The direct chill (DC) casting technique to produce billets for extrusion and ingots for rollingwas developed in the 1930s. The principle, which is still valid, is a two-stage cooling with a primary cooling at a mould surface followed by water spraying directly on the surface. Improvements of this technique have mainly focused on changes to the primary cooling, where a water-cooled metal mould has been replaced by different techniques to minimize cooling at this stage. The drive for development comes from the extrusion industry, which can increase the productivity and quality of extruded profiles by improving the billet surface appearance and structure. Hot top casting supported by airflow against the casting surface during the primary cooling is currently the standard procedure to achieve acceptable billet surfaces. The goal is to minimize the depth of the surface segregation zone, which is the governing factor for the appearance of different phases in the surface region. Billet surface quality is evaluated by quantifying surface appearance, segregation zone thickness, and  occurrence of large Mg2Si and β-particles near the surface. The β-Al5FeSi intermetallic phase and coarse Mg2Si particles have negative effects on extrudability and workability of 6xxx Al alloys billets. To achieve extruded products with a high surface quality the as-cast billets are  heat-treated before extrusion. During heat treatment the undesired intermetallic particles, i.e., β-AlFeSi platelets are transformed to rounded α-Al(FeMn)Si intermetallic phases. In this  research the formation of the surface segregation for smooth defect-free surfaces in both as-cast and homogenized billets was studied. In addition, the surfaces with defects such as wavy, spot and vertical drag defects were investigated and possible mechanisms for initiation of those defects were explained. Moreover, for a better understanding of the homogenization process in-situ studies of the heat treatment of 6082, 6005, 6060 and 6063 Al alloys were carried out by using a transmission electron microscope (TEM). Based on the observations, an explanation of the probable mechanisms taking place during transformation from β-to α-phase was presented. / <p>Vid tidpunkten för disputationen var följande delarbeten opublicerade: delarbete 5 manuskript, delarbete 6 inskickat och delarbete 7 inskickat.</p><p>At the time of the doctoral defence the following papers were unpublished: paper 5 manuscript, paper 6 submitted, paper 7 submitted.</p>

Par l'utilisation de techniques statistiques poussées, l'approche de population rend l'estimation des propriétés pharmacocinétiques (étude des phénomènes d'absorption, distribution, métabolisme et élimination du médicament dans l'organisme) possible chez les patients inclus dans les études de Phase III, en dépit d'un nombre de prélèvements sanguins réduit. Elle permet également d'évaluer, parmi les caractéristiques des patients, les sources de variabilité interindividuelle (covariables) pouvant expliquer les différences potentielles observées dans telle ou telle sous-population.Après un bref rappel bibliographique de la technique, nous présentons les résultats des analyses effectuées sur trois candidats-médicaments en fin de développement clinique. Le premier exemple détaille le processus d'une analyse de population réalisée chez plus de 3000 patients ainsi que les résultats d'une analyse pharmacocinétique/pharmacodynamique. Dans la deuxième partie, nous insistons sur une technique particulière de validation (le bootstrap) et détaillons l'étape de simulation mise en place pour appuyer les conclusions de l'analyse. La dernière analyse présente enfin un modèle pharmacocinétique de population combinant les données d'un produit parent et de son métabolite actif, l'autre originalité de l'analyse étant l'utilisation du randomization test afin de vérifier l'inclusion de covariables dans le modèle.Les conclusions de ces analyses permettent de mieux appréhender la cinétique des trois molécules dans leur population cible par la mise en évidence d'éventuelles sous-populations à risque et, ainsi, de veiller à leur efficacité et à leur absence de toxicité. / Using sophisticated statistical techniques, the population approach allows estimating the pharmacokinetic properties (study of the absorption, distribution, metabolism and elimination phenomena of a drug into the body) in patients included in Phase III studies, despite a low number of blood samples collected. It also allows evaluating, from the patients' characteristics, the sources of interindividual variability (covariates) that may explain the potential differences observed in a given subpopulation.After a brief review of the technical aspects of the population approach, the results of the analyses performed on three drugs in the end of their clinical development will be presented. The first example details the process of a population analysis carried out in more than 3000 patients, together with the results of a pharmacokinetic/pharmacodynamic analysis. In a second part, we underline a validation technique (the bootstrap) and the simulation study performed to emphasize the conclusions of the study. The last example presents a population pharmacokinetic model applied to the simultaneous fit of data from a parent drug and its active metabolite, the other originality of the analysis being the use of the randomization test to verify the covariates inclusion in the model.The conclusions of these analyses allow a better understanding of the kinetics of the three drugs in their target population by emphasizing potential subpopulations at risk and, hence, participate to verify their efficacy and their absence of toxicity.

