Density fingering of exothermic autocatalytic fronts in vertically oriented porous media and Hele-Shaw cells is studied theoretically for chemical reactions where the solutal and thermal contribution to density changes have opposite signs. The competition between these two effects leads to thermal plumes for ascending fronts. The descending fronts behave strikingly differently as they can featu...

The underlying working principle of detecting impulsive stimulated scattering signals in a differential configuration of heterodyne diffraction detection is unraveled by involving optical scattering theory. The feasibility of the method for the thermoelastic characterization of coating-substrate systems is demonstrated on the basis of simulated data containing typical levels of noise. Besides t...

Two-dimensional electromagnetic crystals formed by rectangular lattices of thin ideally conducting cylinders periodically loaded by bulk reactive impedances are considered. An analytical theory of dispersion and reflection from this medium is presented. The consideration is based on the local field approach. The transcendental dispersion equation is obtained in the closed form and solved numeri...

The propagation of Lamb-like waves in sandwich plates made of anisotropic and viscoelastic material layers is studied. A semi-analytical model is described and used for predicting the dispersion curves (phase velocity, energy velocity, and complex wave-number) and the through-thickness distribution fields (displacement, stress, and energy flow). Guided modes propagating along a test-sandwich pl...

We evaluated the performance of the classical and spectral finite element method in the simulation of elastodynamic problems. We used as a quality measure their ability to capture the actual dispersive behavior of the material. Four different materials are studied: a homogeneous non-dispersive material, a bilayer material, and composite materials consisting of an aluminum matrix and brass inclu...

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...

This brief note reports on a study that applies the reassigned spectrogram (the reassigned energy density spectrum of the short-time Fourier transform [STFT]) to develop the dispersion curves for multimode Lamb waves propagating in an aluminum plate. The proposed procedure first uses the spectrogram to operate on a single, laser-generated and detected waveform to develop the dispersion relation...

We demonstrate dispersion tailoring by coupling the even and the odd modes in a line-defect photonic crystal waveguide. Coupling is determined ab-initio using group theory analysis, rather than by trial-error optimisation of the design parameters. A family of dispersion curves is generated by controlling a single geometrical parameter. This concept is demonstrated experimentally with very good ...

Fast field-cycling MRI offers access to sources of endogenous information not available from conventional fixed-field imagers. One example is the T(1) dispersion curve: a plot of T(1) versus field strength. We present a pulse sequence that combines saturation-recovery/inversion-recovery T(1) determination with field cycling and point-resolved spectroscopy localization, enabling the measurement ...