HAL Portal UTC Université de Technologie de Compiègne
Not a member yet
11652 research outputs found
Sort by
Craquage catalytique du toluène sur un lit de biochars issus de la biomasse
No full textThermochemical conversion processes, such as pyrolysis and gasification, transform part of the biomass and waste into a solid product called biochar. While the main product in some thermochemical processes is synthesis gas and/or oils, the solid co-product or biochar cannot be neglected, and its recovery can offer economic potential for these processes. Syngas from gasification can be used as a fuel to power a heat engine or gas turbine. The tars present in these gases impose serious limitations on the development of these processes. Syngas must be cleaned, by removing or reducing tars, before use to avoid damaging engines or turbines. Low levels of tars are imposed, often less than 50 mg.Nm-3 for combustion engines and less than 0.5 mg.Nm-3 for gas turbines. The catalytic cracking of tars in the presence of a biochar is promising option, both technically and economically, and biochars appear to have excellent catalytic potential for this purpose. Understanding this type of process is crucial to its design, scale-up and optimization. We began by studying the influence of activation conditions on the textural properties (specific surface area and pore size distribution) of biochar derived from beechwood. We showed the effect of the conversion rate during activation and of the activating agent (H2O and CO2) on the textural properties, and therefore on the quality of the biochar obtained. In addition, we found a compromise between surface development and biochar consumption during activation in order to maximize the available surface area. In the second part of the study, we investigated the influence of biochar properties on the catalytic cracking of toluene. We demonstrated the effect of physical activation of biochar on toluene cracking. The toluene conversion rate increased from 28% during thermal cracking to 99% in the presence of certain activated biochars. We have shown that increasing the specific surface area of biochars after the activation step improves their catalytic activity. The porous network developed after activation would improve the diffusion of pollutants within the biochar and multiply the number of active sites available for cracking. We have also shown that the pore size distribution plays a role in the deactivation of the biochar by coke deposition during toluene cracking. Deactivation is faster for microporous biochars than for those with a mesoporous part. Finally, a numerical model of these phenomena was proposed in order to understand and characterize the toluene cracking process on a bed of activated biochar and its subsequent deactivation.Les procédés de conversion thermochimique, pyrolyse et gazéification, transforment une partie de la biomasse et des déchets en un produit solide appelé biochar. Si le produit principal dans certains procédés thermochimiques est le gaz de synthèse et/ou les huiles, le co-produit solide ou biochar ne peut pas être négligé, et sa valorisation peut présenter un potentiel économique pour ces procédés. Le gaz de synthèse issu de la gazéification peut être utilisé comme combustible et ainsi alimenter un moteur thermique ou une turbine à gaz. Les goudrons présents dans ces gaz imposent de sérieuses limitations au développement de ces procédés. Un traitement des gaz de synthèse est ainsi nécessaire avant leur utilisation afin de rendre le gaz « propre », et ne pas endommager les moteurs ou les turbines. Par « propre », on entend des teneurs en goudrons suffisamment faible, souvent inférieure à 50 mg.Nm-3 pour les moteurs thermiques, et inférieure à 0,5 mg.Nm-3 pour les turbines à gaz. Le craquage catalytique des goudrons constitue une voie très intéressante et prometteuse, de points de vue technique et économique, et les biochars semblent détenir un excellent potentiel catalytique à ce but. Le craquage catalytique des goudrons, en présence d’un biochar, est un procédé multiphasique qui fait intervenir une phase gazeuse, le gaz de synthèse chargé en goudrons, et une phase solide, le biochar. La compréhension d’un tel type de procédé est primordiale pour sa conception, son scale-up, et son optimisation. Dans un premier temps, nous avons étudié l'influence des conditions d'activation sur les propriétés texturales (surface spécifique et distribution de la taille des pores) du biochar issu de bois de hêtre. Nous avons montré l'effet du taux de conversion lors de l'activation et de l'agent d'activation (H2O et CO2) sur les propriétés texturales, et donc sur la qualité du biochar obtenu. En outre, nous avons trouvé un compromis entre le développement de la surface et la consommation de biochar pendant l'activation afin de maximiser la surface disponible. Dans la deuxième partie de l’étude, nous avons étudié l’influence des propriétés des biochars sur le craquage catalytique du toluène, une molécule modèle des goudrons. Nous