Search results for "Colors"

showing 10 items of 37 documents

Coupling Between Periodic and Aperiodic Variability in SAX J1808.4-3658

2003

We detect a significant broadening in the wings of the 401 Hz peak in the power spectrum of the accreting millisecond binary pulsar SAX J1808.4-3658. This feature is consistent with the convolution of the red noise present in the power spectrum with the harmonic line. We conclude that the flux modulated by the spin period shows aperiodic variability similar to the red noise in the overall flux, suggesting such variability also originates at the magnetic caps close to the neutron star surface. This is analogous to the results found in some longer period, higher magnetic field pulsators in high mass X-ray binaries.

PhysicsAstrophysics::High Energy Astrophysical PhenomenaAstrophysics (astro-ph)FluxSpectral densityFOS: Physical sciencesAstronomy and AstrophysicsAstrophysicsAstrophysicsBinary pulsarMagnetic fieldNeutron starSpace and Planetary ScienceAperiodic graphColors of noiseAstrophysics::Solar and Stellar AstrophysicsLine (formation)
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Correlation dimension and affinity of AE data and bicolored noise

1993

This paper is concerned with the general question of the dynamics of the magnetosphere. In general, to solve the dynamics of the magnetosphere one has to solve magnetohydrodynamic equations with some appropriate set of boundary conditions. This results in a very complex solution, which gives indications of being chaotic. The question of the chaotic nature of the magnetospheric dynamics has been addressed by various authors by looking at the correlation dimension of the auroral electrojet index. There has been disagreement on the outcome of such experiments, so the authors report on a detailed analysis of the auroral electrojet index time series. They find a correlation dimension of 3.4. For…

PhysicsCorrelation dimensionSeries (mathematics)ChaoticElectrojetMagnetosphereTheoretical physicsGeophysicsFractalColors of noisePhysics::Space PhysicsSubstormGeneral Earth and Planetary SciencesStatistical physicsGeophysical Research Letters
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Noise-induced enhancement of stability in a metastable system with damping

2010

5 páginas, 5 figuras.-- PACS number(s): 05.40.-a, 02.50.-r

PhysicsFluctuation phenomena random processes noise and Brownian motionCondensed matter physicsProbability theory stochastic processes and statisticFunction (mathematics)Stability (probability)Settore FIS/03 - Fisica Della MateriaProbability theory stochastic processes and statistics; Fluctuation phenomena random processes noise and Brownian motionColors of noiseMetastabilityQuantum mechanicsParticleFirst-hitting-time modelNoise (radio)Brownian motion
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Noise effects in two different biological systems

2009

We investigate the role of the colored noise in two biological systems: (i) adults of Nezara viridula (L.) (Heteroptera: Pentatomidae), and (ii) polymer translocation. In the first system we analyze, by directionality tests, the response of N. viridula individuals to subthreshold signals plus noise in their mating behaviour. The percentage of insects that react to the subthreshold signal shows a nonmonotonic behaviour, characterized by the presence of a maximum, as a function of the noise intensity. This is the signature of the non-dynamical stochastic resonance phenomenon. By using a “soft” threshold model we find that the maximum of the input-output cross correlation occurs in the same ra…

PhysicsFluctuation phenomena random processes noise and Brownian motionQuantitative Biology::BiomoleculesCondensed matter physicsBistabilityStochastic resonanceStochastic processMolecular dynamics Brownian dynamicThermal fluctuationsMolecular interactionWhite noiseNoise in biological systemCondensed Matter PhysicsMolecular physicsSettore FIS/07 - Fisica Applicata(Beni Culturali Ambientali Biol.e Medicin)Electronic Optical and Magnetic MaterialsColors of noiseBrownian dynamicsPolymermembrane-protein interactionsNoise (radio)Biophysical mechanisms of interaction
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Dynamics of a FitzHugh-Nagumo system subjected to autocorrelated noise

2008

We analyze the dynamics of the FitzHugh-Nagumo (FHN) model in the presence of colored noise and a periodic signal. Two cases are considered: (i) the dynamics of the membrane potential is affected by the noise, (ii) the slow dynamics of the recovery variable is subject to noise. We investigate the role of the colored noise on the neuron dynamics by the mean response time (MRT) of the neuron. We find meaningful modifications of the resonant activation (RA) and noise enhanced stability (NES) phenomena due to the correlation time of the noise. For strongly correlated noise we observe suppression of NES effect and persistence of RA phenomenon, with an efficiency enhancement of the neuronal respo…

