150 research outputs found
Méthode de désagrégation statistico-dynamique adaptée aux forçages atmosphériques pour la modélisation de l'océan atlantique : développement, validation et application au climat présent
L'océan joue un rÎle majeur dans la régulation du climat terrestre et sa bonne représentation par les modÚles de climat est essentielle pour une bonne estimation de l'état moyen et de la variabilité du systÚme climatique. Les modÚles de climat présentent cependant des biais dans leur représentation de l'océan, dus en partie à une résolution spatiale trop basse ainsi qu'à une mauvaise estimation des variables atmosphériques à l'interface air-mer.
Cette thĂšse se propose de mettre en Ćuvre une mĂ©thode dite de dĂ©sagrĂ©gation statistico-dynamique, afin de permettre une meilleure estimation de l'Ă©tat moyen et de la variabilitĂ© ocĂ©aniques sur l'ocĂ©an Atlantique par la rĂ©duction des biais systĂ©matiques des modĂšles de climat. La mĂ©thode consiste dans un premier temps Ă reconstruire les variables atmosphĂ©riques de surface par relation statistique avec la dynamique atmosphĂ©rique de grande Ă©chelle estimĂ©e en termes de rĂ©gimes de temps. Le jeu de forçage ainsi reconstruit est ensuite utilisĂ© pour forcer un modĂšle d'ocĂ©an plus
haute résolution que celle classiquement utilisée dans les modÚles de climat.
Une fois cette méthode construite et validée à partir des données observées sur la deuxiÚme moitié du 20Úme siÚcle, elle est ensuite appliquée à la dynamique atmosphérique de grande échelle de la simulation historique du modÚle de climat CNRM-CM3. L'analyse du jeu de forçage reconstruit et de la simulation océanique associée permet de mettre en avant les performances de la méthode qui, malgré quelques faiblesses, mÚne à bien son rÎle de correcteur de biais du modÚle de climat CNRM-CM3.Ocean plays a main role in climate regulation. Its good representation by climate models is necessary to have a correct estimation of mean state and variability of the climate system. However, some biases are present in the representation of the ocean by climate models. This is partly due to their too low horizontal resolution and a poor representation of the atmospheric variables at the ocean surface.
In this thesis, a statistico-dynamical downscaling method is carried out. The objective is to obtain a better estimation of oceanic mean state and variability over the Atlantic basin, by reducing the systematic biases of climate models. First, the method consists in reconstructing the surface atmospheric variables by statistical relationship with the large scale atmospheric dynamic, estimated by weather regimes. The resulting forcing set is used afterward to force an oceanic model at a higher resolution than the classical resolution used for the ocean in climate models.
Once this method built and validated with the observations over the second half 20th century, it is applied to the large scale atmospheric dynamic from the historical simulation of the CNRM-CM3 climate model. The analysis of the reconstructed forcing and its associated oceanic simulation emphasizes the efficiency of the method. In spite of some weaknesses, the method fully accomplishes its role in correcting climate models biases
Huez â Brandes-en-Oisans
La programmation 2012-2014 Ă©tait centrĂ©e sur le secteur B 121, partie du quartier industriel occidental de lâagglomĂ©ration de Brandes-en-Oisans. Dans ce complexe, se dĂ©roulait le processus dâenrichissement du minerai autour de la source Font-Morelle et de la canalisation C1. LâĂ©tude du fonctionnement de cette chaĂźne opĂ©ratoire est inscrite Ă Brandes dans les problĂ©matiques centrĂ©es sur « Lâeau et ses usages dans une grande entreprise miniĂšre mĂ©diĂ©vale » et dĂ©veloppĂ©es depuis 1994. Ce thĂšme a ..
