Ce travail de thèse démontre l’importance d’intégrer des outils théoriques à des observations expérimentales dans le but d’étudier le rôle des interactions non-covalentes et plus précisément de la dispersion dans la chimie des métaux de transition. Plusieurs thèmes ont ainsi été abordés comme les interactions d’empilement entre chélates de métaux de transition à l’état solide; l’influence de la chiralité sur l’oligomérisation en solution de complexes plans carrés de Rh(I) isonitrile; la stabilité et inactivité inhabituelles de complexes de type cis-platine en solution concentrée. Les résultats obtenus par titration calorimétrique isotherme ont permis d’évaluer la capacité de méthodes théoriques à reproduire avec précision les résultats expérimentaux. Les calculs ont démontré qu’un traitement théorique approprié des effets de la dispersion et de la solvatation, donne des valeurs cohérentes avec les résultats expérimentaux. Cependant, des améliorations supplémentaires sont nécessaires. / This thesis has shown the importance of integration of theoretical calculations and experimental investigations in studying the role of non-covalent interactions and particularly dispersion interactions in transition metal chemistry. Several subjects were addressed, such as stacking interactions of chelates in transition metal complexes in solid state, influence of chirality on the oligomerization of Rh(I) isonitrile complexes in solution and the stability of the cis-platin type complexes in concentrated solutions. Isothermal titration calorimetry proved to be very useful in the studies by providing accurate experimental data on the thermochemistry of addressed processes. This data was used to gauge the ability of the theoretical methods to accurately reproduce the experimental results. Calculations have shown that the proper treatment of dispersion effects and solvation by theoretical models gives values in relatively good agreement with experiments, but further improvements are needed.

No presente trabalho, foram processados compósitos de polietileno de alta densidade (PEAD) com hidroxiapatita deficiente de cálcio (HA), com o objetivo de obter materiais com melhores propriedades mecânicas e bioatividade. A adição da HA deficiente de cálcio proporcionou um aumento no módulo de elasticidade (maior rigidez), menor resistência ao impacto e decréscimo do grau de cristalinidade do PEAD, proporcionando uma maior bioatividade ao material. A análise térmica exploratória (sistema não isotérmico) foi realizada por meio da técnica de calorimetria exploratória diferencial (DSC) e foram avaliados os teores de fosfato de cálcio e a velocidade de rotação da rosca no processamento dos materiais. No estudo da cristalização não-isotérmica observou-se uma diminuição da temperatura de cristalização com o aumento da taxa de resfriamento para todos os materiais sintetizados. A energia de ativação (Ea) da cristalização dos materiais foi avaliada por meio dos métodos Kissinger e Ozawa. A amostra com 5% de HA deficiente de cálcio e velocidade de processamento de 200 rpm foi a que apresentou menor valor de energia de ativação, 262 kJ/mol, menor desvio da linearidade e a que mais se assemelhou à matriz de PEAD sem HA. O teor de hidroxiapatita deficiente de cálcio não favorece o processo de cristalização devido à alta energia de ativação determinada pelos métodos descritos. Provavelmente, a velocidade de rotação, favorece a dispersão da carga na matriz de PEAD, dificultando o processo de cristalização. Na aplicação do método de Osawa-Avrami, os coeficientes de correlação indicaram perda na correlação linear. Estas perdas podem estar associadas a uma pequena percentagem de cristalização secundária e/ou à escolha das temperaturas utilizadas para determinar a velocidade de cristalização. Na determinação dos parâmetros pelo método de Mo, as menores percentagens de cristalização apresentaram um grande desvio da linearidade, com coeficiente de correlação bem menor que 1 e com o aumento da percentagem de cristalização, o desvio da linearidade diminui, ficando próximo de 1. Os resultados obtidos mostraram que o modelo de Mo e de Osawa-Avrami não foram capazes de definir o comportamento cinético dos materiais produzidos neste trabalho. / In this work, composites of high density polyethylene HDPE with calciumdeficient hydroxyapatite were synthesized in order to obtain materials with good mechanical properties and bioactivity. The addition of calcium-deficient hydroxyapatite resulted in an increase in elastic modulus (high rigidity), lower impact resistance and lower HDPE crystallinity degree, promoting, in these materials, a higher bioactivity. Scanning thermal analysis (non-isothermal system) was carried out by differential scanning calorimetry (DSC), and it was evaluated the calcium phosphate content added and the screw speed in the processing. In non-isothermal crystallization studies it was observed a decrease in crystallization temperature as the cooling rate was increased for all produced materials. The activation energy of crystallization was evaluated by Kissinger and Ozawa methods. The sample with 5 wt.% of calcium-deficient hydroxyapatite and processed at 200 rpm screw speed showed the lower value of activation energy (262 kJ/mol) and the lower deviation from linearity. Calcium-deficient hydroxyapatite does not promote the crystallization process due to the high activation energy determined by the described methods. Probably the screw speed promotes the dispersion of the filler in the HDPE matrix and hinders the crystallization process. Correlation coefficients in Osawa-Avrami method indicated loss in the linear correlation. These losses might be associated with a small percentage of secundary crystallization and/or the temperatures chosen to determine the crystallization rate. The parameters obteined from Mo method, the lower percentages of crystallization showed a great deviation from linearity, with correlation coefficient much smaller than 1, when increasing the percentage of crystallization, the deviation from linearity decreases, getting closer to 1.The results of Mo and Osawa-Avrami models were not able to set the kinetic behavior of the materials produced in this study.

