Assessing financial impact of maritime ergonomics on company level: a case study

The present paper reports a case study examining a conceptual framework for assessing financial impact of occupational maritime ergonomics in a Swedish shipping company. Specifically, the aim was to study the availability and applicability of suggested determinants for operational performance, routines for estimating the effects of ergonomics and the customer’s (sea transport buyer’s) demands for ergonomics management on the case company. The results show that the determinants and subcategories for operational performance in terms of productivity, efficiency and quality are present and applicable, albeit not measured to any large extent. No routines or specific methods for measuring or estimating cost and effects of ergonomics investments, accidents and operational disturbances were found. Further, the results show that the sea transport buyers increasingly express interest for and place demands related to maritime ergonomics, for instance, through compliance of specific standards and guiding principles linked to maritime ergonomics. It is concluded that in order to support and enable managers’ ability to make well-informed decisions and prioritizations, between investments, ergonomic or other, increased knowledge is needed of the financial effects of ergonomics on company core value processes. There is also a need to develop and implement usable tools to simplify these measuring procedures.     

The impact of activity chaining on the duration of daily activities

There is a broad body of theoretical and empirical literature dealing with trip chaining behaviour. This paper adds to the literature while focusing on the impact of activity chaining on the duration of time spent on individual purposes. Two questions in particular are addressed: first, does an additional purpose added to a trip chain affect the duration of the activities included? Second, is there any pattern of included activities that explains differences in duration? Duration data models are employed using German data. We find evidence that the number of purposes influences duration significantly. Leisure, shopping and personal business activities are affected by the occurrence of obligatory activities (work, school/university). We cannot find any evidence that personal business or leisure activities influence the duration of shopping, whereas the opposite is supported. Therefore, in terms of daily activities, obligatory and shopping activities are superior to leisure and personal business. We conclude that activity chaining and especially the pattern of combined purposes affect the duration of activities allocated to single purposes while controlling for a wide range of other explanatory variables. The results can be used in transport and simulation models.     

用Rankine波幅函数预报高速三体／五体船主体与侧体的兴波阻力干扰

基于兴波阻力的薄船理论,作者曾提出用兰金体波幅函数(RWAF)代替实际船型的波幅函数,确定了高速双体船片体间的阻力干扰因子,从而可计算得到双体船的兴波阻力.本文将该方法用于高速三体船侧体与主体之间的兴波阻力干扰计算,以探讨主、侧体尺度及相对位置变化对于兴波阻力干扰因子τO、τOM的影响及其变化规律.基于这一研究结果,可实现用单体船阻力的实验资料,经过侧体、主体间的兴波干扰影响理论修正,来估算高速三体船的阻力;同时可用于对于最小阻力三体船片体尺度与布局之优化.     

产品平台思想——把其他行业成功的思想引入到铁道车辆制造行业

概述了在铁道车辆制造领域引入产品平台这一生产管理思想，分析了从汽车领域引入标准化加工的可能性，阐述了铁道车辆工业开始运用的情况，并介绍了一个功能强大的IT弹性开发工具，利用该工具，可允许按照用户的特殊要求，对完全参数化的车辆模型进行快速修改，并可使用标准化的程序，生产出适应用户有特殊要求的车辆。     

Design and Evaluation of Robust Cooperative Adaptive Cruise Control Systems in Parameter Space

This paper is on the design of cooperative adaptive cruise control systems for automated driving of platoons of vehicles in the longitudinal direction. Longitudinal models of vehicles with simple dynamics, an uncertain first order time constant and vehicle to vehicle communication with a communication delay are used in the vehicle modeling. A robust parameter space approach is developed and applied to the design of the cooperative adaptive cruise control system. D-stability is chosen as the robust performance goal and the feedback PD controller is designed in controller parameter space to achieve this D-stability goal for a range of possible longitudinal dynamics time constants and different values of time gap. Preceding vehicle acceleration is sent to the ego vehicle using vehicle to vehicle communication and a feedforward controller is used in this inter-vehicle loop to improve performance. Simulation results of an eight vehicle platoon of heterogeneous vehicles are presented and evaluated to demonstrate the efficiency of the proposed design method. Also, the proposed method is compared with a benchmark controller and the feedback only controller. Time gap regulation and string stability are used to assess performance and the effect of the vehicle to vehicle communication frequency on control system performance is also investigated.     

