Irreversible processes and the accelerated-decelerated phases of the Universe

A model for the Universe is proposed where it is considered as a mixture of scalar and matter fields. The particle production is due to an irreversible transfer of energy from the gravitational field to the matter field and represented by a non-equilibrium pressure. This model can simulate three distinct periods of the Universe: (a) an accelerated epoch where the energy density of the scalar field prevails over the matter field, (b) a past decelerated period where the energy density of the matter field becomes more predominant than the scalar energy density, and (c) a present acceleration phase where the scalar energy density overcomes the energy density of the matter field.Comment: 6 pages, 2 figures, to be published in Brazilian Journal of Physic

Characterizing Weak Chaos using Time Series of Lyapunov Exponents

We investigate chaos in mixed-phase-space Hamiltonian systems using time series of the finite- time Lyapunov exponents. The methodology we propose uses the number of Lyapunov exponents close to zero to define regimes of ordered (stickiness), semi-ordered (or semi-chaotic), and strongly chaotic motion. The dynamics is then investigated looking at the consecutive time spent in each regime, the transition between different regimes, and the regions in the phase-space associated to them. Applying our methodology to a chain of coupled standard maps we obtain: (i) that it allows for an improved numerical characterization of stickiness in high-dimensional Hamiltonian systems, when compared to the previous analyses based on the distribution of recurrence times; (ii) that the transition probabilities between different regimes are determined by the phase-space volume associated to the corresponding regions; (iii) the dependence of the Lyapunov exponents with the coupling strength.Comment: 8 pages, 6 figure

The behaviour of GFRP reinforced concrete columns under monotonic and cyclic axial compression

PRAXIS XXI Project nº CEG 3/3.1/2572-95Retrofitting reinforced concrete columns with FRP materials is a recent but established technique based on their high strength/weight ratio and on other relative advantages, including the fact that FRP external shells prevent or mitigate environmental degradation of the concrete and consequent corrosion of the steel reinforcement. These techniques require, nevertheless, further studies and this paper presents and discusses experimental results obtained in tests of RC columns jacketed with GFRP under monotonic and cyclic axial compression, topic especially relevant when interventions on seismic zones are required. In order to evaluate the effect of the loading type on strength and ductility, 27 circular columns with 750mm height and 150 mm diameter, either of plain concrete or of RC, were tested. Among these circular columns, 11 were confined with two plies of CFRP whereas six were confined with three plies of GFRP. Comparison of results with proposed empirical models is shown.authorsversionpublishe

Cevadilha vacariana (Bromus auleticusTrinius): histórico, utilização e perspectivas.

Histórico e importância; Resultados de pesquisa e considerações gerais; Considerações finais e perspectivas.bitstream/item/64232/1/DT88.pdfTambém publicado na versão impressa

Obtenção de cultivares de malva sem dormência nas sementes com boa produção e boa qualidade de fibra.

bitstream/item/60208/1/CPATU-PA155.pd

Desenvolvimento de um ceifador enleirador de plantas de feijoeiro.

Este trabalho teve o objetivo de desenvolver um ceifador enleirador de plantas de feijoeiro simplificado, de pequeno porte para ser acionado por um trator médio e com capacidade de ceifar as plantas rente ao solo.CONAFE

Avaliação de cultivares de aveia branca em Dourados, MS, no período de 2002 a 2004.

A aveia branca é uma importante espécie para produção de grãos e forragens no período de outono/inverno, mas é pouco cultivada em Mato Grosso do Sul. Identificar e indicar cultivares com boa adaptação às condições edafoclimáticas da Região Sul de Mato Grosso do Sul podem contribuir para a expansão da área semeada com este cereal.bitstream/item/38722/1/BP200631.pdfDocumento on-line

Competição entre cultivares de juta local vs linhagens introduzidas da Índia.

bitstream/item/67238/1/Belem-ComTec3.pd

Avaliação de cultivares de triticale em Dourados, MS, no período de 2002 a 2004.

O triticale, híbrido natural entre o trigo e o centeio, é uma importante espécie para produção de grãos para consumo humano e animal, além de palha para a cobertura do solo, mas é pouco cultivado no período outono/inverno em Mato Grosso do Sul. Identificar e indicar cultivares com boa adaptação às condições edafoclimáticas da Região Sul de Mato Grosso do Sul podem contribuir para a Expansão da área semeada com este cereal.bitstream/item/38724/1/BP200632.pdfDocumento on-line