Esta pesquisa estuda o comportamento de blocos de concreto armado sobre duas estacas com cálice totalmente embutido, utilizado na ligação pilar-fundação de estruturas de concreto pré-moldado. Particularmente, foi avaliado o efeito que a viga de travamento provoca no bloco quando apoiada nas paredes laterais do cálice. Foi desenvolvida análise numérica tridimensional utilizando programa baseado no método dos elementos finitos (MEF), na qual foi considerada a não-linearidade física dos materiais. Para avaliação do programa adotado, realizou-se análise comparativa de resultados experimentais e numéricos obtidos por meio de outro programa. Nos blocos estudados variou-se a espessura e o tipo de conformação das paredes do cálice, o ângulo de inclinação da biela e a intensidade das ações na viga de travamento. Os resultados indicam que a presença da viga de travamento não altera de modo significativo o comportamento do bloco, e que a parede do cálice é capaz de transferir a força proveniente da viga em direção às estacas de modo eficaz. Por meio das tensões nas barras da armadura principal, foi possível obter a força no tirante e o ângulo de inclinação da biela antes da ruína dos modelos. Constatou-se que os ângulos apresentaram maior inclinação do que as utilizadas no dimensionamento, que por sua vez foi feito baseado nos modelos de bielas e tirantes. / The present research studies the behavior of two pile caps reinforced concrete with embedded socked used in connections of pre-cast concrete structures. It was particularly evaluated the effect provoked by the locking beam on the pile-caps when supported by the socket lateral walls. Three-dimensional numerical analyses using software based on finite element method (FEM) were developed considering the nonlinear physical behavior of the material. To evaluate the adopted software, a comparative analysis was made using numerical and experimental results obtained from other software. In the pile caps studied, it was noticed a variation in the wall thickness, socket interface, strut angle inclination and action on beam. The results show that the presence of beam does not change significantly the pile caps behavior and that the socket wall is able to transfer effectively the force from the beam to the pile caps. By the tensions on the bars of longitudinal reinforcement, it was possible to obtain the force on the tie and the strut angle inclination before the collapse of models. It was found that the angles present more inclinations than those used in the design, which was made based on strut and tie model.

A disponibilização de fontes ópticas multi-comprimento de onda de baixo custo certamente é um dos aspectos fundamentais para viabilizar a implantação de redes WDMPON (Wavelength Division Multiplexing-Passive Optical Network). Na literatura, são encontradas propostas de algumas tecnologias para a construção de tais dispositivos como a utilização de fontes ópticas sintonizáveis, uso de um vetor de lasers DFB (Distributed Feedback Laser) ou, até mesmo, o fatiamento espectral de uma fonte de banda larga. Contudo, essas propostas apresentam custo elevado, ou limitações de operação, tornando-se inapropriadas para a aplicação de interesse. Uma alternativa que vem sendo amplamente utilizada é o travamento óptico de diodos laser de Fabry-Pérot (FP-LD - Fabry-Pérot laser diode), realizado por meio da injeção de sinal óptico externo provindo do fatiamento espectral de uma fonte de banda larga. O travamento óptico possibilita o controle espectral do FP-LD, e o seu baixo custo torna essa fonte óptica atrativa na implantação de redes WDM. O entendimento do mecanismo de travamento torna-se, então, crucial na descrição da dinâmica de tais fontes ópticas. Desta forma, nesta dissertação, foi desenvolvido o estudo dos modelos matemáticos que descrevem a dinâmica de lasers travados, assim como foi investigado o desempenho de redes WDM-PON empregando estas fontes ópticas. / The availability of low cost multi-wavelength optical sources is certainly one of the fundamental aspects to allow the deployment of WDM-PON networks. Several technologies for the implementation of such optical sources are discussed in the literature, including tunable lasers, DFB arrays and spectral slicing of a broadband light source. However, those propositions suffer from high cost or operational limitations. One alternative is the optical injection locking of a Fabry Pérot laser diode (FPLD), in which the external optical injection signal is obtained from the spectral slicing of a broadband light source. This option has been widely investigated because the optical injection locking process allows for the FP-LD optical spectral control and wavelength selection. In addition, the low cost of such device makes this optical source an attractive solution for WDM-PON widespread deployment. In this context, the understanding of the locking mechanism becomes important in the optimization of such optical sources. Thus, in this dissertation, we conducted a study of mathematical models that describe the dynamics of locked lasers as well as investigated the performance of WDM-PON based on those optical sources.

