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On the enumeration of non-dominated spanning trees with imprecise weights
No full textInternational audienceMany works within robust combinatorial optimisation consider interval-valued costs or constraints. While most of these works focus on finding unique solutions such as minimax ones, a few consider the problem of characterising a set of non-dominated optimal solutions. This paper is situated within this line of work, and consider the problem of exactly enumerating the set of non-dominated spanning trees under interval-valued costs. We show in particular that each tree in this set can be obtained through a polynomial procedure, and provide an efficient algorithm to achieve the enumeration
Cooperative control strategy for an airplane landing on a mobile target
No full textInternational audienceThis paper presents a cooperative control strategy for landing a fixed-wing drone on a mobile target vehicle. The control strategy focuses on guiding the drone along a desired trajectory while the target vehicle's speed is controlled so that both reach the desired position simultaneously. The system model is composed by the kinematic model of a fixed-wing drone and a ground vehicle. A state feedback control based on Lie derivatives is determined applying the input-output analysis. The system stability is obtained by using Lyapunov stability theory. The proposed control strategy is evaluated in numerical simulations to validate its performance
GUIDELINES FROM LITERATURE TO PRACTICE: FIRST KEY TO IMPLEMENT ECO-INNOVATION IN AN INNOVATION LABORATORY
No full textInternational audienceToday, eco-innovation is a major challenge for companies. This new innovation approach requires to renew current practices to meet new societal and environmental issues. To do this, more and more companies create innovation laboratories to support them in this process, by providing different tools and methods adapted to their needs. To integrate eco-innovation in these new spaces, tools must answer to differents criteria. The only tool proposed by the literature is the guidelines tool but by confronting it with current practices, limits of this tool and of the innovation laboratory practices were defined. In this paper we will question and deconstruct guidelines tool in order to propose a new vision of it through identification of eco-innovation attributes
Hydrodynamique dans les vaisseaux sanguins et implications possibles dans la recherche en cancérologie
No full textInternational audienceDans une perspective de discussions multidisciplinaires, un travail de veille scientifique sera présenté pour montrer comment la connaissance et la maîtrise des écoulements aux abords et dans les tumeurs peuvent être utiles pour des recherches en cancérologie. On peut en effet citer différentes stratégies faisant l'objet de travaux actuellement:- le transport et relargage ciblé de substances médicamenteuses ou produits de contraste par des nano-vecteurs- les études sur la perméabilité vasculaire pour les échanges entre l'intérieur des vaisseaux et les tissus environnants- l'imagerie IRM des tumeurs et de leur vascularisation- le chauffage localisé de la tumeur à l'aide de nanoparticules magnétiques- l'utilisation de nano-particules qui absorbent les rayons X en radiothérapie dans le but d'augmenter leur efficacité en libérant une quantité importante d'énergie dans les cellules cancéreuses- le contrôle de l' angiogenèse tumorale, pour empêcher le développement de nouveaux vaisseaux sanguins et priver la tumeur d'oxygène et de nutriments- la compréhension de l'extravasation des cellules tumorales circulantes grâce à des modèles microfluidiques de "vaisseaux sur puces", dans le but de lutter contre la dissémination des métastases- les approches de "médecine personnalisée", basées sur des modèles in vivo ou in silico représentatifs des conditions cliniques
Geometrically exact beam theory with embedded strong discontinuities for the modeling of failure in structures. Part I: Formulation and finite element implementation
No full textInternational audienceWe introduce a three-dimensional geometrically nonlinear Reissner beam theory with embedded strong discontinuities for the modeling of failure in structures and discuss its finite element implementation. Existing embedded beam theories are geometrically linear or two-dimensional, motivating the need for the present work. We propose a geometrically nonlinear beam theory that accounts for cracks through displacement discontinuities in 3D. To represent the three modes of fracture inside an element, we enrich each displacement field with an incompatible mode parameter in the form of a jump, an additional degree of freedom. We then eliminate these nodeless degrees of freedom through static condensation and evaluate them within the framework of inelasticity by utilizing an operator split solution procedure. Seeing that the coupled strain-softening problem is non-convex, we present an alternating minimization (staggered) algorithm, thus retaining a positive definite stiffness matrix. Finally, the four-parameter representation by quaternions describes a three-dimensional finite rotation. We demonstrate a very satisfying and robust performance of these new finite elements in several numerical examples, including the fracture of random lattice structures with application to fibrous materials. We show that accounting for geometrical nonlinearity in the beam formulation is necessary for direct numerical simulations of fiber networks regardless of the density
