹管管坯高效加工技术

对多模变薄拉深过程进行了详细分析。指出多模变薄拉深工艺可以充分发挥材料的塑性变形能力 ,使原来需要经过几次单模变薄拉深才能制成的管坯一次即可完成。在对多模变薄拉深变形过程进行分析的基础上 ,将多模变薄拉深工艺技术应用于波纹管管坯大批量生产中。     

Intermec强力推新品

"世界上第一台带彩色照相机的工业级功能、世界上第一台同时具备四个无线收发模块的(广域网、局域网、内置全球定位、蓝牙)、世界上第一台支持第三代移动通信系统高速数据传输……"全球供应链解决方案公司美国易腾迈公司(Intermec)10月24日在中国宣布其C N 3移动计算机新品具有的三个世界第一,引起了诸多关注.这是Intermec本次发布的两款新品中的一款,另一新品名为CV30.     

钢箱梁顶推施工过程分析

文章结合某特大桥工程实例,对顶推施工中导梁结构形式选择及截面尺寸的确定作了简单介绍,采用有限元方法对结构进行了数值分析,分别对施工过程中导梁在自重荷载作用下的稳定性、各墩支反力、钢箱梁抗倾覆稳定性、钢箱梁应力等进行计算。结果表明:顶推过程中,导梁稳定性满足要求;钢箱梁在上墩前弯曲应力最大,相应剪应力值则相对较小;墩顶支点反力、抗倾覆稳定性均符合设计规范要求。     

山区高速公路大跨度钢箱梁顶推技术应用分析

文章以山东省临临高速公路悦庄枢纽互通立交钢箱梁桥的顶推施工建设为背景,从钢箱梁顶推方案制作与评审、厂内加工与制作、顶推施工三方面探讨了钢箱梁顶推施工的难点,重点分析了顶推支架受力与支撑体系,并建立有限元分析模型,从理论和实际监测数据结果可知,该专项保护措施满足了支架的变形控制要求。     

公路沥青面层碎石加工标准化工艺初探

公路沥青路面的建设质量与水平一定程度上受限于面层碎石的质量,而沥青面层石料的品质受料源分布、加工工艺以及料场管理水平的综合影响。依托于青海省西部四条高速公路建设工程,从碎石的加工特性出发提出了破碎机类型组合方案以及不同规格碎石的加工筛网尺寸,同时针对碎石加工场建设与管理提出了优化建议,对青海省公路沥青面层碎石加工标准化工艺进行了初步探讨。     

Modal shift from road haulage to short sea shipping: a systematic literature review and research directions

ABSTRACT

Modal shift from road haulage to short sea shipping (SSS) has been advocated by authorities and researchers for more than two decades. This paper provides a review of literature on modal shift and pinpoints paths for future research on topics in six categories: (1) factors influencing SSS competitiveness, (2) the policy-oriented perspective, (3) environmental legislation, (4) SSS performance, (5) port characteristics, and (6) the multi-agent perspective. In particular, we propose first, in evaluating the performance of SSS versus road haulage in different trade corridors, three performance-related dimensions – the economic dimension (e.g. external costs), the environmental dimension, and the dimension of service quality – should be considered. Second, researchers should use rich, real-world, numerical data and operational research techniques to identify the relative importance of individual drivers and barriers for a modal shift from road haulage to SSS. Third proposed direction is related to assessing which groups of actors certain policies should target. In doing so, researchers should extend their policy-related focus beyond the European Union, which has long encompassed the major geopolitical scope of research on the modal shift. Fourth, to moderate the adverse impact of environmental legislation on SSS, strategic solutions need to be identified. Fifth, we also suggest that the influence of contingencies, particularly port strikes and cyberattacks, on SSS operations and approaches for managing them should be investigated. Sixth, the economic and financial advantages of coordination and alliance for each transport chain agent need to be evaluated.     

