Dissertationen zum Thema „Imagerie de Microstructure par Diffraction“
Geben Sie eine Quelle nach APA, MLA, Chicago, Harvard und anderen Zitierweisen an
Machen Sie sich mit Top-50 Dissertationen für die Forschung zum Thema "Imagerie de Microstructure par Diffraction" bekannt.
Neben jedem Werk im Literaturverzeichnis ist die Option "Zur Bibliographie hinzufügen" verfügbar. Nutzen Sie sie, wird Ihre bibliographische Angabe des gewählten Werkes nach der nötigen Zitierweise (APA, MLA, Harvard, Chicago, Vancouver usw.) automatisch gestaltet.
Sie können auch den vollen Text der wissenschaftlichen Publikation im PDF-Format herunterladen und eine Online-Annotation der Arbeit lesen, wenn die relevanten Parameter in den Metadaten verfügbar sind.
Sehen Sie die Dissertationen für verschiedene Spezialgebieten durch und erstellen Sie Ihre Bibliographie auf korrekte Weise.
Ribart, Clément. „Essais 4D multimodaux et simulations numériques appliqués à l'étude de la plasticité cristalline“. Electronic Thesis or Diss., Université Paris sciences et lettres, 2024. http://www.theses.fr/2024UPSLM001.
Der volle Inhalt der QuelleEstablishing microstructure-property relationships is a critical challenge for the design of structural materials. Metals dis-play an heterogeneous polycrystalline organisation which drives their performance, hence the need to access to themechanical quantities of interest at the grain and sub-grain scales. A variety of characterization techniques now givesaccess to those levels of details. Recent progress in synchrotron and laboratory X-ray techniques have contributed to therise of multimodal experiments, especially by allowing non destructive in situ testing. In particular, Diffraction ContrastTomography (DCT), which belongs to the Diffraction Microcrostructure Imaging (DMI) techniques family, allows the re-construction of 3D grain maps with their associated orientations field and actual morphology. These digital twins canbe used directly for simulations. Improved convergence of experimental and numerical modalities leads to unified andmassive databases. This represents an opportunity to unlock the understanding of the complex physical mechanisms atstake. The main objective of the present work is to contribute, with concrete use cases, to demonstrate the potential ofthis approach. We introduce two in situ multimodal datasets applied to incipient crystal plasticity on a commercially puretitanium. First, we assess the performance of the EBSD, synchrotron DCT and LabDCT techniques used. A statisticalregistration technique allows to compare rigorously these modalities. Typical plasticity mechanisms are observed at thesurface and in the volume (grains rotation, plastic slip and intragranular transmission, GND dislocations accumulation atgrain boundaries), as well as the formation of sub grains, an unprecedented observation only enabled by the DCT. Inaddition, the FFT simulation performed on a DCT volume allowed us to validate the performance of the continuous crystalplasticity model, excepted in the vicinity of the non modelized precipitates. The last chapter presents a complementarynumerical study of the performance of the LabDCT algorithm, commercialized by XNovo Technology, on a microstructurein the deformed state. This study lies in the scope of extending the reconstruction applications of DMI techniques. Weshowed good performance of the algorithm for tracking grains rotations during the deformation. On the other hand, the program is not able to reconstruct a reliable intragranular orientation field
Ge, Xunyou. „Imagerie ultrarapide à l'échelle nanométrique par diffraction XUV cohérente“. Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00828058.
Der volle Inhalt der QuelleGe, Xunyou. „Imagerie ultrarapide à l’échelle nanométrique par diffraction XUV cohérente“. Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112361/document.
Der volle Inhalt der QuelleUltrafast imaging of isolated objects with nanometric spatial resolution is a great challenge in our time. The lensless imaging techniques have shown great potential to answer this challenge. In lensless imaging, one can reconstruct sample images from their diffraction patterns with computational algorithms, which replace the conventional lens systems. Using ultrafast and coherent light sources, such as free electron laser and high order harmonics, one can investigate dynamic phenomena at the femtosecond time scale. In this thesis work, I present the lenless imaging experiments using XUV radiation provided by a laser driven high order harmonic beamline. The manuscript is composed of an introduction, a chapter of theoretical background, three chapters of main research work and a general conclusion with perspectives. The first part of this work concerns the development of the harmonic beamline to optimize the illumination condition for lensless imaging. The second part concentrates on the imaging techniques: the Coherent Diffraction Imaging (CDI), the Fourier Transform Holography (FTH) and the Holography using extended references (HERALDO). The reconstructions have achieved 78 nm spatial resolution in case of CDI and 112 nm resolution in case of HERALDO, both in single-shot regime corresponding to a temporal resolution of 20 fs. The third part presents the first physical application on the harmonic beamline using the lensless imaging. Samples with magnetic nano-domains have been studied with sub-100 nm spatial resolution, which paves the way for ultrafast magnetic dynamic studies. At the end, single-shot 3D imaging and further beamline development have been discussed
Wang, Fan. „Imagerie nanométrique 2D et 3D ultrarapide par diffraction cohérente“. Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112226/document.
Der volle Inhalt der QuelleCoherent diffraction is an amazing art by its experimental simplicity: a coherent XUV source illuminates a single, isolated sample, and the diffraction pattern of the object is recorded by a CCD camera. An inversion of the diffraction pattern to an image in real space is possible through an approach based on iterative algorithms. The techniques for Fourier transform holography, for which reference is placed near the object to be imaged, allow the direct reconstruction of the image, even when the quality of the experimental data is worse. We have a laboratory sufficiently intense compact XUV source for this type of experience. The ultrashort XUV pulses (from femtosecond to attosecond) are produced by selecting high order harmonics of a femtosecond infrared laser which is focused into a cell of rare gas. We recently demonstrated the feasibility of using this source for coherent diffraction imaging with a spatial resolution of 78 nm. Furthermore, we demonstrated experimentally a holographic technique with extended reference and obtained a resolution of 110 nm in single shot (i.e. an integration time of 20 femtoseconds). A perception of an object in three dimensions gives us a better understanding thereof. A nanoscale 3D imaging techniques are from tomographic techniques of electron microscopy. However, many shots required (from different angles) make these techniques obsolete during the study time-resolved irreversible phenomena on non-reproducible samples. In this context, the aim of my thesis is to extend the 2D imaging techniques for 3D perception of nanoscale (physical, biological ) objects, while preserving the ultrafast appearance. The development of a new technology of 3D coherent imaging in single view, named ‘ankylography’, proposed by Professor Miao J. UCLA [Raines et al., Nature 2010] was made in progress. This technique allows reconstructing a 3D image of the sample after a single diffraction image. Its basic principle is to find the depth of a 3D object by the longitudinal constructive interference. However, this technique is more requested in both the quality of experimental data and the computer hardware and analysis. The other idea for 3D imaging is to imitate human vision using two coherent beams X arriving simultaneously on the sample but with a small angle. In this scheme, we use references near the target object (i.e. holography) to improve the signal to noise ratio in the diffraction pattern (hologram). Two holograms are then collected on the same detector. The inverse Fourier of each hologram forms two images from different views of the object. Parallax is thus produced. The stereo reconstruction of the object is performed by computer. Finally, the demonstration of applications will be considered after my thesis. This imaging of biological objects (such as nanoplanktons already collected and prepared CEA). And we are also interested in the study of 3D nanoscale objects (azo-polymers) movement on ultrashort time. Furthermore, another important application will be to study the ultra-fast phase transition such as nano-magnetic field where demagnetization phenomena induced by femtosecond pulse occurs
Mastropietro, Francesca. „Imagerie de nanofils uniques par diffraction cohérente des rayons X“. Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00716410.