Numerical and experimental analysis of spherical and non-spherical particles in a rotary drum: Metamodels for calibrating the friction coefficients in a rotary drum from DEM simuations
No full textInternational audienceRotary drums are suitable tools to process a large range of granular materials in several applications, especially in the food industry. The efficiency of rotary drums is highly dependent on the flow dynamics, so predicting the flow behavior of particles is important for the equipment design and optimization of processes. In recent years, it has seen a growing trend toward the use of numerical simulations to describe the granular flow in various applications, including the flow in rotary drums. For this purpose, the discrete element method (DEM) is a consolidated tool. However, this technique requires knowledge about the input parameters related to the properties of particles and their interactions. A common approach reported in the literature (Xiao et al., 2023; Coetzee, 2020) is to choose the DEM input parameters by calibrating the DEM model against experimental measurements, i.e., adjusting the input parameters until the outputs match the bulk experimental observations. This technique is preferable to the direct measurement of the parameters because it considers the bulk response of the flow dynamics. Many efforts can be found in the literature to calibrate these parameters for spherical particles (e.g., Brandão et al., 2020). Still, the granular systems in food applications usually are constituted of particles whose shape is not spherical; hence, studying their flow behavior can thus be more complicated. So, this paper aimed to calibrate the DEM input parameters, named static friction and rolling friction coefficients, of two food grains almost spherical, (quinoa grains and pearl pasta) and of one food grain, named crozet pasta, that exhibits a platy shape. The experimental protocol involved firstly the observation of the dynamic repose angle and the mixing phenomena inside a rotary drum with a diameter of 84 mm, and then the comparison, using image analysis, to the simulated results obtained by the open-source DEM code LIGGGHTS. The results contribute to validating experimentally the flow behavior of food materials with different shapes, as a previous step to model the coupled heat transfer phenomena.XIAO, X., LI, Y., PENG, R., GAO, J., HU, C. Parameter calibration and mixing uniformity of irregular gravel materials in a rotating drum. Powder Technol. 414 (2023).COETZEE, C. Calibration of the discrete element method: Strategies for spherical and non-spherical particles. Powder Technol. 365 (2020).BRANDÃO, R.J., LIMA, R.M., SANTOS, R.L., DUARTE, C.R., BARROZO, M.A.S. Experimental study and DEM analysis of granular segregation in a rotating drum. Powder Technol. 364 (2020)
Contribution à une théorie de la valeur des actifs physiques
No full textThis thesis proposes an innovative theory on physical asset value, centered on 21st-century urban dynamics. Its aim is to assess this value's impact on urban maintenance and renovation, offering coherent policy and strategy avenues for buildings and infrastructure. The first section traces the evolution of urban environments since the onset of capitalism. It emphasizes how the COVID-19 pandemic has exposed the fragility of our economy, stressing the importance of physical assets. Cities, the heart of economic power since the rise of capitalism in Venice, have consistently adapted their management in the face of successive challenges. The current era, marked by increasing demographics and unprecedented ecological challenges, calls for a shift towards a circular economy. Chapter 4 introduces a new concept, the "mathem-ethics", a fusion of ethics and mathematics, for a more systemic, multi-factorial and multi-causal assessment of the value of physical assets. The second section offers an original contribution to a theory on value with the PACKiT model, dedicated to the physical asset management. This model proposes a revolutionary view of asset valuation, focused on their usage value, their loss of usage value, and their characteristics. Contrary to traditional approaches based on linear depreciation or approximation by industrial life cycles, PACKiT provides a qualitative perspective, addressing the coexistence of three fundamental life cycles and seamlessly integrating with current standards. It is illustrated with a concrete example: the management of a portfolio of 226 school buildings. The thesis suggests the use of innovative tools, like the physical obsolescence index or asset condition index, for optimal resource management. In parallel, the author explores the philosophical history of capitalism. He criticizes the "calculocentric" vision inherited from Descartes, which, combined with rising capitalism, has reduced human value to its consumption capacity. Against this backdrop, the author draws on Edgar Morin's “complex thinking”, which advocates a holistic and empathetic understanding. This paradigm shift is crucial for rethinking the physical asset management in a