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Study of the fluid-structure interaction of a mat reinforcement with a thermoplastic resin
No full textInternational audienceThe aim of this work was to study the compression behavior of a mat reinforcement. The compaction stages of the dry and wet reinforcement and its relaxation over time as a function of several pressure levels have been characterized with a custom-designed bench. The compression behavior of the reinforcement can be modeled by a power law. The coefficients of the law are changing with the rupture of the fibers during compression. The study of the reinforcement compressibility enables an optimized composite manufacturing, to obtain materials without porosity and without increasing the thickness induced by a polymer excess
Conception de réacteurs et transducteurs ultrasonores optimisés, pour des applications de la cavitation acoustique et la sonochimie
No full textThis thesis focuses on the modeling and characterization of sonochemical reactors using high-power ultrasonics at a frequency of 20 kHz. The objective is to understand complex acoustic interactions by examining the effects of reactor geometry. Characterization techniques have shown the existence of optimal geometries for efficient cavitation. A comprehensive model of the sono-reactor has been developed and validated. Experiments have revealed the importance of the mechanical impedance perceived by the transducer as an indicator of the cavitation state in the reactor and of its sonochemical effects. These results contribute to the understanding of complex acoustic phenomena related to cavitation, opening perspectives for sizing and optimizing industrial processes using high-power ultrasonics.Cette thèse se focalise sur la modélisation et la caractérisation des réacteurs sonochimiques mettant en œuvre des ultrasons de puissance à une fréquence de 20 kHz. L'objectif est de comprendre les interactions acoustiques complexes en examinant les effets de la géométrie du réacteur. Des techniques de caractérisation ont montré l'existence de géométries optimales pour une cavitation efficace. Un modèle complet du sonoréacteur a été développé et validé. Les expériences ont révélé l'importance de l'impédance mécanique, perçue par le transducteur, comme indicateur de l'état de cavitation dans le réacteur et de ses effets sonochimiques. Ces résultats contribuent à la compréhension des phénomènes acoustiques complexes liés à la cavitation, ouvrant des perspectives pour développer et optimiser les procédés industriels utilisant des ultrasons de puissance
On Solving the Physicians Scheduling Problem at an Emergency Department: A Case Study from Canada
No full textInternational audienceEmergency departments play a pivotal role in healthcare delivery since they represent the first line in hospitals to face emergency patients. This department is where medical care is provided to patients whose arrival rate is uncertain and a high fluctuation in the daily requirements is presented. Yet, managing its human resources efficiently is imperative to improve the quality of its services and provide the right treatments at the right time. This work aims to establish a schedule for physicians in emergency departments which represents a challenging task as it requires respecting several rules incorporating diverse aspects. The objective of this study is to allocate workdays and shifts to emergency department physicians to align physicians’ productivity with patients’ demands, without decreasing physicians’ preferences, to maximize the number of patients treated at the emergency department. Taking into consideration the stochastic and time-varying patients’ demand, we presented a mathematical programming approach that determines feasible physicians’ schedules respecting the emergency department’s hard requirements, minimizing patients’ coverage violations, along with the violation of physicians’ preferences. A real-life case study was carried out in a public Hospital in Quebec, Canada. Different scenarios were then created to study the effect of each goal on the problem. Afterward, we applied a meta-heuristic solution approach belonging to the iterative evolutionary algorithms with several feature configurations to solve the physicians scheduling problem. The results obtained from the computational study of the several scenarios were discussed as a function of the degree of satisfaction of the goals under which the system operates allowing to conclude the best scenario that generates a one-month schedule respecting all goals without deterioration
Development of tristearin-based formulations for hot-melt coating: effect of additives on polymorphic transitions monitored by raman spectroscopy and atomic force microscopy
