Teses / dissertações sobre o tema "Prédiction de contacts"
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Coulon, Sandrine. "Prédiction de la durée de vie des contacts ponctuels lubrifiés en présence d'indentations". Lyon, INSA, 2001. http://www.theses.fr/2001ISAL0038.
Texto completo da fonteThe purpose of this work is to predict the rolling contact fatigue (RCF) life reduction and analyze the failure process for lubricated indented point contacts. A first part studies the influence of a dent on the pressure and stress field from a numerical and analytical point of view. An analytical relation of the pressure peak versus two geometric dent parameters is obtained: slope, ratio between the dent depth over the dent diameter, and shoulder radius of curvature. The stress analysis leads to a damage criterion. Based on a local approach, the endurance limit criterion is representative of the contact severity. Complemented with a stressed volume analysis, a damaged risk is defined. Finally, a damage risk abacus as a function of the two parameters mentioned previously is presented. The results predicted with these two criteria are compared to RCF tests performed on a two disk-machine. A second part is dedicated to the damage process and its analysis. Two kinds of defects are studied, artificial ones made with a Rockwell penetrator, and natural ones obtained from solid particles passing through the contact. Whatever the considered dent, the plastic deformation due to the over rolling occurs in the very first cycles, quickly leading to a stabilized geometry. Depending on the test conditions (load, speed, slide to roll ratio), geometric and hydrodynamic damage effects are identified. The analysis of the direction of the crack propagation is studied using cross-sections. This work represents a step forward in the prediction and understanding of the influence of solid particle contamination on fatigue life
Allain, Fabrice. "Calcul efficace de la structure des protéines à partir de contacts évolutifs". Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066366/document.
Texto completo da fonteStructural prediction methods provide a relatively effective alternative to experimental approaches to provide a first insight into native folding of a protein. The gap between the number of structures and protein sequences available in databases has steadily increased since the advent of high throughput sequencing technologies. This strong growth of genomic information helped bring to light prediction tools using coevolutionary data. Conservation of a specific function implies strong restraints on interacting residues involved in the folding and function. Once detected, these interactions can help to model the conformation of a protein. Some important aspects needs to be improved during the modelling process including the detection of false positive among the predicted contacts. Limitations in the field are similar to those encountered in nuclear magnetic resonance spectrometry structure determination where data integration is a clearly established and largely automated process. The Ambiguous Restraints for Iterative Assignment (ARIA) software uses the concept of ambiguous distance restraints and follows an iterative process to assign and refine the list of nearby nuclei in space to compute a set of structural models in accordance with the data. This work aims to adapt this approach to de novo predict the structure of a protein using evolutionary information
Allain, Fabrice. "Calcul efficace de la structure des protéines à partir de contacts évolutifs". Electronic Thesis or Diss., Paris 6, 2017. http://www.theses.fr/2017PA066366.
Texto completo da fonteStructural prediction methods provide a relatively effective alternative to experimental approaches to provide a first insight into native folding of a protein. The gap between the number of structures and protein sequences available in databases has steadily increased since the advent of high throughput sequencing technologies. This strong growth of genomic information helped bring to light prediction tools using coevolutionary data. Conservation of a specific function implies strong restraints on interacting residues involved in the folding and function. Once detected, these interactions can help to model the conformation of a protein. Some important aspects needs to be improved during the modelling process including the detection of false positive among the predicted contacts. Limitations in the field are similar to those encountered in nuclear magnetic resonance spectrometry structure determination where data integration is a clearly established and largely automated process. The Ambiguous Restraints for Iterative Assignment (ARIA) software uses the concept of ambiguous distance restraints and follows an iterative process to assign and refine the list of nearby nuclei in space to compute a set of structural models in accordance with the data. This work aims to adapt this approach to de novo predict the structure of a protein using evolutionary information
Muscat, Maureen. "Machine learning and co-evolution methods for protein-protein interactions". Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS507.
Texto completo da fonteIn this thesis, we focus on the use of machine learning to solve the problem of the prediction of protein-protein interactions (PPI). The study of PPI is a central problem in biology, as proteins interact with each other to form complex networks that carry out the biological functions of cells. Experimental techniques to determine when and how proteins interact are very costly and time-consuming, so there is a great need for computational methods that can predict PPIs. We will explore the use of machine learning based on coevolution and deep learning for PPI prediction. Coevolutionary methods such as Direct Coupling Analysis have been used successfully for a number of different tasks, such as the prediction of intra-protein contacts, inter-protein contacts, and the prediction of mutational landscape. During my Ph.D., I developed a supervised machine learning algorithm to predict inter-domain and inter-protein contact maps called FilterDCA. The aim was to add some supervision, using typical contact patterns, while keeping the tool interpretable. I have also worked on PPIs in the SARS-CoV2 virus and on a multi-protein complex present in some bacteria membranes
Laporte, Julie. "Etude et modélisation de l'endurance électrique de micro-contacts soumis à des sollicitations de fretting-usure : caractérisation de nouveaux dépôts base Argent". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEC034/document.
