Dissertations / Theses on the topic 'Leg Tomography'
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Philippe, Julien. "Développement d'une presse portative pour les études in et ex situ sous conditions extrêmes de pression, température et déformation." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066008.
Full textHigh pressures are essential in several scientific field. This will be the case in this thesis with the development of a new device enabling new possibilities tomography and deformation under high pressure and high temperature. It brings the possibility of further scientific studies in the various disciplines that are Earth science, mechanical chemistry, physics of materials and liquids physics
Boutet, Jérôme. "Localisation d'inclusions fluorescentes dans les milieux diffusants à l'aide de techniques laser. Application au diagnostic médical in vivo." Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENY009/document.
Full textFluorescence tomography is a preclinical and clinical imaging method which aims to localize fluorescent probes injected into a living organism. In this thesis work, we defined the optimal design and parameters of a continuous wave fluorescent tomograph applied to thin tissue observation. We handled the problem of observing heterogeneous and highly absorbing organs. Secondly, we showed the advantage of time of flight measurement for inclusion detection through thicker tissues. The detection performances of two types of system capable of these measurements were compared and we proposed a protocol to optimize their main parameters. This process was applied to the problematic of prostatic biopsy guiding. It would also be used to detect and localize other pathologies by means of a simple adaptation
Krasnoshlyk, Victoria. "Etude multi-échelles et multiphysiques des mécanismes de fissuration dans les matériaux à base de fibres naturelles." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI028/document.
Full textMaterials made up of synthetic or natural fibres are increasingly developed in various domains: papermaking, composite, automotive and aeronautic industries for structural, packaging, air filtration or medical applications. Despite the variety of manufacturing processes of such materials, all of them can be considered as being formed by a network of fibres interconnected via bonds. For instance, in the case of materials made up of natural cellulosic fibres such as papers or boards, fibres are chemically linked.Crack propagation phenomena in such materials remain poorly understood even though it can be presumed that such mechanisms depend on:- (i) the geometrical and mechanical properties of the constituents of individual fibres and fibre-fibre bonds,- (ii) the architecture of the fibrous network, for example the spatial distributions of fibres, bonds and pores and the size distributions of pores and bonds,- (iii) the applied mechanical loadings.In such materials, scale effects must be investigated in order to improve the classical approaches used to understand crack propagation mechanisms. Recent progresses in both experimental mechanics and numerical simulation approaches allow such a study from the fibre scale up to the fibre network scale to be carried out.The proposed PhD aims first at developing an original experimental approach to analyse microstructure changes and crack propagation phenomena for low density papers. For that purpose x-ray microtomography or ESEM, and stereo-correlation experiments will be carried out to investigate microstructural changes and deformation mechanisms at all relevant scales (see the illustration given in )
Potin, Bertrand. "Les Alpes occidentales : tomographie, localisation de séismes et topographie du Moho." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAU022/document.
Full textThe Alpine chain, which stretches in the middle of Europe across six countries, is probably the most studied mountain range in the world. Geology and metamorphism studies contributed for a large part to the current understanding of the geodynamics and history of this region. Since the second half of the 20th century, geophysical methods were employed to study its lithosphere and several crustal cross-sections where performed, mainly using controlled-source seismology. In parallel, dense seismic networks were also deployed in France, Italy, and Switzerland in order to study the usually low-magnitude activity of the western Alps. Over the past 25 years, these networks have permitted to locate tens of thousands of local earthquakes. In the last two decades, local or regional tomographic studies have been conducted using subsets of this data, which substantially improved our understanding of the deep structure of the Alps.Here, and based on 36,000 seismic events, 375 stations and more than 791,000 P and S-waves arrival times, we performed a tomographic study on a 456x414 km2 area covering the western Alps. Even if most of these earthquakes occurred within the first 15 km beneath surface, a large part of the data is composed of refracted-waves, letting us insight the deep structure of the crust. The interest of such a large dataset relies on the accuracy ensured by the law of large numbers, but the unavoidable presence of outliers requires a specific approach in order to handle it. The a priori earthquake locations were computed using the LOCIN algorithm developed in this study, which is basically a grid-search algorithm combined with a probabilistic approach.Tomography of the crust and upper mantle based on travel-times analysis was conducted using the INSIGHT algorithm which was developed in this study (based on a V. Monteiller and B. Valette algorithm). Our model consists of a set of vP and vP/vS values given at each node of a three-dimensional, regularly-spaced grid, which constitutes the inversion grid. Transition between crust and mantle is modelled by a continuous change in velocity, as we do not introduce any a priori information on the Moho interface. Earthquake locations and site-effect residuals at each station (analogous to "static corrections" in seismic prospecting) are also determined in the process. The forward computation of travel times in the 3D model is performed by integrating slowness along the rays, which are determined by a finite-difference resolution of the eikonal equation. Inversion is carried out using a non-linear least-squares approach based on a stochastic description of data and model. The smoothing and damping parameters are adjusted by means of L-curves analysis.The Moho topography is determined by matching two informations: (i) the maximum of the vP gradient within this preliminary tomographic model, taken in a 7.3-7.6~km/s range and (ii) information provided by previous studies to fix Moho depth in the border area of our study zone, where our model is poorly resolved. As our tomographic model relies on a large set of refracted waves, the Moho topography we build is detailed and presents interesting new insights for the western Alps. This Moho interface is then used as an a priori discontinuity in a new tomography process. Parameters within the crust and the upper mantle are then decorrelated, letting refracted-waves to be more correctly modelled. By this approach, we are able to compute not only the first- but also the second-arrival travel-time which corresponds to the direct wave in the crust for focus-station distances greater than 100-125 km. This allows us to add more than 100,000 new data to our dataset, which of course improves the resolution in the crust.Both tomographic models, the Moho topography and the earthquake relocations provides new evidences and constraints on the deep structure of the western Alps
Flores, Jiménez Alejandro. "Atmospheric Tomography Using Satellite Radio Signals." Doctoral thesis, Universitat Politècnica de Catalunya, 2000. http://hdl.handle.net/10803/6881.
Full textLa tecnología de los receptores GPS ha evolucionado con una sorprendente rapidez, resultando en instrumentos con suficiente calidad de medida para ser utilizados en estudios geodésicos, comparables a los resultados de técnicas como la interferometría de muy larga base (VLBI), y estudios atmosféricos cuyos resultados pueden ser usados en meteorología.
En la tesis Tomografía Atmosférica utilizando Señales Radio de Satélites nos hemos centrado en el uso del sistema GPS por disponer mayor cantidad y calidad de referencias y herramientas para el procesado de los datos. No obstante, se ha demostrado la posibilidad de extender el concepto a cualquier sistema de transmisión radio desde satélite como sondeador atmosférico. La estructura de la tesis se ha dividido en dos áreas: el procesado de datos GPS para extraer información referente a los parámetros atmosféricos de interés, y la aplicación de técnicas tomográficas para la resolución de problemas inversos. En particular, la tomografía se ha aplicado a la ionosfera y la atmósfera neutra. En ambos casos, los resultados tienen un innegable impacto socio-económico: a) la monitorización del estado ionosférico es fundamental por las perturbaciones que la ionosfera provoca en las transmisiones radio que la atraviesan, y b) la estimación del contenido de vapor de agua de la troposfera es de utilidad en la predicción meteorológica y climática.
La tomografía ionosférica se empezó a desarrollar usando únicamente datos de la red global IGS. A continuación se mejoró la resolución vertical mediante la utilización de datos de ocultaciones del experimento GPS/MET. La mejora de la resolución se ve limitada a la región en la que estos datos existen. Finalmente, se utilizaron datos de altimetría del satélite TOPEX/POSEIDON para mejorar los mapas y para demostrar la posibilidad de calibración instrumental de los altímetros radar usando técnicas tomográficas.