Keys to successful implementation of a French national quality indicator in health care organizations: a qualitative study
International audienceBackground: Several countries have launched public reporting systems based on quality indicators (QIs) to increase transparency and improve quality in health care organizations (HCOs). However, a prerequisite to quality improvement is successful local QI implementation. The aim of this study was to explore the pathway through which a mandatory QI of the French national public reporting system, namely the quality of the anesthesia file (QAF), was put into practice
A kriging-based analysis of cloud liquid water content using CloudSat data
Spatiotemporal statistical learning has received increased attention in the past decade, due to spatially and temporally indexed data proliferation, especially data collected from satellite remote sensing. In the meantime, observational studies of clouds are recognized as an important step toward improving cloud representation in weather and climate models. Since 2006, the satellite CloudSat of NASA is carrying a 94 GHz cloud-profiling radar and is able to retrieve, from radar reflectivity, microphysical parameter distribution such as water or ice content. The collected data are piled up with the successive satellite orbits of nearly 2 h, leading to a large compressed database of 2 Tb (http://cloudsat.atmos.colostate.edu/, last access: 8 June 2022). These observations offer the opportunity to extend the cloud microphysical properties beyond the actual measurement locations using an interpolation and prediction algorithm. To do so, we introduce a statistical estimator based on the spatiotemporal covariance and mean of the observations known as kriging. An adequate parametric model for the covariance and the mean is chosen from an exploratory data analysis. Beforehand, it is necessary to estimate the parameters of this spatiotemporal model; this is performed in a Bayesian setting. The approach is then applied to a subset of the CloudSat dataset
Pyroséquençage pour le développement d'EST et de SNP aviaires
Le but du programme est de combler les dĂ©ficits en marqueurs observĂ©s pour trois espĂšces aviaires : la caille, le canard et la poule. La stratĂ©gie choisie est l'obtention, Ă partir de plusieurs individus de lignĂ©es d'intĂ©rĂȘt, de SNP (Single Nucleotide Polymorphism, polymorphisme d'un nuclĂ©otide) par une nouvelle technologie de sĂ©quençage Ă haut dĂ©bit (sĂ©quenceur 454 GS-FLX, Roche). Nous sĂ©quençons des reprĂ©sentations rĂ©duites du gĂ©nome, en sĂ©lectionnant d'une part des fragments de restriction d'ADN gĂ©nomique - les mĂȘmes chez tous les individus - et d'autre part les transcrits qui reprĂ©sentent globalement la partie du gĂ©nome correspondant aux gĂšnes exprimĂ©s. Ces expĂ©rimentations sont rĂ©alisĂ©es Ă partir d'Ă©chantillons d'ADN ou d'ARN issus d'individus de lignĂ©es Ă l'origine de croisements existants, pour chacune des trois espĂšces. Les donnĂ©es gĂ©nĂ©rĂ©es par plusieurs "runs" de sĂ©quence seront traitĂ©es in silico : contigage Ă haut dĂ©bit, recherche de SNP, comparaison avec les banques de sĂ©quences connues...En plus de l'intĂ©rĂȘt que reprĂ©sente la production d'un trĂšs grand nombre de SNP nouveaux, cette technologie devrait permettre de mieux sĂ©quencer les rĂ©gions riches en (G+C) correspondant aux plus petits des microchromosomes pour lesquels il n'y a pas de sĂ©quence chez la poule. La comparaison des sĂ©quences des transcrits obtenues chez la caille et le canard avec la sĂ©quence du gĂ©nome de la poule permettra d'Ă©tablir une "cartographie virtuelle" des SNP obtenus, grĂące Ă la grande conservation de syntĂ©nie existant entre ces trois espĂšces
A global water resources ensemble of hydrological models: The eartH2Observe Tier-1 dataset
The dataset presented here consists of an ensemble of 10 global hydrological and land surface models for the period 1979â2012 using a reanalysis-based meteorological forcing dataset (0.5° resolution). The current dataset serves as a state of the art in current global hydrological modelling and as a benchmark for further improvements in the coming years. A signal-to-noise ratio analysis revealed low inter-model agreement over (i) snow-dominated regions and (ii) tropical rainforest and monsoon areas. The large uncertainty of precipitation in the tropics is not reflected in the ensemble runoff. Verification of the results against benchmark datasets for evapotranspiration, snow cover, snow water equivalent, soil moisture anomaly and total water storage anomaly using the tools from The International Land Model Benchmarking Project (ILAMB) showed overall useful model performance, while the ensemble mean generally outperformed the single model estimates. The results also show that there is currently no single best model for all variables and that model performance is spatially variable. In our unconstrained model runs the ensemble mean of total runoff into the ocean was 46âŻ268âŻkm3âŻyrâ1 (334âŻkgâŻmâ2âŻyrâ1), while the ensemble mean of total evaporation was 537âŻkgâŻmâ2âŻyrâ1.This research received funding from the
