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    Authors: Lévy, Léa;

    The electrical signature of volcanoes is affected by several characteristics of rocks: volume and salinity of pore fluid, abundance of conductive minerals, rock temperature and presence of molten crust (magma). Electromagnetic soundings are widely used to image the underground structure of volcanoes and look for high-temperature geothermal resources. However, the relative contribution of the above-mentioned elements to the measured resistivity is often an unsolved question when interpreting resistivity inversions. This thesis aims at improving the interpretation of electrical resistivity structures at active volcanoes, in order to develop innovative tools for the assessment of high-enthalpy geothermal resources. Focus is on conductive minerals, which can either be solid ionic conductors (clay minerals, in particular smectite) or electronic semi-conductors (pyrite and iron-oxides). Also investigated are the effects of porosity, salinity, temperature and melting. Iron-oxides are mostly formed during the primary crystallization of magma, while smectite and pyrite are formed upon hydrothermal alteration of volcanic rocks, thereby witnessing hydrothermal convections. Krafla volcano, Iceland, is used as a laboratory area, where extensive literature, borehole data, core samples, surface soundings and infrastructures are available. The contribution of smectite to the electrical conductivity of volcanic samples saturated with pore water at different salinity is first investigated in the laboratory (room temperature) by electrical impedance spectroscopy, also called complex resistivity. Non-linear variations of the conductivity at 1 kHz with salinity are observed and interfoliar conduction is suggested as an important mechanism by which smectite conducts electrical current. The influence of pyrite and iron-oxides on the charge-storage (capacitive) properties of the rock is then analyzed, using the frequency-dependent phase-angle of the impedance. Maximum phase-angle (MPA) higher than 20 mrad can be attributed to pyrite if the rock is conductive and to iron-oxides if the rock is resistive. Moreover, the MPA increases by about 22 mrad for each additional volumetric per cent of pyrite or iron-oxide. These laboratory frequency-domain findings are partly upscaled to interpret field time-domain complex resistivity tomography at Krafla: smectite, pyrite and iron-oxides can be identified down to about 200 m with the measurements carried out. The in-situ temperature, higher than in laboratory conditions, appears to significantly increase the conductivity associated to smectite. In general, time-domain complex resistivity measurements are recommended as a complementary method to electromagnetic soundings for geothermal exploration. Rafeiginleikar bergs, bæði eðlisviðnám og fasvik, á eldfjallasvæðum eru m.a. háðir póruhluta (holrýmd) bergs, styrk uppleystra jóna í póruvökvanum (seltu), magni rafleiðandi steinda í berginu, hita þess og hvort það er bráðið eða storkið. Rafsegulmælingar eru notaðar til þess að skoða innri gerð eldfjalla og kanna háhitasvæði með því að búa til viðnámslíkön af þeim. Túlkun þeirra er oft flókin og vandasamt er að greina á milli fyrrnefndra þátta sem hafa áhrif á eðlisviðnám og fasa. Þessari ritgerð er ætlað að auka skilning á eðlisviðnámi jarðlaga í virkum eldstöðvum í því skyni að þróa þá tækni sem notuð er til þess að meta stærð og eiginleika háhitasvæða. Ritgerðin fjallar einkum um rafleiðandi steindir, sem eru annað hvort málmleiðarar (leirsteindir, einkum smektít) eða hálfleiðarar (pýrít og járnoxíð). Einnig eru rannsökuð áhrif póruhluta, styrks jóna í póruvökva, hita og bráðnunar bergs. Járnoxíð eru að mestu frumsteindir, þ.e.a.s. þau kristallast þegar bergkvikan kólnar. Smektít og pýrít myndast hins vegar sem útfellingar eða við ummyndun og bera vitni um hringrás jarðhitavökva. Notuð eru gögn frá eldstöðvakerfi Kröflu en þar eru til miklar heimildir eins og borholugögn, borkjarnar og yfirborðsmælingar og góð aðstaða til rannsókna. Áhrif smektíts í bergi á eðlisviðnám bergsýna voru mæld við stofuhita í tilraunastofu. Pórur þeirra voru mettaðar vökva með breytilegum styrk jóna og áhrifin könnuð með litrófsmælingu á eðlisviðnámi og fasa (tvinntöluviðnám). Niðurstöður sýna ólínulegar breytingar í viðnámi við 1 kHz tíðni sem fall af seltu vökvans. Sú tilgáta er sett fram að leiðni milli atómlaga í kristöllum, interfoliar conduction, eigi mikilvægan þátt í rafleiðni smektíts. Áhrif pýríts- og járnoxíðsteinda á rafrýmd bergs var könnuð með því að skoða hvernig fasahorn tvinntöluviðnáms er háð tíðni. Ef hámark fasahornsins (MPA) er stærra en 20 mrad stafar það af tilvist pýríts ef bergið er velleiðandi en járnoxíða ef bergið er torleiðandi. Þá eykst MPA um 22 mrad við hverja prósentu-aukningu í rúmmáli pýrits- eða járnoxíðsteinda. Þessar niðurstöður úr tilraunastofumælingum á tíðniháðu tvinntöluviðnámi voru nýttar til þess að túlka yfirborðsmælingar á tvinntöluviðnámi á Kröflusvæðinu. Tvinntöluviðnámslíkan frá Kröflusvæðinu sýnir að greina má tilvist smektíts, pýríts og járnoxíðs niður á um 200 m dýpi í mælingunum sem gerðar voru. Hiti jarðlaga, sem er hærri en í tilraunastofumælingum, virðist hækka verulega leiðni bergs sem inniheldur smektít. Lagt er til að mælingar á tvinntöluviðnámi verði notaðar til viðbótar við hefðbundnar rafleiðnimælingar við jarðhitarannsóknir vegna þeirra viðbótarupplýsinga sem fást með slíkum mælingum. Paris Sciences et Lettres; IMAGE FP7 European Project (grant agreement 608553); GEMex H2020 European Project (grant agreement 727550). Final thesis

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    Doctoral thesis . 2019
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    Authors: Castanet, Cyril; Nondédéo, Philippe; Dussol, Lydie; Testé, Marc; +17 Authors

