Rozprawy doktorskie na temat „Tritium – Teneur en hydrogène”
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Bacchetta, Audrey. "Analyse et spéciation du tritium dans des matrices environnementales". Electronic Thesis or Diss., Paris 6, 2014. http://www.theses.fr/2014PA066026.
Pełny tekst źródłaThis study deals with environmental monitoring. The main aims are (i) the optimisation of the analytical procedure for the tritium in organic form determination, and (ii) the identification of the tritium bearing molecules which are responsible for its transfer from the environment to man. The study was divided into three stages. First an analytical method was developed to determine hydrogen content of several samples, which is a key element to calculate accurate organically bound tritium activities. Secondly, the impact of the organically bound tritium fractions separation (labile exchange) for the determination of the representative fraction of the level of environmental tritium activity was then evaluated. For that, the amount of solubilised sample was estimated. Finally, the speciation of tritium in environmental samples was investigated. Several molecules classes and organic compounds dissolved in the labile exchanges solvent were identified. The results show that the distribution of tritium in organisms depends on both properties of the chemical bond in which it is involved and chemical properties of tritium bearing molecules. The identified compounds belong to the molecules classes such as carbohydrates or amino acids, constitutive of living organisms. It would now be of interest to study the tritium distribution in an environmental sample to target molecules of interest and study the impact of tritium from the environment to man
Paul, Alexia. "Dynamique couplée de l’hydrogène et du carbone organiques des sols : approches par isotopes stables pour la prévision du devenir du 3H, 2H, 13C et 14C". Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0068/document.
Pełny tekst źródłaRadiocarbon (14C) and tritium (3H) are naturally released into the environment but also through nuclear activities. The releases are expected to persist for the next decades, it is important to predict their fate and their residence time in soils. The objective of this thesis is to propose a quantitative prediction and a simple modeling of the fate of 14C and 3H in soil organic matter (SOM). The originality of this work is twofold: first, we hypothesize that the incorporation and fate of NEH atoms in the soil are coupled to the carbon dynamics. Second, we chose to trace carbon and hydrogen by natural or artificial 13C and 2H tracing.Through natural in situ 13C tracing, we quantified the carbon recently incorporated by vegetation in few decades. Deep horizons contain a large part of this carbon (typically 20 to 30%). We adapted the RothC model to the deep soil C dynamics. This allowed us to predict that 10% of C will persist for several centuries in the deeper layers. The labelling experiments showed that the microbial activity is driving the incorporation of hydrogen from water into SOM, and allowed us to establish the CH stoichiometry of biotransformations. These experiments were a mean to propose a model of the coupled C and H dynamics of the SOM in the short and medium term (decades). The results of this thesis contribute as well to the improvement of the interpretation of natural abundances in 13C and 2H stable isotopes. A meta-analysis of the correlations between the 13C and 14C concentrations of global soils has demonstrated that the 13C enrichment of deep organic matter can be fully explained by the 13C/12C ratio of the vegetation from which they are derived
Nivesse, Anne-Laure. "Spéciation du tritium organiquement lié dans les matrices environnementales". Thesis, Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2020. http://www.theses.fr/2020IMTA0216.
Pełny tekst źródłaTritium is the radioactive isotope of hydrogen and can thus integrate the organic molecules of a living organism following the water cycle and form the organically bound tritium fraction (OBT). The existence of two forms of OBT is commonly accepted: an exchangeable fraction (E-OBT) and a non-exchangeable fraction (NE-OBT). However, a scientific consensus to date is lacking to describe the exact distribution of these two forms in an organic molecule, which generates controversies and a lack of clarity on the behavior of tritium in the environment. Therefore, this study consists first of all in establishing and understanding the involvement of specific molecular structures of the usual biomolecules of plant biomass on the speciation of OBT in environmental matrices. An overview is obtained on the exchange capacities of the hydrogen atom found in a large panel of environmental matrices and their major constituent. A major interest is focused on the cellulose molecule with its semi-crystalline structure and the storage capacities of tritium in soils are explored through a study of the exchange and deprotonation capacities of hydrogen atoms in matter rich in humic substances. Secondly, a comparative study is proposed between two isotopic exchange methods for the analysis of the NE-OBT fraction and their reliability is evaluated within the environmental monitoring scope, but also for the apprehension of the distribution of OBT in environmental matrices
Moysan, Isabelle. "Application des solutions solides à base de palladium, platine et rhodium au stockage solide des isotopes de l'hydrogène : structure électronique, stabilité sous hydrogène et vieillissement sous tritium". Dijon, 2001. http://www.theses.fr/2001DIJOS037.
