Дисертації з теми "Modélisation végétale"
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Duchesne, Isabelle. "L'effet du climat sur les plantes fourragères au Québec: estimation des pertes par la modélisation." Thesis, Université Laval, 2010. http://www.theses.ulaval.ca/2010/26822/26822.pdf.
Richard, Romain. "Transestérification éthanolique d'huile végétale dans des microréacteurs : transposition du batch au continu." Phd thesis, Toulouse, INPT, 2011. http://oatao.univ-toulouse.fr/6960/1/richard.pdf.
Prat, Laurent E. "Modélisation d'un réacteur thermo-mécano-chimique bi-vis utilisé en fractionnement de la matière végétale." Toulouse, INPT, 1998. http://www.theses.fr/1998INPT019C.
Penard, Cédric. "Détection satellitaire et modélisation opérationnelle de la production végétale non-fixée dans la bande côtière bretonne." Brest, 2009. http://www.theses.fr/2009BRES2044.
Eutrophication is more and more important in the coastal environment. It is one major impact of human activity on environment. The eutrophication phenomena are growing continuously. Over the last decades, the number of sites affected has been rising over the world. Eutrophication of French Brittany coastal shelf is a recurrent problem, always more worrying. The objective of this work is multiple: it aims at highlighting and understanding the impact and the role of the contributions in nutrients on the primary production and the eutrophication of the coastal environment. This work also has the ambition of identifying and understanding the causes of the phenomena and thus to make it possible to bring solutions or tracks of improvement. Lt also has an objective of short-term forecast of the biological state of the zone. This work led to the implementation of a real-time model, which results can be visualised and compared to satellite measurements on w. Previmer. Org. The main tool for this work is a coupled physical-biogeochemical model. The hydrodynamic part is provided by the code Mars3D (3D hydrodynamic Model for Application At Regional Scale) developed by IFREMER. The biogeochemical model of IFREMER, with its model of nitrogen, phosphorus and silicon cycles, is coupled to the hydrodynamic code Mars3D. We added to this basic model a specific kind of phytoplankton which can be harmful: Pseudo-Nitzschia. Indeed, this phytoplankton has the capacity to synthesize domoic acid which is a toxin responsible for the ASP syndrome (Amnesic Shellfish Poisoning). The model reproduces overall the same zones of toxicity as measurements of the REPHY, and gives encouraging results
Ravaz, Nathalie. "Croissance de populations levuriennes mixtes : effet Killer : analyse et modélisation." Toulouse, INPT, 1992. http://www.theses.fr/1992INPT058G.
Helbert, Jérôme. "Estimation et modélisation de la distribution spatiale de l'eau au sein d'un couvert végétal : mise en oeuvre d'un dispositif multipôle fonctionnant en régime quasi-statique." Versailles-St Quentin en Yvelines, 2001. http://www.theses.fr/2001VERS0014.
Cerdan, Olivier. "Analyse et modélisation du transfert de particules solides à l'échelle de petits bassins versants cultivés." Orléans, 2001. http://www.theses.fr/2001ORLE2017.
Colson, Josiane. "Développement reproducteur du soja-impact des conditions de culture et modélisation du potentiel de production variétal." Toulouse 3, 1992. http://www.theses.fr/1992TOU30139.
Sow, Demba. "Contribution à l'étude expérimentale et à la modélisation de la digestion anaérobie de Euphorbia tirucalli et d'autres plantes à latex sahéliennes : euphorbia balsamifera et calotropis procera." Châtenay-Malabry, Ecole centrale de Paris, 1993. http://www.theses.fr/1993ECAP0323.
N'diaye, Senghane. "Fractionnement de la matière végétale : mise au point d'un procédé thermo-mécano-chimique et modélisation du fonctionnement du réacteur bi-vis." Toulouse, INPT, 1996. http://www.theses.fr/1996INPT040G.
Gosseau, Florie. "Développement de nouveaux idéotypes de tournesol par une approche associant génétique quantitative et modélisation du couvert végétal." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30267.
Assessing the performance and the characteristics (e.g. yield, quality, disease resistance, abiotic stress tolerance) of new varieties is a key component of crop performance improvement. However, the variety testing process is presently exclusively based on experimental field approaches. This reduces the number and the diversity of experienced combinations of varieties x environment x management conditions and of course testing in future climatic conditions generated by climate change. Testing, understanding genetically and predicting phenotyic plasticity of crop performance constitutes therefore a challenge for basic and applied research in order to adapt varieties to future climatic conditions and technical practices. Our aim is to design tools to leverage phenotypic plasticity and better use genetic and environmental resources to reduce yield gaps currently observed between the genotypic potential and the agricultural production. We developed two approaches to identify genetic markers associated to yield and its stability in various production situations. Both approaches are based on the combination of quantitative genetics models and crop simulation models to capture phenotypic plasticity. The first approach ("plasticity") aims to identify the genetic architecture of yield plasticity in a multi-environment trial, while the second ("optimization") rather focus of the genetic architecture of plant traits that are optimal for yield and its variance in specific growing conditions. In the first "plasticity" approach, the crop simulation model allowed assessing abiotic stress levels occurring in a multi environment trial. We then calculated yield plasticity for each genotype in a hybrid panel as the regression of the yield of the hybrid against the stress level in the environment (reaction norms). Finally, a genome-wide association study (GWAS) identified genetic markers linked to yield plasticity. In the second "optimization" approach, the key step was to design a multiscale model to predict the performance of new hybrids in new environments. We proceed in two steps: (1) build whole genome prediction models to predict a set of component traits as a function of allelic combination of genotypes and (2) use a crop simulation model to predict the hybrid yield as a function of component traits, environmental variables and management practices. We found that the accuracy of our multi-scale model was worse than the accuracy of a sole genome prediction model directly predicting crop yield, but we identified new bottlenecks related to the design of such models. We nevertheless used this model in an experimental simulation-based optimisation method, which allowed identifying plant traits associated to high yield level and stability in specific growing conditions and we discussed their genetic architecture. In both approaches, association studies identified numerous genomic regions controlling yield plasticity in responses to abiotic stresses and highlighted its complexity. Such information is available to plant breeders to develop new genotypes adapted to increasingly variable cropping conditions drived by climate change to fulfill the societal need to switch to more sustainable agricultural management
Maltas, Alexandra. "Analyse par expérimentation et modélisation de la dynamique de l’azote dans les systèmes sous semis direct avec couverture végétale des Cerrados brésiliens." Montpellier, ENSA, 2007. http://www.theses.fr/2007ENSA0011.
Moity, Laurianne. "Conception, modélisation et caractérisation de solvants agro-sourcés." Thesis, Lille 1, 2013. http://www.theses.fr/2013LIL10075.