The social dimension in action: A multilevel,personal networks model of social activity frequency between individuals

This paper presents a social activity-travel generation model, which explicitly incorporates the individual’s social dimension through the concept of personal networks, modeling the multilevel structure of social relations defined by these networks. The objective of the analysis is to study the relevance of the social dimension as a source of explanation of social activity-travel generation behavior between an individual and each relevant person of their social life. The paper uses a disaggregated perspective of personal networks, explicitly incorporating the characteristics of each network member as well as the characteristics of the overall social structure. Using an ordinal multilevel specification that accounts for the social network in which individuals are embedded, four dimensions are studied: personal characteristics, “with whom” activities are performed, social network composition and structure, and ICT (information and communication technology) interaction. The results show that a proper and complete understanding of social activity generation requires going beyond the individualistic paradigm, explicitly incorporating the role of the social dimension in the study of this decision-making process.     

On modeling telecommuting behavior: option, choice, and frequency

The current study contributes to the already substantial scholarly literature on telecommuting by estimating a joint model of three dimensions—option, choice and frequency of telecommuting. In doing so, we focus on workers who are not self-employed workers and who have a primary work place that is outside their homes. The unique methodological features of this study include the use of a general and flexible generalized hurdle count model to analyze the precise count of telecommuting days per month, and the formulation and estimation of a model system that embeds the count model within a larger multivariate choice framework. The unique substantive aspects of this study include the consideration of the “option to telecommute” dimension and the consideration of a host of residential neighborhood built environment variables. The 2009 NHTS data is used for the analysis, and allows us to develop a current perspective of the process driving telecommuting decisions. This data set is supplemented with a built environment data base to capture the effects of demographic, work-related, and built environment measures on the telecommuting-related dimensions. In addition to providing important insights for policy analysis, the results in this paper indicate that ignoring the “option” dimension of telecommuting can, and generally will, lead to incorrect conclusions regarding the behavioral processes governing telecommuting decisions. The empirical results have implications for transportation planning analysis as well as for the worker recruitment/retention and productivity literature.     

Interactive geovisualization of activity-travel patterns using three-dimensional geographical information systems: a methodological exploration with a large data set

A major difficulty in the analysis of disaggregate activity-travel behavior in the past arises from the many interacting dimensions involved (e.g. location, timing, duration and sequencing of trips and activities). Often, the researcher is forced to decompose activity-travel patterns into their component dimensions and focus only on one or two dimensions at a time, or to treat them as a multidimensional whole using multivariate methods to derive generalized activity-travel patterns. This paper describes several GIS-based three-dimensional (3D) geovisualization methods for dealing with the spatial and temporal dimensions of human activity-travel patterns at the same time while avoiding the interpretative complexity of multivariate pattern generalization or recognition methods. These methods are operationalized using interactive 3D GIS techniques and a travel diary data set collected in the Portland (Oregon) metropolitan region. The study demonstrates several advantages in using these methods. First, significance of the temporal dimension and its interaction with the spatial dimension in structuring the daily space-time trajectories of individuals can be clearly revealed. Second, they are effective tools for the exploratory analysis of activity diary data that can lead to more focused analysis in later stages of a study. They can also help the formulation of more realistic computational or behavioral travel models.     

Why do you care what other people think? A qualitative investigation of social influence and telecommuting

The effect of social interactions on decision-making is a topic of current interest in the travel behavior literature. These interactions have been investigated primarily from an intra-household perspective, but increasingly too in other types of social settings. In the case of interactions within a workplace, it has been suggested that the decision to telecommute may have some important social components. Previous research has concentrated on social isolation, and the effect on job satisfaction of qualitatively different (i.e., telecommunications-mediated) relationships with managers and colleagues. A topic that remains unexplored is the way social norms, in effect the influence of other people’s behavior, may influence the decision to adopt telecommuting. In this paper we set to investigate, within a qualitative framework, the role of social contact in the process of acquiring information on, and making decisions about, telecommuting. The results indicate that social contact does play a subtle but non-trivial role in the adoption and continuation process, and offer some insights about the importance of the social dimension, institutional set-up, and how they interact to influence the decision to telecommute.     

