Dissertations / Theses on the topic 'Générateur à rayons X'
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Loumani, Youssef. "Etudes expérimentales et théoriques d'un générateur de rayons X." Paris 11, 2005. http://www.theses.fr/2005PA112272.
Full textThe aim of the study exposed in the present thesis is the improvement of the photon beam features created by an X-ray generator, used for the preionization of industrial excimer lasers. The research has been focused on the WIP (Wire Ion Plasma) discharge, which plays the basic role for the generator operation. The WIP electrical discharge is excited around thin positive wires at a low gas pressure. To obtain a stable and homogeneous discharge, one needs to know the chronological sequence of the involved phenomena. Experimental and theoretical studies reveal three successive stages taking place during the discharge development. The first one (breakdown) highlight the near-anode localisation of the plasma ionisation; with electrons confined in the anodic area. The second stage (discharge development before arising of the electrodes sheaths) emphasizes the importance of the secondary emission induced at the cathode by ionic bombardment. Then, the last stage (discharge sustaining) is closed to the hollow cathode discharge. A criterion of the stability of the WIP discharge was found. The unstable phase of the discharge was also studied. In parallel, a numerical study was carried out in order to check the proposed theoretical hypothesis. A PIC-1D (Particle-In-Cell) & MCC-3D (Monte-Carlo-Collisions) code was developed. Some mechanisms proposed by the theory have been so confirmed numerically, namely: the electrode sheaths potential and the presence of two energetic groups of plasma electrons. Thanks to better understanding of phenomena implicated in the WIP discharge development, we have succeeded the upgrading of the device
Sow, Amadou Tidiane. "Evaluation de la fiabilité d'un générateur à rayons X pour application médicale." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0120/document.
Full textMedical imaging systems, mainly X-rays imaging systems, have become essential in the diagnosis and treatment of complex diseases. X-rays generator is one of the critical subsystems of a medical system. Its technology became more complex and constraints seen by the components increase. An assessment of X-rays generator reliability is therefore necessary to optimize its lifetime. In this thesis, a reliability assessment method of an X-rays generator is proposed. The methodology is based on the assessment of the reliability from component to system. Aging tests are first performed for X-rays generator critical components in order to identify failure mechanisms and build lifetime curves for performing reliability prediction. FIDES guide parameters were also used to construct critical components lifetime curves. A reliability prediction method based on the assumption of cumulative damage with Miner's rule is proposed to evaluate critical components lifetime under thermomechanical stresses. This method uses rainflow counting rules for the temperature cycles distribution of critical components. A reliability block diagram is finally used to estimate the lifetime of each X-ray generator subsystem through its critical components
Akkari, Anis. "Synthèse et caractérisations physico-chimiques de couches minces de sulfure d'étain en vue de leur utilisation dans des dispositifs photovoltaïques." Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20039/document.
Full textThe present work deals with the fabrication of SnS thin films as a potential substitute to CuInS2 absorber material in thin film solar cells. The Chemical Bath Deposition method (CBD) is applied to this binary material, as it is non toxic and relatively inexpensive. Structural, chemical, morphological and optical properties of the fabricated layers are investigated by X-Ray diffraction, profilometry, scanning electron microscopy associated with energy dispersive spectrometry, atomic force microscopy, and visible to infrared spectrophotometry. Annealing and doping of the SnS thin layer is also investigated. Theoretical modelling of the thin film thickness is obtained from optical transmission and reflexion spectra based on the envelope of interference fringes
Colson, Louis. "Conception et réalisation d'un dosimètre opérationnel pour la chirurgie interventionnelle assistée par radioscopie X." Thesis, Normandie, 2021. http://www.theses.fr/2021NORMC208.
