Canard Cycles and Poincar\'e Index of Non-Smooth Vector Fields on the Plane

This paper is concerned with closed orbits of non-smooth vector fields on the plane. For a subclass of non-smooth vector fields we provide necessary and sufficient conditions for the existence of canard kind solutions. By means of a regularization we prove that the canard cycles are singular orbits of singular perturbation problems which are limit periodic sets of a sequence of limit cycles. Moreover, we generalize the Poincar\'e Index for non-smooth vector fields.Comment: 20 pages, 25 figure

Convergent decomposition techniques for training RBF neural networks.

In this article we define globally convergent decomposition algorithms for supervised training of generalized radial basis function neural networks. First, we consider training algorithms based on the two-block decomposition of the network parameters into the vector of weights and the vector of centers. Then we define a decomposition algorithm in which the selection of the center locations is split into sequential minimizations with respect to each center, and we give a suitable criterion for choosing the centers that must be updated at each step. We prove the global convergence of the proposed algorithms and report the computational results obtained for a set of test problems

Symmetric periodic orbits near heteroclinic loops at infinity for a class of polynomial vector fields

For polynomial vector fields in R3, in general, it is very difficult to detect the existence of an open set of periodic orbits in their phase portraits. Here, we characterize a class of polynomial vector fields of arbitrary even degree having an open set of periodic orbits. The main two tools for proving this result are, first, the existence in the phase portrait of a symmetry with respect to a plane and, second, the existence of two symmetric heteroclinic loops

Estudo de classificação e quantificação das lamas geradas no processo de beneficiamento de rochas ornamentais.

No município de Cachoeiro de Itapemirim/ES, as lamas de beneficiamento de rochas ornamentais (LBROs) constituem um resíduo sólido (RS) muito impactante ao meio ambiente, uma vez que são geradas em grande quantidade e que ainda não está implementada no Estado do Espírito Santo a Política Estadual de Resíduos Sólidos que direcione o gerenciamento deste RS.Desta forma, observa-se no município um gerenciamento inadequado em que grande parte das LBROs são depositadas em tanques escavados no solo, sem qualquer tipo de proteção de modo a evitar a contaminação do solo e de corpos dágua. De encontro a este problema ambiental, a presente pesquisa foi desenvolvida junto a um grupo de empresas do setor de rochas ornamentais associadas à AAMOL, localizadas no município de Cachoeiro de Itapemirim, com o objetivo principal de classificar e quantificar as LBROs, de acordo com a NBR 10004/2004, NBR 10005/2004, e NBR 10006/2004. Para tanto, desenvolveu-se uma metodologia que se mostrou viável para o RS em estudo, a LBRO. A metodologia contemplou visita e aplicação de questionários às empresas associadas à AAMOL, quantificação dos blocos desdobrados e chapas polidas e consumo de insumos no processo de desdobramento. Também contemplou a elaboração de um plano de amostragem, de acordo com os critérios estabelecidos na NBR 10007/2004, para a coleta das amostras de matérias-primas, insumos e LBROs. Da classificação das LBROs verificouse que 77% das amostras foram classificadas como Resíduo Classe IIA Não- Inertes e 23% como Resíduo Classe IIB Inertes, sendo os parâmetros Al, Ba, Cd, Pb, Cl-, Cr, fenol, Fe, F-, Hg, Ag, Na e SO4 2-, aqueles que contribuíram para a não inerticidade das amostras. Foram obtidos neste estudo também o indicadores de quantidade de geração de LBRO por bloco desdobrado e chapa polida nas umidades em que são geradas as lamas, 95% e 99,7%, obtendo-se o ILD95% = 22,14 t/bloco, o ILP99,7% = 19,191 kg/chapa, além dos indicadores na umidade máxima permitida de 30% para a disposição final em aterro, obtendose o ILD30% = 14,76 t/bloco e o ILP30% = 12,493 kg/chapa, que demonstraram ser bastante eficiente o processo de desidratação para o gerenciamento deste RS, uma vez que contribui para o melhor manejo e redução nos custos do transporte e da disposição final

Is Moodle Accessible for Visually Impaired People?

Proceedings of: 7th International Conference on Web Information Systems and Technologies. Noordwijkerhout, The Netherlands, May 6-9, 2011.Most educational centers are currently using e-learning tools to provide the pedagogical resources for the students, especially in higher education. Nevertheless, some students are not able to access to this information because these authoring tools are not as accessible as they should be. The main aim of this paper is to evaluate if one of the most widely e-learning tool used around the world, Moodle, is accessible for visually impaired people. The evaluation shows that the accessibility guidelines provided by the World Wide Web Consortium (W3C) are not accomplished by the tool. Moreover, it shows that people using screen readers are not able to access to the majority of the functionality of Moodle.The work presented in this paper has been partially founded by MA2VICMR (S2009/TIC-1542), GEMMA (TSI-020302-2010-141) and SAGAS (TSI-020100-2010-184) research projects.Publicad

Closed-Loop Control of Local Magnetic Actuation for Robotic Surgical Instruments

We propose local magnetic actuation (LMA) as an approach to robotic actuation for surgical instruments. An LMA actuation unit consists of a pair of diametrically magnetized single-dipole cylindrical magnets, working as magnetic gears across the abdominal wall. In this study, we developed a dynamic model for an LMA actuation unit by extending the theory proposed for coaxial magnetic gears. The dynamic model was used for closed-loop control, and two alternative strategies-using either the angular velocity at the motor or at the load as feedback parameter-were compared. The amount of mechanical power that can be transferred across the abdominal wall at different intermagnetic distances was also investigated. The proposed dynamic model presented a relative error below 7.5% in estimating the load torque from the system parameters. Both the strategies proposed for closed-loop control were effective in regulating the load speed with a relative error below 2% of the desired steady-state value. However, the load-side closed-loop control approach was more precise and allowed the system to transmit larger values of torque, showing, at the same time, less dependence from the angular velocity. In particular, an average value of 1.5 mN·m can be transferred at 7 cm, increasing up to 13.5 mN·m as the separation distance is reduced down to 2 cm. Given the constraints in diameter and volume for a surgical instrument, the proposed approach allows for transferring a larger amount of mechanical power than what would be possible to achieve by embedding commercial dc motors