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S'adapter ou disparaître, le Service des poudres face au défi atomique (1945 - 1971)
No full textThe Powder Service, a former state body responsible for the production of munitions and explosives for the French armed forces, is at the heart of the institutional, technical and conceptual changes in armaments over the last century. It modernizes in a professional form, leading to the first of the world war, which responds to the defeats of modern warfare. This upheaval of modernization is a historical institution which is gradually passing through new armies, and not the nuclear army.This nuclearization powder magazine contributes to a repositioning of the Powder Service within the arms industry. The search for institutional recognition of military powder engineers encouraged their rapprochement and cooperation with the Atomic Energy Commission within the framework of the atomic weapons program, starting in the 1950s.This thesis seeks to grasp the transformations produced by this powder orientation towards military nuclear power on the Powder Service, its actors and its sites (the powder mills of Bouchet in Essonne, Saint-Médard in Gironde, Ripault in Indre-et -Loire and the fort of Vaujours).The issue of self-propulsion (propellants) is also directing the Powder Department towards a renewal of its activities to respond to a booming missile industry. This trajectory joins that of atomic weaponry through nuclear missiles.The subject thus leads to understanding the evolution of an industrial system in a highly strategic area. The Powder Department adapts and achieves powder nuclear power essential for atomic armament. However, he suffered relegation within the Defense players and ended up disappearing in 1971. This thesis sheds light on this paradox.Le Service des poudres, ancien organisme d'Etat chargé de la production des munitions et explosifs pour les forces armées françaises, est au cœur des changements institutionnels, techniques et conceptuels de l'armement au cours du siècle dernier. Il se modernise en profondeur, depuis la Première Guerre mondiale, afin de répondre aux défis de la guerre moderne. Cette modernisation bouleverse une institution historique qui se tourne peu à peu vers de nouveaux armements, dont le nucléaire militaire.Cette nucléarisation poudrière participe à un repositionnement du Service des poudres au sein des acteurs de l'armement. La recherche de reconnaissance institutionnelle des ingénieurs militaires des poudres favorise leur rapprochement et leur coopération avec le Commissariat à l'énergie atomique dans le cadre du programme de l'arme atomique, à partir des années cinquante.Cette thèse cherche à saisir les transformations produites par cette orientation poudrière vers le nucléaire militaire sur le Service des poudres, ses acteurs et ses sites (les poudreries du Bouchet dans l'Essonne, de Saint-Médard en Gironde, du Ripault en Indre-et-Loire et le fort de Vaujours).L'enjeu de l'autopropulsion (les propergols) oriente également le Service des poudres vers un renouvellement de ses activités pour répondre à une industrie missilière en plein essor. Cette trajectoire rejoint celle de l'armement atomique à travers les missiles nucléaires.Le sujet amène ainsi à comprendre l'évolution d'un système industriel dans un domaine hautement stratégique. Le Service des poudres s'adapte et parvient à une nucléarité poudrière essentielle pour l'armement atomique. Pourtant, il subit la relégation au sein des acteurs de la Défense et finit par disparaître en 1971. Cette thèse éclaire ce paradoxe
Optimisation de la performance et de la récupération des athlètes de haut-niveau engagés dans la réitération d'exercices à haute-intensité : exemple du 400 m
No full textFrench elite athletes specializing in long sprints in track and field face challenges in maintaining optimal performance during international competitions. In this context, the overarching goal of this doctoral research was to adopt a holistic approach to optimize the repetition of high-intensity exercises andenhance athlete recovery during international events. To achieve this, two aspects related to stress were explored: first, the study examined the impact of psychophysiological stress during competition on the regulation of the autonomic and neuroendocrine nervous systems, as well as the evaluation of innovative stress management strategies such as cardiac coherence to improve neuroendocrine regulation and sleep quality during competitions.Additionally, during high-intensity exercises, energy production induces significant metabolic disruptions, such as marked metabolic acidosis (with blood pH below 7 observed after 400 m events), which may hinder performance. To address this, nutritional and hydration strategies, including specific diets and hydration with bicarbonate-rich water, were tested to better regulate metabolic stress.Initial studies revealed psychophysiological disruptions related to competitive stress, with a significant decrease in parasympathetic activity and increased salivary stress biomarkers (cortisol and alpha-amylase). These disruptions, observed during both qualifying phases and finals, correlated withheightened anxiety and reduced recovery capacity (Studies 1 and 2). Interindividual variability highlighted some athletes' heightened sensitivity to competitive stress, emphasizing the need for individualized approaches to better manage these responses.The introduction of coherente breathing as a stress management technique improved autonomic nervous system regulation, reduced