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Bergara, Tomas. "Réversibilité de l'adhérence dans des assemblages structuraux modèles". Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14445.
Pełny tekst źródłaStructural adhesives are nowadays widely used in numerous industries like automotive, aerospace, avionics or microelectronics … for many reasons such as easy processing or weight and cost savings. A strong effort has been achieved so far to enhance the level of adherence in structural assemblies and in this particular case a new challenge appears: the easy dismantling of structural bonded joints. This innovative concept results from industrial constrains like maintenance or recycling needs.This work studies a process which offers a simple and efficient solution to the disassembling of structural bonds. Based on the use of specific additives activated by heating at a certain temperature, this new technology allows the drastic decrease of the bonding performance and allow the dismantling in a very short time. It fulfills the main characteristics required by this application, like no change in processing (implementation, curing conditions,…) and no or slight modification of the mechanical properties. The results of the influence of adding additive is evaluated.This process is based on the incorporation. of specific chemicals in the adhesive or primer formulations. These additives are selected according to specific properties like decomposition temperature. An innovative aspect of this technology lies in the localization of the dismantling. The first step of the additive action is migration from the bulk of the adhesive to the interface. In a second time, once at the interface, the decomposition gases generated by the additive (mainly steam and nitrogen) induce constrains and stresses. After a certain time, theses stresses are sufficient enough to overcome the adhesion forces and the adhesive debonds from the substrate, adhesive failure occurs. One logical consequence of this interfacial action is the use of a dismantling primer, which enables to improve the efficiency of the technology and allows additive savings.This work proposes mecanisms based on experimental results in order to explain what happens in the adhesive bulk and on the interfaces. Finally, an application of this process is described related to the use of debondable adhesive for structural coupling during ground tests in the frame of GAIA telescope. Its main structure is a multi segments brazed torus in silicon carbide. In order to test each segment, a structural and debondable epoxy adhesive was developed, allowing structural bonding at room temperature and easy dismantling with interfacial failure after thermal activation. After testing and dismantling, segments were reused for final application
Perfilov, Viacheslav. "Modèles mathématiques des procédés de séparation membranaire". Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTG037/document.
Pełny tekst źródłaIn this work have been developed general predictive models for direct contact membrane distillation (DCMD) and sweeping gas membrane distillation (SGMD) as well as a hydrodynamic model for anaerobic membrane bioreactors (AnMBRs) equipped with the induced membrane vibration (MMV) system. The DCMD and SGMD models allow simulating hollow fibre and flat sheet configurations under wide range of process conditions without empirical mass and heat transfer coefficients or laboratory experiments. The models have been validated with experimental and literature data. Indeed, the influence of operating conditions and membrane geometric characteristics on the process performance has been investigated. The model for AnMBRs with MMV studies the effect of the membrane vibration on the hydrodynamics of the AnMBR tank. The parametric study allows knowing, the effects of the vibration frequency and amplitude on the fluid velocity and volume fraction of solids. The conducted studies prove that all the proposed models would be potentially applied for the pre-experimental study, optimization of process conditions, design of membrane modules as well as for the further cost estimation of the processes
Thiaucourt, Jonas. "Méthodes et modèles pour l’étude de faisabilité des navires propulsés au gaz naturel liquéfié". Thesis, Ecole centrale de Nantes, 2019. http://www.theses.fr/2019ECDN0032/document.
Pełny tekst źródłaIn proportion to the ton of cargo, shipping is a relatively “clean” transportation mode. Nevertheless, due to global trade intensification, its share in the global greenhouse gas (GHG) emissions should increase. Aware that GHG adverse effects are a major concern for humanity, united nation member states impose, via the international maritime organization, a regulatory framework so that this vital sector in a global economy remains sustainable. Short (2020) and medium (2050)-term goals are set. According to the weak version of Porter’s hypothesis, strict environmental regulations encourage innovations. Hence, in the shipping industry solutions flourish among which the use of Liquefied Natural Gas (LNG) as a fuel. On a thermodynamic basis, the unavoidable heat leaks into the cryogenic tanks cause variations of the tank pressure and the natural gas quality at engine inlet. Depending on the ship’s operational profile, those two phenomena will impact significantly the LNG as a fuel option relevance. One major bottleneck slowing the uptake of LNG as a marine fuel is the lack of methods and models to perform, at a concept design level, the feasibility study. In response, this thesis proposes 0D models to assess from the operational profile:1. the tank pressure evolution;2. the gas quality evolution at engine inlet.In the first part, models are proposed to simulate heat leaks into the tanks, LNG vaporization, ageing (the alteration of natural gas thermophysical properties by a differentiate vaporization of its compounds) and methane number evolution at engine inlet. Then, the models are put together and applied on a case study. The ship concept is proposed by a freight company
Carcaud, Pierre. "Étude de quelques modèles cinétiques décrivant le phénomène d'évaporation en gravitation". Phd thesis, Université Rennes 1, 2014. http://tel.archives-ouvertes.fr/tel-01018326.
Pełny tekst źródłaYoussef, Moafaq Mohamed. "Exploration of novel fuels for gas turbine (ENV-406) : modeling of T60 test rig with diesel & biodiesel fuels". Master's thesis, Université Laval, 2014. http://hdl.handle.net/20.500.11794/25332.
Pełny tekst źródłaIn this thesis, a CFD model was proposed to simulate the liquid combustion of conventional and non-conventional biodiesel fuels, in particularly the B20 biodiesel blend. The numerical test matrix consists of four reacting flow cases, and one non-reacting liquid fuel injection case. The models are computed using FLUENT™ v.14 in a 3D steady-state fashion. The turbulent non-premixed diffusion flames are modeled using the steady laminar flamelet approach; with a joint presumed Probability density function (PDF) distribution. Validation is achieved by comparing available experimental measurements with the obtained CFD results. Combustor aerodynamics and the outer wall temperatures are captured with a satisfactory degree of accuracy. Validation of the main combustion products, such as: CO2, H2O, and O2, shows satisfactory results for all the reacting flow cases; however, some inconsistencies were found for the CO emissions. It is believed that the test rig (combustor geometry and operating condition) is not sufficiently adequate for burning liquid fuels. On the other hand, from a numerical combustion point of view, the steady laminar flamelet approach was found not reasonably able to capture the deep non-equilibrium effects associated with the slow formation process of a pollutant, such as CO.
Roy, Xavier. "Propriétés moyennes des modèles inhomogènes en cosmologie relativiste". Phd thesis, Université Claude Bernard - Lyon I, 2011. http://tel.archives-ouvertes.fr/tel-00864219.
Pełny tekst źródłaPerrotin, Lydie. "Hydroconversion du n-hexadécane : application à la 3ème étape du procédé "gas-to-liquids"". Montpellier 2, 2001. http://www.theses.fr/2001MON20133.
Pełny tekst źródłaPlein, Fränk. "When Bilevel Optimization Meets Gas Networks: Feasibility of Bookings in the European Entry-Exit Gas Market: Computational Complexity Results and Bilevel Optimization Approaches". Doctoral thesis, Universite Libre de Bruxelles, 2021. https://dipot.ulb.ac.be/dspace/bitstream/2013/325604/3/TOC.pdf.
Pełny tekst źródłaTransport et commerce de gaz sont découplés depuis la libéralisation des marchés européens du gaz, qui sont désormais organisés en systèmes dit d'entrée-sortie. Au cœur de ce système de marché se trouvent les réservations et les nominations, deux contrats spéciaux de droit à la capacité qui permettent aux négociants d'accéder au réseau de gaz. Ce dernier est exploité par une entité distincte, appelée gestionnaire de réseau de transport~(GRT), qui est chargée du transport du gaz entre les nœuds d'entrée et de sortie. À moyen et long terme, les négociants signent un contrat de réservation avec le GRT pour obtenir des capacités d'injection et d'extraction aux nœuds d'entrée et de sortie, respectivement. Au jour le jour, ils désignent ensuite, dans les limites des capacités réservées, un flux de charge équilibrée des quantités de gaz prévues à injecter et à extraire le lendemain. La propriété essentielle est qu'en signant un contrat de réservation, le GRT est obligé de garantir la transportabilité de tous les flux de charge équilibrée respectant les capacités réservées. Pour évaluer la faisabilité d'une réservation, il est donc nécessaire de vérifier la faisabilité d'une infinité de nominations. Par conséquent, décider si une réservation est réalisable est un problème mathématique difficile, que nous étudions dans cette thèse.Nos résultats vont des réseaux passifs, constitués uniquement de pipelines, aux réseaux actifs, contenant des éléments contrôlables pour influencer les flux de gaz. Comme l'étude de ces derniers conduit naturellement à un cadre biniveau, nous considérons d'abord certaines propriétés plus générales de l'optimisation biniveau. Pour le cas de l'optimisation biniveau linéaire, nous étudions la difficulté de valider l'exactitude des constantes de type big-M souvent utilisées dans la résolution de ces problèmes via une reformulation à un seul niveau. Nous déduisons également une famille d'inégalités valides à utiliser dans un algorithme de branch-and-cut adapté au biniveau comme alternative à l'approche utilisant des big-Ms.Nous nous tournons ensuite vers l'étude des réservations réalisables. D'abord, nous présentons nos résultats sur les réseaux passifs, pour lesquels les approches biniveaux ne sont pas nécessaires. Une caractérisation des réservations réalisables sur les réseaux passifs est déduite en termes d'un ensemble fini de nominations. Bien que le calcul de ces nominations soit une tâche difficile en général, nous présentons des algorithmes polynomiaux pour les cas particuliers des réseaux passifs en forme d'arbre ou contenant un cycle unique. Enfin, nous considérons les réseaux avec des éléments actifs modélisés à l'aide de contraintes linéaires. Après avoir obtenu un modèle biniveau, permettant de déterminer la faisabilité d'une réservation dans ce cas, nous dérivons diverses reformulations à un seul niveau pour résoudre le problème. En outre, nous obtenons de nouvelles caractérisations des réservations réalisables sur les réseaux actifs, qui généralisent notre caractérisation dans le cas passif. La performance de ces différentes approches est comparée dans une étude de cas réalisée sur deux réseaux de la littérature, dont l'un est une version simplifiée du réseau de gaz grec.
