Tesi sul tema "Microstructure Complexe"
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Aouak, Taïeb. "Homopolymérisation et copolymérisation des alcynes monosubstitués amorceées par les complexes de Ziegler-Natta : étude de réactions conduites en présence de catalyseurs solubles formés en associant un carboxylate de fer(III) et un alkylaluminium, caractérisation des polyalcynes". Vandoeuvre-les-Nancy, INPL, 1994. http://docnum.univ-lorraine.fr/public/INPL_T_1994_AOUAK_T.pdf.
Khal, Jeaidi Hana El. "Relations frittage - microstructure - propriétés électriques des céramiques de type LAMOX". Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI069/document.
The La_2 Mo_1,5 W_0,5 O_9 (LMW05) material is an ionic conductor of the LAMOX family which has recently shown a great potential as a solid electrolyte in high temperature electrochemical systems. The aim of this thesis is double: firstly, to study the effects of certain microstructural parameters, essentially the porosity, on the electrical response of LMW05 ceramic samples and, on the other hand, to apply the flash sintering process for the preparation of dense samples. Porous samples were obtained by varying the sintering temperature in the range of 750 to 1100 °C. Complex impedance spectroscopy was systematically used to evaluate the effect of porosity on the electrical response of LMW05. The electrical response, observed at high frequency (HF) on the impedance diagrams, is greatly affected by the porosity. It depends on the morphology and the location of pores. Effective medium theories were used for the interpretation of obtained results. The Bruggeman approximation proved to be better suited to describe the high frequency electrical response for 0 < P ≤ 22%. Compared with YSZ-type ceramics, the porous LMW05 was found to have a low blocking factor α_R. This low value is related to the morphology of the pores which are spherical in shape and large in size. The contacting of two dense pellets allowed us to simulate the contact between two grains of LMW05.The flash sintering process has been successfully tested for the preparation of LMW05 samples. Particular attention is paid to optimizing the conditions of the flash sintering onset. We have shown that the sintered LMW05 samples exhibit the same electrical behavior independently to the employed sintering process
Badetti, Michel. "Rhéologie des matériaux granulaires non saturés". Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1020/document.
With this doctoral research, we report on the solid and liquid-like mechanical behaviors of wet granular materials, which exhibit viscous and capillary effects. Such systems, standing between dry and immersed granular materials, are studied both in experiments and discrete numerical simulations, from the microstructural aspects to the mechanical behavior. We therefore adopt a multiscale approach whose purposes are to understand the origins and roles of capillary and viscous effects in constitutive laws and to include a microstructural description within these laws. We are interested in the simple bridge model for the illustration of viscous and capillary effects in the case of quasistatic and inertial flows, where the confining forces, the Coulomb friction and the liquid quantity can vary. To answer such questions, this thesis is articulated around the 3 following topics :- A study based on macroscopic rheological experiments with a simple model material (monodisperse polystyrene beads, wetted with a Newtonian silicon oil) which enables us to distinguish the flow regimes and to characterize the influence of cohesive effects. The experimental framework allows for long time shearing experiments, where the materials can reach their steady state behavior. Alike dry systems, wet granular materials still exhibit a quasistatic and an inertial regime with increasing flow velocity. We show the noticeable influence of capillary effects which strongly increases the shear resistance and reduces the materials density.- X-ray microtomographic experiments enabling the microstructural study of static samples. We witness a good homogeneity of our samples whether slightly or strongly saturated. A non-negligible number of very complex capillary bonds were detected, which stresses, when compared with macroscopic rheological results, their lack of influence on the flow properties. This result is very noticeable as it demonstrates the ability of the simple bridge model to illustrate the behavior of materials which would not be included a priori within its reach.- Discrete numerical simulations allowing us to strongly improve the range of the parameters of the study, especially in the case of material characteristics such as Coulomb friction. The micromechanical study emerging from simulations, allows us to analyze anisotropy, coordination and capillary stresses questions. We underline the great importance of long-range capillary interactions when using an effective stress model. The limits of such model, usually adopted to describe the behavior in the quasistatic regime, are also tested and debated in the inertial regime. The good agreement between numerical and experimental results enabled us to validate and calibrate a numerical model which, in return, offered a reliable analysis of microstructural effects for the understanding of the mechanical behavior and for the transition from the microscopic to the macroscopic scale
Lian, Weidong. "Contribution à l'homogénéisation numérique du comportement élastique de matériaux à microstructure complexe caractérisés par imagerie". Ecole centrale de Nantes, 2011. http://www.theses.fr/2011ECDN0004.
Computational homogenization approaches are now widely used. Moreover, imaging techniques allow a highly accurate representation of material microstructure, and classically leads to voxel-based finite element models. Another computational approach for image-based modeling has been recently proposed, based on X-FEM and level set method. These two approaches are compared and it is shown that X-FEM/levelset approach is more efficient and accurate than the voxel-based FEM. Using microstructure images highlights its randomness, which raises the problem of the determination of the sizeof the RVE (reprentative volume element). It's shown that homogenization approaches with uniform strins or stresses boundary conditions lead to overcome these edge effects. At last a three scale homogenization approach is presented for problems where the macroscale is much larger than the microscale. An intermediate mescoscale is considered, with a size lower than the RVE size. At this mesoscale computed apparent properies are random variables. These are represented using polynomial chaos expensions identified from samples which are extracted from the image. Macroscopic samples are then generated, with a mesoscopic modeling scale, and a spacial distribution of apparent properties coming form the previous step. Applying again classical homogenization methods at this new scale allows the determination of RVE size
Dischler, Jean-Michel. "La génération de textures 3D et de textures a microstructure complexe pour la synthese d'images". Université Louis Pasteur (Strasbourg) (1971-2008), 1996. http://www.theses.fr/1996STR13015.
