Motion response prediction by hybrid panel-stick models for a semi-submersible with bracings

A diffraction-radiation analysis is usually required when the hydrodynamic interactions between structural members occur in short waves. For bracings or small cylindrical members, which play important roles in the vicinity of the natural frequency of a floating platform, special care should be taken into account for the effect of viscous damping. Two hybrid panel-stick models are, therefore, developed, through the combination of the standard diffraction-radiation method and the Morison’s formulae, considering the effect of small members differently. The fluid velocity is obtained directly by the panel model. The viscous fluid force is calculated for individual members by the stick model. A semi-submersible type platform with a number of fine cylindrical structures, which is designed as a floating foundation for multiple wind turbines, is analyzed as a numerical example. The results show that viscous force has significant influence on the hydrodynamic behavior of the floating body and can successfully be considered by the proposed hybrid models.     

Large-eddy simulation of cross-flow around ship sections

The present work is motivated by phenomena occurring in the flow field around ship-like bodies with an incoming lateral flow (cross-flow, 90 ° drift angle). Three-dimensional unsteady flows around different ship sections are investigated by using computational fluid dynamic (CFD) tools with large-eddy simulation (LES) subgrid-scale turbulence model. The simulation results are compared to measurements at several Reynolds numbers in the 90–200,000 range. Focus in our investigation is on the characterization of the motion of vortex structures generated by the separated flow. Another target in the study is to obtain better knowledge of the hydrodynamic forces acting on the sections. Computed pressure and drag coefficients are compared with experimental measurements. The comparison between simulations and measurements shows that an LES model can predict the flow field around ship sections in detail and the hydrodynamic forces acting on the sections.     

燃料电池轿车氢瓶保护系统设计分析研究

相对于传统汽车,燃料电池汽车配有对安全性要求相当高的氢气瓶,必须设计有效的保护系统对其进行约束和保护.文章基于显式有限元理论,按照CMVDR294法规对国内自主开发的某燃料电池轿车进行正面碰撞分析,对比分析两种氢瓶保护系统设计方案的计算结果,为最终的方案确定提供参考依据.     

发动机曲轴轴承损伤原因探析

通过汽车发动机曲轴轴承的损伤形式、损伤原因、载荷状况、润滑条件等的分析,提出减少汽车发动机曲轴轴承的损伤和延长使用寿命的措施。     

串联式燃料电池混合动力汽车零部件选型和匹配优化研究

采用两种优化算法对燃料电池混合动力汽车的两种能量管理策略进行了优化仿真.结果符合实际的设计要求,可以作为零部件选型和匹配的依据.     

轨道横向动力特性振型叠加法分析

本文对包括两根钢轨、轨枕、道床的点支承欧拉梁轨道横向振动力学模型,用振型叠 加法进行了分析,得到了20一500比频率范围内的位移响应.它与轨道实际情况有良 好的一致性。计算结果表明,本方法分析频率范围广,计算量小,是分析软道横向动力 特性的有效方法。      

The stabilization control of underactuated surface vessels

The problem of stabilization control of underactuated surface vessels with two independent control inputs is in vestigated inthis paper. Through transformation, a cascade property of the system is revealed. And the original nonlinear system could be divided into two subsystems: a linear subsystem and a nonlinear subsystem. The stabilization laws are derived for the two subsystems separately. A smooth time - varying feedback stabilization law with exponentially convergence rate is obtained. The proposed stabilization law guarantees all the system states converge to the equilibrium exponentially. The aim of stabilization control of underactuated surface vessels is achieved. At last, the effectiveness of the proposed algorithm is illustrated by simulation tests.     

Reliable routing algorithm in marine ad hoc networks

A routing algorithm called DNH for increasing efficiency of mobile ad hoe network is presented, which is based on a new cflteflon called TSS (Temporarily Steady State), combining with wireless transmission theory that makes networks topology correspondingly stabilization. Also the DNH algorithm has the characteristics of giving up queuing in a node, but selecting another idle node instead of the node for forwarding data packets if the node has a full throughput. Simulation evaluation shows that selecting another node is better than queuing in a full throughout node if some conditions are satisfied, especially during a sea battle, every warship in ad hoe network wants to contest time and increase propagation reliability. The DNH algorithm can help decrease routing time, and raise efficiency of marine ad hoe networks.     

Special requirements for alumina ceramic of ESG electrode bowl

At present ESG (Electrostatic Suspended Gyro) is the most precise inertia element in the world. The electrode bowl, which has direct effect on the precision of ESG, is a key part to ESG. Through the analysis of the function and characteristic of the electrode bowl in hollow rotor ESG and the present situation of new material development in the world, the alumina ceramic is regarded as the best material for the electrode bowl of hollow rotor ESG. By analyzing the present situation of alumina ceramic in the world, main technique requirements have been put forward for the alumina ceramic of ESG electrode bowl which is also fit for solid rotor ESG.     

Image segmentation based on competitive learning

lmage segment is a primat.‘y step in image analysis of unexploded ordnance (UXO) detection by ground penetrating radar (GPR) sensor which is accompanied with a lot of noises and other elements that affect the recognition of real target size. In this paper we bring forward a new theory, that is, we look the weight sets as target vector sets which is the new cues in semi-automatic segmentation to form the final image segmentation. The experiment results show that the measure size of target with our method is much smaller than the size with other methods and close to the real size of target.