Resonant Effects
Mostrando 13-24 de 37 artigos, teses e dissertações.
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13. Environmental factors influence evaluation on the structure, dynamics and optical properties of the aquatic humic substances form the "Rio Negro" - Amazonas / Avaliação da influência de fatores ambientais na estrutura, dinâmica e propriedades ópticas das substâncias húmicas aquáticas do Rio Negro
Nowadays, one of the major world concerning is focused in the increasing of the damaging ultraviolet (UV) radiation and its impact on the aquatic ecosystems. In addition, the Rio Negro, one of the principal tributaries of the Amazon Basin, is an appropriate site for studying the influence of the UV radiation in the dissolved organic matter (DOM) biogeochemis
Publicado em: 2007
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14. Interação de nanotubos de carbono com segmentos de DNA
Single- and double-stranded DNA (deoxyribonucleic acid) molecules can strongly bind to single-walled carbon nanotubes (SWNT) via non-covalent interactions. Under certain conditions, the DNA molecule spontaneously self-assembles into a helical wrapping around the tubular structure of the carbon nanotubes to form DNA/SWNT hybrids, which are both stable and sol
Publicado em: 2007
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15. Multimodal vibration damping through piezoelectric patches and optimal resonant shunt circuits
Piezoelectric elements connected to shunt circuits and bonded to a mechanical structure form a dissipation device that can be designed to add damping to the mechanical system. Due to the piezoelectric effect, part of the vibration energy is transformed into electrical energy that can be conveniently dissipated. Therefore, by using appropriate electrical circ
Journal of the Brazilian Society of Mechanical Sciences and Engineering. Publicado em: 2006-09
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16. "Estudo das contribuições térmica e eletrônica na variação do índice de refração de materiais dopados com íons emissores" / Study of thermal and electronic contribution to the refractive index variation of materials doped with ions emiters
In this work we have studied the thermal and optical properties of emitters ions by using the thermal lens and z-scan time resolved techniques. It was obtained the thermal lens photothermal spectra of Yb3+ doped samples, and several other photothermal parameters. Also, it was done a study on the optical nonlinearity saturation effects over the determination
Publicado em: 2006
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17. Laser de faces clivadas com regiões ativas nanoestruturadas bombeados por injeção eletronica / Cleaved face laser with nanostructured active region pumped by electronic injection
This masters dissertation presents the theoretical studies on the calculation of optical gain in nanostructures based on the InGaAs/InGaAsP/InP system. From the time dependent perturbation theory, where perturbation is the interaction of an electromagnetic wave with matter, and the Kanes theory for semiconductors band structure, relating the transition m
Publicado em: 2006
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18. Vibrações ressonantes não-lineares em estruturas tipo viga sob excitação paramétrica e combinada / Nonlinear resonance vibrations in beam type structures under parametric and combined excitations
This document presents results of theoretical and experimental investigations on the non-linear vibration characteristics of an important class of flexible structures. The motivation for such a study arises mainly from the increasing need for lightweight structural members. The weight reduction associated to the use of novel materials contribute to the incre
Publicado em: 2006
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19. Controle coerente em Ãtomos de Rb por manipulaÃÃo da fase de pulsos ultracurtos
Coherent quantum control aims to drive a quantum system towards a desired final state. Nowadays its study is widely employed to manipulate transitions in atomic systems, to break molecular bonds and to optimize the output of chemical reactions, for instance. In this thesis experimental and theoretical results of partial temporal coherent control in two diffe
Publicado em: 2005
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20. SPIN AND CORRELATION EFFECTS IN NANOSCOPIC TRANSPORT / EFEITOS DE SPIN E CORRELAÇÃO EM TRANSPORTE NANOSCÓPICO
We investigated spin polarized transport properties through a quantum dot connected with two terminals. An electric current that circulates in our system can have its polarization modulated with an external potential that controls the spin orbit coupling (Rashba effect). We studied the effect of spin polarization n a transistor constituted by a quantum dot w
Publicado em: 2005
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21. Efeitos nÃo lineares em lÃquidos orgÃnicos e meios nanoestruturados
In this thesis, we report studies of nonlinear transverse effects in organic liquids, carbon disulfide (CS2) and dimetil sulfoxide (DMSO), and of fluorescent emission effects in nanostructured media, more specifically, frequency upconversion in erbium doped barium titanate nanocrystals (BaTiO3:Er3+) and laserlike emission from inverted opal nanostructure of
Publicado em: 2004
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22. Estudo de ordenamento multipolar eletrico de holmio por difração de raios-X
Multipolar ordering in metallic holmium 4f shell was extensively studied for the first time, by resonant and non resonant X-ray scattering at the helical antiferromagnetic and conical ferromagnetic phases. The strong spin-orbit coupling drives the multipolar order as it was experimentally confirmed through the temperature dependence of the ordering wave-vect
Publicado em: 2003
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23. Efeito de esforços vibracionais na estrutura do tecido vegetal
The present work aims to study the effects of cyclic loading on selected mechanical properties of vegetative tissues. Farm machinery operations involved in all agricultural processes since seedling up to harvesting, transportation, packaging and storage is here considered as a potential generators of vibrating loading. Experiments were carried out on specime
Publicado em: 2003
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24. The role of alpha particles in the emission of plasma waves inside solar ejecta
The enhancement of the resonant instability of right-hand polarized electromagnetic ion cyclotron waves by alpha particles for physical parameters corresponding to coronal mass ejections is studied. We focus on the effects of alpha thermal anisotropy and relative He++/H+ abundance on growth and absorption rates. The first parameter governs directly wave emis
Brazilian Journal of Physics. Publicado em: 2002-06