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Experimental and Numerical Study of Expanded Graphite Packing Ring for Fugitive Emissions Applications in Valves
No full textInternational audienceNowadays, environmental protection and the energy transition are at the heart of global concerns and are driving action and efforts at every level. In this context, the nuclear, petrochemical and chemical industries are working thoroughly to control and reduce fugitive emissions from their valves in order to minimize their impact. Reduction of these emissions can be achieved through improvements in the sealing of stuffing boxes. The aim of this work is to develop the knowledge of stuffing boxes and more precisely the mechanical behavior of flexible graphite rings. First, an experimental study was conducted, based on the results of free compression tests and compression tests of a flexible graphite ring in a special apparatus imitating the operation of a valve stuffing box. Axial stress-strain curves are extracted from the free compression tests and from the compression tests of the packing in the casing as well as radial stress distribution in the special apparatus. Then, a finite element model reproducing the packing was performed. Material parameters of an original Hyper-Hysteresis behavior model [1] were determined to fit the stress-strain behavior of a single packing ring under load. Finally, experimental and numerical data was compared in order to determine the validity of the model
From Laboratory to Practice: Characterizing Fresh and Cured Printed Materials
No full textInternational audienceCompared with the cast concrete used in traditional construction methods, 3D concrete printing imposes new specifications in the fresh state (Roussel 2018; Nicolas et al. 2022) and induces a potentially more complex anisotropic mechanical behavior in the hardened state (Asprone et al. 2018; Mechtcherine et al. 2021, 2022; Bos et al. 2022). These new constraints require the implementation of a comprehensive characterization process throughout the lifecycle of the printed element and material. This process necessitates numerous tests at different phases of the printing project
Les algues marines : une piste pour de nouveaux aliments riches en protéines
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Ensuring Personal Data Compliance by integrating Legal Constraints into Digital Twin Design Methodology
No full textInternational audienceAdvancements of digital twin technology have brought new use cases involving the presence of personal data. Considering the importance of this data, ensuring compliance towards the applicable legislation is mandatory. Through European provisions and especially the GDPR, this study aims to point out the various legal implications linked to the presence of personal data in the digital twin. Ensuring that processing operations comply with European regulations is not only a necessity, but also a key factor in risk management. In this paper, we propose an innovative approach where these constraints are formalized and integrated into an existing design methodology for digital twins. This study focuses on industrial digital twins in connection with maintenance operations.When used for maintenance purposes, the use of a digital twin necessarily implies data sharing. These data flows must be considered and anticipated right from the design stage. It is necessary to conform to a framework that is comprehensible and accessible to its designers, to respect the binding rules linked to data processing in the architecture of the digital twin. To achieve a complete result towards compliance that is adapted to the specific use of the industrial digital twin, three steps will be discussed.Firstly, the legal constraints must be identified directly from the use cases of digital twin technology. Secondly, the provisions of the GDPR are taken as a starting point to propose concrete measures that can be integrated when designing digital twins (record of processing activities, Data Protection Impact Assessment or DPIA, erasing policy). Finally, all these compliance operations will be brought together in a proposed methodology directly applicable to the design of digital twins. The design of this methodological framework represents an innovation in the field of digital twins : to ensure compliance with European standards, provide a framework for its design, and raise awareness among stakeholders designing digital twins.</div
Inside the kink-bands of archaeological flax artefacts via sub-micrometer resolution micro-CT: A comprehensive microstructural analysis to better understand degradation mechanisms of fibres
No full textInternational audienceThis work explores how the morphology of kink-band zones in flax fibres impacts the mechanical properties of the elementary fibres. Kink-bands are structural defects and are particularly sensitive to physical and biological stresses, on isolated fibres or in bio-based composite materials. To this end, a panel of archaeological samples from different time periods and preserved under different environmental conditions were selected and studied using synchrotron micro-tomography. It is demonstrated that although kink-bands are generally more numerous in ancient fibres, their degree of severity is sometimes less. This underlines the importance of fibre extraction methods, which are principally responsible for kink-band formation. The results also show that kink-band are weaknesses points, allowing rapid development of internal porosity (up to 25 %) when the fibres are used or stored in extreme environments, and that this porosity can also extend to healthy areas of the fibres. However, in some cases, even after millennia of conservation, it appears that the fibres can present morphologies comparable to modern samples, probably due to their good initial quality. Thanks to the findings of the present work, simplified schemes of degradation in kink-band zones, useable on single fibres but also in composite materials, are proposed. These results confirm the importance of fibre extraction processes on fibre quality and durability, and subsequent use for sustainable and high-performance composite materials and textiles