    Dans les Basses-Terres mayas, des travaux récents fondés sur l’étude d’archives sédimentaires et de MNT LiDAR ont fait sauter des verrous scientifiques et techniques, renouvelant ainsi l’étude des dynamiques socio-environnementales aux échellesterritoriales. Cette étude de la nature et de la dynamique du socio-écosystème du territoire de subsistance de la cité maya de Naachtun, Guatemala, repose sur des développements méthodologiques systémiques, interdisciplinaires et multiscalaires (géoarchéologie, archéogéographie, paléoécologie, archéobotanique, archéozoologie, archéologie et géochronologie). Les résultats révèlent la complexité des territoires, milieux géographiques et paysages palimpsestes mayas et leur production durant la période ~1500 BCE – 1000 CE. Le socio-écosystème a évolué selon six principales périodes pluriséculaires. L’évolution des ressources (hydriques, éda-phiques, biologiques, minérales) et de leurs gestions est décrite en regard du climat et de la demande sociale. Les Mayas ont adapté leurs stratégies de gestion des ressources à ces changements. La gestion des risques environnementaux et la résilience des sociétés ont conditionné la durabilité du socio-écosystème. In the Maya Lowlands, recent work based on the study ofsedimentary archives and LiDAR DEM has contributed to remove scientific and technical barriers, and renew the study of socio-environmental dynamics at the territorial scale. This study of the nature and dynamics of the socio-ecosystem of the subsistence territory of the city of Naachtun is based on systemic, interdisciplinary and multi-scale methodological developments (geoarchaeology, archaeogeography, paleoecology,archaeobotany, zooarchaeology and geochronology). The results reveal the complexity of Maya palimpsest territories and landscapes and their production during the period from approximately 1500 BCE to 1000 CE. The socio-ecosystem evolved in relation to six main multi-secular periods. The evolution of resources (hydric, edaphic, biological, and mineral) and their management is described in relation to the climate and to the social demand. The Maya societies adapted their resource management strategies to these major changes. The management of environmental risks and the resilience of societies contributed to the sustainability of the socio-ecosystem

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    Authors: Camara, Mohamed Ansoumane;

    Le stockage par supercondensateurs de l'énergie photovoltaïque est modélisé afin de disposer d'un modèle suffisamment fin et accessible permettant de les intégrer dans des chaînes de conversion de l'énergie solaire. Les supercondensateurs sont modélisés par un circuit multibranche comportant des résistances et capacités variables suivant la tension, dont les valeurs sont déterminées par une expérience de caractérisation ayant une bonne précision. Par ailleurs, tous les éléments d'une chaîne typique de conversion de l'énergie photovoltaïque sont modélisés avec le logiciel Matlab/Simulink (gisement solaire, conversion photovoltaïque des panneaux, régulateur, batterie et charges). Le modèle de stockage de l'énergie photovoltaïque par supercondensateurs est ensuite validé par la bonne concordance des mesures relevées en conditions réelles avec les résultats donnés par les simulations. Enfin, deux exemples d'exploitation du modèle sont proposés et discutés : la détermination du temps de charge des supercondensateurs suivant l'éclairement solaire et la température ambiante, et l'intégration des supercondensateurs dans la chaîne d'alimentation électrique d'un moteur à courant continu permettant de réduire les sollicitations électriques sur la batterie lors de l'appel de puissance nécessaire au démarrage du moteur The storage by ultracapacitors of photovoltaic energy is modeled in order to have an accurate and accessible model to integrate ultracapacitors into solar energy conversion systems. Ultracapacitors are modeled by a multibranch circuit representation composed of resistors and capacitors with variable voltage whose values are determined by an accurate characterization experiment. Moreover, all the elements of a typical photovoltaic energy conversion system are modeled by using the Matlab/Simulink software (solar radiation, photovoltaic panels, batteries and charges). The energy storage model by ultracapacitors is then validated by the good agreement of measured values taken in real conditions with the results provided by simulations. Finally, two examples are proposed and discussed: the determination of the storage duration of ultracapacitors versus solar irradiance and ambient temperature, and the integration of ultracapacitors in the electrical feeding system of a DC motor to reduce the electrical current peak of the battery at the start of the motor

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  • Authors: Maïzia, Mindjid;
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    Authors: Amicy, Anne-Suze;

    This research is part of a dynamics of quality assessment and applicability of education on the environment in the science curriculum in elementary Haiti, while taking into account what is being practiced in France and Canada (Ontario). The analysis of the content of curricula of experimental sciences of these three (3) countries has served to mark such an approach. Irresponsible behaviors towards the environment faced with serious problems are aggravating factors that directly affect the entire population. Accelerated environmental degradation of the Republic of Haiti is a major concern that requires to look for more concrete and lasting actions in order to greatly contribute to solving these numerous problems. These findings require a different approach, a different way of thinking. It is a matter of orienting education and teaching to new paradigms including education on the environment enshrined in international forums as an important tool in the resolution of environmental problems and whose aim is to create citizens endowed with genuine environmental awareness. The analysis of the sciences curricula of elementary schools of the three countries under study allows to see that the school systems are moving more towards an education which tends to transmit and to make acquire knowledge about EE for the environment instead of placing the child in the real learning environment where he may develop close relationships with the environment. This observation led us to interview 50 school officials and 212 teachers of the fundamental level in Haiti about their vision, their knowledge and the place reserved to this concept in their teaching schedules. The result of the analysis of these data shows great ignorance of the concept in the school environment under study and in addition to that EE just widens the gap of school inequalities already obvious in Haiti. Cette recherche s’inscrit dans une dynamique d’évaluation de la qualité et de l’applicabilité de l’ERE dans le programme scolaire des deux premiers cycles du niveau fondamental en Haïti, tout en tenant compte de ce qui se fait en France et au Canada (Ontario). Des comportements irresponsables à l’égard de l’environnement constituent des facteurs aggravants ayant des incidences directes sur l'ensemble de la population. La dégradation écologique accélérée de la République d'Haïti est une préoccupation majeure qui oblige à tourner le regard vers des actions plus concrètes et durables susceptibles de contribuer grandement à la résolution de ces nombreux problèmes. Ce constat impose une autre approche, une autre forme de pensée. Il s’agit d’orienter l’éducation et l’enseignement vers de nouveaux paradigmes incluant l’ERE consacrée par les instances internationales comme un outil important dans la résolution des problèmes environnementaux et dont la finalité est de créer des citoyens dotés d’une vraie conscience écologique. L’analyse des curricula des sciences à l’élémentaire des trois pays étudiés permet de constater que les systèmes scolaires s'orientent plus vers une éducation qui tend à transmettre et à faire acquérir des connaissances en ERE plutôt que de placer l'enfant dans un contexte réel d'apprentissage où il peut développer des rapports étroits avec l’environnement. Cette observation nous amène à interroger 50 responsables d’établissements scolaires et 212 enseignants des écoles fondamentales en Haïti sur leur vision, leurs connaissances et la place réservée à cette notion dans leurs planifications pédagogiques. Le résultat de l’analyse de ces données démontre une grande méconnaissance de la notion dans le milieu scolaire étudié et qu'en outre l’ERE vient élargir le fossé des inégalités scolaires déjà criantes en Haïti.

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    Authors: Ortar, Nathalie; André, Michel; Bouzouina, Louafi; Contreras, Carla; +11 Authors

    L’objectif du projet TransEnergy financé par l’ANR Villes Durables 2010 était d’apporter des éléments de connaissance sur les stratégies d’adaptation des ménages et des entreprises à la transition énergétique en comparant les choix de localisation des ménages et des entreprises des métropoles de Lille et de Lyon. La recherche, conçue sur une analyse systémique, s’est appuyée sur une analyse des différentes échelles du territoire, des secteurs d’activités industriels et des contraintes des ménages. Elle a été produite grâce à une complémentarité disciplinaire (ont été mobilisées la sociologie, l’anthropologie, l’aménagement et les sciences de l’ingénieur) et des modes d’investigation du réel comprenant l’usage de méthodologies tant quantitatives que qualitatives.

