Teses / dissertações sobre o tema "Son – Absorption – Matériaux"
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GUIGNOUARD, PHILIPPE. "L'absorption acoustique des materiaux poreux predictions et mesures". Le Mans, 1991. http://www.theses.fr/1991LEMA1018.
Texto completo da fonteLafarge, Denis. "Propagation du son dans les matériaux poreux à structure rigide saturés par un fluide viscothermique : définition de paramètres géométriques, analogie électromagnétique, temps de relaxation". Le Mans, 1993. http://cyberdoc.univ-lemans.fr/theses/1993/1993LEMA1009.pdf.
Texto completo da fonteThe important role played by the characteristic lengths A, A' , is demonstrated by impedance measurements, for different materials such as reticulated polyurethane foams, and glass wool. There follows a discussion of the very definition of the geometrical parameters, the symmetry between viscous and thermal effects, and the viscous and thermal relaxation times. An electromagnetic analogy is used, in order to characterize the physical definition of the problem. A connection between the various degrees of approximation and the successive moments of the relaxation times distributions is demonstrated. As a result, the so-called "universality" appears as being nothing but the approximation of degree 0. Finally, departures from the universality theory are briefly investigated
Cérézo, Véronique. "Propriétés mécaniques, thermiques et acoustiques d'un matériau à base de particules végétales : approche expérimentale et modélisation théorique". Lyon, INSA, 2005. http://theses.insa-lyon.fr/publication/2005ISAL0037/these.pdf.
Texto completo da fonteThis thesis deals with the measurement of physical properties (mechanical, thermal, acoustical) of various formulations of concrete containing vegetable particles. Such material is made up with hemp shives mixed with lime binders. Shives are very porous considering the ratio of capillaries. That fact explains that particles are lightweight, sensible to water and they can be highly strained. The ductile binder is a mixed between hydraulic and aerated lime with sometimes a volume of sand. Depending on the binder proportion, three microstructures of concrete are determined. Moreover, this material presents a microscopic porosity (shives) and a macroscopic porosity. These networks are connected. Vegetable concrete presents a ductile behavior. . The maximum stress and the Young modulus are limited as compare to other building materials but the bearable level of strain is rhigh. A theoretical model made with self-consistent method allows to calculate the Young modulus as a function of the mixture proportion and the compactness level. A comparison with experimental measurements shows a good accuracy of the results. Then, the dry thermal conductivity of vegetable concrete is studied. Considering its high sensibility to water, the level of sorption and the impact on thermal conductivity are evaluated. A self-consistent method leads to a model of dry and wet conductivity taking into account the physical properties (proportions, compactness) and the hygrometry. Lastly, the sound absorption of vegetable concrete is measured. The values are high. This first step in the study of the acoustical properties shows a behavior, which can be compared to materials with a double porosity
Gareton, Vincent. "Contribution à l'acoustique de conduits traités avec un matériau poreux : mesures de constantes élastiques et effets de la température". Nantes, 2003. http://www.theses.fr/2003NANT2104.
Texto completo da fonteOlny, Xavier. "Absorption acoustique des milieux poreux a simple et double porosité : modelisation et validation experimentale". Lyon, INSA, 1999. http://www.theses.fr/1999ISAL0114.
Texto completo da fontePorous materials are widely used as passive absorbers in noisy buildings or outdoor environment. It appears useful to be able to describe and adapt the material to wanted performances. Acoustics of simple porosity media is recalled using an homogenisation technique of periodic separated scale media (HSP). The main phenomenological existing models are also presented. Then the HSP method, well adapted to double porosity media, is used to point out the diversity of interscale couplings in realistic media. The theory is compared to experimental measurements performed on artificial double porosity materials made of micro porous perforated panels. It is shown that the behaviour of multi-scale porous media can be significantly different from single porosity material. Two microporous media are used to build double porosity media corresponding to the cases of high and low permeability contrast. It appears that a second network of pores can greatly improved the absorption of the initial microporous material in a wide range of frequencies. Regarding the experimental set-up, the low frequency measurements have been performed in a large standing waves tube using an adaptation of the single microphone transfer function method. Also, Periodic sinusoidal pseudo-random test signals have been shown to improve the quality of the measurement regarding the distortion effects
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.
Texto completo da fonteCastel, Franck. "Modélisation numérique de matériaux poreux hétérogènes : application à l'absorption basse fréquence". Lyon, INSA, 2005. http://theses.insa-lyon.fr/publication/2005ISAL0029/these.pdf.
Texto completo da fonteThis PhD thesis deals with the numerical modelling of the low frequency absorption of porous heterogeneous materials. A quadratic finite element method based on Biot-Allard's theory and on an equivalent fluid formulation has been implemented and validated. An auto adaptative meshing procedure has been developed and validated in the case of the equivalent fluid formulation. An a posteriori error estimator was used to evaluate the interpolation errors using a finite difference like derivative of the pressure gradient at the mesh nodes. A criterion has been established in order to control the mesh refinement. The developed tool has been used for the modelling of double porosity materials (materials with a double scale of pores). The results obtained confirm Olny's analytical results. The distinctive peak found on the absorption spectra is well predicted. Its position can be determined analytically for periodic homogeneisable materials. The dissipated powers within the mesh elements are used to interpret the diffusion layer and the associated absorption peak. Moreover, an optimisation technique based on a surface response method is also proposed for double porosity materials. The developed tool is finally used for a parameters study of double layer materials with lateral leaks. It is shown that air leaks affect more the first layer. This effect increases with the layer thickness and flow resistance. This study shows in particular that it is possible to enhance the absorption of materials with air partitions. The developed tool is reliable and easy to use. However, the proposed auto adaptative meshing technique is limited to the equivalent fluid formulation
Lemarinier, Pavel. "Propagation du son dans des mousses et une laine de verre a structures rigides saturees par de l'air : validation experimentale de modeles thermiques, analogie dielectrique, impregnation polymere d'une mousse". Le Mans, 1997. http://www.theses.fr/1997LEMA1004.
