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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Structure spatiale des lipopolysaccharides et son rôle dans la coagulation sanguine / Spatial structure of lypopolysaccharides and its role in blood coagulation

Galochkina, Tatiana 02 November 2017 (has links)
Lipopolysaccharides (LPS) représentent le composant principal de la membrane externe des bactéries Gram-négatives. Étant libérés dans le flux sanguin, les LPS induisent une forte réponse immunitaire accompagnée d'une coagulation intensifiée du sang activée à la fois par l'endommagement de la paroi vasculaire et par l'activation de la voie de contact. Dans cette thèse, nous développons des modèles théoriques pour élucider les détails de la coagulation sanguine induite par les molécules LPS. Dans les deux premiers chapitres, nous décrivons l'état de l'art du problème et les méthodes utilisées. Le troisième chapitre est consacré à l'analyse des modèles mathématiques de la coagulation sanguine. Nous déterminons les conditions de l'existence de solutions en ondes progressives dans le modèle de la croissance du caillot, estimons la vitesse de leur propagation et démontrons l'existence de la solution en forme de pulse déterminante la valeur critique de la condition initiale qui assure le processus de coagulation. Ensuite, nous étudions le modèle de la formation de caillot dans l'écoulement sanguin et déterminons la taille critique de la zone endommagée conduisante à l'occlusion complète du vaisseau par le caillot. Enfin, nous développons et analysons le modèle de l'activation du système de contact par les agrégats des LPS. Dans le quatrième chapitre, nous modélisons la structure supramoléculaire des LPS, qui a un impact crucial sur leur activité biologique. Nous développons des modèles de la dynamique moléculaire des LPS, de leurs agrégats et des membranes des compositions variées, et analysons le comportement conformationnel des LPS en fonction de leur environnement / The outer membrane of the Gram-negative bacteria cell wall is composed of lipopolysaccharide (LPS) molecules. Being released to the blood flow during sepsis, LPS induce strong immune response accompanied by pathological blood clotting. Blood coagulation is activated both due to the vessel wall damage, and the activation of the contact pathway. The details of the mechanisms involved remain obscure despite the extensive experimental studies. In the present work we develop theoretical models of the different time and space scales to elucidate the details of the LPS-induced blood coagulation during the Gram-negative sepsis. In the first two chapters we provide the state of the art of the problem and describe the methods we use. The third chapter is devoted to the analysis of the mathematical models of blood coagulation. We determine the conditions of the existence of the traveling wave solutions in the model of the self-sustained clot growth, estimate the speed of their propagation and demonstrate existence of the pulse solution determining the critical value of the initial condition. Then, we consider the model of blood coagulation under flow conditions and determine the critical size of the damaged zone leading to the complete vessel occlusion by the clot. Finally, we develop and analyze the model of the contact system activation by the LPS aggregates. In the fourth chapter we model the LPS supramolecular structure, which has crucial impact on the LPS biological activity. We develop molecular dynamics models of the LPS molecules, their aggregates and LPS-containing membranes of different composition and analyze LPS conformational behavior in different environment
52

Méthodes variationnelles : Applications à l'analyse d'image et au modèle de Frenkel-Kontorova

Issa, Samar 19 December 2011 (has links) (PDF)
Cette thèse est décomposée en deux parties. La première est consacrée à l'étude de la restauration d'image et la seconde partie est consacrée à l'étude d'un modèle de Frenkel-Kontorova par des méthodes issues du calcul variationnel et des équations aux dérivées partielles. Au chapitre 1, nous présentons les questions essentielles que nous traiterons dans cette thèse, puis on fait des rappels sur les définitions et quelques propriétés d'espace des fonctions à variations bornées BV , l'espace d'Orlicz et le modèle de Frenkel-Kontorova. Au chapitre 2, nous montrons que les problèmes de minimisation non convexe (restauration d'image) contenant des termes de régularisation sous-linéaires sont mal posés. Au chapitre 3, nous étudions un modèle de restauration avec un terme de régularisation à croissance non standard, proposé par Blomgren et al. : le module du gradient est élevé a une puissance qui dépend elle même du gradient. On montre qu'elle est semi-continue inférieurement pour la topologie faible d'un certain espace d'Orlicz-Sobolev qui lui est associé, ce qui permet un résultat d'existence de la solution. Au chapitre 4, nous étudions un modèle de Frenkel-Kontorova, dont on montre l'existence d'au moins une solution de type travelling wave, u.
53

