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Enhancing the Diffusion Channels of Silica‐Alginate Capsules for Microbial Encapsulation
No full textInternational audienceSilica‐alginate capsule (G‐0) has recently been used in fermentation processes to encapsulate microbial cells for several benefits, including facilitating continuous flow processes and simplifying cell recovery and reuse. However, these conventional silica‐coated alginate capsules suffer from poor diffusion channels, which are critical for efficiently transporting substrates and products. This study aimed to develop a novel method for producing silica‐coated alginate capsules with improved diffusion channels (G‐3). The Ca‐alginate capsule was fabricated via a simple dripping method, where a solution of calcium chloride (CaCl 2 ) and carboxymethylcellulose (CMC) was dripped into an alginate solution. For the traditional silica coating (G‐0), the alginate capsule was mixed with a silica source (hydrolyzed 3‐aminopropyl triethoxysilane) under specific conditions. In the modified method, glucose was introduced as a pore‐forming agent (PFA), with varying amounts (0.75, 1.5, and 3 g) resulting in capsules labeled G‐0.75, G‐1.5, and G‐3, respectively. The diffusion coefficient for G‐3 was found to be the highest, for example, at 313.15 K, it was calculated as compared to for G‐0. This finding highlights the effectiveness of PFA in enhancing membrane porosity and diffusivity, which is promising for microbial cell immobilization where mass transfer is a significant concern
Vers un Plan Industriel et Commercial orienté risque (Thèse sous embargo)
No full textIn an increasingly uncertain business environment, Sales and Operations Planning (S&OP) has become a priority for organizations seeking to balance demand and supply in the face of rapid market shifts, and unexpected uncertainties. Traditional S&OP processes often assume stable conditions, leaving companies unprepared for uncertainties. This thesis aims to integrate uncertainty management into S&OP, ensuring that S&OP decisions align with broader tactical and financial objectives under uncertain conditions. First, the thesis proposes a Risk-Driven S&OP Maturity Model, addressing the need to assess how organizations incorporate uncertainties into their S&OP processes. Second, the thesis proposes a Risk-Driven S&OP Process, offering a standardized, BPMN-based workflow for each S&OP sub-process, ranging from demand and supply reviews to financial integration and the final executive meeting. Third, the thesis proposes a Scenario-Based S&OP Driven by a Financial Calculation Model, an S&OP model designed with an emphasis on scenario planning and calculating financial KPIs. This model “financializes” each scenario's outcomes, producing metrics such as working capital requirement to guide data-driven S&OP decisions. The objective of this model is to help companies weigh the trade-offs of various decisions and select the best based on the financial KPIs.To validate these contributions, the thesis conducted an industrial use case involving a French aerospace company manufacturing aluminum parts under uncertain demand, which demonstrated the applicability and relevance of the proposed solutions.Dans un environnement commercial de plus en plus incertain, le Plan Industriel et Commercial (PIC) s'impose comme une priorité pour les entreprises qui cherchent à équilibrer la demande et l'offre face à l'évolution rapide des marchés et aux incertitudes. Cette thèse vise à intégrer la gestion des incertitudes au sein du PIC, afin de garantir que les décisions PIC demeurent en phase avec des objectifs tactiques et financiers plus larges, même dans des conditions incertaines. Premièrement, la thèse explore un modèle de maturité PIC orienté risque qui a pour objectif de répondre au besoin d'évaluer la manière dont les entreprises prennent en compte les incertitudes dans leurs processus PIC. Ensuite, la thèse propose un processus PIC orienté risque, offrant un flux de travail standardisé (sous forme de BPMN) pour chaque sous-processus PIC, qu'il s'agisse de la revue de la demande, de l'offre, de l'intégration financière ou de la réunion exécutive finale. Enfin, la thèse explore un PIC basé sur des scénarios pilotés par un modèle de calcul financier. Ce modèle “financiarise” les résultats des scénarios, en générant des métriques telles que le besoin en fonds de roulement, permettant ainsi de guider des décisions PIC. Pour valider ces contributions, la thèse présente une étude de cas industrielle chez une entreprise aéronautique française produisant de pièces en aluminium sous une demande incertaine. La mise en place des trois contributions a permis à l'entreprise de comparer en temps réel divers scénarios d'incertitude, d'estimer les pertes de revenus et de choisir des actions de contingence, démontrant l'applicabilité et la pertinence des solutions proposées
Synergy between microstructure anisotropy and size effects on the ductile failure of Hastelloy X printed by Laser Power Bed Fusion
