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Structure-preserving discretization of port-Hamiltonian plate models
Get PDFMethods for discretizing port-Hamiltonian systems are of interest both for simulation and control purposes. Despite the large literature on mixed finite elements, no rigorous analysis of the connections between mixed elements and port-Hamiltonian systems has been carried out. In this paper we demonstrate how existing methods can be employed to discretize dynamical plate problems in a structure-preserving way. Based on convergence results of existing schemes, new error estimates are conjectured; numerical simulations confirm the expected behaviors
Numerics for Physics-Based PDEs with Boundary Control: the Partitioned Finite Element Method for Port-Hamiltonian Systems
Get PDFThe numerical simulation of complex open multiphysics systems in Computational Science and Engineering is a challenging topic. Based on energy exchanges, the port-Hamiltonian formalism aims at describing physics in a structured manner. One of the major interests of this approach is its versatility, allowing for coupling and interconnection that preserve this structure.
We propose a Finite Element based technique for the structure-preserving discretization of a large class of port-Hamiltonian systems. Assuming a partitioned structure of the system associated to an integration-by-parts formula, it is possible to derive a consistent weak-formulation sharing the main features of the original boundary-controlled PDE. This allows using Galerkin approximations to obtain finite-dimensional systems that mimic the properties of the original distributed ones: the Partitioned Finite Element Method producing sparse matrices enables the use of dedicated algorithms in scientific computing. Indeed, this method can be easily implemented using well-established and robust libraries. This strategy is illustrated by means of physically motivated PDEs: acoustic waves, Mindlin and Kirchhoff plates, heat equation, Maxwell's equation. Interactive Jupyter notebooks are available, relying on the FEniCS open-source software. Advanced applications include multiphysics problems, e.g. fluid-structure interactions, thermoelasticity, and modular modelling of complex systems, e.g. multibody dynamics
Impact de l'exposition fœtale au bisphénol A sur la réponse insulinique à une hyperglycémie chez le fœtus ovin
Get PDFLe bisphénol A (BPA) est un composé majoritairement présent dans la fabrication de matières plastiques. Classé au rang des perturbateurs endocriniens, celui-ci peut agir sur les fonctions reproductives et métaboliques. Dans notre étude pilote, le fœtus ovin a été utilisé comme modèle pour étudier les effets d’une exposition au bisphénol A sur la réponse insulinique à une hyperglycémie. Les résultats ont montré une grande variabilité de la glycémie et de la réponse insulinique à un challenge hyperglycémique. Ils suggèrent que le BPA diminue les concentrations plasmatiques d’insuline associées au challenge hyperglycémique, ce qui pourrait expliquer des niveaux correspondant de glycémie plus élevés. Ces résultats doivent être confirmés avec un plus grand nombre d’individus et au cours d’expositions chroniques et initiées au début du développement fœtal
Mise en place d'une méthode de détection et d'identification moléculaire de l' à partir de prélèvements environnementaux
Get PDFLe barcoding est un outil récent développé à des fins d’identification d’organismes à partir de séquences d’ADN courtes situées sur des gènes communs à un groupe d’organismes et dont les fines différences permettent de distinguer les espèces. Cet outil a peu été utilisé dans le cadre d’études d’interfaces entre faune domestique et faune sauvage. Pourtant il est indispensable d’identifier les espèces en jeu au niveau de ces interfaces afin de mieux comprendre les contacts possibles. Ainsi, dans cette thèse nous proposons d’utiliser cette technique et mettant en place un protocole adapté de techniques déjà décrites. Une étude préliminaire est donc menée afin de faire le point sur les connaissances en forte évolution et d’adapter l’outil à l’étude et à ses spécificités. La mise à l’épreuve de différents kits d’extraction, de méthodes de traitement de l’échantillon de départ, et de différentes paires d’amorces ont pu permettre d’optimiser les méthodes en usant du matériel et des technologies disponibles. Nous avons pu mettre en place une méthode systématisée basée sur une concentration de l’ADN par filtration puis une extraction par un kit d’extraction commercial générique suivi d’une amplification par PCR quantitative à l’aide d’amorces spécifiques (Aves 02) et finalement d’un séquençage par méthode Sanger. Les séquences obtenues, confrontées à la base de données Genbank©, conduisent à l’identification des espèces présentes dans l’échantillon. Ce protocole de metabarcoding vise à terme la détection et la caractérisation d’espèces d’oiseaux sauvages évoluant en contact direct d’élevages avicoles par l’exploitation de prélèvements environnementaux
Conceptual Design for Long-Endurance Convertible Unmanned Aerial System
Get PDFThis research is aimed at analysing the effect of design parameters on critical aerodynamic performance of convertible unmanned aerial vehicle (UAV) with vertical take-off and landing (VTOL) capabilities and providing a sizing tool for its conceptual design. The research was based on new aerodynamic models specifically developed and validated for convertible aircraft, performed using mission-based optimisation techniques. To accommodate a wide range of convertible aircraft configurations, a non-linear lifting-line method was used to efficiently analyse different combinations of lifting surface and propeller arrangements. Propeller loads were calculated using a blade element momentum approach and corrected for high incidence angle conditions according to numerical and experimental studies. Propeller-wing interactions were considered by modifying local boundary conditions at wing sections immersed in propeller slipstream. Previous studies have suggested that the design of convertible aircraft is sensitive to typical mission requirements, notably the endurance breakdown between near-hover flight and cruise flight. A clear sizing law for wing and propeller according to given mission specification could greatly improve the understanding of compromises between hover and high speed flight
Impedance analysis of the barrier effect of coil-coated materials: Water uptake and glass transition variations
