Exact solution to the vibration of rectangular plates is available only for plates with two opposite edges subject to simply supported conditions. Otherwise, they are analysed by using approximate methods. There are several approximate methods to conduct a vibration analysis, such as the Rayleigh-Ritz method, the Finite Element Method, the Finite Difference Method, and the Superposition Method. The Rayleigh-Ritz method and the finite element method give upper bound results for the natural frequencies of plates. However, there is a disadvantage in using this method in that the error due to discretisation cannot be calculated easily. Therefore, it would be good to find a suitable method that gives lower bound results for the natural frequencies to complement the results from the Rayleigh-Ritz method. The superposition method is also a convenient and efficient method but it gives lower bound solution only in some cases. Whether it gives upper bound or lower bound results for the natural frequencies depends on the boundary conditions. It is also known that the finite difference method always gives lower bound results. This thesis presents bounded eigenvalues, which are dimensionless form of natural frequencies, calculated using the superposition method and the finite difference method. All computations were done using the MATLAB software package. The convergence tests show that the superposition method gives a lower bound for the eigenvalues of fully clamped plates, and an upper bound for the completely free plates. It is also shown that the finite difference method gives a lower bound for the eigenvalues of completely free plates. Finally, the upper bounds and lower bounds for the eigenvalues of fully clamped and completely free plates are given.

Reconnaître des mots parlés implique de résoudre un problème de localisation de frontières lexicales dans le flux sonore. La segmentation lexicale est envisagée dans ce travail de recherche comme résultant du guidage ascendant des traitements par la prosodie, et descendant par la structure du lexique.<br />Les résultats présentés montrent :<br />- qu'un code prososyllabique structure le signal de parole et contraint fortement le traitement lexical;<br />- que la présence d'une superposition lexicale à l'initiale d'un mot facilite sa reconnaissance.<br />SLEXS, un modèle mathématique de prégnance perceptive des mots parlés, est proposé pour expliquer ce phénomène de facilitation, qui serait lié à un processus récursif de construction du percept. Aucune des données obtenues ne permet de conclure que la compétition lexicale soit un mécanisme essentiel lors de la reconnaissance des mots parlés.

Nous proposons de montrer que la signature Lorentzienne de la métrique d'espace-temps (+++-) n'est plus fixe à l'échelle de Planck lp et présente des "oscillations quantiques" entre les formes Lorentzienne et Euclidienne (+++±) jusqu'à l'échelle 0 où elle prend la forme Euclidienne (+ + + +). 1- Au plan algébrique, nous suggérons l'existence d'un "chemin de fluctuation" (3, 1)-(4, 0) excluant la signature ultra-hyperbolique (2, 2). Nous construisons l'espace topologique quotient *top décrivant la superposition des métriques Lorentzienne et Riemannienne. Nous montrons que *top comporte un point singulier S correspondant à l'origine de l'espace de superposition. En termes de groupes quantiques, nous établissons le lien entre q-déformation et "déformation" de la signature, notre principal résultat étant la construction du nouveau produit bicroisé cocyclique Mc(H). Une telle construction nous a permis de réaliser l'unification des signatures Lorentzienne et Euclidienne au sein du produit bicroisé cocyclique entre le groupe quantique Lorentzien Uq(so(3, 1)) et le groupe quantique Euclidien Uq(so(4))op. Nous suggérons aussi que la "semidualisation" de Majid décrit la transition q-Euclidien Æ q-Lorentzien. De même, la q-déformation de l'espace-temps indique que les structures naturelles Rq(4) et Rq(3,1) , covariantes sous Uq(so(4)) et Uq(so(3, 1)) sont reliées par semidualité. 2- Au plan physique, dans le cadre de la supergravité N=2, nous considérons qu'à l'échelle de Planck, le (pré)espace-temps est en état KMS (Kubo-Martin-Schwinger), le paramètre d'échelle ß du système étant complexe. L'algèbre de von Neumann associée à l'état non trivial des mesures sur la métrique à l'échelle de Planck est un facteur sans trace, de type IIIl. Nous étendons alors à l'échelle de supergravité la gravité relativiste et adoptons le Lagrangien L-supergravité = R2 + ßR + RR* incluant des termes de courbure quadratiques en R2, avec une composante physique (le terme d'Einstein ) associée à la signature Lorentzienne et une composante topologique (le terme topologique ) associée à la signature Euclidienne. La limite infrarouge de la théorie de superposition est alors donnée, à l'échelle de Planck, par le terme en R (+++-) tandis que la limite ultraviolette est donnée, à ß = 0, par le terme topologique RR* (++++). Nous proposons une dualité nouvelle entre instantons (secteur topologique) et monopôles (secteur physique) en dimension 4 représentant la superposition des métriques. 3- Au plan cosmologique, nous décrivons la Singularité Initiale de l'espace-temps par l'invariant topologique Is = Tr(-1)S, analogue au premier invariant de Donaldson. La Singularité Initiale, dont nous proposons la solution dans le cadre de la théorie topologique des champs, est ici identifiée à un instanton gravitationel singulier de rayon r = 0. Les observables physiques sont alors remplacées, à l'échelle 0, par des cycles d'homologie dans l'espace des modules des instantons. Nous conjecturons l'existence d'une amplitude topologique associée à une phase "d'expansion topologique" du pré-espace-temps de l'échelle 0 à l'échelle de Planck, précédant la phase d'expansion conventionnelle. L'expansion topologique du pré-espace-temps à partir de l'échelle 0 devrait alors correspondre à une pseudo-dynamique en temps imaginaire, que nous décrivons par le semi-groupe à un paramètre des automorphismes de l'algèbre M0,1 des pseudo-observables du système, M0,1 est un facteur à trace de type II*, associé à l'état ergodique de la mesure au voisinage de la Singularité Initiale.