European Union Seventh Framework Programme (FP7/2007-2013)
under grant agreement no. 603608, âGlobal Earth Observation for
integrated water resource assessmentâ: eartH2Observ
A global water resources ensemble of hydrological models: the eartH2Observe Tier-1 dataset
The dataset presented here consists of an ensemble of 10 global hydrological and land surface models for the period 1979â2012 using a reanalysis-based meteorological forcing dataset (0.5° resolution). The current dataset serves as a state of the art in current global hydrological modelling and as a benchmark for further improvements in the coming years. A signal-to-noise ratio analysis revealed low inter-model agreement over (i) snow-dominated regions and (ii) tropical rainforest and monsoon areas. The large uncertainty of precipitation in the tropics is not reflected in the ensemble runoff. Verification of the results against benchmark datasets for evapotranspiration, snow cover, snow water equivalent, soil moisture anomaly and total water storage anomaly using the tools from The International Land Model Benchmarking Project (ILAMB) showed overall useful model performance, while the ensemble mean generally outperformed the single model estimates. The results also show that there is currently no single best model for all variables and that model performance is spatially variable. In our unconstrained model runs the ensemble mean of total runoff into the ocean was 46âŻ268âŻkm3âŻyrâ1 (334âŻkgâŻmâ2âŻyrâ1), while the ensemble mean of total evaporation was 537âŻkgâŻmâ2âŻyrâ1. All data are made available openly through a Water Cycle Integrator portal (WCI, wci.earth2observe.eu), and via a direct http and ftp download. The portal follows the protocols of the open geospatial consortium such as OPeNDAP, WCS and WMS. The DOI for the data is https://doi.org/10.1016/10.5281/zenodo.167070
Resistive switching study of binary oxides (HfO2, TiO2) deposited by molecular beam epitaxy and integrated in metal/oxide/metal memristive type devices : effect of doping and implantation
A lâĂšre du « big data » et de lâintelligence artificielle, les recherches pour trouver de nouvelles façons de stocker et traiter lâinformation se multiplient. Dans le domaine des mĂ©moires non volatiles, cette Ă©mulation a conduit Ă lâĂ©mergence de nouveaux composants, dont les OxRAM (oxide-based resistive random access memories) auxquels nous nous sommes intĂ©ressĂ©s dans cette thĂšse. Il sâagit dâun empilement mĂ©tal-oxyde-mĂ©tal oĂč la couche dâoxyde commute entre au moins deux Ă©tats de rĂ©sistance stables lorsquâune tension est appliquĂ©e. Nos travaux ont portĂ© sur l'Ă©tude Ă©lectrique de dispositifs en croix, de dimensions submicroniques (500 x 500 nm2 ou 100 x 100 nm2) avec, comme oxyde diĂ©lectrique, le dioxyde dâhafnium HfO2 ou le dioxyde de titane TiO2. Pour l'Ă©laboration des oxydes, nous avons mis en oeuvre le dĂ©pĂŽt par jets molĂ©culaires (ou MBE pour molecular beam epitaxy), technique trĂšs peu utilisĂ©e jusquâici dans la communautĂ© des OxRAM. Cette technique d'ultravide permet d'obtenir des films trĂšs purs alors qu'avec lâALD (pour atomic layer deposition), le prĂ©curseur employĂ© induit une contamination en carbone, azote ou chlore. L'une des clĂ©s de lâoptimisation des propriĂ©tĂ©s Ă©lectriques se trouve dans le contrĂŽle de la quantitĂ© et de la distribution des lacunes dâoxygĂšne. A cet effet, nous avons explorĂ© lâincorporation de divers Ă©lĂ©ments aux couches de HfO2 et TiO2. La microstructure et la composition des films d'oxyde ainsi dopĂ©s ont Ă©tĂ© analysĂ©es, puis les dispositifs OxRAM ont Ă©tĂ© fabriquĂ©s et leurs caractĂ©ristiques Ă©lectriques (courant-tension) ont Ă©tĂ© Ă©tudiĂ©es. Pour les OxRAM Ă base de HfO2 (mettant en jeu un mĂ©canisme filamentaire), nous avons tout d'abord optimisĂ© l'Ă©laboration de HfO2 par MBE. Nous avons obtenu des dispositifs dont les propriĂ©tĂ©s Ă©lectriques se situent au niveau de l'Ă©tat de l'art international, notamment pour la fenĂȘtre mĂ©moire. GrĂące Ă la croissance par MBE, nous obtenons une plus petite tension de forming et une plus grande fenĂȘtre mĂ©moire que pour des composants similaires, que nous avons fabriquĂ©s Ă partir de films prĂ©parĂ©s par ALD. Nous suggĂ©rons un lien entre contaminants carbonĂ©s et largeur de la fenĂȘtre mĂ©moire. Par rapport Ă l'Ă©tat de l'art, nos objectifs Ă©taient dâabaisser les courants de fonctionnement et dâattĂ©nuer la variabilitĂ© entre nombreux cycles ainsi qu'entre composants. Nous avons pour cela examinĂ© les effets de l'ajout dans HfO2 des Ă©lĂ©ments Al, La ou Ti (de quelques % jusqu'Ă 30 %), par co-dĂ©pĂŽt avec Hf. GrĂące Ă ces additions, nous parvenons Ă rĂ©duire le courant de reset, la tension de forming et la variabilitĂ© du courant de reset. De plus, les mesures XPS (pour X-ray photoelectron spectroscopy) montrent une augmentation du taux de lacunes dans les couches La-HfO2, Ti-HfO2 et Al-HfO2. Concernant les composants Ă base de TiO2 (impliquant des mĂ©canismes de type interfacial Ă l'une des deux interfaces avec les Ă©lectrodes, dite