Get PDFIn the present work, an industrial polyester coil-coated steel sample was characterized by electrochemical impedance spectroscopy. The diagrams were obtained for various immersion times in a 0.5 M NaCl solution for three different initial states of the same coil coating (as received, dried and dried after the impedance measurements). The aim of the study was to have a better knowledge of how the water uptake influences the coil coating physical properties and to extract relevant parameters of the ageing processes. From the high-frequency part of the impedance diagrams, the water uptake was calculated using a linear rule of mixtures. Two sorption regions were observed for the dried samples suggesting the presence of porosities already filled with ambient moisture for the as-received sample. It was shown that the water uptake was a slow process and, independently of the initial state of the sample, a saturation plateau was never reached, even after 456 h of immersion. A time constant, clearly visible on the phase angle of the impedance diagrams, was analysed through the dielectric permittivity formalism and attributed to the signature of the dielectric manifestation of the glass transition. This time constant was shifted to higher frequencies with increasing water fraction (increasing immersion time), consistent with a plasticization effect. This result was supported by differential scanning calorimetry measurements. Finally, the data obtained for the different initial states of the coating highlighted that, even if the water uptake was reversible, the sorption kinetics was different for the sample dried after the impedance measurements. This could be of importance in the degradation process of the coil coated steel
Comparative study of the microstructure between a laser beam melted 17-4PH stainless steel and its conventional counterpart
Get PDFThe aim of this work was to compare the microstructures of 17-4PH martensitic stainless steels (MSSs) obtained by conventional manufacturing (CM), and additive manufacturing (AM) using laser beam melting (LBM) process. Both materials were studied after the same H900 heat treatment. Significant differences in microstructure were observed between the two MSSs, with a higher austenite content for the AM-H900 sample, as compared to the CM-H900 sample. Transmission electron microscopy (TEM) analyses allowed to identify both retained and reversed austenite in the AM-H900 sample, but most part of the austenite detected was found to be reversed austenite. The high amount of reversed austenite in the AM-H900 sample was attributed to a heterogeneous distribution in austenite-stabilising elements in the solution heat treated AM sample, leading to a decrease in Ms value and subsequent increase in the driving force for the martensite to austenite transformation during the ageing at 480 °C. Moreover, TEM analyses highlighted thinner martensite laths for the AM-H900 steel as compared to the CM-H900 one. This was interpreted as an increase in both nucleation sites and growth rate for reversed austenite. Despite those differences in microstructure, the AM-H900 and CM-H900 samples showed similar tensile behaviour, with similar UTS and Rp0.2 values, but a decrease in the strain to fracture was observed for the AM-H900 sample, probably related to the pores and/or to intergranular carbides
Multifidelity aeroelastic optimization applied to har wing
Get PDFAs part of a global effort toward the reduction of CO2 emissions, the study of High Aspect Ratio wings is a particularly promising avenue of research. Considering this type of configuration at preliminary design stage is thus critical for optimization purposes. The use of multifidelity can help reduce computational costs by mainly running low-fidelity computations and only resorting to high-fidelity computations when necessary. The goal of this study is to develop a sufficiently accurate aero-structural model in order to fully exploit the drag reduction potential of HAR wings. The first step is to develop and apply a multifidelity approach on the CRM wing by creating a low-fidelity model. It is made sure that there is an adequate correlation between the structural modes of both high-fidelity and low-fidelity models. The so obtained low-fidelity structural model is then implemented within a in-house aeroelastic analysis and optimization framework. Afterwards, a modi ed version of the CRM wing with a higher aspect ratio (AR=13.5) is considered in order to apply the same methodology with the goal to reduce significantly computational costs
Gestion du poulain nouveau-né en France par les éleveurs équins et place de la néonatalogie équine chez les vétérinaires praticiens
Get PDFLa néonatalogie équine est un réel défi aussi bien pour les éleveurs que pour les vétérinaires. Cette étude vise à faire un état des lieux des pratiques en France dans ce domaine. Deux questionnaires ont été diffusés en ligne. Le premier (454 réponses) vise à identifier les gestes réalisés couramment sur le terrain en matière de soins et de réanimation du poulain nouveau-né et à évaluer le lien entre les pratiques et le degré de professionnalisation des élevages. Le second, destiné aux vétérinaires équins (164 réponses) permet d’appréhender le ressenti des vétérinaires sur cette discipline. Il ressort de cette enquête que 30% des éleveurs n’évaluent jamais la qualité du colostrum et 38% ne surveillent pas la quantité de colostrum ingérée par le poulain. En revanche, 94% des éleveurs désinfectent le cordon ombilical. Pour ce qui est de la formation en néonatalogie équine, 74% des éleveurs estiment avoir besoin de formation contre 60% des vétérinaires équins
Global Model of Aircraft Design: from Performance Requirements towards Architectures Optimization
Get PDFSystems engineering is a transdisciplinary approach that seeks the successful realisation of a system. In order to reach that, it is necessary to satisfy a series of needs and stakeholders, which have to be defined as a group of requirements to be fulfilled. Design approaches such as MDAO, MBSE, and MBSA have been created to help better designing aircraft in different aspects. However, there has never been an aircraft design method which combines all the mentioned design approaches and that, nowadays, has an increasing interest in the industry. Therefore, the paper aim is to produce aircraft design tools and methodology which link all the three design approaches together by using a surveillance UAV as a study case. As a part of the MDAO-MBSE global project, a MDAO model has been developed using a web application (WhatsOpt) and a MDAO platform (OpenMDAO)
on Python, while the tool considered to develop the MBSE model is Eclipse Papyrus, a powerful tool that allows to use XML for export their models. Some promising results show the coupling between MDAO and MBSE based on XML file exchange