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Detection and characterization of damages on mechanical parts via 3D point cloud processing
No full textInternational audienceThis paper presents an approach for defect detection and characterization on aeronautical metallic or composite surfaces, by processing 3D point clouds. For defect detection, we employed deep learning techniques, specifically segmentation models. To obtain a sufficient amount of training data, we developed a custom pipeline for generating synthetic point clouds that represent surfaces with various types of damage. In the testing phase, we used only real point clouds collected using a 3D scanner. For the characterization step, our system aims to provide precise measurements of the geometric properties of the detected defects, such as depth and surface area. For measuring the width and length of the defects, we utilized segmentation masks generated during the detection phase. To address the challenge of measuring defect depth, we relied on traditional computer vision techniques applied to 3D point clouds. We reconstructed an ideal, defect-free surface from points classified as non-defective, and then determined the defect depth as the maximum distance between the defective points and this reconstructed surface
Optimisation factorielle à plusieurs niveaux du rapport acide/minerai et de la concentration des solides dans la récupération hydrométallurgique du nickel à partir de minerais latéritiques
No full textInternational audienceThis study applies a multilevel factorial design to optimise nickel (Ni) extraction in a High-Pressure Acid Leaching (HPAL) autoclave, examining the influence of slurry solid content and acid-to-ore (A/O) ratio on Ni yield, selectivity (Ni/(Al+Fe)), and scale formation. A regression model was established to predict these responses across varying A/O ratios and solid contents. Using Minitab® statistical software, response surface methodology (RSM) was employed to identify process conditions that balance maximised Ni yield, enhanced selectivity and reduced scale formation. To predict outputs beyond the experimental range, the complex models generated in Minitab® were simplified into ‘linear + quadratic + interaction terms’ using the least squares method in Matlab®. Results indicate that higher Ni yield (> 95 wt.%) is achieved at a lower slurry solid content (< 27 wt.%) and higher A/O ratios (> 0.35), whereas higher solution purity (selectivity > 3) is favoured at lower A/O ratios with preferably lower solid content (∼22 wt.%). Scale formation increases significantly with higher solid content and A/O ratios exceeding 0.35. Optimisation revealed that a compromise between Ni yield, selectivity, and scale minimisation is necessary, with the highest composite desirability (0.68) obtained at 22 wt.% solid content and an A/O ratio of 0.35. The findings provide valuable insights for industrial leaching process optimisation, highlighting the trade-offs between maximising Ni recovery, limiting impurity dissolution and minimising scale formation
Recognizing and adjusting: developing an adaptive team information seeking framework for emergency situation assessment
No full textInternational audienceEffective situation assessment requires response teams to adapt their information seeking during emergencies. However, research on team adaptation often overlooks the specific cues and processes that support information seeking. Meanwhile, studies of collaborative information seeking and sensemaking rarely address how teams adapt to address emergent information needs. This study bridges this gap by proposing an integrative framework of adaptive team information seeking developed through a case study in which emergency response teams recognized cues of ambiguity and uncertainty and adjusted their search goals and tasks to address information needs that arose during a 2020 shooting incident in Phoenix, Arizona. Findings also highlight the need for teams to recognize goal and task interdependencies, and coordinate adjustments to broad and targeted searches within time and resource constraints. The introduced framework describes the process of adaptive team information seeking and can guide evaluations of systems designed to support adaptation in team situation assessment
Heptafluorobutyronitrile (c4f7n), hydrolysis, a density functional theory (dft) investigation
