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Solubility of cefuroxime axetil in supercritical CO2: measurement and modeling
No full textInternational audienceIn this study, an analytical dynamic method was optimized for small amounts of drugs and used to measure the solubility of cefuroxime axetil in supercritical CO2. After validating the experimental procedure with nimesulide, an active ingredient already studied in the literature, the solubility of cefuroxime axetil in supercritical CO2 was measured at temperatures varying from 308 to 328 K and pressures ranging between 8 and 25 MPa. Experimental values varied between 2.2 × 10-7 and 11.24 × 10-6 (in mole fraction) and a retrograde solubility behavior was observed.The solubility was correlated with semi-empirical density-based models: Kumar and Johnston, Mendez-Santiago and Teja, and Chrastil models. All three models successfully correlated the solubilities of cefuroxime axetil with an average deviation lower than 15 %
Carbon dioxide plasma treated PVDF electrospun membrane for the removal of crystal violet dyes and iron oxide nanoparticles from water
No full textInternational audienceHere we reported a reactive plasma treatment of polyvinylidene fluoride (PVDF) electrospun membrane by using carbon dioxide (CO2) plasma in order to reduce the hydrophobicity of the PVDF membrane and thereby used to remove toxic crystal violet dye (CV) and iron oxide (Fe2O3) nanoparticles from water. The demonstrated plasma treated PVDF electrospun membrane showed a decrement in the hydrophobicity after plasma treatment. Most of the microfiltration membranes based on PVDF were fabricated via phase inversion technique and solvent casting. The main drawback of these methods is that to obtain membranes with uniform pore size. Moreover, the membranes fabricated via phase inversion and solvent casting process have low surface area whereas in the membranes via electrospinning technique have interconnected pore structure with high surface area and uniform pore size. The contact angle of the neat PVDF electrospun membrane and plasma treated PVDF electrospun membrane were 141°and 102°respectively. FTIR studies revealed that, after CO2 plasma treatment, highly negative carboxylate (COO-) groups were formed on the surface of the PVDF electrospun membrane. With the 10 mg/L of crystal violet (CV) aqueous solution, the dye adsorption capacity was 1.368 mg/g of the membrane for neat PVDF membrane and 3.84 mg/g of the membrane for plasma treated PVDF membrane. It was found that, the CO2 plasma treated PVDF membrane had two- or three-times greater adsorption capacity then neat PVDF membrane against crystal violet dyes which was due to the strong electrostatic interaction between the highly negative carboxyl groups on the surface of plasma treated PVDF electrospun membrane and protonated CV dye. Both neat PVDF membrane and plasma treated PVDF membrane showed excellent filtration capacity against Fe2O3 nanoparticles. The demonstrated plasma treated PVDF membrane could successfully remove iron oxide nanoparticles and crystal violet dyes from water via size exclusion and adsorption mechanism respectively
From municipal solid wastes to green hydrogen production: case study of VABHYOGAZ3 project
No full textInternational audienceMunicipal solid wastes (MSW) are generally managed by incineration and landfill as the two major technologies in the world. The incineration has advantages to be fast, to strongly reduce wastes’ volume and to limit land utilization. However, it needs high initial investment cost, high operation cost for flue gas treatment as well as high maintenance cost. On the contrary, landfill is much less expensive in terms of investment, operation and maintenance. But the kinetic of wastes’ degradation is slow and the deployment of this technology particularly needs large land surface. In general, countries in development adapt landfill while developed countries use both techniques. As example, France manages around 70% of its MSW by incineration and around 30% by landfill.Landfill allows transforming slowly MSW to biogas as the main product, commonly called landfill gas. It mainly contains CH4, CO2, and notable amounts of N2, O2 and various pollutants (H2S, SO2, light hydrocarbons, siloxanes etc.). In Europe, landfill gas must be nowadays recovered for valorization to avoid the emission of CH4, CO2 – two major greenhouse gases – into the atmosphere. Landfill gas can be purified and enriched to meet the quality of natural gas by partially removing CO2 before being injected in gas network. This is now deployed at large industrial scale in developed countries, i.e. France. Laboratory and industrial research focuses now on the valorization of landfill gas into high added-value products like green hydrogen for mobility. This is the main objective of the current VABHYOGAZ3 project in France.VABHYOGAZ3 project aims to develop a complete process to transform landfill gas to liquid hydrogen for utilization in hydrogen vehicles. This process includes different steps: landfill gas reforming, water-gas-shift, PSA separation, hydrogen liquefaction, transport, and distribution, as illustrated in the scheme below. This technology can be now commercialized by the consortium of the VABHYOGAZ3 project
Rolling process modelling & related challenges towards floating roll simulation
No full textInternational audienceThe existing Finite Element simulation of Roll Compaction Process (RCP) [1] was performed using an Arbirary Lagrangian Eulerian (ALE) formulation. In this method, the mesh and therefore the final shape and the gap need to be fixed prior the simulation. This limitation does not allow modelling fluctuation of the gap with the flow change of incoming materials. This paper presents a Coupled Eulerian-Lagrangian (CEL) model, attempting to take into account the fluctuation of the gap by allowing simulating the free flow of the material between and outside the rolls. The increase or the decrease of the gap is managed by a spring-stiffness with a given rigidity and miming the action of the hydrostatic pressure, which controls the gap between the rollers. Preliminary results clearly show an increase in the gap between the rollers as a function of the stiffness of the spring and the force reaction of the roller. This work, still at the initial stage, constitutes a promising basis for further development of the model to simulate the actual operation of a roller press (adjustment of the gap as a function of the flow of material controlled by the feed screw)
