Propagation of acoustic waves

The pulsed time stracture, typically at megahertz rates, permits stroboscopic topography of very rapid cychc phenomena such as the propagation of acoustic waves. 

A piezoelectric mass sensor is a device that measures the amount of material adsorbed on its surface by the effect of the adsorbed material on the propagation of acoustic waves. Piezoelectric devices work by converting electrical energy to mechanical energy. There are a number of different piezoelectric mass sensors. Thickness shear mode sensors measure the resonant frequency of a quartz crystal. Surface acoustic wave mode sensors measure the amplitude or time delay. Flexure mode devices measure the resonant frequency of a thin Si3N4 membrane. In shear horizontal acoustic plate mode sensors, the resonant frequency of a quartz crystal is measured. 

Numerical difference schemes able to simulate discontinuous media in a simple fashion require the basic laws of physics governing propagation of acoustic waves to be carefully transformed into numerical analogues. Hence these basic physical principles (1 ) will be briefly reconsidered. 

The acoustic response of many elastomeric fluids can be adequately described by assuming that the contribution of p to the propagation of acoustic waves is negligible ( 5 ). Under this assumption... 

Since equation (84) shows that coj decreases as L increases, it is reasonable to neglect spatial variations of the pressure within the chamber, which are produced by propagation of acoustic waves, if L is sufficiently large. 

Let us consider an acoustic medium. The propagation of acoustic waves can be described by the scalar wave equation... 

The thermal motion naturally found within a solid matrix results in the propagation of acoustic waves from lattice nodes. Comparable with the photon description of electromagnetic radiation these acoustic waves can be described as phonons and are similarly quantized. The density of phonons pa of a particular frequency co (v/2tt), in a solid continuum that contains N atoms in a sample of volume V has been deduced by Abragam [3] to be,... 

The propagation of acoustic waves in piezoelectric materials is governed by the mechanical equations of motion and Maxwell s equations for electrical behavior. The elastic behavior of piezoelectric media is governed by the Newton s law ... 

Another method for measuring mechanical properties on the macroscopic scale uses the relation between mechanical properties and the propagation of acoustic waves [89]. The velocity of sound waves and also the damping thereof can be directly deduced from the elastic and viscous properties. For polymers, ultrasound can be used since the damping of the acoustic waves is decreased at high frequencies. However, this method seems not to have been applied to fuel cell-related membrane materials so far. 

Surface Acoustic Waves. All of the discussion so far has dealt with the propagation of acoustic waves in bulk pol5uners. In addition to longitudinal and shear waves, however, a surface or Rayleigh wave, called a surface acoustic wave, can also be propagated. 

The physical theory which describes the forces and energies involved in the propagation of acoustic waves through solids and fluids is well established, albeit somewhat complex mathematically. The treatment below is intended to provide the reader with a brief overview in order to allow an understanding of how such properties as elasticity, density, and viscosity affect the operation of piezoelectric transducers and their application to chemical sensing. A detailed description of acoustic waves in solids may be found in several texts (1-3). To simplify notation, vectors and tensors are presented without subscripts, and it is assumed that mathematical operations are summed over the appropriate dimensions. 

Sorokin BP, Turchin PP, Burkov SI, Glushkov DA, Alexandrov KS (1996) Influence of static electric field, mechanical pressure and temperature on the propagation of acoustic waves in LasGasSiOn piezoelectric single crystals. Proceedings of IEEE international frequency control symposium, pp 161-169... 

A stronger tendency towards applied research has always been a part of Prof. VuCelid s character. Hence, in the past few years he has tried to apply pure biophysical methods to medical research. This has resulted in a new method for the diagnosis of skin diseases based on the propagation of acoustic waves through complex skin interphases and to a new hypothesis about the cause of Balkan nephropathy. 

Biagi E., Frosini S., Masotti L., Borchi E., The Propagation of acoustic waves in polycrystals with axial texture. Phys.Stat.Sol, (a), 1968, 93, 151-162. 

Likewise, the wave equation for the propagation of acoustic waves in a three-dimensional medium (e.g., quartz crystal) can be described by [11] ... 

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