Invariant Theory
Mostrando 1-12 de 82 artigos, teses e dissertações.
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1. Synthesis, Spectroscopic Characterization, DFT Calculations and Preliminary Antifungal Activity of New Piperine Derivatives
Four new piperine derivatives, PC1-PC4, were synthesized, and their structures were fully characterized by infrared (IR) and 1H and 13C nuclear magnetic resonance (NMR) spectroscopies. Quantum chemical calculations were performed using density functional theory (DFT) with the B3LYP-D3/6-31G(d,p) and 6-311+G(2d,p) basis sets. Electronic properties, such as th
J. Braz. Chem. Soc.. Publicado em: 2021-03
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2. Perceived Environmental Supportiveness Scale: Portuguese Translation, Validation and Adaptation to the Physical Education Domain
Abstract Aim: Grounded on Self-Determination Theory, this study aimed to translate, adapt and validate the Perceived Environmental Supportiveness Scale (PESS) in a sample of Portuguese physical education students. Methods: The global sample was comprised of 964 students (518 females), divided in two groups: the calibration (n = 469) and the validation on
Motriz: rev. educ. fis.. Publicado em: 01/07/2019
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3. ROBUST CONTROL OF WIENER SYSTEMS: APPLICATION TO A pH NEUTRALIZATION PROCESS
Abstract In this paper, the robustness of a typical control scheme for Wiener systems is studied. These systems consist of the cascade connection of a linear time invariant system and a static nonlinearity. To control this kind of systems, several approaches were discussed in the literature. Most of these control schemes involve transformation of the measure
Braz. J. Chem. Eng.. Publicado em: 2016-03
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4. Solubility measurement and solid-liquid equilibrium model for the ternary system MgBr2 + MgSO4 + H2O at 288.15 K
The solubility of magnesium minerals and the refractive index of the ternary system MgBr2 + MgSO4 + H2O at 288.15 K were investigated using an isothermal dissolution method. It was found that there are two invariant points in the phase diagram and the solubility isotherm of this ternary system consists of three branches, corresponding to equilibrium crystall
Braz. J. Chem. Eng.. Publicado em: 2014-06
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5. Família de aplicações bilhares geradas pelo fluxo de curvatura / Family of billiards maps generated by curvature flow
Descrevemos algumas propriedades dinâmicas de uma família de aplicações bilhares sobre curvas convexas (ovais) as quais são deformadas pelo fluxo de curvatura. Quando a mesa se deforma, a razão entre as curvaturas mínima e máxima converge a 1 e por um resultado clássico de Gage e Hamilton, depois de uma normalização, as curvas tendem a um círculo
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 07/12/2011
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6. Processamento de sinais de descargas parciais em tempo real com base em wavelets e seleção de coeficientes adaptativa espacialmente
On-line partial discharge (PD) analysis is a highly pursued feature due to the economy related to scheduled shutdowns, disassembling and transport. Nevertheless, on-site PD measurements are frequently limited by interferences found in high-voltage facilities, a situation that imposes the continued development of PD signal processing methods. In the last year
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 04/11/2011
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7. Teoria Espectral e o Problema de Isomorfismo de Grafos Regulares
Spectral Graph Theory (SGT) studies graph properties by graph representation matrix and its spectrum. A property from SGT, the eigencentrality, provides an important invariant to Graph Isomorphism Problem: if two graphs are isomorphic, they have proportional eigencentralities. However, this property can not be directly used for solving the Regular Graph Isom
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 29/08/2011
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8. Geometria e simetrias do emaranhamento
In the present work we present a geometric method to identify and measure the degree of entanglement of a two-qubit state. It is based on writing a map of the system state, from a non-unitary transformation. By introducing new parameters for such 4X4 matrix, the product of eigenvalues, two by two, acquire the form of squared 4D distances, having a Minkowski
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 20/05/2011
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9. REMARKS ABOUT THE INVARIAN SUBSPACE PROBLEM / CONSIDERAÇÕES SOBRE O PROBLEMA DO SUBESPAÇO INVARIANTE
The Invariant Subspace Problem is the most important open question in Operator Theory. Although, there are many partial results, the question remains open for operators on complex, infinite-dimensional, separable Hilbert spaces. To prove that every operator has a non-trivial invariant subspace might be the beginning of a general structure theory for Hilbert
Publicado em: 2011
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10. Teoria de regularidade para equaÃÃes elÃpticas totalmente nÃo lineares com potenciais singulares e problemas de fronteira livre assintÃticos / Fully nonlinear singularly perturbed elliptic equations and limiting free boundary problems
In this work we develop a fully nonlinear theory for singularly perturbed elliptic equations problems with high energy activation. We esta-blish uniform and optimal gradient estimates of solutions and prove that minimal solutions are non-degenerated. For problems governed by concave equations, we establish uniform weak geometric properties of approximating l
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 05/11/2010
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11. Is it possible to accommodate massive photons in the framework of a gauge-invariant electrodynamics?
The construction of an alternative electromagnetic theory that preserves Lorentz and gauge symmetries, is considered. We start off by building up Maxwell electrodynamics in (3+1)D from the assumption that the associated Lagrangian is a gauge- invariant functional that depends on the electron and photon fields and their first derivatives only. In this scenari
Brazilian Journal of Physics. Publicado em: 2010-09
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12. 10-dimensional cosmology with Gauss-Bonnet gravity in generalized scalar-tensor theories from superstring theories
Superstring theories are promising candidates for unifying gravity with all matter interactions. In this work, we discussed a particular 10-dimensional cosmology based on Gauss-Bonnet invariant term coupled to a generalized scalar-tensor theory as resulting from superstring theories. Some interesting features concerning the late-time dynamics are explored an
Brazilian Journal of Physics. Publicado em: 2010-06