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Relaxation of Powders Beds Under Stress: New Experiments and Review on Modelling-Simulation
No full textInternational audienc
Élaboration et caractérisation du comportement mécanique de composites stratifiés à matrice organique avec tapis de nanotubes verticalement alignés
No full textContinuous Fibre Reinforced Polymer Composites are increasingly used in structural applications, particularly in the fields of aeronautics and space. These materials indeed have several advantages such as good corrosion resistance, low density, and good mechanical properties. However, certain properties remain to be improved, such as resistance to delamination, particularly critical for impact resistance. The PhD work is carried out within the framework of the collaborative project FUI ATIHS aimed at the improvement of the resistance of satellite structures to hypervelocity impacts from space debris. It concerns the incorporation of VACNTs (Vertically Aligned Carbon Nanotubes) mats within an organic matrix composite with long carbon fibers with the aim of developing a new composite material with improved mechanical properties for static and impact loads. A first part of the work is devoted to the development and implementation of the process for the manufacture of a new laminated composite material by placing mats of nanotubes at the inter-plies. The first step is to control the transfer of the VACNTs mats onto M55J-M18 prepreg, by regulating through time, temperature and pressure control the capillary rise of the resin and then separating the VACNTs from its growth substrate. The second step is to consolidate the laminated composite while maintaining the initial morphology of the VACNTs and avoiding the formation of porosity. Through observations from the microscopic to the macroscopic scales, the work has enabled the identification of process parameters meeting these objectives and a better understanding of the mechanisms involved. After a development stage carried out at small scale, the process for developing the new composite has been validated on a larger scale allowing structural applications to be considered. A second part of the work consists in the study of the mechanical behavior of the new composite material under different types of static tests, in particular those stressing the plies interfaces. The approach is based on a comparison with the unreinforced reference material. It combines analyzes of mechanical test results and microstructural observations at different scales. It again permitted a better understanding of the damage mechanisms at the inter-plies of laminated composites. Shifts in damage zones have been observed due to the introduction of VACNTs to the inter-folds, which opens up prospects for the further development of carbon nanotube-reinforced composites with improved performances.Les matériaux composites à matrice organique et à fibres longues occupent une place grandissante dans des applications structurales, notamment dans les domaines de l’aéronautique et du spatial. Ces matériaux présentent en effet un ensemble d’atouts tels qu’une bonne résistance à la corrosion, une faible masse volumique et de bonnes propriétés mécaniques. Néanmoins, certaines propriétés restent à améliorer comme la résistance au délaminage, notamment critique pour des sollicitations d’impact. Le travail de thèse est réalisé dans le cadre du projet collaboratif FUI ATIHS (Amélioration de la Tenue des structures satellites aux Impacts Hypervitesse de débris Spatiaux). Il porte sur l’incorporation de tapis de nanotubes de carbone verticalement alignés, ou tapis de VACNTs (Vertically Aligned Carbon Nanotubes) dans un composite à matrice organique à fibres longues de carbone dans l’objectif de développer un nouveau matériau composite aux propriétés mécaniques améliorées pour des sollicitations statiques et à l’impact. Une première partie du travail de thèse est consacrée au développement et à la mise en œuvre du procédé d’élaboration d’un nouveau matériau composite stratifié en plaçant des tapis de nanotubes aux interplis. Il s’agit en premier lieu de maîtriser le transfert des tapis de VACNTs sur un pré-imprégné M55J-M18, par montée capillaire partielle de la résine puis séparation du substrat de croissance des VACNTs. Dans un deuxième temps, il s’agit de consolider le composite stratifié en conservant la morphologie initiale des VACNTs et en évitant la formation de porosité. Par des observations de l’échelle microscopique à l’échelle macroscopique, le travail a permis une identification de paramètres procédé répondant à ces objectifs et une meilleure compréhension des mécanismes mis en jeu. Après une étape de mise au point réalisée à petite échelle, le procédé d’élaboration du nouveau composite a été validé à une échelle permettant d’envisager des applications structurales. Une deuxième partie du travail concerne l’étude du comportement mécanique du nouveau matériau composite sous différents types d’essais statiques, notamment ceux sollicitant les interfaces. La démarche est basée sur une comparaison avec le matériau de référence non renforcé. Elle couple des analyses des résultats d’essais mécaniques et d’observations microstructurales à différentes échelles. Elle permet à nouveau une meilleure compréhension des mécanismes d’endommagement. Des déplacements des zones d’endommagement ont été constatés du fait de l’introduction des VACNTs aux interplis, ce qui permet de dégager des perspectives pour la poursuite du développement de composites renforcés de nanotubes de carbone
