共查询到20条相似文献,搜索用时 31 毫秒
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两类小波函数的性质和作用 总被引:1,自引:0,他引:1
本文简要地介绍了信号的时-频两维分析的目的、意义,分析对比了小波分析和短时富里叶分析、Wigner 谱分析的异同及主要优点。简述了离散小波变换、离散二进小波变换和离散二进正交小波变换的数字实现方法。文中详细论述了反对称小波和对称小波两类不同小波函数的性质及对小波变换的影响,并分析了它们在异常信号检测中的不同作用。最后介绍了离散二进小波变换滤波器的设计方法,给出了小波互补滤波器的幅频特性公式,并列举了两个滤波器设计实例。 相似文献
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小波函数性质及其对小波分析结果的影响 总被引:14,自引:0,他引:14
分析了小波变换在图像处理、语音处理领域和设备故障诊断领域的应用特点 ,指出了两者的不同之处。并进一步讨论了小波函数的性质及其对小波变换结果的影响 ,指出在用小波变换进行诊断信号分析和特征提取时 ,小波函数的影响是不容忽视的 相似文献
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一种无频带错位的小波包算法 总被引:5,自引:0,他引:5
研究了数字信号处理中的小波分析方法。基于多尺度分析的思想,提出了信号的小波分解及重构新算法和小波包算法。由于算法中采用了频移技术,在小波分解中避免了频率的折叠现象,同时在小波包算法中也解决了频带的错位问题。算法在工程中更具实用价值 相似文献
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针对地铁低速行驶时的轨道振动信号,分析小波去噪参数的选取对去噪效果的影响。以北京某地铁站附近的隧道断面的轨道铅垂向振动加速度信号为例,对轨道振动信号进行小波分解、阈值去噪和重构。以信噪比作为去噪质量评价指标,采用Kruskal-Wallis非参数检验方法分析小波系、小波阶数、小波分解层数和阈值的选取对去噪效果的影响。基于信噪比最大化原则,确定地铁低速行驶时轨道振动信号的最优小波去噪参数。结果表明:显著性水平0.05下,小波系、小波阶数的选取对地铁轨道振动信号小波去噪效果没有显著影响,不同的小波分解层数、阈值对地铁轨道振动信号小波去噪效果的影响不全相同;以SymletsA小波系的4阶小波为去噪小波基,经过3层小波分解,基于无偏似然估计阈值和软阈值函数进行小波去噪后的信号获得最大的信噪比,去噪后的振动信号保留了原始信号的峰值特征,同时信号曲线的光滑性有了显著改善。 相似文献
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为了进一步推动小波理论的应用,近些年来在离散数据环境中开始了对框架小波(也称为framelets)和框架小波包的研究工作.在$\ell^2(Z)$中构造$J$-级框架小波包的方法已经由鲁大勇和易华给出.然而,如何去使用这类小波包的细节却没有给出.为了进一步丰富由鲁和易提出的$J$-级框架小波包理论体系,该文给出了快速的分解和重构算法,运用该算法可以建立不同尺度层之间小波框架系数的关系.另外,为了方便该类框架小波包的应用,文中给出了$\ell^2(Z)$中一些实用框架小波包的具体数据.文中最后通过一个数值实验展示了该类框架小波包的完美重构性质. 相似文献
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Analytic Parameter Design 总被引:1,自引:0,他引:1
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Robertt A. F. Valente Ant��nio Andrade-Campos Jos�� F. Carvalho Paulo S. Cruz 《Optimization and Engineering》2011,12(1-2):129-152
Simulation of metal forming processes using the Finite Element Method (FEM) is a well established procedure, being nowadays possible to develop alternative approaches, such as inverse methodologies, in solving complex problems. In the present paper, two types of inverse approaches will be discussed, namely the parameter identification and the shape optimization problems. The aim of the former is to evaluate the input parameters for material constitutive models that would lead to the most accurate set of results respecting physical experiments. The second category involves determining the initial geometry of a given specimen leading to a desired final geometry after the forming process. The purpose of the present work is then to formulate these inverse problems as optimization problems, introducing a straightforward methodology of process optimization in engineering applications such as metal forming and structural analysis. To reach this goal, an integrated optimization approach, using a finite element code together with a numerical optimization program, was employed. A gradient-based optimization method, as a combination of the steepest-descent method and the Levenberg-Marquardt techniques, was used. Numerical applications in the parameter optimization category include, namely, the characterization of a non-linear elasto-plastic hardening model and the determination of the parameters for a nonlinear hyperelastic model. It is also discussed the simultaneous identification of both constitutive material model parameters and the friction coefficient parameters. From the point of view of shape optimization problems, the determination of the initial geometry of a specimen in a upsetting billing problem as well as a methodology for defining the most suited blank shape to be formed in a square cup, are discussed. The final results for both categories show that this kind of algorithms have great potential for future developments in more demanding and realistic benchmarks. It is also worth noting that the presented integrated methodology can be easily applied to a first introduction of optimization techniques and numerical simulation to undergraduate courses in engineering. 相似文献
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Although the regularization increased the popularity of parameter identification due to its capability of deriving a stable solution, the significant problem is that the solution depends upon the regularization parameters chosen. This paper presents a technique for deriving solutions without the use of the parameters and, further, an optimization method, which can work efficiently for problems of concern. Numerical examples show that the technique can efficiently search for appropriate solutions. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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基于ARMAX模型及MA参数修正的框架结构动态参数识别 总被引:3,自引:0,他引:3
结构动态参数识别和特征提取是工程,特别是重大工程质量和寿命全过程监控的核心研究内容,本文用ARMAX模型对结构的输出数据建模,然后识别结构的步和阻尼,在识别过程中为了消除相位多值性而带来的ARMAX模型对结构的输出建模,然后识别结构的频率和阻尼进行识别,最后对此方法在十六层框架结构模型上进行了试验验证,计算结果表明,该方法获得较好的效果。 相似文献
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《技术计量学》2013,55(4):284-292
When there exists strong noise factors in the process, robust parameter design alone may not be effective, and a control strategy can be used to compensate for the effect of noise. In this article a parameter design methodology in the presence of a feed-forward control is developed. In particular, performance measures for evaluating control factor settings in measurement systems, simple response systems, and multiple target systems are developed. Strategies for the design and analysis of experiments are discussed. The approach is illustrated using an example on gold plating. 相似文献