Showing papers on "Wavelet transform modulus maxima method published in 2007"
TL;DR: In this paper, the authors analyzed the VHF electromagnetic noise intensity data at several stations in the Tohoku area of Japan during the period of a rather large (with magnitude of 7.2) earthquake (Miyagi-ken oki earthquake) taken place on 16 August 2005, by means of different fractal analysis methods, including (1) spectral slope estimation, (2) multi-fractal detrended fluctuation analysis and (3) multifractal wavelet transform modulus maxima method.
Abstract: . The VHF electromagnetic noise intensity data at several stations in the Tohoku area of Japan during the period of a rather large (with magnitude of 7.2) earthquake (Miyagi-ken oki earthquake) taken place on 16 August 2005, are analyzed by means of different fractal analysis methods, including (1) spectral slope estimation, (2) multi-fractal detrended fluctuation analysis and (3) multi-fractal wavelet transform modulus maxima method. It seems to the authors that there is no definite analysis method for the analysis of any seismogenic phenomenon, so that the only way we have to take, is to apply different methods to the same data for the detailed comparison of the results. This comparison enables us to deduce the properties commonly observed by the above methods. Because the most important feature common to these three methods, is that significant changes in fractal scaling characteristics are observed just during the earthquake (mainly before the earthquake) only at one station of Kunimi. Finally, we can come to the definite conclusion on the self-organization of VHF emissions only at one station in the present case.
11 citations
Journal Article•
TL;DR: In this paper, wavelet transform modulus maxima method based on Marr wavelet is utilized for the ZrO_2 ceramic coating with the thickness ranging from 250μm to 350μm.
Abstract: It is difficult to recognize the overlapping signal of the front and bottom echoes from the thin layer structure In order to measure the thickness of the thin layer, wavelet transform modulus maxima method based on Marr wavelet is utilized for the ZrO_2 ceramic coating with the thickness ranging from 250μm to 350μmThe results of ultrasonic method accords with that of metallographical results
2 citations
TL;DR: In this article, the complex and highly varying temporal nature of emission from an X4.8 flare is studied across seven X-ray energy bands, and the existence of a power-law scaling of wavelet coefficients across timescales is in agreement with the creation of a fractal current sheet diffusion region.
Abstract: The complex and highly varying temporal nature of emission from an X4.8 flare is studied across seven X-ray energy bands. A wavelet transform modulus maxima method is used to obtain the multifractal spectra of the temporal variation of the X-ray emission. As expected from the Neupert effect, the time series of the emission at low energies (3-6, 6-12 keV; thermal) is smooth. The peak Holder exponent, around 1.2, for this low-energy emission is indicative of a signal with a high degree of memory and suggestive of a smooth chromospheric evaporation process. The more bursty emission at higher energies (100-300, 300-800 keV; nonthermal) is described by a multifractal spectrum that peaks at a smaller Holder exponent (less than 0.5 for the largest singularities), indicative of a signal with a low degree of memory. This describes an antipersistent walk and indicates an impulsive, incoherent driving source. We suggest that this may arise from bursty reconnection, with each reconnection event producing a different and uncorrelated nonthermal particle source. The existence of a power-law scaling of wavelet coefficients across timescales is in agreement with the creation of a fractal current sheet diffusion region.
TL;DR: In this paper, the multiscale edge images of supported polyethylene (PE) catalysts are extracted by wavelet transform modulus maxima (WTMM) method and the distribution of edge points on the edge image at every scale is studied with fractal and multifractal method.
Abstract: Surface morphologies of supported polyethylene (PE) catalysts are investigated by an approach combining fractal with wavelet. The multiscale edge (detail) pictures of catalyst surface are extracted by wavelet transform modulus maxima (WTMM) method. And, the distribution of edge points on the edge image at every scale is studied with fractal and multifractal method. Furthermore, the singularity intensity distribution of edge points in the PE catalyst is analyzed by multifractal spectrum based on WTMM. The results reveal that the fractal dimension values and multifractal spectrums of edge images at small scales have a good relation with the activity and surface morphology of PE catalyst. Meanwhile the catalyst exhibiting the higher activity shows the wider singular strength span of multifractal spectrum based on WTMM, as well as the more edge points with the higher singular intensity. The research on catalyst surface morphology with hybrid fractal and wavelet method exerts the superiorities of wavelet and fractal theories and offers a thought for studying solid surfaces morphologies.