A dynamic model and algorithm for fleet planning

By analysing the merits and demerits of the existing linear model for fleet planning, this paper presents an algorithm which combines the linear programming technique with that of dynamic programming to improve the solution to linear model for fleet planning. This new approach has not only the merits that the linear model for fleet planning has, but also the merit of saving computing time. The numbers of ships newly added into the fleet every year are always integers in the final optimal solution. The last feature of the solution directly meets the requirements of practical application. Both the mathematical model of the dynamic fleet planning and its algorithm are put forward in this paper. A calculating example is also given.     

地铁盾构区间工程造价分析

介绍地铁盾构区间的施工方法,阐述盾构区间土建工程造价构成、基本指标。通过对武汉、昆明、江苏等地盾构区间概算分析,找出影响盾构区间土建工程造价的因素,为以后盾构区间土建工程概算编制提供参考。     

INVESTIGATION ON FRACTAL CHARACTERISTICS OF WORN SURFACES OF POLYMER TAPES BY SAND DUST PARTICLES

Objective To characterize the abrasive wear of polymer tapes in ATM （Auto Teller Machine） servicing in sand dust environment. Aethods The abrasive wear experiment of polymer tapes, PEN （polyethylene-2, 6-naphthalenedicarboxylate） and PI （polyimide）, by sand dust particles is performed in ATM tribosystem. The fractal characteristics of the worn surface of polymer tapes and the corresponding wear mechanisms are examined. ReSults As main results, the worn surfaces of polymer tapes show bi-fractal characteristics, and PI tape shows higher fractal dimensions and finer wear profiles than PEN tape. Wear mechanism examination shows macro and micro ploughing and cutting grooves and micro fracture characters, which gives reasonable explanation of bi-fractal character of worn polymer tapes. Conclusion Worn polymer tape shows fractal character and bi-fractal can be used in accurately characterizing the abrasive wear of polymer tapes of ATM in sand dust environment.     

补给工作艇收放装置选型设计分析

工作艇是军辅船的常用设备,目前,国内对其在高海况下的安全收放问题尚无很好的解决办法.通过对"C"型单点起吊方案和"A"型双点起吊方案的对比分析、适用的状态分析,指出了各自的优缺点,同时在挂钩中设置了波浪补偿装置,综合考虑解决双点同步性的问题,从而保证了工作艇收放的安全性.     

水下隧道合理覆盖层厚度的有限元模拟研究

水下隧道覆盖层厚度目前基本上是凭经验确定的,采用不同的经验公式得到的计算结果差异很大。文章针对目前情况提出了采用有限元的求解方法,并结合公路隧道施工规范,模拟了拟建的重庆朝天门两江隧道在不同隧道覆盖层厚度时的拱顶位移和拉应力的分布及大小。通过与标准隧道的比较,得出了该隧道的合理覆盖层厚度,对同类工程有一定的参考价值。     

港口合作竞争模式研究

我国港口发展迅速,现已初步形成协调发展的三大港口群,但是港口群内的港口和港口群之间的竞争激烈,导致港口资源的严重浪费。本文借鉴外国港口合作经验,在分析我国港口竞争现状的基础上,提出可行性的港口整合方案,以充分利用港口资源,发挥其在区域经济发展中的巨大作用。     

浅坑式钢轨翻转机

浅坑式钢轨翻转机用于对承轨台上的钢轨通过翻转进行调正、倒扣和平移,文章介绍沈阳铁路局科学技术研究所设计制造的浅坑式钢轨翻转机的技术参数和结构特点。     

异步牵引电动机容积功率、折算转矩和通用性问题的分析

提出异步牵引电动机容积功率和转矩折算的概念，并分析其与异步牵引电动机体积，质量，成本价格及通用性的关系。有利于异步牵引电动机的通用化，系列化设计。     

滑模变结构控制技术在舰船自动舵中的应用研究

本文介绍了船舶自动操舵仪的发展历程和滑变结构控制技术的特点,论述了舰船航向变结构控制的意义,对未来自动操舵仪的发展趋势进行了展望。