Radiating sources in higher-dimensional gravity

We study a time-dependent 5D metric which contains a static 4D sub-metric whose 3D part is spherically symmetric. An expansion in the metric coefficient allow us to obtain close-to Schwarzschild approximation to a class of spherically-symmetric solutions. Using Campbell's embedding theorem and the induced-matter formalism we obtain two 4D solutions. One describes a source with the stiff equation of state believed to be applicable to dense astrophysical objects, and the other describes a spherical source with a radial heat flow.Comment: Latex, 20 pages, no figures. to appear in J. Math. Phy

Time-Dependent Solution for a Star Immersed in a Background Radiation

We study a time-dependent and spherically-symmetric solution with a star-like source. We show that this solution can be interpreted as an exterior solution of a contracting star which has a decreasing temperature and is immersed in a homogenous and isotropic background radiation. Distribution of the temperature in the fields and close-to Schwarzschild approximation of the solution are studied. By identifying the radiation with the cosmic background one, we find that the close-to-Schwarzschild approximate solution is valid in a wide range in our solar system. Possible experimental tests of the solution are discussed briefly.Comment: Latex, 7 pages, no figures, to appear in J. Math. Phys.(2002

Pereyra, J.S. (2011). Métodos en neurociencias cognoscitivas. México: Manual Moderno

La presente obra fue realizada por el doctor Juan Silva Pereyra, en conjunto con colaboradores en su mayoría de la Universidad Nacional Autónoma de México y de civestav. Es una iniciativa que pretende clarificar términos y conocimientos básicos relacionados con el área de las neurociencias cognitivas, además de describir los métodos y técnicas utilizadas desde el nivel de la fisiología celular hasta aquellos métodos que intentan estudiar cerebro-mente desde una aproximación neuropsicológica para relacionar la conducta y las estructuras cerebrales involucradas. Este libro presenta varios valores añadidos, primero por abordar los métodos empleados en las neurociencias y segundo porque ambiciona cubrir en detalle los procedimientos y las técnicas utilizadas hasta el momento, así como definir conceptos y términos relevantes del área, por lo que podrá transformarse en una referencia para quien desea iniciarse en esta área de investigación, especialmente en los cursos de maestría y doctorado

Nonlinear impedance matching control for a submerged wave energy converter

Abstract The impedance matching control, also known as approximate complex conjugate control (ACC), is one of the main strategies for improving the capture of energy by point absorber wave energy converters. Such a strategy shapes the mechanical impedance related to the floater dynamics via the control law. Since the traditional ACC is given by a linear control law, this work proposes a generalization denoted as nonlinear complex conjugate control (NCC) that considers the presence of nonlinear viscous damping in addition to the usual linear damping and stiffness. The energy maximization conditions for the proposed NCC are derived in the frequency domain through the describing function method. These conditions show that the ACC is a special case of the NCC when the total damping on the floater is approximated as a linear function of its velocity. From numerical simulations of a point absorber wave energy converters with nonlinear damping, which is based on the Archimedes wave swing prototype, it is shown that the NCC provides greater energy conversion than the ACC, as well as a robust performance in the presence of variations of the damping coefficient and the excitation force peak frequency