Semeadura de milho - correção da razão de distribuição de sementes através do ajuste no espaçamento entre linhas da semeadora.

bitstream/CNPT-2010/40573/1/p-co208.pd

Vertical Mulching: prática conservacionista mitigadora de perdas por erosão hídrica em sistema plantio direto.

bitstream/CNPT-2010/40326/1/p-bp53.pd

Semeadoras para plantio direto de parcelas experimentais.

bitstream/CNPT-2010/40524/1/p-co159.pd

Influência de gesso agrícola e modelos de produção na estabilidade de agregados.

Orientador: José Eloir Denardin

Efeito de mecanismos sulcadores de solo em semeadoras para plantio direto em pequenas unidades produtivas.

bitstream/CNPT-2010/40328/1/p-bp55.pd

Heterogeneidade física de um latossolo argiloso manejado sob sistema plantio direto.

bitstream/CNPT-2010/40741/1/p-bp70.pd

Linear study of the precessional fishbone instability

The precessional fishbone instability is an m = n = 1 internal kink mode destabilized by a population of trapped energetic particles. The linear phase of this instability is studied here, analytically and numerically, with a simplified model. This model uses the reduced magneto-hydrodynamics (MHD) equations for the bulk plasma and the Vlasov equation for a population of energetic particles with a radially decreasing density. A threshold condition for the instability is found, as well as a linear growth rate and frequency. It is shown that the mode frequency is given by the precession frequency of the deeply trapped energetic particles at the position of strongest radial gradient. The growth rate is shown to scale with the energetic particle density and particles energy while it is decreased by continuum damping

Efeito de elementos rompedores de solo em semeadoras para plantio direto na resistência do solo à tração mecânica.

bitstream/CNPT-2010/40740/1/p-bp69.pd

Nonlinear evolution of the magnetized Kelvin-Helmholtz instability: from fluid to kinetic modeling

The nonlinear evolution of collisionless plasmas is typically a multi-scale process where the energy is injected at large, fluid scales and dissipated at small, kinetic scales. Accurately modelling the global evolution requires to take into account the main micro-scale physical processes of interest. This is why comparison of different plasma models is today an imperative task aiming at understanding cross-scale processes in plasmas. We report here the first comparative study of the evolution of a magnetized shear flow, through a variety of different plasma models by using magnetohydrodynamic, Hall-MHD, two-fluid, hybrid kinetic and full kinetic codes. Kinetic relaxation effects are discussed to emphasize the need for kinetic equilibriums to study the dynamics of collisionless plasmas in non trivial configurations. Discrepancies between models are studied both in the linear and in the nonlinear regime of the magnetized Kelvin-Helmholtz instability, to highlight the effects of small scale processes on the nonlinear evolution of collisionless plasmas. We illustrate how the evolution of a magnetized shear flow depends on the relative orientation of the fluid vorticity with respect to the magnetic field direction during the linear evolution when kinetic effects are taken into account. Even if we found that small scale processes differ between the different models, we show that the feedback from small, kinetic scales to large, fluid scales is negligable in the nonlinear regime. This study show that the kinetic modeling validates the use of a fluid approach at large scales, which encourages the development and use of fluid codes to study the nonlinear evolution of magnetized fluid flows, even in the colisionless regime