No full textInternational audienceThis work addresses the effect of the microstructural anisotropy, both morphological and crystallographic due to fabrication strategy, and the size-effects on the fracture behavior of Hastelloy X superalloys printed by Laser Power Bed Fusion (LPBF-HX). It aims at specifically investigating the role played by crack orientation (perpendicular or co-linear to sample lasing planes) on the fracture toughness values of LPBF-HX. Micro-cantilever bending tests have been conducted on vertically or horizontally built specimens to estimate the fracture toughness at the microscopic scale depending on the initial notch orientation. LPBF-HX results in complex microstructural features at the micro- and mesoscale, which significantly impair the fracture mechanisms. At both microscopic and macroscopic scales, cracking occurs along with a ductile tearing. A simple analytical model has been applied to account for the size effect on the fracture behavior depending on the building direction and notch orientation. This model provides internal characteristic lengths, , which is a key parameter for transition rules from small to large scale. In horizontal specimens, the value of is equal to 1.33 mm, whereas it slightly increases to 1.57 mm in vertical specimens. The knowledge of the size effect law using internal characteristic lengths is crucial for the determination of the R-curve at different scales
Vers une gestion orientée flux et processus des systèmes éducatifs
No full textEducational systems face VUCA conditions that blur governance and strain resources. This dissertation delivers two methodological advances: EducSCOR, a SCOR-inspired reference model for education that structures 13 orchestration and six core processes into a unified performance language ; and Skill-Flow, a discrete-time flow model capturing the Learner → Graduate → Trainer loop and its Residual Capability Indicator (RCI), which quantifies a system's ability to regenerate critical human capital. An abductive design fuses process mapping, Hollnagel's resilience grid and capacity simulations. Applied to the French Compagnons du Devoir craft-training network, the models expose capacity bottlenecks and enhance strategic coherence through a continuous improvement cycle. The thesis demonstrates that process and flow-oriented management helps align governance, operations and metrics, prevents skill-rupture dynamics, and supports decision-making under instability. Beyond the case study, it opens avenues for standardised diagnostics of educational organisations, integration of prospective simulation into public policy, and extension of the models to other education and training sectors.Dans un contexte VUCA où les systèmes éducatifs peinent à rester lisibles et résilients, cette thèse propose deux artefacts : EducSCOR, adaptation du modèle SCOR aux processus éducatifs (13 processus d'orchestration / 6 métiers) pour aligner stratégie, opérations et indicateurs ; Skill-Flow, modèle discret simulant la boucle Apprenant → Qualifié → Formateur et son Indicateur de Capabilité Résiduelle (ICR), qui mesure la capacité de renouvellement des compétences clés. Une démarche abductive combine cartographie de processus, grille de résilience de Hollnagel et simulation de flux. L'étude du réseau des Compagnons du Devoir révèle des goulots capacitaires et un gain de cohérence stratégique grâce à des boucles d'amélioration. Le travail démontre qu'une gestion orientée processus et flux a le potentiel de prévenir les ruptures de compétences et outille la décision dans des environnements instables. Ces résultats ouvrent des perspectives pour la standardisation des diagnostics de systèmes éducatifs, l'intégration de la simulation prospective dans les politiques publiques et l'extension du modèle à d'autres secteurs d'éducation et de formation
Comparing the kinetic and thermodynamic behavior of mango kernel and its two main components through pyrolysis and combustion
No full textInternational audienceThe agro-industrial and food industry generates tons of bio-waste such as mango waste (Mangifera Indica) that has a negative impact on the environment if not managed effectively. This study characterized the physicochemical properties and thermal behavior of mango kernel and its components (seed and pericarp) to propose a suitable thermochemical conversion route for its valorization. The study revealed that mango kernel (MK), seed (MS), and pericarp (MP) possess high volatile matter and fixed carbon contents, making them well-suited for pyrolysis to generate biofuel and biochar. MK and MS showed better combustion performance than MP due to higher lower heating values (LHV) and lower ash content. Moreover, MK and MS exhibited greater potential for gasification and potassium recovery due to favorable thermal, chemical, and mineral compositions. Thermogravimetric analysis (TGA) using iso-conversional methods demonstrated significant thermal stability and non-spontaneous reactions across all samples, while Gibbs free energy changes (ΔG) indicated considerable energy extraction potential. Catalytic indices derived from metal content further confirmed the suitability of mango waste for thermochemical valorization. Although the components showed compatibility without negative synergistic effects, separating the seed and pericarp from the kernel could improve energy efficiency, product quality, and process flexibility. Kinetic analyses revealed activation energies (Ea) during pyrolysis ranging from 149–310 kJ/mol for MK, 190–407 kJ/mol for MS, and 157–366 kJ/mol for MP, with ΔG up to 194 kJ/mol. Combustion required lower activation energies, 122 kJ/mol for MK and ∼133 kJ/mol for MS and MP, indicating easier ignition of MK. Reaction mechanism modeling confirmed complex kinetic transitions with the conversion. These findings offer a solid foundation for optimizing the thermochemical conversion of mango waste into energy products and enabling the synthesis of advanced materials
Hyfill: heavy-duty hydrogen vehicles refuelling station modelling tool. description and validation