La aplicación a la troposfera se obtuvo tras la mejora y refinamiento tanto del procesado de datos GPS como del proceso de inversión tomográfica. Los primeros resultados se obtuvieron mediante los datos experimentales de la red permanente en Kilauea, Hawaii, por la configuración particular de los receptores. Estos resultados demostraban la capacidad de obtener representaciones espacio-temporales de la troposfera mediante datos GPS. El análisis de los datos de la campaña REGINA, realizada en el Onsala Space Observatory, nos permitió la descripción de un fenómeno meteorológico complejo mediante la tomografía troposférica usando datos GPS y su verificación por comparación directa con medidas realizadas por radiosondeo.
En conclusión, se ha demostrado la posibilidad de aplicar tomografía a la atmósfera utilizando señales radio de satélites y, en particular, la constelación GPS.
The Global Navigation Satellite Systems (GPS and GLONASS) have become a basic tool to obtain geodetic measurements of the Earth and a source of data for the atmospheric analysis. Since these systems provide a global, dense and permanent coverage with precise and accurate data, the radio signals they transmit can be used for the spatio-temporal representation of the atmosphere.
GPS receivers technology has evolved at a surprising pace: nowadays they have sufficient measurement quality as to be used in geodetic studies, together with other techniques such as the Very Long Base Interferometry (VLBI), and in atmospheric studies whose results can be input into meteorological analysis.
In the thesis "Atmospheric Tomography Using Satellite Radio Signals" we have focused on the use of GPS system due to the better quality and quantity of references and tools for the data processing. This notwithstanding, we have proven the possibility to broaden the concept to include any other radio signal transmitting satellite system as an atmospheric sounder. The thesis has been divided into two main areas: GPS data processing to extract the information related to the atmospheric parameters under study, and the implementation of tomographic techniques to the solution of the inverse problem. In particular, tomography has been applied to the ionosphere and to the neutral atmosphere. In both cases, results have a socio-economic impact: a) monitoring the ionosphere is essential for radio transmissions across it because of the perturbations it may produce on the signal, and b) estimating water vapour content in the troposphere is highly useful for meteorological and climate forecast
For the ionospheric tomography we initally only used the data from the global IGS network. Vertical resolution was afterwards improved using the occultation data of the GPS/MET experiment. The improvement, however, was limited to the region where these data existed. Finally, we used altimeter data from the TOPEX/POSEIDON satellite to improve the maps and to prove the radar altimeter calibration capability of the tomographic technique.
The application to the troposphere was possible after the improvement and refinement of both the GPS data processing and the tomographic inversion. The first results were obtained using the experimental data from the permanent network in Kilauea, Hawaii. The particular geometry of the receivers in this local network made it highly suited for these initial results, which proved the possibility of obtaining spatio-temporal representations of the troposphere using GPS data. The data analysis of the REGINA campaign, which took place at the Onsala Space Observatory, provided the description of a complex meteorological phenomenon using only GPS data tropospheric tomography. We verified the results with a direct comparison with radiosonde data.
Concluding, we have demonstrated the capabilities of atmospheric tomography using satellite radio signals, with particular emphasis on the GPS signals.
Arciniegas, Mosquera Andrés Felipe. "Analyse de méthodes statistiques en traitement du signal pour les tomographies acoustique et ultrasonore des arbres sur pied." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4746/document.
Full textAcoustic tomography is an imaging technique used to perform two-dimensional mappings of the radial-transverse plane of trees, based on the velocity (or the slowness) of low frequency elastic waves (<20 kHz). The images currently obtained with the commercial devices have a low spatial resolution (of the order of a few centimeters) and are difficult to interpret. These resolution is limited by the use of low frequency waves, the low number of sensors and the fact of not taking into account the properties of wood (anisotropy, heterogeneity). To date, there are no field devices using ultrasound, specially adapted for standing trees imaging. Taking into account the limitations mentioned previously, we present hereby two studies that aim to improve the quality of acoustic and ultrasonic tomography images. In the first part of this work we compare signal-processing methods for the measurement of the propagation time and we specify experimental limits of validity. The approach developed permitted to choose the signal-processing methods by characterizing their systematic and random errors associated with the noise level. In the second part of this work, a numerical study of the robustness of reconstruction algorithms is proposed. Two new reconstruction algorithms are presented and compared to two conventional algorithms used in the commercial devices. These comparison is based on the criteria related to experimental constraints (low number of sensors and noisy measurements) and technical requirements (low computation time) for use in the field
Ouksili, Zehor. "Compensation du mouvement respiratoire dans les images TEP/TDM thoraciques." Thesis, Toulouse, INPT, 2010. http://www.theses.fr/2010INPT0025/document.
Full textThis thesis deals with respiratory motion in PET/CT images. It is well known that PET is a modality that requires a long exposure time. During this time, patients moves and breath. These motions produce undesirable artefacts that alter seriously the images and their precision. This has important consequences when diagnosing thoracic, and particularly pulmonary, cancer. Tumours appear larger than they really are and their activity is weaker. This thesis proposes to contribute to solving these problems.We propose the architecture of an integrated PET/CT acquisition system synchronized to respiration. We also develop signal and image processing methods that can be applied to eliminating respiratory artefacts in CT and PET images. The thesis brings three main contributions : An original respiratory signal segmentation and characterization to detect "normal" respiratory patterns, a 4D-CT reconstruction method that creates 3D images of the whole body for any respiratory level and an enhanced iterative algorithm for reconstructing 4D-PET images without respiratory artefacts. The developed methods have validated and tested on simulated, phantom and real patients' data
Ding, Yang. "Analyse morphologique de la microstructure 3D de réfractaires électrofondus à très haute teneur en zircone : relations avec les propriétés mécaniques, chimiques et le comportement pendant la transformation quadratique-monoclinique." Phd thesis, Ecole Nationale Supérieure des Mines de Paris, 2012. http://pastel.archives-ouvertes.fr/pastel-00743511.
Full textSperlich, B., D. P. Born, K. Kaskinoro, K. K. Kalliokoski, and Marko Laaksonen. "Squeezing the Muscle : Compression Clothing and Muscle Metabolism during Recovery from High Intensity Exercise." Mittuniversitetet, Avdelningen för hälsovetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-18973.
Full text:doi 10.1371/journal.pone.0060923
Tireira, Aly. "Endommagement dans les alliages AlSi12 pour moteurs automobiles : Observations in situ et modélisation micromécanique." Thesis, Saint-Etienne, EMSE, 2015. http://www.theses.fr/2015EMSE0780/document.
Full textThis thesis focuses on the mechanisms of deformation and damage in cast aluminum alloysfor automotive industry. Studies were carried on a model alloy containing 12% silicon and added element like iron and nickel. The material was prepared by squeeze-casting process at the Vienna University of Technology in Austria with which this thesis was held in collaboration. In situ tensile test with X-rays tomographic observations as well as with Scanning Electron Microscope observations were performed. They allowed following microstructure evolution under mechanical loading. Particular attention was paid to the mechanisms of initiation and propagation of damage. Furthermore the technic of Digital Image Correlation (DIC) developed to be applied to SEM images was used to visualize 2D strain localization mechanisms at second phases particles scale. DIC were also applied on tomographic images and allowed to measure accurately in 3D damage evolution under loading. Experimental data obtained from DIC were used to identify parameters of a Gurson Tvergaard Needleman model and allow to simulate by Finite Element Modeling the damage evolution. At last stages micro mechanical studies were performed by FEM using microstructure obtained from tomographic images. Algorithms were developed to measure and identify statistics parameters of the microstructure. In consideration of the mechanism of deformations and second phase particles morphology, generatedmicrostructures are proposed to simulate the behavior of the material. This approach aims to simplify the FEM models by reducing the number of degree of Freedom and, then reduce computation time. It also enables to insert complex mechanisms in the model to be as close as possible the actual behavior of the material
Ourak, Mouloud. "Asservissement visuel direct fondé sur les ondelettes pour le positionnement automatique d'une sonde de tomographie par cohérence optique." Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2052/document.
