Time-reversal focusing of elastic surface waves with an asymmetric surface layer

Abstract

The effectiveness of time-reversal focusing is evaluated in the presence of an asymmetric surface layer that changes the direction of the propagating waves, but does not continually scatter or block the propagating wave front. Interactions between the wave front and the surface layer are dependent on the depth and material properties of the asymmetric surface layer and its orientation in the medium with respect to the incident wave. Time-reversal focusing is shown to perform significantly better than other excitation methods for the purpose of delivering energy to the location of a buried land mine.

Nonlocal scale effect on Rayleigh wave propagation in porous fluid-saturated materials

“…Following the mathematical procedure in Ref. [16], the ratio of  and can be obtained as (27) in which vs  and vf  are the volume strains of solid and fluid, respectively. Taking advantage of Eq.…”

“…Among the potential applications, it is capable of estimating the shear wave velocity and the quality factor by the inversion of surface waves [24,25]. It is also useful for the design of detecting landmines [26,27]. Hence, understanding the characteristics of Rayleigh surface waves is highly essential in nature.…”

Ultrasonic focusing and scanning with multiple waves

“…Due to this characteristic, the time reversal method has been widely used in many fields, such as ultrasonic testing. [4][5][6][7][8][9] The principle of ultrasonic time reversal focusing is to use a transducer array to receive an acoustic signal from a sound source or scattering from a scatter, which is then reversed and re-transmitted. This re-transmitted signal will be focused selfadaptively on the location of the source or the scatter.…”

The application and research of high-frequency ultrasonic reflection technique used in the measurement of small diameter’s tube cavity size

“…It is easily affected by external factors and its accuracy is not ideal. Therefore, this is the reason why we propose the ultrasound-based precision measurement method of cavity size [1,2]. 2.…”