No full textInternational audienceHeptafluorobutyronitrile (C3F7CN) has received much consideration as an effective substitute to sulfur hexafluoride (SF6) in the electrical industrial sector over the last decade. However, liability is the key to emerging technology, and the thermoelectric aging of the insulation gases may produce unavoidable consequences that raise concerns for the operator and human safety. Recently, numerous pieces of literature mentioned the production of crystals in the form of amide and dimer (ligand) generated from the aging of C4F7N with few ppm of water molecules. It was found that the hydrolysis of fluoronitrile chemical reactions initial with the production of amide (C4H2F7NO) and following, with the addition of C4F7N molecules, accelerates the reaction to produce dimer (C8H2F14N2O), trimer (C12H2F21N30), tetramer (C16H2F28N40), and finally a triazine (C12F21N3) molecule. Thermodynamically, Rc is the favorable chemical reaction with a 23 kcal/mol energy barrier that generates a dimer molecule. Furthermore, with the presence of copper (Cu) metal, these dimers make the Cu complex as violet crystals. Gibbs free energy at elevated temperature indicates the driving force is needed to accelerate the reaction except Rd, whose energy values throughout remain consistent. Theoretical calculations reveal the water acts as a strong catalytic that can abruptly reduce the energy barrier from 59 to 10 kcal and open the pathway to generate the byproducts
Managing uncertainties within sales and operations planning (S&OP): a systematic literature review: review
No full textInternational audienceSales and Operations Planning (S&OP) is a crucial business process that enables the alignmentof strategic plans with daily operational activities. However, the dynamic nature of modernbusiness environments poses challenges to achieving the desired objectives of S&OP. Thisresearch aims to address this gap by examining how the literature addresses the managementof uncertainties within the S&OP process. A Systematic Literature Review (SLR) was conducted,analysing a sample of 44 articles from a total of 662 articles identified in the literature. Thesearticles were examined across six key dimensions of S&OP, namely: Process, Tools, People,Objectives, Decisions, and Key Performance Indicators (KPIs). The review of literature revealedseveral gaps and limitations in the existing research pertaining to uncertainty management inS&OP. Future research should focus on developing well-defined procedures for effectivelyaddressing uncertainties within the S&OP process. This includes areas such as scenario plan-ning methodologies, decision-making frameworks that account for uncertainties, and theintegration of KPIs
Représentation de la microstructure de la matrice d'un CMC oxyde/oxyde par un réseau d'éléments de type connecteur pour modéliser le comportement mécanique du composite
No full textOxide/oxide ceramic matrix composites are currently used as structural materials in aeronautical and spatial applications. They are likely to supplant some metals for intermediate temperatures (between 500 °C and 900 °C) and/or for oxidizing or corrosive environments. Most of oxide/oxide composites relay on the weak matrix principle which is achieved using a porous matrix. From this subclass of material, the composites obtained by the combination of the Nextel fibres and a matrix composed of α-alumina and amorphous silica are great candidates. Indeed, they present good mechanical properties while having a low temperature and duration sintering process which lower the manufacturing cost and preserve the integrity of the fibres. This favourable behaviour is due to the flowing of the silica under a viscous state during sintering which leads to the formation of silica bridges between alumina particles. The matrix therefore densifies under the effect of the surface tension between the solid and viscous phases. Performances of the composite are heavily dependent on the mismatch of mechanical properties between fibres and matrix. Yet, this difference is induced by the porosity level which is itself controlled by the manufacturing process. Literature display only a few numerical models which account for the link between porosity, composition and mechanical properties of alumina/silica matrix. The objective of the Ph.D. work is the formulation of a numerical model able to account for this dependence of matrix properties while conserving a low computational cost. It will be based on a multi-scale approach and will be able to adapt to the composite simulation by the addition of the fibres influence. The model is mainly based on the similarity between the microstructure of partially sintered ceramics and a truss in which links would correspond to the silica bridges and nodes would be the centres of alumina particles. The positioning and characterization of the links is based on the matrix macroscopic characteristics. Links are then converted to 2 nodes connector elements and their stiffnesses have been calculated thanks to silica bridge modelling. The use of these elements allows limiting the computational cost associated with structures containing close to 10000 alumina particles. Furthermore, they support a wide variety of resolution schemes (implicit, explicit, quasi-static, dynamic, modal analysis). A homogenization method of elastic properties by modal analysis has been designed. Results obtained by this method highlight the model capacity