Texto completo da fonteChedly, Slaheddine. "Compromis choc acoustique des matériaux poreux : relations procédé – produit - performances". Reims, 2008. http://theses.univ-reims.fr/exl-doc/GED00000856.pdf.
Texto completo da fonteIn car industry, security is an important subject in recent years and car manufacturers involve in the development of new technologies so that their products are more reliable for passengers. In the current context concerning both pedestrian shock and vehicles noise, materials selection offering good compromise between these aspects is an important concern of vehicle manufacturers. One possibility is the use of poroelastic materials stuck under engine cowling, which offer good energy dissipation upon impact, and good attenuation of acoustic waves emitted by the engine. For this, knowledge of Process - Product - Performances relationships is necessary. Modeling tools (Responses Surface Method, Kriging,…) are used to build empirical models expressing shock and acoustic performances of porous materials in order to quantify the relationship Process - Performances and Product - Performances. In this brief, the choice of inputs, outputs and experimental design type is crucial in the prospect of building meta-models. Genetic algorithms were effective tool when searching porous materials shock - acoustic compromise according to process conditions and intrinsic characteristics. The purpose of this work is searching ideal material offering good performances in shock absorption and acoustic isolation in the design area of design
Houdouin, Alexandre. "Vers une paroi acoustique absorbante en technologie MEMS". Thesis, Le Mans, 2014. http://www.theses.fr/2014LEMA1020/document.
Texto completo da fonteThe work presented in this thesis focuses on the development of a sound absorbent thin solution able to absorb sound waves of low frequency (500 - 1500 Hz). Noise is, actually, the primary source of environmental pollution raised by the public. This discomfort requires the establishment of acoustic solutions in order to improve the acoustic comfort. However, under certain conditions, the thickness of absorbent solutions strongly limit their use. Indeed, in general, more frequencies are low more the acoustic solutions used must be thick. The sound absorption noise of the solution presented in this work is based on a network of miniature electrodynamic transducers controlled from appropriate electrical loads connected to the terminals of the transducers. An analytical model of the behavior of sound absorbing wall was developed. This model takes into account the behavior of electrodynamic transducers used and the acoustic coupling between the various sources that are particularly important in the area of low frequencies. This model has been validated by two means : i) finite element modeling and ii) measuring the absorption of acoustic prototypes. Two types of absorbent walls were made. One is based on commercial micro-speakers, the other on a miniature MEMS transducer of similar dimensions but the conversion efficiency is an order of magnitude greater than conventional micro-speakers. Analytical modeling has shown two ways of improvements that have been undertaken, the first on the removal of short circuits present at the transducer, the second on optimizing the force factor for improving the conversion efficiency of electro-mechanics. The results sound absorption obtained from the MEMS transducers show that the solution has a real interest in the low frequency range where conventional solutions are not very effective
Nennig, Benoit. "Contribution à l'étude de matériaux absorbants acoustiques en présence d'écoulement". Compiègne, 2010. http://www.theses.fr/2010COMP1858.
Texto completo da fonteThe propagation and absorption of sound waves in ducts with flow is a major issue in applied acoustics. The practical applications of such work range from noise transmission in vehicle exhaust systems, through ventilation and air conditioning ducts, to the prediction of more complex three-dimensional fields in aircraft engine-duct systems. In this work, we propose two methods in order to model non-locally reacting liners in the frequency domain. The Biot's model, which describes both solid phase and fluid phase acoustic interactions, is used in the absorbing poroelastic material. Depending on the problem, two approaches have been investigated: (i) A mode matching scheme has been developed in the case of a uniform mean flow and for circular ducts. This model has been shown to produce fast and accurate results when compared with a full FEM model. The technique allows us to identify respectively the influence of the elastic skeleton of the absorbing material well as the convection effects due the mean flow. (ii) To tackle more complex geometries, a finite element model based on Galbrun's equation (equivalent to the Linearized Euler Equations) has been developed. The refraction effects in the boundary layer on the Transmission Loss of dissipative silencers are shown
Thenail, Denis. "Contrôle actif d'impédance et optimisation des performances d'un matériau poreux". Ecully, Ecole centrale de Lyon, 1995. http://www.theses.fr/1995ECDL0011.