Pełny tekst źródłaBoyer, Cécile. "Étude des transferts du tritium atmosphérique chez la laitue: étude cinétique, état d'équilibre et intégration du tritium sous forme organique lors d'une exposition atmosphérique continue". Phd thesis, Université de Franche-Comté, 2009. http://tel.archives-ouvertes.fr/tel-00464333.
Pełny tekst źródłaTrentin, Valérie. "Séparation des isotopes de l'hydrogène par chromatographie en phase gazeuse". Vandoeuvre-les-Nancy, INPL, 1992. http://www.theses.fr/1992INPL079N.
Pełny tekst źródłaStephant, Alice. "Le Rapport isotopique de l'hydrogène dans le système solaire interne : à la recherche des sources physico-chimiques de l'eau planétaire". Paris, Muséum national d'histoire naturelle, 2014. http://www.theses.fr/2014MNHN0022.
Pełny tekst źródłaCurrent dynamical models of Solar System formation and geochemical models agree on a likely chondritic origin for the terrestrial water. Indeed, primitive meteorites, called chondrites, have undergone an aqueous alteration process on their parent bodies. Moreover, these meteorites are one of the considered sources for the existence of water in lunar minerals. This thesis lies on hydrogen isotopic ratios and water contents measured using NanoSIMS in the carbonaceous chondrite Paris and lunar soils from the Apollo missions. Chondrules in Paris meteorite seem to have registered a water source distinct from the one of the parent body aqueous alteration. For the moon, water retained in soils is majority formed by implantation of the solar wind hydrogen
Mahloul, Noureddine. "Influence des impuretés soufre et phosphore sur les propriétés des alliages fer-nickel-carbone : conséquences vis-à-vis des mécanismes de fragilisation par l'hydrogène". Châtenay-Malabry, Ecole centrale de Paris, 1996. http://www.theses.fr/1996ECAP0443.
Pełny tekst źródłaLanier, Sandy. "Mise au point d’un mortier de piégeage à réseau poreux contrôlé". Thesis, Centrale Lille Institut, 2020. http://www.theses.fr/2020CLIL0027.
Pełny tekst źródłaThis PhD is part of the MACH3project funded by the French Investment Plan (PIA) -2nd phase. It contributes to the management of tritiated radioactive waste produced by the ITER fusion facility. The acceptance of this waste on a storage site requires a low rate of degassing of Tritium (radioactive isotope of H2). This research has developed cement mortars for conditioning tritiated nuclear waste,making it possible to limit the degassing of tritium by irreversible trapping of its gaseous forms. Composite mortars were formulated, based on conventional Portland cement, and integrating a hydrogen getter (Ag2O/MnO2), meeting the safety criteria of a radioactive waste storage facility and complying with the industrial specifications. After three months of maturation, their trapping performance, without preliminary drying, is between 75 and 95% (measured following a gamma irradiation test, generating H2in situ)
Azinheira, José. "Caractéristiques locales dans des écoulements réactifs : détermination des masses volumiques et populations rotationnelles par des techniques laser". Châtenay-Malabry, Ecole centrale de Paris, 1986. http://www.theses.fr/1986ECAP0002.
Pełny tekst źródłaBrazzale, Pietro. "Numerical and experimental study at the pilot scale of the hydrogen injection into liquid sodium by permeation through nickel membrane". Thesis, Toulouse, INPT, 2020. http://www.theses.fr/2020INPT0101.
