Nonlinear Time Reversal Tomography of Structural Defects

Imaging of human tooth using ultrasound based chirp-coded nonlinear time reversal acoustics

“…Localization of the nonlinear signature could be confirmed using signal processing tomography method taking into account the real geometry of the tooth section [41]. The proposed TR-NEWS imaging results from an angular scanning with large angle aperture (280°) which was also possible because the tooth was extracted from its initial position in the mouth.…”

Nonlinear signal processing for ultrasonic imaging of material complexity

“…The focusing is independent of the distance between the transducer and the laser receiver. However, the most important advantage of chirp-coded TR-NEWS, which was used previously with another complex medium in the context of NDT [9], is the fact that the focusing of ultrasound is generated exactly at the position where laser surface velocity measurements are performed, and provides TR-NEWS with an advantage for localization of cracks and also the possibility of applying a surfacic stress, which could be combined to fractography [19], and with ESAM-DORT [14] for their localization and imaging.…”

“…3) filtered by the measurement system (laser vibrometer or transducer). An arbitrary waveform of the temporal shape can be constructed using amplitude modulation of Γ c (t) or by a simple delay i Γ(−(t + τ i )) in order to construct, using the "virtual transducer" concept [14], optimized shapes such as solitonic ones. The main idea of the "virtual transducer" is in the generation of a single excitation signal, which replaces many separate excitations.…”

“…As the excitations required by the third-order ESAM are complex rather than real signals, the amplitude variation and post-treatment of real signal excitation is preferred in practice. Taking into account that real excitations are used, it can be shown [14] that the corresponding nonlinear coefficients N 2 and N 3 are picked out with…”

Theoretical Study of Memristor and \\ Time Reversal based\\ Nonlinear Elastic Wave Spectroscopy

“…If one uses transducers which emit and receive signals, the time reversed signal can be emitted before receiving the signal. Vejvodka, Prevorovsky and Dos Santos [26] proposed nonlinear time reversal tomography using emitting and receiving transducers array in a cubic domain. When amplitude inverted pulses are emitted in non-linear medium, the received signals do not cancel in certain time domain, and property of nonlinear medium can be detected.…”