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1
Shen, Jonah Wai. "Finite difference methods applied to biot theory in porous medium." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA306214.
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Thesis (M.S. in Engineering Acoustics) Naval Postgraduate School, September 1995.Thesis advisor(s):, Clyde Scandrett,Anthony A. Atchley. "September 1995." Bibliography: p. 43. Also available online.
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Lind, Nordgren Eleonora. "A study of tailoring acoustic porous material properties when designing lightweight multilayered vehicle panels." Doctoral thesis, KTH, MWL Marcus Wallenberg Laboratoriet, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-100701.
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The present work explores the possibilities of adapting poro-elastic lightweight acoustic materials to specific applications. More explicitly, a design approach is presented where finite element based numerical simulations are combined with optimization techniques to improve the dynamic and acoustic properties of lightweight multilayered panels containing poro-elastic acoustic materials. The numerical models are based on Biot theory which uses equivalent fluid/solid models with macroscopic space averaged material properties to describe the physical behaviour of poro-elastic materials. To systematically identify and compare specific beneficial or unfavourable material properties, the numerical model is connected to a gradient based optimizer. As the macroscopic material parameters used in Biot theory are interrelated, they are not suitable to be used as independent design variables. Instead scaling laws are applied to connect macroscopic material properties to the underlying microscopic geometrical properties that may be altered independently. The design approach is also combined with a structural sandwich panel mass optimization, to examine possible ways to handle the, sometimes contradicting, structural and acoustic demands. By carefully balancing structural and acoustic components, synergetic rather than contradictive effects could be achieved, resulting in multifunctional panels; hopefully making additional acoustic treatment, which may otherwise undo major parts of the weight reduction, redundant. The results indicate a significant potential to improve the dynamic and acoustic properties of multilayered panels with a minimum of added weight and volume. The developed modelling techniques could also be implemented in future computer based design tools for lightweight vehicle panels. This would possibly enable efficient mass reduction while limiting or, perhaps, totally avoiding the negative impact on sound and vibration properties that is, otherwise, a common side effect of reducing weight, thus helping to achieve lighter and more energy efficient vehicles in the future.QC 20120815
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Nordgren, Eleonora. "A study of tailoring acoustic porous material properties when designing lightweight multilayered vehicle panels." Phd thesis, Conservatoire national des arts et metiers - CNAM, 2012. http://tel.archives-ouvertes.fr/tel-00780756.
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The present work explores the possibilities of adapting poro-elastic lightweight acoustic materials to specific applications. More explicitly, a design approach is presented where finite element based numerical simulations are combined with optimization techniques to improve the dynamic and acoustic properties of lightweight multilayered panels containing poro-elastic acoustic materials.The numerical models are based on Biot theory which uses equivalent fluid/solid models with macroscopic space averaged material properties to describe the physical behaviour of poro-elastic materials. To systematically identify and compare specific beneficial or unfavourable material properties, the numerical model is connected to a gradient based optimizer. As the macroscopic material parameters used in Biot theory are interrelated, they are not suitable to be used as independent design variables. Instead scaling laws are applied to connect macroscopic material properties to the underlying microscopic geometrical properties that may be altered independently.The design approach is also combined with a structural sandwich panel mass optimization, to examine possible ways to handle the, sometimes contradicting, structural and acoustic demands. By carefully balancing structural and acoustic components, synergetic rather than contradictive effects could be achieved, resulting in multifunctional panels; hopefully making additional acoustic treatment, which may otherwise undo major parts of the weight reduction, redundant.The results indicate a significant potential to improve the dynamic and acoustic properties of multilayered panels with a minimum of added weight and volume. The developed modelling techniques could also be implemented in future computer based design tools for lightweight vehicle panels. This would possibly enable efficient mass reduction while limiting or, perhaps, totally avoiding the negative impact on sound and vibration properties that is, otherwise, a common side effect of reducing weight, thus helping to achieve lighter and more energy efficient vehicles in the future.
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Boulos, Mario. "Déshydratation mécano-thermique d’un milieu poreux déformable : modélisation des transferts et développement d’outils de caractérisation adaptés." Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14074/document.
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Ces travaux de thèse portent sur la caractérisation des milieux poreux fortement déformables afin de modéliser le transfert réalisé au cours du séchage. La théorie de consolidation de Biot traduit le couplage hydromécanique se produisant durant la déshydratation d’un milieu poreux déformable. Le modèle de Cáceres s’appuie sur cette théorie et sur la loi classique de Darcy. Il est adapté aux grandes déformations du squelette solide et utilise un tenseur de contraintes de décomposition Terzaghi. Une simulation de la déshydratation par l’intermédiaire de ce modèle nécessite au préalable le renseignement de celui-ci en termes de caractéristiques thermophysiques. Deux dispositifs expérimentaux ont été mis en place : l’un mesurant la relaxation de charge, l’autre réalisant la pressurisation dynamique (DP). La 1ère expérience nous a permis de caractériser la perméabilité, le coefficient de Poisson et le module d’Young en fonction de la teneur en eau du gel. La 2ème expérience a révélé l’importance de la prise en considération de la compressibilité de la phase solide dans la modélisation du séchage du gel d’agar ainsi que, la nécessité de corriger la valeur du module de compressibilité de l’eau contenant du gaz dissout. Suite à cette étape expérimentale, nous avons concentré nos efforts sur la modélisation liée à notre étude. Tout d’abord, la DP étant conforme à l’hypothèse de faibles déformations, un modèle numérique basé sur les équations de Biot a été réalisé afin de valider les paramètres mesurés et de corriger la valeur estimée de la perméabilité. Un second modèle traduit le couplage thermo-hydro-mécanique lors du séchage convectif d’un milieu poreux fortement déformable comme les gels d’agar et d’alumine. Ce dernier s’appuie sur la théorie de Biot et d’une part s’adapte aux fortes déformations et d’autre part utilise l’approche eulérienne. Ce modèle constitue donc un compromis entre les modèles de Biot et de Cáceres et s’appuie sur l’étude thermodynamique de Coussy ce qui est une avancée dans la modélisation des gels déformablesThis thesis focuses on the characterization of strongly deformable porous media in order to model the transfer taking place during drying. The theory of consolidation of Biot reflects the hydro-mechanical coupling occurring during dehydration of a deformable porous medium. Cáceres developed a model based on this theory and on the classical Darcy’s law. It is suitable for large deformations of the solid skeleton and the stress tensor is decomposed according to the so-called Terzaghi’s principle. A simulation using this model requires the information in thermo-physical terms of characteristics. Two experimental setups were developed : one measuring the relaxation charge, the other called dynamic pressurization (DP). The first experiment allowed us to characterize the permeability, Poisson’s ratio and Young’s modulus as functions of water content of the gel. The second experiment showed the importance of taking into account the compressibility of the solid phase in the modeling of the drying of agar gel as well as the effect of the existence of bubbles on the bulk modulus of the water. The establishment of two models followed this experimental study. First, the DP is consistent with the hypothesis of small deformations, a numerical model based on Biot’s equations was carried out to validate the parameters measured and to correct the estimated value of the permeability. A second model reflects the thermo-hydro-mechanical coupling in the convective drying of highly deformable porous media such as agar gel and alumina. The latter is based on the Biot’s theory and on the thermodynamics study of Coussy. It uses the Euler’s method while staying adapted to large deformations
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Barbagallo, Mathias. "Statistical energy analysis and variational principles for the prediction of sound transmission in multilayered structures." Doctoral thesis, KTH, MWL Marcus Wallenberg Laboratoriet, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-118427.
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Multilayered structures have many application in industry and society: they have peculiar properties and serve a variety of purposes, like structural support, thermal insulation, vibrational and acoustic isolation. This thesis concerns the prediction of sound transmission in multilayered structures. Two problems are herein investigated: the transmission of energy through structures and the transmission of energy along structures. The focus of the analysis is on the mid to high frequency range. To predict sound transmission in these structures, statistical energy analysis (SEA) is used.SEA models are devised for the prediction of the sound reduction index for two kinds of multilayered structures, double-walls used in buildings and trim-panels in vehicles; the double-walls comprise an air cavity in between flat plasterboard or glass plates, whereas the trim-panels a porous layer in between curved aluminium and rubber layers. The SEA models are based upon the wave-types carrying energy. The novelty in these SEAs is an element describing the waves in the air cavity, or in the porous layer, fully coupled to the mass-impeded external layers. Compared to measurements, the proposed SEA performs well: for double-walls, it performs better than previous models; for trim-panels, it is an original result. The parameters of the new SEA element, such as modal density, are derived from the coupling equations describing the fully coupled waves. For double-walls, these equations are derived via Newton's laws. For trim-panels, a variational approach based upon a modified Hamilton's principle valid for non-conservative systems is preferred, because it is a powerful machinery for deriving equations of motion and coupling conditions of a medium as complex as the porous layer. The modified Hamilton's principle for non-conservative systems is based upon a self-adjoint functional analogous to the Lagrangian, inspired by Morse and Feshbach's construction. A self-adjoint variational principle for Biot's equations in the displacement formulation is devised. An equivalent mixed formulation is obtained changing the coordinates of the displacement formulation via Lagrange multipliers. From this mixed formulation, the Lagrangian for a porous material with a limp frame is derived, which yields the continuity of the total displacement of the porous layer. Lagrange multipliers help to obtain the correct coupling functionals between a porous material and a solid. The Lagrange multipliers introducing the continuity of the frame and the solid displacements equal the traction of the in-vacuo frame, thus disappearing if the latter is limp. Measurements to gather material parameters for a Biot model of the porous layer have been conducted.The effects of spatial energy decay in the transmission along structures predicted by SEA is studied: a major effect is the increased relevance of indirect coupling loss factors between SEA elements. This may jeopardize the usefulness of SEA at higher frequencies.QC 20130218
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Barrière, Julien. "Atténuation et dispersion des ondes P en milieu poreux partiellement saturé : approche expérimentale." Phd thesis, Université de Pau et des Pays de l'Adour, 2011. http://tel.archives-ouvertes.fr/tel-00734463.