Texto completo da fonteIn its most developed version, active control of sound aims to create a cancelling secondary acoustic wave, which destructively interferes with the undesired noise. The performance of this noise reduction strategy is limited by the coherance level of the acoustic field, and by the volume of the zone to be made quiet. For a "large" system, in the presence of an incoherent field, the only potentially effective method to achieve a global noise reduction is to control the acoustic impedance at the walls, and hence to maximize acoustic absorption. Our first method for the active controL of acoustic impedance consists of processing the acoustic pressure and velocity informations close to the control actuator, in order to match the impedance with that of the air. In a KUndt's tube, this method works best for very low frequency excitations. Then, the active absorber is implemented along the lateral wall of a duct. The intensity measurements taken do show the absorption by the control speaker. It is shown through numerical calculations, that sound absorption has to be performed over an extensive area of the surface, as compared to the acoustic wavelenghts in the system. Therefore, we present a second method, which uses active control means to improve the acoustic absorption by a porous layer. We demonstrate through a model and experiments, that the impedance control can be reduced to a simpler acoustic pressure control at the rear face of the absorbent material. Thus, we can consider an extensive application of active absorption of sound at lower cost, a necessary constraint for practical applications
Roche, Jean-Michel. "Simulation numérique de l'absorption acoustique de matériaux résonants en présence d'écoulement". Le Mans, 2011. http://www.theses.fr/2011LEMA1027.
Texto completo da fontePerforated honeycomb panels are set in the aircraft inlet nacelles to reduce fan noise. The absorption of these resonant liners can be analytically predicted at low sound level, without a flow, but not when they are excited by high-level sound waves coupled with a grazing flow. Therefore, in order to improve their acoustic properties, a better understanding of their dissipation mechanisms and of the associated variations of their impedance is needed: this is the purpose of this PhD work. To achieve this aim, the behavior of a resonator impacted by different kinds of excitations is numerically computed, by three-dimensional direct numerical simulations (the compressible Navier-Stokes equations are solved) performed on the ONERA CFD CEDRE code. The effects of a rise of sound level over the acoustic properties of the resonator are first highlighted and evaluated, for a normal incidence and then for a grazing one, by "global" approaches (based only on the fluctuating fields in areas far from the resonator opening) and "local'' approaches (based on the fluctuating fields in the opening inlet). The relative efficiency of the dissipation mechanisms by wall friction and by vortex shedding is studied and the nature of the nonlinearity of absorption is clarified and discussed. The more complex configuration of an acoustic excitation coupled with a stationary 0. 1 Mach number flow is then studied. The additional nonlinearities generated by the presence of the flow are highlighted by numerical simulation and validated by comparison with Laser Doppler Velocimetry measurements carried out on the aerotherrno-acoustic bench of ONERA. Their impact on the impedance of the resonator is quantified, the results being ultimately compared to empiric models
Hu, Ying. "Développement de panneaux hybrides passifs/actifs pour l'acoustique". Phd thesis, Ecole Centrale de Lyon, 2010. http://tel.archives-ouvertes.fr/tel-00627868.
Texto completo da fonteLacour, Olivier. "Réduction du bruit par contrôle actif d'impédance : application à des problèmes vibroacoustiques internes". Lyon 1, 1998. http://www.theses.fr/1998LYO10113.
Texto completo da fonteDupont, Samuel. "Caractérisation de matériaux acoustiques par antennes microphoniques sphériques et hémisphériques". Thesis, Le Mans, 2020. http://www.theses.fr/2020LEMA1016.
Texto completo da fonteSound absorbing materials such as foams, textiles or carpets are used in many areas to absorb sound. This can be for protection (workers) or comfort (buildings, cars, airplanes, etc.).In order to dimension and choose which material to use according to each situation, predictive calculations are used based on characterizations giving the absorption coefficients and/or surface impedance of the said materials.The characterizations are typically carried out in the laboratory using standardized measurements techniques such as the impedance tube or the reverberation chamber method. However, these have many limitations. The problematic of this PhD project is to find solutions by using a microphone antenna system to determine the properties of acoustic materials in a reliable and robust way while overcoming the limitations of conventional methods. This document is a synthesis of the work carried out in this direction. The problem is addressed through two main approaches, the holographic type approaches where one reconstructs the sound pressure and the normal particle velocity to estimate the surface impedance and the model matching (optimization) approaches where one identifies the surface impedance that minimizes the error between the measurements and the model.These models are presented for different microphone antenna geometries: spherical, hemispherical and planar. They are separated between methods that depend on one geometry and those that can be applied to several geometries.Simulations and experiments are shown to validate the developed models
Valibouse, Pierre. "Mesure des caractéristiques intrinsèques des matériaux dans l'eau, avec un tube à impédance en incidence normale". Compiègne, 1990. http://www.theses.fr/1990COMPD317.
Texto completo da fonteHuang, Weichun. "Acoustic properties of natural materials". Thesis, Le Mans, 2018. http://www.theses.fr/2018LEMA1031/document.
Texto completo da fonteStraw-inspired metamaterials for sound absorption are investigated in this Thesis. A straw stack is idealized as a highly concentratedresonant anisotropic porous medium constituted of a periodic arrangement of densely packed cylindrical hollow tubes. The approach tothis metamaterial relies on the two-scale asymptotic homogenization of a permeable array of perfectly rigid resonators, where the physicsis further enriched by tailoring inner resonances. The main features of such sound absorbing medium are the possibility for the effectivecompressibility to become negative around the tube resonance and the drastic reduction of the effective sound speed (slow sound) at verylow frequency in the system. Moreover, an optimal configuration for sound absorption is designed, based on the critical couplingcondition, in which the energy leakage out of the open resonant system is perfectly compensated by the intrinsic losses induced by thevisco-thermal losses both in the anisotropic matrix and in the resonators. Impedance tube measurements are performed on 3-D printedsamples with controlled parameters to validate the theoretical results. This metamaterial is a sub-wavelength absorber that can achievetotal absorption at a very low frequency and possesses a quasi-band-gap around the tube resonance. Furthermore, the anisotropic nature ofthe configuration gives rise to high absorption at low-frequency range for all incidences and diffuse field excitation. It paves the way tothe design of angular and frequency selective sound absorber. To conclude, the results of this Thesis show that straw is a good candidatefor perfect sound absorption
Amiot, Marion. "Mise en œuvre et étude de structures de nontissés et de composites poreux multifonctionnels en para-aramide : absorption acoustique et résistance à l’impact". Thesis, Lille 1, 2012. http://www.theses.fr/2012LIL10047.