Der volle Inhalt der QuelleGuillermin, Régine. „Caractérisation d'objets enfouis dans des sédiments marins par imagerie acoustique“. Aix-Marseille 2, 2000. http://www.theses.fr/2000AIX22068.
Der volle Inhalt der QuelleCassin, Rémy. „Imagerie nanométrique ultra-rapide par diffraction cohérente de rayonnement XUV produit par génération d'harmoniques d'ordre élevés“. Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS591/document.
Der volle Inhalt der QuelleThe aim of this dissertation is todevelop new lensless single shot imagingtechnique in 2D and 3D with XUV harmonicsources which can be applied to study biologicalobjects and phase objects. Firstly, we introducethe theory underlying lensless imagingtechniques and we describe the methods usedduring this thesis to reconstruct the light fielddiffracted by the studied object. The imagingtechniques are split in two categories: iterativeand holographic. The iterative methodsreconstruct the phase of the diffracted wavefront using constraints in the Fourier space andthe reel space. With the holographic techniques,the phase is encoded directly in the interferencefringes between the reference and the objectwithin the diffraction pattern. We discuss theexperimental parameters required to achieve animage reconstruction and we compare therespective advantages of the two types ofmethod. Then, we describe the experimentalparameters of the XUV beam produced by highharmonic generation (HHG) and we brieflyexplain the theory of the HHG. The next sectiondiscusses the parameters the quality of thereconstructed image. We show how to improvethe resolution and the signal to noise ratio usingthe HERALDO technique in the low fluxregime.We then show the result of a new technique forthe single shot characterization of the spatialcoherence of XUV beams. Indeed, the spatialcoherence is a critical parameter for coherentdiffractive imaging techniques. Using a NRA ofreference holes, we measure the spatialcoherence for each distance between each pairof holes, without the knowledge of the intensitydistribution on the sample. We show that thespatial coherence has a gaussian distribution andthat its diameter varies according to thegeneration parameters of the harmonic beam.We also study quantitatively the effect of multishotsaccumulation of the diffraction pattern onthe apparent coherence of the beam. We alsoshow the result of phase object imaging usingcoherent diffractive imaging with a harmonicsource. To our knowledge, this if the first timesuch result has been achieved. The rest of thedissertation present new lensless imaging 3Dtechniques using harmonic sources. The first ofthe last two experiments shown is a lenslesssingle shot stereo 3D technique. It is the first oneallowing a 3D reconstruction from a singleacquisition, with a nanometer spatial resolutionand a femtosecond temporal resolution, withoutusing \textit{a priori} knowledge of the samplestudied. This method has a vast spectrum ofapplication and is particularly interesting for thestructural study of biological sample sensitive toradiation damage and for the study of nonreversibledynamical phenomena in 3D.Furthermore, this can easily be implemented inFELs and synchrotrons to reach even betterspatial resolution. The second 3D experimentshown in this thesis is a proof of concept ofcryptotomography using a high harmonic sourcein a low flux regime. To reconstruct the 3Dvolume of the sample, cryptotomographie usesdiffraction pattern acquired for unknown sampleorientations and therefore non-classified. Thelow flux regime used here simulate the flux of aharmonic source generated in the water window.We conclude from this experiment that, with theproper experimental conditions, the diffractionsignal is sufficient to allow the classification byorientation of the diffraction patterns. Withenough diffraction pattern and angles of thesample recorded, we can achieve a 3Dreconstruction of the sample. This result impliesthat the cryptotomography of biological objectsusing a water window harmonic source ispossible
Herail, Christophe. „Etude et réalisation d'un système de mesure rapide de champs acoustiques : applications à l'imagerie médicale en tomographie par diffraction“. Paris 11, 1989. http://www.theses.fr/1989PA112194.
Der volle Inhalt der QuelleThis thesis contributes to the experimental study of ultrasound imaging with the so-called diffraction tomography method in which the diffraction phenomena inside the object under investigation are taken into account. The work was carried out in three steps: - Implementing a linear network of electronically scanned sensors within an ongoing experiment and solving the problem of inter-element coupling. - Designing and making a new electronic device in order to measure the acoustical pressure field then exploited by a microcomputer which both drives the experimental set-up and computes the images. This device was carefully conceived and made, so as to obtain performances (e. G. Noise level, accuracy, temperature stability) compatible with the requirement of the reconstruction method. - Conducting various experiments on objects of simple shapes (phantoms) and on a real biological object, and last, carrying out a qualitative study of thermography with differential imaging
Gauthier, David. „Imagerie nanométrique ultra-rapide par diffraction cohérente de rayonnement extrême-UV produit par génération d'harmoniques d'ordre élevé“. Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00734344.
Der volle Inhalt der QuelleVarlet, Joël. „Microstructure et propriétés mécaniques d'alliages de polymères polypropylène - polyamide 12 stabilisés par un tiers corps“. Lyon, INSA, 1990. http://www.theses.fr/1990ISAL0071.
Der volle Inhalt der Quelle[The blends have been studied by means of variations complementary techniques in order to obtain information on several levels of the microstructure:-The crystal lattice level (scale of a few Angstroms), the crystalline regions level (scale of a few hundred of Angstroms), and the homopolymers regions level (scale of a few microns). - By X-ray techniques (eg W. A. X. S. And S. A. X. S. ), we have characterized an orientation of the crystalline phases which occur in. The samples as a result of the injection-moulding preparation technique. The mechanical spectrometry and scanning electron microscopy results have been combined to show the specific geometrical arrangement of the homopolymer regions, as well as the changes that occur in these regions as they are mixed. Nucleating effects of the third component (TC) on the crystalline phase of polypropylene have been detected. The microstructural information thus obtained was used to interpret the main features of the large deformation response of the blends, such as its anisotropic nature and the large influence of TC]
Mariotti, Jean-Marie. „Imagerie à la limite de diffraction en infrarouge proche : méthodes et résultats astrophysiques“. Lyon 1, 1987. http://www.theses.fr/1987LYO10048.
Der volle Inhalt der QuelleReinhart, Guillaume, Henri Nguyen-Thi, Bernard Billia und Joseph Gastaldi. „Dynamique de formation de la microstructure de solidification d'alliages métalliques : caractérisation par imagerie X synchrotron“. Phd thesis, Université Paul Cézanne - Aix-Marseille III, 2006. http://tel.archives-ouvertes.fr/tel-00371700.