Many of the traditional organic solvents (halogenated compounds, aromatics, glycols ethers) are banned or about to be, as a result of the recent awareness of the environmental and health risks associated with their use. There is therefore an urgent need to find alternatives with good ESH (Environment, Safety and Health) profiles, preferably coming from renewable feedstock: the so-called biosolvents. In this work, these alternative solvents have been listed, modeled, and compared to classical organic ones to give a purely predictive landscape obtained thanks to the COSMO-RS approach. This tool can be used to help in finding substitution solutions and also highlights the needs for new biosolvents. A Computer-Assisted Organic Synthesis program, named GRASS, has been developed to help in the rational design of biosolvents from a bio-based building block (glycerol, itaconic acid, isosorbide, etc.) through industrially-relevant chemical transformations. Then, all the virtual derivatives generated have been sorted out thanks to property prediction models in order to select the most relevant ones. Biosolvents coming from glycerol and isosorbide (ethers, esters, acetals) have been selected, synthesized and experimentally evaluated as solvents considering their physico-chemical properties (m.p., b.p., d, η, stabilities to hydrolysis and to oxidation), their capacities to solubilise two agrochemicals, and their hydrotropic properties. These experimental data have then been compared to various prediction models
Moity, Laurianne. "Conception, modélisation et caractérisation de solvants agro-sourcés." Electronic Thesis or Diss., Lille 1, 2013. http://www.theses.fr/2013LIL10075.
Many of the traditional organic solvents (halogenated compounds, aromatics, glycols ethers) are banned or about to be, as a result of the recent awareness of the environmental and health risks associated with their use. There is therefore an urgent need to find alternatives with good ESH (Environment, Safety and Health) profiles, preferably coming from renewable feedstock: the so-called biosolvents. In this work, these alternative solvents have been listed, modeled, and compared to classical organic ones to give a purely predictive landscape obtained thanks to the COSMO-RS approach. This tool can be used to help in finding substitution solutions and also highlights the needs for new biosolvents. A Computer-Assisted Organic Synthesis program, named GRASS, has been developed to help in the rational design of biosolvents from a bio-based building block (glycerol, itaconic acid, isosorbide, etc.) through industrially-relevant chemical transformations. Then, all the virtual derivatives generated have been sorted out thanks to property prediction models in order to select the most relevant ones. Biosolvents coming from glycerol and isosorbide (ethers, esters, acetals) have been selected, synthesized and experimentally evaluated as solvents considering their physico-chemical properties (m.p., b.p., d, η, stabilities to hydrolysis and to oxidation), their capacities to solubilise two agrochemicals, and their hydrotropic properties. These experimental data have then been compared to various prediction models
Del, Masto Alessandra. "Transition d’échelle entre fibre végétale et composite UD : propagation de la variabilité et des non-linéarités." Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCD022/document.
Although plant-fiber reinforced composites (PFCs) represent an attractive solution for the design of lightweight, high performance and low environmental cost structures, their development requires in-depth studies of the mechanisms underlying their nonlinear tensile behavior, as well as variability of mechanical properties. Given their multi-scale nature, this thesis aims to contribute, using a numerical approach, to the study of the propagation of behavior across the scales of PFCs. Firstly, the study focuses on the fiber scale: a 3D model of the behavior of the wall is first implemented in an EF calculation, in order to establish the influence of fiber morphology on the tensile behavior. Once the non-negligible impact of the morphology has been determined, a study of the links between morphology, material and ultrastructure and tensile behavior is conducted via a sensitivity analysis in the case of flax and hemp. The second part of the work is dedicated to the composite ply scale. A new stochastic multi-scale approach is developed and implemented. It is based on the definition of an elementary volume (VE) with random microstructure to describe the behavior of the ply. The approach is then used to study the sensitivity of VE behavior to nano, micro and mesoscopic parameters. Sensitivity analysis, conducted via the development of the response on the basis of polynomial chaos, allows us to construct a metamodel of the tensile behavior of the ply
Xiong, Tou Cheu. "Le noyau de la cellule végétale est-il autonome en matière de signalisation calcique?" Toulouse 3, 2005. http://www.theses.fr/2005TOU30197.
Here we describe the first evidence establishing that nuclei isolated from plant cells perceive physical stimuli (temperature and mechanical shocks) and convert them into specific changes in free calcium concentrations in the nucleoplasm. Mathematical modeling suggests that the nucleus behaves as a close system. Under these conditions, calcium movements in isolated nuclei depend upon calcium channel activities (InsP3 operated- or TRP-type channels) located in the inner nuclear membrane. Changes in free nuclear calcium are induced by sphingolipids some of them being activators of TRP channels. In intact cells, the cytosol controls the effects of sphingolipids (located in the nucleus) on the homeostasy of nuclear calcium. Collectively, our data strengthen the controversial idea that the nucleus is partially autonomous in terms of calcium signalling. They show further that different signaling pathways are connected in the nucleus
Teles, dos Santos Moisés. "Conception des triacylglycérides à propriétés contrôlées : formulation et modélisation." Thesis, Toulouse, INPT, 2010. http://www.theses.fr/2010INPT0101/document.
The search for sustainable development is an incentive for renewable resources usage in chemical industry. Vegetable oils (triacylglycerol-based mixtures) are raw-materials that match this criterion and they are currently and potentially used in a wide range of sectors, such as: food industry, lubricants, solvents, cosmetics, pharmaceutical, among others. Aiming to aid product design using such raw-materials, this work deals with phase equilibrium modeling and the development of a computational tool for properties prediction. The models used are totally predictive and they deal with the existence of solid polymorphism. The liquid state and the crystals are treated as ideal phases. The activity coefficients of phases ’ and (notideal) are estimated using Margules model, for which the binary molecular interaction parameters are calculated in a predictive manner by means of correlations with the similarity degree between fatty acids chains in the glycerol. By direct optimization of Gibbs Free Energy, the Solid Fat Content is computed, a fundamental property for vegetable oils–based products functionality. The results of phase equilibrium in different temperatures allow simulating melting curves and Differential Scanning Calorimetry curves, allowing a computational evaluation of how molecular structure and composition changes affect desired properties. The calculated results were applied and compared with experimental data in a wide range of systems: pure systems, binary and ternary triacylglycerol mixtures, natural vegetable oils and mixture of vegetable oils (hundreds of components). Chemical interesterification reaction, widely applied to change fats and oils composition and properties, were also simulated and the results compared with experimental data in different compositions and temperatures. The good agreement between computational results and experimental data enables the computational tool validation and its predictive nature makes it suitable for the study of mixtures in temperatures and compositions not yet evaluated. Consequently, the experimental efforts (cost and time) can be concentrated on the most promised molecules/mixtures
A busca pelo desenvolvimento sustentável é um incentivo para o uso de recursos renováveis na indústria química. Óleos vegetais (misturas de triacilgliceróis) são matérias-primas que atendem a este critério e apresentam aplicações atuais e potenciais em diversos setores, tais como indústria de alimentos, lubrificantes, solventes, cosméticos, farmacêutica, dentre outros. Com o objetivo de auxiliar no desenvolvimento de produtos utilizando tais matérias-primas, o presente trabalho trata da modelagem do equilíbrio de fases em misturas de triacilgliceróis e do desenvolvimento de uma ferramenta computacional preditiva de propriedades. Os modelos usados são totalmente preditivos e consideram a existência de polimorfismo na fase sólida. O estado líquido e o polimorfo são considerados ideais. Os coeficientes de atividade das fases e (não-ideais) são estimados através do modelo de Margules, no qual os coeficientes de interação molecular binária são calculados de forma preditiva através de correlações com o grau de similaridade entre as cadeias de ácidos graxos no glicerol. Através da otimização direta da Energia Livre de Gibbs, é calculado o Conteúdo de Gordura Sólida, uma propriedade fundamental para funcionalidade de produtos baseados em óleos vegetais. Através do cálculo do equilíbrio de fases em diversas temperaturas são simuladas curvas de fusão e curvas de Calorimetria Exploratória Diferencial, permitindo uma avaliação computacional do efeito que alterações na estrutura molecular e composição apresentam nas propriedades de interesse. Os resultados calculados foram aplicados e comparados com dados experimentais em diversos sistemas: triacilgliceróis puros, misturas binárias e ternárias de triacilgliceróis, óleos vegetais naturais e misturas de diversos óleos vegetais (centenas de triacilgliceróis). Reações de interesterificação química, amplamente utilizadas para alterar a composição e propriedades de óleos e gorduras, foram igualmente simuladas e os resultados comparados com dados experimentais em diversas composições e temperaturas. A boa concordância entre os dados simulados e experimentais permite validar a ferramenta computacional e seu caráter preditivo a torna útil no estudo de misturas em temperaturas e composições ainda não avaliadas, de forma que os esforços experimentais (custo e tempo) possam ser direcionados às misturas mais promissoras
Blanc, Nicolas. "Etude de la fragmentation de milieux granulaires : modélisation numérique à l'échelle du grain et analyse expérimentale du broyage de matières minérales et végétale." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS039/document.
