Ankle sprains are one of the most common type of sports injury. They occur most frequently when the foot is in a supine or inverted position. Recovery from an ankle sprain can take from one and up to 26 weeks depending on the severity of the injury. During that period the individual will be unable to participate in any meaningful sports activity and as such it is important to be able to prevent the occurrence of such injuries. Prevention of ankle sprain injuries would require a better understanding of the risk factors of this injury. Several studies attempted to assess such risk actors by inducing foot inversion or supination however the platforms used in these studies were shown to be limited. Hence the main aim of this project is to develop a system that can be used to assess the effect of sudden foot and ankle inversion/supination on the musculoskeletal system of dynamic subjects (e.g. walking, running, jumping, etc.). For this purpose a three degrees of freedom (DOF) rotating platform has been designed, manufactured and installed in the Institute of Motion Analysis and Research (IMAR) Sports Laboratory. The platform rotates around 3 different axes allowing inversion or supination of the foot and ankle of dynamic subjects. The degree of rotation around each axis can easily be set by the researcher/operator. A strain gauge was used to detect foot strike to the platform. As a safety measure laser emitter/receivers check that the entire foot is on the footplate before the platform rotates. Optical encoders provide essential feedback of rotation angles, speed and acceleration. The necessary software and user interface for controlling the platform were also written and tested. The platform was synchronised with a bilateral four-channel EMG (electromyography) system and a 12 camera Vicon® MX-13 system thus allowing measurement of muscle activity and kinematic data during the supination of the foot. A set of software modules were written to allow automated management and processing of the data generated by the new system. The new system was then implemented in a study to validate it and to assess the role of shoes in ankle sprains. In this study, subjects would walk in three different foot conditions: barefoot, and with two different types of sports shoes, along the walkway of the Sports Laboratory where the platform was fitted. When a subject steps on the embedded platform, it rotates causing the subject's foot to supinate. At the same time, the EMG data from the peroneus longus, tibialis anterior, and lateral gastrocnemius muscles are recorded, along with the kinematics of the subject's whole body. The obtained results demonstrated the validity of the newly developed system. Data from the validation study also revealed increased muscle activity following induced foot supination in shod conditions compared to barefoot. Muscle activity of the rotating platform step was found to be significantly higher than the steps before and after. The platform rotation was also found to have an observable effect on body kinematics. The newly developed system is hoped to help provide a better understanding of the risk factors of ankle sprain injury and how to prevent this injury. The system can be used to help improve the design of current footwear and identify which footwear provides better protection against ankle sprain injury. The system can also be used to assess the effectiveness of different ankle injury rehabilitation schemes and different training programs that aim to reduce ankle sprain injuries. The new system can be utilised to identify individuals who are at risk of sustaining an ankle sprain injury. The system can also be utilised in studies outside the scope of ankle sprain injuries.

Un modèle géologique tridimensionnel des Pyrénées et de leurs bassins d'avant-pays est construit avec le logiciel GeoModeller. Ce modèle tient compte de toutes les informations géologiques et géophysiques disponibles et couvre l'ensemble des Pyrénées, de l'Océan Atlantique à la Mer Méditerranée, et de la Chaîne Ibérique au Massif Central, jusqu'à 70 km de profondeur. Il est capable d'expliquer les principales caractéristiques des anomalies de Bouguer et des temps de trajet sismiques. Des inversions 3D sont réalisées pour affiner ce modèle. La modélisation et l'inversion géologiques et géophysiques révèlent des différences dans la structure crustal entre les Pyrénées occidentales et centrales et les Pyrénées orientales. Elles montrent en outre la présence de manteau exhumé et enfermé dans la croûte sous le Massif du Labourd et à Saint-Gaudens ainsi que la nécessité d'une anomalie de faible densité dans les Pyrénées orientales. / A three-dimensional geological model of the Pyrenees and their foreland basins is constructed with the GeoModeller software. This model accounts for all the geological and geophysical information available and covers the whole Pyrenees, from the Atlantic Ocean to the Mediterranean Sea, and from the Iberian Range to the Massif Central, down to 70 km depth. It is able to explain main features of Bouguer gravity anomalies and of seismic travel times. 3D inversion is performed to refine this model. Joint geological and geophysical modeling and inversion reveal differences in the crustal structure between the western and central Pyrenees and the eastern Pyrenees. They show furthermore the presence of exhumed mantle material enclosed in the crust beneath the Labourd Massif and Saint-Gaudens, as well as the necessity of a low density anomalie in the eastern Pyrenees.

