No description available.

No description available.

This dissertation presents both analytical and numerical approaches to optimizing thrust and thrust efficiency of harmonically deforming thin airfoils and membrane wings. A frequency domain unsteady aerodynamic theory for deformable thin airfoils, with Chebychev polynomials as the basis functions is presented. Stroke-averaged thrust and thrust efficiency expressions are presented in a quadratic matrix form. The motion and deformation of the airfoil is optimized for maximum thrust and efficiency. Pareto fronts are generated showing optimum deformation conditions (magnitude and phase) for various reduced frequencies and constraints. It is shown that prescribing the airfoil to deform in a linear combination of basis functions with optimal magnitude and phase results in a larger thrust as compared to rigid plunging, especially at low reduced frequencies. It is further shown that the problem can be constrained significantly such that thrust is due entirely to pressure with no leading edge suction, and associated leading edge separation. The complete aeroelastic system for a membrane wing is also optimized. The aerodynamic theory for deformable thin airfoils is used as the forcing in a membrane vibration problem. Due to the nature of the two dimensional theory, the membrane vibration problem is reduced to two dimensions via the Galerkin method and nondimensionalized such that the only terms are nondimesional tension, mass ratio and reduced frequency. The maximum thrust for the membrane wing is calculated by optimizing the tension in the membrane so that the the aeroelastic deformation due to wing motion leads to optimal thrust and/or efficiency. A function which describes the optimal variation of spanwise tension along the chord is calculated. It is shown that one can always find a range of membrane tension for which the flexible membrane wings performs better than the rigid wing. These results can be used in preliminary flapping wing MAV design. / Ph. D.

The vibration of a uniform geometrically nonlinear shear deformable beam subjected to a transverse harmonic excitation is investigated by the method of numerical simulation. Rotatory and axial inertia are included in the model. The beam is simply supported with supports a fixed distance apart. The nonlinear partial differential equations of motion are discretized in space by the Rayleigh-Ritz method, resulting in a set of nonlinear ordinary differential equations in time. The ordinary differential equations are integrated numerically to produce a time history of the solution of the equations. Transverse displacement, axial displacement, and cross sectional rotation are approximated by series of the corresponding linear natural mode shapes of the beam. Solutions of the equations of motion are compared to corresponding solutions where shear deformation and rotatory inertia are neglected. The effect of slenderness on the difference between the shear deformable case and the non shear deformable case is investigated by considering two beam configurations. In the simulations considered, the difference between the shear deformable model and the non shear deformable model increases as excitation frequency is increased and the length to thickness ratio of the beam is decreased. / Master of Science

Segmented analysis of subcortical structures within the nonhuman primate can potentially have a profound impact on studying the relationship between volumetric characteristics and alcohol dependencies. Image segmentations have been widely used in quantifying structural information. There are a variety of methods in which users can extract desired structures from a medical image; ranging from manual segmentations to fully-automated segmentations and 2-D to 3-D. The implications of this possibility can have tremendous applicability to medical research and diagnosis. The primary goal of my thesis is to investigate different implementation methodologies for segmenting subcortical structures such as the hippocampus and striatum and then apply that knowledge towards the development of an approach to segment these two structures from a group of alcohol-dependent Rhesus Macaque monkeys. Using the Level Set Deformable Model (LSDM) with a priori structural information, a series of T1-weighted MR images of Rhesus Macaque hippocampi and striatum were segmented in an effort to compare the structural hippocampal and striatal volumes between early and late stages of alcohol dependency. The results suggest that the volumes of both subcortical structures are affected negatively by alcoholism. Volume deficits of as much as 5% for the hippocampus and 8% for the caudate were found. / Master of Science