Although grinding is a widespread operation in industrial processes, it remains poorly understood. The difficulty to model grinding not only lies in the complexity of the fragmentation, which depends on material properties and loading dynamics, but also on the stress transmission from the grinder to the particles. The development of grinding technologies has led to an empirical know-how, and much more effort is still needed to understand the the mechanisms of the comminution of particles. This objective can be achieved only by increasing knowledge on the phenomena involved at different scales (sub-particle heterogeneities, particle, powder bed and boundary conditions of the process).In this PhD work, we investigate the key parameters influencing comminution mechanisms and the energetic efficiency of grinding. A numerical model of particle breakage including a subparticle distribution of cleavages was developed. This model allowed us to analyze the cracks patterns, fragment sizes and probability distribution of failure. At the scale of the process, an extensive experimental study of comminution was carried out using a laboratory mill. An energy evolution inspired by Rittinger model but taking into account the agglomeration phenomena was proposed. This model was then extended to other grinding technologies to compare the energy efficiency for grinding minerals, vegetal particles and their comilling
Pervanchon, Frank. "Modélisation de l'effet des pratiques agricoles sur la diversité végétale et la valeur agronomique des prairies permanentes en vue de l'élaboration d'indicateurs agri-environnementaux." Vandoeuvre-les-Nancy, INPL, 2004. http://www.theses.fr/2004INPL061N.
We set out the hypothesis according which it is necessary to elaborate a mathematical model for the prediction of vegetal diversity and of agronomical value of permanent grasslands. The fmal aim is to set up indicators of permanent grassland management according to the agricultural practices applied there. We demonstrate that multiple regression analysis does not allow obtaining effective models of vegetal diversity. Nevertheless, the prediction of pastoral value is rather effective when considering the environmental factors (pH, moisture, etc. ). However, these results do not concern the mixed grasslands of Lorraine, because of a weak number of available data. Ln order to predict vegetal diversity and agronomic value, we propose a model based on expert systems associated to fuzzy logic. This modelisation is one of the ftrst concrete applications of the theory of functional groups based on life traits of plant species. We show that it is possible to diagnose and predict vegetation (list of vegetal species) and the patrimonial value of grassland, without realizing floristic relevés, by being based only on the life traits already identified in litterature. Lndicators are obtained by reporting the model's results on an abacus ofregional values of vegetal diversity and ofpastoral value
Taconet, Odile. "Analyse de la thermographie infrarouge satellitaire pour la modélisation de l'évaporation sur une région agricole." Paris 11, 1987. http://www.theses.fr/1987PA112494.
Maire, Vincent. "Des traits des graminées au fonctionnement de l'écosystème prairial : une approche de modélisation mécaniste." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2009. http://tel.archives-ouvertes.fr/tel-00725487.
Maire, Vincent. "Des traits des graminées au fonctionnement de l'écosystème prairial : une approche de modélisation mécaniste." Phd thesis, Clermont-Ferrand 2, 2009. http://www.theses.fr/2009CLF21934.
Toquet, Dominique. "Le système-irrigation en Basse-Normandie : "Adéquation des ressources du cycle de l'eau aux besoins hydriques de la production végétale agricole par modélisation de l'irrigation"." Caen, 2000. http://www.theses.fr/2000CAEN1289.
Laruelle, Élise Raphaëlle. "Vers une modélisation des grands plans d’organisation de l’embryon d'Arabidopsis thaliana." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS074/document.
During embryonic development, the major body plans of the plant are implemented. This process gives rise to a mature embryo which possess all the characteristics of a young seedling and is associated with a morphological change. These two processes are stereotyped in Arabidopsis thaliana embryo development.Over the developmental process, the embryo shape switches from a globular form, with a radial symmetry, to a heart form with a bilateral symmetry. These changes are based on a differential cellular growth and on particular cell division plane orientation in the embryo, mechanisms that are tightly regulated and under control of molecular factors.If a number of cellular and molecular steps are known, the evolution of the symmetry and the acquisition of the specific embryo shape have not yet been explored.To understand the origin of the heart shape, we proceed to a detailed multi-scale description and quantification of embryo shape changes during embryo stages. We completed a collection of fixed embryo images with 35 embryos distributed along the embryo development over eight cell generations. The embryos have been digitized in 3D and cell segmented. From these images, embryo cell lineages have been reconstructed and their cell organizations characterized.The evolution of parameter measurements showed a progressive change of the shape. The change has begun at an early embryo stage where morphology still look like a globular form.To correlate the morphological change and the cells events, the division and the cell growth were inferred through measurements. The cell growth behavior changed in the globular embryo. Changes in the division behavior were also observed. The division plan orientations stopped to be stereotyped. Despite the variability, similar behaviors were observed over cell generations and also among precursor of tissues and organs of the embryo.The cell division behavior has been further analyzed by a search of the realized division rules which explain observations with a stochastic model of volume partition. A division rule based on a stochastic 3D surface area minimization has reproduced all observed division plane orientations depending on the volume repartition among daughter cells. The hypothesis of a stochastic division rule based on the cell geometry with a surface area minimization of surface passing through the mother cell centroid seemed to become apparent. But divisions in older cell generations suggested a progressive action of another factor on the division plane.The overall phenotyping the embryo early development should provide a framework for the analysis of molecular factors involved in the heart shape
Roudier, Agnès. "Analyse multi-échelle du comportement hygro-mécanique des fibres de lin." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2012. http://tel.archives-ouvertes.fr/tel-00741951.