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  • Authors: Colombert, Morgane; Salagnac, J.L.; Morand, Denis; Diab, Youssef;

    De l'observation du climat urbain à la modélisation plus ou moins fine des phénomènes physiques en jeu, les climatologues ont pu décrire et comprendre avec de plus en plus de précision la formation du climat urbain. Si les premiers travaux étaient avant tout consacrés à l'îlot de chaleur urbain observé globalement sur toute l'agglomération, les climatologues se sont progressivement intéressés à d'autres paramètres climatiques (pluviométrie, vent, etc.) puis à des échelles inférieures à la ville mettant ainsi en exergue l'importance de la géométrie urbaine et des matériaux de construction. La climatologie urbaine est aujourd'hui un domaine de recherche investi à la fois par les climatologues et les géographes, mais également par les architectes et les urbanistes. Ceci permet de mettre en place une démarche pluridisciplinaire et d'intégrer à la pratique de l'aménagement urbain et de l'architecture des éléments de climatologie urbaine. Climatologues, géographes et aussi urbanistes et architectes réfléchissent ainsi ensemble ou parallèlement à l'intérêt de prendre en compte le climat urbain dans l'aménagement, l'urbanisme et l'architecture. Plus que le développement de nouveaux outils permettant de prendre en compte le climat urbain dans la conception urbaine, il s'agit aujourd'hui d'abord de promouvoir et d'organiser une meilleure synergie entre les différentes actions menées en faveur de l'environnement. Les trames vertes urbaines en sont un bel exemple. Initialement mises en oeuvre pour favoriser les flux d'espèces animales et végétales et donc la biodiversité, elles peuvent également améliorer la qualité climatique des espaces quand il s'agit d'espaces verts ou de végétation. With the observation of the urban climate and after the modeling of the physical phenomena, the climatologists are and were able to describe and to understand with more and more precision the formation of the urban climate. The first works were above all dedicated to the urban heat island observed globally on all the urban area. The climatologists were gradually interested in the other climatic parameters (pluviometry, wind, etc.) and in lower scales than the city, highlighting the importance of the urban geometry and the building materials. The urban climatology is a research thematic investigated at the same time by the climatologists and the geographers, but also by the architects and the town planners. This allows to set up a multidisciplinary approach and to integrate into the practice of the urban planning and the architecture some elements of urban climatology. So climatologists, geographers, town planners and architects could reflect together on the interest to take into account the urban climate in the urban planning and the architecture. We need some tools allowing to take into account the urban climate in the urban conception but priory has to be given to promote and to organize a better synergy between the various actions led in favour of the environment. Green infrastructures are a good example. Initially implemented to provide connexions between natural habitats of species by corridors, they can also improve the climatic quality of spaces

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    Authors: Kanjanapinyowong, Natthaporn;

    En raison du changement climatique, le monde doit de plus en plus faire face aux urgences environnementales. Plusieurs questions écologiques, notamment énergétiques, surgissent globalement d’une manière préoccupante et impose dans les esprits la nécessité d’une « transition énergétique » comme solution. Cette transition implique des changements économiques, politiques et sociétaux n’engagent plus la seule responsabilité gouvernementale. Et c’est au nom de ce principe que les autorités ont appelé tout à chacun à se prononcer sur ces questions lors du Débat National sur la Transition Énergétique (DNTE) en France en 2013. L’objectif principal de cette thèse est d’exposer les spécificités discursives et textuelles de ce débat national, depuis son origine jusqu’à son aboutissement présenté sous forme de synthèse. En situant dans le cadre théorique de l’analyse du discours, ce travail recourt à diverses approches : historique, communicationnelle, socio-politique et linguistique. Il entend en particulier décrire la fabrication des synthèses de ce débat et leur dimension textuelle pour à la fois rendre compte des caractéristiques propres du DNTE et son issue, laquelle devant permettre en principe au gouvernement de délibérer et décider sur des politiques à adopter. Due to climate change, the world is experiencing numerous environmental problems, which are in urgent need of solutions. Among the major ecological concerns being discussed globally are energy-related problems. The "energy transition" is known as an effective solution to such a situation. This implies the economic, political and societal changes that the government is no longer solely responsible for this global issue. In France, everyone is called upon to take a stand as evidenced by the National Debate on Energy Transition (DNTE) in 2013. The main objective of this thesis is to demonstrate the discursive and textual specificities of this national debate, from its origin to its completion presented in the form of synthesis. Within the theoretical framework of the French discourse analysis, this thesis combines historical, communicational, socio-political and linguistic approaches to analyze the debate. It focuses particularly on describing the production of the synthesis of this debate and their textual dimension in order to show the specific characteristics of the DNTE as well as its result which allows the government to deliberate and decide on the policies to adopt.

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    Authors: Kraiem, Manel;