Yes / Reverse roll coating is probably the most widely used coating operation, yet its full potential has not been exploited as it is shown in this paper which considers operation with a negative gap. We demonstrate through a wide range of experimental data that such operation can yield very thin and stable films with no ribbing or cascade instabilities when low viscosity fluids are used. Typically, stable film thickness less than 5μm can be obtained at speeds up to 150 m/min when a rubber roller is used at -100 μm gap with fluids of viscosity in the range 10-200 mPa.s. These film thicknesses can be made to decrease further down to 1 or 2 microns with a judicious choice of speed ratios (applicator to metering roller) and rubber hardness. Such new findings make this simple coating method an attractive roll to roll technique for application in the newer coating technologies, such as in the production of solar cells and plastic electronics. The data obtained in this study have been underpinned by a model based on the classical lubrication theory, well developed for such flow situations. Essentially it is shown that the film thickness non dimensionalised with respect to the set negative gap is controlled through a single parameter, the elasticity number Ne which combines all the operating parameters. Of course, this flow problem has complexities, particularly at high speed ratios and at zero gap so the data obtained here can serve as a basis for more comprehensive modelling of this classical fluid mechanic problem. / Films R&D Centre of Toyobo Co. Ltd., Otsu, Japan and the Thin Films Research Group of the University of Bradford, UK.

In wavelength division multiplexed (WDM) optical communication networks, signals are amplified periodically by optical amplifiers. Since the gain profiles of optical amplifiers are not flat, equalizers are usually used to maintain signal powers at different wavelengths in equal to avoid crosstalk and data loss. However, fixed attenuation can only compensate fixed input power and amplification. In active network, input power and amplifier gain change with time. Active level compensation at each wavelength is needed. An adaptive attenuator is a device with a chromatically variable transmissivity used to equalize channel powers in wavelength-division multiplexing (WDM) fiber-optic communication lines. In this thesis, a method of Fourier analysis of multi-beam interference is developed. It is shown that the total electric field and relative phase delay of each beam form a Fourier transform pair. Thus methods and properties of Fourier analysis are applicable in multi-beam interference analysis and design. Fourier transform based design is presented. Novel devices that apply such design principles are introduced. Principles and structures of novel adaptive attenuators based on various technologies such as segment deformable mirror, liquid crystal, phase modulation array are given. Simulation results for segment deformable mirror based adaptive attenuator are presented. / Master of Science

In bats, the directivity patterns for reception are shaped by the surface geometry of the pinnae. Since many bat species are capable of large ear deformations, these beampatterns can be time-variant. To investigate this time-variance using numerical methods, a digital model that is capable of representing the pinna geometry during the entire deformation cycle has been developed. Due to large deformations and occlusions, some of the surfaces relevant to sound diffraction may not be visible and the geometry of the entire pinna has to be computed from limited data. This has been achieved by combining a complete digital model of the pinna in one position with time-variant sparse sets of three dimensional landmark data. The landmark positions were estimated using stereo vision methods. A finite element model based on elasticity was constructed from CT scans of the pinna post mortem. This elastic model was deformed to provide a good fit to the positions of the landmarks and retain values of smoothness and surface energy comparable to life. This model was able to handle ratios of data to degrees of freedom around 1:5000 and still effect life-like deformations with an acceptable goodness of fit. / Master of Science