No full textInternational audienceThe heavy-duty transport sector is responsible for 25% of greenhouse gas emission from road transport and for 6% of total EU GHGs emissions. The EU Commission aim to reduce these emissions of 90% by 2040 (European Commission, 2024). Heavy -duty hydrogen fuel-cell vehicles (HD-FCEV) have the potential to reduce it. To develop the heavy hydrogen mobility sector, it is necessary to decrease the hydrogen cost at the dispenser and to ensure a safe and fast refuelling. Hence, hydrogen refuelling station (HRS) designs should guarantee performances in terms of rapidity and safety of the fillings, while remaining economically attractive. To achieve this goals, modelling HRS can allow to evaluate innovative designs or develop new refuelling protocols. This enables to support the realisation of innovative projects, as it allows to understand the thermodynamic behaviour of the station components and their interactions (Genovese et al., 2023). This is why ENGIE Lab CRIGEN developed in collaboration with IMT Mines Albi a HRS modelling tool named HyFill. It includes all the main components of a HRS: high-pressure cascade storage system, pressure-control valve, heat-exchanger, pre-cooling system, fuelling line, vehicle storage system (Rothuizen, 2013). This work presents the development of HyFill and focuses on the choices made to model the components. To predict with precision and low computational cost the thermodynamic behaviour of the station components, the model is built with a lump approach. Each component model is based on energy balance, mass balance and thermodynamic properties of hydrogen (H2) (Kunz and Wagner, 2012). For certain components, the use of empirical correlations is necessary for modelling. These correlations are either taken from the literature or supplied by the manufacturers. At the core of the HyFill tool is the tank model, which describes the gas thermodynamic behaviour during refuelling and defueling. The model considers the effect of tank geometry and material properties to model the heat transfer between gas, tank wall, and ambient. Validation work was conducted with experimental data from filling and defueling of several different tanks in various working conditions. HyFill can predict the final gas temperature with a precision of ±3 K. HyFill can be used to simulate the refuelling of a HD-FCEV, predict the performances of a given station, and test refuelling protocols. In perspective, the development of HyFill could enable the simulation of consecutive refuelling of vehicles, the prediction of the station performance on back-to-back refuelling and more complex scenarios. The final objective is to define a new methodology to conceive optimal design for heavy-duty HRS
Micro-thermoreflectometry applied to in situ monitoring of changes in the optical properties of a MCrAlY coating during high-temperature oxidation
No full textInternational audienceThe paper deals with the characterization of the formation of high-temperature oxides formed on the surface and subsurface in MCrAlY alloys, and more generally nickel-based single-crystal superalloys, using an in-situ method of measuring thermo-optical properties. The suggested method, denoted micro-thermoreflectometry, involves fullfield measurement of the bidirectional reflectivity at the microscale using high-resolution cameras operating in the visible and near-infrared (NIR) spectral range, with a spatial resolution of 0.625 µm. Prior to measurement, a reflectometric calibration of the thermo-reflectometry method was carried out to determine the model between the intensity delivered by each pixel and the reference value of the bidirectional reflectivity of a Lambertian surface given by a Spectralon® standard. This model was validated on Lambertian surfaces with attenuations of 80 and 50 % relative to Spectralon® by comparison with the bidirectional reflectivity measurement performed by Fourier's transform infrared spectrometer (FTIR). Both measurements are coherent and perfectly fitted for the three micro-thermoreflectometry measurement wavelengths. By measuring bidirectional reflectivity fields, the detection and the identification were performed on the various oxidation compounds that are formed either at the surface or beneath the semi-transparent Al 2 O 3 -layer. A multispectral image was provided revealing differences between oxides formed at the surface and subsurface of the MCrAlY alloys
Role of crystallographic and morphological textures on wear resistance of an additive-manufactured Ni-based superalloy
No full textInternational audienceThis study employs the LPBF process to design components with specific scanning strategies,particularly emphasising the crystallographic texture. The present study aims to assess the rela-tionships between the microstructural features and the tribological behaviour of a novel Ni-basedsuperalloy developed explicitly for additive manufacturing. The tribological tests are conductedwith a reciprocating ball-on-flat rig without lubrication at room temperature. The analysis of theas-built microstructures and wear tracks was primarily conducted using SEM and XRD techniques.A variety of scanning strategies are investigated to tailor the microstructures. The specific wear rateis sensitive to changes in microstructure, with values ranging from 2.82 ± 0.58 x 10−7mm3/(N.mm)to 4.75 ± 0.43 x 10−7mm3/(N.mm). However, it is observed that samples manufactured using dif-ferent scanning strategies but with the same resulting crystallographic texture exhibit differentwear rates. Consequently, the crystallographic texture does not significantly affect the wear rate.Cellular structure, in terms of size, morphology and heterogeneities among melt pools, and cover-age rate by oxidised layers exert a more pronounced influence. The SEM observations of the weartracks indicate that the primary main wear mechanisms are abrasive and oxidative wear
