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Registros recuperados: 7
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Detection of patients with functional dyspepsia using wavelet transform applied to their electrogastrogram BJMBR
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
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Fine-scale gas distribution in marine sediments assessed from deep-towed seismic data ArchiMer
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
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Multiresolution seismic data fusion with a generalized wavelet-based method to derive subseabed acoustic properties ArchiMer
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
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Multiscale seismic attributes: A wavelet-based method and its application to high-resolution seismic and ground truth data ArchiMer
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
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Multiscale seismic attributes: source-corrected wavelet response and application to high-resolution seismic data ArchiMer
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
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Wavelet and Fourier analysis of ventricular and main arteries pulsations in anesthetized dogs Biol. Res.
JIMÉNEZ,RAÚL F; TORRES,PATRICIO; GÜNTHER,BRUNO; MORGADO,ENRIQUE; JIMÉNEZ,CLAUDIA A.
The purpose of this study was to characterize time-frequency behavior using the Continuous Wavelet Transform (CWT) and Fast Fourier Transform (FFT) to analyze ventricular and arterial pressure signals from anesthetized mongrel dogs. Both ventricular and arterial pressure pulsations were recorded using catheter-tip manometers and the CWT was applied to these signals to obtain module coefficients, associated contours, and the 3-D representation of these modules. FFT was applied to obtain the Fourier spectrum. The mathematical analysis of the cardiovascular pressure pulsations permitted the identification of the evolution of the frequency components for the aortic and pulmonary valve functions as well as the intra-ventricular and respiratory influences on the...
Tipo: Journal article Palavras-chave: Wavelet transform; Fourier transform; Time-frequency-amplitude; Ventricular and arterial pressures.
Ano: 2004 URL: http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602004000300008
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Wavelet-domain elastic net for clustering on genomes strains Genet. Mol. Biol.
Ferreira,Leila Maria; Sáfadi,Thelma; Ferreira,Juliano Lino.
Abstract We propose to evaluate genome similarity by combining discrete non-decimated wavelet transform (NDWT) and elastic net. The wavelets represent a signal with levels of detail, that is, hidden components are detected by means of the decomposition of this signal, where each level provides a different characteristic. The main feature of the elastic net is the grouping of correlated variables where the number of predictors is greater than the number of observations. The combination of these two methodologies applied in the clustering analysis of the Mycobacterium tuberculosis genome strains proved very effective, being able to identify clusters at each level of decomposition.
Tipo: Info:eu-repo/semantics/article Palavras-chave: Elastic net; Genome; GC-content; Cluster analysis; Wavelet transform.
Ano: 2018 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572018000500884
Registros recuperados: 7
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