Nach der Liberalisierung der europäischen Gasmärkte, welche nun als sogenannte Entry-Exit Systeme organisiert sind, sind Transport und Handel von Gas entkoppelt. Im Zentrum dieses neuen Marktsystems sind Buchungen und Nominierungen, zwei spezielle Kapazitätrechtsverträge, die Händlern Zugang zum Gasnetz gewähren. Letzteres wird von einem separaten Akteur betrieben, dem sogenannten Fernleitungsnetzbetreiber (FNB), der für den Transport des Gases von den Einspeise- zu den Ausspeiseknoten verantwortlich ist. Händler schließen mittel- bis langfristig einen Buchungsvertrag mit dem FNB ab, um Ein- und Ausspeisekapazitäten zu erhalten. Täglich nominieren sie dann innerhalb der gebuchten Kapazitäten einen bilanzierten Lastfluss der geplanten Gasmengen, die am nächsten Tag eingespeist und entnommen werden sollen. Die Haupteigenschaft ist, dass der FNB sich durch Unterzeichnung eines Buchungsvertrages für die Transportierbarkeit aller bilanzierten Lastflüsse innerhalb der gebuchten Kapazitäten verpflichtet. Um die Zulässigkeit einer Buchung zu bestimmen ist es daher notwendig, die Zulässigkeit von unendlich vielen Nominierungen zu prüfen. Die Entscheidung, ob eine Buchung zulässig ist, ist daher ein anspruchsvolles mathematisches Problem, das wir in dieser Dissertation untersuchen.Unsere Ergebnisse reichen von passiven Netzen, die nur aus Rohren bestehen, bis hin zu aktiven Netzen, die steuerbare Elemente zur Beeinflussung der Gasflüsse enthalten. Da die Untersuchung aktiver Netze uns auf natürlichem Wege zu Bilevel-Problemen führt, betrachten wir zunächst einige allgemeinere Eigenschaften der Bilevel-Optimierung. Für den Fall der linearen Bilevel-Optimierung betrachten wir die Schwierigkeit, Big-Ms zu validieren, die oft bei der Lösung dieser Probleme mittels einer einstufigen Reformulierung verwendet werden. Wir leiten außerdem eine Familie gültiger Ungleichungen ab, die in einem Bilevel-spezifischen Branch-and-Cut Algorithmus als big-M-freie Alternative verwendet werden können.Wir wenden uns dann der Untersuchung von zulässigen Buchungen zu. Zunächst stellen wir unsere Ergebnisse zu passiven Netzwerken vor, für die Bilevel-Ansätze nicht erforderlich sind. Eine Charakterisierung zulässiger Buchungen in passiven Netzwerken wird in Bezug auf eine endliche Menge an Nominierungen hergeleitet. Während die Berechnung dieser Nominierungen im Allgemeinen eine schwierige Aufgabe ist, präsentieren wir polynomielle Komplexitätsergebnisse für die Spezialfälle baumförmiger oder einzyklischer passiver Netze. Schließlich betrachten wir Netze mit linear modellierten aktiven Elementen. Nachdem wir ein Bilevel-Modell hergeleitet haben, mit dem wir die Zulässigkeit einer Buchung in diesem Fall bestimmen können, leiten wir verschiedene einstufige Reformulierungen zur Lösung des Problems ab. Darüber hinaus erhalten wir neuartige Charakterisierungen zulässiger Buchungen auf aktiven Netzen, die unsere Charakterisierung im passiven Fall verallgemeinern. Die Anwendbarkeit dieser verschiedenen Ansätze wird in einer Fallstudie an zwei Netzen aus der Literatur verglichen, wovon eines eine vereinfachte Version des griechischen Gasnetzes ist.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
Wang, Yining. "CFD investigation of gas-solid flow dynamics in monolithic micro-circulating fluidized bed reactors". Master's thesis, Université Laval, 2008. http://hdl.handle.net/20.500.11794/20312.
Pełny tekst źródłaVavasseur, Arthur. "Modèles cinétiques de particules en interaction avec leur environnement". Thesis, Université Côte d'Azur (ComUE), 2016. http://www.theses.fr/2016AZUR4086/document.
Pełny tekst źródłaThe goal of this PhD is to study a generalisation of a model describing the interaction between a single particle and its environment. We consider an infinite number of particles represented by their distribution function. The environment is modelled by a vibrating scalar field which exchanges energy with the particles. In the single particle case, after a large time, the particle behaves as if it were subjected to a linear friction force driven by the environment. The equations that we obtain for a large number of particles are close to the Vlasov equation. In the first chapter, we prove that our new system has a unique solution. We then care about some asymptotic issues; if the wave velocity in the medium goes to infinity, adapting the scaling of the interaction, we connect our system with the Vlasov equation. Changing also continuously a function that parametrizes the model, we also connect our model with the attractive Vlasov-Poisson equation. In the second chapter, we add a diffusive term in our equation. It means that we consider that the particles are subjected to a friction force and a Brownian motion. Our main result states that the distribution function converges to the unique equilibrium distribution of the system. We also establish the diffusive limit making the wave velocity go to infinity at the same time. We find a simpler equation satisfied by the spatial density. In chapter 3, we prove the validity of both equations studied in the two first chapters by a mean field limit. The last chapter is devoted to studying the large time asymptotic properties of the equation that we obtained on the spatial density in chapter 2. We prove some weak convergence results
Gulas, Michal. "Growth of carbon nanotubes by plasma enhanced hot filament catalytic chemical vapour deposition : Correlation between gas phase and substrate surface". Université Louis Pasteur (Strasbourg) (1971-2008), 2008. http://www.theses.fr/2008STR13144.
Pełny tekst źródłaNaillon, Antoine. "Écoulements liquide-gaz, évaporation, cristallisation dans les milieux micro et nanoporeux : études à partir de systèmes modèles micro et nanofluidiques". Phd thesis, Toulouse, INPT, 2016. http://oatao.univ-toulouse.fr/17681/1/Naillon.pdf.
Pełny tekst źródłaMorel, Christophe. "Modélisation multidimensionnelle des écoulements diphasiques gaz - liquide : application à la simulation des écoulements à bulles ascendants en conduite verticale". Châtenay-Malabry, Ecole centrale de Paris, 1997. http://www.theses.fr/1997ECAP0543.
Pełny tekst źródłaBell, Mbea. "Three essays in the economics of greenhouse gas emissions' mitigation in the electricity sector". Doctoral thesis, Université Laval, 2018. http://hdl.handle.net/20.500.11794/28367.