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Afin d'analyser le rôle de la saturation partielle sur la vitesse de phase et l'atténuation des ondes P directes, nous avons élaboré une expérience en laboratoire dans la gamme du kiloHertz. Celle-ci permet une corrélation avec les mesures de terrain et limite les effets d'échelle induits par l'utilisation des traditionnelles mesures ultrasoniques. Le montage expérimental est composé d'un container rempli de sable, équipé d'accéléromètres et de sondes de teneur en eau. Une propagation d'onde est générée par une source mécanique constituée d'une bille en métal frappant une plaque de granite. Plusieurs cycles d'imbibition/drainage sont réalisés entre les saturations résiduelles en eau et en air. Une transformée continue en ondelette a été choisie pour le traitement des données sismiques et validée numériquement par une simulation de propagation d'ondes dans un milieu viscoélastique 2D (code Specfem2D). En imbibition et en drainage, la vitesse de phase décroît avec l'augmentation de la saturation, ce qui peut être expliqué par la limite Biot-Gassmann-Wood (BGW) de la théorie de Biot. Ce comportement, typique des mesures de terrain, indique qu'il est possible de considérer le mélange de fluides (eau et air) comme un fluide effectif. L'interprétation de l'atténuation est plus complexe et ne peut être expliquée par le mécanisme de relaxation de flux macroscopique de la théorie de Biot. Il est nécessaire d'introduire une contribution viscoélastique reliée aux pertes frictionelles grain-à-grain et décrite par un modèle à Q constant. De plus, un hystérésis entre imbibition et drainage est observé et expliqué en introduisant une perméabilité effective du mélange, dépendante des perméabilités relatives à l'eau et à l'air.
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Lei, Lei. "Étude des matériaux poreux thermo compressés pour la modélisation des écrans acoustiques automobiles." Thesis, Compiègne, 2018. http://www.theses.fr/2018COMP2428/document.
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Ce travail a été réalisé dans le cadre du projet EcOBEx, qui consiste à réduire le bruit du groupe motopropulseur rayonné à l'extérieur par l'ajout d'écrans acoustiques dans le compartiment moteur du véhicule. Les écrans acoustiques sont fabriqués par thermocompression de matériaux poreux uniformes. Les propriétés et l'épaisseur du matériau évoluent en fonction du degré de compression subit par le matériau. L'objectif de ce travail est de proposer des lois pour prédire l'évolution des propriétés des matériaux à partir du taux de compression et de leurs valeurs initiales avant compression. Dans un premier temps, on s'intéresse aux paramètres du modèle de fluide équivalent de Johnson-Champoux-Allard-Lafarge (JCAL) : porosité, résistivité au passage d'air, tortuosité, longueurs caractéristiques visqueuse et thermique, perméabilité thermique statique. Des expressions analytiques sont proposées pour prédire la variation de ces paramètres en fonction de la compression. Elles sont développées à partir d'un modèle de matériaux fibreux à fibres cylindriques où les variations d'orientation des fibres induites par la thermocompression peuvent être prises en compte. Les résultats sont en bon accord avec les mesures effectuées sur deux types de matériaux (mousse à cellules ouvertes et fibreux). Un modèle empirique généralisé est finalement proposé pour la résistivité au passage d'air. Dans un deuxième temps, on s'attache aux paramètres élastiques dont la connaissance est essentielle pour prendre en compte la vibration du squelette. La méthode expérimentale quasistatique est d'abord appliquée pour étudier l'évolution du module de Young par rapport au taux de compression pour les fibres et les mousses. Une loi de puissance est alors proposée pour prédire ces variations. Enfin, une méthode inverse pour estimer les propriétés élastiques d'un matériau poroélastique orthotrope à partir d'une mesure vibratoire d'un écran tricouche thermo comprimé est proposée. Cette méthode permet de caractériser les propriétés élastiques du matériau poreux dans une situation proche de son application réelleThis work was carried out in the framework of the project EcOBEx, whose main objective was to reduce the passby noise by mean of acoustic shields in the engine compartment of the vehicle. The acoustic shields are manufactured by thermocompression of uniform porous materials. The material’s properties and thickness evolve according to the degree of compression experienced by the material. The objective of this work is to propose some laws to predict the evolution of the materials properties from their initial non compressed values and the compression rate. Firstly, we focus on the parameters of the Johnson-Champoux-Allard-Lafarge (JCAL) equivalent fluid model : porosity, air-flow resistivity, tortuosity, viscous characteristic lengths, thermal characteristic length, static thermal permeability. Some analytical expressions are proposed to predict the variation of these parameters as a function of compression. They are derived from a physical model of cylindrical fibres where the fibre orientation variations induced by the thermocompression can be taken into account. The results are in good agreement with the measurements made two types of materials (open cell foam and fibrous). A generalized empirical model is finally proposed for the air-flow resistivity.In a second part, we focus on the elastic parameters, which are necessary to take into account the vibration of the skeleton. The quasi-static experimental method is first applied to study the evolution of the Young’s modulus along the compression rate for fibrous and open cell foams. A power law is then proposed to predict these variations. Finally, an inverse method for estimating the elastic properties of an orthotropic poro-elastic material from a vibratory measurement of a thermocompressed three layer sandwich structure is proposed. This method allows us to characterize the elastic properties of a porous material in a situation close to its actual application
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Aichele, Johannes. "Elastic waves in complex conditions : from the onset of rupture to viscous dispersion in foams." Electronic Thesis or Diss., Lyon, 2019. http://www.theses.fr/2019LYSE1217.
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Ces travaux s'inscrivent dans la continuité des recherches académiques du Labtau (Laboratory of therapeutic applications of ultrasound) et de l’ ISTerre (Institut des sciences de la terre) à l'interface entre imagerie médicale et sismologie, deux disciplines reposant sur la propagation des ondes élastiques. La nature de la propagation des ondes élastiques dans des milieux complexes est étudiée à travers l'imagerie ultrasonore ultrarapide - également connue sous le nom d'imagerie d’ondes de cisaillement. Cette technique d'imagerie médicale permet de récupérer un champ d'onde de cisaillement se propageant dans un milieu élastique mou. Elle est habituellement utilisée comme modalité d’imagerie cartographiant les élasticités d’organes tels que le foie ou le sein. La première partie se penche sur le comportement des ondes dans des milieux poreux. La dispersion de l'onde de cisaillement et de l'onde de compression secondaire dans des matériaux imitant le poumon est analysées expérimentalement, puis comparées à la théorie de poro-élasticité de Biot. Les résultats quant à l'onde de cisaillement sont conformes à la théorie, et ceux de l’onde de compression y correspondent qualitativement. Pour conclure, dans le cas des milieux mous, poreux et élastiques, la dispersion des ondes élastiques est gouvernée par les propriétés du fluide visqueux. Ainsi, les résultats présentés au cours de cette thèse pourraient consolider la théorie nécessaire à une imagerie de l’élasticité pulmonaire. Potentiellement d’autres organes pourraient en bénéficier : en effet, le foie et la rate sont constitués d'un pourcentage élevé de sang. Ce fluide non-Newtonien présente une forte variabilité de la viscosité. Celle-ci implique la nécessité d’étudier le rôle du sang vis-à-vis de l'élastographie du foie, pas encore expliquée par les modèles visco-élastique. En outre, la preuve expérimentale de l'onde de compression secondaire est utile dan l’étude de la propagation d'ondes poro-élastiques. Il est important de noter que l’onde de compression secondaire a été objet principal d’études approfondies en géophysique et n’a été observée que dans quelques rares cas. La partie suivante s’intéresse à une problématique de la géophysique explorée au moyen de l’imagerie de l’onde de cisaillement : Que pourrait révéler sur la nature de la rupture dynamique d’une instabilité de friction l’étude du champs d’onde élastique ? Comment la rupture, le processus responsable des tremblements de terre, est générée? En observant la carte du champ d’onde de cisaillement pendant la rupture d’une aspérité granulaire au point source et dans le milieu, il est possible d’acquérir une meilleure compréhension de la propagation de la rupture. L’expérience qui se base sur l’utilisation de fantômes mous et élastiques montre une multitude de phénomènes qui sont aussi présents dans la friction des roches en laboratoire, ainsi que dans la Terre. Par exemple, les ruptures supershear, sub-Rayleigh, une phase de nucléation et la friction du type stick-slip ont été observés. Toutefois, ni un mécanisme de source d’une force unique, ni un double-couple n’arrivent à expliquer l’ensemble des ruptures observées. De plus, pour analyser la complexité spatio-temporelle des ruptures de cette expérience, un workflow semi-automatique intègrant la segmentation d’image et la vision numérique est suggéréThis thesis is part of the research at Labtau (Laboratory of therapeutic applications of ultrasound) and ISTerre (Institut des sciences de la terre - earth science institute) at the interface of medical imaging and seismology, two research disciplines that are based on the propagation of elastic waves. It investigates the nature of elastic wave propagation in complex conditions by ultrafast ultrasound imaging, also known as transient elastography or shear wave imaging. This medical imaging technique allows for retrieval of the dynamic shear wave field inside a soft elastic material and is commonly applied in hospitals for elasticity mapping in, e.g., the liver and breast. In the present manuscript, two research questions of interest for bio- and geophysics are tackled. The first part treats elastic wave propagation in porous materials. The dispersion of the shear and secondary compression wave in lung-mimicking materials is analyzed experimentally and compared to Biot's theory of poro-elasticity. The results show a good agreement for the shear wave and qualitative agreement for the secondary compression wave. This has direct implications for elasticity imaging: the properties of the viscous fluid govern the shear wave dispersion in highly porous soft elastic materials. The thesis thus contributes to the emerging branch of lung elasticity imaging. The results could have clinical implications for other organs as well. The liver and spleen contain a high percentage of blood, a non-Newtonian fluid which exposes a highly varying viscosity. The conclusions drawn from the comparison of the experimental results and poro-elastic theory imply, that the role of the pore-filling fluid should be investigated in liver elastography: The clinically observed dispersion of shear waves in the liver remains partly unexplained by purely visco-elastic models. Furthermore, the experimental proof of the secondary compression wave is of general interest for poroelasticity. Originally, this wave has been the object of geophysical studies and has scarcely been shown experimentally. In the second part, the ultrafast ultrasound shear wave imaging technique is applied to a geophysical research question. What does the elastic wavefield, which is emitted by a frictional instability, reveal about the nature of dynamic rupture propagation? How does rupture, the process behind earthquakes, nucleate? By mapping the shear wave-field during rupture of a granular asperity at the source point and in the medium, unique insights into rupture nucleation are gained. The experimental setup, which relies on soft elastic phantoms, is shown to reproduce many characteristics of sliding friction that have been show for real rocks in the earth and the laboratory. These include supershear and sub-Rayleigh rupture propagation, a nucleation phase and stick-slip friction. Neither a singular-force nor a double-couple source mechanism explain the entirety of observed rupture modes. Finally, in order to statistically analyze the complex spatio-temporal evolution of the presented experiment, a semi-automated data analysis workflow, taking advantage of image segmentation and computer vision, is suggested
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Shabani, Behnam. "Wave-Associated Seabed Behaviour near Submarine Buried Pipelines." Thesis, The University of Sydney, 2008. http://hdl.handle.net/2123/3532.
