双向受载裂纹板的碳纤维复合材料补片的胶接修补分析

建立了碳纤维复合材料补片胶接修补双向受载裂纹板的3D有限元模型,分析了补片的单面胶接修补效果,探讨了补片材料、铺层顺序、补片长度及载荷比等对裂纹应力强度因子的影响规律。结果表明:复合材料补片的存在使裂纹板垂直裂纹方向载荷和平行裂纹板方向载荷发生耦合作用,从而影响补片修补效果。平行裂纹方向的压应力可降低裂纹尖端的应力集中因子,而拉应力可提高裂纹尖端的应力集中因子。     

火灾现场勘验中危险因素探究

火灾现场勘验中存在多种危险因素,严重威胁着勘验人员的人身安全。对倒塌、烟气和触电等火灾现场中几种常见的危险因素,在深入分析其形成机理和危害特征的基础上,有针对性地提出了各种危险因素的预防措施。     

铝合金板材相对均匀性的声-超声评价研究

基于Ritec-SNAP系统建立了声-超声技术实验系统,阐述了该实验系统的原理及应力波因子的定义,分析了在声-超声技术评价过程中用声信号的幅频特性及应力波因子表征材料相对均匀性的可行性。利用建立起来的实验系统,对铝板的相对均匀性进行了声-超声评价的实验研究。实验结果表明,用应力波因子评价铝合金板材的相对均匀性具有可行性。     

基于神经网络的舰船目标识别研究

为了实现对水下目标的识别,在现有特征提取方法的基础上,提出了一种从DEMON谱线谱和DEMON谱连续谱提取的特征方法,并设计了一个基于BP神经网络和多神经网络分类识别器的舰船目标识别系统。通过对实际舰船噪声目标进行识别,识别效果比较满意。这对舰船目标识别的发展具有一定的参考价值。     

Data‐driven variation source identification for manufacturing process using the eigenspace comparison method

Variation reduction of manufacturing processes is an essential objective of process quality improvement. It is highly desirable to develop a methodology of variation source identification that helps quickly identify the variation sources, hence leading to quality improvement and cost reduction in manufacturing systems. This paper presents a variation source identification method based on the analysis of the covariance matrix of process quality measurements. The identification procedure utilizes the fact that the eigenspace of the quality measurement covariance matrix can be decomposed into a subspace due to variation sources and a subspace purely due to system noise. The former subspaces for different samples will be the same if the same variation sources dominate. A testing procedure is presented, which can determine the closeness of the subspaces under sampling uncertainty. A case study is conducted to illustrate the effectiveness of this methodology. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2006.     

基于ICA的多姿态人脸表示

将独立成分分析(ICA)应用于多姿态人脸识别。对比分析了ICA和主成分分析(PCA)两种人脸识别方法的差异,并重点研究了多姿态人脸的独立成分(IC)表示。在基于权向量幅值的方法基础上,引入了基于比例因子的IC核选择的新方法。实验表明,新方法有利于提高识别的准确率和识别的效率。     

基于改进差分进化算法的内弹道参数优化

火炮内弹道参数直接影响其计算结果,内弹道参数优化设计是内弹道分析计算的重要环节。基于经典内弹道计算模型,以火药内弹道计算中最为敏感的燃速指数及其燃速系数为设计参量,以最大膛压及弹丸初速的计算值与测试值一致性为目标,对差分进化算法群体的初始化、变异因子及变异模式进行了改进,对某型火炮的内弹道参数进行了优化计算。优化设计结果表明改进后的差分进化算法满足内弹道设计工程实践要求,为内弹道参数优化设计提供了一种有效的算法。     

低谐波注入的大功率三相整流电路

给出了三相桥式PWM整流电路主电路 ,分析了其实现单位输入功率因数和不对电网注入谐波的工作原理。在此基础上 ,提出了一种新型大功率三相PWM整流电路系统结构 ,其主电路采用了双模块并联的方式。与此同时 ,还探讨了其控制方法和相应的控制系统以及IGBT的驱动保护电路等。最后对所研制的容量为 10 0kW的实验样机进行了实验研究 ,结果证实了它的良好性能     

Efficient budget allocation strategies for elementary effects method in stochastic simulation

This paper focuses on extending the Morris' elementary effects method (MM) for sensitivity analysis/factor screening originated in the context of deterministic computer experiments to the stochastic simulation setting. Given a fixed simulation budget to expend, the main objective is to provide efficient and accurate estimates of main and interaction (or nonlinear) effects coined by the standard MM for characterizing the importance of each factor, despite the impact of simulation errors. Taking into account both the factor/input sampling uncertainty rooted in MM and the random errors inherent in a stochastic simulation, we develop efficient budget allocation strategies for implementing MM in this new context. Under each strategy proposed, we derive its corresponding optimal budget partition and optimal budget allocation rules. Numerical results corroborate the practical effectiveness of the proposed budget allocation strategies.     

Rayleigh分布环境因子的经验Bayes估计及仿真

讨论了Rayleigh分布环境因子的定义和估计问题。基于逐次截尾模型,在LINEX损失函数下,给出环境因子的经验Bayes估计。最后利用Monte-Carlo方法对经验Bayes估计和极大似然估计进行了分析比较。结果表明,经验Bayes估计优于极大似然估计。