Teses / dissertações sobre o tema "Perte hybride"
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Attar, Saad-Eddin. "Palier hybride : contribution des alvéoles au champ de pression et au couple de frottement". Poitiers, 1995. http://www.theses.fr/1995POIT2329.
Texto completo da fonteAlimonti, Luca. "Développement d'une méthode hybride éléments finis-matrice de transfert pour la prédiction de la réponse vibroacoustique de structures avec traitements acoustiques". Thèse, Université de Sherbrooke, 2014. http://hdl.handle.net/11143/5988.
Texto completo da fonteNondowou, Bassimie. "Les nouvelles générations togolaises entre la tradition et l'influence occidentale : Le cas des Kabyé". Rouen, 1995. http://www.theses.fr/1995ROUEL218.
Texto completo da fonteSince the Kabye society came into contact with the european culture through colonization and evangelization, it has become, as all dominated societies, more and more hybrid and ambivalent. Today's Kabye generations have difficulty to define themselves is regard to both cultures. Three fundamental factros explain this traidtional values destabilization : economic, cultural, and religious factors. Economically speaking Kabye people were sent by the colonial authorities for hard labours in the central and south areas of Togo, far from their living environnement, when released from hard labours, they worked in private and public plantations to survive. They discovered then money. Henceforth, this money will replace the traditional exchange and modify relationship not only between people but also within families. The school education supplanted the traditional education wich remained a folklore. Youth clubs and associations replaced former age groups. The christian religion put the finishing touches to this work buy running down and fighting the animism, the exclusive religion of the traditional Kabye people. As result, we attend to a victory of the universal model the standardization of the "imaginary"
Fonseca, Armando. "Comparaison de machines à aimants permanents pour la traction de véhicules électriques et hybrides". Phd thesis, Grenoble INPG, 2000. http://www.theses.fr/2000INPG0065.
Texto completo da fonteA modelling methodology is proposed to study PM synchronous motor for electric drives. A non-linear model is presented to take saturation effects into account. FEM accuracy is combined. To analytical modelling to quicker reach motor performances whatever operating point. A new FEM magnetic 10ss estimation is exploited to obtain efficiency maps (Copper and core 10ss). Influence of active length shortening is stridied. Surface PM shape modification reduces high speed core. Loss. Inset and Interior PM motors are compared. Driving cycle consumption of Interior PM motor is improved by an airgap induction shape modification. Another analytical model is dedicated to conception. It uses a reluctance network. Constrained optimisation ofPM motors is then performed to reach cost and volume reduction
Zhao, Zhou. "Heart Segmentation and Evaluation of Fibrosis". Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS003.
Texto completo da fonteAtrial fibrillation is the most common heart rhythm disease. Due to a lack of understanding in the matter of underlying atrial structures, current treatments are still not satisfying. Recently, with the popularity of deep learning, many segmentation methods based on deep learning have been proposed to analyze atrial structures, especially from late gadolinium-enhanced magnetic resonance imaging. However, two problems still occur: 1) segmentation results include the atrial-like background; 2) boundaries are very hard to segment. Most segmentation approaches design a specific network that mainly focuses on the regions, to the detriment of the boundaries. Therefore, in this dissertation, we propose two different methods to segment the heart, one two-stage and one end-to-end trainable method. And then, for evaluating the fibrosis degree, we also proposed two methods, one is to combine deep learning with morphology, and the other is to use deep learning directly. Finally, the efficiency of the proposed approach is verified on some public datasets
Laureau, Raphaëlle. "Genomic diversity of hybrid yeast cells upon meiosis and return to growth". Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066684.
