The diffusive-viscous wave equation plays an important role in seismic exploration and it can be used to explain the frequency-dependent reflections observed both in laboratory and field data. The numerical solution to this type of wave equation is needed in practical applications because it is difficult to obtain the analytical solution in complex media. Finite-difference method (FDM) is the m...

we have calculated the phonon frequencies of kc1 along symmetry directions using an approach which is a combination of the frozen phonon and force constants methods. we also calculated griineisen parameters for all modes at x and l points in the brillouin zone. finally, the slope of acoustic dispersion curves around zone center were used to calculate the three independent elastic coefficients c...

Accurate knowledge of the velocity dispersion of Lamb modes is important for ultrasonic nondestructive evaluation methods used in detecting and locating flaws in thin plates and in determining their elastic stiffness coefficients. Lamb mode dispersion is also important in the acoustic emission technique for accurately triangulating the location of emissions in thin plates. In this research, the...

The design of phononic crystals and acoustic metamaterials with tunable and adaptive wave properties remains one of the outstanding challenges for the development of next generation acoustic devices. We report on the numerical and experimental demonstration of a locally resonant acoustic metamaterial with dispersion characteristics, which autonomously adapt in response to changes of an incident...

To elucidate the three-way relationship among a crystal’s structure, its phonon dispersion characteristics, and its thermal conductivity, an analysis is conducted on layered diatomic Lennard-Jones crystals with various mass ratios. Lattice dynamics theory and molecular dynamics simulations are used to predict the phonon dispersion curves and the thermal conductivity. The layered structure gener...

Two ultrasonic nondestructive evaluation methods have been applied to systematically characterize the mechanical properties of nanostructured physical vapor deposited diamond-like carbon (DLC) ultra-hard coatings. A photoacoustic guided-wave technique is used to generate broadband surface acoustic waves (SAW) on the coating surfaces, and dispersion relations of the SAW for DLC coatings are meas...

The shallow and uniform water depth of the eastern Bering Sea shelf results in an acoustic waveguide. Propagation within this waveguide produces waveform dispersion which is dependent upon range. We present a means for using dispersed waveforms to determine range to calling whales from a single autonomous acoustic recording instrument. The predominant North Pacific right whale (Eubalaena japoni...