Article
The representation of 3D gaussian beams by means of inhomogeneous waves
Department of Mechanical Construction and Production, Ghent University, Gand, Flemish, Belgium
Ultrasonics (Impact Factor: 1.94). 05/2004; 42(19):2736. DOI: 10.1016/j.ultras.2004.01.020 Source: PubMed
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 "Gaussian beams are widely used to model acoustic and optical wavefields converging to or diverging from focal regions. According to the source power and propagation distance of the Gaussian beam, particles can be trapped by the beam acoustical wave in the focal region (Wu and Du 1990; Prange and Shenoy 1996; Ding et al. 2003; Declercq et al. 2004). Most of the theoretical investigations of the Gaussian beam involve the interaction of waves with spherical particles (Wu 1991). "
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ABSTRACT: The Rayleigh wave velocity for a coated substrate must have a value in between the ones for the substrate material and the coating material. Nevertheless, Adler and McCathern [J. Appl. Phys. 49, 2576 (1978)] have performed measurements, based on the Schoch effect, on a stainless steel substrate covered with an aluminum oxide coating that contradict this phenomenon. The current letter describes the frequency band gap effect for Rayleigh waves on coated substrates and explains how this phenomenon is related to the cited measurements. The existence of such a gap can be very important for the development of frequency filters.  [Show abstract] [Hide abstract]
ABSTRACT: If a bounded beam is described using a superposition of infinite inhomogeneous waves, the values of the coefficients attributed to each inhomogeneous wave are found using a classical optimization procedure, whence it is impossible to describe the obtained values analytically. In this paper, we develop a new and easy to apply straightforward analytical method to find the appropriate values of the sought coefficients. Supplementary to its analytical and straightforward nature, the method proves to reduce the inherent instabilities found in the inhomogeneous wave decomposition.