Influence of the Hall effect on convection in plasmas

The influence of the Hall effect on stationary convection in shearless current-carrying plasma columns is considered. It is shown that the Hall effect can inhibit the formation of convection cells generated by viscosity and resistivity.

Construção de um sistema de caracterização das propriedades de transporte de filmes finos pelo efeito Hall

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Scanning tunneling microscope operating as a spin diode

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Lorentz symmetry breaking and planar effects from non-linear electrodynamics

We propose a modification of standard linear electrodynamics in four dimensions, where effective non-trivial interactions of the electromagnetic field with itself and with matter fields induce Lorentz violating Chern-Simons terms. This yields two consequences: it provides a more realistic and general scenario for the breakdown of Lorentz symmetry in electromagnetism and it may explain the effective behavior of the electromagnetic field in certain planar phenomena (for instance, Hall effect). A number of proposals for non-linear electrodynamics is discussed along the paper. Important physical implications of the breaking of Lorentz symmetry, such as optical birefringence and the possibility of having conductance in the vacuum are commented on.

Relaxation effects on the negatively charged Mg impurity in zincblende GaN

The electronic structure of Mg impurity in zincblende (c-)GaN is investigated by using the ab initio full potential linear-augmented plane-wave method and the local density-functional approximation. Full geometry optimization calculations, including nearest and next-nearest neighbor displacements, are performed for the impurity in the neutral and negatively charged states. A value of 190 ± 10 meV was obtained for the Franck-Condon shift to the thermal energy, which is in good agreement with that observed in recent low temperature photoluminescence and Hall-effect measurements. We conclude that the nearest and next-nearest neighbors of the Mg impurity replacing Ga in C-GaN undergo outward relaxations which play an important role in the determination of the center acceptor energies.

Estudo comparativo de medição de força de corte no processo de retificação

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Caracterização de filmes finos de ZnO dopados com Al e Mn depositados em substrato vítreo pelo método de Spray Pirólise

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Transport properties of polycrystalline boron doped diamond

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Fresamento de madeiras de média densidade: MDF

The technological expansion and market manufactured wood as wood paneling makes the research of processes involving this material are increasingly necessary . The present study examines the milling process MDF - fiberboard with average density endmill with helical teeth , with the analysis of the surface finish by evaluating the surface roughness ( Ra) and analysis of the power consumption . We analyzed three types of cuts in milling : concordant , discordant , and cut top . We used 5 rpm (6000 , 8000 , 10000 , 12000 and 14000 RPM) , establishing five-speed cutting, 301 , 402 ,502, 603 and 703 m / min respectively. Five forward speeds and 4, 6, 8, 10 and 12 m / min. Each condition was repeated six times , totaling 180 tests. The results of roughness were obtained from rugosimeter data and the power consumption were obtained by Hall-effect sensor . These results were statistically analyzed using analysis of variance and Tukey test . Finally it was concluded that there are few significant differences between the results themselves vary roughness when cutting speeds and feed and no major differences in power consumption . The best surface quality and lower power consumption were for cutting speed of 703 m / min . To varying forward speed , the speed of 4 m / min showed better surface quality and lower power consumption

Neural models for predicting hole diameters in drilling processes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Neural models for predicting hole diameters in drilling processes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Análise do acabamento superficial e da potência consumida na usinagem de fresamento frontal e cilíndrico tangencial da madeira de eucalipto

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Impacto da redução do nível de tensão na iluminação residencial em uma rede inteligente

In this paper, we will present an overview of the smart grid defining the three main systems that compose it: smart infrastructure system, smart management system and smart protection system. We will conceptualize a functionality of smart management system, the conservative voltage reduction, citing its benefits and its history of application. And, finally, we'll cover a test in which we reduce the nominal voltages on incandescent bulbs, CFL and LED, in the context of residential lighting, and on LED and HPS, in the context of public lighting. The test aims to check whether the voltage reduction adversely affects sources of lighting by measuring the temperature manually with a thermal imaging camera FLIR and illuminance with a LUX meter. The set of power factor, total harmonic distortion, and input power values will be collected automatically through the power quality Analyzer Fluke 345 with a probe Fluke Hall Effect Current. For residential lighting, it was found that both CFL and LED had good performance with the smallest variations in illuminance. Between both, the LED source had the lowest harmonics and the lowest power consumption, on the other hand incandescent bulbs had a bad performance as expected. Public light sources also had a good performance and obtained power factors within the standards, as opposed to the CFL and LED residential sources. The data collected clearly shows the feasibility for nominal voltage reductions. Even with small reductions, there are possibilities of savings which can be passed on to the utilities and consumers

Comment on Effect of spin-orbit interaction on the plasma excitations in a quantum wire

We comment on the recent results [Phys. Rev. B 70, 235314 (2004)] showing the dispersion relations of single-particle and collective excitations in quantum wires in the presence of the Rashba spin-orbit interaction (SOI). We claim that those calculations performed in the absence of SOI, and used as a strong reference to the interacting case, are unlikely to be correct. We show the correct omega-q plane of the system in the absence of Rashba SOI.

Effect of spin-polarized subbands in the inhomogeneous hole gas providing the indirect exchange in GaMnAs bilayers

The magnetic order resulting from the indirect exchange in the metallic phase of a (Ga,Mn)As/GaAs double layer structure is studied via Monte Carlo simulation. The polarization of the hole gas is taken into account, establishing a self-consistency between the magnetic order and the electronic structure. The Curie-Weiss temperatures calculated for these low-dimensional systems are in the range of 50-80 K, and the dependence of the transition temperature with the GaAs separation layer is established. (C) 2003 Published by Elsevier B.V.