4,617 research outputs found
Wigner instability analysis of the damped Hirota equation
We address the modulation instability of the Hirota equation in the presence
of stochastic spatial incoherence and linear time-dependent
amplification/attenuation processes via the Wigner function approach. We show
that the modulation instability remains baseband type, though the damping
mechanisms substantially reduce the unstable spectrum independent of the
higher-order contributions (e.g. the higher-order nonlinear interaction and the
third-order dispersion). Additionally, we find out that the unstable structure
due to the Kerr interaction exhibits a significant resilience to the
third-order-dispersion stabilizing effects in comparison with the higher-order
nonlinearity, as well as a moderate Lorentzian spectrum damping may assist the
rising of instability. Finally, we also discuss the relevance of our results in
the context of current experiments exploring extreme wave events driven by the
modulation instability (e.g. the generation of the so-called rogue waves).Comment: 7+4 pages. 3 figures. Comments are welcome. To appear in Physica
Neural networks and spectra feature selection for retrival of hot gases temperature profiles
Proceeding of: International Conference on Computational Intelligence for Modelling, Control and Automation, 2005 and International Conference on Intelligent Agents, Web Technologies and Internet Commerce, Vienna, Austria 28-30 Nov. 2005Neural networks appear to be a promising tool to solve the so-called inverse problems focused to obtain a retrieval of certain physical properties related to the radiative transference of energy. In this paper the capability of neural networks to retrieve the temperature profile in a combustion environment is proposed. Temperature profile retrieval will be obtained from the measurement of the spectral distribution of energy radiated by the hot gases (combustion products) at wavelengths corresponding to the infrared region. High spectral resolution is usually needed to gain a certain accuracy in the retrieval process. However, this great amount of information makes mandatory a reduction of the dimensionality of the problem. In this sense a careful selection of wavelengths in the spectrum must be performed. With this purpose principal component analysis technique is used to automatically determine those wavelengths in the spectrum that carry relevant information on temperature distribution. A multilayer perceptron will be trained with the different energies associated to the selected wavelengths. The results presented show that multilayer perceptron combined with principal component analysis is a suitable alternative in this field.Publicad
Topological magnetoelectric response in passive magnetic devices
Despite the prospect of next-generation electronic technologies has spurred
the investigation of the remarkable topological magnetoelectric response, it
remains largely unexplored its potential in the application of basic electronic
devices. In this paper, we undertake this task at the theoretical level by
addressing the -electrodynamics and examine electromagnetic properties
(e.g. tunable inductance, operating frequency range, and power consumption) of
three fundamental passive magnetic devices endowed with this effect: the
primitive transformer, the bilayer solenoid inductor, and the solenoid
actuator. We further exploit the methodology of magnetic circuits to obtain an
extended Hopkinson's law that is valid for both topological and ordinary
magnetoelectric responses (provided it is uniform in the bulk). Under low-power
conditions, we find out that the functionally passive part of the
topological-magnetoelectric transformer, solenoid inductor as well as solenoid
actuator is indistinguishable from the conventional situation up to
second-order in the magnetoelectric susceptibility; and argue that the main
benefit of using topological insulators essentially relies on a lower power
consumption. Our theoretical framework is also convenient to analyse
magnetoelectric inductors endowed with a relatively large magnetoelectric
susceptibility, they display a broad inductance tunability of over 250% up to
10 MHz. Conversely, our treatment predicts that the operating frequency range
could be restricted below the ultra low frequency by a significantly strong
magnetoelectric response (e.g. retrieved by certain multiferroic
heterostructures).Comment: 22+6 pages, 8 figures. Comments are welcom
El fracaso del krauso-institucionismo en Mallorca
Abstract not availabl
Exploring a rheonomic system
A simple and illustrative rheonomic system is explored in the Lagrangian
formalism. The difference between Jacobi's integral and energy is highlighted.
A sharp contrast with remarks found in the literature is pointed out. The
non-conservative system possess a Lagrangian not explicitly dependent on time
and consequently there is a Jacobi's integral. The Lagrange undetermined
multiplier method is used as a complement to obtain a few interesting
conclusion
EFECTOS ULTRA FRONTERA Y CONVERGENCIA REGIONAL. UNA REFLEXIĂ“N A PARTIR DEL MAC 94-99 EN ANDALUCĂŤA.
En este trabajo se evalĂşan los efectos ex-post del MAC 1994-1999 en AndalucĂa (España), los efectos directos e indirectos de las inversiones dentro de la regiĂłn y los efectos fuga producidos hacia el resto del paĂs (cross-border leakage). Utilizando un modelo multisectorial de dos regiones, la andaluza y el resto de España, se comparan los estĂmulos inducidos por los fondos estructurales en es resto de la economĂa nacional con los producidos en la economĂa andaluza. Los resultados muestran que, al menos a corto y medio plazo, los resultados sobre la convergencia real pueden ser poco o nada relevantes. PodrĂa afirmarse que las regiones más desarrolladas del paĂs han sido grandes beneficiarias indirectas de los fondos destinados a las regiones de objetivo 1.Structural Funds Evaluation; Regional Convergence; Cross- Border Leakages
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