Les écoulements diphasiques en fracture se produisent dans de nombreuses applications industrielles et environnementales. Pour modéliser ces écoulements, il est important de connaître le rôle des caractéristiques géométriques des surfaces constituant les fractures.L’objectif de ce travail de thèse est d’étudier expérimentalement les écoulements diphasiques et la dispersion de traceurs dans des fractures réelles dont on connaît la cartographie des surfaces et d’en proposer une modélisation adéquate.L’écoulement diphasique inertiel a été modélisé à l’aide de la généralisation de la loi de Darcy couplée à l’approche de la fonction F. Le modèle proposé permet de prédire les perméabilités relatives et les saturations en fonction des débits des deux fluides avec deux paramètres d’ajustement.Les profils de concentration obtenus lors des expériences de dispersion ont été interprétés avec différents modèles afin d'évaluer leur capacité à décrire la dispersion dans les fractures et donc l’hétérogénéité de celles-ci. Les résultats montrent que le modèle stratifié, avec un seul paramètre estimé, donne des résultats satisfaisants et permet de quantifier l'hétérogénéité.Enfin, avec cinq paramètres estimés, à partir de la courbe de la concentration de traceur à la sortie des fractures, le modèle CTRW permet de décrire avec une bonne précision les profils de concentration de toutes les abscisses / The two-phase flows through fractures occur in many industrial and environmental processes.Modelling these flows needs understanding the role of geometric characteristics of the fractures surfaces. The objective of this thesis is to study experimentally the two-phase flow and the dispersion of tracers in fractures which the aperture map is known and propose a suitable model.The inertial two-phase flow model is based on the generalization of the single-phase full cubiclaw that accounts for non-Darcian effects by using the F function approach. On this approach,the presence of a second fluid is taken into account through a multiplier function introduced into the superficial velocity of each fluid. This model let us predict the relative permeability and the saturation as a function of the two fluid flows with two adjustment parameters.The concentration profiles obtained during dispersion experiments were interpreted with different models to study their ability to describe the dispersion in fractures and hence the heterogeneity of them. The results show that the classical convection-dispersion is not appropriate due to the heterogeneity of the fractures. On the other hand, the stratified model,with only one estimated parameter, gives satisfactory results and allows quantifying heterogeneity. Finally, with five estimated parameters, from the concentration curve at the outlet of the fractures, the CTRW model can describe the concentration profiles of all abscissas with good accuracy

