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Description en espaces de chemins et méthode de Monte Carlo pour les transferts thermiques couplés dans les structures fluides et solides, une approche compatible avec l'informatique graphique
No full textThe present manuscript deals with the coupling of thermal heat transfers. More precisely, it adresses this coupling by making use of the Monte Carlo method and the sampling of random paths. This choice was made in the perspective of building algorithms that do not present constraints regarding the complexity of the studied geometry. Indeed, the combined use of this kind of statistical approaches, and acceleration tools coming from the image synthesis community, already allowed for an exact resolution of radiative transfer in arbitrary geometries. Regarding diffusive heat transfers, exact results using random paths are only achievable in academic configurations. Thus, approximate random paths are commonly used to account for this kind of thermal transport. Among the possible choices, we will use random paths built on ray tracing, therefore allowing to benefit once again from all the advantages of the tools developed in computer graphics. A proof of concept of the insensitivity of the computation time of the resolution of thermal transfers in porous exchangers to the number of pores by making use of conducto-convecto-radiative random paths will be presented. Beyond this result, an analysis of the behaviour of this method in ducts heat exchangers will allow to clarify when this kind of insensitivity can indeed be observed. This analysis will induce the concept of thermal thickness, by analogy with optical thickness for radiative transfer.Les travaux présentés dans ce manuscrit abordent la thématique du couplage des transferts thermiques. En particulier, ils s’inscrivent dans une réflexion actuelle autour de l’échantillonnage de chemins aléatoires par la méthode de Monte Carlo. Ce choix est justifié par un souhait d’obtenir des algorithmes ne présentant pas de contraintes sur la complexité des géométries étudiées. En effet, l’utilisation conjointe de ce type d’approches statistiques et des outils d’accélération de la synthèse d’image (grilles accélératrices) permet d’ores et déjà une résolution exacte du transfert radiatif en géométrie quelconque. Pour les transferts thermiques de type diffusif, l’exactitude des approches en espaces de chemins n’est atteignable que pour des configurations simples. On choisit donc d’utiliser des chemins statistiques approchés pour rendre compte de ce type de phénomènes thermiques dans des géométries quelconques. Parmi les choix disponibles, on retiendra des espaces de chemins construits autour du lancer de rayon, qui permettront donc de bénéficier de l’ensemble des avantages des outils développés par la communauté de l’informatique graphique. Une preuve de concept de l’insensibilité du temps de calcul au nombre de pores de la résolution thermique d’un échangeur poreux par l’utilisation de marches aléatoires conducto-convecto-radiatives sera ainsi présentée. Au-delà de ce résultat, une analyse du comportement de la méthode sur des échangeurs à canaux permettra de classifier des situations d’insensibilité, ou pas, à la complexité des milieux poreux étudiés. La capacité à expliquer les limites de cette insensibilité et le comportement de ce temps de calcul fera alors émerger un concept d’épaisseur thermique homologue à la problématique de l’épaisseur optique en transfert radiatif
Corrélation entre taux de service, taux de charge et paramètres du DDMRP : utilisation d’abaques réalisés par simulation
No full textLe congrès a pour titre "Nouvelles avancées et défis pour des industries durables et avisées"International audienceLe Demand Driven Material Requirements Planning (DDMRP) est une méthode assez récente mêlant gestion à flux poussé et à flux tiré. Bien qu’elle se dise être la solution aux limites des méthodes traditionnelles, la méthode DDMRP fonctionne à capacité infinie : on lance des ordres de fabrication ou d’approvisionnement selon une logique de recomplètement des stocks définis comme buffers. Cet article propose une évaluation de la gestion de capacité, à l’aide d’abaques réalisés par simulation. Ces abaques permettent de corréler le taux de charge d’une ressource goulot à un taux de service en prenant en compte l’un des paramètres de la méthode DDMRP : le Decoupled Lead Time (DLT). Ils permettent également de connaître jusqu’à quel taux de charge ces DLT sont représentatifs des temps de défilement des ordres de fabrication. En conclusion, il semblerait plus intéressant de chercher à maîtriser les temps de défilement (en jouant sur la capacité) plutôt que d’ajuster le paramètre DLT
Pyrolysis and gasification of solid waste and its components in a lab scale induction-heating reactor
