The harmonic wavelet transform is employed to analyze various kinds of nonstationary signals common in aseismic design. The effectiveness of the harmonic wavelets for capturing the temporal evolution of the frequency content of strong ground motions is demonstrated. In this regard, a detailed study of important earthquake accelerograms is undertaken and smooth joint time-frequency spectra are p...

This paper discusses recent studies on Chirp Slope Keying (CSK) as a scheme suitable for underwater communications and presents a new study on the performance of a time-frequency receiver in a Rayleigh fading environment. As expected, CSK proves to be a digital modulation scheme inferior in the AWGN channel as compared to traditional schemes but very promising in more detrimental channels prese...

The Hilbert-based time-frequency analysis has promising capacity to reveal the time-variant behaviors of a system. To admit well-behaved Hilbert transforms, component decomposition of signals must be performed beforehand. This was first systematically implemented by the empirical mode decomposition (EMD) in the Hilbert-Huang transform, which can provide a time-frequency representation of the si...

The variation of frequency content with time is an important seismo-stratigraphic indicator. This paper discusses the analysis of local frequency content of seismic reeection data with quadratic joint time-frequency representations. Signal adaptive quadratic time-frequency representations have considerably better time-frequency localization properties (resolution) than more standard approaches ...

Time-frequency distributions have been used extensively for nonstationary signal analysis, they describe how the frequency content of a signal is changing in time. The Wigner-Ville distribution (WVD) is the best known. The draw back of WVD is cross-term artifacts. An alternative to the WVD is Gabor transform (GT), a signal decomposition method, which displays the time-frequency energy of a sign...

This correspondence studies the formulation of members of the Cohen-Posch class of positive time-frequency energy distributions. Minimization of cross-entropy measures with respect to different priors and the case of no prior or maximum entropy were considered. It is concluded that, in general, the information provided by the classical marginal constraints is very limited, and thus, the final d...

most geologic changes have a seismic response but sometimes this is expressed only in certain spectral ranges hidden within the broadband data. spectral decomposition is one of the methods which can be utilized to help interpreting such cases. there are several time-frequency methods including: short-time fourier transform (stft), continuous wavelet transform (cwt), wigner-ville distribution (w...

elastic energy of seismic wave is lost through propagation into the earth. various factors affect seismic energy. some of them are frequency independent and recovered in processing steps. but other factors such as intrinsic absorption of medium are frequency dependent and cannot be recovered by processing methods. lost energy caused by these factors is called attenuation. there are various meth...