Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Nous proposons d'explorer dans le cadre de la thèse des solutions originales permettant d'obtenir des caractéristiques de rayonnement peu dépendantes du support de l'antenne. Les antennes étudiées et conçues visent à être utilisées pour des applications GNSS et plus précisément pour des applications multi-bandes du GNSS. Nous les développerons donc en respectant un cahier des charges associé. Deux axes de recherche indépendants sont explorés. Le premier montre les propriétés naturelles d'une antenne composée de plusieurs structures rayonnantes. Nous associons ainsi une structure hélicoïdale équivalente à un dipôle magnétique et un plan métallique équivalent à un dipôle électrique. La taille et les performances de l'antenne ainsi réalis ée sont comparables par bien des aspects aux antennes que l'on trouve actuellement dans le commerce pour les applications GNSS. L'antenne réalisée est une antenne mono-bande en polarisation rectiligne ; ce qui n'est pas en accord avec les spécifications de l'application envisagée. Pour compléter cette première étude et satisfaire les exigences d'applications GNSS multi-bandes, nous nous orientons vers une autre technologie qui est exposé dans le second axe. Dans le second axe, nous associons une antenne électrique et un plan ré ecteur particulier : une Surface Haute Impédance. L'association de ces deux éléments permet en théorie de réduire l'épaisseur qu'aurait un dispositif classique composé d'une antenne électrique et d'un plan réflecteur métallique. Nous commençons donc par étudier la particularité du plan réflecteur choisi, c'est-à-dire la Surface Haute Impédance. Cette surface étant composé de motifs périodiques nous étudierons le motif qui permet d'obtenir les caractéristiques les plus proches de celles de l'application visée. Nous débutons par une étude en monobande suivi de l'étude d 'un motif bi-bande. Le motif mono-bande conçu en simulation présente une très bonne bande-passante (13%) au vue de sa taille minimale (2,5mm). Le motif bi-bande réalisé par imbrication de motifs mono-bande permet d'obtenir en simulation des performances conformes aux attentes dans deux bandes GNSS choisies. L'étude de cette surface se poursuit par une phase de mesure. Le but de l'étude étant de pouvoir placer une antenne au-dessus de la surface fabriquée, une collection d'antennes sera développée afin de régler la surface haute impédance et dans le même temps de tester le dispositif complet. Ainsi dans un premier temps, nous utiliserons des dipôles pour tester et régler la Surface Haute Impédance. Dans cette partie le couplage entre l'antenne et la surface haute impédance placée en-dessous sera notamment étudié. Dans un deuxième temps, afin d'obtenir une polarisation circulaire nous utiliserons d'autres antennes supportant cette polarisation (dipôle croisé et spirale). Dans chaque phase de mesure, le réglage antenne et Surface Haute Impédance sera optimisé et divers paramètres de réglage seront identifiés. Pour les deux axes de recherche, ce sont non seulement le rayonnement que nous cherchons à maîtriser mais aussi la taille de la structure. Ainsi les structures réalisées sont les plus compactes possibles surtout en terme de finesse. Nous concluons sur les performances des antennes réalisées par rapport au cahier des charges et aux autres antennes existantes et exposons les perspectives du travail réalisé.

La thèse étudie le vaporeformage catalytique du méthane avec captage de CO2. Les catalyseurs bi-fonctionnels choisis se composent de nickel, efficace en vaporeformage, de CaO pour la sorption de CO2 et d'aluminate de calcium (Ca12Al14O33) pour permettre une bonne dispersion du métal et de CaO. La méthode de synthèse privilégiée était la méthode d'autocombustion assisté par microondes. Le rapport Ca/Al a été optimisé et un large excès de CaO est nécessaire (75%CaO ; 25%Ca12Al14O33) pour la sorption de CO2. Le reformage du méthane est total dès 650 °C (H2O/CH4 de 1 ou 3) et la sélectivité en hydrogène de 100% durant 7h ou 16h selon les conditions opérationnelles, validant le concept de vaporeformage du méthane assisté par l'absorption de CO2.

