Dipolar Interactions
Mostrando 1-12 de 48 artigos, teses e dissertações.
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1. Superradiance pulse manipulation via atomic interactions / Manipulação do pulso superradiante via interações atômicas
O fenômeno da superradiância é caracterizado por um processo de ordenamento das transições dos dipolos atômicos em amostras excitadas, moderadamente densas, decorrente das correlações induzidas entre os átomos desenvolvidas pela radiação coerente emitida pelos próprios átomos. O processo superradiante que é iniciado a partir de uma total desord
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 28/02/2012
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2. Zeros de Fisher e aspectos críticos do modelo de Ising dipolar / Fisher\ s zeros and critical aspects of the dipolar Ising model
We study the critical behavior of the dipolar Ising model on two-dimensional regular lattices. This model presents a phenomenologically rich scenario due to the effect of frustration caused by the competition between the pure Ising interaction and the dipolar one. To study the criticality of this model we apply finite size scaling relations for the partition
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 06/06/2011
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3. Interações em condensados de Bose-Einstein: temperatura finita e gás dipolar / Interactions in Bose-Einstein condensates: finite temperature and dipolar gas
Neste trabalho investigamos os efeitos das interações na expansão de um condensado de átomos de Rb. Dois problemas são abordados: o efeito de temperatura finita e as alterações introduzidas pela interação dipolar. No primeiro caso, dados experimentais não puderam ser explicados por meio da aproximação de Thomas-Fermi (TF) no regime de T = 0. Num
Publicado em: 2010
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4. Formação de sólitons em condensados de Bose-Einstein e em meios ópticos / Formation of solitons in Bose-Einstein condensates and in photorefractive media
Different kinds of solitons have already been observed in various nonlinear optical media, and their behavior has been explained in the frameworks of such mathematical models as the nonlinear Schrödinger and generalized nonlinear Shrödinger equations for different dimensions and geometries. However, there are situations when many solitons are generated so
Publicado em: 2010
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5. Transições de fase em modelos magnéticos bi-dimensionais com interações dipolares.
In this work we have used the numerical Monte Carlo simulations to simulate the planar to paramagnetic phase transition in the anisotropic Heisenberg model with dipolar interactions (AH-d model). We concentrated our attention in three slightly different models the AH-d model in a bilayer system with a cut-off in the dipolar interactions, the dipolar Planar R
Publicado em: 2009
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6. Simulações numéricas de Monte Carlo aplicadas no estudo das transições de fase do modelo de Ising dipolar bidimensional / Numerical Monte Carlo simulations applied to study of phase transitions in two-dimensional dipolar Ising model
Two-dimensional spin model with nearest-neighbor ferromagnetic interaction and long-range dipolar interactions exhibit a rich phase diagram, whose characteristics have been exploited by several studies in the recent literature. Furthermore, the possibility of explain observed phenomena in ultrathin magnetic films, which have many technological applications,
Publicado em: 2009
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7. Propriedades magnÃticas do nanocompÃsito (Fe1-xCox)y(MnO)1-y
In the present work were investigated the magnetic properties of ferromagnetic nanocomposites (Fe1−xCox)y(MnO)1−y, x = 0.4 and 0.6 e y = 0.35, 0.65 and 1, produced by mechanical-alloying. Structural and morphological characterization were made by x-ray diffraction using Scherrer equation, Williamson-Hall plot and Rietveld refinement. The refineme
Publicado em: 2009
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8. Efeitos de tamanho finito e interface em nanopartículas e nanocolóides magnéticos
In this work, we investigated magnetic nanoparticles based on copper ferrite, with mean sizes ranging between 3,5 nm e 10,7 nm. Such nanomaterials are chemically synthesized by hydrothermal coprecipitation and allow elaborating magnetic nanocolloids in aqueous and acidic medium thanks to a core-shell strategy that prevent the nanoparticles from dissolution.
Publicado em: 2008
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9. Caracterização eletroquímica de colóides magnéticos visando a aplicações nanotecnológicas nanobiotecnológicas
Electric Double Layered Magnetic Fluids (EDL-MF) are stable colloidal dispersions of spinel ferrite type nanoparticles in water medium. The thermodynamic stability is achieved by balancing the van der Waals and magnetic dipolar attractions with the introduction of repulsive electrostatic interactions between particles in order to avoid the agglomeration phen
Publicado em: 2008
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10. Physical properties of systems with competing interactions / Propriedades fisicas de sistemas com interações competitivas
Um dos objetivos centrais das Ciências Naturais é relacionar as estruturas dos mais diversos sistemas com as funções particulares que os caracterizam. Por exemplo, no que se refere a materiais, sejam eles sintéticos ou biológicos, a ciência está constantemente buscando a predição de diferentes propriedades macroscópicas a partir do conhecimento da
Publicado em: 2008
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11. Síntese de compostos com potenciais atividades biológicas ou magnéticas
This thesis is divided in two parts and presents the results of our studies on the synthesis and the study of biological or magnetic proprieties of a series of ligands and their transition metal complexes. Firstly we prepared a series of dithiacarboxilic acids and their metal complexes to investigate the biological activity of these compounds against fungi,
Publicado em: 2008
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12. Microscopic theory of spin waves in magnetic nanowires / Teoria microscÃpica de ondas de spin em nanofios magnÃticos
The dynamical behavior of spins in magnetic materials is affected by its geometry and dimensionality. One can find several new results in the literature exploiting the magnetic properties of low dimension systems with different geometries, since the development of new devices such as: nanosensors, high density magnetic storage, etc., is closely related to ne
Publicado em: 2007