As fraturas do ângulo mandibular são muito frequentes dentre as fraturas mandibulares e um das formas de tratamento é a utilização de fixação interna com placas e parafusos. Neste estudo o objetivo foi avaliar comparativamente a resistência de três tipos de fixação em réplicas de mandíbula de poliuretano. Foram utilizadas 63 mandíbulas dentadas, submetidas a seccionamento simulando uma fratura linear e desfavorável de ângulo mandibular esquerdo. As fixações foram realizadas com placas do sistema 2,0 mm, dispostas da seguinte forma: uma placa reta de quatro furos, uma placa reta de quatro furos com extensão (ponte) e uma placa 3D 4 furos. Cada grupo (n = 21) foi submetido ao teste de resistência linear com aplicação de carga no sentido súpero-inferior em três pontos distintos da mandíbula, de modo não simultâneo (região do primeiro molar ipsilateral à secção, primeiro molar contralateral e incisivos centrais) em máquina de ensaio universal EMIC DL 2000. Foram mensurados valores de carga no deslocamento de 1 mm, 2 mm e 5mm. Os resultados obtidos foram submetidos à análise estatística, utilizando a análise de variância (ANOVA), nível de significância de 5%. Os valores obtidos, não apresentaram diferença estatisticamente significante entre as placas. Os resultados mostraram que as placas 3D produzem escores similares às placas usadas convencionalmente. Com base nos resultados obtidos, pode-se concluir que os três tipos de fixação se comportam de forma similar. / Mandibular angle fractures are very frequent among the mandibular fractures and a form of treatment is the use of internal fixation with plates and screws. In this study, the objective was to evaluate the resistance of three types of fixation in mandibular replicas of polyurethane. Sixty three toothed mandibles were used, subject to sectioning simulating a linear and unfavorable fracture of left mandibular angle. The fixations were performed with straight plates system 2.0 mm, prepared as follows: one plate with 4-holes, one 4-holes and extension (bridge) and one plate 3D 4-holes .Each set was submitted for loading test with load application towards in three distinct points of the mandible, so do not simultaneously (molar region on the side ipsilateral of section, the central incisors and contralateral molar) in universal testing machine EMIC DL 2000. Load values were measured at offset 1 mm, 2 mm and 5mm and was noted the final dislocation. The results were submitted to statistical analysis, using analysis of variance (ANOVA), a significance level of 5%. the values obtained showed no statistically significant difference between the plates. The results show that the 3D plate can reproduce similar mechanical scores to the plates used conventionally. It can be concluded that the three types of fasteners behaved similarly.

Natural frequencies of the double and triple-walled carbon nanotubes are determined exactly and approximately for both types. Approximate solutions are found by using Bubnov-Galerkin and Petrov-Galerkin methods. For the first time explicit expressions are obtained for the natural frequencies of double and triple-walled carbon nanotubes for different combinations of boundary conditions. Comparison of the results with recent studies shows that the above methods constitute quick and effective alternative techniques to exact solution for studying the vibration properties of carbon nanotubes. The natural frequencies of the clamped-clamped double-walled carbon nanotubes are obtained; exact solution is provided and compared with the solution reported in the literature. In contrast to earlier investigation, an analytical criterion is derived to establish the behavior of the roots of the characteristic equation. Approximate Bubnov-Galerkin solution is also obtained to compare natural frequencies at the lower end of the spectrum. Simplified version of the Bresse-Timoshenko theory that incorporates the shear deformation and the rotary inertia is proposed for free vibration study of double-walled carbon nanotubes. It is demonstrated that the suggested set yields extremely accurate results for the lower spectrum of double-walled carbon nanotube. The natural frequencies of double-walled carbon nanotubes based on simplified versions of Donnell shell theory are also obtained. The buckling behavior of the double-walled carbon nanotubes under various boundary conditions is studied. First, the case of the simply supported double-walled carbon nanotubes at both ends is considered which is amenable to exact solution. / Then, approximate methods of Bubnov-Galerkin and Petrov-Galerkin are utilized to check the efficacy of these approximations for the simply supported double-walled carbon nanotubes. Once the extreme accuracy is demonstrated for simply supported conditions, the approximate techniques are applied to two other cases of the boundary conditions, namely to clamped-clamped and simply supported-clamped double-walled carbon nanotubes. For the first time in the literature approximate expression for the buckling loads are reported for these boundary conditions. The dynamic deflection of a single-walled carbon nanotube under impact loading is analyzed by following a recently study reported on the energy absorption capacity of carbon nanotubes under ballistic impact. / by Demetris Pentaras. / Thesis (Ph.D.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

