Perturbation Theory
Mostrando 13-24 de 113 artigos, teses e dissertações.
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13. Recent developments of some asymptotic methods and their applications for nonlinear vibration equations in engineering problems: a review
This review features a survey of some recent developments in asymptotic techniques and new developments, which are valid not only for weakly nonlinear equations, but also for strongly ones. Further, the achieved approximate analytical solutions are valid for the whole solution domain. The limitations of traditional perturbation methods are illustrated, vario
Lat. Am. j. solids struct.. Publicado em: 2012-04
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14. SAPT: ligação de hidrogênio ou interação de van der Waals?
It is through the application of an electronic partition approach called Symmetry-Adapted Perturbation Theory (SAPT) that the nature of hydrogen bonds and van der Waals interactions can be unveiled according to the contribution of electrostatic, charge transfer, exchange repulsion, polarization, and dispersion terms. Among these, electrostatic partition gove
Quím. Nova. Publicado em: 2012
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15. Influence of physical and geometrical system parameters uncertainties on the nonlinear oscillations of cylindrical shells
This work investigates the influence of physical and geometrical system parameters uncertainties and excitation noise on the nonlinear vibrations and stability of simply-supported cylindrical shells. These parameters are composed of both deterministic and random terms. Donnell's non-linear shallow shell theory is used to study the non-linear vibrations of th
J. Braz. Soc. Mech. Sci. & Eng.. Publicado em: 2012
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16. Perfis de espalhamento Raman ressonante em estruturas unidimensionais de carbono: cadeias lineares e nanotubos quiralmente enriquecidos
In resonant Raman scattering experiments using several laser lines, the intensity profile of the spectra as a function of the laser energy is related to the vibrational and electronic structure of the material. In this work, we have measured and interpreted the resonant Raman profiles for samples of chirality enriched single-walled carbon nanotube and for po
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 20/12/2011
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17. Efeitos de solvente sobre propriedades elétricas de compostos mesoiônicos / Solvent effects on electrical properties of mesoionic compounds
In this work we study the electric properties of mesoionic compounds in the gaseous phase in different solvents, with a special attention to the first hyperpolarizability (β ). The Hartree-Fock (HF) method and the second-order MøllerPlesset perturbation theory (MP2) were used to describe the electronic structure. The solvent effects were modelled using
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 27/07/2010
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18. A structure-preserving iteration method of model updating based on matrix approximation theory
Some theories and a method are discussed on updating a generalized centrosymmetric model. It gives a generalized centrosymmetric modified solution with partial prescribed least square spectra constraints. The emphasis is given on exploiting structure-preserving algorithm based on matrix approximation theory. A perturbation theory for the modified solution is
Computational & Applied Mathematics. Publicado em: 2010-06
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19. How specialists can be generalists: resolving the "parasite paradox" and implications for emerging infectious disease
The parasite paradox arises from the dual observations that parasites (broadly construed, including phytophagous insects) are resource specialists with restricted host ranges, and yet shifts onto relatively unrelated hosts are common in the phylogenetic diversification of parasite lineages and directly observable in ecological time. We synthesize the emergin
Zoologia (Curitiba). Publicado em: 2010-04
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20. Controle de caos e saltos entre atratores em um sistema com impactos / Control of caos and basin hopping in a system with impacts
For a mechanical system, described by the impact-pair model, we studied the control of chaos by a parametric perturbation and the basin-hopping phenomeno. For this nonintegrable system, we obtained numerically the evolution of its dynamical variables for a large set of initial conditions and control parameters. For this analysis, we used phase planes, Poinca
Publicado em: 2010
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21. Determinação de alguns parâmetros da teoria de perturbação quiral / Determination of some parameters of Chiral Perturbation Theory
A teoria de perturba ca o quiral (ChPT) e aceita, atualmente, como a teoria efetiva da cromodinamica quantica (QCD) para baixas energias. Ela foi colocada na sua versa o moderna com os artigos de Gasser e Leutwyler, na primeira metade da d ecada de 80 e, durante os 25 anos que se seguiram, ocorreu um aumento considera vel da variedade de fenomenos por ela de
Publicado em: 2010
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22. The spin dynamics of molecular magnets beyond Kubo's linear response theory
The description of quantum dynamics of nanomagnets is a central issue in most applications proposed for those systems. In this paper, we put forward a modified perturbation approach to study the spin dynamics of a molecular magnet in the presence of time-dependent magnetic fields.The non-perturbed Hamiltonian H0, which defines the interaction picture, may be
Brazilian Journal of Physics. Publicado em: 2009-09
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23. Leptonic decays of the B charged meson and B → Xsγ in the Two Higgs Doublet Model type III
We consider the Two Higgs Doublet Model (2HDM) of type III which leads to Flavour Changing Neutral Currents (FCNC) at tree level. In the framework of this model we calculate the NLO contribution for b → sγ and the branchings for the meson decays B+ → l+ν. We examine the limits on the new parameters λbb and M H±. We take into account the relationship
Brazilian Journal of Physics. Publicado em: 2008-12
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24. The role of crossing symmetry for a low energy pion-nucleon scattering from dispersive method
The slow convergence of chiral perturbation theory for heavy baryons (HBChPT) suggests that any attempt to unitarize the amplitude following from this method will fail to describe the experimental phase shifts. However, it was possible to obtain a ChPT pion nucleon amplitudes respecting exact unitarity relation by using the Inverse Amplitude Method (IAM), bu
Brazilian Journal of Physics. Publicado em: 2008-09