Based on signal from carbon fiber composite defects such as lamination , hole , looseners in ultrasonic testing , this paper performs wavelet packet transform on the ultrasonic signals to extract statistics of approximation coefficients and detail coefficients that contain a great part of signal energy as sample - features 摘要本文以碳纤维复合材料常见缺陷分层、孔隙、疏松的超声波检测缺陷信号为研究对象,对超声波检测信号进行小波包变换,提取包含信号绝大部分能量的近似系数波形特征及细节系数的统计量作为样本的特征值。
One of the key technologies of deep space communication is channel code . there are differences between deep space communication and the common space communication . because the former one has some characteristics , such as extending information transmission , and seriously reducing signal energy , it is necessary to ensure the information transmission band and the exactness by using the special means 信道编译码是深空通信中的关键技术之一,深空通信与一般的空间通信不同,深空通信具有信息传输时延大、信号能量衰减严重等特点,必须有特殊的手段保证其信息传输的带宽和准确。
To meet the needs of the third mobile communication system for higher speech quality and greater system capacity , the cdma systems employ variable rate speech coding technologies , which select the encode rate dynamically according to the signal energy and background noise . this method insures the speech quality as well as reduces , the average encode rate , so the system capacity is increased 为了满足第三代移动通信系统对高质量语音和大容量系统的需要,在cdma系统中普遍采用了变速率语音编码技术,根据话音的信号能量和背景噪声动态地决定编码速率,这种方法既保证了话音的质量,又降低了平均编码速率,从而增加了系统容量。
Stochastic resonance ( sr ) is different from traditional methods ( such as correlation , equality superposition , filter etc ) in faint signal detection . sr can turn parts of noise energy into signal energy and enhance signal while wiping off noise , so that increasing the signal - to - noise rate ( snr ) 随机共振检测技术与传统的弱信号检测方法(如相关、平均叠加或滤波等)不同,它可以把部分噪声能量转换成信号能量,实现增强信号能量的同时去除噪声,从而提高了信噪比。
According to the time variation and feature extraction difficulty of rotating machinery vibration signals , the rule of choosing wavelet basis function and wavelet denoising soft - thresholding value is proposed after making further research on wavelet transform technique , using for denoising rotating machinery vibration signals the conception of " energy " is proposed , based on the theory that signals energy in all frequency can be affected by faults deeply , to construct feature vectors of rotating machinery vibration signals which can give a convenient disposal way to fault feature extraction and fault intellectual diagnosis 针对旋转机械振动信号的非平稳性及特征难以提取的特点,通过对小波变换技术的进一步研究,提出旋转机械振动信号处理的小波基函数选择原则及小波包消噪的软阀值原则。利用小波包变换对旋转机械振动信号进行消噪处理和特征提取。并以“能量”为元素,构造旋转机械振动信号的特征向量,从而为旋转机械振动信号的故障特征提取以及后续的故障智能诊断提供了一种便捷的处理方法。