Texto completo da fonteThe aim of this thesis is to develop fibrous structures in view of using them as core material in sandwich structures, for impact resistance and acoustic applications. Thick para-aramid nonwovens have hence been manufactured, with porosities above 90% and densities below 150 kg/m3. Their thickness was around 10 mm. Porous composites have been obtained from these nonwovens, using various resins (namely epoxy), and with a technique that allows to keep a high porosity level of 80% in the final structure.The internal porous architecture has been studied through different methods and parameters: the equivalent pore sizes, the isotropy, the fibre distribution/orientation and the degree of fibre entanglements have been evaluated with different experimental techniques (air permeability; tensile/compression tests; capillarity; porometry) and using theoretical models (permeability, van Wyk). The structural parameters have been related to the process parameters. The acoustic measurements have shown that our nonwovens were good acoustic absorbers at frequencies above 4000 Hz. The use of two models, Delany and Bazley, and Jonhson and Allard, has shown that the acoustic absorption behaviour can be modelled with the material characteristics (thickness, resistivity and an equivalent pore diameter). The capacity of our materials to absorb and dissipate energy has been evaluated with compression testing. The main mechanisms involved are fibre friction, fibre breakage and structure deformation. Finally, the impact tests performed on nonwovens and their composites have demonstrated the real potential of nonwovens to be used at the core of sandwiches to absorb impact
Bardot, Anne. "Modélisation acoustique basses fréquences de cavités en présence d'absorbants sur parois rigides ou élastiques". Compiègne, 1992. http://www.theses.fr/1992COMP0424.
Texto completo da fonteBardot, Anne. "Modélisation acoustique basses fréquences de cavités en présence d'absorbants sur parois rigides ou élastiques". Compiègne, 1992. http://www.theses.fr/1992COMPD424.
Texto completo da fonteRégniez, Margaux. "Amortissement des vibrations de réflecteur d'antenne de satellite par micro-perforations". Thesis, Le Mans, 2015. http://www.theses.fr/2015LEMA1022/document.
Texto completo da fonteThis thesis work is about the study of the microperforations influence on the vibratory response of a cellular structure as a honeycomb sandwich panel. Satellites' antenna's reflectors placed on telecommunication satellites, as many satellites' elements, are manufactured in this kind of materials. During the launcher take-off for putting satellite into orbit, the mechanical stresses applied to the system are acoustical and vibration borne stress. The acoustic stress, linked to the high level diffuse acoustic field inside the launcher fairing is the most important. It plays a part in the antenna's reflector size and conception. The issue of the thesis is to evaluate the potential of a treatment using microperforations on this panel in order to reduce its vibration. The microperforations effect on the vibration response of the antenna's reflector is double. On one hand, the acoustic loading applied by the exciter pressure is reduced by an absorption mechanism due to the presence of microperforations, coupled to cavities formed by honeycomb cells. This effect, well known in the litterature, is for instance described by the acoustic impedance model developped by D.-Y. Maa, coupled to an impedance model of honeycomb cavity and taking into account the inner and outer radiations of the microperforation. On the other hand, a vibro-acoustical effect is induced by the coupling between panel vibrations and acoustic movements inside microperforations. The modelling of this effect, not well described in the litterature, constitutes an original element of the thesis work: a discrete model constructed using the acoustic impedance of an orifice, allows the computation of an elementary damping force and then leads, after an homogenisation, to an estimation of the modal damping of the microperforated panel. Both modellings proposed for the acoustic loading reduction and the damping added by microperforations, show that the panel vibration response is weakly reduced in the frequency band of interest, which confirms experimental tests like: response comparison of non microperforated and microperforated panels placed in reverberant room and noise chamber. The acoustic loading modification induced by the microperforation of both sides of the honeycomb sandwich panel is modelling in the thesis last chapter and allows an increase of the effect on the frequency band aimed
Donda, Krupali. "Low-frequency Absorbing Acoustic Metasurfaces : Deep-learning Approach and Experimental Demonstration". Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0268.
Texto completo da fonteThe advent and development of acoustic metamaterials and metasurfaces in recent years has overturned conventional means in all aspects of acoustic waves propagation and manipulation. In the context of the sound absorption and noise conrtol, it has offered an unprecedented expansion of our ability to attenuate the low-frequency sound beyond the classical physical limits. The main aim of this PhD dissertation is to conceive and design acoustic metasurfaces for extreme low-frequency absorption (<100Hz). First, the concept of multicoiled metasurface absorber (MCM) is proposed and discussed. The effectiveness of its physical mechanism is theoretically, numerically, and experientially demonstrated. The presented multicoiled metasurface is capable of fully absorbing acoustic energy at extreme low-frequency of 50Hz with a deep subwavelength thickness (λ/527). To circumvent the conventional physics- and rule-based approaches and accelerate the design process, novel deep learning-based framework is introduced in this dissertation. Specifically, the convolutional neural network (CNN) and conditional generative adversarial networks (CGAN) are implemented to simulate and optimize complex metasurface absorber structures. The developed deep learning-based framework for the acoustic metasurface absorbers can be potentially extended to the design and optimization of other acoustic devices and structures. This dissertation provides a new way for deep learning-enabled acoustic metasurface designs that will allow acoustics community to focus more on truly creative and pragmatic ideas. This will be led to solving complex design problems that have yet to be explored by the machine, rather than on tedious trial and error processes
Chan, Charles. "Outil d’aide à la conception d’un traitement acoustique basé sur des matériaux poreux pour la réduction du bruit de soufflante". Thesis, Compiègne, 2015. http://www.theses.fr/2015COMP2253.
