Nowadays, one of the solutions considered in order to face the issue of global warming and to move towards a carbon neutral society relies on the use of solar energy as a renewable and bountiful primary source. And, if photovoltaic technologies account for a large part in the solar energy market, recent years have witnessed the growth of non-concentrated and concentrated solar thermal technologies. Among them, concentrated solar power technology (CSP) which uses the optical concentration of direct solar irradiation to generate high pressure and high temperature steam in the absorber tubes of the plant, has become a promising approach reaching 4.9 GWe of installed capacity by the end of 2015 [1]. However, one of the main challenges faced by CSP technology concerns the variability of solar energy related for example to sunrise, sunset, passing clouds… In addition to that, when it comes to direct steam generation, the presence of a two-phase flow regime inside the absorber tubes leads to a strong dynamic behavior of the steam generation. It is consequently necessary to be able to simulate this dynamic behavior in order to better handle the design and operation of CSP plants. Such simulation tools can then be used for the implementation and the test of reliable control systems aimed at maintaining desired operating conditions in spite of changes in solar irradiation. In this context, the National Institute for Solar Energy (INES), part of the French Alternative Energies and Atomic Energy Commission (CEA) wishes to upgrade their dynamic simulation tool that would enable its teams to reproduce the behavior of a prototype based on the Fresnel solar field technology including direct steam generation which was built and commissioned at Cadarache, Aix-en-Provence. This Master thesis work takes place within this framework and aims at developing a multi-domain dynamic model of the aforementioned prototype. To do so, three models respectively in the thermalhydraulic, the optical and the control-command domains are built and combined using a co-simulation approach relying on an in-house simulation platform called PEGASE. More specifically the development of the following models has been addressed:  a thermal-hydraulic model of the two-phase flow circulating inside the vaporizer field of the prototype and realized with the thermal-hydraulic code CATHARE [2] (Advanced ThermalHydraulic Code for Water Reactor Accidents) applied to solar thermal biphasic issues,  an optical model of the receiver programmed using the Modelica language and the Dymola (Dynamic Modelling Laboratory) simulation software,  control-command models (PID controller, control architecture…) adapted and built upon blocks taken from a modelling library included in the PEGASE platform. Each model was first developed and tested on a standalone basis. These models were then coupled using the PEGASE co-simulation platform. A sunny day was simulated using the multi-domain model and the controllability of the plant was analyzed. At this stage, the study focused on the steam separator level regulation. A thermal-hydraulic study also focused on potential instabilities in the vaporizer that can occur under certain circumstances of water temperature at vaporizer inlet and solar heat flux. This analysis was carried out with a CATHARE standalone model. Perspectives of the present work include a complete validation of the developed models from future experimental data and further developments should aim to extend the modelling scope of the numerical simulator towards a representation of all the hydraulic parts of the CSP prototype. Control schemes and regulation tools would have to be extended as well in order to move towards a more representative control architecture of the prototype. Particularly, the steam quality at vaporizer outlet is an important variable to regulate. Indeed, this parameter is usually kept between 60% and 80% [3]. It must be high enough to limit the power consumption of the recirculation pump but not too high in order to prevent