Les aciers bainitiques sont utilisés industriellement pour leur bon compromis entre résistance, ductilité et ténacité. Cependant, après obtention de sa microstructure d'emploi, l’acier peut subir des maintiens additionnels en température (soit en fin de fabrication et/ou lors de son utilisation), susceptibles de dégrader ses propriétés. Ces travaux de thèse cherchent à comprendre les origines microstructurales de cette dégradation. Pour ce faire, des traitements thermiques contrôlés ont été appliqués à des aciers de nuances modèles FeNiC et FeNiMnC. Une première série de traitements a permis de fabriquer des microstructures bainitiques supérieure, inférieure, martensitique et mixtes. Ces produits de transformation bruts ont été caractérisés et analysés en détail, en particulier par EBSD en résolution angulaire améliorée. Les données ont été exploitées pour reconstruire les ex-grains austénitiques et distinguer les différents produits de transformation par l'organisation spatiale de leurs variants cristallographiques. Une deuxième série de traitements a consisté à soumettre ces microstructures à des maintiens isothermes prolongés. Nous avons montré que ces microstructures bainitiques en lattes ne sont pas stables dans certaines conditions ultérieures de maintien isotherme. Dans les cas les plus sévères, nous avons observé un processus de « granularisation » de la microstructure en lattes avec disparition des variants fortement désorientés et une maturation des carbures. Ces phénomènes sont observés sur nos alliages modèles y compris sur des temps courts (<1h) à basses températures (300°C). Ces évolutions ainsi que leurs cinétiques ont été investiguées à différentes échelles en couplant des observations en MEB, EBSD, MET et aussi in situ par DRX Haute Energie sur grands instruments. La composition chimique et la microstructure initiale affectent sensiblement les cinétiques. Mais nous avons surtout pointé le rôle majeur de la présence (même résiduelle) de bainite dite supérieure dans la microstructure initiale pour amorcer le processus de granularisation, indépendamment de la température de dénaturation. L’ensemble des résultats permet de discuter les possibles mécanismes sous-jacents et leurs forces motrices et ouvre une discussion plus large sur la classification des bainites / Bainitic steels are widely used in industry thanks to their good combinations of strength, toughness and ductility. Meanwhile, after obtaining the targeted microstructure, the steel can undergo additional isothermal holdings (either during manufacturing and/or during usage) prone to degrade its properties. The thesis work aims at understanding the microstructural origins of this degradation. To achieve this, we applied controlled heat treatments on model FeNiC and FeNiMnC steel grades. A first set of heat treatments allowed us to obtain different microstructures; upper and lower bainites, martensite and mixed concepts. These transformation products were characterized and analyzed in detail, particularly by EBSD with improved angular resolution. Data was operated to reconstruct prior austenitic grains and to distinguish the different transformation products according to their crystallographic variant spatial organization. A second set of heat treatments consisted in aging these microstructures by extended isothermal holdings. We show that lath-like bainitic microstructures are not stable under certain isothermal conditions. In the most advanced cases, we observed a « granularization » process of the lath microstructure, associated with high misoriented variant disappearance and carbides ripening. These phenomena were observed for the studied model alloys, even within short holding times (<1h) and at low temperatures (300°C). These highlighted evolutions as well as their kinetics were investigated at different scales, coupling SEM observations, EBSD, TEM and in situ XRD High Energy on large instruments. The initial microstructure and the steel chemical composition affect significantly the « granularization » kinetics. But we have above all put the light on the major role of the presence of an upper bainite fraction (even a residual one) in the initial microstructure, to start the granularization phenomenon, independently of aging temperature. All of these results allow discussing possible mechanisms with their respective driving forces and opening larger discussion about bainite classification