Texto completo da fonteIn somatic cells, recombination between the homologous chromosomes, followed by equational segregation, leads to loss of heterozygosity events (LOH), allowing the expression of recessive alleles and the production of novel allele combinations that are potentially beneficial upon Darwinian selection. However, inter-homolog recombination in somatic cells is rare, thus reducing the potential to generate recombinants. Here, we explored the property of S. cerevisiae to enter the meiotic developmental program, induce meiotic Spo11-dependent double-strand breaks genome-wide and return to mitotic growth, a process known as Return To Growth (RTG). Whole genome sequencing of 36 RTG strains derived from the hybrid S288c/SK1 diploid strain demonstrates that the RTGs are bona fide diploids with mosaic recombined genome. Individual RTG genotypes comprised 5 to 87 homozygous regions due to loss of heterozygous (LOH) events of various lengths, varying between a few nucleotides up to several hundred kilobases. Furthermore, we show that the iteration of the RTG process orderly increments the percentage of homozygosity. Phenotype/genotype analysis of the RTG strains for the auxotrophic and arsenate resistance traits validates the potential of this procedure of genome diversification to rapidly map complex traits loci (QTLs) in diploid strains, without going through sexual reproduction
Naud, Olivier. "Modélisation hybride pour la supervision de systèmes mécatroniques : application à la stabilité en pente de machines mobiles". Toulouse, INSA, 2003. http://www.theses.fr/2003ISAT0003.
Texto completo da fonteWe present a design approach for supervision-oriented hybrid models of mechatronic devices. We chose to express the qualitative states taken by such systems in the guise of a finite automaton. We proposed a method to build the automaton from an essentially continuous model. This method relies on our so-called half-causal graph which represents the algebraic and differential complexity of the continuous model. This diagram uses the causal semantics of the bond-graph, which is based on the effort-flow duality. It is annotated with intervals on the variables. Semantic values are attached to these intervals, which we call modalities. We distinguish, in particular, structural modalities, which correspond to limit conditions or changes in the continuous model, and functionnal modalities, which provide the qualitative information on the usage and monitoring. So as to validate this approach, we applied it to the modeling of the bogies of a forest machine. The goal was to prevent the machine from overturning on slopes. Simulations of the whole machine dynamics proved that the discrete model we obtained was very representative of the changes of the instability risk
Nguyen, Phi-Hung. "Impacts des modèles de pertes sur l’optimisation sur cycle d’un ensemble convertisseur – machine synchrone : applications aux véhicules hybrides". Thesis, Cachan, Ecole normale supérieure, 2011. http://www.theses.fr/2011DENS0049/document.
Texto completo da fonteAlmost all studies of permanent magnet synchronous machines (PMSM) for for hybrid vehicle applications relate to their performances on a specific point of a driving cycle of the vehicle (the base point, the point at high speed or the most used point). However, these machines often operate at different torques and at different speeds. This thesis studies therefore PMSM performances in order to optimize during an entire driving cycle. In this thesis, the author contributed to develop models of torque, field weakening, copper losses and iron losses and methods of calculating these losses at no-load and at load for four MSAP (three concentrated flux machine and a surface mounted PMSM) and for three driving cycles (New Eurepean Driving Cycle, Artemis-Urban and Artemis-Road). An experimental validation of these models was realized on a test bench with two prototypes of MSAP. Then, the MSAP were sized for a minimization of average power losses during the cycle and of the RMS current at the base point. This combination is designed to increase the efficiency of the electrical machine and minimize the size of the associated voltage inverter. This problem of multi-objective optimization was performed using the genetic algorithm, Non-Dominated Sorting Genetic Algorithm (NSGA-II). Thus, a Pareto front of optimal solutions can be derived. The impacts of loss models (at no-load and at load) on the PMSM optimization during the cycle are studied and the interest of each model is presented. Models and calculation methods proposed in this thesis can be applied to all cycles, at different MSAP and for other applications
Basti, Ahmed. "Développement de méthodes de synthèse pour la conception de filtres hyperfréquences compacts et optimisés en pertes". Thesis, Limoges, 2014. http://www.theses.fr/2014LIMO0023/document.
Texto completo da fonteFor satellite communication systems, high performance filters are needed in order to reject unwanted signals in many parts of the communication chain. High quality factor (Q) technologies can meet this requirement, but they often lead to bulky devices. On the other hand, compact technologies are generally low Q and suffer from a degradation of electrical performances in terms of insertion loss, selectivity and flatness. To meet a growing demand concerning size reduction, it is essential to develop compact microwave filters with improved electrical performances.For a receive filter, the challenge is to design a compact bandpass filter with a flat response in the passband and a sharp transition in the passband edges. The insertion loss is not crucial and it can be compensated by the amplifier, leaving a room to the design of a lossy filter. Such a filter accepts additional losses, which can be distributed in the network in order to provide a flat transmission in the passband and a sharp selectivity.In this thesis, new synthesis methods for filtering devices have been studied and developed to improve performances while maintaining a small footprint. These methods have been validated for the design of filters for a receiver in payload satellites as part of collaboration between the Xlim laboratory, the France National Space Centre and Thales Alenia Space
Laureau, Raphaëlle. "Genomic diversity of hybrid yeast cells upon meiosis and return to growth". Electronic Thesis or Diss., Paris 6, 2015. http://www.theses.fr/2015PA066684.
