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Modélisation, conception et expérimentation d’un nano-drone bio-inspiré à ailes vibrantes
No full textThis thesis deals with the design and production of a bio-inspired nano-drone with vibrating wings, known as a “Nano-Air Vehicle” (NAV). It was conducted in partnership between IEMN (Institut d'Électronique, de Microélectronique et de Nanotechnologie) and LISPEN (Laboratoire d'Ingénierie des Systèmes Physiques et Numériques) at Arts et Métiers. It is part of the ANR project ASTRID 19-ASTR-0023, jointly led by LISPEN, IEMN and ESPCI (École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris). The aim of the project is to launch the lightest NAV possible, using its vibratory properties and microfabrication techniques to reproduce the flight kinematics of insects. Insects have unrivalled flight capabilities, particularly in terms of hovering, agility and energy efficiency, and their performance relies mainly on unsteady aerodynamic mechanisms and special kinematics, using vibrations of the thorax and wings.Cette thèse porte sur la conception et la réalisation d’un nano-drone bio-inspiré à ailes vibrantes, appelé en anglo-saxon « Nano-Air Vehicle » (NAV). Elle a été dirigée en partenariat entre l’IEMN (Institut d’Électronique, de Microélectronique et de Nanotechnologie) et le LISPEN (Laboratoire d’Ingénierie des Systèmes Physiques et Numériques) des Arts et Métiers. Elle s’inscrit dans le cadre du projet ANR ASTRID 19-ASTR-0023 mené conjointement par le LISPEN, l’IEMN et l’ESPCI (École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris). L’objectif du projet est de faire décoller le NAV le plus léger possible, en utilisant ses propriétés vibratoires et des techniques de microfabrication pour reproduire la cinématique de vol des insectes. Ces derniers présentent des capacités de vol inégalées, notamment en vol stationnaire, en agilité et en efficacité énergétique et leurs performances reposent principalement sur des mécanismes aérodynamiques instationnaires et une cinématique particulière, utilisant les vibrations du thorax et des ailes
Weak and very weak solutions of the Laplace equation and the Stokes system with prescribed regularity
No full textTo verify theoretical results it is sometimes important to use a numerical example where the solution has a particular regularity. The paper describes one approach to construct such examples. It is based on the regularity theory for elliptic boundary value problems
A unifying perspective on defect evolution in light of configurational mechanics
No full textInternational audienceIn this contribution, we develop a theoretical study of defect propagation in solid media,in which a unifying approach to the onset and evolution of both topological and materialdefective phenomena is addressed. We recall that, in the field of Continuum Mechanics,we speak of “defect” to denote both alterations in the topology of a material—such ascrack advancement or rotation and changes in the volume of inclusions or voids [1]—andinhomogeneities, i.e., spatial changes in the material properties of a medium. [2, 3].The kinematic behavior of defects is specified by assigning their specific mode of propagationand, based on the principles of Eshelbian (Configurational) Mechanics [2, 3], wecompute the energy release rate, or driving force, associated with their advancement. Furthermore,we recognise the individual contributions of this force, categorizing them intomechanical, topological, and those arising from material inhomogeneities [2, 3].To better illustrate the application of our modelling framework, we review some classicalexamples of defect mechanics taken from the existing literature, integrating them intoour approach [4]. Finally, we compare our findings with results obtained from variationalmethods grounded in conservation laws [1, 5].[1] Knowles J. K., Sternberg, E.: On a class of conservation laws in linearized and487finite elastostatics.Arch. Rat. Mech. Anal. 44(3):187–211 (1972)[2] Maugin G. A. Configurational Forces. Thermomechanics, Physics, Mathematics, and Numerics CRCPress. (2016)[3] Gurtin M. E.: Configurational forces as basic concepts of continuum physics. Vol. 137.493. SpringerScience & Business Media (1999).[4] Di Stefano S., Binetti C., Puglisi G., Giordano S.: A unified Eshelby-like approach to defect propagation.In preparation.[5] Podio-Guidugli P.: Configurational balances via variational arguments. Interface Free Bound 3, 323–332.(2001
Le concept de compétence en analyse du discours ‘française’ : pour une étude de l’appropriation et de la production de contraintes du dicible par les locuteurs
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Poésie et dissolution des identités : le féminin et le masculin hors-norme chez Rimbaud et Michaux
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Thermal fluctuations effects on crack nucleation and propagation