Simulation de l’acoustique, du champ de bulles et du streaming dans un sono-réacteur à lit fluidisé
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Toward the use of Symbolic Monte Carlo for combined heat transfer in complex geometries
No full textInternational audienceThe interest of using SMC (a) method to obtain a transfer function for combined conduction-convection-radiation coupling in complex geometries is presented. The SMC method was successfully used for radiative transfer in a decoupled manner, but no attempt has been yet reported to extend its use to radiation coupled with other modes. The transfer function 1) enables to decrease the computation time when the function needs to be evaluated numerous times for different values of the parameters as in optimization or control algorithms and 2) can be used an analysis tool for inverse problems
Visual predictive control of robotic arms with overlapping workspace
No full textInternational audienceThis paper deals with multi-arms fruits picking in orchards. More specifically, the goal is to control the arms to approach the fruits position. To achieve this task a VPC strategy has been designed to take into account the dynamic of the environment as well as the various constraints inherent to the mechanical system, visual servoing manipulation and shared workspace. Our solution has been evaluated in simulation using on PR2 arms model. Different models of visual features prediction have been tested and the entire VPC strategy has been run on various cases. The obtained results show the interest and the efficiency of this strategy to perform a fruit picking task
Digital Image Correlation method for monitoring tensile tests at high temperature. Part 1: comparing the speckle quality produced by various methods at high temperature
No full textNational audienceIn order to improve the thermo-mechanical models proposed for hot forming processes, the identification and validation of the numerical simulations could take advantage of continuous kinematic full field measurements achieved during different production steps. This kind of measurements could especially be obtained by Digital Image Correlation. Although this method is relatively mastered at room temperature, it is more complex to implement at high temperature (typically from 600°C to 800°C). This is due to a number of factors, including the mirage effect (phenomena of gradient of refractive index), the loss of image contrast and the speckle flaking observed during thermo-mechanical experiments. This study focus on fabrication methods of speckle and its characteristics at high temperature. The first part introduces different techniques for creating the speckle (paint spraying, anodization, laser engraving and combination between anodization and laser engraving). In order to compare these methods, the same mask (prepared from a synthetic image) is systematically used. The pattern obtained therefore meets certain criteria (density, size, correlation length, etc.) and can be reproduced. Images of the speckled surface are then captured at different temperatures and compared in term of contrast, gray level distribution, etc. The first results show that the speckle obtained by combining laser marking and anodizing leads to better contrast when compared with other techniques at room temperature. However, this result is no more certain at high temperature because of the oxidation layer that develops. In the second part, the adhesion on the surface of a Ti-6Al-4V alloy of the speckles produced using different methods is evaluated. Tensile tests performed at high-temperature with large strain are then performed. In conclusion, a guideline for choosing an appropriate speckle deposition method for studying conditions of hot forming process is suggested.L'objectif globale de cet étude est de développer une méthodologie afin d'améliorer la mesure cinématique pendant des essais mécaniques sur le matériau d'alliage de titane dans condition d'emboutissage à chaud. Afin de contribuer à l'optimisation de la méthode corrélation d'image (DIC) dans ce contexte spécifique, la génération de mouchetis adapté aux conditions de mesure est proposée. Dans un premier temps, les mouchetis préparés par plusieurs méthodes différentes sont comparés en termes de la qualité. Pour pouvoir comparer objectivement, un mouchetis numérique est systématiquement utilisé. Dans un deuxième temps, les images de surfaces mouchetées sont capturées à différentes températures et puis comparées selon plusieurs critères variées par exemple le contraste, le niveau de gris, etc…. A température ambiante, le premier résultat montre que le mouchetis préparé par la méthode anodisation présente le meilleur contraste. Cependant, à haute température, cette observation est plus valable à cause de l'oxydation développée. Troisièmement, l'adhésion du mouchetis sur la surface des éprouvettes en alliage de titane Ti-6Al-4V en grande déformation est évaluée. Mouchetis préparé par la méthode gravure laser résiste à la rupture. En même temps, le mouchetis préparé par la peinture s'écaille au début de la déformation plastique. En conclusion, une suggestion de choix du mouchetis adapé aux conditions de mise en forme à chaud est proposée
Representative Benchmark for Concurrent Product and Process Configuration Problem: Definitions and Some Problem Instances
No full textInternational audienceThis paper considers the Optimization of Concurrent Product and Process Configuration problems (O-CPPC) that satisfy various number of criteria, which rely on the customer’s requirements and the objectives of the company. Various works have proposed evolutionary optimization algorithms dedicated to this concurrent configuration problem with generic model propositions due to this paper is relevant to the evaluation of these optimization algorithms. The aim of this paper is to define a set of instances of the generic model that represent a large family of problems. First, a background of the Optimization of Concurrent Product and Process Configuration problems is introduced. Next, some basic definitions of an O-CPPC generic model are analyzed. Then, the main general parameters to define an instance are presented (Product Structure, Process Structure, Model Size and Model Constraint Density) in order to propose some general evaluation tests. And finally, to be consistent with the previous works, some basic cases are described to show how to deal with this kind of problem in an organized way