Dissertations / Theses: 'Continual mixer'

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Černý, Jan. "Dvoušnekový mísič kontinuální." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-442867.

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This work focuses on the process of mixing particulate materials and the design of the screw mixer for this activity. The theoretical part describes the mixing and properties of particulate matter. Subsequently, individual devices serving for different types of mixing are analyzed. The practical part contains calculations of the main dimensions and the required power consumption. The choice of suitable drive, bearings and gear is followed. Finally, the analysis of the blade shaft load and the strength analysis of the mixer blade using Autodesk Inventor are performed. Part of this work is enclosed drawing documentation of equipment assembly and selected partial components.

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Černý, Jan. "Dvoušnekový mísič kontinuální." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-433469.

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This work focuses on the process of mixing particulate materials and the design of the screw mixer for this activity. The theoretical part describes the mixing and properties of particulate matter. Subsequently, individual devices serving for different types of mixing are analyzed. The practical part contains calculations of the main dimensions and the required power consumption. The choice of suitable drive, bearings and gear is followed. Finally, the analysis of the blade shaft load and the strength analysis of the mixer blade using Autodesk Inventor are performed. Part of this work is enclosed drawing documentation of equipment assembly and selected partial components.

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Pelka, Tomáš. "Šnekový mísič kontinuální." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229978.

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This diploma project works out and is focused on the continual mixing process of the particular matters. The project is divided into following chapters. Chapter 1 includes mixing theory and information of the experimental work of the particular matters for blade using. In chapter 2 there is Evaluation and calculation of the technical parameters for the mixer. Chapter 3 deals with the engine proposal and chapter 4 includes calculation and design work of the gear transmission. Chapter 5 includes the stress analysis of the shaft and blade with the I-deas software. In attachment there are also the mixer arrangement drawing and detailed drawings of the key parts and groups for the mixer.

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Nancib, Ayacha. "Production d'acide lactique par Lactobacillus casei subsp. rhamnosus sur jus de datte : cinétique et optimisation en cultures discontinues, semi-continues et continues." Thesis, Vandoeuvre-les-Nancy, INPL, 2007. http://www.theses.fr/2007INPL074N/document.

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L’objectif de ce travail a été de développer un procédé performant de production d’acide lactique par Lactobacillus casei subsp. rhamnosus sur jus de datte. Dans une première partie, des cultures en mode discontinu ont été réalisées afin d’étudier les besoins nutritionnels de la souche. Ces études ont pour but de décrire les effets des sources carbonées, azotées et les vitamines sur la production d’acide lactique. Nous avons montré que le sulfate d’ammonium est une bonne alternative économique et nous avons pu déterminer la faisabilité de minimiser l’ajout de l’extrait de levure par l’utilisation partielle de l’extrait de levure combinée avec du sulfate d’ammonium plus l’ajout de vitamines du groupe B. Des cultures pures et mixtes de Lactobacillus casei et Lactococcus lactis ont été réalisées. Le système de culture mixte donne de meilleurs résultats concernant la production d’acide lactique et l’utilisation des sucres comparés à ceux obtenus en cultures pures de Lactobacillus casei ou Lactococcus lactis. L’effet des sucres purs (glucose et fructose) et mixtes (glucose/fructose) sur la production d’acide lactique a été étudié. La production d’acide lactique est plus importante avec un mélange de sucres qu’avec des sucres non mélangés ce qui explique les performances de fermentation sur jus de datte. Dans une seconde partie, une stratégie d’alimentation du réacteur en culture semi-continue a été mise en œuvre, permettant d’améliorer les performances de la fermentation. Les deux facteurs influençant le bon fonctionnement sont le débit et la concentration du milieu d’alimentation. Dans une troisième partie, une étude cinétique a été développée en réacteurs continus. Nous avons étudié l’influence du taux de dilution sur la croissance, l’utilisation du substrat et la production d’acide lactique. La productivité du procédé continu a été considérablement augmentée en comparaison avec le procédé discontinu. Enfin, dans une dernière partie, un modèle a été établi. Ce modèle, bien qu’imparfait, permet apparemment de simuler la croissance, la consommation des sucres de jus de datte et la production d’acide lactique en culture discontinue
The aim of this work was to develop an efficient process of lactic acid production by Lactobacillus casei subsp. rhamnosus on date juice In a first part, the batch cultures were realized to carry out the nutritional requirement of the strain. These studies allowed us to describe the effects of carbon substrates, nitrogen substrates and vitamins on the lactic acid production. We showed that ammonium sulphate is a satisfying economic alternative and we have determined feasibility of minimizing the addition of the yeast extract by the partial use of yeast extract combined with the ammonium sulphate plus the addition of vitamins of the group B. Pure and mixed cultures of Lactobacillus casei and Lactococcus lactis were carried out. The mixed system gives better results concerning the lactic acid production and the use of the sugars compared with those obtained in pure cultures of Lactobacillus casei or Lactococcus lactis. The effect of pure sugars (glucose and fructose) and mixed sugars (glucose/fructose) on the lactic acid production was studied. The lactic acid production is more important on mixed sugars than on pure sugars what explains the performances of fermentation on date juice. In a second part, a mode of fed batch operations was defined to improve the performances of the fermentation. The two factors influencing the process are the feeding rate and the concentration of the feeding medium. In a third part, kinetic study in continuous culture was developed. We studied the influence of dilution rate on growth, substrate utilization and lactic acid production. The productivity of the continuous process was considerably increased in comparison with the batch process. Finally, a tentative model has been established for the fermentation process. The corresponding model, although not perfect, is apparently able to simulate growth rate, substrates uptake and lactic acid production in batch culture

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Oualha, Khaled. "Étude expérimentale et numérique de l'hydrodynamique de l’écoulement dans un réacteur continu." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCD082/document.

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Au cours de ce travail de thèse, sur l'hydrodynamique de l'écoulement dans le un réacteur continu, où les propriétés des nanomatériaux élaborés dépendent des caractéristiques morphologiques et structurales de la solution colloïdale issue du réacteur, nous avons d'abord optimisé les conditions d'utilisation (Re ≈ 6000), ainsi que la géométrie du T-mélange dans le but d'améliorer la qualité du micro-mélange. Ensuite, des mesures expérimentales ont permis de vérifier que la condition de Damköhler est respectée (Da ≤ 1). Enfin, ce résultat a été validé numériquement. Au delà de cette valeur de Re critique (Re* ≈ 8000), nous avons mis en évidence le phénomène de cavitation dans le T-mélange. Ce phénomène à été étudié expérimentalement, par des mesures SLS, et numériquement par des simulations CFD. Les résultats obtenus par ces deux approches concordent. Enfin, des mesures DLS ont été effectuées pour étudier et caractériser les bulles de cavitation. Ces dernières ont permis d'évaluer la taille des bulles ainsi que leur trajectoire le long de l'axe Z à la sortie du T-mélange. Cette étude a été suivie par des simulations numériques de la cavitation et du modèle multiphasique dans notre écoulement. Les deux études, expérimentale et numérique, ont confirmé que la diminution de l'intensité de la lumière diffusée mesurée par SLS le long de l'axe Z est due à l'évolution du nombre et de la taille des bulles
During this Phd work, on the hydrodynamics of flow in a continuous reactor, where the properties of the elaborated nanomaterials depend on the morphological and structural characteristics of the colloidal solution out coming from the reactor, we first optimized the conditions of use of the latter (Re ≈ 6000), as well as the geometry of the T-mixer in order to improve the quality of the micro-mixing. Then, experimental measurements allowed us to verify that the condition of Damköhler is respected (Da ≤ 1). Finally, this result has been validated numerically. Beyond this Re critical value (Re * ≈ 8000), we have highlighted the phenomenon of cavitations in the T-mixer. This phenomenon has been studied experimentally, by SLS measurements, and numerically by CFD simulation. The results obtained by these two approaches are in agreement. Finally, DLS measurements were made to study and characterize cavitations bubbles. These measurements allowed us to evaluate the size of the bubbles as well as their trajectory along the Z axis 121 at the outlet of the T-mixer. This study was followed by numerical simulations of the cavitations and the multiphase model in our flow. Both experimental and numerical studies confirmed that the decrease in the intensity of scattered light measured by SLS along the Z axis is result to the changes of the number and the size of bubbles

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Dimagiba, Richard Raymond N. "Application of the Boundary Element Method to three-dimensional mixed-mode elastoplastic fracture mechanics." Thesis, University of Sheffield, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310815.

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Crawford, Ben. "“FROM SCHOOL OF CRISIS TO DISTINGUISHED”: HOW ONE SCHOOL CONTINUES TO DEFEAT THE ODDS." UKnowledge, 2018. https://uknowledge.uky.edu/stem_etds/9.

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Despite conditions that would work against a small rural school in an impoverish area of rural Kentucky, Fairway Elementary School has managed to excel in its accountability measures. This study used a mixed-methods approach with data collected through interviews and MAP student growth scores in reading and mathematics. Five themes emerged from the qualitative data regarding school success: (1) a well-organized intervention system, (2) a focus on and overall enjoyment of the discipline of mathematics, (3) involvement of parents in school functions, (4) transparency of needs and organization of resources, and (5) an overall school culture that is competitive, impactful, and student-centered. Quantitative data revealed large improvements in student growth in reading and mathematics after the adoption of standard-aligned curricular programs in both subjects. Fairway Elementary continues to succeed in their efforts to improve not only student achievement, but the culture of their school within an impoverished community.

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Mariotti, Giulia. "Mixed-use corrugated skyscraper: progetto di un grattacielo in Dubai con studio di superficie continua ondulata derivata da funzioni periodiche." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8671/.