Pełny tekst źródłaIn the framework of the SFR (Sodium-cooled Fast Reactors), the management of tritium contamination in sodium circuits and the control of its release in atmosphere is fundamental. In order to capture and recover the tritium, it is necessary to maintain a certain amount of hydrogen dissolved in the liquid sodium stream. The hydrogen injection by permeation through nickel dense membranes has been proposed to provide a continuous hydrogen intake to liquid sodium stream, thus allowing the desired hydrogen concentration to be reached. Similar nickel-based membranes have been developed in the past for SFR (i.e. hydrogen-meters), but a lack of knowledge and applications is found for what concerns the hydrogen injection by permeation. In this study, an original permeator prototype has been designed and an experimental activity at pilot-scale has been carried out on an experimental sodium loop, under different operating conditions (temperature: 375°C-450°C; hydrogen supply partial pressures: 5 kPa-28 kPa). A dedicated measurement system, based on the gas chromatography on the retentate side, coupled to the hydrogen detection inside sodium (through a dedicated hydrogen-meter using mass spectrometry), has provided an accurate estimation of the hydrogen permeation flowrate. Tests are carried out for both a gas-vacuum and a gas-sodium configuration: in both cases, the global hydrogen permeation flowrate depends linearly on the square root of the hydrogen partial pressure in the feed side up to 20 kPa, thus demonstrating that the process in this range is limited by the hydrogen diffusion inside the nickel membrane. In particular, the presence of sodium in the permeate side does not affect significantly the whole mass transfer process. The results, compared to the permeation theoretical laws, provide an experimental permeability coefficient, specific to the prototype geometry and configuration. Comparison to values from the literature results for small nickel samples, showed that some metal-lattice phenomenon, probably linked to the membranes deformation by cold-working, could affect the hydrogen permeation in this study. In fact, slightly higher permeation coefficient with a lower activation energy is found here if compared to the literature. Finally, the experimental process has been successfully validated, thus demonstrating the feasibility of this application at the pilot-scale. An analytical 1D model has been set up with a multi-physics approach, in order to assess the radial hydrogen mass transfer in steady conditions over three physical domains, including gas, nickel and liquid sodium. It includes benchmark literature correlations for the convective mass transfer inside gas and sodium phase in tubular geometry, the Sieverts law for the H-Ni and H-Na equilibrium, coupled to the Richardson’s law for the hydrogen permeation through the nickel membrane, assumed to be diffusion-limited. CFD simulations, performed in a 2D axial-symmetric geometry with the software Comsol Multiphysics, have provided a better comprehension of the transport phenomena taking place and have confirmed the results of the straightforward 1D model under certain conditions, specific to the experimental prototype. Finally, the experimental results have shown a good agreement with the 1D model and CFD simulations in the whole temperature interval and up to a hydrogen partial pressure of 20 kPa. By resuming all the elements provided by this study, both at the experimental and numerical stage, a single equation law has been defined to describe the prototype performance and to enhance the industrial scale-up design activity
Defouilloy, Céline. "Le rapport isotopique de l'hydrogène dans les météorites de fer". Paris, Muséum national d'histoire naturelle, 2012. http://www.theses.fr/2012MNHN0009.
Pełny tekst źródłaIrons meteorites are generally considered as remains of differentiated planetesimal cores. Yet, there are still some uncertainties regarding their formation. One proxy that could be used to confirm or not the different hypothesis regarding the formation of Iron meteorites is the Hydrogen isotopic ratio. Indeed, the Hydrogen isotopic ratio varies according to the bearing species and the process that had happened on the parent bodies. The Hydrogen isotopic ratio, as well as its concentration, have been measured in several Iron meteorites using an ion microprobe IMS 3f. Hydrogen isotopic ratios vary from 93 ± 9 to 126 ± 11 x10-6, while the concentrations vary from 0,5 ± 0,1 ppb to 120 ± 130 ppb. Two groups can be distinguished in regard of the concentrations. The magmatic irons have a very low H content while the non-magmatic irons are systematically richer in H
Benzaid, Aïcha. "Etude du dégagement d'hydrogène sur électrode verticale en acier 42CD4, par la méthode du bruit électrochimique : application à la fragilisation par l'hydrogène". Châtenay-Malabry, Ecole centrale de Paris, 1992. http://www.theses.fr/1992ECAP0234.
Pełny tekst źródłaDemange, David. "Mesure non intrusive de l'activité de fûts de déchets tritiés par modélisation d'une fuite 3He et sa quantification par spectrométrie de masse". Besançon, 2002. http://www.theses.fr/2002BESA2016.
Pełny tekst źródłaVigouroux, Eric. "Diffusivité de l'hydrogène dans la wadsleyite : estimation de la teneur en eau de la zone de transition du manteau terrestre". Thesis, Lille 1, 2014. http://www.theses.fr/2014LIL10016/document.