No full textInternational audienceThe present study investigates the thermochemical conversion of solid recovered fuel, represented by selected “model materials”. A laboratory-scale induction heated device was specifically developed to achieve gasification conditions close to those encountered in a fluidized bed reactor. The novel device can handle up to 5 grams of solid, allowing fast heating rates (near 70°C/s) and a homogeneous distribution of temperature all along the reactor. Pyrolysis tests of a SRF sample and four model materials (Polyethylene (PE), Polyethylene Terephthalate (PET), beech wood, cardboard) were performed at 800°C. The yield and composition of the produced gas for each sample were determinated. Experimental results will help to elucidate the relation between the initial components of waste derived fuels and the obtained reaction products
An AI framework and a metamodel for collaborative situations: Application to crisis management contexts
No full textInternational audienceIdentifying, designing, deploying and maintaining accurate collaborative networks of organizations (e.g. responders in a crisis situation) are key activities in nowadays ecosystems. However, there is a lack regarding formal approaches dedicated to characterize collaborative networks of organizations. Formal descriptions of collaborative situations, that could be used, transformed, computed and exploited would be of great benefit for the quality of such collaborative networks. This article presents a model‐based AI framework for describing collaborative situations and the associated formal metamodel dedicated to be instantiated to characterize collaborative situations in a very wide range of application domains. This metamodel (describing collaborative situation between organizations) is structured according to four complementary dimensions: the context (social, physical and geographical environment), the partners (the involved organizations, their capabilities resources and relations), the objectives (the aims of the network, the goals to be the achieved and the risks to avoid, etc.) and the behaviour (the collaborative processes to be implemented by the partners to achieve the objectives in the considered context). Besides, this metamodel can be extended for some precise application domains. This article focuses on this mechanism in the specific context of crisis management
Measurement of Elastic and Rotation Fields during Irreversible Deformation using Heaviside-Digital Image Correlation
No full textInternational audienceThe recent development of the high resolution and discontinuity-tolerant digital image correlation technique enables the extraction of discontinuities within a displacement field. The technique provides quantitative analysis of discontinuities arising from slip, shear bands, cracks, and grain boundary sliding in a variety of material systems, including polycrystalline metallic materials. The discontinuity-tolerant digital image correlation method can be implemented to retrieve not only quantitative discontinuity analysis but also the local strain and rotation fields that operate near these discontinuities. The present implementation includes high-resolution digital image correlation (HR-DIC) measurements collected in a scanning electron microscope for analysis of both the plastic and elastic fields that develop during deformation of polycrystalline metallic materials. The combination of the discontinuity-tolerant DIC technique with the computation of internal gradients enables extraction of non-localized strain and rotation fields during plastic deformation of a nickel-based superalloy. Therefore the lattice rotation/expansion and plastic localization that occur during deformation can be determined in a single experiment. This method is validated using synthetic images with preset deformation, and experimental measurements using the electron back scatter diffraction (EBSD) technique
Formal Specification, Implementation, and Evaluation of the AdoBPRIM Approach
No full textInternational audienceModeling is one of the fundamental aspects of Risk-aware Business Process Management. The conceptualization of new modeling approaches needs to integrate all abstraction layers of risk and business process concepts and requires a highly specialized knowledge in conceptual modeling foundations and formal specification of meta-models. This paper introduces a risk-aware business process modeling approach based on the BPRIM method. In order to comprehensively and unambiguously specify the proposed approach, we revert to the FDMM formalism. Furthermore, a corresponding software prototype called AdoBPRIM has been implemented using the ADOxx meta-modeling platform to assess the technical feasibility of the approach. The usability of the tool has been empirically evaluated and a healthcare process-based example is presented as a proof-of-concept. We show that the AdoBPRIM approach enables Risk-aware Business Process Management with an excellent usability. In summary, this paper constitutes a best-practice for formally specifying, technically implementing, and empirically evaluating modeling method conceptualizations