Full textThis thesis concerns the design of an operational dosimeter for surgeons operating under X-rays. X-rays were discovered in 1895 by Wilhelm Röntgen. Since then, they have been very employed, whether for checks carried out at airports or in the medical field. Very useful for treating people, they are not without danger whether it is for patients or hospital practitioners. Normally, patients are subjected occasionally to irradiation. On the other hand, some hospital practitioners are confronted with daily irradiation. A distinction is made here between “radiography” for diagnostic, who are normally protected during irradiation of the patient, and certain surgeons who use X-rays as a control during the operation and for whom they are close to the irradiated area. This is the issue that this thesis is interested in. The study that we are proposing in partnership with the digital science research laboratory GREYC and the School of Military Applications of Atomic Energy (EAMEA) both located in Cherbourg, is therefore intended to design and produce an X-ray detector for medical applications aimed at giving information for low dose and low energies. The simulation and validation (irradiation)part was done at EAMEA. The rest of the work took place within the GREYC laboratory which has acquired, for several years, real experience in the field of sensors.We started by performing Monte-Carlo simulations using the GEANT4 calculation code in order to define the optimal geometry of the sensor. Following these simulation results, we produced the sensor by rf magnetron sputtering by successive deposition of thin layers. The sensitive layer of the sensor was subject to Raman characterization, the results of which were compared with the literature. Once the sensor had been produced, we carried out a characterization under a flow of X-rays emitted from a continuous X-ray generator. The various tests with the generator continued made it possible to develop a signal acquisition chain in order to test the sensor under a pulsed radiation field in the Centre Hospitalier Public du Cotentin
Majeri, Nassim. "Production de rayons X par plasma ECR." Thesis, Orléans, 2009. http://www.theses.fr/2009ORLE2077/document.
Full textDuring this thesis we have characterised and developed a new X-ray source with an ECR plasma(electron cyclotron resonance) generating energetic electrons from 10 to 120 keV, which will emit adeceleration radiation (the Bremsstrahlung). The improvements of the installation permit to obtain astable source, which can work during one day (eight hours) without stop. In first part of theexperimental study we have studied and determined the optimal parameters of the source: pressure,micro-wave power and the magnetic configuration on the X radiation of the plasma. We also confirmedthe localisation of the energetic electron on a ring due to the magnetic configuration. The low intensityand the non punctual emission size of the X radiation, don’t allow the use of the source, so a target isinserted in the trajectory of the energetic electron to solve these two weaknesses.The main advantage of our source compared with X-ray tubes, is the absence of high voltage (20 to400 kV). For heating the electron, we use a 2,45 GHz wave, that is the industrial frequency authorizedfor the micro-wave oven, delivered by the magnetron. The simple elements that compose our sourceare less expensive than the classical X-ray tubes, due to mainly the high cost of the X-ray generator.Moreover, we don’t need a high vacuum, mandatory for the X-ray tubes; an ECRX operates at aresidual pressure of 0,1 mPa. And finally, we have a compact source. Applications will be various frommedical, like radiological, sterilization, to non-destructive industrial control
Bonjour, Philippe. "Criteres de choix des scanners a rayons x." Aix-Marseille 2, 1990. http://www.theses.fr/1990AIX20852.
Full textFischer, Irmengard. "Diffusion inélastic par rayons x des matériaux polycristallins." Phd thesis, Université Joseph Fourier (Grenoble), 2008. http://tel.archives-ouvertes.fr/tel-00349859.
Full textMagnin, Isabelle. "Imagerie tridimensionnelle par sources codées de rayons X." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37607518h.
Full textPayot, Étienne. "Reconstruction vasculaire tridimentionelle en imagerie par rayons X /." Paris : École nationale supérieure des télécommunications, 1997. http://catalogue.bnf.fr/ark:/12148/cb36165911z.
Full textMagnin, Isabelle. "Imagerie tridimensionnelle par sources codées de rayons X." Lyon, INSA, 1987. http://www.theses.fr/1987ISAL0039.
Full textPayot, Étienne. "Reconstruction vasculaire tridimensionnelle en imagerie par rayons x." Paris, ENST, 1996. http://www.theses.fr/1996ENST0034.