Full textThe technological advances have facilitated the optical biopsy approaches, unlike physical methods to take advantage of a minimally invasive, real time and repetitive procedure. The optical coherence tomography system is one of the optical biopsy techniques used in this thesis to prospect in the human body with robotized OCT endoscopic probes. Nevertheless, their control once inside the body becomes difficult, especially if the goal is following changes in the target area. The visual servoing is an ideal tool for the control and positioning of the robot. However, the amount of information present in the images allows the use of several types of visual features. In this thesis, we propose to use an innovative visual servoing feature based on wavelets. This representation developed as the evolution of the Fourier transform for non-stationary signals provides a time-frequency representation of the signal with a better extraction of the relevant information. Indeed, two visual servoing approaches based on wavelets were developed. The first approach is a 2D pose visual servoing based on spectral continuous wavelets, which ensures convergence over a larger area and decoupled control. The second is a direct 2D visual servoing based on multiresolution wavelets, mainly for small displacements positioning. However, the latter covers the 6 DOF when the previous one is limited to 3 DDL with a CCD camera. Both approaches have proven their ability to make the positioning of B-Scan OCT images. After that, we have proposed a method of partitioned positioning, that we can qualify by hybrid because it uses two image modalities to ensure SE(3) positioning of a sample. On the other side, we proposed a calibration method of B-Scan and 3D-Scan OCT images, due to the distortions generated by the optical path of the laser beam in OCT. Finally, these thesis is a beginning work for applications in positioning of 3D-Scan OCT, physiological motion compensation and monitoring tools by OCT images
Mary, Benjamin. "Développement de l'imagerie des systèmes racinaires dans les ouvrages hydrauliques en remblai par tomographie électrique et acoustique." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4386/document.
Full textWoody vegetation from earth dikes or dams is a fragility factor which can promote mechanisms of degradation such as erosion. An accurate assessment of root system structure, from geophysical non-destructive methods, of root position into the embankment (depth, extension), and a good knowledge of soil conditions are critical in order to anticipate the consequences of vegetation development for the hydraulic structure’s safety. Laboratory experiments allowed determining intrinsic acoustical and electrical root properties leading to identify relevant signatures and discriminate anomalies related to roots in the field. The establishment of adapted experimental devices led us progressively to assess different parameters (roots mass, water content. . . ) under controlled conditions. Experiments in semi-controlled conditions with trees planted into a homogenous soil, were conducted to assess the relevance of different methodologies, such as the use of temporal induced polarization in complex resistivity tomography or the geometry of sensors for acoustical tomography. Innovative data processing such as wavelet analysis were used to valorize the rich database. The results were validated by the determination of actual root position.Finally, field investigations into an embankment have been performed to highlight a spatial variability of dike structures associated with trees presence. A methodology adapted to the geophysical diagnostic of vegetation roots in embankments was developed
Puszka, Agathe. "Tomographie optique diffuse : une approche résolue en temps pour les mesures en réflectance à courtes distances entre sources et détecteurs." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENY051/document.
Full textDiffuse optical tomography (DOT) is an emerging medical imaging technique using near-infrared light to probe biological tissues. This technique can retrieve three-dimensional maps of absorption and scattering coefficients inside organs from non-invasive measurements. With a multispectral approach, the spatial distribution of endogenous chromophores (hemoglobin, water) can even be obtained. For some clinical applications, it is desirable to carry out the measurements for DOT with a compact probe including all sources and detectors. However, the depth sensitivity is a real challenge in this configuration. We propose to tackle this challenge by using time-resolved measurements. A time-resolved approach is developed to perform DOT with reflectance measurements at short source-detector separation. This approach involves methodological aspects including the processing of time-resolved signals by DOT algorithms based on the Mellin-Laplace transform. Then, this approach consists in optimizing the detection chain on two aspects for enhancing the detection and localization of absorption contrast in depth in diffusive media. First, the impact of the temporal response of the detector is studied with commercially available single-photon detectors (classical and hybrid photomultipliers). Second, the enhancements in probed depth permitted with fast-gated single-photon avalanche diodes are explored in a joint work with the Politecnico di Milano. To finish, a study is carried out to illustrate the performance of the proposed approach with respect to spatial resolution in depth for different configurations of sources and detectors in the optical probe. Probes with a width limited to a few centimeters open the gate to multiple clinical interests. They could access intern organs like the prostate or facilitate the measurements on extern organs like the breast or the brain
Ducros, Nicolas. "Tomographie optique de fluorescence dans les milieux diffusants : apport de l'information temporelle." Phd thesis, Université Claude Bernard - Lyon I, 2009. http://tel.archives-ouvertes.fr/tel-00473766.
Full textHenriques, de Figueiredo Bénédicte. "Evaluation de l’integration des donnees issues de la tomographie par emission de positons en radiotherapie : application à deux modèles cliniques : les cancers ORL et les cancers pulmonaires." Thesis, Bordeaux 2, 2013. http://www.theses.fr/2013BOR22125/document.
Full textObjective: To study the impact of Positron Emission Tomography (PET) data on radiotherapy (RT) planning through two clinical models: the head-and-neck cancers (HNC) and the pulmonary cancers. Methods and Materials: For HNC, after a previous phantom study in order to determinate an automatic segmentation method with adaptive thresholding, two series of nine and 15 patients selected for RT, underwent PET with 18F-Fluorodeoxyglucose (FDG) and 18F-Fluoromisonidazole (FMISO). The impact on RT target volumes (TV) and dosimetries was evaluated. For FMISO-PET, several time acquisitions and several segmentation methods were assessed. For pulmonary cancers, the use of a four-dimensional (4D) FDG-PET with partial volume effect (PVE) correction and several segmentation methods was evaluated through the first seven patients enrolled in the PULMOTEP protocol performed by the CHU of Bordeaux. Results: For HNC, FDG-PET led to a RT TV reduction of 40%, with mismatches between PET and CT data. For FMISO-PET images, a better contrast was obtained 4h after FMISO injection. However, segmented volumes obtained at 3 and 4h were not statistically different allowing PET- acquisitions at 3h in routine clinical practice. The use of FMISO-PET allows considering « dose escalation » on hypoxic TV with an increase of tumour control probability by 18,1% without excessive increase of toxicities. For pulmonary cancers, there was no impact of the respiratory motion correction but only one patient on seven presented a mobile tumour. PVE correction had impact on RT TV with an increase of the maximal tumoural activity by 27% and a volume reduction of 15%. Conclusion: For HNC, the validation of these results needs clinical and prospective studies. For pulmonary cancers, the use of 4D-PET must be decided case by case. On the other side, the implementation of automatic software for PVE correction seems interesting
Kobchenko, Maya. "Fracturation durant la production interne de fluides dans les roches : application à la migration primaire d'hydrocarbures." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENU035/document.
Full textThis thesis presents the experimental work and the results on fracturing of rock samples and analogue materials due to internal fluid generation during chemical reaction. The first two papers concentrate on time-resolved 3D X-ray imaging experiment on organic-rich shale samples. Paper 1 describes fracture formation due to hydrocarbon generation in the shale induced by organic matter decomposition during heating. Paper 2 gives an overview of the experimental procedure and image analysis workflow, which were used to obtain results presented in the first paper. The other two papers are focused on fracturing of gelatin mixed with yeast and sugar, which generates CO2. Paper 3 describes the mechanism of fracture network formation during draining of CO2 out of a gelatine layer. Paper 4 focuses on the temporal evolution of the drainage network and the mechanism of fracture opening and closing. The last paper presents a study in which X-ray microtomography was used to characterize porosity distribution in weathered andesite samples. The scientific methods developed in this project have potential application in studying dehydration of sediments, formation of mud volcanoes, methane hydrate exploration and assessment, geological sequestration of carbon dioxide CO2 and hydraulic fracturing of unconventional reservoirs
Jardin, Axel. "Utilisation du rayonnement X-mou pour l'étude du transport des impuretés dans les plasmas de tokamaks." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0482/document.