active), nos objectifs Ă©taient de diminuer les courants de fonctionnement et dâaugmenter le nombre dâĂ©tats de rĂ©sistance accessibles stables. A cette fin, nous avons privilĂ©giĂ©, lĂ aussi, des stratĂ©gies matĂ©riaux. Nous avons modifiĂ© l'interface active du dispositif en y incorporant des hĂ©tĂ©roĂ©lĂ©ments (Ne, N et B) par implantation ionique. La teneur en lacunes dâoxygĂšne a Ă©tĂ© analysĂ©e par XPS tandis que la mobilitĂ© des lacunes a Ă©tĂ© quantifiĂ©e via leur Ă©nergie dâactivation de diffusion Ea. Afin de dĂ©terminer Ea, nous avons mis au point un protocole expĂ©rimental original. Ainsi, nous avons Ă©tabli que l'azote, dopant de type p dans TiO2, accroĂźt la mobilitĂ© des lacunes tandis que le bore, dopant de type n, lâentrave et le nĂ©on, inerte, n'a pas d'incidence. L'Ă©nergie d'activation est minimale (0,4 eV) pour une implantation en azote de 1018 ions/cm3. La mobilitĂ© des lacunes n'est cependant pas le seul paramĂštre Ă amĂ©liorer : le transport des Ă©lectrons Ă travers la barriĂšre Schottky TiO2/Pt joue Ă©galement un rĂŽle crucial. [...]In the age of big data and artificial intelligence, researches to find new ways to process and store the information multiply. In the field of non-volatile memories, this emulation has led to the emergence of new components, such as OxRAM (for oxide-based random access memories) in which we have been interested in during this PhD. It is a metal-oxide-metal stack where the oxide layer is able to switch between at least two stable resistance states under an applied voltage. In this work, we have studied sub-micrometer cross-point devices (500 x 500 nm2 or 100 x 100 nm2) with hafnium dioxide (HfO2) or titanium dioxide (TiO2) as dielectric oxide. The oxides have been deposited by molecular beam epitaxy (MBE), a technique that has rarely been used so far in the OxRAM community. With this ultra-vide technique, we can obtain very pure films whereas with atomic layer deposition (ALD), precursors induce carbon, nitrogen or chlorine contaminations. For the electrical properties optimization, one of the keys is the concentration and distribution control of oxygen vacancies. Regarding that, we have explored the incorporation of various elements in HfO2 and TiO2 layers. The microstructure and the composition of these doped films have been analyzed, afterward OxRAM devices have been fabricated and their electrical characteristics (current-voltage) have been studied. For HfO2-based OxRAM (involving a filamentary mechanism), we have firstly optimized the MBE HfO2 deposition. The devices then obtained have electrical properties which are as good as those of the state-of-the-art components, in particular for the memory window. Moreover, these MBE deposited devices have a smaller forming voltage and a larger memory window than equivalent components that we have fabricated with ALD grown layers. So, we suggest a link between carbon impurities and memory width. In light of the state of the art, our objectives were to lower working currents and to reduce the variability between numerous cycles and between components too. To this end, we have examined the effects of adding Al, La or Ti elements in HfO2 (from few % to 30 %), by co-deposition with Hf. Thanks to these additions, we manage to decrease the reset current, the forming voltage and the variability of the reset current. Furthermore, X-ray photoelectron spectroscopy (XPS) measurements show an increase of vacancies amount in La-HfO2, Ti-HfO2 and Al-HfO2 layers. Concerning TiO2-based components (for which the mechanism is interfacial and takes place at one of the two electrode interfaces, said active), our goals were to diminish working currents and to augment the number of accessible stable resistance states. For this purpose, we have also focused on material strategies. We have modified the active interface by heteroelements ion implantation (Ne, N and B). The oxygen vacancies content has been analyzed by XPS while the vacancies mobility has been quantified via their activation energy diffusion Ea. In order to determine Ea, we have developed an original experimental protocol. In this way, we establish that nitrogen, which is a p-type dopant in TiO2, heightens the oxygen vacancies mobility, whereas boron, which is a n-dopant, hinders it and the neon, inert, does not have any effect on vacancies mobility. The activation energy is minimal (0.4 eV) for a nitrogen dose of 1018 ions/cm3. However, the oxygen vacancies mobility is not the only parameter that we have to improve: the electronic transport through the TiO2/Pt Schottky barrier plays also a crucial role. The results achieved during this PhD attest to the pertinence of the MBE utilization and of an analysis that combines ionic and electronic aspects in order to improve the resistive switching phenomenon understanding and the OxRAM performances
EnquĂȘte rĂ©alisĂ©e par le Groupe AFFDU - Montpellier
Minvielle Marie-Claire. EnquĂȘte rĂ©alisĂ©e par le Groupe AFFDU - Montpellier . In: DiplĂŽmĂ©es, n°187, 1998. pp. 291-301
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