Polyetheretherketone (PEEK) is a designation given to materials of the polyaryletherketone family having a characteristic distribution of ether and ketone groups in the polymer backbone. PEEK materials have high strength and chemical resistance as well as very high melting points and glass transition temperatures. Because of this combination of properties, PEEK materials find use for wear application in extreme environments where they provide a light-weight and corrosion resistant bearing material that often does not require lubrication. An initial study focused on determining the effects of supplier and molecular weight on the wear of particular PEEK materials, in addition to the effect of contact pressure. This work is significant because it highlights the fact that tribologically relevant polymers, such as PEEK materials, vary greatly in terms of their polymer morphology and processing history, and this variation must be recognized by investigators when reporting wear data. Because of their light weight, chemical resistance, and self-lubricating properties, polymers are used in applications ranging from biomedical to aerospace. Some polymers exhibit significant differences in wear resistance based on whether they are in unidirectional or multidirectional sliding. Shear induced polymer chain orientation is believed to be responsible for this behavior. Polyetheretherketone (PEEK) has excellent wear resistance, but its multidirectional sliding behavior has not been thoroughly investigated. A factorial multidirectional pin-on-plate wear study of PEEK was conducted with a focus on molecular weight and sliding path directionality. These factors were studied for their correlation to overall wear performance. Additionally, transfer film thickness was measured at locations along the wear path using white light interferometry. A result of this work has been a greater understanding of PEEK wear mechanisms in various sliding configurations and how they relate to transfer film formation. A major outcome was the development of a quantitative metric to describe transfer film thickness and continuity. It was found that thinner more continuous transfer films form under sliding conditions that change direction rather than overlapping along the same path. The thinner more continuous transfer film was found to also correspond with statistically lower wear behavior. Scanning electron microscope (SEM) investigation of the transfer film and pin wear surface confirmed the relationship between transfer film quality and wear.

Published in 2011, Teju Cole’s second novel Open City tells the story of one year of walking in New York and Brussels narrated from the perspective of the novel’s first-person narrator, Julius. In this manner the reader is offered ample insights into Julius’s thoughts and memories. This is a narrative based on the memories of the protagonist as well as the memories shared by the people he meets, which together create a narrative “fugue” that both hides and illuminates the central conflicts of the novel. Julius can be described both as fugueur (someone who is in a dissociated mental state and travels compulsively) and flaneur (someone who walks the streets and is obsessively observant), two concepts of ambiguity. This paper will analyze the main character’s development through three stages: reunion, repression, and reconstruction, in relation to Walter Benjamin’s reading of the flaneur as both criminal and detective, and Ian Hacking’s book on fugueurs in the 19th century. Furthermore, this memory-based narrative can be read in relation to Wai Chee Dimock’s idea of deep time, as well as Rothberg’s view of memory as multidirectional and productive, two theories that can be linked to “mad” travelling and obsessive observation. This paper tries to bring clarity to this opaque novel of solitude and repression, and sort out the clues given by the narrator.

This Thesis investigates the damage sensing capabilities of the electrical potential measurement technique in carbon fibre reinforced polymer composites. Impact damage was introduced in multidirectional laminates and its effect on potential distribution studied. It was found that delaminations and fibre breakages within the laminate can be detected and located by measuring potential changes on the external composite surface. The extent and size of potential changes were significantly affected by the position of the current electrodes in relation to the potential measurement probes. A numerical model was developed investigating the effect of different size delaminations, located in various positions within the lamina, on electrical potential distributions on the external ply, and a quantitative analysis of the numerical results is presented. The numerical simulations demonstrated that the measured potential changes on the external ply were in proportion to the delamination size. The numerical and experimental results were compared and the optimum configuration of current electrodes and potential probes for damage detection selected. The response of electrical potential to mechanical strain, in unidirectional and multidirectional samples was also investigated. It was found that the conductive medium, used for introducing the current, defines the piezo-resistance performance of the composite. A finite element model was developed able to predict the effect of inhomogeneous current introduction in unidirectional specimens on electrical potential and piezo-resistance. The effects of temperature and water absorption on potential measurements were also presented.

Directed by: Professor James E. Young This dissertation explores where historical memories concerning colonization, genocide, and racism intersect, merge, and overlap in multidirectional ways. The text opens by exploring the possibilities of using a multidirectional model of world history and then moves to a discussion of certain aspects of world political history that interrogates why some nations have dominated others. The focus then shifts to England's attitude toward perceived "others" in the crucial late sixteenth and early seventeenth centuries by examining contemporary theater drama. From there, the text moves on to current voices that have spoken out against the racism and genocide that have emerged as byproducts of empire building. Finally, possibilities for where we, as citizens of the world, can go from here in thinking through framing justice and equality for all its occupants is given the final voice in this text. My approach may be thought of as somewhat philosophical.