Texto completo da fonteThe constant need to reduce noise emissions from aircraft engine leads to a real demand for developing new acoustic treatments. Conventional liners based on resonatorlike structure continue to be used and provide narrow-band attenuation in spite of an increasing degree of freedom. A possible alternative is the use of porous materials (nonlocally reacting), which offer the possibility of broadening the attenuation spectrum. This report deals with the modelling of an acoustic treatment based on porous materials for aeroengine nacelle inlet. A semi-analytical model is developed for predicting the transmission loss of a treated cylindrical duct containing uniform mean flow. Then, a parametrical study is carried out in order to target the optimal liner characteristics for a given turbofan duct application. Also, experiments have been performed on a small-scale duct and have shown agreement with the simulation. Finally, for a better theoretical unv derstanding of the problem, a preliminary study on the effect of a boundary layer is conducted and shows that its consideration seems to be essential for optimal choice of acoustic lining, espacially at high frequencies
Primus, Julien. "Détermination de l'impédance acoustique de matériaux absorbants en écoulement par méthode inverse et mesure LDV". Thesis, Toulouse, INSA, 2012. http://www.theses.fr/2012ISAT0026/document.
Texto completo da fonteWhile aircraft noise constraints become increasingly stringent, efficient duct treatment of turbofan engines requires an accurate knowledge of liner impedance with grazing flow at high acoustic levels. This thesis aims at developing an impedance eduction method in the presence of grazing flow. The inverse process is based on acoustic velocity fields acquired by Laser Doppler Velocimetry (LDV) above the liner. The liner acoustic impedance is obtained by minimization of the distance between the measured acoustic velocity field and the simulated one. Computations rely on the resolution of the 2D linearized Euler equations in the harmonic domain, spatially discretized by a discontinuous Galerkin scheme. The gradient of the objective function is achieved by the resolution, at each iteration on the liner impedance, of the direct and adjoint equations. The solver is first validated on academic test cases, then on experimental results of acoustic pressure measurements at the rigid wall opposite the liner. Secondly the method is applied to acoustic velocity measurements obtained by LDV above the liner without flow, in the ONERA B2A test bench. The last step consists in taking into account the effects of a sheared grazing flow. The impedances educed from LDV measurements in the presence of flow namely allowed to gain insight into the absorption phenomena occuring in the B2A test bench
Leroy, Pierre. "Les mousses adaptatives pour l'amélioration de l'absorption acoustique : modélisation, mise en oeuvre, mécanismes de contrôle". Phd thesis, Université de Provence - Aix-Marseille I, 2008. http://tel.archives-ouvertes.fr/tel-00352363.
Texto completo da fonteXiong, Lei. "Use of mode coupling to enhance sound attenuation in acoustic ducts : effects of exceptional point". Thesis, Le Mans, 2016. http://www.theses.fr/2016LEMA1017/document.
Texto completo da fonteTwo strategies are presented to use the mode coupling effects to enhance sound attenuation in acoustic ducts. The strategy is to couple the incoming propagative mode with the localized mode, which is also called Fano resonance. This strategy is presented and validated in a duct-cavity system and a waveguide partially lined with a locally reacting material. The R-matrix method is introduced to solve the propagation problems. A zero in the transmission is present, due to the excitation of a trapped mode which is formed by the interferences of two neighboured modes. It is also linked to the avoided crossing of the eigenvalues and exceptional point. In the second strategy, a set of periodic rigid inclusions are embedded in a porous lining to enhance sound attenuation at low frequencies. The mode coupling is due to the presence of the embedded inclusions. Floquet - Bloch theorem is proposed to investigate the attenuation in a 2D periodic waveguide. Crossing is observed between the mode attenuations of two Bloch waves. The most important and interesting figure is that near the frequency where the crossing appears, an attenuation peak is observed. This phenomenon can be used to explain the transmission loss peak observed numerically and experimentally in a 3D waveguide partially lined by a porous material embedded with periodic inclusions. Finally, the acoustical behaviours of a purely reacting liner in a duct in absence and presence of flow are investigated. The results exhibit an unusual acoustical behaviour : for a certain range of frequencies, no wave can propagate against the flow. a negative group velocity is found, and it is demonstrated that the sound can be slowed down and even stopped
David, Sylvain. "Aza-bodipy pour la limitation optique aux longueurs d'onde des télécommunications : synthèse des chromophores, optimisation de matériaux hybrides et études photophysiques". Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEN010.