Investigations On Frequency Beam Scanning Microstrip (bsms) Antenna Structures

Dundar, Burhan 01 September 2009 (has links) (PDF)
Beam scanning Microstrip (BSMS) antenna is designed to work at center frequency of 10 GHz for using in the scanning applications of 9 GHz to 11 GHz band. The design parameters are defined and by using an Electromagnetic Simulation software program, the parameters are optimized. A Beam Scanning Microstrip Antenna is produced as a prototype and the measurement&rsquo / s results are compared with theoretical results. In conclusion, the values of deviation between theoretical and experimental results are discussed.
54

AN EVALUATION OF THE TRAVELING WAVE ULTRASONIC MOTOR FOR FORCE FEEDBACK APPLICATIONS

Venkatesan, Nishant 01 January 2009 (has links)
The traveling wave ultrasonic motor is considered for use in haptic devices where a certain input-output relation is desired between the applied force and the resulting motion. Historically, DC motors have been the standard choice for this purpose. Owing to its unique characteristics, the ultrasonic motors have been considered an attractive alternative. However, there are some limitations when using the ultrasonic motor for force-feedback applications. In particular, direct torque control is difficult, and the motor can only supply torque in the direction of motion. To accommodate these limitations we developed an indirect control approach. The experimental results demonstrate that the model reference control method was able to approximate a second order spring-damper system.
55

New concept, implementation and analysis of the multicell piezoelectric motor for the control of the car seat position / Conception, réalisation et caractérisation d'un moteur piézoélectrique multicellulaire, pour applications automobiles

Ryndzionek, Roland 29 September 2015 (has links)
L’étude présentée est le fruit d’une collaboration entre le groupe de recherche de l'Electrodynamique du INP-ENSEEIHT (Toulouse), LAPLACE Laboratoire de Recherche et l'École Polytechnique de Gdańsk, le Département Génie Electrique et Automatique. L’objectif de cet projet est la conception d’un moteur piézoélectrique multicellulaire composé de plusieurs stators de moteurs à rotation de mode (3 au minimum) permettant de garantir des fréquences de résonance élevées ainsi qu’une répartition des efforts de frottement plus favorables. Le dimensionnement du moteur s’appuiera sur un cahier des charges du domaine de l’automobile, en visant une structure la plus simple possible à mettre en oeuvre. Outre un travail important concernant la conception, il faudra procéder à sa caractérisation après la réalisation du prototype. La dernière étape concernera la définition des stratégies d’alimentation et de commande d’une telle structure qui posera inévitablement le problème de l’autoadaptativité des cellules résonantes à une même fréquence de résonance. Le moteur multicellular (MPM) proposé sera une combinaison du moteur à onde progressive annulaire (Shinsei) et moteur à rotation de mode. Il combine les avantages des deux moteurs par une combinaison de trois cellules élémentaires de moteurs à rotation de mode. La combinaison de ces deux concepts, accroît le nombre de surface de contact. Les dimensions préliminaires et les paramètres de la MPM prototype ont été vérifiés en utilisant son modèle développé analytique (géométrique) et méthodes numériques (MÉF). Le modèle analytique de la MPM a été développé sur la base de circuit équivalent de la Langevin actuateur. La model analytique a été fait dans Matlab. Les principaux paramètres calculés sont: fréquence de résonance 26.2 kHz, couple bloque 0.4 Nm et la vitesse 40 tr/mn. En utilisant le modèle MÉF les fréquences de résonance et les valeurs du stress de la MPM prototype ont été déterminés. . Des simulations ont été effectuées pour sélectionner la fréquence de résonance et la forme pour concevoir le contre mass. Les fréquences de résonances résultantes sont 25.6 kHz et simulations du stress moins de 9 N/mm2. Comparaison des résultats fréquence de résonance calcule à modèle analytique (26.2 kHz) et le modèle FEM (25.6 kHz) du une prototype MPM, il convient de noter, que de modèle analytique est fortement modèle précis. Enfin, la réalisation des pièces par imprimante 3D a été décidée (contre-mass et carter) et les matériaux: aluminium et nylatron. Les autres parties ont été réalisés sur une machine à commande numérique à l'aide de l'acier. Les mesures de la MPM prototype ont été effectuées. L'étape suivante a consisté à tester le moteur et vérifier la fréquence de résonance, et la mesure de déplacement, résonances fréquences résultantes sont 22 kHz et déplacement 1.1 μm sur rotor/stator point du contact. Finalement, les paramètres mécaniques ont été mesurés. Les meilleurs paramètres mécaniques ont été obtenus sur dSpace support de laboratoire: vitesse - 46-48 tr/mn, et le couple bloqué – 0.4 Nm. Les résultats sont satisfaisants et donnent un bon point de départ pour les futurs travaux. / The research works in the frame of the dissertation have been carried out with the cooperation between the University INP - ENSEEIHT - LAPLACE (Laboratory on Plasma and Conversion of Energy), Toulouse, France, and the Gdańsk University of Technology, Faculty of Electrical and Control Engineering, Research Unit Power Electronics and Electrical Machines, Gdańsk, Poland. The main scope of the dissertation was following: development a novel concept, implementation and analysis of the multicell piezoelectric motor (MPM) for the control of the car seat position. The new concept of the MPM is based on a combined topology using the working principles of the traveling wave motor/actuator (known as the Shinsei motor), and the electromechanical structure of the rotating-mode motor/actuator. The electromechanical structure of each rotating-mode motor has been considered as an independent one – referred to as a "single cell". The application of the novel MPM for the control of the car seat position will reduce the number of gears due to its direct coupling with the driving/movement shaft of the seat positioning system. The achieved effects of a such integrated structure will be following: a higher efficiency, a lower noise of performance, a low cost of manufacturing, and in general a lower pollution of the environment. The preliminary dimensions and parameters of the prototype MPM have been verified using its developed analytical (geometrical) model and numerical methods (FEM). The prototype MPM has been manufactured. Finally, the laboratory measurements of the MPM prototype has been carried out.
56

