Guided waves in a free isotropic plate (symmetric S(n) and antisymmetric A(n) Lamb modes) exhibit a resonant behavior at frequencies where their group velocity vanishes while their phase velocity remains finite. Previous studies of this phenomenon were limited to isotropic materials. In this paper, the optical generation and detection of these zero-group velocity (ZGV) Lamb modes in an anisotro...

Drastic hardware simplification and cost reduction of Guided Waves (GWs) based systems can be achieved by using shaped transducers that present inherent directional capabilities when generating and sensing elastic waves. Directional transducers for GW generation and sensing are achieved by patterning the piezoelectric material lay-out and the electrodes. The peculiar electrodes’ shape produces ...

seismic waves travelling through inelastic media are attenuated by the conversion of elastic energy into heat. upon being attenuated, the travelling wave changes: amplitude is reduced, travelling waveform is modified due to high-frequency content absorption, and phase is delayed. attenuation is usually quantified through the quality factor q: the ratio between the energy stored and lost in each...

The use of numerical and phased array techniques to focus guided waves and perform inspection of plates and pipes has not been widely used; it represents an interesting solution for defect detection and localization. In addition, imaging of ultrasonic guided wave results using color coded B-Scans is also considered a highly valuable tool for data interpretation. While commercial ultrasonic phas...

We present an overview of the properties of nonlinear guided waves and (bright and dark) spatial optical solitons in a periodic medium created by linear and nonlinear waveguides. First we consider a single layer with a cubic nonlinear response (a nonlinear slab waveguide) embedded in a periodic layered linear medium and describe nonlinear localized modes (guided waves and Bragg-like localized g...

Guided waves are being considered for structural health monitoring (SHM) applications, and they can also be used to reduce subsequent inspection times once defects are detected. One proposed SHM method is to use an array of permanently attached piezoelectric transducers to generate and receive guided waves between the various transducer pairs. The interrogation can be done on a continuous or pe...

in this study, absorption of high frequency radio waves in the ionospheric plasma have beeninvestigated. the wave equation was obtained in terms of ionospheric parameters. the numerical values ofthe absorption have been calculated for 4 mhz, 4.5 mhz and 5 mhz waves. the necessary parameters forcalculation have been obtained using an international reference ionosphere (iri) model. the altitudina...

The main focus of this study is to develop an efficient frequency-wavenumber code to synthesize high-frequency (say, 10 Hz) regional seismograms (up to a distance of more than 1000 km) in a medium consisting of a large number of crustal layers, and investigate effects of regional waveguides on L, waves. In this newly developed code, the frequency-wavenumber response is evaluated by using the Fi...