6,210 research outputs found
Bloch-like oscillations in a one-dimensional lattice with long-range correlated disorder
We study the dynamics of an electron subjected to a uniform electric field
within a tight-binding model with long-range-correlated diagonal disorder. The
random distribution of site energies is assumed to have a power spectrum with . Moura and Lyra [Phys. Rev. Lett. {\bf
81}, 3735 (1998)] predicted that this model supports a phase of delocalized
states at the band center, separated from localized states by two mobility
edges, provided . We find clear signatures of Bloch-like
oscillations of an initial Gaussian wave packet between the two mobility edges
and determine the bandwidth of extended states, in perfect agreement with the
zero-field prediction.Comment: 4 pages, 5 figure
A new data reduction scheme to obtain the mode II fracture properties of Pinus Pinaster wood
In this work a numerical study of the End Notched Flexure (ENF) specimen was performed
in order to obtain the mode II critical strain energy released rate (GIIc) of a Pinus pinaster wood in the RL crack propagation system. The analysis included interface finite elements and a progressive damage
model based on indirect use of Fracture Mechanics.
The difficulties in monitoring the crack length during an experimental ENF test and the inconvenience of performing separate tests in order to obtain the elastic properties are well known. To avoid these
problems, a new data reduction scheme based on the equivalent crack concept was proposed and validated. This new data reduction scheme, the Compliance-Based Beam Method (CBBM), does not require crack measurements during ENF tests and additional tests to obtain elastic properties.FCT - POCTI/EME/45573/200
Finite element analysis of the ECT test on mode III interlaminar fracture of carbon-epoxy composite laminates
In this work a parametric study of the Edge Crack Torsion (ECT) specimen was performed
in order to maximize the mode III component (GIII) of the strain energy release rate for carbon-epoxy laminates.
A three-dimensional finite element analysis of the ECT test was conducted considering a
[90/0/(+45/-45)2/(-45/+45)2/0/90]S lay-up. The main objective was to define an adequate geometry to obtain an almost pure mode III at crack front. The geometrical parameters studied were specimen dimensions, distance between pins and size of the initial crack.
The numerical results demonstrated that the ratio between the specimen length and the initial crack length had a significant effect on the strain energy release rate distributions. In almost all of the tested
configurations, a mode II component occurred near the edges but it did not interfere significantly with the dominant mode III state.FCT - POCTI/EME/45573/200
Acessos de mandioca açucarada coletados no Nordeste paraense possuem o mesmo genótipo detectado por marcadores microssatélites.
A mandioca Ă© encontrada na regiĂŁo Norte do Brasil e Ă© usada como fonte de subsistĂȘncia para muitas famĂlias. A mandioca açucarada ou mandiocaba, Ă© um tipo de mandioca que armazena em suas raĂzes, alĂ©m do amido, açĂșcares livres como reservas. Atualmente, vĂȘm recebendo destaque pelo seu potencial para uso na fabricação de ĂĄlcool combustĂvel, devido ao acĂșmulo de glicose que pode ser convertida em etanol diretamente. Foi realizado teste para avaliar a diversidade genĂ©tica de acessos de mandiocas açucaradas coletadas em diferentes locais do estado do ParĂĄ mantidos no banco de germoplasma da Embrapa AmazĂŽnia Oriental. Foi realizada a genotipagem molecular de nove acessos de mandioca açucarada e um acesso de mandioca brava com marcadores microssatĂ©lites. Para isso, foram utilizados 13 primers microssatĂ©lites e a corrida dos produtos amplificados foi realizada em gĂ©is de poliacrilamida 6%. ApĂłs a anĂĄlise dos gĂ©is, foi verificado que todas as nove amostras de mandioca açucarada possuĂam o mesmo genĂłtipo, sendo verificada baixa variabilidade genĂ©tica para esse grupo de mandiocas
Delocalization and wave-packet dynamics in one-dimensional diluted Anderson models
We study the nature of one-electron eigen-states in a one-dimensional diluted
Anderson model where every Anderson impurity is diluted by a periodic function
. Using renormalization group and transfer matrix techniques, we provide
accurate estimates of the extended states which appear in this model, whose
number depends on the symmetry of the diluting function . The density of
states (DOS) for this model is also numerically obtained and its main features
are related to the symmetries of the diluting function . Further, we show
that the emergence of extended states promotes a sub-diffusive spread of an
initially localized wave-packet.Comment: 6 pages, 6 figures, to appear in EPJ
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