    La consommation énergétique mondiale croissante depuis plusieurs décennies se heurte à la raréfaction des ressources fossiles et aux risques planétaires. Face à ces problèmes, le stockage de chaleur moyennant des matériaux à changement de phase solide -liquide « MCPs » présente une solution prometteuse. Il permet de bénéficier pleinement des énergies renouvelables et il contribue à la gestion thermique des systèmes énergétiques. Les MCPs ont la capacité de stocker et libérer de l'énergie thermique lors du passage d'une phase à une autre. Cependant, l’utilisation de ces matériaux est pénalisée par leurs faibles conductivités thermiques qui limitent les puissances du stockage de chaleur. Ce travail de thèse vise à étudier les paraffines type RT21-27-35HC et RT50 et leurs imprégnations dans des mousses métalliques. La première partie de cette contribution est consacrée à la caractérisation thermophysique de ces paraffines en fonction de la température. Des analyses calorimétriques différentielles « DSC » et thermogravimétriques « TGA » ont été menées. Les conductivités et les diffusivités thermiques ont été mesurées à différentes températures en utilisant la méthode « Hot disk ». La thermodépendance de leurs masses volumiques a été investiguée. Comme le comportement des MCPs au cours du changement de phase solide-liquide est piloté par la dynamique des transferts de chaleur, une étude expérimentale de la fusion de la paraffine RT27 a été menée dans une seconde partie. Elle a été réalisée en utilisant un nouveau dispositif expérimental développé spécialement au laboratoire. La visualisation de l’interface solide/liquide et les mesures de température dans le MCP mettent en exergue les régimes de transfert de chaleur pilotant la fusion : régime conductif, régime mixte et régime de convection. L’étude de l’évolution de la fraction liquide en fonction du temps permet d’analyser la cinétique de fusion et de déterminer l’évolution de la chaleur stockée lors de la fusion de RT27. L’étude des composites mousses métalliques/paraffines a été effectuée dans la troisième section du ce travail. Les paraffines RT21-27-35HC ont été imprégnées dans des mousses métalliques type aluminium et nickel. Les facteurs d’imprégnation des échantillons préparés ont montré le succès du protocole de préparation réalisé au laboratoire. Les mesures des conductivités thermiques montrent que l’utilisation des mousses d’aluminium et de nickel engendrent des intensifications atteignant 1751,4% et 666,8%. Les conductivités thermiques expérimentales ont été comparées ensuite à des modèles théoriques. Les masses volumiques et les chaleurs spécifiques des composites ont été également déterminées. Une étude des composites mousses métalliques/RT27 par plaque chaude gardée transitoire « PCGT » a été finalement réalisée. Elle a visé à comparer les conductivités thermiques mesurées par « hot disk » et les chaleurs spécifiques calculées à celles obtenues par « PCGT ». The word energy consumption increased in the last decades and a continues increase in the future is predicted. An effective utilization of energy is highly required due to the scarcity of fossils fuels and to the rise of greenhouse gas emissions. In this context, thermal energy storage using solid-liquid phase change materials «PCMs» is a promising solution for saving energy. It attracts a great growing interest in many applications such as buildings, thermal control of electronic devices and thermal management of Li-ion batteries. However, it is hampered by the low thermal conductivities of PCMs which limits the storage/release rate. Hence, the enhancement of the thermal conductivity of PCMs is an important issue for the latent storage systems. This thesis studies paraffins RT21-27-35HC- RT50 and metal foams/paraffins composites. The determination of the thermophysical properties of paraffins at different temperature is firstly carried out. The differential scanning calorimetry « DSC » measurements and thermogravimetric analyses « TGA » were performed. The thermal conductivities and diffusivities of PCMs were measured by the « Hot disk» method at different temperatures. The thermodependency of their densities was also studied. Since the thermal behavior of PCMs during the solid-liquid phase change is controlled by the heat transfer mechanisms, an experimental investigation of the melting of the paraffin RT27 was conducted in the second part of this work. A new experimental device was set up in the laboratory to study the heat transfer characteristics. The visualization of the melting interface and the recording of temperature in the PCM indicate the heat transfer regimes controlling the melting process: conduction, transition regime and natural convection. The evolution of the melting fraction was used to study the kinetic of the melting process and the temporal evolution of the heat stored in RT27. The last part of this work was dedicated to the investigation of metal foams/paraffins composites. The paraffins RT21-27-RT35HC were impregnated in aluminum and nickel foams. The impregnation ratios of the composites highlighted the effectiveness of the procedure preparation. The thermal conductivities of the composites metal foams/paraffins at the solid phase were measured by the « hot disk » method. The results revealed that the thermal conductivities of aluminum foam/paraffins and nickel foams/paraffins are increased drastically until 1751,4% and 666,8% respectively. The experimental results were compared to the theoretical models. Densities’ measurements of metal foams filled with paraffins were realized. The specific heats of samples were calculated from experimental results. A study of the composites metal foams/ RT27 was conducted finally by the transient guarded hot plate « TGHP». It aims to compare the thermal conductivities obtained by « hot disk» and the calculated specific heats to those measured by « TGHP».

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    Authors: Lafaye, Paul;

    Les alliages de zirconium sont utilisés comme matériaux de gainage des combustibles nucléaires dans les réacteurs à eau pressurisée. Ces gaines sont utilisées dans un milieu extrêmement radiatif et corrosif, elles peuvent dans certains cas être le siège de fortes variations de température et doivent répondre à des sollicitations mécaniques importantes, que ce soit en conditions de service ou accidentelles. Dans un tel contexte, il est intéressant de pouvoir prédire les transformations de phases ayant lieu au sein de la gaine en fonction des variations de température et de composition chimique, la précipitation de phases fragiles induites par la présence des éléments d’alliages, mais aussi de tester de nouvelles compositions d’alliages afin de l’optimiser.La méthode la plus adaptée pour la modélisation thermodynamique de systèmes multiconstitués est la méthode Calphad (CALculation of PHAse Diagrams). Il s’agit d’une méthode semi-empirique, consistant à modéliser les enthalpies libres des différentes phases constitutives d’un système par ajustement de certains paramètres, dans le but de reproduire les données expérimentales.Ce mémoire détaille la construction d’une base de données thermodynamiques du système quinaire Cr-Fe-Nb-Sn-Zr selon la méthode Calphad. L’originalité de notre démarche est liée à l’utilisation des calculs DFT de manière systématique et massive. Il s’agit en particulier de calculer par DFT les enthalpies de formation de tous les end-members des phases intermétalliques constitutives du système quinaire. De plus, des calculs sur des mailles « quasi aléatoires » (SQS) sont également effectués de manière systématique afin de déterminer les enthalpies de mélange des solutions solides binaires en structure fcc, bcc et hcp. En outre, une étape importante de ce travail consiste à compléter les données expérimentales de la littérature par de nouvelles mesures sur des systèmes choisis. En particulier, nous nous sommes employés à décrire quelques équilibres de phases des systèmes ternaires Cr-Nb-Sn, Cr-Fe-Sn, Cr-Sn-Zr et Fe-Nb-Sn qui n’avaient jamais été déterminés expérimentalement. Nous avons ensuite utilisé ces calculs et ces nouvelles données expérimentales en complément de données de la littérature comme données d’entrée pour la modélisation thermodynamique des vingt sous-systèmes binaires et ternaires du système quinaire considéré. Enfin, le pouvoir prédictif de notre base de données a pu être vérifié en confrontant ces prédictions à des données expérimentales relatives à des alliages quinaires industriels ou à de nouveaux concepts de gaines Currently, zirconium alloys are used as fuel cladding materials in PWR (Pressurized Water Reactors). The claddings stand in a very corrosive and radiative environnement, and can be submitted to temperature variations. In addition, the claddings will be subjected to mechanical stresses in reactor or accidental conditions. Thus, it appears useful to have a better understanding of phase transformations occurring in these alloys, as a function of temperature and chemical composition variations, but also to forecast the precipitation of fragile phases induced by the addition of alloying elements. At last, the ability to test new alloy compositions may allow to optimize it.The most suitable method for the thermodynamic modeling of multicomponent systems is the Calphad method (CALculation of PHAse Diagrams). The Calphad method is a widely used technique of semi-empirical modelling of phase diagrams. It consists in the description of the Gibbs energies of the different phases by fitting parameters allowing to describe the experimental data.This report details the design of a thermodynamic database considering the five following elements Zr, Cr, Fe, Nb, and Sn. The originality of this database lies in a systematic use of DFT calculations. Indeed, DFT calculations are performed to predict the formation enthalpy of the intermetallic phases appearing in these systems. Moreover, the SQS method (Special Quasirandom Structure) is used to predict the mixing enthalpy of the fcc, bcc and hcp binary solid solutions. Besides, experimental investigations are an important step of this thesis. Since no experimental data were available for the Cr-Fe-Sn, Cr-Nb-Sn, Cr-Sn-Zr and Fe-Nb-Sn ternary systems, new experimental data are provided, within this study, on the isothermal sections of these systems at different temperatures. All these calculated data in addition to the experimental data and the data from literature are used as input data for the Calphad modelling of the twenty binary and ternary systems which are then combined in the new database. A last part is dedicated to comparisons between predictions obtained with our new database and experimental results on industrial quinary alloys and a new concept of claddings