Texto completo da fonteIn somatic cells, recombination between the homologous chromosomes, followed by equational segregation, leads to loss of heterozygosity events (LOH), allowing the expression of recessive alleles and the production of novel allele combinations that are potentially beneficial upon Darwinian selection. However, inter-homolog recombination in somatic cells is rare, thus reducing the potential to generate recombinants. Here, we explored the property of S. cerevisiae to enter the meiotic developmental program, induce meiotic Spo11-dependent double-strand breaks genome-wide and return to mitotic growth, a process known as Return To Growth (RTG). Whole genome sequencing of 36 RTG strains derived from the hybrid S288c/SK1 diploid strain demonstrates that the RTGs are bona fide diploids with mosaic recombined genome. Individual RTG genotypes comprised 5 to 87 homozygous regions due to loss of heterozygous (LOH) events of various lengths, varying between a few nucleotides up to several hundred kilobases. Furthermore, we show that the iteration of the RTG process orderly increments the percentage of homozygosity. Phenotype/genotype analysis of the RTG strains for the auxotrophic and arsenate resistance traits validates the potential of this procedure of genome diversification to rapidly map complex traits loci (QTLs) in diploid strains, without going through sexual reproduction
Barthes, Julien. "Adressage et contrôle de nanosources optiques par plasmonique intégrée ou fibrée". Thesis, Dijon, 2015. http://www.theses.fr/2015DIJOS011/document.
Texto completo da fonteSurface plasmon polariton (SPP) can confine light on subwavelength dimensions. Since they are not diffraction limited, they are of great interest for addressing and controlling optical nanosources. For example, a metal nanowire defines 1D plasmonic waveguide with a great potential for either addressing or coupling quantum emitters. Therefore, SPP opens great opportunities for integrated optical applications. However, SPP suffer from ohmic losses that jeopardize the applications of plasmonic components. In this context, we study the possibilities provided by an hybrid plasmonic-photonicstructure to couple efficiently an emitter to a fiber mode. Such a structure paves the way for fibered single photon nanosource or high resolution optical probe. In this thesis manuscript, we first study the coupling rate between a fluorescent molecule and a metallic nanowire thanks to Green’s dyad formalism. This leads us to distinguish the different relaxation channels and the enhancement of the energy transferred into the plasmonic guided mode by optimizing the shape of the guide (crystalline nano-wire,slow modes). Then, we investigate the energy propagation in a metal coated taperedoptical fiber. Finally, we achieve an optimal configuration for which more than 50% of the energy emitted by a quantum emitter laid on a substrat is transferred into an optical fiber
Li, Li. "Etude et mise au point d'une nouvelle famille d'alterno-démarreur pour véhicules hybrides et électriques". Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00639305.
Texto completo da fonteNguyen, Phi-Hung. "Impacts des modèles de pertes sur l'optimisation sur cycle d'un ensemble convertisseur - machine synchrone : applications aux véhicules hybrides". Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2011. http://tel.archives-ouvertes.fr/tel-00648727.
Texto completo da fonteFabre, Thierry. "Contribution à l'élaboration de biomatériaux hybrides dans le cadre de la réparation de pertes de substance nerveuse périphérique". Bordeaux 2, 1999. http://www.theses.fr/1999BOR28702.
Texto completo da fonteYang, Minhao. "Conception rationnelle de nano-hybrides de carbone 1D pour l'application de nanocomposites diélectriques". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLC088/document.