Full textLIU, ZEWEN. "Lithographie profonde par rayons-x sur rayonnement synchrotron." Paris 11, 1997. http://www.theses.fr/1997PA112064.
Full textGhiringhelli, Giacomo. "Spectroscopies résonnantes de rayons X mous polarisés circulairement." Université Joseph Fourier (Grenoble), 2001. http://www.theses.fr/2001GRE10234.
Full textHadj-Bachir, Mokrane. "Laser à rayons X ultra-compact Raman XFEL." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0400/document.
Full textThe quest for a compact X-ray laser has long been a major objective of laser science. Several schemes using optical undulators are currently considered, in order to trigger the amplification of back scattered radiation, in Compton or inverse Compton regime. We have proposed a new concept of compact XFEL based on a combination between the physics of free electron lasers, of laser-plasma interactions, and of nonlinear optics. In this thesis, we study the necessary steps to trigger a X-ray laser during the interaction between a free relativistic electron bunch and an optical lattice created by the interference of two intense transverse laser pulses. For this purpose I developed a particular tracking code dubbed RELIC. RELIC allowed us to study the dynamics and injection process of a bunch of relativistic electrons into the optical lattice. Thanks to RELIC, we distinguished several interaction regimes depending on the relativistic electron bunch parameters, and on those of the optical lattice and its geometry. These studies are applied to the X ray amplification and supported by PIC simulations. RELIC also allowed us to model and analyze the first experiment conducted in october 2015 on the ”Salle Jaune” laser facility at LOA. This first experiment was very important to validate our theoretical models, and should prove to be an essential milestone for the development of a Raman X-ray free electron laser
Marot, Laurent. "Développement d'un nouveau système d'implantation ionique en immersion plasma et analyses des processus de nitruration." Phd thesis, Université de Poitiers, 2001. http://tel.archives-ouvertes.fr/tel-00003632.
Full textChesne, Marie-Laure. "Utilisation de la diffusion anomale de l'uranium pour déterminer la structure de macromolécules biologiques : des rayons X durs aux rayons X mous." Université Joseph Fourier (Grenoble), 2002. http://www.theses.fr/2002GRE10206.
Full textMontagner, Florian. "Nouvelles méthodes de tri des déchets par rayons X." Phd thesis, INSA de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00932692.
Full textElzo, Aizarna Marta Ainhoa. "Diffraction résonnante des rayons X dans des systèmes multiferroïques." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00870407.
Full textShi, Qihan. "Étude multiéchelle des composites par tomographie de rayons X." Paris, CNAM, 2003. http://www.theses.fr/2003CNAM0490.
Full textIn this dissertation, one presents a multiscaled research by the X-ray computerized tomography to characterize the wooden plastic materials and rubbers about their physicochemical and viscoelastic properties, as well as their damage and fracture behaviours. At mesoscopic level, the homogeneous study on phase and the non-destructive control on defects and inclusions demonstrate the powerful capacity of our medical scanner. On the microscopic scale, the phenomena of crystallisation by tension and under the low temperature have been interpreted by the linear coefficient of X-rays attenuation. From macroscopic point of view, the data obtained from various mechanical tests such as fracture, cavitations, relaxation and creep have been compared with tomographic results. Finally, a table is shown to compare the CT with other microscopic method
Herzog, Charlotte. "imagerie plénoptique : de la lumière visible aux rayons X." Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0116.