Detection and quantification of SF6 substitute g3 (C4F7N/CO2/O2) byproducts: An experimental and theoretical study
No full textInternational audienceSF6 is a most prevalent insulation gas widely used in the electrical industry worldwide, declared as one of six (GWP) global warming potential gases in the Kyoto Protocol held in 1999. The search to find alternatives to SF6 was challenging. In this regard, GE VERNOVA researchers proposed an insulation g3 gaseous mixture containing C4F7N/CO2/O2, which proved to be the most promising substitute for SF6. Thermoelectric stress in the circuit breaker decomposes the g3 (C3F7CN/CO2/O2) gas mixture in their corresponding byproducts. The byproducts could be toxic or corrosive in nature and should be identified and quantified with the help of GC-MS technology to maintain operator and instrument safety. For this instance, we developed the GC-MS and FTIR methodologies for the detection as well as quantification of prominent polluted gas molecules, ranging from ppm to % level. Furthermore, density functional theory (DFT) simulation could help us to determine the chemical reaction mechanism and their corresponding absorbed energies during the arcing process. Optimized GC-MS methodology gives us the range of byproducts, including CF4, C2F6, C3F8, CF3CN, C2F5CN, C2F2, (CN)2, CO, COF2, and (C2F7NH2O) amide, present in heavily arced g3 gas sample. Certain molecules, such as SiF(CH3)3, were also detected by the chemical reaction of the GC column with HF. Three standard gas samples containing CF4, C2F6, C3F8, CF3CN, and COF2 molecules in various concentration levels were employed for the calibration. The regression curve of the standard gases was established, and the slight movement of the curve was observed after the 60-day duration. However, the COF2 quantification was not possible by GC-MS due to the strong chemical reaction with column stationary phase and uneven peak area results in consecutive measurements. Thus, COF2 calibration via FTIR technology is established due to the utilization of only a gas cell in the infrared instrument without the interaction of the column with a standard sample for molecule separation. Furthermore, HF cannot be identified by GC-MS technology due to its limitation; therefore, we employ the GASTEC tube that quantifies the HF by color alternation and is also safe to use. Among all, CF4, C2F6, C3F8, CF3CN, C2F5CN, (CN)2, and COF2, HF are the main byproducts occurring during the breaking in a typical circuit breaker with a g3 gaseous mixture.The chemical reaction mechanism of g3 gas with the help of density functional theory is also investigated. Geometry optimization and transition state with one imaginary frequency were simulated by M062X hybrid functional with the combination of 6-311+G(d,p) basis sets, executed in Gaussian 16 software packages. Thermoelectric aging of the g3 gas mixture can open the various complicated channels of chemical reaction; nevertheless, we proposed the two main routes of decomposition coming from C4F7NO and C4F7NO2 intermediates, and a total of 34 and 6 chemical reactions can be obtained by their decomposition. Among the three primary dissociation reactions of the C4F7NO molecule, (R5) C4F7NO C3F3NO + CF4 and (R6) C4F7NO C2F5CN + CF2O, bond fission pathways are identified as the thermodynamically favorable route. The energy barrier values for these two reactions are 8.1 kcal mol-1 and 8.0 kcal mol-1, respectively. This paper could deliver a strong experimental and theoretical foundation for understanding the various natures of decomposition of byproducts in a diverse range generated during arcing in a typical circuit breaker
Comprehensive exploration of geometric effects in sonoreactors: An extensive comparison of KI dosimetry, luminol maps and calorimetric power
No full textInternational audienceThis study investigates sonochemistry results of Weissler reaction using a 20 kHz transducer immersed in three different glass vessels, under a total of 65 experimental geometrical configurations, already characterized in our previous papers through electrical, calorimetric and luminol measurements, and numerical simulation. In the first set of experiments, the transducer immersion depths is varied at constant liquid volume whereas in the second, the liquid level is altered at constant immersion. The study aims to identify the geometric conditions that maximize reaction rate, as measured by the concentration of triiodide ions obtained after a given reaction time, and the overall sonochemical efficiency , measuring the numbers of moles produced per joule dissipated in the liquid. By incorporating insights from the comparison between sono-chemiluminescence (SCL) of luminol and dosimetry, this study establishes connections between global sonochemical effects and luminol mapping. For the three vessels considered, both indicators and evolve non-monotonically in function of either immersion or liquid level, and exhibit extrema for some specific configurations. No definite correlation could be established between maximal sonochemical effects and the corresponding shape and size of the luminol bright zones. Furthermore, the production of does not correlate well with the volumetric energy density, suggesting that a fraction of the cavitation bubbles may heat the liquid without producing noticeable sonochemistry