Au cours des dix dernières années, les performances des lasers à cascade quantique dans le moyen infrarouge ont connu une progression rapide: Les rendements ont atteint des valeurs supérieures à 20% avec une puissance d’émission de 5W en régime continu, à température ambiante. Ces valeurs ont été atteintes notamment grâce à la diminution de la sensibilité des lasers à l’échauffement, avec des températures caractéristiques T0 s’approchant de 300K. Les performances sont donc actuellement limitées par la puissance injectée, qui est proportionnelle à la taille de la zone de gain. Les travaux de cette thèse présentent une solution innovante, consistant à combiner un réseau d’émetteurs de petites tailles de façon monolithique. Nous démontrons expérimentalement pour la première fois, des dispositifs jusqu’à 32 émetteurs de 2µm de larges, émettant en phase par couplage évanescent. De plus, nous mettons en évidences des résistances thermiques record. Ces résultats mettent en évidence la possibilité de fabriquer des sources de hautes puissances (supérieures à 10W) dans le moyen-infrarouge avec une très bonne qualité de faisceau. / During the last 10 years, the quantum cascade lasers performances in the mid-infrared have been considerably improved: the wall plug efficiency has reached values superior to 20%, with output power up to 5W in continuous wave operation, at room temperature. Those values have been achieved due to the reduction of the temperature sensibility of the lasers, with characteristic temperature T0 reaching 300K. The output power is now limited to the injected power, which is proportional to the gain region size. This thesis reports an innovating solution consisting on beam combining an array of narrow emitters, monolithically. We experimentally demonstrate for the first time devices of up to 32 emitters of 2µm width emitting in phase by evanescent coupling. Moreover, we show record thermal resistance. Those results highlight the possibility to fabricate high power sources (superior to 10 W) in the mid-infrared, with a good beam quality.