Der volle Inhalt der QuelleLian, Weidong. „Contribution à l'homogénéisation numérique du comportement élastique de matériaux à microstructure complexe caractérisés par imagerie“. Ecole centrale de Nantes, 2011. http://www.theses.fr/2011ECDN0004.
Der volle Inhalt der QuelleComputational homogenization approaches are now widely used. Moreover, imaging techniques allow a highly accurate representation of material microstructure, and classically leads to voxel-based finite element models. Another computational approach for image-based modeling has been recently proposed, based on X-FEM and level set method. These two approaches are compared and it is shown that X-FEM/levelset approach is more efficient and accurate than the voxel-based FEM. Using microstructure images highlights its randomness, which raises the problem of the determination of the sizeof the RVE (reprentative volume element). It's shown that homogenization approaches with uniform strins or stresses boundary conditions lead to overcome these edge effects. At last a three scale homogenization approach is presented for problems where the macroscale is much larger than the microscale. An intermediate mescoscale is considered, with a size lower than the RVE size. At this mesoscale computed apparent properies are random variables. These are represented using polynomial chaos expensions identified from samples which are extracted from the image. Macroscopic samples are then generated, with a mesoscopic modeling scale, and a spacial distribution of apparent properties coming form the previous step. Applying again classical homogenization methods at this new scale allows the determination of RVE size
Reinhart, Guillaume. „Dynamique de formation de la microstructure de solidification d' alliages métalliques : caractérisation par imagerie synchrotron“. Aix-Marseille 3, 2006. http://www.theses.fr/2006AIX30039.
Der volle Inhalt der QuelleWe studied in situ and real-time the directional solidification of thin samples of binary alloys and a quasicrystal using both X-ray radiography and topography techniques. On Al-3. 5wt%Ni non-refined alloys, we studied the formation of the initial state and the solidification front morphology (cellular then dendritic growth). Mechanical strains wer highlighted. The Columnar to Equiaxed Transition was studied on Al-3. 5wt%Ni refined alloys. We described the blocking of the columnar front and the following equiaxed growth regime. The refining particles efficiency reaches a limit. An analysis of the microstructure morphology was performed. The study of the i-AlPdMn quasicrystal shows the growth of faceted dodecahedral grains. Thermosolutal convection effects were highlighted. Strain visualisation shows a strong deformation of grains. The apparition of porosity was observed during fusion of grains
Daoud-Aladine, Moursidali Aziz. „Etudes par diffraction des corrélations entre magnétisme et structure des manganites à ordre de charges“. Paris 11, 2001. http://www.theses.fr/2001PA112340.
Der volle Inhalt der QuelleThis thesis dedicates itself to diffraction studies of the structural and magnetic transitions in the manganites of the system Pr_(1-x)Ca_xMnO_3. For dopings going from x = 0. 33 to 0. 5, the (x, T) phase diagram presents only insulating phases. On the basis of the superexchange theory (SE), their fundamental state can be interpreted as the existence of an Mn3̂+ /Mn4̂+ -type of charge ordering, concomitant with an ordering of the d_z2̂ orbitals on the Mn3̂+ ions. These samples display also giant magnetoresitance properties in this state. One can understand qualitatively the phenomenon by considering that antiferromagnetic (AF) and ferromagnetic (F) phases which are attributed to an insulating and a conductive state respectively, are coexisting. In this scope, the magnetoresitance would result in the growth and percolation of the ferromagnetic fraction of the sample under the application of a magnetic field. The conclusion of the structural and microstructural studies led in this thesis contrasts with these ideas. The powder and the single crystalline samples studied are displaying homogeneous crystalline phases at zero field. To resolve such a contradiction, we present a neutron diffraction study on a twinned single crystal of Pr_O. 60Ca_0. 4OMnO3̂ of the structure of the charge ordered phase. This study allows us to invalidate the mixed valence Mn3̂+/Mn4̂+ for the electronic state of Mn in these compounds, on which the SE theory is based. The structural distortions we find indicate another type of charge order, that consists in the localization of the electrons on Mn dimers. These electron are involved a double exchange process, coupling ferromagnetically the Mn spins of each pair. The novelty of this interpretation invite to reconsider several interpretations of the properties of manganite : in particular, it shows that the understanding of the magnetism of their insulating phases, put forward the role of the magnetic exchange frustration in these systems, when we go beyond the super-exchange theory
Boyer, Marina. „Synthèse de nouvelles céramiques polycristallines transparentes par cristallisation complète du verre“. Thesis, Orléans, 2016. http://www.theses.fr/2016ORLE2024/document.
Der volle Inhalt der QuelleTransparent polycrystalline ceramic is an emerging class of optic and photonic materials. During this thesis, we used an innovative method to elaborate such materials: the full glass crystallization. This process permits to obtain new transparent polycristalline ceramics through the lack of porosity, inherent to the parent glass and to access to new crystalline phases. Two studies were leaded to improve the glass forming ability of the BaAl₄O₇ composition (1st transparent ceramic obtained from full glass crystallization). Surprising results were obtained with the crystallization of a new phase (BaGa₄O₇) or with the synthesis of two-phase transparent ceramics (BaAl₄O₇ – BaAl₂O₄) where the transparency is considerably enhanced compared to the BaAl₄O₇ ceramic thanks to a second phase crystallization (BaAl₂O₄), limiting the growth of the birefringent BaAl₄O₇ grains. Transparent polycristalline ceramics belonging to the melilite family, with Sr₁₊xRE₁₋xGa₃O₇₊x∕₂ (RE: rare earth) general formulae were also synthesized. White light emission properties have been demonstrated from the SrGdGa₃O₇ and SrYbGa₃O₇ compositions. This family opens the way to others applications where the total absence of porosity with the elaboration of new crystalline phases unattainable by solid state reaction are key factors. These possibilities were demonstrated in the case of transparent polycristalline ceramics showing an important ionic conductivity
Martin, Franck. „Microstructure, contraintes des multicouches métalliques Mo (110) / Ni (111) élaborées par pulvérisation ionique : influence sur les propriétés élastiques“. Poitiers, 2003. http://www.theses.fr/2003POIT2266.
Der volle Inhalt der QuelleWe investigated interfacial effects on properties of Mo(110)/Ni(111) multilayers by X-ray diffraction techniques and Brillouin light scattering. We observe a large softening of the shear modulus up to 65% of the predicted value. The interplanar spacings evolution and numbers of planes in Mo sub-layers suggest a Ni interdiffusion. . Considering an elastically soft interfacial layer in determining the C44 modulus allow to estimate it's specific modulus and the chemical interdiffusion length. The epitaxied multilayers showed a "Nishiyama-Wassemann" orientation relationship and a decrease of the "stress free" parameter, in Mo sub-layers, with decreasing period confirming the Ni diffusion in Mo. MoxNi1-x solid solutions showed metastable phases, for solute concentration below 27%, with a large decrease of the shear modulus up to 50% of the predicted value and above 27% alloys are amorphous and the shear modulus is stabilized
Chhann, Sorphal. „Etude de la recristallisation de l'Invar (alliage Fe-36%Ni) déformé par laminage asymétrique“. Paris 11, 2007. http://www.theses.fr/2007PA112105.