Development of a Risk-aware Business Process Modeling Tool for Healthcare processes
No full textInternational audienceHealthcare organizations are environments of high management complexity and are subject to risk. Indeed, risk management is one of the most relevant aspects put forward in the literature which highlights the necessity to perform comprehensive analyses intended to uncover the root causes of risks. However, the healthcare sector still suffers from a lack of attention in this context, especially with regard to the establishment of risk management and process-oriented management, which is the motivation for the study described in this paper. In light of these observations, it would be essential for healthcare organizations to explore new risk management approaches. Contributing to this field, the present paper applies a risk-aware business process management method to work out a systemic methodology to study risks impacting healthcare processes. This framework aims to improve healthcare organizations’ maturity towards risk management. A case study related to the management of potential risks in a given healthcare process shall illustrate the usage of the developed framework
Proceedings of the 23rd international configuration workshop (cws/confws2021), Vienna, Austria, from September 16-17, 2021
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Rheological and crystallization behaviors of low processing temperature poly(aryl ether ketone)
No full textInternational audienceA new low melting temperature poly(aryl ether ketone) (PAEK) thermoplasticpolymer (Victrex AE 250) was investigated through thermal and rheologicalanalysis of films and flakes. DSC was assigned to evaluate the influence ofcooling rate on crystallinity and thermal transitions. Rheometry was used toassess its flowing behavior through the evaluation of dynamic moduli andcomplex viscosity in the melted state. The relaxation times were found fromthe rheological curves: they are between a few ms to 200 ms for AE 250, lowerthan those found for PEEK 450, meaning a faster mobility of macromolecules.The thermal activation energy,Eaobtained from Time Temperature Superposi-tion is the same for films and flakes in spite of a lower viscosity for flakes. Themolecular weight between entanglements is evaluated at 8000 g.mol1forFMc and 13,000 for FLc, it is compared to the value of about 2000 g.mol1found for PEEK 450 with the same procedure. Also, the viscosity was com-pared to other commercial PAEK such as PEEK and PEKK based on data fromthe literature. This polymer appears very efficient to compete with high perfor-mance thermoplastics to be processed by compression molding, out of auto-clave consolidation, additive manufacturing, and welding
Design and thermal characterization of an induction-heated reactor for pyrolysis of solid waste
No full textInternational audienceA small-scale induction heated reactor (IHR) was specifically developed to study fast pyrolysis, here investigated as the first step of gasification process, representing some of the reaction conditions encountered in a fluidized bed reactor. First, the thermal response of the system was characterized at transient and steady state, and CFD calculations were performed to have a complete description of the temperature profiles inside the reactor. The novel device can handle a few grams of solid at temperatures up to 900 °C, allowing high heating rates (near 80 °C/s) and a uniform distribution of temperature in the sample. Secondly, the pyrolysis of a solid recovered fuel (SRF) sample was carried out at 800 °C, and the distribution and composition of reaction products were analyzed and compared with tests performed in a pilot scale fluidized bed reactor (FBR). The results obtained in the IHR showed a good reproducibility. The same main gas and tar species were measured in the IHR and FBR, with however some differences in gas and tar composition that were attributed to the extent of secondary reactions, enhanced by higher heat transfer rates and the presence of bed material in the FBR
Incidence and risk factors for incisional hernia and recurrence: retrospective analysis of the French national database