Les travaux de cette thèse s'efforcent d'apporter une solution au problème persistant de grande pauvreté des lasers à fibre à modes bloqués, en termes de fonctionnalités et de flexibilité. La thèse propose une cavité laser fibrée ayant comme spécificité d'être multifonctionnelle. La cavité est dotée de composants accordables, qui apportent la flexibilité nécessaire pour réaliser des fonctions allant de la génération d’impulsions aux profils complexes (solitons, bi-solitons, tri-solitons, etc) jusqu’à la sculpture des profils d’impulsion, en passant par la régulation des puissances crête, et la régénération de profils d’intensités sévèrement dégradés. La cavité laser que nous proposons a comme spécificité d'être pilotée par un composant clé, qui est un miroir à boucle optique non-linéaire (NOLM : Nonlinear Optical Loop Mirror) multifonction. Nous avons conçu ce NOLM en apportant des modifications structurelles dans l'architecture usuelle de ce dispositif, et en lui adjoignant : une fibre compensatrice de dispersion, un filtre passe bande à bande passante accordable, et un amplificateur (précédé d'un filtre égaliseur de gain, selon le besoin). Le NOLM ainsi conçu est doté de deux paramètres manuellement accordables, à savoir: la bande passante du filtre passe bande et la puissance de pompage de l'amplificateur. Ces deux paramètres permettent de régler sa fonction de transfert, et à accroître ainsi ses fonctionnalités et sa flexibilité. Ainsi, en plus de son rôle comme élément déclencheur du blocage de modes, ce NOLM réalise des fonctions optiques essentielles telles que la régénération des profils d'intensité fortement dégradés par des phénomènes de propagation ; ce qui contribue au renforcement de la stabilité du laser. Nous démontrons également la possibilité de réguler la puissance crête des impulsions, en la verrouillant à une valeur prédéfinie. Nous montrons enfin que le laser multifonction offre la possibilité de réaliser la sculpture des profils d'impulsion, c'est-à-dire, de générer des impulsions dotées d'une puissance crête et une largeur temporelle fixés à l'avance via un réglage approprié des paramètres de contrôle du NOLM.Les applications visées par ce laser multifonction, concernent toutes les activités qui requièrent des sources d'impulsions finement accordables, tant au niveau de puissance crête des impulsions que de leur largeur temporelle. Ces activités, nombreuses dans le domaine Télécom, incluent les opérations de remise en forme des porteuses d'information, les opérations de compression ou étirement de profil d'impulsion, les diagnostics de composants optiques et contrôles non destructifs des lignes de transmission par réflectométrie. / The work of this thesis strives to provide a solution to the persistent problem of poverty of mode-locked fiber lasers, in terms of functionality and flexibility. The thesis proposes a fiber-laser cavity having the specificity of being multifunctional. The cavity is equipped with tunable components, which provide the flexibility to realize functions ranging from the generation of pulses with complex profiles (solitons, bi-solitons, tri-solitons, etc.) up to the carving of pulse profiles, passing through the regulation of peak powers, and the regeneration of severely degraded intensity profiles. The laser cavity that we propose has the specificity of being controlled by a key component, which is a multifunctional nonlinear optical loop mirror (NOLM). We have designed this NOLM by making structural modifications in the usual architecture of this device, and by adding to it: a dispersion compensating fiber, a bandpass filter with tunable bandwidth, and an amplifier (preceded by a gain flattening filter, as needed) with tunable gain. These two parameters make it possible to adjust its transfer function, and thus to increase its functionalities and its flexibility. Thus, in addition to its role as a trigger for mode locking, this NOLM performs essential optical functions such as the regeneration of strongly degraded intensity profiles; which contributes to strengthening the stability of the laser.We also show the possibility of regulating the pulse peak power by locking it around a predefined value. Finally, we show that the multifunction laser offers the possibility to carve pulse profiles, that is, to generate pulses endowed with a peak power and a temporal width set in advance through an appropriate adjustment of the NOLM control parameters. The applications targeted by this multifunction laser are those requiring pulses with finely tunable peak power and temporal width. These activities, include the pulse reshaping in Telecoms, operations of compression or stretching of pulse profiles, optical component diagnostics, and non-destructive control of transmission lines

NIL

In this thesis, we present a new continuously variable high frequency standing wave oscillator and demonstrate its use in generating the phase locked clock signal of a digital IC. The ring based standing wave resonant oscillator is implemented with a plurality of wires connected in a mobius configuration, with a cross coupled inverter pair connected across the wires. The oscillation frequency can be modulated by coarse and fine tuning. Coarse modification is achieved by altering the number of wires in the ring that participate in the oscillation, by driving a digital word to a set of passgates which are connected to each wire in the ring. Fine tuning of the oscillation frequency is achieved by varying the body bias voltage of both the PMOS transistors in the cross coupled inverter pair which sustains the oscillations in the resonant ring. We validated our PLL design in a 90nm process technology. 3D parasitic RLCs for our oscillator ring were extracted with skin effect accounted for. Our PLL provides a frequency locking range from 6 GHz to 9 GHz, with a center frequency of 7.5 GHz. The oscillator alone consumes about 25 mW of power, and the complete PLL consumes a power of 28.5 mW. The observed jitter of the PLL is 2.56 percent. These numbers are significant improvements over the prior art in standing wave based PLLs.