Pełny tekst źródłaClimate change is one of the biggest challenges that the world is facing. In order to limit global warming, each political jurisdiction must implement a drastic climate policy to mitigate anthropogenic greenhouse gases (GHGs). In this challenge, the electricity generation sector has a central role to play. On the one hand, it is a major contributor to the total GHG emissions, and on the other hand, this sector offers several alternatives for generating electricity without emissions, such as renewable sources or fossil fuel generators equipped with carbon capture and sequestration (CCS) capacity. In three essays, this thesis examines cost-efficient solutions to reducing GHG emissions and promoting climate-friendly technologies in the electricity sector. The first essay compares an emissions tax and a clean energy standard using a calibrated general equilibrium model of electricity generation. The structure of electricity production features two plants: one that generates its output based on renewable sources and the other based on fossil source emitting CO2. The model is calibrated to match selected macroeconomic aggregates of the economy of British Columbia. The calibrated model is then used to conduct conceptual experiments that pit the overall cost of achieving the optimal emissions reduction target with a given policy instrument against the counterfactual cost of achieving the same target with an alternative policy instrument. The experiments lead to the conclusion that an emissions tax is more environmentally effective as well as more cost-effective than a clean energy standard. The second essay extends the comparison between a clean electricity standard and a carbon tax on cost-effectiveness grounds by adding innovation and market power. In our model, a two-stage competition in the electricity sector between a clean plant and its "dirty" rival anchors a two-sector general equilibrium model of climate change intervention. The dirty plant can innovate to reduce its emissions, and the clean plant can innovate to reduce its pre-existing cost-disadvantage. The model is calibrated to selected US macroeconomics aggregates. Results in this essay overturn those obtained in the first, where perfect competition was the feature of the electricity industry. The second essay thus shows cost-effective choice of climate policy instruments depends on the industrial organization of the electricity sector, as well as on the mechanisms plants use to respond to climate policy. Whereas the first two essays are only concerned with abatement incentives the third, by contrast, considers a climate policy action aimed, not only at incentivizing abatement, but also at promoting clean electricity solutions to climate change. These solutions have two competing sources. On the one hand, there are climate change solutions consisting of technological innovations that mitigate the intermittency and variability problems associated with renewable sources of electricity. Such solutions, when adequate, reduce the cost-disadvantage of renewable sources at reaching large-scale deployment. On the other hand, there are climate change solutions consisting of carbon abatement technologies that mitigate the trade-off between abatement effort and electricity output among fossil fuel generators. CCS technologies are an essential component of these fossil fuel-based climate change solutions. The main contribution of this essay is to show that, in countries with an abundant supply of fossil fuels, subsidizing fossil fuel-based climate change solutions can be an integral part of a cost-effective climate policy action aimed at achieving ambitious emissions reductions.
Lalande, Mathieu. "Processus induits par l'irradiation de modèles peptidiques de la triple hélice du collagène en phase gazeuse". Thesis, Normandie, 2018. http://www.theses.fr/2018NORMC235/document.
Pełny tekst źródłaCollagen is the most abundant protein in mammals, and the main constituent of the extracellular matrix of cartilage. The mechanical properties of this tissue are due to the particular triple helical structure of collagen. In this thesis, we focused on peptidic models of the collagen triple helix in thegas phase, which allows reaching their intrinsic properties, including fundamental processes induced by ionizing radiations. An ion mobility spectrometry study of these systems proved that they retain their structural and stability properties in the absence of solvent. In addition, these stability properties also play a role after irradiation with ionizing photons in an ion trap. Furthermore, we have observed, thanks to mass spectrometry, a transition between photo-excitation and photoionization as the energy of the absorbed photon increases in the VUV-X range. Part of this energy is also redistributed in the vibration modes of the system, increases with photon energy, and induces intramolecular as well as intramolecular fragmentation of the triple helix. For the first time, we irradiated peptides in the gas phase by a carbon ion beam having a kinetic energy relevant in the context of hadrontherapy. A process that was absent from studies with photons has been observed : proton detachment. In the last chapter, the validation of a new experimental device dedicated to the irradiation of proteins and DNA strands in a cross-beam configuration, as well as the first results obtained, will be reported
Herisson, Alexandre. "Flottation réactive à l'ozone de contaminants modèles issus de papiers récupérés : étude hydrodynamique et réactivité". Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAI104.
Pełny tekst źródłaThe decrease of the recovered paper collection quality and the accumulation of dissolved substances in process water affect the deinking line efficiency and contaminate more and more the liquid effluents. In this context the LGP2 has developed an innovative deinking process, the ozone reactive flotation, to chemically degrade dissolved pollutants in parallel with ink removal. To better understand the mechanisms involved, air and ozone/oxygen flotation trials have been conducted on three model contaminants selected in a preliminary bibliographic review, in a two-phase gas/liquid system, in the absence of fibers. Experiments have been carried out on two instrumented laboratory pilots: a bubble column operating only with air for the study of the hydrodynamics of the reactor (bubbles size and distribution, gas hold-up) in the presence of dissolved contaminants, and a second one, similar in its conception but built using materials resistant to corrosive gas, dedicated to the study of the oxidation reactions with ozone. The evaluation of the hydrodynamics related to gas flow and injection system selected, studied with air but supposed to be the same with ozone/oxygen gas mixture, shows that the bubble size, with or without contaminants, is optimal for an efficient flotation process. The study of ozone mass transfer and reactivity with the three model contaminants, for several temperatures and ozone concentrations, leads to the calculation of kinetic constants and shows that the contaminants, depending on their nature, have been oxidized or depolymerized. Although the COD of the treated solutions does not decrease a lot after the ozone reactive flotation, the effluent quality has been improved in terms of biodegradability since contaminants are partially degraded
Kangni-Foli, Ekoé. "Apport de matériaux cimentaires modèles à la description des cinétiques de carbonatation de bétons bas-pH : conséquences sur la microstructure le transport de gaz et les déformations". Electronic Thesis or Diss., Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLET056.
Pełny tekst źródłaAndra, the agency in charge of the radioactive waste management in France, is responsible for the design and the conception of the future deep geological disposal facility purposed to host among others the intermediate level long lived wastes (ILW-LL). The design proposed envisaged the sealing of the disposal ILW-LL wastes’ cells by a swelling clay and two low-pH concrete plugs. Those Low-pH cementitious materials are obtained by massive incorporation of siliceous bearing materials in usual cements, which aimed to lower the materials’ alkalinity (pH). The recourse to commonly used cementitious materials for the sealing would lead to an inhibition of the swelling properties of the clays due to the cements’ high alkalinity.Recent studies have highlighted for low-pH materials an increased permeability, cracking and pore size distribution upon carbonation. IRSN as a French nuclear safety expert raised the question (through this study) of the durability of Low-pH materials in the framework of the carbonation. The carbonation is defined in cementitious materials as the reaction of calcium (Ca) from Ca-bearing phases with the dissolved CO2 in the pore structure, initially present in the atmosphere. A model material approach was adopted in order to unveil the chemical changes and to allow mass balances after carbonation. The results obtained evidenced the role of the calcium content and the aluminum content. Materials with high Ca content evidenced the slower carbonation kinetic. In presence of aluminium and high calcium content TAH and pentahedral Al species were formed, their presence and reactivity correlated with a decreased rate of C-A-S-H degradation compared to the one induced by high ca content. The microstructural evolutions and the changes in volumes and the shrinkage were quantified, the coupling between the chemistry and the transport properties was demonstrated comparing the model materials and the industrials low-pH material
Cabaret, Sébastien. "Algorithmes de contrôles avancés pour les installations à gaz du Large Hadron Collider au CERN suivant le framework et l'approche dirigée par les modèles du projet Gas Control System". Amiens, 2008. http://www.theses.fr/2008AMIE0104.
Pełny tekst źródłaThis thesis highlights my final research results at CERN (European Nuclear Research Center). It deals with advanced control algorithms integrated for the 21 Gas System installations of the new particles accelerator named LHC (Large Hadron Collider). The process is enclosed into the strategic GCS project (Gas Control System): producing the overall control systems by recursive declinations via an automation production application. The controls equipments engage are industrials Programmable Logic Controllers combine with SCADA systems (System Control And Data Acquisition). In this context some advanced control algorithms are well adapted by its capability to comply with these typical needs: the Smith Predictor (dead time compensation), the predictive methods (robustness and convivial tuning), the RST controller (open structure and polynomial resolution) and the online parametric identification methods. The work presented is structured in four points. First, it deals with the synthesis of advanced control loop and identification methods for an industrial Programmable Logic Controller. Second, it exposes the implementation validity. Third, it develops the systemic use of advanced control loops in a large scale project build with two innovative methodologies: a framework of development and a model driven realization. Fourth, it concludes by providing to the Gas process experts a standard interface allowing an efficient use of advanced control algorithms
Royer, Julien. "Processus ARCH d'ordre infini, Bêtas dynamiques et applications financières". Electronic Thesis or Diss., Institut polytechnique de Paris, 2022. http://www.theses.fr/2022IPPAG012.