inflammation (IL-1β), and enhanced sleep quality, essential for recovery between events. Athletes practicing this technique demonstrated improved hormonal and inflammatory regulation, although no direct impact on competition performance was observed (Study 3).Subsequent studies addressing metabolic stress regulation demonstrated that consuming bicarbonate-rich water combined with an alkalizing diet (as opposed to an acidifying diet) significantly increased blood and urinary pH, improved lactate clearance after repeated exercises, and optimized bufferingcapacity (Studies 4 and 5). These metabolic adjustments enabled athletes to maintain or improve performance, particularly on the third day of high-intensity competition (Studies 5).In conclusion, this research highlights the importance of integrating strategies that combine pre-competitive stress management, particularly through coherent breathing, with tailored nutritional and hydration approaches during international competitions. These strategies promote better regulation ofthe autonomic and neuroendocrine nervous systems, enhance sleep quality, and help manage competition-induced metabolic acidosis. Together, these approaches can improve both performance and recovery for high-level athletes in demanding competitive contexts.Les athlètes de haut-niveau français, spécialistes des sprints longs en athlétisme, rencontrent des difficultés à maintenir des performances optimales lors des compétitions internationales. Dans ce contexte, l'objectif général de ce travail de thèse a été, à travers une approche holistique, de chercher àoptimiser la réitération d'exercices de haute-intensité et d'améliorer la récupération des athlètes lors des compétitions internationales. Pour ce faire, deux axes relatifs au stress ont été explorés : tout d'abord, nous avons analysé l'impact du stress psychophysiologique en compétition sur la régulation du système nerveux autonome et du système nerveux neuro-endocrinien, ainsi que l'évaluation de stratégies innovantes de gestion du stress telles que la cohérence cardiaque pour améliorer la régulation neuroendocrinienne et la qualité du sommeil des athlètes au cours des compétitions. Par ailleurs, aucours des exercices de haut-intensité, la production énergétique entraîne d'importantes perturbations métaboliques, telles qu'une acidose métabolique marquée (avec un pH sanguin inférieur à 7, relevé à l'issue des épreuves de 400 m), pouvant constituer un frein à la performance. Pour y remédier, nousavons appréhendé un second axe de recherche sur la régulation de l'équilibre acido-basique au cours de l'exercice et la récupération, à travers la mise en place de stratégies nutritionnelles et hydriques, incluant une alimentation spécifique et une hydratation à base d'eau riche en bicarbonates.Les premières études ont révélé des perturbations psychophysiologiques liées au stress compétitif, avec une diminution significative de l'activité du système parasympathique et une augmentation des biomarqueurs salivaires du stress (cortisol et alpha-amylase). Ces perturbations, observées lors desphases qualificatives et en finales, sont corrélées à une anxiété accrue associée à une capacité de récupération réduite des athlètes (études n°1 et n°2). Une variabilité interindividuelle a été constatée, certains athlètes se montrant particulièrement sensibles au stress compétitif, ce qui souligne l'importanced'approches individualisées pour mieux gérer ces réponses. Par ailleurs, l'introduction de la cohérence cardiaque comme méthode de gestion du stress a permis d'améliorer la régulation du système nerveux autonome, de réduire l'inflammation (IL1-β) et de favoriser une meilleure qualité du sommeil, essentielle pour récupérer entre les épreuves. Les athlètes pratiquant cette technique ont montré une meilleure régulation hormonale et inflammatoire, même si aucun impact direct sur les performances en compétition n'a été observé (étude n°3). Puis, les études suivantes de ce travail de thèse, relatives à la régulation du stress métabolique, ont démontré que la consommation d'eau riche en bicarbonates, associée à un régime alimentaire alcalinisant (à la différence d'une régime acidifiant), augmente significativement le pH sanguin et urinaire des athlètes, améliore la clairance du lactate après desexercices répétés et optimise la capacité tampon (études n°4 et n°5). Ces ajustements métaboliques ont permis aux athlètes de maintenir ou d'améliorer leurs performances, notamment lors du troisième jour de compétition à haute-intensité (études n°5).En conclusion, les résultats de ce travail de thèse soulignent l'importance d'intégrer des stratégies combinant la gestion du stress précompétitif, notamment à travers la pratique de la cohérence cardiaque, ainsi que d'avoir une approche nutritionnelle et hydrique adaptée au moment des compétitions internationales. Ces stratégies favorisent en effet une meilleure régulation du système nerveux autonome et du système nerveux neuro-endocrinien, améliorent la qualité du sommeil, et contribuent à une gestion optimisée de l'acidose métabolique induite au cours de la compétition afin d'améliorer à la fois les performances et la récupération des athlètes de haut niveau
Adaptive Critic Control With Knowledge Transfer for Uncertain Nonlinear Dynamical Systems: A Reinforcement Learning Approach
