Rapport M/L de disques de galaxies issus de modèles CSPE et contrôle des contraintes mécaniques dans la conception de revêtements optiques

La thèse qui suit est organisée en deux volets: un premier volet portant sur les modèles de masse de galaxies et un second volet sur la conception de revêtements optiques et le contrôle de leurs propriétés mécaniques. Les modèles de masse présentés dans cette thèse ont été réalisés sur un sous-échantillon de dix galaxies de l'étude SINGS comprenant neuf galaxies normales et une galaxie naine. Ce travail visait à fixer le rapport masse-luminosité du disque à tout rayon en utilisant les résultats de modèles d'évolution galactique chimio-spectrophotométriques ajustés spécifiquement à chaque galaxie grâce à son profil de photométrie multi-bandes. Les résultats montrent que les disques stellaires tels que normalisés par les rapports masse-luminosité issus des modèles ont des masses cohérentes dans toutes les bandes étudiées de l'ultra-violet, du visible ainsi que du proche infrarouge (bandes FUV à IRAC2). Ces disques peuvent être considérés comme maximaux par rapport aux données cinématiques des galaxies étudiées. Ceci est dû au fait que le rapport M/L est plus élevé au centre que sur les bords. Les disques étant maximaux et physiquement justifiés, on ne peut dès lors ignorer les effets de composants tels que les bulbes ou les barres et les corrections nécessaires doivent être apportées aux profils de luminosité et de vitesses de rotation de la galaxie. Dans les travaux de la seconde partie, le logiciel en développement libre OpenFilters a été modifié afin de tenir compte des contraintes mécaniques dans la conception numérique de revêtements optiques. Les contraintes mécaniques dans les couches minces ont un effet délétère sur leurs performances optiques. Un revêtement destiné à rendre réflectives les lames d'un étalon Fabry-Perot utilisé en astronomie a été conçu et fabriqué afin d'évaluer les performances réelles de la méthode. Ce cas a été choisi à cause de la diminution de la finesse d'un étalon Fabry-Perot apporté par la courbure des lames sous l'effet des contraintes. Les résultats montrent que les mesures concordent avec les modèles numériques et qu'il est donc possible à l'aide de ce logiciel d'optimiser les revêtements pour leur comportement mécanique autant que pour leurs propriétés optiques.

Design de nouvelles fonctionnelles en théorie de la fonctionnelle de la densité et conception de polymères pour application à la photovoltaïque organique

La présente thèse porte sur les calculs utilisant la théorie de la fonctionnelle de la densité (DFT) pour simuler des systèmes dans lesquels les effets à longue portée sont importants. Une emphase particulière est mise sur les calculs des énergies d’excitations, tout particulièrement dans le cadre des applications photovoltaïques. Cette thèse aborde ces calculs sous deux angles. Tout d’abord, des outils DFT déjà bien établis seront utilisés pour simuler des systèmes d’intérêt expérimental. Par la suite, la théorie sous-jacente à la DFT sera explorée, ses limites seront identifiées et de nouveaux développements théoriques remédiant à ceux-ci seront proposés. Ainsi, dans la première partie de cette thèse, des calculs numériques utilisant la DFT et la théorie de la fonctionnelle de la densité dépendante du temps (TDDFT) telles qu’implémentées dans le logiciel Gaussian [1] sont faits avec des fonctionnelles courantes sur des molécules et des polymères d’intérêt expérimental. En particulier, le projet présenté dans le chapitre 2 explore l’utilisation de chaînes latérales pour optimiser les propriétés électroniques de polymères déjà couramment utilisés en photovoltaïque organique. Les résultats obtenus montrent qu’un choix judicieux de chaînes latérales permet de contrôler les propriétés électroniques de ces polymères et d’augmenter l’efficacité des cellules photovoltaïques les utilisant. Par la suite, le projet présenté dans le chapitre 3 utilise la TDDFT pour explorer les propriétés optiques de deux polymères, le poly-3-hexyl-thiophène (P3HT) et le poly-3-hexyl- sélénophène (P3HS), ainsi que leur mélange, dans le but d’appuyer les observations expérimentales indiquant la formation d’exciplexe dans ces derniers. Les calculs numériques effectués dans la première partie de cette thèse permettent de tirer plusieurs conclusions intéressantes, mais mettent également en évidence certaines limites de la DFT et de la TDDFT pour le traitement des états excités, dues au traitement approximatif de l’interaction coulombienne à longue portée. Ainsi, la deuxième partie de cette thèse revient aux fondements théoriques de la DFT. Plus précisément, dans le chapitre 4, une série de fonctionnelles modélisant plus précisément l’interaction coulombienne à longue portée grâce à une approche non-locale est élaborée. Ces fonctionnelles sont basées sur la WDA (weighted density approximation), qui est modifiée afin d’imposer plusieurs conditions exactes qui devraient être satisfaites par le trou d’échange. Ces fonctionnelles sont ensuite implémentées dans le logiciel Gaussian [1] et leurs performances sont évaluées grâce à des tests effectués sur une série de molécules et d’atomes. Les résultats obtenus indiquent que plusieurs de ces fonctionnelles donnent de meilleurs résultats que la WDA. De plus, ils permettrent de discuter de l’importance relative de satisfaire chacune des conditions exactes.

