In the mammalian auditory system, specifically in the cochlea of the inner ear, the Basilar Membrane (BM) and hair cells are responsible for transducing incoming acoustic waves into electrical signals. These acoustic signals are carried as traveling waves by the BM and propagate from the base of the cochlea toward its apex where the helicotrema is located. An impressive feature of the mammalian auditory system is to prevent the propagated waves from reflecting which allows mammals to hear sounds without any reflection or overlap. This extraordinary characteristic of the inner ear is the main inspiration for this work. In the present study, the dynamic behavior of a beam structure with one or more attached spring-damper (SD) systems as passive absorbers is studied when excited by a harmonic force. The location of the spring-damper system divides the beam into two dynamic regions: one which exhibits non-reflecting traveling waves and the other with standing waves. In this work, the separation of traveling and standing waves is studied analytically, numerically, and experimentally. To the best of the author's knowledge, this is the first time in the literature that traveling and standing wave separation in a beam is realized experimentally using a single-point excitation and a spring-damper. Experimental results are used to validate the models of the system. Moreover, a parametric study is performed to gain a better understanding of the effect of different parameters on the quality of the generated waves in the structure. Furthermore, the effect of attaching the second spring-damper to the system is presented. Adding the secondary SD system results in increasing the excitation frequency range so that wave separation can be achieved. The results of this work can be used in various applications such as vibration suppression, energy absorption, particle transportation, and in exploring possible explanations for the BM and helicotrema functions in the cochlea. / Doctor of Philosophy / In the inner ear of the mammalian auditory system, the sound waves travel inside the cochlea where they are converted to electrical signals sent to the brain. A fascinating characteristic of the mammalian auditory system is that the sound waves traveling in the cochlea do not reflect when they reach its apex where the helicotrema is located. Therefore, we are able to hear sounds without any reflection or overlap. This work is inspired by the biological behavior of the inner ear and studies the dynamic behavior of a simple structure such as a beam with one (or two) attached spring-damper(s). In this work, the attached spring-damper system(s) prevents the waves traveling from the source to the beam's boundary from reflecting. This is similar to what happens in the inner ear. The location of the spring-damper divides the beam into two dynamic regions, one which exhibits non-reflecting traveling waves and the other with standing waves. The wave separation and parameters affecting the wave quality and its reflective or non-reflective features are studied analytically, numerically, and experimentally. To the best of the author's knowledge, the experiments carried out to generate the aforementioned wave types coexisting with each other on the beam are one of a kind. Furthermore, the results of this study showed a very good agreement between the experimental and theoretical results. The outcomes of this work can potentially be used in exploring possible explanations for the function of the cochlea and helicotrema and various applications such as particle transportation and suppression of unwanted vibrations.

<p>The presence of vibration is an important problem in many engineering applications. Various passive techniques have traditionally been used in order to reduce waves and vibrations, and their harmful effects. Passive techniques are, however, difficult to apply in the low frequency region. In addition, the use of passive techniques often involve adding mass to the system, which is undesirable in many applications.</p><p>As an alternative, active techniques can be used to manipulate system dynamics and to control the propagation of waves and vibrations. This thesis deals with modeling, estimation and active control of systems that have resonant dynamics. The systems are exposed to stochastic disturbances. Some of them excite the system and generate vibrational responses and other corrupt measured signals. </p><p>Feedback control of a beam with attached piezoelectrical elements is studied. A detailed modeling approach is described and system identification techniques are employed for model order reduction. Disturbance attenuation of a non-measured variable shows to be difficult. This issue is further analyzed and the problems are shown to depend on fundamental design limitations.</p><p>Feedforward control of traveling waves is also considered. A device with properties analogous to those of an electrical diode is introduced. An `ideal´ feedforward controller based on the mechanical properties of the system is derived. It has, however, poor noise rejection properties and it therefore needs to be modified. A number of feedforward controllers that treat the measurement noise in a statistically sound way are derived.</p><p>Separation of overlapping traveling waves is another topic under investigation. This operation also is sensitive to measurement noise. The problem is thoroughly analyzed and Kalman filtering techniques are employed to derive wave estimators with high statistical performance. </p><p>Finally, a nonlinear regression problem with close connections to unbalance estimation of rotating machinery is treated. Different estimation techniques are derived and analyzed with respect to their statistical accuracy. The estimators are evaluated using the example of separator balancing. </p>