Pseudoalteromonas Strains as Biofilm Control Agents in Ostrea edulis Aquaculture: Reducing Biofilm Biovolume While Preserving Microbial Diversity
No full textInternational audienceBiofilms in aquaculture tanks pose significant challenges, hindering cleaning processes and contributing to antibiotic resistance. This study investigated the effects of four Pseudoalteromonas strains on flat oyster (Ostrea edulis) rearing, with a specific focus on biofilm control and microbial communities. After confirming the safety of these strains for O. edulis, we monitored biofilm development and bacterial communities during a 4-month sexual maturation period. Biofilm biovolume was quantified using confocal laser scanning microscopy (CLSM), and bacterial community composition was analyzed via 16S rRNA gene metabarcoding of both biofilm and seawater samples. Our results revealed differences in bacterial community structure between biofilms and seawater. Furthermore, the presence of specific Pseudoalteromonas strains significantly impacted the composition of bacterial communities within the tanks. β-diversity analyses demonstrated that each strain exerted a unique influence on the bacterial community structure. Some Pseudoalteromonas strains effectively reduced biofilm biovolume without negatively impacting bacterial richness or diversity. These observations suggest that certain Pseudoalteromonas strains can effectively control biofilm formation while maintaining a diverse and potentially beneficial microbial community in O. edulis rearing tanks. The use of these strains as additives in aquaculture systems could offer several advantages, including reduced cleaning time and costs and a potential decrease in biocide usage
Evaluating the accuracy of electrochemical techniques in predicting the industrial alkaline hydrogen production electrolyzer performance: Impacts of electrocatalyst surface changes
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Water impact of V-shaped wedge at constant velocity: Influence of deadrise angle and stiffness panels
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Coupling of X‐AES Transitions and XPS Photopeaks to Assess the Oxide Formation of Ga and in CuIn 0.7 Ga 0.3 Se 2 Material During Air Aging
No full textInternational audienceABSTRACT The solar absorber Cu (In 0.7 Ga 0.3 )Se 2 (CIGS) undergoes a process of evolution upon exposure to the atmosphere, resulting in the growth of oxide phases. This phenomenon can potentially affect the interfacial properties of CIGS, which in consequence may impact the efficiency of the solar cell. X‐ray photoelectron spectroscopy (XPS) is an appropriate method to analyze the degradation of CIGS upon air aging. However, many photopeaks and Auger lines of the constitutive elements are distributed along the energy scale, and the exact determination of the degradation within the CIGS absorber requires specific care to select peaks to consider to ensure that information arise from similar escape depths. In this study, we propose to investigate the kinetics of degradation of Ga and In at similar depths probed by coupling not only photopeaks but also X‐Auger electron spectroscopy (X‐AES) transitions in the absence of photopeaks in the same energy range. If photopeaks modeling is well established for In and Ga, a decomposition procedure of the X‐AES transitions must be developed. Both linear and nonlinear least square fitting were used and compared, starting to model CIGS, In 2 O 3 , and Ga 2 O 3 references to deploy it after on Auger transitions measured on aged samples. Thanks to the determination of the degradation ratios (oxide phase over CIGS phase) at 3, 7, and 9 nm depth, we show that both In and Ga exhibit similar kinetic of oxide formation, which proceeds gradually by O penetration through the subsurface of the material, this penetration being more and more attenuated deeper
Synthèse d’un opérateur de polarisation elliptique
No full textWe prove a theorem for transforming the polarization eigenstates of an arbitrary elliptical birefringent device into the eigenstates of another similar device by means of a birefringent device. The theorem is applied to synthesize a specific birefringent device from a circular birefringent device, and a practical setup is described. The resulting birefringence and birefringent axis of the synthesized device can be independently set or modulated. Finally, the theorem is extended to elliptical dichroic devices and elliptical polarizers.Se demuestra un teorema sobre la transformación, por medio de un birrefringente, de los estados de polarización propios de un birrefringente elíptico dado en los estados propios de otro dispositivo similar. El teorema se aplica para sintetizar un birrefringente elíptico dado a partir de un poder rotatorio, y se describe una configuración experimental. La birrefringencia y el eje del dispositivo así obtenido se pueden arreglar o modular de forma independiente. El teorema se generaliza a dispositivos dicroicos y polarizadores elípticos.Nous démontrons un théorème portant sur la transformation, au moyen d’un biréfringent, des états de polarisation propres d’un biréfringent elliptique arbitraire en états propres d’un autre biréfringent elliptique. Le théorème est appliqué à la synthèse d’un biréfringent donné à partir d’un pouvoir rotatoire, et un montage expérimental est décrit. La biréfringence et l’axe du biréfringent résultant peuvent se régler et être modulés indépendant l’un de l’autre. Le théorème est étendu aux dichroïques et aux polariseurs elliptiques