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Questo lavoro di tesi verte sulla progettazione architettonica di un grattacielo ad uso misto nel cuore di Dubai. E’ stato scelto come sito di collocazione proprio Dubai in quanto fiorente cittadina in grande e continua espansione. In uno skyline così eterogeneo, caratterizzato da grattacieli imponenti, è stato possibile progettare un edificio dall’importante volumetria e dalla particolare conformazione. Partendo da un modello di riferimento in campo biologico, il Saguaro Cactus, si è tratto spunto al fine di creare un ambiente che, seppure nella sua imponenza, potesse, dal suo interno, trasmettere un senso di spazio fluido e continuo ai suoi fruitori. A raggiungimento di tal scopo si è pensato ad una superficie fluida, continua, scanalata che avvolgesse tutta la struttura, creando rientranze, aggetti ed aperture trattandone

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Theron, Félicie. "Conception et mise en œuvre d'un procédé intensifié continu de microencapsulation par polycondensation interfaciale." Thesis, Toulouse, INPT, 2009. http://www.theses.fr/2009INPT045G/document.

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De nombreux produits encapsulés sont utilisés dans la vie quotidienne. Crèmes cosmétiques, peintures, et pesticides en sont quelques exemples. De nos jours, de plus en plus de technologies innovantes mettent en jeu des substances encapsulées. La microencapsulation a permis à de nouveaux « textiles intelligents » de voir le jour, tels que les textiles sur lesquels sont fixées des microcapsules qui libèrent un principe actif amincissant, odorant, hydratant ou encore répulsif pour les insectes. Les microcapsules sont des produits à fortes valeur ajoutée, dont les propriétés sont nombreuses, et délicates à maîtriser toutes à la fois. Si l'étape de formulation a pour objectif de trouver la recette optimale pour répondre le mieux possible au cahier des charges, le type de procédé de fabrication choisi doit garantir une production homogène dans le temps, sans écarts par rapports aux propriétés attendues. L'objectif de ces travaux est de proposer une alternative continue aux procédés batch traditionnellement mis en œuvre pour l'encapsulation par polycondensation interfaciale, coûteux en termes d'investissement et de frais de fonctionnement. L'encapsulation par polycondensation interfaciale est constituée d'une étape d'émulsification suivie d'une étape réactive. Nous proposons un procédé découplant ces deux étapes grâce à deux technologies adaptées aux contraintes hydrodynamiques respectives de chaque étape. Cette étude est réalisée sur la base d'un système modèle espèce encapsulée / membrane polymérique. L'étape d'émulsification est réalisée en mélangeurs statiques en régime turbulent. Des mesures de pertes de charge en écoulements monophasiques ont permis de mettre en évidence l'apparition de ce régime et d'établir des corrélations représentant ces pertes de charge a travers l'emploi des nombres adimensionnels que sont le nombre de Reynolds et le facteur de friction. Concernant l'émulsification, nous évaluons l'influence de différents paramètres sur les performances de l'opération en termes de tailles de gouttes obtenues en fonction du coût énergétique. Nous comparons également les performances de trois designs de mélangeurs statiques commercialisés par la société Sulzer, et corrélons les résultats obtenus en termes de diamètres moyens de Sauter en fonction des nombres de Reynolds et de Weber. L'étape réactive est tout d'abord mise en œuvre en réacteur agité afin d'étudier la cinétique de la réaction, et d'acquérir des temps de réactions qui permettent par la suite de dimensionner le réacteur continu. Enfin cette étape est réalisée dans deux types de réacteurs continus : le réacteur Deanhex, développé et étudié par Anxionnaz et al. (2009), ainsi qu'un réacteur tubulaire en serpentin. Cette dernière étude consiste d'une part à valider le passage au continu à travers la conservation de la granulométrie des gouttelettes de l'émulsion durant la réaction, et la conservation de la vitesse apparente de la réaction. Enfin, les conditions hydrodynamiques favorables présentées par les réacteurs continus permettent d'apporter de nouvelles voies d'intensification au procédé en augmentant d'une part la concentration en capsules dans le réacteur, et en s'affranchissant de l'emploi du tensioactif utilisé pour stabiliser les gouttes de l'émulsion. Ce procédé, proposé pour la production en continu de microcapsules, offre une amélioration en termes de qualité du produit et de coût par rapport aux procédés traditionnels en batch mis en œuvre dans l'industrie
The aim of the present work is to propose a continuous alternative to batch processes classically used to carry out encapsulation by interfacial polycondensation that represent high investment and working costs. Encapsulation by interfacial polycondensation consists in an emulsification step followed by a reactive step. We propose here a process decoupling these two steps using technologies well adapted to hydrodynamic issues of each step. This study is realised on the basis of model system. The emulsification step is carried out in static mixers under turbulent flow. Pressure drop measurements in single-phase flow enable to highlight this flow regime and to establish correlations representing these pressure drops in terms of dimensionless numbers: the Reynolds number and the friction factor. About emulsification we evaluate the influence of different parameters on the operation performances in terms of mean droplets size as a function of energy cost. We compare the performances of three different Sulzer static mixers and correlate results obtained in terms of Sauter mean diameter as a function of Reynolds and Weber numbers. The reactive step has been first carried out is stirred tank in order to study the reaction kinetics and to acquire reaction times necessary to design continuous reactors. Finally this step has been realised using two continuous reactors: the Deanhex reactor (Anxionnaz et al., 2009) and a coiled tube reactor. This last study consists first in validating the continuous process through the conservation of the emulsion size distribution during encapsulation and the conservation of the apparent kinetics. Finally the favourable hydrodynamic conditions presented by continuous reactors offer new ways of intensification to the process. In fact it is possible to increase the microcapsule concentration in the reactor and to work without surfactant to stabilize the emulsion. This continuous process for microcapsules production offers improvements in terms of product quality and working costs compared to traditional batch process used in the industry

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Ammarcha, Chawki. "Mélange des poudres en continu : modèles dynamiques et caractérisation des mélanges en ligne." Thesis, Toulouse, INPT, 2010. http://www.theses.fr/2010INPT0138/document.

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La généralisation des mélangeurs continu dans l'industrie est freinée par le manque de connaissance générale sur ces procédés et en particulier d'une stratégie de contrôle commande de ce procédé. Se plaçant dans cette perspective, ce travail se penche, tant du point du vue expérimental et modélisation, sur la dynamique du procédé de mélange en continu, en particulier durant les phases transitoires que sont le démarrage, la vidange ou le changement de consigne. On étudie l'effet des variables opératoires, vitesse d'agitation et débit, sur la répartition massique et les débits internes des particules dans le mélangeur, ainsi que sur les variations d'homogénéité du mélange en sortie. A ce titre, un protocole expérimental spécifique basé sur l'analyse d'images est développé pour mesurer en ligne la qualité du mélange à une échelle d'observation que l'on peut ajuster. Un cadre de modélisation Markovienne est proposé pour décrire les phénomènes observés aux échelles macro et méso. Le modèle permet de décrire la composition du mélange dans les différentes zones du mélangeur ainsi qu'en sortie de l'appareil, quel que soit le régime envisagé, notamment lors de fortes perturbations de vitesse de rotation, dont l'intérêt est discuté
The implementation of a continuous mixer in the industry requires detailed studies for a better understanding of this process, with essential aim the development of a control process strategy. The present work reports experimental and modelling results concerning the dynamics of a continuous powder mixer in steady and unsteady states. In particular, we will focus on the transitory phases that are likely to occur : starting, emptying, feeder's feeding, accidental perturbation, etc. We investigate the effect of operating variables, as rotational speed of the stirrer and the inflow rate, on the distribution of particles mass in the mixer and the intermediates flow rates, as well as that of the homogeneity of binary mixtures at the outlet of continuous mixer. A specific experimental protocol, based on image analysis, has been developed for determining mixture quality. The scale of scrutiny can be adjusted and mixture homogeneity can be calculated for this scale in real time. AMarkov chain model is proposed to describe the phenomena observed at both macro-and meso-scales. The model allows to describe the composition of the mixture in different zones of the mixer as well as in the outlet of the vessel, during steady and unsteady regimes and especially at high speed perturbations, whose interest is discussed

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Biggers, Mandy Sue. "Elementary teachers' ideas about, planning for, and implementation of learner-directed and teacher-directed inquiry: a mixed methods study." Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/2438.

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Using a framework for variations of classroom inquiry (National Research Council [NRC], 2000, p. 29), this study explored 40 inservice elementary teachers' planning, modification, and enactment of kit-based science curriculum materials. As part of the study, a new observation protocol was modified from an existing protocol (Practices of Science Observation Protocol [P-SOP]) to measure the amount of teacher direction in science inquiry lessons (Practices of Science Observation Protocol + Directedness [P-SOPd]). An embedded mixed methods design was employed to investigate four questions: 1. How valid and reliable is the P-SOPd? 2. In what ways do inservice elementary teachers adapt existing elementary science curriculum materials across the inquiry continuum? 3. What is the relationship between the overall quality of inquiry and variations of inquiry in elementary teachers' enacted science instruction? 4. How do inservice elementary teachers' ideas about the inquiry continuum influence their adaptation of elementary science curriculum materials? Each teacher chose three lessons from a science unit for video-recorded observation, and submitted lesson plans for the three lessons. Lesson plans and videos were scored using the P-SOPd. The scores were also compared between the two protocols to determine if a correlation existed between the level of inquiry (measured on the P-SOP) and the amount of teacher direction (measured on the P-SOPd). Findings indicated no significant differences between planned and enacted lessons for the amount of teacher direction, but a correlation existed between the level of inquiry and the amount of teacher direction. In effect, the elementary teachers taught their science curriculum materials with a high level of fidelity for both the features of inquiry and the amount of teacher direction. A smaller group of three case study teachers were followed for the school year to give a more in-depth explanation of the quantitative findings. Case study findings revealed that the teachers' science instruction was teacher-directed while their conceptions of inquiry were student-directed. This study contributes to existing research on preservice teachers' learning about the continuum (Biggers & Forbes, 2012) and inservice teachers' ideas about the five features of inquiry (Biggers & Forbes, in press).

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Coidakis-Barss, Christina. "INTERPROFESSIONAL TEAMS IN HEALTHCARE: A MIXED-METHODS STUDY." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1428068372.