PhysicsFluctuation phenomena random processes noise and Brownian motionSettore FIS/02 - Fisica Teorica Modelli E Metodi MatematiciAutocorrelationDynamics (mechanics)Mean and predicted responseModels of single neurons and networks; Noise in the nervous system; Fluctuation phenomena random processes noise and Brownian motion; Nonlinear dynamics and chaosFOS: Physical sciencesNoise in the nervous systemModels of single neurons and networkCondensed Matter PhysicsFitzhugh nagumoNonlinear dynamics and chaosStability (probability)Electronic Optical and Magnetic MaterialsPeriodic functionNoiseColors of noiseBiological Physics (physics.bio-ph)Statistical physicsPhysics - Biological Physics
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EFFECTS OF COLORED NOISE IN SHORT OVERDAMPED JOSEPHSON JUNCTION

2008

We investigate the transient dynamics of a short overdamped Josephson junction with a periodic driving signal in the presence of colored noise. We analyze noise induced henomena, specifically resonant activation and noise enhanced stability. We find that the positions both of the minimum of RA and maximum of NES depend on the value of the noise correlation time tau_c. Moreover, in the range where RA is observed, we find a non-monotonic behavior of the mean switching time as a function of the correlation time tau_c.

PhysicsJosephson effectPhysics and Astronomy (miscellaneous)Condensed matter physicsCondensed Matter - SuperconductivityFOS: Physical sciencesResonant activationJosephson junction; Colored noise; Resonant activation; Noise enhanced stabilityColored noiseStability (probability)SignalSettore FIS/03 - Fisica Della MateriaSuperconductivity (cond-mat.supr-con)Switching timeColors of noiseJosephson junctionRange (statistics)Transient (oscillation)Noise enhanced stabilityNoise (radio)International Journal of Quantum Information
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Noise induced effects in overdamped Josephson junction in the presence of colored noise

2007

We analyze the role of the correlated fluctuations, with a correlation time τc, in the dynamics of an overdamped Josephson junction in the presence of a periodic driving signal.

PhysicsJosephson effectmean switching timeJosephson phaseCondensed matter physicsNoise inducedJosephson junction; mean switching time; colored noiseNoise (electronics)SignalSettore FIS/03 - Fisica Della MateriaPi Josephson junctioncolored noiseColors of noiseCondensed Matter::SuperconductivityJosephson junctionElectronic engineeringSuperconducting tunnel junction
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Harmonic Coupling of the Red Noise in X‐Ray Pulsars

1997

The power spectra of X-ray pulsars often show the presence of a red-noise component. This noise is produced by aperiodic variability believed to be associated with instabilities that seem to occur in accretion flows onto compact objects. In this paper we discuss how, independently of the details of the physical processes that generate these instabilities, a careful analysis of the power spectra can furnish some constraints on the distance from the stellar surface at which the sudden energy release associated with the instabilities occurs. In particular, any aperiodic variability coming from the accretion flow funneled toward the magnetic poles should be modulated at the pulsar spin period (…

PhysicsPulsarSpace and Planetary ScienceColors of noiseAperiodic graphHarmonicsX-rayAstronomy and AstrophysicsAstrophysicsLight curveAccretion (astrophysics)Spectral lineThe Astrophysical Journal
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Magnetostochastic resonance under colored noise condition

2012

Stochastic resonance (SR) is an amplification of the system output in correspondence of well-defined finite values of the noise strength that is injected into the system [Gammaitoni et al., Rev. Mod. Phys. 70, 223 (1998), Grigorenko et al., IEEE Trans. Magn. 31, 2491 (1995), Mantegna et al., J. Appl. Phys. 97, 10E519 (2005)]. In order to clarify the influence of a colored noise, in this paper magnetostochastic resonance (MSR) in magnetic systems described by the dynamic Preisach model is numerically investigated in the presence of colored noise. In this paper it is shown that: a) noise spectrum affects MSR; b) white noise, 1/f and 1/f(2) noise induce in magnetic systems described by the dyn…

PhysicsStochastic resonanceSTOCHASTIC RESONANCEPREISACH MODELNoise spectral densityGeneral Physics and AstronomyResonanceWhite noiseSettore ING-IND/32 - Convertitori Macchine E Azionamenti ElettriciMagnetic hysteresisNuclear magnetic resonanceColors of noiseQuantum mechanicsHYSTERESISNoise (radio)Noise strengthJournal of Applied Physics
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How does environmental variation translate into biological processes?

2001

Birth and death rates, as so many other biological processes, are usually not linearly related to environmental variation. Common examples of non-linear response forms include unimodal ‘‘optimum-type’’ responses and various saturating responses. These responses filter the signal coming from the environment to a corresponding biological process. We explored how different types of environmental signal may be transformed to a biological process. We were interested in the effect of the filter on modulation of (1) the variance of the signal, on (2) the variance-covariance structure between the signal and the filtered signal, and on (3) the match between the power spectra of the signal and the fi…

Physicseducation.field_of_studyColors of noiseModulationPopulationSpectral densityFilter (signal processing)Biological systemeducationSignalEcology Evolution Behavior and SystematicsBirth–death processPower (physics)Oikos
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