Full textGlobal energy consumption has increased significantly during the last century and will continue to grow in the coming decades. The development of sustainable energies alternative to fossil fuels is a crucial issue for the future generations. In this context, controlled thermonuclear fusion is a good candidate for the energy transition. Magnetic confinement fusion and tokamaks are currently the most promising solution to control the fusion reaction and use it for civil purposes.In tokamak plasmas, heavy impurities such as tungsten sputtered from plasma-facing components can migrate to the core plasma and strongly degrade fusion performance by radiation. The goal of this PhD thesis is to use this radiation in the soft X-ray range in order to obtain valuable information on tungsten transport in the core plasma. The final perspective is to control the impurity concentration and identify actuators that can act on this distribution
Charalampidou, Elli Maria. "Etude expérimentale sur la localisation des déformations dans les grès poreux." Thesis, Grenoble, 2011. http://www.theses.fr/2011GRENI090/document.
Full textThis PhD thesis presents a laboratory study aiming at a better understanding of the stress-strain response of the Vosges sandstone (porous rock) tested at a range of confining pressures (i.e., 20-190 MPa) and different axial strain levels. Localised deformation was captured at different scales by a combination of full-field experimental methods, including Ultrasonic Tomography (2D), Acoustic Emissions (3D), X-ray Tomography (3D), and 3D volumetric Digital Image Correlation, plus thin section and Scanning Electron Microscope observations (2D). These experimental methods were performed before, during and after a number of triaxial compression tests. The combined use of the experimental techniques, which have different sensitivity and resolution, described the processes of shear band and shear-enhanced compaction band generation, which formed at low to intermediate and relatively high confining pressures, respectively. Pure compaction bands were not identified. The deformation bands were characterised as zones of localised shear and/or volumetric strain and were captured by the experimental methods as features of low ultrasonic velocities, places of inter- and intra-granular cracking and structures of higher density material. The two main grain-scale mechanisms: grain breakage (damage) and porosity reduction (compaction) were identified in both shear band and shear-enhanced compaction band formation, which presented differences in the proportions of the mechanism and their order of occurrence in time
Suard, Elodie. "Limitation du colmatage dans les bioréacteurs à membranes à l'échelle industrielle : modélisation et caractérisation de l'hydrodynamique." Thesis, Toulouse, INPT, 2018. http://oatao.univ-toulouse.fr/24558/1/Suard%20elodie.pdf.
Full textBobelin, Laurent. "Tomographie depuis plusieurs sources vers de multiples destinations dans les réseaux de grilles informatiques hautes performances." Aix-Marseille 2, 2008. http://theses.univ-amu.fr.lama.univ-amu.fr/2008AIX22084.pdf.
Full textNowadays grids connect up to thousands communicating resources that may interact in a partially or totally coordinated way. Consequently, applications running upon this kind of platform often involve massively concurrent bulk data transfers. In order to optimize overall completion times, those transfers have to be scheduled based on knowledge about network performances and topology. Identifying and inferring performances of a network topology is a classic problem. Achieving this by using only end-to-end measurements at the application level is a method known as network tomography. When topology reflects capacities of sets of links with respect to a metric, the model used to represent the topology obtained is called a Metric-Induced Network Topology (MINT). Such a type of representation, obtained using statistical methods, has been widely used in order to represent performances of client/server communication protocols. However, it is no longer accurate when dealing with grids. In this thesis, we introduce a novel representation of the infered knowledge from multiple source and multiple destination measurements, algorithms in order to reconstruct such representations, methods to probe network in order to obtain an initial set of data from which we can reconstruct such topology. We also describe the tool we have designed an implemented in order to achieve these goals and experiences we have made in order to validate our methods and algorithms
Loignon-Houle, Francis. "Optimisation de l’extraction de lumière de scintillation dans les matrices de détecteurs pixellisés pour des applications en tomographie d’émission par positrons (TEP) et en tomodensitométrie (TDM)." Mémoire, Université de Sherbrooke, 2016. http://hdl.handle.net/11143/9776.
Full textAbstract : The performance of scintillation detectors, made up of a scintillating crystal coupled to a photodetector, critically depends on the collection and extraction efficiency of scintillation photons from the crystal by the sensor. In highly pixelated imaging systems (e.g. PET, CT), scintillators must be arranged in compact arrays with form factors detrimental to light transport, deteriorating the detector performance. The goal of the study was to optimize the pixelated detectors performance by identifying the light loss sources related to the spectral, spatial and angular characteristics of the scintillation photons impinging on scintillators faces. Such information acquired by Monte Carlo simulations enables adequate weighting for the evaluation of achievable gains through structuring of the scintillators for enhanced light extraction to the photodetector. The magnitude of parameters affecting the light collection in arrays, such as adhesive materials absorption and reflector opacity that both have high impact on light output, was evaluated through a factorial design. A frequently used reflector because of its outstanding optical performance was characterized in more realistic conditions compared to air immersion in which its reflectivity is always reported. An important reflectivity quenching of the reflector in optically bonded scintillator arrays was discovered by simulation and confirmed experimentally. This explains the high light crosstalk measured in pixelated arrays as well as paving the way to assembling methods limiting or taking advantage, depending on the application, of this unsuspected transparency.
Li, Jia. "Simulation par éléments finis de la propagation de fissures de fatigue dans les matériaux polycristallins imagés par tomographie aux rayons X." Thesis, Paris, ENMP, 2015. http://www.theses.fr/2015ENMP0079/document.
Full textThe short fatigue crack propagation in polycrystal materials depends strongly on microstructure. Although numerous studies of characterisation and of simulation, the prediction of the short fatigue crack propagation remains a challenge.In order to understand the mechanisms of short fatigue crack propagation, an in-situ characterisation by X-ray tomography was carried out at ESRF, using two techniques of tomography. Diffraction Contrast Tomography (DCT) that is a non-destructive method can be used to obtain 3D morphology and grain orientations in an undeformed state of polycrystal materials. Couple with Phase Contrast Tomography (PCT), it allows to characterise the short fatigue crack propagation at different loading stages. Access to this information, it is possible to simulate the short fatigue crack propagation using a 3D reel microstructural mesh reconstructed from the tomographic images.In this work, the elastic anisotropic behaviour in a 3D microstructural mesh is performed. The elastic strain tensors averaged in grains are also compared to the experimental measurements. Then, a new numerical approach is proposed to simulate crack propagation. From a crystal plasticity FE simulation, the crack growth direction is determined by a post processing. Next, the crack is propagated through remeshing. This approach is firstly applied to the single crystals, then to the polycrystal mesh reconstructed from the tomographic images. The grain boundary effects and the crack growth rate are also analysed. By comparing between simulation and experimental crack, the damage indicator is discussed at the end
Grésillaud, Alain. "Prise en compte de l'anisotropie sismique dans les tomographies lithosphériques." Université Louis Pasteur (Strasbourg) (1971-2008), 1994. http://www.theses.fr/1994STR13015.
Full textKunach, Margaret. "Effets du sexe biologique et des habitudes de vie sur les anomalies du métabolisme postprandial des acides gras chez les patients intolérants au glucose." Mémoire, Université de Sherbrooke, 2015. http://hdl.handle.net/11143/7607.
