Time reversal of ultrasonic fields represents a way to focus through an inhomogeneous medium. This may be acomplished by a time-reversal mirror ("M) made from an array of transmit-receive transducers that respond linearly and allow the incident acoustic pressure to be sampled. The pressure field is then time-reversed and re-emitted. This process can be used to focus through inhomogeneous media ...

Radiation from monopole antennas on spherical-lossy earth is analyzed by the finitedifference time-domain (FDTD) method in spherical coordinates. A novel generalized perfectly matched layer (PML) has been developed for the truncation of the lossy soil. For having an accurate modeling with less memory requirements, an efficient "non-uniform" mesh generation scheme is used. Also in each time step...

In brane-world theory in five dimensions, the bulk metric is usually written in gaussian coordinates, where g 4µ = 0 and g 44 = −1. However, the choice g 44 = −1 is not mandatory. The presence of matter in the brane can generate temporal and spatial variations of g 44 , which in turn backreact on the brane. In this paper we study the consequences of having g 44 = ǫΦ 2 , where ǫ = ±1 and Φ is a ...

Diffusion in inhomogeneous materials can be described by both the Fick and Fokker–Planck diffusion equations. Here, we study a mixed problem with coefficients rapidly oscillating space time. We obtain macroscopic models performing homogenization limit means of unfolding technique.

Uniaxial optical anisotropy in the geometrical-optics approach is a classical problem and most of the theory is known for at least fifty years. Although the subject appears frequently in the literature, it is nearly silent about wave propagation through inhomogeneous anisotropic media. At the same time, the rapid advances in liquid-crystal lenses call for a good overview of the theory on wave p...