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Soil surrounding a submarine buried pipeline consolidates as ocean waves propagate over the seabed surface. Conventional models for the analysis of soil behaviour near the pipeline assume a two-dimensional interaction problem between waves, the seabed soil, and the structure. In other words, it is often considered that water waves travel normal to the orientation of pipeline. However, the real ocean environment is three-dimensional and waves approach the structure from various directions. It is therefore the key objective of the present research to study the seabed behaviour in the vicinity of marine pipelines from a three-dimensional point of view. A three-dimensional numerical model is developed based on the Finite Element Method to analyse the so-called momentary behaviour of soil under the wave loading. In this model, the pipeline is assumed to be rigid and anchored within a rigid impervious trench. A non-slip condition is considered to exist between the pipe and the surrounding soil. Quasi-static soil consolidation equations are then solved with the aid of the proposed FE model. In this analysis, the seabed behaviour is assumed to be linear elastic with the soil strains remaining small. The influence of wave obliquity on seabed responses, i.e. the pore pressure and soil stresses, are then studied. It is revealed that three-dimensional characteristics systematically affect the distribution of soil response around the circumference of the underwater pipeline. Numerical results suggest that the effect of wave obliquity on soil responses can be explained through the following two mechanisms: (i) geometry-based three-dimensional influences, and (ii) the formation of inversion nodes. Further, a parametric study is carried out to investigate the influence of soil, wave and pipeline properties on wave-associated pore pressure as well as principal effective and shear stresses within the porous bed, with the aid of proposed three-dimensional model. There is strong evidence in the literature that the failure of marine pipelines often stems from the instability of seabed soil close to this structure, rather than from construction deficiencies. The wave-induced seabed instability is either associated with the soil shear failure or the seabed liquefaction. Therefore, the developed three-dimensional FE model is used in this thesis to further investigate the instability of seabed soil in the presence of a pipeline. The widely-accepted criterion, which links the soil liquefaction to the wave-induced excess pressure is used herein to justify the seabed liquefaction. It should be pointed out that although the present analysis is only concerned with the momentary liquefaction of seabed soil, this study forms the basis for the three-dimensional analysis of liquefaction due to the residual mechanisms. The latter can be an important subject for future investigations. At the same time, a new concept is developed in this thesis to apply the dynamic component of soil stress angle to address the phenomenon of wave-associated soil shear failure. At this point, the influence of three-dimensionality on the potentials for seabed liquefaction and shear failure around the pipeline is investigated. Numerical simulations reveal that the wave obliquity may not notably affect the risk of liquefaction near the underwater pipeline. But, it significantly influences the potential for soil shear failure. Finally, the thesis proceeds to a parametric study on effects of wave, soil and pipeline characteristics on excess pore pressure and stress angle in the vicinity of the structure.
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Shabani, Behnam. "Wave-Associated Seabed Behaviour near Submarine Buried Pipelines." University of Sydney, 2008. http://hdl.handle.net/2123/3532.
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Master of Engineering (Research)Soil surrounding a submarine buried pipeline consolidates as ocean waves propagate over the seabed surface. Conventional models for the analysis of soil behaviour near the pipeline assume a two-dimensional interaction problem between waves, the seabed soil, and the structure. In other words, it is often considered that water waves travel normal to the orientation of pipeline. However, the real ocean environment is three-dimensional and waves approach the structure from various directions. It is therefore the key objective of the present research to study the seabed behaviour in the vicinity of marine pipelines from a three-dimensional point of view. A three-dimensional numerical model is developed based on the Finite Element Method to analyse the so-called momentary behaviour of soil under the wave loading. In this model, the pipeline is assumed to be rigid and anchored within a rigid impervious trench. A non-slip condition is considered to exist between the pipe and the surrounding soil. Quasi-static soil consolidation equations are then solved with the aid of the proposed FE model. In this analysis, the seabed behaviour is assumed to be linear elastic with the soil strains remaining small. The influence of wave obliquity on seabed responses, i.e. the pore pressure and soil stresses, are then studied. It is revealed that three-dimensional characteristics systematically affect the distribution of soil response around the circumference of the underwater pipeline. Numerical results suggest that the effect of wave obliquity on soil responses can be explained through the following two mechanisms: (i) geometry-based three-dimensional influences, and (ii) the formation of inversion nodes. Further, a parametric study is carried out to investigate the influence of soil, wave and pipeline properties on wave-associated pore pressure as well as principal effective and shear stresses within the porous bed, with the aid of proposed three-dimensional model. There is strong evidence in the literature that the failure of marine pipelines often stems from the instability of seabed soil close to this structure, rather than from construction deficiencies. The wave-induced seabed instability is either associated with the soil shear failure or the seabed liquefaction. Therefore, the developed three-dimensional FE model is used in this thesis to further investigate the instability of seabed soil in the presence of a pipeline. The widely-accepted criterion, which links the soil liquefaction to the wave-induced excess pressure is used herein to justify the seabed liquefaction. It should be pointed out that although the present analysis is only concerned with the momentary liquefaction of seabed soil, this study forms the basis for the three-dimensional analysis of liquefaction due to the residual mechanisms. The latter can be an important subject for future investigations. At the same time, a new concept is developed in this thesis to apply the dynamic component of soil stress angle to address the phenomenon of wave-associated soil shear failure. At this point, the influence of three-dimensionality on the potentials for seabed liquefaction and shear failure around the pipeline is investigated. Numerical simulations reveal that the wave obliquity may not notably affect the risk of liquefaction near the underwater pipeline. But, it significantly influences the potential for soil shear failure. Finally, the thesis proceeds to a parametric study on effects of wave, soil and pipeline characteristics on excess pore pressure and stress angle in the vicinity of the structure.
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Matta, Sandrine. "Propagation des ondes acoustiques dans une multicouche composée de couches viscoélastiques liquides, solides et poreuses." Thesis, Valenciennes, 2018. http://www.theses.fr/2018VALE0035/document.
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Cette thèse propose un formalisme général pour modéliser la propagation des ondes acoustiques dans une multicouche composée de toute combinaison de couches liquides, solides élastiques isotropes et poro-élastiques isotropes, la méthode ayant la flexibilité d'être développée pour inclure d'autres natures de couches. Dans un premier lieu, un algorithme stable est développé, basé sur l'approche récursive de la matrice de rigidité, pour modéliser la propagation d'une onde plane incidente sur la multicouche en fonction de son angle d'incidence et de sa fréquence. Cet algorithme fusionne de manière récursive les matrices de rigidité des couches individuelles de la structure en une matrice de rigidité totale et permet ensuite le calcul des coefficients de réflexion et de transmission, ainsi que les composantes de déplacement et de contrainte à l'intérieur de la multicouche pour chaque direction d'incidence des ondes planes. Deuxièmement, pour modéliser la propagation d'un faisceau délimité d'ondes incidentes, la technique du spectre angulaire est utilisée, basée sur la décomposition de ce faisceau en un spectre d'ondes planes se propageant dans des directions différentes. Par la suite, le faisceau d'onde réfléchi dans le milieu d'incidence et le faisceau d'onde transmis dans le milieu de transmission, ainsi que la distribution des champs (composantes de déplacement et de contrainte) à l'intérieur de la multicouche sont obtenus en superposant la contribution de toutes les ondes planes se propageant dans les différentes directions. Comme application numérique, une tri-couche solide-poreuse-solide immergée dans l'eau est simulée. La réflexion et la transmission qui en résultent, ainsi que les composantes de déplacement et de contrainte dans la multicouche, correspondants à l’onde plane incidente et au faisceau limité incident, révèlent la stabilité du procédé et la continuité des déplacements et des contraintes aux interfacesThis thesis proposes a general formalism to model the acoustic wave propagation in a multilayer consisting of any combination of fluid, isotropic elastic solid, and isotropic poroelastic layers, the method having the flexibility to be extended to include other layer-natures. At a first stage, a stable algorithm is developed, based on the recursive stiffness matrix approach, to model the propagation of a plane wave incident on the multilayer as a function of its incidence angle and frequency. This algorithm merges recursively the structureindividual layers stiffness matrices into one total stiffness matrix and allows then the calculation of the reflection and transmission coefficients, as well as the displacement and stress components inside the multilayer for every incident plane wave direction. Secondly, to model the propagation of a bounded incident wave beam, the angular spectrum technique is used which is based on the decomposition of this beam into a spectrum of plane waves traveling in different directions. The corresponding reflected wave beam in the incidence medium, and the transmitted wave beam in the transmission medium, as well as the fields distributions (displacement and stress components) inside the multilayer are obtained by summing the contribution of all the plane waves traveling in different directions. As a numerical application, a three-layered solid-porous-solid structure immersed in water is simulated. The resulting reflection and transmission as well as the displacement and stress components in the multilayer corresponding to both, the incident plane wave in different directions and the incident bounded beam reveal the stability of the method and the continuity of the displacements and stresses at the interfaces
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Zhao, Jieyu. "Stochastic bit stream neural networks : theory, simulations and applications." Thesis, Royal Holloway, University of London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338916.