Full textAbstract : Insulin resistance is a major risk factor for the development of type 2 diabetes. Abnormalities in postprandial metabolism, which are characterized by a relative decrease in fatty acid storage capacity in adipose tissue leading to fatty acid spillover into the systemic circulation, give rise to ectopic fat deposition in non adipose tissues such as the heart, the liver and skeletal muscles. This phenomenon, commonly referred to as lipotoxicity, arises within the context of a chronic positive energy balance which is the direct result of excessive food consumption together with decreased energy expenditure and may be different in men and women. Many studies have shown, however, that metabolic abnormalities are reversible with changes in lifestyle habits. Our laboratory has developed a unique non-invasive method to study dietary fatty acid (DFA) metabolism using a radioactive tracer, 14(R,S)-[[superscript 18]F]-fluoro-6-thia-heptadecanoic acid ([superscript 18]F-FTHA), a long-chain fatty acid analogue, in combination with positron emission tomography. Our previous work demonstrated that patients with impaired glucose tolerance (IGT+) display an increase in myocardial DFA partitioning associated with a decreased left ventricular ejection fraction and stroke volume. Following a one-year lifestyle intervention regimen in IGT+ subjects, a reduction in myocardial DFA uptake as well as an improvement in cardiac function parameters was observed. However, IGT+ subjects who participated in a short-term caloric restriction while maintaining their usual level of physical activity, experienced an increase in myocardial DFA partitioning in parralel with a decreased left ventricular ejection fraction. Caloric restriction, physical activity and weight loss all have an impact on energy substrate metabolism and cardiac function in IGT+ patients, but gender is a major determinant as well. Increased myocardial DFA uptake in men is driven largely by elevated circulating chylomicron-TG levels whereas in women it appears to be associated with obesity. Although it was not possible for us to establish a link between IGT+ patients’ lifestyle habits and the postprandial metabolic abnormalities that they display nor to identify which lifestyle changes contributed to the metabolic improvements in the heart observed after the intervention, our studies helped redefine our methodological tools for assessing lifestyle parameters and underlined the importance of considering gender differences in our future studies.
Tonnellier, Alice. "Ecoute sismique des glissements de terrain dans les roches argilo-marneuses : détection et identification des sources intervenant dans la progression des glissements." Phd thesis, Université de Strasbourg, 2012. http://tel.archives-ouvertes.fr/tel-00873617.
Full textDelprat-Jannaud, Florence. "Tomographie de reflexion : quelle est l'information contenue dans les temps d'arrivee?" Paris 11, 1991. http://www.theses.fr/1991PA112308.
Full textGirard, Didier Laurent Pierre Jean. "Les méthodes de régularisation optimale et leurs applications en tomographie nouveaux algorithmes performants de reconstruction d'images /." S.l. : Université Grenoble 1, 2008. http://tel.archives-ouvertes.fr/tel-00311758.
Full textNguyen, Cong Doan. "Etude expérimentale de l'impact de l'érosion par suffusion sur les propriétés physiques et mécaniques des sols." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0676/document.
Full textThis thesis work has investigated, on the one hand, the mechanism of internal erosion by suffusion in earthen hydraulic structures, and, on the other hand, the consequences suffusion can cause on the mechanical behavior of soils, the main objective being to improve our understanding of both the suffusion process and the behavior of eroded soils. The approach adopted was mainly experimental, by a multi-scale scope: from macroscopic, at the material scale, to microscopic, at the grain scale. At the macroscopic scale, suffusion experiments were performed on gap-graded cohesionless soil samples using a newly developed testing device, called the suffusion permeameter. Then, the eroded samples are transferred by a freeze/thaw procedure to a triaxial device to study their behavior under mechanical loading. The achieved results provide a general overview of the suffusion mechanism at the sample scale and highlight its impact on soil shear resistance properties. At the microscopic scale, the suffusion mechanism has been studied by performing a suffusion test with in-operando x-ray tomography and using local visualization based on optical techniques in an artificial soil. Subsequent grain-scale analysis has provided a deeper understanding of suffusion process through the characterization of the eroded soil microstructure, particularly highlighting the occurrence and development of strong heterogeneities, which appear to play a key role in the macroscopic mechanical behavior of eroded soils
Lasalle, Audrey. "Les céramiques venues du froid... : Formulation, congélation et structuration par ice-templating." Phd thesis, INSA de Lyon, 2011. http://tel.archives-ouvertes.fr/tel-00717722.
Full textSix, Pierre. "Estimation d'état et de paramètres pour les systèmes quantiques ouverts." Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEM019/document.
Full textIn recent years, the scientifical community has succeeded in experimentally building simple quantum systems on which series of measurements are successively acquired along quantum trajectories, without any reinitialization of their state (density operator) by the physicist. The subject of this thesis is to adapt the quantum tomography techniques (state and parameters estimation) to this frame, in order to take into account the feedback of the measurement on the state, the decoherence and experimental imperfections.During the measurement process, the evolution of the quantum state is then governed by a hidden-state Markov process (Belavkin quantum filters). Concerning continuous-time measurements, we begin by showing how to discretize the stochastic master equation, while preserving the positivity and the trace of the quantum state, and so reducing to discrete-time quantum filters. Then, we develop,starting from trajectories of discrete-time measurements, some maximum-likelihood estimation techniques for initial state and parameters. This estimation is coupled with its confidence interval. When it concerns the value of parameters (quantum process tomography), we provide a result of robustness using the formalism of particular filters, and we propose a maximization technique based on the calculus of gradient by adjoint method, which is well adapted to the multi-parametric case. When the estimation concerns the initial state (quantum state tomography), we give an explicit formulation of the likelihood function thanks to the adjoint states, show that its logarithm is a concave function of the initial state and build an intrinsic expression of the variance, obtained from asymptotic developments of Bayesian means, lying on the geometry of the space of density operators.These estimation techniques have been applied and experimentally validated for two types of quantum measurements: discrete-time non-destructive measurements of photons in the group of cavity quantum electro-dynamics of LKB at Collège de France, diffusive measurements of the fluorescence of a supra-conducting qubit in the quantum electronics group of LPA at ENS Paris
Shen, Chengyi. "Études expérimentales et numériques de la propagation d'ondes sismiques dans les roches carbonatées en laboratoire." Thesis, Pau, 2020. http://www.theses.fr/2020PAUU3012.
Full textThe present study is an experimental and numerical work on the propagation of seismic waves in carbonate rocks at the laboratory-scale. We aim at producing seismic data that are comparable with field data so as to transfer the knowledge and techniques acquired and developed in field into the laboratory. In return, well-controlled laboratory-scale data can contribute to benchmarking tests on the latest imaging approaches as well as data processing procedures. Ultrasonic probes on natural rocks are fairly common in numerous engineering fields such as geophysical logging, civil engineering and materials science. In terms of ultrasonic sources, both the conventional piezoelectric transducer (PZT) and the laser-ablation pulse are used as a seismic source in our experimental configurations. In terms of receivers, a single-point Laser Doppler Vibrometer (LDV) is employed in most of the experimental setups. Additionally, a 3D wavefield-scan LDV has been used to perform multi-component measurements. The originality of this work consists in the comprehensive characterization of the laser source in a geophysical context and its use as a point-like megahertz source on the carbonate cores, which enabled us to propose original and efficient core-probing configurations for both experimentation and simulations. We developed and validated an experimental prototype featuring PZT-LDV or Laser-pulse-LDV as source-receiver configurations for high-resolution measurements. As to the numerical simulation, we adapted a Fortran code, initially dedicated to method developments at the field-scale, to the numerical production at the high-frequency (HF) laboratory-scale. We will show the results of calibrations on both the experimental and numerical tools including the polarization analysis on multi-component data, the results of the laser pulsed source characterization and the main tomography results from the First Arrival Travel-time (FAT) Tomography (FATT) featuring multi-grids, along with the parallelized 2D/3D simulations featuring the Interior Penalty Discontinuous Galerkin method (IPDGm). A brief demonstration of anisotropy analyses from FAT will also be given at the end. The latest generation of imaging method involves both the observed and synthetic data, such as the promising Full Waveform Inversion (FWI) that can push further the resolution limits of the classical tomography, which is the key motivation of our studies involving both the experiment and simulation
Comte, Jean-Christophe Travi Yves. "Apport de la tomographie électrique à la modélisation des écoulements densitaires dans les aquifères côtiers application à trois contextes climatiques contrastés (Canada, Nouvelle-Calédonie, Sénégal) /." Villeurbanne : TEL, 2009. http://tel.archives-ouvertes.fr/docs/00/38/19/05/PDF/Comte_THESE_2009-05-06.pdf.
Full textNerot-Salhi, Sophie. "Techniques d'analyse d'images appliquées à l’étude des structures dans les écoulements." ENSMP, 1996. http://www.theses.fr/1996ENMP0719.
