Modular zk-Rollup On-Demand

The rapid expansion of the use of blockchain-based systems often leads to a choice between customizable private blockchains and more secure, scalable and decentralized but expensive public blockchains. This choice represents the trade-off between privacy and customization at a low cost and security, scalability, and a large user base but at a high cost. In order to improve the scalability of secure public blockchains while enabling privacy and cost reduction, zk-rollups, a layer 2 solution, appear to be a promising avenue. This paper explores the benefits of zk-rollups, including improved privacy, as well as their potential to support transactions designed for specific applications. We propose an innovative design that allows multiple zk-rollups to co-exist on the same smart contracts, simplifying their creation and customization. We then evaluate the first implementation of our system highlighting a low overhead on existing transaction types and on proof generation while strongly decreasing the cost of new transaction types and drastically reducing zk-rollup creation costs

Vers de nouveaux modèles économiques des structures vétérinaires françaises mixtes

L’offre de soins de santé par les vétérinaires consiste en un ensemble d'activités assurant le bien-être des animaux. Elle contribue également à la lutte contre les maladies infectieuses et à la sécurité alimentaire. En pratique générale, la plupart des activités génèrent des revenus pour les vétérinaires, notamment les actes (consultations, chirurgie, etc.) et les ventes (médicaments, aliments pour animaux de compagnie, etc.). Dans un contexte de croissance rapide du marché de la santé des animaux de compagnie, la question de la profitabilité économique des activités vétérinaires se pose. En effet, au-delà d'un certain seuil, les vétérinaires peuvent être tentés de délaisser les actes relatifs aux animaux d'élevage pour se concentrer sur les actes relatifs aux animaux de compagnie, généralement reconnus comme plus profitables et plus attractifs pour les nouvelles générations de vétérinaires. Les actes sont réalisés à des tarifs permettant une profitabilité nette limitée voire négative dans certains cas extrêmes. La délivrance de médicament permet de compenser la profitabilité. L’arrêt des remises arrières sur les antibiotiques et l’évolution des négociations entre praticiens et laboratoires pharmaceutiques influencent probablement les recettes réellement dégagées par la délivrance des médicaments, mais cette relation reste mal quantifiée. Ce manuscrit contribue à mieux décrire comment la diversité des activités vétérinaires conduit à la diversité des modèles économiques. L'analyse est proposée sous trois axes, correspondant à trois approches différentes, et aux trois chapitres de résultats. Les résultats de ces études montrent que le temps de travail est un élément clé de la profitabilité économique des actes vétérinaires ; certains actes prennent plus de temps que d’autres (chirurgie et suivi d’élevage par exemple), ainsi que les ressources requises pour chaque acte sont différentes (frais de déplacement pour le suivi d’élevage, coûts du bâtiment et des assistants pour les consultations canines…). La performance économique représentée par le chiffre d'affaires des structures vétérinaires échantillonnés est principalement associé et augmenté par (i) le nombre d'heures d’ouverture des structures, (ii) le nombre d'associés et de salariés au sein de la structure, (iii) la surface de la structure, et (iv) le pourcentage d'actes canins. Le temps passé sur chaque activité différait entre les vétérinaires et est positivement associé au statut des vétérinaires, et au niveau d’expérience. L’arrêt des remises arrières sur les antibiotiques affecte les prix auxquels les vétérinaires s’approvisionnent sur le marché de médicaments et modifie les pratiques des structures vétérinaires. Les résultats de cette thèse offrent la possibilité de concevoir les éléments clés de profitabilité économique des structures vétérinaires et peuvent aider à la prise de décision pour la gestion des structures vétérinaires

Liens entre le parasite d'amphibiens Batrachochytrium dendrobatidis et les biofilms benthiques de lacs de montagne pyrénéens