The layered structure and bulk composition of continental crust contains important clues about its history of mountain-building, about its magmatic evolution, and about dynamical processes that continue to happen now. Geophysical and geological features such as gravity anomalies, surface topography, lithospheric strength and the deformation that drives the earthquake cycle are all directly related to deep crustal chemistry and the movement of materials through the crust that alter that chemistry. The North American continental crust records billions of years of history of tectonic and dynamical changes. The western U.S. is currently experiencing a diverse array of dynamical processes including modification by the Yellowstone hotspot, shortening and extension related to Pacific coast subduction and transform boundary shear, and plate interior seismicity driven by flow of the lower crust and upper mantle. The midcontinent and eastern U.S. is mostly stable but records a history of ancient continental collision and rifting. EarthScope’s USArray seismic deployment has collected massive amounts of data across the entire United States that illuminates the deep continental crust, lithosphere and deeper mantle. This study uses EarthScope data to investigate the thickness and composition of the continental crust, including properties of its upper and lower layers. One-layer and two-layer models of crustal properties exhibit interesting relationships to the history of North American continental formation and recent tectonic activities that promise to significantly improve our understanding of the deep processes that shape the Earth’s surface. Model results show that seismic velocity ratios are unusually low in the lower crust under the western U.S. Cordillera. Further modeling of how chemistry affects the seismic velocity ratio at temperatures and pressures found in the lower crust suggests that low seismic velocity ratios occur when water is mixed into the mineral matrix, and the combination of high temperature and water may point to small amounts of melt in the lower crust of Cordillera.

The term “homeland security”, seems to have become synonymous with terrorism in the minds of the general public. However, there are other threats to the security of the United States homeland that can be just as, if not more, devastating than terrorism. Included among these other threats is the potential of an asteroid collision with Earth. Historically, asteroid impact events have been responsible for the devastation of our planet and many of the mass extinction events encountered throughout the geologic record. Knowledge of physical parameters such as structure and rotational dynamics of the asteroid are critical parameters in developing interception and deflection techniques, as well as assessing the risk associated with these bodies and mitigation planning in the event of impact. This thesis encompasses the study of eight potentially hazardous asteroids identified in conjunction with NASA’s OSIRIS REX Mission and observed via the Target Asteroid Project, along with observations from the Robotically Controlled Telescope, and the Asteroid Light Curve Database of Photometry. Photometric data was extracted from all observations. Rotation periods of each target were confirmed using Lomb-Scargle time series analysis, with possible secondary periods indicated in the cases of Hathor (2.2169 hours), Bede (161.1501 hours), and Phaethon (4.5563 hours). Shape models for 2002 FG7, 2004 JN13, and Icarus were produced using light curve inversion techniques These are believed to be the first such models for these asteroids.

The Apollo Command Module had a tendency to flip over upon impact with the ocean surface after returning from space (9/19 times). In an effort to better characterize the inversion process for future water landing vehicles, experimental results for a simplified buoyant cylindrical puck impacting the water surface are presented. This study focuses on the dependence of inversion upon vertical velocity, horizontal velocity, and the pitch angle of the puck relative to the free surface. High-speed images reveal an asymmetric cavity that forms upon water impact. The asymmetric cavity then collapses, applying a moment, which can be sufficient to invert the puck after impact. Increasing the vertical velocity increases the likelihood of inversion. The puck never flipped over below a vertical velocity of 3.75 m/s. Increasing the horizontal velocity also slightly increases the likelihood of inversion. However, the largest effect of increasing horizontal velocity is to shift the range of impact angles for which the puck will invert to lower angles. The buoyant cylindrical puck used in this study requires a higher Froude number (4.34) to invert than previous geometries which have been studied.