O objetivo principal deste trabalho é apresentar uma associação dos cálculos elástico e plástico, para análise de lajes-cogumelo. Foram considerados painéis retangulares, com carregamento uniformemente distribuído. O cálculo elástico é utilizado como pré-dimensionamento, fornecendo a razão entre os momentos de vão e permitindo a fixação dos momentos de plastificação negativos. O cálculo plástico é feito através da Teoria das Charneiras Plásticas, que é utilizada na obtenção dos momentos de plastificação, com os quais é feito o dimensionamento. Também se apresentam dois exemplos completos, para comparar os resultados do cálculo elástico com aqueles relativos ao procedimento ora proposto. O cálculo elástico foi feito através do Processo dos Pórticos Equivalentes. Não houve diferença significativa entre os resultados obtidos com os dois processos, para os exemplos considerados. Novas pesquisas são sugeridas para aprimorar o procedimento proposto. / The main aim of this work is to present an association of elastic plate theory and plastic analysis, to beamless slabs (flat slabs and flat plates) analysis. Rectangular panels uniformly loaded were considered. Elastic plate theory is used to predimensioning, determining the relation between positive bending moments and permiting to fix the ultimate negative moments of resistance. Plastic analysis is made by Yield Line Theory, that is used to obtain ultimate moments of resistance, which are used in dimensioning. Two complete examples are also presented, to compare results of elastic plate theory with those relative to proposed proceeding. Elastic calculus is made by Equivalent Frame Method. There was not significant difference between results obtained with the two processes in the considered examples. New researches are suggested in order to perfect proposed proceeding.

Este trabalho trata da formulação do método dos elementos de contorno para a análise não linear de pavimentos de concreto armado. A teoria utilizada é a de Reissner, que mostrou-se eficiente tanto para placas esbeltas quanto para as moderadamente espessas. Considera-se a ocorrência de cargas concentradas, distribuídas em sub-regiões da placa e em linha. Admite-se também a possibilidade de um campo de momentos iniciais, que viabiliza o estudo da não linearidade física nos problemas. Foram utilizados campos de momentos iniciais aplicados apenas em pontos internos ao domínio. As integrais que envolvem as células de domínio foram modificadas, eliminando-se os núcleos complexos e as aproximações através de séries. Foi desenvolvida uma formulação para a análise de placas vinculadas a estruturas quaisquer em seu domínio, com o uso de cargas aplicadas incógnitas atuando como enrijecedores. O acoplamento MEC/MEF foi empregado utilizando-se modelos simples, porém robustos. O sistema de equações algébricas foi otimizado com a utilização da técnica dos mínimos quadrados. O concreto foi modelado adotando-se o modelo de dano de Mazars; para as armaduras um modelo elastoplástico uniaxial com endurecimento isótropo. A análise não linear do problema é efetuada utilizando-se procedimento incremental-iterativo. São apresentados alguns exemplos simples que mostram a precisão da técnica usada. / This work refers to the formulation of the boundary element method for non-linear analysis of building floor structures. The plate bending theory adopted to develop the work wad due to Reissner, which has demonstrated to be efficient for thick, moderated thick and thin plates. The kinds of load applied on the plate medium surface have been taken into account: concentrated loading, distributed over sub-domains; distributed along internal lines. The presence of initial moment fields convenient to model temperature effects and to be used to build up non-linear solutions has also been considered in the formulation. The domain integrals containing complex kernels to take into account the initial moment field influences were modified by introducing their primitive functions, avoiding therefore using series expansions. To integrate the initial moments fields only approximations based on internal nodal points were used. The resulting cell integrals have been transformed to the cell boundary which results into regular integral only. A boundary element formulation to treat structural system defined by combining plates with other structural element was developed, using interface force as unknowns. The BEM/FEM coupling developed to treat this case is simple but robust; only displacements have been coupled avoiding important singularities that may happen when coupling rotations. The resulting system of algebraic equations has been regularized by using the least square method. The concrete material was modeled by using the Mazar\'s damage model, while the steel reinforcement was assumed to behave as elastoplastic material with isotropic hardening. Finally, some examples are shown to illustrate the accuracy of the presented formulation and the numerical schemes proposed in this work.