absorber dry-out. / Solenergi, som är en förnybar och riklig primärkälla, är en av de lösningarna som anses kunna lösa problemet med global uppvärmning och bidrar i omvandlingen till ett kolneutralt samhälle. Andelen fotovoltaiska teknologier på energimarknaden är övervägande, men andelen koncentrerad och ickekoncentrerad solterminsteknik har ökat under de senaste åren. Bland solterminsteknikerna är koncentrerad solenergiteknik (CSP), som använder den optiska koncentrationen av direkt strålning för att generera högtrycks- och högtemperaturånga i anläggningens absorberarrör, ett lovande tillvägagångssätt som har nått 4.9 GWe installerad kapacitet i slutet av 2015 [1]. En av de största utmaningarna med CSP-tekniken är solenergins variation vid till exempel soluppgång, solnedgång och passerande moln, vilket beror på varierad tillgång av solljus. Det finns också utmaningar med direkt ånggenerering via tvåfasflödes regimer inuti absorberarrören eftersom det leder till ett starkt dynamiskt beteende vid ånggenereringen. Det är följaktligen nödvändigt att kunna simulera detta dynamiska beteende för att bättre hantera design och drift av CSP-anläggningar. Sådana simuleringsverktyg kan sedan användas för att genomföra tester för att erhålla tillförlitliga styrsystem som upprätthåller önskade driftsförhållanden trots förändringar i solstrålningen I detta sammanhang vill National Institute for Solar Energy (INES), som är en del av den franska alternativa energikommissionen och atomenergi kommissionen (CEA), förbättra dess dynamiskt simuleringsverktyg som skulle möjliggöra för sina team att reproducera beteendet hos en prototyp baserad på Fresnel solfältsteknik inklusive direkt ånggenerering som byggts och beställts vid Cadarache, Aix-enProvence. Denna masteruppsats sker inom ramen för detta och syftar till att utveckla en dynamisk modell med flera domäner av den ovan nämnda prototypen. Tre modeller i termisk-hydraulisk, optisk och kontrollkommando domäner har byggts och kombinerats med hjälp av en co-simuleringsmetod som bygger på en intern simuleringsplattform som heter PEGASE. Mer specifikt om utvecklingen av modellerna enligt nedan:  En termisk-hydraulisk modell av tvåfasflöde som cirkulerar inuti förångarens fält på prototypen har realiserats med termisk-hydraulisk kod CATHARE [2] (Advanced Thermal-Hydraulic Code for Water Reactor Accidents) som appliceras på soltermisk bifasiska frågeställningar.  En optisk modell av mottagaren har programmerats med hjälp av Modelica-språket och simuleringsprogrammet Dymola (Dynamic Modeling Laboratory).  Modeller av kontrollkommandon (PID-kontroller, kontrollarkitektur ...) har byggts och anpassats i moduler som hämtats från modelleringsbibliotek som ingår i PEGASE-plattformen. Varje modell utvecklades och testades på fristående basis. Modellerna kopplades sedan samman i PEGASE-co-simuleringsplattformen. En solig dag simulerades därefter med en flerdomänmodell och styrningsförmågan av anläggningen analyserades. Vid detta stadium fokuserade studien på att reglera nivån av ångseparerande. En termisk-hydraulisk studie fokuserade sedan på potentiella instabiliteter i förångaren som kan uppstå under vissa omständigheter av vatteninloppstemperatur och solvärmeflöde. Denna analys genomfördes med en CATHARE fristående modell. Perspektiven för det aktuella arbetet omfattar en fullständig validering av de utvecklade modellerna med hjälp av framtida experimentella data. Vid en vidareutveckling bör inriktningen vara att utvidga modellernas omfattning av den numeriska simulatorn till att representera alla hydrauliska delar av CSP prototypen. Styrsystem och regleringsverktyg skulle också behöva förbättras för att få en mer representativ kontroll arkitektur av prototypen. I synnerhet är ångkvaliteten vid förångarens utlopp en viktig variabel att reglera. Faktum är att den här parametern vanligtvis hålls mellan 60% och 80% [3]. Det måste vara tillräckligt högt för att begränsa recirkulationspumpens elförbrukning men inte för hög för att förhindra att absorberen torkar ut.