No full textInternational audienceThis paper investigates the impact of thermal effects on fracture propagation, a subject that poses significant theoretical and experimental challenges across multiple scales. While previous experimental and numerical studies have explored the relationship between temperature fluctuations and mechanical behavior, a comprehensive theoretical framework in fracture mechanics that rigorously incorporates temperature effects is still absent. Building upon the Griffith energetic approach and equilibrium statistical mechanics, we incorporate entropic effects into the overall energy balance of the system and replace the total mechanical energy with free energies. Indeed, our model captures the energetic interplay between elastic deformation, external loads, fracture energy, and entropic contributions. We propose a simplified approach in which both discrete and continuum representations are formulated concurrently, reflecting a multiscale paradigm. The discrete model leverages statistical mechanics to account for temperature effects, while the continuum model provides a mesoscopic description of the fracture process. This framework provides (temperature dependent) analytical expressions for key mechanical parameters, such as the stress and displacement fracture thresholds, the energy release rate, the fracture surface energy, and the J-integral. Notably, we identify a critical temperature at which the system undergoes a phase transition from an intact to a fractured state in the absence of mechanical loading. We believe that this approach lays the foundation for a new theoretical framework, enabling a rigorous multiscale understanding of thermal fluctuations in fracture mechanics. We finally propose a comparison with numerical data concerning the fracture of graphene as a function of temperature exhibiting the efficiency of the model in describing thermal effects in fracture behavior.</div
Sparse guided wave imaging in highly anisotropic plates with phase skewing and amplitude focusing compensation
No full textInternational audienceThis paper introduces a sparse beamforming algorithm designed to compensate for guided wave dispersion while addressing phase skewing and energy focusing in highly anisotropic composite plates. Developed for structural health monitoring, this algorithm targets impact-induced defects, such as barely visible impact damages (BVIDs), using a limited number of arbitrarily positioned transducers. Validation is first performed on finite element simulated data with the A0 mode in an eight-ply unidirectional composite with significant anisotropy and a delamination defect, highlighting the critical role of phase skewing compensation. Additionally, energy focusing compensation strategies are introduced, improving image contrast in highly anisotropic materials. Experimental validation is carried out on a real BVID caused by a 6.3 J impact on an aerospace-grade composite plate and compared to a simulation with a similar size delamination. Results show good agreement between experiments and simulations, with significant enhancements in imaging resolution when considering dispersion compensation compared to the commonly used delay-and-sum algorithm. The proposed algorithm improves image dynamics and reduces focal spot area by a factor of more than 100. Finally, the study quantifies errors introduced by neglecting phase skewing in dispersion compensation, demonstrating coherence with observed imaging results for both composite materials studied in this paper
New Electromagnetic Interference Shielding Materials: Biochars, Scaffolds, Rare Earth, and Ferrite-Based Materials
No full textInternational audienceIn this review, a comprehensive systematic study of the research background, developments, classification, trends, and advances over the past few years in research on new electromagnetic interference (EMI) shielding materials will be described. The following groups of new materials for EMI shielding will be discussed: biochars, scaffolds, rare earth, and ferrite-based materials. We selected two novel, organic, lightweight materials (biochars and scaffolds) and compared their shielding effectiveness to inorganic materials (ferrite and rare earth materials). This article will broadly discuss the EMI shielding performance, the basic principles of EMI shielding, the preparation methods of selected materials, and their application prospects. Biochars are promising, eco-friendly, sustainable, and renewable materials that can be potentially used as a filter in polymer composites for EMI shielding, along with scaffolds. Scaffolds are new-generation, easy-to-manufacture materials with excellent EMI shielding performance. Rare earth (RE) plays an important role in developing high-performance electromagnetic wave absorption materials due to the unique electronic shell configurations and higher ionic radii of RE elements. Ferrite-based materials are often combined with other components to achieve enhanced EMI shielding, mechanical strength, and electrical and thermal conductivity. Finally, the current challenges and future outlook of new EMI shielding materials will be highlighted in the hope of obtaining guidelines for their future development and application.</div
Introduction par la pratique à LATEX pour les sciences historiques. Manuel de formation à destination des chercheurs et étudiants
No full textInternational audienceMasterCe document est issu du cours d'introduction à LaTeX donné pour les étudiantes et étudiants du master « Histoire Européenne » de l'université de Lille durant l'année universitaire 2024-2025. Il se présente comme un modeste manuel regroupant l'ensemble des commandes et environnements appris en cours, ainsi que quelques focus complémentaires sur les bonnes pratiques de balisage et gestion d'un projet. Il a vocation à être lu et exploré au sein d'un éditeur LaTeX afin de pouvoir comprendre le code associé, tel qu'Overleaf. Nous recommandons donc aux lecteurs de se munir du code disponible dans ce repository : https://gitlab.huma-num.fr/vdecraene/manuel-latex-masters-histoir
Supply chain network design and Circular Economy
No full textInternational audienceRedesigning transport and distribution networks to facilitate reverse logistics and the management of closed-loop supply chains. The integration of the "R "s of the circular economy (Reuse, Recycle, Repair, Recover) into the supply chain requires logistical optimization and adapted transport models