Texto completo da fonteAn optical power limiter (OPL) is a device which can change its optical properties depending on the input light power. Ideally transparent at low incident power, the OPL transmission decreases when the incident power rises, allowing the protection of an optical detector placed beyond the OPL and avoiding temporary or permanent damages. This thesis presents the synthesis of aza-bodipy dyes with OPL properties in the telecommunication spectral range, particularly around 1500 nm. The OPL properties of these aza-bodipy dyes are based on simultaneous two-photon absorption and excited state absorption.The first part of this thesis describes the synthesis of new aza-bodipy dyes for the study of two photon absorption and excited state absorption enhancement in order the optimize the OPL performances of the dyes. A study about aza-bodipy solubility has also been conducted.The second part of this thesis presents the use of aza-bodipy chromophores in new optimized sol-gel hybrid materials. Class-II sol-gel materials development permitted to spectacularly increase the maximum dye-doping concentration, which resulted in a strong enhancement of the OPL properties compared to previously described materials
Caturla, Latour Virginie. "Elaboration, caractérisation et mise en oeuvre pour la décontamination d'effluents gazeux, de matériaux photocatalytiques originaux à base de photosensibilisateurs supportés". Pau, 2004. http://www.theses.fr/2004PAUU3026.
Texto completo da fonteThe goal of this work was to evaluate a photocatalytic process in the gas phase on test pollutants, i. E. Dimethylsulfide (DMS) and toluene. Original photocatalytic materials, based on aromatic sensitizers in a silica network, were elaborated and their efficiency was compared to that of titanium dioxide. In a first step, the oxidation of DMS and toluene was studied in solution with different sensitizers, and only 9,10-dicyanoanthracene (DCA) and 9,10-anthraquinone (ANT) were found to fulfil the defined requirements. In a second step, for gas phase treatment, the chosen photosensitizers were fixed on silica, either by encapsulation in sol-gel monoliths or by physisorption on commercial silica beads. These hybrids materials were characterised and their photocatalytic activity at the gas-solid interface estimated by DMS and toluene oxidation. The choice of the photosensitizers, (photocatalytic efficacy, activation in the visible range) and the matrix properties (transparency and capacity of adsorption) are key parameters. DCA encapsulated sol-gel monoliths were found to be the most efficient materials for DMS conversion. On the contrary hydrophobic materials with better absorption capacity appear to be promising for the photoxidation of toluene. These results indicate that supported photosensitizers may find some possible applications for the treatment of polluted gases
Chateau, Denis. "Etude de l'influence de la structure et de la composition de matériaux hybrides monolithiques sur les propriétés optiques (luminescence et absorption non-linéaire)". Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2013. http://tel.archives-ouvertes.fr/tel-00863807.
Texto completo da fonteBinois, Remy. "Etude de l'efficacité des silencieux à baffles parallèles et conception de solutions optimisées en basses fréquences". Electronic Thesis or Diss., Paris 6, 2014. http://www.theses.fr/2014PA066523.
Texto completo da fonteBaffle-type silencers are widely used in the heating, ventilation and air conditioning (HVAC) systems of buildings to reduce noise being emitted from air-moving devices such as fans and air conditioners. These silencers generally consist of several baffles inserted in a duct with a rectangular cross section. Each baffle is made of sound absorbing material such as rockwool or glasswool. Usually, a metallic fairing is also placed at each end of the baffle. This thesis aims to analyze the effectiveness of these acoustic silencers to improve performance at low frequencies. First, a two-dimensional multimodal model is developed to predict the transmission loss for a wide variety of this type of silencer. The numerical model relies mainly on the computation of approximate acoustic modes for the mean pressure in each layer corresponding either to the airway or the baffle. The method offers the advantage that it greatly simplifies the mode matching procedure at the junction between successive domains and it can be used to tackle relatively complex geometrical configurations with the possibility of taking into account the presence of resistive screens between the porous baffle and the air domain. It is also an easy-to-implement and relatively inexpensive model suitable for optimization purposes. It has been experimentally validated in two measurement campaigns at reduced and actual scales. In a second step, the developed model is used to investigate different ways of improving performance at low frequencies. Suggested improvements are discussed in the case of standard silencers regarding the influence of the number of baffles, symmetry and periodicity of the silencer on the modal coupling and acoustic performance. For confidentiality reasons, other suggested improvements and optimized solutions are not included in this version
Devillers, Philippe. "Couplages thermohydromécaniques en milieux poreux : application à la consolidation d'un sol non saturé". Montpellier 2, 1998. http://www.theses.fr/1998MON20069.
Texto completo da fontePiquemal, Philippe. "Élaboration d'un nouveau matériau isolant phonique et thermique en verre expansé et mise au point d'un procédé utilisant un chauffage diélectrique". Nancy 1, 1988. http://www.theses.fr/1988NAN10203.
Texto completo da fonteWang, Irène. "Matériaux organiques microstructurés et optique non linéaire : 1. Nanocristaux organiques en matrice sol-gel pour l'optique quadratique, 2. Polymérisation initiée par absorption à deux photons pour la microfabrication 3D". Phd thesis, Université Joseph Fourier (Grenoble), 2002. http://tel.archives-ouvertes.fr/tel-00008089.
Texto completo da fonteLagarrigue, Clément. "Métamatériaux performants dans la gamme des fréquences audibles : simulations et validations expérimentales". Thesis, Le Mans, 2013. http://www.theses.fr/2013LEMA1037/document.