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    Authors: Lévy, Léa;

    The electrical signature of volcanoes is affected by several characteristics of rocks: volume and salinity of pore fluid, abundance of conductive minerals, rock temperature and presence of molten crust (magma). Electromagnetic soundings are widely used to image the underground structure of volcanoes and look for high-temperature geothermal resources. However, the relative contribution of the above-mentioned elements to the measured resistivity is often an unsolved question when interpreting resistivity inversions. This thesis aims at improving the interpretation of electrical resistivity structures at active volcanoes, in order to develop innovative tools for the assessment of high-enthalpy geothermal resources. Focus is on conductive minerals, which can either be solid ionic conductors (clay minerals, in particular smectite) or electronic semi-conductors (pyrite and iron-oxides). Also investigated are the effects of porosity, salinity, temperature and melting. Iron-oxides are mostly formed during the primary crystallization of magma, while smectite and pyrite are formed upon hydrothermal alteration of volcanic rocks, thereby witnessing hydrothermal convections. Krafla volcano, Iceland, is used as a laboratory area, where extensive literature, borehole data, core samples, surface soundings and infrastructures are available. The contribution of smectite to the electrical conductivity of volcanic samples saturated with pore water at different salinity is first investigated in the laboratory (room temperature) by electrical impedance spectroscopy, also called complex resistivity. Non-linear variations of the conductivity at 1 kHz with salinity are observed and interfoliar conduction is suggested as an important mechanism by which smectite conducts electrical current. The influence of pyrite and iron-oxides on the charge-storage (capacitive) properties of the rock is then analyzed, using the frequency-dependent phase-angle of the impedance. Maximum phase-angle (MPA) higher than 20 mrad can be attributed to pyrite if the rock is conductive and to iron-oxides if the rock is resistive. Moreover, the MPA increases by about 22 mrad for each additional volumetric per cent of pyrite or iron-oxide. These laboratory frequency-domain findings are partly upscaled to interpret field time-domain complex resistivity tomography at Krafla: smectite, pyrite and iron-oxides can be identified down to about 200 m with the measurements carried out. The in-situ temperature, higher than in laboratory conditions, appears to significantly increase the conductivity associated to smectite. In general, time-domain complex resistivity measurements are recommended as a complementary method to electromagnetic soundings for geothermal exploration. Rafeiginleikar bergs, bæði eðlisviðnám og fasvik, á eldfjallasvæðum eru m.a. háðir póruhluta (holrýmd) bergs, styrk uppleystra jóna í póruvökvanum (seltu), magni rafleiðandi steinda í berginu, hita þess og hvort það er bráðið eða storkið. Rafsegulmælingar eru notaðar til þess að skoða innri gerð eldfjalla og kanna háhitasvæði með því að búa til viðnámslíkön af þeim. Túlkun þeirra er oft flókin og vandasamt er að greina á milli fyrrnefndra þátta sem hafa áhrif á eðlisviðnám og fasa. Þessari ritgerð er ætlað að auka skilning á eðlisviðnámi jarðlaga í virkum eldstöðvum í því skyni að þróa þá tækni sem notuð er til þess að meta stærð og eiginleika háhitasvæða. Ritgerðin fjallar einkum um rafleiðandi steindir, sem eru annað hvort málmleiðarar (leirsteindir, einkum smektít) eða hálfleiðarar (pýrít og járnoxíð). Einnig eru rannsökuð áhrif póruhluta, styrks jóna í póruvökva, hita og bráðnunar bergs. Járnoxíð eru að mestu frumsteindir, þ.e.a.s. þau kristallast þegar bergkvikan kólnar. Smektít og pýrít myndast hins vegar sem útfellingar eða við ummyndun og bera vitni um hringrás jarðhitavökva. Notuð eru gögn frá eldstöðvakerfi Kröflu en þar eru til miklar heimildir eins og borholugögn, borkjarnar og yfirborðsmælingar og góð aðstaða til rannsókna. Áhrif smektíts í bergi á eðlisviðnám bergsýna voru mæld við stofuhita í tilraunastofu. Pórur þeirra voru mettaðar vökva með breytilegum styrk jóna og áhrifin könnuð með litrófsmælingu á eðlisviðnámi og fasa (tvinntöluviðnám). Niðurstöður sýna ólínulegar breytingar í viðnámi við 1 kHz tíðni sem fall af seltu vökvans. Sú tilgáta er sett fram að leiðni milli atómlaga í kristöllum, interfoliar conduction, eigi mikilvægan þátt í rafleiðni smektíts. Áhrif pýríts- og járnoxíðsteinda á rafrýmd bergs var könnuð með því að skoða hvernig fasahorn tvinntöluviðnáms er háð tíðni. Ef hámark fasahornsins (MPA) er stærra en 20 mrad stafar það af tilvist pýríts ef bergið er velleiðandi en járnoxíða ef bergið er torleiðandi. Þá eykst MPA um 22 mrad við hverja prósentu-aukningu í rúmmáli pýrits- eða járnoxíðsteinda. Þessar niðurstöður úr tilraunastofumælingum á tíðniháðu tvinntöluviðnámi voru nýttar til þess að túlka yfirborðsmælingar á tvinntöluviðnámi á Kröflusvæðinu. Tvinntöluviðnámslíkan frá Kröflusvæðinu sýnir að greina má tilvist smektíts, pýríts og járnoxíðs niður á um 200 m dýpi í mælingunum sem gerðar voru. Hiti jarðlaga, sem er hærri en í tilraunastofumælingum, virðist hækka verulega leiðni bergs sem inniheldur smektít. Lagt er til að mælingar á tvinntöluviðnámi verði notaðar til viðbótar við hefðbundnar rafleiðnimælingar við jarðhitarannsóknir vegna þeirra viðbótarupplýsinga sem fást með slíkum mælingum. Paris Sciences et Lettres; IMAGE FP7 European Project (grant agreement 608553); GEMex H2020 European Project (grant agreement 727550). Final thesis

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    Doctoral thesis . 2019
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    Authors: Castanet, Cyril; Nondédéo, Philippe; Dussol, Lydie; Testé, Marc; +17 Authors

