228 research outputs found
Efficient harmonic oscillator chain energy harvester driven by colored noise
We study the performance of an electromechanical harmonic oscillator chain as
an energy harvester to extract power from finite-bandwidth ambient random
vibrations, which are modelled by colored noise. The proposed device is
numerically simulated and its performance assessed by means of the net
electrical power generated and its efficiency in converting the external
noise-supplied power into electrical power. Our main result is a much enhanced
performance, both in the net electrical power delivered and in efficiency, of
the harmonic chain with respect to the popular single oscillator resonator. Our
numerical findings are explained by means of an analytical approximation, in
excellent agreement with numerics
Efficient time series detection of the strong stochasticity threshold in Fermi-Pasta-Ulam oscillator lattices
In this work we study the possibility of detecting the so-called strong
stochasticity threshold, i.e. the transition between weak and strong chaos as
the energy density of the system is increased, in anharmonic oscillator chains
by means of the 0-1 test for chaos. We compare the result of the aforementioned
methodology with the scaling behavior of the largest Lyapunov exponent computed
by means of tangent space dynamics, that has so far been the most reliable
method available to detect the strong stochasticity threshold. We find that
indeed the 0-1 test can perform the detection in the range of energy density
values studied. Furthermore, we determined that conventional nonlinear time
series analysis methods fail to properly compute the largest Lyapounov exponent
even for very large data sets, whereas the computational effort of the 0-1 test
remains the same in the whole range of values of the energy density considered
with moderate size time series. Therefore, our results show that, for a
qualitative probing of phase space, the 0-1 test can be an effective tool if
its limitations are properly taken into account.Comment: 5 pages, 2 figures; accepted for publication in Physical Review
Covariant hydrodynamic Lyapunov modes and strong stochasticity threshold in Hamiltonian lattices
We scrutinize the reliability of covariant and Gram-Schmidt Lyapunov vectors
for capturing hydrodynamic Lyapunov modes (HLMs) in one-dimensional Hamiltonian
lattices. We show that,in contrast with previous claims, HLMs do exist for any
energy density, so that strong chaos is not essential for the appearance of
genuine (covariant) HLMs. In contrast, Gram-Schmidt Lyapunov vectors lead to
misleading results concerning the existence of HLMs in the case of weak chaos.Comment: 4 pages, 4 figures. Accepted for publication in Physical Review
Introducció a la Transfenomenologia de les emocions
La proposta que es presenta aquí (només amb caràcter introductori) és certament intempestiva: la Transfenomenologia de les emocions invoca la potència performativa de les emocions a través d'una aproximació enactiva per donar explicació d'aquest estar-en-el-món, espai prereflexiu de la percepció i la precomprensió, veritable camp d'acció que pot garantir un terra bàsic (ground floor) per tothom on poder explorar zones on la intercorporeïtat i l'expressió lliure de la diferència adquireixen plena significació.La propuesta que se presenta aquí (solo con carácter introductorio) es ciertamente intempestiva: la transfenomenologia de las emociones invoca la potencia performativa de las emociones a través de una aproximación enactiva para dar explicación de este estar-en-el-mundo, espacio prereflexivo de la percepción y la precomprensión, verdadero campo de acción que puede garantizar un suelo básico (ground floor) para todo el mundo donde poder explorar zonas donde la intercorporeidad y la expresión libre de la diferencia adquieren plena significación.The proposal presented here (only introductory) is certainly untimely: the transfenomenology of emotions invokes the performative power of emotions through an enactive approach to explain this being-in-the-world, prereflective space of perception and pre-understanding, a true field of action that can guarantee a basic floor (ground floor) for everyone where to explore areas where intercorporeity and free expression of difference acquire full significance
Macroscopic evidence of microscopic dynamics in the Fermi-Pasta-Ulam oscillator chain from nonlinear time series analysis
The problem of detecting specific features of microscopic dynamics in the
macroscopic behavior of a many-degrees-of-freedom system is investigated by
analyzing the position and momentum time series of a heavy impurity embedded in
a chain of nearest-neighbor anharmonic Fermi-Pasta-Ulam oscillators. Results
obtained in a previous work [M. Romero-Bastida, Phys. Rev. E {\bf69}, 056204
(2004)] suggest that the impurity does not contribute significantly to the
dynamics of the chain and can be considered as a probe for the dynamics of the
system to which the impurity is coupled. The () entropy, which measures
the amount of information generated by unit time at different scales of
time and of the observable, is numerically computed by methods of nonlinear
time-series analysis using the position and momentum signals of the heavy
impurity for various values of the energy density (energy per degree
of freedom) of the system and some values of the impurity mass . Results
obtained from these two time series are compared and discussed.Comment: 7 pages, 5 figures, RevTeX4 PRE format; to be published in Phys. Rev.
Thermal rectification in mass-graded next-nearest-neighbor Fermi-Pasta-Ulam lattices
We study the thermal rectification efficiency, i.e., quantification of asymmetric heat flow, of a one-dimensional mass-graded anharmonic oscillator Fermi-Pasta-Ulam lattice both with nearest-neighbor (NN) and next-nearestneighbor (NNN) interactions. The system presents a maximum rectification efficiency for a very precise value of the parameter that controls the coupling strength of the NNN interactions, which also optimizes the rectification figure when its dependence on mass asymmetry and temperature differences is considered. The origin of the enhanced rectification is the asymmetric local heat flow response as the heat reservoirs are swapped when a finely tuned NNN contribution is taken into account. A simple theoretical analysis gives an estimate of the optimal NNN coupling in excellent agreement with our simulation results.J.M.L.thanks Direccion General de Investigación Científica y Técnica, MINECO (Spain) for financial support through the project No. FIS2014-59462-P
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