Texto completo da fonteAdvanced instrumentation in mechanical systems (aeronautical, automobile etc…) goes hand in hand with an ever increased use of electrical connectors. However, the unfavorable operating environment (chemical attack and vibrational loads) causes more or less severe degradation of electrical contacts, which in turn perturbs their electrical conductivity. Gold plating is usually applied in electrical contacts in order to limit damage and to ensure connector stability. However, economic constraints and the high cost of gold require cheaper alternatives. Amongst conductive metals, silver is the best candidate. Hence, the purpose of this PhD project is to investigate the electrical response and the degradation of silver coatings when subjected to fretting loadings. The study is divided into three main research axes. The first axis consists in realizing a complete study of a homogeneous silver/silver contact in order to identify the degradation mechanisms that are responsible for the electrical failure, both in fretting loadings and reciprocating sliding. It was possible to formalize a predictive model, using an energy density approach, allowing to extrapolate the lifetime of the contact as a function of various loading parameters. A complementary study also showed the impact of a corrosive sulfur atmosphere on these electric contacts. As part of the second research axis, an investigation of the tribological and electrical behavior of novel silver-based materials, solely synthesized as a gold replacement, was performed. The analysis of these homogeneous contacts allowed to explain the degradation mechanism and the mechanical behavior of these contacts when subjected to a wet environment. In the last research axis a study was led on the same silver-based materials but in a heterogenous configuration against a gold coating in order to identify the tribological and electrical behavior of these contacts when composed by materials with similar or opposite properties
Parent, Marie-Océane. "Prédiction de la stabilité en contact rotor-stator dans les turboréacteurs d'avion". Thesis, Ecully, Ecole centrale de Lyon, 2015. http://www.theses.fr/2015ECDL0004/document.
Texto completo da fonteThis work aims to predict the dynamic stability of a turbofan engine submitted to light contacts between blade tips and casing. Reducing the clearance between the rotating blades and the casing improves indeed the performances of turbomachines ; however, it also increases the possible contacts between rotating and stationary parts, which can cause unstable dynamic behavior. The approach is based on a hybrid model which introduces a simplified bladed wheel and a flexible casing to a rotor-shaft model. A 3D contact formulation has also been implemented ; it considers the model kinematic and introduces the local geometry of the contact area. The model behavior with blade-to-casing contacts is analyzed through two approaches : the first one assumes permanent contacts while the other one allows contact intermittence. The results highlight the importance of couplings in the outbreak of unstable phenomena and the relevance of the 3D contact formulation in predicting the stability of the system
Legrand, Mathias. "Modèles de prédiction de l'interaction rotor/stator dans un moteur d'avion". Phd thesis, Ecole centrale de nantes - ECN, 2005. http://tel.archives-ouvertes.fr/tel-00011631.
Texto completo da fonteFourty, Guillaume. "Recherche de contraintes structurales pour la modélisation ab initio du repliement protéique". Paris 7, 2006. http://www.theses.fr/2006PA077101.
Texto completo da fonteUnderstanding the protein folding process and predicting protein structures from sequence data only remain two challenging questions for structural biologists. In this work, we first observe highly frequent proximities between N- and C-termini of protein domain, probably reflecting early stages of folding. Then we address the problem of polymer folding on regular lattices. We enumerate Hamiltonian Orbits and Cyclic Hamiltonian Orbits on n x n square lattices to evaluate the conformational space reduction associated to the termini contact constraint. Exhaustive Exploration of those maximally compact structures provides a baseline for minimum search algorithm in the HP- folding problem. Finally, we study multiple alignments at low sequence identity and introduce topohydrophobicity, a measure of topohydrophobicity conservation. We use it through decision tree to predict structural features such as Central/Edge position of beta strands in beta sheets and solvent accessibility (RAPT - Relative Accessibility Prediction Tool). These data can be used in ab initio prediction procedures of protein structures
Degré, Fabien. "Prédiction numérique des caractéristiques d'une pièce traitée par galetage : application au secteur du décolletage". Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00729061.
Texto completo da fonteCaignot, Alain. "Prédiction par essais virtuels de l'amortissement dans les structures spatiales". Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2009. http://tel.archives-ouvertes.fr/tel-00422291.
Texto completo da fonteCaignot, Alain. "Prédiction par essais virtuels de l'amortissement dans les structures spatiales". Phd thesis, Cachan, Ecole normale supérieure, 2009. http://www.theses.fr/2009DENS0018.
