This thesis is concerned with the derivation of bioprocess models intended for engineering purposes. In contrast with other techniques, the methodology used to derive a macroscopic model is based on available intracellular information. This information is extracted from the metabolic network describing the intracellular metabolism. The aspects of metabolic regulation are modeled by representing the metabolism of cultured cells with several metabolic networks. Here we present a systematic methodology for deriving macroscopic models when such metabolic networks are known. A separate model is derived for each “phase” of the culture. Each of these models relies upon a set of macroscopic bioreactions that resumes the information contained in the corresponding metabolic network. Such a set of macroscopic bioreactions is obtained by translating the set of Elementary Flux Modes which are well-known tools in the System Biology community. The Elementary Flux Modes are described in the theory of Convex Analysis. They represent pathways across metabolic networks. Once the set of Elementary Flux Modes is computed and translated into macroscopic bioreactions, a general model could be obtained for the type of culture under investigation. However, depending on the size and the complexity of the metabolic network, such a model could contain hundreds, and even thousands, of bioreactions. Since the reaction kinetics of such bioreactions are parametrized with at least one parameter that needs to be identified, the reduction of the general model to a more manageable size is desirable. Convex Analysis provides further results that allow for the selection of a macroscopic bioreaction subset. This selection is based on the data collected from the available experiments. The selected bioreactions then allow for the construction of a model for the experiments at hand.

Le processus d’évapotranspiration (ETR) reste actuellement difficile à évaluer. L’objectif poursuivi par cette recherche est de proposer une méthode suffisamment robuste pour pouvoir être appliquée à l’échelle pluriannuelle tout en permettant un suivi à pas de temps fin au cours de la journée. En s’appuyant sur l’état de l’art, l’étude s’intéresse successivement au cas idéalisé des surfaces homogènes puis à celui des surfaces hétérogènes. Depuis quelques années, l’IRM a entrepris d’automatiser son réseau de stations synoptiques. Un sous-ensemble de stations a été choisi afin d’être doté d’un équipement plus complet comprenant un mât météorologique destiné à effectuer des mesures de la température et de la vitesse du vent à plusieurs niveaux. Ces nouvelles données sont exploitées dans la méthode préconisée. Celle-ci combine la théorie de Monin-Obukhov et l’évaluation du bilan énergétique de surface pour calculer les flux turbulents de chaleur sensible et de chaleur latente ainsi que le flux d’ETR. La télédétection offre quant à elle la possibilité d’observer de vastes territoires. Un modèle diagnostique est proposé pour estimer les flux turbulents de surface et l’ETR sur l’ensemble de la Belgique. Il s’agit d’une variante simplifiée du schéma « Isba » de transfert sol-végétation-atmosphère. Des flux radiatifs déduits d’images du satellite Meteosat sont exploités en entrée. La résolution spatiale est celle du capteur infra-rouge utilisé jusque Meteosat-7 (5*9 km). L’application est réalisée sur la période 1994-2003 avec un pas de temps horaire ce qui représente une première dans le domaine. Des comparaisons sont effectuées avec les résultats obtenus aux stations automatiques de l’IRM et avec des données récentes des stations belges du réseau Fluxnet. Les résultats sont très satisfaisants. Le travail s’achève sur des perspectives de développements futurs, la recherche en la matière étant encore en pleine évolution.