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Arenas, Calderon Edward Julián. "Étude de l'élaboration en continu d'émulsions de bitime [i.e.bitume] à taille de gouttes maîtrisée à l'aide de mélangeurs statiques." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0050/document.

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Cette étude porte sur l'émulsification en continu du bitume à l'aide de mélangeurs statiques de type SMX, dans le domaine des émulsions concentrées, voire très concentrées. Ce travail suit une approche intégrant trois types de paramètres : procédé, formulation physico-chimique et composition, avec pour objectif ultime la maîtrise de la taille de gouttes. Il a été montré qu'une combinaison de fortes teneurs en bitume et de hautes températures d'émulsification favorisent l'obtention de très petites tailles de gouttes (diamètre médian inférieur ou égal à 1 µm). Cette observation contraste avec l'émulsification à forte teneur en phase dispersée en procédé discontinu. Ces résultats mettent en évidence une compétition entre les aspects énergétiques de l'émulsification et la formulation physico-chimique. Il a été mis en évidence, que lors de l'émulsification en continu à des fractions massiques en bitume supérieures à 90 %, la taille des gouttes n'est pas une fonction de l'énergie fournie mais que ce sont les paramètres de formulation qui contrôlent l'émulsification. Le suivi de la cinétique de l'émulsification et de la morphologie de l'émulsion au cours du processus d'émulsification a montré que le mécanisme d'émulsification à très fortes concentrations en bitume (90 % massique) passe par une étape d'inversion de phases catastrophique, suivie d'un affinage de l'émulsion dû aux effets de cisaillement et d'élongation lors de la phase finale de mélange. Une méthodologie basée sur une analogie de Poiseulle pour la mesure en ligne de la viscosité de procédé a été développée, permettant l'évaluation in-line du comportement rhéologique d'un fluide à travers des mesures de débit et de perte de charge
This work focuses on the continuous emulsification process (using SMX static mixers) of bitumen for concentrated and highly concentrated emulsions. This work uses an approach that integrates the process, the physic-chemical formulation and composition parameters, with the main objective of controlling the drop size of the emulsions. It was shown that the emulsification carried out at high bitumen concentrations and high temperatures favours the production of emulsions with very small droplets sizes (mean diameter ? 1 mm). This is in contrast with emulsification process in batch mode, in the same concentration and temperature conditions. These results demonstrate the competition between energy and physic-chemical formulation aspects. It was also revealed that when continuous emulsification is carried out at 90 % wt. of bitumen, droplet sizes are not a function of the energy provided and, hence, the emulsification process is controlled by the formulation parameters. Morphological analyzes, coupled with kinetics of emulsification obtained by in-situ monitoring of the viscosity, allowed the description of the mechanisms occurring during the emulsification at high internal phase ratio. It was possible to identify two principal steps in the mechanism: a catastrophic phase inversion followed by a droplet reduction by agitation, the largest size reduction being achieved thanks to the effects of shear and elongation in the static mixer. An inline process viscosity measurement methodology was developed. This methodology, based on a Poiseuille analogy, allows the evaluation of the rheological behavior of a fluid through flow rate and pressure drop measurements

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de, Cabo Portugal Sebastian. "Non Visuals : Material exploration of non-visual interaction design." Thesis, Umeå universitet, Designhögskolan vid Umeå universitet, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-182466.

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Design is all about visuals, or that is what I have found out during this thesis, from the process materials to the outcome our main entry point to any problem is how will we solve it visually so it’s understandable for the general user. This aspect is problematic in itself due to the fact that we, as humans, understand the world and the things around using all our senses continuously, even though we can forget as visuals are so overpowering. There is a huge opportunity area in exploring our other senses and bringing them back to technology, and this can be seen in works in the past like Tangible Interactions [1] or Natural User Interfaces [2]. But in this moment in time, where all these new technologies like VR/AR and IoT are about to enter our lives and change them forever, this topic is more important than ever. We have already seen what happens when we turn humans into mere machines with some fingers as interactive inputs, and barely any senses to process all the information given to us. Now that these technologies are still young and malleable, we can direct the future to where we want it instead of being guided by the technology itself. To do this we need to reimagine the design process, not reinvent the wheel, but add experts which we currently leave behind and I argue are key to unlock these technologies, experts not only of the technological side of things but on the human side too, like physiotherapists and dancers. Add also people who we never think about when we think of VR like visually impaired users, which could make these technologies inclusive since early on, instead of as an afterthought like we usually do. Not only people, but we also need to add new materials to understand how we use our senses and explore ways that we can understand and explore them differently; like bodystorming and improv theatre because when things aren’t visual, how do you sketch it? A sketch turns into a video about movement. The end result provides a wide breadth of examples of the types of innovations that can come out of using these new design materials, and to open new frontiers. From a VR game with no visuals whatsoever to an AR location based story game, to a home sized multimodal operating system containing several different apps controlled through physical movement. The examples open up the space instead of closing into a single solution. This is just the tip of the iceberg, a hope that others will be inspired by it and continue with this journey that has just started, to guide the future into one that is more technological and at the same time more human than ever before. What we know is that VR does not equate Visual Reality.

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Di, Patrizio Nicolas. "Précipitation continue de produits minéraux : étude de l'influence des conditions de mélange à la précipitation sur les caractéristiques d'oxydes mixtes de cérium et de zirconium." Thesis, Paris, ENMP, 2015. http://www.theses.fr/2015ENMP0001/document.

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Une installation de mélange rapide entièrement automatisée permet d'étudier l'influence des conditions de mélange sur la co-précipitation d'oxydes mixtes de cérium et de zirconium. L'intensité du mélange est contrôlée par le débit d'entrée des solutions réactives. Un modèle d'engouffrement à iso-volume a permis d'estimer le temps de mélange à partir de la mesure d'un indice de ségrégation par le système de Villermaux Dushman pour trois mélangeurs Hartridge Roughton de géométries différentes. Pour une même puissance spécifique dissipée, le mélange est plus intense lorsqu'un rétrécissement est présent. L'intensification du mélange diminue la température maximale de réductibilité et augmente les contraintes du réseau cristallin des oxydes mixtes synthétisés et calcinés à 1100 °C. Cela est interprété par une meilleure homogénéité des particules. L'étude des particules directement en sortie du mélangeur rapide montre que pour les débits étudiés le mélange parfait avant précipitation n'est pas atteint. Une partie des particules se forme en milieu acide, incorporant des nitrates dans leur structure. Une modélisation simple des phénomènes de mélange couplée à une prise en compte des équilibres chimiques confirme ce résultat expérimental
An automated experimental set-up with rapid mixers is used to study the influence of mixing conditions on the co-precipitation of cerium-zirconium mixed oxides. The intensity of mixing is controlled by the inlet flowrates of the reacting solutions. An engulfment model is used to estimate a mixing time from the measurement of a segregation index by the Villermaux-Dushman reaction system. Three geometries of Hartridge Roughton mixers are compared. Mixing performance is better when a separate mixing chamber upstream of a narrower outlet pipe is present. A better mixing decreases the maximal reducibility temperature of the material and increases the crystal strains of the particles calcined at 1100 °C. This is probably due to a better homogenization of the particles content. The important incorporation of nitrates in the particle at the outlet of the mixers shows precipitation occurs while the mixing process is not finished. This experimental result was confirmed by numerical simulation and an estimation of sursaturations during the mixing process

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Doussau, de Bazignan Adélaïde. "Essais cliniques de recherche de dose en oncologie : d'un schéma d'essai permettant l'inclusion continue à l’utilisation des données longitudinales de toxicité." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA11T013/document.

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L’objectif des essais de phase I en oncologie est d’identifier la dose maximale tolérée (DMT). Le schéma « 3+3 » nécessite d’interrompre les inclusions en attendant l’évaluation d’une cohorte de trois patients pour définir la dose à attribuer aux patients suivants. Les investigateurs d’oncologie pédiatrique ont proposé l’adaptation Rolling 6 pour éviter cette suspension temporaire des inclusions. Dans une étude de simulation, nous avons montré qu’un schéma adaptatif avec attribution des doses basées sur un modèle statistique permettait de pallier ce problème, et identifiait plus fréquemment la DMT. Néanmoins ces trois schémas restent limités pour identifier la DMT, notamment du fait que le critère de jugement est un critère binaire, la survenue de toxicité dose-limitante sur un cycle de traitement. Nous avons proposé un nouveau schéma adaptatif utilisant les données ordinales répétées de toxicité sur l’ensemble des cycles de traitement. La dose à identifier est celle associée au taux de toxicité grave maximal par cycle que l’on juge tolérable. Le grade maximal de toxicité par cycle de traitement, en 3 catégories (grave / modéré / nul), a été modélisé par le modèle mixte à cotes proportionnelles. Le modèle est performant à la fois pour détecter un effet cumulé dans le temps et améliore l’identification de la dose cible, sans risque majoré de toxicité, et sans rallonger la durée des essais. Nous avons aussi étudié l’intérêt de ce modèle ordinal par rapport à un modèle logistique mixte plus parcimonieux. Ces modèles pour données longitudinales devraient être plus souvent utilisés pour l’analyse des essais de phase I étant donné leur pertinence et la faisabilité de leur implémentation
Phase I dose-finding trials aim at identifying the maximum tolerated dose (MTD). The “3+3” design requires an interruption of enrolment while the evaluation of the previous three patients is pending. In pediatric oncology, investigators proposed the Rolling 6 design to allow for a more continuous enrollment. In a simulation study, we showed that an adaptive dose-finding design, with dose allocation guided by a statistical model not only minimizes accrual suspension as with the rolling 6, and but also led to identify more frequently the MTD. However, the performance of these designs in terms of correct identification of the MTD is limited by the binomial variability of the main outcome: the occurrence of dose-limiting toxicity over the first cycle of treatment. We have then proposed a new adaptive design using repeated ordinal data of toxicities experienced during all the cycles of treatment. We aim at identifying the dose associated with a specified tolerable probability of severe toxicity per cycle. The outcome was expressed as the worst toxicity experienced, in three categories (severe / moderate / no toxicity), repeated at each treatment cycle. It was modeled through a proportional odds mixed model. This model enables to seek for cumulated toxicity with time, and to increase the ability to identify the targeted dose, with no increased risk of toxicity, and without delaying study completion. We also compared this ordinal model to a more parsimonious logistic mixed model.Because of their applicability and efficiency, those models for longitudinal data should be more often used in phase I dose-finding trials

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Mariano, André Augusto. "Mixed Simulations and Design of a Wideband Continuous-Time Bandpass Delta-Sigma Converter Dedicated to Software Dfined Radio Applications." Thesis, Bordeaux 1, 2008. http://www.theses.fr/2008BOR13644/document.

