Do frequent satisfying trips by public transport impact its intended use in later life?

Transportation - Previous studies have indicated that factors such as the built environment, attitudes and past behaviour can influence travel behaviour. However, the possible effect of travel...     

船体纵骨典型节点疲劳裂纹扩展寿命评估

基于有限元软件ABAQUS,结合虚拟裂纹闭合法、裂纹扩展判据及子结构技术,应用脚本语言Python开发出模拟疲劳裂纹扩展的程序(FCG-System)。对含初始裂纹的油船纵骨典型节点在侧面压力作用下进行疲劳裂纹扩展数值模拟,并探讨了软趾、背肘板及防倾肘板对疲劳裂纹扩展路径和寿命的影响。结果表明,增设软趾、背肘板或防倾肘板都会使裂纹扩展路径曲率增大,且软趾、防倾肘板可使裂纹扩展寿命增大,背肘板可使裂纹扩展寿命减小。     

Learning to navigate: the centrality of instructions and assessments for developing students’ professional competencies in simulator-based training

Despite the promises of simulations to contribute to learning in safe-critical domains, research suggests that simulators are poorly implemented in maritime education and training systems. From the current state of research, it is far from evident how instruction in simulator-based should be designed and how skills trained in bridge simulators should be assessed and connected to professional practice. On this background, this article aims to investigate the role of instructions and assessments for developing students’ professional competencies in simulation-based learning environments. The research draws on ethnographic fieldwork and detailed analyses of video-recorded data to examine how maritime instructors make use of simulator technologies in a navigation course. Our results reveal an instructional practice in which the need to account for general principles of good seamanship and anti-collision regulations is at the core of basic navigation training. The meanings of good seamanship and the rules of the sea are hard to teach in abstraction because their application relies on an infinite number of contingencies that have to be accounted for in every specific case. Based on this premise, we stress the importance of instructional support throughout training (from briefing thorough scenario to debriefing) in order for the instructor to bridge theory and practice in ways that develop students’ competencies. Our results highlight, in detail, how simulator technologies enable displaying and assessing such competencies by supporting instructors to continuously monitor, assess, and provide feedback to the students during training sessions. Moreover, our results show how simulator-based training is related to the work conditions on board a seagoing vessel through the instructor’s systematic accomplishments. Finally, our results highlight the close relationship between technical and non-technical skills in navigation, and how these are intertwined in training for everyday maritime operations.     

Predicting auto-ignition characteristics of RCCI combustion using a multi-zone model

The objective of new combustion concepts is to meet emission standards by improving fuel air mixing prior to ignition. Since there is no overlap between injection and ignition, combustion is governed mainly by chemical kinetics and it is challenging to control the phasing of ignition. Reactivity Controlled Compression Ignition (RCCI) combustion aims to control combustion phasing by altering the fuel ratios of the high- and low octane fuel and injection timings. In this study the dual fuel blend is prepared with gasoline and diesel fuels. The applied injection timings of the diesel are very early (90 to 60° CA bTDC). In the detailed reaction mechanism, n-heptane and iso-octane represent diesel and gasoline fuel, respectively. A multi-zone model approach is implemented to perform RCCI combustion simulation. Ignition characteristics are analyzed by using CA50 as the main parameter. In the experiments for the early direct injection (DI) timing advancing the injection time results in a later ignition. Qualitatively, the trend effect of the diesel injection timing and the effect of the ratio gasoline/diesel are captured accurately by the multi-zone model.     