Kim, Hae Koo. "Modélisation du contrôle environnemental et génétique du tallage chez le sorgho." Montpellier 2, 2008. http://www.theses.fr/2008MON20074.
This thesis develops a conceptual modelling framework formalizing the environmental (E) and genetic (G) components of tillering control by carbohydrate (C) assimilate availability in sorghum (supply/demand ratio, S/D). This concept was elaborated and tested across five experiments and six contrasting genotypes in terms of tillering ability. The results showed that regulation of tillering was strongly related to its competition with main stem development and leaf morphogenesis, by influencing the appearance frequency of the lower-rank tillers. An indicator of internal competition for C, S/Dindex, was developed and allowed to explain tillering response across the range of G and E investigated. Once confirmed by analysis of sugar distribution within the plant, this indicator was applied (i) to support a genetic study, which identified three quantitative trait loci (QTLs) associated with tillering ability, two of which could be specifically associated with genetic components of S/Dindex (related to leaf width and a S/D threshold for tillering); and (ii) to improve and evaluate an existing plant model (EcoMeristem). Results of this study open new opportunities to investigate the following: (i) G and E bases of the relationship between C dynamics and tillering ability, (ii) the stability of model-based QTLs and (iii) further improvement of EcoMeristem and other models such as APSIM to connect them to genetic information and help develop new sorghum ideotypes
Reyes, Gomez Victor Manuel. "Quantification et modélisation des flux hydriques, thermiques et azotés dans les systèmes de culture en semis direct avec couverture végétale dans la région des Cerrados brésiliens." Montpellier 2, 2002. http://www.theses.fr/2002MON20085.
Landry, Clara. "Modélisation des dynamiques de maladies foliaires de cultures pérennes tropicales à différentes échelles spatiales : cas de la cercosporiose noire du bananier." Thesis, Antilles-Guyane, 2015. http://www.theses.fr/2015AGUY0835/document.
This thesis concerns the modeling of the dynamics of foliar diseases of tropical tree crops at different spatial scales. This modeling approach is applied to black Sigatoka of banana. It is to explore and determine the environmental parameters and host resistance has a significant influence on the spatiotemporal dynamics of the disease and to provide elements associated with the control of Sigatoka noire.Deux models were developed as part of this thesis. The epidemiological dynamics at the plant is described by a mechanistic model decomposed into a growth model of the plant and an epidemiological unit describing the pathogen epidemic cycle. The architecture of the banana is taken into account through foliar compartments positioned in space. The model was validated by an independent data set. Numerical experiments and model sensitivity analysis performed by the methods of Morris and e-FAST enabled to better understand the functioning of this epidemic disease and identify the parameters affecting the most dynamic epidemic especially speed extension of the lesions, the incubation period and efficiency of Bayesian .L'approche infection allowed to take into account prior information available for these three parameters that were the statistical inference. The model sensitivity analysis also identified the influence of two parameters related to plant growth: the number of leaves on a plant and rate of leaf emission A dynamic model of space-time Black Sigatoka has been developed at the scale of a territory from surveys enMartinique during the period of invasion of the disease from September 2010 to May 2012. The data collected being censored, inference of model parameters has was performed in a Bayesian framework, using a data augmentation algorithm. The model developed and inference possible to reconstruct the spatiotemporal dynamics of the invasion and predict the end of the invasion territoire.Les two spatio-temporal dynamics models developed at two different spatial scales has been gained important information for build tools design method of control of black Sigatoka of banana
Qi, Jianbo. "Modélisation 3D du transfert radiatif dans les couverts végétaux et reconstruction de forêts à partir de mesures LiDAR." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30048.
Remote sensing is needed for better managing vegetation covers. Hence, three-dimensional (3D) radiative transfer (RT) modeling is essential for understanding remote sensing signals of complex 3D vegetation covers. Due to the complexity of 3D models, one-dimensional (1D) RT models are commonly used to retrieve vegetation parameters, e.g., leaf area index (LAI), from remote sensing data. However, 1D models are not adapted to actual vegetation covers because they abstract them as schematic 1D layers, which is not realistic. Much effort is devoted to the conception of 3D RT models that can consider the 3D architecture of vegetation covers. However, developing an efficient 3D RT model that works on large and realistic scenes is still a challenging task. Major difficulties are the intensive computational costs of 3D RT simulation and the acquisition of detailed 3D canopy structures. Therefore, 3D RT models usually only work on abstracted scenes or small realistic scenes. Scene abstraction may cause uncertainties, and the small-scale approach is not compatible with most satellite observations (e.g., MODIS). The computer graphics community provides the most accurate and efficient models (i.e., renderers). However, the initial renderer models were not designed for accurate RT modeling, which explains the difficulty to use them for remote sensing applications. Recently emerged advanced techniques in computer graphics and light detection and ranging area (LiDAR) make it more possible to solve the above problems. 3D RT can be greatly accelerated due to the increasing computer power and improvement of rendering algorithms (e.g., ray-tracing acceleration and computational optimization). Also, 3D high-resolution information from LiDARs and photogrammetry become more accessible to reconstruct realistic 3D scenes. This approach requires new processing methods to combine 3D information and 3D RT models, which is of great importance for better remote sensing survey of vegetation. This thesis is focused on 1) Development of a 3D RT model based on recent ray-tracing techniques and 2) Retrieval of 3D leaf volume density (LVD) for constructing 3D forest scenes. This first chapter presents the development of an efficient 3D RT model, named LESS (LargE-Scale remote sensing data and image Simulation framework). LESS makes full use of ray-tracing algorithms. Specifically, it simulates multispectral BRF and scene radiative budget with a weighted forward photon tracing method, and sensor images (e.g., fisheye images) or large-scale (e.g. 1 km2) spectral images are simulated with a backward path tracing method. In the forward mode, a "virtual photon" algorithm is used to simulate accurate BRF with few photons. The backward mode is used to simulate thermal infrared images and also atmosphere RT. LESS efficiency and accuracy were demonstrated with a model intercomparison and field measurements. In addition, LESS has an easy-to-use graphic user interface (GUI) to input parameters, construct and visualize 3D scenes. 3D forest reconstruction is done with a simulated LiDAR dataset to assess approaches that retrieve LVD from airborne LiDAR data. The dataset is simulated with the discrete anisotropic radiative transfer model (DART)
Gachet, Sophie. "Organisation de la biodiversité forestière : vers une modélisation de la dynamique du sous-bois en fonction des pratiques sylvicoles." Aix-Marseille 3, 2002. http://www.theses.fr/2002AIX30061.