Organizations today are adopting business intelligence (BI) systems at a fast pace with the expectation that these systems will help them make better business decisions and improve their performance. But with the ever changing industry dynamics and variable business needs of end-users, the BI requirements of organizations are also getting unpredictable and increasingly harder to deliver by the service providers. Additionally, the advancement of web 2.0 & enterprise 2.0 technologies has opened up more possibilities for the development of user-centric innovative business applications. Enterprise BI Mashups are a specific breed of such technologies that have the potential to empower end-users with self-service capabilities and facilitate problem-solving in ad-hoc situational BI scenarios. This research project attempts to explore the current landscape of Business Intelligence (BI) Mashups and to identify gaps in technology with respect to user requirements and corporate objectives. Through an empirical investigation of BI mashups use cases, specific issues and challenges associated with the use of mashups in BI have been ascertained. Working in collaboration with IBM Cognos, we have formulated a taxonomy and utility framework for Enterprise BI Mashups. The formulated taxonomy provides a basic framework for understanding the domain of BI mashups and is aimed to aid application development initiatives for creating BI mashups toolkits. The utility framework draws upon real-world use cases for BI Mashups as well as pertinent software design patterns that can facilitate the development of BI mashup tools and services. These frameworks are expected to advance an understanding of business process requirements that can be satisfied through the use of Enterprise BI Mashups, and also aid in the development of mashup toolkits targeted at BI end-users.

Vapor generation in atomic spectrometry is a well established technique for the determination of elements that can be volatilized by chemical reactions. In-situ trapping in graphite furnaces is nowadays one of the most popular methods to increase the sensitivity. In this study, resistively heated W-coil was used as an online trap for preconcentration and revolatilization of volatile species of Bi, Cd and Pb. The collected analyte species were revolatilized rapidly and sent to a quartz Ttube atomizer for AAS measurement. Although the nature of revolatilized species of Bi and Pb are not clear, they are probably molecular since they can be transported at least 45 cm without any significant decrease in the peak height values. However, cadmium is revolatilized from the trap surface as atoms. The experimental parameters were optimized for the highest vapor generation, trapping and revolatilization efficiencies. The concentration limits of detection calculated by the 3 of blank solution were found to be 0.0027, 0.0040 and 0.015 ng/mL for Bi (18 mL), Cd (4.2 mL) and Pb (2 mL), respectively / enhancement factors in the sensitivity were 130, 31 and 20, respectively. These values are comparable with those obtained by in-situ trapping in graphite furnaces or even ICP-MS found in the literature or better. Sensitivity can be improved further for Bi and Cd using larger sample volumes, but purification of blank is required for Pb. Certified standard reference materials were analyzed for the assessment of accuracy of developed method.

The Method of Moments (MoM) has been used extensively to solve electromagnetic problems. Its popularity is largely attributed to its adaptability to structures with various shapes and success in predicting the equivalent induced currents accurately. However, due to its dense matrix, especially for large structures, the MoM suffers from long matrix solution time and large storage requirement. In this thesis it is shown that use of wavelet basis functions result in a MoM matrix which is sparser than the one obtained by using traditional basis functions. A new wavelet system, different from the ones found in literature, is proposed. Stabilized Bi-Conjugate Gradient Method which is an iterative matrix solution method is utilized to solve the resulting sparse matrix equation. Both a one-dimensional problem with a microstrip line example and a two-dimensional problem with a rectangular patch antenna example are studied and the results are compared.

Polyacrylonitrile (PAN)/carbon nanotube (CNT) composite fibers were made using various processing methods such as conventional solution spinning, gel spinning, and bi-component gel spinning. The detailed characterization exhibited that the smaller and longer CNT will reinforce polymer matrix mostly in tensile strength and modulus, respectively. Gel spinning combined with CNT also showed the promising potential of PAN/CNT composite fiber as precursor fiber of the next generation carbon fiber. High resolution transmission electron microscopy showed the highly ordered PAN crystal layer on the CNT, which attributed to the enhanced physical properties. The subsequent carbonization study revealed that carbonized PAN/CNT fibers have at least 50% higher tensile strength and modulus as compared to those of carbonized PAN fibers. Electrical conductivity of CNT containing carbon fiber was also 50% higher than that of carbonized PAN fiber. In order to have carbon fiber with high tensile strength, the smaller diameter precursor fiber is preferable. Bi-component gel spinning produced 1-2 µm precursor fiber, resulting in ~1 µm carbon fiber. The tensile strength of the carbonized bi-component fiber (islands fibers) is as high as 6 GPa with tensile modulus of ~500 GPa. Further processing optimization may lead to the next generation carbon fiber.