This essay’s primarily focus is on the common discourse about the persisting effects of the past in the present in Margaret Atwood’s The Handmaid’s Tale(1985)and Octavia E. Butler’s Kindred (1979).These novels are the testimonies of the protagonists Offred and Dana who shares their experience of traumatic violence and oppression. Dana, with her ability to time travel, will see her present time in clearer light as she experiences the life of a slave on an antebellum plantation. Offred, the Handmaiden owned by the totalitarian regime Gilead, portrays her contemporary life in parallel to remembering her former and thus describing Gilead’s increasing authority. Based on different theorists and concepts in the field of cultural memory studies, this essay examines the tension between memory and history, the distantness towards the past and the problematics with representations of traumatic events. As I argue that the voices of Dana and Offred calls attention to the importance of perspective and of sharing stories, they are also an act of hope, therapy and resistance; an act that also make possible a critique of the processes of the production of historical knowledge.

Le roman indien et pakistanais de langue anglaise est habité par le trauma de la Partition à travers des tropes de l’esthétique moderniste comme la fragmentation et l’ellipse. Il est aussi structuré par des métaphores de mutilation, de déracinement, d’exil, ainsi que par la figure symbolique du réfugié. Non exploré jusqu’ici, le trope visuel et poétique des ombres inscrit en creux dans la fiction la violence inexprimable de la Partition. Signes prémonitoires de la rupture cataclysmique de 1947, dans le roman Twilight in Delhi (1940), les ombres dramatisent les conséquences dévastatrices de la modernité coloniale sur la haute culture musulmane de l’Inde. Dans quatre romans publiés après la fracture du sous-continent – Sunlight on a Broken Column (1961), Clear Light of Day (1980), The Shadow Lines (1988), Burnt Shadows (2009) –, les ombres sont les traces-mémoires indélébiles, poreuses, et instables qui imprègnent la cartographie régionale et les psychés individuelles. Associée aux tropes ambivalents du fantôme et du miroir, l’ombre subvertit l’historiographie officielle en ouvrant un espace mémoriel dans lequel les souvenirs d’individus et de familles subalternes, transmis sur plusieurs générations, lient la Partition à d’autres traumas internationaux à travers des nœuds de mémoire multidirectionnelle. Par sa dimension visuelle, l’ombre produit une mémoire corporelle qui implique le lecteur dans une sémiotique empathique et réflexive du regard. / Partition inhabits the Indian and the Pakistani novel in English through modernist tropes such as ellipsis and fragmentation, metaphors of mutilation, dislocation and exile, and the symbolic figure of the refugee. The unspeakable violence of this trauma is also embedded within the narrative through the visual and poetic trope of the shadows, which has not been examined yet. In the novel Twilight in Delhi (1940), the shadows are premonitions of the cataclysm of 1947 as they stage the devastating impacts of colonial modernity on the high Muslim culture of India. In four novels published after the division of the subcontinent – Sunlight on a Broken Column (1961), Clear Light of Day (1980), The Shadow Lines (1988), Burnt Shadows (2009) –, the shadows are indelible, porous and unstable memory-traces that permeate the regional cartography and individual psyches. Together with the dual motives of the ghost and the mirror, these shadows subvert the official historiography and open up a discursive space in which the memories of subaltern individuals and families, transmitted over several generations, connect Partition to other international traumas via knots of multidirectional memory. Through their visual dimension, the shadows shape a body memory which involves the reader in an empathic and reflexive semiotics of the gaze.