Full textPlenoptic imaging is a technique that acquires spatial and angular information of the light rays incoming from a scene. After a single acquisition, numerical data treatment allows image manipulation such as synthetic aperture, changing viewpoint, refocusing at different depths, and consequently 3D reconstruction of the scene. Visible plenoptic has been widely studied. However, transposition from visible to X-rays has never been done and remains challenging. X-ray plenoptic would be beneficial to the X-ray imaging panorama. A single acquisition should be sufficient to reconstruct a volume, against 1000’s for X-ray tomography that is the today reference in 3D X-ray imaging.In this thesis, we consider plenoptic camera composed of a main lens, a microlens array and a detector. So far, two different configurations have been developed: the traditional and the focused plenoptic setups. Although these configurations are usually studied separately, they only differ by the distances between the optical elements. These two configurations were studied in detail to choose the most suitable for X-ray imaging, considering the constraints of X-ray optics. We observed a full continuity between the two systems. Therefore, we extended the previous work to more general formulas about optical configuration and theoretical resolutions. Theory about resolution along the depth axis was refined, as depth reconstruction and extraction are the main interest of X-ray plenoptic. Specific study was done on the evolution of contrast along depth as being a key parameter for depth reconstruction. We realized that contrast decreases when moving away from a privileged depth. This is important to consider as it can affect image reconstruction and quality of depth extraction.We also worked on refocusing algorithms. The refocusing algorithms are usually developed for each configuration separately. We worked to go beyond this separation. We developed a new algorithm valid for any configurations. Moreover, our algorithm is based on real distances between the optical elements, allowing generating images at any distances from the plenoptic camera. We defined a new parameterization between object and image spaces. Using geometrical optics, we calculated the matrix transformation between the two spaces. This allows back-projecting data from the acquired raw image to the object space, and reconstructing the pixels one by one, until the whole object. With this algorithm, we were able to simulate the process of image acquisition, and create synthetic plenoptic data. Reconstruction of these data was used to quantify the accuracy of the novel algorithm and prove its consistency.The refocusing algorithm allows reconstructing the depth planes one by one. Each refocused plane contains information about the whole 3D scene that has to be disentangled. The elements physically present at the refocused depth are intrinsically sharp, whereas the ones located at other depths are blurred. We used this contrast property to extract depth from the refocused images. We tested several existing methods derived from the field of depth from focus and studied their efficiency when applied to our images.In collaboration with European teams, we realized the first X-ray plenoptic camera that was tested at P05 beamline of PETRA III synchrotron. Based on the theoretical work developed in this thesis, we defined the best optical configuration, mounted the plenoptic camera, acquired X-ray plenoptic images, numerically refocused them using the new algorithm and verified the experimental resolutions and contrasts. Depth from focus techniques applied on the refocused stack allow to retrieve the expected depth plane. These are the first images acquired with an X-ray plenoptic camera
RIVA, RUDIMAR. "Etude du laser xecl photo-declenche par rayons x." Paris 11, 1993. http://www.theses.fr/1993PA112329.
Full textGotte, Vincent. "Etudes structurales par spectroscopie d'absorption des rayons X polarisés." Nancy 1, 1999. http://docnum.univ-lorraine.fr/public/SCD_T_1999_0248_GOTTE.pdf.
Full textSaktoun, Abdeslam. "Etude d'un détecteur à gaz bidimensionnel pour rayons X." Grenoble 1, 1991. http://www.theses.fr/1991GRE10073.
Full textBELORGEY, OLIVIER. "Reflexion des rayons x sur les films noirs de savon." Paris 11, 1991. http://www.theses.fr/1991PA112265.
Full textMenut, Denis. "Contribution au développement de la ligne MARS pour l’analyse au rayonnement synchrotron d’aciers à dispersion d’oxydes irradiés aux neutrons : évolution des phases secondaires sous irradiation." Caen, 2016. http://www.theses.fr/2016CAEN2020.