The subject of this dissertation is use of computer models as data analysis tools in several different geoscience settings, including integrated surface water/groundwater modeling, tephra fallout modeling, geophysical inversion, and hydrothermal groundwater modeling. The dissertation is organized into three chapters, which correspond to three individual publication manuscripts. In the first chapter, a linear framework is developed to identify and estimate the potential predictive consequences of using a simple computer model as a data analysis tool. The framework is applied to a complex integrated surface-water/groundwater numerical model with thousands of parameters. Several types of predictions are evaluated, including particle travel time and surface-water/groundwater exchange volume. The analysis suggests that model simplifications have the potential to corrupt many types of predictions. The implementation of the inversion, including how the objective function is formulated, what minimum of the objective function value is acceptable, and how expert knowledge is enforced on parameters, can greatly influence the manifestation of model simplification. Depending on the prediction, failure to specifically address each of these important issues during inversion is shown to degrade the reliability of some predictions. In some instances, inversion is shown to increase, rather than decrease, the uncertainty of a prediction, which defeats the purpose of using a model as a data analysis tool. In the second chapter, an efficient inversion and uncertainty quantification approach is applied to a computer model of volcanic tephra transport and deposition. The computer model simulates many physical processes related to tephra transport and fallout. The utility of the approach is demonstrated for two eruption events. In both cases, the importance of uncertainty quantification is highlighted by exposing the variability in the conditioning provided by the observations used for inversion. The worth of different types of tephra data to reduce parameter uncertainty is evaluated, as is the importance of different observation error models. The analyses reveal the importance using tephra granulometry data for inversion, which results in reduced uncertainty for most eruption parameters. In the third chapter, geophysical inversion is combined with hydrothermal modeling to evaluate the enthalpy of an undeveloped geothermal resource in a pull-apart basin located in southeastern Armenia. A high-dimensional gravity inversion is used to define the depth to the contact between the lower-density valley fill sediments and the higher-density surrounding host rock. The inverted basin depth distribution was used to define the hydrostratigraphy for the coupled groundwater-flow and heat-transport model that simulates the circulation of hydrothermal fluids in the system. Evaluation of several different geothermal system configurations indicates that the most likely system configuration is a low-enthalpy, liquid-dominated geothermal system.

The aim of this thesis is to develop procedures for the modelling and inversion of teleseismic P and S waveforms which are as flexible as possible. This flexibility is necessary in order to obtain accurate source depth and mechanism estimates for small to moderate size events, such as those that are relevant in the context of monitoring the Comprehensive Nuclear-Test-Ban Treaty (CTBT). ¶ The main challenge for extending source depth and mechanism inversion methods to smaller events is to ensure that sufficiently accurate synthetic seismograms are available for comparison with observed records. An accurate phase-adaptive reflectivity method has therefore been developed, against which the performance of less computationally intensive approximations can be judged. The standard reflectivity method has been modified to allow for different crustal and upper mantle structures at the source and receiver, and the full effects of reverberations and conversions in these structures can be allowed for. Core reflections and refractions can also be included; these phases can become important at certain distance ranges. A slowness bundle approach has been developed, where a restricted slowness integration about the geometric slowness for the direct wave is undertaken at each frequency, allowing accurate results to be obtained whilst avoiding the expense of a full reflectivity technique. ¶ Inversion using the neighbourhood algorithm (NA) is performed for source depth, mechanism and time function, by modelling direct P and S and their surface reflections (pP, sP and pS, sS) at teleseismic distances. Both SV and SH data are exploited in the inversion, in addition to P data, in order to obtain improved constraints on the source mechanism, including any isotropic component. Good results are obtained using a simple generalised ray scheme, however, the use of a flexible derivative-free inversion method means that more accurate synthetics are able to be used in the inversion where appropriate. The NA makes use of only the rank of the data misfits, so that it is possible to employ any suitable misfit criterion. In the few cases where control on the source mechanism is limited, good depth resolution is still usually obtained. ¶The structures near the source and receiver play an important role in shaping the detail of the teleseismic waveforms. Although reasonable results can be achieved with simple synthetics and a standard velocity model, significant improvement can be made by modifying the representation of structure near the source and receiver. In the case of sub-oceanic events it is important to allow for the effects of water reverberations. The crustal structure near the receiver can also have quite a large influence on the waveforms through reverberations and conversions. This is exploited in receiver function inversion, which is again accomplished using the NA approach.