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Analysing the modifications of carbon black and other fillers after pyrolysis of model tyres
No full textInternational audienceCarbon blacks (CBs) that are used as fillers to reinforce rubber contribute to recycling issues of tyres.Although it has been shown that recovered carbon black produced from the thermoconversion of waste tyres (rCB) has poor reinforcing abilities in non-polar rubbers. The exact origin of the difference between rCBs and CBs requires investigation. The characteristics of the rCBs produced from the hybrid pyrolysis of model laboratory-reinforced rubbers, with or without silica added, were analysed and compared to the pristine N330 CB. X-Ray Diffraction showed no discernible changes in the basic structural units and nanotexture of the primary particles. Nevertheless, qualitative background analysis of the diffractograms revealed that the quantity of unorganised carbon in the rCB increased by about 25% after pyrolysis. The carbonaceous deposits affected the filler texture, and part of the ultra-microporosity (i.e., pores within the diameter range 0.34-0.76 nm), which had a three-fold decrease in the rCB sample. The recovered fillers, with and without silica, had more oxygenated functional groups than the CB. Total CO and CO2 evolved during the decomposition of these functional groups was 2.8, 5.3 and 3.5 mmol/g for CB, rCB and rCB-SiO2, respectively. The dispersibility and stability of the colloidal suspensions was affected by the increased surface oxygenated functionalities. Reductive hydrogenation was utilised to remove the excess oxygen allowing an improved understanding regarding the origin of the differences between the pristine and recovered materials. Reducing the surface chemistry rCB was not sufficient to fully recover the pristine N330 CB properties, post-treatment via surface reduction reduced oxygen content by 80% in the rCbs. This post-treatment method therefore shows potential in improving the recyclability of rubber via pyrolysis.</div
Tablet microstructures induced by embossed features of compacting punch : case study analysis
No full textInternational audienceThis poster presents an experimental and numerical development for studying powder compaction under punches with deep grooves. Comparison between predicted density distribution using FEM modelling and computed density from X-ray tomography measurements, shows good agreements, particularly in the area near the grooves and in between the faced grooves
Stability of a Hydroxyapatite-Supported Nickel Catalyst in Dry Reforming of Methane
No full textInternational audienceAt a large industrial scale, hydrogen is mainly produced from natural gas as feedstock via methane steam reforming. The latter is a highly intensive energy process, leading to high cost and high environmental impact of the final product. Alternative ways for producing green hydrogen with low environmental impact have largely been studied during the last decades. Among them, the valorization of landfill gas, containing mainly methane and carbon dioxide, into green hydrogen, via dry reforming of methane (DRM) appears as a promising route. In fact, DRM allows converting both CO2 and CH4 into syngas. However, catalysts in DRM have usually problems of being deactivated during the reaction, due to thermal sintering at high temperatures (700–950 °C) or due to solid carbon deposition. This paper mostly focuses on the stability of a hydroxyapatite-supported nickel catalyst and its generation in DRM reaction
Adsorption et désorption du phosphore des eaux usées par des adsorbants à base d'alumine
No full textThis work proposes a study on the identification and understanding of phosphorus (P) sorption and desorption mechanisms from two alumina-based sorbents (pure alumina and doped alumina). Characterization is a key step in understanding the behavior of alumina during sorption and desorption. For this, physical, chemical, thermal and surface characterization of the alumina were carried out. Sorption experiments were carried out in a batch reactor and in a fixed-bed column. The batch sorption results showed a phosphorus sorption efficiency of up to 2gP/kg, i.e. the total amount of phosphorus introduced for an initial phosphorus concentration of 15 mg/L. Phosphorus sorption takes place in two stages: (i) diffusion through the liquid film surrounding the particle and (ii) diffusion into the pores. In the column experiments, the influence of bed height (5 cm, 7.5 cm and 10 cm) on phosphorus sorption in the column was studied. The results of these experiments show a phosphorus sorption capacity for alumina of around 20 gP/kg alumina for all 3 heights. The results showed that the increase in alumina bed height is not proportional to the increase in alumina sorption