Pełny tekst źródłaThe modeling of financial time series is made difficult by the presence of stylized facts. These empirical statistical properties led to the development of heteroskedastic nonlinear models. Infinite ARCH specifications have been introduced to allow finer modeling of these stylized facts, and in particular the phenomenon of strong persistence of volatility shocks. We present new extensions to these flexible models and study their inference. First, we consider an asymmetric infinite ARCH model. We prove the existence of a stationary solution and establish the asymptotic properties of the quasi-maximum likelihood estimator in this framework. In particular, we allow the parameter to lie on the boundary of the parameter space, precluding asymptotic normality. Moreover, we introduce a portmanteau test assessing the goodness-of-fit of the model on data. We also propose a test for the presence of memory and asymmetry. In a second time, we consider the modeling of the coefficients of a conditional linear regression. Linear factor models are key to many financial models and regression coefficients are often wrongfully assumed constant. We propose a model allowing for dynamic beta coefficients within the framework of multivariate infinite ARCH models. In particular, we allow the addition of exogenous variables in the dynamics of conditional betas and discuss potential candidates. We establish the conditions of existence of a stationary solution and discuss the existence of its moments. Finally, we consider an asset pricing exercise based on dynamic betas. To this end, we extend the results of statistical tests in the case of score-driven betas and propose a bootstrap procedure. Additionally, we introduce a two-step estimation method to measure the dynamic risk premia underlying the asset pricing model
Sáinz-García, Álvaro. "Dynamique de stockage souterrain de gaz : aperçu à partir de modèles numériques de dioxyde de carbone et d'hydrogène". Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30187/document.
Pełny tekst źródłaClimate change mitigation is one of the major challenges of our time. The anthropogenic greenhouse gases emissions have continuously increased since industrial revolution leading to global warming. A broad portfolio of mitigation technologies has to be implemented to fulfill international greenhouse gas emissions agreements. Some of them comprises the use of the underground as a storage of various substances. In particular, this thesis addresses the dynamics of carbon dioxide (CO2) and hydrogen (H2) underground storage. Numerical models are a very useful tool to estimate the processes taking place at the subsurface. During this thesis, a solute transport in porous media module and various multiphase flow formulations have been implemented in COMSOL Multiphysics (Comsol, 2016). These numerical tools help to progress in the understanding of the migration and interaction of fluids in porous underground storages. Three models that provide recommendations to improve the efficiency, monitoring and safety of the storages are presented in this manuscript: two in the context of carbon capture and storage (CCS) and one applied to underground hydrogen storage (UHS). Each model focus on a specific research question: Multiphase model on CCS. The efficiency and long-term safety of underground CO2 storage depend on the migration and trapping of the buoyant CO2 plume. The wide range of temporal and spatial scales involved poses challenges in the assessment of the trapping mechanisms and the interaction between them. In this chapter a two-phase dynamic numerical model able to capture the effects of capillarity, dissolution and convective mixing on the plume migration is applied to a syncline-anticline aquifer structure. In anticline aquifers, the slope of the aquifer and the distance of injection to anticline crest determine the gravity current migration and, thus, the trapping mechanisms affecting the CO2. The anticline structure halts the gravity current and promotes free-phase CO2 accumulation beneath the anticline crest, stimulating the onset of convection and, thus, accelerating CO2 dissolution. Variations on the gravity current velocity due to the anticline slope can lead to plume splitting and different free-phase plume depletion time is observed depending on the injection location. Injection at short distances from the anticline crest minimizes the plume extent but retards CO2 immobilization. On the contrary, injection at large distances from anticline crest leads to large plume footprints and the splitting of the free-phase plume. The larger extension yields higher leakage risk than injection close to aquifer tip; however, capillary trapping is greatly enhanced, leading to faster free-phase CO2 immobilization. Reactive transport model on convective mixing in CCS. Dissolution of carbon-dioxide into formation fluids during carbon capture and storage (CCS) can generate an instability with a denser CO2-rich fluid located above the less dense native aquifer fluid. This instability promotes convective mixing, enhancing CO2 dissolution and favouring the storage safety
Kuidjo, Kuidjo Emmanuel Vianney. "Towards a predictive model to reproduce flow regime transitions in gas-liquid flows with Neptune CFD : from a dispersed to a separated regime". Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0456.
Pełny tekst źródłaIn nuclear reactors, several regimes of gas-liquid flows may occur with some transitions between them. The main challenges associated with simulating these transitions in 3D CFD codes are associated with deformable interfaces of different sizes, accounting for coalescence and breakup interactions between gas structures and developing flow regime independent closure relations. This work aims at modelling and simulating the hydrodynamics of adiabatic gas-liquid flows thanks to a three-field two-fluid model in Neptune CFD. In a first step, a model with one continuous liquid field and two dispersed gas fields for small and large bubbles is used to simulate cap and churn flows with a void fraction up to 0.5 and a focus is put on the interfacial area prediction. In a second step, the second dispersed field is replaced by a hybrid continuous/dispersed field representing both large bubbles and continuous gas regions. The model is validated on several flow regimes in large diameter pipes and in confined rectangular channels
Kilani, Meriam. "Multiple product-project decisions coordination support : application to oil and gas development projects". Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPAST027.
Pełny tekst źródłaThe major challenge addressed in this research concerns the coordination of the multiple interdependent decisions that must be made during the project, either technical, financial, or contractual. Interdependence means that making one decision without considering the impacts for other decisions may imply some underperformance, or even dead ends, iterations, and rework.To overcome this challenge, a more adaptable multi-decision-making process has been proposed, consisting of three blocks: 1/ modeling the decision network and formulating the multi-decision problem; 2/ structuring the problem to propose relevant and plausible scenarios assembled from elementary decision alternatives; 3/ solving the problem by selecting and recommending scenarios.Building the multi-decision-making process is based on multiple possibilities for each block. The decision-maker selects from a set of possible choices to adapt the decision-making process to the precise context.For block #1, we have first articulated the need to build a global decision network that models the decisions under study and the interdependencies they may have with other decisions. We have then argued that graphs and matrices can be used to fulfill this need. Both methods allow to include all decisions and interdependencies of the decision network in one single model, each of them having its advantages and drawbacks, with a kind of complementarity.Then, to formulate the local multi-decision problem, two interactions-based clustering approaches are proposed: the top-down approach (considering decision interdependencies) and the bottom-up approach (with an additional due date-based grouping of decisions). Both help to delineate the focus of decision makers on a specific set of decisions, since considering the whole network of decisions at the same time can be challenging.In block #2, to structure the problem, two matrix-based and one graph-based methods have been proposed. These methods offer the possibility to generate possible scenarios considering compatibility and performance criteria, either sequentially (morphological analysis), simultaneously (QFD), or with a hybrid way (graph exploration). For the two matrix-based methods, an algorithm was proposed to facilitate the identification of plausible scenarios. As for the graph-based method, a lighter heuristic can be applied on live during a decision meeting.Finally, to solve the problem in block #3, several MCDA methods have been listed for evaluating and selecting a recommended scenario: absolute compensatory methods, relative pairwise comparison methods, and relative comparison to reference point methods.According to industrial actors, such a process could improve coordination mechanisms between the major decisions of their projects. Even though decisions were interdependent, they were not often considered as such, and our proposed process permits (according to them) to have a better vision of the decisions to be made together and of the consequences of the choices. A fictitious case study, inspired by real past projects, was used to illustrate the proposed multi-decision coordination process.We are convinced that our research will provide a solid basis for further studies on the coordination of multiple interdependent decisions in complex projects, although there are academic and industrial perspectives that need to be tackled
Parasiliti, Rantone Giuseppe. "Physical, mathematical and numerical modelling of a gas flow in pipeline networks with low Mach number expansion". Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS547.
Pełny tekst źródłaThis project aims to develop a model for low Mach flow in pipelines and an industrial code implementing it. The model can describe low mach regimes while avoiding blunt approximations, improving over legacy approaches like Boussinesq; as a result, our program is more accurate. In order to build our model and program, we investigate gas flow at low velocities in a network of pipes. We consider a one-dimensional system of equations obtained by averaging the Navier-Stokes equations for a compressible fluid over the pipe section. In contrast to the classical Boussinesq approximation, we employ the Low Mach Expansion to describe asymptotically compressible effects, aiming for a more accurate solution capable of characterizing flows with significant temperature variations. We first apply the model we obtained thus far to a well-known configuration of pipes called the "thermosyphon.". This setup consists of a loop of two horizontal adiabatic pipes and two vertical pipes with prescribed wall temperatures, resulting in a temperature gradient that drives the flow. The application of the model to this configuration gives us an exact but semi-implicit solution under laminar and steady-state conditions. This solution serves as a benchmark against which we validate our numerical results. By comparing our computed values with the quasi-exact solution, we demonstrate the accuracy and reliability of our approach. To implement the low Mach averaged model, we use a numerical method based on the characteristics method and the projection technique. We incorporate in our algorithm the treatment of periodic conditions and Dirac distributions as derivatives of the discontinuous gravity term at the corners. To generalize the model to more complex configurations of pipes, we propose laws that govern the junctions between multiple pipes. We study the "three-rung ladder," a closed configuration consisting of horizontal adiabatic pipes and vertical ones with imposed wall temperatures to induce a temperature-driven flow. %From this setup, more complex pipeline configurations can be derived. To tackle the challenges junctions pose in this context, we implemented an algorithm in the program capable of ensuring proper transmission conditions. Whenever feasible, we provide quasi-exact solutions under laminar and steady-state conditions to validate our numerical results further. Overall, this study investigates further low Mach number gas flows, employing advanced numerical techniques and validating our findings against established benchmarks
Benghalem, Mohammed Amine. "Interactions entre morphologies, acidités et diffusion dans les zéolithes beta : éléments de réponse par spectroscopie infrarouge, réactions modèles et chromatographie à flux inversés". Thesis, Poitiers, 2017. http://www.theses.fr/2017POIT2295/document.