Der volle Inhalt der QuelleLn this study, we are interested in the development of recrystallized texture of invar deformed by asymmetrical rolling. The texture and the microstructure have been characterized at different scales using XXray and neutron diffraction, Scanning Electron Microscopy (SEM) associated with Electron Back Scattered Diffraction (EBSD) and Transmission Electron Microscopy (TEM). The deformed microstructure consists of elongated bands with a dislocation network substructure. There is not any cellular substructure. Concerning the texture, classical rolling components are obtained. However, in the case of the one-way asymmetrical rolling, the texture is Iightly turned around the transverse direction. After annealing, the recrystallized grains are more or less equiaxe, and the texture contained a large fraction of the cubic component associated with its twin. For the same thickness reduction, the acuity of the cubic component is larger after asymmetrical rolling than after symmetrical rolling. Concerning the microstructure evolution during annealing, we have observed the evolution of the dislocation networks into cellular substructures. Recovery is faster in the grains with the éubic orientation. As a consequence, the difference in stored energy between grains with the cubic orientation and the other orientation increases and explain the nucleation b Strain Induced Bounda Mi ration SIBM mechanism
Bimbault, Laurent. „Analyses des contraintes résiduelles, de la microstructure et des constantes élastiques de multicouches métalliques élaborées par PVD“. Poitiers, 1998. http://www.theses.fr/1998POIT2251.
Der volle Inhalt der QuelleKluender, Rafael. „Mesures en trois dimensions des distorsions cristallines par imagerie en diffraction de Bragg : application aux cristaux de glace“. Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00635598.
Der volle Inhalt der QuelleZontone, Federico. „Imagerie par diffraction ("topographie") à l'installation européenne de rayonnement synchrotron ("ESRF") : ligne de lumière, possibilités et premières expériences“. Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10037.
Der volle Inhalt der QuelleRoyer, Agnès. „Evolutions thermique et mécanique de la microstructure de superalliages monocristallins étudiées par diffusion centrale et diffraction (neutrons, rayons [gamma])“. Grenoble 1, 1993. http://www.theses.fr/1993GRE10097.
Der volle Inhalt der QuelleVo, Quoc Thang. „Imagerie d'essais mécaniques sur des composites à matrice métallique : contribution expérimentale à la validation de méthodes d'homogénéisation et identification de propriétés mécaniques par phases“. Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20151/document.
Der volle Inhalt der QuelleThis work is focused on a matrix/inclusion metal composite. A simple method is proposed to evaluate the elastic properties of one phase while the properties of the other phase are assumed to be known. The method is based on both an inverse homogenization scheme and mechanical field's measurements by 2D digital image correlation. The originality of the approach rests on the scale studied, i.e. the microstructure scale of material: the characteristic size of the inclusions is about few tens of microns. The evaluation is performed on standard uniaxial tensile tests associated with a long-distance microscope. It allows observation of the surface of a specimen on the microstructure scale during the mechanical stress. First, the accuracy of the method is estimated on ‘perfect' mechanical fields coming from numerical simulations for four microstructures: elastic or porous single inclusions having either spherical or cylindrical shape. Second, this accuracy is estimated on real mechanical field for two simple microstructures: an elasto-plastic metallic matrix containing a single cylindrical micro void or four cylindrical micro voids arranged in a square pattern. Third, the method is used to evaluate elastic properties of inclusions with arbitrary shape in an oxidized Zircaloy-4 sample of the fuel cladding of a pressurized water reactor after an accident loss of coolant accident (LOCA). In all this study, the phases are assumed to have isotropic properties
Brin, Christophe. „Approche métallurgique des processus d'usure par glissement dans un acier inoxydable austénitique“. Poitiers, 1999. http://www.theses.fr/1999POIT2363.
Der volle Inhalt der QuellePierron, Jean. „Microstructure de cristaux liquides cholestériques et de leur dispersion dans une matrice polymère, observés par microscopie électronique en transmission“. Toulouse 3, 1995. http://www.theses.fr/1995TOU30160.
Der volle Inhalt der QuelleLorut, Frédéric. „Etude de monocristaux de KTiOPO4 sous champ électrique : mesures électriques, observations optiques et imagerie par diffraction aux rayons X“. Université Joseph Fourier (Grenoble), 2000. http://www.theses.fr/2000GRE10211.
Der volle Inhalt der QuelleComblet, Fabrice. „Détection, localisation et identification de cibles radar par imagerie électromagnétique bistatique“. Phd thesis, Université de Bretagne occidentale - Brest, 2005. http://tel.archives-ouvertes.fr/tel-00011931.
Der volle Inhalt der QuelleMirea, Iulia. „Analyse de la microstructure 3D du tissu cardiaque humain à l’aide de la micro-tomographie à rayons X par contraste de phase“. Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI076/document.
Der volle Inhalt der QuelleCardiovascular diseases remain one of the most serious health problems, motivating research to deepen our understanding of the myocardial function. To succeed, there is a need to get detailed information about the spatial arrangement of the cardiac tissue components. Currently, our understanding of the cardiac microarcInstitut de Technologie de Harbin - Chineecture is limited by the lack of 3D descriptions of the cardiac tissue at the microscopic scale. This thesis investigates the 3D cardiac tissue microstructure using X-Ray µ-CT phase contrast imaging available at the ESRF. For the first time, 9 human cardiac left ventricle (LV) wall samples are imaged at an isotropic resolution (3.5 µm) and analysed. We focus on the description of the cardiac extracellular matrix (CEM) that is one of the main components of the tissue. The CEM includes: the endomysium that surrounds and separates individual myocytes and capillaries, the perimysium that surrounds groups of myocytes and the epimysium that surrounds the entire heart muscle. Each reconstructed sample is about 30 Gb which represents a large amount of data to process and display. To succeed, we developed an automatic image processing algorithm to binarise each sample by selecting the CEM. We extract statistical features of the ECM, mainly the thickness of the cleavage planes (CP) and the inter-CP distances. The results show that the local 3D arrangement of the CP differs according to their location in the LV (posterior, anterior, septal) and their distance from the apex (more complex). The thickness of the CP extracted from all the samples roughly ranges from 24 µm to 59 µm and the inter-CP distances from 70 µm to 280 µm with significant local variations of the standard deviation. Those new quantitative markers of the ECM of the human cardiac are of main interest for a better understanding of the heart function
Meneau, Caroline. „Croissance de nitrure d'aluminium par traitements plasma de surface d'Al ; corrélations entre microstructure, état micromécanique et comportement tribologique“. Poitiers, 1998. http://www.theses.fr/1998POIT2304.
Der volle Inhalt der QuelleVincent, Christophe. „Recalage et fusion pour la reconstruction de surfaces 3D obtenues par projection de franges : application à un système de vision dédié à l'orthopédie“. Saint-Etienne, 2003. http://www.theses.fr/2003STET4001.