En s’éloignant de l’idée des frontières qui marque une compréhension de la construction des États-nations en tant qu’entités souveraines et homogènes, cette thèse adopte une approche différente en considérant les portes et les murs comme deux métaphores centrales de transgression et de transformation qui amplifient l’expérience des réfugiés et permettent une vision transnationale et trans-mnémonique de divers souvenirs dans deux romans: « Exit West » de Mohsin Hamid et « Go, Went, Gone » de Jenny Erpenbeck. Dans mon premier chapitre, j’explore comment les souvenirs des Allemands sont dialogiquement liés aux souvenirs des réfugiés à travers les paradigmes de l’espace et du temps, ainsi que du passé et du présent, en examinant l’impact durable du mur de Berlin dans « Go, Went, Gone ». Mon deuxième chapitre étudie la métaphore des portes dans « Exit West » qui défient les frontières et la revendication de souveraineté des États-nations. L’objectif de mon chapitre est de comprendre comment ces portes facilitent la mobilité sans contraintes à travers l’espace et le temps, en nous encourageant à réévaluer l’universalité de la migration. Je me réfère principalement au concept de mémoire multidirectionnelle de Rothberg, en relation avec l’étude de Brand sur les mémoires collectives et interconnectées de la traite transatlantique des esclaves qui mobilise les portes comme dispositifs mnémoniques. J’utilise également la notion du « living in the Wake » en relation avec « Afterlife of slavery » de Sharpe pour comprendre comment les souvenirs des réfugiés et des citoyens des États-nations sont dialogiques à travers différentes géographies et temporalités. De plus, je m’appuie sur le concept de « de-borderization » d’Achille Mbembe en lien avec les perspectives de Gloria Anzaldúa sur les frontières pour une meilleure compréhension de l’expérience des réfugiés. / Moving away from borders that signal an understanding of the construction of nation-states as sovereign and homogenous entities, this thesis takes a different approach by considering doors and walls as two central metaphors of transgression and transformation that dramatize the refugee experience and enable a transnational and trans-mnemonic reading of various memories in two novels: Mohsin Hamid’s Exit West (2017) and Jenny Erpenbeck’s Go, Went, Gone (2015). The first chapter of the thesis addresses how memories of Germans are dialogically connected to the memories of refugees across the paradigms of space and time, past and present, through an exploration of the enduring impact of the Berlin Wall in Go, Went, Gone. The second chapter studies the metaphor of doors in Exit West that move beyond borders and challenge the nation-states’ claim to sovereignty to understand how they allow free movement across space and time and rethink the universality of migration. The thesis builds on Michael Rothberg’s concept of multidirectional memory in relation to Dionne Brand’s study of collective and interconnected memories of the slave trade that mobilizes doors as mnemonic devices, and Jenny Sharpe’s notion of “living in the wake” in connection to the afterlife of slavery to understand how memories of refugees and natives of nation-states are dialogical across different geographies and temporalities. Additionally, I rely on Achille Mbembe’s notion of “de-borderization” and relate it to Gloria Anzaldúa’s views on borders to better understand literary representations of the refugee experience.

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Ces travaux de thèse portent sur le développement de nouveaux systèmes piézoélectriques récupérateurs d’énergie à partir de vibrations mécaniques environnementales. L’objectif recherché est d’apporter des solutions à certaines contraintes fortes liées à la miniaturisation de ces systèmes, en vue de leur intégration en technologie MEMS. Les 2 axes majeurs suivis lors de ces travaux sont :(i) la nanostructuration par porosification du substrat silicium. Ce procédé permet de créer des zones fonctionnalisées possédant des propriétés locales de masse volumique et de rigidité plus faibles que celles du substrat silicium. Ceci permet d’une part d’améliorer le coefficient de couplage électromécanique global de la structure et, d’autre part, de maintenir la fréquence de résonance du mode fonctionnel dans une gamme fréquentielle basse (< que 1KHz) compatible avec le spectre de nombreuses sources vibratoires usuelles. Une série de modélisation par éléments finis d’un convertisseur type (poutre avec masse sismique) a établi les paramètres dimensionnels optimaux de la zone nanostructurée. L’efficacité de ce procédé de nanostructuration localisée a ensuite été évaluée expérimentalement sur des membranes en silicium. Il a été observé une réduction de la fréquence de résonance du mode fondamental, tout en minimisant les pertes par un choix judicieux de l’emplacement et de la largeur de la zone poreuse. (ii) Le développement de dispositifs récupérateurs à sensibilité multidirectionnelle. Ces dispositifs permettent de récupérer l’énergie quel que soit la direction de la sollicitation externe. Ils exploitent 3 modes propres distincts de flexion sollicités chacun par une composante particulière (ax, ay ou az) du vecteur accélération caractéristique de la sollicitation. Ces dispositifs basés sur une structure planaire de type double poutres orthogonales avec masse sismique centrale sont facilement intégrables et peuvent être déclinés de l’échelle centimétrique à l’échelle millimétrique en utilisant dans ce cas les technologies de type MEMS. Un modèle analytique simple a d’abord mis à jour les mécanismes énergétiques qui permettent d’obtenir une quantité d’énergie constante lorsque le dispositif est soumis à un vecteur sollicitation de direction quelconque. L’optimisation du coefficient de couplage électromécanique de chaque mode fonctionnel, ainsi que l’ajustement de leur fréquence de résonance ont été obtenu à l’aide d’un modèle à éléments finis. L’ensemble de ces résultats théoriques a été expérimentalement validé à l’aide de prototypes centimétriques. / This thesis work focuses on the development of new piezoelectric energy recovery systems from environmental mechanical vibration. The goal is to provide solutions to some strong constraints on the miniaturization of these systems, their integration in MEMS technology. The 2 major lines followed in this work are: (i) the nanostructuring by porosification silicon substrate. This method allows to create functionalized areas having local properties of density and lower rigidity than those of the silicon substrate. This allows on the one hand to improve the overall electromechanical coupling coefficient of the structure and, secondly, to maintain the resonant frequency of the operational mode in a low frequency range (< 1KHz) compatible with the spectrum of Many conventional vibratory sources. A series of finite element modeling of a type converter (beam with seismic mass) established the optimum dimensional parameters of nanostructured area. The effectiveness of this localized nanostructuring method was then evaluated experimentally on silicon membranes. It was observed a reduction of the resonance frequency of the fundamental mode, while minimizing losses by a judicious choice of the location and the width of the porous zone. (Ii) The development of recovery devices multidirectional sensitivity. These devices allow to recover energy regardless of the direction of the external load. They use 3 different eigenmodes bending each solicited by a particular component (ax, ay and az) vector solicitation characteristic acceleration. These devices based on a planar structure type double orthogonal beams with central seismic mass can be easily integrated and can be broken down to centimeter scale at the millimeter scale using in this case the MEMS technologies. A simple analytical model was first updated energy mechanisms that enable a constant amount of energy when the device is subjected to a bias vector in any direction. The optimization of the electromechanical coupling coefficient of each functional mode, and the adjustment of their resonance frequency were obtained using a finite element model. All these theoretical results has been experimentally validated using centimeter prototypes.