Ce travail a pour but l’acquisition de connaissances fondamentales dans les équilibres de phases et les transformations de phases des alliages ternaires contenant du fer, du nickel et du cuivre.Cette étude est composée de trois parties : la première est consacrée aux équilibres de phase entre600°C et 1000°C dans le coin riche en fer du système ternaire Cu-Fe-Ni, la seconde concerne l’analyse des transformations de phases dans des alliages modèles suivant deux vitesses de refroidissement et la troisième étudie les alliages industriels.Cette approche expérimentale est appuyée par des calculs thermodynamiques. Une comparaison est effectuée avec les données issues de la littérature. Les sections isothermes à 600°C, 800°C et1000°C ont été reconfirmées. Les domaines triphasés αFe/γFe/γCu ont été déterminés à 600°C et800°C et semblent décalés vers de plus fortes teneurs en Ni. La lacune de miscibilité est moins étendue que celle calculée et ce particulièrement du côté du binaire Cu-Ni.Les transformations de phase γ→α apparaissant lors du refroidissement d’alliages Fe-xCu-10Ni et Fe-10Cu-xNi (0<x<15 % en masse) ont été étudiées. Elles sont observées dans tous les alliages refroidis lentement par dilatométrie sauf dans l’alliage binaire Fe-Cu. Les températures de transformation sont systématiquement inférieures aux températures d’équilibre et cet écart augmente lorsque les teneurs en Ni et Cu augmentent. La formation de la ferrite bainitique est favorisée par l’addition de Cu dans les alliages trempés Fe-xCu-10Ni et par l’addition de Ni dans les alliages Fe-10Cu-xNi tandis que la ferrite massive se forme préférentiellement lors du refroidissement lent. Une diminution des températures de transformation se produit lorsque la taille de grains est affinée et est reliée au processus d’accommodation plastique liée à la transformation.La composition et la vitesse de refroidissement jouent un rôle sur la dureté de ces alliages via la présence de Ni en solution solide ainsi que le nombre et la taille des précipités de Cu. / This work aims in getting fundamental knowledge of phase equilibria and microstructures of ternary alloys containing copper, nickel and iron. The thesis is composed of three parts: a first part is devoted to phase equilibria in the Fe-rich corner of the ternary Cu-Fe-Ni system between 600°C and 1000°C, a second part is devoted to the microstructures in these materials for model alloys, for two cooling rates and a third part is devoted to industrial alloys.Phase equilibria of the system are investigated in the range 600-1000°C using diffusion multiples in conjunction with selected equilibrated alloys. This experimental approach is supplemented by thermodynamic calculations. A comparison is drawn with data reported in the literature. The isothermal sections at 600°C, 800°C and 1000°C have been reconfirmed. The three-phase regions αFe/γFe/γCu are determined at 600°C and 800°C and appear shifted to a higher Ni content. The miscibility gap is narrower than the calculated, particularly on the Cu-Ni binary sides.Austenite/ferrite phase transformations occurring on cooling in Fe-xCu-10Ni and Fe-10Cu-xNi alloys,0<x<15 (mass%), have been studied. The influence of copper and nickel additions and of the cooling rate on the microstructure is discussed. Metastable transformations in slowly cooled alloys have been detected by dilatometry in all alloys except in the binary Fe-10Cu alloy: all the cooling transformation temperatures are systematically lower than the equilibrium temperature and the Ni and Cu addition decrease this transformation temperature. The formation of bainitic ferrite is favoured by copper additions in quenched Fe-xCu-10Ni alloys and by Ni addition in Fe-10Cu-xNi alloys while massive ferrite form preferentially during slow cooling. A decrease of the transformation temperatures is recorded when the alloys have a finer grain size likely related to plastic accommodation processes.The composition and cooling rate influence the hardness of the alloys mostly dependant on the amount of Ni in solid solution and on the rate and size of Cu precipitates.

L'objectif de ce travail était de comprendre les mécanismes menant à la formation de SiC-3C sur substrats de SiC hexagonaux lors de la croissance par mécanisme Vapeur-Liquide-Solide (VLS) à partir d'une phase liquide Si-Ge. Notre étude s'est concentrée sur les premiers instants de l'interaction liquide/SiC, c'est-a-dire sans ajout de phase gazeuse réactive (propane). Nous avons montré qu'il se formait très rapidement des îlots de SiC-3C à la surface des germes. L'étude en fonction de divers paramètres (température et durée de plateau, vitesse de chauffage, nature du germe) a permis de mettre en évidence l'influence prononcée du creuset en graphite dans lequel est confinée la réaction. Les observations expérimentales associées à des calculs thermodynamiques ont permis de montrer que l'étape prépondérante, pour la formation du 3C, est sans doute la réaction transitoire entre un liquide très riche en germanium et le germe de SiC. Des considérations d'ordre cinétiques sont cependant à prendre en compte pour expliquer le caractère hors équilibre de la réaction / The aim of this work was to understand the mechanisms that lead to the 3C-SiC formation on hexagonal SiC substrates during the Vapor-Liquid-Solid (VLS) growth from a Si-Ge liquid phase. Our study focused on the early stages of the liquid/SiC interaction, i.e. without reactive gaseous phase (propane) addition. We have shown that 3C-SiC islands were very rapidly formed upon seeds surface. The study of several parameters (such as temperature and duration of the plateau, heating rate, nature of the seed) evidenced the huge influence of the graphite crucible that contains the reaction. Experimental observations combined with thermodynamic calculations show that the most important step for the 3C formation, is the transient reaction between a germanium very rich liquid and the SiC seed. Kinetic effects have to be taken into account to explain the out-of-equilibrium nature of the reaction.