Texto completo da fonteDielectric polymer nanocomposites with a high dielectric constant and low dielectric loss have received broad interest for use in the field of the electrostatic capacitor and they are usually composed of dielectric polymers as matrix and inorganic or organic nanofillers as the reinforcement. Generally, the improved dielectric performance of nanocomposites is decided by the type and nature of selected polymers and nanofillers as well as interfacial coupling effect between matrices and nanofillers. Among these factors, the physical properties, geometries, component structures of nanofillers play a critical role in deciding the dielectric performance of nanocomposites. According to the conductivities of nanofillers, the dielectric polymer nanocomposites can be classified into two types: conductive-dielectric polymer nanocomposites (CDPNs) and dielectric-dielectric polymer nanocomposites (DDPNs). However, the accompanied high dielectric loss in the vicinity of the percolation threshold for CDPNs and high loading of ceramic nanofillers hinders the development of high performance dielectric polymer nanocomposites.Firstly, ternary BNNSs/CNTs/PVDF nanocomposites were fabricated. The incorporation of BNNSs into the binary CNTs/PVDF nanocomposites improved the dispersion of CNTs and optimized the conductive network, which contributed to the enhanced dielectric constant. The direct connection between CNTs could be hindered by increasing the content of BNNS.Secondly, core-shell structured CNTs@AC hybrids were prepared by CVD method. The amorphous carbon layer not only hindered the direct contact of CNTs but also improved the dispersibility of CNTs in the PVDF matrix. The percolation threshold increased with the prolongation of carbon deposition time. More importantly, the dielectric loss underwent a sharp decrease after the coating process, which was attributed to the decrease in leakage current. The results suggested that the influence of AC interlayer on the final dielectric performance after percolation was much more obvious than that before percolation.Thirdly, BNNSs@C hybrids with different carbon contents were synthesized by the CVD method. The carbon fraction in the BNNSs@C hybrids could be accurately adjusted through controlling the carbon deposition time. The dielectric properties of BNNSs@C/PVDF nanocomposites could be accurately tuned by adjusting the carbon content. The improved interfacial polarizations of BNNSs/C and C/PVDF interfaces endowed the nanocomposites with enhanced dielectric performance.Fourthly, core-shell structured TiO2@C NW hybrids were synthesized by a combination of a hydrothermal reaction and the CVD method. The carbon shell thickness in the obtained TiO2@C NW hybrids could be precisely tuned by controlling the carbon deposition time. The TiO2@C NWs/PVDF nanocomposites exhibited a percolative dielectric behavior. Moreover, the dielectric properties of the TiO2@C NWs/PVDF nanocomposites could be accurately adjusted by tuning the carbon shell thickness. The enhanced interfacial polarizations of the TiO2/C and C/PVDF interfaces endowed the nanocomposites with excellent dielectric performance.Lastly, core@double-shells structured TiO2@C@SiO2 nanowires were synthesized by a combination of modified hydrothermal reaction, CVD, and sol-gel reaction. The introducing of carbon as an inner shell between the TiO2 core and SiO2 outer shell induced two additional types of interfacial polarization. The obtained PVDF nanocomposites with TiO2@C@SiO2 NWs exhibited simultaneously enhanced dielectric constant and suppressed dielectric loss characteristics. The dielectric constant and loss of nanocomposites increased with the increase of carbon inner shell thickness and decreased with the increasing of SiO2 outer shell thickness. The relationship between the dielectric loss and SiO2 outer shell thickness was further demonstrated by the finite simulation results
Seoudi, Tarek. "Non-intrusive CdSe-based quantum dots for sensing pressure and temperature in lubricated contacts". Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI009.