    Dans les Basses-Terres mayas, des travaux récents fondés sur l’étude d’archives sédimentaires et de MNT LiDAR ont fait sauter des verrous scientifiques et techniques, renouvelant ainsi l’étude des dynamiques socio-environnementales aux échellesterritoriales. Cette étude de la nature et de la dynamique du socio-écosystème du territoire de subsistance de la cité maya de Naachtun, Guatemala, repose sur des développements méthodologiques systémiques, interdisciplinaires et multiscalaires (géoarchéologie, archéogéographie, paléoécologie, archéobotanique, archéozoologie, archéologie et géochronologie). Les résultats révèlent la complexité des territoires, milieux géographiques et paysages palimpsestes mayas et leur production durant la période ~1500 BCE – 1000 CE. Le socio-écosystème a évolué selon six principales périodes pluriséculaires. L’évolution des ressources (hydriques, éda-phiques, biologiques, minérales) et de leurs gestions est décrite en regard du climat et de la demande sociale. Les Mayas ont adapté leurs stratégies de gestion des ressources à ces changements. La gestion des risques environnementaux et la résilience des sociétés ont conditionné la durabilité du socio-écosystème. In the Maya Lowlands, recent work based on the study ofsedimentary archives and LiDAR DEM has contributed to remove scientific and technical barriers, and renew the study of socio-environmental dynamics at the territorial scale. This study of the nature and dynamics of the socio-ecosystem of the subsistence territory of the city of Naachtun is based on systemic, interdisciplinary and multi-scale methodological developments (geoarchaeology, archaeogeography, paleoecology,archaeobotany, zooarchaeology and geochronology). The results reveal the complexity of Maya palimpsest territories and landscapes and their production during the period from approximately 1500 BCE to 1000 CE. The socio-ecosystem evolved in relation to six main multi-secular periods. The evolution of resources (hydric, edaphic, biological, and mineral) and their management is described in relation to the climate and to the social demand. The Maya societies adapted their resource management strategies to these major changes. The management of environmental risks and the resilience of societies contributed to the sustainability of the socio-ecosystem

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    Authors: Camara, Mohamed Ansoumane;

    Le stockage par supercondensateurs de l'énergie photovoltaïque est modélisé afin de disposer d'un modèle suffisamment fin et accessible permettant de les intégrer dans des chaînes de conversion de l'énergie solaire. Les supercondensateurs sont modélisés par un circuit multibranche comportant des résistances et capacités variables suivant la tension, dont les valeurs sont déterminées par une expérience de caractérisation ayant une bonne précision. Par ailleurs, tous les éléments d'une chaîne typique de conversion de l'énergie photovoltaïque sont modélisés avec le logiciel Matlab/Simulink (gisement solaire, conversion photovoltaïque des panneaux, régulateur, batterie et charges). Le modèle de stockage de l'énergie photovoltaïque par supercondensateurs est ensuite validé par la bonne concordance des mesures relevées en conditions réelles avec les résultats donnés par les simulations. Enfin, deux exemples d'exploitation du modèle sont proposés et discutés : la détermination du temps de charge des supercondensateurs suivant l'éclairement solaire et la température ambiante, et l'intégration des supercondensateurs dans la chaîne d'alimentation électrique d'un moteur à courant continu permettant de réduire les sollicitations électriques sur la batterie lors de l'appel de puissance nécessaire au démarrage du moteur The storage by ultracapacitors of photovoltaic energy is modeled in order to have an accurate and accessible model to integrate ultracapacitors into solar energy conversion systems. Ultracapacitors are modeled by a multibranch circuit representation composed of resistors and capacitors with variable voltage whose values are determined by an accurate characterization experiment. Moreover, all the elements of a typical photovoltaic energy conversion system are modeled by using the Matlab/Simulink software (solar radiation, photovoltaic panels, batteries and charges). The energy storage model by ultracapacitors is then validated by the good agreement of measured values taken in real conditions with the results provided by simulations. Finally, two examples are proposed and discussed: the determination of the storage duration of ultracapacitors versus solar irradiance and ambient temperature, and the integration of ultracapacitors in the electrical feeding system of a DC motor to reduce the electrical current peak of the battery at the start of the motor

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  • Authors: Maïzia, Mindjid;
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    Authors: Amicy, Anne-Suze;

    This research is part of a dynamics of quality assessment and applicability of education on the environment in the science curriculum in elementary Haiti, while taking into account what is being practiced in France and Canada (Ontario). The analysis of the content of curricula of experimental sciences of these three (3) countries has served to mark such an approach. Irresponsible behaviors towards the environment faced with serious problems are aggravating factors that directly affect the entire population. Accelerated environmental degradation of the Republic of Haiti is a major concern that requires to look for more concrete and lasting actions in order to greatly contribute to solving these numerous problems. These findings require a different approach, a different way of thinking. It is a matter of orienting education and teaching to new paradigms including education on the environment enshrined in international forums as an important tool in the resolution of environmental problems and whose aim is to create citizens endowed with genuine environmental awareness. The analysis of the sciences curricula of elementary schools of the three countries under study allows to see that the school systems are moving more towards an education which tends to transmit and to make acquire knowledge about EE for the environment instead of placing the child in the real learning environment where he may develop close relationships with the environment. This observation led us to interview 50 school officials and 212 teachers of the fundamental level in Haiti about their vision, their knowledge and the place reserved to this concept in their teaching schedules. The result of the analysis of these data shows great ignorance of the concept in the school environment under study and in addition to that EE just widens the gap of school inequalities already obvious in Haiti. Cette recherche s’inscrit dans une dynamique d’évaluation de la qualité et de l’applicabilité de l’ERE dans le programme scolaire des deux premiers cycles du niveau fondamental en Haïti, tout en tenant compte de ce qui se fait en France et au Canada (Ontario). Des comportements irresponsables à l’égard de l’environnement constituent des facteurs aggravants ayant des incidences directes sur l'ensemble de la population. La dégradation écologique accélérée de la République d'Haïti est une préoccupation majeure qui oblige à tourner le regard vers des actions plus concrètes et durables susceptibles de contribuer grandement à la résolution de ces nombreux problèmes. Ce constat impose une autre approche, une autre forme de pensée. Il s’agit d’orienter l’éducation et l’enseignement vers de nouveaux paradigmes incluant l’ERE consacrée par les instances internationales comme un outil important dans la résolution des problèmes environnementaux et dont la finalité est de créer des citoyens dotés d’une vraie conscience écologique. L’analyse des curricula des sciences à l’élémentaire des trois pays étudiés permet de constater que les systèmes scolaires s'orientent plus vers une éducation qui tend à transmettre et à faire acquérir des connaissances en ERE plutôt que de placer l'enfant dans un contexte réel d'apprentissage où il peut développer des rapports étroits avec l’environnement. Cette observation nous amène à interroger 50 responsables d’établissements scolaires et 212 enseignants des écoles fondamentales en Haïti sur leur vision, leurs connaissances et la place réservée à cette notion dans leurs planifications pédagogiques. Le résultat de l’analyse de ces données démontre une grande méconnaissance de la notion dans le milieu scolaire étudié et qu'en outre l’ERE vient élargir le fossé des inégalités scolaires déjà criantes en Haïti.

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    Authors: Ortar, Nathalie; André, Michel; Bouzouina, Louafi; Contreras, Carla; +11 Authors

    L’objectif du projet TransEnergy financé par l’ANR Villes Durables 2010 était d’apporter des éléments de connaissance sur les stratégies d’adaptation des ménages et des entreprises à la transition énergétique en comparant les choix de localisation des ménages et des entreprises des métropoles de Lille et de Lyon. La recherche, conçue sur une analyse systémique, s’est appuyée sur une analyse des différentes échelles du territoire, des secteurs d’activités industriels et des contraintes des ménages. Elle a été produite grâce à une complémentarité disciplinaire (ont été mobilisées la sociologie, l’anthropologie, l’aménagement et les sciences de l’ingénieur) et des modes d’investigation du réel comprenant l’usage de méthodologies tant quantitatives que qualitatives.

