Propeller torque load and propeller shaft torque response correlation during ice-propeller interaction

Ships use propulsion machinery systems to create directional thrust. Sailing in ice-covered waters involves the breaking of ice pieces and their submergence as the ship hull advances. Sometimes, submerged ice pieces interact with the propeller and cause irregular fluctuations of the torque load. As a result, the propeller and engine dynamics become imbalanced, and energy propagates through the propulsion machinery system until equilibrium is reached. In such imbalanced situations, the measured propeller shaft torque response is not equal to the propeller torque. Therefore, in this work, the overall system response is simulated under the ice-related torque load using the Bond graph model. The energy difference between the propeller and propeller shaft is estimated and related to their corresponding mechanical energy. Additionally, the mechanical energy is distributed among modes. Based on the distribution, kinetic and potential energy are important for the correlation between propeller torque and propeller shaft response.     

Interference resistance of pentamaran ship model with asymmetric outrigger configurations

An experimental investigation is performed to assess the relation of interference performance on the total resistance of a pentamaran model advancing in calm water. For this motivation, the total drag of the ship is performed for several values of asymmetric outrigger configuration and hull separation, altering the Froude number in the range 0.3–0.9. Our results indicate that remarkable changes in resistance require notable changes in transverse distance values (hull separation) when wave interference may occur. In addition, there is no single configuration that consistently outperforms the other configurations across the entire speed range and the optimum interference factor ?0.2 appears at a Froude number of 0.45 in S/L=0.33 with the outrigger outer position: asymmetric outboard for A3 configuration.     

Vehicle routing problem and driver behaviour: a review and framework for analysis

Vehicle routing problems (VRPs) whose typical objective is to minimise total travel costs over a tour have evolved over the years with objectives ranging from minimising travel times and distances to minimising pollution and fuel consumption. However, driver behaviour continues to be neglected while planning for vehicle routes. Factors such as traffic congestion levels, monotonous drives and fatigue have an impact on the behaviour of drivers, which in turn might affect their speed-choice and route-choice behaviours. The behaviour of drivers and their subsequent decision-making owing to these factors impact the revenue of transport companies and could lead to huge losses in extreme cases. There have been studies on the behaviour of drivers in isolation, without inclusion of the objectives and constraints of the traditional routing problem. This paper presents a review of existing models of VRP, planner behaviour models in the VRP context and driver behaviour models and provides a motivation to integrate these models in a stochastic traffic environment to produce practical, economic and driver-friendly logistics solutions. The paper provides valuable insights on the relevance of behavioural issues in logistics and highlights the modelling implications of incorporating planner and driver behaviour in the framework of routing problems.     

Shallow water processes govern system-wide phytoplankton bloom dynamics: A modeling study

A pseudo-two-dimensional numerical model of estuarine phytoplankton growth and consumption, vertical turbulent mixing, and idealized cross-estuary transport was developed and applied to South San Francisco Bay. This estuary has two bathymetrically distinct habitat types (deep channel, shallow shoal) and associated differences in local net rates of phytoplankton growth and consumption, as well as differences in the water column's tendency to stratify. Because many physical and biological time scales relevant to algal population dynamics decrease with decreasing depth, process rates can be especially fast in the shallow water. We used the model to explore the potential significance of hydrodynamic connectivity between a channel and shoal and whether lateral transport can allow physical or biological processes (e.g. stratification, benthic grazing, light attenuation) in one sub-region to control phytoplankton biomass and bloom development in the adjacent sub-region. Model results for South San Francisco Bay suggest that lateral transport from a productive shoal can result in phytoplankton biomass accumulation in an adjacent deep, unproductive channel. The model further suggests that turbidity and benthic grazing in the shoal can control the occurrence of a bloom system-wide; whereas, turbidity, benthic grazing, and vertical density stratification in the channel are likely to only control local bloom occurrence or modify system-wide bloom magnitude. Measurements from a related field program are generally consistent with model-derived conclusions.     