No presente trabalho, foram processados compósitos de polietileno de alta densidade (PEAD) com hidroxiapatita deficiente de cálcio (HA), com o objetivo de obter materiais com melhores propriedades mecânicas e bioatividade. A adição da HA deficiente de cálcio proporcionou um aumento no módulo de elasticidade (maior rigidez), menor resistência ao impacto e decréscimo do grau de cristalinidade do PEAD, proporcionando uma maior bioatividade ao material. A análise térmica exploratória (sistema não isotérmico) foi realizada por meio da técnica de calorimetria exploratória diferencial (DSC) e foram avaliados os teores de fosfato de cálcio e a velocidade de rotação da rosca no processamento dos materiais. No estudo da cristalização não-isotérmica observou-se uma diminuição da temperatura de cristalização com o aumento da taxa de resfriamento para todos os materiais sintetizados. A energia de ativação (Ea) da cristalização dos materiais foi avaliada por meio dos métodos Kissinger e Ozawa. A amostra com 5% de HA deficiente de cálcio e velocidade de processamento de 200 rpm foi a que apresentou menor valor de energia de ativação, 262 kJ/mol, menor desvio da linearidade e a que mais se assemelhou à matriz de PEAD sem HA. O teor de hidroxiapatita deficiente de cálcio não favorece o processo de cristalização devido à alta energia de ativação determinada pelos métodos descritos. Provavelmente, a velocidade de rotação, favorece a dispersão da carga na matriz de PEAD, dificultando o processo de cristalização. Na aplicação do método de Osawa-Avrami, os coeficientes de correlação indicaram perda na correlação linear. Estas perdas podem estar associadas a uma pequena percentagem de cristalização secundária e/ou à escolha das temperaturas utilizadas para determinar a velocidade de cristalização. Na determinação dos parâmetros pelo método de Mo, as menores percentagens de cristalização apresentaram um grande desvio da linearidade, com coeficiente de correlação bem menor que 1 e com o aumento da percentagem de cristalização, o desvio da linearidade diminui, ficando próximo de 1. Os resultados obtidos mostraram que o modelo de Mo e de Osawa-Avrami não foram capazes de definir o comportamento cinético dos materiais produzidos neste trabalho. / In this work, composites of high density polyethylene HDPE with calciumdeficient hydroxyapatite were synthesized in order to obtain materials with good mechanical properties and bioactivity. The addition of calcium-deficient hydroxyapatite resulted in an increase in elastic modulus (high rigidity), lower impact resistance and lower HDPE crystallinity degree, promoting, in these materials, a higher bioactivity. Scanning thermal analysis (non-isothermal system) was carried out by differential scanning calorimetry (DSC), and it was evaluated the calcium phosphate content added and the screw speed in the processing. In non-isothermal crystallization studies it was observed a decrease in crystallization temperature as the cooling rate was increased for all produced materials. The activation energy of crystallization was evaluated by Kissinger and Ozawa methods. The sample with 5 wt.% of calcium-deficient hydroxyapatite and processed at 200 rpm screw speed showed the lower value of activation energy (262 kJ/mol) and the lower deviation from linearity. Calcium-deficient hydroxyapatite does not promote the crystallization process due to the high activation energy determined by the described methods. Probably the screw speed promotes the dispersion of the filler in the HDPE matrix and hinders the crystallization process. Correlation coefficients in Osawa-Avrami method indicated loss in the linear correlation. These losses might be associated with a small percentage of secundary crystallization and/or the temperatures chosen to determine the crystallization rate. The parameters obteined from Mo method, the lower percentages of crystallization showed a great deviation from linearity, with correlation coefficient much smaller than 1, when increasing the percentage of crystallization, the deviation from linearity decreases, getting closer to 1.The results of Mo and Osawa-Avrami models were not able to set the kinetic behavior of the materials produced in this study.

