Forecasting high waters at Venice Lagoon using chaotic time series analisys and nonlinear neural netwoks

Time series analysis using nonlinear dynamics systems theory and multilayer neural networks models have been applied to the time sequence of water level data recorded every hour at 'Punta della Salute' from Venice Lagoon during the years 1980-1994. The first method is based on the reconstruction of the state space attractor using time delay embedding vectors and on the characterisation of invariant properties which define its dynamics. The results suggest the existence of a low dimensional chaotic attractor with a Lyapunov dimension, DL, of around 6.6 and a predictability between 8 and 13 hours ahead. Furthermore, once the attractor has been reconstructed it is possible to make predictions by mapping local-neighbourhood to local-neighbourhood in the reconstructed phase space. To compare the prediction results with another nonlinear method, two nonlinear autoregressive models (NAR) based on multilayer feedforward neural networks have been developed. From the study, it can be observed that nonlinear forecasting produces adequate results for the 'normal' dynamic behaviour of the water level of Venice Lagoon, outperforming linear algorithms, however, both methods fail to forecast the 'high water' phenomenon more than 2-3 hours ahead.Publicad

Pairs-Production of Higgs in Association with Bottom Quarks Pairs at e+e−e^+e^- Colliders

In a previous paper, we studied the Higgs pair production in the standard model with the reaction $e^{+}e^{-}\to t \bar t HH$. Based on this, we study the Higgs pair production via $e^{+}e^{-}\to b \bar b HH$. We evaluate the total cross section of $b\bar bHH$ and calculate the number total of events considering the complete set of Feynman diagrams at tree-level, and compare this process with the process $e^{+}e^{-}\to t \bar t HH$. The numerical computation is done for the energy which is expected to be available at a possible Next Linear $e^{+}e^{-}$ Collider with a center-of-mass energy $800, 1000, 1600$ $GeV$ and luminosity 1000 $fb^{-1}$.Comment: 12 pages, 6 figure

Bounds on the dipole moments of the tau-neutrino via the process e+e−→ννˉγe^{+}e^{-}\rightarrow \nu \bar \nu \gamma in a 331 model

We obtain limits on the anomalous magnetic and electric dipole moments of the $\nu_{\tau}$ through the reaction $e^{+}e^{-}\rightarrow \nu \bar \nu \gamma$ and in the framework of a 331 model. We consider initial-state radiation, and neglect $W$ and photon exchange diagrams. The results are based on the data reported by the L3 Collaboration at LEP, and compare favorably with the limits obtained in other models, complementing previous studies on the dipole moments.Comment: 13 pages, 4 figures, to be published in The European Physical J C. arXiv admin note: substantial text overlap with arXiv:hep-ph/060527

Efecto de las resistencias aerodinámicas sobre el alcance de lanzamientos de martillo masculinos y femenino de atletas de élite

El alcance del lanzamiento de martillo está determinado por las condiciones cinemáticas en el momento de salida de las manos del lanzador, en concreto por la velocidad, el ángulo y la altura de salida. A partir de ahí, la distancia teórica alcanzada por el martillo, proveniente por las ecuaciones de los proyectiles, puede ser determinada. La diferencia encontrada entre la distancia real y la teórica calculada, nos aportaría el objetivo planteado en este estudio basado en conocer el efecto de las resistencias aerodinámicas sobre el alcance del lanzamiento. La muestra utilizada se ha basado en los seis finalistas masculinos y femeninos del campeonato del mundo de atletismo de Sevilla 1999. Los lanzamientos fueron filmados por cámaras de video SVHS (50 Hz) siguiendo posteriormente la metodología de análisis tridimensionales de video (50 Hz) ubicada en el Laboratorio de Biomecánica de la Universidad de Granada. Los resultados obtenidos muestran los parámetros cinemáticos producidos en el momento de la salida del martillo, siendo la velocidad la variable en la cual se han encontrado diferencias significativas entre hombres y mujeres, 28.64 y 26.90 m/s, respectivamente y las diferencias encontradas utilizando diferentes metodologías entre los alcances teóricos calculados y los reales siendo la pérdida de alcance de un 13,23% y de un 8,85% en los lanzamiento femeninos y masculinos respectivamente. Los datos obtenidos confirman que las grandes diferencias encontradas entre los lanzamientos masculinos y femeninos (11.28 m), aún siendo la masa del martillo diferentes (7.26 kg en hombres y 4 kg en mujeres) se deben en gran medida a los factores aerodinámicos

Discontinuities without discontinuity: The Weakly-enforced Slip Method

Tectonic faults are commonly modelled as Volterra or Somigliana dislocations in an elastic medium. Various solution methods exist for this problem. However, the methods used in practice are often limiting, motivated by reasons of computational efficiency rather than geophysical accuracy. A typical geophysical application involves inverse problems for which many different fault configurations need to be examined, each adding to the computational load. In practice, this precludes conventional finite-element methods, which suffer a large computational overhead on account of geometric changes. This paper presents a new non-conforming finite-element method based on weak imposition of the displacement discontinuity. The weak imposition of the discontinuity enables the application of approximation spaces that are independent of the dislocation geometry, thus enabling optimal reuse of computational components. Such reuse of computational components renders finite-element modeling a viable option for inverse problems in geophysical applications. A detailed analysis of the approximation properties of the new formulation is provided. The analysis is supported by numerical experiments in 2D and 3D.Comment: Submitted for publication in CMAM