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La chaîne de réception des téléphones mobiles de dernière génération utilisent au moins deux étages de transposition en fréquence avant d'effectuer la démodulation en quadrature. La transposition en fréquence augmente la complexité du système et engendre de nombreux problèmes tels que la limitation de l'échelle dynamique et l'introduction de bruit issu de l'oscillateur local. Il est alors nécessaire d'envisager une numérisation du signal le plus près possible de l'antenne. Cette dernière permet la conversion directe d'un signal analogique en un signal numérique à des fréquences intermédiaires. Elle simplifie ainsi la conception globale du système et limite les problèmes liés aux mélangeurs. Pour cela, des architectures moins conventionnelles doivent être développées, comme la conversion analogique-numérique utilisant la modulation Sigma-Delta à temps continu. La modélisation comportementale de ce convertisseur analogique-numérique, ainsi que la conception des principaux blocs ont donc été l'objet de cette thèse. L'application d'une méthodologie de conception avancée, permettant la simulation mixte des blocs fonctionnels à différents niveaux d'abstraction, a permis de valider aussi bien la conception des circuits que le système global de conversion. En utilisant une architecture à multiples boucles de retour avec un quantificateur multi-bit, le convertisseur Sigma-Delta passe bande à temps continu atteint un rapport signal sur bruit (SNR) d'environ 76 dB dans une large bande de 20MHz
Wireless front-end receivers of last generation mobile devices operate at least two frequency translations before I/Q demodulation. Frequency translation increases the system complexity, introducing several problems associated with the mixers (dynamic range limitation, noise injection from the local oscillator, etc.). Herein, the position of the analog-to-digital interface in the receiver chain can play an important role. Moving the analog-to-digital converter (ADC) as near as possible to the antenna, permits to simplify the overall system design and to alleviate requirements associated with analog functions (filters, mixers). These currently requirements have led to a great effort in designing improved architectures as Continuous-Time Delta-Sigma ADCs. The behavioural modeling this converter, although the circuit design of the main blocks has been the subject of this thesis. The use of an advanced design methodology, allowing the mixed simulation at different levels of abstraction, allows to validate both the circuit design and the overall system conversion. Using a multi-feedback architecture associated with a multi-bit quantizer, the continuous-time Bandpass Delta-Sigma converter achieves a SNR of about 76 dB in a wide band of 20MHz

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Wium, Anna-Marie. "The development of a support programme for foundation phase teachers to facilitate listening and language for numeracy." Thesis, University of Pretoria, 2010. http://hdl.handle.net/2263/24685.

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Various assessments and international studies have shown that learners in South African schools experience challenges and perform poorly with respect to literacy and numeracy. To become competitive in the global arena, there is an urgent need to raise the standards of education. Language is required for all learning, including numeracy and mathematics. Many young learners in South Africa struggle to develop adequate language skills because of an inherent pathology and/or barriers in their learning environment. Learners who do not develop adequate listening and language skills during their early years are most likely to experience difficulty in acquiring literacy and numeracy skills, resulting in poor academic progress. By supporting learners to overcome their developmental delays as early as in the foundation phase, future learning problems may be prevented. To raise education standards, teachers need to heighten their attempts to facilitate literacy and numeracy in the foundation phase. Teachers currently have to adapt to a new national curriculum statement (NCS) that is based on an outcomes-based education (OBE) approach (Department of Education, 1997:16). Many teachers, especially those in black townships and other previously disadvantaged areas, find this difficult as they have not been sufficiently trained or are not adequately qualified. Educational changes have necessitated the need for high quality staff development and support. Speech-language therapists (SLTs) working within a collaborative approach in the education context can support the learners who need to acquire listening and language skills, as well as the teachers who have to facilitate these skills. This study developed a support programme for foundation phase teachers to facilitate listening and language for numeracy. The multifaceted programme consisted of training, mentoring, and practical components, which aimed at developing the participants’ competence (foundational, practical, and reflective competence). The programme integrated the principles of adult learning within an OBE approach while taking culture and diversity into consideration. The programme was evaluated within a Logic Model framework. The research made use of a concurrent, equal status triangulation design where triangulation was obtained by transforming QUAL data into QUAN data to be compared. In the QUAN strand, data were collected from 96 teacher participants (who were selected by using a convenience sampling method) by means of questionnaires, portfolio assignments, attendance registers, and financial statements. Qualitative data were collected from eight focus group discussions (using a nested design with 12 participants at a time) as well as a research diary, testimonials, and various correspondences. The findings indicated that all the participants have gained knowledge, skills, and confidence, but to varying degrees. Factors that affected the outcomes included aspects related to time, the choice of venue, age, prior support and qualifications, as well as motivation related to the context. Group learning was identified as a suitable strategy for teacher support in these contexts. Provided that specific factors are considered to increase effectiveness, the outcomes indicated that the programme could be used to support foundation phase teachers in these specific contexts.
Thesis (DPhil)--University of Pretoria, 2010.
Speech-Language Pathology and Audiology
unrestricted

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McKay, Ian Ross. "Assessing orientations to cultural difference of the faculty of a university foundation programme in the Gulf Cooperation Council : a mixed-methods approach informed by the Intercultural Development Continuum and using the Intercultural Development Inventory." Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/13781.

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This study examined the orientations to cultural difference of sojourner educators in the Foundation Program at Qatar University to determine if orientations were correlated with select demographic and experiential variables, including gender, age, time overseas, education level, formative region, ethnic minority status, job position, length of time in Qatar, intercultural marriage, default language, formal teacher training, and overseas development organization experience. This study used a sequential mixed-method design. Perceived and Developmental Orientations were measured using the Intercultural Development Inventory© (V.3), which produced a measure of each respondent’s orientation to cultural difference. Focus group interviews were conducted to engage participants in explaining and interpreting the findings. Five focus groups of three to six participants each were conducted. Most of the teachers were found to operate from within the transitional orientation of Minimization, although individual scores ranged from Denial to Adaptation. On average, the educators were found to overestimate their orientations by 31 points. A positive correlation between orientation and formative region was found, with participants from North America showing the highest orientation. Statistically significant differences emerged for orientations when comparing Middle East and North African (MENA) and North American formative regions. Formative region was found to account for 4.8% of the variance in orientation and is a significant fit of the data. Focus groups participants speculated that (a) core differences regarding multiculturalism in MENA and North American cultures help explain the results, (b) aspects of the workplace culture and both the broader MENA and local Qatari culture encourage a sense of exclusion, and (c) external events further complicate cross-cultural relations. The study findings add to the literature by providing baseline orientation data on sojourner educators in post-secondary education in the GCC region, and by confirming some of the findings of similar studies. The study provides practitioners with suggestions for staffing and professional development. Future research should focus on the measurement of orientations in broader samples of educators, changes in orientation over time in Qatar and other cultural contexts, differences in orientation among short-term vs. long-term expatriates, the impact of employment systems and societal structures on orientations in sojourner educators, the impact of educator orientation to cultural difference on student achievement, and the design of effective cross-cultural professional development for educators.

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Hessel, Gianna. "The impact of participation in ERASMUS study abroad in the UK on students' overall English language proficiency, self-efficacy, English use anxiety and self-motivation to continue learning English : a mixed-methods investigation." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:7ae490c6-2303-4889-ae67-df3deb5eb870.

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It is widely assumed that participation in study abroad contributes to developing second language (L2) proficiency, as well as related outcomes such as higher levels of L2 learning motivation and intercultural competence. However, empirical studies into the outcomes of participation in study abroad have been affected by a series of methodological limitations, including complete reliance on participant self-assessment, the omission of longitudinal design elements, failure to control for non-equivalent comparison groups where these are included and insufficient sample sizes for testing programme effects. Thus, the present study investigates further the impact of studying abroad with the EU's ERASMUS programme on the participants' overall L2 proficiency, their self-efficacy and anxiety in using the L2 with native and non-native speakers and on their self-motivation to continue learning the L2. To this end, a longitudinal mixed methods design was employed in which 143 German university students who applied for an ERASMUS exchange with a British university for the academic year 2012-2013 and were either accepted or rejected/ withdrawn formed the abroad and comparison groups. All students completed C-tests of overall English language proficiency and questionnaires that inquired into the students' mobility history, their L2 learning background, L2 motivation, intergroup attitudes and aspects of the study abroad experience itself. Both instruments were administered online at the onset of the study abroad period (September 2012), one term into the programme (December 2012) and prior to the students' return (either December 2012 or June 2013). This predominantly quantitative group-level study served to establish the outcomes of participation in study abroad for the students' linguistic and motivational development. Repeated interviews with a sub-sample of 15 participants served to illuminate the observed outcome patterns in terms of the motivational dynamics during study abroad, as well as common factors associated with individual differences in linguistic development. The results of the study show that during the first 3 months abroad the ERASMUS students made significantly higher gains in overall English proficiency than the group of potentially mobile students who continued to study at home. The effect of the learning context was large and highly significant (p =.001), even after the influence of pre-existing participant characteristics on the students' proficiency development was controlled for. During the subsequent 6 months of the study abroad period, however, progress among the ERASMUS group slowed and the between-group differences were no longer significant. The participants' L2 proficiency level at programme entry emerged as the strongest predictor of overall L2 proficiency gain, explaining up to 31.5% of the variance. The students' attitudes towards their own national group, their perceptions of self-efficacy and feelings of anxiety when using English in social interactions, the perceived present-future L2 self-discrepancy and gender explained another 13.6% of the variance in overall L2 proficiency gain. Learner-external factors, including participation in English language instruction, participation in clubs and societies, the number of academic contact hours and type of enrolment, and free time spent with co-national peers, including friends and family back home explained a further 10.9%. The qualitative analysis of the students' accounts provided further insights into the ways in which these factors play out in L2 learning abroad, as well as into the students' perceptions of aspects of studying abroad that contributed most to their linguistic development. Regarding the motivational impact of the study abroad experience, the study found that ERASMUS students tended to develop significantly higher levels of self-efficacy in using English in social interactions as compared to the group of potentially mobile students who continued to study at home, while both the levels of perceived present-future self-discrepancy and English use anxiety with native and non-native speakers fell during the first 3 months abroad. While the overall impact of the study abroad experience on the students' motivation to continue learning the L2 was perceived as positive by the vast majority of participants, a decline in learning motivation was observed for most students after the initial 3-month period. The qualitative analysis showed that this decline can be plausibly explained by developments in the students' English self-concept that occurred in response to the study abroad experience. Evidence-based recommendations are made regarding ways in which the linguistic and motivational development of ERASMUS students can be more effectively supported by higher education institutions.