La relation scalaire entre contrainte et déformation obtenue par le cisaillement simple dans les rhéomètres classiques n'est pas assez riche pour décrire les écoulements complexes. Pour obtenir plus d'information, nous superposons deux écoulements orthogonaux en utilisant la géométrie plan-plan. Le fluide, sous forme cylindrique, peut alors être cisaillé par la rotation mais aussi écrasé par le rapprochement (ou étiré par l'éloignement) des disques. Nous détaillons les calculs théoriques permettant de déterminer les liens entre contraintes et taux de cisaillement et les efforts et vitesses macroscopiques associés. Ensuite, nous décrivons précisément le dispositif expérimental mis en place pour imposer toutes sortes d'écoulements combinant des cisaillements stationnaires ou oscillants, en rotation ou en écrasement. Puis nous présentons les résultats de la comparaison entre l'écoulement de rotation et l'écoulement d'écrasement. Nous présentons enfin les expériences de superposition des deux écoulements. Nous créons des écoulements complexes et divers afin, entre autres, de mesurer et comprendre la loi d'écoulement 3D et le critère d'écoulement 3D des fluides à seuil

The mechanical property of polymeric materials changes over time, especially when they are subjected to long-term loading scenarios. To predict the time-dependent viscoelastic behaviors of epoxy-based adhesive materials, it is imperative that reliable accelerated tests be developed to determine their long-term performances under different exposed environments. A neat epoxy resin system and a commercial structural adhesive system for bonding aluminum substrates are investigated. A series of moisture diffusion tests have been performed for more than three months in order to understand the influence of the absorbed moisture on creep behavior. The material properties, such as elastic modulus and glass transition temperature, are also studied under different environmental conditions. The time-temperature superposition method produces a master curve allowing the long-term creep compliance to be estimated. The physics-based Coupling model is found to fit well the long-term creep master curve. The equivalence of the temperature and moisture effect on the creep compliance of the epoxy adhesives is also addressed. Finally, a methodology for predicting the long-term creep behavior of epoxy adhesives is proposed.

Extrusion compounding addresses such problems as the non-homogeneity of the mixture and separation of fiber from the polymer during rotational molding, which consequently affect the mechanical and physical properties of the resulting composites. <p>Using triethoxyvinylsilane as chemical pre-treatment on flax fibers and linear low density polyethylene (LLDPE) and high density polyethylene (HDPE) as polymer matrices, this study focused on the effects of flax fiber content (0%, 12.5% or 25%) and extrusion parameters such as barrel zone temperatures (75-110-120-130-140°C or 75-120-130-140-150°C) and screw speed (110 or 150 rpm) on the extrudate and composite properties (extrudate color, extrudate density, extrudate melt flow index, extrudate morphology, composite color, composite density, composite morphology, composite tensile strength and composite water absorption). <p>A mixture of chemically pre-treated flax fibers and powdered polyethylene matrices underwent extrusion compounding using a twin-screw extruder. The extrudates were then pelletized, ground, rotationally molded and cut into test specimens (composites). The mechanical and physical properties of both the extrudates and the composites from different treatments were then measured and compared. <p>Using multiple linear regression, models were generated to show quantitatively the significant effects of the process variables on the response variables. Finally, using response surface methodology and superposition surface methodology on the preceding data, the following optimum values for fiber content and extrusion parameters were determined: for LLDPE composites, fiber content = 6.25%, temperatures = 75-117.3-127.3-137.3-147.3°C, screw speed = 117.5 rpm; for HDPE composites, fiber content = 5.02%, temperatures = 75-118.1-128.1-138.1-148.1°C, screw speed = 125.56 rpm.