In the context of an intensive upgrade plan for the Large Hadron Collider (LHC) in order to provide proton beams of increased luminosity, a revision of the data readout electronics of the Liquid-Argon-Calorimeter of the ATLAS detector is scheduled. This is required to retain the efficiency of the trigger at increased event rates despite its fixed bandwidth. The focus lies on the early digitization and finer segmentation of the data provided to the trigger. Furthermore, there is the possibility to implement new energy reconstruction algorithms which are adapted to the specific requirements of the trigger. In order to constitute crucial design decisions, such as the digitization scale or the choice of digital signal processing algorithms, comprehensive simulations are required. High trigger efficiencies are decisive at it for the successful continuation of the measurements of rare StandardModel processes as well as for a high sensitivity to new physics beyond the established theories. It can be shown that a significantly improved resolution of the missing transverse energy calculated by the trigger is achievable due to the revised segmentation of the data. Various energy reconstruction algorithms are investigated in detail. It can be concluded that these will facilitate reliable trigger decisions for all expected working conditions and for the whole possible energy range.

Martensitic phase transformation in NiTi shape memory alloys (SMA) occurs over a hierarchy of spatial scales, as evidenced from observed multiscale patterns of the martensitic phase fraction, which depend on the material microstructure and on the size of the SMA specimen. This paper presents a methodology for the multiscale tracking of the thermally induced martensitic phase transformation process in NiTi SMA. Fine scale stochastic phase field simulations are coupled to macroscale experimental measurements through the compound wavelet matrix method (CWM). A novel process for obtaining CWM fine scale wavelet coefficients is used that enhances the effectiveness of the method in transferring uncertainties from fine to coarse scales, and also ensures the preservation of spatial correlations in the phase fraction pattern. Size effects, well-documented in the literature, play an important role in designing the multiscale tracking methodology. Molecular dynamics (MD) simulations are employed to verify the phase field simulations in terms of different statistical measures and to demonstrate size effects at the nanometer scale. The effects of thermally induced martensite phase fraction uncertainties on the constitutive response of NiTi SMA is demonstrated.

The purpose of this investigation is to make more detailed studies of transformations. Fourteen compounds have been examined by high temperature X-ray diffraction for this purpose. The investigations have been carried out in such a way as to reveal: 1. the existence of transformations, 2. the influence of polarizability on thermal expansion, 3. the anisotropy of expansion, and 4. the discontinuity of thermal expansion.

Energy storage using Phase Change Materials (PCMs) offers the advantage of higher heat capacity at specific temperature ranges, compared to single phase storage. Incorporating PCMs in lightweight buildings can therefore improve the thermal mass, and reduce indoor temperature fluctuations and energy demand. Large atrium buildings, such as Airport terminal spaces, are typically thermally lightweight structures, with large open indoor spaces, large glazed envelopes, high ceilings and non-uniform internal heat gains. The Heating, Ventilation and Air-Conditioning (HVAC) systems constitute a major portion of the overall energy demand of such buildings. This study presented a case study of the energy saving potential of three different PCM systems (PCM floor tiles, PCM glazed envelope and a retrofitted PCM-HX system) in an airport terminal space. A quasi-dynamic coupled TRNSYS®-FLUENT® simulation approach was used to evaluate the energy performance of each PCM system in the space. FLUENT® simulated the indoor air-flow and PCM, whilst TRNSYS® simulated the HVAC system. Two novel PCM models were developed in FLUENT® as part of this study. The first model improved the phase change conduction model by accounting for hysteresis and non-linear enthalpy-temperature relationships, and was developed using data from Differential Scanning Calorimetry tests. This model was validated with data obtained in a custom-built test cell with different ambient and internal conditions. The second model analysed the impact of radiation on the phase change behaviour. It was developed using data from spectrophotometry tests, and was validated with data from a custom-built PCM-glazed unit. These developed phase change models were found to improve the prediction errors with respect to conventional models, and together with the enthalpy-porosity model, they were used to simulate the performance of the PCM systems in the airport terminal for different operating conditions. This study generally portrayed the benefits and flexibility of using the coupled simulation approach in evaluating the building performance with PCMs, and showed that employing PCMs in large, open and thermally lightweight spaces can be beneficial, depending on the configuration and mode of operation of the PCM system. The simulation results showed that the relative energy performance of the PCM systems relies mainly on the type and control of the system, the night recharge strategy, the latent heat capacity of the system, and the internal heat gain schedules. Semi-active systems provide more control flexibility and better energy performance than passive systems, and for the case of the airport terminal, the annual energy demands can be reduced when night ventilation of the PCM systems is not employed. The semi-active PCM-HX-8mm configuration without night ventilation, produced the highest annual energy and CO2 emissions savings of 38% and 23%, respectively, relative to a displacement conditioning (DC) system without PCM systems.