Déléris, Jacqueline. "Plutonisme bimodal en contexte décrochant panafricain : étude pétro-structurale du complexe de Toro (Nigeria)". Toulouse 3, 1995. http://www.theses.fr/1995TOU30212.
Karam, Marie-Céleste. "Réhydratation des protéines laitières dans un milieu complexe : influence de l'état d'hydratation sur les propriétés texturales des gels acides". Thesis, Université de Lorraine, 2013. http://www.theses.fr/2013LORR0132/document.
The main objectives of this work were to elucidate the rehydration mechanism of the two major milk proteins (micellar casein and whey protein) into a complex and opaque medium such as milk and to assess the influence of hydration state (defined as a function of rehydration length after 5,120,180,240,300, 480, 900 and 1440 minutes of rehydration) on the rheological, textural, physical properties and microstructure of the obtained acid milk gels. Whereas, micellar casein presented a long rehydration process into milk characterized by three stages: a wetting, swelling and dispersion phase, whey protein displayed a quick rehydration process characterized by an overlapping of wetting and dispersion phase. Furthermore, an extended rehydration time of micellar casein powder into the milk base was associated with a postponed onset of gelation and enhanced physical, textural as well as rheological properties of the obtained acid milk gels characterized by increases in gel firmness, strength, and decreases in syneresis susceptibility and grains formation. In contrast, acid milk gels prepared with whey protein powder exhibited comparable overall textural properties regardless the different rehydration times. Nevertheless, denaturation of whey protein powder (by dry heating) was associated with a deterioration of the textural properties of the acid milk gels. Finally, acid gels prepared with whey proteins displayed better overall textural quality than those prepared with micellar casein (except for grains formation)
Bibalou, Pascal Blaise. "Copolymérisation du 2,5 furannédione 3 méthyle et de l'acétate de vinyle influence d'un complexe entre comonomères sur la microstructure des copolymères". Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb37596030f.
Du, Kou. "Modélisation micromécanique de géomatériaux en prenant en compte des anisotropies microstructurale et matricielle". Electronic Thesis or Diss., Université de Lorraine, 2021. http://docnum.univ-lorraine.fr/public/DDOC_T_2021_0254_DU.pdf.
The mechanical properties of heterogeneous geomaterials are evaluated by simultaneously taking into account the microstructural anisotropy as well as the one of matrix. To this end, the microstructural anisotropy is represented by the complexity of porous shape which is considered in the present work as concave or convex by particular attention to the superspherical and the axisymmetrical superspheroidal pores. The concentration and contribution tensors are numerically computed using Finite Element Method (FEM), which are next approximated by analytical expressions for the case of the concavity parameter being p<1, to evaluate the associated effective properties, such as effective elastic and thermal responses. Specifically, to solve the 2nd Eshelby problem (Eshelby (1961)) in the case of 3D non-ellipsoidal inhomogeneities, we make use of a recently developed adapted boundary condition (Adessina et al. (2017)) based on far-field solution (Sevostianov and Kachanov (2011)) to incorporate the matrix anisotropy and to correct the bias induced by the bounded character of the mesh domain, which allows to accelerate the computation convergence without sacrificing its accuracy. Simultaneously by complying with the numerical homogenization technique, the compliance/resistivity contribution tensors are computed for different forms of pores (particular attention of superspheroidal and superspherical ones) embedded in a transversely isotropic matrix. The proposed numerical method is shown to be efficient and accurate after several appropriate assessments and validation by comparing its predictions, in some particular cases, with analytical results and some available numerical ones. On the basis of these "3D" Finite Element Modeling, approximate relations of the property contribution tensors in the two aforementioned reference concave cases, supersphere and axisymmetric superspheroid, are developed for both elastic and thermal problems. Note here that the spherical pore (i.e. concavity parameter p=1) and circular crack (i.e. aspect ratio γ → 0), which can be considered as two particular cases, are also numerically studied. This allows to assess and validate the proposed method in the present work. Moreover, in the frame of homogenization, application to the typical porous geomaterials with transversely isotropic matrix such as clay rocks is presented to illustrate the impact of the concavity parameter and the matrix anisotropy on overall properties through several micromechanical homogenization schemes such as non-interaction approximation, Mori-Tanaka-Benveniste scheme and Maxwell scheme. The methodology of evaluation of the elastic and thermal properties of heterogeneous material aforementioned is proposed based on micromechanical homogenization via multiscale modeling. The overall properties of composites with regular pores are also predicted using direct finite element approaches and then compared against micromechanical modeling. The effect of microstructure is analyzed by considering periodic RVEs containing random arrangements of pores formed by transversely isotropic phases
Lucas, Iris. "Dynamique et contrôle d'un marché financier avec une approche système multi-agents". Thesis, Normandie, 2018. http://www.theses.fr/2018NORMLH39/document.