Cette étude porte sur le calcul numérique du champ acoustique rayonné par des écoulements subsoniques turbulents présentant des inhomogénéités de température. Des méthodes hybrides sont développées grâce à un développement de Janzen-Rayleigh des équations de Navier-Stokes. L'écoulement est résolu par un calcul quasi incompressible puis les perturbations acoustiques sont propagées selon deux méthodes : les équations d'Euler linéarisées (EEL) et l'approximation à faible nombre de Mach perturbée(PLMNA). Les méthodes sont validées sur des cas simples puis appliquées à une couche de mélange isotherme et anisotherme en développement spatial. / This study focuses on the numerical calculation of the acoustic field radiated by subsonic turbulent flows with temperature inhomogeneities. Hybrid methods are developed through a Rayleigh-Janzen expansion of the Navier-Stokes equations. The flow is solved in a quasi-incompressible way then the acoustic disturbances are propagated by two methods : the linearized Euler's equations (EEL) and the perturbed low Mach number approximation (PLMNA). The methods are validated on simple cases and then applied to an isothermal and non isothermal spatially evolving mixing layer.

Submitted by Marlene Santos (marlene.bc.ufg@gmail.com) on 2018-08-01T17:33:51Z No. of bitstreams: 2 Dissertação - Maythsulene Inácio de Sousa Oliveira - 2015.pdf: 3135445 bytes, checksum: a08e11c7f2df635f3ff7726cfde58f49 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-08-02T11:09:15Z (GMT) No. of bitstreams: 2 Dissertação - Maythsulene Inácio de Sousa Oliveira - 2015.pdf: 3135445 bytes, checksum: a08e11c7f2df635f3ff7726cfde58f49 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-08-02T11:09:15Z (GMT). No. of bitstreams: 2 Dissertação - Maythsulene Inácio de Sousa Oliveira - 2015.pdf: 3135445 bytes, checksum: a08e11c7f2df635f3ff7726cfde58f49 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2015-04-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Common bean (Phaseolus vulgaris L.) is grown in Brazil in three different cropping seasons, and in diverse agroecosystems. In such different environments, the crop is exposed to several constraints responsible for yield losses, such as pathogenic organisms. Among common bean relevant diseases, fusarium wilt (Fusarium oxysporum f. sp. phaseoli), dry root-rot (Fusarium solani) and Curtobacterium wilt (Curtobacterium flaccumfaciens pv. flaccumfaciens) have similar symptoms, hindering diagnosis in the field, and whose identification in seed health testing is also limited. In both cases, identification at species level is an important step to manage this root pathogen complex, whose detection can be improved by molecular biology tools. Therefore, this study aimed to: 1) to develop and validate a multiplex PCR (m-PCR) method for simultaneous identification of three common bean pathogens, F. oxysporum f. sp. phaseoli, F. solani and C. flaccumfaciens pv. flaccumfaciens; and 2) develop an isothermal amplification of DNA (LAMP) method to detect of F. oxysporum f. sp. phaseoli on seeds. M-PCR method was developed for identification of isolated colonies, as well as infected seeds. In seeds, total DNA was obtained by alkaline lysis method, which inactivates nucleases during the extraction process. M-PCR allowed the identification of all pathogens, with detection of C. flaccumfaciens pv. flaccumfaciens, F. oxysporum f. sp. phaseoli and F. solani amplicons in agarose gel with respectively 306, 609 and 143 base pairs. Furthermore, m-PCR also reduced costs and time to detect Fusarium oxysporum f. sp. phaseoli from 10 days to three hours. It was not possible to develop an optimized protocol for detection of F. oxysporum f. sp. phaseoli by the LAMP method, using only the tf1 gene for design of primers, since such primers were functional only for amplifying large amounts of target DNA. Based on the negative results with LAMP, it is suggested that further studies should be performed using other DNA sequences available in GenBank database. / O feijoeiro-comum (Phaseolus vulgaris L.) é cultivado durante todo o ano no território brasileiro, em três épocas distintas e em vários agroecosistemas. Nestes ambientes distintos, a cultura está exposta a diversos fatores que causam perdas de rendimento, como o ataque de patógenos. Dentre as doenças do feijoeiro-comum encontram-se a murcha-de-fusarium (Fusarium oxysporum f. sp. phaseoli), a podridão-radicular-seca (Fusarium solani) e a murcha-de-curtobacterium (Curtobacterium flaccumfaciens pv. flaccumfaciens) que apresentam sintomas semelhantes, dificultando seu diagnóstico no campo, e cuja identificação em testes de sanidade de sementes também é limitada. Em ambos os casos, a identificação