Texto completo da fonteIn the context of a significant cost reduction in the design of space launchers, it is on crucial to control all the factors involved in the dimensionning process. The decrease in mass is compensated by an increase in stiffness and results in a decrease of damping, which is the parameter that determines the level of the dynamic response. At the present time, the damping is taken into account in a global model and most often identified on the final structure. The objective of this work is to improve the launcher design process by introducing the capability to predict damping a priori. In order to do that, the idea is to develop a database containing the dissipation due to the materials and the dissipation relative to the joints in the launcher for each type and each level of solicitation. . . Damping in materials is relatively well-known in the case of the composites which make up the launcher. Therefore, the challenge is the prediction of the damping in the joints where the dissipations can be very important. The experimental approaches are expensive and complex to implement, that is why this work is based on a finite element computation of the joints. This type of simulations is beyond the reach of standard industrial computing codes ans has needed the development of specific parallel computationnal code based on the LATIN method. The robustness of the numerical tool has been studied and its results validated from experimental values obtained in a previous study. Finally, the computation of different joints of the launcher has been done as well as the methodology for integrating these results in the design process of Ariane
Rousseau, Clément. "Prédiction par transfert inverse d'un champ de conductance thermique de contact dans un mur de réacteur métallurgique". Mémoire, Université de Sherbrooke, 2011. http://savoirs.usherbrooke.ca/handle/11143/1636.
Texto completo da fonteMedjiah, Samir. "Optimisation des protocoles de routage dans les réseaux multi-sauts sans fil à contraintes". Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14663/document.
Texto completo da fonteGreat research efforts have been carried out in the field of challenged multihop wireless networks (MWNs). Thanks to the evolution of the Micro-Electro-Mechanical Systems (MEMS) technology and nanotechnologies, multihop wireless networks have been the solution of choice for a plethora of problems. The main advantage of these networks is their low manufacturing cost that permits one-time application lifecycle. However, if nodes are low-costly to produce, they are also less capable in terms of radio range, bandwidth, processing power, memory, energy, etc. Thus, applications need to be carefully designed and especially the routing task because radio communication is the most energy-consuming functionality and energy is the main issue for challenged multihop wireless networks.The aim of this thesis is to analyse the different challenges that govern the design of challenged multihop wireless networks such as applications challenges in terms of quality of service (QoS), fault-tolerance, data delivery model, etc., but also networking challenges in terms of dynamic network topology, topology voids, etc. Our contributions in this thesis focus on the optimization of routing under different application requirements and network constraints. First, we propose an online multipath routing protocol for QoS-based applications using wireless multimedia sensor networks. The proposed protocol relies on the construction of multiple paths while transmitting data packets to their destination, i.e. without prior topology discovery and path establishment. This protocol achieves parallel transmissions and enhances the end-to-end transmission by maximizing path bandwidth and minimizing the delays, and thus meets the requirements of QoS-based applications. Second, we tackle the problem of routing in mobile delay-tolerant networks by studying the intermittent connectivity of nodes and deriving a contact model in order to forecast future nodes' contacts. Based upon this contact model, we propose a routing protocol that makes use of nodes' locations, nodes' trajectories, and inter-node contact prediction in order to perform forwarding decisions. The proposed routing protocol achieves low end-to-end delays while using efficiently constrained nodes' resources in terms of memory (packet queue occupancy) and processing power (forecasting algorithm). Finally, we present a topology control mechanism along a packet forwarding algorithm for event-driven applications using stationary wireless sensor networks. Topology control is achieved by using a distributed duty-cycle scheduling algorithm. Algorithm parameters can be tuned according to the desired node's awake neighbourhood size. The proposed topology control mechanism ensures trade-off between event-reporting delay and energy consumption
Del, Bufalo Aurelia. "Effets des sensibilisants sur la synthèse de la prostaglandine E2 : Mécanismes et intérêt dans la prédiction de l’allergie de contact". Thesis, Paris, AgroParisTech, 2012. http://www.theses.fr/2012AGPT0003/document.