Cette thèse aborde le thème de la maîtrise des flux physiques dans les systèmes manufacturiers. Le mémoire présente dans un premier temps quelques réflexions et premières analyses sur les flux en général. Deux éléments particuliers y sont discutés : la nature et l'échelle d'observation des flux. Dans un second temps, deux approches pour le contrôle des flux sont présentées : la première classique est celle du contrôle par les activités et la seconde, plus récente est celle du contrôle par le produit. L'approche proposée dans cette thèse est ensuite positionnée par rapport aux deux approches précédentes.<br /><br />La partie bibliographique du mémoire expose des définitions courantes et les principes généraux utilisés pour l'étude des flux, puis deux approches particulières : l'approche énergétique et la théorie du trafic. Sur ces bases est ensuite proposée une liste de variables pouvant qualifier un flux à trois niveaux différents et considérés comme complémentaires (les produits dans le flux, les supports du flux et le flux lui-même). <br />Sur les bases des analyses bibliographiques menées, des propositions de différents ordres sont ensuite faites. La première d'entre elles se concentre sur la définition de variables ou concepts pouvant qualifier un flux hétérogène d'objets discrets. La seconde est une adaptation du tétraèdre de Paynter aux flux manufacturiers. Enfin, un macro-modèle de simulation des flux manufacturiers est proposé. <br />Ces propositions sont partiellement validées par simulation.

Thèse d'exercice : Pharmacie : Nancy 1 : 2008. / Titre provenant de l'écran-titre.

Mercury (Hg) is a potent human toxin and a persistent global pollutant with unique properties and environmental behaviours which make it difficult to model and understand. While anthropogenic mercury sources are well understood along with the impacts on ecosystems and human populations, the processes and transformations which govern environmental cycling lack the same level of understanding. Concentrations in Arctic environments are a specific concern, along with cycling behaviours in regions spanning from temperate to Arctic climates. The objective of this experiment was the investigation and characterization of the mechanisms which promote elemental mercury (Hg^0) flux from soils in these environments during simulated seasonal cycling. A laboratory scale experiment was conducted which used a Dynamic Flux Chamber (DFC) to monitor Hg^0 flux from a naturally Hg enriched soil during temperature cycling relevant to cold environments. The results, which were split into freeze-thaw (FT) and sub-zero (SZ) cycles, showed that Hg^0 flux from frozen soils remains active during temperature cycling. During FT cycles, Hg^0 flux is controlled by soil temperature and energy entering the system, with a linear increase in flux for increases in energy. This response is produced from the entire soil column. During SZ cycles, Hg^0 flux is produced only in the thin soil surface layer and is controlled by the air temperature at the soil-air interface. A decrease in the DFC air temperature was observed to produce an increase in flux, with an inverse relationship controlled by a separate mechanism than the FT cycle response. Recommendations for modifications to the experimental set-up and methodology have been made to improve the accuracy of the results and confirm the behaviours characterized during this study. / Natural Sciences and Engineering Research Council of Canada (NSERC)

No description available.

The objective of this thesis is to study the effects of flux deposition non uniformity on spreading of molten metal. Flux deposition non-uniformity here means as to whether the amount of flux deposited in a non-uniform or uniform pattern helps in the better wetting and spreading characteristics of the molten metal or is detrimental to the process. The material selection constraint to the study was imposed by selecting brazing of aluminum i.e., aluminum alloy melting and flow over an aluminum alloy substrate. The study was carried out by conducting a number of Hot Stage microscopy tests using aluminum silicon alloy as the filler metal and Potassium Fluoro Aluminate (Nocolok) as the flux. The flux was applied in different spatial distribution patterns to uncover the varying effects of its distribution on spreading. The uneven pattern of flux deposition indicates the influence on spreading but due to the efficient spreading of flux prior to aluminum melting and associated fuzziness of the achieved coverage distribution the effects are not always conclusive. It has been concluded that non uniform flux deposition does not necessarily mean uneven or less uniform spreading of the molten liquid metal if the spreading of the molten flux is beyond the distance of ultimate metal spreading. This is because, in spite of uneven flux deposition, the flux melts approximately at 560C-570C and spreads on the surface of the metal thereby promoting appreciable spreading and wetting of the molten liquid metal that happens at temperatures above 577C.