The primary goal of this thesis is to evaluate vibration control of an all-clamped plate having an unknown disturbance. The vibration control is implemented using a piezoelectric actuator placed at an optimal location. The first part of this thesis considers a robust actuator placement with respect to varying spatial distributions of disturbances. The treatment here, is different from performance-based LQR approaches, since it is based on minimizing the effect of the disturbance distributions. The second part of this thesis addresses a more general case where the plate is under an unknown disturbance. An unknown disturbance is also characterized by the case where the disturbance signal moves randomly over the entire spatial domain. An optimal switching controller algorithm is developed, based on LQR performance, which switches between piezoelectric actuators employed for the vibration control of the plate. A single actuator is selected from the various actuator locations during each time interval, which leads to performance enhancement.

[pt] Placas de ancoragem embutidas em concreto são empregadas, geralmente, com a finalidade de permitir a fixação de elementos para a introdução de cargas concentradas nas estruturas de concreto, bem como viabilizar as ligações estruturais entre componentes pré-fabricados. As placas são ancoradas no concreto através de pinos soldados a elas. Estas placas são bastante empregadas em estruturas de usinas nucleares onde um grande número de equipamentos e tubulações são apoiados na estrutura de concreto. A pesquisa é de natureza experimental e tem como objetivo investigar a redução da resistência à tração de placas de ancoragem com grupo de chumbadores, placas instaladas com pequena distância dos bordos do elemento de concreto, e também de duas placas adjacentes, devido a interferência de seus cones de ruptura. A eficiência de uma armadura de suspensão (que transmite a carga além do cone de ruptura), também é verificada. Os resultados experimentais sugerem uma notável redução da resistência à tração para placas com grupo de chumbadores, e que o uso da armadura de suspensão para placa instalada nas proximidades do bordo do elemento de concreto não é muito eficiente. A armadura de suspensão apresentou um bom rendimento quando foi empregada em placas com grupo de chumbadores. Os resultados teóricos obtidos através de equações desenvolvidas para estimativa da carga de ruptura, apresentaram, de maneira geral, uma boa aproximação quando comparados com os resultados experimentais. / [en] Anchorage plates embedded in concrete are used with the purpose of allowing the fixation of elements for the introduction of concentrated loads into concrete structures, as well as to make possible the structural connections between prefabricated components. The plates are anchored in the concrete through studs welded to them. These plates are used in structures of nuclear power stations where a great number of equipments and pipings are fixed in the concrete structure. The research is of experimental nature and its objective is to investigate the reduction of the tensile strength of multiple studs group, anchorage plates located close to a free edge, and also of two adjacent plates, due to interference of failure concrete cones. The efficiency of an additional reinforcement (that transfers the load beyond the concrete cone), is also addressed. The experimental results suggest a significant reduction of the tensile strength for plates with studs group, and that the use of the additional reinforcement for anchorage plates located close to a free edge is not too efficient. The additional reinforcement presented a good efficiency when it was used in plates with studs group. The theoretical results obtained from equations developed to estimate the concrete failure load show, in a general way, a good agreement with the experimental results.