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Masmoudi, Khaled. "Schémas de codage bio-inspirés." Phd thesis, Université de Nice Sophia-Antipolis, 2012. http://tel.archives-ouvertes.fr/tel-00850287.
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Le but de mon travail de thèse est de concevoir de nouveaux codeurs d'images inspirées de la rétine. En effet, alors que la question du codage est importante pour l'économie d'énergie et de bande passante, nous sommes convaincus que peu est encore à gagner si aucun changement n'est fait dans la philosophie qui sous-tend la conception de la nouvelle image codeurs / décodeurs. Donc, mon travail vise à jeter les bases de la conception de l'image originale et les systèmes de compression vidéo qui sont basées sur des modèles de systèmes visuels biologiques. Ici, nous allons nous concentrer sur la rétine comme il est l'organe responsable de l'acquisition du stimulus visuel et le premier dispositif de codage dans le système visuel humain. Le sujet traité est très difficile et motivant pour deux raisons principales. La première est que les techniques de compression vidéo sont aujourd'hui indispensables pour la plupart des équipements standards tels que HDTV et DVD, et que le récent progrès technique nous permet d'imaginer des schémas de codage plus sophistiqués. Le second est que les récentes découvertes en neurosciences sur le système visuel humain pourrait être une source d'inspiration pour proposer de nouvelles idées, surtout si nous sommes en mesure de mieux comprendre le code neural de la rétine. Ainsi, nous nous attendons à une approche interdisciplinaire qui peut aider à atteindre nos objectifs. Cette approche permettrait de combiner les techniques de traitement du signal et les connaissances acquises par les neurophysiologistes. Nous espérons que ce travail va conduire à de nouveaux algorithmes de codage qui vont au-delà des normes.
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Alexopoulos, Kyriakos. "Phase spectral representation for low bit rate speech coding." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249314.
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Easton, Mark. "Fast algorithms for low bit rate digital speech coding." Thesis, University of Liverpool, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240500.
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Kweh, Teck Hock. "Improved quality block-based low bit rate video coding." Thesis, University of Surrey, 1998. http://epubs.surrey.ac.uk/844563/.
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The aim of this research is to develop algorithms for enhancing the subjective quality and coding efficiency of standard block-based video coders. In the past few years, numerous video coding standards based on motion-compensated block-transform structure have been established where block-based motion estimation is used for reducing the correlation between consecutive images and block transform is used for coding the resulting motion-compensated residual images. Due to the use of predictive differential coding and variable length coding techniques, the output data rate exhibits extreme fluctuations. A rate control algorithm is devised for achieving a stable output data rate. This rate control algorithm, which is essentially a bit-rate estimation algorithm, is then employed in a bit-allocation algorithm for improving the visual quality of the coded images, based on some prior knowledge of the images. Block-based hybrid coders achieve high compression ratio mainly due to the employment of a motion estimation and compensation stage in the coding process. The conventional bit-allocation strategy for these coders simply assigns the bits required by the motion vectors and the rest to the residual image. However, at very low bit-rates, this bit-allocation strategy is inadequate as the motion vector bits takes up a considerable portion of the total bit-rate. A rate-constrained selection algorithm is presented where an analysis-by-synthesis approach is used for choosing the best motion vectors in term of resulting bit rate and image quality. This selection algorithm is then implemented for mode selection. A simple algorithm based on the above-mentioned bit-rate estimation algorithm is developed for the latter to reduce the computational complexity. For very low bit-rate applications, it is well-known that block-based coders suffer from blocking artifacts. A coding mode is presented for reducing these annoying artifacts by coding a down-sampled version of the residual image with a smaller quantisation step size. Its applications for adaptive source/channel coding and for coding fast changing sequences are examined.
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Laurenson, Lawrie Jon Bain. "Colonisation theory and invasive biota : the Great Fish river, a case history." Thesis, Rhodes University, 1986. http://hdl.handle.net/10962/d1005905.
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Colonisation theory relative to introduced populations was examined with a view to determining the usefulness of theoretical concepts in the prediction of the success of an invasion by a species. To this end, the Great Fish River, with reference to species introduced by the Orange/Fish Tunnel, was used as a case history. It was concluded that theoretical descriptions of population growth, control and decline are useful only when considering individual ecosystems or species. The highly variable nature of species and environments nullifies attempts to simplify behavioural characteristics into a predictive framework. There is an abundance of terminology associated with introduced organisms and frequently many of these terms are used synonymously. Eleven terms have been defined in this thesis with a view to standardising terminology. Characteristics of species and environments which enhance their susceptibility to invasions by exotic ichthyofauna were discussed and summarised. Distribution data concerning exotic fish introduced into the Great Fish River by the Orange/Fish Tunnel has demonstrated that, with the exception of Clarias gariepinus, all remaining exotics have restricted distributions. Only Barbus aeneus appears to be extending its range down the drainage. Age, Growth, reproduction and condition data support the conclusion that, excluding B. aeneus and C. gariepinus, invasive species in the drainage are not performing well. Of the five invasive species (B. aeneus, Labeo capensis, L. umbratus, Gephyroglanis sclateri and Cyprinus carpio), only two have established populations (B. aeneus· and C. gariepinus). Labeo umbratus and C. carpio were present on the Great Fish River prior to the construction of the tunnel and populations of the species could not be distinguished. It was concluded that there is no evidence to suggest that exotic species introduced into the Great Fish River are having a deleterious effect on indigenous, endangered ichthyofauna. Monitoring of the drainage should be continued to ensure that a danger to indigenous species does not develop.
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Gouvianakis, Nikolaos. "Speech coding at medium bit rates using analysis by synthesis techniques." Thesis, Loughborough University, 1989. https://dspace.lboro.ac.uk/2134/27741.
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Yeldener, Suat. "Sinusoidal model based low bit rate speech coding for communication systems." Thesis, University of Surrey, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359842.
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Atungsiri, Samuel Asangbeng. "Joint source and channel coding for low bit rate speech communication systems." Thesis, University of Surrey, 1991. http://epubs.surrey.ac.uk/989/.
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Xu, Chunmei. "Sparsity optimization and RRSP-based theory far l-bit compressive sensing." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6443/.
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Due to the fact that only a few significant components can capture the key information of the signal, acquiring a sparse representation of the signal can be interpreted as finding a sparsest solution to an underdetermined system of linear equations. Theoretical results obtained from studying the sparsest solution to a system of linear equations provide the foundation for many practical problems in signal and image processing, sample theory, statistical and machine learning, and error correction. The first contribution of this thesis is the development of sufficient conditions for the uniqueness of solutions of the partial l\(_0\)-minimization, where only a part of the solution is sparse. In particular, l\(_0\)-minimization is a special case of the partial l\(_0\)-minimization. To study and develop uniqueness conditions for the partial sparsest solution, some concepts, such as l\(_p\)-induced quasi-norm, maximal scaled spark and maximal scaled mutual coherence, are introduced. The main contribution of this thesis is the development of a framework for l-bit compressive sensing and the restricted range space property based support recovery theories. The l-bit compressive sensing is an extreme case of compressive sensing. We show that such a l-bit framework can be reformulated equivalently as an l\(_0\)-minimization with linear equality and inequality constraints. We establish a decoding method, so-called l-bit basis pursuit, to possibly attack this l-bit l\(_0\)-minimization problem. The support recovery theories via l-bit basis pursuit have been developed through the restricted range space property of transposed sensing matrices. In the last part of this thesis, we study the numerical performance of l-bit basis pursuit. We present simulation results to demonstrate that l-bit basis pursuit achieves support recovery, approximate sparse recovery and cardinality recovery with Gaussian matrices and Bernoulli matrices. It is not necessary to require that the sensing matrix be underdetermined due to the single-bit per measurement assumption. Furthermore, we introduce the truncated l-bit measurements method and the reweighted l-bit l\(_1\)-minimization method to further enhance the numerical performance of l-bit basis pursuit.
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Rice, Malachy. "Analysis and simulation of high bit-rate digital transmission over wire-pair channels." Thesis, Queen's University Belfast, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361303.
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Chan, C. F. "Low bit-rate speech coding : A parallel processing approach using digital signal processors." Thesis, University of Essex, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375652.
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REBILLARD, PASCAL. "Prediction de l'impedance de surface des materiaux poreux stratifies par la theorie de biot." Le Mans, 1991. http://www.theses.fr/1991LEMA1006.
