Effect of current corrugations on the stability of the tearing mode

The generation of zonal magnetic fields in laboratory fusion plasmas is predicted by theoretical and numerical models and was recently observed experimentally. It is shown that the modification of the current density gradient associated with such corrugations can significantly affect the stability of the tearing mode. A simple scaling law is derived that predicts the impact of small stationary current corrugations on the stability parameter $\Delta'$. The described destabilization mechanism can provide an explanation for the trigger of the Neoclassical Tearing Mode (NTM) in plasmas without significant MHD activity.Comment: Accepted to Physics of Plasma

Viriato: a Fourier-Hermite spectral code for strongly magnetised fluid-kinetic plasma dynamics

We report on the algorithms and numerical methods used in Viriato, a novel fluid-kinetic code that solves two distinct sets of equations: (i) the Kinetic Reduced Electron Heating Model (KREHM) equations [Zocco & Schekochihin, Phys. Plasmas 18, 102309 (2011)] (which reduce to the standard Reduced-MHD equations in the appropriate limit) and (ii) the kinetic reduced MHD (KRMHD) equations [Schekochihin et al., Astrophys. J. Suppl. 182:310 (2009)]. Two main applications of these equations are magnetised (Alfvenic) plasma turbulence and magnetic reconnection. Viriato uses operator splitting (Strang or Godunov) to separate the dynamics parallel and perpendicular to the ambient magnetic field (assumed strong). Along the magnetic field, Viriato allows for either a second-order accurate MacCormack method or, for higher accuracy, a spectral-like scheme composed of the combination of a total variation diminishing (TVD) third order Runge-Kutta method for the time derivative with a 7th order upwind scheme for the fluxes. Perpendicular to the field Viriato is pseudo-spectral, and the time integration is performed by means of an iterative predictor-corrector scheme. In addition, a distinctive feature of Viriato is its spectral representation of the parallel velocity-space dependence, achieved by means of a Hermite representation of the perturbed distribution function. A series of linear and nonlinear benchmarks and tests are presented, including a detailed analysis of 2D and 3D Orszag-Tang-type decaying turbulence, both in fluid and kinetic regimes.Comment: 42 pages, 15 figures, submitted to J. Comp. Phy

REPRESENTAÇÕES SOCIAIS DE FORMAÇÃO CONTINUADA DOS PROFESSORES DE EDUCAÇÃO FÍSICA DE ESCOLAS PÚBLICAS DO ESTADO DO ESPÍRITO SANTO

O principal objetivo do trabalho é compreender o pensamento, o sentimento e as ações tomadas pelos professores de Educação Física em relação a sua formação continuada. Para tanto escolhe a grande teoria das Representações Sociais, especialmente devido a importância que essa teoria atribui ao senso comum, que é uma das noções centrais para o conceito de representação social. Optando pela Abordagem Estrutural, que corresponde a uma das três correntes que compõem aquela grande teoria, levanta hipóteses explicativas para a existência da representação social de formação continuada, tratando de sua organização interna e da dimensão cognitiva da mesma. Trata-se de uma pesquisa qualitativa que se utiliza da Técnica de Livre Associação (e o tratamento dos dados alcançados por meio do software EVOC 2000) e da Técnica de Escolhas Hierarquizadas Sucessivas que são duas ferramentas de pesquisa bastante comuns nas investigações sobre representações sociais , aliadas com a realização de entrevistas semiestruturadas. Aponta para a ocorrência de um fenômeno que tem deslocado o núcleo central da representação social de formação continuada da aprendizagem para a qualificação tornando a busca por qualificação na formação continuada um atributo individual, de responsabilidade única e exclusiva do professor

Solution of hyperbolic bioheat transfer problems by numerical green's functions: the ExGA-linear θ method

This paper presents a time-domain formulation called Explicit Green's approach (ExGA) linear θ method for the solution of the bioheat equation. Starting from the hyperbolic bioheat equation, which includes the parabolic one as a special case, the linear method is incorporated into the standard ExGA time marching scheme. The numerical Green's function is firstly computed in the Laplace transform domain and then back-transformed to the time domain through the Stehfest inversion algorithm. The proposed formulation has the properties of stabilizing the results and suppressing numerical oscillations that appear in the presence of discontinuous solutions as assessed through the analysis of some bioheat transfer problems.

Avaliação do desempenho de um pivo central da baixa pressão equipado com tubos de descida.

At the Corn and Sorghum National Research Center in Sete Lagoas, Minas Gerais State, an evaluation was made of the performance of a low pressure central pivot equipped with drop sparay, operating at 100% of its displacement capacity. The tests carried out were the following: without drop spray; drop spray of 1.2m; 2.0m and 2.6m lenght. For each test, the uniformity coefficients of Christiansen (CUC) and distribution (CUD), the application efficiency, in potential (EPa), and the highest precipitation intensity were determined. It was concluded that: The lenght of drop spray did not affect distribution uniformity; The collected water plate at the end of the pivot line showed a large variation; Topographic characteristics influenced distribution uniformity; Drop spray increased application efficiency, in potential, reducing pressure at the diffusor exit. Proximity of the diffusor to the ground decreased the covering diameter and increase precipitation density