[pt] Em muitos problemas de engenharia, e.g., no projeto de próteses biomédicas flexíveis ou em dispositivos de absorção de energia, estruturas sofrem grandes deslocamentos. Nestes casos, a não linearidade geométrica deve ser levada em conta na resposta estrutural. Contudo, algoritmos de otimização topológica considerando não linearidades, e modelados segundo o método de elementos finitos, sofrem instabilidades numéricas causadas por distorções excessivas nas regiões de baixa densidade dentro do domínio de projeto. Em particular, a matriz de rigidez pode não ser positiva definida comprometendo a convergência do processo de otimização. Esta dissertação visa estudar um esquema de interpolação entre as formulações lineares e não lineares de elementos finitos para aliviar tais distorções. Em cada etapa da otimização, para determinar a configuração de equilíbrio, o sistema de equações não-lineares é resolvido pelo procedimento de Newton-Raphson. Utilizando-se das informações dos gradientes calculadas através do método adjunto, o Método das Assíntotas Móveis é empregado para atualizar as variáveis de projeto. Por meio de problemas de referência considerando grandes deslocamentos, são demonstradas a eficácia e a eficiência deste esquema de interpolação. Mais especificamente, as topologias otimizadas estão de acordo com aquelas obtidas na literatura e exibem a dependência esperada em relação ao nível de carga. O esquema de interpolação em estudo desempenha papel crucial na solução de problemas não lineares em níveis elevados de carga, permitindo que a rotina de otimização convirja e se obtenha a distribuição de material ótima. / [en] In many engineering problems, e.g., design of flexible biomedical prostheses or energy absorption devices, structures undergo large displacements. In those problems, the structural response must take into account the geometric nonlinearity. However, topology optimization algorithms regarding nonlinearities, and based on the finite element method, typically suffer from numerical instabilities caused by excessive distortions of low-density regions within the design domain. In particular, the stiffness matrix may be no longer positive definite, which can jeopardize the convergence of the optimization process. This thesis aims to study an interpolation scheme between linear and nonlinear finite element formultation to alleviate this convergence issue. At each step of the optimization, the nonlinear state equation is solved by the Newton-Raphson procedure to determine the equilibrium configuration. Making use of the gradient information computed from the adjoint method, the Method of Moving Asymptotes is employed to update the design variables. Through several benchmark problems considering large displacements, it is demonstrated the effectiveness and efficiency of this interpolation scheme. More specifically, the optimized designs are in agreement with those obtained in the literature and exhibit correct load-level dependence. The investigated interpolation scheme plays a crucial role in the solution of nonlinear problems with high load levels, allowing the optimization routine to converge and to obtain the optimal material arrangement.

<p></p><p>This doctoral dissertation takes the reader through a journey where applied shear rheology and flow-velocimetry are used to understand the mesoscopic factors that control the flow behavior of three microstructured fluids. Three individual protocols that measure relative physical and mechanical properties of the flow are developed. Each protocol aims to advance the particular transformation of novel soft materials into a commercial product converging in the demonstration of the real the chemical, physical and thermodynamical factors that could potentially drive their successful transformation. </p> <p> </p> <p>First, this dissertation introduces the use of rotational and oscillatory shear rheometry to quantify the solvent evaporation effect on the flow behavior of polymer solutions used to fabricate isoporous asymmetric membranes. Three different A-B-C triblock copolymer were evaluated: polyisoprene-<i>b</i>-polystyrene-<i>b</i>-poly(4-vinylpyridine) (ISV); polyisoprene-<i>b</i>-polystyrene-<i>b</i>-poly(<i>N</i>,<i>N</i>-dimethylacrylamide) (ISD); and polyisoprene-<i>b</i>-polystyrene-<i>b</i>-poly(<i>tert</i>-butyl methacrylate) (ISB). The resulting evaporation-induced microstructure showed a solution viscosity and film viscoelasticity strongly dependent on the chemical structure of the triblock copolymer molecules. </p> <p> </p> <p>Furthermore, basic shear rheometry, flow birefringence, and advanced flow-velocimetry are used to deconvolute the flow-microstructure relationships of concentrated surfactant solutions. Sodium laureth sulfate in water (SLE₁S) was used to replicate spherical, worm-like, and hexagonally packed micelles and lamellar structures. Interesting findings demonstrated that regular features of flow curves, such as power-law shear thinning behavior, resulted from a wide variety of experimental artifacts that appeared when measuring microstructured fluids with shear rheometry.</p> <p> </p> <p>Finally, the successful integration of shear rheometry to calculate essential parameters to be used in a cost-effective visualization technique (still in development) used to calculate the dissolution time of polymers is addressed. The use of oscillatory rheometry successfully quantify the viscoelastic response of polyvinyl alcohol (PVA) solutions and identify formulations changes such as additive addition. The flow behavior of PVA solutions was correlated to dissolution behavior proving that the developed protocol has a high potential as a first screening tool.</p><br><p></p>

