Fractional S transform-Part 1:Theory

The S transform, which is a time-frequency representation known for its local spectral phase properties in signal processing, uniquely combines elements of wavelet transforms and the short-time Fourier transform （STFT）. The fractional Fourier transform is a tool for non-stationary signal analysis. In this paper, we define the concept of the fractional S transform （FRST） of a signal, based on the idea of the fractional Fourier transform （FRFT） and S transform （ST）, extend the S transform to the time-fractional frequency domain from the time- frequency domain to obtain the inverse transform, and study the FRST mathematical properties. The FRST, which has the advantages of FRFT and ST, can enhance the ST flexibility to process signals. Compared to the S transform, the FRST can effectively improve the signal time- frequency resolution capacity. Simulation results show that the proposed method is effective.

High-frequency compensation for seismic data based on adaptive generalized S transform

The low-pass fi ltering eff ect of the Earth results in the absorption and attenuation of the high-frequency components of seismic signals by the stratum during propagation.Hence,seismic data have low resolution.Considering the limitations of traditional high-frequency compensation methods,this paper presents a new method based on adaptive generalized S transform.This method is based on the study of frequency spectrum attenuation law of seismic signals,and the Gauss window function of adaptive generalized S transform is used to fi t the attenuation trend of seismic signals to seek the optimal Gauss window function.The amplitude spectrum compensation function constructed using the optimal Gauss window function is used to modify the time-frequency spectrum of the adaptive generalized S transform of seismic signals and reconstruct seismic signals to compensate for high-frequency attenuation.Practical data processing results show that the method can compensate for the high-frequency components that are absorbed and attenuated by the stratum,thereby eff ectively improving the resolution and quality of seismic data.

基于S变换的叠梁闸门水脉动压力特性研究

以叠梁闸门脉动水压力为研究对象,采用S变换方法对叠梁闸门泄水过程的脉动压力信号进行时频分析处理,研究脉动压力信号能量在时频内的分布规律,确定脉动水压力在不同泄水方案下的优势频率。通过脉动压力优势频率和叠梁闸门的固有频率分析比较,判定在泄水过程中叠梁闸门发生共振现象的可能。结果表明,脉动水压力为低频分布,不同时刻的频率明显不同;不同取水方案时频率成分有明显的变化,随着取水高程的增加,脉动能量分布越来越广泛,频率成分也越来越丰富。在泄水过程中脉动水压力频率较小,远小于叠梁闸门固有频率,闸门运行过程中不会出现共振现象。

基于S变换的结肠压力信号时频域分析

采用S变换对肠道压力信号在时频域进行分析与处理.与短时傅立叶变换(STFT)和Wigner分布相比,S变换解决了STFT窗函数长度不易确定的问题,并且S变换不存在交叉干扰和负频率问题.将S变换应用于结肠压力信号的分析,结合已知的肠动力理论,能够更直接地分析人体结肠的动力特性.结果表明,运用S变换对结肠压力进行时频域分析,可以有效获取信号的有用特征.

经验模态分解的人体结肠压力信号分析

结肠测压技术可以提供整个结肠动力活动的信息,是广泛使用的评价消化道功能的检查手段.采用经验模态分解(EMD)方法将人体结肠压力信号分解为不同的固有模态函数,并对该固有模态函数进行Hilbert变换,于是可以清楚地辨别信号的特征.通过对于14例样本数据的第三个固有模态函数进行Hilbert变换,可以区分出正常(3例)和非正常(11例)的人体结肠压力信号,结果说明EMD方法是一种分析结肠压力信号的有效方法.

人体结肠压力信号的时频分析

结肠测压对结肠运动障碍疾病的诊断有较高的价值。但是由于现有资料中对结肠运动功能的认识还比较欠缺,因此对测压结果的分析还需要不断地积累经验。对实际采集的结肠压力信号进行时频分析,并与结肠基本功能相对照。结果表明,这种方法对正常和异常的结肠压力信号的区分有明显的作用。和传统的时域观察或者频域分析相比,本方法可以使噪声信号很好的局域化,具有较好的时频分辨率,适于分析结肠压力这一非平稳的信号。