Four-wheel vehicle kinematic and geometric constraints for definition of tire slip angle

When considering vehicle safety, tires and all that they represent are a fundamental topic. Tire studies have received a considerable amount of attention from the research community because their improvement has a direct and strong impact on vehicle handling and braking. Within this eld of analysis lies an important behavioral feature: the tire slip angle, which is a consequence of lateral forces acting on the tire. This characteristic is predicted in some cases and evaluated experimentally in others. This paper addresses another way to assess the slip angle. We propose a mathematical model that describes a constraint linking the slip angle and steering angle that make a vehicle turn. We present a simplied kinematic model (based on the classic bicycle model) and a four-wheel model, which makes all of the angles involved compatible with each other. In our case, the match will be given by the determination of the turning radius. Two different scenarios, understeering and oversteering vehicles, were simulated, and the results and conclusions reached are presented herein.     

Wind-induced mesoscale circulation off the Ebro delta, NW Mediterranean: a numerical study

It is well known that the general circulation on the Catalan continental slope is dominated by a quasi-permanent southwestward geostrophic jet associated to the so-called Catalan front [Millot, C., 1987. Circulation in the western Mediterranean sea. Oceanol Acta 10, 143–149; Font, J., Salat, J., Tintoré, J., 1988. Permanent features of the circulation in the Catalan Sea. Oceanol. Acta 9, 51–57]. On the continental shelf, however, the flow is modified by the action of friction which enhances also other nonlinear interactions. Several authors have hypothesized that the shelf circulation is anticyclonic north of the Ebro delta [Salat, J., Manriquez, M., Cruzado, A., 1978. Hidrografia del golfo de Sant Jordi. Campaña Delta (Abril 1970). Investigación Pesquera 42 (2), 255–272; Ballester, A., Castellví, J., 1980. Estudio hidrográfico y biológico de las plataformas continentales españolas: I. Efecto de los efluentes de una planta de energía nuclear en el Golfo de San Jorge (Febrero 1975–Octubre 1976). Informes Técnicos del Instituto de Investigaciones Pesqueras 76, 70 pp.]. A quasi-3D finite element code based on the shallow-water equations has been used to explore the effect of several mechanisms which might be responsible for such a local circulation pattern, and in particular of wind. The obtained numerical results suggest that the basic anticyclonic structure of the mean flow is controlled by the bathymetry and that the clockwise-rotating mean flow pattern is not a permanent circulation feature. It is seen that the characteristic local wind stress fields—computed through interpolation of the records of a local network of meteo stations—may ‘enhance' or ‘delete' the anticyclonic gyre depending on the sign of their relative vorticity. According to the analysis of a 2-yr record of local wind data, the net contribution of wind events with a duration longer than 24 h is to reinforce the anticyclonic circulation (over 70% of these wind fields supply negative relative vorticity to the study area).     

台湾海底隧道之接头与管段变化研析及对策

台湾唯一之海底隧道系采沉埋方式施工,该隧道不仅处于具高度盐份腐蚀之不利环境,且位于软弱地盘上.于营运二十余年后,轻微异状已有显现,如管段接头锈蚀、管体渗漏及管体裂损等异状.上述异状可能为接头构件变形、管体变位/变形及结构劣化等影响隧道安全之前兆,甚至降低其耐震能力;因该隧道肩负港区及区域经济发展之运输重任,如何藉由整体性体检进行安全评估及研订适当之维护补强对策,为计划执行重点;故本文将说明隧道接头、结构体等隧道重要构件之检测调查(如地球物理、钢筋腐蚀、裂缝深度、氯离子试验、防蚀电位、接头防水等项目)、数值分析及自动化监测(接缝计、单元沉陷仪、结构倾斜仪、电位计等)等综合评估结果及维护补强对策,以提供工程界日后参考.     

Two-dimensional Continuum Modeling Approach to Transportation Problems

The continuum modeling approach to transportation models is now gaining much attention because of its advantages in dealing with dense-network models, macroscopic problems, and initial phase planning. This paper aims to provide a comprehensive review of the development and applications of the two-dimensional continuum modeling approach. The theoretical development and models with specific or arbitrary region configurations are first discussed, and then the applications of the continuum modeling approach to the determination of facility location, route choice, pedestrian flow, and policy and socio-economical analysis are reviewed. Finally, some prospective directions for future research are proposed.