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O'Carroll, Veronica. "Practice mentors' attitudes and perspectives of interprofessional working, and interprofessional practice learning for students : a mixed-methods case study." Thesis, University of St Andrews, 2017. http://hdl.handle.net/10023/10482.

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The demands on health and social care organisations require professions to work more collaboratively. During pre-registration training, health care and social work students learn within practice settings, supported by practice mentors. These settings are rich learning environments to experience interprofessional working (IPW) and for students to learn together through interprofessional practice learning (IPPL). There is, however, evidence that students' experiences of both are varied or limited. The value placed on IPW, and IPPL, is therefore of interest. This thesis will investigate practice mentors' attitudes to IPW and IPPL, and explore their perspectives of the enablers and barriers to these occurring in practice settings. A mixed-methods case study approach was used to measure the attitudes of practice mentors from health and social work, and to identify enablers and barriers to IPW, and IPPL for students. Online surveys and semi-structured face to face interviews were carried out with a range of professions within one Scottish health board and associated local authority. Results showed that attitudes to IPW, and IPPL for students were generally positive. Attitudes were not significantly affected by governing body, gender, area of work, years of experience, or prior experience of IPE. IPW was perceived to be enabled by shared processes and policies, IPPL for staff, effective communication, established teams, and shared processes and policies. Proximity to other professions and shared spaces encouraged informal communication and positive interprofessional relationships. Regular structured IPPL opportunities for students were limited. However, where opportunities did occur, this was linked to areas where practice mentors perceived that there was a strong interprofessional team identity. Although attitudes to IPW, and IPPL for students are positive, further work is needed to identify systems for improving IPW, to strengthen professions' identity as interprofessional teams, and to increase IPPL opportunities for students.

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Breteau, Jean-Marc. "Etude de materiaux dopes ni**(2+) et co**(2+) pour laser accordable a fonctionnement continu dans le proche infrarouge." Paris 6, 1986. http://www.theses.fr/1986PA066357.

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Les composes mgf::(2): ni, mgf::(2): co, kznf::(3): ni, kznf::(3): co et mga1::(2)o::(4): ni font l'objet d'une etude spectroscopique pour determiner leurs caracteristiques en tant que materiaux pour laser accordable a fonctionnement continu dans le proche i. R. (1 mu m a 2 mu m). Nous montrons le role de la concentration en ions actifs sur l'intensite et la duree de vie de fluorescence i. R. Ainsi que l'importance des transferts d'energie et de la reabsorption dans l'etat excite. Pour l'ensemble des materiaux, les transitions radiatives et non radiatives font l'objet d'une etude approfondie qui met en evidence des differences de comportement comparees a des etudes similaires sur les terres rares ainsi que la relation existant entre le niveau de dopage et la force du couplage electron-phonon. Une description detaillee de l'etude et de la realisation du laser accordable mgf::(2) : ni est faite

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Seydou, Hassane Ramatou. "Contribution au développement des techniques ensemblistes pour l’estimation de l’état et des entrées des systèmes à temps continu : application à la détection de défauts." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14669/document.

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Cette thèse traite du problème d'observation et d'estimation des variables caractéristiques des systèmes dynamiques. Il s’agit d’une problématique fondamentale qui est au cœur de nombreux domaines relavant des sciences de l'ingénieur. Les travaux sont conduits dans un contexte ensembliste. Les techniques développées pour l’estimation de l’état et des variables d’entrées ont pour objectif final le contrôle de cohérence des systèmes non linéaires à temps continu. Une première approche conjugue les relations de parité et les différentiateurs à modes glissants pour l’estimation des entrées d’un système non linéaire. Les domaines des entrées compatibles avec les mesures sont alors reconstruits grâce à l’analyse par intervalles et aux techniques de satisfaction de contraintes. Il est montré que la relaxation des contraintes de stabilité/coopérativité pour la construction d’un observateur intervalle peut se faire grâce à des changements de base déterminés de différentes manières et pouvant être variants ou invariants dans le temps. Des simulations numériques illustrent les techniques proposées. Une application à un système aéronautique est également présentée à l’aide d’un jeu de données réelles
This thesis deals with the problem of a dynamical system observation and the estimation of its characteristic variables; the latter point constitutes the core element in many engineering science fields. The final aim is to build a general framework for integrity control and fault detection of such systems within a bounded error context. The developments offered herein make use of parity relations, sliding mode differentiators, interval observers and constraint satisfaction problems. Input reconstruction techniques are developed for a general class of nonlinear continuous-time systems. Domains are reconstructed for the input values which are consistent with the measurements using interval analysis and constraint satisfaction techniques. It is shown that time-varying or invariant coordinate changes may relax the applicability conditions (stability/cooperativity) of the interval observer design methods. Sliding mode differentiators were also used to enhance interval observer accuracy. The proposed approaches are illustrated through computer simulations and they have been applied to aircraft servo loop control surface for robust and early detection of abnormal positions

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Coons, Marc P. L. "Solvent Effects for Vertical Ionization Processes in Liquid Water and at the Liquid-Vapor Interface." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1503014629752161.

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Cao, Trong Son. "Modélisation de l’endommagement ductile sous trajets de chargement complexes." Thesis, Paris, ENMP, 2013. http://www.theses.fr/2013ENMP0038/document.

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Ce travail de thèse vise à une meilleure compréhension et prise en compte des mécanismes d'endommagement ductile au cours des procédés de mise en forme à froid. Le tréfilage, le laminage de fils et le laminage à pas de pèlerin sont pris comme exemples d'application. Une grande attention est portée également à la méthodologie d'identification des paramètres des modèles d'endommagement implémentés. Trois approches de l'endommagement ductile ont été étudiées : des critères de rupture phénoménologique, des modèles phénoménologiques couplés et des modèles micromécaniques. Ces modèles ont été implémentés dans Forge®, et les algorithmes ont dû être adaptés à sa formulation mixte vitesse-pression et à son élément fini (P1+/P1). Parallèlement aux développements numériques, différents essais mécaniques ont été effectués sur trois matériaux différents (acier haut carbone, acier inoxydable et alliage de zirconium) pour identifier les paramètres des modèles d'écrouissage et d'endommagement. Des essais de traction in situ sous micro-tomographie aux rayons X ont été exploités pour l'identification des mécanismes d'endommagement ductile (germination, croissance et coalescence), ainsi que l'identification du modèle micromécanique. Enfin, la dernière partie de ce travail a consisté à réaliser des études comparatives de ces différents modèles d'endommagement pour les différents procédés de mise en forme et différents matériaux. Concernant le tréfilage et le laminage de l'acier inoxydable, un bon accord entre les simulations numériques et les résultats expérimentaux a été obtenu. Pour l'acier à haute teneur en carbone (perlitique), le modèle micro-mécanique GTN a donné le meilleur résultat à la fois qualitativement et quantitativement pour le tréfilage ultime. Par ailleurs, la comparaison entre les différents modèles sur différents procédés (laminage du fil avec l'acier haut carbone, laminage à pas de pèlerin avec l'alliage de zirconium) a aidé d'une part à mettre en évidence le rôle important du troisième invariant de la contrainte déviatorique sur la localisation de l'endommagement dans les procédés de mise en forme où le cisaillement est dominant. D'autre part, elle montre que le processus d'identification lui-même devrait se fonder sur la mesure de la microstructure afin de garantir un résultat précis lors de l'application aux procédés
The present PhD thesis aims at a better understanding and modeling of ductile damage mechanisms during cold forming processes, with wire drawing, rolling and cold pilgering as examples. In addition, special attention is paid to implemented damage models parameters identification methodology. All three approaches of ductile damage were investigated: uncoupled phenomenological fracture criteria; coupled phenomenological models; micromechanical model. These models have been implemented in Forge®, which required adaptation of algorithms to its mixed velocity-pressure formulation and to its finite element (P1+/P1). Parallel to the numerical work, various mechanical tests on three different materials (high carbon steel, stainless steel and zirconium alloy) were carried out for work hardening, and damage models parameters identification. In situ X-ray micro-tomography tensile tests have also been exploited for the identification of ductile damage mechanisms (nucleation, growth and coalescence) as well as the identification of micromechanical model. Finally, we carried out comparative studies of these models on our three abovementioned forming processes and materials. Regarding wire drawing and rolling of stainless steel, good agreement between numerical simulations and experimental results was found. For high carbon perlitic steel ultimate wire drawing, the GTN micro-mechanical model has given the best result, both qualitatively and quantitatively. Moreover, the comparison of the different models on different processes (wire rolling on high carbon steel, cold pilgering on zirconium alloy) highlights on the one hand the important role of the third deviatoric stress invariant in damage localization for shear-dominated forming processes. It shows on the other hand that the identification process itself should be based on microstructure measurements to provide accurate results in forming application

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Hardy, Emmanuel. "Etude et développement d'un amplificateur audio de classe D intégré haute performance et basse consommation." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4722/document.