This thesis suggests reflection in studying financial markets through complex systems prism.First, an original mathematic description for describing agents' decision-making process in case of problems affecting by both individual and collective behavior is introduced. The proposed method is particularly applicable when studied system is characterized by non-linear, path dependent and self-organizing interactions. An application to financial markets is proposed by designing a multi¬agent system based on the proposed formalization.In this application, we propose to implement a computational agent-based financial market in which the system is described in both a microscopie and macroscopic levels are proposed. The agents' decision-making process is based on fuzzy logic rules and the price dynamic is purely deten-ninistic according to the basis matching rules of a central order book as in NYSE-Euronext-Paris. We show that, while putting most parameters under evolutionary control, the computational agent- based system is able to replicate several stylized facts of financial time series (distributions of stocks returns showing a heavy tau l with positive excess kurtosis and volatility clustering phenomenon).Thereafter, with numerical simulations we propose to study three system's properties: self-organization, resilience and robustness. First a method is introduced to quantify the degree of selforganization which ernerges in the system and shows that the capacity of self-organization is maximized when the agents' behaviors are heterogeneous. Secondly, we propose to study the system's response when market shock is simulated. in both cases, numerical results are presentedI and analyzed, showing how the global market behavior emerges from specific individual behavior interactions.Our results notably show that the emergence of collective herding behavior when market shock occurs leads to a temporary disruption on the system self-organization. Finaily, numerical simulations highlight that our artificial financial market can be able to absorb strong mono-shock but be lead to the rupture by low but repeated perturbations
Yven, Béatrice. "Minéralogie, microstructure et propriétés physiques des roches volcaniques des Champs Phlégréens (Italie) : contribution des données de laboratoire et de diagraphie à la description de la structure interne du complexe". Paris 7, 2001. http://www.theses.fr/2001PA077054.
Lagouin, Méryl. "Caractérisation et optimisation multiphysiques d'une paroi bicouche bio et géosourcée". Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30258.
As a key sector in the fight against climate change and in the energy transition, the building industry must re-think and transform its activity. The use of raw and bio-based materials can help to respond to this environmental challenge effectively, enabling natural resources to be saved thanks to the recovery of agricultural waste and by-products, the consumption of fossil raw materials to be reduced, greenhouse gas emissions to be limited, and new economic sectors to be created and developed. In this context, this thesis research project aims to develop a constructive bio- and geo-based solution with low environmental impact. A thermally self-insulating vegetal concrete, used to fill a load-bearing structure, is considered. For the mix design of this lightweight concrete, the potential of two agricultural by-products, maize and sunflower, is evaluated. These two locally available aggregates are considered as substitutes for hemp shiv, which is currently the most commonly used of such products even though little is available. They are then mixed with a binder. Two mineral matrices are considered in the study: a lime-based preformulated binder and a metakaolin-based pozzolanic binder. The exploration of the microstructure of both vegetal concretes and their components, together with studies of the chemical interactions between the lignocellulosic particles and the mineral binder, provide a better understanding of the hygrothermal and mechanical performances of the bio-based materials developed. The very open and interconnected pore structure of pozzolanic-based composites is responsible for their higher moisture buffering capacity than those obtained with lime-based materials, while the water-soluble components of maize disturb the setting time and the mechanical behaviour of mineral binders after hardening, thus preventing the use of maize-based concrete in construction. From the standpoint of suitability for use, pozzolanic binder and sunflower bark chips appear to be the most promising combination of raw materials for designing a hygrothermally and mechanically effective bio-aggregate based concrete. In practice, vegetal concrete walls are rarely left uncoated in a building. The presence of wall coating is likely to influence the hygrothermal behaviour of the wall. The second part of the thesis work consists of evaluating and optimising the performances of an unfired earth-based finish coating. In this type of plaster, the clayey phase ensures the global cohesion of the material by acting as a binder for the sand grain skeleton. Depending on the water state of the material, more or less affected by the soil mineralogical composition, clay can induce drying shrinkage of the mortar, leading to cracking of the plaster. [...]
Duc, Sandrine. "Synthèse de (co)polymères d'hex-1-yne et de phénylacétylène par les catalyseurs de Ziegler-Natta et de métathèse : caractérisation de la microstructure des chaines par couplage pyrolyse - chromatographie en phase gazeuse/spectrométrie de masse". Vandoeuvre-les-Nancy, INPL, 1997. http://www.theses.fr/1997INPL044N.
Ballesta, Pierre. "Instabilité de Faraday dans les fluides complexes". Phd thesis, Université Sciences et Technologies - Bordeaux I, 2006. http://tel.archives-ouvertes.fr/tel-00811893.
Primicerio, Kevin. "Comportement des traders institutionnels et microstructure des marchés : une approche big data". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLC036/document.
The thesis is divided into four parts.Part I introduces and provides a technical description of the FactSet Ownership dataset together with some preliminary statistics and a set of stylized facts emerging from the portfolio structure of large financial institutions, and from the capitalization of recorded securities.Part II proposes a method to assess the statistical significance of the overlap between pairs of heterogeneously diversified portfolios. This method is then applied to public assets ownership data reported by financial institutions in order to infer statistically robust links between the portfolios of financial institutions based on similar patterns of investment. From an economic point of view, it is suspected that the overlapping holding of financial institution is an important channel for financial contagion with the potential to trigger fire sales and thus severe losses at a systemic level.Part III investigates the collective behaviour of fund manager and, in particular, how the average portfolio structure of institutional investors optimally accounts for transactions costs when investment constraints are weak. The collective ability of a crowd to accurately estimate an unknown quantity is known as the Wisdom of the Crowd. In many situation, the median or average estimate of a group of unrelated individuals is surprisingly close to the true value.In Part IV, we use more than 6.7 billions of trades from the Thomson-Reuters Tick History database and the ownership data from FactSet. We show how the tick-by-tick dynamics of limit order book data depends on the aggregate actions of large funds acting on much larger time scale. In particular, we find that the well-established long memory of marker order signs is markedly weaker when large investment funds trade in a markedly directional way or when their aggregate participation ratio is large. Conversely, we investigate to what respect an asset with a weak memory experiences direction trading from large funds
Nguyen, Thanh Tung. "Modeling of complex microcracking in cement based materials by combining numerical simulations based on a phase-field method and experimental 3D imaging". Thesis, Paris Est, 2015. http://www.theses.fr/2015PESC1152/document.