In-situ measurement of loading stresses with X-ray diffraction for yield locus determination

The application of the X-ray diffraction method is introduced to solve the problem of inhomogeneous deformation fields in the specimens used for sheet metal characterization. In this method, strains are measured on one side of a specimen with optical measurement systems. On the other side, loading stresses on a specimen are captured with an X-ray diffractometer mounted on a universal testing machine. By this way, the whole stress-strain history of a material point is tracked during testing. The method was first applied to uniaxial tension tests, whereby the applicability of the theory of stress factors and effective X-ray elastic constants were tested. The relaxation behavior of a sheet material which shows itself as stress drops during in-situ experimentation was characterized and compensated by a visco-plastic material model for different stress states. The proposed method was applied to characterize aluminum alloy AA5182 under plane strain tension and shear conditions and the results were compared with the conventionally obtained yield locus. Numerical analyses of a workpiece with the Vegter and Yld2000-2D material models show that the enriched yield locus definition with accurate plane strain tension and shear stresses captures the experimentally obtained surface strains more precisely.     

新型相变水泥砂浆热力学性能研究

为降低温度变化对隧道水泥砂浆材料强度和变形的影响，在隧道工程中引入具有自调温能力的相变材料，制备成相变材料水泥砂浆。首先,将石蜡、高密度聚乙烯和膨胀石墨熔融共混，获得复合相变材料；然后，掺入水泥砂浆中，得到新型相变水泥砂浆。通过搭建热响应测试平台，分析其热应变随温度变化规律，评估其蓄热性能,并对比得出相变材料对不同水灰比砂浆试样的热力学性能影响。结果表明： 复合相变水泥砂浆能发挥相变材料的蓄热性能，其相变潜热为34.82 J/g，热应变比普通水泥砂浆材料最大降低36.63%。相变材料的掺入有效降低了试样的表面温度和热应变，这对改善水泥砂浆材料的温度变形及控制裂缝的发展具有重要作用，可为能源地铁隧道及其裂缝修复等提供新型材料。     

A study on time constraints and task deviations at sea leading to accidents – a cultural-historical perspective

The high frequency of maritime accidents and incidents occurring at sea has been a major challenge for the maritime industry in the last decades. The majority of these accidents are attributed to seafarers’ poor performance. This, despite the fact that the international maritime domain continues to adopt and update conventions regulating maritime safety to mitigate these accidents from occurring. In this paper, utilising a qualitative research approach, we show through a socio-cultural contextual perspective that time constraints as a major influencing factor in causing task deviations at sea which leads to dangerous situations. We analyse how some of the present barriers in place to prevent accidents at sea are in effect prompt seafarers who are working under time pressure to deviate from their task. Moreover, the paper discusses the social constituents such as job insecurity and the seafarers’ viewpoint towards the ship operators’ commitment to safe ship operations are crucial in motivating seafarers’ deviating from the task at hand when faced with time pressure.     

Modelling and optimisation of online container stacking with operational constraints

Container transportation plays a critical role in the global shipping network and container terminals need to improve their operations to increase efficiency. Storage yard of a container terminal is a temporary area where the containers stay until they are shipped to their next destination. We concentrate on increasing the efficiency of the storage yard by developing online stacking policies for each incoming container. An unproductive move of a container, performed to reach another container stored underneath, is called reshuffling. The objective in container stacking problem is to minimise the number of reshuffles, thereby increasing the efficiency of terminal operations. Additional weight-related operational constraints bring additional complexity to the online stacking decisions. We propose a mathematical model for the optimal online assignment of an incoming export, transit, import or empty container. We also propose an optimal online stacking policy and compare it with a random policy through simulation. Additionally, lower bounds for the performance measures are obtained through simulation by relaxing the operational constraints of the problem in a third stacking policy. We present and discuss the computational results in terms of four main performance measures.