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De nombreux dispositifs embarqués récents comme les téléphones portables, les GPS ou encore les consoles de jeu, possèdent un ou des haut-parleurs, chacun étant piloté par un amplificateur audio sur circuit intégré. De tels amplificateurs audio doivent répondre le mieux possible à quatre contraintes : une qualité audio satisfaisante, une immunité aux perturbations induites par le système, une faible consommation et une surface de silicium minimale. Ce travail de thèse sous contrat CIFRE a pour origine la création de l’entreprise Primachip en mai 2009 par Christian Dufaza et Hassan Ihs. Cette startup a été bâtie sur une architecture innovante d’amplificateur audio de classe D intégré. Son originalité repose sur le principe de rétroaction partielle qui s’applique à une boucle contenant un modulateur numérique Delta Sigma (ΔΣ) qui pilote l’étage de puissance et un convertisseur analogique-numérique (ADC) effectuant la rétroaction. Cela permet d’obtenir la stabilité de cette boucle tout en offrant une excellente réjection des bruits de l’étage de puissance. Un prototype sur silicium de l’architecture d’amplificateur de classe D numérique a été conçu et fabriqué. Un nouvel ADC ΔΣ temps continu a été développé pour ce prototype, afin d’obtenir des performances supérieures ou égales à l’état de l’art. Les résultats obtenus sur le circuit se sont révélés encourageants, bien que toutes les spécifications n’aient pas été atteintes. L’analyse des erreurs de ce premier circuit doit permettre la réalisation d’un amplificateur intégré exploitant au mieux cette architecture de classe D numérique
Most current embedded devices, such as smartphones, GPS or portable consoles, feature one speaker or more, those speakers being driven by an integrated audio amplifier. This type of amplifier must meet four specifications: an adequate audio quality, to be immune to system disturbances, low power consumption and the smallest silicon area. This work takes its origin from the creation of Primachip in May 2009 by Christian Dufaza and Hassan Ihs. The aim of this startup was to develop and sell an innovative audio class-D amplifier for mobile market: the digital class-D concept. A partnership with the IM2NP laboratory was decided to propose a PhD topic under CIFRE contract (PhD in an industrial environment), in order to study and improve the amplifier architecture. Its originality is in the partial feedback concept which applies to a loop made of a digital ΔΣ modulator driving the power stage, with an analogue-to-digital converter (ADC) in the feedback path. It makes it possible to achieve stability while offering an outstanding power supply rejection. An integrated prototype of the class-D amplifier was designed, fabricated and evaluated. A new continuous-time ΔΣ ADC has been added to enable the digital class-D loop to achieve performances superior or equal to state of the art. The circuit measurement results were encouraging, although not ideal. The analysis of the prototype errors was performed. The conclusions should allow the design of an integrated audio amplifier making the best of the digital class-D architecture

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Morice, Erwan. "Fissuration dans les matériaux quasi-fragiles : approche numérique et expérimentale pour la détermination d'un modèle incrémental à variables condensées." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2014. http://tel.archives-ouvertes.fr/tel-01048626.

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La rupture des matériaux quasi-fragiles, tels que les céramiques ou les bétons, peut être représentée schématiquement par la succession des étapes de nucléation et de coalescence de micro-fissures. Modéliser ce processus de rupture est un enjeu particulièrement important lorsque l'on s'intéresse à la résistance des structures en béton, en particulier à la prédiction de la perméabilité des structures endommagées. La démarche choisie est une vision multi-échelle où le comportement global est caractérisé par la mécanique de la rupture, et le comportement local représenté par la méthode des éléments discrets. Le modèle représente la fissuration par des grandeurs généralisées, qui seront définies dans le cadre de la mécanique de la rupture. Afin de prendre en compte l'aspect non linéaire de la fissuration dans les matériaux quasi-fragiles, la cinématique usuelle de la mécanique de la rupture est enrichie par l'ajout de degrés de libertés supplémentaires chargés de représenter la part non linéaire du champ de vitesse. L'évolution du comportement est alors condensé par l'évolution de facteurs d'intensité. Le modèle proposé permet de prédire le comportement lors de chargements de mode mixte I+II proportionnel et non-proportionnel. Enfin, une campagne d'essais visant à caractériser le comportement en fissuration du mortier à été réalisée. Les résultats obtenus montrent un rôle important de la fissuration par fatigue. La méthode de changement d'échelle a également été appliquée sur les champs de vitesse en pointe de fissure, confirmant la représentation du comportement en pointe de fissure par une cinématique enrichie.

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Excoffier, Mathilde. "Chance-Constrained Programming Approaches for Staffing and Shift-Scheduling Problems with Uncertain Forecasts : application to Call Centers." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112244/document.

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Le problème de dimensionnement et planification d'agents en centre d'appels consiste à déterminer sur une période le nombre d'interlocuteurs requis afin d'atteindre la qualité de service exigée et minimiser les coûts induits. Ce sujet fait l'objet d'un intérêt croissant pour son intérêt théorique mais aussi pour l'impact applicatif qu'il peut avoir. Le but de cette thèse est d'établir des approches en contraintes en probabilités en considérant l'incertitude de la demande.Tout d'abord, la thèse présente un modèle en problème d'optimisation stochastique avec contrainte en probabilité jointe traitant la problématique complète en une étape afin d'obtenir un programme facile à résoudre. Une approche basée sur l'idée de continuité est proposée grâce à des lois de probabilité continues, une nouvelle relation entre les taux d'arrivées et les besoins théoriques et la linéarisation de contraintes. La répartition du risque global est faite pendant le processus d'optimisation, permettant une solution au coût réduit. Ces solutions résultantes respectent le niveau de risque tout en diminuant le coût par rapport à d'autres approches.De plus, le modèle en une étape est étendu pour améliorer sa représentation de la réalité. D'une part, le modèle de file d'attente est amélioré et inclus la patience limitée des clients. D'autre part, une nouvelle expression de l'incertitude est proposée pour prendre la dépendance des périodes en compte.Enfin, une nouvelle représentation de l'incertitude est considérée. L'approche distributionally robust permet de modéliser le problème sous l'hypothèse que la loi de probabilité adéquate est inconnue et fait partie d'un ensemble de lois, défini par une moyenne et une variance données. Le problème est modélisé par une contrainte en probabilité jointe. Le risque à chaque période est définie par une variable à optimiser.Un problème déterministe équivalent est proposé et des approximations linéaires permettent d'obtenir une formulation d'optimisation linéaire
The staffing and shift-scheduling problems in call centers consist in deciding how many agents handling the calls should be assigned to work during a given period in order to reach the required Quality of Service and minimize the costs. These problems are subject to a growing interest, both for their interesting theoritical formulation and their possible applicative effects. This thesis aims at proposing chance-constrained approaches considering uncertainty on demand forecasts.First, this thesis proposes a model solving the problems in one step through a joint chance-constrained stochastic program, providing a cost-reducing solution. A continuous-based approach leading to an easily-tractable optimization program is formulated with random variables following continuous distributions, a new continuous relation between arrival rates and theoritical real agent numbers and constraint linearizations. The global risk level is dynamically shared among the periods during the optimization process, providing reduced-cost solution. The resulting solutions respect the targeted risk level while reducing the cost compared to other approaches.Moreover, this model is extended so that it provides a better representation of real situations. First, the queuing system model is improved and consider the limited patience of customers. Second, another formulation of uncertainty is proposed so that the period correlation is considered.Finally, another uncertainty representation is proposed. The distributionally robust approach provides a formulation while assuming that the correct probability distribution is unknown and belongs to a set of possible distributions defined by given mean and variance. The problem is formulated with a joint chance constraint. The risk at each period is a decision variable to be optimized. A deterministic equivalent problem is proposed. An easily-tractable mixed-integer linear formulation is obtained through piecewise linearizations

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Nduwayo, Placide. "Formulations mathématiques et algorithmes pour le problème d'affectation des quais du cross-dock." Thesis, Valenciennes, Université Polytechnique Hauts-de-France, 2020. http://www.theses.fr/2020UPHF0013.

