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Contribution à l'étude des champs électriques très basses fréquences en milieu océanique

Abstract : The measurement of the electromagnetic fields of very low frequencies in oceanic medium interests of many scientific disciplines, of oceanography to geophysics while passing by the underwater detection. The study of the electric field, complementary to that of the magnetic field, however did not arouse until now an interest as important as its counterpart. This thesis thus proposes a contribution to the study of the very low frequencies electric fields in oceanic medium. Initially, in order to show the interest of the measurement of the electric field, we present the electromagnetic phenomena observable at sea at very low frequencies. A review of the state of the art of electrometry in oceanic medium highlights the difficulties and the limitations at the level of the high-sensitivity instrumentation. We describe then the design and the development of an experimental model of electrometer using an original physical principle. The system, gauged in laboratory, posts a sensitivity about the nV/m in a frequency band going down up to 0,01 Hz, which locates it among the best existing apparatuses. Some experiments of measurement are presented, aiming to the description of very weak electric fields of physical origin (electrodynamic) or electrochemical (corrosion). In margin of electrometry, we are also interested in a general, theoretical and experimental way, with the electromagnetic fields generated by the phenomena of corrosion. We present finally a three-dimensional modeling of our electrometer by the finite element method, validated by comparison with a method integrals of border. Theoretical developments proved to be necessary to make it possible the method to take into account discontinuities of interfaces. These developments exceed the framework of the application to lead to a general method and a new class of interfacial finite elements.
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Submitted on : Sunday, April 1, 2007 - 11:17:58 PM
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  • HAL Id : tel-00139537, version 1


Valéry Poulbot. Contribution à l'étude des champs électriques très basses fréquences en milieu océanique. Autre. Ecole Centrale de Lyon, 1993. Français. ⟨tel-00139537⟩



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