Der volle Inhalt der QuelleThe work concerns the extension of a 3D digitalisation system by fringe projection for the generation of leg prostheses. The data acquisition, surface reconstruction and computer aided design are improved there. Concerning acquisition, an adaptive technique of sinusoidal fringe fitting is presented. The theoretical aspects of self-calibration of video-camera/projector pairs is investigated. In the 3D reconstruction, an original algorithm of self-indexing of fringes starting from multiple views, based on an iterative registration of reconstructed surfaces, is proposed. Moreover, an iterative registration of 2D profiles on 3D surfaces is used for the reconstruction of stumps. Lastly, computer-aided design tools have been developed for the generation of prostheses, in particular by fusion of 3D objects with 2D metamorphoses. The work undertaken has resulted in an operational system for generation of prostheses and has led to a possible definition for a new portable sensor
Friedrich, Corentin. „Méthodes de reconstruction en tomographie de diffraction 3-D“. Thesis, Ecole centrale de Nantes, 2016. http://www.theses.fr/2016ECDN0013.
Der volle Inhalt der QuelleThis thesis is focused on microwave tomography. This imaging technique consists in estimating a three-dimensional mapping of the dielectric properties of an unknown volume from measurements of the electromagnetic field from a known incident wave and scattered by this volume. This is a promising technique that is used in various applications (medical imaging, geophysics, non- destructive testing,...) but suffers from high computational costs. This is a reason why microwave imaging is not widely used in industry. Microwave imaging is considered as an inverse problem, where the error between the measurements and a forward model that describes the scattered field is minimized as a function of the properties of the volume. This inverse problem is ill-posed because the number of unknowns is higher than the number of measurements. It is tackled through the minimization of a regularized least-squares cost function, which is addressed by local iterative optimization algorithms. Moreover, the forward model is non-linear. Thus,reconstruction is a difficult and expensive procedure. The computation of the objective function and its gradient requires the resolution of a high number of linear systems, which are performed at each iteration of the optimization algorithm and represent most of the computational cost. In this thesis, we propose to reduce the computational costs of the reconstruction algorithms by focusing on the resolution of these linear systems. Two contributions are presented. The first one is a procedure in order to reduce the number of linear systems depending on the configuration of the measurement setup. The second contribution offers an efficient way to speed up the resolutions of the systems. We adapt block resolution algorithms, in order to jointly solve multiple linear systems involving a common operator matrix. These methods are validated on simulated, realistic, 3D problems, and applied to the reconstruction of real objects from experimental measurements of scattered fields. satisfactory results are obtained, where the computation time can be reduced by a factor of two, in particular for the most difficult reconstruction problems
Asserin, Olivier. „Analyse des contraintes résiduelles dans un acier martensitique F82H soudé par faisceau d'électrons“. Reims, 2000. http://www.theses.fr/2000REIMS034.
Der volle Inhalt der QuelleConchon, Florine. „Défauts et déformations au sein de couches d’oxydes épitaxiées : étude par diffraction des rayons X en haute-résolution“. Limoges, 2008. https://aurore.unilim.fr/theses/nxfile/default/c899b395-9d15-454b-98c0-9a1bf4d72251/blobholder:0/2008LIMO4010.pdf.
Der volle Inhalt der QuelleThis work deals with microstructural analysis in epitaxial oxides films by X-ray diffraction. In this aim, different scattering techniques have been used both on laboratory and synchrotron equipments. A model, combining a microscopic description of the shape and size effects of the crystallites and a phenomenological description of the lattice distortions has been developed in order to account for the effects arising from defects on the scattering profiles. Two oxides systems have been investigated. Firstly, the ZrO2/MgO system, characterized by a high lattice mismatch, exhibits two subsets of misfit dislocations. The first one, is a square network of misfit dislocations randomly distributed and is characterized by a low density of dislocations, whereas the second network constituted by periodic dislocations and characterized by a high density of dislocations is responsible for the strain accommodation between ZrO2 and MgO. The second oxides system, SmNiO3/SrTiO3, presents a low lattice mismatch. The analysis of the reciprocal space maps allowed us to separate the mechanical effect from the chemical effect on the global strain relaxation. The mechanisms responsible for this strain relaxation are respectively the formation of misfit dislocations and the formation of oxygen vacancies. These two mechanisms have been evidenced by a careful interpretation of the transverse scattering profiles of the SmNiO3 films et by valence bond calculations. Finally, a correlation between strain relaxation and the transport properties of the films has been established
De, Carvalho Pinheiro Bianca. „Étude par diffraction des rayons X des modifications microstructurales en cours de fatigue“. Thesis, Lille 1, 2011. http://www.theses.fr/2011LIL10063/document.
Der volle Inhalt der QuelleThe present work aims to evaluate the microstructural mechanisms associated with the initiation of fatigue damage of steels used in the oil and gas industry. Microdeformations and residual stresses (macrostresses) were evaluated by X-ray diffraction in real time during alternating bending fatigue tests performed on flat test pieces taken from a pipe sample. Microdeformations were estimated from measurements of the full width at half maximum (FWHM) of the diffraction peak and residual stresses from the peak displacement. The fatigue tests were performed at five different stress levels. Three stages of changes during the evolution of microdeformation were detected. We show that their amplitude and duration are proportional to the level of alternating stress. Similar variations were observed for the residual stresses, with duration identical to those of the microdeformation. Changes in the density and distribution of dislocations were observed by transmission electron microscopy using the technique of focused ion beam. To understand the role of the initial structure, fatigue tests on annealed samples were performed under the same test conditions. Again, three stages of changes are observed but with an increase of the microdeformations instead of a decrease during the first stage due to the initial state of the dislocation network. The results are very encouraging for the consideration of the microstructural evolutions in the construction of a future counter of fatigue damage initiation in materials
Fekecs, André. „Élaboration de photoconducteurs d’InGaAsP par implantation d'ions de fer pour des applications en imagerie proche-infrarouge et spectroscopie térahertz“. Thèse, Université de Sherbrooke, 2015. http://hdl.handle.net/11143/6840.
Der volle Inhalt der QuelleGirard, Gabriel. „Tractographie de la matière blanche orientée par a priori anatomiques et microstructurels“. Thesis, Nice, 2016. http://www.theses.fr/2016NICE4014/document.