An approach combining numerical simulations and experimental techniques is developed to model complex microcracking in heterogeneous cementitious materials. The proposed numerical model allowed us to predict accurately in 3D the initiation and the propagation of microcracks at the scale of the actual microstructure of a real sample subjected to compression. Its predictions have been validated by a direct comparison with the actual crack network characterized by 3D imaging techniques. In a first part, the numerical simulation tools are developed and tested. More specifically, the phase-field method is applied to microcracking simulations in highly heterogeneous microstructures and its advantages for such simulations are discussed. Then, the technique is extended to account for interfacial cracking, possibly occurring at inclusion/matrix interfaces. In a second part, the experimental methods used and developed in this work are described. The procedures to obtain the evolution of the 3D crack network within the samples by means of X-rays computed microtomography and in-situ mechanical testing are presented. Then, we focus on the developed image processing tools based on digital volume correlation to extract with good accuracy the cracks from the grey level images. In a third part, we compare the predictions of the numerical model with experimental results obtained, first, with a model material made of expanded polystyrene beads embedded in a plaster matrix, and second, to a more complex lightweight concrete. More precisely, we use the experimental data to identify by inverse approaches the local microstructural parameters, and use the experimental displacements measured by digital volume correlation to define boundary conditions to be applied on sub-domains within the sample for the simulations. The obtained direct comparisons of 3D microcrack networks and their evolutions demonstrate the very good predictive capability of the numerical model
Maiko, Khumo Gwendoline. "Multidimensional separation of complex polymers according to microstructure". Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86227.
ENGLISH ABSTRACT: Complex polymer systems have multiple distributions with regard to molecular parameters such as molar mass, functionality, chemical composition, molecular architecture and microstructure. These distributions affect the properties of the polymers making it necessary to develop separation methods to be able to correlate structure to property. A single onedimensional chromatographic method is usually not sufficient to separate these complex polymers with respect to all the distributions. Hence, multidimensional liquid chromatography is necessary for the complete analysis of complex polymers using two or more chromatographic techniques before detection. In this work, two novel liquid chromatographic methods were developed to separate complex polymers according to microstructure. Comprehensive two-dimensional liquid chromatography (LC x LC) was carried out to observe the correlation between microstructure and molar mass. The separation according to microstructure was coupled to NMR (LC-NMR) to observe, identify and quantify the different microstructural components during chromatographic elution. The first chromatographic method separated hydrogenated and deuterated polystyrene homopolymers with respect to the isotope effect. For the LC x LC experiments, liquid chromatography at critical conditions (LCCC) was employed as the first dimension separating according to the isotope effect and size exclusion chromatography (SEC) as the second dimension separating according to molar mass. The LC x LC results of the blends showed that there was an improvement in isotopic separation with an increase in molar mass. The LCNMR coupling using both 1H and 2H NMR detection allowed for the identification of low molar mass blend components which were not sufficiently separated by liquid chromatography. The second chromatographic method separated stereoregular poly(methyl methacrylate)s (PMMAs) with respect to tacticity. The LC x LC experiments of stereoregular PMMAs utilised solvent gradient liquid chromatography as the first dimension to separate according to tacticity and size exclusion chromatography (SEC) as the second dimension to separate according to molar mass. The LC x LC results showed a change in the triad composition with elution of the stereoregular PMMAs with a slight influence of molar mass. The LC-NMR coupling allowed the observation of the triad composition during chromatographic elution.
AFRIKAANSE OPSOMMING: Komplekse polimeriese sisteme het meervoudige verspreidings ten opsigte van molekulêre parameters, soos byvoorbeeld, molêre massa, funksionaliteit, chemiese samestelling, molekulêre argitektuur en mikrostruktuur. Hierdie verspreidings beïnvloed die eienskappe van die polimere en dus is dit nodig om skeidingsmetodes te ontwikkel ten einde polimeerstruktuur met polimeereienskappe te kan korreleer. ‘n Enkele een-dimensionele chromatografiese metode is gewoonlik nie voldoende om hierdie komplekse polimere te skei met betrekking tot al die verspreidings nie. Multidimensionele vloeistofchromatografie, met die insluiting van twee of meer chromatografiese tegnieke, is dus nodig om polimere te skei voor waarneming kan plaasvind. Twee nuwe chromatografiese metodes is ontwikkel om komplekse polimere volgens mikrostruktuur te skei. Twee-dimensionele vloeistofchromatografie (LC x LC) is uitgevoer ten einde die korrelasie tussen mikrostruktuur en molêre massa te ondersoek. Daarna is die skeiding wat op mikrostruktuur gebasseer is, gekoppel aan KMR (LC-KMR) om die verskillende mikrostrukturele komponente gedurende chromatografiese eluering waar te neem, te identifiseer en te kwantifiseer. Die eerste chromatografiese metode het die gehidrogeneerde en gedeutereerde polistireen geskei met betrekking tot die isotoopeffek. Hier het die LC x LC skeiding bestaan uit vloeistofchromatografie onder kritiese kondisies (LCCC) as die eerste dimensie, wat skeiding bewerkstellig het gebasseer op die isotoopeffek, en grootte-uitsluitingschromatografie (SEC) as die tweede dimensie, wat skeiding bewerkstellig het gebasseer op die molêre massa. Die LC x LC resultate van die vermengings het ‘n verbetering in isotopiese skeiding met ‘n toename in molêre massa getoon. Deur gebruik te maak van die LC-KMR koppeling, waar beide 1H en 2H KMR waarneming gebruik is, was dit moontlik om die lae-molêre-massakomponente van vermengings wat nie volledig d.m.v. LC geskei kon word nie, te identifiseer. Die tweede chromatografiese metode het stereoreëlmatige polimetielmetakrilate (PMMAs) m.b.t. taktisiteit geskei. Die LC x LC skeiding van stereoreëlmatige PMMAs het bestaan uit oplosmiddel -gradiënt-LC as eerste dimensie om volgens taktisiteit te skei, en SEC as tweede dimensie om volgens molêre massa te skei. Die LC x LC resultate het ‘n molêre massa afhanklikheid van stereoreëlmatige PMMAs op taktisiteit getoon. Die LC-KMR koppeling het dit moontlik gemaak om die triade-samestelling gedurende chromatografiese eluering waar te neem.