Mountain freshwater ecosystems provide essential services to humanity, such as the provision of clean water, but are strongly affected by anthropogenic global change despite their apparent isolation. Benthic biofilms, communities of organisms living in a matrix adhering to submerged surfaces, have critical functions in mountain lakes: among others, they detoxify water and form the basis of food webs. However, their composition and biodiversity are still poorly understood. Also, in the Pyrenees, some amphibian populations are threatened by chytridiomycosis, an infectious disease caused by the zoosporic fungus Batrachochytrium dendrobatidis (Bd). Its epidemiology is not fully understood but may depend on biofilms, which are abundant in mountain lakes and form the food of tadpoles. Here, I had two main objectives: first, to study the spatio-temporal variations of biofilm microbial biodiversity; second, to investigate the potential role(s) of biofilms in the epidemiology of Bd infections. To do this, I performed a metataxonomic analysis of the prokaryotic and microeukaryotic assemblages of 230 biofilm samples collected from 2016 to 2020 in 26 Pyrenean mountain lakes. Combining this with Bd infection data from tadpoles sampled in the same lakes, I explored the links between the microbial composition of biofilms and the distribution, frequency and population impacts of Bd infections. In the laboratory, I also tested whether a biofilm could affect the free-living, infectious stage of Bd, the zoospore. My hypotheses were that the biodiversity of biofilms would decrease and their assemblages would change over the course of the study, that biofilms from lakes with less infected/impacted amphibian populations would contain more Bd antagonists than biofilms from other lakes, and that biofilms produced in the laboratory would not affect the number of zoospores unless they contained Bd consumers. The diversity in both prokaryotic and micro-eukaryotic biofilm assemblages decreased over the study period. Their compositions also changed over the five years, with an increase in cyanobacteria (possibly toxigenic organisms) in prokaryotes and a decrease in diatoms (indicator organisms) in micro-eukaryotes. Taken together, these results show that benthic biofilm communities are degrading with potentially negative implications for the entire aquatic ecosystem and water quality. In addition, I found that biofilms in lakes where amphibians are less infected and less impacted by Bd had a higher abundance of Bd-inhibiting or Bd-consuming organisms. Finally, I showed that biofilms, even when they do not contain Bd consumers but only a phototrophic alga, can affect Bd zoospores by inactivating them or forcing them to immobilise. My transdisciplinary research illustrates the interactions between environmental health and animal and public health. Contemporary environmental changes are deteriorating biofilms, the very basis of food webs in mountain lakes. This is likely to have profound cascading effects on mountain socio-ecosystems as a whole, such as a potential increase in the risk of Bd infection and chytridiomycosis for amphibians, and cyanotoxicosis for all vertebrates that frequent mountain lakes, including humans and livestock. If mountain freshwater ecosystems are to continue to provide services rather than disservices, the factors contributing to biofilm change will need to be rapidly identified and mitigated

Modelling and structure-preserving discretization of the Schrödinger equation as a port-Hamiltonian system, and simulation of a controlled quantum box

The modelling of the Schrödinger Equation as a port-Hamil- tonian system is adressed. We suggest two Hamiltonians for the model, one based on the probability of presence and the other on the energy of the quantum system in a time-independent potential. In order to simulate the evolution of the quantum system, we adapt the model to a bounded domain. The model is discretized thanks to the structure- preserving Partitioned Finite Element Method (PFEM). Simulations of Rabi oscillations to control the state of a system inside a quantum box are performed. Our numerical experiments include the transition between two levels of energy and the generation of Schrödinger cat states

Chapter 12: "GNC Verification and validation"

Modern Spacecraft Guidance, Navigation, and Control: From System Modeling to AI and Innovative Applications provides a comprehensive foundation of theory and applications of spacecraft GNC, from fundamentals to advanced concepts, including modern AI-based architectures with focus on hardware and software practical applications. Divided into four parts, this book begins with an introduction to spacecraft GNC, before discussing the basic tools for GNC applications. These include an overview of the main reference systems and planetary models, a description of the space environment, an introduction to orbital and attitude dynamics, and a survey on spacecraft sensors and actuators, with details of their modeling principles. Part 2 covers guidance, navigation, and control, including both on-board and ground-based methods. It also discusses classical and novel control techniques, failure detection isolation and recovery (FDIR) methodologies, GNC verification, validation, and on-board implementation. The final part 3 discusses AI and modern applications featuring different applicative scenarios, with particular attention on artificial intelligence and the possible benefits when applied to spacecraft GNC. In this part, GNC for small satellites and CubeSats is also discussed. Modern Spacecraft Guidance, Navigation, and Control: From System Modeling to AI and Innovative Applications is a valuable resource for aerospace engineers, GNC/AOCS engineers, avionic developers, and AIV/AIT technicians

Disturbance growth in a laminar separation bubble subjected to free-stream turbulence