em nível de espécie é uma importante etapa do manejo deste complexo de patógenos, cuja detecção pode ser aperfeiçoada com a adoção de ferramentas de biologia molecular. Portanto, este estudo teve como objetivos: 1) Desenvolver e validar um método de multiplex PCR (m-PCR) para identificação simultânea de três espécies de patógenos do feijoeiro-comum, F. oxysporum f. sp. phaseoli, F. solani e C. flaccumfaciens pv. flaccumfaciens; e 2) desenvolver a técnica de amplificação isotérmica de DNA (LAMP) para detecção de F. oxysporum f. sp. phaseoli em sementes. O método de m-PCR foi desenvolvido para identificação de colônias isoladas bem como sementes infectadas. Nas sementes, o DNA total foi obtido pela lise alcalina, método que inativa nucleases durante o processo de extração. A m-PCR possibilitou a identificação de todos os patógenos, com detecção de C. flaccumfaciens pv. flaccumfaciens, F. oxysporum f. sp. phaseoli e F. solani em bandas formadas em gel de agarose respectivamente com 306, 609 e 143 pares de base. Além disso, a extração do DNA total das sementes pela lise alcalina em combinação com a m-PCR também possibilitou redução de custos e tempo de realização do diagnóstico de Fusarium oxysporum f. sp. phaseoli, de 10 dias para três horas. Não foi possível estabelecer um protocolo otimizado para detecção de F. oxysporum f. sp. phaseoli pelo método LAMP, utilizando somente o gene tf1 para desenho dos iniciadores, uma vez que, os iniciadores revelaram-se funcionais apenas para a amplificação com grandes quantidades de DNA alvo. Diante dos resultados obtidos com LAMP, sugere-se que estudos posteriores sejam realizados empregando outras sequências de DNA disponíveis no banco de dados GenBank.

Submitted by Marco Antonio Oliveira da Silva (maosilva@ipen.br) on 2016-12-22T11:28:11Z No. of bitstreams: 0 / Made available in DSpace on 2016-12-22T11:28:11Z (GMT). No. of bitstreams: 0 / O rejeito radioativo como qualquer outro tipo de resíduo, precisa receber tratamento adequado. É necessário considerar suas características físico-químicas e radiológicas para a escolha da ação apropriada para o tratamento e a deposição final do rejeito. Muitas técnicas de tratamento utilizadas hoje são economicamente dispendiosas, inviabilizando muitas vezes o seu uso e impulsionando o estudo de outras técnicas de tratamento. Uma dessas técnicas é a biossorção, que demonstra alto potencial quando aplicada a rejeitos radioativos. Essa técnica utiliza materiais de origem biológica para a remoção de metais. Dos potenciais biossorventes encontrados, as macrófitas aquáticas apresentam-se vantajosas e possibilitam a remoção do urânio presente no rejeito radioativo líquido a baixo custo. O objetivo deste estudo foi avaliar a capacidade de biossorção das macrófitas aquáticas Pistia stratiotes, Limnobium laevigatum, Lemna sp e Azolla sp no tratamento dos rejeitos radioativos líquidos. Este trabalho foi dividido em duas etapas, uma de caracterização e preparação e outra de ensaios de biossorção, realizados com soluções de urânio e com rejeito real. As biomassas foram testadas na sua forma bruta e os ensaios de biossorção foram realizados em frascos de polipropileno contendo 10 mL de solução de urânio ou 10 mL de rejeito radioativo e 0,20 g de biomassa. O comportamento das biomassas foi avaliado por meio da cinética de sorção e modelos de isotermas. As maiores capacidades de sorção foram observadas com as macrófitas Lemna sp com 162,1 mg/g e para a Azolla sp com 161,8 mg/g. Os tempos de equilíbrio obtidos foram de 1 hora para a Lemna sp, e de 30 minutos para a Azolla sp. Com o rejeito real, a macrófita Azolla sp apresentou uma capacidade de sorção de 2,6 mg/g. Estes resultados sugerem que a Azolla sp possui maior capacidade de biossorção, sendo a mais indicada para estudos mais detalhados de tratamento de rejeitos radioativos líquidos. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

Le stockage d’énergie par air comprimé est une des technologies nécessaires à l’emploi massif des énergies renouvelables intermittentes, d’origine solaire ou éolienne. La compression d’air par piston liquide permet d’augmenter l’efficacité du stockage d’énergie en favorisant un échange thermique intense dans la chambre de compression. La description et l’évaluation de cet échange convectif pour des chambres de compression à faible rapport alésage/course ne sont cependant que peu étudiées dans la littérature scientifique. A l’aide d’une étude expérimentale menée sur deux bancs d’essais, l’échange convectif interne dans la chambre de compression est étudié. Une méthode inverse, couplée à la mesure de la température de l’air comprimé et de la position du piston, est employée afin de déterminer les transferts thermiques