CARLOS MATEO GUTIERREZ NI�O PACHECO - Profile on Academia.edu (original) (raw)
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Papers by CARLOS MATEO GUTIERREZ NI�O PACHECO
Localizing time-lapse changes with multiply scattered waves
Localizing time-lapse changes with single scattered waves
SEG Technical Program Expanded Abstracts 2003, 2003
Previous formulations of coda wave interferometry make it possible to assess the average change o... more Previous formulations of coda wave interferometry make it possible to assess the average change of the medium, but they do not allow for the spatial localization of this change . We present an approach for localizing temporal changes in the medium using strongly scattered waves, and test it with numerical models for 2D scalar waves. Using an integral representation for the diffuse wavefield, we derive an expression for the mean traveltime perturbation due to a small perturbation in the slowness. We validate the theory using synthetic seismograms calculated with a finite-difference algorithm. In general, for localized slowness perturbations, the theory predicts the mean traveltime change of the diffuse wavefield in a multiplescattering medium. The technique presented here can be used in many applications such as medical imaging, non-destructive testing, and reservoir monitoring, to infer temporal changes of the multiple-scattering medium.
The Journal of the Acoustical Society of America, 2005
Existing techniques in correlation spectroscopy, such as coda wave interferometry and diffusing a... more Existing techniques in correlation spectroscopy, such as coda wave interferometry and diffusing acoustic wave spectroscopy, determine the average motion of scatterers or change in the propagation velocity from the temporal change of multiply scattered sound. However, neither of them gives an indication of the spatial extent of the change in the medium. This study is an extension of the technique coda wave interferometry, where multiply scattered waves are used to determine the change in the wave field due to a localized perturbation in the propagation velocity. Here, the propagation of multiply scattered sound is described using the diffusion approximation, which allows the cross-correlation function of the unperturbed and perturbed wave fields to be related to the localized change in the propagation velocity. The technique is tested numerically for two-dimensional (2D) acoustic waves using synthetic seismograms calculated using finite-differences before and after a small perturbati...
Geophysical Journal International, 2006
We present a technique based on the single-scattering approximation that relates time-lapse local... more We present a technique based on the single-scattering approximation that relates time-lapse localized changes in the propagation velocity to changes in the traveltime of singly scattered waves. We describe wave propagation in a random medium with homogeneous statistical properties as a single-scattering process where the fluctuations of the velocity with respect to the background velocity are assumed to be weak. This corresponds to one of two end-member regimes of wave propagation in a random medium, the first being single scattering, and the second multiple scattering. We present a formulation that relates the change in the traveltime of the scattered waves to a localized change in the propagation velocity by means of the Born approximation for the scattered wavefield. We validate the methodology with synthetic seismograms calculated with finite differences for 2-D acoustic waves. Potential applications of this technique include non-destructive evaluation of heterogeneous materials and time-lapse monitoring of heterogeneous reservoirs.
A sexualidade humana e a relacao que cada individuo apresenta diante da sociedade, sendo esta, ma... more A sexualidade humana e a relacao que cada individuo apresenta diante da sociedade, sendo esta, manifestada pelas suas acoes, desejos sexuais, afeto, carinho, respeito, ousadia, prazer, o que esta ligado ao erotico. O presente artigo tem como objetivo abordar metodologias para se trabalhar sexualidade humana dentro de salas de aula. Sendo este realizado atraves da revisao literaria de livros e sites da internet. O estudo apontou que a sexualidade humana compreende parte da historia do pais, sendo muito critico sua aceitacao dentro do ambiente escolar encontrando muitos preconceitos e tabus vindouros de uma cultura desconhecedora da importância da educacao sexual. Ainda, grandes dificuldades por parte dos professores em ensinar sexualidade e apresentar maneiras de e se trabalha-la nesse contexto, e a relacao que, pais, educadores e escola tem no auxilio da preparacao dos jovens para uma sexualidade sadia. Ficou evidente ainda que diante de uma sociedade jovem onde os desejos e a vonta...
