Quasi Fields
Mostrando 13-24 de 26 artigos, teses e dissertações.
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13. Self-energies for interacting fields with a compactified spatial dimension
We study the self-energy of a model with a tri-linear coupling among spinless fields on a manifold with one spatial dimension compactified. The model is considered to be composed by a quantized scalar field interacting with a classical scalar one. In order to improve the compactification we take the quantum field satisfying quasi periodic boundary conditions
Brazilian Journal of Physics. Publicado em: 2008-06
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14. A numerical study about the determination of parameters in an incompressible and linearly elastic solid / Estudo numérico sobre a determinação de parâmetros em um sólido elástico-linear e incompressível
The theory of classical linear elasticity is used to model of problems in medical physics that are related to the determination of elastic parameters of biological tissues from the measurement in vivo, or, in vitro of either displacements or strains. Based on experimental observations, which indicate that the abnormal biological tissues have different mechan
Publicado em: 2008
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15. Sociologia, Modernidade e questÃo social
The objective of this thesis is to analyze the shaping of social issue as a âgreat social inventionâ of modernity, where the social and political forces, sociological process and the creation of the national States were directly arranged in a regular, overlapping pattern. It aims at answering two important questions: How does the âsocial issueâ emerge wi
Publicado em: 2008
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16. The design of a very high-Q superconductor electromechanical clock
We discuss the properties of an electromechanical oscillator whose operation is based upon the cyclic, quasi-conservative conversion between gravitational potential, kinetic, and magnetic energies. The system consists of a strong-pinning type-II superconductor square loop subjected to a constant external force and to magnetic fields. The loop oscillates in t
Brazilian Journal of Physics. Publicado em: 2007-06
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17. Persistence of order on ferromagnetic models in the presence of quasi random auto-similar fields / Persistência de ordem em modelos ferromagnéticos na presença de campos auto-similares quase aleatórios"
In this work we study the existence of long range order for ferromagnetic models in the presence of an external field whose configuration has a pattern typically random. We prove, via the Peierlsargument modified by Griffiths in his study of an antiferromagnet, that the two dimensional ferromagnetic Ising model for a staggered field exhibits long-range order
Publicado em: 2007
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18. Alloying in GeSi:Si (001) epitaxial nanocrystals / Formação de ligas em nanocristais epitaxiais de GeSi:Si (001)
The structural and electronic properties of nanoscale materials strongly depend on the chemical composition, as well as their size and shape. A big variety of morphologies can be achieved by controlling the experimental conditions during the epitaxial growth of Ge on a Si(001) substrate. In particular, three-dimensional islands with well defined size and sha
Publicado em: 2007
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19. Magnetization peaks in type II superconductors / Picos da magnetização em supercondutores do tipo II
In this thesis we have studied possible origins for the Second Magnetization Peak (SMP) in high and low critical temperature superconductors, using samples of Bi2Sr2CaCu2O8+d and Nb single crystals. To study the SMP we did measurements of magnetization curves (M x H) and AC susceptibility (vs. h and T). We obtained the creep exponent in the SMP region, using
Publicado em: 2005
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20. Finite element-based model for crack propagation in polycrystalline materials
In this paper, we use an extended form of the finite element method to study failure in polycrystalline microstructures. Quasi-static crack propagation is conducted using the extended finite element method (X-FEM) and microstructures are simulated using a kinetic Monte Carlo Potts algorithm. In the X-FEM, the framework of partition of unity is used to enrich
Computational & Applied Mathematics. Publicado em: 2004-12
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21. Quasi-stationary waves in the southern hemisphere: observations and climate simulations over South America / Ondas quase-estacionárias no hemisférico sul: observações e simulações climáticas sobre a América do Sul
Characteristics of the quasi-stationary waves in the Southern Hemisphere with emphasis on their behavior over South America are discussed. In the first part, an observational study is performed using the NCEP/NCAR reanalysis data. The nature of seasonal and inter anual variabilities is analyzed. A comparison between the of the quasi-stationary wave s amplitu
Publicado em: 2004
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22. O papel da interação elétron-elétron no regime Hall quântico interio.
Experimental and theoretical studies of the aspects of particle-like and collective behavior of electrons in the proximity of the edges of two-dimensional (2DES) and quasi-one-dimensional (Q1DES) systems, named quantum wires (QWs), in semiconductor heterostructures reveal the important role of the electron-electron interaction on the edge states in the integ
Publicado em: 2004
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23. Cordas cosmicas e vortices em relatividade geral : pertubações radiais de soluções estaticas e estacionarias
A linearized theory of the dynamics of small perturbations of certain cylindrically symmetric systems in general relativity is presented. Firstly, we deal with straight, static cosmic strings of finite thickness in the U(l) gauge theory coupled to the Einstein equations. Taking into account the asymptotic behavior of the solution and certain integral ide
Publicado em: 1994
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24. Modulation by applied electric fields of Purkinje and stellate cell activity in the isolated turtle cerebellum.
Quasi steady-state electric fields were applied across the isolated turtle cerebellum to study the relationship between applied field, neuronal morphology and the modulation of the neuronal spike firing pattern. Spiking elements were identified electrophysiologically using extracellular recording methods and by subsequent horseradish peroxidase injection, wh