No full textInternational audiencePurposeTo determine the rate of incisional hernia (IH) repair and risk factors for IH repair after laparotomy.MethodsThis population‐based study used data extracted from the French (PMSI) database. All patients who had undergone a laparotomy in 2010, their hospital visits from 2010‒2015, and patients who underwent a first IH repair in 2013 were included. Risk factors identified previously included: age, gender, high blood pressure (HBP), obesity, diabetes and chronic obstructive pulmonary disease (COPD).ResultsAmong the 431 619 patients who underwent a laparotomy in 2010, 5% underwent IH repair between 2010 and 2015. A high‐risk list of the most frequent surgical procedures (>100) with a significant risk of IH repair (>10% at 5 years) was established including 71 863 patients (17%, 65 procedures). Overall IH repair rate from the list was 17%. Gastrointestinal (GI) surgery represented 89% of procedures with the majority of patients (72%) undergoing lower GI tract surgery. IH repair rate was 56% at 1 year and 79% at 2 years. Risk factors for IH repair included obesity (31% vs. 15%, p<0.001), COPD (20% vs. 15%), HBP (19% vs. 15%) and diabetes (19% vs. 16%). Even for recurrence after IH repair, obesity was the main risk factor (19% vs. 13%, p<0.001)ConclusionFrom the PMSI database, the real rate of IH repair after laparotomy was 5%, increasing to 17% after digestive surgery. Obesity was the main risk factor with an IH repair rate of 31% after digestive surgery. Because of the important medico‐economic consequences, prevention of IH after laparotomy in high‐risk patients should be considered
Vers une approche globale pour soutenir le processus Adaptive Sales and Operations Planning
No full textInternational audienceIn an increasingly uncertain context, companies are always looking for relevant means able to optimize their supply chain planning. Since 2011, some authors propose a new approach called DDAE/DDMRP which is supposed to allow reacting in an agile way in a complex and volatile context. Is the grail there? This approach is meeting with growing success among practitioners and scholars, but this multi-level hierarchical planning system (operational, tactical, strategical) has many grey areas that remain to be cleared up. This study focuses on the strategic level of this model: the AS&OP process. For now, AS&OP is not accurately defined and equipped. Consequently, we propose to develop a dedicated decision support system. This study brings two distinct contributions: a modeling of the AS&OP business processes and an associated software approach to support the decision mechanism. We study the potential of using decision trees and risk management approaches to develop a scenario-oriented planning with this perspective. This experimentation platform called AS&OP- DSS is tested on a theoretical case. The article concludes on the feasibility of this approach and opens avenues for future research.Dans un contexte de plus en plus incertain, les entreprises sont toujours à la recherche de l’optimisation de la planification de leur supply chain. Depuis 2011, des auteurs proposent une nouvelle approche appelée DDAE/DDMRP censée permettre de réagir de manière agile dans un contexte complexe et volatile, le graal est-il là ? Cette approche rencontre un succès grandissant au niveau des industriels et des scientifiques mais ce système de planification hiérarchisée multi-niveaux (opérationnel, tactique, stratégique) comporte de nombreuses zones d’ombres qui restent à éclaircir. Cette étude se porte sur le niveau stratégique de ce modèle : le processus AS&OP. A date, AS&OP n’étant pas suffisamment précisément défini et outillé, nous proposons de développer un système d’aide à la décision dédié. Cette étude apporte deux contributions distinctes : une modélisation du processus métier AS&OP ainsi qu’une approche logicielle associée permettant de soutenir l’aide à la décision. Nous étudions le potentiel de l’utilisation des arbres de décisions et de la gestion des risques pour développer une planification scénarisée dans cette optique. Cette plateforme d’expérimentation appelé AS&OP-DSS est testée sur un cas illustratif. L’article conclut sur la faisabilité de cette approche et ouvre sur un ensemble de perspectives de recherche
Pyrolysis of solid waste and its components in a lab scale induction-heating reactor
No full textInternational audienceThe present study investigates the thermochemical conversion of Solid Recovered Fuel (SRF), represented by selected “model materials”. A laboratory-scale induction heated device was specifically developed to achieve fast pyrolysis conditions close to those encountered in a fluidized bed reactor. The novel device can handle up to 5 grams of solid, allowing fast heating rates (near 70°C/s) and a homogeneous distribution of temperature all along the reactor. Pyrolysis tests of a SRF sample and four model materials (Polyethylene, Polyethylene Terephthalate, beech wood, cardboard) were performed at 800°C. The yield and composition of the produced gas for each sample were determined. Experimental results will help to elucidate the relation between the initial components of waste derived fuels and the obtained reaction products