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Apres avoir rappele les lois de l'elasticite et les definitions des grandeurs acoustiques regissant le comportement des milieux monophasiques, nous etudions d'une facon simplifiee les phenomenes visco-thermiques et introduisons les expressions des parametres physiques caracteristiques d'un milieu poreux. A partir de la theorie de biot, nous modelisons la propagation du son dans les materiaux poreux stratifies, sous incidence oblique, en tenant compte de la contribution des ondes longitudinales de premiere et de seconde espece, et aussi de l'onde transverse. L'utilisation de matrices de transfert, permet de calculer simplement l'impedance de surface des materiaux poreux stratifies comportant eventuellement des ecrans impermeables ou poreux. La procedure de mesure de l'impedance de surface par la methode du doublet microphonique est exposee, puis, a titre de validation des modeles prealablement etablis, les resultats de mesures sont compares a ceux obtenus par calcul pour divers materiaux stratifies comprenant des couches poreuses, des ecrans minces poreux, et des ecrans impermeables. Il apparait que les modeles proposes peuvent donner une description correcte du comportement acoustique des materiaux consideres
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Chilton, Edward. "Factors affecting the quality of linear predictive coding of speech at low bit-rates." Thesis, University of Surrey, 1990. http://epubs.surrey.ac.uk/843568/.
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This thesis aims to examine those factors which affect the quality and performance of low bit-rate coding algorithms for speech, based on linear prediction, operating between 4-16kb/s. While coding algorithms at 64kb/s and 32kb/s are now accepted CCITT standards, and a similar standard will be shortly adopted at 16kb/s, speech coding systems operating below these rates are not yet in wide-spread use, except for one or two specific systems such as GSM. Yet low bit-rate digital speech systems will become an essential part of many of the proposed mobile networks, based on both cellular and satellite technology. Of several possible candidates for low bit-rate applications, it is linear predictive coders that appear to offer the best in terms of quality and efficiency, and many developments, based on linear prediction, have been reported in the literature over the past twenty years. What is less clear is whether there is the potential for linear predictive coders to be developed further with better quality at even lower rates. This thesis sets out to examine some of those issues. The first part of the thesis develops a general theory for speech coding in terms of a hierarchical model of speech communication and identifies a dual function in the redundancies that exist at each layer of the hierarchical structure. The operation of linear predictive coding, in terms of this model is described, and it is shown that the limits to performance are determined by the ability of the encoder to efficiently transfer communication from a lower to a higher level in the hierarchy. The thesis then turns its attention towards the specific performance of linear prediction analysis on speech signals. It is shown that there is a limit to the performance that can be obtained with conventional linear prediction analysis due to the assumptions upon which the theory of linear prediction is based. A range of sub-classes of linear predictive coder are then compared in terms of the general model and the analysis procedures in the encoder stage are identified as being the key to coder performance. The central part of this thesis examines, specifically, a range of pitch determination algorithms which may be employed to enable accurate extraction of pitch correlations from the speech signal. A number of candidates are identified and compared. An investigation into the robustness of these algorithms to noisy speech is presented and a new highly robust algorithm is described. Finally, an investigation into robust linear prediction is reported. This falls into two parts - the performance of linear prediction on noisy speech and the performance of linear prediction during voiced speech. A range of methods for improving linear prediction during voiced speech are compared and the recently proposed method of Lee is examined in depth. Results of the application of Lee's method to speech coding is given and an improved version of the algorithm is described.
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Lavayen, Farfán Daniel. "Non-linear beam theory in context of bio-inspired sensing of flows." Master's thesis, Pontificia Universidad Católica del Perú, 2016. http://tesis.pucp.edu.pe/repositorio/handle/123456789/8324.
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The thesis at hand is part of a research project that attempts to study and develop
vibrissa inspired tactile sensors for object and fluid flow detection. The main focus of the thesis
is on the development of a model for a vibrissa-like sensor for obstacle contour recognition under
fluid loads. To this end, a mechanical model – based on the non-linear Euler-Bernoulli beam theory
– is established. The model includes the main characteristics found in a natural vibrissa, such as
elasticity of the base, that acts as the vibrissa follicle; the intrinsic curvature; and conicity.
The characteristics are represented as parameters of the model. The model is subjected to a contact
load and a fluid flow load, represented by a concentrated load and a distributed load,
respectively. Then, the model is transformed into a dimensionless representation for further
studies to achieve more general assertions. A variation of the magnitude of these loads, as well as
the vibrissa parameters is also analyzed. A direct numerical approximation using the finite
difference method, along with the shooting method, is used to obtain a solution of the model.
Subsequently, the model is used to simulate an ideal contact between an obstacle and the vibrissa.
This simulation considers a quasi-static sweep of the artificial vibrissa with the contour of a
profile, while measuring and recording the forces and moment at the base. This procedure is then
repeated in combination of a distributed force acting on the vibrissa, simulating the effect of a
fluid flow. Two types of contact phases are identified and the conditions for each one are set.
Finally, the measured quantities, which represent the observables an animal solely relies on, are
used to obtain the magnitude of the fluid load and to reconstruct the profile contour of the
obstacle. The developed model is used again for the reconstruction, an analysis of the observables
is performed to identify and predict which contact phase the vibrissa is in. The results
successfully show identification of the fluid flow load as well as reconstruction of the profile,
the difference between the reconstructed profile and the
original profile is then calculated as a measure of reconstruction quality.Tesis
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Kritzinger, Carl. "Low bit rate speech coding." Thesis, Stellenbosch : University of Stellenbosch, 2006. http://hdl.handle.net/10019.1/2078.
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Thesis (MScIng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006.Despite enormous advances in digital communication, the voice is still the primary tool with which people exchange ideas. However, uncompressed digital speech tends to require prohibitively high data rates (upward of 64kbps), making it impractical for many applications. Speech coding is the process of reducing the data rate of digital voice to manageable levels. Parametric speech coders or vocoders utilise a-priori information about the mechanism by which speech is produced in order to achieve extremely efficient compression of speech signals (as low as 1 kbps). The greater part of this thesis comprises an investigation into parametric speech coding. This consisted of a review of the mathematical and heuristic tools used in parametric speech coding, as well as the implementation of an accepted standard algorithm for parametric voice coding. In order to examine avenues of improvement for the existing vocoders, we examined some of the mathematical structure underlying parametric speech coding. Following on from this, we developed a novel approach to parametric speech coding which obtained promising results under both objective and subjective evaluation. An additional contribution by this thesis was the comparative subjective evaluation of the effect of parametric speech coding on English and Xhosa speech. We investigated the performance of two different encoding algorithms on the two languages.
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Chen, Wei 1976. "Perceptual postfiltering for low bit rate speech coders." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=112563.
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Adaptive postfiltering has become a common part of speech coding standards based on the Linear Prediction Analysis-by-Synthesis algorithm to decrease audible coding noise. However, a conventional adaptive postfilter is based on empirical assumptions of masking phenomena, which sometimes makes it hard to balance between noise reduction and speech distortion.This thesis introduces a novel perceptual postfiltering system for low bit rate speech coders. The proposed postfilter works at the decoder, as is the case for the conventional adaptive postfilter. Specific human auditory properties are considered in the postfilter design to improve speech quality. A Gaussian Mixture Model based Minimum Mean Squared Error estimation of the perceptual postfilter is performed with the received information at the decoder. Perceptual postfiltering is then applied to the reconstructed speech to improve speech quality. Test results show that the proposed system gives better perceptual speech quality over conventional adaptive postfiltering.
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Furbeck, David S. "Fast determination of bit error rates on impulsive noise channels." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/15656.
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Woynarski, Lisa Christine. "Towards an ecological performance aesthetic for the bio-urban : a non-anthropocentric theory." Thesis, Royal Central School of Speech & Drama, 2015. http://crco.cssd.ac.uk/551/.
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As current precarious ecological conditions require urgent and multi-scalar responses, performance has an opportunity to creatively respond to the ecological situation, opening up new ways of thinking and engaging the public’s imagination. Problematising differentiating practices that divide humans from ‘nature’, I suggest performance may highlight the interconnectedness of humans and the more-than-human world by theorising, revealing and critiquing ecological relationships. My research into an ecological performance aesthetic takes up this opportunity and conceives of new ways of critically thinking about performance. I engage a range of ecological philosophy, combined with ecodramaturgical analysis of performance, to theorise the intersection of performance and ecology. Ecodramaturgy (May 2010) combines ecocritical and applied approaches to performance with ecological ways of performance-making, and represents a critical extension to the discipline of performance studies. Drawing on the ecomaterialism of Bennett (2010), Latour (2004), Alaimo (2013) and Barad (2012), I theorise ‘nature’ as a set of interconnected relationships, which disrupts the binaries between urban/nature, nature/culture, human/nonhuman. I coin the neologism the bio-urban to reflect the vibrancy and material agency of ecological relationships in urban settings. The focus on urban-based practice resists the rural bias present in much ecological writing (Harvey 1993b) and addresses a gap in scholarship around urban ecology in relation to performance. This research centres on a wide variety of illustrative, broadly site-based performance events, including urban gardening performances (and my own practice), walking and cycling performances, installation, live art, theatre pieces and work in places such as streets, mountains, (urban) meadows, cemeteries and rivers. I consider the way in which performance engages with the world, through the interrelated and overlapping discourses of postcolonial ecology, human geography and urban ecology. An ecological performance aesthetic informs modes of practice, presentation and reception, within current ecological conditions. From the provocation of the bio-urban, I theorise immersion and ‘environmental participation’, drawing on the corporeality of our relationship to the space around us, following ecological phenomenology. I then examine oikos as (earthy or planetary) home and consider it in relation to dwelling, suggesting that ecological performance opens up a space for critiquing these ideas. The complex relationship between the local and global is characterised in performance through eco-cosmopolitanism (Heise 2008). Finally, I suggest a non-anthropocentric paradigm for performance, one that employs an ‘ecological anthropomorphism’ that accounts for the material agency of the more-than- human, as well as the human as a geophysical force (Chakrabarty 2012). The aim of the research is to articulate an ecological performance aesthetic, extending and developing the field of performance and ecology.
