DEPARTAMENTO SISTEMAS COMPLEJOS Y ALTAS ENERGÍAS

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https://nuclea.cnea.gob.ar/handle/20.500.12553/5208

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Examinando DEPARTAMENTO SISTEMAS COMPLEJOS Y ALTAS ENERGÍAS por Autor "Caceres, Manuel Osvaldo"

Mostrando 1 - 4 de 4
  • Miniatura
    ÍtemAcceso Abierto
    Assessing the growth rate of endangered Franciscana dolphin in Argentina, South America
    (Board, 2020) Caceres, Manuel Osvaldo; Cáceres-Saez, Iris; Secchi, Eduardo R.; Negri, María Fernanda; Panebianco, Maria Victoria; Cappozzo, Humberto Luis
    Cetacean populations are vulnerable to decline due to anthropogenic threats and life history traits. The Franciscana dolphin (Pontoporia blainvillei) has been considered the most affected small dolphin in the Southwestern Atlantic Ocean. In this study a method is presented for estimating the growth rate of the Franciscana dolphin affected by incidental mortality (bycatch) in coastal marine areas of Argentina, South America. We used a general approach based on vital parameters information such as reproductive rates and survival probabilities for an age-structured population. The Franciscana’s growth rate was estimated using Leslie’s approach through an algorithm implemented in a 14 x 14 matrix model. Then, the population was characterized analysing the discrete-time evolution of the age–population vector. We found that the potential growth rate <1 indicates that Franciscanas in Argentina are susceptible to decline under current levels of incidental mortality.
  • Miniatura
    ÍtemAcceso Abierto
    Emergence of stationary multimodality under two-timescaled dichotomic noise
    (American Physical Society, 2020) Budini, Adrián Adolfo; McHardy, Isaias; Caceres, Manuel Osvaldo; Nizama, Marco
    We study a linear Langevin dynamics driven by an additive non-Markovian symmetrical dichotomic noise. It is shown that when the statistics of the time intervals between noise transitions is characterized by two well differentiated timescales, the stationary distribution may develop multimodality (bi- and trimodality). The underlying effects that lead to a probability concentration in different points include intermittence and also a dynamical locking of realizations. Our results are supported by numerical simulations as well as by an exact treatment obtained from a Markovian embedding of the full dynamics, which leads to a third-order differential equation for the stationary distribution.
  • Miniatura
    ÍtemAcceso Abierto
    Finite-Velocity Diffusion in Random Media
    (Board, 2020) Caceres, Manuel Osvaldo
    We investigated a diffusion-like equation with a bounded speed of signal propagation (the so called telegrapher’s equation) in a random media. We discuss some properties of the mean-value solution in a well-defined perturbation theory. The frequency-dependent effective-velocity of propagation is studied in the long and short time regime. We show that due to the wave-like character of telegrapher’s equation the effective-velocity is a complex dispersive function in time. Exact results and asymptotic perturbative long-time behaviors (for an exponential space-correlated binary disorder) are presented, showing their agreement and corroborating the goodness of the effective medium approximation in continuous system.
  • Miniatura
    ÍtemAcceso Abierto
    Stochastic PDEs, random fields and exact mean-values
    (IOP science, 2020) Caceres, Manuel Osvaldo
    Introducing projector-operator technique and algebra of Terwiel's cumulants we study stochastic linear partial differential equations with global and local disorder. We present the evolution equation for the mean-value of the field as a series in terms of Terwiel's cumulant operators. Then, we prove that if we use binary disorder with time exponential-correlated structure, as source of the stochastic perturbation, this series cuts leading to a treatable evolution equation. We apply this approach to find the exact mean-value solution of electromagnetic waves with stochastic absorption of energy in conducting media. This model shows the occurrence of novel time-scale separation phenomena. Local disorder in telegrapher's equation is also presented. Thus we show that strong disorder leads to anomalous behavior at short and long time regimes. In addition, other physical systems with global disorder are worked out to find exact mean-value solutions: finite-velocity diffusion in the presence of a deterministic force (Smoluchoswki-like process generalizing, in this way, Feynman–Kac's formula for its numerical solution); Lorentz' force on a fluctuating charge model (we calculate the diffusion coefficient transverse to the applied magnetic field); and a generalized non-Maxwellian velocity distribution (Ornstein–Uhlenbeck like process showing a noise-induced transition in the stationary distribution).