avons montré l’effet de l’activation physique de biochar sur le craquage de toluène. En effet, le taux de conversion du toluène est passé de 28% lors du craquage thermique jusqu’à 99% en présence de certains biochars activés. Nous avons montré que la hausse de la surface spécifique des biochars après l’étape d’activation améliore leur activité catalytique. Le réseau poreux développé après l’activation améliorerait la diffusion des polluants au sein du biochar et multiplierait le nombre de sites actifs disponibles pour le craquage. Nous avons également montré que la distribution de taille des pores, quant à elle, intervient dans le phénomène de désactivation du biochar, par dépôt de coke, au cours du craquage de toluène. En effet, la désactivation est plus rapide pour des biochars microporeux que ceux présentant une partie mésoporeuse. Enfin, un modèle numérique de ces phénomènes a été proposé afin de comprendre et caractériser le processus de craquage du toluène sur un lit de biochar activé et sa désactivation par la suite
Pressure-induced nonlinear resonance frequency changes for extracting Young’s modulus of nanodrums
No full textInternational audienceAbstract The resonance frequency of ultra-thin layered nanomaterials changes nonlinearly with the tension induced by the pressure from the surrounding gas. Although the dynamics of pressurized nanomaterial membranes have been extensively explored, recent experimental observations show significant deviations from analytical predictions. Here, we present a multi-mode continuum model that captures the nonlinear pressure-frequency response of pre-tensioned membranes undergoing large deflections. We validate the model using experiments conducted on polysilicon nanodrums excited opto-thermally and subjected to pressure changes in the surrounding medium. We demonstrate that considering the effect of pressure on the nanodrum tension is not sufficient for determining the resonance frequencies. In fact, it is essential to also account for the change in the membrane’s shape in the pressurized configuration, the mid-plane stretching, and the contributions of higher modes to the mode shapes. Finally, we show how the presented high-frequency mechanical characterization method can serve as a fast and contactless method for determining Young’s modulus of ultra-thin membranes
Développement d'un modèle humain de stéatose hépatique non alcoolique (NAFLD) à l'aide de la technologie des organes sur puce
No full textNon-Alcoholic Fatty Liver Disease (NAFLD) is a growing global health concern, closely linked to the rise in obesity and metabolic syndrome. It encompasses a range of liver conditions, from simple fat accumulation (steatosis) to more severe forms like non-alcoholic steatohepatitis (NASH) and fibrosis, leading to cirrhosis and hepatocellular carcinoma. Despite its widespread impact and potential for severe health consequences, effective treatments for NAFLD remain elusive due to its complex and multifaceted dynamics. Indeed, the multifactorial nature of NAFLD involves several interactions among genetics, diet, lifestyle, and metabolic processes, making it difficult to solve. This challenge is exacerbated by the limitations of traditional research models, both in vitro and in vivo. These models often fall short when it comes to capturing the intricate dynamics of this disease with other health condition such as diabetes, hindering our ability to decipher its underlying mechanisms and develop targeted therapies. In this context, emerging technologies like organ-on-chip models offer new hope. By replicating the features of the microenvironment of the liver, these platforms can provide deeper insights into NAFLD pathogenesis and facilitating drug development. Therefore, this thesis tackles the need for a more physiologically relevant NAFLD model by harnessing the potential of organ-on-chip technology. The objective is to create a human NAFLD model that faithfully replicates the liver's microenvironment, including cellular interactions, fluid dynamics, and metabolic processes. First, experiments with HepG2/C3A cells were conducted to determine the most effective treatment for inducing liver steatosis, by analyzing mRNA levels and the expression of hepatic markers. Subsequently, we studied metabolomic profiles of the different conditions and correlated them with specific metabolic pathways. We also expanded the liver-on-chip model by incorporating hepatocyte-like cells (HLC) derived from hiPSCs, demonstrating the feasibility of HLCs for investigating steatosis and lipid accumulation.La stéatose hépatique non alcoolique (NAFLD) est une maladie chronique étroitement liée à l'augmentation de l'obésité et du syndrome métabolique. Elle englobe toute une gamme de troubles du foie, allant de l'accumulation simple de graisse (stéatose) à des formes plus graves telles que la stéato-hépatite non alcoolique (NASH) et la fibrose, qui conduisent à la cirrhose et au carcinome hépatocellulaire. Malgré son impact généralisé sur la santé, il