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  • Authors: Colombert, Morgane; Salagnac, J.L.; Morand, Denis; Diab, Youssef;

    De l'observation du climat urbain à la modélisation plus ou moins fine des phénomènes physiques en jeu, les climatologues ont pu décrire et comprendre avec de plus en plus de précision la formation du climat urbain. Si les premiers travaux étaient avant tout consacrés à l'îlot de chaleur urbain observé globalement sur toute l'agglomération, les climatologues se sont progressivement intéressés à d'autres paramètres climatiques (pluviométrie, vent, etc.) puis à des échelles inférieures à la ville mettant ainsi en exergue l'importance de la géométrie urbaine et des matériaux de construction. La climatologie urbaine est aujourd'hui un domaine de recherche investi à la fois par les climatologues et les géographes, mais également par les architectes et les urbanistes. Ceci permet de mettre en place une démarche pluridisciplinaire et d'intégrer à la pratique de l'aménagement urbain et de l'architecture des éléments de climatologie urbaine. Climatologues, géographes et aussi urbanistes et architectes réfléchissent ainsi ensemble ou parallèlement à l'intérêt de prendre en compte le climat urbain dans l'aménagement, l'urbanisme et l'architecture. Plus que le développement de nouveaux outils permettant de prendre en compte le climat urbain dans la conception urbaine, il s'agit aujourd'hui d'abord de promouvoir et d'organiser une meilleure synergie entre les différentes actions menées en faveur de l'environnement. Les trames vertes urbaines en sont un bel exemple. Initialement mises en oeuvre pour favoriser les flux d'espèces animales et végétales et donc la biodiversité, elles peuvent également améliorer la qualité climatique des espaces quand il s'agit d'espaces verts ou de végétation. With the observation of the urban climate and after the modeling of the physical phenomena, the climatologists are and were able to describe and to understand with more and more precision the formation of the urban climate. The first works were above all dedicated to the urban heat island observed globally on all the urban area. The climatologists were gradually interested in the other climatic parameters (pluviometry, wind, etc.) and in lower scales than the city, highlighting the importance of the urban geometry and the building materials. The urban climatology is a research thematic investigated at the same time by the climatologists and the geographers, but also by the architects and the town planners. This allows to set up a multidisciplinary approach and to integrate into the practice of the urban planning and the architecture some elements of urban climatology. So climatologists, geographers, town planners and architects could reflect together on the interest to take into account the urban climate in the urban planning and the architecture. We need some tools allowing to take into account the urban climate in the urban conception but priory has to be given to promote and to organize a better synergy between the various actions led in favour of the environment. Green infrastructures are a good example. Initially implemented to provide connexions between natural habitats of species by corridors, they can also improve the climatic quality of spaces

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    Authors: Kanjanapinyowong, Natthaporn;

    En raison du changement climatique, le monde doit de plus en plus faire face aux urgences environnementales. Plusieurs questions écologiques, notamment énergétiques, surgissent globalement d’une manière préoccupante et impose dans les esprits la nécessité d’une « transition énergétique » comme solution. Cette transition implique des changements économiques, politiques et sociétaux n’engagent plus la seule responsabilité gouvernementale. Et c’est au nom de ce principe que les autorités ont appelé tout à chacun à se prononcer sur ces questions lors du Débat National sur la Transition Énergétique (DNTE) en France en 2013. L’objectif principal de cette thèse est d’exposer les spécificités discursives et textuelles de ce débat national, depuis son origine jusqu’à son aboutissement présenté sous forme de synthèse. En situant dans le cadre théorique de l’analyse du discours, ce travail recourt à diverses approches : historique, communicationnelle, socio-politique et linguistique. Il entend en particulier décrire la fabrication des synthèses de ce débat et leur dimension textuelle pour à la fois rendre compte des caractéristiques propres du DNTE et son issue, laquelle devant permettre en principe au gouvernement de délibérer et décider sur des politiques à adopter. Due to climate change, the world is experiencing numerous environmental problems, which are in urgent need of solutions. Among the major ecological concerns being discussed globally are energy-related problems. The "energy transition" is known as an effective solution to such a situation. This implies the economic, political and societal changes that the government is no longer solely responsible for this global issue. In France, everyone is called upon to take a stand as evidenced by the National Debate on Energy Transition (DNTE) in 2013. The main objective of this thesis is to demonstrate the discursive and textual specificities of this national debate, from its origin to its completion presented in the form of synthesis. Within the theoretical framework of the French discourse analysis, this thesis combines historical, communicational, socio-political and linguistic approaches to analyze the debate. It focuses particularly on describing the production of the synthesis of this debate and their textual dimension in order to show the specific characteristics of the DNTE as well as its result which allows the government to deliberate and decide on the policies to adopt.

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    Authors: Kraiem, Manel;