Full textX-Ray Diffraction coupled with X-ray Absorption Fine Structure analyses at the MARS beamline of the synchrotron SOLEIL facility were used to study the microstructural evolution of oxides phases found in ODS steels irradiated in Material Testing Reactors. Two hold generations of ODS steel grades (DY and MA957) irradiated up to high fluencies (~75 dpa) were studied. These experiments have required specific developments, in particular a dedicated sample holder. An important milestone was overcome integrating the MARS beamline to the nuclearized facilities accessible for CEA. First, XRD analysis provide new results concerning intermediate sizes of precipitates (around 100 nm) essentially from crystallographic point of view, the nano-sized oxides (from 1 to 10 nm) being not detected, due to the material itself, sample preparation as thin foil and experimental set-up calibration. Secondly, XAFS analysis is not a discriminating technique as soon as the absorber atom is involved in the chemical composition of various precipitates found in ODS. Nevertheless, the stability of the Ti with a coordination number of 5 is evidenced whatever the irradiation conditions. As our experimental study was not able to detect the nano-sized oxides, an alternative way is to perform modeling approach of the behavior of massive oxides under irradiation, compared to experimental analyses under ion irradiations. We have shown that the defect-fluorite is an intermediate phase of the crystal-to-amorphous phase transition of the pyrochlore oxide structure, whatever the irradiation conditions and the ratio of the cationic radii, the Ti coordination number remaining around 5 in the amorphous state
Masiello, Fabio. "Diffraction et imagerie aux rayons X en utilisant un faisceau cohérent : applications aux optiques rayons X et au cristaux comportant des hétérogénéités de phase." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00609216.
Full textMastropietro, Francesca. "Imagerie de nanofils uniques par diffraction cohérente des rayons X." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00716410.
Full textMoussetad, Mohamed. "Mesures cristallographiques par rayons X sur monocristaux à applications industrielles." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb376082256.
Full textRICHEBOEUF, LAURENT. "Etude du laser chimique hf photo-declenche par rayons x." Paris 11, 1996. http://www.theses.fr/1996PA112386.
Full textVezin, Vincent. "Caractérisation par diffusion centrale des rayons x du silicium poreux." Poitiers, 1991. http://www.theses.fr/1991POIT2311.
Full textMercère, Pascal. "Mesure et correction de surfaces d'onde dans les rayons X." Paris 6, 2005. http://www.theses.fr/2005PA066102.
Full textMikulik, Petr. "Réflectivité des rayons X par des multicouches planaires et structurées." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10056.
Full textChamard, Virginie. "Etudes structurales du silicium poreux par techniques de rayons X." Université Joseph Fourier (Grenoble), 2000. http://www.theses.fr/2000GRE10136.
Full textMoussetad, Mohamed. "Mesures cristallographies par rayons X sur monocristaux à applications industrielles." Université de Franche-Comté. UFR des sciences et techniques, 1987. http://www.theses.fr/1987BESA2033.
Full textBourgeon-Martin, Nelly. "Études électrochimiques de Li1,2V3O8 : intérêt des spectroscopies d'absorption des rayons X et de photoélectrons X." Nantes, 2003. http://www.theses.fr/2003NANT2111.
Full textThis work, dealing with the study of Li1,2V3O8 as positive electrode for lithium batteries, aims to understand and characterize the factors responsible for the differences in electrochemical performance of compounds prepared at different temperatures. Many characterization techniques have been performed, such as analysis of the X-ray diffraction lines profiles, X-ray absorption, X photoelectrons, potential step spectroscopies, cycling in different conditions and chemical analysis of dissolved species. We have shown that the capacity fading upon cycling of the compound prepared at 350ʿC occurs during the 2. 6V two-phase transformation, through a reaction with the electrolyte leading to vanadium dissolution and accumulation of an hybrid organic-vanadium surface layer, which displays an original electrochemical behavior. The cyclability becomes intrinsically better when the crystallite size increases, with an optimum for 580ʿC
Mirioni, Laurent. "Sources X Ultra-Lumineuses : Contreparties Optiques." Phd thesis, Université Louis Pasteur - Strasbourg I, 2002. http://tel.archives-ouvertes.fr/tel-00007374.
Full textRenaud, Alain. "Etude de la structure tridimensionnelle de la gammachymotrypsine par diffraction aux rayons X." Paris 5, 1994. http://www.theses.fr/1994PA05P121.
