非线性结构系统可靠性理论及其模拟算法

系统阐述了非线性结构系统可靠性理论的主体框架和模拟算法,重点分析了全局分枝-约界法、快速概率积分法、响应面法、随机有限元法和Monte Carlo模拟法的主要优缺点,及其对强非线性问题和存在失效演化历程的复杂结构系统可靠性分析和评估问题的适应能力.在此基础上,对当前研究工作中存在的一些共同性问题进行了剖析,对将智能化方法引入非线性结构系统可靠性工程领域的可行性和具体实现途径进行了阐述.     

Performance analysis of neural networks for classification of medical images with wavelets as a feature extractor

In this article, we analyze the performance of artificial neural network, in classification of medical images using wavelets as feature extractor. This work classifies the mammographic image, MRI images, CT images, and ultrasound images as either normal or abnormal. We have tested the proposed approach using 50 mammogram images (13 normal and 37 abnormal), 24 MRI brain images (9 normal and 15 abnormal), 33 CT images (11 normal and 22 abnormal), and 20 ultrasound images (6 normal and 14 abnormal). Four kind of neural network models such as BPN (Back Propagation Network), Hopfield, RBF (Radial Basis Function), and PNN (Probabilistic neural network) were chosen for study. To improve diagnostic accuracy, the feature extracted using wavelets such as Harr, Daubechies (db2, db4, and db8), Biorthogonal and Coiflet wavelets are given as input to the neural network models. Good classification percentage of 96% was achieved using the RBF when Daubechies (db4) wavelet based feature extraction was used. We observed that the classification rate is almost high under the RBF neural network for all the dataset considered. © 2015 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 25, 33–40, 2015     

Evaluation of orthogonal and biorthogonal wavelets for video steganography

ABSTRACT

In recent years, information security over the internet has gained enormous immersion due to a technological escalation in communication via digital media. Nowadays, videos are the most common form of media over the internet, and they have gained the attention of video steganography research community for the security of the communication. This paper implemented video steganography using a widely-known transform technique, discrete wavelet transform (DWT) which consists of different orthogonal and biorthogonal filters used for the decomposition of a frame/image. The aim of this paper is to provide a comparative evaluation for orthogonal and biorthogonal DWT filters with different matrices such as MSE, PSNR. The performance of the different filters has been evaluated both quantitatively and qualitatively to investigate the best among them. Also, the best of orthogonal and biorthogonal filters have been further evaluated with other metrics such as SSIM, BER and histogram analysis. Further, the embedding algorithm has been compared with the existing video steganography techniques. The experimental results illustrate that bior 6.8 (biorthogonal filter) outperforms the other orthogonal and biorthogonal filters in terms of visual distortion.     

一种基于网络的设备在线故障诊断系统研究

针对生产过程中设备参数时变、非稳态特点,提出了基于网络的故障诊断系统结构,用于设备的远程监测与故障诊断。设计了TE过程与模拟电路故障实验,结果表明应用该结构对设备进行监控可以提高设备故障诊断的准确率,降低系统维修成本,提高生产效率。针对快速性问题,采用提升小波与递推最小二乘支持向量机相混合的快速故障诊断方法;通过快速算法训练最小二乘支持向量机分类器,节省了存储空间和运算时间,增加了诊断模型的适应性。根据设计要求设计了工业故障诊断研究实验平台,并在此平台上对提出的方法进行了验证。该应用平台采用C/S,B/S的混合模式,集成Matlab,力控等专业软件系统,并采用OPC,ODBC,数据库技术实现了故障诊断系统的基本功能。     

Daubechies条件小波混合有限元法在梁计算中的应用

常规的Daubechies小波有限元法是以挠度为基本未知量的单变量有限元法,其弯矩函数需要通过挠度函数的二阶求导间接求解,故弯矩的计算精度一般比挠度低。此外,目前常用的Daubechies小波有限元法需要借助于转换矩阵引入位移边界条件,大大影响了计算精度。结合广义变分原理,将边界条件作为附加条件构造修正泛函,以该修正泛...     

基于非下采样三通道不可分对称小波的多光谱图像融合

针对IHS变换融合方法不能保持好的光谱信息,张量积小波变换融合方法生成的融合结果图像空间分辨率偏低、且易产生方块效应等不足.提出了一种基于三通道不可分对称小波的多光谱图像融合方法.利用矩阵扩充的方法,给出了三通道不可分对称小波滤波器组的构造方法,用所构造的不可分小波滤波器组分别对多光谱图像的亮度分量和全色图像作非下采样...     

基于小波收缩的噪声图像恢复新型算法实现与验证

小波变换技术是近20年发展起来的新的信号处理技术,但对小波的研究由来已久。随着小波理论的不断完善,它以自身良好的时频特性在图像去噪领域受到越来越多的关注。图像去噪是信号处理中的一个经典问题,传统的去噪方法多采用平均或线性方法进行,但是其去噪效果不好,本文基于此目的,采用了连续两次半软阈值去噪的方法,来去除含噪图像的噪声,最后通过MATLAB软件仿真此方法的去噪效果,并与其它去噪方法进行比较,得出本文提出的方法去噪效果更优越。     

Damage identification in composite plates using two-dimensional B-spline wavelets

In this paper the construction of general order two-dimensional B-spline wavelets was presented and applied for damage identification in polymeric composite plates. At the very beginning the algorithm of one- and two-dimensional discrete wavelet transform and formulation of one- and two-dimensional B-spline wavelets with examples were presented. The fully clamped square layered composite plate was modeled using finite element-based software. Estimated natural modes of vibration with various damage configurations were analyzed using the two-dimensional sixth-order B-spline wavelet, and the method of damage identification was presented. The effective damage identification is based on the evaluation of the singularities in horizontal, vertical and diagonal details coefficients. Results obtained based on the numerical data were verified experimentally. Research results show the effectiveness of B-spline wavelets in application to the diagnostics and structural health monitoring.     

基于Daubechies小波和工件面形误差的机床导轨误差相关性分析

提出一种基于Daubechies小波和车削面形误差的导轨误差辨识的新方法,根据检测结果的特征分析结果,识别出引起此特征的机床误差源。为了了解小波分析的误差,对工件面形检测信号用不同紧支集的Daubechies小波族在1～9尺度下进行分解和重构,对比重构信号和原始信号发现,紧支集为[0,1]的Db1小波用于工件面形信号分解时误差最小。误差源对加工结果影响的仿真结果与实际加工工件的面形检测结果对比,分离出的表面形貌的单尺度上的信息与原信息除了会有相位时移外,还有很多特征相关性。利用小波的变焦特性,采用特征相关性分析方法,从检测结果中确定出引起加工结果的机床误差源。     

基于扩散小波的社会网络多尺度分析简

针对社会网络中的同质性关系提出一个基于扩散小波的多尺度分析框架,通过局部相似性度量构造扩散算子,在统一的框架下对社会网络中的结构、内容、用户行为等进行多尺度分析。在合成和真实网络数据上进行实验,与典型算法的对比表明,本算法在无参数的条件下快速收敛并得到更好的结果。