Texto completo da fonteContact sensitizers are defined as reactive molecules (electrophilic) which have the ability to modify skin proteins to form an antigen (hapten). In addition to the haptenation mechanism, danger signals, leading to the activation of dendritic cells, are described to be crucial for the effective induction of an hapten-specific T cell immune response. In the context of the 7th amendment to the Cosmetic Directive, the cosmetic industry is concerned by the challenge of finding non-animal approaches to assess the sensitizing potential of chemicals. While danger signals induced by sensitizers in steady-state conditions have already been analyzed, we chose to investigate the impact of sensitizers on the course of an inflammatory response. For this purpose we used the U937 cell line differentiated with PMA and activated with LPS. In these conditions, cells produce a large amount of inflammatory mediators (IL-β, TNF-α, IL-6, IL-10, IL-8, PGE2, PGD2, TxB2) through the activation of pathways leading to the activation of the transcription factors NF-κB and Nrf2 and through AA metabolism by the cPLA2/COX-2 cascade. Interestingly, we showed that 6 contact sensitizers with various potential (DNCB, PPD, HQ, PG, CIN, EUG) significally and specifically decrease the production of prostanoïds and in particular of PGE2 induced by PMA/LPS. We further demonstrated that there is no unique inhibition profile of the sensitizers even if the majority (except for DNCB) of the effects applies on COX-2 (i.e. inhibition of the expression and/or activity). For DNCB, inhibition mechanism appears to be dependant of its capacity to react with thiols residues and in particular to deplete intracellular glutathione possibly leading to the inactivation of the PG-synthases. In parallel, we assess a statistical analysis on 160 molecules that allow us to define the test parameters (a molecule is a sensitizer if the PGE2 inhibition at 24h is more than 60%) and to calculate the test performance toward LLNA (78%). Moreover we demonstrated that the PGE2 test could be complementary to other already existing in vitro tests like MUSST or Nrf2-HTS. In summary, we add here a new insight into the multiple biochemical effects described so far for sensitizers. Even if the underlying biological relevance remains unclear, the parameter “PGE2 inhibition” is good test for skin sensitization evaluation. Further studies will precise how this parameter could be implemented into an alternative testing strategy for the evaluation of skin sensitization
Kharboutly, Mohamed. "Modélisation, réalisation et commande d'un système de micro-manipulation sans contact par diélectrophorèse". Phd thesis, Université de Franche-Comté, 2011. http://tel.archives-ouvertes.fr/tel-00582992.
Texto completo da fonteChauvineau, Guillaume. "Modélisation de la dynamique des boîtes de vitesses automobiles soumises à des sollicitations acycliques : applications à la prédiction du bruit de grenaille et validation expérimentale". Thesis, Ecully, Ecole centrale de Lyon, 2014. http://www.theses.fr/2014ECDL0022.
Texto completo da fonteThe gearbox is an important component of an automobile and its development is complex. Numerous constraints must be taken into account, particularly its noise and vibration behavior. This aspect of the conception is nowadays poorly mastered and the noise pollution of gearboxes, such as the rattle noise, are often discovered late. The aim of this work was the development of a numerical model of gear dynamics adapted to gearboxes’ modelling and allowing to predict the conditions of gear rattle noise appearance. The model proposed in this thesis is based on an original combination of different models and is applicable to the vast majority of gearboxes. Flexible components, such as shafts and housings are modeled by the finite element method. A gear model based on Kelvin-Voigt contact model is developed. It allows to take into account the contact losses and the back side contacts. To complete this model, mechanical loss models are implemented in order to take into account the influence of the bearings, plain bearings, synchronizers and gears’ immersion in oil. This model coupled with a noise indicator allows for sensitivity analyzes to identify influential parameters on the rattle noise but also to compare the dynamic behavior of different configurations. Finally, a test campaign on an industrial gerbox is conducted and simulation results are confronted to measurements
Del, Bufalo Aurelia. "Effets des sensibilisants sur la synthèse de la prostaglandine E2 : Mécanismes et intérêt dans la prédiction de l'allergie de contact". Phd thesis, AgroParisTech, 2012. http://pastel.archives-ouvertes.fr/pastel-01016611.
Texto completo da fonteBelloula, Amar. "Contribution à l’étude de la prédiction de la durée de vie en fretting-fatigue : application à un contact acier-alliage d’aluminium". Thesis, Lille 1, 2013. http://www.theses.fr/2013LIL10029/document.
Texto completo da fonteThe purpose of this study is to predict fretting fatigue crack nucleation of a mono contact steel/aluminum at different applied loads.An experimental device was first designed and adapted on a multiaxial fatigue apparatus. Tests were conducted aluminum alloy at constant amplitude loading under both different load levels and load ratios. As expected, the fretting fatigue life was found lower compared to uniaxial fatigue under the same loading conditions. Finite element analysis was conducted using \textit{Abaqus} software. The computed stress and strain fields were used to estimate the parameters of different multiaxial fatigue criteria based on the critical plane approach. When using stress and strain values corresponding to the material point exhibiting the maximum value of the considered parameter, we have found that, whatever the multiaxial fatigue parameter, conservative fatigue life estimates due to the severe gradients in the contact zone. An averaging method of the mechanical quantities over a given reference volume was then used to attenuate these gradients effects. The estimates show a good correlation with experimental results. However, the size of the reference volume depends on both the multiaxial fatigue criteria and on loading conditions applied. So that it could not be directly linked to the grain size for the material studied. Finally, we made an attempt to extend these criteria and the developed method to variable loadings. Fretting fatigue tests using two and four blocks loadings were performed and the previous criteria were coupled with two damage laws. The estimates we have obtained seems very promising
Filali, Oussama. "Approche multi physique du contact frottant en grande déformation plastique : prédiction numérique du grippage d'alliages d'aluminium en mise en forme à froid". Thesis, Valenciennes, Université Polytechnique Hauts-de-France, 2020. http://www.theses.fr/2020UPHF0035.