Une écoulement de cavité ouverte tridimensionnel saturé non-linéairement est étudié par une approche spatio-temporelle utilisant des données expérimentales résolues à la fois en temps et en espace. Ces données ont été acquises dans deux plans longitudinaux, respectivement perpendiculaire et parallèle au fond de la cavité, dans le régime incompressible, en air ou en eau. À l'aide de multiples méthodes de décompositions globales en temps et en espace, les ondes et les structures cohérentes constituant la dynamique dans le régime permanent et pouvant être produites par des mécanismes d'instabilités différents sont identifiées et caractérisées.Tout d'abord, on approfondit la compréhension de l'effet des non-linéarités sur les oscillations auto-entretenues de la couche cisaillée impactante et leurs interactions avec l'écoulement intra-cavitaire. En particulier, l'analyse spectrale d'une portion de l'espace des paramètres permet de mettre en évidence un lien entre l'accrochage des modes d'oscillations auto-entretenues, la modulation d'amplitude au niveau du coin impactant et l'intermittence de ces modes. De plus, l'observation des basses fréquences intéragissant fortement avec les oscillations de la couche de mélange démontre l'existence d'une dynamique tridimensionnelle intrinsèque à l'intérieur de la cavité malgré les perturbations causées par la couche cisaillée instable.Les analyses de stabilité linéaire ont montré que des instabilités centrifuges peuvent résulter de la courbure induite par la recirculation. L'étude de la dynamique après saturation révèle de nombreuses structures cohérentes dont les propriétés sont quantifiées et classées en s'appuyant sur la forme des instabilités sous-jacentes: des ondes transverses progressives ou stationnaires. Enfin, certains comportements des structures saturées suggèrent que les mécanismes non-linéaires gouvernant le développement de l'écoulement une fois sorti du régime linéaire pourraient être étudiés dans le cadre des équations d'amplitude. / A space-time study of a three-dimensional nonlinearly saturated open cavity flow is undertaken using time-resolved space-extended experimental data, acquired in both cross-stream and spanwise planes, in incompressible air and water flows. Through use of multiple modal decompositions in time and space, the waves and coherent structures composing the dynamics in the permanent regime are identified and characterised with respect to the instabilities arising in the flow.Effects of nonlinearities are thoroughly investigated in the impinging shear layer, regarding the self-sustained oscillations and their interactions with the inner-flow. In particular, the analysis conducted throughout the parameter space enlightens a global connection between the selection of locked-on modes and the amplitude modulation at the impingement and the mode switching phenomenon. Furthermore, observations of low frequencies interacting drastically with the shear layer flapping motion underline the existence of intrinsic coherent three-dimensional dynamics inside the cavity in spite of the shear layer disturbances.Linear stability analyses have demonstrated that centrifugal instabilities are at play along the main recirculation. The present investigation of the dynamics after onset of the saturation reveals numerous space-time coherent structures, whose properties are quantified and classified with respect to the underlying instabilities: travelling or standing spanwise waves. Finally, some patterns exhibited by the saturated structures suggest that the nonlinear mechanisms governing the mutations of the flow after the linear regime could gain more insight in the frame of amplitude equations.

Indiana University-Purdue University Indianapolis (IUPUI) / Break-induced replication (BIR) is a mechanism to repair double-strand breaks (DSBs) that possess only a single end that can find homology in the genome. This situation can result from the collapse of replication forks or telomere erosion. BIR frequently produces various genetic instabilities including mutations, loss of heterozygosity, deletions, duplications, and template switching that can result in copy-number variations (CNVs). An important type of genomic rearrangement specifically linked to BIR is half crossovers (HCs), which result from fusions between parts of recombining chromosomes. Because HC formation produces a fused molecule as well as a broken chromosome fragment, these events could be highly destabilizing. Here I demonstrate that HC formation results from the interruption of BIR caused by a defective replisome or premature onset of mitosis. Additionally, I document the existence of half crossover instability cascades (HCC) that resemble cycles of non-reciprocal translocations (NRTs) previously described in human tumors. I postulate that HCs represent a potent source of genetic destabilization with significant consequences that mimic those observed in human diseases, including cancer.