capacity. The evolution of pH at the column outlet, for all 3 heights, highlights an ion exchange phenomenon. Mathematical models were applied to the experimental results to identify the mechanism driving the phosphorus sorption process (mass transfer, surface complexation). These results show that external transfer does not limit phosphorus sorption, but rather internal diffusion. Scanning electron microscope characterization of saturated alumina particles shows a homogeneous distribution of phosphorus both inside and on the particle surface. A comparative desorption study was carried out on a laboratory and pilot scale. Different desorbents (saline, acidic and alkaline solutions) were tested at laboratory scale to select the most effective one. The experimental works was carried along with the kinetic modeling. The results showed that the alkaline solution is the most effective desorbent. Laboratory-scale desorption experiments (0.05 L) were conducted to set up the operating conditions for pilot-scale trials (20 L). The pilot-scale experiments identified a compromise between desorption efficiency and cost as shown in the preliminary economic analysis made. Thus, 67% of the phosphorus can be desorbed with 0.5 mol/L NaOH for a solid-liquid ratio of 40 and a contact time of 6h. A second reuse of this NaOH solution (0.5 mol/L) desorbed 50% of the phosphorus at a solid-liquid ratio of 40 and a contact time of 6h. Preliminary laboratory-scale alumina regeneration experiments show a recovery of 85% of the alumina sorption capacity and 45% the doped alumina sorption capacity.Ce travail propose une étude sur l'identification et la compréhension des mécanismes d'adsorption et de désorption du phosphore (P) contenu dans les effluents liquides à partir de deux adsorbants à base d'alumine (alumine pure et alumine dopée). La caractérisation est une étape clé pour comprendre le comportement des alumines lors de l'adsorption et la désorption. Pour cela une combinaison de caractérisation physique, chimique, thermique et de surface des alumines a été réalisée. Les expériences d'adsorption ont été réalisées dans un réacteur batch et dans une colonne à lit fixe. Les résultats des expériences d'adsorption en batch ont montré une efficacité d'adsorption du phosphore allant jusqu'à 2 gP/kg soit la quasi-totalité du P introduite pour une concentration initiale en phosphore de 15 mg/L. L'adsorption du phosphore s'effectue en deux étapes : (i) la diffusion à travers le film liquide entourant la particule et (ii) la diffusion dans les pores. Quant aux expériences en colonne l'influence de la hauteur de lit (5 cm, 7,5 cm et 10 cm) sur l'adsorption du phosphore en colonne a été étudiée. Les résultats de ces expériences montrent une capacité d'adsorption du phosphore de l'alumine autour de 20 gP/kg d'alumine pour les 3 hauteurs. Les résultats ont montré que l'augmentation de la capacité d'adsorption de l'alumine n'est pas proportionnelle à l'augmentation de la hauteur de lit d'alumine. L'évolution du pH en sortie de colonne, pour les 3 hauteurs, met en évidence un phénomène d'échange d'ions. Des modèles permettant de décrire la dynamique d'adsorption en colonne ont été appliqués aux résultats expérimentaux afin d'identifier le mécanisme régissant le processus d'adsorption du phosphore (transfert de masse, complexation de surface). Ces résultats montrent que le transfert externe ne limite pas l'adsorption du phosphore mais plutôt la diffusion interne. La caractérisation au microscope électronique à balayage des particules d'alumines saturées montre une distribution homogène du phosphore à l'intérieur et à la surface de la particule. Une étude comparative de désorption a été réalisée à l'échelle laboratoire et à l'échelle pilote. Différents désorbants (solution : saline, acide et basique) ont été testés à l'échelle laboratoire afin de choisir le désorbant le plus efficace. Cette étude a été complétée par un travail de modélisation de la cinétique des processus mis en œuvre. Les résultats montrent que la base forte est le désorbant le plus efficace. Les expériences de désorption à l'échelle laboratoire (0,05 L) ont permis de fixer les conditions opératoires pour les essais à l'échelle pilote (20 L). Les expériences à l'échelle pilote ont permis d'identifier un compromis entre efficacité de désorption et coût. Ainsi 67% du phosphore peut être désorbés avec 0,5 mol/L de NaOH pour un rapport solide-liquide de 40 et un temps de contact de 6h. Une deuxième réutilisation de cette solution de NaOH (0,5 mol/L), a permis de désorber 50% du phosphore pour un rapport solide-liquide de 40 et un temps de contact de 6h. Une estimation économique préliminaire a également été réalisée. Des expériences préliminaires de régénération des alumines à l'échelle laboratoire montrent un rétablissement de 85% la capacité d'adsorption de l'alumine et 45% de la capacité d'adsorption de l'alumine dopée