Ce travail de thèse porte sur l’analyse et le traitement des signaux ultrasonores pour la caractérisation de l’os cortical. La première partie est dédiée à l’analyse des signaux acquis par un prototype de sonde de transmission axiale à 1 MHz. Nous montrons qu’une contribution arrivant après le premier signal présente un intérêt pour la caractérisation ultrasonore de l’os cortical. En effet, cette contribution évaluée sur des radius humains in vitro est associée à une onde de flexion propagée dans l’os qui est dépendante de l’épaisseur corticale. L’analyse de cette contribution a nécessité le développement d’une technique de séparation d’ondes. Cette contribution étant plus basse fréquence que le premier signal et associée à un mode de propagation différent, nous montrons ainsi qu’une analyse plus poussée du signal peut permettre une approche multi-modes/multi-fréquences. Dans une seconde partie, nous montrons l’intérêt de l’évaluation de l’atténuation ultrasonore pour la caractérisation de l’os cortical. Lors d’une étude expérimentale in vitro sur des échantillons corticaux bovins, nous montrons la dépendance d’un paramètre d’atténuation aux propriétés osseuses et à la micro-structure. De plus, ce paramètre semble plus sensible aux propriétés osseuses que ne l’est la vitesse de l’onde longitudinale. Ainsi, l’atténuation évaluée en complément de la vitesse pourrait permettre de caractériser de manière plus complète l’os cortical / This work deals with the ultrasonic characterization of cortical bone. In a first part, the signals acquired with a 1-MHz axial transmission device are analyzed. A later contribution occuring after the first arriving signal is studied after the application of a wave separation procedure. This contribution is shown to be of interest for the ultrasonic characterization of cortical bone. Indeed, experiments performed in vitro on human radii show that this contribution is associated with a flexural wave guided which is dependent on the cortical thickness. In addition, this contribution has a lower frequency content than the first arriving signal and is associated with a different propagation mode. Therefore, a more thorough analysis of the ultrasonic signals enables a multi-modal/multi-frequency approach. In a second part, the ultrasonic attenuation is evaluated in an in vitro experimental study on bovine cortical bone samples. Ultrasonic attenuation is shown to be dependent on bone properties and micro-structure. Furthermore, this parameter seems to be more sensitive than the longitudinal wave velocity to bone parameters. Attenuation, in combination with ultrasonic wave velocity, is of interest and may provide a more comprehensive characterization of cortical bone

The presence of vibration is an important problem in many engineering applications. Various passive techniques have traditionally been used in order to reduce waves and vibrations, and their harmful effects. Passive techniques are, however, difficult to apply in the low frequency region. In addition, the use of passive techniques often involve adding mass to the system, which is undesirable in many applications. As an alternative, active techniques can be used to manipulate system dynamics and to control the propagation of waves and vibrations. This thesis deals with modeling, estimation and active control of systems that have resonant dynamics. The systems are exposed to stochastic disturbances. Some of them excite the system and generate vibrational responses and other corrupt measured signals. Feedback control of a beam with attached piezoelectrical elements is studied. A detailed modeling approach is described and system identification techniques are employed for model order reduction. Disturbance attenuation of a non-measured variable shows to be difficult. This issue is further analyzed and the problems are shown to depend on fundamental design limitations. Feedforward control of traveling waves is also considered. A device with properties analogous to those of an electrical diode is introduced. An `ideal´ feedforward controller based on the mechanical properties of the system is derived. It has, however, poor noise rejection properties and it therefore needs to be modified. A number of feedforward controllers that treat the measurement noise in a statistically sound way are derived. Separation of overlapping traveling waves is another topic under investigation. This operation also is sensitive to measurement noise. The problem is thoroughly analyzed and Kalman filtering techniques are employed to derive wave estimators with high statistical performance. Finally, a nonlinear regression problem with close connections to unbalance estimation of rotating machinery is treated. Different estimation techniques are derived and analyzed with respect to their statistical accuracy. The estimators are evaluated using the example of separator balancing.