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Hurley, M. T. "The application of Biot's theory to sea-bed sediments." Thesis, Bangor University, 1989. https://research.bangor.ac.uk/portal/en/theses/the-application-of-biots-theory-to-seabed-sediments(db8adbfb-ed81-4cc9-a064-87a8da3bf815).html.
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Biot's theory - which explains how sediments respond to stresses - has been applied to different sea-bed sediments. To successfully use Biot's theory as a predictive tool, sensitivity studies showed the following experimental measurements are required: the frame bulk modulus. the shear modulus, the tortuosity, the permeability and the porosity. These properties were determined for turbidite sediments from the North Atlantic Ocean (Site 1). and carbonates from the Western Indian Ocean -. (Site 2). The following experimental observations " were made: the permeability varies over 7 orders of magnitude for turbidites from Site 1 due to technique dependent and intrinsic reasons; in-situ shear moduli are 4 times greater than values determined from samples in the laboratory; shear modulus results from resonant column and bender element transducer techniques agree well: experiments designed for obtaining the frame bulk modulus are problematic, and it is difficult to determine pore size / geometry parameters apart from the tortuosity. Biot's theory was used to predict the response of sea-bed sediments to hydrodynamic and ultrasonic stresses. A new low frequency hydrodynamic boundary-value solution was developed from Biot's theory, allowing predictions of tidally-induced pore-pressures. Comparisons between predictions and in-situ measurements at Site 1 were favourable, verifying Biot's theory at low frequencies. At ultrasonic frequencies, Biot predictions of the velocity and attenuation of fast and slow compressional waves were compared to experimental measurements. The slow wave was argued to be induced at free-flow boundaries. and was found to be very difficult to detect in soft water-saturated sediments. A qualitative agreement was shown between Biot fast wave attenuation predictions and new experimental attenuation measurements on a bar of sandstone. For Sites 1 and 2, Biot predictions for the increases in the fast wave velocity for high porosity - permeability sediments agreed with experimental measurements. Elsewhere in the literature, this behaviour has been linked to an increase of the frame bulk modulus with increases in porosity. Alternatively, it was argued such increases in fast wave velocity can be attributed to Biot's dispersion mechanism. and hence are a verification of his theory at high frequencies.
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Kim, Choon S. "Low bit-rate subband coding of image and video signals using vector quantization." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/15889.
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Chu, Chung Cheung. "Tree encoding of speech signals at low bit rates." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65459.
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Huang, Yuheng. "Bit-interleaved coded modulation with iterative decoding for wireless communications /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/5903.
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Kim, Hyun Soo Electrical Engineering & Telecommunications Faculty of Engineering UNSW. "Speech analysis techniques useful for low or variable bit rate coding." Awarded by:University of New South Wales. School of Electrical Engineering and Telecommunications, 2005. http://handle.unsw.edu.au/1959.4/22050.
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We investigate, improve and develop speech analysis techniques which can be used to enhance various speech processing systems, especially low bit rate or variable bit rate coding of speech. The coding technique based on the sinusoidal representation of speech is investigated and implemented. Based on this study of the sinusoidal model of speech, improved analysis techniques to determine voicing, pitch and spectral estimation are developed, as well as noise reduction technique. We investigate the properties and limitations of the spectral envelope estimation vocoder (SEEVOC). We generalize, optimize and improve the SEEVOC and also compare it with LP in the presence of noise. The properties and applications of morphological filters for speech analysis are investigated. We introduce and investigate a novel nonlinear spectral envelope estimation method based on morphological operations, which is found to be very robust against noise. This method is also compared with the SEEVOC method. A simple method for the optimum selection of the structuring set size without using prior pitch information is proposed for many purposes. The morphological approach is then used for a new pitch estimation method and for the general sinusoidal analysis of speech or audio. Many of the new methods are based on a novel systematic analysis of the peak features of signals, including the study of higher order peaks. We propose a novel peak feature algorithm, which measure the peak characteristics of speech signal in time domain, to be used for end point detection and segmentation of speech. This nonparametric algorithm is flexible, efficient and very robust in noise. Several simple voicing measures are proposed and used in a new speech classifier. The harmonic-plus-noise decomposition technique is improved and extended to give an alternative to the methods used in the sinusoidal analysis method. Its applications to pitch estimation, speech classification and noise reduction are investigated.
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Sipitca, Mihai. "A conditional entropy approach to encoding DCT coefficients for low bit rate video compression." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/13404.
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Lee, Im Soo. "Computational Techniques for Efficient Solution of Discretized Biot's Theory for Fluid Flow in Deformable Porous Media." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/28179.
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In soil and rock mechanics, coupling effects between geomechanics field and fluid-flow field are important to understand many physical phenomena. Coupling effects in fluid-saturated porous media comes from the interaction between the geomechanics field and the fluid flow. Stresses subjected on the porous material result volumetric strains and fluid diffusion in the pores. In turn, pore pressure change cause effective stresses change that leads to the deformation of the geomechanics field. Coupling effects have been neglected in traditional geotechnical engineering and petroleum engineering however, it should not be ignored or simplified to increases reliability of the results. The coupling effect in porous media was theoretically established in the poroelasticity theory developed by Biot, and it has become a powerful theory for modeling three-dimensional consolidation type of problem.
The analysis of the porous media with fully-coupled simulations based on the Biotâ s theory requires intensive computational effort due to the large number of interacting fields. Therefore, advanced computational techniques need to be exploited to reduce computational time. In order to solve the coupled problem, several techniques are currently available such as one-way coupling, partial-coupling, and full-coupling. The fully-coupled approach is the most rigorous approach and produces the most correct results. However, it needs large computational efforts because it solves the geomechanics and the fluid-flow unknowns simultaneously and monolithically. In order to overcome this limitation, staggered solution based on the Biotâ s theory is proposed and implemented using a modular approach. In this thesis, Biotâ s equations are implemented using a Finite Element method and/or Finite Difference method with expansion of nonlinear stress-strain constitutive relation and multi-phase fluid flow. Fully-coupled effects are achieved by updating the compressibility matrix and by using an additional source term in the conventional fluid flow equation. The proposed method is tested in multi-phase FE and FD fluid flow codes coupled with a FE geomechanical code and numerical results are compared with analytical solutions and published results.Ph. D.
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DE, POLLIER CLAUDE. "Theorie de biot et prediction des proprietes acoustiques des materiaux poreux : propagation dans les milieux acoustiques desordonnes." Le Mans, 1989. http://www.theses.fr/1989LEMA1001.
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Modelisation de la propagation du son dans les milieux poreux absorbants. Signification physique des trois termes de couplage. Prediction de l'impedance de surface des materiaux stratifies a partir d'un formalisme matriciel original. Contribution a l'etude de la propagation du son dans les milieux desordonnes. Mise en evidence du phenomene de localisation d'anderson
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Sarkar, Mitradeep. "Hybrid surface plasmon modes in metallic nanostructures : Theory, numerical analysis and application to bio-sensing." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS251/document.
