|
|
|
|
| |
|
|
| Chacón,M.; Curilem,G.; Acuña,G.; Defilippi,C.; Madrid,A.M.; Jara,S.. |
| The aim of the present study was to develop a classifier able to discriminate between healthy controls and dyspeptic patients by analysis of their electrogastrograms. Fifty-six electrogastrograms were analyzed, corresponding to 42 dyspeptic patients and 14 healthy controls. The original signals were subsampled, filtered and divided into the pre-, post-, and prandial stages. A time-frequency transformation based on wavelets was used to extract the signal characteristics, and a special selection procedure based on correlation was used to reduce their number. The analysis was carried out by evaluating different neural network structures to classify the wavelet coefficients into two groups (healthy subjects and dyspeptic patients). The optimization process of... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Functional dyspepsia; Electrogastrography; Wavelet transform; Neural networks. |
| Ano: 2009 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2009001200014 |
| |
|
| |
|
|
| Ker, Stephan; Le Gonidec, Y.; Gibert, D.. |
| In the context of multiscale seismic analysis of complex reflectors, that takes benefit from broad-band frequency range considerations, we perform a wavelet-based method to merge multiresolution seismic sources based on generalized Lévy-alpha stable functions. The frequency bandwidth limitation of individual seismic sources induces distortions in wavelet responses (WRs), and we show that Gaussian fractional derivative functions are optimal wavelets to fully correct for these distortions in the merged frequency range. The efficiency of the method is also based on a new wavelet parametrization, that is the breadth of the wavelet, where the dominant dilation is adapted to the wavelet formalism. As a first demonstration to merge multiresolution seismic... |
| Tipo: Text |
Palavras-chave: Wavelet transform; Wave propagation; Acoustic properties. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00157/26824/24935.pdf |
| |
|
|
| Pouliquen, G; Sailhac, P. |
| The interpretation of marine magnetic anomalies usually consists either in determining the magnetization distribution assuming the source geometry and magnetization direction or in determining the magnetic layer thickness assuming the magnetization direction and intensity. In this paper, we introduce a new technique that allows modeling of the thickness of the magnetic source layer with very few a priori assumptions about the magnetization: the magnetic layer is assumed to be made of a series of bodies, each having a constant unknown magnetization and an unknown size. This technique is based upon the application of the continuous wavelet transform recently introduced for the interpretation of potential field data as a multipole decomposition. We present... |
| Tipo: Text |
Palavras-chave: Wavelet transform; Multipole decomposition; Magnetic anomalies; Source layer thickness; Mid-ocean ridges. |
| Ano: 2003 |
URL: https://archimer.ifremer.fr/doc/00224/33551/32040.pdf |
| |
|
|
| Ker, Stephan; Le Gonidec, Yves; Gibert, D.; Marsset, Bruno. |
| We propose a wavelet-based method to characterize acoustic impedance discontinuities from a multiscale analysis of seismic reflected waves. Our approach relies on the analysis of ridge functions which contain most of the information of the wavelet transform in a sparse support. This method falls in the framework of the wavelet response (WR) introduced by Le Gonidec et al. which analyses the impedance multiscale behaviour by propagating dilated wavelets into the medium. We further extend the WR by considering its application to broad-band seismic data. We take into account the bandpass filter effect related to the limited frequency range of the seismic source. We apply the method to a deep-water seismic experiment performed in 2008 during the ERIG3D cruise... |
| Tipo: Text |
Palavras-chave: Wavelet transform; Seismic attenuation; Wave propagation; Acoustic properties. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00049/15994/13449.pdf |
| |
|
|
| Ker, Stephan; Le Gonidec, Yves; Gibert, Dominique. |
| A wavelet-based method was presented in a previous work to introduce multiscale seismic attributes for high-resolution seismic data. Because of the limited frequency bandwidth of the seismic source, we observed distortions in the seismic attributes based on the wavelet response of the subsurface discontinuities (Le Gonidec et al.). In this paper, we go further in the seismic source-correction by considering L´evy alpha-stable distributions introduced in the formalism of the continuous wavelet transform (CWT). The wavelets are Gaussian derivative functions (GDF), characterized by a derivative order. We show that a high-resolution seismic source, after a classical signature processing, can be taken into account with a GDF. We demonstrate that in the... |
| Tipo: Text |
Palavras-chave: Wavelet transform; Wave propagation; Acoustic properties. |
| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00090/20155/17828.pdf |
| |
|
|
| Ker, Stephan; Le Gonidec, Y.; Marsset, Bruno; Westbrook, Graham; Gibert, D.; Minshull, T. A.. |
| In the context of seismic imaging of gas/gas-hydrate systems, the fine-scale structure of subseabed gas-related reflections is assessed by taking advantage of the source signature of the deep-towed high-resolution SYSIF seismic device. We demonstrate the value of an original wavelet-based method and associated multiscale seismic attributes, applied to seismic data recently acquired on the western margin of the Arctic archipelago of Svalbard. From analysis in the wavelet domain, we recognize two types of gas-related reflections associated with submetre-scale distribution of gas. We identify a thin gas-charged layer associated with an apparent normal polarity reflection, and we detect gas patches associated with a reverse-polarity bright spot with... |
| Tipo: Text |
Palavras-chave: Wavelet transform; Gas and hydrate systems; Wave propagation; Acoustic properties; Arctic region. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00175/28602/27019.pdf |
| |
|
|
|