Recent advances in near-field acoustical holography (NAH) have expanded the theory to interior spaces where multiple sources and/or reflections are present. In 1990, Tamura presented the spatial Fourier transform separation method to measure the reflection coefficient at oblique angles using two measurement planes in the wave number domain. This paper adapts the spatial Fourier transform separation method for application in interior NAH. A practical exploration of important experimental parameters is performed, which include the relative amplitudes of primary and disturbing sources, the measurement plane separation distance, and an acceptable noise floor. This technique is successfully applied in a reverberant environment to reconstruct the velocity of a clamped vibrating plate. NAH methods based on the measurement of pressure and particle velocity have led to the ability to reduce the required measurement locations. Other recent advances in NAH have expanded the theory to interior spaces where multiple sources and/or reflections are present. This paper investigates the use of interpolation techniques to reduce the required measurement locations for interior NAH. Specifically, the benefits of a bi-cubic Hermite surface patch interpolation are discussed and compared to other interpolation routines. Although the required inputs for the Hermite interpolation can be measured using a variety of devices, a scanning six-microphone probe in a tetrahedral configuration is suggested. The six microphones are utilized to simultaneously sample pressure on two parallel planes and estimate the pressure gradients on both of these planes. The two interpolated measurement holograms are used to separate the incoming and outgoing waves using the spatial Fourier-transform method. Analytical simulations of simply supported plates are shown as well as experimental results in a reverberation room to characterize the reduction in measurement locations. Depending on the spatial frequency of the hologram, a measurement location reduction of 20–80% was observed.

Cette thèse s'attache à la compréhension des phénomènes de couplages sismo-électromagnétiques survenant dans des milieux poreux contenant des fluides, ainsi qu'au développement de méthodes d'imagerie géophysique basées sur ces conversions. Deux axes de travail sont investigués. Le premier concerne le traitement des données sismo-électromagnétiques et notamment l'extraction des réponses interfaciales, qui peuvent renseigner sur le sous-sol en profondeur. Nous comparons l'impact de plusieurs méthodes de filtrage sur les amplitudes et les formes d'onde de ces réponses, dont une nouvelle technique de filtrage en domaine des curvelets, qui s'appuie sur les similarités entre les données sismiques et cosismiques. D'autre part, nous étendons la théorie de la propagation couplée des ondes sismiques et électromagnétiques à des milieux partiellement saturés pour le cas d'un mélange air/eau. Nous adaptons un programme de simulation numérique des ondes sismo-électromagnétiques à ces conditions. / This thesis aims to improve our understanding of seismo-electromagnetic coupling phenomena occuring in fluid-containing porous media and to develop geophysical imaging techniques based on conversions.Two areas of work are explored. The first encompasses seismoelectromagnetic data processing, especially the extraction of interface responses, which may provide information about the subsurface at depth. We compare the influence of several filtering techniques on the amplitudes and waveforms of the interface responses, among which a new filtering technique in the curvelet domain, taking advantage of the similarity between seismic and coseismic data. Furthermore, we extend the theory for the coupled propagation of seismic and electromagnetic waves here to partially saturated media for the case of a water/air mixture. We adapt a seismoelectromagnetic wave modelling program to these conditions.

