高速公路长大纵坡沥青路面施工技术研究

在山区修建高速公路,将面临较平原区更严格的要求。结合当前山区高速公路施工的现状,就山区高速公路长大纵坡路段的施工技术进行了探讨。     

水下爆炸作用下箱形梁模型响应试验研究

对模拟水面舰船结构的箱形梁模型在水下爆炸作用下的响应进行试验,借助高速摄像机观测气泡脉动过程和结构响应过程,发现箱形梁结构在水下爆炸作用下的响应可以分为三个阶段.不同的爆点位置,气泡脉动能够激起不同振动形式的鞭状响应运动.     

Numerical simulations of fatigue crack initiation and propagation based on re-tensile plastic zone generating load criterion for in-plane gusset welded joints

Many accidents are caused by fatigue in welded built-up steel structures, and so it is important to estimate the fatigue lives of such structures quantitatively for safety reasons. By assuming that fatigue cracks cannot grow without an accumulation of alternating tensile/compressional plastic strain, one of the authors identified an improved effective stress intensity factor range ΔK _RPG based on the re-tensile plastic zone generating (RPG) load, which represents the driving force for fatigue cracks, and suggested that ΔK _RPG should be used as the parameter to describe fatigue crack growth behavior. The “FLARP” numerical simulation code in which ΔK _RPG is implemented as the fatigue crack growth parameter, was developed in order to predict fatigue crack initiation and propagation behavior. In this paper, it is demonstrated that FLARP gives accurate estimates for fatigue life by comparing the estimated fatigue crack growth curves and S–N curves with the experimental results for in-plane gusset welded joints, which are used in many welded steel structures. Moreover, the effect of induced bending moment due to the linear misalignment in the out of plane direction on the fatigue strength of in-plane gusset welded joints is investigated through numerical simulations.     

Workspace analysis to generate a collision-free torch path for a ship welding robot

We propose a method to determine the optimal initial location and to generate torch paths for a ship welding robot with 6 degrees of freedom (DOF). The optimal initial location is determined using an objective function, which is set up by combining constraints on the torch posture, manipulability, and the range of each joint angle to avoid collisions. A genetic algorithm (GA) is used to optimize the objective function because it does not require additional derivatives. After the initial location is determined, torch paths are generated by interpolating the starting point, endpoints and torch postures using inverse kinematics. Our method can be applied to automate the welding job for each block during ship building, irrespective of the shape of the robots, by changing the objective function.     

港口工程建设对湿地生态承载力的影响

采用以生态适宜性分析为基础的区域生态承载力评价,在地理信息技术的支持下定量获取各评价指标的信息,研究港口工程建设对湿地环境承载力的影响。研究表明,该方法是生态承载力评价方法的有效补充,弥补了生态承载力评价的不足。     

船体外加电流阴极保护系统设计中问题的探讨

船体外加电流阴极保护系统国家标准(GB/T3108-1999)中关于设计电流密度的选取并由此计算船体的保护电流总量.由于船舶的结构布局等因素,往往使电极不能按理想的设计方案在船体E进行布置与安装,致使有些部位电流不足,导致部分船体得不到充分的保护.经实船实验证明,在船体设计安装外加电流阴极保护系统的同时,应在艉部等部位相应没计安装部分牺牲阳极以弥补辅助阳极电流之不足.     

基于天线选择的准正交空时码的自适应设计

为充分利用信道信息(Channel State Information,CSI)来改善准正交空时码(Quasi Orthogonal Space-Time Block Code,QSTBC)系统的性能,提出基于天线选择的QSTBC系统自适应设计方案,对QSTBC的编码结构添加自适应系数,使信道矩阵正交化,消除码间串扰.推导了系统的瞬时输出信噪比,以此作为天线选择准则.仿真结果表明,相对于未经过自适应编码设计的天线选择QSTBC系统,新系统的误码率性能有明显改善.     

气泡艉流场特征及其研究综述

船舶气泡艉流场特征研究蕴含着重要的军事和民用价值.从气泡艉流场的几何特征、声光物理特征以及尾流中气泡的数密度、尺度分布特征等方面,总结了当前国内外关于船舶气泡艉流场特征研究的主要成果,进而通过分析它们在遥感探测、制导等领域的应用情况,进一步阐明了船舶气泡艉流场特征研究的重要性,并提出了应加强对气泡艉流场的探测技术和抑制消除技术研究的发展建议.     

T型焊接接头疲劳性能研究

T型焊接接头在船舶与海洋工程结构中广泛应用,研究T型焊接接头的疲劳性能对于提高船舶与海洋工程结构的强度具有重要意义.针对工程中常用的四种焊趾形式的T型焊接接头,利用有限元计算和模型试验两种方法对其疲劳性能进行了研究.结果表明,平面型焊趾是较优的T型接头焊趾形式.     

基于LM算法的组合导航系统的故障诊断

LM (Levenberg-Marquardt)算法是梯度下降法与高斯-牛顿法的结合,在训练次数与精度上明显优于标准的BP算法.介绍了BP神经网络,采用LM算法对标准BP算法进行改进,并应用于船舶组合导航系统的故障诊断.仿真结果表明,LM算法可有效地提高学习速度,缩短训练时间,诊断效果好.