Pełny tekst źródłaThis manuscript presents an experimental study of hydrogen (H) diffusion in wadsleyite at low temperatures and ambient pressure and an infrared spectroscopy (FTIR) analysis of H-related defects for wadsleyite and ringwoodite, the main components of the mantle transition zone (TZ; from 410 to 670 km depths). These mineral phases ability to incorporate high H-contents suggests that the mantle TZ is an important potential H reservoir. Hydrogen-deuterium (H-D) isotopic exchange experiments have been done at low temperatures (between 450 and 300°C) and ambient pressure and evolution of wadsleyite H-defects is followed by FTIR spectroscopy in function of annealing time. These experiments show two clearly distinct kinetics of extraction with 6 slower OH bands that polarized FTIR spectroscopic measurements on monocrystals, other at very low temperatures (-194 to 50°C) tend to link with defects involving tetrahedral sites.The measured H-D exchange diffusion coefficients show that the H “self diffusivity” in wadsleyite is delimitated by two diffusion laws in m2/s: logDH=-6.04(±1.49)-153(±11)/RTln(10) for the lower limit and logDH=-4.26(±1.36)-164(±10)/RTln(10) for the upper limit.According to the Earth’s electrical conductivity models and assuming this one as the only product of the proton’s mobility, we show that water content in TZ is most likely higher than 0.1 wt% H2O and potentially up to saturation concentrations. This implies a water content at least 10 times higher than the previous estimate from the diffusion study of Hae et al.(2006) and compatible with the recent discovery of a natural 1wt%H2O water content ringwoodite sample included in a diamond (Pearson et al.,2014)
Teukam, Hangouan Zephirin Symplice. "Etude de la diffusion de l'hydrogène dans le diamant et contribution à la réalisation de diamant de type n". Versailles-St Quentin en Yvelines, 2004. http://www.theses.fr/2004VERS0002.
Pełny tekst źródłaThe objective of this work is the investigation of the hydrogen diffusion properties and the hydrogen-dopant interactions in homoepitaxial diamond. The epilayers have been characterized by secondary ion mass spectrometry, electrical measurements and infrared spectroscopy before and after deuterium diffusion. We have determined the temperature dependence of the effective diffusion coefficient of deuterium (D) in p-type boron doped diamond and deduced the dissociation energy of (B,D) pairs (2. 5 eV). We have also revealed the existence of hydrogen deep traps in boron-doped diamond. The D diffusion is very weak in n-type diamond. The results on D diffusion in boron-doped diamond show the possibility to obtain a reversible p-type to n-type conversion under deuteration. As a result of this conversion, high n-type electrical conductivity diamond at 300 K has been fabricated for the first time. The ionization energy of the donors at the origin of the n-type conductivity is 0. 34 eV. A model based on the formation of (B,D2) complex donors has been proposed. The last part presents deuterium diffusion results in GaN:Mg and undoped ZnO
Zhang, Peipei. "Hydrogen diffusion in NAMs : andradite garnet and zircon". Thesis, Lille 1, 2015. http://www.theses.fr/2015LIL10023/document.
Pełny tekst źródłaThe hydrogen mobilities in andradite and zircon were investigated by performing H-D exchange experiments under ambient pressure in a horizontal furnace flushed with a gas mixture of Ar/D2(10%). The temperature range investigated was 400˚C-700˚C for andradite and 800˚C-1100˚C for zircon. At contrary to the same type of experiments performed in NAMs, it was not possible to replace all hydrogen atoms in the structure by deuterium, 15% to 35% for andradite and 25% to 40% for zircon of OH remaining after completion of the exchange. However, a steady-state equilibrium was reached at the end of the experiments and it was possible to determine the diffusion law of the exchange process. The activation energy is similar to those of hydrogen diffusion in grossular, but the diffusivity is more than 2 orders of magnitude faster. Our results demonstrate that, composition has a major effect on H diffusion and it must be considered in any discussion of δD signatures in garnets. In zircon, hydrogen diffusion is anisotropic, slightly faster along [001] than along [100] and [010]. H diffusion in zircon has much higher activation energy and slower diffusivity than other NAMs. During H-D exchange zircon incorporates also deuterium. For the first time, the hydration reaction U5+ + OH- = U4+ + O2- + 1/2H2, involving uranium reduction is observed. The kinetics of deuterium incorporation is just slightly slower than hydrogen diffusion, suggesting that the reaction is limited by hydrogen diffusion. It confirms that hydrogen isotopic memory of zircon is higher than other NAMs. Zircons will be moderately retentive of H signatures at mid-crustal metamorphic temperatures
Bai, Jinbo. "Nocivité des hydrures dans le zircaloy-4". Châtenay-Malabry, Ecole centrale de Paris, 1991. http://www.theses.fr/1991ECAP0194.
