Probing material nonlinearity at various depths by time reversal mirrors

Ultrasonic Time Reversal Mirrors

For more than ten years, time reversal techniques have been developed in many different fields of applications including detection of defects in solids, underwater acoustics, room acoustics and also ultrasound medical imaging and therapy. The essential property that makes time reversed acoustics possible is that the underlying physical process of wave propagation would be unchanged if time were...

Time - reversal mirrors

On time reversal mirrors

The concept of time reversal (TR) of scalar wave is reexamined from basic principles. Five different time reversal mirrors (TRM) are introduced and their relations are analyzed. For the boundary behavior, it is shown that for paraxial wave only the monopole TR scheme satisfies the exact boundary condition while for the spherical wave only the MD-mode TR scheme satisfies the exact boundary condi...

Numerical Simulation of Acoustic Time Reversal Mirrors

We study the time reversal phenomenon in a homogeneous and non-dissipative medium containing sound-hard obstacles. We propose two mathematical models of time reversal mirrors in the frequency domain. The first one takes into account the interactions between the mirror and the obstacles. The second one provides an approximation of these interactions. We prove, in both cases, that the time revers...

Probing the depths

W scientists from HMS Challenger dredged animals from over 5km depth, they finally laid to rest the azoic hypothesis of Edward Forbes, that life could not exist in cold dark depths of the ocean, and thereby opened the doors to true deep-sea biology. The past decade has witnessed a further sea change in our view of marine diversity, if I may be permitted the pun, a change driven to a large exten...