n’existe pour l’instant aucun traitement médicamenteux approuvé de la NAFLD en raison de la dynamique complexe et multifactorielle de la pathologie ainsi que les limites des modèles de recherche in vitro et in vivo traditionnels. Dans ce contexte, les technologies émergentes tels que les modèles d'organes-sur-puce offrent un nouvel espoir. En reproduisant les caractéristiques du microenvironnement du foie, ces plateformes peuvent fournir des informations plus approfondies sur la pathogenèse de la NAFLD et faciliter le développement traitement médicamenteux. Par conséquent, cette thèse répond au besoin d'un modèle de NAFLD physiologiquement pertinent en exploitant le potentiel de la technologie des organes-sur-puce. L'objectif est de créer un modèle de NAFLD humain qui reproduit fidèlement le microenvironnement du foie, y compris les interactions cellulaires, la dynamique des fluides et les processus métaboliques. Tout d'abord, des expériences avec les cellules HepG2/C3A ont été menées pour déterminer le traitement le plus efficace pour induire la stéatose hépatique, en analysant les niveaux d'ARNm et l'expression des marqueurs hépatiques. Ensuite, nous avons étudié les profils métabolomiques des différentes conditions et les avons corrélés à des voies métaboliques spécifiques. Nous avons également amélioré le modèle de foie-sur-puce en incorporant des cellules hépatiques dérivées de cellules souches pluripotentes induites (hiPSC), démontrant la faisabilité de ces cellules pour l'étude de la stéatose non alcoolique
Ontology-based crisis simulation system for population sheltering management
No full textInternational audienceClimate change has led to an increase in the frequency and intensity of natural disasters, necessitating the development of efficient crisis management strategies for population sheltering. However, existing research on this topic primarily focuses on the use of public resources such as ambulances and fire trucks, which may sometimes be insufficient due to high demand and impacted locations, worsening the shortage of resources. This research introduces an ontology-based crisis simulation system for population sheltering management that focuses on the integration and distribution of citizen–volunteer drivers/vehicles into the evacuation process. Recognizing the limitations of public resources in current crisis management models, our approach incorporates citizen resources to enhance overall evacuation capacity. We develop an ontology to standardize crisis management knowledge, frame vehicle distribution as a recommendation problem, and design a simulation module incorporating a constraint-based recommender system. The proposed scenario illustrates how the simulation system can recommend citizen resources during crisis situations by considering the constraints to be satisfied. With our system, we aim at helping stakeholders to be prepared for various disaster scenarios: optimizing resource allocation and reducing time to make decisions by decision-makers
Acoustic Velocity Estimation in the Presence of Steady Flow Using Particle Image Velocimetry
No full textInternational audiencePhase-locked PIV measurement technique is used to estimate the acoustic velocity in the presence of turbulent flow inside a rectangular duct. The acoustic field is generated by compression drivers mounted on the sides of a rectangular duct. The PIV measurements are synchronized with the compression drivers. The measured velocity fields can be decomposed to mean flow velocity, turbulent fluctuations and acoustic velocity. A post-processing technique is proposed to extract the acoustic velocity field from the total measured velocity field. Also, the uncertainty of the estimated acoustic velocity is calculated using two different techniques, namely peak ratio method and particle disparity method. The estimated acoustic velocity agrees with the acoustic velocity estimated from classical microphone’s measurement technique. The estimated uncertainty of the acoustic velocity is found to be 18%
Evolution of Bladder Cancer Estimated by Using a State-Space Model with a Semi-Markov Process and Censored Data: A Case Study
No full textInternational audienceWe consider a Semi-Markov Process (SMP) to model the evolution of bladder cancer, which takes different states over time. Amulti-state model has been constructed and applied to data collected from 847 patients during a period of fifteen years. Biomedicinedatabases usually contain censored data and this study shows that,despite this, a good fit of the main survival measures is achieved byusing our specific model. This paper aims to present estimators forthe semi-Markov kernel, the survival function and the mean timeto disease progression. The strong consistency properties of the estimators are proved
Effects of direct sulfonation on the catalytic activity and recyclability of novel lignin-based solid acid catalysts from agri-food waste