Solid oxide fuel cells (SOFCs) are very attractive as energy generation devices because they are clean, reliable, and almost entirely pollution-free. SOFCs have flexible fuel selections compared with other fuel cell technologies. The main disadvantage of SOFCs is their high operating temperature (~1000ºC for conventional SOFCs) which leads to cell cracking and formation of non-conducting compounds at electrolyte/electrode interfaces. Therefore, intermediate temperature SOFCs (ITSOFCs) in the range of 500-700 ºC has attracted extensive research interests. To achieve high cell performance at reduced temperatures, it requires high-catalytic activity, high ionic conductivity, and comparable thermal expansion coefficient (TEC) of the cell components. To address the above issues, the research focuses on two main approaches (i.e., the interlayer approach and the electrolyte approach) in order to improve the overall cell performance. First, the design of a thin layer of a vertically-aligned nanocomposite (VAN) structure as an interlayer between the electrolyte and cathode is demonstrated. The development of the VAN structures consisted of the cathode material as a perovskite or ordered double perovskite structure, La0.5Sr0.5CoO3 (LSCO) or PrBaCo2O5 delta (PBCO), and the electrolyte material as a fluorite structure, Ce0.9Gd0.1O1.95 (CGO or GDC), were achieved for thin film solid oxide fuel cell (TFSOFCs). The VAN structure significantly improves the overall performance of the TFSOFC by increasing the interfacial area between the electrolyte and cathode and also acts as a transition layer that improves adhesion and relieves both thermal stress and lattice strain. Second, microstructural and electrical properties of Gd-doped CeO2 (GDC, Ce0.9Gd0.1O1.95) thin films electrolyte are studied for intermediate temperature solid oxide fuel cells (SOFCs). The GDC thin film electrolytes with different grain sizes and grain morphologies were prepared by varying the deposition parameters such as substrate temperature, oxygen partial pressure, target repetition rate, and laser ablation energy. The electrical property of the GDC thin film is strongly affected by the grain size. Third, bilayer electrolytes composed of a gadolinium-doped CeO2 (GDC) layer (~6 micrometer thickness) and an yttria-stabilized ZrO2 (YSZ) layer with various thicknesses (~330 nm, ~440 nm, and ~1 micrometer) are achieved by a pulsed laser deposition (PLD) technique for thin film solid oxide fuel cells (TFSOFCs). One effective approach is to incorporate YSZ thin film as a blocking layer in between the GDC and anode for preventing chemical reduction of GDC and electrical current leakage. This bilayer approach effectively improves the GDC's chemical/ mechanical stability and reduces the OCV loss under reducing conditions. The results suggest that the YSZ thin film serves as a blocking layer for preventing electrical current leakage in the GDC layer and also provides chemical, mechanical, and structural integrity in the cell, which leads to the overall enhanced performance.