Texto completo da fonteThe thesis proposes a new approach to predict the galling defect encountered during cold forming of aluminum alloys. Numerous experimental studies show that this defect is strongly linked to the conditions of contact and friction and is a function of the roughness of the manufacturing tools. Models to predict the appearance of this defect are rare and are generally based on indirect observables, such as pressure or temperature fields, without explicitly taking into account the influence of first-order factors such as lubrication and 'surface condition of the materials in contact. The proposed methodology of our work assumes that the defect appears when the material of the part near its contact surface reaches a critical level of damage. However, in a previous study, it was shown that damage models based exclusively on hydrostatic pressure, such as GTN or Lemaitre models, were only able to predict damage if they model roughness. surfaces. This leads to multi-scale numerical simulations which are very costly in terms of computation time and incompatible with the modeling of real industrial processes. To get around this difficulty, the present study proposes to use damage models considering the shear effects generated by the friction contact. The influence of roughness is then based on a relevant choice of the friction law. First, a bibliographical chapter deals with damage models. Particular attention is paid to models using the Lode parameter to consider the effect of shear stresses on the evolution of damage variables. Secondly, a bibliographical review of friction and lubrication models is presented. The study notably highlights models based on a mesoscopic approach to lubrication, with the modeling of the crushing of roughness during rubbing contact. At the end of these chapters, the damage model developed by L. Xue and a lubrication model explicitly considering the value of surface roughness is used to predict seizure in different contact configurations. Initially, this numerical methodology is applied to the study of the flat drawing process of 6082-T4 aluminum alloy plates. Then the methodology is applied to a pion / plane contact on 6082-T6 alloy plates. Finally, a process for spinning before cylindrical slips is studied with the same digital tools. These different configurations are tested with or without lubricant and with tools having different roughness values. The results show that the proposed procedure allows in most of the cases tested to predict the appearance of the defect, whether in configurations with or without lubricant. The predictions are nevertheless optimistic, the slip distances before the onset of digital seizure being generally greater than the distances measured experimentally. The results are however promising, and several perspectives are presented to improve the precision of the proposed methodology
Belaid, Abedessalem. "Modélisation tridimensionnelle du comportement mécanique de la garniture de forage dans les puits à trajectoires complexes : application à la prédiction des frottements garniture-puits". Paris, ENMP, 2005. http://www.theses.fr/2005ENMP1323.
Texto completo da fonteDrilling an oil well rapidly and at lower cost is now becoming a challenge in the drilling industry. To face and carry out this challenge, a good design of the drilling installation is essential. Therefore, predicting correctly friction losses, known as “Torque&Drag”, between the drill string and the borehole is a major asset especially for directional wells with complex trajectories. The existing models of friction calculation show some weaknesses in the case of complex trajectory wells. A new mechanical model of friction calculations inside complex trajectory wells was developed and validated. This model uses a 3D method of wellpath calculations called “Minimum of Torsion” that includes two geometric parameters: curvature and torsion. Unlike traditional models, which assume that the drilling structure lies, by gravity, on the low side of the borehole and often neglect the stiffness of the drill string, the new “Stiff String” model calculates the deformation state of the drilling assembly inside the hole via an iterative contact algorithm. Furthermore, the new model, by using a direct integration method of equilibrium equations, is much more faster than other one solved with finite element method. A comparison with the widely used “Soft String” model was carried out on several actual and theoretical wells. The comparison shows that the new model rectify many weaknesses of the existing model. Confrontations with measured data, in the case of wells having smooth trajectory (low tortuosity), show agreement of both models with field measurements. However the new model has better friction losses prediction when wellpath tortuosity increases
Toumi, Mohamed Yessine. "Étude de l'endommagement des composants mécaniques soumis à de la fatigue de roulement dans le cadre d'une maintenance prédictive : cas des butées à billes". Thesis, Reims, 2015. http://www.theses.fr/2015REIMS033.