Nuclear incompressibility in the quasilocal density functional theory

We explore the ability of the recently established quasilocal density functional theory for describing the isoscalar giant monopole resonance. Within this theory we use the scaling approach and perform constrained calculations for obtaining the cubic and inverse energy weighted moments (sum rules) of the RPA strength. The meaning of the sum rule approach in this case is discussed. Numerical calculations are carried out using Gogny forces and an excellent agreement is found with HF+RPA results previously reported in literature. The nuclear matter compression modulus predicted in our model lies in the range 210230 MeV which agrees with earlier findings. The information provided by the sum rule approach in the case of nuclei near the neutron drip line is also discussed.

Valoración de opciones bajo el modelo de Kou aplicando transformada de Fourier

En esta Tesis se presenta el modelo de Kou, Difusión con saltos doble exponenciales, para la valoración de opciones Call de tipo europeo sobre los precios del petróleo como activo subyacente. Se mostrarán los cálculos numéricos para la formulación de expresiones analíticas que se resolverán mediante la implementación de algoritmos numéricos eficientes que conllevaran a los precios teóricos de las opciones evaluadas. Posteriormente se discutirán las ventajas de usar métodos como la transformada de Fourier por la sencillez relativa de su programación frente a los desarrollos de otras técnicas numéricas. Este método es usado en conjunto con el ejercicio de calibración no paramétrica de regularización, que mediante la minimización de los errores al cuadrado sujeto a una penalización fundamentada en el concepto de entropía relativa, resultaran en la obtención de precios para las opciones Call sobre el petróleo considerando una mejor capacidad del modelo de asignar precios justos frente a los transados en el mercado.

Eigenvalues of a one-dimensional Dirac operator pencil

We study the spectrum of a one-dimensional Dirac operator pencil, with a coupling constant in front of the potential considered as the spectral parameter. Motivated by recent investigations of graphene waveguides, we focus on the values of the coupling constant for which the kernel of the Dirac operator contains a square integrable function. In physics literature such a function is called a confined zero mode. Several results on the asymptotic distribution of coupling constants giving rise to zero modes are obtained. In particular, we show that this distribution depends in a subtle way on the sign variation and the presence of gaps in the potential. Surprisingly, it also depends on the arithmetic properties of certain quantities determined by the potential. We further observe that variable sign potentials may produce complex eigenvalues of the operator pencil. Some examples and numerical calculations illustrating these phenomena are presented.

Multiple stationary solutions of an irradiated slab

A mathematical model describing the heat budget of an irradiated medium is introduced. The one-dimensional form of the equations and boundary conditions are presented and analysed. Heat transport at one face of the slab occurs by absorption (and reflection) of an incoming beam of short-wave radiation with a fraction of this radiation penetrating into the body of the slab, a diffusive heat flux in the slab and a prescribed incoming heat flux term. The other face of the slab is immersed in its own melt and is considered to be a free surface. Here, temperature continuity is prescribed and evolution of the surface is determined by a Stefan condition. These boundary conditions are flexible enough to describe a range of situations such as a laser shining on an opaque medium, or the natural environment of polar sea ice or lake ice. A two-stream radiation model is used which replaces the simple Beer’s law of radiation attenuation frequently used for semi-infinite domains. The stationary solutions of the governing equations are sought and it is found that there exists two possible stationary solutions for a given set of boundary conditions and a range of parameter choices. It is found that the existence of two stationary solutions is a direct result of the model of radiation absorption, due to its effect on the albedo of the medium. A linear stability analysis and numerical calculations indicate that where two stationary solutions exist, the solution corresponding to a larger thickness is always stable and the solution corresponding to a smaller thickness is unstable. Numerical simulations reveal that when there are two solutions, if the slab is thinner than the smaller stationary thickness it will melt completely, whereas if the slab is thicker than the smaller stationary thickness it will evolve toward the larger stationary thickness. These results indicate that other mechanisms (e.g. wave-induced agglomeration of crystals) are necessary to grow a slab from zero initial thickness in the parameter regime that yields two stationary solutions.