In the French Mediterranean region, several forest ecosystems are undergoing significant evolution as a result of historical and ecological factors. Knowledge of how forestry practices may affect the biodiversity of these evolving ecosystems is important for their management. At Mont Ventoux (Vaucluse, southern France), a new, natural dynamic of invasion and expansion of deciduous trees is taking place in existing Pinus nigra var. Austriaca forests, planted as part of a mountain reforestation program in around 1900. Using floristic inventories, the effects of these changes on the understory species were recorded, both taxonomically and functionally (using vital attributes). From this information, four models have been built and compared, linking dendrometric parameters of the forests and the proportion of each vital attribute (biological spectra). The combined evolution of the forest populations and understory populations were then simulated over a period of one hundred years
Dupont, Sylvain. "Modélisation de la micrométéorologie à l'échelle de paysages complexes." Habilitation à diriger des recherches, Université Paul Sabatier - Toulouse III, 2009. http://tel.archives-ouvertes.fr/tel-00443770.
Fakih, Mahmoud. "Modélisation numérique discrète de la croissance racinaire dans un sol : relation force-forme." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT323/document.
Plant roots play an important role in the growth and development of plants, and it is well known that the mechanical interactions between a growing root and the surrounding soil can have a major impact on root growth and consequently on plant biomass production. These mechanical interactions are one of numerous factors that explain the variability of root architecture, including genetics, environment and developmental instability. But this factor has often been under-estimated. I hypothesize that the heterogeneous structure of soil at the particle scale, demonstrated by the broad distribution of forces, can significantly influence root growth trajectories. This thesis aims at determining how grains in granular soils are reorganized under the action of growing roots, and in return how the resulting forces acting on root tips modify their development, including the kinematics of their trajectories, in order to develop a general biophysical law of root-soil mechanical interactions. I developed a 2D numerical model of root growth in a granular medium using a Discrete Element Model (DEM). The model is able to compute grain-grain and root-grain contact forces within a granular medium. The root system is modelled using chains of connected spheroline elements. The orientation of root growth at every growth step is determined by the dynamics of the whole root under the action of its internal elastic forces and reaction forces exerted by the grains, which are the mechanical interactions that control numerical growth in the model.Parametric studies were carried out in order to (i) estimate the influence of granular structure (grain diameter distribution, cohesion, volume fraction) and root mechanical properties (root bending stiffness) on the axial force signal acting on the root tip, and on the root trajectories and (ii) define general physical laws that can be used further to analyze experimental data. The distribution curves of computed root tip-grain forces normalized by the mean force during a given period of growth were characterized by a decreasing power law for forces below the mean force, and an exponential fall-off for forces above the mean force, thus reflecting the broad distribution of forces inside the granular material. An analysis of the standard deviation of the local deformations of root trajectories resulted in two different regimes with regard root stiffness. In the first regime, soil controlled the root deformation and in the second, the root trajectory was straighter and displaced more significantly the surrounding grains during growth
Niez, Benjamin. "Acclimatation de l'arbre aux flexions répétées et conséquences sur le comportement mécanique et les propriétés hydrauliques du bois vert : Biologie végétale." Thesis, Université Clermont Auvergne (2017-2020), 2018. http://www.theses.fr/2018CLFAC046/document.
Trees, anchored in the ground, adjust their development to their fluctuating environment and particularly to the mechanical conditions daily imposed by wind. Storms of last decades enlightened that acclimation of trees to mechanical stresses due to wind is a vital requirement for their long-term survival. Wind mainly leads to repeated bending of the branches and stems of trees that swing during windy events. These bending cause a modulation of trees growth in height, in diameter or at the level of the root system but also imply the formation of a wood with specific anatomy and properties; this wood was defined as “Flexure wood”. In our work, we developed original experimental setups in order to apply a treatment of repeated unidirectional bending to the stem of young poplars, while controlling the magnitude of the strains applied to the stem. The setup controlled different levels of hydric stress too. The monitoring of the growth during a growing season showed that the mechanical acclimation is a process that, although costly in terms of biomass construction, turns out to be essential and takes place even under severe hydric stress. Besides, we demonstrated that the increase of biomass, linked to this acclimation, is mainly provided in the areas where tissue strains are the highest; leading to specific cross-section geometries that considerably increase the stem bending rigidity. A mechanical modelling using Finite Elements also enlightens that these configurations, due to acclimation, lead to a better distribution of mechanical stresses, especially by decreasing the intensity of maximal compressive stresses endured by wood. In order to investigate the microscopic scale, original experimental devices were developed at the tissue scale to measure the effect of different mechanical stresses (repeated compression and/or tension), applied by stem bending, on the hydraulic and mechanical properties of green wood; as much in terms of usual properties (elastic behaviour, hydraulic conduction) as in terms of security functions (rupture, sensibility to cavitation, …). Thus, we enlighten the specific behaviour of wood formed under repeated compressive stresses that shows a significant increase of its ability to withstand high levels of strains with a very reduced damaging. The whole experimental and modelling results, as much at the tissue scale as at the tree scale, points out that the acclimations of secondary growth and wood properties provide a mechanical benefit for tree sustainability in its fluctuating windy environment
Romero, Gilles. "Contribution à l'étude et à la modélisation de la réflexion de la lumière sur une matière végétale : application au tri d'aspect de fruits par faisceau laser multiraies." Bordeaux 1, 1993. http://www.theses.fr/1993BOR10615.
Dias, Alves Thomas. "Modélisation du déséquilibre de liaison en génomique des populations par méthodes d'optimisation." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAS052/document.
We present a new formalism and new methods to model linkage disequilibrium and to account for haplotype structure of population genomics data. Modeling relies on an optimization problem with constraints that is solved using dynamic programming. The algorithmic cost of proposed methods is linear, which is a desirable property to process large datasets.First, we applied our framework to study admixed populations and perform local ancestry inference. Our method is applied to simulated genotypes of admixed human populations and to real genotypes from admixed Populus species.Second, we developed our optimization framework to perform haploptype phasing and imputation based on a population of genotypes. All optimization methods have been developed in a Python package called Loter
Rizzetto, Simon. "Prédiction de la sensibilité biogéochimique et écologique des écosystèmes forestiers français aux dépôts atmosphériques azotés dans un contexte de changement global." Phd thesis, Toulouse, INPT, 2017. http://oatao.univ-toulouse.fr/19558/1/Rizzetto.pdf.
KALLEL, Abdelaziz. "Inversion d’images satellites « haute résolution » visible / infrarouge pour le suivi de la couverture végétale des sols en hiver par modélisation du transfert radiatif : fusion de données et classification." Paris 11, 2007. http://www.theses.fr/2007PA112333.