Measuring the impact of efficient household travel decisions on potential travel time savings and accessibility gains

Using the conceptual framework of time–space geography, this paper incorporates both spatio-temporal constraints and household interaction effects into a meaningful measure of the potential of a household to interact with the built environment. Within this context, personal accessibility is described as a measure of the potential ability of individuals within a household not only to reach activity opportunities, but to do so with sufficient time available for participation in those activities, subject to the spatio-temporal constraints imposed by their daily obligations and transportation supply environment. The incorporation of activity-based concepts in the measurement of accessibility as a product of travel time savings not only explicitly acknowledges a temporal dimension in assessing the potential for spatial interaction but also expands the applicability of accessibility consideration to such real-world policy options as the promotion of ride-sharing and trip chaining behaviors. An empirical application of the model system provides an indication of the potential of activity-based modeling approaches to assess the bounds on achievable improvements in accessibility and travel time based on daily household activity patterns. It also provides an assessment of roles for trip chaining and ride-sharing as potentially effective methods to facilitate transportation policy objectives.     

A conceptual and methodological framework of leisure activity loyalty accommodating the travel context

As leisure travel continues to grow, it has become a critical subject for planners and decision-makers since it significantly impacts regional economic and social development as well as contributes to emission levels and congestion. Despite being a significant percentage of our travel, however, leisure travel behavior is still not very well understood. The goal of this article is to contribute to our understanding of leisure activity participation by considering leisure activity loyalty within the travel context. In particular, this study focuses on one specific dimension of travel context: travel extent (i.e., whether an individual participates in a leisure activity on a daily versus a long-distance basis). As such, this article first introduces a unified conceptual framework for measuring leisure activity loyalties within a travel context, based on two distinct dynamics of leisure loyalty behavior—destination attachment and activity involvement. Additionally, this article uses a unique 2001 NHTS dataset comprised of households’ daily and long-distance leisure activities to undertake a unique empirical analysis of five distinct leisure activities using the conceptual framework and a copula-based model methodology. The findings confirmed that households demonstrate significant loyalties to travel contexts across all leisure activities, especially resting and sightseeing.     

Resilience and accessibility of Swedish and Dutch municipalities

Recent years have shown a rising popularity of the concept of resilience—both theoretically and empirically—in complex systems analysis. There is also a rising literature on resilience in the transport and spatial-economic field. The pluriform interpretation of resilience (e.g., engineering vs. ecological resilience) is related to methodological differences (e.g., stability in dynamics vs. evolutionary adaptivity). But in all cases the fundamental question is whether a complex system that is subjected to an external shock is able to recover, and if so, to which extent. The present paper [Based on presentation from cluster 6 (Accessibility) of the Nectar 2015 conference in Ann Arbour, USA.] aims to add a new dimension to resilience analysis in spatial systems, by addressing in particular the relationship between spatial accessibility at a municipality level and the resilience outcomes of the spatial system concerned. It does so by investigating to which extent accessibility of Swedish and Dutch municipalities has mitigated the local shock absorption from the recent economic recession. In our study the shock absorption capacity of municipal accessibility is estimated by analysing the relevant resilience indicators for the period concerned. In this context, conventional resilience indicators based on either multivariate complex data (in particular, the Foster Resilience Capacity Index) or employment data (in particular, the Martin Resilience-Employment Index) are confronted with spatial connectivity data based on local accessibility measures, so that geographical mobility may be regarded as one of the shock-mitigating factors. The empirical analysis is carried out for two countries which have both proven to be rather shock-resistant during the recent economic crisis, viz. Sweden and The Netherlands. Clearly, the geographical structure of these countries forms a sharp mutual contrast, viz. a spatially dispersed economy with a few distinct urban concentrations versus a spatially dense economy with one major metropolitan centre (the Randstad), respectively. Our experiments are carried out for the 290 municipalities in Sweden and 40 COROPs in The Netherlands. Our research findings show relevant and new insights into differences in the local recovery potential in Sweden and The Netherlands.     

基于投影寻踪模型的公路目标持续性综合评价

投影寻踪法具有变高维数据为低维数据,适用于处理非线性、离散数据的特点。文章针对公路目标持续性综合评价中指标的多样性、模糊性特点,提出了基于投影寻踪模型的公路目标持续性综合评价方法,并通过实例分析,证明了该方法使评价过程更客观、准确、简洁,具有一定的理论意义和应用价值。     

基于分形理论的级配评价与抗车辙性能研究

文章基于分形理论,对常用的沥青混合料AC-20、AC-16、AC-13的微观结构进行了分析,建立了质量分形维数与级配走向的相关关系,探讨了粗细集料比例变化下不同级配分形维数对沥青混合料抗车辙性能的影响。