to account for the influence of ceramic characteristics and the homogenized mechanical properties. This method has then been coupled to Nextel fibres modelled by continuous elements in the aim to represent the microstructure of the composite microstructure. This hybrid model allowed the application of quasi-static mechanical solicitations which highlights its coherence. The use of connector elements in this type of modelling opens the way to the numerical simulation of the microstructure of porous ceramics and associated composites, with a low computational cost.Les composites à matrice céramique oxyde/oxyde sont utilisés en tant que matériaux structuraux dans plusieurs applications aéronautiques ou spatiales. Ceux-ci sont amenés à supplanter certains métaux pour des températures intermédiaires (500 °C à 900 °C) et/ou pour des environnements oxydants ou corrosifs. La plupart des composites oxyde/oxyde reposent sur le principe de matrice faible. Celle-ci est poreuse afin de diminuer ses propriétés mécaniques. Dans cette catégorie de matériaux, ceux produits à partir de fibres Nextel, ainsi que d'une matrice composée d'alumine α et de silice amorphe, sont de très bons candidats. En effet, ils présentent de bonnes propriétés mécaniques tout en ayant des températures et des durées de frittage relativement faibles, ce qui diminue les coûts de fabrication et préserve les fibres. Ces modalités avantageuses de fabrication sont dues à l'écoulement de la silice sous forme de phase visqueuse lors du frittage, qui conduit à la formation de ponts entre les particules d'alumine. La matrice se densifie sous l'action de la tension de surface entre les phases visqueuse et solide. Les performances de ce type de composites à matrice céramique dépendent fortement de la différence de propriétés mécaniques entre la matrice et la fibre. Or cette différence est induite par le niveau de porosité de la matrice, qui est lui-même contrôlé par le processus de fabrication. La littérature ne contient que peu de modèles numériques permettant de rendre compte du lien entre la porosité, la composition d'une matrice alumine/silice et ses propriétés mécaniques. L'objectif de ces travaux de thèse est la formulation d'un modèle numérique rendant compte de cette dépendance des propriétés de la matrice en un temps de calcul limité. Ce modèle est basé sur une approche multi-échelle et a la possibilité de s'adapter au composite par l'ajout de l'influence des fibres Nextel. Le modèle s'appuie principalement sur la similarité entre la microstructure de la céramique partiellement frittée et une structure treillis, dans laquelle les liens correspondent aux ponts de silice et les nœuds sont le centre des particules d'alumine. Le positionnement et la caractérisation des liens ont été calculés à partir des caractéristiques de la matrice. Les liens ont ensuite été convertis en éléments connecteurs à 2 nœuds, dont les rigidités ont été calculées à partir de simulations numériques de ponts de silice. L'utilisation de ces éléments connecteurs permet de limiter le temps de simulation associé à des structures contenant environ 10000 particules d'alumine. De plus, ces éléments finis spécifiques tolèrent une grande variété de schémas de résolution (implicite, explicite, quasi-statique, dynamique, analyse modale, etc.). Une méthode d'homogénéisation des propriétés élastiques par analyse modale de ces structures a pu être conçue. Les résultats obtenus ont mis en évidence la capacité du modèle à refléter l'influence des caractéristiques de la céramique poreuse sur les propriétés mécaniques homogénéisées. Cette méthode a ensuite été couplée à des fibres modélisées par éléments continus, afin de produire des représentations de la microstructure d'un composite. Ce modèle hybride a permis l'application de sollicitations quasi-statiques qui ont mis en avant sa cohérence. L'utilisation de connecteurs dans ce type de simulations numériques ouvre la voie à des simulations de microstructures de céramiques poreuses et des composites associés, en un temps de calcul limité
Maîtrise des Interactions Rayonnement-Matière et transferts énergétiques lors de la fabrication par SLS de composites polymères particulaires