Spatial spread of rabies in wildlife

January 2013 (has links)
abstract: Rabies disease remains enzootic among raccoons, skunks, foxes and bats in the United States. It is of primary concern for public-health agencies to control spatial spread of rabies in wildlife and its potential spillover infection of domestic animals and humans. Rabies is invariably fatal in wildlife if untreated, with a non-negligible incubation period. Understanding how this latency affects spatial spread of rabies in wildlife is the concern of chapter 2 and 3. Chapter 1 deals with the background of mathematical models for rabies and lists main objectives. In chapter 2, a reaction-diffusion susceptible-exposed-infected (SEI) model and a delayed diffusive susceptible-infected (SI) model are constructed to describe the same epidemic process -- rabies spread in foxes. For the delayed diffusive model a non-local infection term with delay is resulted from modeling the dispersal during incubation stage. Comparison is made regarding minimum traveling wave speeds of the two models, which are verified using numerical experiments. In chapter 3, starting with two Kermack and McKendrick's models where infectivity, death rate and diffusion rate of infected individuals can depend on the age of infection, the asymptotic speed of spread $c^\ast$ for the cumulated force of infection can be analyzed. For the special case of fixed incubation period, the asymptotic speed of spread is governed by the same integral equation for both models. Although explicit solutions for $c^\ast$ are difficult to obtain, assuming that diffusion coefficient of incubating animals is small, $c^\ast$ can be estimated in terms of model parameter values. Chapter 4 considers the implementation of realistic landscape in simulation of rabies spread in skunks and bats in northeast Texas. The Finite Element Method (FEM) is adopted because the irregular shapes of realistic landscape naturally lead to unstructured grids in the spatial domain. This implementation leads to a more accurate description of skunk rabies cases distributions. / Dissertation/Thesis / Ph.D. Mathematics 2013
57