Experiments were conducted to study the transition and flow development in a laminar separation bubble (LSB) formed on an aerofoil. The effects of a wide range of free-stream turbulence intensity (0.15 % < Tu < 6.26 %) and streamwise integral length scale (4.6mm<Λu < 17.2 mm) are considered. The co-existence of modal instability due to the LSB and non-modal instability caused by streaks generated by free-stream turbulence is observed. The flow field is measured using hot-wire anemometry, which showed that the presence of streaks in the boundary layer modifies the mean-flow topology of the bubble. These changes in the mean flow field result in the modification of the convective disturbance growth, where an increase in turbulence intensity is found to dampen the growth of the modal instability. For a relatively fixed level of Tu, the variation of Λu has modest effects. However, a slight advancement of the nonlinear growth of disturbances and eventual breakdown with the decrease in Λu is observed. The data show that the streamwise growth of the disturbance energy is exponential for the lowest levels of free-stream turbulence and gradually becomes algebraic as the level of free-stream turbulence increases. Once a critical turbulence intensity is reached, there is enough energy in the boundary layer to suppress the laminar separation bubble, resulting in the non-modal instability taking over the transition process. Linear stability analysis is conducted in the fore position of the LSB. It accurately models incipient disturbance growth, unstable frequencies and eigenfunctions for configurations subjected to turbulence intensity levels up to 3 %, showing that the mean-flow modification due to the non-modal instability dampens the modal instability

Multi-fidelity Bayesian optimization strategy applied to Overall Drone Design

Nowadays, drones can be developed for a wide range of use cases, from infrastructure monitoring to sea rescue, urban mobility or military purposes. Which drone design is best suited for a specific mission? To answer this question, we need to solve a constrained optimization problem based on a multi-disciplinary design model that takes the mission into account. The model generally being a computationally expensive numerical model whose gradients are not available all the time encourages us to consider a Bayesian optimization approach. Such strategy is well known to achieve a trade-off between exploitation and exploration in order to find interesting minimal area with a reduced number of function evaluations. A multi-fidelity approach can improve even more the computational efficiency of the Bayesian optimization strategy. In this work, we aim at designing a fixed-wing drone (fully electric) for long range surveillance mission. Two fidelity level electric drone models are developed. For a given mission requirement, the final battery state of charge is optimized with respect to drone design variables. Optimizations are performed on several missions using both a mono and a multi-fidelity Bayesian optimization strategy. The interest of using a multi-fidelity method for overall drone design has been assessed. The multi-fidelity super-efficient global optimization algorithm (MFSEGO) appeared to need less budget to reach convergence than the mono-fidelity algorithm and to be more robust to the initial design of experiments

Port inversions of parametric Two-Input Two-Output Port models of flexible substructures

In the context of multi-body modeling techniques, this paper details the port inversion operations, which can be performed on the Two-Input-Two-Output Port (TITOP) model of a flexible substructure to take into account various boundary conditions and to assemble it with the other substructures of the whole system. From the model obtained considering the body is clamped at a parent point and free at some others child points, it is shown that the dynamics obtained under the free-free, free-clamped, clamped-clamped boundary conditions can be characterized analytically. The clamped-clamped condition and its link with the CRAIG-BAMPTON formulation are more particularly investigated, since it is required to model closed-kinematic chains of flexible bodies, like in truss structures, using a sub-structuring approach. Furthermore, the channel inversion operations are extended to the case of parameter varying models. The model of a triangular mechanism, fully parameterized according to the cross section parameters of each mechanism beams, is developed and validated. This model is used to illustrate the capabilities of this parametric approach to import the model in multi-domain simulation software and the possibility to optimize directly the mechanism design

Absorption réactive en écoulement de Taylor dans le contexte du lavage de gaz acides : étude du transfert de matière dans les phases gaz et liquide