post-capitalist era. In summary, this thesis invites a radical reevaluation of how we perceive and manage the value of physical assets in urban built environments. The PACKiT model emerges as a key tool for adaptive asset management, placing ethics at the center of decisions. In conclusion, the author suggests a broader exploration, encompassing 30 key areas, illustrating the transformative scope of this research for the future.Cette thèse propose une théorie innovante sur la valeur des actifs physiques, centrée sur la dynamique urbaine du XXIème siècle. Son but est d'évaluer comment cette valeur influence la maintenance et la rénovation de l’environnement construit, et offre ainsi des pistes pour une politique cohérente et une stratégie efficiente en matière de bâtiments et d’infrastructures. La première section retrace l'évolution des milieux urbains depuis les débuts du capitalisme. Elle souligne comment la pandémie de COVID-19 a révélé la fragilité de notre économie, insistant sur l'importance des actifs physiques. Les villes, cœur du pouvoir économique depuis l'essor du capitalisme à Venise, ont constamment adapté leur gestion face aux défis successifs. L'ère actuelle, marquée par une démographie croissante et des défis écologiques sans précédent, appelle une transformation vers l’économie circulaire. Enfin, on introduit un nouveau concept, la « mathém-éthique », une fusion de l'éthique et des mathématiques, pour une évaluation multifactorielle et multi-causale de la valeur. La seconde section propose une contribution originale à une théorie sur la valeur avec le modèle PACKiT, dédié à la gestion d'actifs physiques. Ce modèle expose une vision révolutionnaire de l'évaluation des actifs, axée sur leur valeur d'usage, leur perte de valeur d’usage et leurs caractéristiques, dont le risque. Contrairement aux approches traditionnelles basées sur la dépréciation linéaire ou l’approximation par des cycles de vie industriels, le PACKiT offre une perspective qualitative, traitant la coexistence de trois cycles de vie fondamentaux et s'intégrant facilement aux normes en vigueur. Il est illustré par un exemple concret : la gestion d'un parc de 226 bâtiments scolaires. La thèse suggère l'utilisation d'outils, comme l'indice de vétusté physique, pour une gestion optimale des ressources. En parallèle, l'auteur explore l'histoire philosophique du capitalisme. Il critique la vision « calculocentrique » héritée de Descartes, qui, en combinaison avec le développement du capitalisme, a réduit la valeur humaine à sa capacité de consommation. Face à cette vision, l'auteur s’inspire de la « pensée complexe » d'Edgar Morin, qui plaide pour une compréhension holistique et empathique. Ce changement de paradigme est crucial pour repenser la gestion des actifs physiques dans une ère où le capitalisme se trouve confronté aux défis écologiques. En somme, cette thèse invite à un renouveau radical de la manière dont nous percevons et gérons la valeur des actifs physiques en milieu urbain. Le modèle PACKiT émerge comme un outil clé pour une gestion adaptative des actifs, plaçant l'éthique au centre des décisions. L'auteur conclut en proposant d’élargir la recherche à trente domaines clés qui illustrent la portée future des transformations à attendre de cette démarche
Développement d'une méthode hybride pour la simulation numérique du bruit large bande de ventilateur axial à basse vitesse pour des applications industrielles
No full textThe goal of this work is to put forward a method suitable for the computation of fan noise. The flow speed in such a system is low enough to separate the computation in two distinct steps : in the first one, the noise sources are estimated, and the wave propagation is computed in the second one. First, several methods for fixed obstacles are compared. An extension to moving obstacles is then attempted by removing a portion of the volume from the computational domain. Although this method yields consistent results, the effect of the rotation is fully ignored and the noise level is underestimated. In order to remedy this, a new method for the computation of the wave propagation is then presented. This method allows us to predict correctly the rotation of the portion of the domain, which may contain moving obstacles and source.Cette thèse a pour objectif de proposer une méthode permettant de simuler le bruit d'origine aérodynamique d'un ventilateur axial. Au vu de la faible vitesse de l'écoulement dans un tel systèmes, cette méthode peut s'appuyer sur une séparation du calcul en deux étapes distinctes : lors de la première étape, les phénomènes à l'origine de la génération du bruit sont déterminés, et la propagation des ondes est calculée pendant la seconde étape. Tout d'abord, plusieurs méthodes applicables dans le cas d'obstacles mobiles sont comparées. Une extension au cas d'obstacles mobiles est étudiée en excluant du domaine de calcul les obstacles tournants. Si cette méthode donne des résultats cohérents, elle n'est pas à même de prédire l'effet de la rotation des obstacles et sous estime le bruit produit. Pour remédier aux lacunes de cette approche, une nouvelle méthode pour le calcul de propagation acoustique est ensuite proposée. Celle-ci permet de simuler correctement la rotation d'une portion du domaine, contenant des obstacles et sources acoustiques