    La consommation énergétique mondiale croissante depuis plusieurs décennies se heurte à la raréfaction des ressources fossiles et aux risques planétaires. Face à ces problèmes, le stockage de chaleur moyennant des matériaux à changement de phase solide -liquide « MCPs » présente une solution prometteuse. Il permet de bénéficier pleinement des énergies renouvelables et il contribue à la gestion thermique des systèmes énergétiques. Les MCPs ont la capacité de stocker et libérer de l'énergie thermique lors du passage d'une phase à une autre. Cependant, l’utilisation de ces matériaux est pénalisée par leurs faibles conductivités thermiques qui limitent les puissances du stockage de chaleur. Ce travail de thèse vise à étudier les paraffines type RT21-27-35HC et RT50 et leurs imprégnations dans des mousses métalliques. La première partie de cette contribution est consacrée à la caractérisation thermophysique de ces paraffines en fonction de la température. Des analyses calorimétriques différentielles « DSC » et thermogravimétriques « TGA » ont été menées. Les conductivités et les diffusivités thermiques ont été mesurées à différentes températures en utilisant la méthode « Hot disk ». La thermodépendance de leurs masses volumiques a été investiguée. Comme le comportement des MCPs au cours du changement de phase solide-liquide est piloté par la dynamique des transferts de chaleur, une étude expérimentale de la fusion de la paraffine RT27 a été menée dans une seconde partie. Elle a été réalisée en utilisant un nouveau dispositif expérimental développé spécialement au laboratoire. La visualisation de l’interface solide/liquide et les mesures de température dans le MCP mettent en exergue les régimes de transfert de chaleur pilotant la fusion : régime conductif, régime mixte et régime de convection. L’étude de l’évolution de la fraction liquide en fonction du temps permet d’analyser la cinétique de fusion et de déterminer l’évolution de la chaleur stockée lors de la fusion de RT27. L’étude des composites mousses métalliques/paraffines a été effectuée dans la troisième section du ce travail. Les paraffines RT21-27-35HC ont été imprégnées dans des mousses métalliques type aluminium et nickel. Les facteurs d’imprégnation des échantillons préparés ont montré le succès du protocole de préparation réalisé au laboratoire. Les mesures des conductivités thermiques montrent que l’utilisation des mousses d’aluminium et de nickel engendrent des intensifications atteignant 1751,4% et 666,8%. Les conductivités thermiques expérimentales ont été comparées ensuite à des modèles théoriques. Les masses volumiques et les chaleurs spécifiques des composites ont été également déterminées. Une étude des composites mousses métalliques/RT27 par plaque chaude gardée transitoire « PCGT » a été finalement réalisée. Elle a visé à comparer les conductivités thermiques mesurées par « hot disk » et les chaleurs spécifiques calculées à celles obtenues par « PCGT ». The word energy consumption increased in the last decades and a continues increase in the future is predicted. An effective utilization of energy is highly required due to the scarcity of fossils fuels and to the rise of greenhouse gas emissions. In this context, thermal energy storage using solid-liquid phase change materials «PCMs» is a promising solution for saving energy. It attracts a great growing interest in many applications such as buildings, thermal control of electronic devices and thermal management of Li-ion batteries. However, it is hampered by the low thermal conductivities of PCMs which limits the storage/release rate. Hence, the enhancement of the thermal conductivity of PCMs is an important issue for the latent storage systems. This thesis studies paraffins RT21-27-35HC- RT50 and metal foams/paraffins composites. The determination of the thermophysical properties of paraffins at different temperature is firstly carried out. The differential scanning calorimetry « DSC » measurements and thermogravimetric analyses « TGA » were performed. The thermal conductivities and diffusivities of PCMs were measured by the « Hot disk» method at different temperatures. The thermodependency of their densities was also studied. Since the thermal behavior of PCMs during the solid-liquid phase change is controlled by the heat transfer mechanisms, an experimental investigation of the melting of the paraffin RT27 was conducted in the second part of this work. A new experimental device was set up in the laboratory to study the heat transfer characteristics. The visualization of the melting interface and the recording of temperature in the PCM indicate the heat transfer regimes controlling the melting process: conduction, transition regime and natural convection. The evolution of the melting fraction was used to study the kinetic of the melting process and the temporal evolution of the heat stored in RT27. The last part of this work was dedicated to the investigation of metal foams/paraffins composites. The paraffins RT21-27-RT35HC were impregnated in aluminum and nickel foams. The impregnation ratios of the composites highlighted the effectiveness of the procedure preparation. The thermal conductivities of the composites metal foams/paraffins at the solid phase were measured by the « hot disk » method. The results revealed that the thermal conductivities of aluminum foam/paraffins and nickel foams/paraffins are increased drastically until 1751,4% and 666,8% respectively. The experimental results were compared to the theoretical models. Densities’ measurements of metal foams filled with paraffins were realized. The specific heats of samples were calculated from experimental results. A study of the composites metal foams/ RT27 was conducted finally by the transient guarded hot plate « TGHP». It aims to compare the thermal conductivities obtained by « hot disk» and the calculated specific heats to those measured by « TGHP».

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    Authors: Lafaye, Paul;

    Les alliages de zirconium sont utilisés comme matériaux de gainage des combustibles nucléaires dans les réacteurs à eau pressurisée. Ces gaines sont utilisées dans un milieu extrêmement radiatif et corrosif, elles peuvent dans certains cas être le siège de fortes variations de température et doivent répondre à des sollicitations mécaniques importantes, que ce soit en conditions de service ou accidentelles. Dans un tel contexte, il est intéressant de pouvoir prédire les transformations de phases ayant lieu au sein de la gaine en fonction des variations de température et de composition chimique, la précipitation de phases fragiles induites par la présence des éléments d’alliages, mais aussi de tester de nouvelles compositions d’alliages afin de l’optimiser.La méthode la plus adaptée pour la modélisation thermodynamique de systèmes multiconstitués est la méthode Calphad (CALculation of PHAse Diagrams). Il s’agit d’une méthode semi-empirique, consistant à modéliser les enthalpies libres des différentes phases constitutives d’un système par ajustement de certains paramètres, dans le but de reproduire les données expérimentales.Ce mémoire détaille la construction d’une base de données thermodynamiques du système quinaire Cr-Fe-Nb-Sn-Zr selon la méthode Calphad. L’originalité de notre démarche est liée à l’utilisation des calculs DFT de manière systématique et massive. Il s’agit en particulier de calculer par DFT les enthalpies de formation de tous les end-members des phases intermétalliques constitutives du système quinaire. De plus, des calculs sur des mailles « quasi aléatoires » (SQS) sont également effectués de manière systématique afin de déterminer les enthalpies de mélange des solutions solides binaires en structure fcc, bcc et hcp. En outre, une étape importante de ce travail consiste à compléter les données expérimentales de la littérature par de nouvelles mesures sur des systèmes choisis. En particulier, nous nous sommes employés à décrire quelques équilibres de phases des systèmes ternaires Cr-Nb-Sn, Cr-Fe-Sn, Cr-Sn-Zr et Fe-Nb-Sn qui n’avaient jamais été déterminés expérimentalement. Nous avons ensuite utilisé ces calculs et ces nouvelles données expérimentales en complément de données de la littérature comme données d’entrée pour la modélisation thermodynamique des vingt sous-systèmes binaires et ternaires du système quinaire considéré. Enfin, le pouvoir prédictif de notre base de données a pu être vérifié en confrontant ces prédictions à des données expérimentales relatives à des alliages quinaires industriels ou à de nouveaux concepts de gaines Currently, zirconium alloys are used as fuel cladding materials in PWR (Pressurized Water Reactors). The claddings stand in a very corrosive and radiative environnement, and can be submitted to temperature variations. In addition, the claddings will be subjected to mechanical stresses in reactor or accidental conditions. Thus, it appears useful to have a better understanding of phase transformations occurring in these alloys, as a function of temperature and chemical composition variations, but also to forecast the precipitation of fragile phases induced by the addition of alloying elements. At last, the ability to test new alloy compositions may allow to optimize it.The most suitable method for the thermodynamic modeling of multicomponent systems is the Calphad method (CALculation of PHAse Diagrams). The Calphad method is a widely used technique of semi-empirical modelling of phase diagrams. It consists in the description of the Gibbs energies of the different phases by fitting parameters allowing to describe the experimental data.This report details the design of a thermodynamic database considering the five following elements Zr, Cr, Fe, Nb, and Sn. The originality of this database lies in a systematic use of DFT calculations. Indeed, DFT calculations are performed to predict the formation enthalpy of the intermetallic phases appearing in these systems. Moreover, the SQS method (Special Quasirandom Structure) is used to predict the mixing enthalpy of the fcc, bcc and hcp binary solid solutions. Besides, experimental investigations are an important step of this thesis. Since no experimental data were available for the Cr-Fe-Sn, Cr-Nb-Sn, Cr-Sn-Zr and Fe-Nb-Sn ternary systems, new experimental data are provided, within this study, on the isothermal sections of these systems at different temperatures. All these calculated data in addition to the experimental data and the data from literature are used as input data for the Calphad modelling of the twenty binary and ternary systems which are then combined in the new database. A last part is dedicated to comparisons between predictions obtained with our new database and experimental results on industrial quinary alloys and a new concept of claddings

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