Der volle Inhalt der QuelleDiffusion-weighted magnetic resonance imaging is a unique imaging modality sensitive to the microscopic movement of water molecules in biological tissues. By characterizing the movement of water molecules, it is possible to infer the macroscopic neuronal pathways of the brain. The technique, so-called tractography, had become the tool of choice to study non-invasively the human brain's white matter in vivo. For instance, it has been used in neurosurgical intervention planning and in neurodegenerative diseases monitoring. In this thesis, we report biases from current tractography reconstruction and suggest methods to reduce them. We first use anatomical priors, derived from a high resolution T1-weighted image, to guide tractography. We show that knowledge of the nature of biological tissue helps tractography to reconstruct anatomically valid neuronal pathways, and reduces biases in the estimation of complex white matter regions. We then use microstructural priors, derived from the state-of-the-art diffusionweighted magnetic resonance imaging protocol, in the tractography reconstruction process. This allows tractography to follow the movement of water molecules not only along neuronal pathways, but also in a microstructurally specific environment. Thus, the tractography distinguishes more accurately neuronal pathways and reduces reconstruction errors. Moreover, it provides the mean to study white matter microstructure characteristics along neuronal pathways. Altogether, we show that anatomical and microstructural priors used during the tractography process improve brain’s white matter reconstruction
Nounouh, Soufiane. „Protocoles de mesure et de calibrage de champs électromagnétiques en vue de l'imagerie par diffraction d'objets faiblement enfouis“. Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4750/document.
Der volle Inhalt der QuelleThis thesis is devoted to the development of a microwave system dedicated to subsurface imaging applications. The analysis of the measured wave after the interaction with the medium allows to retrieve the electromagnetic properties of the probed structure. Here, we choose a single frequency operating mode combined with a multistatic configuration in order to improve the information diversity.Quantitative imaging requires a high-precision calibration of the measured data even after a careful correction of experimental errors. Thus, a calibration method is proposed, exploiting the measurement in free-space of the radiation pattern of each antenna. These patterns are quantitatively modeled thanks to an optimized linear combination of elementary sources positioned on the antenna's aperture. This simple and efficient calibration avoids additional measurements with calibration objects. This method provides successful results in a 2D free space scattering problem, as well as in the shallowly buried targets case.The calibrated data serve as inputs to inversion algorithms. As localization is concerned, very satisfactory detection results are obtained. Regarding the characterization aspects, the results indicate that the stratified configuration is less suitable than the free space configuration, due to its lack of spatial information. In order to improve the signal-to-noise ratio, some amendments are made to the experimental configuration (different antennas with or without orientation). Although the permittivity reconstructions are perfectible, the first results are promising especially since no a-priori on the targets has been inserted in the inversion algorithm so far
Ayasso, Hacheme. „Une approche bayesienne de l'inversionApplication à l'imagerie de diffraction dans les domaines micro-onde et optique“. Paris 11, 2010. http://www.theses.fr/2010PA112251.
Der volle Inhalt der QuelleLn this work, we are interested in scattering imaging in 2D and 3D configurations, where our objective is to reconstruct an image (contrast function) of an unknown object using measurements of the scattered field that results from the interaction between the unknown object and a known incident field whose propagation direction and frequency can be varied. The difficulty of this problem lies in the non-linearity of the forward model and in the ill-posed nature of the inverse problem which requires the introduction of prior information (regularization). For this purpose, we use a Bayesian approach with a joint estimation of the object contrast, currents induced inside the objects and other model parameters. The forward continuous model is described by two coupled integral equations. The discrete counterparts of the latter are obtained by means of the method of moments (MoM). For the inversion, the Bayesian approach allows us to model our knowledge about the object in a probabilistic way. For the given applications, the object under test is known to be composed of a finite number of materials, which implies that the desired image consists of a finite number of compact homogeneous regions. This justifies the choice of a prior model based upon a mixture of Gaussian with a hidden Markovian variable that represents the label of the regions. The nonlinear nature of the forward model and the use of this prior leads to joint posterior estimators which are intractable. Therefore, an approximation of the posterior distribution is needed. Two approaches are possible: a numerical approach, for example MCMC, and an analytical approach as the variational Bayesian approach. We have tested both approaches and both of them yield very good reconstruction results compared to classical methods. However, the variational Bayesian approach allows a much faster reconstruction as compared to the MCMC stochastic sampling method
Deleuze, Camille. „Méthodologie d'analyse des contraintes résiduelles par diffraction des rayons X sur des pièces d'alliage de titane de nuance Ti-10V-2Fe-3Al“. Phd thesis, Paris, ENSAM, 2010. http://pastel.archives-ouvertes.fr/pastel-00537861.
Der volle Inhalt der QuelleJi, Vincent Ning Foct Jacques. „Contribution à l'analyse par diffraction des rayons X de l'état microstructural et mécanique des matériaux hétérogènes“. [S.l.] : [s.n.], 2003. http://www.univ-lille1.fr/bustl-grisemine/pdf/extheses/50376-2003-177-178.
Der volle Inhalt der QuelleN° d'ordre (Lille 1) : 384. Résumé. Pagination multiple pour les deux volumes d'annexes. Bibliogr. à la suite de chaque chapitre.
Dumoulin, Matthieu. „Verres nanostructurés par séparation de phases dans le système silice – oxyde d’étain : Elaboration par voie sol-gel et caractérisation microstructurale“. Limoges, 2013. https://aurore.unilim.fr/theses/nxfile/default/fef4cb4e-9eef-47cb-a507-6d4f7c956cbf/blobholder:0/2013LIMO4046.pdf.
Der volle Inhalt der QuelleThis work deals with the feasibility of the electrochemical hydrogen insertion into the substoichiometric titanium carbides TiCx (0. 5 ≤ x ≤ 1) obtained by conventional reactive sintering (natural and hot pressing), and under the form of thin films, as obtained by magnetron reactive sputtering. The electrochemical hydrogen insertion in this material strongly depends on several parameters : (i) the elaboration process ; (ii) the crystalline structure ; and (iii) the stoichiometry of the carbide. The carbides TiCx obtained by hot pressing with x lower or equal to 0. 70 present an ordered crystalline structure where the (111) carbon plans are partially empty, allowing the hydrogen insertion into the material. On the contrary, the carbides prepared by reactive sintering at high temperature (2100°C) do not allow the hydrogen insertion whatever the carbide stoichiometry, because of the disorder of the carbon vacancies inside the crystalline structure. Nevertheless, it is possible to order these carbon vacancies by annealing at low temperature (730°C), this treatment rendering again the carbon plans (111) partially empty, and so, allowing the hydrogen to penetrate inside the titanium carbide with a diffusion coeffcient estimated at 1. 2 X 10-13 cm2. S-1 in TiC0. 60. The electrochemical reaction of oxidation of the titanium carbide was also studied, and it is demonstrated that TiC oxidizes into TiO2 accompanied by a CO2 release
Cobo, Elie. „Capteur d'images CMOS à sensibilité améliorée dans le proche infrarouge par des nanostructures optiques“. Electronic Thesis or Diss., Toulouse, ISAE, 2022. http://intranet.isae-supaero.fr/intradoc/intranet/doc/theses/2022_Cobo_Elie.pdf.
