Search results for "singular"
showing 10 items of 589 documents
Algebraic-geometric techniques for the feedback classification and robustness of the optimal control of a pair of Bloch equations with application to…
2017
The aim of this article is to classify the singular trajectories associated with the optimal control problems of a pair of controlled Bloch equations. The motivation is to analyze the robustness of the optimal solutions to the contrast and the time-minimal saturation problem, in magnetic resonance imaging, with respect to the parameters and B1-inhomogeneity. For this purpose, we use various computer algebra algorithms and methods to study solutions of polynomial systems of equations and inequalities which are used for classification issues: Gröbner basis, cylindrical algebraic decomposition of semi-algebraic sets, Thom's isotopy lemma.
Local monomialization of generalized real analytic functions
2011
Generalized power series extend the notion of formal power series by considering exponents ofeach variable ranging in a well ordered set of positive real numbers. Generalized analytic functionsare defined locally by the sum of convergent generalized power series with real coe cients. Weprove a local monomialization result for these functions: they can be transformed into a monomialvia a locally finite collection of finite sequences of local blowingsup. For a convenient frameworkwhere this result can be established, we introduce the notion of generalized analytic manifoldand the correct definition of blowing-up in this category.
Sur le rôle des singularités hamiltoniennes dans les systèmes contrôlés : applications en mécanique quantique et en optique non-linéaire.
2012
This thesis has two goals: the first one is to improve the control techniques in quantum mechanics, and more specifically in NMR, by using the tools of geometric optimal control. The second one is the study of the influence of Hamiltonian singularities in controlled systems. The chapter about optimal control study three classical problems of NMR : the inversion problem, the influence of the radiation damping term, and the steady state technique. Then, we apply the geometric optimal control to the problem of the population transfert in a three levels quantum system to recover the STIRAP scheme.The two next chapters study Hamiltonian singularities. We show that they allow to control the polar…
Actitudes, percepciones y prácticas del profesorado sobre inclusión educativa en un centro de compensación educativa
2020
En esta tesis doctoral se analiza y reflexiona sobre la relación entre las percepciones, actitudes y las prácticas del profesorado sobre la inclusión educativa en un Centro de Acción Educativa Singular (CAES). Además, de conocer las características de la escuela inclusiva, en cuanto se ocupa de la educación compensatoria, así como analizar la normativa que regula este tipo de educación, y examinar la participación de la familia en el proceso educativo del alumnado. Los objetivos específicos que se pretenden son: 1. Conocer y analizar, a través de las percepciones del equipo directivo, las características de un centro de educación compensatoria relacionadas con la inclusión educativa. 2. Dil…
Parabolic equations with nonlinear singularities
2011
Abstract We show the existence of positive solutions u ∈ L 2 ( 0 , T ; H 0 1 ( Ω ) ) for nonlinear parabolic problems with singular lower order terms of the asymptote-type. More precisely, we shall consider both semilinear problems whose model is { u t − Δ u + u 1 − u = f ( x , t ) in Ω × ( 0 , T ) , u ( x , 0 ) = u 0 ( x ) in Ω , u ( x , t ) = 0 on ∂ Ω × ( 0 , T ) , and quasilinear problems having natural growth with respect to the gradient, whose model is { u t − Δ u + ∣ ∇ u ∣ 2 u γ = f ( x , t ) in Ω × ( 0 , T ) , u ( x , 0 ) = u 0 ( x ) in Ω , u ( x , t ) = 0 on ∂ Ω × ( 0 , T ) , with γ > 0 . Moreover, we prove a comparison principle and, as an application, we study the asymptotic behav…
A new reading of a bilingual votive inscription from Germisara thermal baths (Dacia superior)
2020
Nueva edición y comentario filológico de una larga y compleja inscripción votiva de la época de Cómodo que consta de un poema en latín (redactado en hexámetros dactílicos) seguido, a modo de complemento y amplificación, de un texto griego en prosa pero con cierto color poético. La inscripción está dedicada a la Ninfa de un santuario termal, mencionada con lo que parece ser un nombre o epíteto local, y consiste tanto en la conmemoración del cumplimiento de un voto determinado como en la narración de las fiestas anuales que la unidad militar (numerus) comandada por el dedicante celebraba, mediante ofrendas votivas y sacrificios, en honor tanto de la Ninfa del lugar como de Asclepio, Panacea, …
Airy-function approach to binary black hole merger waveforms: The fold-caustic diffraction model
2022
From numerical simulations of the Einstein equations, and also from gravitational wave observations, the gravitational wave signal from a binary black hole merger is seen to be simple and to possess certain universal features. The simplicity is somewhat surprising given that non-linearities of general relativity are thought to play an important role at the merger. The universal features include an increasing amplitude as we approach the merger, where transition from an oscillatory to a damped regime occurs in a pattern apparently oblivious to the initial conditions. We propose an Airy-function pattern to model the binary black hole (BBH) merger waveform, focusing on accounting for its simpl…
I. Glass Transition. Theoretical concepts on the glass transition of polymers and their test by computer simulation
1996
Various organic molecules, in particular polymers, are extremely good glass formers and allow the study of supercooled melts near the glass transition in metastable equilibrium. Theories of the glass transition imply such an equilibrium (e.g. mode-coupling theory, or Gibbs-di Marzio theory) and can hence be tested in these systems. Simplified lattice models for polymer melts (e.g. the bond fluctuation model) have been developed that can very efficiently be studied by Monte-Carlo simulation, and although they fail to accurately describe the local structure, they describe many features of the experiments very well. In this model, the mechanism of the glass transition is a competition between …
Temperature dependence of the static structure factor of ortho-terphenyl in the supercooled liquid regime close to the glass transition
1993
Abstract Studying the temperature dependence of the static structure factor of ortho-terphenyl from the liquid state down to the glass we find that the main peak of S ( Q ) is split into two maxima which behave quite differently. While the maximum at Q =1.4 A −1 is not much affected by the temperature variation the one at 1.9 A −1 is significantly enhanced. This effect is connected with a change of the short range order, i.e. of the intermolecular distances, but evolves continuously. Thus the dynamic anomalies that have been observed in this system around a characteristic temperature T c ≈290 K are not simply due to a discontinuous change in S ( Q ) but can be attributed to the existence of…
Off-diagonal estimates for bi-parameter commutators
2022
Tutkimme kahden parametrin singulaari-integraalien kommutaattoreiden rajoit-tuneisuutta iteroitujen avaruuksien[b, T]:Lp1Lp2→Lq1Lq2välillä kunqi, pi∈(1,∞)ja erityisesti fraktionaalisessa tilanteessaqi6=pi. Yhteensä seitsemässä ta-pauksessa yhdeksästä saavutamme täyden karaterisoinnin rajoittuneisuudella symboliabkoskevillaoskillatorisilla testiehdoilla. We study the boundedness of commutators of bi-parameter singular integrals between mixed spaces [b,T]:Lp1Lp2→Lq1Lq2 in the off-diagonal situation qi,pi∈(1,∞) where we allow qi≠pi. Boundedness is fully characterized in terms of oscillatory testing conditions on the function b for a total seven out of the nine possible arrangements of the inte…