L’opto-pyrotechnie (amorçage de la détonation par système optique) est l’une des innovations les plus prometteuses en termes de fiabilité, de sécurité et de performances pour les futurs lanceurs spatiaux. Le but de la thèse est d’étudier et de modéliser le premier des deux étages d’un Détonateur Opto-Pyrotechnique, constitué d’un explosif confiné dans une chambre de combustion fermée où se déroulent les premières phases d’une Transition Déflagration-Détonation. L’amorçage par laser de l’explosif puis la combustion en chambre isochore sont traités par le code EFAE, lequel est couplé au logiciel LS-DYNA qui simule la déformation et la rupture du disque de fermeture de la chambre, puis la propulsion du projectile résultant vers le second étage. En parallèle, diverses techniques expérimentales (adsorption de gaz, vélocimétrie hétérodyne, microscopie) ont mis en valeur plusieurs procédés physiques, ce qui a permis de tester le couplage entre EFAE et LS-DYNA, puis de déterminer et de hiérarchiser les paramètres affectant les critères industriels. / Opto-pyrotechnics (ignition of detonation by optical systems) is one of the most promising innovations to improve reliability, safety and performances on future space launchers. This thesis aims at studying and modeling the first stage from a two-stage opto-pyrotechnic detonator that consists of a condensed explosive confined in a closed combustion chamber, in which the beginning of a Deflagration-to-Detonation Transition occurs. The laser ignition of the explosive and its isochoric combustion are modeled by the EFAE code. This code is coupled with LS-DYNA software to deal with the deformation and the rupture of the metallic disk that closes the combustion chamber, and then with the subsequent propulsion of the projectile to the second stage. In parallel, various experimental technics (gas adsorption, photonic Doppler velocimetry, microscopy) have underlined several physical processes that allow first to test the coupling between EFAE and LS-DYNA, then to determine and classify influent parameters that affect the industrial specifications.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O bi-dimensionalismo epistêmico é a tese de que os estados mentais de um indivíduo tem uma dupla divisão, tendo, então, um conteúdo amplo e um conteúdo estreito. Um conteúdo amplo é aquele cuja determinação depende em parte de propriedades extrínsecas ao sujeito: ou seja, é aquele que possui relação com o mundo externo ao sujeito, seja físico ou social. Já o conteúdo estreito é o conteúdo plenamente determinado por propriedades intrísecas ao sujeito, sem precisar recorrer a nada externo. Este conteúdo estreito será, de acordo com o bi-dimensionalismo de Jackson e de Chalmers, o conteúdo representativo de um estado mental, dado através de descrições sobre aquilo que o sujeito sabe e acredita sobre o mundo ao seu redor. O objetivo desta dissertação ao tratar sobre esta forma de bi-dimensionalismo é o de apresentá-lo como uma possível resposta para dois problemas gerados pela afirmação externalista de que nomes próprios e termos de tipos naturais são designadores rígidos e pela afirmação de que todo conteúdo de um estado mental é amplo. Estes dois problemas são a incompatibilidade do conteúdo amplo com o acesso privilegiado e a sua incompatibilidade com o papel explicatório que estados mentais intencionais parecem ter em relação aos comportamentos de um indivíduo, pois, se os indivíduos não possuem um acesso privilegiado aos conteúdos dos seus estados mentais, tal conteúdo amplo não poderá ser visto como sendo um causalmente relevante para os seus comportamentos. Contudo, os argumentos apresentados pelo externalismo semântico parecem ainda convincentes demais para considerar tais consequências como sendo um bom motivo para se abandonar a tese externalista. Além disso, vários exemplos do funcionamento da linguagem (como os casos do uso de nomes próprios e termos de espécies naturais) parecem indicar que o externalismo semântico é correto. Assim, neste trabalho, analisarei a teoria bi-dimensional à luz das afirmações externalistas sobre o significado e sobre a individuação dos conteúdos dos estados mentais, ou seja, como podendo ser uma teoria que, além de ser uma capaz de fornecer uma resposta viável para estes dois problemas, é também compatível com o conteúdo amplo da forma como é afirmado pelo externalismo. / The epistemic two-dimensionalism is the thesis that the mental states of a person have double division, possessing, therefore, a broad content and a narrow content. A broad content is the one whose determination depends partially on properties extrinsic to the individual: i.e., it is the one which is related to the world external to the individual, be it physical or social. On the other hand, the narrow content is the one completely determined by properties intrinsic to the individual, without the need of anything external. This narrow content is, according to Jacksons and Chalmers two-dimensionalism, the representative content of a mental state, presented through description of what the individual knows of and believes in the world around him. The objective of this dissertation dealing with this form of two-dimensionalism is to present it as a possible answer to two problems generated by the externalist affirmative that proper names and natural kind terms are rigid designators and the affirmative that all content in a mental state is broad. These two problems are the incompatibility of the broad content and the privileged access and its incompatibility with the explanatory role that intentional mental states seem to have regarding a persons behavior, for if people have no privileged access to the content of their mental states, such broad content cannot be seen as being causally relevant to their behaviors. However, the arguments presented by semantic externalism still seem too convincing to consider such consequences as being enough reason to all-together abandon the externalist thesis. Besides, a number of examples of languages functioning (as the use of proper names and natural kind terms) seem to point to the fact that semantic externalism is correct. Therefore, in this work, I shall analyze the two-dimensional theory under the light of externalist affirmatives on the meaning and on the individuation of the content of mental states, i.e., as being a thesis that not only is able to provide a viable answer to these two problems, but also is compatible with broad content as regarded by externalism.