Estimation of vegetation features from space is of high interest for hydrologist community since land cover during winter in agricultural regions strongly influences soil erosion processes and water quality. The object of this PhD Thesis is then the estimation of the vegetation cover (more precisely its density thought the vegetation cover fraction, fCover) using ‘high resolution’ remote sensing data in the Visible and the Near Infrared domain. The Yar experimental watershed (in Britain) was used for our work validation. First, we have studied the modelling (direct and inverse models) of the interaction between the solar radiation and the vegetation in the visible and Near Infrared domains, using the Radiative Transfer (RT) theory. The proposed direct RT model is based on Adding and SAIL formalisms, enhancing the modelling of the diffuse fluxes and taking into account the multi hot spot effect. Then, to inverse the fCover, we pitch on a semi-empirical model based on the fCover isoline parameterization using the coupled model SAIL/Adding. Then, to improve the estimation of the fCover, we propose to combine the results provided by our inverse model with other vegetation indices. For this, in the framework of the evidence theory, a new combination rule taking into account the correlation between indices was developed. Finally, in order to obtain a map of the fCover classes, we have proposed a new Markov classification relaxing the assumption of stationary of neighbourhood form to use an adaptive neighbourhood for each pixel
Meridja, Samir. "Approche biophysique des processus de développement et de croissance des couverts végétaux : Interaction avec le stress hydrique et optimisation des pratiques culturales en climat méditerranéen." Phd thesis, AgroParisTech, 2011. http://pastel.archives-ouvertes.fr/pastel-00776775.
Rahantaniaina, Marie Sylviane. "Vers une meilleure compréhension des systèmes antioxydants chez la plante face aux contraintes environnementales : approches expérimentales et modélisation mécaniste." Electronic Thesis or Diss., Sorbonne université, 2018. http://www.theses.fr/2018SORUS246.
The most important metabolic pathways in the control of oxidative stress remain to be elucidated in plants. Those linked to glutathione play an important role. However, the reactions responsible for its oxidation have not been clearly identified. Here, analysis based on available biochemical, transcriptomic and genetic data emphasized likely important questions to be elucidated for a full understanding of how stress-related redox regulation might impinge on phytohormone-related signaling pathways. Using a reverse genetics approach and the photorespiratory conditional cat2 mutant, we studied the response and functional importance of three potential routes for glutathione oxidation pathways mediated by glutathione S-transferases, glutaredoxin dependent peroxiredoxins, and dehydroascorbate reductases (DHAR) in Arabidopsis during oxidative stress. Hence, interplay between different DHARs appears to be necessary to couple ascorbate and glutathione pools and to allow glutathione-related signaling during enhanced H2O2 metabolism. In addition to experimental work, modelling is another way to investigate H2O2 production and its metabolism related to catalase activity and ascorbate glutathione pathway. This approach led to major conclusions, that catalase and ascorbate peroxidase can share the load in H2O2 processing even in optimal growth conditions. Furthermore, simulations propose that NADPH availability may determine glutathione oxidation through its influence on monodehydroascorbate reduction. Taken together, experimental results and our kinetic model strengthen that the sensitivity of glutathione status to oxidative stress acts as a suitable sensor of increased H2O2
Djedjig, Rabah. "Impacts des enveloppes végétales à l’interface bâtiment microclimat urbain." Thesis, La Rochelle, 2013. http://www.theses.fr/2013LAROS421/document.
This study was conducted in the framework of the National Program "ANR-VegDUD Project : Role of vegetation in sustainable urban development, an approach related to climatology, hydrology, energy management and environments" (2010 -2013). It deals with the experimental and numerical modeling of green roofs and green facades to evaluate their thermohydric effects on buildings and urban microclimates. A physical model describing the thermal and water transfer mechanisms within the vegetated building envelopes has been developed. The model’s program has been implemented in a building simulation program. Using this tool, we are able to predict the impact of green roofs and green facades on building energy performance. This approach is extended to the street canyon in order to assess the microclimatic interaction in building simulation. An experimental mockup modeling an urban scene at reduced scale is designed to study the impact of different types of green roofs and walls. The comparison of the measurements carried out on vegetated buildings and streets with the reference highlights the hygrothermal and radiative impacts of vegetated buildings envelopes. In addition, these experimental data are used to verify and validate the reliability of developed tools. The results show that thermal and water transfers are strongly coupled. Hence, the thermal behavior of green roofs and green walls depend on the water availability within the growing medium. In summer and winter, measurements and numerical simulations show that green envelopes improve the energy efficiency of buildings and reduce the urban heat island
Villemin, Thomas. "Modélisation des échanges énergétiques entre la surface d’une toiture végétalisée extensive et un panneau photovoltaïque." Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0118.
The increasing densification and artificialization of the urban environment have induced many negative impacts on the scale of the city and make this environment ultra-constrained from the point of view of energy needs and thermal comfort. Moreover, energy demand has increased considerably and the building sector alone is responsible for 44% of the energy consumed in France each year. The negative impacts are already perceptible for the inhabitants and the phenomenon of Urban Heat Island (UHI) is observed in most large cities. The total surface of flat roofs in a typical city represents about 20 to 25% of the city. However, these surfaces are globally unexploited although they are the privileged place for thermal and mass transfers between the building and its environment. An interesting solution to green the urban environment and promote energy production in the city consists in the introduction of extensive green roofs on flat roofs associated with photovoltaic panels. The vegetated roof allows to fulfill ecosystemic functions and the photovoltaic panels produce electricity at the place of consumption. In recent years this solution has not been seen as an opportunity and the two systems have instead been put in competition. In this context, this thesis is intended to evaluate the individual and reciprocal impacts, both positive and negative, of the two subsystems when combined. Indeed, it is expected that the evapotranspiration flow of the green roof induces a lowering of the temperature of the photovoltaic cells, favouring the electrical production. The work carried out has allowed to experimentally evaluate the performance of vegetated plots on the electrical production of photovoltaic panels. In addition, several models were developed to simulate the thermal behavior of the panels according to the weather conditions in which they are located using the Monte Carlo method. These models were applied to evaluate the energy performance at the scale of the photovoltaic system alone but also at the scale of the building in order to determine its energy needs (heating and cooling needs). A Monte Carlo model has also been implemented at the scale of the photovoltaic cell with promising first results for such systems in real operating conditions
Mayrand, Flavie. "Modélisation du fonctionnement hydrologique du sol et de la biodiversité des communautés végétales. Application à l'analyse de la performance écologique d'un aménagement paysager autoroutier." Phd thesis, AgroParisTech, 2012. http://pastel.archives-ouvertes.fr/pastel-00948342.
Mayrand, Flavie. "Modélisation du fonctionnement hydrologique du sol et de la biodiversité des communautés végétales. Application à l'analyse de la performance écologique d'un aménagement paysager autoroutier." Electronic Thesis or Diss., Paris, AgroParisTech, 2012. http://www.theses.fr/2012AGPT0086.
