Focusing Waves in Unknown Media by Modified Time Reversal Iteration

Time Reversal for Waves in Random Media

In time reversal acoustics experiments, a signal is emitted from a localized source, recorded at an array of receivers-transducers, time reversed, and finally re-emitted into the medium. A celebrated feature of time reversal experiments is that the refocusing of the re-emitted signals at the location of the initial source is improved when the medium is heterogeneous. Contrary to intuition, mult...

Time reversal for waves in time-dependent random media

s : Regularization through stochastic forcing and its impact on nonlinear time-reversal A. Nachbin IMPA, Est. D. Castorina, 110, J. Botanico, CEP 22460-320, Rio, RJ, Brasil A large amount of mathematical theory has been developed for the time-reversal of linear waves in random media. This work concerns the extension to one-dimensional, weakly nonlinear water waves. Weakly dispersive water waves...

Subwavelength focusing in bubbly media using broadband time reversal

Thanks to a multiple-scattering theory algorithm, we present a way to focus energy at the deep subwavelength scale, from the far field, inside a cubic disordered bubble cloud by using broadband time reversal (TR). We show that the analytical calculation of an effective wavenumber performing the independant scattering approximation (ISA) matches the numerical results for the focal extension. Sub...

Time Reversal for Classi al Waves in Random Media

Solving time-fractional chemical engineering equations by modified variational iteration method as fixed point iteration method

The variational iteration method(VIM) was extended to find approximate solutions of fractional chemical engineering equations. The Lagrange multipliers of the VIM were not identified explicitly. In this paper we improve the VIM by using concept of fixed point iteration method. Then this method was implemented for solving system of the time fractional chemical engineering equations. The ob...