A mathematical model of crystallization in an emulsion

A mathematical model incorporating many of the important processes at work in the crystallization of emulsions is presented. The model describes nucleation within the discontinuous domain of an emulsion, precipitation in the continuous domain, transport of monomers between the two domains, and formation and subsequent growth of crystals in both domains. The model is formulated as an autonomous system of nonlinear, coupled ordinary differential equations. The description of nucleation and precipitation is based upon the Becker–Döring equations of classical nucleation theory. A particular feature of the model is that the number of particles of all species present is explicitly conserved; this differs from work that employs Arrhenius descriptions of nucleation rate. Since the model includes many physical effects, it is analyzed in stages so that the role of each process may be understood. When precipitation occurs in the continuous domain, the concentration of monomers falls below the equilibrium concentration at the surface of the drops of the discontinuous domain. This leads to a transport of monomers from the drops into the continuous domain that are then incorporated into crystals and nuclei. Since the formation of crystals is irreversible and their subsequent growth inevitable, crystals forming in the continuous domain effectively act as a sink for monomers “sucking” monomers from the drops. In this case, numerical calculations are presented which are consistent with experimental observations. In the case in which critical crystal formation does not occur, the stationary solution is found and a linear stability analysis is performed. Bifurcation diagrams describing the loci of stationary solutions, which may be multiple, are numerically calculated.

The influence of ocean flow on newly forming sea ice

The heat and mass balance of the Arctic Ocean is very sensitive to the growth and decay of sea ice and the interaction between the heat and salt fields in the oceanic boundary layer. The hydraulic roughness of sea ice controls the detailed nature of turbulent fluxes in the boundary layer and hence is an important ingredient in model parameterizations. We describe a novel mechanism for the generation of corrugations of the sea ice–ocean interface, present a mathematical analysis elucidating the mechanism, and present numerical calculations for geophysically relevant conditions. The mechanism relies on brine flows developing in the sea ice due to Bernoulli suction by flow of ocean past the interface. For oceanic shears at the ice interface of 0.2 s−1, we expect the corrugations to form with a wavelength dependent upon the permeability structure of the sea ice which is described herein. The mechanism should be particularly important during sea ice formation in wind-maintained coastal polynyas and in leads. This paper applies our earlier analyses of the fundamental instability to field conditions and extends it to take account of the anisotropic and heterogeneous permeability of sea ice.

Optimal power management strategy for energy storage with stochastic loads

In this paper, a power management strategy (PMS) has been developed for the control of energy storage in a system subjected to loads of random duration. The PMS minimises the costs associated with the energy consumption of specific systems powered by a primary energy source and equipped with energy storage, under the assumption that the statistical distribution of load durations is known. By including the variability of the load in the cost function, it was possible to define the optimality criteria for the power flow of the storage. Numerical calculations have been performed obtaining the control strategies associated with the global minimum in energy costs, for a wide range of initial conditions of the system. The results of the calculations have been tested on a MATLAB/Simulink model of a rubber tyre gantry (RTG) crane equipped with a flywheel energy storage system (FESS) and subjected to a test cycle, which corresponds to the real operation of a crane in the Port of Felixstowe. The results of the model show increased energy savings and reduced peak power demand with respect to existing control strategies, indicating considerable potential savings for port operators in terms of energy and maintenance costs.

Análise de projetos de investimentos : uma abordagem teórico-prática

The objective of this work is to search a real case of capital budgeting, relating the practical technical aspects of the elaboration of project, with theoretical referential and following secondary objectives: (i) to analyze the relations established between the bibliographical material and the found practical technical problems of capital budgeting in the enterprise; (ii) to search and to describe the necessary pacing to the economic and financial elaboration of an project, from the prospecting of the demand, the projection of revenues and expenditures and the evaluation of the necessary investments to its development; (iii) to relate and to exemplify the influences of the restrictions presented for the methods of capital budgeting, correlating the practical theoretical referential with the enterprise; (iv) to analyze the yield of the investment project, (v) to verify the influence of the financing, on the yield of the project; and, finally, (vi) to demonstrate the choice process among some alternatives of supply, when used as tools of aid to the purchase decision, the methods of the Internal Tax of Return and the Net Present Value. To the end of the study one concluded that the methods of the Internal Tax of Return and the Net Present Value are powerful tools in the yield evaluation and viability of investments projects. However, to only understand the methods through what they teach in books is not enough for the daily practical of capital budgeting. Literature starts from two basic points: (i) the investments analyst dominates all the countable revenues, expenditures, and investments concepts.(ii) the numerical examples are simple and easy to understand, to infer its practical applications is a contouring question to be raised and passed by the analyst. This study intends to show the conjunction of the bibliography with the practical one, therefore, from the instant that demonstrates the countable concept of the prescription, it also explains as it was constituted from the calculation of the demand, until its inclusion in the project. Thus, searching concepts of revenues, expenditures, depreciation and capital assets, disclosing its constitution and, over all, the application inside of the project, it all takes the analyst to the final part of the process, that consists in the determination of the numerical calculations, allowing to dedicate more time to the difficult task to interpret the data. Finally, understood the analysis of the economic viability of the project, the study guides the purchase of the equipment under the economic-financial point of view.