极限工况下湿式制动器摩擦特性模拟仿真研究

文中在充分考虑全封闭湿式制动器多构层、有间隙结构特点的基础上,建立了全封闭湿式多盘制动器摩擦元件的有限元分析模型。分别从制动强度和制动时间两方面定义极限工况,进而来研究湿式制动器热源、温度场、应力场的特性及变化规律。建立了温度、应力与制动时间、摩擦盘半径的关系曲线,掌握湿式制动器温度场—热变形—热应力三者之间的影响规律并建立相关模型,对改进湿式制动器结构,为制动器冷却系统的设计及冷却时间的循环周期选取提供依据,对提高使用寿命有非常重要的指导意义。     

Activities,resources and inter-organizational relationships: key factors in port competitiveness

In the last decade, the port economics literature has given great emphasis to the Supply Chain Management approach as the new paradigm for the definition of port competitiveness. SCM supports the development of partnerships between the actors of the supply chain and considers the integration of activities and resources along business processes as source of competitive advantage. Nevertheless, the application of SCM approach to the port is particularly compiex given the traditional hostile relationships between port actors. In the effort to overcome such complexity, some authors have considered ports as Logistics Service Providers and interpreted their role within supply chains through the integrative practices undertaken by Global Players–mainly Shipping Companies and Terminal Operators–in the supply of integrated logistics services. Even tough these actors are crucial for the port competitiveness, they determine a passive role of port in the new competitive scenario. The definition of a potential and pro-active role of port in the supply chains is the objective of this paper that presents, through a literature review on SCM and port competitiveness, a new framework for port competitiveness. According to this framework, that is based on the value constellation concept value is generated by joint effort of port actors in the satisfaction of clients' needs, through the exploitation of different I mterdependencies (serial, pooled and reciprocal) between supply chains. In this context, Port Authority has a I fundamental role in identifying those resources–the so called critical assets–that encourage the development of inter-organisational relationships between port actors in the value generation process.     

The changing role of ports in supply-chain management: an empirical analysis

As integrated supply-chain management (SCM) is now at the epicentre of business transformation, firms are breaking down boundaries between internal functions, as well as between the enterprise itself and key partners in the value chain (e.g. customers, distributors, suppliers and carriers). One of the main goals of such new management approach is to get everyone in the supply chain into a common platform of logistics transactions and information systems.

Against such background, the aim of this work is to analyse how and if port operators can face the challenge of higher integration, on the assumption that the higher the integration between the actors the higher the competitiveness of the whole supply chain.

Accordingly, we adopted an SCM approach in the analysis of the port of Le Havre in Renault's supply chain. More specifically, we referred to the Lambert tri-dimensional model based on supply chain's structure (actors), key business processes and links between actors. The field work—which mainly consisted of semi-structured interviews to Renault, logistics and port operators, and, finally, to the Le Havre Port Authority—was crucial to gather the needed information.     

Valuing the Prevention of Road Accidents in Belgium

Abstract

In a recent international comparison of the social costs of road accidents, Trawén et al. (2003) noted that cost data are not available for Belgium and, by consequence, play no part in Belgian policy‐making. The purpose of the present paper is, therefore, to value the costs per casualty type and per accident in Belgium. Empirical data are provided on human and economic production losses as well as on direct accident costs such as medical costs, hospital visiting costs, accelerated funeral costs, property damage, administrative costs of insurance companies, litigation costs, police and fire department costs, and congestion costs. In Belgium the marginal unit value of preventing a road casualty is estimated at €2 004 799 per fatal casualty, €725 512 per seriously injured and €20 943 per slightly injured victim. The unit cost per accident amounts to €2 355 763, €850 033, €34 944 and €2571 for fatal, serious, slight injury and property damage only accidents, respectively. These results are consistent with valuations reported in other high‐income countries. Finally, the total costs of road accidents in 2002 are valued at €7.2 billion (2004 prices), or 2.6% of gross domestic product.     

敷设粘弹性阻尼的加筋板振动和阻尼分析

对敷设粘弹性阻尼的加筋板的固有频率和模态损耗因子进行了分析。考察了在加筋板结构上加自由阻尼层和加粘弹性筋梁的两种情况，分析了粘弹性阻尼材料模量、损耗因子、阻尼层厚度以及粘弹性梁剖面尺寸的影响。对粘弹性筋梁的讨论，拓宽了加筋板的粘弹性阻尼的敷设形式。