The subject of this thesis is the exploration of new concepts for compact solid-state lasers in the visible and near-infrared spectral range using new components such as volume Bragg gratings for wavelength stabilisation and wavelength tuning. Also single-walled carbon nanotubes for mode-locking and Q-switching of lasers have been studied.We have developed a new method for the tuning of solid-state lasers by replacing a dielectric mirror with a transversally chirped volume Bragg grating, which allows smooth wavelength tuning without additional elements inside the laser cavity. The result is a more compact laser, since the tuning mechanism and output coupler are incorporated in one component. Another benefit is an increased efficiency, since additional elements inside the cavity will always add to the total loss of the laser. This has been demonstrated for a broadband ytterbium laser around 1 µm and a single-longitudinal-mode Nd:YVO4 laser around 1.06 µm. A volume Bragg grating has also been used to construct an efficient, narrow-linewidth ytterbium fiber laser and the employment of a volume Bragg gratingas the pump mirror of a solid-state laser for frequency-doubling has been investigated. Both lasers represent a practical solution, eliminating the use of additional intracavity elements. Second-harmonic generation is an efficient way to access the visible spectral range using diode-pumped solid-state lasers. However, these lasers can suffer from large amplitude fluctuations, which has been analyzed in more detail for an optically-pumped semiconductor disk-laser and a volume Bragg grating locked ytterbiumlaser. The control of those amplitude fluctuations is very important, since many applications like fluorescence microscopy require a laser with a constant output power and as little noise as possible. In addition to this, we have demonstrated, that saturable absorbers based on quan-tum dots and carbon nanotubes can be used to mode-lock compact laser at a wavelength around 1.03 µm. Those lasers have many interesting applications incommunications, clock generation, metrology and life sciences. / <p>QC 20130507</p>

La thèse est décomposée en trois parties. Dans la première partie, les modèles de la CUF sont présentés. La CUF permet d’obtenir, dans un formalisme générale, de nombreux modèles qui diffèrent 1) selon l’ordre d’expansion dans l'épaisseur choisie pour les variables primaires; 2) selon le type de modèle: modèles couche équivalente (ESL) ou couche discrète (LW); 3) selon le principe variationnel : “Principle of Virtual Displacements” (raffinée) ou “Reissner’s Mixed Variational Theorem” (avancée). Des géométries cylindrique et à double courbure sont traités. La deuxième partie de la thèse est consacrée à l'obtention des équations fondamentales en utilisant différentes méthodes: la méthode analytique de Navier et deux méthodes numériques approchées; la “Finite Element Method” (FEM) et la “Radial Basis Functions” (RBF). La méthode RBF est une méthode sans maillage “meshless” et peut être considérée comme une méthode alternative à la FEM. La FEM est la plus utilisée dans la littérature et le sujet principal de cette thèse.Dans la dernière partie, différents problèmes sont proposés. Navier est utilisé pour l’analyse thermomécanique de coques FGM, l’analyse de coques piézo-électrique et l’analyse dynamique de nanotubes de carbone. Un élément fini coque, présenté dans cette thèse, est utilisé pour l’analyse de coques composites et FGM. Les résultats obtenus démontrent la supériorité de cet élément par rapport aux éléments finis basés sur les théories classiques pour l’analyse des matériaux avancés. Enfin, la méthode RBF est utilisée pour l’analyse de coques composites, permettant d'illustrer l'avantage des méthodes sans maillage. / The dissertation is organized in three main parts. In the first part, the shell models contained in the CUF are presented. The CUF permits to obtain, in a general and unified manner, several models that can differ by 1) the chosen order of expansion in the thickness direction, 2) the equivalent single layer or layer wise approach and 3) the variational statement used: “Principle of Virtual Displacements” (refined models) or “Reissner’s Mixed Variational Theorem” (advanced models). Both the cylindrical and the double-curvature geometries are considered. The second part is devoted to the derivation of the governing equations by means of different methods: an analytical method, that is the Navier method, and two approximated numerical methods, that are the Finite Element Method (FEM) and the Radial Basis Functions (RBF) method. The RBF method is based on a meshless approach and it can be considered a good alternative to the FEM. The finite element method is the most common method used in literature and it is the main topic of this thesis. In the last part, different problems are analyzed. The thermo-mechanical analysis of FGM shells, the electromechanical analysis of piezoelectric shells and the dynamic analysis of carbon nanotubes are performed by means of the Navier method. Then, the CUF shell finite element, presented in this thesis, is tested and used for the analysis of composite and FGM shells. The superiority of this element in respect to finite elements based on classical theories is shown. Finally, the RBF method is combined with the CUF for the analysis of composite and FGM shells in order to overcome the numerical problems relative to the mesh that usually affect the finite elements.

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