Proust, Gwenaelle Kalidindi Surya. "Identifying the complete space of feasible anisotropic properties in polycrystalline microstructures /". Philadelphia, Pa. : Drexel University, 2005. http://dspace.library.drexel.edu/handle/1860/463.
Blackburn, J. "Time evolution of microstructure in complex systems : a computer simulation study". Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596696.
Li, Xiaoxiao [Verfasser]. "Microstructure-property relationship in cold rolled complex phase steel / Xiaoxiao Li". Aachen : Shaker, 2018. http://d-nb.info/1188550640/34.
Kim, Eunhye. "Dynamics and microstructure of colloidal complex fluids : a lattice Boltzmann study". Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/3926.
Vicic, Michael Brady John F. "Rheology and microstructure of complex fluids : dispersions, emulsions and polymer solutions /". Diss., Pasadena, Calif. : California Institute of Technology, 1999. http://resolver.caltech.edu/CaltechETD:etd-04072005-160903.
Sellemi, Houssem. "Synthèse par chimie douce et caractérisations microstructurale et électrique du conducteur anionique La2Mo2O9". Thesis, Le Mans, 2014. http://www.theses.fr/2014LEMA1032/document.
La2Mo2O9 based oxides (LAMOX) exhibit high ionic conductivity but can be mixed conductors if they are reduced under low-oxygen atmosphere. In this work, new synthesis methods of La2Mo2O9 by soft chemistry (sol gel route and polyol process) are optimized to facilitate the sample shaping depending on the desired application.Concerning the sol gel syntheses, pure La2Mo2O9 compound was obtained from lanthanum acetate and ammonium molybdate or molybdenum chloride. The influence of several synthesis parameters was determined. The addition of two surfactants was tested: dimethyl dioctadecyl ammonium bromide (DDAB) and F127. The final powders are almost pure after heat treatment at 950 °C for 2 hours, which prevents from high specific surface areas.In the case of the polyol process, pure La2Mo2O9 was obtained as desert roses by agglomeration of very fine polycrystalline platelets built from crystallites of a few tens of nanometers size, after a heat treatment at a lower temperature of about 550°C. The effect of various parameters on the morphology and purity of the powder was tested. In particular, agglomerated spherical particles have been obtained using ethylene glycol as solvent in the presence of urea. The addition of DDAB surfactant enables a doubling the specific surface area comparatively to samples without surfactant, from 16 to 30 m2.g-1. Finally, first tests were carried out as attempts to obtain thin films by centrifugation.Conductivity measurements were recorded on pellets presenting closed porosity (relative density greater than 92%), obtained without the help of a milling step. Conductivity measurements showed that, depending on the synthesis parameters, the grain conductivity can be slightly increased.The study of the reducibility, under diluted H2, of powders resulting from the synthesis by the polyol process, shows that the oxygen losses are faster and larger than with powders synthesized by solid state reaction. Reoxidation of amorphous powders is also faster and occurs at much lower temperature in the case of powders obtained by the polyol pathway
Benrhaiem, Souad. "Composites eutectiques et hypo-eutectiques Mg/gamma-Mg17Al12 : microstructures et comportement mécanique à l’ambiante et à chaud". Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI094/document.
For a 31 at.% Al content, the Mg-Al system shows a eutectic mixture formed by Mg fibers embedded in a matrix of a complex metallic phase, the gamma-Mg17Al12 phase. During the thesis, eutectic and hypoeutectic Mg-Al alloys have been prepared by solidification to obtain in situ composites with various volume fractions of complex phases. These alloys appear as a new kind of composites containing complex metallic phases. The mechanical behaviour at room temperature shows that plasticity is possible even for high volume fraction of the gamma-Mg17Al12 phase, a phase which is very hard but brittle at room temperature. At high temperature (250°C-350°C), for all composites, compression tests exhibit a stress peak followed by a pronounced softening. Microstructural studies suggest that the room temperature plasticity is related to the fine scale microstructure of the complex metallic phase gamma-Mg17Al12. At high temperature, the mechanical behavior results preferentially from dynamic recrystallisation and grain boundary sliding
Tong, Xiao Thomas. "Statistical Learning of Some Complex Systems: From Dynamic Systems to Market Microstructure". Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:10917.
Statistics
Boitte, Jean-Baptiste. "Contribution à l’étude de systèmes divisés alimentaires par observation de microstructures au cours de traitements thermo-mécaniques". Thesis, Paris, AgroParisTech, 2012. http://www.theses.fr/2012AGPT0064/document.