Pełny tekst źródłaBoulif, Rachid. "Potentialité d'hydrogénation de l'acier lors de traitements de galvanisation". Châtenay-Malabry, Ecole centrale de Paris, 1993. http://www.theses.fr/1993ECAP0280.
Pełny tekst źródłaMilanovic, Mirjana. "Contribution à l’étude de la réaction sodium-eau : application à la télédétection de l’hydrogène". Thesis, Paris 10, 2020. http://www.theses.fr/2020PA100078.
Pełny tekst źródłaThe common thread of this work has been the safety problems of energy installations, whether they are nuclear, such as the fast neutron channel that uses sodium as a heat transfer fluid, or for hydrogen as a storage medium for renewable energies. An experimental and modelling study undertaken with CEA Cadarache first focused on understanding the poorly understood mechanism of the sodium-water reaction based on the determination of temperature and concentration fields in the immersion of a sodium ball in a volume of water. We have shown that the reaction kinetics characterized by a fairly long latency time, which we have modeled, progresses like the vapour pressure of solid and then liquid sodium until it reaches 250°C, where disintegration occurs and then the explosion, which may be of the Coulomb type. The temperature of the effluent then peaks at 1400°C. In a second part we used the developments we had previously made in the remote sensing of hydrogen by the Raman effect. The remote detection of this odorless and colorless gas is one of the conditions for the development of hydrogen, the "fuel of the future". With the picosecond laser used, and although the Raman effect is particularly weak, we can determine the concentration of a leak and also what is original the temperature of a flame at distances up to a hundred meters
Holliger, Laurent. "Modélisation à l'échelle atomique des transformations de phase dans le système H-Zr". Thesis, Lille 1, 2010. http://www.theses.fr/2010LIL10043/document.
Pełny tekst źródłaIn nuclear industry, the hydride precipitation leads to a severe embrittlement of cladding devices made of zirconium alloys. By means of ab initio-based cluster expansions, a powerful interpolation tool for the configuration energy of crystals, the present atomic-scale study of the H-Zr system allowed to characterize the metastable phases influencing the first stages of precipitation. We investigated in detail the elaboration of a cluster expansion model designed for the yet poorly studied hexagonal symmetry of H-Zr, with particular emphasis on the key-notions of invariance and reciprocal-space expansion. In spite of its efficiency for elastic effects, the latter still remain scarcely used, and in the case of H-Zr, an original approach has been proposed, allowing for interactions of arbitrary range. This study also provided the opportunity to extend the reciprocal-space formalism to alloys with multisite unit cells, whereas all previous works were merely concerned with cubic symmetry and monatomic cells. As a main result, our cluster expansion simulations have evidenced new coherent hydrides gamma' and chi. The gamma' compound being of same composition as the incoherent gamma hydride, it should probably play a role in the precipitation of the latter, and its structural similarity with the zeta hydride suggests a relation between these two metastable phases.The chi compound, with composition close to delta, may also be an intermediate step in the precipitation sequence. Finally, this work points out the limited thermal stability of the experimentally observed zeta hydride, which may be a hint of the influence of external stresses
Marchenko, Arina. "Analyse multi-échelles de la viscoplasticité à froid et de la rupture différée du titane en relation avec ses teneurs en hydrogène et oxygène". Thesis, Paris, ENMP, 2015. http://www.theses.fr/2015ENMP0030/document.