pariétaux instantanés au cours des compressions.Après avoir mis en lumière la présence systématique d’une transition du régime convectif de type laminaire vers un régime turbulent dans le volume d’air comprimé, de nouvelles corrélations d’échange convectif sont recherchées. Sur la base de 73 expérimentations, plusieurs formes de corrélations basées sur des nombres sans dimension sont optimisées puis comparées. Deux nouvelles corrélations du nombre de Nusselt, l’une en régime laminaire et l’autre en régime turbulent, sont ensuite sélectionnées. Un modèle instationnaire thermodynamique 1D de la chambre de compression est alors construit dans l’environnement Matlab / Simulink afin de tester la qualité de ces corrélations. Les résultats numériques sont ainsi comparés aux données expérimentales. Finalement, deux essais expérimentaux supplémentaires, réalisés sur un banc d’essai différent, permettent de confirmer la qualité des nouvelles corrélations d’échange convectif proposées. / Energy storage by compressed air would be one of the required technologies for enabling massive use of intermittent solar or wind renewable energy sources. Air compression using a liquid piston enables an increase in the energy storage efficiency by inducing an intense heat exchange in the compression chamber. Few studies reported in the literature have focused on the description and evaluation of the convective heat exchange for a low ratio compression chamber (L/D). Using an experimental study and two test benches, the internal convective heat transfer during compression has been studied. In addition to measuring liquid piston position and air pressure, an inverse method was used to determine the instantaneous parietal convective heat flow during compression. After highlighting the presence of a systematic transition from laminar to turbulent convective regime in the compressed air, new convective heat transfer correlations were sought. On the basis of 73 experiments, several correlation forms based on dimensionless numbers were optimized and compared. Two new Nusselt number correlations, one for laminar and the other for turbulent flow, were then selected. A 1D thermodynamic transient model of the compression chamber was built using Matlab / Simulink environment in order to test the quality of these correlations. Thus, numerical results and experimental data were compared. Finally, results from two additional experiments carried out on a different test bench have confirmed the quality of the new proposed correlations for convective heat exchange.

Metallocene based polypropylene (mPP) with very narrow distribution of molecular weight was peroxide-degraded to materials of four different molecular weights including the original mPP labeled MET1–MET3 and MET0, respectively. Double bonds formed after peroxide-degradation was proved on material surfaces by FTIR-ATR (attenuated total reflection of Fourier-transformed infrared spectroscopy). The decreasing molecular weight led to gradual decrease of the tensile strength, tensile modulus as well as the strain and to the decrease of the temperature of thermal decomposition. Confocal laser scanning microscopy (CLSM) of chemically etched surfaces of MET0–MET3 revealed supramolecular structure of commonly occurred structure (radical spherulites) but also supramolecular structure of form (sheaf-like structure). The latter was proved by XRD together with the fact that the content of form decreases with decreasing molecular weight. The mentioned structure differences were not visible on DSC curves because the amount of structure was small and melting temperature, temperature of crystallization and the degree of crystallinity remained the same for all four types of mPP. The structure of the original materials was also characterized after isothermal crystallization performed on differential scanning calorimetry (DSC) and under polarizing optical microscope (POM). The first was performed at 120–126 °C and the latter at 130 °C (Tic). The materials obtained on DSC always contained the structure and its amount increased with increasing Tic whereas higher content of form was always in MET0 with respect to MET3. The structure was proved by XRD and also by DSC heating run followed immediately after the isothermal process. The latter revealed two endotherms belonging to melting of and forms. The presence of form was on the surfaces proved by CLSM. The formation of structure was in-situ observed on POM and the amount of it decreased with decreasing molecular weight. The spherulite growth rate increased with decreasing molecular weight whereas the rate of crystalline portion expressed as half-time of crystallization decreased with decreasing molecular weight.

