Numerical modelling of fish eggs dispersion at the Patos Lagoon estuary — Brazil

The Patos Lagoon estuary is the most important nursery ground for commercially relevant species of fish and crustaceans in the South of Brazil, maintaining fisheries that sustain 3500 fisher families throughout the Rio Grande do Sul State coastline. Around 80% of the interior estuarine area is very shallow (< 2 m), and recruitment of fish eggs and larvae to the inner parts of the Patos Lagoon estuary is directly related to the circulation pattern in the area, which is controlled by local and non-local wind effects and freshwater discharge. The objective of this study is to investigate the processes controlling the transport of estuarine dependent fish eggs between the Atlantic Ocean and the Patos Lagoon estuary.An integrated numerical system based on a bi-dimensional hydrodynamic model and a Lagrangean transport model of passive particles is applied to a selection of scenarios representing the passage of weather fronts over the area. At this stage, fish eggs are represented as buoyant passive particles. Modelling results are compared against field data for the period under investigation (September/October 1999) and historical records. Short term results are analysed in terms of the meteorological conditions (wind direction, intensity and duration) controlling the transport of eggs to the inner parts of the estuary and the extension of their excursion. This experiment is the first attempt to couple biological and physical information to study fish eggs transport, and to enhance the current knowledge about recruitment of important fisheries resources in southern Brazil.     

The applicability of non-cooperative game theory in transport analysis

Various models that incorporate concepts from Non-Cooperative Game Theory (NCGT) are described in the transport literature. Game Theory provides powerful tools for analysing transport systems, but these tools have some drawbacks that should be recognised. In the current paper we review games that describe transport problems and discuss them within a uniform context. Although the paper does not introduce new tools, it presents insights concerning the relations between transport models and games. We divide existing games into groups and show that some common features characterise multiple games. We distinguish between games that make a conceptual contribution and games that are suitable for application. Compact or symmetric game structures make remarkable observations but often do not support actual decision-making. Less aesthetic formats, most of which are Stackelberg games between authorities and travellers, are stronger as instruments that assist in determining real-life policies; these formulations can be treated by practitioners as mathematical programs with equilibrium constraints and not as games. Yaron Hollander is currently conducting economic research of bus reliability at the Institute for Transport Studies at the University of Leeds. He previously worked for the Technion—Israel Institute of Technology; for the Israel Institute for Transportation Planning and Research; and for the public transport department at Ayalon Highways Co. Joseph N. Prashker is a professor at the Faculty of Civil and Environmental Engineering at the Technion—Israel Institute of Technology. Till recently he served as head of the Transportation Research Institute at the Technion. His interests are behavioural demand models, network analysis, and Game Theory applications in transportation.     

Container liner fleet deployment: A systematic overview

Container liner fleet deployment (CLFD) is the assignment of containerships to port rotations (ship routes) for efficient transport of containers. As liner shipping services have fixed schedules, the ship-related operating cost is determined at the CLFD stage. This paper provides a critical review of existing mathematical models developed for the CLFD problems. It first gives a systematic overview of the fundamental assumptions used by the existing CLFD models. The operating characteristics dealt with in existing studies are then examined, including container transshipment and routing, uncertain demand, empty container repositioning, ship sailing speed optimization and ship repositioning. Finally, this paper points out four important future research opportunities: fleet deployment considering ship surveys and inspections, service dependent demand, pollutant emissions, and CLFD for shipping alliances.     

燃气轮机性能的数学模型及其优化解法

本文建立了流量残量方程组形式的燃气轮机性能的新数学模型，并提出了用Newton-Raphson和DFP－BFS优化组合解法来求解该模型。计算实践表明，该法不仅稳定性高、收敛速度快，而且求解精度高，可在任何工况下都得到较为满意的结果，在燃气轮机设计中有一定的实用价值。     

港内拖轮协助操船仿真数学模型的研究

本文为研制高精度、多功能的船舶操纵模拟器和进行船舶操纵安全评价的需要，首次提出了拖轮流体动力和拖轮Ｚ型导管螺旋桨四象限推力系数的实用估算方程。在此基础上，建立了港内拖轮协助操船仿真的数学模型。最后介绍了在港口引航实践中的两个仿真应用例。     

综合考虑各影响因素下浅埋室顶板最大安全荷载预测

以新疆乌鲁木齐“世纪花苑”三期工程人防地道为例,运用快速拉格朗日差分分析程序,通过逐渐调整上部荷载大小,使其达到临界状态下的数值模拟方法,系统分析不同影响因素(如洞跨、顶拱高跨比、顶板厚度、荷载范围等)对人防地道顶板最大安全荷载的影响及相关变化规律。结果表明,顶板最大安全荷载与洞跨及荷载范围成反比,而与顶拱高跨比、顶板厚度和荷载偏心率成正比。在此基础上,用数理统计方法得出能综合考虑各影响因素下顶板最大安全荷载的预测方程。     

船舶动力定位系统的数学模型

阐述了船舶动力定位系统的发展，给出了完整的动力定位系统的船舶低频与高频运动、推力器、风、浪、流等数学模型，最后给出了综合运动模型。     

船舶综合电力系统暂态仿真研究

根据船舶综合电力系统的特点,开发描述其暂态过程的仿真软件。以VC 6.0作为编写软件的平台,以船舶相关设备的数学模型为编程的理论依据,以数据库作为数据支持,以可视化曲线的形式输出暂态仿真结果,直观的反映出暂态过程。最后,应用典型的系统进行验证,结果表明了相关数学模型建立的正确性,以及暂态仿真软件的可靠性和实用性。     

多年冻土隧道工程中的隔热层参数优化设计研究

隔热层经常被用于多年冻土隧道中,来防止隧道结构的冻融破坏。文章根据多年冻土特点及优化理论,推导了多年冻土隧道隔热层的数学优化模型;并以风火山隧道为例进行求解,分析研究了隔热层用于多年冻土隧道的合理性和经济性。结果表明,该多年冻土隧道隔热层的数学优化模型是合理的,求解方法是可行的;对于多年冻土隧道,地表温度对隧道围岩影响深度是有限的,因此多年冻土隧道隔热层应根据隧道埋深、年平均温度以及年较差分段设计,才能达到既合理又经济的目的。     

南槽航道航船下沉量数学模型研究

文章深入剖析了长江口南槽航道的通航环境,研究分析了该航道航船下沉量的数学模型,实证表明,该模型算法取值安全,符合航道实际,对南槽航道航船富裕水深确定以及避免搁浅事故发生具有指导意义,同时也为航道监管部门合理利用航道资源提供参考。