Localizing time-lapse changes with multiply scattered waves
Localizing time-lapse changes with single scattered waves
SEG Technical Program Expanded Abstracts 2003, 2003
Previous formulations of coda wave interferometry make it possible to assess the average change o... more Previous formulations of coda wave interferometry make it possible to assess the average change of the medium, but they do not allow for the spatial localization of this change . We present an approach for localizing temporal changes in the medium using strongly scattered waves, and test it with numerical models for 2D scalar waves. Using an integral representation for the diffuse wavefield, we derive an expression for the mean traveltime perturbation due to a small perturbation in the slowness. We validate the theory using synthetic seismograms calculated with a finite-difference algorithm. In general, for localized slowness perturbations, the theory predicts the mean traveltime change of the diffuse wavefield in a multiplescattering medium. The technique presented here can be used in many applications such as medical imaging, non-destructive testing, and reservoir monitoring, to infer temporal changes of the multiple-scattering medium.
The Journal of the Acoustical Society of America, 2005
Existing techniques in correlation spectroscopy, such as coda wave interferometry and diffusing a... more Existing techniques in correlation spectroscopy, such as coda wave interferometry and diffusing acoustic wave spectroscopy, determine the average motion of scatterers or change in the propagation velocity from the temporal change of multiply scattered sound. However, neither of them gives an indication of the spatial extent of the change in the medium. This study is an extension of the technique coda wave interferometry, where multiply scattered waves are used to determine the change in the wave field due to a localized perturbation in the propagation velocity. Here, the propagation of multiply scattered sound is described using the diffusion approximation, which allows the cross-correlation function of the unperturbed and perturbed wave fields to be related to the localized change in the propagation velocity. The technique is tested numerically for two-dimensional (2D) acoustic waves using synthetic seismograms calculated using finite-differences before and after a small perturbati...
Geophysical Journal International, 2006
We present a technique based on the single-scattering approximation that relates time-lapse local... more We present a technique based on the single-scattering approximation that relates time-lapse localized changes in the propagation velocity to changes in the traveltime of singly scattered waves. We describe wave propagation in a random medium with homogeneous statistical properties as a single-scattering process where the fluctuations of the velocity with respect to the background velocity are assumed to be weak. This corresponds to one of two end-member regimes of wave propagation in a random medium, the first being single scattering, and the second multiple scattering. We present a formulation that relates the change in the traveltime of the scattered waves to a localized change in the propagation velocity by means of the Born approximation for the scattered wavefield. We validate the methodology with synthetic seismograms calculated with finite differences for 2-D acoustic waves. Potential applications of this technique include non-destructive evaluation of heterogeneous materials and time-lapse monitoring of heterogeneous reservoirs.
A sexualidade humana e a relacao que cada individuo apresenta diante da sociedade, sendo esta, ma... more A sexualidade humana e a relacao que cada individuo apresenta diante da sociedade, sendo esta, manifestada pelas suas acoes, desejos sexuais, afeto, carinho, respeito, ousadia, prazer, o que esta ligado ao erotico. O presente artigo tem como objetivo abordar metodologias para se trabalhar sexualidade humana dentro de salas de aula. Sendo este realizado atraves da revisao literaria de livros e sites da internet. O estudo apontou que a sexualidade humana compreende parte da historia do pais, sendo muito critico sua aceitacao dentro do ambiente escolar encontrando muitos preconceitos e tabus vindouros de uma cultura desconhecedora da importância da educacao sexual. Ainda, grandes dificuldades por parte dos professores em ensinar sexualidade e apresentar maneiras de e se trabalha-la nesse contexto, e a relacao que, pais, educadores e escola tem no auxilio da preparacao dos jovens para uma sexualidade sadia. Ficou evidente ainda que diante de uma sociedade jovem onde os desejos e a vonta...