No full textInternational audienceCatalytic systems derived from lignin are emerging as quite efficient and profitable materials in many catalyzed transformations. However, these catalysts have been predominantly synthesized by carbonization. Alternatively, we prepared direct sulfonation lignin (DSL) and compared it to the carbonized-sulfonated lignin (CSL) catalyst, aiming to reveal the effects of direct functionalization of lignin on its catalytic performance and to simplify its preparation. Both catalysts were well characterized by several physicochemical techniques, and their catalytic activities were assessed by catalyzed esterification. Using CSL, the yield reached 94.11 % under the optimal conditions (60 °C, 4 h and 50 mg loading), while DSL yielded 93.97 % with only 2 h under the same conditions, which is attributed to the abundant catalytic active sites in DSL (0.62 mmol/g of SO3H against 0.39 mmol/g for CSL). Furthermore, the activation energies were found to be 21 and 16 kJ mol−1 for CSL and DSL, respectively, suggesting that esterification can occur with less energy input using DSL. Reusability showed that leaching of SO3H groups and mass loss are inherently responsible for deactivation. However, both lignin-based catalysts show good stability and can be reused for 4 successive cycles. Direct lignin functionalization can be an alternative to conventional catalyst processing
Editorial: Risk assessment of mycotoxins in food
No full textInternational audienceSinapine is a phenolic compound found in mustard (Brassica juncea) seed meal. It has numerous beneficial properties such as antitumor, neuroprotective, antioxidant, and hepatoprotective effects, making its extraction relevant. In this study, the extraction of sinapine was investigated using three methods: (i) from a mustard seed meal defatted by a supercritical CO2 (SC-CO2) pretreatment, (ii) by the implementation of high-voltage electrical discharges (HVEDs), (iii) and by the use of ultrasound. The use of SC-CO2 pretreatment resulted in a dual effect on the valorization of mustard seed meal, acting as a green solvent for oil recovery and increasing the yield of extracted sinapine by 24.4% compared to the control. The combination of ultrasound and SC-CO2 pretreatment further increased the yield of sinapine by 32%. The optimal conditions for ultrasound-assisted extraction, determined through a response surface methodology, are a temperature of 75 °C, 70% ethanol, and 100% ultrasound amplitude, resulting in a sinapine yield of 6.90 ± 0.03 mg/g dry matter. In contrast, the application of HVEDs in the extraction process was not optimized, as it led to the degradation of sinapine even at low-energy inputs
Free vibration analysis of thin to thick straight or curved beams by a solid-3D beam finite element method
No full textInternational audienceA solid-3D beam finite element method is presented for the vibration analysis of thin to thick beam-like structures. This method is efficient for a spatial beam and considers all mechanical effects: membrane, bending and torsion. The structure is discretized with solid elements and contains several elements throughout the cross-section. Displacement fields of first-order or higher-order beam theories are met by directly applying kinematic relations on the solid finite element model, throughout the cross-section. This leads to a set of linear equations applied at slave nodes. Only the master nodes are kept in the final model, resulting in a model size reduction. The effectiveness of this method is demonstrated through two numerical examples, including a straight and a curved beam. The modal shapes and natural frequencies obtained by the proposed method are compared with the complete solid model and classical beam model. The size of these solid-beam models is slightly larger than that of an approach with classical beam element
L'autonomie: un concept support au déploiement des méthodes de management de projet hybrides dans les projets industriels?
No full textInternational audienceCet article présente le concept d'autonomie dans le cadre du management de projet. D'abord, une discussion théorique analyse ce concept et le présente comme étant au cøeur des principes agiles de management des projets. Partant de l'hypothèse qu'il doit être intégré aux approches de management de projets hybrides pour ne pas dénaturer leur pertinence, une proposition de déploiement est faite. Elle s'appuie sur une échelle comportant 6 niveaux d'autonomie construite en s'appuyant sur 26 entretiens réalisés auprès de 21 praticiens dans le secteur automobile. Le caractère dynamique de l'autonomie est présenté ainsi que les tensions entre autonomie et responsabilité puis entre autonomie et intégration. Nous en déduisons des principes, organisations et méthodes qu'il faudrait mettre en øeuvre pour bénéficier des avantages de l'autonomie sans pâtir de ses limites : principe de découpage en sous-projet, d'identification des spécificités des sous-projets et de leurs équipes pour y associer un niveau d'autonomie initial, puis de mécanismes de régulation et de coordination entre équipes