Simulation study of the inhomogeneous Olami-Feder-Christensen model of earthquakes

Statistical properties of the inhomogeneous version of the Olami-Feder-Christensen (OFC) model of earthquakes is investigated by numerical simulations. The spatial inhomogeneity is assumed to be dynamical. Critical features found in the original homogeneous OFC model, e.g., the Gutenberg-Richter law and the Omori law are often weakened or suppressed in the presence of inhomogeneity, whereas the characteristic features found in the original homogeneous OFC model, e.g., the near-periodic recurrence of large events and the asperity-like phenomena persist.Comment: Shortened from the first version. To appear in European Physical Journal

The Effect of a Single Supernova Explosion on the Cuspy Density Profile of a Small-Mass Dark Matter Halo

Some observations of galaxies, and in particular dwarf galaxies, indicate a presence of cored density profiles in apparent contradiction with cusp profiles predicted by dark matter N-body simulations. We constructed an analytical model, using particle distribution functions (DFs), to show how a supernova (SN) explosion can transform a cusp density profile in a small-mass dark matter halo into a cored one. Considering the fact that a SN efficiently removes matter from the centre of the first haloes, we study the effect of mass removal through a SN perturbation in the DFs. We found that the transformation from a cusp into a cored profile is present even for changes as small as 0.5% of the total energy of the halo, that can be produced by the expulsion of matter caused by a single SN explosion.Comment: 6 pages, 4 figures, accepted for publication in MNRA

Adaptation of Hybrid ANN/HMM Models using Linear Hidden Transformations and Conservative Training

International audienceA technique is proposed for the adaptation of automatic speech recognition systems using Hybrid models combining Artificial Neural Networks with Hidden Markov Models. The application of linear transformations not only to the input features, but also to the outputs of the internal layers is investigated. The motivation is that the outputs of an internal layer represent a projection of the input pattern into a space where it should be easier to learn the classification or transformation expected at the output of the network. A new solution, called Conservative Training, is proposed that compensates for the lack of adaptation samples in certain classes. Supervised adaptation experiments with different corpora and for different adaptation types are described. The results show that the proposed approach always outperforms the use of transformations in the feature space and yields even better results when combined with linear input transformations

Poisson-Bracket Approach to the Dynamics of Nematic Liquid Crystals. The Role of Spin Angular Momentum

Nematic liquid crystals are well modeled as a fluid of rigid rods. Starting from this model, we use a Poisson-bracket formalism to derive the equations governing the dynamics of nematic liquid crystals. We treat the spin angular momentum density arising from the rotation of constituent molecules about their centers of mass as an independent field and derive equations for it, the mass density, the momentum density, and the nematic director. Our equations reduce to the original Leslie-Ericksen equations, including the inertial director term that is neglected in the hydrodynamic limit, only when the moment of inertia for angular momentum parallel to the director vanishes and when a dissipative coefficient favoring locking of the angular frequencies of director rotation and spin angular momentum diverges. Our equations reduce to the equations of nematohydrodynamics in the hydrodynamic limit but with dissipative coefficients that depend on the coefficient that must diverge to produce the Leslie-Ericksen equations.Comment: 10 pages, to be published in Phys. Rev. E 72(5

Dinâmica da produção de cevada no Brasil no período de 1975 a 2003.

A observação do comportamento da evolução de uma determinada cultura em termos de magnitude e localização e o estudo das razões do processo observado são elementos importantes para avaliação de cenário e para formulação de estratégias para desenvolvimento desta cultura nos próximos anos. Este trabalho teve por objetivo analisar a dinâmica espacial da produção de cevada no Brasil no período de 1975 a 2003, mediante a análise de estatísticas descritivas, de indicadores de assimetria e concentração, distâncias, centros de gravidade e mapas,tomando por base os anos de 1975, 1985, 1995 e 2003. A evolução da área colhida, da quantidade produzida e da produtividade de cevada no Brasil no período de 1975-2003 apresentou crescimento, sendo o mesmo mais expressivo nas décadas de 70 e 80. Observa-se que a cultura da cevada tem permanecido circunscrita a uma área tradicional de cultivo, a região sul do Brasil, sendo as região sul-sudeste do PR e norte do RS destaques na participação da área colhida e quantidade produzida. Das 33 a 46 microrregiões com registro de cultivo de cevada nos anos estudados, observou-se que 8a 11 microrregiões foram suficientes para reunir 75% a área colhida ou da quantidade produzida. Pelos indicadores encontrados pode-se supor que há um grupo pequeno de microrregiões que possuem alta representatividade na produção do cereal e mantém-se estável no cultivo de cevada e um grande grupo de microrregiões de baixa expressão no cultivo do cereal e que o faz de maneira não constante. Em termos espaciais, a cultura de cevada não apresentou grande deslocamento da distribuição ponderada do cultivo.bitstream/item/35616/1/Dinamica-da-producao-de-cevada.pd

Dinâmica da produção de aveia grão no Brasil no período de 1975 a 2003.

bitstream/CNPT-2010/40311/1/p-bp38.pd

Dinâmica da produção de trigo no Brasil no período de 1975 a 2003.

bitstream/CNPT-2010/40309/1/p-bp36.pd

A recent appreciation of the singular dynamics at the edge of chaos

We study the dynamics of iterates at the transition to chaos in the logistic map and find that it is constituted by an infinite family of Mori's $q$-phase transitions. Starting from Feigenbaum's $\sigma$ function for the diameters ratio, we determine the atypical weak sensitivity to initial conditions $\xi _{t}$ associated to each $q$-phase transition and find that it obeys the form suggested by the Tsallis statistics. The specific values of the variable $q$ at which the $q$-phase transitions take place are identified with the specific values for the Tsallis entropic index $q$ in the corresponding $\xi_{t}$. We describe too the bifurcation gap induced by external noise and show that its properties exhibit the characteristic elements of glassy dynamics close to vitrification in supercooled liquids, e.g. two-step relaxation, aging and a relationship between relaxation time and entropy.Comment: Proceedings of: Verhulst 200 on Chaos, Brussels 16-18 September 2004, Springer Verlag, in pres