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Les Plasmons de surface à l’interface d’un métal et d’un diélectrique sont des oscillations collectives des électrons libres. Pour une interface plane, les plasmons se manifestent comme des champs électromagnétiques évanescents, confinée à quelques centaines de nanomètres de la surface métallique et se propagent le long de l'interface. Ce mode plasmonique, appelé plasmon propagatif de surface (PSP), est un mode fondamental. D’autres modes fondamentaux, non-propagatifs, sont appelé plasmons localisés (LSP) et apparaissent dans les nano-particules métalliques. Dans ce travail, nous avons calculé analytiquement la polarisabilité de géométries métalliques complexes et les résultats obtenus permettent d’expliquer les conditions de résonance des différents modes plasmoniques.Parmi les divers modes plasmoniques, plusieurs modes fondamentaux ont été étudiés en détail et décrits par une formulation analytique. Tout d’abord, dans un réseau binaire de lignes métalliques, des plasmons propagatifs confinés par la dimension finie des lignes sont générés. Ce mode plasmonique est appelé plasmons propagatifs confinée (CPP). D’autre part, dans des réseaux périodiques de nano-particules métalliques, déposées sur un film métallique, des modes de Bragg (BM) sont excités par la diffraction des PSP. De plus, dans de telles structures, un couplage harmonique entre les LSP des nano-particules et le PSP du film métallique sous-jacent se traduit par l’apparition d’un mode hybride (HLP). Les caractéristiques de ce mode hybride pour un réseau de nano-cylindres métalliques sur un film métallique sont présentées en détails, en particulier son intérêt en bio-détection.L'effet du milieu diélectrique environnant sur les modes plasmoniques est utilisé dans les détecteurs basés sur la résonance des plasmons de surface (SPR). Ces systèmes mesurent le décalage de la résonance d’un mode plasmonique, qui est fonction de l’indice de réfraction du milieu diélectrique. L’un des buts de ce travail est d'optimiser les détecteurs SPR pour des expériences typiques sondes – cibles où les molécules sonde sont greffées à la surface du capteur. Nous avons montré que par une fonctionnalisation sélective de la surface métallique, une amélioration de la performance de détection peut être obtenue en terme de quantité de molécules cibles détectable. L'amélioration de champ proche joue aussi un rôle majeur dans les techniques de diffusion Raman exaltée de surface (SERS). La présence de certains des modes plasmoniques étudiés dans les substrats nano-structurés permet d’augmenter significativement l'intensité du signal SERS.Pour réaliser ce travail, des méthodes numériques adaptées à la géométrie particulière des structures étudiées ont été développés pour calculer les distributions des champs proches et lointains dans ces structures. Les caractéristiques de ces modes plasmoniques ont été mesurés expérimentalement et leurs performances en détection SPR ont été démontrées en utilisant une configuration basée sur une interrogation angulo-spectrale en configuration de Kretschmann. Des expériences de SERS ont également été réalisées en collaboration avec le CSPBAT à Paris 13. Les différentes structures ont été fabriquées par lithographie électronique à l’IEF à Paris 11. Les résultats expérimentaux concordent avec les résultats numériques et analytiques.Cette description détaillée des modes plasmoniques offre une compréhension plus complète du phénomène de résonance des plasmons de surface dans les nanostructures métalliques et permet d’optimiser les structures selon l’application souhaitée. Le modèle présenté dans ce travail est relativement général et peut être utilisé pour décrire les propriétés électromagnétiques de différentes géométries et configurations expérimentales. De la représentation complète des modes plasmoniques, différents aspects des interactions photons-plasmons peuvent ainsi être étudiésThe surface plasmons on metallic surfaces are excited by the collective oscillations of free electrons. They satisfy certain resonance conditions and their dispersion can be considered as modes of the system. The plasmons at uniform metal-dielectric interfaces manifest as evanescent electromagnetic (EM) fields confined to a few hundreds of nanometers from the metallic surface and propagate along the interface. This mode is called the Propagating surface plasmon (PSP) and is a fundamental plasmonic mode. The other fundamental modes, which are non-propagative, results from collective oscillations of free electrons on curved surfaces of metallic nano-particles. They are called localized surface plasmon (LSP) modes. We have shown that the polarizability of complex geometries with an underlying substrate can be calculated analytically and the results obtained closely approximate the resonance conditions for such geometries.In this work, various other plasmonic modes originating from the two fundamental modes were studied in details and described by their corresponding analytical formulation. In a binary metallic arrays on glass substrate, plasmonic modes are excited by diffraction orders, called the Wood-Rayleigh modes (WRM). In metallic strips the PSP is confined by the finite edges of the strips and propagate along the length of the strips, called the confined propagating plasmons (CPP).For arrays of metallic nano-particles on a metallic film, the Bragg modes (BM) are excited by diffraction of the PSP. In such structures the LSP of the nano-particles and the PSP of the film can undergo a harmonic coupling to give rise to the hybrid lattice plasmon (HLP). The characteristics of the HLP mode for an array of metallic nano-cylinders on a metallic film is presented in details.The effect of the surrounding medium on the plasmonic modes is used in surface plasmon resonance (SPR) detectors which probe the shift in resonance condition of the modes. Such shift is dependent on the intrinsic dispersion of the modes. The aim of this work is to optimize the SPR detectors for affinity biosensing where probe and analyte molecules are bound to the metallic surface. We have shown that by selective functionalization of the metallic biochip surface, an enhancement of the performance of such detection can be achieved in terms of the amount of analyte used. Also the near field enhancement plays a major role in surface enhanced Raman scattering (SERS). We have shown that the presence of certain modes in the system can enhance the recorded SERS intensity.Rigorous numerical methods, adapted to the particular geometry under study, were developed to compute the near and far field characteristics of different structures. The experimental excitation of the modes and their application in SPR detection was demonstrated using a setup based on a spectral scanning modality operating in the Kretschmann configuration. The various structures were fabricated on a biochip using e-beam lithography at IEF, University Paris Sud and the reflectivity dispersion from the biochip was recorded. Such experimental results were shown to be in close agreement with the theoretical results. SERS experiments were carried out in collaboration with CSPBAT at University Paris 13 and the results were seen to fit closely the theoretically predicted trends.Such detailed description of plasmonic modes can offer a complete understanding of the surface plasmon resonance phenomenon in metallic structures and be optimized as per required for various applications. The theories presented in this work can be used to effectively describe the EM properties of different geometries and experimental configurations. From a comprehensive representation of plasmonic modes, different aspects of the photon-plasmon interactions can thus be elucidated
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McCorkle, Warren Benson Jr. "Tongue, nib, block, bit: rhetorical delivery and technologies of writing." The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1125329989.
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Abdullah, S. N. "Data transmission at 9600 bit/sec over an HF radio link." Thesis, Loughborough University, 1986. https://dspace.lboro.ac.uk/2134/7432.
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The thesis is concerned with serial data transmission at 9600 bit/sec over a voiceband channel, where the main impairments are additive noise and intersymbol interference, and the latter varles slowly with time. The thesis includes a brief description of the ionospheric propagation medium and presents an equivalent baseband model of the HF channel, suitable for computer simulation of quadrature amplitude modulation (QAM) systems. A study of 16-point QAM signals transmitted over voiceband HF channels is then carr-iod out usj-ng the given channel model. Several cost effective near-maximum-likelihood detection processes have been developed for HF modems. Each detector is here preceded by an adaptive linear filter that is adjusted to make the sampled impulse response of the channel and filter minimum phase. These detectors require an accurate knowledge of the sampled impulse response of the channel, if their full potential is to be achieved. The results of computer-simulation tests on the near-maximum-likelihood detectors are given, where these tests assume that other receiver operations such as channel estimation and adaptive linear filtering, together with element timing synchronisation and Doppler shift correction, are carried out perfectly. A recently developed HF channel estimator employing a simple feedforward transversal-filter and requiring knowledge of the number of skywaves is next investigated and a starting up procedure is developed for such an estimator. The technique is then made fully adaptive in the sense that it continues to operate correctly when the number of skywaves changes. Results of computer simulation tests are then presented showing the performance of the above detectors when operating with a channel estimator and adaptive linear filtering. Finally modem synchronisation is studied and various techniques of element timing and carrier frequency synchronisation are proposed.
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Simard, Jean-Raymond. "Classical and quantum strategies for bit commitment schemes in the two-prover model." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101174.
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We show that the long-standing assumption of "no-communication" between the provers of the two-prover model is not sufficiently precise to guarantee the security of a bit commitment scheme against malicious adversaries. Indeed, we show how a simple correlated random variable, which does not allow to communicate, can be used to cheat a simplified version (sBGKW) of the bit commitment scheme of Ben-Or, Goldwasser, Kilian, and Wigderson [BGKW88]. Instead we propose a stronger notion of separation between the two provers which takes into account correlated computations. To emphasize the risk that entanglement still represents for the security of a commitment scheme despite the stronger notion of separation, we present two variations of the sBGKW scheme that can be cheated by quantum provers with probability (almost) one. A complete proof of security against quantum adversaries is then given for the sBGKW scheme. By reduction we also obtain the security of the original BGKW scheme against quantum provers. For the unfamiliar reader, basic notions of quantum processing are provided to facilitate the understanding of the proofs presented.
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Pujaico, Rivera Fernando 1982. "Algoritmos bit-flipping para decodificação conjunta de fontes correlacionadas em canais ruidosos." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/260833.
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Orientador: Jaime PortugheisTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
Made available in DSpace on 2018-08-25T19:09:11Z (GMT). No. of bitstreams: 1 PujaicoRivera_Fernando_D.pdf: 1689945 bytes, checksum: b226b1d9cf87f31fc3d470ac895b0e33 (MD5) Previous issue date: 2014
Resumo: Esta tese propõe um sistema de transmissão de informação de várias fontes correlacionadas sobre canais ruidosos. Inicialmente se aborda o problema da codificação fonte-canal conjunta. Para este problema se definirá conceitos de taxas ótimas e se apresentará a maneira de obtê-las. Posteriormente, será proposto um algoritmo de decodificação conjunta com complexidade tratável. Diversos resultados de desempenho do algoritmo proposto serão apresentados. Estes resultados mostram um bom compromisso entre desempenho e complexidade quando comparados com a decodificação independente. Finalmente, o algoritmo de decodificação conjunta seguido de uma proposta de regra de fusão é usado no problema CEO e o desempenho deste novo algoritmo é apresentado
Abstract: This thesis proposes a system that transmits information from various correlated sources over noisy channels. Initially, it addresses the problem of joint source-channel coding. To solve this problem, concepts of optimal rates will be defined and the way to obtain them will be presented. Subsequently, a joint decoding algorithm with a tractable complexity is proposed. Several performance results of the proposed algorithm will be presented. These results show a good compromise between performance and complexity when compared to the non-joint decoding. Finally, the joint decoding algorithm, followed by a proposal for a fusion rule is used in the CEO problem and the performance of this new algorithm is presented
Doutorado
Telecomunicações e Telemática
Doutor em Engenharia Elétrica
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Xiao, Hong. "Joint source-channel coding for noisy channels and its applications for low-bit-rate multimedia transmission." Thesis, The University of Sydney, 2001. https://hdl.handle.net/2123/27824.
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C. E. Shannon’s classical coding theorem pointed out the source and channel coding may
be separately designed with any optimization if the source and channel code block—length is
infinite. However, for a practical communication system this assumption obviously can not
be realized since only limited complexity and delay are allowable and acceptable in a practical
system. This fact actually forces the practical system to use the finite block—length codes
inevitably both for the source and channel coding. Under this constraint, the principle of the
separate source and channel coding is no longer optimum for a practical system. However,
Shannon did not tell us how to design a good code with a finite block-length.
Joint source-channel coding (JSCC) as an efficient method to improve the practical system
performance has been explored in the last past decade. It has been shown that, to achieve
a good performance on a system over a noisy channel, consideration must be given to use
the continuous or soft information provided by the channel instead of using the conventional
discrete or hard information. However, the issue how to use the soft information provided by
the channel decoder to design an optimum source encoder/decoder pair (codec) in a coded
system has not been addressed, not to mention any applications of this issue to the real-time
communication systems.