[pt] A técnica de Perfuração com Gerenciamento de Pressão está em crescente expansão no contexto das operações marítimas. Devido à complexidade dos reservatórios e das novas fronteiras de exploração e produção de petróleo, a perfuração com Gerenciamento de Pressão se apresenta como uma forma de redução de custo e aumento da segurança operacional para um grande volume das reservas de petróleo. Em alguns casos, a tecnologia é utilizada como viabilizadora, sendo a única forma de se perfurar os poços. Neste cenário, o entendimento do comportamento de migração de gás, quando da aplicação da técnica de Pressurized Mud Cap Drilling (PMCD), permite a elaboração do projeto de poço mais econômico além de contribuir para o aumento da segurança operacional. O presente estudo tem por objetivo apresentar um modelo matemático capaz de simular o comportamento da perda de fluido de perfuração para a formação com a ocorrência de influxo simultâneo e da migração de gás para a superfície, durante a perfuração com esta técnica, com robustez. É utilizado o modelo bifásico Drift-Flux associado ao método numérico Advection Upstream Splitting Method (AUSMV) para simular o comportamento descrito anteriormente. Antes da apresentação de estudos de casos de simulação com migração de gás, os resultados de cenários mais simples são comparados com os resultados de um software comercial tido, como referência na indústria para validação do programa. Através dos casos simulados é possível verificar a robustez do modelo matemático proposto, que se mostra capaz de fornecer respostas compatíveis quanto ao comportamento esperado do gás. A análise dos resultados obtidos permite estabelecer procedimentos para o monitoramento do que ocorre no poço de forma a otimizar as operações de bullhead no cenário de PMCD. / [en] The use of the Manage Pressure Drilling (MPD) is spreading in offshore operations. The increasing complexity in the new exploratory frontiers is demanding for new techniques to reduce costs and increase operational safety. MPD appears as an answer for that demand and sometimes it is the only viable way to drill some of the challenging wells. In that way, understanding the gas migration behavior while drilling in PMCD mode allows an optimized well design concerning cost and operational safety. The present study validates a mathematical model capable of simulating a scenario where loss of drilling fluid in the bottom of the well is present while having an influx from the same reservoir and observing gas migration to the surface in a PMCD operation. A Drift Flux Two Phase Flow Model is used in association with the Advection Upstream Splitting Method (AUSMV). Before the presentation and discussion of the complete PMCD scenario, two simple cases were simulated and the results were compared to the ones from a computer application considered as a reference to the industry, validating the proposed model. The results of the simulations can be used as a base for the elaboration of operational procedures to monitor gas behavior and optimize bullhead in PMCD scenarios.

Doctor of Philosophy / Department of Agronomy / Eduardo Alvarez Santos / Measurements of methane (CH₄) emissions from livestock production could provide invaluable data to reduce uncertainties in the global CH₄ budget and to evaluate mitigation strategies to lower greenhouse gas (GHG) emissions. The eddy covariance (EC) technique has recently been applied as an alternative to measure CH₄ emissions from livestock systems, but heterogeneities in the source area and fetch limitations impose challenges to EC measurements. The main objectives of this study were to: 1) assess the performance of a closed-path EC system for measuring CH₄, CO₂, and H₂0 fluxes; 2) investigate the spatial variability of the EC fluxes in a cattle feedlot using flux footprint analysis; 3) estimate CH₄ emission rates per animal (Fanimal) from a beef cattle feedlot using the EC technique combined with two footprint models: an analytical footprint model (KM01) and a parametrization of a Lagrangian dispersion model (FFP); and 4) compare CH₄ emissions obtained using the EC technique and a footprint analysis with CH₄ emission estimates provided by a well-stablished backward-Lagrangian stochastic (bLS) model. A closed-path EC system was used to measure CH₄, CO₂, and H₂0 fluxes. To evaluate the performance of this closed-path system, a well-stablished open-path EC system was also deployed on the flux tower to measure CO₂ and H₂0 exchange. Methane concentration measurements and wind data provided by that system were used to estimate CH₄ emissions using the bLS model. The performance assessment that included comparison of gas cospectra and measured fluxes from the two EC systems showed that the closed-path system was suitable for the EC measurements. Flux values were quite variable during the field experiment. A one-dimensional flux footprint model was useful to interpret some of the flux temporal and spatial dynamics. Then, a more comprehensive data analysis was carried out using two-dimensional footprint models (FFP and KM01) to interpret fluxes and scale fluxes measured at landscape to animal level. The monthly average Fanimal, calculated using the footprint weighed stocking density ranged from 83 to 125 g animal⁻¹ d⁻¹ (KM01) and 75–114 g animal⁻¹ d⁻¹ (FFP). These emission values are consistent with the results from previous studies in feedlots however our results also suggested that in some occasions the movement of animals on the pens could have affected CH₄ emission estimates. The results from the comparisons between EC and bLS CH₄ emission estimates show good agreement (0.84; concordance coefficient) between the two methods. In addition, the precision of the EC as compared to the bLS estimates was improved by using a more rigorous fetch screening criterion. Overall, these results indicate that the eddy covariance technique can be successfully used to accurately measure CH₄ emissions from feedlot cattle. However, further work is still needed to quantify the uncertainties in Fanimal caused by errors in flux footprint model estimates and animal movement.

