We consider the ray limit of propagating ultrasound waves in three-dimensional bodies made from a homogeneous, isotropic, elastic material. Using a Monte Carlo approach, we simulate the propagation and proliferation of elastic rays using realistic angle-dependent reflection coefficients, taking into account mode conversion and ray splitting. For a few simple geometries, we analyze the long-time...

Sudden stratospheric warmings (SSWs) are the most prominent vertical coupling process in the middle atmosphere, which occur during winter and are caused by the interaction of planetary waves (PWs) with the zonal mean flow. Vertical coupling has also been identified during the equinox transitions, and is similarly associated with PWs. We argue that there is a characteristic aspect of the autumn ...

UPV as non-destructive technique can effectively contribute to the low invasive in situ analysis and diagnosis of masonry elements related to the conservation, rehabilitation and strengthening of the built heritage. The use of non-destructive and non-invasive techniques brings all the times many advantages in diagnostic activities on pre-existing buildings in terms of sustainability; moreover, ...

Abstract It has been reported that in principle sludge and blockages in pipes can be detected and characterized by using ultrasonic guided waves. The model idealised the sludge to be an asymmetrically uniform layer that is well bonded to the internal surface of the pipe wall. However, in practice, sludge layers normally have a very irregular shape, an asymmetrical circumferential profile and al...

We optically generated and observed GHz ultrasonic waves on liquid surfaces and a liquid/liquid interface for the first time using the transient reflecting grating ~TRG! method. Four kinds of samples were used for measurement of the surfaces; two types of black ink, an aqueous solution of crystal violet ~CV aq solution! and ethanol aqueous solutions of CV. A cyclohexane/CV aq solution interface...

The propagation of Lamb waves in elastic plates is analyzed both numerically and experimentally. A Scanning Laser Doppler Vibrometer (SLDV) is here used to detect and visualize transient waveforms propagating in an elastic plate at low ultrasonic frequencies. The waves are excited by a piezoelectric crystal glued to the plate surface and actuated by sinusoidal pulses of varying frequency. The p...

We report a study of transient ultrasonic waves inside a reverberant cavity containing moving scatterers. We show that the elastic mean free path and the dynamics of the scatterers govern the evolution of the autocorrelation of acoustic wave field. A parallel is established between these results and a closely related technique, diffusing acoustic wave spectroscopy. Excellent agreement is found ...

Molecular-dynamics-derived numerical probability density functions (PDFs) have been used to illustrate the effect of different models for thermal motion on the parameters refined in a crystal structure determination. Specifically, anharmonic curved or asymmetric PDFs have been modelled using the traditional harmonic approximation and the anharmonic Gram-Charlier series treatment. The results sh...

In the aircraft industry safety, maintenance costs, and optimum weight are three of the most important factors to consider in design. Composite materials, such as carbon fiber reinforced polymers (CFRPs), are increasingly used in aerospace applications due to their high strength to weight ratio. However, there are still many challenges to overcome in order to have full confidence in the use of ...