活塞蓄能器式管路阻尼器的理论与试验研究

It can be beneficial to reduce vibrations in shipboard piping, so the authors designed a new kind of piping damper with a plunger-type accumulator. Special requirements for the piping damper included low impact displacement, low speed, as well as an appropriate locking speed. Inside the damper, a plunger-type accumulator was installed and on the outside of the piston rod, a tube with exposed corrugations was added. Between the piston and the cylinder, a clearance seal was added. Using mathematical modeling, the effects of the dynamic performance of the damper’s impact displacement on vibrations were observed. Changes to the clearance between the piston and the cylinder, the stiffness of the spring in the accumulator, the throttle valve size, and locking speed resistance of the damper were respectively simulated and studied. Based on the results of the simulation, dampers with optimal parameters were developed and tested with different accumulator spring stiffnesses and different throttles. The simulation and experimental results showed that parameters such as seal clearance between piston and cylinder, accumulator spring stiffness and throttle parameters have significant effects on the damper’s impact displacement, low speed resistance and locking speed.     

水下潜器改进S面控制及控制系统仿真

S surface controllers have been proven to provide effective motion control for an autonomous underwater vehicle (AUV). However, it is difficult to adjust their control parameters manually. Choosing the optimum parameters for the controller of a particular AUV is a significant challenge. To automate the process, a modified particle swarm optimization (MPSO) algorithm was proposed. It was based on immune theory, and used a nonlinear regression strategy for inertia weight to optimize AUV control parameters. A semi-physical simulation system for the AUV was developed as a platform to verify the proposed control method, and its structure was considered. The simulation results indicated that the semi-physical simulation platform was helpful, the optimization algorithm has good local and global searching abilities, and the method can be reliably used for an AUV.     

蒙皮效应对轻型门式刚架性能影响的分析

通过ANSYS软件,对轻型门式刚架结构进行不考虑蒙皮效应和考虑蒙皮效应两种情况的计算,计算可得出刚架的最大应力、刚架侧移,分析比较两种情况的差异,量化蒙皮效应对轻型门式刚架结构的影响,为蒙皮效应在轻钢结构中的应用提供参考。     

老码头改造中新老结构结合处理的实践

以镇江港某老码头改造的成功案例为背景,通过桩帽、轨道梁节点、新增污水池及端梁支座等4个典型结合部位的设计和施工实践,总结了在处理新老结构结合问题时常见的技术难点,并详细介绍了相应的处理措施以及一些新技术、新工艺的应用.     

Steady streaming of viscous surface layer in waves

An investigation of the drift velocity induced by water waves of a contminated surface layer is carried out. The theoretical analysis is based on a thin boundary layer on the free surface. The results of the analysis reveal that the drift velocity of a viscous layer on the water surface is 7/4 times the Stokes prediction ofc(ak) ² wherec is the wave celerity andak the wave slope. The present experimental investigation confirms the validity of the theoretical prediction for the drift velocity for a lightly contaminated surface layer; however, for a heavily contaminated surface layer, the experimental results exceed the theoretical prediction. An investigation for a heavily contaminated layer is carried out assuming an inextensible surface layer. Thus, in the experiment, vinyl sheets are used to substitute the contaminated layers. By balancing the wave-induced mean thrust force with the mean drag force, the drift velocity is obtained and compared with the experimental results. Based on the theoretical and experimental analyses, formulae for predicting the drift velocities for laminar and turbulent flow conditions are proposed.     

Multiple USV cooperative algorithm method for hunting intelligent escaped targets北大核心CSCD

[目的]针对无人艇协同围捕过程中逃跑目标具备智能性,现有无人艇策略难以围捕成功的问题,提出一种基于双层切换策略的多无人艇协同围捕算法。[方法]第1层围捕策略采用改进势点法,以无人艇与势点的总直线距离最小为优化目标,采用匈牙利算法为无人艇动态分配势点,并采用人工势场法实现无人艇的协同避碰;第2层围捕策略利用了阿波罗尼奥斯圆的性质,在两艘无人艇前往逃跑目标的目标点进行拦截,剩余无人艇运动方向保持与逃跑目标相同,以不断缩紧包围区域;为应对逃跑目标不同的逃跑方式,第1层围捕策略和第2层围捕策略可互相转化。[结果]仿真实验表明,该算法相较于顺序分配势点算法和极角分配势点算法,围捕时间更少或持平,证明了该算法的有效性和先进性。[结论]该多无人艇协同双层围捕算法,对具备典型智能性的逃跑目标具有围捕效果。     

水面舰船声学特性的类比及其评价

传统的水面舰船声学设计评价方法在应用上存在着局限性，为进一步发展和完善，通过对总声级声学特性类比、声频范围和超声频段声学特性、实船检测声学特点和实船声隐身战术技术要求制订等进行广泛论述与类比探讨的基础上，指出了现有方法在总声级确定、声学特性预报和实船检测等方面的不足，提出了较为合理的水面舰船声学特性的类比及其评价方法，即以特定频段的线谱分析来评定其声学性能。     

基于NURBS的船体曲面切割和排板技术的探讨

船体曲线和曲面的分割与曲面排板是船舶计算机辅助设计与制造中的一项关键技术。本文使用一种新的算法实现了船体NURBS曲面的切割以及外板曲面的生成,并对某集装箱船的船体曲面和船体某外板曲面进行了计算,验证了该算法的正确性和可行性。     

水面舰艇船体防腐和阴极保护的优化设计方法

海水及海洋大气对船体金属的腐蚀是困扰舰船的一大难题，现代水面舰船防腐蚀设计的重要性日趋明显。介绍国内外水面舰船防腐蚀设计的现状、现代水面舰船防腐蚀和阴极保护优化设计的方法、耐腐蚀材料的选用和应注意的事项。阐述目前国内现代水面舰船防腐蚀存在的主要问题和今后的发展趋势。     

斜拱结构的强度及经济性探讨

探讨了竖直拱两种衍生形式——斜拱和出平面有约束斜梁的强度及经济性问题。通过斜拱平面内和平面外内力的比较,可以得出当跨度较大时,不宜采用斜拱面结构;通过竖直拱和斜拱在不同跨度下的应力比较,可以充分肯定竖直拱的经济性;通过斜拱在不同倾斜角下应力的比较,可以得出当角从45°增大到55°就可以大大减小斜拱出平面的内力。竖直拱的另一种衍生结构——出平面有约束斜梁,通过增加斜拱出平面方向的位移约束可以大大改善斜拱的内力,同时可以满足经济性的要求。最后还讨论了斜拱的曲线形状对结构内力的影响。