Emerging 4G standards, such as WiMAX and LTE have adopted the proven technique of Adaptive Modulation and Coding (AMC) to dynamically react to channel fluctuations while maintaining bit-error rate targets of the transmission. This scheme makes use of the estimated channel state indication (CSI) to efficiently utilize channel capacity for next transmission, but it brings with it the stale CSI problem due to the frequently channel fluctuations. As its objective, this thesis focuses on mitigating the vicious effect of stale CSI by proposing a novel framework that incorporate AMC with layered transmission through Superposition Coding (SPC) is introduced. A layered multi-step finite-state Markov chain model (FSMC) is developed under this framework, to effectively assist the system in selecting the optimal modulation and coding scheme as well as the power allocated for each layer in every multi-resolution unicast transmission. Extensive simulations are conducted to verify the proposed framework and compare its performance with other counterparts. The effects of changing key parameters, such as the complexity factor and step size, are also investigated to get close to real world performance. Results demonstrate that the proposed framework can achieve better spectrum efficiency than similar counterparts, due to its improved robustness to the stale CSI problem for each multi-resolution modulated transmission, also these show that the performance of two-layer scheme is good enough for layer allocation, without need of more layers.

Extrusion compounding addresses such problems as the non-homogeneity of the mixture and separation of fiber from the polymer during rotational molding, which consequently affect the mechanical and physical properties of the resulting composites. <p>Using triethoxyvinylsilane as chemical pre-treatment on flax fibers and linear low density polyethylene (LLDPE) and high density polyethylene (HDPE) as polymer matrices, this study focused on the effects of flax fiber content (0%, 12.5% or 25%) and extrusion parameters such as barrel zone temperatures (75-110-120-130-140°C or 75-120-130-140-150°C) and screw speed (110 or 150 rpm) on the extrudate and composite properties (extrudate color, extrudate density, extrudate melt flow index, extrudate morphology, composite color, composite density, composite morphology, composite tensile strength and composite water absorption). <p>A mixture of chemically pre-treated flax fibers and powdered polyethylene matrices underwent extrusion compounding using a twin-screw extruder. The extrudates were then pelletized, ground, rotationally molded and cut into test specimens (composites). The mechanical and physical properties of both the extrudates and the composites from different treatments were then measured and compared. <p>Using multiple linear regression, models were generated to show quantitatively the significant effects of the process variables on the response variables. Finally, using response surface methodology and superposition surface methodology on the preceding data, the following optimum values for fiber content and extrusion parameters were determined: for LLDPE composites, fiber content = 6.25%, temperatures = 75-117.3-127.3-137.3-147.3°C, screw speed = 117.5 rpm; for HDPE composites, fiber content = 5.02%, temperatures = 75-118.1-128.1-138.1-148.1°C, screw speed = 125.56 rpm.

In this work, a highly linear broadband Low Noise Amplifier (LNA) is presented. The linearity issue in broadband Radio Frequency (RF) front-end is introduced, followed by an analysis of the specifications and requirements of a broadband LNA through consideration of broadband, multi-standard front-end design. Metal-Oxide- Semiconductor Field-Effect Transistor (MOSFET) non-linearity characteristics cause linearity problems in the RF front-end system. To solve this problem, feedback and the Derivative Superposition Method linearized MOSFET. In this work, novel linearization approaches such as the constant current biasing and the Derivative Superposition Method using a triode region transistor improve linearization stability against Process, Supply Voltage, and Temperature (PVT) variations and increase high power input capability. After analyzing and designing a resistive feedback LNA, novel linearization methods were applied. A highly linear broadband LNA is designed and simulated in 65nm CMOS technology. Simulation results including PVT variation and the Monte Carlo simulation are presented. We obtained -10dB S11, 9.77dB S21, and 4.63dB Noise Figure with IIP3 of 19.18dBm for the designed LNA.

Symmetrical Multilevel Diversity Coding (SMDC) is a network compression problem for which a simple separate coding strategy known as superposition coding is optimal in terms of achieving the entire admissible rate region. Carefully constructed induction argument along with the classical subset entropy inequality of Han played a key role in proving the optimality. This thesis considers a generalization of SMDC for which, in addition to the randomly accessible encoders, there is also an all-access encoder. It is shown that superposition coding remains optimal in terms of achieving the entire admissible rate region of the problem. Key to our proof is to identify the supporting hyperplanes that define the boundary of the admissible rate region and then build on a generalization of Han's subset inequality. As a special case, the (R0,Rs) admissible rate region, which captures all possible tradeoffs between the encoding rate, R0, of the all-access encoder and the sum encoding rate, Rs, of the randomly accessible encoders, is explicitly characterized. To provide explicit proof of the optimality of superposition coding in this case, a new sliding-window subset entropy inequality is introduced and is shown to directly imply the classical subset entropy inequality of Han.