Full textBarbusse, Danielle. "Contribution à la caractérisation des matériaux : étude des couches minces, multicouches et superréseaux III-V et II-VI par double diffraction des rayons X (composition, qualité, contraintes) : étude structurale par absorption X au seuil K d'une série de complexes du cobalt et du fer, XANES et EXAFS de laboratoire." Montpellier 2, 1991. http://www.theses.fr/1991MON20189.
Full textKharchi, Djoudi. "Mise au point d'un dispositif permettant l'utilisation de la diffraction des rayons x pour la mesure de contraintes à haute température." Perpignan, 1996. http://www.theses.fr/1996PERP0246.
Full textHuré, Laurent. "Etude de l'application de la fluorescence induite par flash de rayonnement X et de la radiographie "éclair" au diagnostic et à la caractérisation de milieux mono- et diphasiques en écoulement." Orléans, 2000. http://www.theses.fr/2000ORLE2043.
Full textCastagnos, Anne-Marie. "Les relaxeurs ferroélectriques BaTi0,65 Zr0,35 O3 et Pb(1-x)BixMg(1+x)3Nb(2-x)/3O3(0< ou égalx." Toulouse 3, 2002. http://www.theses.fr/2002TOU30197.
Full textDielectric relaxation (frequency dispersion of the dielectric permittivity) is explained by the impossibility for the polar order to establish at long range. In PbMg1/3Nb2/3O3, this is attributed to a complex nanostructure where a local chemical order (ordering of the cations on the B site) coexists with a local polar order due to correlations of atomic displacements. These correlations expand up to a temperature known as freezing point, where they block. The Pb lone pair also plays a role in relaxation. In order to specify the role of each component, we have synthesised and studied the following relaxors. .
Caby, Béranger. "Développement de l’analyse combinée par Réflectométrie de rayons X (XRR) et Fluorescence des rayons X en Incidence Rasante (GIXRF) pour des applications micro et nano-électroniques." Caen, 2015. http://www.theses.fr/2015CAEN2055.
Full textDue to recent developments in microelectronics, new in-depth characterization techniques are needed. Combined Grazing Incidence X-ray Fluorescence (GIXRF) and X-ray Reflectivity (XRR) analysis is as a promising alternative technique. Indeed, this technique allows obtaining, in a non-destructive way, the depth-profile composition and density of multilayered samples. In the literature, only few works using the potentiality of the XRR-GIXRF technique have been reported. Therefore, in order to accelerate the development of its application in materials characterization, a collaborative international group has been set up between laboratories to share expertise, equipment and analysis software. The objective was to apprehend the methodologies for the XRR-GIXRF acquisition, measurements analysis as well as the physical principles along with the possible limitations of the technique. In this work, after a presentation of the analysis protocols and software, the solutions implemented in different software in order to handle instrumental effects and quantification problems, are discussed. Subsequently, applications of the combined XRR-GIXRF technique on samples of interest are presented. In particular, through the investigation of Ultra-Shallow junctions and various multilayers, the qualitative and quantitative depth-profiling capabilities are demonstrated and compared to classical characterization techniques. Finally, limitations of the technique and possible outlooks are discussed
CHAMBET, YVES. "Etude experimentale de la diffusion des rayons x rasants par les multicouches pour optiques x-uv." Paris 11, 1993. http://www.theses.fr/1993PA112341.
Full textCommeinhes, Frédéric. "Structure tridimentionnelle de la carboxypeptidase A par diffraction des rayons X." Paris 5, 1994. http://www.theses.fr/1994PA05P019.
Full textLemarchand, Gwénaël. "Caractérisation mécanique et simulation numérique d'une anode tournante de rayons X." Phd thesis, École Nationale Supérieure des Mines de Paris, 2003. http://pastel.archives-ouvertes.fr/pastel-00000467.