Der volle Inhalt der QuelleImage sensors occupy nearly half of the optoelectronic components market with a size of $19.1 billion. Their performance and the low production cost make them the leading technology for imaging in the visible range (400 nm -700 nm). On the other hand, near-infrared imaging (700 nm - 1400 nm) is also growing rapidly. Applied in the medical field, it allows the visualization of fluorescent agents in vivo, in real time and in a non-invasive way to assist in surgery, the study of diseases and diagnosis. Near-infrared medical imaging will represent $216 million in 2021 with a projection of $405 million in 2028. But the medical field is not the only application : eye tracking, gesture and facial recognition, and improved visibility at night are all features that can be leveraged for better computer vision, so the NIR sensor market is expected to grow by almost 10% annually from 2020 to 2025. Unfortunately, to take advantage of the growth of the CMOS image sensor market for near-infrared imaging faces a major problem: the imagers manufactured by the CMOS process are designed from silicon, which is certainly a very good candidate for visible absorption, but much less so for wavelengths above 800 nm. Indeed, if only a few hundred nanometers of silicon are enough to absorb light at 400 nm, it is necessary to count tens or even hundreds of micrometers for the wavelengths higher than 800 nm. To address this issue, foundries have begun to offer sensors with a deeper sensitive area, for example from 3 µm thickness optimized for the visible to 12 µm. If this process allows an improvement of the sensitivity, it deteriorates at the same time the spatial resolution of the imager induced by the increase of the crosstalk. Other solutions involving photon traps, in particular by texturing silicon, are recently investigated but require the addition of new manufacturing steps to the standard process. In this work , we have demonstrated, by opto-electrical si mulations, the design of a diffraction grating integrated from the layer of fabrication of the poly-silicon transistors gate, layer that is already present in the standard manufacturing of a CMOS image sensor. This grating has the dual function of increasing the effective propagation length in the silicon and of acting as an antireflection layer. This implementation of a grating in the image sensor with the addition of deep isolation trenches to confine the diffracted light inside the pixel, allowed a relative improvement of the external quantum efficiency of 35.5% at a wavelength of 850 nm as well as an improvement of the crosstalk of 6.9%. This architecture with an active thickness of 3 µm allows to obtain an improvement equivalent to that of an increase of the active layer by a factor of 3 without deteriorating the crosstalk that comes with this epitaxial enlargement. To go further, we studied the integration of this grating designed from the transistor gate layer to a CMOS image sensor with backside illumination. Thus, by using the grating not in transmission but in reflection, we have shown a significant improvement of the absorption in the near infrared over a wide spectral band (from 650 nm to 1100 nm). Indeed, the absorption of an image sensor with a mirror at the back face designed from a poly-silicon grating and the first aluminum metallization layer is more than twice the absorption of a standard image sensor at a wavelength of 850 nm
Debelle, Aurélien. „Contraintes, microstructure et sollicitation sous irradiation aux ions de films minces élaborés par pulvérisation ionique : modélisation et application à l'étude des effets interfaciaux dans des multicouches métalliques“. Phd thesis, Université de Poitiers, 2005. http://tel.archives-ouvertes.fr/tel-00126193.
Der volle Inhalt der QuelleNous avons montré que les films déposés par voie thermique présentent une légère contrainte de croissance en tension (~ 0.6 GPa), qui peut être expliquée par le modèle de relaxation des joints de grains, alors que les films élaborés par pulvérisation ionique développent de fortes contraintes en compression (de - 2 à - 4 GPa). Celles-ci résultent du bombardement du film en cours de croissance par les particules énergétiques mises en jeu durant le processus de pulvérisation (phénomène d' "atomic peening"), qui conduit à la production de défauts dans les couches, ce qui génère des distorsions volumiques du réseau cristallin. Nous avons développé un modèle de contrainte qui permet de rendre compte de ces déformations volumiques par l'intermédiaire d'une contrainte hydrostatique et qui surtout donne accès au paramètre de maille non contraint et libre de défauts a0, paramètre directement et uniquement lié aux effets chimiques. Des preuves quantitatives que les défauts créés sont de nature interstitielle et qu'ils sont éliminés lors du processus de relaxation sous irradiation sont fournies.
Dans le cas de couches de Mo épitaxiées, il a été possible de séparer les contraintes de cohérence des contraintes de croissance en raison de leur cinétique de relaxation différente sous irradiation. Ainsi, la modélisation a permis de déterminer la valeur de a0 dans les sous-couches de Mo constitutives des multicouches Mo/Ni, en fonction de L et des conditions de dépôt. Une tendance à la formation d'un gradient chimique par ‘ségrégation' de nickel dans le molybdène est observée, indépendamment des conditions de dépôt. Ce résultat suggère que des forces thermodynamiques sont favorables au mécanisme d'échange. Néanmoins, l'amplitude de cet effet de mélange est clairement accentuée par les effets balistiques.
Kaouache, Belkhiri. „Analyse multiéchelles de la transformation martensitique induite par contrainte dans les alliages à mémoire de forme: corrélation contraintes-microstructure“. Phd thesis, Paris, ENSAM, 2006. http://pastel.archives-ouvertes.fr/pastel-00002209.
Der volle Inhalt der QuelleBuffet, Adeline. „ETUDE IN SITU, PAR COMBINAISON DE TECHNIQUES D'IMAGERIE SYNCHROTRON (RADIOGRAPHIE X / TOPOGRAPHIE X), DE LA FORMATION DE LA MICROSTRUCTURE DE SOLIDIFICATION D'ALLIAGES METALLIQUES“. Phd thesis, Université Joseph Fourier (Grenoble), 2008. http://tel.archives-ouvertes.fr/tel-00335142.
Der volle Inhalt der QuelleNous avons également pu quantifier l'évolution de la composition de l'alliage tout au long du processus de solidification. Nous avons montré comment à partir des images 2D obtenues en diffraction, il est possible – en utilisant la théorie dynamique de la diffraction - de reconstruire une représentation 3D des dendrites avant leur mûrissement. Nous avons pu observer et quantifier des phénomènes mécaniques réversibles (rotation) ou irréversibles (fléchissement) au sein de la microstructure dendritique.
Enfin, nous avons étudié les déformations apparues suite à la solidification de la phase eutectique.
Touma, Rita. „Approche matricielle de l’imagerie sismique passive par ondes de volume“. Thesis, Université Grenoble Alpes, 2022. http://www.theses.fr/2022GRALU011.