Ce travail présente les développements récents réalisés sur le pénétromètre PANDA 3. Il s'agit d'un pénétromètre dynamique instrumenté qui permet à partir de la mesure puis du découplage des ondes créées par l’impact sur l’appareil, d’obtenir pour chaque coup une courbe charge-enfoncement σp-sp du sol ausculté. L’exploitation de cette courbe permet de déterminer des paramètres de résistance (résistance de pointe qd), de déformation (module dynamique Ed P3), des caractéristiques d’amortissement Js et de célérité d'ondes (CsP3 et CpP3) des sols auscultés en fonction de la profondeur tout au long du sondage. Cependant, et bien que la méthode soit très intéressante, celle-ci est restée au stade d’un prototype de laboratoire. Il est donc nécessaire de réaliser une étude plus approfondie sur l'essai lui-même et sur l’information contenue dans la courbe σp-sp en vue de fiabiliser la mesure et d’améliorer son exploitation. Dans un premier temps, nous présentons un bref aperçu sur les techniques de reconnaissance géotechnique et plus particulièrement celle des essais de pénétration dynamique. Le principe général du PANDA 3 est également présenté. La deuxième partie est consacrée au développement d'un nouveau prototype de pénétromètre PANDA 3. Ce développement s’appuie sur plusieurs études visant à valider la qualité des informations recueillies, leur bonne reproductibilité et le traitement des signaux d’acquisition. De même, un modèle numérique discret du battage pénétrométrique développé à l’aide du logiciel Particle Flow Code (Itasca) est présenté permettant de valider la technique de mesure. La troisième partie traite d'une étude comparative des résultats obtenus avec le PANDA 3 et d’autres techniques d'auscultation in situ afin de valider les résultats obtenus et l’utilisation de l’appareil dans des conditions réelles. Par ailleurs l’extension de cette technique de mesure au cas des pénétromètres lourds est appliquée dans le but de mesurer l'énergie transmise et d’étalonner le système de battage. Enfin, la dernière partie est consacrée à l'interprétation et l'exploitation des signaux en pointe afin d'affiner le modèle d'interprétation de la courbe charge-enfoncement. L'analyse de l'ensemble des signaux enregistrés au laboratoire a permis d’approcher une méthodologie d'exploitation de la courbe. L'application de la méthode proposée a été réalisée pour différents sols aussi bien au laboratoire que sur le terrain. Les résultats obtenus ont été confrontés avec d'autres types d’essais. / This work presents the recent developments made on the penetrometer PANDA®3. The instrumented dynamic penetrometer allowing, from the measurement and the decoupling of waves created by the impact, to obtain the load-penetration curve σp-sp of the soil. The exploitation of this curve allows determining the failure parameter (tip resistance qd), deformation (dynamic modulus EdP3), damping characteristics (Js) and wave speed (CsP3 and CpP3) of the investigated soil according to depth all along the sounding. However, although the proposed method is very interesting, it has remained at the stage of a laboratory prototype. It is therefore necessary to conduct a more thorough study of the test itself and the information provided from the σp-sp curve in order to obtain reliable measurement and improve their exploitation. First of all, we are presenting a brief overview of the geotechnical in-situ testing particularly that of the dynamic penetration tests as well as the general principle of PANDA 3 is presented. The second part is devoted to the development of a new prototype of the PANDA 3 penetrometer. This development is based on several studies aiming at validating the quality of the information, good reproducibility and treatment of the acquisition signals. Similarly, a discrete numerical model of the penetrometer developed using the Particle Flow Code software (Itasca) is presented to validate the measurement technique. The third part deals with a comparative study of the results obtained with the PANDA 3 and other in situ investigation techniques to validate the obtained results and the use of the device in real conditions. Moreover, the extension of this measurement technique in the case of heavy penetrometer is applied in order to measure the transmitted energy and to calibrate the driving system. The last part is devoted to refining the interpretation and exploitation of the load-penetration curve. The analysis of all the signals recorded in the laboratory allowed to approach a methodology of curve exploitation. The application of the proposed method was carried out for different soils both in the laboratory and on field. The results were confronted with other types of tests.

This thesis presents validation and application of advanced soil constitutive models in cases of seismic loading conditions. Firstly, results of three advanced soil constitutive models are compared with examples of shear stack experimental data for free field response in dry sand for shear and compression wave propagation. Higher harmonic generation in acceleration records, observed in experimental works, is shown to be possibly the result of soil nonlinearity and fast elastic unloading waves. This finding is shown to have high importance on structural response, real earthquake records and reliability of conventionally employed numerical tools. Finally, short study of free field response in saturated soil reveals similar findings on higher harmonic generation. Secondly, two advanced soil constitutive models are used, and their performance is assessed based on examples of experimental data on piles in dry sand in order to validate the ability of the constitutive models to simulate seismic soil-structure interaction. The validation includes various experimental configurations and input motions. The discussion on the results focuses on constitutive and numerical modelling aspects. Some improvements in the formulations of the models are suggested based on the detailed investigation. Finally, the application of one of the advanced soil constitutive models is shown in regard to temporary natural frequency wandering observed in structures subjected to earthquakes. Results show that pore pressure generated during seismic events causes changes in soil stiffness, thus affecting the natural frequency of the structure during and just after the seismic event. Parametric studies present how soil permeability, soil density, input motion or a type of structure may affect the structural natural frequency and time for its return to the initial value. In addition, a time history with an aftershock is analysed to investigate the difference in structural response during the earthquake and the aftershock.