Método dinâmico aplicado para antenas cilíndricas

Nowadays there has been a major breakthrough in the aerospace area, with regard to rocket launches to research, experiments, telemetry system, remote sensing, radar system (tracking and monitoring), satellite communications system and insertion of satellites in orbit. This work aims at the application of a circular cylindrical microstrip antenna, ring type, and other cylindrical rectangular in structure of a rocket or missile to obtain telemetry data, operating in the range of 2 to 4 GHz, in S-band. Throughout this was developed just the theoretical analysis of the Transverse transmission line method which is a method of rigorous analysis in spectral domain, for use in rockets and missiles. This analyzes the spread in the direction "ρ" , transverse to dielectric interfaces "z" and "φ", for cylindrical coordinates, thus taking the general equations of electromagnetic fields in function of e [1]. It is worth mentioning that in order to obtain results, simulations and analysis of the structure under study was used HFSS program (High Frequency Structural Simulator) that uses the finite element method. With the theory developed computational resources were used to obtain the numerical calculations, using Fortran Power Station, Scilab and Wolfram Mathematica ®. The prototype was built using, as a substrate, the ULTRALAM ® 3850, of Rogers Corporation, and an aluminum plate as a cylindrical structure used to support. The agreement between the measured and simulated results validate the established processes. Conclusions and suggestions are presented for continuing this work

Wannier functions of isolated bands in one-dimensional crystals

We present a simple procedure to obtain the maximally localized Wannier function of isolated bands in one-dimensional crystals with or without inversion symmetry. First, we discuss the generality of dealing with real Wannier functions. Next, we use a transfer-matrix technique to obtain nonoptimal Bloch functions which are analytic in the wave number. This produces two classes of real Wannier functions. Then, the minimization of the variance of the Wannier functions is performed, by using the antiderivative of the Berry connection. In the case of centrosymmetric crystals, this procedure leads to the Wannier-Kohn functions. The asymptotic behavior of the Wannier functions is also analyzed. The maximally localized Wannier functions show the expected exponential and power-law decays. Instead, nonoptimal Wannier functions may show reduced exponential and anisotropic power-law decays. The theory is illustrated with numerical calculations of Wannier functions for conduction electrons in semiconductor superlattices.

Resistivity in the dynamic current sheath of a field reversed configuration

The resistivity of a field reversed configuration in a theta-pinch with slow rising current was investigated during the turbulent phase from the moment of field reversal until end of plasma radial implosion. This transport coefficient was obtained in a hydrogen plasma by local measurements with magnetic probe and compared to numerical calculations with Chodura resistivity and evolution of lower hybrid drift instability. The values of resistivity are higher than those predicted by classical binary collision. During early phase of confinement, the doubly layer structure of current sheath in the low electric field machine was theoretically well reproduced with anomalous collision frequency calculated with Chodura resistivity that provides appropriate conditions for onset of lower hybrid drift instability and the regular evolution of pinch. The plasma dynamic, radial profiles of magnetic field during the radial compression and resistivity values were equally close to those observed by the measurements. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3698405]

Boson-boson effective nonrelativistic potential for higher-derivative electromagnetic theories in D dimensions

The problem of computing the effective nonrelativistic potential U-D for the interaction of charged-scalar bosons, within the context of D-dimensional electromagnetism with a cutoff, is reduced to quadratures. It is shown that U-3 cannot bind a pair of identical charged-scalar bosons; nevertheless, numerical calculations indicate that boson-boson bound states do exist in the framework of three-dimensional higher-derivative electromagnetism augmented by a topological Chern-Simons term.

Stability analysis of the D-dimensional nonlinear Schrodinger equation with trap and two- and three-body interactions

Considering the static solutions of the D-dimensional nonlinear Schrodinger equation with trap and attractive two-body interactions, the existence of stable solutions is limited to a maximum critical number of particles, when D greater than or equal to 2. In case D = 2, we compare the variational approach with the exact numerical calculations. We show that, the addition of a positive three-body interaction allows stable solutions beyond the critical number. In this case, we also introduce a dynamical analysis of the conditions for the collapse. (C) 2000 Published by Elsevier B.V. B.V. All rights reserved.