Civil engineers are presently faced with the challenge of strengthening and repairing many existing structures to assure or increase their structural safety. The reasons for this include changes in the use of structures, and increased traffic loads on bridges. In Iraq, for example, several highway bridges needed to accommodate increased axle load during the transportation of huge turbines for electricity generating stations. The requirement for structural strengthening and repair methods is, however, driven by the worldwide need to ensure the safety and sustainability of our aging infrastructure which is deteriorating at a rate faster than it can be renovated. The ever increasing damage caused by environmental effects and the corrosion of steel and deterioration of concrete, reduce structural safety and lead to disruption for the users, which can have serious economic consequences. In a plate girder bridge, the plate girders are typically I-beams made up from separate structural steel plates (rather than rolled as a single cross-section), which are welded or, in older bridges, bolted or riveted together to form the vertical web and horizontal flanges of the beam. The two primary functions of the web plate in a plate girder are to maintain a relative distance between the top and bottom flanges and to resist the induced shear stresses. In most practical ranges of plate girder bridges’ spans, the induced shear stresses are relatively low compared to the bending stresses in the flanges induced by flexure. As a result the web plate is generally chosen to be much thinner than the flanges. The web panel consequently buckles at a relatively low shear force. For steel girder structures dominated by cyclic loading, as is the case with repeated vehicle axle loads on bridges, this can lead to the so-called ‘breathing’ phenomenon; an out-of-plane buckling displacement that can induce high secondary bending stresses at the welded plate boundaries. In the current work, a novel FRP strengthening technique using bonded shapes is applied to resist these out of plane deformations, and hence reduce the breathing stresses, and improve the fatigue life of the plate girder which is very different to the majority of applications of FRP strengthening that exploit the FRP for its direct tensile strength and stiffness. The objective of the current experimental programme is to strengthen thinwalled steel girders against web shear buckling using a corrugated CFRP or GFRP panel bonded externally along the compression diagonal of the web plate. The programme was divided into three main phases, including: (1) the development of a new preformed corrugated FRP panel, and (2, 3) testing its performance in two main experimental series. The initial series involved tests on 13 steel plates strengthened with the proposed preformed corrugated FRP panel and subjected to in-plane shear loading using a specially manufactured “picture-frame” arrangement designed to induce the appropriate boundary conditions and stresses in the web plates. This initial test series investigated the performance of different forms of strengthening under static load, in preparation for another series of cyclic tests to investigate their fatigue performance. The test variables included FRP type (CFRP or GFRP), form of FRP (closed or open section), number of FRP layers, and orientation of GFRP fibres used to produce the FRP panel. In the second series, six specimens were manufactured to simulate the end panel of a plate girder. These were strengthened with the optimized FRP panel from the initial series and tested for shear buckling under repeated cyclic loading with a stress range 40-80% of the static ultimate capacity. A considerable increase in the stiffness of the strengthened specimens is evident in the observed reductions of the maximum out-of-plane displacement. The stiffness of the strengthened specimens is assessed to be increased by a factor ranging between 3 to 9 times the stiffness of the corresponding unstrengthened specimen, depending upon the type of the FRP panel used and the aspect ratio of the tested specimens. The breathing phenomena is also significantly reduced, consequently the surface, membrane and secondary bending stresses are reduced. The 45° strengthening scheme succeeded the best both in reducing the breathing stresses and increasing the ultimate shear capacity of the specimen by 88%. Fatigue analyses indicated that the proposed strengthening technique is able to considerably elongate the life expectancy of the strengthened plate girders by a factor ranging between 2.5 and 7 depending on the applied cyclic load amplitude. In addition, the proposed strengthening technique did not show any debonding or delamination under both static and cyclic loading which makes it a good candidate for strengthening thin-walled structural members, especially, when ductility is a concern. In fact, the proposed strengthening technique succeeded in improving the energy absorption capacity of the strengthened specimens by a factor ranging between 1.5 and 2.5 times the corresponding control specimen which means that the ductile failure type associated with shear buckling of steel plate girders is not only maintained, but it was improved as well. This type of ductile failure is not common in other types of FRP strengthening techniques. Finally, a geometrical and material non-linear finite element model is presented both for the steel and composite sections which showed very good correlation with test results and was capable of predicting both the strength and deformational behaviour of the tested specimens. This numerical model is used for a parametric study to support the proposed design method.