Système d'aide à la décision pour une planification industrielle et commerciale adaptative
No full textThe Demand Driven Adaptive Enterprise (DDAE) approach, proposed by the Demand Driven Institute (DDI), has attracted growing interest among academics and professionals in recent years. The present research focuses on the strategic side of this model, specifically on the Adaptive Sales & Operations Planning (AS&OP) process. AS&OP is supposed to provide managers with visibility to control variability, improve ROI and adapt to frequent market fluctuations. Although these benefits have been claimed previously by other methodologies, many have failed to deliver on these promises. As a result, AS&OP has captured the attention of many professionals. However, little formal research has yet validated its effectiveness, and no operational tools have been established. This doctoral thesis evaluates the relevance and scope of the AS&OP process. The aim has been to identify the limitations of current methods in the literature, and to highlight perspectives to be explored further, such as risk, flow, finance, capacity, market, etc., as well as decision variables, coordination mechanisms, organizational structures, and performance indicators. In practice, this research presents the development of an AS&OP-DSS decision support system for dynamic simulation, including associated methodology and algorithmics. First, an aggregated model of the DDMRP (Demand Driven Requirement Planning) approach is developed and integrated within this system. Subsequently, a strategy for including uncertainties, risks and opportunities is proposed, while evaluating each scenario via ad hoc performance indicators. This system proposes to facilitate scenario generation and evaluation using dynamic simulation based on what-if planning. Finally, the proposal integrates a capability-based approach to planning in order to better support the strategic decisions to be taken. The results of this research are corroborated at each stage by field studies involving companies adopting the DDAE approach. Thus, the study is structured around two main axes: a theoretical dimension and a practical dimension.L'approche de l'entreprise adaptative basée sur la demande (Demand Driven Adaptive Enterprise DDAE), proposée par le Demand Driven Institute (DDI), a suscité un intérêt croissant parmi les universitaires et les professionnels ces dernières années. La présente recherche se penche sur le volet stratégique de ce modèle, spécifiquement sur le processus de planification adaptative des ventes et des opérations (Adaptive Sales and Operations Planning AS&OP). L'AS&OP est supposé procurer aux gestionnaires une visibilité permettant de maîtriser la variabilité, d'améliorer le retour sur investissement et de s'adapter aux fluctuations fréquentes du marché. Bien que ces avantages aient été revendiqués précédemment par d'autres méthodologies, bon nombre d'entre elles n'ont pas réussi à concrétiser ces promesses. En conséquence, l'AS&OP a capté l'attention de nombreux professionnels. Cependant, peu de recherches formelles ont encore validé son efficacité, et aucun outillage opérationnel n'a été établi. Cette thèse de doctorat évalue la pertinence et la portée du processus AS&OP. L'objectif a été de cerner les limitations des méthodes actuelles dans la littérature, et de mettre en avant les perspectives à approfondir, telles que le risque, le flux, la finance, la capacité, le marché, etc., ainsi que les variables décisionnelles, les mécanismes de coordination, les structures organisationnelles, et les indicateurs de performance. En pratique, cette recherche présente le développement d'un système d'aide à la décision AS&OP-DSS (Decision Support System) pour une simulation dynamique, incluant méthodologie et algorithmie associées. En premier lieu, un modèle agrégé de l'approche DDMRP (Demand Driven Requirement Planning) est élaboré et intégré au sein de ce système. Par la suite, une stratégie pour inclure les incertitudes, risques, et opportunités est proposée, tout en évaluant chaque scénario via des indicateurs de performance ad hoc. Ce système propose de faciliter la génération et l'évaluation de scénarios en utilisant une simulation dynamique basée sur la planification scénarisée (What-if). Enfin, la proposition intègre une approche capacitaire de la planification afin de mieux supporter les décisions stratégiques à prendre. Les résultats de cette recherche sont corroborés à chaque étape par des études de terrain, impliquant des entreprises adoptant l'approche DDAE. Ainsi, l'étude est structurée autour de deux axes principaux : une dimension théorique et une dimension pratique