Full textGoudeau, Philippe. "Diffusion centrale anormale des rayons X application à des alliages métallurgiques." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb375979785.
Full textRieutord, François. "Réflectivité et diffraction des rayons X appliquées aux films minces organiques." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb376093669.
Full textFreud, Nicolas Babot Daniel. "Modélisation et simulation de systèmes d'imagerie par rayons X ou gamma." Villeurbanne : Doc'INSA, 2005. http://docinsa.insa-lyon.fr/these/pont.php?id=freud.
Full textChap. 2 et 4 rédigés en anglais. En appendice, 1 article rédigé en anglais intitulé "Optimal calibration via virtual X-ray imaging for dual-energy techniques : application to glass wool", issu du Colloque "Six international Conference on quality control by artificial vision" et paru dans la revue "SPIE", vol. 5132, 2003, p. 422-432. Titre provenant de l'écran-titre. Bibliogr. p. 143-155.
Dupraz, Maxime. "Diffraction des rayons X cohérents appliquée à la physique du métal." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI103/document.
Full textThe mechanical properties of small objects deviate strongly from the bulk behaviour, as soon as their size becomes comparable or smaller to the dislocation mean free path (typically a few microns). For instance, their elastic limit increase when their size is reduced. On a another hand, nanostructures are exposed to strong constraints, such as that imposed by epitaxial relations with a substrate. Altogether, there is a clear need (supported by industrial interests) for a better understanding of the fundamental phenomena that govern the mechanical properties of materials at the nanometre scale. The lab SIMaP is engaged in this research and tackles the topic by combining sample growth, laboratory characterisation methods, numerical models, and synchrotron techniques.One key experiment developed by our team is the in situ characterisation of the deformation mechanism induced by an AFM tip on a nanostructure using Coherent X-ray Diffraction (CXD). CXD is an emerging synchrotron technique that allows the detailed measurement of the crystal structure,including strain field and defects, of micro/nano-objects. In principle, a 3D image of the structure of the sample can be obtained from the CXD data. However, it remains difficult in realistic cases, when the strain is very inhomogeneous and crystal defects numerous. The problem is further complicated by the wavefront of the beam, which is usually far from a plane wave, particularly when the AFM tip shadows part of the incoming beam. In this PHD work, it is demonstrated that a 3D image of the object can be reconstructed in case of moderately complex systems
Vuong, My Ha. "Recherche d'effets d'irradiation par les rayons X dans la matière interstellaire." Paris 11, 2004. http://www.theses.fr/2004PA112024.
Full textThe main goal of this thesis is to study the dense interstellar matter mainly using X-ray and intra-red observations. We show that for the rho Oph dark cloud, the low gas-to-dust ratio can be explained by the lower metalicity of this dense cloud relative to the diffuse galactic medium. Moreover, by cross-correlating X-ray absorption and abundance measurements, we show that the new abundances at metals of the solar photosphere, of the photospheres of young F and G stars, of the local diffuse and dense interstellar medium are all identical within 10%. This lazy nucleosynthesis would indicate the stellar formation has been less active in the Galaxy at the distance of the Sun over large time scales. We are interested in the massive star forming region M17, where strong X-ray emission has been detected and the ISO data reveal spatially extended and highly ionized gas. We show that the X-ray irradiation effect can not be constraint by O2+. A study of the X-ray irradiation in a neutral medium shows partly the contribution of X-rays to the ionization and excitation of C+ at large distances up to 5 pc from the OB cluster. We complement our study by searching young low-mass stars and studying their physical properties in the Cha II star-forming region. The method consists of identifying as many as possible low-mass young stars using the near-IR DENIS survey. We search stars with an IR excess, and select 51 young candidates. Our spectroscopic follow-up observations confirm the nature of these candidats, with at least 20% of them showing Halpha emission characteristic of their young nature. From this, we deduce that these stars belong to the ChaII cloud