Pełny tekst źródłaWidely used for aircraft or rocket engine manufacturing titanium and its alloys are prone to the room-temperature creep that leads to the phenomenon of sustained load subcritical crack growth. One of the major cause of such unusual viscoplastic behavior of titanium is the phenomena of static and dynamic strain aging which represents an interaction between dislocations and interstitial atoms of oxygen and hydrogen. The aim of the present experimental and numerical multiscale study is to investigate the influence of the interstitial hydrogen and oxygen on the viscoplastic behavior and the resistance to sustained load cracking in commercially pure titanium of phase alpha.In a first step, a scenario of static and dynamic strain aging was proposed. The presence of the stress peak was attributed to the segregation of interstitial atoms of oxygen on the edge dislocations. In case of dynamic strain aging, the observed instabilities, typical for the Portevin-Le Chatelier effect, were associated with the non-planar core of screw -type dislocations. The crystal plasticity was introduced into the phenomenological model in order to capture the strain aging phenomena and the anisotropy of the mechanical properties. The modeling approach for strain aging suggested by Kubin-Estrin-McCormick is based on the internal variable called the aging time which corresponds to the waiting time of a dislocation in a pinned state. Finite element simulations were then performed on the polycrystalline aggregates for different number of grains. At the next step, fracture toughness and sustained load cracking tests were performed on the material with different levels of hydrogen. Finally, numerical simulations of toughness and sustained load cracking tests using the identified viscoplastic model were carried out for all experimental conditions. A cohesive zone model was then introduced ahead of the crack tip to simulate crack propagation
Yver, Camille. "Estimation des sources et puits du dihydrogène troposphérique : développements instrumentaux, mesures atmosphériques et assimilation variationnelle". Phd thesis, Université de Versailles-Saint Quentin en Yvelines, 2010. http://tel.archives-ouvertes.fr/tel-00633825.
Pełny tekst źródłaHedayati, Ali. "Production in situ d'hydrogène pur par reformage d'éthanol dans un réacteur catalytique à membrane". Thesis, Nantes, Ecole des Mines, 2016. http://www.theses.fr/2016EMNA0246/document.
Pełny tekst źródłaIn this work, in-situ production of fuel cell grade hydrogen (pure hydrogen) via catalytic ethanol steam reforming (ESR) in a membrane reactor (MR) was investigated. A mixture of pure ethanol and distilled was used as the fuel. ESR experiments were carried out over a Pd-Rh/CeO2 catalyst in a Pd-Ag membrane reactor – named as the fuel reformer – at variety of operating conditions regarding the operating temperature, pressure, fuel flow rate, and the molar ratio of water-ethanol (S/C ratio). The performance of the catalytic membrane reactor (CMR) was studied in terms of pure hydrogen production, hydrogen yield, andhydrogen recovery.Thermodynamic evaluation of the CMR was presented as a supplement to the comprehensive investigation of the overall performance of the mentioned pure hydrogen generating system. Exergy analysis was performed based on the experimental results aiming not only to understand the thermodynamic performance of the fuel reformer, but also to introduce the application of the exergy analysis in CMRs studies. Exergy analysis provided important information on the effect of operating conditions and thermodynamic losses, resulting in understanding of the best operating conditions.In addition to the experimental and thermodynamic evaluation of the reforming system, the simulation of the dynamics of hydrogen production (permeation) was performed as the last step to study the applicability of such a system in connection with a real end user, which can be a fuel cell. The simulation presented in this work is similar to the hydrogen flow rate adjustments needed to set the electrical load of a fuel cell, if fed on line by the studied pure hydrogen generating system
Demol, Benjamin. "Méthodes d'intégration des images à résonance magnétique dans les calculs de dose Monte Carlo appliqués à la stéréotaxie intracrânienne". Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10097/document.
Pełny tekst źródłaIn the context of quality assurance of radiotherapy treatment , magnetic resonance imaging (MRI)-only treatment planning removes contour uncertainties originating from image registration between MRI and computed tomography (CT). The main aim of the thesis is to develop methods to generate synthetic CT (pCT) from MRI and to evaluate uncertainties on Monte Carlo planned dose within the framework of stereotactic radiosurgery. In the first chapter, stoichiometric calibration of the CT was realized. This was integrated into our Monte Carlo-based treatment plan quality control system. Using this calibration, we demonstrated that only the hydrogen content of tissues is required to perform accurate Monte Carlo dose calculations. Tissue hydrogen quantification from MRI sequences was then theoretically and experimentally studied. The second part concerns pCT generation from a conventional 3D T1-weighted sequence using an in-house atlas-based deformation method, where MRI intensity is taken into account while generating the pCT. A dosimetric study on a patient cohort was performed to evaluate the performance of the method. Several solutions were proposed in order to improve the results in the case of a particular patient anatomy. pCT generation from MRI will allow to remove the CT exam from routine practice, which will lead to a workflow simplification, a cost diminution, and a consistent integration of clinical practice when using treatment machines with an integrated MRI scanner
Arcanjo, Caroline. "Etudes des effets de l'eau tritiée sur les stades de développement précoces chez le poisson zèbre (Danio rerio) : caractérisation des modes d'action". Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0379/document.