Texto completo da fonteSince several decades, photonic and phononic crystals are the center of numerous studies and in particular in the optics,electromagnetism and acoustics fields. These metamaterials, created by a periodic array of inclusions, have propertiesimpossible to obtain with usual materials. They can, for example, bend the waves or stop the waves for some frequencyranges (band gap). By changing the characteristic of the unit cell, it is possible to combine transmission losses linked to theperiodicity, with low frequency resonances linked to the type of scatterer (rigid, resonator...) and obtain very low transmissioncoefficient or very high absorption coefficient on very large frequency ranges depending on the device. Two metamaterialsdevices are studied to find alternative solutions, for acoustics problems, by using periodic array of scatterers. The first deviceis a sonic crystal used has an noise barrier and built with drilled bamboo rods, that have low frequency transmission losses(around 300 Hz and around 2000 Hz). The second device is a periodic array of resonant inclusions embedded in a porousplate that can absorb almost all the waves for a wide frequency range that correspond to wavelength up to 10 times bigger than de thickness of the plate. The behavior of this two devices are studied theoretically, experimentally and numerically by using several methods (Plane Waves Expansion, Multiple Scattering Theory for the first device and finite element method for the second). All this methods allow to bring out the very good performances of this metamaterials devices in audiblefrequency range
Bindini, Elisa. "Understanding in vivo degradation of mesoporous silica therapeutic vectors through in situ ellipsometry". Electronic Thesis or Diss., Sorbonne université, 2018. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2018SORUS115.pdf.
Texto completo da fonteDans les dernières 15 ans, la recherche biomédicale a exploré en profondeur l’utilisation de nanoparticules pour la délivrance ciblée de médicaments. Parmi plusieurs matériaux étudiés, la silice mesoporeuse représente une plateforme exceptionnelle pour ce type d’applications puisque elle est biocompatible et capable d’être chargé avec une quantité élevée de médicament, tout en étant facile à synthétiser et à fonctionnaliser .La connaissance des interactions entre nanoparticules de silice et environnement biologique est nécessaire pour concevoir des vecteurs thérapeutiques efficaces et pas toxiques. Cet étude a développé une nouvelle méthode d’analyse in situ pour suivre les interactions entre silice mesoporeuse et fluides biologiques réels (serum et sang), employant une cellule d’analyse microfluidique et l’ellipsometrie en réflexion totale interne. Nous avons ainsi réalisé le suivi dynamique de la dégradation de vecteurs models à base de silice poreuse structuré dans une solution tampon à pH physiologique et une solution concentré de protéines. Ces analyses ont permis d’évaluer l’influence de la structure poreuse, de l’adsorption de protéines sur la surface et de la vitesse du flux sur la dissolution de la silice mesoporeuse
Ruiz, Thierry. "Eléments de modélisation et contribution expérimentale à l'étude du transport réactif dans un sol non saturé". Montpellier 2, 1998. http://www.theses.fr/1998MON20134.
Texto completo da fonteBinois, Remy. "Etude de l'efficacité des silencieux à baffles parallèles et conception de solutions optimisées en basses fréquences". Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066523.
Texto completo da fonteBaffle-type silencers are widely used in the heating, ventilation and air conditioning (HVAC) systems of buildings to reduce noise being emitted from air-moving devices such as fans and air conditioners. These silencers generally consist of several baffles inserted in a duct with a rectangular cross section. Each baffle is made of sound absorbing material such as rockwool or glasswool. Usually, a metallic fairing is also placed at each end of the baffle. This thesis aims to analyze the effectiveness of these acoustic silencers to improve performance at low frequencies. First, a two-dimensional multimodal model is developed to predict the transmission loss for a wide variety of this type of silencer. The numerical model relies mainly on the computation of approximate acoustic modes for the mean pressure in each layer corresponding either to the airway or the baffle. The method offers the advantage that it greatly simplifies the mode matching procedure at the junction between successive domains and it can be used to tackle relatively complex geometrical configurations with the possibility of taking into account the presence of resistive screens between the porous baffle and the air domain. It is also an easy-to-implement and relatively inexpensive model suitable for optimization purposes. It has been experimentally validated in two measurement campaigns at reduced and actual scales. In a second step, the developed model is used to investigate different ways of improving performance at low frequencies. Suggested improvements are discussed in the case of standard silencers regarding the influence of the number of baffles, symmetry and periodicity of the silencer on the modal coupling and acoustic performance. For confidentiality reasons, other suggested improvements and optimized solutions are not included in this version
Bindini, Elisa. "Understanding in vivo degradation of mesoporous silica therapeutic vectors through in situ ellipsometry". Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS115/document.
Texto completo da fonteDans les dernières 15 ans, la recherche biomédicale a exploré en profondeur l’utilisation de nanoparticules pour la délivrance ciblée de médicaments. Parmi plusieurs matériaux étudiés, la silice mesoporeuse représente une plateforme exceptionnelle pour ce type d’applications puisque elle est biocompatible et capable d’être chargé avec une quantité élevée de médicament, tout en étant facile à synthétiser et à fonctionnaliser .La connaissance des interactions entre nanoparticules de silice et environnement biologique est nécessaire pour concevoir des vecteurs thérapeutiques efficaces et pas toxiques. Cet étude a développé une nouvelle méthode d’analyse in situ pour suivre les interactions entre silice mesoporeuse et fluides biologiques réels (serum et sang), employant une cellule d’analyse microfluidique et l’ellipsometrie en réflexion totale interne. Nous avons ainsi réalisé le suivi dynamique de la dégradation de vecteurs models à base de silice poreuse structuré dans une solution tampon à pH physiologique et une solution concentré de protéines. Ces analyses ont permis d’évaluer l’influence de la structure poreuse, de l’adsorption de protéines sur la surface et de la vitesse du flux sur la dissolution de la silice mesoporeuse
Campagne, Benjamin. "Non linéarités optiques dans les matériaux xérogels et polymères dopés. Application a la protection passive de senseurs contre les impulsions laser". Phd thesis, Université Paris Sud - Paris XI, 1999. http://pastel.archives-ouvertes.fr/pastel-00713905.