Devido à variação na qualidade e ao ruído nas imagens médicas, a aplicação de técnicas tradicionais de segmentação é geralmente ineficiente. Nesse sentido, apresenta-se um novo algoritmo a partir de duas técnicas: o modelo de contornos deformáveis por fluxo do vetor gradiente (GVF deformable contours) e a técnica de espaço de escalas utilizando o processo de difusão. Assim, foi realizada uma revisão bibliográfica dos modelos que trabalham com os contornos deformáveis, os quais foram classificados em modelos paramétricos e geométricos. Entre os modelos paramétricos foi escolhido o modelo de contornos deformáveis por fluxo do vetor gradiente (GVF). Esta aproximação oferece precisão na representação de estruturas biológicas não observada em outros modelos. Desta forma, o algoritmo apresentado mapeia as bordas (edge map) e aperfeiçoa a condução da deformação utilizando uma técnica baseada em operações recursivas. Com este cálculo apoiado no comportamento de espaço de escalas, obtem-se a localização e correção de sub-regiões do edge map que perturbam a deformação. Por outro lado, é incorporada uma nova característica que permite ao algoritmo realizar atividades de classificação. O algoritmo consegue determinar a presença ou ausência de um objeto de interesse utilizando um valor mínimo de deformação. O algoritmo é validado através do tratamento de imagens sintéticas e médicas comparando os resultados com os obtidos no modelo tradicional de contornos deformáveis GVF. / Due to the variation of the quality and noise in medical images, the classic image segmentation techniques are usually ineffective. In this work, we present a new algorithm that is composed of two techniques: the gradient vector flow deformable contours (GVF) and the scale-space technique using a diffusion process. A bibliographical revision of the models that work with deformable contours was accomplished, they were classified in parametric and geometric models. Among the parametric models the gradient vector flow deformable contours (GVF) was chosen. This approach offers precision in the representation of biological structures where other models does not. Thus, the algorithm improves the edge map to guide the deformation using recursive operations. With this estimation based on the behavior of the scale-space techniques it is realized, the localization and correction of sub-areas of the edge map that disturb the deformation. On the other hand, it was incorporated a new characteristic that allows the algorithm to accomplish classification activities. That is, the algorithm determines the presence or absence of a target object using a minimal deformation area. Our method was validated on both, simulated images and medical images making a comparison with the traditional GVF deformable contours.