Rheo-optic is a recent technique which can be used to create links between rheological properties and meso/microsctructures of model or complex (food) systems. A novel rheo-optical shearing device was designed for studying this relationships within complex food systems. The device has been build to be adapted on an inverted confocal microscope. Specifications of the shear cell are: a) a controlled translational shear between 2 parallel plates with three different motion modes (continuous, oscillatory, strain jump); b) a thermal control; and c) an observation on an inverted confocal microscope. Due to a vacuum system, the set up of an experiment is easy and fast ensuring reproducible optical properties (planarity, parallelism). Temperature, responsible of numerous modifications of structures in a food matrix, is also controlled. A piloting software allows an easy use of the shear cell. Validation of the motion modes has been carried out using a microgel, containing fluorescent probes (spheres) and tracking some of the particles. Next, in order to test and develop methods of observation under shear, taking into account the optical-mechanical balance, bread dough observation has been performed. Well known and described in the lab, bread dough is a dispersion of air bubbles and starch granules in a gluten network. Evolution on this gluten network depending on the formulation of the bread dough has been studied under oscillatory shearing. The composition effect on the microstructure and its evolution were observed and will be commented. Image analysis based on grayscale mathematical morphology has been carried out in order to try to quantify the rheological properties and microstructures. Finally, by a controlled increase of temperature, the growth of an air bubble in bread dough containing yeast was followed during proofing. The influence and the disposition of fat globules at the bubble air-protein interface along this growing process were followed. Thanks to the rheo-optical device, images of microstructures obtained under controlled shear are compared to their rheological behaviour
Zhang, Shuyu. "Directional organic light-emitting diodes using photonic microstructure". Thesis, University of St Andrews, 2014. http://hdl.handle.net/10023/6356.
Martin, Pauline. "Plasticity and damage mechanisms in specific multiphased steels with bainitic matrix under various mechanical loading paths : influence of temperature". Thesis, Normandie, 2019. http://www.theses.fr/2019NORMC227.
This PhD work investigates plasticity and damage mechanisms of complex phase steels. The bainitic microstructures of such steels, which feature retained austenite islands, result in these steels exhibiting good formability properties, which are of interest to automotive companies. However, the complexity of these microstructures, which are characterised by a high amount of grain boundaries and a high density of dislocations, influences plasticity and damage mechanisms. In order to estimate the impact of a steel's microstructure on these properties, the investigation of metallurgical features of complex phase steels provided by the company Faurecia is performed. Plasticity mechanisms are then investigated by tension-compression tests to determine the influence of long- and short-range interactions on the motion dislocation. Thereafter, the evolution of damage within microstructures is analysed at different stress triaxialities in order to obtain the volume area fraction and the number and average diameter of voids as functions of plastic strain. Finally, to examine the thermal stability of these parameters (microstructure, plasticity, and damage), experiments are performed at a range of temperatures between 20°C and 600°C
Wan, Muhammad Wan Mujtahiddin. "FEM assisted analyze of the spring-back phenomena for steel sheet with complex microstructure". Master's thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-38165.
Sonon, Bernard. "On advanced techniques for generation and discretization of the microstructure of complex heterogeneous materials". Doctoral thesis, Universite Libre de Bruxelles, 2014. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209087.
The critical ingredients of this second type of investigation are (I) the generation of sets of representative volume elements ( RVE ) describing the geometry of microstructures with a satisfying control on the morphology relevant to the material of interest and (II) the discretization of governing equations of a model representing the investigated physics on those RVEs domains. One possible reason for the under-representation of morphologically detailed RVEs in the related literature may be related to several issues associated with the geometrical complexity of the microstructures of considered materials in both of these steps. Based on this hypothesis, this work is aimed at bringing contributions to advanced techniques for the generation and discretization of microstructures of complex heterogeneous materials, focusing on geometrical issues. In particular, a special emphasis is put on the consistent geometrical representation of RVEs across generation and discretization methodologies and the accommodation of a quantitative control on specific morphological features characterizing the microstructures of the covered materials.
While several promising recent techniques are dedicated to the discretization of arbitrary complex geometries in numerical models, the literature on RVEs generation methodologies does not provide fully satisfying solutions for most of the cases. The general strategy in this work consisted in selecting a promising state-of-the-art discretization method and in designing improved RVE generation techniques with the concern of guaranteeing their seamless collaboration. The chosen discretization technique is a specific variation of the generalized / extended finite element method that accommodates the representation of arbitrary input geometries represented by level set functions. The RVE generation techniques were designed accordingly, using level set functions to define and manipulate the RVEs geometries.
The RVE methodologies developed are mostly morphologically motivated, incorporating governing parameters allowing the reproduction and the quantitative control of specific morphological features of the considered materials. These developments make an intensive use of distance fields and level set functions to handle the geometrical complexity of microstructures. Valuable improvements were brought to the RVE generation methodologies for several materials, namely granular and particle-based materials, coated and cemented geomaterials, polycrystalline materials, cellular materials and textile-based materials. RVEs produced using those developments have allowed extensive testing of the investigated discretization method, using complex microstructures in proof-of-concept studies involving the main ingredients of RVE-based morphological parameter studies of complex heterogeneous materials. In particular, the illustrated approach offers the possibility to address three crucial aspects of those kinds of studies: (I) to easily conduct simulations on a large number of RVEs covering a significant range of morphological variations for a material, (II) to use advanced constituent material behaviors and (III) to discretize large 3D RVEs. Based on those illustrations and the experience gained from their realization, the main strengths and limitations of the considered discretization methods were clearly identified.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
GHAT, MOHAMED SAAD SHEHATA RIZK. "Physical modelling of the high temperature deformation of complex microstructure materials for aeronautical applications". Doctoral thesis, Università Politecnica delle Marche, 2020. http://hdl.handle.net/11566/274085.
