Collision risk assessment for ships

Efficient maritime navigation through dynamic obstructions at close range is still a serious issue faced by mariners. There have been studies focusing on collision risk assessment in the past, but the majority were based on the first person perspective, with area-based ship domain concepts that are defined around either the ownship or the obstacle. Such methods are acceptable for encounters where the ownship is required to manoeuvre according to the collision regulations (COLREGs), but they will not work correctly if the ownship is the stay-on party. This article presents an alternative method of assessing the collision risk for surface ships in close-range encounters that is compliant with the COLREGs as well as other ships from different perspectives.     

Collecting longitudinal data from freight operators: survey design and implementation ideas and challenges

Freight transport research has generally been limited by a lack of data of the breadth and quality available for passenger transport, particularly in terms of behavioural data. This paper discusses the survey design and implementation of a survey intended to collect longitudinal behavioural data on the responses of freight transport firms to environmental policies. The design of the survey is centred around a hypothetical scenario where respondents are asked how they would complete a given freight task within common constraints. One of the key components of the survey design is a dynamic component intended to simulate the changing business environment. The paper illustrates the many challenges in getting complex freight related surveys in the field.     

基于SP调查的天津市居民出行行为时间价值

为揭示天津市居民出行行为时间价值的一般规律,采用SP调查中的卡片式面谈调查法,运用市场细分法确定调查规模及抽样率,采用计算包容性检查矩阵等数据处理手段,估算天津市居民出行行为时间价值。比较了出行行为时间价值与单位工作时间价值之间的关系,并分析了不同出行方式、出行目的、出行时段的时间价值,研究了出行收入与时间价值的变化规律。得出现阶段天津市居民出行行为时间价值的分布,表明大部分出行者不愿为出行支付较高费用,但随着收入增加,出行行为时间价值将会快速增长,使个体机动化出行方式的需求增大,城市出行方式结构可能出现拐点。     

Improving Tidal Turbine Performance Through Multi-Rotor Fence Configurations

Constructive interference between tidal stream turbines in multi-rotor fence configurations arrayed normally to the flow has been shown analytically, computationally, and experimentally to enhance turbine performance. The increased resistance to bypass flow due to the presence of neighbouring turbines allows a static pressure difference to develop in the channel and entrains a greater flow rate through the rotor swept area. Exploiting the potential improvement in turbine performance requires that turbines either be operated at higher tip speed ratios or that turbines are redesigned in order to increase thrust. Recent studies have demonstrated that multi-scale flow dynamics, in which a distinction is made between device-scale and fence-scale flow events, have an important role in the physics of flow past tidal turbine fences partially spanning larger channels. Although the reduction in flow rate through the fence as the turbine thrust level increases has been previously demonstrated, the within-fence variation in turbine performance, and the consequences for overall farm performance, is less well understood. The impact of turbine design and operating conditions, on the performance of a multi-rotor tidal fence is investigated using Reynolds-Averaged Navier-Stokes embedded blade element actuator disk simulations. Fences consisting of four, six, and eight turbines are simulated, and it is demonstrated that the combination of device- and fence-scale flow effects gives rise to cross-fence thrust and power variation. These cross-fence variations are also a function of turbine thrust, and hence design conditions, although it is shown simple turbine control strategies can be adopted in order to reduce the cross-fence variations and improve overall fence performance. As the number of turbines in the fence, and hence fence length, increases, it is shown that the turbines may be designed or operated to achieve higher thrust levels than if the turbines were not deployed in a fence configuration.

     

A logistics and supply chain management approach to port performance measurement

Although there is widespread recognition of the potential of ports as logistics centres, widely accepted performance measurements for such centres have yet to be developed. The essence of logistics and supply chain management is an integrative approach to the interaction of different processes and functions within a firm extended to a network of organizations for the purpose of cost reduction and customer satisfaction [1]. The logistics approach often adopts a cost trade-off analysis between functions, processes and even supply chains [2]. This approach could be beneficial to port efficiency by directing port strategy towards relevant value-added logistics activities. This paper seeks to show that through conceptualizing ports from a logistics and supply chain management approach, it is possible to suggest a relevant framework of port performance. A proposed framework is tested in a survey of port managers and other international experts.     

The 50<Superscript>th</Superscript> anniversary of container shipping the Admiral Sheldon Kinney (USN) lectures

The paper offers a historical overview of the container revolution. It starts from the origin more than 50 years ago, presenting how the pioneer Malcom McLean came to this idea that has changed the nature of Shipping. It then presents how and why container shipping was gradually accepted and what has been the main trends during the last 50 years: the increase in vessels’ and containers’ size and in vessels’ speed. Finally, the paper investigates what the future will bring and notably sheds light on the increase in containers’ size and on the improvements in terminal and rail services.