A Integral de Melnikov e uma aplicação em combustão em um meio poroso

Armas, Vladimir Alfredo Dionisio 14 July 2015 (has links)
Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-05-16T13:10:56Z No. of bitstreams: 1 vladimiralfredodionisioarmas.pdf: 1154081 bytes, checksum: 21752bffdb1d22af7d8e8fdff40e121b (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-06-27T21:30:35Z (GMT) No. of bitstreams: 1 vladimiralfredodionisioarmas.pdf: 1154081 bytes, checksum: 21752bffdb1d22af7d8e8fdff40e121b (MD5) / Made available in DSpace on 2016-06-27T21:30:35Z (GMT). No. of bitstreams: 1 vladimiralfredodionisioarmas.pdf: 1154081 bytes, checksum: 21752bffdb1d22af7d8e8fdff40e121b (MD5) Previous issue date: 2015-07-14 / Neste trabalho é apresentado um estudo sobre a Integral de Melnikov para duas classes de sistemas de equações diferenciais ordinárias. A primeira delas é um sistema Hamiltoniano associado a uma perturbação uniparamétrica. A segunda classe é um sistema geral, associada a uma perturbação bidimensional. O trabalho termina com um estudo sobre a existência e unicidade de solucões do tipo de onda viajante para um modelo matemático de combustão em um meio poroso. / This work presents a study about the Melnikov’s Integral for two classes of ordinary differential equations. In the first one, we study the Melnikov’s Integral for a Hamiltonian system associated with one-parameter perturbation. The second class, we study the Melnikov’s Integral for any system associated with a two-dimensional perturbation. The work finishes with a study on the existence and uniqueness of traveling wave solutions of the mathematical model describing combustion in porous medium.
58

High-Yield Optical Undulators Scalable to Optical Free-Electron Laser Operation by Traveling-Wave Thomson-Scattering

Steiniger, Klaus 18 April 2018 (has links) (PDF)
All across physics research, incoherent and coherent light sources are extensively utilized. Especially highly brilliant X-ray sources such as third generation synchrotrons or free-electron lasers have become an invaluable tool enabling experimental techniques that are unique to these kinds of light sources. But these sources have developed to large scale facilities and a demand in compact laboratory scale sources providing radiation of similar quality arises nowadays. This thesis focuses on Traveling-Wave Thomson-Scattering (TWTS) which allows for the realization of ultra-compact, inherently synchronized and highly brilliant light sources. The TWTS geometry provides optical undulators, through which electrons pass and thereby emit radiation, with hundreds to thousands of undulator periods by utilizing pulse-front tilted lasers pulses from high peak-power laser systems. TWTS can realize incoherent radiation sources with orders of magnitude higher photon yield than established head-on Thomson sources. Moreover, optical free-electron lasers (OFELs) can be realized with TWTS if state-of-the-art technology in electron accelerators and laser systems is utilized. Tilting the laser pulse front with respect to the wavefront by half of this interaction angle optimizes electron and laser pulse overlap by compensating the spatial offset between electrons and the laser pulse-front at the beginning of the interaction when the electrons are far from the laser pulse axis. The laser pulse-front tilt ensures continuous overlap between electrons and laser pulse while the electrons cross the laser pulse cross-sectional area. Thus the interaction distance can be controlled in TWTS by the laser pulse width rather than laser pulse duration. Utilizing wide, petawatt class laser pulses allows realizing thousands of optical undulator periods. This thesis will show that TWTS OFELs emitting ultraviolet radiation are realizable today with existing technology for electron accelerators and laser systems. The requirements on electron bunch and laser pulse quality of these ultraviolet TWTS OFELs are discussed in detail as well as the corresponding requirements of TWTS OFELs emitting in the soft and hard X-ray range. These requirements are derived from scaling laws which stem from a self-consistent analytic description of the electron bunch and radiation field dynamics in TWTS OFELs presented within this thesis. It is shown that these dynamics in TWTS OFELs are qualitatively equivalent to the electron bunch and radiation field dynamics of standard free-electron lasers which analytically proves the applicability of TWTS for the realization of an optical free-electron laser. Furthermore, experimental setup strategies to generate the pulse-front tilted TWTS laser pulses are presented and designs of experimental setups for the above examples are discussed. The presented setup strategies provide dispersion compensation, required due to angular dispersion of the laser pulse, which is especially relevant when building compact, high-yield hard X-ray TWTS sources in large interaction angle setups. An example of such an enhanced Thomson source by TWTS, which provides orders of magnitude higher spectral photon density than a comparable head-on interaction geometry, is presented, too
59