Texto completo da fonteThis thesis is dedicated to the measurement of local pressure and temperature and to compare the heat generation in all-steel and silicon nitride-steel (hybrid) elastohydrodynamic (EHD) contacts. The ultimate goal of this work is to develop a new non-intrusive in situ technique, exploiting the sensitivity of the photoluminescence (PL) of CdSe/CdS/ZnS quantum dots (QDs) to pressure and temperature. Dispersible in small concentration in lubricants, it is shown that the QDs doesn’t modify the rheological behavior of the carrier fluid and that shearing is not perturbative to the QDs PL response. The calibration of QDs in the suspension confirms the QDs PL dependence on temperature and pressure. The in situ measurements were conducted in EHD contacts using a ball-on-disc test rig. Comparisons between pressure and temperature measurements and predictions, using an in–house finite element thermal EHD model, showed a good agreement which demonstrates the feasibility of the proposed methodology. The effects of sliding and normal loading on pressure, temperature and heat generation are indicated. The effect of the thermal properties of the solid materials is underlined and the partition of the generated heat between the contacting solids is investigated. The energy equilibrium between the mechanical energy and the internal thermal energy generated by compression and shearing is demonstrated by comparing experimental power losses and numerical heat generation, in steel-steel and hybrid contacts
Biron, Frédéric. "Conceptions de profils d'impédances actifs pour la compensation des pertes, la réduction de taille et l'augmentation de sélectivité de structures de filtrages planaires microondes". Limoges, 2001. http://www.theses.fr/2001LIMO0026.
Texto completo da fonteGourari, Djamel Eddine. "Synthèse par arc électrique de nanotubes de carbone hybrides incorporant de l'azote et/ou du bore". Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30170/document.
Texto completo da fonteIn opposition to carbon nanotubes which are semi-conductors with so-called "small gap" and which electronic properties are entirely determined by their geometry, single-wall heterogeneous carbon nanotubes BxCyNz yield to great scientific interest due to their tunable electronic properties. Successfully synthesising these heterogeneous nanotubes would indeed allow tuning this gap by acting on their chemical composition instead of their geometry. BxCyNz nanotubes resulting from the substitution of some carbon atoms in the graphene lattice by heteroatoms (B and/or N) could have numerous applications, in particular in photo-luminescent materials, field emission devices, or high operating temperature nano transistors... This work is dedicated to the synthesis of this new generation of nanotubes by electric arc. This technique offers the advantage to perform in-situ substitution of carbon atoms by the heteroatoms. It was carried out using an original approach based on the correlation of plasma characteristics (temperature and concentration fields of the various species) with the morphology and the composition of the carbon nanostructures characterized by various techniques (HRTEM, EDX, XPS, EELS). These results bring a better understanding of the phenomena involved in the growth of heteronanotubes in plasma conditions and also of the structure and chemical environment of the doping elements in the graphene lattice of carbon nanoforms such as boron- or nitrogen-doped nanotubes, and doped graphene layers
Fonseca, Armando. "Comparaison de machines à aimants permanents pour la traction de véhicules électriques et hybrides". Phd thesis, Grenoble INPG, 2000. http://tel.archives-ouvertes.fr/tel-00688674.
Texto completo da fonteBétourné, Aurélie. "Conception et caractérisation de nouvelles fibres optiques à cristal photonique dites hybrides et applications à l'optique non linéaire". Thesis, Lille 1, 2010. http://www.theses.fr/2010LIL10170/document.
Texto completo da fonteThis thesis focuses both on theoretical and experimental studies of a recent class of Photonic Crystal Fibers (PCF): the solid-core PCF which guide light thanks to a Photonic BandGap (PBG) effect. The main goal of this work is then to better understand their propagation mechanisms (in order to improve their transmission properties) as well as to explore their potentials for non linear purposes. The study of these fibers (dispersion diagrams interpretation, emphasis of a scaling law and also of a light level of bend losses restrictive for their practical uses) leads us to develop a new kind of PCF for which wave guidance is a combination of PBG effect and more common Total Internal Reflexion (TIR). These fibers, called hybrid PCF, are made here by adding air holes in the all-solid structures previously studied. Particularly, two hybrid structures are proposed and fabricated, exhibiting a huge reduction of confinement and bend losses. Finally, we show that their unique disoersive properties enable to obtain a phase index matching between two fundamental modes (one is guided by PBG and the other by TIR) for second or third harmonic generation, and to effectively generate a supercontinuum for which the spectral broadening can be controlled by the opto-geometrical properties of the structure
Khan, Hamid. "Optimised space vector modulation for variable speed drives". Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2012. http://tel.archives-ouvertes.fr/tel-00999475.
Texto completo da fonteKüttler, Sulivan. "Dimensionnement optimal de machines synchrones pour des applications de véhicules hybrides". Phd thesis, Université de Technologie de Compiègne, 2013. http://tel.archives-ouvertes.fr/tel-01023815.
