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Caractérisation ultrasonore d'échantillons hétérogènes multiplement diffuseurs

Abstract : In this thesis, we studied various aspects of ultrasonic multiple scattering in random media. Experimentally, we worked on prototype media made up of thousands vertical steel stems randomly distributed in the plane, as well as "real" samples like trabecular bones and metal alloys used in industry. In the first chapter, we present the effective media theory and undertake experiments of coherent transmission. The effect of absorption and correlations between scatterers is discussed by comparing several theoretical approaches. in fine, we obtain an evaluation of the elastic mean free path versus frequency. the second chapter deals with the time-resolved multiply scattered intensity. First of all, we show that the coherent backscattering effect allows to measure the diffusion coefficient D in a reliable way and independently from intrinsic absorption. Secondly, the time of flight distribution in transmission enables us to evaluate absorption losses. The third chapter is devoted to the stationary regime : we show that the transport mean free path cannot be evaluated by the coherent backscattering effect under our experimental conditions. Lastly, the limits of time reversal focusing in resonant scattering media is discussed.
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https://tel.archives-ouvertes.fr/tel-00010852
Contributor : Victor Mamou <>
Submitted on : Wednesday, November 2, 2005 - 10:05:43 PM
Last modification on : Thursday, March 11, 2021 - 4:04:02 PM
Long-term archiving on: : Friday, April 2, 2010 - 10:55:27 PM

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  • HAL Id : tel-00010852, version 1

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Victor Mamou. Caractérisation ultrasonore d'échantillons hétérogènes multiplement diffuseurs. Acoustique [physics.class-ph]. Université Paris-Diderot - Paris VII, 2005. Français. ⟨tel-00010852⟩

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