Human activities are responsible for high modifications in ecosystems functioning. It is recognized that these impacts cause definitive and high losses rate of biodiversity in every components of wildlife. Due to regulation, construction companies are bound to evaluate environmental impacts of the infrastructure construction projects (eg: roads), and more particularly, impacts on biodiversity. Companies are also bound to propose measures to avoid, reduce or mitigate residuals impacts by the creation or restoration planning of biodiversity. Unfortunately, there are not existing tools and methods clearly defined by regulation for such plans. Most of the time, predictions and environmental evaluations fail in measuring the impacts on biodiversity and efficiency of conservation planning. The research program that we conducted aimed at (i) proposing a new methodological approach in order to characterise processes and abiotic parameters which impact biodiversity of plant communities, (ii) analysing conservatory plans efficiency and (iii) proposing measures for biodiversity valuation in our study case. Our study was realised in a landscaping project zone along the A19 highway, Loiret, France. Seedling and planting were done two years before our study began. Only hydrological processes were studied based on mechanistic modelling using Hydrus-1D software. Last and final summary in the thesis
Siméon, Alexandre. "Modélisation régionale et télédétection spatiale des propriétés d’absorption des aérosols de feux de biomasse dans la région de l’Atlantique Sud-Est." Thesis, Lille 1, 2020. http://www.theses.fr/2020LIL1R027.
Aerosol absorption is a key property to assess aerosol radiative impacts, both direct and on cloud properties, on regional climate. Recent studies have shown that some aerosol organic compounds (OC) called "brown carbon" (BrOC), mainly emitted by biomass burning, can absorb radiation significantly in the ultraviolet-visible-near-infrared spectrum. The main objective of this work is to improve the representation of the absorption properties of aerosols in regional climate models. We focus on biomass burning particles plumes transported above clouds in the Southeast Atlantic region, off the west coast of Africa. This is a region highlighted as a natural laboratory to better understand the complexity of aerosol-cloud interactions. The methodology relies on regional aerosol numerical simulations from the coupled meteorology-chemistry WRF-Chem model combined with a detailed state-of-the-art biomass burning emission inventory and different sets of innovative aerosol remote sensing observations, both in clear and cloudy skies from the POLDER-3/PARASOL satellite sensor. Current literature indicates that brown carbon absorbs more efficiently UV-blue radiation than pure black carbon (BC). The idea is to exploit this specificity by comparing the spectral dependence of the single scattering albedo retrieved from POLDER-3 observations in the 443-1,020 nm to the one simulated for different proportions of BC, OC and BrOC. Two main constraints are used to build up these sensitivity tests: keeping realistic clear-sky/above-cloud aerosol optical thickness and BC-to-OC mass ratio. Modeling experiments are presented and discussed to provide new estimates of the black, organic and brown carbon contents in the African biomass burning aerosol plumes transported over the Southeastern Atlantic region
Siméon, Alexandre. "Modélisation régionale et télédétection spatiale des propriétés d’absorption des aérosols de feux de biomasse dans la région de l’Atlantique Sud-Est." Electronic Thesis or Diss., Université de Lille (2018-2021), 2020. http://www.theses.fr/2020LILUR027.
Aerosol absorption is a key property to assess aerosol radiative impacts, both direct and on cloud properties, on regional climate. Recent studies have shown that some aerosol organic compounds (OC) called "brown carbon" (BrOC), mainly emitted by biomass burning, can absorb radiation significantly in the ultraviolet-visible-near-infrared spectrum. The main objective of this work is to improve the representation of the absorption properties of aerosols in regional climate models. We focus on biomass burning particles plumes transported above clouds in the Southeast Atlantic region, off the west coast of Africa. This is a region highlighted as a natural laboratory to better understand the complexity of aerosol-cloud interactions. The methodology relies on regional aerosol numerical simulations from the coupled meteorology-chemistry WRF-Chem model combined with a detailed state-of-the-art biomass burning emission inventory and different sets of innovative aerosol remote sensing observations, both in clear and cloudy skies from the POLDER-3/PARASOL satellite sensor. Current literature indicates that brown carbon absorbs more efficiently UV-blue radiation than pure black carbon (BC). The idea is to exploit this specificity by comparing the spectral dependence of the single scattering albedo retrieved from POLDER-3 observations in the 443-1,020 nm to the one simulated for different proportions of BC, OC and BrOC. Two main constraints are used to build up these sensitivity tests: keeping realistic clear-sky/above-cloud aerosol optical thickness and BC-to-OC mass ratio. Modeling experiments are presented and discussed to provide new estimates of the black, organic and brown carbon contents in the African biomass burning aerosol plumes transported over the Southeastern Atlantic region
Bouyer, Julien. "Modélisation et simulation des microclimats urbains - Étude de l'impact de l'aménagement urbain sur les consommations énergétiques des bâtiments." Phd thesis, Université de Nantes, 2009. http://tel.archives-ouvertes.fr/tel-00426508.
Moulin, Thibault. "Modélisation mathématique de la dynamique des communautés herbacées des écosystèmes prairiaux." Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCD075/document.
Dynamic modelling of ecological systems is an essential method to understand, predict and control thedynamics of semi-natural ecosystems, which involves complex processes. The main objective of this PhDthesis is to develop a simulation model of the medium- and long-term dynamics of the herbaceous vegetationin permanent grasslands, taking into account both biodiversity and productivity. Grasslandecosystems are often hot spots of biodiversity, which contributes to the temporal stability of their services.On an agricultural perspective, this important biodiversity contributes to the forage quality, andbesides, it induces a higher ability of the vegetation cover to resist to different climatic scenarios (globalwarming, heat and drought waves).However, this key aspect of biodiversity is only poorly included in grassland models : often absent ofmodelling or included in a very simple form. Building on those considerations, this PhD work exposes thewriting of a process-based succession model, described by a system of Ordinary Differential Equationsthat simulates the aboveground vegetation dynamics of a temperate grassland. This model implementedthe main ecological factors involved in growth and competition processes of herbaceous species, and couldbe adjust to any level of diversity, by varying the number and the identity of species in the initial plantcommunity. This formalism of mechanistic models allows us to analyse relationships that link diversity,productivity and stability, in response to different climatic conditions and agricultural management.In mathematical grassland models, plant communities may be represented by a various number of statevariables, describing biomass compartments of some dominant species or plant functional types. The sizeof the initial species pool could have consequences on the outcome of the simulated ecosystem dynamicsin terms of grassland productivity, diversity, and stability. This choice could also influence the modelsensitivity to forcing parameters. To address these issues, we developed a method, based on sensitivityanalysis tools, to compare behaviour of alternative versions of the model that only differ by the identityand number of state variables describing the green biomass, here plant species. This method shows aninnovative aspect, by performing this model sensitivity analysis by using multivariate regression trees. Weassessed and compared the sensitivity of each instance of the model to key forcing parameters for climate,soil fertility, and defoliation disturbances. We established that the sensitivity to forcing parameters ofcommunity structure and species evenness differed markedly among alternative models, according tothe diversity level. We show a progressive shift from high importance of soil fertility (fertilisation level,mineralization rate) to high importance of defoliation (mowing frequency, grazing intensity) as the sizeof the species pool increased.These results highlight the need to take into account the role of species diversity to explain the behaviourof grassland models. Besides, to properly take into account those interactions in the grassland cover, theconsidered species pool size considered in the model needs to be high enough. Finally, we compare modelsimulations of the aboveground vegetation to measures from two experimental sites, the mowing grasslandof Oensingen, and the grazing grassland of Laqueuille. Results of these comparison are promising andhighlight the relevance of the choice and the representation of the different ecological processes includedin this mechanistic model.Thus, this PhD work offers a model, perfectly fitting with current needs on grassland modelling, whichcontribute to a better understanding of the herbaceous vegetation dynamics and interactions betweenproductivity, diversity and stability
Betene, Ebanda Fabien. "Etude des propriétés mécaniques et thermiques du plâtre renforcé de fibres végétales tropicales." Thesis, Clermont-Ferrand 2, 2012. http://www.theses.fr/2012CLF22298/document.