Le sang est une suspension concentrée (45 % en volume) de cellules déformables, les globules rouges, dans un liquide newtonien, le plasma. Dans la microcirculation, i.e. le sous-ensemble du système de circulation sanguine où s'effectuent les échanges de matière entre le sang et les tissus, les tailles de vaisseaux sont comparables à la taille d'un globule rouge (environ 10 µm). En conséquence, les effets dynamiques liés à la présence de ces cellules induisent des comportements rhéologiques complexes, qui jouent un rôle important dans le transport de l'oxygène vers les tissus. En particulier, aux bifurcations microvasculaires divergentes, les débits de globules rouges et de plasma peuvent se répartir de façon non proportionnelle entre les deux branches filles. La fraction volumique de globules rouges (hématocrite) dans l'une des branches filles est alors plus élevée que celle de la branche d'entrée, et la fraction volumique dans l'autre branche y est plus faible. Cet effet, connu sous le nom d'effet de séparation de phase, induit une très grande hétérogénéité de l'hématocrite d'un vaisseau à l'autre dans la microcirculation. Il induit également un couplage entre l'architecture du réseau microvasculaire et la dynamique de l'écoulement sanguin dans ce réseau. L'objectif de ce travail de thèse est d'étudier finement l'effet de séparation de phase in vitro, dans un régime représentatif des conditions physiologiques, au moyen de dispositifs microfluidiques modélisant les bifurcations microvasculaires et de suspensions de globules rouges. Dans ce but, un dispositif expérimental microfluidique a d'abord été élaboré. Puis, les aspects métrologiques spécifiques aux suspensions concentrées ont été abordés afin de quantifier les paramètres de l'écoulement. En particulier, la technique de dual-slit a été comprise et optimisée, assurant une mesure précise de profils de vitesse de globules rouges en microcanaux. Des métrologies spécifiques à nos conditions expérimentales ont également été mises en place pour déterminer l'hématocrite. Ces techniques ont été validées par vérification du principe de conservation de la masse entre les trois branches d'une bifurcation, et elles nous ont permis de caractériser les écoulements de globules rouges dans des micro-canaux de différentes tailles (10 à 100 µm), et ce pour de larges gammes de débits et de concentrations. Enfin, l'écoulement de suspensions de globules rouges a été étudié au niveau de micro-bifurcations, dans l'objectif de caractériser l'effet de séparation de phase pour des tailles de canaux et des gammes d'hématocrites qui n'ont pas été étudiés auparavant en conditions d'écoulement maîtrisées. / Blood is a concentrated suspension (45% by volume) of deformable red blood cells, flowing in a Newtonian fluid called plasma. The microcirculation is the part of the blood circulation system where the exchanges of material (e.g. nutrients, oxygen) between the blood and tissues take place. The microvessels are characterized by diameters less than 100 microns, which is similar in size to the size of a red blood cell ( 10 microns). As a result, the presence of these cells considerably influences the dynamics of microvascular flows and induces complex rheological behaviors. In particular, at diverging microvascular bifurcations, red blood cells and plasma may be nonproportionally distributed between two daughter vessels : one gets a higher red blood cell volume fraction (hematocrit) than the feeding vessel, while the other gets a lower one. This effect, known as the phase separation effect, causes a tremendous heterogeneity of the hematocrit among vessels in microvascular networks and induces a coupling between the microvascular architecture and the blood flow dynamics. The aim of this thesis is to investigate the phase separation effect in vitro, in physiological conditions, using red blood cell suspensions and microfluidic devices modeling microvascular bifurcations. For this purpose, a microfluidic experimental device was first developed. Then the metrological aspects specific to concentrated suspensions were addressed in order to quantify all the flow parameters. In particular, the dual-slit technique has been understood and optimized, ensuring accurate measurement of velocity profiles of red blood cells in microchannels. Measurement methods for our experimental conditions were also implemented to determine the hematocrit. All these techniques have been validated by verification of the principle of mass conservation between the three branches of a bifurcation. They allowed us to characterize the flow of red blood cells in microchannels of different sizes (10 to 100 microns) and for wide ranges of flow rates and concentrations. Finally, the flow of red blood cell suspensions was investigated at micro-bifurcations, with the aim of characterizing the phase separation effect for channel sizes and hematocrit ranges never studied in controlled flow conditions.