Full textPlatel, Hervé. "Les composantes structurales de la perception musicale : etude en tomographie d'emission de positons." Caen, 1994. http://www.theses.fr/1994CAEN1160.
Full textWe have carried out an activatioin study on healthy subjects with the positron emission tomography technique. We studied the effects on cerebral metabolism for selective and divided attention on psychoacoustics parameters like pitch, timbre and rhythm, and for a semantic musical task called familiarity. The results obtained show prevalent and specific activations for the right hemisphere are only observed for the timbre task. The results are discussed with relevance to the neuropsychological literature. Our hypotheses was confirmed, and these results demonstrated the pertinence of the activation paradigm used. This paradigm is relevant to show the cerebral responses specificaly implicated for cognitions strategies used by subjects in order to do the tasks
Moussallem, Mazen. "Optimisation de la délimitation automatique des tumeurs pulmonaires à partir de l'imagerie TEP/TDM pour les planifications dosimétriques des traitements par radiothérapie." Phd thesis, Université Claude Bernard - Lyon I, 2011. http://tel.archives-ouvertes.fr/tel-00864905.
Full textUhry, Cyril. "Optimisation du procédé de tomographie X appliqué à la détection des défauts dans les matériaux composites." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI083/document.
Full textThe carbon-fiber-reinforced-polymer (CFRP) materials display excellent properties considering their weight. However, they also can display defects that can significantly decrease their properties. In order to verify the internal structure of the composite materials, non destructive control is required. In this document, the X-ray computed tomography is used. Nevertheless, the distinction of the defects is difficult because of the chemical proximity between the carbon and the resin. In order to improve the detection of the defects, this document proposes to study the different physical phenomena happening during the tomography process such as the study of the acquisition parameters and the phenomena that decrease the image quality. In order to help to understand the different phenomena, the simulation tool is used. It allows to study the different phenomena independently to the others. After the presentation of the composite materials and the x-ray computed tomography in the first part, the features of the used acquisition system are presented in the second part. The features of the simulation of the acquisition system are also presented. The third part propose a study of the different phenomena contributing to the image. The comparison of the results between the simulation and the experimental allows to highlight a backscattering phenomenon happening inside the detector. A protocol allowing to determine these phenomena experimentally and to add it on the computed projections is presented. Furthermore, the simulation does not take the noise on the projection into account. Another protocol is presented, allowing to determine it experimentally. The fourth part displays the study of the optimization of the image quality using the simulation. The choice of the accelerating voltage is studied as well as the influence of the object scatter radiation. The fifth part proposes an experimental validation of the results. Especially, a correction of the backscattering is presented and applied to the composites objects
Leblanc, Béatrice. "Etude du débit sanguin cérébral par la méthode du SPECT (Single photon emission Computed Tomography) dans les spasmes infantiles." Bordeaux 2, 1992. http://www.theses.fr/1992BOR2M116.
Full textLe, Digarcher Sandrine. "Détection automatique de fixations radioactives dans les images TEP oncologiques." Lyon, INSA, 2009. http://theses.insa-lyon.fr/publication/2009ISAL0119/these.pdf.
Full textTherapeutic follow-up of patients with cancer is nowadays of main interest in research. Positron Emission Tomography (PET) appears to become a reference exam for monitoring treatment of cancers, particular in lymphoma. This PhD thus lieas on the development of a computer aided detection (CAD) tool focused on hardly visible tumors for whole-body 3D PET images. To achieve such a goal, we proposed an approach based on the combinaison of two classifiers, the Linear Discriminant Analysis (LDA) and the Support Vector Machines, associated with wavelet image features. Each classifier gives a 3D score map quantifying the probability of its voxels to correspond to a tumor. We proposed a 3D evaluation strategy based on the use of simulated images giving the targeted tumor characteristic gold standard. Such database was developed in this PhD from hundred Monte Carlo simulations of the Zuba phantom. It includes hundred images presenting 375 sperical tumors of calibrated contrasts. Results of the CAD obtained from the binary detection maps are promising. They open the perspective of enriching the binary information generally given to the clinician with parametric indices quantifying the pertinence of each detected tumor
Gariani, Gianluca. "Déchiffrer les matériaux, l'origine, et les procédés de fabrication des "Madonne di gesso" : étude technique de reliefs en stuc des maitres sculpteurs de la Renaissance Italienne." Thesis, Cergy-Pontoise, 2019. http://www.theses.fr/2019CERG1027.
Full textThe production of devotional reliefs flourished in 15th century Florence, where original marble models from Renaissance Masters were moulded to be reproduced in series. Among the materials mostly used to this purpose was the so-called “stucco”. Despite the wide diffusion of stucco reliefs, details concerning their constitutive materials and manufacturing processes are fragmentary and poorly studied. In the framework of a multidisciplinary project fostered by the Louvre Museum, this thesis explored three research lines in order to: 1) identify and characterise stucco mineral constituents; 2) determine raw material provenance; 3) investigate manufacturing techniques and serial casting processes.A multi-analytical approach was devised to investigate composition (SEM-EDX, PIXE, LA-ICP-MS) and structure (XRD, FEG-SEM, SµCT) of micro samples obtained from 30 representative artworks attributed to 7 Florentine Masters.Results showed that all the artworks are made of a gypsum based stucco (40-44 wt% CaO and 52-56 wt% SO3) with secondary mineral phases (anhydrite, calcite, dolomite, celestine and clay minerals) in few weight percentage maximum.PIXE and LA-ICP MS trace elements analyses, the study of W/P ratio and pores morphology by SEM-EDX and SµCT, pointed out that about 20 reliefs present similar compositional and structural parameters. This confirms the hypothesis of common practices and of a common production centre according to the Florentine attribution of the artworks.A geological survey was performed in 3 quarries in the surroundings of Florence and the provenance of the raw gypsum was investigated by means of geochemical and isotopic composition. In particular synsedimentary clay minerals with variable amounts of K, Mg and Fe, related trace elements (e.g. Ti and REE), and multi isotopic fingerprint (S, O, Sr) have been tested as provenance markers. Usefulness and pitfalls of the approach were verified through a first promising comparison with data obtained on stucco reliefs. Miocene quarries seems to have compatible signature with the ones measured on artworks.Nonetheless, small differences related both to accessory minerals proportions, to trace element contents, and to pores microstructures suggest that some of the stucco reliefs after models of Donatello and A. Rossellino might have been produced following different practices or particularly by using different raw materials. These evidences, corroborated by the activity of these artists in many Italian regions, raise the hypothesis of the production of these casts outside the Florentine area.In parallel, THz-TDI, Xray radiography and Computed Tomography were tested for the non-invasive investigation of the internal stratigraphy of plaster layers possibly revealing different manufacturing techniques.Finally, serial manufacturing techniques were investigated on 3 groups of replicas belonging to 3 models after Donatello & B. Bellano, D. da Settignano and A. Rossellino. Structured light 3D scanner and mesh comparison of the 3D models obtained on stucco casts proved to be a very useful tool. The method allowed to measure millimetric differences of shapes and topography among reliefs stored at the Louvre, Bargello and Bardini Museum. This helped to find direct correlations between casts, to verify which ones were most likely produced with the same mould, and to propose a chronology within the same casting series.Results obtained disclosed new and important insights on the practices of 15th century Florentine botteghe and on the manufacturing of these artworks. This work and the large set of data produced will also provide solid basis for further investigations and will hopefully prompt interest on this topic worth to be studied with increased attention
Zanotti, Fregonara Paolo. "Extraction de la fonction d'entrée artérielle des traceurs pour les études cérébrales en tomographie par émission de positrons." Paris 13, 2009. http://www.theses.fr/2009PA132003.