The plaster is a material of high availability and very known for its qualities : it is favourable to the protection of the environment, quite malleable, of low density, its functional properties are remarkable (firewall, thermal insulation, regulator of the hygroscopy of enclosures), decorative, ... What justifies the interest attached to this material for constructions. Its great alarming brittleness is at the origin of the research tasks in the whole world for its strengthening. The glass fibers and sisal are the more used reinforcements to this day. The strengthening by plant fibers is more and more researched. The microstructure of the plaster is porous ; that promotes its heat insulation character. The textures implemented so far are limited to porosities ranging between 30 and 55%. The reduction of cost of this material for a wide use is still possible and desired. Two levers are exploited in this work, in particular a lightening of the plaster weight to increase the proportion of air voids and a reinforcement of the mechanical resistance with locally produced fibers. The objective of this work is to evaluate the mechanical, thermal and hygrometrical characteristics of a material made up of harden plaster, with high porosity, strengthened by a new plant fiber : the Rhecktophyllum Camerunense (RC), a fiber of humid equatorial forests. The sisal fiber, of known use for the strengthening of the plaster, serves as a reference for comparison purposes. A serie of experiments is conducted to this effect. A physicochemical characterization of constituents is performed. Mechanical tests of tensile and of bending are performed on the constituents and the resulting plaster/fiber composite materials. The kinetic adsorption of moisture by the constituents is followed. The thermal behaviour of plaster and plaster/fiber is also measured. The fibers used, sisal and RC are with high rates of cellulose (between 49 and 78.8% ), the fiber of RC is tubular with 35.5 % of porosity. The plaster is dissolved in demineralized water to a mass ratio W/P equals to 1 from the powder of semihydrate β. Its crystalline microstructure is composed of gypsum crystals in the form of needles tangled with the empty intercristallins. As far as the mechanical behavior is concerne, the result reveals that the plaster is weak, its Young’s modulus in tensile is 1.72 GPa, its tensile strength is 0.86 MPa and its elongation at break is 1.16 %. In three points bending test, its modulus of elasticity is 0.64 GPa and its constraint at break is 0.13 MPa. The sisal fiber is stiff and fragile. Its Young’s modulus is between 9 and 21 GPa, it admits an elongation at break of 3 to 7 %. On the other side, the fiber of RC is quite ductile : the means of Young’s module is 7 GPa and the elongation at break is 24.2 %. The adhesion of the plaster on the fiber surface is low : it adheres more on the sisal than on the RC. The sisal strengthened better the plaster with a sensitive increase of the Young’s modulus of 42.5 %, against 16.3 % for the RC. But the RC fiber gives rather high elastic ductility. The fibers of RC deliver maximum capacity in tensile to the plaster when they are woven into unidirectional. They offer high capacity in bending when they are uniformly distributed inside the volume according to the longitudinal direction of the structure. (...)
Falcoz-Vigne, Léa. "Caractérisation et modélisation des interactions cellulose - hémicelluloses au sein des microfibrilles de cellulose (MFC)." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAV091/document.
The study was motivated by the necessity to reduce the high energy costs of Micro-Fibrillated Cellulose (MFC) production, which is a limiting factor for its industrial development and aimed at understanding the cellulose/hemicelluloses interaction within this system. MFC resulting from different chemical pulps were characterized by solid-state NMR spectroscopy to get information on the hemicelluloses content and molecular conformation. By optimizing an extraction protocol, more than 60% of the residual hemicelluloses were extracted from birch kraft MFC and characterized as a high purity homopolymer of β-1,4 linked xylan of DP 75.Turbidimetry was used to qualify the quality of the suspensions, which strongly depended on the pulping and drying history. Positive correlations between the state of dispersion, specific surface and mechanical properties of MFC-reinforced handsheets were evidenced.Cellulose/xylan interactions were investigated using solid-state NMR and atomistic molecular dynamics (MD) simulation. NMR spectra confirmed that xylan in contact with cellulose altered its conformation, from the three-fold helix to a presumable cellulose-like two-fold one. In combination with specific surface area measurements, the conformational change was shown to happen only for the first layer of xylan adsorbed in direct interaction with the cellulose surface. MD simulations showed that adsorbed xylan tends to align parallel to the cellulose chain direction fully extended. Interaction energy between xylan chain and cellulose surface estimated with MD was 9kJ/xylose. Then a three-layers system made of xylan between two cellulose films were built to perform adhesion tests that showed strong adhesion between xylan and cellulose surfaces. Xylanase was proposed as a pulp pretreatment for MFC production
Journé, Valentin. "Influence du climat lors de l'investissement des ressources dans la reproduction chez les arbres forestiers : une approche par modélisation mécaniste." Thesis, Aix-Marseille, 2020. http://theses.univ-amu.fr.lama.univ-amu.fr/200217_JOURNE_229kn950dq423kitgvy940umn_TH.pdf.
Global changes affect species distribution and ecosystems functioning due to long term climatic trends and extreme climatic events. Forests are notably subject to massive growth decline and even mortality. One of the major processes of forest dynamics is sexual reproduction, but there are still many uncertainties about the effect of climate on trees reproduction, especially on when and how resources are allocated to pollen and seeds. Reproduction also allows species to persist over generations, through adaptation and migration. The main objective of this thesis is to develop an approach based on resource and phenology modelling, in order to understand and predict climate effects on forest trees reproduction. First, I used statistical model to investigate temporal and spatial variation of fruit production. Second, I quantified the allocation of resources between vegetative versus reproductive functions, with a hierarchical Bayesian model and observation of growth, male and female reproduction over several years. Results allowed us to identify trade-off during floral initiation, and highlighted the importance of resources levels to ensure reproduction. Lastly, I developped a process-based model of reproduction and included it in an existing model of forest functioning (CASTANEA). The reproduction model, which runs from flower initiation to seed maturation, simulates spatial and temporal patterns of seed production. The model was calibrated and validated on silver fir on Mont-Ventoux and used to investigate how climate change will impact fruit production