Texto completo da fonteNie, Chunyang. "Etude de nanocristaux unidimensionnels confinés dans des nanotubes de carbone". Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30214/document.
Texto completo da fonteFilling carbon nanotubes (CNTs) has been considered as an easy approach to synthesize various nanocrystals since the inserted materials are forced to adopt a nearly one-dimensional morphology arising from their very high aspect ratio, especially in the case of single-walled CNTs (SWCNTs) or double-walled CNTs (DWCNTs). Nanocrystals/nanowires of transition metals, especially those with very narrow diameters, are predicted to exhibit peculiar magnetic property differing from the bulk metals. Filling CNTs provides a possible way for the synthesis of such metal nanocrystals/nanowires. There are several methods for filling CNTs including the in situ method, gas phase method, molten phase method, solution method, etc. Among them, molten phase has been very popular for filling various types of nanotubes due to the possibility to reach high filling rates, simplicity and versatility. However, for materials with high melting point such as metals, it is difficult to insert them into CNTs directly. To solve this problem, we also took advantage of the inner cavity of CNTs which not only templates the growth but also acts as a nanoreactor in order to perform chemical reactions. The insertion of materials with high melting point is typically achieved by first filling CNTs with a precursor, and then transforming the precursor into the desired 1D nanostructure by post-treatments. In this thesis, (i) filling DWCNTs with iodine and various halides via the molten phase method was performed and the influence of the relevant physical and chemical properties of the halides on the filling rate was investigated. The role of the redox potential as a main parameter driving the filling efficiency is pointed out, and explained; (ii) peculiar structures of the nanocrystals confined within DWCNTs were imaged by transmission electron microscopy (TEM) and corresponding modeling of the observed crystal nanostructures and related TEM images were proposed; (iii) different in situ transformations on the iodide-filled DWCNTs were attempted and the chemical composition of the encapsulated 1D nanocrystals before and after post-filling treatments was systematically identified by means of electron energy loss spectroscopy (EELS)
Neurouth, Adrien. "Etude de la performance énergetique d’une transmission de puissance haute vitesse". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI017/document.
Texto completo da fonteA way to improve both electric and hybrid vehicles is to use high speed motors, operating over than 42.000rpm. The goal is to increase the power density and the efficiency of powertrains. Using these new motors, new gearboxes should be developed. This must be done without generating significant additional cost regarding already mastered low speed solutions. High energy performance level also has to be maintained. This PhD comes before the design phase of a high-speed oil bath lubricated gearbox. It aims to identify the warm-up and power loss problems, and propose ways to improve efficiency. This work proposes a thermomechanical modelling of the gearbox’s first stage, using the thermal network method. This model links power losses with temperatures. Particular attention is paid to high speed bearing modelling. A new thermomechanical model of rolling element bearing is developed. As churning losses being significant at high speeds, a method to greatly reduce this power loss is characterized
Maleki, Kamran. "Contribution à l'étude du comportement des micropieux isolés et en groupe". Phd thesis, Ecole Nationale des Ponts et Chaussées, 1995. http://tel.archives-ouvertes.fr/tel-00523150.
Texto completo da fonteZeaiter, Amal. "Thermal Modeling and Cooling of Electric Motors : Application to the Propulsion of Hybrid Aircraft Thermal Sensitivity Analysis of a High Power Density Electric Motor for Aeronautical Application Numerical Approach to Determining Windings’ Thermal Conductivity Electro-thermal Models and Design Approach for High Specific Power Electric Motor for Hybrid Aircraft Determination of electric motor losses and critical temperatures through an inverse approach". Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2020. http://www.theses.fr/2020ESMA0015.
