局部保形映射和AdaBoost方法在滚动轴承故障诊断中的应用

针对滚动轴承故障振动信号的随机性和非平稳性,提出基于局部保形投影(LPP)特征提取和自适应Boosting算法的滚动轴承故障诊断方法。首先对信号构建原始样本数据集合,提取时域、频域及时频域的相关特征,将该特征作为LPP的输入样本,得到维数降低的新数据集合并能尽可能保持原始局部流形结构。将此降维特征向量作为Adaboost输入,建立故障模型,用以识别滚动轴承故障类型。分析滚动轴承正常状态、内圈故障、外圈故障及滚动体故障特性。通过对比试验表明,基于LPP与Adaboost诊断方法识别率较高,可准确有效地对滚动轴承状态和故障进行分类。     

一种模式匹配快速算法

在定义模式串的特征值之后,给出了判断两等长串匹配的必要条件以及两相邻子串的特征值之间的递推关系.在此基础上,提供一种模式匹配快速算法,其时间复杂度可达O(n).该算法彻底避免了回溯现象,执行效率要比RK算法高.     

基于噪声子空间特征值重构的DOA估计算法

该文针对非等功率信号波达方向(DOA)估计问题,提出一种基于噪声子空间特征值重构(Eigenvalue Reconstruction of Noise Subspace, ERNS)的超分辨算法。算法对接收信号自相关矩阵进行特征值分解,通过重构噪声空间特征值以及引入虚拟信源来构造新的接收信号自相关矩阵,对该矩阵进行特征值分解得到新的噪声空间特征值。当虚拟信源与实际信源入射方向相同时,新噪声空间特征值与重构后噪声空间特征值保持不变,利用这一特性来估计信源入射方向。该文给出算法的原理及实现步骤,并通过仿真进行原理验证与性能分析,仿真结果表明与其他子空间算法和MUSIC 算法相比,ERNS算法能够提高弱信号估计成功的概率。     

一种新的基于特征向量合并的超宽带系统分集方案

针对超宽带系统在室内环境中面临严重的多径衰落问题,通常在接收端需使用RAKE接收机来收集多径能量改善性能。该文提出了一种新的分集方案,在发送端信号进行预处理,在接收端使用RAKE合并收集多径能量,同时给出了基于信道矩阵特征值估计的最佳合并权重和时延参数估计算法。理论分析和仿真结果都表明,该算法得到的输出信噪比总是大于传统的RAKE接收机输出信噪比。     

自适应拟牛顿子空间跟踪算法分析

该文对自适应拟牛顿子空间跟踪算法进行了详细分析,证明了其本质上类似于幂法,但一般来说暂态性能劣于幂法。给出了在相邻数据之间只做一次迭代时特征值、特征向量估计的误差,计算机仿真结果证明了该文分析的正确性。     

特征值平移超分辨率算法

本文分析了逆幂迭代算法的收敛速度。为了克服逆幂迭代算法矩阵求逆的过程,提出了特征值平移幂迭代算法,并分析了它的收敛速度,给出了计算机模拟结果。     

泛函分析对线性代数的点滴应用

本文利用泛函分析方法,论述了线性方程组理论与二次型,为工科线性代数教材的改革,提供了一个方案。     

Multiparameter singular perturbation problems: Iterative expansions and asymptotic stability

Recursive formulae are derived which yield asymptotic expansions for the eigenvalues of multiparameter singular perturbation problems. These formulae follow readily from an exact expression for the eigenvalues which involves an implicit matrix function. The implicit function satisfies an algebraic matrix Riccati equation reminiscent of a similar equation of the single parameter theory. The results also explicate the ‘block D-stability’ criterion for asymptotic stability previously introduced by Khalil and Kokotovic.     

NETWORK ANALYSIS OF EIGENVALUE PROBLEM FOR MULTILAYER DIELECTRIC WAVEGUIDE CONSISTING OF ARBITRARY NUMBER OF LAYERS

In this paper,the eigenvalue problem of a multilayer dielectric waveguide consisting of arbitrarynumber of layers is solved by the microwave network method.A general program with the function of com-puter graphics has been developed for analyzing the dispersion characteristics and the electromagnetic fielddistributions of an N layer dielectric waveguide.As an example of practical applications,the procedure ofmode conversion and mode separation in dielectric branching waveguides is vividly demonstrated throughanalyzing the field distributions of asymmetric multilayer dielectric structures and the general rules of modeconversion are discussed.     

Interfacial crack tip field in anisotropic/isotropic bimaterials

The co-cured joint is more efficient than the adhesively bonded joint for composite structures because of its several advantages. However, failure analysis of the co-cured joint has just a little been reported since the co-cured joining method was introduced. Observing based on the experimental results, failure starts at the interface corner of the co-cured joint. Therefore, it is important to consider stress intensities at the interface corner of the co-cured joint.

In this paper, the eigenvalue problem was used to determine asymptotic stress and displacement fields near the interface corner between composite and steel adherends. For obtaining stress intensities at the interface corner a path independent conservative line integral was used.