In this thesis, we first propose an efficient joint trellis-coded modulation (TCM) and turbo
coding scheme for high—quality very low-bit-rate multimedia wireless transmissions over the
bandwidth-limited channels. Then we develop a generalized JSCC algorithm for designing
optimum vector quantization (VQ) source codecs over coded systems. Uncoded system as
a special case of coded systems is considered for performance comparisons. AWGN and the
Rayleigh fading channels are introduced.
Application of the proposed algorithm to low-bit-rate speech transmissions is studied. The
purpose of this application is to design the optimum low-bit—rate speech codecs, and thus
to improve the decoded speech quality over the noisy channels. It is known that the lowbit-
rate speech transmission is actually the transmission of speech parameters. Therefore,
the proposed algorithm designs and optimizes the speech parameter encoder/decoder pairs
by minimizing the transmitted parameter end—to-end distortions. As a result, the speech
distortion over the noisy channel is minimized, reproducing a quality decoded speech signal.
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Davis, Thomas A. "The evolution of literary theory towards a bio-cultural approach to literature through Jane Austen's Northanger Abbey /." Diss., Click here for available full-text of this thesis, 2006. http://library.wichita.edu/digitallibrary/etd/2006/t075.pdf.
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Davis, Thomas Arthur. "The evolution of literary theory: towards a bio-cultural approach to literature through Jane Austen’s Northanger Abbey." Thesis, Wichita State University, 2006. http://hdl.handle.net/10057/390.
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This thesis attempts to develop a synthesis of two traditionally conflicting epistemological approaches to literary theory and criticism. Over the past ten years, poststructuralist theory and the developing branch of cognitive and evolutionary literary theory have been at odds with one another. The overall purpose of this thesis strives to find a common ground between the two epistemological approaches to literature. In recent years, the emergence of a third epistemological position, situated between the two binary dichotomies, has sought to resolve the realist/relativist polemic through biocultural approaches to literature. This thesis will attempt to apply the bio-cultural approach to literature. The thesis first evaluates an existing poststructuralist argument, Jacqueline Howard’s Bakhtinian analysis of Jane Austen’s Northanger Abbey. Following this evaluation, an overview of cognitive and evolutionary theories’ connection to the Romantic period’s development of a brain-science will establish a biocultural approach to Austen’s Northanger Abbey and will situate cognitive and evolutionary theory within a cultural context. Finally, an analysis of Northanger Abbey from a cognitive and evolutionary standpoint will provide a synthesis of Howard’s basic premise and achieve a bio-cultural deconstruction of the realist/relativist polemic.Thesis (M.A.)--Wichita State University, Dept. of English.
"May 2006."
Includes bibliographic references (leaves 36-39)
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Freitas, Salgueiredo Camila. "Biomimicry and the low carbon vehicle : generation of innovative bio-inspired concepts using the C-K theory." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLE021/document.
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Le biomimétisme ou conception bio-inspirée est une approche qui propose l'utilisation du vivant en tant que source d'inspiration pour améliorer ou concevoir de nouvelles technologies. Intégrer la conception bio-inspirée au processus d'innovation des entreprises pourrait ainsi permettre la génération de concepts à la fois innovants et durables.Cette thèse, réalisée au sein de Renault avait deux objectifs: comprendre les mécanismes de la conception bio-inspirée et les appliquer à un cas concret dans l'automobile pour stimuler la génération de concepts en rupture.Pour comprendre les mécanismes de la bio-inspiration, nous nous sommes appuyés sur la littérature scientifique ainsi que sur les inventions et concepts bio-inspirés. Pour analyser le raisonnement de conception de ces exemples, nous avons choisi une théorie de la conception, la théorie C-K. Le cadre issu de la théorie C-K nous a permis de proposer un modèle général pour la conception bio-inspirée.Nous avons appliqué ce modèle au champ d'innovation du véhicule décarboné. Ce champ traite des questions liées au développement d'innovations permettant aux véhicules de réduire leur empreinte environnementale, principalement par la réduction des émissions de dioxyde de carbone (CO2), un puissant gaz à effet de serre qui contribue également au phénomène du changement climatique. L'identification des voies où la rupture serait nécessaire a débuté par la réalisation d'un arbre des concepts, à l'aide des connaissances internes disponibles en entreprise auprès des experts leaders. Un travail de réorganisation de ces concepts et la création d'une base de connaissances rassemblant articles scientifiques et expertises sur le sujet des émissions de gaz à effet de serre ont été effectués. Ce travail a permis de cartographier le champ d'innovation du véhicule décarboné. Les véhicules multi-énergies ont été la voie choisie pour la recherche de concepts bio-inspirés.Une recherche générale sur l'énergie dans le vivant nous a conduits à identifier l'énergie dans les cellules animales et particulièrement chez les humains comme une base de connaissances biologiques particulièrement intéressante. L'énergétique humaine possède un certain nombre de propriétés qui pourraient permettre une révision des connaissances sur les véhicules multi-énergie, notamment sur le stockage et la transformation d’énergie. La performance sportive humaine s'est aussi révélée être une base de connaissances intéressante par les différentes techniques utilisées pour les entrainements et en course afin de mieux mobiliser des sources d'énergie.L'application du modèle du processus de bio-inspiration avec C-K nous a conduit à formuler un concept inspiré des observations réalisées sur des coureurs pendant des courses supérieures à 1 500m. En effet, les profils de vitesse enregistrés pour des athlètes indiquent qu'une variation de vitesse est choisie par le coureur pour lui permettre de mieux utiliser ses réserves anaérobies limitées. Pour un véhicule, ceci pourrait impliquer qu'une variation de vitesse pourrait conduire à des meilleurs résultats en termes de consommation de carburant qu'une vitesse stabilisée. Ce concept a été exploré dans cette thèse à l’aide de la réalisation d'essais sur piste et des simulations avec des modèles numériques. Ces explorations montrent le potentiel de ce concept pour des véhicules conventionnels et aussi ses limitations.Ces travaux ouvrent des perspectives pour la gestion d'énergie des véhicules considérant la façon dont l'énergie est produite, stockée et utilisée chez le vivant. Les systèmes énergétiques étudiés par la physiologie humaine représentent un terrain intéressant pour le développement de véhicules adaptables à différents cas d'utilisation. De plus, l'étude du processus de la bio-inspiration a permis d'éclairer les raisons de faire appel à cette démarche et les conditions qui permettraient son application plus systématique dans les processus d'innovation en entrepriseBiologically inspired design, also called bioinspired design, biomimetics or biomimicryproposes the use of Nature, or biological knowledge, as a source of inspiration to improve orconceive new designs. Integrating the biologically inspired design approach into theinnovation process of companies could then allow the generation of more innovative and sustainable concepts.This thesis, realized during three years at a French automaker (Renault) research and development department had two objectives: to understand the mechanisms of the biologically inspired design and to apply this approach to a case belonging to an innovation field of the automotive sector.In order to understand the mechanisms of biologically inspired design we studied theliterature about bio-inspired concepts and inventions.We have chosen a design theory, the C-K theory, to analyse the design process of these literature examples. This allowed us to propose a model for bio-inspiration.We applied this model inspired by the C-K theory to the low carbon vehicle innovation field.This field includes the development of innovations allowing passenger cars to reduce theirenvironmental footprint, mainly the reduction of carbon dioxide (CO2) emissions. Thecarbon dioxide is a greenhouse gas that contributes to the climate change phenomena. Theidentification of the path where concept partitioning is required in this field began with theconstruction of a concepts space, using knowledge of company experts on the subject.Reorganizing these concepts and building a knowledge base on the strategies for CO2 emissions allowed us to map this innovation field. The vehicles with more than oneenergy source, such as electrified internal combustion engine vehicles and hybrid vehicleswere the path chosen for the research of bio-inspired concepts.A research about energy in nature led us to identify the energy in animal cells, particularlythose in humans as an interesting biological knowledge base. Human energy properties suchas cells with more than one kind of energy storage, with at least two metabolic pathways torecharge these stores are interesting to revise the knowledge about energy store andconversion in multi-energy vehicles. Besides, the human sportive performance has appearedto be an interesting knowledge base, as the training techniques and the running techniquesduring a race can influence the way athletes use their energy.These two biological bases have led us to formulate a bio-inspired concept based on therunning patterns observed in runners during races superior to 1500~m. The speed profilesrecorded show a spontaneous speed variation chosen by the runner, in order to better use itslimited anaerobic energy stores. For a vehicle, this could mean that varying its speed couldallow a lower fuel consumption than using a constant speed. This bio-inspired concept wasexplored in this thesis with the realization of tests in a dedicated test track and simulations. These tests show the potential of this concept for conventional vehicles and its limitations.This work opens the way for analysing the vehicle energetics in the light of human energetics.The versatility of human activities could help on the development of vehicles adapting todifferent use cases. Further research could also use the knowledge about the dynamic modelling of energy in vehicles to complete the empirical approaches used to model the human energy management, allowing a betteroptimization of running strategies. The study of the bio-inspiration process using a designtheory also allowed a better comprehension of the reasons for using this approach and of theconditions for successfully applying it in the innovative process of a company
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Docef, Alen. "Telemedicine applications of subband image coding at very low bit rates." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/14776.
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Cai, Jianfei. "Robust error control and optimal bit allocation for image and video transmission over wireless channels /." free to MU campus, to others for purchase, 2002. http://wwwlib.umi.com/cr/mo/fullcit?p3052158.
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Liu, Sam J. "Low bit-rate image and video compression using adaptive segmentation and quantization." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/14850.
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