Professor of Physics, Catholic University of America, Washington DC 20064, USA (since 1964) . Field of research: Theoretical Physics (acoustics, ultrasonics, clastic and electromagnetic waves, nuclear physics) Acoustics: Advancement of the theory of surface waves in acoustic scattering. Pioneering development of acoustic resonance scattering theory . Channeling in under-ocean sound propagation ...

This paper describes the use of genetic algorithms (GAs) for the optimal design of phononic bandgaps in periodic elastic two-phase media. In particular, we link a GA with a computational finite element method for solving the acoustic wave equation, and find optimal designs for both metal–matrix composite systems consisting of Ti/SiC, and H2O-filled porous ceramic media, by maximizing the relati...

Theory of wave scattering by small particles of arbitrary shapes was developed by A. G. Ramm in papers (Ramm, 2005; 2007;a;b; 2008;a; 2009; 2010;a;b) for acoustic and electromagnetic (EM) waves. He derived analytical formulas for the S-matrix for wave scattering by a small body of arbitrary shape, and developed an approach for creating materials with a desired spatial dispersion. One can create...

We investigate the role of the spatial evolution of the acoustic field in stimulated Brillouin scattering processes in short high-gain structures. When the gain is strong enough that the gain length becomes comparable to the acoustic wave decay length of order 100 microns, standard approximations treating the acoustic field as a local response no longer apply. Treating the acoustic evolution mo...

LLE Review, Volume 72 177 In stimulated Brillouin scattering1 (SBS) an incident (pump) light wave is scattered by the electron-density fluctuations associated with an ion-acoustic (sound) wave. This process generates a frequency-upshifted (anti-Stokes) light wave and a frequency-downshifted (Stokes) light wave. For most scattering angles the anti-Stokes wave is driven nonresonantly and can be n...

General asymptotic formulas are given for the coefficient Cl of the term of multipole number l in the temperature correlation function of the cosmic microwave background, in terms of scalar and dipole form factors introduced in a companion paper. The formulas apply in two overlapping limits: for l ≫ 1 and for ld/dA ≪ 1 (where dA is the angular diameter distance of the surface of last scattering...