Interatomic potential structures in highly ionized scattering systems

The interatomic potential of the ion-atom scattering system I^N+-I at small intermediate internuclear distances is calculated for different charge states N from atomic Dirac-Focker-Slater (DFS) electron densities within a statistical model. The behaviour of the potential structures, due to ionized electronic shells, is studied by calculations of classical elastic differential scattering cross-sections.

Elastic nuclear scattering at intermediate and relativistic energies

The classical scattering cross section of two colliding nuclei at intermediate and relativistic energies is reevaluated. The influence of retardation and magnetic field effects is taken into account. Corrections due to electron screening as well as due to attractive nuclear forces are discussed. This paper represents an addendum to [l].

Realistic many electron coupled channel calculations in heavy ion scattering

The time dependent Dirac equation which describes a heavy ion-atom collision system is solved via a set of coupled channel equations with energy eigenvalues and matrix elements which are given by a selfconsistent field many electron calculation. After a brief discussion of the theoretical approximations and the connection of the many particle with the one particle interpretation we discuss first results for the systems F{^8+} - Ne and F{^6+} - Ne. The resulting P(b) curves for the creation of a Ne K-hole are in good agreement with the experimental results.

Scattering and absorption by acoustic resonators

by Karl Uno Ingard.

Orden de Predicadores Dominicos -OP-Dominicos- Congregación Dominicas de la Anunciata. Dominicas de la Enseñanza de la Inmaculada Concepción.

La orden de los Predicadores es fundada por Santo Domingo de Guzmán en el siglo XIII y desde sus orígenes está vigente la vocación de educar. El desafío educativo que persigue esta orden es la búsqueda de la verdad, y su estilo educativo está en desentrañar, con habilidad y respeto, el sentido de verdad que se esconde en las personas y en la naturaleza. Contemplar y estudiar son objetos que pueden ayudar a encontrar la verdad. Los principios educativos de la orden dominica son educar la interioridad, educar para ejercer adecuadamente la libertad, educar para la relación con los otros y educar para pensar. Adjunta una ficha con los datos y direcciones de la congregación.

Pedro y el Lobo : Sergei Prokofiev, cuento musical para narrador y orquesta, op. 67.

Resumen tomado de la publicación

Pedro eta Otsoa : Sergei Prokofiev kontalari eta orkestrarako musika-ipuina, op. 67. 'Pedro y el Lobo : Sergei Prokofiev, cuento musical para narrador y orquesta, op. 67'.

Resumen tomado de la publicación

Análisis de op. 23, núm. 1 de Schoenberg.

Se comentan algunos de los rasgos que caracterizan la escritura de Schoenberg y se analiza la primera pieza del Opus 23, proponiendo una guía de audición y actividades para el aula.

A collocation method for high frequency scattering by convex polygons

We consider the problem of scattering of a time-harmonic acoustic incident plane wave by a sound soft convex polygon. For standard boundary or finite element methods, with a piecewise polynomial approximation space, the computational cost required to achieve a prescribed level of accuracy grows linearly with respect to the frequency of the incident wave. Recently Chandler–Wilde and Langdon proposed a novel Galerkin boundary element method for this problem for which, by incorporating the products of plane wave basis functions with piecewise polynomials supported on a graded mesh into the approximation space, they were able to demonstrate that the number of degrees of freedom required to achieve a prescribed level of accuracy grows only logarithmically with respect to the frequency. Here we propose a related collocation method, using the same approximation space, for which we demonstrate via numerical experiments a convergence rate identical to that achieved with the Galerkin scheme, but with a substantially reduced computational cost.

Efficient evaluation of highly oscillatory acoustic scattering surface integrals

We consider the approximation of some highly oscillatory weakly singular surface integrals, arising from boundary integral methods with smooth global basis functions for solving problems of high frequency acoustic scattering by three-dimensional convex obstacles, described globally in spherical coordinates. As the frequency of the incident wave increases, the performance of standard quadrature schemes deteriorates. Naive application of asymptotic schemes also fails due to the weak singularity. We propose here a new scheme based on a combination of an asymptotic approach and exact treatment of singularities in an appropriate coordinate system. For the case of a spherical scatterer we demonstrate via error analysis and numerical results that, provided the observation point is sufficiently far from the shadow boundary, a high level of accuracy can be achieved with a minimal computational cost.

A Galerkin boundary element method for high frequency scattering by convex polygons

In this paper we consider the problem of time-harmonic acoustic scattering in two dimensions by convex polygons. Standard boundary or finite element methods for acoustic scattering problems have a computational cost that grows at least linearly as a function of the frequency of the incident wave. Here we present a novel Galerkin boundary element method, which uses an approximation space consisting of the products of plane waves with piecewise polynomials supported on a graded mesh, with smaller elements closer to the corners of the polygon. We prove that the best approximation from the approximation space requires a number of degrees of freedom to achieve a prescribed level of accuracy that grows only logarithmically as a function of the frequency. Numerical results demonstrate the same logarithmic dependence on the frequency for the Galerkin method solution. Our boundary element method is a discretization of a well-known second kind combined-layer-potential integral equation. We provide a proof that this equation and its adjoint are well-posed and equivalent to the boundary value problem in a Sobolev space setting for general Lipschitz domains.