The cochlea is an organ which extracts frequency information from the input sound wave. It also produces nerve signals, which are further analysed by the brain and ultimately lead to perception of the sound. An existing model of the cochlea by Fragni`ere is first analysed by simulation. This passive model is found to have the properties that the living cochlea does in terms of the frequency response. An analog VLSI circuit implementation of this cochlear model in CMOS weak inversion is proposed, using log-domain filters in current domain. It is fabricated on a chip and a measurement of a basilar membrane section is performed. The measurement shows a reasonable agreement to the model. However, the circuit is found to have a problem related to transistor mismatch, causing different behaviour in identical circuit blocks. An active cochlear model is proposed to overcome this problem. The model incorporates the effect of the outer hair cells in the living cochlea, which controls the quality factor of the basilar membrane filters. The outer hair cells are incorporated as an extra voltage source in series with the basilar membrane resonator. Its value saturates as the input signal becomes larger, making the behaviour rather closer to that of a passive model. The simulation results show this nonlinear phenomenon, which is also seen in the living cochlea. The contribution of this thesis is summarised as follows: a) the first CMOS weak inversion current domain basilar membrane resonator is designed and fabricated, and b) the first active two-dimensional cochlear model for analog VLSI implementation is developed.

La caractérisation sismique des réservoirs pétroliers nécessite l'intégration de plusieurs techniques telles que la lithosismique, la géomodélisation, la géostatistique, l'utilisation des algorithmes évolutionnaires et la pétrophysique. L'information sismique est d'abord utilisée pour la description de l'architecture externe des réservoirs car son utilisation pour la description des faciès ne se fait pas sans difficultés. L'objectif de cette thèse est d'apporter des outils nouveaux pour aider à l'utilisation de l'information sismique pour caractériser les réservoirs.<br />Un premier travail a consisté à évaluer l'impact des incertitudes structurales sur les inversions pétroélastiques et les conséquences en terme de classification de faciès. Ensuite, nous considérons la modélisation sismique comme aide à l'évaluation du modèle réservoir. Cette modélisation permettra de faire le lien entre les simulateurs réservoir ou les géomodeleurs et la réponse sismique du réservoir. <br />Nous développons ensuite deux approches alternatives aux méthodes traditionnelles en inversion pétroélastique et pétrophysique. La première utilise la méthode géostatistique des déformations graduelles pour créer des réalisations de propriétés réservoirs. Elle permet de créer des propriétés à l'échelle réservoir, conditionnées aux puits, tout en respectant une fonction coût basée sur la comparaison des données sismiques réelles et issues de ces réalisations. <br />La seconde méthode repose sur le principe de la classification supervisée et utilise des réseaux de neurones pour analyser la forme des traces sismiques. Une première étape consiste à générer un volume d'apprentissage contenant tous les modèles pétrophysiques envisageables pour un champ donné. Ces modèles sont analysés par les réseaux de neurones. Les neurones ainsi identifiés sont appliqués aux données réelles, pour identifier des relations pétrophysique/sismique identiques aux données d'apprentissage.<br />Toutes les méthodologies sont validées sur plusieurs réservoirs choisis pour leurs particularités géologiques (complexité structurale, lithologie du réservoir).

La mesure des dérivées spatiales du champ de pesanteur, ou gradiométrie en gravimétrie, est née au début du XXe siècle avec la balance de torsion d'Eötvös, premier gradiomètre. Utilisée avec succès pour la prospection géophysique, cette technique fut cependant délaissée pour un temps au profit de la gravimétrie, plus facile et moins coûteuse. Cependant, les développements instrumentaux en gradiométrie ont continué, et les gradiomètres actuels permettent la mesure simultanée des gradients de pesanteur dans trois directions indépendantes de l'espace. La gradiométrie en gravimétrie connaît ainsi une renaissance, et l'Agence Spatiale Européenne lancera en 2008 le satellite GOCE, avec à son bord le premier gradiomètre spatial, permettant la cartographie globale de la pesanteur avec une résolution spatiale sans précédent. Cette étude est consacrée au signal de gradiométrie en gravimétrie, de l'acquisition des données à leur interprétation. Plus spécifiquement, dérivant d'un même potentiel, l'accélération de la pesanteur et ses dérivées peuvent être considérées comme des mesures interdépendantes d'une même quantité. Nous avons élaboré une méthode permettant, en exploitant cette redondance, de réduire le bruit dans les données de gradiométrie et, plus efficacement, dans celles de gravimétrie. Nous utilisons également une propriété spécififique des gradients de pesanteur, l'existence d'invariants scalaires combinant les différents gradients, que nous relions à la géométrie des sources à l'origine des anomalies de pesanteur. Nous avons ainsi développé une méthode, complémentaire à la déconvolution d'Euler des données de gravimétrie, qui améliore la localisation de ces sources.