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Le cross-docking est une stratégie utilisée pour optimiser les opérations à l’intérieur de l’entrepôtdans le cadre de l’optimisation de la chaine logistique . Comme pour les entrepôts traditionnels,les produits sont collectés depuis plusieurs origines de production tels que les fournisseurs,les usines, les fabricants, etc., par des camions, puis ils sont acheminés vers des plateformes appeléescross-docks. Arrivés au cross-dock, les produits sont d’abord déchargés sur des quais d’entréedu cross-dock. Ils sont ensuite triés selon leurs destinations et sont immédiatement transférés,à l’aide des matériels de manutention, vers des quais de sortie correspondants pour, quelquesfois être consolidés avec d’autres produits allant à la même destination et sont rechargés dansdes camions sortants. Contrairement aux entrepôts traditionnels où la durée de stockage desproduits est indéfinie, pour le cross-dock, ils sont déchargés et rechargés le même jour sans attendredans la zone de stockage temporaire, ou peuvent attendre moins d’un jour. Dans cettethèse, nous étudions le problème d’optimisation NP-difficile apparaissant dans le cross-dock appelé“Cross-dock Door Assignment Problem (CDAP)”. Le CDAP consiste à affecter des camionsentrants et sortants, respectivement aux quais d’entrée et de sortie du cross-dock. Le but estde minimiser le coût total de transport à l’intérieur du cross-dock. La formulation quadratiquestandard du CDAP inclut le problème d’affectation généralisée comme sous-problème. Dans cettethèse, nous effectuons une revue de littérature étendue du cross-docking. Nous nous concentronsensuite sur la modélisation mathématique du CDAP via une formulation quadratique standard,ainsi que sur la linéarisation standard de ce modèle. À partir de cette étude approfondie, nousproposons plusieurs nouveaux modèles linéaires non standard pour formuler le CDAP. Nous comparonsensuite ces modèles entre eux et ensuite avec les modèles récents de la littérature afinde déterminer le meilleur modèle linéaire. Nous proposons ensuite une Relaxation Lagrangiennepour produire de meilleures nouvelles bornes inférieures à la valeur de la solution optimale. LaRelaxation Lagrangienne est appliquée au modèle qui produit de meilleures bornes inférieuresde la relaxation continue. Le dual lagrangien est résolu par l’algorithme du sous-gradient. Lesexpérimentations montrent que les instances de grande taille ne peuvent pas être résolues parune méthode exacte en temps et ressources mémoires raisonnables. Nous proposons et implémentonsdonc deux heuristiques basées sur la recherche taboue probabiliste pour pouvoir traiterefficacement les instances de grande taille du CDAP. Pour évaluer l’efficacité de ces deux heuristiques,nous comparons leurs performances, d’abord entre elles, ensuite avec celles d’heuristiquesrécentes de la littérature. Les résultats obtenus montrent l’efficacité de nos méthodes sur des jeuxde données de la littérature
Cross-docking is a strategy originally introduced to optimize operations inside a warehouseas part of the optimization of the Supply Chain. Like traditional warehouses, productsare collected from numerous freight yards such that suppliers, factories, manufactures,etc., usingtrucks, and are moved towards processing centers named cross-docks. At cross-dock yard, productsfirst get unloaded on inbound dock doors. Afterwards, they are sorted according to theirdestinations and are immediately transferred, using handling devices, to appropriate outbounddock doors to be sometimes consolidated with other products of the same destination and arereloaded into shipping trucks. Unlike traditional warehouse where storage period of productsis indefinite, for cross-dock, goods are unloaded and reloaded the same day without waiting intemporary storage area or can wait less than one day. In this PhD thesis, we study an NP-hardoptimization problem raised by cross-dock referred to “Cross-dock Door Assignment Problem(CDAP)”. The CDAP consists in assignment of incoming and outgoing trucks to inbound andoutbound dock doors of cross-dock, respectively. The goal is to minimize the total transportationcost inside the cross-dock. The standard quadratic formulation of the CDAP includes theGeneralized Assignment Problem as subproblem. In this dissertation, we perform an extensivecross-docking literature review. Then, we carry out a broad analysis of the standard quadraticformulation as well as the standard linearization of the CDAP. From this in-deph study, wepropose several new non standard Mixed Integer Linear Programming models for the CDAP. Todetect the best linear model among those we propose and those existing, we compare the performanceof these models on instances proposed in the literature. We next propose a LagrangianRelaxation approach to produce the best new lower bounds to optimal solution value. This LagrangianRelaxation is applied to the model that produces the best LP relaxation bounds. TheLagrangian dual is solved using a subgradient algorithm. According to the experiments it seemsthat large-scale instances cannot be solved with an exact method in reasonable running times andmemory requirements. Thus, we propose and implement two heuristics based on “ProbabilisticTabu Search” to operate efficiently with larger instances of the CDAP. To assess the effectivenessof these proposed heuristics, we compare their performance, first between them and thenwith recent heuristics in the literature. The results demonstrate the efficiency of the proposedapproaches on data sets from the literature

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Sienkiewicz, Magdalena. "Méthodologie de localisation des défauts soft dans les circuits intégrés mixtes et analogiques par stimulation par faisceau laser : analyse de résultats des techniques dynamiques paramétriques." Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14028/document.

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Cette thèse s’inscrit dans le domaine de la localisation de défauts de type «soft» dans les Circuits Intégrés (CI) analogiques et mixtes à l’aide des techniques dynamiques de stimulation laser en faible perturbation. Les résultats obtenus à l’aide de ces techniques sont très complexes à analyser dans le cas des CI analogiques et mixtes. Ce travail porte ainsi particulièrement sur le développement d’une méthodologie facilitant l’analyse des cartographies laser. Cette méthodologie est basée sur la comparaison de résultats de simulations électriques de l’interaction faisceau laser-CI avec des résultats expérimentaux (cartographies laser). L’influence des phénomènes thermique et photoélectrique sur les CI (niveau transistor) a été modélisée et simulée. La méthodologie a été validée tout d’abord sur des structures de tests simples avant d’être utilisée sur des CI complexes que l’on trouve dans le commerce
This thesis deals with Soft failure localization in the analog and mixed mode Integrated Circuits (ICs) by means of Dynamic Laser Stimulation techniques (DLS). The results obtained using these techniques are very complex to analyze in the case of analog and mixed ICs. In this work we develop a methodology which facilitates the analysis of the laser mapping. This methodology consists on combining the experimental results (laser mapping) with the electrical simulations of laser stimulation impact on the device. The influence of photoelectric and thermal phenomena on the IC (transistor level) has been modeled and simulated. The methodology has been validated primarily on test structures before being used on complex Freescale ICs existing in commerce

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LeBlanc, Graham. "Design and simulation of a control continuum for tetherless underwater vehicles." 2011. http://hdl.handle.net/10222/14176.

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There exists a need for a new class of underwater vehicle that can perform both close control tasks, as well as long-range exploration, without manual reconfiguration. A tetherless underwater vehicle (TUV) with acoustic communications to an operator station has potential to fulfill this need, while also removing much of the operating costs associated with tether management. The problem with TUVs is the limited communications bandwidth and time lag increasing with range from the transmitter. This thesis introduces a new class of controller for TUV vehicles that isolates the operator from the time-varying delay. This isolation is achieved through the formation of a continuum of control comprised of existing control paradigms, such as predictive and autonomous control. A smooth evolution through the continuum is formulated based on the time delay. The resulting controller permits operator close control for extended ranges without manual reconfiguration of the vehicle or controller.

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Bhat, Pradeep Prabodha. "The dynamics of filaments of complex liquids analyzed by continuum and mixed continuum-stochastic methods." Thesis, 2007. http://hdl.handle.net/1911/20576.

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Formation and breakup of filaments of liquids is of fundamental importance in established and cutting edge technologies such as ink-jet printing, atomization of coolants in electronic systems, and micro-arraying of DNA. Most of the liquids encountered in these processes have macromolecules (e.g., DNA) which make them viscoelastic. The dynamics of such viscoelastic filaments is analyzed in this thesis using state-of-the-art numerical techniques. A transient flow solver, based on the finite element algorithm of Pasquali and Scriven (2002), is developed and used in the computations. Viscoelasticity is modeled using a single macroscopic variable, the conformation tensor, which is computed by solving a generalized constitutive equation (Pasquali 2000). The dynamics of stretching filaments in the low capillary number regime is analyzed using three different weakly strain hardening models. Among thern, Giesekus filaments show the most drastic necking. The dependence of the transient Trouton ratio on the capillary number in this model is demonstrated. Cohesive necking failure due to elastic unloading in the filaments is investigated using both kinematic (Yao et al. 1998) and energy arguments. The thinning in the Giesekus filaments is aided by the elastic unloading, which increases with growing elasticity. The analysis of pinch-off of viscoelastic filaments, to date, relied on simple one-dimensional approximations. In this work, two-dimensional analysis o fpinch-off of FENE-P filaments is conducted for the first time. Scalings of physical variables calculated near pinch-off accord with asymptotic theoretical results. The liquid-gas interface in the neck region of low viscosity FENE-P filaments overturn before breakup when the Ohnesorge number, suitably redefined with the maximum extensional viscosity, is lower than a critical value. A multi-scale algorithm, in which viscoelasticity is modeled using an ensemble of Brownian configuration fields (Hulsen et al. 1997), is developed to solve axisymmetric free surface flows. The new method reproduces filament stretching results with Hookean dumbbells, within statistical error bars, when compared with equivalent macroscopic calculations. Inclusion of hydrodynamic interactions reduces the extension of the dumbbells thereby decreasing the growth of extensional stresses in the filaments.

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Ciucci, Francesco. "Continuum Modeling of Mixed Conductors: A Study of Ceria." Thesis, 2009. https://thesis.library.caltech.edu/5273/1/thesis.pdf.

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In this thesis we have derived a new way to analyze the impedance response of mixed conducting materials for use in solid oxide fuel cells (SOFCs), with the main focus on anodic materials, in particular cerium oxides.

First we have analyzed the impact of mixed conductivity coupled to electrocatalytic behavior in the linear time-independent domain for a thick ceria sample. We have derived that, for a promising fuel cell material, Samarium Doped Ceria, chemical reactions are the determining component of the polarization resistance.

As a second step we have extended the previous model to the time-dependent case, where we focused on single harmonic excitation, the impedance spectroscopy conditions. We extended the model to the case where some input diffusivities are spatially nonuniform. For instance we considered the case where diffusivities change significantly in the vicinity of the electrocatalytic region.

As a third and final step we use to model to capture the two dimensional behavior of mixed conducting thin films, where the electronic motion from one side of the sample to the other is impeded. Such conditions are similar to those encountered in fuel cells where an electrolyte conducting exclusively oxygen ions is placed between the anode and the cathode. The framework developed was also extended to study a popular cathodic material, Lanthanum Manganite.

The model is used to give unprecedented insight in SOFC polarization resistance analysis of mixed conductors. It helps elucidate rigorously rate determining steps and to address the interplay of diffusion with diffusion losses. Electrochemical surface losses dominate for most experimental conditions of Samarium Doped Ceria and they are shown to be strongly dependent on geometry.

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Sunyk, Rudolf [Verfasser]. "On aspects of mixed continuum atomistic material modelling / von Rudolf Sunyk." 2004. http://d-nb.info/972145435/34.

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(5929553), Ernesto Camarena. "Multiscale Continuum Modeling of Piezoelectric Smart Structures." Thesis, 2019.