No full textInternational audienceThis paper presents an online transfer heuristic dynamic programming (THDP) control approach for a class of nonlinear discrete systems. The proposed approach integrates transfer learning with adaptive critic control. To design a robust optimal control strategy for the nonlinear discrete systems, we utilize sample data collected from a source task to acquire prior knowledge. This prior knowledge is subsequently used to guide the online control process of nonlinear systems of target tasks. To avoid negative transfer effects and conserve computational resources, we introduce a novel attenuation function with a truncation mechanism. Additionally, we develop a disturbance compensation control mechanism to address uncertainties. Furthermore, we demonstrate that the properties of the uncertain nonlinear systems under robust optimal control, as well as the weight error of neural networks, are ultimately uniformly bounded given certain conditions. Finally, two simulations are conducted to verify the performance of the proposed algorithm Note to Practitioners - Adaptive dynamic programming (ADP) is one of the main methods to solve the Hamilton-Jacobi-Bellman (HJB) equation. However, when using neural network approximation, it often requires a long time of iteration and a large amount of computational process, wasting a lot of computational resources. For this reason, we propose an ADP control scheme with enhanced detection speed: that is, by learning a class of similar tasks to obtain prior knowledge to assist in the online control of our actual system. At the same time, this paper considers system disturbances, which means that they are more universal and robust. After simulation experiments, it has been proven that this scheme has good performance
Performance and ergonomics of automated versus manual validation for AR-supervised industrial operations
No full textInternational audienceValidation tasks in AR-supervised environments can be automated to improve process quality in industrial contexts. However, human-centered approaches urge us to study the impact of such methods on operator's acceptance. The paper presents a study on 24 participants to compare 4 modalities of validation of operations. SCRAM, a WebXR application is developed to compare validation tasks on 2 types of devices: tablets and HMDs. All scenarios are tested with an assembly use case through performance, task load, usability and acceptance criteria. Result show significant differences regarding the choice of the device but do not highlight any difference between scenarios with automated validation of operations and scenarios with manual validation
A mesh based improved plane wave expansion method for complex 2-D phononic crystals
No full textInternational audienceThis paper introduces a spectral method based on free triangular meshes, termed the mesh based improved plane wave expansion method (MIPWEM), aimed at simplifying the design and analysis of phononic crystals (PnCs) in complex scenarios. This method, built upon the improved plane wave expansion method (IPWEM) theoretical framework, incorporates free triangular meshes to approximate various complex geometries, significantly reducing the derivation costs associated with handling complex inclusions. By varying factors such as the number of plane waves and mesh generation, this paper investigates the computational efficiency of the proposed MIPWEM from different perspectives. Additionally, the method is successfully applied to compute cases with complex geometries. These results further validate the advantages of the new method in handling complex geometries, computational speed, and other aspects. The MIPWEM with superior efficiency, shows great potential for PnCs research in multiphysics and high-frequency applications
Drift estimation for rough processes under small noise asymptotic : trajectory fitting method
No full textWe consider a process X ε solution of a stochastic Volterra equation with an unknown parameter θ ⋆ in the drift function. The Volterra kernel is singular and given by K(u) = cu α-1/2 ½u>0 with α ∈ (0, 1/2). It is assumed that the diffusion coefficient is proportional to ε → 0. From an observation of the path (X ε s ) s∈[0,T ] , we construct a Trajectory Fitting Estimator, which is shown to be consistent and asymptotically normal. We also specify identifiability conditions insuring the L p convergence of the estimator
Cys-tRNAj as a Second Translation Initiator for Priming Proteins with Cysteine in Bacteria
No full textInternational audienceWe report the construction of an alternative protein priming system to recode genetic translation in Escherichia coli by designing, through trial and error, a chimeric initiator whose sequence identity points partly to elongator tRNA Cys and partly to initiator tRNA f Met . The elaboration of a selection based on the N-terminal cysteine imperative for the function of glucosamine-6phosphate synthase, an essential enzyme in bacterial cell wall synthesis, was a crucial step to achieve the engineering of this Cys-tRNA j . Iterative improvement of successive versions of Cys-tRNA j was corroborated in vitro by using a biochemical luciferase assay and in vivo by selecting for translation priming of E. coli thymidylate synthase. Condensation assays using specific fluorescent reagent FITC-Gly-cyanobenzothiazole provided biochemical evidence of cysteine coding at the protein priming stage. We showed that translation can be initiated, by N-terminal incorporation of cysteine, at a codon other than UGC by expressing a tRNA j with the corresponding anticodon. The optimized tRNA j is now available to recode the priming of an arbitrary subset of proteins in the bacterial proteome with absolute control of their expression and to evolve the use of xenonucleotides and the emergence of a tXNA j in vivo
