Exact and simplified estimations for elastic buckling pressures of structural pipe-in-pipe cross sections under external hydrostatic pressure

Structural pipe-in-pipe cross sections have significant potential for application in offshore oil and gas production systems because they combine thermal insulation performance with structural strength and self weight in an integrated way. Such cross sections comprise inner and outer thin-walled pipes with the annulus between them fully filled by a selectable filler material to impart an appropriate combination of properties. Structural pipe-in-pipe cross sections can exhibit several different collapse mechanisms, and the basis of the preferential occurrence of one over the others is of interest. This article presents an exact analysis for predicting the elastic buckling behaviours of a structural pipe-in-pipe cross section when subjected to external hydrostatic pressure. Simplified approximations are also investigated for elastic buckling pressure and mode when the outer pipe and its contact with the filler material is considered as a pipe on an elastic foundation. Results are presented to show the variation of elastic buckling pressure with the relative elastic modulus of the filler and pipe materials, the filler thickness, and the thicknesses of the inner and outer pipes. Case studies based on realistic application scenarios are used to show that the simplified approximations are sufficiently accurate for practical structural design purposes.     

软土地基地段动态设计的理念和方法

简要介绍了秦沈客运专线软土和松软地基处理方案和路基工后沉降量控制标准，通过秦沈客运专线动态设计实践，强调在高速铁路建设过程中开展动态设计的意义，并从沉降断面布置、设备选择、观测频度、数据处理方法、数据分析的基本原理和应用等方面，系统介绍动态设计的方法和步骤。     

INS/GPS姿态组合导航系统卡尔曼滤波器设计

在建立用于卡尔曼滤波的INS和GPS姿态误差模型基础上,给出INS/GPS姿态组合系统的误差方程和量测方程,仿真结果表明：在通常的利用位置和速度作为观测量的INS/GPS组合导航系统中,加入GPS姿态观测量后,INS的位置误差、速度精度及姿态精度都得到较大提高,同时INS元件误差也能得到较好的估计。     

光纤通信与IP传送技术

本文对光纤通信的发展现状作一简要总结与分析,并对未来的可能发展趋势作了展望;结合ATM,SDH,WDM等技术特点讨论了几种IP传送新技术.     

Casualty analysis of large tankers

This article presents detailed results of a comprehensive analysis of recorded accidents of large oil tankers (deadweight greater than 80 000 tonnes) occurring between 1978 and 2003. The analysis encompasses a thorough review of available raw accident data and their postprocessing in a way to produce appropriate statistics useful for the implementation of risk-based assessment methodologies. The processing of the captured data led to the identification of significant qualitative historical trends of tanker accidents and of quantitative characteristics of large tanker accidents, such as overall accident rates per ship-year. Data were also analyzed for all major accident categories separately, taking into account tanker ship size/type, the degree of accident severity, and the oil spill tonne rates per ship-year; this led to the identification of heavily polluted worldwide geographical areas as a result of large tanker accidents.     

促机车修制改革提升铁路运输装备水平

提高运输能力和提升运输装备技术水平是铁路实现和谐发展的出发点和落脚点。作为铁路运输的”火车头”．机务系统肩负着重要的历史使命。从某种意义上看．提高铁路运输能力，除运输组织、调度指挥的因素外．关键就是提高机车的牵引能力和运用效率。我国由于受经济发展水平和铁路基础条件的限制．铁路机务运输装备技术水平不可能在一个很短的历史时期内迅速得到全面提升。     

治理赣江老虎滩泥石流刍议

以赣江老虎滩为例,论述了该滩的泥石流形成机理,对该滩泥石流的治理提出了作者独特的见解。     

Phase change analysis of an underwater glider propelled by the ocean＇s thermal energy

The phase change characteristic of the power source of an underwater glider propelled by the ocean＇s thermal energy is the key factor in glider attitude control. A numerical model has been established based on the enthalpy method to analyze the phase change heat transfer process under convective boundary conditions. Phase change is not an isothermal process, but one that occurs at a range of temperature. The total melting time of the material is very sensitive to the surrounding temperature. When the temperature of the surroundings decreases 8 degrees, the total melting time increases 1.8 times. But variations in surrounding temperature have little effect on the initial temperature of phase change, and the slope of the temperature time history curve remains the same. However, the temperature at which phase change is completed decreases significantly. Our research shows that the phase change process is also affected by container size, boundary conditions, and the power source＇s cross sectional area. Materials stored in 3 cylindrical containers with a diameter of 38ram needed the shortest phase change time. Our conclusions should be helpful in effective design of underwater glider power systems.     

Sulzer RT-flex柴油机WECS-9500控制系统

主要介绍瓦锡公司(RT-Flex系统)电控共轨式柴油机WECS-9500控制系统的技术及其特点,指出目前存在和需要解决的问题。     

水下航行体应用鱼类仿生推进技术的试验研究

水下仿生推进技术将是水下航行体推进技术的革命，这种推进方式是仿生学和水下航行体推进结合的产物，突破了传统的螺旋桨推进理论。初步研究了水下航行体仿生推进技术，以及波状摆动推进中C形起动模式使用不同形状尾鳍的流场结构及动力性能。一般可以将尾鳍形状划分为对称与不对称两大类，选择矩形和三角形作为这两类尾鳍的代表，对其进行了流动显示以及力矩和力测量。研究发现，两种尾鳍模型具有截然不同的流场结构：矩形会在翼尖处产生一个主涡环，而三角形会在尖角上下出现两个涡环。不同的尾迹流场结构有着不同的动力学效果。据此对比分析了不同形状的尾鳍在波状摆动推进中各自的优缺点，在此基础上进一步分析了尾鳍形状在实际工程中的应用。