Full textFor the in vivo modelisation of radioactive tracer kinetics, it is necessary to know the input function, i. E the variation of arterial plasma tracer concentration over time. The input function is usually obtained by arterial blood sampling. Some studies have shown the possibility to calculate the input function directly from dynamic TEP images, using the time-activity curves obtained from large vascular structures. However, for brain studies, the largest blood vessels in the camera field of view are the internal carotids, the diameter of which is about 5mm. This aim of this work is to evaluate comparatively the existing methods for the segmentation of the internal carotids and for the PVE correction. We are proposed an original method for PVE corection as well, which be evaluated comparatively to the methods proposed in the literature
Laidevant, Aurélie. "Méthodes optiques résolues en temps pour la tomographie de fluorescence dans les milieux diffusants." Phd thesis, Université Joseph Fourier (Grenoble), 2006. http://tel.archives-ouvertes.fr/tel-00122185.
Full textRen, Yong. "Etude du manteau terrestre sous les Amériques : approche par tomographie régionale et fonctions récepteurs." Paris, Institut de physique du globe, 2006. http://www.theses.fr/2006GLOB0017.
Full textWe used seismic tomography and S receiver functions to study structures ofthe Earth's manteau beneath the Americas. In the first part, we combined Pand S-wave velocity models provided by the seismic tomography at regionalscale and plate motion history to investigate slabs of subductedlithosphere in the lower mantle beneath the Americas. We have been able toidentify different fast velocity anomalies observed in our tomographicimages with fragments of slabs that have subducted into the mantle; inparticular, we can follow the fragmentation of the Farallon plate withtime. Our interpretations are consistent with the volume and length ofslabs estimated from the tomographic images and those calculated from theplate history reconstruction. In the second part, we have used S receiverfunction technique to investigate seismic discontinuities in the uppermantle beneath the North-Western America. Stacks of receiver functionsshowed clear evidences of the Moho and the "410-km" discontinuity which isprobably depressed by about 15 km. The Lehmann discontinuity at 220 km isobserved in the area under the oceanic plate in the azimuth range around236°, whereas there is no clear evidence of this discontinuity for theazimuth ranges around 136° and 306°. Finally, we detect also a lowvelocity layer atop the "410-km" discontinuity and the stacking at CommunConversion Point show that its depth is around 380 km
Etxegarai, Aldami Etxebarria Maddi. "Etude du couplage hydromécanique dans les roches par analyse d'images obtenues par tomographie neutronique." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAI010/document.
Full textThe behaviour of subsurface-reservoir porous rocks is a central topic in resource engineering industry and has relevant applications for hydrocarbon and water production or CO2 sequestration. One of the key open issues is the effect of deformations on the hydraulic properties of the host rock, specifically in saturated environments. Deformation in geomaterials is rarely homogeneous because of the complex boundary conditions they undergo as well as for their intrinsic tendency to localise. This non uniformity of the deformation yields a non uniform permeability field, meaning that the traditional macroscopic analysis methods are outside their domain of validity. These methods are in fact based on measurements taken at the boundaries of a tested sample, under the assumption of internal homogeneity. At this stage, our understanding is in need of direct measurements of the local fluid permeability and its relationship with localiseddeformation.This doctoral dissertation focuses on the acquisition of such local data about the hydro mechanical properties of porous geomaterials in full-field, adopting neutron and x-ray tomography, as well as on the development of novel analysis methods. While x-ray imaging has been increasingly used in geo-sciences in the last few decades, the direct detection of fluid has been very limited because of the low air/water contrast within geomaterials. Unlike x-rays, neutrons are very sensitive to the hydrogen in the water because of their interaction with matter (neutrons interact with the atoms’ nuclei rather than with the external electron shell as x-rays do). This greater sensitivity to hydrogen provides a high contrast compared to the rock matrix, in neutron tomography images that facilitates the detection of hydrogen-rich fluids. Furthermore, neutrons are isotope-sensitive, meaning that water (H 2 0) and heavy water (D20), while chemically and hydraulically almost identical, can be easily distinguished in neutron imaging.The use of neutron imaging to investigate the hydromechanical properties of rocks is a substantially under-explored experimental area, mostly limited to 2D studies of dry, intact or pre-deformed samples, with little control of the boundary conditions. In thiswork we developed a new servocontrolled triaxial cell to perform multi-fluid flow experiments in saturated porous media, while performing in-situ loading and acquiring 4-dimensional neutron data.Another peculiarity of the project is the use of high-performance neutron imaging facilities (CONRAD-2, in Helmholtz Zentrum Berlin, and NeXT-Grenoble, in Institut Laue-Langevin), taking advantage of the world’s highest flux and cutting edge technology to acquire data at an optimal frequency for the study of this processes. The results of multiple experimental campaigns covering a series of initial and boundary conditions of increasing complexity are presented in this work.To quantify the local hydro-mechanical coupling, we applied a number of standard postprocessing procedures (reconstruction, denoising, Digital Volume Correlation) but also developed an array of bespoke methods, for example to track the water front andcalculate the 3D speed maps.The experimental campaigns performed show that the speed of the water front driven by imbibition in a dry sample is increased within a compactant shear band, while the pressure driven flow speed is decreased in saturated samples, regardless of the volumetric response of the shear band (compactant/dilatant). The 3D nature of the data and analyses has revealed essential in the characterization of the complex mechanical behaviour of the samples and the resultant flow speed.The experimental results obtained contribute to the understanding of flow in porous materials, ensure the suitability of the analysis and set an experimental method for further in-situ hydromechanical campaigns
Courjault, Nicolas. "Contribution à l'étude de solutions non destructives pour la détection et la localisation de défauts électriques dans les structures électroniques 3D." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30313/document.
Full textThe thesis purpose was to explore several failure analysis techniques (Magnetic microscopy, Lock-in Thermography, X-rays Tomography, Time Domain Reflectometry) on their capabilities to localize the electrical defect (Short circuit, open circuit, resistive open, etc.) on 3D electronic component and system. Assessment possibilities of these techniques are suggested in order to ensure the defect localization in these new components. In particular, implementations of magnetic analysis in tilted sample as well as introduction of phase and amplitude magnetic images have been realized. This work also proposes to couple information obtain from magnetic microscopy to X-rays Tomography where the all system would be driven by 3D magnetic simulation
Junet, Arnaud. "Étude tridimensionnelle de la propagation en fatigue de fissures internes dans les matériaux métalliques." Thesis, Lyon, 2021. http://www.theses.fr/2021LYSEI006.
Full textFatigue is the main phenomenon causing the failure of mechanical structures. For very long service lives the initiation of cracks leading to the failure of in service mechanical parts changes from surface to volume. Due to experimental difficulties the propagation of internal cracks has only been studied to a limited extent in situ and in 3D. However, it is crucial from a dimensional point of view to know the behaviour of such cracks. In this work, in situ monitoring of the initiation and propagation of internal cracks was carried out by X-ray tomography (synchrotron source). Firstly, a method for manufacturing specimens was developed to enable systematic, non-destructive, and 3D visualization of the propagation of internal cracks in a titanium alloy (Ti-6Al-4V) at 20 Hz. For this purpose, an artificial defect was drilled on the surface of a rolled sheet of this material. A second sheet, placed on top of the first one, was diffusion bonded by spark plasma sintering, making it possible to make the defect volumetric. In situ fatigue tests showed the crucial role of the environment (vacuum) and, to a lesser extent, that of the crystallographic texture on the internal crack propagation rates. Secondly, an ultrasonic fatigue machine (cycling frequency of 20 kHz) allowing in situ testing at the synchrotron was used to study the 3D propagation of internal cracks in A357-T6 aluminium alloy specimens containing an artificial internal defect. The 3D grain distribution obtained by Diffraction Contrast Tomography (DCT) was used to study the interaction mechanisms between the microstructure and the 3D crack path
Wang, Long. "Etude de l’influence de la microstructure sur les mécanismes d’endommagement dans des alliages Al-Si de fonderie par des analyses in-situ 2D et 3D." Thesis, Ecole centrale de Lille, 2015. http://www.theses.fr/2015ECLI0004/document.