Pełny tekst źródłaIn order to study the impact of the size and morphology of zeolite crystals on the textural, chemical and diffusion properties, a series of beta zeolites was studied.The logical increase of the porous surfaces and volumes with the decrease in crystal size is observed. In addition, this also implies a decrease in the overall acidity as well as strength of the adsorption sites. However, understanding the complex acidity of these materials requires advanced characterization techniques.The adsorption of probe molecules (pyridine, CO, ethylene) followed by infrared as well as ammonia thermodesorption were correlated to model reactions of ethanol conversion and n-hexane cracking. In this case, the morphology of the crystals has little influence and performance is mainly dictated by the Brønsted sites. The presence of extra-framework aluminums makes it possible to exalt the acid strength of the protonic sites. With the transformation of ethanol, better activities and stabilities are observed in the case of hierarchical zeolites.The study of diffusion by the reversed-flow gas chromatography (RF-IGC) showed that if the diffusion coefficients increase as opposed to crystal size, the secondary porosity reduces the diffusion path. Moreover, the weak sites predominantly present on the hierarchized materials facilitate the desorption of the molecules and are involved in the lateral interactions measured by RF-IGC.This work thus provides elements of response to the stability and the complex catalytic behaviors observed on the beta zeolite
Ho, Minh Tuan. "Kinetic modeling of the transient flows of the single gases and gaseous mixtures". Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4741/document.
Pełny tekst źródłaA gas inside the microsystems or the porous media is in its non-equilibrium state, due to the fact that the molecular mean free path is comparable to the characteristic dimension of the media. The same state of a gas, called rarefied, is found at high altitude or in the vacuum equipment working at low pressure. All these types of flow can be described by the kinetic models derived from the Boltzmann equation. This thesis presents the development of the numerical tools for the modeling and simulations of the rarefied gas flows. The two models of the full Boltzmann equation, the Shakhov model (S-model) for the single gas and the McCormack model for the gas mixture, are considered. The discrete velocity method is used to the numerical discretization in the molecular velocity space and the TVD-like scheme is implemented in the physical space. The main aspect of this work is centered around the transient properties of the gas flows and, especially, on the transient heat and mass transfer behaviors. However, for some configurations only steady-state solutions are considered and the implicit scheme is developed to reduce the computational cost. Using the proposed numerical approach several types of the transient rarefied single gas flows as well as the binary mixture of the monoatomic gases are studied
Laurent, Charlelie. "Low-order modeling and high-fidelity simulations for the prediction of combustion instabilities in liquid rocket engines and gas turbines". Thesis, Toulouse, INPT, 2020. http://www.theses.fr/2020INPT0038.
Pełny tekst źródłaOver the last decades, combustion instabilities have been a major concern for a number of industrial projects, especially in the design of Liquid Rocket Engines (LREs) and gas turbines. Mitigating their effects requires a solid scientific understanding of the intricate interplay between flame dynamics and acoustic waves that they involve. During this PhD work, several directions were explored to provide a better comprehension of flame dynamics in cryogenic rocket engines, as well as more efficient and robust numerical methods for the prediction of thermoacoustic instabilities in complex combustors. The first facet of this work consisted in the resolution of unstable thermoacoustic modes in complex multi-injectors combustors, a task that often requires a number of simplifications to be computationally affordable. These necessary physics-based assumptions led to the growing popularity of acoustic Low-Order Models (LOMs), among which Galerkin expansion LOMs have displayed a promising efficiency while retaining a satisfactory accuracy. Those are however limited to simple geometries that do not incorporate the complex features of industrial systems. A major part of this work therefore consisted first in clearly identifying the mathematical limitations of the classical Galerkin expansion, and then in designing a novel type of modal expansion, named a frame expansion, that does not suffer from the same restrictions. In particular, the frame expansion is able to accurately represent the acoustic velocity field, near non-rigid-wall boundaries of the combustor, a crucial ability that the Galerkin method lacks. In this work, the concept of surface modal expansion is also introduced to model topologically complex boundaries, such as multi-perforated liners encountered in gas turbines. These novel numerical methods were combined with the state-space formalism to build acoustic networks of complex systems. The resulting LOM framework was implemented in the code STORM (State-space Thermoacoustic low-ORder Model), which enables the low-order modeling of thermoacoustic instabilities in arbitrarily complex geometries. The second ingredient in the prediction of thermoacoustic instabilities is the flame dynamics modeling. This work dealt with this problem, in the specific case of a cryogenic coaxial jet-flame characteristic of a LRE. Flame dynamics driving phenomena were identified thanks to three-dimensional Large Eddy Simulations (LES) of the Mascotte experimental test rig where both reactants (CH4 and O2) are injected in transcritical conditions. A first simulation provides a detailed insight into the flame intrinsic dynamics. Several LES with harmonic modulation of the fuel inflow at various frequencies and amplitudes were performed in order to evaluate the flame response to acoustic oscillations and compute a Flame Transfer Function (FTF). The flame nonlinear response, including interactions between intrinsic and forced oscillations, were also investigated. Finally, the stabilization of this flame in the near-injector region, which is of primary importance on the overall flame dynamics, was investigated thanks to muulti-physics two-dimensional Direct Numerical Simulations (DNS), where a conjugate heat transfer problem is resolved at the injector lip
Chaix, Estelle. "Caractérisation et modélisation des transferts de gaz (O2/CO2) dans le système emballage/aliment en lien avec les réactions de croissance microbienne (microbiologie prévisionnelle)". Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20159/document.
Pełny tekst źródłaPackaging is a key player on reducing food losses, by defining around the food, via the mass transfer of gases (O2, CO2, N2) through the packaging, a headspace atmosphere whose composition is able to reduce physical-chemical (namely oxidation), microbial and physiological (for respiring foods) food degradation rate. In Modified Atmosphere Packaging (MAP) of fresh produce, the gaseous composition of the headspace is chosen in order to prevent microorganism growth (usually low O2 and high CO2 concentrations are chosen). This work aimed at initiating and developing a generalised approach permitting to study and quantitatively model the impact of gas transfer (O2/CO2/N2) occurring in the food packaging system on microbial growth. In this purpose, existing models of predictive microbiology will be coupled to mass transfers (permeation through packaging and solubilisation/diffusion within food) using numerical methods such as ODE (Ordinary Differential Equation) solvers. If the permeation is relatively well known, the two other parameters, O2 and CO2 solubilities and diffusivities, required in mass transfer models are less known, especially for solid food matrices. Experimental acquisition of these parameters was thus required. Some dedicated methodologies have been developed in the framework of this study in order to gain missing data of solubility and diffusivity in solid food matrices for the two studied gases, O2 and CO2. The methods of O2 diffusivity and solubility measurement relied on the use of luminescence-based sensors while for CO2, the methodologies were based on chemical titration. A processed cheese was used as solid model food and the O2 and CO2 solubilities and diffusivities were characterized in this model food as in other real food products: cooked ham and butter. A peculiar attention was paid on the validation of Henry's law in the case of CO2 that links CO2 partial pressure to the dissolved content into the product. The O2 diffusion within lipid-based model materials was studied with a deep analysis of the impact of temperature and viscosity. The energy of activation of oxygen diffusivity in model matrix (Miglyol 812) was found equal to 25 kJ mol-1 for temperature ranging from 5 to 30°C. A mathematical model of gas transfer was developed for the overall food/packaging system and was coupled to existing equations of predictive microbiology. This generalised model was compared with experimental data obtained in the case of mono-directionnal transfers, on the mass transfer and microbiological part (on processed cheese voluntarily contaminated by Listeria monocytogenes with an initial biomass equal to 10^3 UFC g-1). This work had permitted to increase knowledge on the behaviour of O2 and CO2 solubilities and diffusivities into solid food products, to understand and quantify the impact of gas transfers in the food/packaging system on the microorganism growth and to build basements for a new decision support system aiming at helping the user in the choice and design of MAP for a given application
Kyulavski, Vladislav Dimitrov. "Greenhouse gas emissions and soil carbon stocks associated with crop residues and organic fertilizers mixtures in sugar cane cropping systems". Thesis, La Réunion, 2019. https://elgebar.univ-reunion.fr/login?url=http://thesesenligne.univ.run/19_27_VDKyulav.pdf.