L’objectif de ce travail consiste à développer la méthode de résolution PGD (Proper Generalized Decomposition), qui est une méthode de réduction de modèle où la solution est recherchée sous forme séparée, à la résolution des équations de Navier-Stokes. Dans un premier temps, cette méthode est appliquée à la résolution d’équations modèles disposant d’une solution analytique. L’ équation de diffusion stationnaire 2D et 3D, l’équation de diffusion instationnaire 2D et les équations de Burgers et Stokes sont traitées. Nous montrons que dans tous ces cas la méthode PGD permet de retrouver les solutions analytiques avec une précision équivalente au modèle standard. Nous mettons également en évidence la supériorité de la PGD par rapport au modèle standard en terme de temps de calcul. En effet, dans tous ces cas, laPGD se montre beaucoup plus rapide que le solveur standard (plusieurs dizaine de fois). La résolution des équations de Navier-Stokes isothermes et anisothermes est ensuite effectuée par une discrétisation volumes finis sur un maillage décalé où le couplage vitesse-pression a été géré à l’aide d’un schéma de prédiction-correction. Dans ce cas une décomposition PGD sur les variables d’espaces uniquement a été choisie. Pour les écoulements incompressibles 2D stationnaire ou instationnaire, de type cavité entrainée et/ou différentiellement chauffé, les résultats obtenus par résolution PGD sont similaires à ceux du solveur standard avec un gain de temps significatif (la PGD est une dizaine de fois plus rapide que le solveur standard). Enfin ce travail introduit une première approche de la résolution des équations de transferts par méthode PGD en formulation spectrale. Sur les différents problèmes traités, à savoir l’équation de diffusion stationnaire, l’équation de Darcy et les équations de Navier-Sokes, la PGD a montré une précision aussi bonne que le solveur standard. Un gain de temps a été observé pour le cas de l’équation de Poisson, par contre, concernant le problème de Darcy ou les équations de Navier-Stokes les performances de la PGD en terme de temps de calcul peuvent encore être améliorées. / Motivated by solving the Navier-Stokes equations, this work presents the implementation and development of a reduced order model, the PGD (Proper Generalized Decomposition).Firstly, this method is applied to solving equations models with an analytical solution. The stationary diffusion equation 2D and 3D, 2D unsteady diffusion equation and Burgers equations and Stokes are processed. We show that in all these cases, the PGD method allows to find analytical solutions with a good accuracy compared to the standard model. We also demonstrate the superiority of the PGD relative to the standard model in terms of computing time. Indeed, in all these cases, PGD was much more rapid than the standard solver (several dozen times). The Navier-Stokes 2D and 3D thermal and isothermal isotherms are then processed by a finite volume discretization on a staggered grid where the velocity-pressure coupling was handled using a prediction-correction scheme. In this case a decomposition of the space variables only was chosen. The results in 2D for Reynolds numbers equal to 100, 1000and 10, 000 are similar to those of the solver standard with a significant time saving (PGD isten times faster than the solver standard). Finally, this work introduces a first approach tosolving the Navier-Stokes equations with a spectral method coupled with the PGD. Different cases were dealed, the stationary diffusion equation, the Darcy equation and the Navier-Sokesequations. PGD showed a good accuracy compared with the standard solver. Saving time was observed for the case of the Poisson equation, on the other hand, about Darcy’s problem or Navier-Stokes’ equations, performance of the PGD in terms of computing time may yet be improved.