Full textAn experimental protocol was developed in this thesis in order to study the influence of casting microstructure on the fatigue behavior in Lost Foam Casting Al-Si alloys in tension and in Low Cycle Fatigue at room temperature. First of all, the microstructures of studied alloys were thoroughly characterized both in 2D and in 3D. The most suitable and representative specimens and Region of Interest (ROIs) where the in-situ monitoring was performed were selected through a preliminary characterization using X-ray tomography, which is also necessary to understand damage mechanisms after failure. In-situ observations performed on surface using Questar long distance microscope and in volume using X-ray tomography allow following cracks initiations and their propagations and thus allow identifying the relation between damage mechanisms and casting microstructure. 2D/3D displacement and strain fields measured using Digital Image Correlation and Digital Volume Correlation allows analyzing the relation between measured fields and damage mechanisms. Postmortem analysis and FEM simulation gave more information for the damage mechanisms. Large pores favor crack initiation as they strongly increase local stress level. Hard inclusions (Si phase, iron intermetallics and copper containing phases) also play an important role in crack initiation and propagation due to strain localizations at these inclusions
Soriano, Ilaria. "Bandes de déformation localisée dans les sables faiblement cimentés : l'exemple de Bédoin (Sud de la France)." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAI047.
Full textAn attempt to study the role of heterogeneities in the occurrence of deformation bands in weakly cemented sands was performed. Depositional structures and later deformation processes were considered as heterogeneities. In artificially cemented samples, they were observed to induce localised deformation across them, but this behaviour was not analysed in natural sands due to the complexity of extracting them from the field without altering their structure.The investigation was performed by using weakly clay-cemented sands from Bédoin (Southern France), whose outcrops are cross-cut by deformation bands. Small chunks of undisturbed cemented sand and of deformation bands were used to prepare polished thin sections, whereas large blocks of material were collected with an innovative field sampler and carried to the laboratory to extract intact samples for mechanical testing.From image analysis with Scanning Electron Microscopy of the thin sections, syntaxial quartz overgrowths were found everywhere, in increasing quantity from undisturbed and dilation band, to single-strand, multi-strand, and finally cluster. The observation of quartz overgrowths and of kaolinite illitization, inside and outside deformation bands, has led to extend the maximum burial depth estimated for the Bédoin outcrops to 2 – 3 km.From the mechanical tests performed with syn-deformation X-ray Computed Tomography, it emerged that depositional layers developed a low degree of shear (at about 0.5 – 1 MPa of confining pressure). However, localised deformation was more affected by other types of heterogeneities: on one hand, a region of enhanced porosity triggered the formation of a shear band across the enhanced pore; on the other hand, an elongated pore surrounded by thick clay cement layer moved the localised deformation far from the pore, instead of triggering it close by. Similarly, a pre-existing dilation band did not attract further localised deformation, but it only partially reactivated showing further dilation with shear.In parallel with tests on natural material, tests on artificially cemented and uncemented sands were performed under the same conditions applied to the natural ones. The cemented samples were composed of the same Bédoin sand cemented with two different clay contents (15% and 20%) fabricated with an innovative cementation procedure and without replicating the heterogeneities observed in the natural material. Natural samples showed earlier, fewer, and sharper bands than the artificially cemented ones, which developed broader networks of shear bands in the samples. The difference in mechanical behaviour is attributed to the heterogeneities, which revealed high mechanical resistance since none of them – region of enhanced porosity, elongated pore, pre-existing dilation band - collapsed under compression. In artificially prepared samples, the cement content was proportional to the sample resistance, but this was reported always lower than the natural samples resistance.X-ray Computed Tomography was also performed on some deformation band samples, in order to calculate porosity and permeability through image processing. Porosity reported a reduction from an average of 30% in undisturbed sands to values lower than 10% in single-strand bands and closer to zero in multi-strand bands. Porosity in the dilation band core was similar to that of undisturbed sands, but it reported contours with half value (about 15%). Permeability was reported to reduce of 3 – 4 orders of magnitude from undisturbed sands to single- and multi-strand bands, whereas the dilation band was one order of magnitude lower than the undisturbed sand.The role of heterogeneities was demonstrated to be not always influent on the localised deformation in the cemented sands of Bédoin. In the absence of heterogeneities, less intense and a more distributed strain localisation would be promoted, e.g., in the form of network of bands
Monier, Vanessa. "Etude des défauts cristallins dans le silicium par diffusion de la lumière." Aix-Marseille 3, 2010. http://www.theses.fr/2010AIX30056.
Full textThe on-going quality improvement of Silicon-On-Insulator wafers motivates further development of Laser Scattering Tomography (LST). This technique enables the investigation of oxygen precipitates and dislocations in silicon by means of infra-red light scattering. After evaluating the LST capability for the investigation of statistical populations of oxygen precipitates, the characterisation of individual precipitates was addressed. The size of specific oxygen precipitates was accurately monitored during their growth for different temperatures and defect morphologies. In the second part of this work, the theory of light scattering by a dislocation was adapted to the silicon case. This development combined with the tomography and polarization LST options makes it possible the complete characterisation of non-decorated dislocation slip systems. The discrimination of decorated vs. Non-decorated dislocations is also achievable by LST
Cadiou, François. "Étude de l'impact de la microstructure sur les propriétés effectives électriques des batteries lithium-ion." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI108.
Full textLi-ion batteries are interesting for applications such as electric vehicles. They have indeed a high energy and power density, which makes them good substitutes for internal combustion engines. However, even if they are now quite widely used in many fields, there is still a need to optimize their performance. This requires a better understanding of the impact of the electrodes microstructure on their effective properties to narrow the gap between ideal and practical performance. Three-dimensional characteristics such as the carbon additive percolation or the tortuosity of the porosity have a strong impact on the electrode charge transport properties and power performance. The use of 3D imaging techniques such as X-ray tomography and serial focused ion beam and SEM tomography (FIB/SEM) is very powerful to quantify the electrode microstructures and interpret their charge transport properties. Furthermore, by processing the reconstructed volumes, one can use them as a basis for numerical simulations. We have chosen the FFT (Fast Fourrier Transform) method with "discrete" Green operator for numerical computations. These simulations can either be used to back calculate the phase (active material or conducting additive/binder) conduction properties from macroscopic electrical measurements by inverse method, or to predict the electrode effective conductivity from the phase conductivities. The 3D numerical microstructures obtained can also be modified in order to predict the influence of compositional changes in the electrode formulation on its properties. This study sets new tools to understand better the relationships between microstructure, effective electrical properties and the performance of Li-ion battery composite electrodes
Baillet, Marion. "Les modifications du sommeil et du cycle veille/sommeil au cours du vieillissement : approche par actimétrie et imagerie cérébrale." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0950/document.
Full textSleep and activity/rest cycle disturbances represent risk factors for the development of cognitive decline and dementia in aging. However, the association between these disturbances and cerebral modifications during aging remains to be explored. The aim of this thesis was to determine if sleep and activity/rest cycle disturbances could constitute a cerebral frailty factor for the development of cognitive decline and dementia in older adults (AMImage cohort). First, we have shown that the discrepancy measured between self-reported sleep questionnaires and actigraphy - used as an objective technique - is influenced by the subject’s mood (Baillet et al., 2016). These results strengthen the use of an objective technique to measure sleep. Thanks to brain imaging, we observed that a reduced 24-h amplitude of the activity/rest cycle is associated with disruption of white matter structural integrity. Our results suggest that cerebral frailty associated with age-related activity/rest cycle dysfunction has a vascular origin (Baillet et al., 2017). Then, we observed that a poor sleep quality is associated with high cerebral amyloid burden, mainly circumscribed to frontal regions. This may be due to a deficit of amyloid-β peptide clearance from the brain during sleep. To conclude, sleep and activity/rest cycle disturbances in older adults may be associated with two separate physiopathological processes leading to cerebral frailty. As sleep and activity/rest cycle are modifiable risk factors, interventions to improve their quality could offer a potential useful strategy for reducing the burden of cognitive impairment and dementia in old age