Pełny tekst źródłaIn the current environmental context, it is crucial to optimize the use of resources to reduce waste and greenhouse gas (GHG) emissions. Renewable resources use and recycling lies at the heart of the circular economy model, in which a waste is a mobilizable, transformable, reusable and therefore renewable resource. In agriculture, the “virtuous circle” of circular economy can be achieved through the recycling of organic wastes as fertilizer and the adoption of an agroecological approach that favors ecosystem services for pest control, soil protection and carbon stocks increase, one of the examples of which is mulching. In sugarcane cropping systems straw left on the soil surface is also increasingly coveted by industrial sector to produce second-generation agrofuels. The emerging competition for biomass use and the underlying environmental issues make it necessary to assess both, the agronomic and the environmental advantages and disadvantages of joint recycling of sugarcane mulch and organic fertilizers. Therefore, the objectives of this work are i) to compare the effect of fertilizers of contrasting physicochemical quality, on the decomposition of a sugarcane mulch, and ii) to evaluate the potential of GHG emissions from mulch-fertilizer mixtures, according to the quantity of straw left and the quality of the fertilizers applied. The research strategy adopted in a first step aimed to detect carbon/nitrogen interactions during the combined recycling of straw and organic fertilizers. We have thus tested the predictability of the mineralization dynamics of C and N of the organic materials alone, or in mixture (straw/fertilizer) in the laboratory, by a simple additive model, and a mechanistic model of carbon and nitrogen transformation in the soil - CANTIS. Our results showed that both models overestimated the C mineralization and did not correctly predict the N mineralization of the mixtures. This antagonistic interaction for the mixtures was corrected by the application of a contact factor in CANTIS, which reflects the bioavailability decrease of C and N, due to distribution heterogeneities at a fine scale within the soil. In a second step, we conducted field trials (under real conditions) to measure both the decomposition of sugarcane straw mixed with organic fertilizers and GHG emissions. The amount of straw decomposed was proportional to the initial amount left and was affected neither by the amount of straw nor the type of fertilizer provided. This proportionality is transposable to the potential for carbon sequestration in the soil and should be considered when setting up carbon sequestration or when exporting the straw for alternative use. The type of fertilizer plays a key role in GHG emissions in the short term after fertilization. The highest average CO2 and N2O emission fluxes were obtained by applying pig slurry, which has a high water content and is rich in mineral N. Conversely, the kinetics of GHG emissions from solid fertilizers have been governed by environmental factors, some of which could be controlled, such as water intake or fertilizer quantity application. The use of organic fertilizers is beneficial when they are rich in organic N and poor in water content, such as dry sewage sludge, but the mineralization of nitrogen in this case is gradual and requires elaboration of a specific application strategies to meet crop needs. A better integration of the interactions between the different N and C sources should be considered, in order to develop modeling as a precise tool for the management of an agroecosystem
Doudard, Rémy. "Flexibilité et interactions de long terme dans les systèmes multi-énergies : analyse technico-économique des nouvelles filières gazières et électriques en France". Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEM067/document.
Pełny tekst źródłaOver the past decade, several new technological pathways have been experimented with a view to reaching national decarbonization targets in France. These include biomethane, synthetic methane from Power-to-Gas, hydrogen, and Carbon Capture and Sequestration (CCS). The potential contributions of these technologies could make it more difficult for stakeholders and public authorities to choose the appropriate solution. In what contexts could these technologies be developed and what are their potential competition/cooperation perspectives?This research analyzes the role of these new technological pathways within the French gas and electricity systems. We propose a long-term, techno-economic assessment of the options at a 2050 horizon applying an optimal paradigm. We analyze the systems balance over several years while addressing the issue of intraday flexibility constraints.To this end, the bottom-up TIMES-FR-GAZEL model has been developed in order to study joint gas and electricity systems optimization with explicit representation of technologies (biomethane production, Power-to-Gas, CCS, etc.).This model allows us to embed trajectory constraints to reach the 2050 horizon. Assessments are conducted based on final energy demand scenarios with contrasted hypotheses on technology availability, decarbonization strategies and energy demand
Poulet, Lucie. "Développement de modèles physiques pour comprendre la croissance des plantes en environnement de gravité réduite pour des apllications dans les systèmes support-vie". Thesis, Université Clermont Auvergne (2017-2020), 2018. http://www.theses.fr/2018CLFAC026/document.
Pełny tekst źródłaChallenges triggered by human space exploration of the solar system are different from those of the International Space Station because distances and time frames are of a different scale, preventing frequent resupplies. Bioregenerative life-support systems based on higher plants and microorganisms, such as the ESA Micro-Ecological Life Support System Alternative (MELiSSA) project will enable crews to be autonomous in food production, air revitalization, and water recycling, while closing cycles for water, oxygen, nitrogen, and carbon, during long-duration missions and will thus become necessary.The growth and development of higher plants and other biological organisms are strongly influenced by environmental conditions (e.g. gravity, pressure, temperature, relative humidity, partial pressure of O2 or CO2). To predict plant growth in these non-standard conditions, it is crucial to develop mechanistic models of plant growth, enabling multi-scale study of different phenomena, as well as gaining thorough understanding on all processes involved in plant development in low gravity environment and identifying knowledge gaps.Especially gas exchanges at the leaf surface are altered in reduced gravity, which could reduce plant growth in space. Thus, we studied the intricate relationships between forced convection, gravity levels and biomass production and found that the inclusion of gravity as a parameter in plant gas exchanges models requires accurate mass and heat transfer descriptions in the boundary layer. We introduced an energy coupling to the already existing mass balance model of plant growth and this introduced time-dependent variations of the leaf surface temperature.This variable can be measured using infra-red cameras and we implemented a parabolic flight experiment, which enabled us to validate local gas transfer models in 0g and 2g without ventilation.Finally, sap transport needs to be studied in reduced gravity environments, along with root absorption and leaf senescence. This would enable to link our gas exchanges model to plant morphology and resources allocations, and achieve a complete mechanistic model of plant growth in low gravity environments
Loquais, Yohan. "Chaînes peptidiques modèles en détente supersonique : refroidissement conformationnel, structures et dynamique des états excités étudiés par modélisation Monte-Carlo, spectroscopies laser et chimie quantique". Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00847711.
Pełny tekst źródłaPrigent, Corentin. "Etude numérique et modélisation du modèle d'Euler bitempérature : point de vue cinétique". Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0201/document.
Pełny tekst źródłaIn various domains of physics, several phenomena can be modeled via the use of nonconservative hyperbolic systems. In particular, in plasma physics, in the process of developping and understanding the phenomena leading to Inertial Confinement Fusion, the bi-temperature Euler sytem can be used to model particle transport phenomena in a plasma. The difficulty of the mathematical study of such systems dwells in the presence of so-called non-conservative products, which prevent the classical definition of weak solutions via distribution theory. To attempt to define these quantities, it is useful to supplement the hyperbolic system with an underlying kinetic model. In this work, the objective is the numerical study of such kinetic systems in order to solve the bi-temperature Euler system.This manuscript is split in two parts. The first one contains the study of the bi-temperature Euler system. In the first chapter, this system in dimension 1 is solved by the use of an underlying kinetic model sprung from plasma physics: the Vlasov-BGK-Ampère system. An asymptotic-preserving numerical method is introduced, and it is shown that the scheme obtained in the limit is consistant with a scheme for teh bi-temperature Euler system. In the following chapter, the same hyperbolic model in dimension 2 is studied, this time via a discrete-BGK type underlying model. An entropy inequality is proved for solutions coming from the kinetic model, as well as a discrete entropy dissipation inequality.In the second part of the manuscript, we are interested in the development of numerical schemes for gas mixture rarefied flows. Firstly, an adaptive kinetic scheme is introduced for inert gas mixtures. By the use of discrete conservation laws, the solution is approximated on a set of discrete velocities that depends on space, time and species. Secondly, an extension of the method is proposed in order to improve the efficiency of the first method. Finally, the two methods are compared to the classical fixed grid method on a series of test cases.In the last chapter, a numerical method is proposed for rarefied flows of reacting mixtures. The setting considered is the case of slow bimolecular reversible chemical reactions. The method introduced is an explicit-implicit treatment of the relaxation operator, which is shown to be stable, linear and conservative
Shalygin, Maxim. "Réalisation et caractérisation du transport sélectif gazeux de contacteurs gaz-liquide à membrane (Selective transport of gases in gas-liquid membrane system)". Thesis, Vandoeuvre-les-Nancy, INPL, 2007. http://www.theses.fr/2007INPL022N/document.