Texto completo da fonteOuoba, Samuel. "Adsorption et transport d'un composé organique volatil (COV) dans un sol hygroscopique : application aux pesticides dans un sol aride". Phd thesis, Montpellier 2, 2009. http://www.theses.fr/2009MON20256.
Texto completo da fonteThe objective of this work is to analyze and model the transport of a pollutant in the surface layer of unsaturated soil. We are particularly interested to hygroscopic soils where components of the liquid phase are strongly linked to the solid phase. Mass transfer occurring in the liquid phase and gas, taking into account the change of phase liquid-gas. Using an original apparatus, we analyze first the isothermal desorption of water, heptane, trichlorethylene (TCE) and the mixture water + TCE in two soils; one containing clay and organic matter, the other, from Burkina Faso (BF), has lower proportions of these constituents. The phase change liquid-gas of TEC has been experimentally studied in the soil of Burkina with different experimental conditions in temperature and pressure. All the bibliographic and experimental works led us to propose a mathematical model. The validation of the model has focused on the transfer of water only by comparison with transfer experiments on soil columns. This model reflects particularly well the flow of water to the surface and changing profiles of water content in columns. This model is also well suited to describe the water transfer at the interface soil-atmosphere in arid zone. In a second part, we examine the transfer of TCE in the surface layer. Sensitivity studies were conducted on thick layer of soil, water content, the initial concentration of TCE, the Henry constant and the coefficient of phase change. This study highlights the importance of different parameters on the transfer of a volatile organic compound showing that it is necessary to conduct parallel investigations in the laboratory and in situ
Ouoba, Samuel. "Adsorption et transport d'un Composé Organique Volatil (COV) dans un sol hygroscopique. Application aux pesticides dans un sol aride". Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2009. http://tel.archives-ouvertes.fr/tel-00731315.
Texto completo da fonteVenet, Saphir. "Stockage du CO2 et séparation CO2/CH4 par des matériaux de silice à porosité et fonctionnalité contrôlées : étude expérimentale et modélisation de dynamique moléculaire". Thesis, Pau, 2018. http://www.theses.fr/2018PAUU3027/document.
Texto completo da fonteThis work aims to evaluate the performance of silica-based materials and to rationalize their synthesis according to their desired adsorption properties (capacity and/or selectivity) by combining experimental approaches and the management of the molecular animal. These materials are ideally suited for CO2 adsorption capacity but also CO2/ CH4 selectivity. The different stages of this work were:- the synthesis and functionalization of the silica materials,- their textural and chemical characterization,- the determination of CO2 adsorption capacities, of their CO2/ CH4 selectivity.- the characterizations by various spectroscopic and microscopic techniques of tests to try to locate the adsorption of CO2 and to measure its mobility,- microscopic identification by the factor of physic-Factors influence the preferential adsorption of CO2 and its diffusivity in the role of hydrophilic / hydrophobic character in silica by functional.These objectives required the preparation of high specific surface materials through a simple sol-gel process. These materials have been modified in order to obtain a degree of functionalization with -CH3 groups sufficient to modify the hydrophilic nature of the material while maintaining a sufficient specific surface area. The influence of pore size was also probed.The adsorption capacities of the gases under pressure were carried out for pure gases but also on CO2/ CH4 mixtures in different proportions. The CH4/ CO2 selectivity, often estimated from the pure body isotherms and / or the IAST method, was in this case determined from the direct measurement of the isotherms of the gas mixtures. It has become apparent that water plays a crucial role in adsorption capacity and selectivity. This parameter is one of those studied through molecular dynamics simulations. The influence of the introduction of hydrophobic groups has also been explored.The results obtained by molecular dynamics are on the whole in good agreement with the experimental data. These two parallel experience / theory approaches have highlighted the selectivity of one of the materials for applications where the gaseous effluent is little loaded with CO2
Yuan, Haifeng. "Caractérisation expérimentale des propriétés de poromécaniques et de transfert de l’argilite du COx". Thesis, Ecole centrale de Lille, 2017. http://www.theses.fr/2017ECLI0030/document.
Texto completo da fonteCOx argillite has been selected as the host rock for the storage of high-activity long-live (HALL) radioactive waste in France. It will suffered the gas and water intrusion, sometimes suffered the severe thermal conditions during the sealing process. Therefore, in order to evaluate the safety of this natural barrier, it is very important to understand the poromechanical properties and transport properties of this material as well as the thermal effects. This work use gas to measure Biot’s coefficient and shows that it is nearly equal to 1 in humid conditions. However, there is a gas adsorption and induced an additional swelling deformation on dry material, this effect also has a significant effect on the transport properties of the gas according to its nature. The transport and saturation properties were examined by gas technique and compared with the usual measurements. The tests also show that the permeability of in situ water is about 10-20-10-21 m² and much lower than gas. Lastly, it is found that Biot’s coefficient is not significantly affected by the thermal effect, but the relative gas permeability of argillite is significantly affected by this effect