La course à l'augmentation de la puissance de calcul qui se déroule depuis de nombreuses années entre les différents producteurs de matériel a depuis quelques années changé de visage: nous assistons en effet désormais à une véritable démocratisation des machines parallèles avec une complexification sans cesse croissante de la structure des processeurs. À terme, il est tout à fait envisageable de voir apparaître pour le grand public des architecture pleinement hétérogènes composées d'un ensemble de cœurs reliés par un réseau sur puce. La parallélisation et l'exécution parallèle d'applications sur les machines à venir soulèvent ainsi de nombreux problèmes. Parmi ceux-ci, nous nous intéressons ici au problème de l'ordonnancement d'un ensemble de tâches sur un ensemble de cœurs, c'est à dire le choix de l'affectation du travail à réaliser sur les ressources disponibles. Parmi les méthodes existantes, on distingue deux types d'algorithmes: en-ligne et hors-ligne. Les algorithmes en-ligne comme le vol de travail présentent l'avantage de fonctionner en l'absence d'informations sur le matériel ou la durée des tâches mais ne permettent généralement pas une gestion efficace des communications. Dans cette thèse, nous nous intéressons à l'ordonnancement de tâches en-ligne sur des plates-formes complexes pour lesquelles le réseau peut, par des problèmes de congestion, limiter les performances. Plus précisément, nous proposons de nouveaux algorithmes d'ordonnancement en-ligne, basés sur le vol de travail, ciblant deux configurations différentes. D'une part, nous considérons des applications pour lesquelles le graphe de dépendance est connu à priori. L'utilisation de cette information nous permet ainsi de limiter les quantités de données transférées et d'obtenir des performances supérieures aux meilleurs algorithmes hors-ligne connus. D'autre part, nous étudions les optimisations possibles lorsque l'algorithme d'ordonnancement connaît la topologie de la plate-forme. Encore une fois, nous montrons qu'il est possible de tirer parti de cette information pour réaliser un gain non-négligeable en performance. Nos travaux permettent ainsi d'étendre le champ d'application des algorithmes d'ordonnancement vers des architectures plus complexes et permettront peut-être une meilleure utilisation des machines de demain. / The race towards more processing power between all different hardware manufacturers has in recent years faced deep changes. We see nowadays a huge development in the use of parallel machines with more and more cores and increasingly complex architectures. It seems now clear that we will witness in a near future the development of cheap Network On Chip computers. Executing parallel applications on such machines raises several problems. Amongst them we take in this work interest in the problem of scheduling a set of tasks on a set of computing resources. Between all existing methods we can generally distinguish on-line or off-line algorithms. On-line algorithms like work-stealing present the advantage to work without informations on hardware or tasks durations but do not generally achieve an efficient control of communications. In this book we take interest in on-line tasks scheduling on complex platforms where networking can impact (through congestion) performance. More precisely, we propose several new scheduling algorithms based on work-stealing targeting two different configurations. In a first study, we consider applications whose dependency graph is known in advance. By taking advantage of this information we manage to limit the amount of data transfered and thus to achieve high performance and even outperform the best known off-line algorithms. Concurrently to that, we also study possible optimisations in the case where knowledge of platform topology is available. We show again that it is possible to use this information to enhance performance. Our work allows therefore to extend the application field of scheduling algorithms towards more complex architectures and we hope will allow a better use of tomorrow's machine.

Thesis. 1976. Sc.D.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering. / Microfiche copy available in Archives and Engineering. / Vita. / Includes bibliographical references. / by Nathan Clay Martin II. / Sc.D.

Thesis. 1978. M.S.--Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERONAUTICS. / Includes bibliographical references. / M.S.