A contribuição e objetivo desta tese é desenvolver um modelo de redes neurais artificiais, baseado em princípios de memória associativa, capaz de resolver o problema de planejamento e controle ponto a ponto de trajetória de um braço mecânico imerso em um ambiente parcialmente conhecido e/ou sujeito a ruídos. O modelo proposto é formado por dois planos: plano seqüência temporal e plano ângulo. Para o plano seqüência temporal, o novo modelo proposto chamado de Memória Associativa Multidirecional Temporal (TMAM) é capaz de armazenar e recuperar n-tuplas de informações, lidar com informações ruidosas e/ou incompletas e aprender seqüências temporais. TMAM utiliza representação contínua e realimentação autoassociativa. O plano ângulo é formado pelo modelo RBF que é responsável por produzir as informações de ângulos das juntas do braço mecânico. A composição dos dois planos forma o sistema completo que é responsável pelo planejamento e controle ponto a ponto de trajetória. Em resumo, o sistema recebe informações do ponto origem e do ponto alvo, estabelece uma trajetória para atingir o ponto alvo a partir do ponto de origem e transforma os pontos espaciais da trajetória em valores de ângulos das juntas. Os resultados obtidos mostram que o modelo TMAM é capaz de recuperar, interpelar e extrapolar pontos nas seqüências, é capaz de gerar trajetórias, de memorizar seqüências de diferentes tamanhos e de lidar com duas trajetórias ao mesmo tempo. O modelo apresenta também rápido treinamento. O modelo RBF é capaz de recuperar as saídas desejadas apresentando um erro pequeno e é capaz de receber um padrão que apresenta um ponto final inatingível e gerar um conjunto de ângulos que representa um ponto final atingível. / The aim of this project is to develop an artificial neural networks model based on principles of associative memory. This neural network model must be able to solve the problem of trajectory planning and point to point control of a robot arm, which is located in a partially known and/or noisy environment. The proposed model is composed by two surfaces: the temporal sequence surface and the angle surface. For the temporal sequence surface the new propose model Temporal Multidirectional Associative Memmy (TMAM) is able to store and recall n-tuplas of information, to deal with noisy and/or incomplete information and to learn temporal sequences. TMAM uses a continuas representation and autoassociative feedback. A RBF model is used to implement the angle surface, which is liable for producing the angle information for the joint of the robot arm. The two surfaces compose the whole system which is liable for the trajectory planning and system control. Hence, the system receives information about the initial point and the target point, constructs the trajectory to reach the target point from the initial point and converts the spatial points which compose the trajectory, in values of joint angles. The obtained results show that TMAM model can recall, interpolate and extrapolate points in the sequences. The model has the ability of generating new trajectories and memorizing different size of sequences at the same time. This model also shows fast learning. The RBF model can recall the desired outputs with a small error and can receive a pattern which is formed by an unreachable final point and generate a set of angles which, in turn, represent a reachable final point.