Foaming of PLA Composites by Supercritical Fluid-Assisted Processes: A Review
No full textInternational audiencePolylactic acid (PLA) is a well-known and commercially available biopolymer that can be produced from different sources. Its different characteristics generated a great deal of interest in various industrial fields. Besides, its use as a polymer matrix for foam production has increased in recent years. With the rise of technologies that seek to reduce the negative environmental impact of processes, chemical foaming agents are being substituted by physical agents, primarily supercritical fluids (SCFs). Currently, the mass production of low-density PLA foams with a uniform cell morphology using SCFs as blowing agents is a challenge. This is mainly due to the low melt strength of PLA and its slow crystallization kinetics. Among the different options to improve the PLA characteristics, compounding it with different types of fillers has great potential. This strategy does not only have foaming advantages, but can also improve the performances of the final composites, regardless of the implemented foaming process, i.e., batch, injection molding, and extrusion. In addition, the operating conditions and the characteristics of the fillers, such as their size, shape factor, and surface chemistry, play an important role in the final foam morphology. This article proposes a critical review on the different SCF-assisted processes and effects of operating conditions and fillers on foaming of PLA composites
Toward an Aggregate Approach for Supporting Adaptive Sales And Operations Planning
No full textInternational audienceThe Demand-Driven Adaptive Enterprise (DDAE) model introduced by the Demand Driven Institute (DDI) few years ago becomes of prime interest for both scholars and practitioners. This research work is investigating the rarely studied strategic part of this DDAE model called Adaptive Sales and Operations Planning (AS&OP) process. One of the main issues regarding this strategic process is to determine how to model it through product family aggregates. Actually, literature analysis demonstrated that no solution exists to support such a process. This research work intends to solve this issue by designing a first AS&OP model allowing an aggregate reasoning. This proposal has been successfully tested on a illustrative but realistic example
Crisis Management Exercises in Virtual Reality
No full textInternational audienceIn crisis management, critical sites are required to carry out regular exercises to be prepared for a potential crisis. However, those exercises present a lot of drawbacks that reduce their efficiency: among other things, they are not frequent enough, not adjustable enough, too demanding and they are very expensive. The EGCERSIS project aims at using virtual reality to make fully configurable exercises to train in digital twins of actual critical sites. In this article, we present this project through a simple use case of a crisis in a subway station, involving three actors of crisis management
Gas Barrier, Rheological and Mechanical Properties of Immiscible Natural Rubber/Acrylonitrile Butadiene Rubber/Organoclay (NR/NBR/Organoclay) Blend Nanocomposites
No full textInternational audienceIn this paper, gas permeability studies were performed on materials based on natural rubber/acrylonitrile butadiene rubber blends and nanoclay incorporated blend systems. The properties of natural rubber (NR)/nitrile rubber (NBR)/nanoclay nanocomposites, with a particular focus on gas permeability, are presented. The measurements of the barrier properties were assessed using two different gases—O2 and CO2—by taking in account the blend composition, the filler loading and the nature of the gas molecules. The obtained data showed that the permeability of gas transport was strongly affected by: (i) the blend composition—it was observed that the increase in acrylonitrile butadiene rubber component considerably decreased the permeability; (ii) the nature of the gas—the permeation of CO2 was higher than O2; (iii) the nanoclay loading—it was found that the permeability decreased with the incorporation of nanoclay. The localization of nanoclay in the blend system also played a major role in determining the gas permeability. The permeability of the systems was correlated with blend morphology and dispersion of the nanoclay platelets in the polymer blend