No full textThe goal of the thesis project is to widen the range of compositions of polymer materials that can be transformed by Selective Laser Sintering (SLS), specifically particulate and flame retarded composites based on polyamides 12, and to evaluate the influence of the addition of inorganic micronic particles on the laser-matter interaction and on the heat transfer to the polymer particles. The understanding of laser-powder energy interactions, via their characterization and modeling, is the major issue of this thesis, with a view to ensure the feasibility of producing complex multi-component compositions applicable to technical parts (aeronautics, nautical, medical), in order to:-optimize mechanical properties and reaction to fire,-Improve the environmental impact of the process through its energy efficiency and the limitation of the non-recyclable fraction.L'objectif général du projet de thèse est de permettre d'élargir l'éventail des compositions de matériaux polymères pouvant être transformées par Selective Laser Sintering (SLS) et notamment des composites particulaires et/ou ignifugés basés polyamides 12, ainsi qu'évaluer l'influence de l'ajout de particules microniques inorganiques sur l'interaction laser matière ainsi que sur le transfert de chaleur vers les particules de polymère. La compréhension des interactions énergétiques laser-poudres, via leur caractérisation et leur modélisation, est la problématique majeure de cette thèse, en vue d'assurer la faisabilité de réalisation de compositions complexes multi-composants applicables à des pièces techniques (aéronautique, nautisme, médical), afin de :- optimiser les propriétés mécaniques et les propriétés de réaction au feu,- améliorer l'impact environnemental du procédé à travers son efficacité énergétique et la limitation de la fraction non recyclable
Configuration de flottes de robots hétérogènes pour la planification de mission: une approche basée programmation par contraintes
No full textNational audienceAvec l'autonomie croissante des robots et la variété des tâches qu'ils sont désormais en mesure de réaliser, ceux-ci sont de plus en plus souvent utilisés dans le cadre de missions complexes et critiques. Cet article s'intéresse au problème de la configuration des flottes de robots pour la planification de mission. Dans nos travaux, la planification d'une mission, avant sa phase d'exécution, repose sur la résolution de trois problèmes de configuration intrinsèquement liés : le problème de configuration d’agents, noté ACP, le problème de configuration de la flotte d'agents, noté FCP et le problème de configuration du plan de mission, noté PCP. Dans cet article, nous considérons la planification de mission comme un seul et unique problème, composé de trois sous-problèmes interdépendants. Un modèle de programmation par contraintes (PPC) est proposé pour le problème global. Notre modélisation est évaluée sur le solveur IBM ILOG CP Optimizer et sur soixante-quatre instances de type Recherche & Sauvetage générées artificiellement
Microstructure development in cellulose fibre reinforced PLA composites during processing: a thermal and rheological study
No full textInternational audienceThis work aims to determine the effect of cellulose fibre content and fibre size and shape on the crystallisation and solidification of polylactic acid (PLA) during cooling to better understand microstructure development in biocomposites. Hot melt twin-screw extrusion and injection moulding was used to prepare cellulose fibre reinforced PLA composites with different microstructures from the diluted to the concentrated regime. Differential scanning calorimetry, temperature-controlled optical microscopy and rheometry were used to study the non-isothermal and isothermal crystallisation and solidification of the composites. The non-isothermal analysis shows that cellulose fibres, regardless of their content, size and shape, did not affect either the PLA thermal characteristics (glass transition, cold crystallisation and melting temperatures), nor its degree of crystallinity. On the other hand, isothermal crystallisation kinetics of PLA is greatly influenced by the fibres, being accelerated when fibre content and length/aspect ratio are increased. Our results also reveal that crystallisation and related rheological behaviour during solidification of PLA can be tuned by modifying the fibre characteristics, thus contributing to better control PLA processing, especially when studying thermoplastic processes involving isothermal steps
AgBr-garlic peel QD system: a promising composite for simultaneous degradation of a binary mixture of cationic and anionic dyes
No full textInternational audienceThe conversion of waste into value-added products is a key focus of modern research. In this study, we synthesized nitrogen (N) and sulfur (S) co-doped carbon quantum dots (CQDs) from garlic peel using a hydrothermal method and incorporated them into silver bromide (AgBr) to enhance the photocatalytic efficiency. The AgBr–QD composite was prepared with QD concentrations of 1, 5, 10, 20, and 30 wt%, and the 20 wt% QD composite exhibited the highest photocatalytic activity. Under visible light irradiation, this optimized composite achieved 92.4% degradation of a dye-contaminant mixture within 15 minutes. The improved performance was attributed to enhanced charge separation and reduced electron–hole recombination, as confirmed by radical trapping experiments, which identified holes as the primary active species in the photodegradation. These findings suggest that garlic peel-derived QDs can significantly enhance the efficiency of AgBr-based photocatalysts for wastewater treatment