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...

Propagation of extensional waves in a piezoelectric semiconductor rod" We studied the propagation of extensional waves in a thin piezoelectric semiconductor rod of ZnO whose c-axis is along the axis of the rod. The macroscopic theory of piezoelectric semiconductors was used which consists of the coupled equations of piezoelectricity and the conservation of charge. The problem is nonlinear becau...

We demonstrate that the propagation of surface acoustic waves, arising from the excitation of the acoustic field on a piezoelectric crystal (lithium niobate) substrate, along the sidewalls of microchannels (50 μm or 280 μm wide and 200 μm deep) fabricated in the substrate, can give rise to throughflow with velocities of the order 10 mm/s. This streaming flow in the direction along which the sur...

Four thin-film adhesion characterization methods are proposed. Two of them are surface acoustic wave based and the two others emphasize the complementary nature between acoustic microscopy, scratch test and tensile experiments. A continuous wave scanning acoustic microscope was used to propagate surface modes in the specimen and to measure the surface acoustic wave velocity as a function of the...

In this study, torsional wave propagation is investigated in a rod that are made of one and two dimensional functionally graded material. Firstly, the governing equations of the wave propagation in the functionally graded cylinder derived in polar coordinate. Secondly, finite difference method is used to discretize the equations. The Von Neumann stability approach is used to obtain the time ste...

To be able to simulate P-wave propagation in a heterogeneous spherical Earth, we solve the acoustic wave equation in spherical coordinates numerically for axi-symmetric media. We employ a high-order nite-diierence scheme which allows us to simulate arbitrary heterogeneous structures with wavelengths as small as 10km. A standard regular gridding in spherical coordinates leads to a continuously d...

19 Waves in Cold Plasmas: Two-Fluid Formalism 1 19.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 19.2 Dielectric Tensor, Wave Equation, and General Dispersion Relation . . . . . 3 19.3 Wave Modes in an Unmagnetized Plasma . . . . . . . . . . . . . . . . . . . . 5 19.3.1 Two-Fluid Formalism . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 19.3.2 ...

21 Waves in Cold Plasmas: Two-Fluid Formalism 1 21.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 21.2 Dielectric Tensor, Wave Equation, and General Dispersion Relation . . . . . 3 21.3 Two-Fluid Formalism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 21.4 Wave Modes in an Unmagnetized Plasma . . . . . . . . . . . . . . . . . . . . 7 2...

the study of wave and its propagation on the water surface is among significant phenomena in designing quay, marine and water structures. therefore, in order to design structures which are exposed to direct wave forces, it is necessary to study and simulate water surface height and the wave forces on the structures body in different boundary conditions. in this study, the propagation of static ...