小水线面双体船兴波阻力特性研究

介绍了基于米切尔Michell瘦船理论的一种小水线面双体船SWATH兴波阻力计算基本原理．运用敞篷函数对船体表面及流场进行了线性近似,建立了数值计算模型,对一类直／斜支柱SWATH兴波阻力进行计算,重点分析了支柱间距、倾角变化对兴波阻力的影响,并将计算结果与实验测试进行对比,二者基本吻合,证明该方法用于计算SWATH的兴波阻力是可行和有效的．     

Numerical simulation to reliability analysis of fault-tolerant repairable system

In the traditional method for the reliability analysis of fault-tolerant system, the system structure is described by means of binary decision diagram (BDD) and Markov process, and then the reliability indexes are calculated. However, as the size of system augments, the size of state space will increase exponentially. Additionally, Markov approach requires that the failure and repair time of the components obey an exponential distribution. In this study, by combining dynamic fault tree (DFT) and numerical simulation based on the minimal sequence cut set (MSCS), a new method to evaluate reliability of fault-tolerant system with repairable components is proposed. The method presented does not depend on Markov model, so that it can effectively solve the problem of the state-space combination explosion. Moreover, it is suitable for systems whose failure and repair time obey an arbitrary distribution. Therefore, our method is more flexible than the traditional method. At last, an example is given to verify the method.     

冲击荷载进行桥梁模态试验的研究

桥梁模态中多通过天然脉动作为激励力,但是很多情况下由于脉动信号的不可控制性而导致试验结果较差,而将力锤的脉冲激励应用到实际桥梁测试中可得到理想的试验结果。分析了不同试验方法在桥梁中使用的特点,对不同激励方法得到的试验效果进行比较,指出在不同情况下使用不同试验方法的效果和限制。介绍了力锤具有能量集中的优点,且其频率范围符合桥梁的特性。最后通过实例介绍力锤激励的方法,并通过试验得到较好的桥梁竖向动力特性。