Texto completo da fonteThe concern of this thesis is the thermal modeling of high-specific power electric motors. The aim is to allow finding the efficient and adequate cooling solutions of the motors designed for hybrid aircraft propulsion application. Two specific power values, 5 kW/kg for the short-term (year 2025) and 10 kW/kg for the long-term (year 2035), are targeted, each with specific requirements. The investigated type of electric motors is the synchronous machine with surface-mounted permanent magnets. This motor type is constrained by relatively low values of maximum allowed temperatures in windings and magnets. Once reached, these temperature values lead to a failure in motor operation or at least to shortening its lifetime. Moreover, with a closed motor design and high heat fluxes generated, the optimization of the cooling is essential.To become acquainted with the issue, a detailed state of the art on electric machine cooling is elaborated. Then, the commonly used techniques and the recent technological advancements are analyzed with respect to our case study. Afterward, in order to predict motor thermal behavior and ensure the monitoring of critical temperatures (windings and magnets), a nodal transient model is implemented and solved on Matlab software. This latter is built for the whole system of the motor and cooling circuit. Specific conditions of the flight are taken into account, particularly the outside air temperature variation in terms of altitude and the flight mission profile. Actually, the motor losses, generating the heat in the machine, vary depending on the motor power during the mission. For the identification of crucial parameters, a Finite-Element study was conducted and corresponding correlations were elaborated to estimate the windings thermal conductivity through polynomial interpolation.Several studies were carried out involving the influence of the thermo-physical properties, the outside temperature, the coolant nature, its flow rate as well as the exchanger surface, on the temperature response of the model. This model has allowed studying several motor designs and proposing adequate cooling solutions. For each target, a final optimal configuration of the motor with its cooling system was adopted.Besides, since the electromagnetic and mechanical losses are hardly estimated in this machine type, a chapter was dedicated to identifying them through an inverse approach. A sequential technique, that uses Beck’s function specification for regularization, was developed. Three cases of unknown losses, with increasing complexity, were studied, proving the method's reliability. Finally, using the same developed low-order model, the real-time procedure also allows monitoring low-accessibility motor temperatures (specifically hot spots)
Zeitouny, Joya. "Advanced strategies for ultra-high PV efficiency". Thesis, Perpignan, 2018. http://www.theses.fr/2018PERP0056.
Texto completo da fonteThe maximum efficiency limit attainable with a single-junction PV cell is ~ 33% according to the detailed balance formalism (also known as Shockley-Queisser model), which remains far from the Carnot limit, predicting a solar to electricity efficiency upper value of 93%. The large gap between both limits is due to intrinsic loss mechanisms, including the inefficient conversion of the solar spectrum and the large discrepancy between the solid angles of absorption and emission. To overcome these losses and get closer to the Carnot limit, three different strategies are considered in this thesis: concentrated multi-junction solarcells, the combination of solar concentration and angular confinement, and hybrid PV/CSP systems. Each strategy is inherently limited by several loss mechanisms that degrade their performances. The objective of this thesis is, hence, to better understand the extent to which these strategies are likely to be penalized by these losses, and to tailor the cell properties toward maximizing their efficiencies. To address these questions, a detailed-balance model of PV cell accounting for the main loss mechanisms was developed. A genetic-algorithm optimization tool was also implemented, aiming at exploring the parameter space and identifying the optimal operation conditions. We demonstrate the uttermost importance of tailoring the electronic properties of the materials used with both multi-junction solar cells undergoing significant series resistance losses, and PV cells operating at temperature levels exceeding ambient temperature. We also investigate the extent to which series resistances losses and non-radiative recombination are likely to affect the ability of PV cells simultaneously submitted to concentrated sunlight and angular restriction of the light emitted by band-to-band recombination
Ben, Nachouane Ayoub. "Modélisation numérique des phénomènes aérothermiques dans les machines électriques en vue d’optimisation de leur conception : application aux machines électriques des véhicules hybrides et électriques". Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2348/document.