Texto completo da fonteThe bearing is an essential element in the design of rotating machines. In an industrial context, bearing failure can have extremely costly consequences. Predictive maintenance minimizes the intervention costs and warns about the state of fatigue of the mechanical component. In this frame, we propose a study of the rolling contact fatigue damage applied to thrust ball bearings. This study is twofold: numerical and experimental. The first axis consists in establishing a dynamic three-dimensional numerical model of the cyclic shift of a ball on a running surface in the presence of an indent, using the finite element method. An estimation of the size evolution of a surface initiated spall depending on loading cycles is also performed. These results are consistent with laboratory tests executed in the same conditions using a fatigue test rig dedicated to ball bearings. The second axis consists in determining a vibratory indicator using modal analysis to estimate the on-line structural damage level of the ball bearing in the presence of an indent. The technique developed in this work enables monitoring the evolution of the modal damping values based on the life cycles determined from tests in static and dynamic modes. This study will contribute to estimate the residual life of the mechanical component after onset of a spall using the finite element method and accounting for the structural damage state
Guda, Vamsi Krishna. "Contributions à l'utilisation de cobots comme interfaces haptiques à contact intermittent en réalité virtuelle". Thesis, Ecole centrale de Nantes, 2022. http://www.theses.fr/2022ECDN0033.
Texto completo da fonteVirtual reality (VR) is evolving and being used in industrial simulations but the possibility to touch objects is missing, for example to judge the perceived quality in the design of a car. The current haptic interfaces do not allow to easily restore the notion of texture, therefore an approach is considered “intermittent contact interface” to achieve this. A cobot positions a mobile surface at the point of contact with a virtual object to allow physical contact with the operator's hand. The contributions of this thesis concern several aspects: the placement of the robot, the modeling of the operator, the management of the displacement and the speed of the robot and the detection of the operator's intentions. The placement of the robot is chosen to allow reaching the different working areas and to ensure passive safety by making it impossible for the robot to hit the head and chest of the operator in a normal working position, i.e. sitting in a chair. A model of the user, including a torso and arms, is designed and tested to follow the user's movements in real time Interaction is possible on a set of predefined poses that the user chains together as desired. Different strategies are proposed to predict the user's intentions. The key aspects of the prediction are based on the gaze direction and the hand position of the user. An experimental study as well as the resulting analysis show the contribution of taking into account the gaze direction. The interest of introducing "safety" points to move the robot away from the operator and allow fast robot movements is highlighted
Djebili, Omar. "Contribution à la maintenance prédictive par analyse vibratoire des composants mécaniques tournants. Application aux butées à billes soumises à la fatigue de contact de roulement". Thesis, Reims, 2013. http://www.theses.fr/2013REIMS030/document.
Texto completo da fonteThe bearing is one of the most important components of rotating machines. Nevertheless, in normal conditions of use, it is subject to fatigue which creates a defect called a rolling fatigue spalling. In this work, we present a follow-up of the thrust bearing fatigue on a test bench. Vibration analysis is a method used to characterize the defect. In order to obtain the fatigue curve more adjusted, we have studied the vibration level according to statistical indicators: the Root Mean Square value (RMS value), which is one of the best indicators to show the evolution of the bearing degradation. The approach follows the working of the bearing until the degradation with an on line acquisition of vibration statements in form of time signals. With the signal treatment, we obtain the values of the vibration amplitudes which characterize the vibration state of the bearing. Consequently, these values allow us to plot the fatigue curves. During our experimental work, this operation is applied for a batch of thrust bearings for which we have obtained similar fatigue curves where the evolution trend follows a mathematical model from the detection of the onset of the first spall. The result of this work will contribute to predict the working residual time before failure
Zhang, Yuanyuan. "Friction prediction for rough surfaces in an elastohydrodynamically lubricated contact". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI063.
Texto completo da fonteThe friction of interfacial surfaces greatly influences the performance of mechanical elements. Friction has been investigated experimentally inmost studies. In this work, the friction is predicted by means of numerical simulation under an elastohydrodynamic lubrication (EHL) rough contact condition. The classical Multigrid technique performs well in limiting computing time and memory requirements. However, the coarse grid choice has an important influence on code robustness and code efficiency to solve the rough problem. In the first part of this work, a coarse grid construction method proposed by Alcouffe et al. is implemented in the current time-independent EHL Multi-Grid code. Then this modified solver is extended to transient cases to solve the rough contact problem. The friction curve is usually depicted as a function of “lambda ratio”, the ratio of oil film thickness to root-mean-square of the surface roughness. However this parameter is less suitable to plot friction variations under high pressure conditions (piezoviscous elastic regime). In the second part of this work, the friction coefficient is computed using themodified EHL code for many operating conditions as well as surface waviness parameters. Simulation results show that there is no single friction curve when the old parameter "lambda ratio" used. Based on the Amplitude Reduction Theory, a new scaling parameter depends on operating condition and waviness parameters is found, which can give a unified friction curve for high pressure situation. For more complex rough surfaces, a power spectral density (PSD) based method is proposed to predict friction variations in the third part of this work. The artificial surface roughness is employed to test the rapid prediction method firstly. Good agreement is found between the full numerical simulation and this rapid prediction. Then the rapid prediction method is applied to analyze the friction variation of measured surface roughness. Both the new scaling parameter and the friction increase predicted by the PSD method show good engineering accuracy for practical use
Belaid, Abdessalem. "Modélisation tridimensionnelle du comportement mécanique de la garniture de forage dans les puits à trajectoires complexes : application à la prédiction des frottements garniture-puits". Phd thesis, École Nationale Supérieure des Mines de Paris, 2005. http://pastel.archives-ouvertes.fr/pastel-00579916.
