AR = cavity aspect ratio a = speed of sound b = cavity half-width ~ C = dynamic compressibility c = phase speed cp = specific heat at constant pressure f = frequency H = cavity depth k = wave number m = propagation constant P = pressure Pr = Prandtl number R = reflection coefficient p = acoustic pressure pi = initial pulse amplitude Re = acoustic Reynolds number s = cavity spacing T = temperatu...

We have developed a low frequency theory for scattering from surface cracks. For the case of halfpenny shaped surface cracks, we are able to relate the reflection coefficient of a Rayleigh wave incident on the crack with the crack size as well as the fracture stress of a sample with the crack in it. Comparisons of the theoretical predictions for the fracture stress with the actual fracture stre...

A pulsed, 193 nm excimer laser is utilized to photoionize the organic gas tetrakisdimethylamino-ethylene ~TMAE!. The laser ionizes a plasma sheet with a width of 7.8 cm and an adjustable thickness of 0.7–1.4 cm. The axial scale length of the plasma density is a function of TMAE neutral pressure and is typically 50 cm. X-band ~10 GHz! microwaves are incident on the plasma with the electric field...

A new method for measuring the scattering coefficient using a metal-plate reflector was developed in order to provide a non-destructive way for the assessment of microwave materials in free space. By displacing the position of the metal-plate reflector on the specimen to be tested, the incident wave and the scattered wave from the measured area were determined without the influence of extraneou...

We present numerical procedures for analyzing the properties of periodic structures and associated couplers based upon time domain simulation. Simple post processing procedures are given for determining Brillouin diagrams and complex field distributions of the traveling wave solutions, and the reflection coefficient of the traveling waves by the input and output. The availability of the reflect...

A modified geometric ray approach is used to predict he V(x,z) or the acoustic material signature of a circular point-focus scanning acoustic microscope for an isotropic surface containing a surface-breaking crack. The microscope r sponse isassumed to consist of a specularly reflected geometric contribution, and the leaky contribution due in part to surface waves cattered from the crack. The lo...

Acoustic bottom-interacting measurements from the Shallow Water '06 experiment experiment (frequency range 1-20 kHz) are presented. These are co-located with coring and stratigraphic studies showing a thin (approximately 20 cm) higher sound speed layer overlaying a thicker (approximately 20 m) lower sound speed layer ending at a high-impedance reflector (R reflector). Reflections from the R ref...

The pulmonary arterial branching pattern suggests that the early systolic forward-going compression wave (FCW) might be reflected as a backward-going expansion wave (BEW). Accordingly, in 11 open-chest anesthetized dogs we measured proximal pulmonary arterial pressure and flow (velocity) and evaluated wave reflection using wave-intensity analysis under low-volume, high-volume, high-volume + 20 ...

The influence of the curvature of a conductor plate used as a reference in free space method is considered both by experiments and by theoretical computations. First, it is observed that the reflection coefficient varies as much as 3 dB by changing the orientation or the surface of the plate. Next, a numerical simulation is performed using physical optics approximation method. It is confirmed t...