Pełny tekst źródłaIn France, tritium is mainly released as tritiated water (HTO) by nuclear power plants and nuclear reprocessing plants. The developmental and reprotoxic effects of tritium have already been studied. However, few studies focus on molecular effects. In this context, the aim of this thesis is to evaluate the effects of HTO on the embryo-larvae stages of the zebrafish (Danio rerio). Two dose rates, 0.4 and 4 mGy/h, were tested. A protocol for the measurement of activity in organisms was developed. It has (i) confirmed that the internalization of HTO is rapid, (ii) allowed the discrimination of the tissue-free-water-tritum and organically bound tritium forms, and (iii) allowed the calculation of the dose permitting to link the observed effects to a received dose. The effects of HTO were evaluated at different biological levels. At the molecular level, a transcriptomic analysis (mRNAseq) showed the modulation of genes involved in muscle contraction and eye development at 24hpf, as well as in the circadian rythm and the response to oxidative stress at 96hpf. Modulation of genes involved in the DNA damage repair was shown. At higher levels of organization, some alterations of muscle fibers were observed for both dose rates. A decrease in swimming velocity was shown at 96 hpf after exposure to 0.4 mGy/h. This work allowed a better understanding of the tritium internalization, to characterize the absorbed dose in organisms and to better understand the effects of tritium
Mainka, Julia. "Impédance locale dans une pile à membrane H2/air (PEMFC) : études théoriques et expérimentales". Thesis, Nancy 1, 2011. http://www.theses.fr/2011NAN10042/document.
Pełny tekst źródłaThe aim of this Ph.D thesis is to contribute to a better understanding of the low frequency loop in impedance spectra of H2/air fed PEMFC and to bring information about the main origin(s) of the oxygen transport impedance through the porous media of the cathode via locally resolved EIS. Different expressions of the oxygen transport impedance alternative to the one-dimensional finite Warburg element are proposed. They account for phenomena occurring in the directions perpendicular and parallel to the electrode plane that are not considered usually: convection through the GDL and along the channel, finite proton conduction in the catalyst layer, and oxygen depletion between the cathode inlet and outlet. A special interest is brought to the oxygen concentration oscillations induced by the AC measuring signal that propagate along the gas channel and to their impact on the local impedance downstream. These expressions of the oxygen transport impedance are used in an equivalent electrical circuit modeling the impedance of the whole cell. Experimental results are obtained with instrumented and segmented cells designed and built in our group. Their confrontation with numerical results allows to identify parameters characterizing the physical and electrochemical processes in the MEA
Yilmaz, Bariş. "Analyse expérimentale et simulation numérique de la combustion de prémélanges turbulents CH4+H2+Air". Thesis, Orléans, 2009. http://www.theses.fr/2009ORLE2063.
Pełny tekst źródłaHydrogenated premixed methane/air flames under lean conditions are simulated in this study. The model of the high pressure chamber setup of Orleans - ICARE (France) has been developed. The flame front properties are investigated by two turbulent premixed combustion models, Zimont and Coherent Flame Model (CFM) models. All modeling studies are performed with Fluent software and compared to experiments. The influence of the pressure on the premixed flame front statistics has been examined as well. The simulations show that increasing the equivalence ratio decreases the flame tip height and the flame brush thickness for methane/air flames. In addition, enriching the methane-air mixture with hydrogen modifies the premixed flame front properties. When the volumetric percentage of hydrogen in the mixture is increased, the flame-end position is reduced and flame brush thickness becomes thinner. It is also observed that the premixed flame properties have been modified with operation at higher pressure conditions
Akkad, Ahmed Nadim. "Perméation de l'hydrogène et de l'azote au travers du fer et des aciers : influence de la présence de couches minces superficielles". Paris 6, 1986. http://www.theses.fr/1986PA066196.
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