Aluminiumschichten werden durch Kaltgasspritzen auf fünf verschiedene poly- und monokristalline keramische Werkstoffe (Al2O3 , AlN, SiC, Si3N4 , MgF2 ) appliziert. Dabei erfolgt eine Variation der Substrattemperatur und der Partikelgröße. Ausgewählte Proben werden einer nachfolgenden Wärmebehandlung unterzogen. Die im Fokus der Arbeit stehende Erforschung der an der Grenzfläche zwischen Aluminium und Keramik wirkenden Haftmechanismen erfolgt sowohl mithilfe einer mechanischen Charakterisierung (Stirnzugversuche) als auch durch verschiedene mikroskopische, spektroskopische und hochauflösende Methoden. Die Bewertung der Untersuchungsergebnisse zeigt, dass im Allgemeinen ein Anstieg der Haftzugfestigkeit mit steigender Substrat- und Wärmebehandlungstemperatur sowie mit zunehmender thermischer Effusivität des Substratwerkstoffs zu verzeichnen ist. Eine vergleichbare Auswirkung hat innerhalb bestimmter Grenzen die Zunahme der Partikelgröße. Mit der Heteroepitaxie wird neben der mechanischen Verklammerung ein weiterer wichtiger Haftmechanismus kaltgasgespritzter metallischer Schichten auf keramischen Substraten identifiziert. Die Ausbildung von quasiadiabatischen Scherbändern und statische Rekristallisationsprozesse wirken dabei als wichtige begleitende Mechanismen. Als Nachweis für heteroepitaktisches Wachstum ist die Existenz von (annähernd) parallelen, senkrecht oder geneigt zur Grenzfläche stehenden Ebenenpaaren, die eine geringe Gitterfehlanpassung aufweisen, zu werten. Der Vergleich mit PVD-Schichten zeigt, dass in Bezug auf die Orientierung von Gitterebenen verschiedene Mechanismen der Heteroepitaxie existieren, die von der atomaren Mobilität des Beschichtungswerkstoffs bestimmt werden.

Aluminiumschichten werden durch Kaltgasspritzen auf fünf verschiedene poly- und monokristalline keramische Werkstoffe (Al2O3 , AlN, SiC, Si3N4 , MgF2 ) appliziert. Dabei erfolgt eine Variation der Substrattemperatur und der Partikelgröße. Ausgewählte Proben werden einer nachfolgenden Wärmebehandlung unterzogen. Die im Fokus der Arbeit stehende Erforschung der an der Grenzfläche zwischen Aluminium und Keramik wirkenden Haftmechanismen erfolgt sowohl mithilfe einer mechanischen Charakterisierung (Stirnzugversuche) als auch durch verschiedene mikroskopische, spektroskopische und hochauflösende Methoden. Die Bewertung der Untersuchungsergebnisse zeigt, dass im Allgemeinen ein Anstieg der Haftzugfestigkeit mit steigender Substrat- und Wärmebehandlungstemperatur sowie mit zunehmender thermischer Effusivität des Substratwerkstoffs zu verzeichnen ist. Eine vergleichbare Auswirkung hat innerhalb bestimmter Grenzen die Zunahme der Partikelgröße. Mit der Heteroepitaxie wird neben der mechanischen Verklammerung ein weiterer wichtiger Haftmechanismus kaltgasgespritzter metallischer Schichten auf keramischen Substraten identifiziert. Die Ausbildung von quasiadiabatischen Scherbändern und statische Rekristallisationsprozesse wirken dabei als wichtige begleitende Mechanismen. Als Nachweis für heteroepitaktisches Wachstum ist die Existenz von (annähernd) parallelen, senkrecht oder geneigt zur Grenzfläche stehenden Ebenenpaaren, die eine geringe Gitterfehlanpassung aufweisen, zu werten. Der Vergleich mit PVD-Schichten zeigt, dass in Bezug auf die Orientierung von Gitterebenen verschiedene Mechanismen der Heteroepitaxie existieren, die von der atomaren Mobilität des Beschichtungswerkstoffs bestimmt werden.