Pełny tekst źródłaCombined gas-liquid membrane systems gather the advantages of membrane and absorption separation techniques. Specifically, selective membrane valves (SMV called flowing liquid membranes) were studied, i.e. creation, gas transport experiments, liquid nature and temperature dependences, and modelling. SMV use a flowing layer of liquid supported between two membranes. The 1st part of the dissertation reports the study of steady and non-steady state gas transports in SMV built out dense polymeric membranes. In the 2nd part is given the development of an original mathematical model for SMV simulation and its experimental assessment for CO2/CH4/H2 mixtures with aqueous solutions of K2CO3. From systematic studies of steady and non-steady state processes, both in flow-through and circulating modes, it was found that increasing of temperature and liquid carrier concentration (K2CO3) leads to the simultaneous rise of permeability and selectivity during CO2 recovery from CO2/H2 mixture
Miloudi, Benchaâ. "Modélisation d’écoulements de gaz raréfiés en vue de l’étude des fuites internes dans les machines volumétriques produisant des vides moyens". Valenciennes, 1994. https://ged.uphf.fr/nuxeo/site/esupversions/a557e18f-4212-4cfe-b66c-5e10a68b4a1c.
Pełny tekst źródłaBensabath, Tsilla. "Approche préventive pour une réduction des Hydrocarbures Aromatiques Polycycliques (HAP) dans les fours à pyrolyse : application à la cémentation gazeuse à basse pression". Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0064/document.
Pełny tekst źródłaLow-pressure gas carburizing is a heat treatment process used to harden surface of steel by enriching the metal with carbon atoms coming from pyrolysis of hydrocarbons. At the same time, a wide variety of molecules and radicals are also formed in the gas phase. They react together, leading to the formation of PAHs. PAHs are toxic and even carcinogenic, and activities such as furnace maintenance may thus represent a risk to workers. Experiments of acetylene pyrolysis were carried out in conditions close to low-pressure gas carburizing processes, at 900°C and 8 kPa. Two kinds of reactors were used: a jet stirred reactor and tubular reactors. At the outlet of the reaction zone, products of pyrolysis were analyzed. Among other products, 16 PAHs classified as priority pollutants by the United States Environmental Protection Agency (US EPA) were observed. Influence of residence time and of reactant dilution was studied. Experimental results were compared to those obtained with a detailed kinetic model. This model was developed in order to describe PAH formation during light hydrocarbon pyrolysis. The focus was placed on formation pathways of the first aromatic rings and of the 16 EPA-PAHs. In addition to the experimental data obtained in this study, the model was validated using experimental data from the literature. The aim of the study is to understand the phenomena of PAH formation and growth in order to find operating conditions to make safer the low-pressure gas carburizing processes
Champon, Isabelle. "Compréhension et modélisation des mécanismes de désactivation d’un catalyseur de méthanation de CO2 au sein d’un réacteur-échangeur milli-structuré à lit fixe". Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAF045.
Pełny tekst źródłaPower-to-SNG aims at storing the renewable electric surplus as SNG (Substitute Natural Gas) via the CO2 methanation reaction with a solid catalyst. For the purpose of the SNG direct injection into the gas network, high conversion rates are needed. Nevertheless, over time, the catalyst deactivates and the SNG may no longer meet the gas network injection specifications. In this work, a methodology is developed to understand the main deactivation mechanisms of a commercial catalyst (Ni/Al2O3) in a milli-structured fixed-bed reactor-heat exchanger in order to model them. Deactivation is dealt with at different experimental scales. A kinetic model and deactivation laws are identified and subsequently implemented in an already existing multi-scale reactor model. Finally, the simulation results are compared with experimental deactivation results obtained at the scale of the milli-structured reactor
Souhabi, Jihane. "Réexamen du comportement vibrationnel des alliages modèles GaAs(1-x)Px et Si(1-x)Gex : modèle de percolation et calculs ab initio". Thesis, Metz, 2010. http://www.theses.fr/2010METZ025S/document.
Pełny tekst źródłaThe 1-bond → 2-TO percolation generic scheme proposed for the basic understanding of the vibra-tion spectra (Raman and Infrared –IR) of usual random semiconductor alloys with zincblende structure, which has recently challenged the standard MREI (modified-random-element-isodisplacement) model with the 1-bond→1-TO behavior, (Chang et Mitra, 1971) developped in the sixties, is here confronted to the cluster model (Verleur et Barker, 1966) which has been accepted through use for the study of the vibration spectra of these particular zincblende alloys, which obviously exhibit more than one phonon mode per bond in their vibration spectra. In fact, the IR reflectivity spectra of GaAs1-xPx, the representative alloy of the last class, i.e. those very ones which motivated the developpement of the cluster model in the sixties, find a natural explanation in the scope of the percolation model on the basis of a perfect random substitution As ↔ P, with no adjusta-ble parameter. With this, GaAs1-xPx and its like are rehabilitated as random alloys in principle, and further, the percolation paradigm generalizes to all types and subtypes of the traditional four-type classification of phonon mode behavior of semiconductor alloys, based on the MREI and cluster models. In a second stage, we investigate to which extent an extension of the percolation scheme to the di-amond structure may help to understand the mysterious nature of the Raman behavior of the representative Si1-xGex alloy. We realize that a good simulation of the Si1-xGex Raman spectra already existing in the literature can be obtained with no adjustable parameter but the Raman efficiency of the Si1-xGex bond within a generic 1-bond→N-TO version of the percolation model, where N indicates a sensitivity to the local environment of the Ge-Ge (N=1 non sensitive), Si-Si (N=2, sensitive to the first neighbor environment) and Si-Ge (N=3, sensitive to the second neighbor environment) bonds. Some differences between the GaAs1-xPx and Si1-xGex percolation patterns are attributed to the different natures of the lattice relaxation in the zincblende and di-amond structures (inversion of the order of like branches in the Si-Ge triplet) and to the spectacular disper-sion of the Ge-Ge like modes (anti parallelism of the unique Ge-Ge branch) and Si-Si (inversion of the order of like branches in the Si-Si doublet), which add to the local constraint effect, the only one usually taken into account in the zincblende alloys examined so far. The assignment of the individual phonons branches in each percolation scheme, i.e. GaAs1-xPx or Si1-xGex, is achieved via home-made ab initio phonon calculations with a focusing on bond-stretching along prototype impurity motives designed as quasi linear so as to be remain in with the spirit of the linear chain approximation on which the percolation model is based
Agaesse, Tristan. "Simulations of one and two-phase flows in porous microstructures, from tomographic images of gas diffusion layers of proton exchange membrane fuel cells". Phd thesis, Toulouse, INPT, 2016. http://oatao.univ-toulouse.fr/17789/1/Agaesse.pdf.
Pełny tekst źródłaBouzarkouna, Zyed. "Optimisation de placement des puits". Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00690456.
Pełny tekst źródłaNoël, Frédérique. "Influence de la ventilation sur les propriétés de transport dans un poumon sain et enflammé". Thesis, Université Côte d'Azur, 2021. http://www.theses.fr/2021COAZ4004.
Pełny tekst źródłaThe main function of the lung is to supply the blood with oxygen and to drain the carbon dioxide from it. The lung captures the oxygen present in the ambient air where it rejects the carbon dioxide taken from the blood. This exchange results from the process of the lung's ventilation that repeatedly makes a volume of ambient air enter and leave the lung. In an idealized view, the ventilation can be characterized by two parameters: the maximum air velocity in the trachea (the amplitude) and the breathing frequency (the period). The goal of this thesis is to study and model the process of oxygen and carbon dioxide transport and exchanges in the lung. Gas transport is modeled by convection-diffusion-reaction equations in an idealized lung. A mathematical analysis of the model has been performed to prove the existence of a unique solution along with an asymptotic periodicity in time. Numerical simulations were performed to study a wide range of physiological configurations. In the healthy human case, the amounts of gas exchanged predicted by our model are close to physiology. The viscous and elastic energies spent during inspiration were then minimized assuming that our body needs in oxygen can be represented in our model by a constraint on the oxygen flow exchanged with the blood. Simulations were carried out for humans but also for any mammals using allometric scaling laws. The predictions of our model show that the ventilation parameters in mammals might be optimized to cost as little energy as possible. Then, we focused on the lung's ventilation of a human subject suffering from a pulmonary infection. The spread of a bronchial infection has been modeled in an idealized way and we studied how the ventilation is affected by the response of the immune system through bronchi wall inflammation. Our results show that the location of the transition zone between convection and diffusion mainly influence the quantity of oxygen exchanged with the blood. The location of this transition can be affected by the infection and hence alter the efficiency of the ventilation and modify its optimal configuration. Finally, to better understand the efficiency of a drug treatment delivered by aerosol, we modeled the deposit of aerosol particles in the first bifurcation of the bronchi of the human lung. Our model takes into account the evolution of the radius of the particles due to the exchange of water vapor and the evolution of the temperature of the particles due to the change of the surrounding environment. Our results show that the modeling of these parameters is important to represent more accurately the deposit of the particles on the walls of the bronchi. This work allows to better understand how the process of lung’s ventilation is adjusted and how it is affected by lung’s pathologies. Moreover, it highlights how ventilation can be used efficiently as a way to deliver drugs in the body
Sun, Chenghai. "Contribution à l'étude de la thermodynamique des gaz sur réseaux : théorie et simulations". Vandoeuvre-les-Nancy, INPL, 1993. http://www.theses.fr/1993INPL012N.