Texto completo da fonteThe integration of an electrical machine into modern hybrid vehicles is associated with new technical constraints such as the integrability into small volume without losing certainly in performance. Therefore, the development of compacter electrical machines is a well-founded argument for car manufacturers as well as electrical machine designers. On the other hand, this finding assumes that the thermal aspects are undertaken not only during the operation of the electrical machine, but also during the design process. The internal heat generated in different areas impacts strongly the power density and the magnet health which deeply reduce the electrical machine reliability. Heat transfer modeling inside electrical machines is a tricky task because of the strong coupling between the different physics governing their operations. Indeed, the generated losses spread inside the electrical machine through three heat transfer modes which are: conduction (heat diffusion), convection(heat transport) and radiation (heat scattering). In terms of geometry, if a first approach can be carried out by considering only radial heat fluxes, the axially-transferred heat must be undertaken when it is also necessary to consider end caps effects, and particularly the heat released by the bearings. In order to carry out relevantly the thermal analysis of a permanent magnets synchronous machine, CFD based methods are used to characterize the convective heat transfer inside this machine over a large operating range. Both natural and forced convection are analyzed and the corresponding heat transfer coefficients are numerically-estimated. Empirical equations are proposed in order to take into account the coupling between thermal and fluid dynamics inside the cavities of the studied totally-enclosed machine. These correlations are integrated then into a detailed and reduced thermal network. Experimental tests are carried out using a test bench in order to measure temperature distribution in different areas of the electrical machine. Afterward, a comparison between estimated and measured temperatures shows that the results of the numerically-enhanced thermal network are in a good agreement with measurements. Thus, the proposed recommendations based on CFD modeling allow the convective heat transfer to be characterize quickly and precisely. These correlations are useful for upcoming studies dealing with convection inside automotive electrical machines as well as high speed electrical machines
Ployard, Maxime. "Efficacité énergétique des machines de production d'électricité". Thesis, Ecole centrale de Lille, 2017. http://www.theses.fr/2017ECLI0010/document.
Texto completo da fonteDuring the design phase of an electrical generator, the topology is generally imposed by preliminary criteria. This thesis aims at providing a decision support for the choice of high power generator structures. The interest for high efficiency machines is driven by strong environmental objectives. Consequently, understanding the origin of losses in power generation machines is a major issue. Thus, a methodology for iron loss calculation is developed for high power generators.In the energy production and conversion sectors, Hybrid Excitation Synchronous Machines have a great potential to respond to the challenges of energy transition. It is important to quantify the impact of these new structures compared with existing solutions. This thesis proposes analytical and lumped models to design a set of generator structures. The modeling approach is also compared with two high power generators, including one for a direct drive wind turbine. Then, this modeling is used in an optimization design process. The optimal Pareto structures are compared according to different specifications. These optimized designs show significant gains compared to the existing solutions, especially on wind profile from a Weibull probability density function
Benlamine, Raouf. "Etude et réalisation d'une machine électrique à forte densité de couple et fort rapport de sur-couple pour des applications de traction automobile". Thesis, Besançon, 2015. http://www.theses.fr/2015BESA2014/document.
Texto completo da fonteThe societal and environmental context in France and Europe during the last few years has been largely favorable to the electrification of transportation means, mainly vehicles, in order to reduce CO2 emissions. The authorities are working hard to make the electrified vehicles more affordable, by providing substantial premiums during the purchase of “clean” vehicles. For their part, the automakers are looking to reduce the cost of electric and hybrid electric vehicles by offering technical solutions that can reduce the manufacturing cost of the car components, mainly batteries, thermal and electric motors, while ensuring high performances. The main objective of this thesis is to study and realize an electric machine, which satisfies very restrictive specifications in terms of axial size and torque density in order to be used as a traction motor for a hybrid electric vehicle. In addition, this machine must be innovative, with a high reliability, low cost and automated manufacturing process. Thus, a state of art about the various electric machines has been achieved. Depending on the requirements of our application, an axial flux machine with buried permanent magnets and concentrated winding has been selected. Initially, a simplified analytical model has been developed and coupled to an optimization tool. The obtained geometrical and electrical parameters have been adjusted using a numerical model based on the 3D finite element. Various modifications have been applied to the initial machine due to the modification of the geometrical and performance specifications. Electromagnetic performances such as torque and power have been analyzed for various operating points. Losses in the permanent magnets have been calculated using a hybrid numerical 3D model based on the finite difference and finite element, which allows to reduce the computation time compared to transient 3D finite element. In order to validate the different results, a prototype of the machine has been realized. This machine has also been modeled using a quasi-3D magnetic equivalent circuits. This semi-analytical model is generic regarding the geometrical and electrical parameters, with an adaptive discretization. Furthermore, the saturation and the slotting effects have been taken into account. The magnetic flux density, the flux linkage and the electromagnetic torque have been calculated with this model, ensuring high accuracy and reduced time computation compared to 3D finite element