Texto completo da fonteLes modèles usuels de prédiction des frottements montrent certaines insuffisances lorsque la trajectoire du puits se complexifie. Un nouveau modèle de calcul de frottements dans les puits de forage à trajectoires complexes a été développé et validé. Ce modèle utilise une méthode tridimensionnelle de reconstitution de la trajectoire intégrant à la fois la courbure et la torsion géométrique. Contrairement aux modèles classiques, qui supposent simplement que la garniture repose par gravité sur la paroi basse du trou de forage et qui négligent souvent la rigidité des tiges, le nouveau modèle rigide calcule la vraie déformée de la garniture de forage à l'intérieur du trou via un algorithme itératif de contact unilatéral. En outre, pour un gain important du temps de calcul, le modèle se base sur une intégration numérique directe des équations d'équilibre local sans avoir recours à la méthode des éléments finis.
La comparaison avec un modèle couramment utilisé dans l'industrie de forage, appelé modèle LISSE, a été effectuée sur plusieurs puits réels et théoriques. Il ressort de cette comparaison que le nouveau modèle vient palier plusieurs faiblesses du modèle LISSE dans le cas des trajectoires à géométrie complexe (surestimation des zones de contacts et des forces de contact en présence de micro-tortuosité, non sensibilité au signe du gradient d'azimut en présence de fort gauchissement, hypothèse de contact sur la paroi basse du trou pas toujours vérifiée). Par ailleurs, la confrontation avec les mesures du terrain pour la plupart des puits à géométrie bidimensionnelle ou faiblement tridimensionnelle avec des faibles dog legs (ne dépassant pas 2 à 3°/30 m) fournit généralement des concordances entre les résultats des deux types de modèles et les valeurs mesurées. En revanche, en présence de tortuosités et dog legs locaux le nouveau modèle fournit une meilleure prédiction des pertes en frottement.
Fremont, Julien. "Etude des contributions aux surfaces de potentiel et couplages non-adiabatiques par calculs ab initio de structures électroniques et mise aux points des Hamiltoniens effectifs pour les prédictions vibrationnelles : applications aux molécules LiH, H+3 et PH3". Reims, 2010. http://theses.univ-reims.fr/sciences/2010REIMS019.pdf.
Texto completo da fonteThis work takes place at the halfway between theoretical chemistry and theoretical molecular spectroscopy by proposing to use at their limits the quantum chemistry methods and then make theoretical predictions on the three molecules LiH, PH3 and H3 +. First of all, a chapter is devoted to quantum chemistry methods used in this work to obtain the potential energy surfaces and electronic states. For applications in molecular spectroscopy, the potential energy surface requires to be very accurate. The second chapter examines the influence of the basis, electronic correlations, relativistic corrections and extrapolation methods on the vibrational levels of LiH molecule. For a molecule with a small number of electrons, it is possible to get such quality on the potential energy surface that the limit the Born-Oppenheimer approximation is reached. The third chapter develops the concepts of contact transformation and effective Hamiltonian. It introduce the terms derived from quantum chemistry calculations needed to finally apply this formalism beyond the Born-Oppenheimer approximation to the LiH molecule. The aim of these two preveiws chapters is to explore the limits of ab-initio methods to characterize the vibrational states of all isotopologues near to the dissociation. The study of molecules with a large number of variables has other types of difficulties. The large number of electrons on one hand makes difficult to quantum chemistry calculations to obtain potential energy surface of good quality, on the other hand, the increase in the number of variables complicates the nuclear wave functions and therefore the calculation of vibrational energy levels. The fourth chapter presents the study within the framework of Born-Oppenheimer of the PH3 molecule containing the derivation of the kinetic energy operator in valence coordinates and calculating the potential energy surface by quantum chemistry method. The molecular symmetries of the Hamiltonian produces effects still poorly understood by scientists. The H3 + molecule in its C3v configuration has a conical intersection where the non-adiabatic effects are revealed. In this final chapter the kinetic energy operator in hyperspherical coordinates and the Jacobian matrix associated with this transformation are derived. The non-adiabatic couplings calculated in Cartesian coordinates are reexpressed hypersheriques. After introducing the adiabatic-diabatic transformation, the geometric phase effects are studied
Germain, Dimitri. "Développement d'un modèle d'efforts de coupe intégrant le contact en dépouille : application au tournage de superfinition du cuivre Cu-c2". Phd thesis, Paris, ENSAM, 2011. http://pastel.archives-ouvertes.fr/pastel-00661684.