Pełny tekst źródłaDubus, Jean-Philippe. "Prise de décision multiattribut avec le modèle GAI". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2010. http://tel.archives-ouvertes.fr/tel-00812558.
Pełny tekst źródłaCoste, Nicolas. "Vers la prédiction de performance de modèles compositionnels dans les architectures GALS". Phd thesis, Grenoble, 2010. http://www.theses.fr/2010GRENM028.
Pełny tekst źródłaValidation, comprising functional verification and performance evaluation, is critical for complex hardware designs. Indeed, due to the high level of parallelism in modern designs, a functionally verified design may not meet its performance specifications. In addition, the later a design error is identified, the greater its cost. Thus, validation of designs should start as early as possible. This thesis proposes a compositional modeling framework, taking into account functional and time aspects of hardware systems, and defines a performance evaluation approach to analyze constructed models. The modeling framework, called Interactive Probabilistic Chain (IPC), is a discrete-time process algebra, representing delays as probabilistic phase type distributions. We defined a branching bisimulation and proved that it is a congruence with respect to parallel composition, a crucial property for compositional modeling. IPCs can be considered as a transposition of Interactive Markov Chains in a discrete-time setting, allowing a precise and compact modeling of fixed hardware delays. For performance evaluation, a fully specified IPC is transformed, assuming urgency of actions, into a discrete-time Markov chain, which can then be analyzed. Additionally, we defined a performance measure, called latency, and provided an algorithm to compute its long-run average distribution. The modeling approach and the computation of latency distributions have been implemented in a tool-chain relying on the CADP toolbox. Using this tool-chain, we studied communication aspects of an industrial hardware design, the xSTtream architecture, developed at STMicroelectronics
Coste, Nicolas. "Vers la prédiction de performance de modèles compositionnels dans les architectures GALS". Phd thesis, Université de Grenoble, 2010. http://tel.archives-ouvertes.fr/tel-00538425.
Pełny tekst źródłaMonestier, Olivier. "Développement et caractérisation de deux modèles murins présentant un phénotype hypermusclé". Limoges, 2012. http://aurore.unilim.fr/theses/nxfile/default/449dba1c-e93c-40ca-9977-2115d7357bf4/blobholder:0/2012LIMO4001.pdf.
Pełny tekst źródłaSkeletal muscle development and growth are tightly regulated processes involving multiple factors which control different cellular programs such as proliferation, differentiation and fusion. Understanding muscle mass regulation represents key issues in public health or agronomy. Thus, the identification of molecular mechanisms participating in muscular hypertrophy has major interest for therapies improvement of muscular atrophy or for applications in meat production. In this context, the work of my thesis concerned the development and characterisation of two mouse lines presenting a hypermuscular phenotype. The analysis of the first model, called surGasp1, showed that the ubiquitous overexpression of the Gasp1 gene leads to a generalized increase of muscular mass due to a hypertrophy of the type I, IIa and IIb fibres without change of the fatty tissue amount. This model provides an excellent tool to study the GASP1 function during the muscular development, in particular its role in relationship with the myostatin, a key factor in muscle growth regulation. I have also undertaken a study of the GASP1 protein during evolution. The substitution rate analysis from the ancestor of Ciona to tetrapods showed that the important domains in the interaction with the myostatin (GDF8) were the most preserved. These data allow me to propose a three dimensional model describing the GASP protein action. The second mouse line, GMA06, resulting from a sensitized mutagenesis screen, presents a hypermuscular phenotype which differs from the one observed in myostatine knockout mice. The identification of the causal mutation in this line will allow to better understand the interactions which could exist between this last one and the myostatin and constitutes an interesting model for functional studies of gene modifiers of the Gdf8-/- phenotype
Queiroz, Sergio. "Modèles graphiques décomposables pour la décision individuelle et collective". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2008. http://tel.archives-ouvertes.fr/tel-00812578.
Pełny tekst źródłaPubill, Aleix. "Procédé thermochimique de production de froid de forte puissance pour application mobile. Etude et caractérisation de la dynamique du système". Thesis, Perpignan, 2017. http://www.theses.fr/2017PERP0060.
Pełny tekst źródłaA better cold chain logistics understanding and control is a major safety issue in deep freezing processes within -20°C/-30°C. Self-cooling solutions based on thermochemical systems appear very suitable for rapid cooling of isothermal containers and its temperature regulation for several hours. Different process concepts and configurations are presented to tackle this problem. Through their dynamic nodal modeling, involving thermodynamic management of one or various reactors, an analysis of their behaviors is performed to evaluate their relevance. A selection of the best performing configurations leads us to an industrial pre-design.To undertake quality measures, a diagnosis approach for possible reactors malfunctions is developed. The methodology is based on a comparison of experimental responses between tested reactor and reference one under the same operating conditions. A database of simulated faulty behaviors will allow the detection and identification of possible malfunctions of reactors coming from the production line
Vu, Duong. "Injection de charge et de spin de GaAs vers des couches métalliques et magnétiques". Palaiseau, Ecole polytechnique, 2010. http://pastel.archives-ouvertes.fr/docs/00/50/65/65/PDF/Final.pdf.
Pełny tekst źródłaOn trouve le résumé suivant sur la plateforme de thèses en ligne Tel le résumé suivant (la thèse elle même inclut un résumé plus détaillé) :This thesis describes experimental and theoretical work concerning photo-assisted tunnelling between optically pumped GaAs and metallic surfaces. In particular, the first evidence for the spin dependence of the tunnel photocurrent into a magnetic surface is presented. The thesis is made up of two separate parts: Part 1: Reports studies of charge and spin injection of photoelectrons from an optically pumped, tipless GaAs microcantilever into both (nonmagnetic) Gold and (magnetic) Cobalt surfaces. A new model, which is used to analyse the bias, tunnel distance and spin dependence of the tunnel photocurrent, correctly predicts the behaviour observed on the Gold surfaces. With the addition of a Pockels' cell, the same experiment is used to modulate the spin polarisation of tunnelling electrons and to the spin dependence of photoelectron injection into Cobalt. A reversal of the relative spin polarisation of the photoelectrons to the magnetisation direction of the Cobalt results in a 6 % variation in the tunnel photocurrent. This compares with a value of 0. 1 % observed on nonmagnetic Gold surfaces. A reduction in this variation with increasing applied bias is attributed to a reduction in the surface recombination velocity. An extension to the model developed for charge injection which accounts for the spin polarisation of the photoelectrons describes the experimental results well. Part 2: Reports studies on charge and spin transport in GaAs using an original polarised photoluminescence microscopy technique. This technique is firstly applied to photoluminescence imaging in GaAs tips to be used in imaging studies of nanomagnetism, in order to estimate the expected electronic polarisations at the tip apex. In combination with studies on equivalent planar geometry samples and by numerically solving the charge and spin diffusion equations, polarisations approaching 40 % are predicted. Independently, polarised luminescence microscopy is used to investigate charge and spin transport in planar oxidized and passivated thin films. Surface recombination is shown to play an important role in determining the effective charge and spin diffusion lengths. The effect of an increase in the surface recombination velocity between the passivated and oxidized sample from 103 cm/s to 107 cm/s reduces the charge and spin diffusion lengths from 21 micron and 1. 3 micron, to 1. 2 micron and 0. 8 micron respectively
Polikarpov, Alexey. "Numerical simulation of rarefied gas flows based on the kinetic approach". Thesis, Aix-Marseille 1, 2011. http://www.theses.fr/2011AIX10088.
Pełny tekst źródłaThis work is devoted to the development of the numerical resolution of the kinetic model equations such as BGK, S-model, ES-model by the discrete velocity method. The different approximations of the Boltzmann equation are presented
Le, Tertre Alain. "Séries temporelles et analyse combinée des liens pollution atmosphérique et santé". Paris 6, 2005. http://www.theses.fr/2005PA066434.
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