Der volle Inhalt der QuelleRevealing the structure of fault zones provides insights required to assess seismic hazards. Reflection imaging methods, in particular migration, are commonly used to image the subsurface. An accurate velocity model is often needed to properly locate the reflectors in depth.Imaging fault zones is challenging due to the complex distribution of velocity. Also, most reflection techniques image fault zones indirectly from the discontinuity of geological layers. Wave diffraction by small-scale heterogeneities, such as cracks and fractures is generally neglected.In this thesis, we propose a matrix imaging approach for geophysical exploration that handles the velocity variation in the crust and allows to resolve heterogeneities of the order of the wavelength throughout the fault zone.The reflection matrix approach is inspired from previous studies in ultrasound and optical imaging of complex media. First, ambient noise cross-correlations are used to retrieve the reflection matrix associated with a dense array of geophones. The body wave components of this matrix contains all the information available on the medium. Second, the presented approach does not require a detailed velocity model of the subsurface. A set of matrix operation is applied to compensate for the mismatch between the actual wave velocity model and its approximate model.In a first application, we use ambient noise records in the frequency band [10 20] Hz from a dense array in order image the San Jacinto Fault, California, at small scale with an horizontal resolution of 80 m. ZZ cross-correlations are computed and arranged as 2D matrix. By applying time delays, the response matrix is projected to depth, using a homogeneous velocity model. A focused reflection matrix is obtained, that contains the impulse response between virtual sources and receivers at depth. From this matrix, the image of the medium is built and the resolution of the image can be quantified.Variations between the considered model and the reality result in phase distortions, i.e aberrations, that have detrimental effects on the image of the medium.We develop an aberration correction process that allows to compensate for these distortions by introducing a novel operator, the distortion matrix. 3D images of the first 4 km of the crust are retrieved. These images reveal the backscattered intensity generated by the heterogeneities in the medium. The location and reflectivity of scatterers are retrieved with a resolution 8 times better than the one in free space. Differences in the scattering between the Northwest and the Southeast of the fault were reported with an intense localized damage zone in the Southeast.In a second application, we image the large scale structure of North Anatolian Fault using [0.1 0.5] Hz horizontal cross-correlations computed between 73 pairs of stations. A multi-layered velocity model is considered. A local correction of the phase distortions is performed. The scattering structure of the crust and the upper mantle is revealed. Differences in the Moho depth are reported, with a step below the northern branch. Strong scattering is observed in the region lying along the northern strand of the fault, coinciding with the limit of the lithospheric blocks. The scattering in the North extends to 60 km depth, suggesting a shear zone that penetrates in the upper mantle beneath the northern strand. The scattering also reveals the deep structure of the main geological blocks.In the last part of this thesis, we propose an approach that paves the route towards a 3D passive tomography of the body wave velocity. Finally, all the presented applications confirm the efficiency of the reflection matrix approach in revealing the structure of the subsurface. It provides new insights into the scattering distribution in the Earth. It can be applied to any scale, scattering regime, and frequency bandwith, if the spatial sampling of the geophones' array satisfies the Nyquist criterion
Marticke, Fanny. „Optimization of an X-ray diffraction imaging system for medical and security applications“. Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAT055/document.
Der volle Inhalt der QuelleX-ray diffraction imaging is a powerful noninvasive technique to identify or characterize different materials. Compared to traditional techniques using X-ray transmission, it allows to extract more material characteristic information, such as the Bragg peak positions for crystalline materials as well as the molecular form factor for amorphous materials. The potential of this technique has been recognized by many researchers and numerous applications such as luggage inspection, nondestructive testing, drug detection and biological tissue characterization have been proposed.The method of energy dispersive X-ray diffraction (EDXRD) is particularly suited for this type of applications as it allows the use of a conventional X-ray tube, the acquisition of the whole spectrum at the same time and parallelized architectures to inspect an entire object in a reasonable time. The purpose of the present work is to optimize the whole material characterization chain. Optimization comprises two aspects: optimization of the acquisition system and of data processing. The last one concerns especially the correction of diffraction pattern degraded by acquisition process. Reconstruction methods are proposed and validated on simulated and experimental spectra. System optimization is realized using figures of merit such as detective quantum efficiency (DQE), contrast to noise ratio (CNR) and receiver operating characteristic (ROC) curves.The first chosen application is XRD based breast imaging which aims to distinguish cancerous tissues from healthy tissues. Two non-multiplexed collimation configurations combining EDXRD and ADXRD are proposed after optimization procedure. A simulation study of the whole system and a breast phantom was realized to determine the required dose to detect a 4 mm carcinoma nodule. The second application concerns detection of illicit materials during security check. The possible benefit of a multiplexed collimation system was examined
Godavarthi, Charankumar. „Optical diffraction tomography microscopy : towards 3D isotropic super-resolution“. Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4337/document.
Der volle Inhalt der QuelleThis PhD thesis is devoted to the three-dimensional isotropic resolution improvement using optical tomographic diffraction microscopy (TDM), an emerging optical microscope technique. The principle is to illuminate the sample successively with various angles of coherent light, collect the complex (amplitude and phase) diffracted field and reconstruct the sample 3D permittivity map through an inversion algorithm. A single TDM measurement was shown to combine several popular microscopy techniques such as bright-field microscope, dark-field microscope, phase-contrast microscope, confocal microscope, 2D and 3D synthetic aperture microscopes. All rely on scalar and linear approximations that assume a linear link between the object and the field diffracted by it, which limit their applicability to retrieve the object quantitatively. Thanks to a rigorous numerical inversion of the TDM diffracted field data which takes into account the polarization of the field and the multiple scattering process, we were able to reconstruct the 3D permittivity map of the object with a λ/4 transverse resolution. A further improvement to λ/10 transverse resolution was achieved by providing a priori information about the sample to the non-linear inversion algorithm. Lastly, the poor axial resolution in microscopes is due to the fundamental asymmetry of illumination and detection. To overcome this, a mirror-assisted tomography configuration was implemented, and has demonstrated a sub-λ/2 axial resolution capability. As a result, TDM can be seen as a powerful tool to reconstruct objects in three-dimensions with their optical material properties at resolution far superior to conventional microscopes
Bourgin, Yannick. „Fabrication par masque de phase de réseaux de diffraction d'aire et de période ultimes“. Phd thesis, Université Jean Monnet - Saint-Etienne, 2010. http://tel.archives-ouvertes.fr/tel-00602512.
Der volle Inhalt der QuelleSaleh, Hassan. „Analogie microonde appliquée à l'étude de la diffraction par des arbres, par des particules atmosphériques et des micro-organismes“. Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0299.
Der volle Inhalt der QuelleThis thesis widens the application of the microwave analogy by adopting the appropriate techniques to create objects of controlled shapes and electromagnetic properties using novel manufacturing technologies, as well as by developing a versatile setup providing accurate measurements. Microwave analogy is a useful approach to investigate a scattering problem when the targets have nanometric or metric sizes. The experiment is scaled to the microwave range and the target is mimicked by a centimeter-sized analog, while maintaining the same initial wavelength over target’s dimension ratio and conserving the same geometric and electromagnetic properties. A special attention is given to low scattering targets with RCS levels down to -60 dBm2. The random noise of the measurement setup was characterized and a novel optimization technique was proposed which consists of an angular decomposition of the bistatic region with different power profiles. The undesired reflections within the anechoic chamber were identified and a Hardgating system was installed, allowing to filter out the stray signals. In addition, additive manufacturing technologies were involved in the fabrication of analogs and a novel technique was proposed to obtain targets with “on-demand” shapes and local values of their complex permittivity. We can manufacture low scattering analogs of the real part of permittivity for any value between 1 and 3 by creating well controlled porous structures. The three main targets are studied: low permittivity spheroids, analogs of microalgae, soot aggregates analogs with complex shape, and scaled forest scene composed of tree analogs with some metal vehicle analogs