Today aerospace industry is growing fast on developing the mechanical component for the hot section part of the jet engine. The prediction of the dynamic behavior of metals is usually investigated by phenomenological models. In this study, we described the hot deformation behavior by using different approaches for constitutive model: Hansel and spittle equation, Garofalo equation and basic modelling. In the present PhD work, three different metals were used (Inconel 718, Ti-6Al-4V and AA2024 – T3) which are extensively used in the aerospace industry. A basic model was applied to pure Ni and then to a single-phase superalloy. In the case of Ti-6Al-4V alloy, the hot deformation behavior was studied by hot compression test in β phase domain. The effects of hot deformation parameters (deformation temperature and strain rate) on flow stress were analyzed. A phenomenological model based on the Hansel and Spittel equation was used to obtain a quite accurate description of the flow curves for processing temperatures between 1010 and 1150 ºC and strain rates of 100 and 0.001 s-¹. The model used gave an accurate excellent experiments result. The high temperature deformation of the superalloy, a solution treated IN718, was investigated by torsion testing in a high-temperature regime (1000–1100 °C). The peak-flow stress dependence on strain-rate and temperature was described by a physically-based constitutive equations, which took into account both dislocation hardening and solid solution strengthening, and represents a substantial advancement over phenomenological models, although, in the present form, it cannot give the full shape of the flow curves.The creep response for AA2024-T3 alloy produced by a friction stir processing (FSP) has been investigated, the same creep modeling based on the theoretical approach. The hardness variation with creep duration was used to quantify the particle strengthening term.
Duchesne, Louise. "Fusion partielle et microstructures associées dans l'auréole de contact du complexe igné de Duluth, Minnesota /". Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2004. http://theses.uqac.ca.
Liu, Xi. "Microstructural characterisation of pearlitic and complex phase steels using image analysis methods". Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/4842/.
Pignol, Valérie. "Évolution et caractérisation de structures cellulaires bidimensionnelles expérimentales, en particulier les mousses de savon, et simulées". Phd thesis, Institut National Polytechnique de Lorraine - INPL, 1996. http://tel.archives-ouvertes.fr/tel-00717860.
Liang, Bowen. "Integrated Multi-Scale Modeling Framework for Simulating Failure Response of Materials with Complex Microstructures". The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1542233231302831.
Clausen, Jonathan Ryan. "The effect of particle deformation on the rheology and microstructure of noncolloidal suspensions". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34680.
Dedecker, Fabian. "Changements d'échelle dans les milieux granulaires à interactions complexes". Ecully, Ecole centrale de Lyon, 1999. http://bibli.ec-lyon.fr/exl-doc/TH_T1787_fdedecker.pdf.
Many works concerning the behaviour of granular materials based on micromechanical approaches have been proposed during the last years. These approaches connect two very different scales : the first one concerns grain and contacts, and the second one concerns the representative volume of a granular material. In opposition to phenomenological models, micromechanical approaches try to describe the behaviour of granular materials based on simple concepts relevant of the local phenomena. The main objective of this study is the improvement of a model based on the micromechanical approach, focusing on some local phenomena, generally neglected in a classical approach. In order to do this, two kinds of approaches have been used : - a theoretical one using a statistical homogenization approach mainly based on orientation of a contact variable ; - a numerical one using a software (PFC2D) based on the Discrete Element Method. A constant comparison of the above two approaches is a key ingredient of this work. This work aims to analyse and improve three topics of micromechanical approach : - the granular materials kinematics : the goal is the study of relations between local kinematics (rolling, sliding and displacements of particles which are not in contact) and strain tensor ; - the influence of contact couples on the microscopic and macroscopic behaviour, as well as the interest of taking them into account in micromechanical approaches ; 0 the study of cemented granular materials rupture : the aim is the definition of macroscopic parameters for rupture from local microscopic characteristics
Borel, Megan E. "A Microstructural and Geochronological Investigation of the Coyote Mountain Metamorphic Core Complex (AZ)". Thesis, University of Louisiana at Lafayette, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10814678.
The Coyote Mountains is a metamorphic core complex that makes up the northern end of the 80-km long Baboquivari Mountain complex. The Baboquivari Mountain complex is composed of Mesozoic rocks, Cenozoic granites, pegmatites, and metasediments (Wright and Haxel, 1982; Haxel et al., 1980, 1984). In the Coyote Mountains, there is an intrusion of the Pan Tak granite, a muscovite-biotite-garnet peraluminous granite dated at 58 Ma based on U-Pb analysis of zircon. The Pan Tak and other intrusions within the Baboquivari Mountains have been interpreted as anatectics melts representing the culmination of a Laramide crustal shortening orogenic event that started in the Late Cretaceous, about ~70 mya (Goodwin and Haxel, 1990). However, field evidence, as well as petrographic and microstructural analyses of metamorphic and deformational fabrics/structures show that the ~58 mya intrusive/magmatic fabric is overprinted by a secondary tectonic event. This event is particularly well recorded in the northern part of the Coyote Mountains, where a northdipping mylonitic shear zone is exposed. This study focuses on the Pan Tak granite with twenty samples from the northern portion of the Coyote Mountains, directly north of Coyote Peak, from the mapped areas of granites and mylonites.
Hodgdon, Travis K. "Cryogenic transmission electron microscopy as a probe of microstructural transitions in complex fluids". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 343 p, 2008. http://proquest.umi.com/pqdweb?did=1691645631&sid=3&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Zhao, Dan. "Study on the creep behavior of clay under complex triaxial loading in relation to the microstructure". Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0372/document.
The objective of this research is to analyze the creep behavior of a typical clay along triaxial tests, moreover, to analyze the microstructural mechanisms of creep. Analysis on the macroscopic results ascertained that both dilatancy and contractancy phenomena could occur during creep. The magnitude of the dilatancy/contractancy during creep was guided by the test conditions: stress level and the over consolidation ratio, which specifically governed the direction of the volumetric strain variations. The results of SEM indicated that the microstructural evolution of the clay after the mechanical loading depend on the stress history. Afterwards, the structural evolution in creep phase depends on the structural pattern developed in monotonic loading
Ehab, Moustafa Kamel Karim. "Image-based modelling of complex heterogeneous microstructures: Application to deformation-induced permeability alterations in rocks". Doctoral thesis, Universite Libre de Bruxelles, 2021. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/320653.
Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
Sarkar, Sujay. "Microstructural evolution model for hot strip rolling of a Nb-Mo complex-phase steel". Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/5650.
Lemaitre, Sophie. "Modélisation des matériaux composites multiphasiques à microstructures complexes : Etude des propriétés effectives par des méthodes d'homogénéisation". Thesis, Normandie, 2017. http://www.theses.fr/2017NORMC217/document.
This thesis focuses on setting up of fast, reliable and automated approaches to design representative volume elements (RVE) of composite materials with complex microstructures (matrix/inclusions) and the evaluation of their effective properties via a homogenization process. We developed algorithms and efficient tools for the random generation of such materials. Inclusions shapes may be spherical, cylindrical, elliptical or any combinations of them. Inflation, deflation, dislocation, undulation and coating are also available to generate RVE. The aim is to approach realistic materials subjected to be damaged during production. Particular attention has been focused on the periodic RVE generation.The homogenized characteristics or effective properties of materials formed from such periodic RVE may then be determined according to the principle of periodic homogenization, by an iterative scheme using FFT (Fast Fourier Transform) via the integral Lippmann-Schwinger or by a finite elements method.The stochastic generation of RVE and the set of morphological parameters studied: number of inclusions, type and shape, volume fraction, orientation of the inclusions lead to achieve an average process. Moreover, a special study has been led to take into account the behavior of altered inclusions. Furthermore, we studied two particular cases on the apparent thermal conductivity of the composite, the first for coated spherical inclusions in order to determine the influence of the layer thickness and the second for laminated polymer and carbon fiber composite sewn by a copper wire, in order to determine the influence of the sewing contribution according to the carbon fiber used
Shinto, Hiroyui. "Interfacial Microstructures and Interaction Forces between Colloidal Particles in Simple and complex Fluids-Molecular Dynamics Simulation-". Kyoto University, 1999. http://hdl.handle.net/2433/77943.
Ponnelle, Sylvain. "Propagation des fissures par fatigue a haute temperature dans l'Inconel 718 : effets de microstructure et de chargements complexes". Paris, ENMP, 2001. http://www.theses.fr/2001ENMP1003.
Luo, Ke. "On the Application of CISAMR for Modeling Hyperelastic Materials Undergoing Finite Deformation". The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1525442256935631.
Menk, Alexander. "Simulation of complex microstructural geometries using X-FEM and the application to solder joint lifetime prediction". Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/2519/.
Bossuyt, Rémy. "Étude et conception de microstructures complexes pour la réalisation de systèmes optiques à destination de la correction ophtalmique". Toulouse 3, 2012. http://thesesups.ups-tlse.fr/2181/.
In this thesis the design and implementation of a pixellised transparent structure for which diffraction and diffusion are imperceptible have been studied and the checkerboard double stacked structure was the most appropriate. A study of lithography techniques for large surfaces is proposed. The object is achieved with a sol-gel, combining an organic and an inorganic phase, which have been modified to be sensitive, of a negative-type and transparent in the visible. The resin is studied in terms of its performance under the specific characteristics of each level (alternating checkered tanks and plots). It sets the gamma of the resin and the optimum parameters of insolation. A new method for determining the gamma tailored to negative resins is proposed. The realization of the multi-level structure by photolithography and lamination has been operated. It allows the separation of different levels due to the deposition of a layer of resin. The pixels of the lower level are sealed in one operation. The dimensional characterizations of objects made during the development process were investigated by SEM and mechanical profilometer. A laser bench which calculates the diffraction of structures has been implemented. The optical characterizations performed with the Haze Gard or DHM have yielded a phase image transmission. This step shows that a compromise between the level of diffraction and diffusion level must be found for the needs of ophthalmic optics
Li, Qiran. "Développement de matériaux d’électrodes à base d’oxydes complexes pour des dispositifs de fortes capacitances". Caen, 2013. http://www.theses.fr/2013CAEN2019.
The aim of the project of the development of electrode materials for devices of high capacitance is to enhance the geometric capacitance of a capacitor by the careful choice of electrode materials and thus to minimize the size of the passive devices in microelectronics. Nowadays, most of the efforts have been made on the development of the dielectric material and the structure of the capacitors to improve the performance of the latter. However, an alternative method for capacitance enhancement is to choose a specific electrode material, such as a 2D electron gas or a strongly correlated system. In this thesis, firstly the synthesis and characterization of an ultrathin film of SrVO3 buried between two LaVO3 films are described. The buried SrVO3 films show good conducting properties with strong electron-electron correlations and, for a thickness of only some unit cells, the characteristics of reduced dimensions. The study of capacitors based on LaVO3/SrVO3 is also presented. The second part is firstly devoted to the study of LaNiO3 thin films, a strongly correlated system, optimizing their conduction performance. Capacitors based on LaAlO3/LaNiO3 presented both enhanced (2 to 2. 5 times) and reduced capacitance values compared to the geometric ones, depending on the types of applied electrodes. These effects have not been identified yet in other similar systems, and demonstrate the importance of the electrode properties on the capacitance
Bibalou, Pascal Blaise. "Copolymérisation du 2,5 furannedione 3 méthyle et de l'acétate de vinyle : influence d'un complexe entre comonomères sur la microstructures des copolymères". Lille 1, 1986. http://www.theses.fr/1986LIL10006.