La capture du CO2 présent dans le gaz naturel ou les effluents industriels est un enjeu économique et écologique majeur. Elle est conventionnellement réalisée par absorption réactive du gaz dans un solvant (solution aqueuse basique). Afin de répondre à une demande croissante en énergie, il est nécessaire d’améliorer les procédés de traitement par le biais de nouvelles technologies ou de nouveaux solvants. Ces solvants, après validation à l’échelle du laboratoire, doivent être entièrement caractérisés pour simuler les performances du procédé industriel. Cette thèse s’est donc orientée sur le développement d’un pilote instrumenté, basé sur un milli-canal vertical parcouru par les phases gaz et liquide à étudier selon l’écoulement dit de Taylor, car son hydrodynamique contrôlée et les coefficients d’échange de masse élevés associés en font un outil avantageux de caractérisation thermodynamique et cinétique de nouveaux solvants pour l’absorption du gaz acide. Il s’agit donc de caractériser les écoulements ainsi que les cinétiques de transferts et réactionnelles s’opérant au sein du canal, et ce pour un solvant d’intérêt pour l’industriel partenaire, la N-méthyldiéthanolamine (MDEA) en solution aqueuse. Avant d’aborder ce système, des études expérimentales sont réalisées pour évaluer séparément les coefficients de transfert de matière côté liquide (kL) et coté gaz (kG). En effet, la solubilité élevée du CO2 pouvant conduire à un effet non négligeable de la résistance côté gaz, cette contribution a dû être évaluée spécifiquement, car la littérature sur les écoulements de Taylor ne donne quasiment aucune information à ce sujet. Les études sont menées à l’échelle d’un canal de diamètre interne 2 mm, avec une injection des phases à co-courant ascendant. Les expériences sont réalisées à températures modérées (<50°C) et une pression proche de l’atmosphère. La technique expérimentale retenue repose sur la mesure locale par ombroscopie de la variation de taille des bulles, respectivement lors de l’évaporation de l’acétate d’éthyle pour kG et lors de l’absorption réactive de CO2 pur dans la soude pour kL. Après extraction des caractéristiques de bulles par traitement d’images, des bilans de matière réalisés à l’échelle d’une cellule unitaire permettent l’obtention de coefficients locaux de transfert. Pour les systèmes réactifs (CO2-NaOH-H2O et N2-CO2-MDEA-H2O), des analyses chimiques des phases liquide et/ou gaz en entrée et sortie de canal permettent également l’obtention de coefficients globaux. À noter que ces systèmes nécessitent le calcul du facteur d’accélération du transfert par la réaction. Les mesures ont révélé que le transfert côté gaz est extrêmement rapide, si bien que la plus grande part des variations de longueur de bulle mesurées dans les différentes zones de visualisation est en fait attribuable à l’évolution de pression le long du canal. Néanmoins, à l’aide du modèle phénoménologique développé, elles ont permis d’obtenir un ordre de grandeur du coefficient kG, autour de 10-2 m.s-1 dans les conditions étudiées. Les valeurs locales de kL obtenues par absorption réactive du CO2 dans la soude se situent entre 1·10-5 et 2,5·10-4 m.s-1. Elles suivent l’évolution croissante attendue avec la vitesse diphasique et sont en général plus faibles pour les bulles les plus longues. Les analyses en entrée-sortie des phases permettent de conforter l’ordre de grandeur obtenu par mesure locale pour la soude. Par ailleurs, les résultats obtenus avec la MDEA et le CO2 dilué ont permis de confirmer que la résistance côté gaz était effectivement négligeable. En complément, des simulations numériques directes sont effectuées sous COMSOL Multiphysics®. Elles permettent de suivre l’évolution des cellules unitaires le long du canal en résolvant pas à pas et de façon couplée l’hydrodynamique et le transport des espèces pour l’estimation des flux transférés. Elles viennent conforter les résultats expérimentaux pour les deux systèmes modèles

Body Force Modeling of the Fan Stage of a Windmilling Turbofan

The determination of the rotational speed and massflow of a windmilling fan is critical in the design of the engine-supporting structure and the sizing of the rudder. Given the very high bypass ratio obtained at windmill (typically around 50), the flow in the fan stage and bypass duct is of prime interest. Classical CFD simulations have been shown to predict such flows accurately, but extensive parametric studies can be needed, stressing the need for reduced-cost modeling of the flow in the engine. A Body Force Modeling (BFM) approach to windmilling simulations is examined in the present contribution. The main objective is to assess the capability of the BFM approach to reproduce the aerodynamics of the flow in the fan stage of a turbofan at windmill, and to propose a method to predict the massflow and the rotational speed of the fan. The available global and local experimental data of a high bypass ratio geared turbofan (the DGEN 380) are used to validate the model. Furthermore, classical RANS simulations are also provided as reference simulations to assess the accuracy of the BFM results. It is found that the overall performance of the fan stage is well predicted by the BFM simulations, in particular at the lowest rotational speed. In terms of local validation, radial profiles are also found to be in good agreement, except close to the shroud due to massive flow separations in both the rotor and stator. A BFM simulation is about 10 times faster than the baseline CFD computation, making this approach very efficient in terms of accuracy-to-cost ratio. Finally, a zero work exchange model is embedded in the BFM computations, such that both the massflow and the rotational speed of the fan become outputs of the simulations. The predictions obtained by the present approach show good agreement (maximal discrepancy of 6.5 %) with engine experimental data