Une compréhension profonde du transport du plasma au bord d'un réacteur à fusion par confinement magnétique est obligatoire pour gérer l'extraction de puissance. Dans les dispositifs de fusion de nouvelle génération, des limites technologiques contraignent le flux de chaleur maximal au divertor. Pour une puissance d'échappement donnée le flux de chaleur maximal est déterminé par l'amplitude de l'empreinte du plasma au mur. Les profils de flux de chaleur au divertor peuvent être paramétrés par deux échelles de longueur du transport. Nous remettons en question l'interprétation actuelle de ces deux échelles de longueur en étudiant l'impact de la géométrie du divertor sur l'échappement. En particulier, un élargissement des profils de flux de chaleur avec la longueur de la jambe du divertor externe est diagnostiqué. Des efforts de modélisation ont montré que les simulations diffusives reproduisent les profils expérimentaux de flux de chaleur pour les plasmas à jambes courtes. Inversement, l'étalement du flux de chaleur pour une longe jambe du divertor est reproduit par un modèle turbulent, soulignant l'importance de la turbulence aussi dans le divertor. Ces résultats remettent en question l'interprétation de la largeur du flux de chaleur comme grandeur liée a la main SOL uniquement. Les configurations magnétiques avec une longe jambe du divertor mettent en évidence l'importance du transport asymétrique dans le divertor. Nous concluons que le transport dans la main SOL et celui dans le divertor ne sont pas à découpler et nous soulignons l'importance de la géométrie magnétique sur le transport turbulent avec l'avantage potentiel d'un inattendu étalement du dépôt de puissance. / A deep understanding of plasma transport at the edge of a magnetically confined fusion device is mandatory for a sustainable and controlled handling of the power exhaust. In the next-generation fusion device ITER, technological limits constrain the peak heat flux on the divertor. For a given exhaust power the peak heat flux is determined by the extent of the plasma footprint on the wall. Heat flux profiles at the divertor targets of X-point configurations can be parametrized by using two length scales for the transport of heat in SOL. In this work, we challenge the current interpretation of these two length scales by studying the impact of divertor geometry modifications on the heat exhaust. In particular, a significant broadening of the heat flux profiles at the outer divertor target is diagnosed while increasing the length of the outer divertor leg. Modelling efforts showed that diffusive simulations well reproduce the experimental heat flux profiles for short-legged plasmas. Conversely, the broadening of the heat flux for a long divertor leg is reproduced by a turbulent model, highlighting the importance of turbulent transport not only in the main SOL but also in the divertor. These results question the current interpretation of the heat flux width as a purely main SOL transport length scale. In fact, long divertor leg magnetic configurations highlighted the importance of asymmetric divertor transport. We therefore conclude that main SOL and divertor SOL transport cannot be arbitrarily disentangled and we underline the importance of the divertor magnetic geometry in enhancing asymmetric turbulent transport with the potential benefit of an unexpected power spreading.