High-Yield Optical Undulators Scalable to Optical Free-Electron Laser Operation by Traveling-Wave Thomson-Scattering

Steiniger, Klaus 18 April 2018 (has links)
All across physics research, incoherent and coherent light sources are extensively utilized. Especially highly brilliant X-ray sources such as third generation synchrotrons or free-electron lasers have become an invaluable tool enabling experimental techniques that are unique to these kinds of light sources. But these sources have developed to large scale facilities and a demand in compact laboratory scale sources providing radiation of similar quality arises nowadays. This thesis focuses on Traveling-Wave Thomson-Scattering (TWTS) which allows for the realization of ultra-compact, inherently synchronized and highly brilliant light sources. The TWTS geometry provides optical undulators, through which electrons pass and thereby emit radiation, with hundreds to thousands of undulator periods by utilizing pulse-front tilted lasers pulses from high peak-power laser systems. TWTS can realize incoherent radiation sources with orders of magnitude higher photon yield than established head-on Thomson sources. Moreover, optical free-electron lasers (OFELs) can be realized with TWTS if state-of-the-art technology in electron accelerators and laser systems is utilized. Tilting the laser pulse front with respect to the wavefront by half of this interaction angle optimizes electron and laser pulse overlap by compensating the spatial offset between electrons and the laser pulse-front at the beginning of the interaction when the electrons are far from the laser pulse axis. The laser pulse-front tilt ensures continuous overlap between electrons and laser pulse while the electrons cross the laser pulse cross-sectional area. Thus the interaction distance can be controlled in TWTS by the laser pulse width rather than laser pulse duration. Utilizing wide, petawatt class laser pulses allows realizing thousands of optical undulator periods. This thesis will show that TWTS OFELs emitting ultraviolet radiation are realizable today with existing technology for electron accelerators and laser systems. The requirements on electron bunch and laser pulse quality of these ultraviolet TWTS OFELs are discussed in detail as well as the corresponding requirements of TWTS OFELs emitting in the soft and hard X-ray range. These requirements are derived from scaling laws which stem from a self-consistent analytic description of the electron bunch and radiation field dynamics in TWTS OFELs presented within this thesis. It is shown that these dynamics in TWTS OFELs are qualitatively equivalent to the electron bunch and radiation field dynamics of standard free-electron lasers which analytically proves the applicability of TWTS for the realization of an optical free-electron laser. Furthermore, experimental setup strategies to generate the pulse-front tilted TWTS laser pulses are presented and designs of experimental setups for the above examples are discussed. The presented setup strategies provide dispersion compensation, required due to angular dispersion of the laser pulse, which is especially relevant when building compact, high-yield hard X-ray TWTS sources in large interaction angle setups. An example of such an enhanced Thomson source by TWTS, which provides orders of magnitude higher spectral photon density than a comparable head-on interaction geometry, is presented, too
60

Pilot Protection Based on Directional Detection

Sefidpour, Sepehr January 2009 (has links)
Nowadays two main types of protection schemes widely used in protection of transmission lines are: distance protection and differential protection schemes. However, it has been noticed from industrial practice that the distance protection scheme used today generally is limited in tripping speed and selectivity. Also differential protection scheme is influenced by the time synchronization of samples in both relays installed at transmission line terminals. On the other hand, among various pilot protection schemes for protection of Extra High Voltage (EHV) / Ultra High Voltage (UHV) transmission lines, the schemes which use communication link only for exchange of local decision making about faults’ status are not affected by time synchronization. This master thesis is dealing with the issue of developing reliable and fast fault detection scheme for protection of EHV/UHV transmission lines which is a requirement in modern power systems. The protection algorithm proposed in this thesis is based on the detection and analysis of traveling waves on transmission lines at inception of the faults. This algorithm relies on directional comparison between initial arrivals of traveling waves at each end of the protected line. This will determine whether or not a fault is inside the protected zone. In addition to, based on high voltage transmission network protection requirements proper phase selection algorithm is developed to handle single- phase tripping. Finally, by simulations carried out in PSCAD environment practical design considerations for implementing the new developed protection algorithm in a numerical relay unit is investigated. The results of simulation show that the proposed pilot protection scheme solves several issues encountered by using the conventional schemes and provide reliable and high speed protection for transmission lines.

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