Mathematical approach for fleet planning under complicated circumstances

In order to facilitate the scientific management of large-sized shipping companies, fleet planning under complicated circumstances has been studied. Based on multiple influencing factors such as the techno-economic status of ships, the investment capacity of company, the possible purchase of new ships, the buying/selling of second-hand vessels and the chartering/renting of ships, a mixed-integer programming model for fleet planning has been established. A large-sized shipping company is utilized to make an empirical study, and Benders decom- position algorithm is employed to test the applicability of the proposed model. The result shows that the model is capable for multi-route, multi-ship and large-scaled fleet planning and thus helpful to support the decision making of large-sized shipping companies.     

型材拉弯成形过程的参数化有限元建模方法

针对传统的预拉-弯曲-补拉(P-M-P)有限元建模方法在型材拉弯成形过程中应用的局限性,提出了一种基于连接器单元的型材拉弯成形参数化建模方法,实现了型材拉弯贴模过程中的边弯边拉模拟。该有限元模型中只需定义型材的伸长量,无需对成形过程中的夹钳轨迹进行计算,简化了仿真计算流程。以轨道交通车辆车顶弯梁作为研究对象,采用有限元模拟和试验方式获取了成形后工件的成形缺陷。对比表明,所提出的参数化有限元模型仿真结果和试验数据更为接近。     

公路除雪作业需要适应性的除雪机械——2008年南方雪灾之后的反思

2008年春运之时,南方部分省市持续20余天的大雪,让人难以忘怀。雪灾而导致机场关闭、公路瘫痪、电网中断、铁路运营受阻,返乡的人们思乡心切,大量滞留在机场和车站,给政府和相关部门带来了前所未有的严峻考验。非常专     

中印市域铁路PPP模式比较分析及启示

在立足中印两国轨道交通PPP(public-private partnership)发展背景和现状基础上,通过对中国台州和印度海得拉巴市域铁路PPP典型案例的比较分析,总结市域铁路采用PPP模式的一般流程、结构设计和关键要点等经验,提出市域铁路PPP发展的启示。研究表明,市域铁路采用PPP模式是可行的,但需要在风险管理、回报机制、政企合作分工、规范实施、聘请专业咨询机构、可持续发展和以人为本等关键方面加强引导。期望形成可复制可推广的模式,为国内市域铁路的发展提供借鉴和决策参考。     

瑞士联邦铁路客运车队的机车车辆

瑞士联邦铁路(SBB)现有客运车队的机车车辆类型极多,除了现代大功率机车、摆式列车、低地板车辆和客车外,还包括在这期间作了改进的旧系列机车车辆.今后的采购政策首先是购置新的区间列车.     

南海海底管道冲刷深度预测（英文）

Scour depth prediction of offshore pipelines is of great significance to the design and construction of the submarine pipeline projects. In this paper, based on the CFD software package FLUENT and User Defined Function(UDF), an Eulerian two-phase model, which includes an Euler-Euler coupled model for water and sediment phases, and a turbulent model for the fluid phase, is adopted to predict the scour depth around pipelines. The model is verified by observation data obtained from laboratory experiments. On the basis of the simulations, the factors affecting the scour depth, including the effects of incipient velocity, pipe diameter and sediment particle size and so on, were investigated. Meanwhile, according to formulas of incipient velocity of various sediments, approximate calculation on theoretical scour depths is developed for pipelines of seven stations in the South China Sea, where engineering application information is available.     

试论"电子运输记录"及其对我国航运业的影响

"鹿特丹规则"首次在公约中对"电子运输记录"做了规定,为国际航运业推动电子运输单证及电子商务的发展构建了基本法律基础,利于航运业与信息技术的融合."电子运输记录"的发展仍面临技术、安全和法律及贸易习惯等诸多挑战.它对中国航运业具有双重影响.