Differential Galois Approach to the Non-integrability of the Heavy Top Problem

We study integrability of the Euler-Poisson equations describing the motion of a rigid body with one fixed point in a constant gravity field. Using the Morales-Ramis theory and tools of differential algebra we prove that a symmetric heavy top is integrable only in the classical cases of Euler, Lagrange, and Kovalevskaya and is partially integrable only in the Goryachev-Chaplygin case. Our proof is alternative to that given by Ziglin ({\em Funktsional. Anal. i Prilozhen.}, 17(1):8--23, 1983; {\em Funktsional. Anal. i Prilozhen.}, 31(1):3--11, 95, 1997).Comment: 31 pages, 1 figur

Small but long koch fractal monopole

A small but long wire fractal antenna based on the Koch curve is presented. Experimental and numerical results show that the antenna improves the features of a common linear monopole. The radiation resistance is increased and the Q is reduced at each fractal iteration, approaching the fundamental limit on small antennas.Peer ReviewedPostprint (published version

Sphenopteris asturica nueva especie

Se describe un ejemplar (holotipo) de la Cuenca de Tineo (Asturias) que se atribuye a una nueva especie del género Sphenopteris caracterizada por sus raquis acanalados que portan pínulas de contorno triangular alargado de bordes lobulados, con nervio central neto y sinuoso decurrente sobre el raquis que emite nervios secundarios de forma pecopterideana. Presenta esta especie semejanzas con Sph. burgkensis Sterzel (= Sph. leptophylla Bunb.) y con Sph. goniopteroides Lesqu.Se figura también un ejemplar de Commentry (Francia) así como dos pequeños fragmentos de Puerto Ventana. Todos los ejemplares figurados así como otro citado procedente de Surroca (Gerona) proceden de niveles estefanienses

Contribution a la connaissance de la flore carbonifère des pyrénñees basques (Larroun et Ibantelly)

In this work we descrive fossil plants collected in Piri- neos mountains. Here are classified 33 species of which thirteen lias been stated in the coaldfield for first time. The coaldfield is dated as the upper Stephanian B or as the low Stepha- nian C

On collisional free-free photon absorption in warm dense matter

The rate of photon absorption in warm dense matter (WDM) induced by free-free electron-ion collisions is derived from Sommerfeld's cross-section for non-relativistic bremsstrahlung emission, making use of detailed balance relations. Warm dense matter is treated as a metal-like state in the approximation of a uniform degenerate electron gas and a uniform ion background. Total absorption rates are averaged over the electron Fermi distribution. A closed expression is obtained for the absorption rate, depending on temperature, density, and photon energy, that scales with ion charge Z. It is evaluated numerically for the full parameter space, which requires different representations of the hypergeometric functions involved. The results are valid for photon frequencies larger than the plasma frequency of the medium. They are compared with approximate formulas in various asymptotic regions

Numerical analysis of the vibrational behavior of the moving assembly of a dynamic loudspeaker

En este trabajo se describe el proceso llevado a cabo para analizar numéricamente mediante el método de los elementos finitos (MEF) el comportamiento vibratorio del conjunto móvil de un altavoz dinámico de bobina con doble suspensión inferior y en ausencia de la superior. El estudio se centra en el rango de baja frecuencia. El calibrado del modelo se realiza en base a medidas experimentales de la frecuencia de resonancia y desplazamiento del diafragma. Se hace énfasis en la importancia de los factores de participación asociados a la fuerza de excitación y en los cambios que se producen en estos al introducir fuerzas no equilibradas. Así mismo, el análisis proporciona datos para decidir sobre la distancia entre suspensiones, su número óptimo de pliegues y la ubicación de las trencillas, siendo estos parámetros de gran interés en el diseño de este tipo de altavoces.This paper describes the process undertaken to analyze numerically the vibrational behavior of the moving assembly of a dynamic loudspeaker with double bottom suspension and in the absence of the above one using the finite element method (FEM). The study focuses on the low frequency range. Model calibration was performed based on experimental measurements of the resonance frequency and diaphragm displacement. The importance of the participation factors associated to the excitation force and the changes produced in these when unbalanced forces are introduced are emphasized. The analysis also provides data to decide on the distance between suspensions, their optimal number of folds and the placement of the lead wires, parameters of great interest on the design of this type of loudspeakers.Peer Reviewe

Datos para la historia de Artá : reconstrucció de la fortalesa de Sant Salvador : Almudayna d'Artá : segle XVI

Abstract not availabl