Ce travail concerne la modélisation du mouvement des piétons via l’approche non régulière du contact dynamique des solides rigides et déformables. Une reformulation de cette approche est proposée en accord avec le formalisme de M.Frémond et celui de J.J.Moreau. L’approche proposée est basée sur la notion de percussion qui est l’intégrale de la force de contact au cours de la durée de la collision. Contrairement aux modèles classiques d’éléments discrets, il est supposé que les percussions ne peuvent être exprimées qu’en fonction de la vitesse avant l’impact. Cette hypothèse est vérifiée pour des lois de comportement classiques de la collision. Les équations de mouvement sont ensuite reformulées en tenant compte de multiples collisions simultanées. L’existence et l’unicité de la solution du nouveau modèle sont discutées en fonction de la régularité des forces (densité de Lebesgue apparaissant au cours de l’évolution régulière du système) et la régularité des percussions (Dirac-densité décrivant la collision). A la lumière des principes de la thermodynamique, une condition sur la percussion interne assurant que la collision est thermodynamiquement admissible, est établi. L’application aux collisions de disques rigides et à l’écoulement dans un sablier en forme d'entonnoir est présentée. L’approche est étendue au mouvement de la foule, en effet ; la circulation des piétons à travers les goulets d’étranglement est étudiée. Une analyse de sensibilité est effectuée pour étudier l’effet des paramètres d’un modèle de mouvement de foule discret 2D sur la nature des collisions et des temps d’évacuation des piétons. Nous avons identifié les paramètres qui régissent une collision de type piéton-piéton et étudié leurs effets sur le temps d'évacuation. Puis une expérience d’évacuation d’une salle avec une sortie de goulot d’étranglement est introduite et sa configuration est utilisée pour les simulations numériques. La question de l’estimation des forces de contact et de la pression générée dans une foule en mouvement est abordée à la fois d’un point de vue discret (un piéton est assimilé à un disque rigide) et continue (la foule est considérée comme un solide déformable). Une comparaison entre le modèle microscopique du second ordre (modèle discret 2D) et l’approche continue est présentée. Les forces de contact sont rigoureusement définies en tenant compte des contacts multiples et simultanés et le non chevauchement entre piétons. Nous montrons que pour une foule dense les percussions (saut de la quantité de mouvement correspondant au contact instantané) deviennent des forces de contact. Pour l’approche continue, la pression est calculée en fonction des contraintes volumiques et surfaciques. Et tenant compte les interactions non locales entre les piétons. Afin de rendre l’approche plus efficace, nous avons modélisé chaque piéton par un solide déformable, le cas unidimensionnel est étudié, une comparaison avec le cas discret est présentée pour un exemple d’écrasement d’une chaîne de piétons dans un obstacle fixe. La solution analytique des équations de contact est développée ce qui permet une calibration de paramètres du modèle et une étude asymptotique des solutions. La théorie non-régulière de la dynamique de solides déformables permet de calculer la vitesse réelle de la foule en tant qu’un milieu continu en tenant compte des interactions avec l’environnement et de la vitesse souhaitée. Une représentation macroscopique donnée par un problème couplé d’équations hyperbolique et elliptique. Une équation hyperbolique décrivant l’évolution de la densité de la foule dont la vitesse est calculée une équation elliptique, celle de l’évolution d’un solide déformable. Un résultat d’existence et unicité est développé concernant l’existence et l’unicité de la solution du problème couplé et la stabilité par rapport à la condition initiale et les conditions aux limites / This work concerns the modeling of pedestrian movement inspired by the non-smooth dynamics approach for the rigid and deformable solids. Firstly, a reformulation of the non-smooth approaches of M.Frémond and J.J.Moreau for rigid body dynamics is developed. The proposed theory relies on the notion of percussion which is the integral of the contact force during the duration of the collision. Contrary to classical discrete element models, it is here assumed that percussions can be only expressed as a function of the velocity before the impact. This assumption is checked for the usual mechanical constitutive laws for collisions. Motion equations are then reformulated taking into account simultaneous collisions of solids. The existence and uniqueness of the solution of the proposed model are discussed according to the regularity of both the forces (Lebesgue-density occurring during the regular evolution of the system) and the percussions (Dirac-density describing the collision). A condition on the internal percussion assuring that the collision is thermodynamically admissible is established. An application to the collision of rigid disks and the flow in a funnel-shaped hourglass is presented. The approach is extended to crowd motion, indeed; the circulation of pedestrians through the bottlenecks is studied and deals with to optimize evacuation and improve the design of pedestrian facilities. A sensitivity analysis is performed to study the effect of the parameters of a 2D discrete crowd movement model on the nature of pedestrian’s collision and on evacuation times. The question of estimation of contact forces and the pressure generated in a moving crowd is approached both from a discrete and continues point of view. A comparison between the second-order microscopic model (2D discrete model) and the continues approaches is presented. Contact forces are rigorously defined taking into account multiple, simultaneous contact and the non-overlapping condition between pedestrians. We show that for a dense crowd the percussions (moment umjump corresponding to instantaneous contact) become contact forces. For continuous approach, the pressure is calculated according to volume and surface constraints. This approach makes it possible to retain an admissible right-velocity (after impact), including both the non local interactions (at a distance interactions) between non neighbor pedestrians and the choice of displacement strategy of each pedestrian. Finally, two applications are presented : a one-dimensional simulation of an aligned pedestrian chain crashing into an obstacle, and a two-dimensional simulation corresponding to the evacuation of a room. In order to make the approach more efficient, we modeled each pedestrian with a deformable solid, the unidimensional case is studied a comparison with the discreet case is presented that corresponding to a crash of a pedestrian chain in a fixed obstacle is treated. The analytical solution of contact equations is developed for both approaches. This allows to calibrate the model parameters and offers an asymptotic study of the solutions. The non-smooth theory of deformable solids makes it possible to calculate the current velocity of the crowd as a continuous medium taking into account the interactions with the environment and their desired velocity. a macroscopic representation is developed through Hyperbolic – Elliptic Equations. indded;the crowd is described by its density whose evolution is given by a non local balance law. the current velocity involved in the equation is given by the collision equation of a deformable solid with a rigid plane. Firstly, we prove the well posedness of balance laws with a non smooth ux and function source in bounded domains, the existence of a weak entropic solution, it’s uniqueness and stability with respect to the initial datum and of the boundary datum. an application to crowdmodeling is presented