Texto completo da fonteFlayols, Thomas. "Exploitation du Retour de Force pour l'Estimation et le Contrôle des Robots Marcheurs". Thesis, Toulouse, INSA, 2018. http://www.theses.fr/2018ISAT0025/document.
Texto completo da fonteIn this thesis, we are interested in the control of walking robots. Controlling these naturally unstable, non-linear, non-convex, large and contact-dependent systems is a major challenge in mobile robotics. Traditional approaches formulate a chain of control formed by a cascade of sub-problems such as perception, planning, full body control and joint servoing. The contributions reported here are all intended to provide state feedback at the whole body control stage or at the planning stage. Specifically, a first technical contribution is the formulation and experimental comparison of two estimators of the robot base. A second contribution is the implementation of a reverse dynamic controller to control the HRP-2 robot in torque. A variant of this controller is also formulated and tested in simulation to stabilize a robot in flexible contact with its environment. Finally, a predictive control operation generator coupled to a whole body controller is presented
Biboulet, Nans. "Influence of indentations on rolling bearing life". Phd thesis, INSA de Lyon, 2008. http://tel.archives-ouvertes.fr/tel-00663264.
Texto completo da fonteShimagaki, Kai. "Advanced statistical modeling and variable selection for protein sequences". Electronic Thesis or Diss., Sorbonne université, 2021. http://www.theses.fr/2021SORUS548.
Texto completo da fonteOver the last few decades, protein sequencing techniques have been developed and continuous experiments have been done. Thanks to all of these efforts, nowadays, we have obtained more than two hundred million protein sequence data. In order to deal with such a huge amount of biological data, now, we need theories and technologies to extract information that we can understand and interpret.The key idea to resolve this problem is statistical physics and the state of the art of machine learning (ML). Statistical physics is a field of physics that can successfully describe many complex systems by extracting or reducing variables to be interpretable variables based on simple principles. ML, on the other hand, can represent data (such as reconstruction and classification) without assuming how the data was generated, i.e. physical phenomenon behind of data. In this dissertation, we report studies of protein sequence generative modeling and protein-residue contact predictions using statistical physics-inspired modeling and ML-oriented methods. In the first part, we review the general background of biology and genomics. Then we discuss statistical modelings for protein sequence. In particular, we review Direct Coupling Analysis (DCA), which is the core technology of our research. We also discuss the effects of higher-order statistics contained in protein sequences and introduces deep learning-based generative models as a model that can go beyond pairwise interaction
Paquin-Lafleur, Stéphanie. "Des délits et des hommes : portrait des auteurs d’actions indécentes du Québec et caractéristiques associées à la récidive et à la commission de crimes sexuels avec contacts". Thesis, 2020. http://hdl.handle.net/1866/25756.
Texto completo da fonteThe crime of indecent act has long been defined by the scientific community and administered by justice more as a nuisance than a sexual crime. This can be explained by the fact that this type of crime does not involve physical sexual contact with the victim and that the negative consequences associated with the assault on the victim are often minimized. Thus, this study is part of an internship at the Crimes Against the Person Division of the Sûreté du Québec. The concrete application of this research is to support the process of targeting potential recidivists for indecent acts in investigation files. The goal is therefore to describe a retrospective portrait of the criminal careers of the 3,572 alleged or proven perpetrators of indecent acts reported in Quebec between 2011 and 2018. Univariate, bivariate and multivariate analyses and a ROC analysis were performed on the study population. The results of the study suggest that nearly 22% of the offenders are repeat offenders in indecent acts and that 18% of the study population have committed a sexual crime with contact with a victim. Both groups were also found to be overwhelmingly male, younger in terms of age, more prolific, and more diverse in terms of the variety of crime categories than those who had never re-offended or committed a contact sexual crime. Finally, the best predictors were found to be the gender of the offenders, the presence of a history of sexual crimes, violent crimes, and crimes in the "Other Criminal Offences" category that may be associated with breaches of orders or failures to comply with court undertakings. However, these individuals remain marginal since the vast majority of the indecent act offender population has not committed a recidivism or a sexual crime involving contact with a victim.