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Among the many active materials in use today, piezoelectric composite patches have enabled notable advances in emerging technologies such as disturbance sensing, control of flexible structures, and energy harvesting. The macro fiber composite (MFC), in particular, is well known for its outstanding performance. Multiscale models are typically required for smart-structure design with MFCs. This is due to the need for predicting the macroscopic response (such as tip deflection under a transverse load or applied voltage) while accounting for the fact that the MFC has microscale details. Current multiscale models of the MFC exclusively focus on predicting the macroscopic response with homogenized material properties. There are a limited number of homogenized properties available from physical experiments and various aspects of existing homogenization techniques for the MFC are shown here to be inadequate. Thus, new homogenized models of the MFC are proposed to improve smart-structure predictions and therefore improve device design. It is notable that current multiscale modeling efforts for MFCs are incomplete since, after homogenization, the local fields such as stresses and electric fields have not been recovered. Existing methods for obtaining local fields are not applicable since the electrodes of the MFC are embedded among passive layers. Therefore, another objective of this work was to find the local fields of the MFC without having the computational burden of fully modeling the microscopic features of the MFC over a macroscale area. This should enable smart-structure designs with improved reliability because failure studies of MFCs will be enabled. Large-scale 3D finite element (FE) models that included microscale features were constructed throughout this work to verify the multiscale methodologies. Note that after creating a free account on cdmhub.org, many files used to create the results in this work can be downloaded from https://cdmhub.org/projects/ernestocamarena.

First, the Mechanics of Structure Genome (MSG) was extended to provide a rigorous analytical homogenization method. The MFC was idealized to consist of a stack of homogeneous layers where some of the layers were homogenized with existing rules of mixtures. For the analytical model, the electrical behavior caused by the interdigitated electrodes (IDEs) was approximated with uniform poling and uniform electrodes. All other assumptions on the field variables were avoided; thus an exact solution for a stack of homogeneous layers was found with MSG. In doing so, it was proved that in any such multi-layered composite, the in-plane strains and the transverse stresses are equal in each layer and the in-plane electric fields and transverse electric displacement are constant between the electrodes. Using this knowledge, a hybrid rule of mixtures was developed to homogenize the entire MFC layup so as to obtain the complete set of effective device properties. Since various assumptions were avoided and since the property set is now complete, it is expected that greater energy equivalence between reality and the homogenized model has been made possible. The derivation clarified what the electrical behavior of a homogenized solid with internal electrodes should be—an issue that has not been well understood. The behavior was verified by large-scale FE models of an isolated MFC patch.

Increased geometrical fidelity for homogenization was achieved with an FE-based RVE analysis that accounted for finite-thickness effects. The presented theory also rectifies numerous issues in the literature with the use of the periodic boundary conditions. The procedure was first developed without regard to the internal electrodes (ie a homogenization of the active layer). At this level, the boundary conditions were shown to satisfy a piezoelectric macrohomogeneity condition. The methodology was then applied to the full MFC layup, and modifications were implemented so that both types of MFC electrodes would be accounted for. The IDE case considered nonuniform poling and electric fields, but fully poled material was assumed. The inherent challenges associated with these nonuniformities are explored, and a solution is proposed. Based on the homogenization boundary conditions, a dehomogenization procedure was proposed that enables the recovery of local fields. The RVE analysis results for the effective properties revealed that the homogenization procedure yields an unsymmetric constitutive relation; which suggests that the MFC cannot be homogenized as rigorously as expected. Nonetheless, the obtained properties were verified to yield favorable results when compared to a large-scale 3D FE model.

As a final test of the obtained effective properties, large-scale 3D FE models of MFCs acting in a static unimorph configuration were considered. The most critical case to test was the smallest MFC available. Since none of the homogenized models account for the passive MFC regions that surround the piezoelectric fiber array, some of the test models were constructed with and without the passive regions. Studying the deflection of the host substrate revealed that ignoring the passive area in smaller MFCs can overpredict the response by up to 20%. Satisfactory agreement between the homogenized models and a direct numerical simulation were obtained with a larger MFC (about a 5% difference for the tip deflection). Furthermore, the uniform polarization assumption (in the analytical model) for the IDE case was found to be inadequate. Lastly, the recovery of the local fields was found to need improvement.

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Negara, Ardiansyah. "Subsurface Flow Modeling in Single and Dual Continuum Anisotropic Porous Media using the Multipoint Flux Approximation Method." Diss., 2015. http://hdl.handle.net/10754/554393.

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Anisotropy of hydraulic properties of the subsurface geologic formations is an essential feature that has been established as a consequence of the different geologic processes that undergo during the longer geologic time scale. With respect to subsurface reservoirs, in many cases, anisotropy plays significant role in dictating the direction of flow that becomes no longer dependent only on driving forces like the pressure gradient and gravity but also on the principal directions of anisotropy. Therefore, there has been a great deal of motivation to consider anisotropy into the subsurface flow and transport models. In this dissertation, we present subsurface flow modeling in single and dual continuum anisotropic porous media, which include the single-phase groundwater flow coupled with the solute transport in anisotropic porous media, the two-phase flow with gravity effect in anisotropic porous media, and the natural gas flow in anisotropic shale reservoirs. We have employed the multipoint flux approximation (MPFA) method to handle anisotropy in the flow model. The MPFA method is designed to provide correct discretization of the flow equations for general orientation of the principal directions of the permeability tensor. The implementation of MPFA method is combined with the experimenting pressure field approach, a newly developed technique that enables the solution of the global problem breaks down into the solution of multitude of local problems. The numerical results of the study demonstrate the significant effects of anisotropy of the subsurface formations. For the single-phase groundwater flow coupled with the solute transport modeling in anisotropic porous media, the results shows the strong impact of anisotropy on the pressure field and the migration of the solute concentration. For the two-phase flow modeling with gravity effect in anisotropic porous media, it is observed that the buoyancy-driven flow, which emerges due to the density differences between the phases, migrates upwards and the anisotropy aligns the flow directions closer to the principal direction of anisotropy. Lastly, for the gas flow modeling in anisotropic shale reservoirs, we observe that anisotropy affects the pressure fields and the velocity fields of the matrix and fracture systems as well as the production rate and cumulative production. It is observed from the results that all of the anisotropic cases produce higher amount of gas compared to isotropic case during the same production time. Furthermore, we have also examined the performance of MPFA with respect to mixed finite element (MFE) method over the lowest-order Raviart-Thomas (RT0) space and the first-order Brezzi-Douglas-Marini (BDM1) space. From the comparison of the numerical results we observe that MPFA method show very good agreement with the BDM1 than RT0. In terms of numerical implementation, however, MPFA method is easier than BDM1 and it also offers explicit discrete fluxes that are advantageous. Combining MPFA with the experimenting pressure field approach will certainly adds another advantage of implementing MPFA method as compared with RT0 and BDM1. Moreover, the computational cost (CPU cost) of the three different methods are also discussed.

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Schmidt, Hansjörg. "Anisotropic Viscoelasticity at Large Strain Deformations." 2018. https://monarch.qucosa.de/id/qucosa%3A23546.

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The aim of this thesis is the fast and exact simulation of modern materials like fibre reinforced thermoplastics and fibre reinforced elastomers. These simulations are in the scope of large strain deformations and contain anisotropic and viscoelastic behaviour. The chapter Differential geometry outlines the necessary tensor analysis and differential geometry. We present the weak formulation in the undeformed domain and use Newton’s method to approximate the solution of this formulation, cf. Section 3.1 and Chapter 4, respectively. For the viscoelasticity we use a special ansatz for the internal variable. Next, we compute all necessary derivations for the Newton system, cf. Sections 4.2 and 4.3. We also investigate the symmetry of the material tensors in Section 4.4. Further, we present three methods to improve the convergence of Newton’s method, cf. Section 4.5. With these three methods we are able to consider more problems, compute them faster and in a more robust way. In Chapter 5 we concisely discuss the FEM and show the appearing matrices in detail. The aim of Chapter 6 is the application of the a posteriori error estimator to this complex material behaviour. We present some numerical examples in Chapter 7. In Chapter 8 the problems that arise in the simulation of fibre-reinforced elastomers are analysed and tackled with help of mixed formulations. We derive a symmetric mixed formulation from a reduced form of the energy density. Also, we reformulate the mixed variable for inextensibility to avoid the numerical cancellation in Section 8.3. The Section 8.4 is about a joined mixed formulation to solve problems with inextensible fibres in an incompressible matrix, like fibre-reinforced rubber. The succeeding section Section 8.5 deals with the arising indefinite block matrix system.:Contents Glossary 5 1 Introduction – motivation 13 2 Differential geometry 15 2.1 From parametrisations to the Lagrangian strain 15 2.2 Derivatives of tensors 20 3 Physical foundations 25 3.1 Large Deformation 25 3.1.1 Balance of forces 25 3.1.2 Energy minimisation 28 3.2 Anisotropic energy density 29 3.3 Viscoelasticity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 4 Newton’s method 37 4.1 Newton system 37 4.2 Anisotropic material tensor 40 4.3 Viscoelastic material tensor 41 4.4 Symmetry of the material tensor 44 4.5 Load steps and line-search 47 4.5.1 Load steps – time steps 47 4.5.2 Backtracking for det ℱ > 0 48 4.5.3 Line search for energy minimisation 49 5 Implementation 53 5.1 Numerical Integration 53 5.2 Finite element discretisation 54 5.3 Voigt notation 56 6 Mesh control 65 7 Numerical results 69 7.1 Semi-analytical example 69 7.2 Cook’s membrane 71 7.2.1 Viscoelastic example 72 7.3 Chemnitz hook – Chemnitzer Haken 72 8 Mixed formulation 75 8.1 Motivation 75 8.2 General considerations 78 8.3 Smooth square root 81 8.4 Joined mixed formulation 84 8.5 Matrix representation 86 9 Conclusion 91 10 Theses 93 11 Appendix 95 11.1 Derivatives of the distortion-invariants with respect to the pseudo invariants 95 Bibliography 101

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Dissertations / Theses on the topic 'Continual mixer'

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