Tutorial TaxTools.

A ferramenta TaxTools foi desenvolvida pelo Laboratório de Inteligência Computacional (Labic) do Instituto de Ciência Matemática e de Computação (ICMC) da Universidade de São Paulo (USP), campus de São Carlos, SP, com o objetivo de auxiliar no processo de mineração de textos. Atualmente, ela tem sido mantida e evoluída pelo Laboratório de Inteligência Computacional (LabIC) da Embrapa Informática Agropecuária. Esse tutorial abrange apenas as opções disponíveis na TaxTools, que completam o processo de obtenção de uma taxonomia de tópicos (MOURA et al., 2008); como clusterização, cálculos de medidas intercluster e de joinability, métodos de podas, métodos de visualização de resultados e algumas opções auxiliares.bitstream/item/30572/1/doc104.pd

Superdiffusion of massive particles induced by multi-scale velocity fields

We study drag-induced diffusion of massive particles in scale-free velocity fields, where superdiffusive behavior emerges due to the scale-free size distribution of the vortices of the underlying velocity field. The results show qualitative resemblance to what is observed in fluid systems, namely the diffusive exponent for the mean square separation of pairs of particles and the preferential concentration of the particles, both as a function of the response time.Comment: 5 pages, 5 figures. Accepted for publication in EP

The Network of Epicenters of the Olami-Feder-Christensen Model of Earthquakes

We study the dynamics of the Olami-Feder-Christensen (OFC) model of earthquakes, focusing on the behavior of sequences of epicenters regarded as a growing complex network. Besides making a detailed and quantitative study of the effects of the borders (the occurrence of epicenters is dominated by a strong border effect which does not scale with system size), we examine the degree distribution and the degree correlation of the graph. We detect sharp differences between the conservative and nonconservative regimes of the model. Removing border effects, the conservative regime exhibits a Poisson-like degree statistics and is uncorrelated, while the nonconservative has a broad power-law-like distribution of degrees (if the smallest events are ignored), which reproduces the observed behavior of real earthquakes. In this regime the graph has also a unusually strong degree correlation among the vertices with higher degree, which is the result of the existence of temporary attractors for the dynamics: as the system evolves, the epicenters concentrate increasingly on fewer sites, exhibiting strong synchronization, but eventually spread again over the lattice after a series of sufficiently large earthquakes. We propose an analytical description of the dynamics of this growing network, considering a Markov process network with hidden variables, which is able to account for the mentioned properties.Comment: 9 pages, 10 figures. Smaller number of figures, and minor text corrections and modifications. For version with full resolution images see http://fig.if.usp.br/~tpeixoto/cond-mat-0602244.pd

ESTIMATION OF BALLISTIC PARAMETERS OF GUN PROPELLANTS THROUGH CLOSED VESSEL EXPERIMENT MODELING

Closed vessels have being used for the regression of lumped ballistic parameters for decades. However, if material and energy balances are coupled with burning rate empirical correlations, several uncorrelated parameters can be estimated, which describe more accurately the thermochemical behavior of the gases generated, even if the chemical composition of the propellant is unknown (as when the propellant is aged, for instance). This research presents such approach leading to a system of differential equations which are integrated to produce a theoretical pressure profile in the vessel, highly dependent on the choice of empirical parameters. Such parameters are manipulated according to the Maximum Likelihood statistical procedure, which leads to the best set of parameters to describe the propellant

Out-of-plane neural microelectrode arrays fabrication using conventional blade dicing

\This paper describes an optimized out-of-plane fabrication method for neural 3D high-aspect-ratio microelectrode array (MEA) based on a dicing technology platform (a standard procedure in semiconductor industry). The proposed MEA fabrication required important modifications in the dicing process. Since electrodes length reaches up to 4 mm, the main hindrance was the 2 mm cutting depth limit allowed for dicing machines with regular blades. This new procedure consisted on modifying Z-axis calibration, so cuts as deep as the exposure of blades were possible. The employment of proper blades for each fabrication step was also mandatory. Thin and high-exposure blades were used for deep cuts in silicon wafers, and V-shaped blades were employed to produce sharpened tips on the electrodes. Moreover, parameters as very low-cut speeds were essential to avoid wafer chipping and microcracks. Results showed high-precision and high-quality cuts in all steps of the 3D MEA fabrication, without unnecessary additional steps of etching post-processing. The optimized fabrication process was successfully demonstrated with a 3D neural probe array comprising 36 individually addressable electrodes