HAL Evry
Not a member yet
19237 research outputs found
Sort by
Tailoring functional properties of Pb (Zr, Sn, Ti)O3 ceramics via lanthanum doping at lower sintering temperature
No full textInternational audienceThe performance of lead-based ceramics in energy storage applications is often hindered by their low energy density and inadequate phase transition properties. The (Pb, La) (Zr, Sn, Ti)O3 (PLZST) antiferroelectric ceramics have attracted much attention as energy storage materials. In this work, ceramics Pb1−1.5x Lax (Zr0.93Sn0.05Ti0.02)O3 at (x = 0.015, 0.025, 0.035, and 0.045) were prepared using a solid-state method, and their dielectric and energy storage characteristics were studied. It was observed that integrating lanthanum significantly improved the perovskite structure, reducing grain size and boosting the polarization intensity. In this present study, a recoverable energy storage density (Wrec) of 6.24 J/cm3 was achieved under an electric field of 270 kV/cm. Moreover, these ceramics demonstrated an impressive discharge energy density (Wdis), with 90% of the energy released within 1.29 μs. The outcomes show that PLZST is a highly effective material for advanced energy storage, pulse power applications, and paving the way for technological advancements
Un modèle heuristique des représentations de l’IA en GRH: Analyse croisée des discours professionnels et de la littérature académique
No full textInternational audienceCette recherche examine les points de convergence et de divergence entre les approches académiques de l’intelligence artificielle (IA) et les perceptions de son usage par les professionnels des ressources humaines au sein des organisations. Elle mobilise une méthodologie originale articulant analyse de discours et scoping review, interprétée à travers le prisme de la théorie de l’appropriation technologique. Les résultats mettent en lumière plusieurs enjeux communs aux chercheurs et aux praticiens, ouvrant la voie à la construction d’un modèle heuristique. Par ailleurs, les divergences identifiées dans les représentations offrent des pistes prometteuses pour de futures recherches sur l’intégration de l’IA en gestion des ressources humaines
Accuracy of tracer-based methane flux quantification: underlying impact of calibrating acetylene measurements
No full textInternational audienceFacility-scale methane emission fluxes can be derived by comparing tracer and methane mole fraction measurements downwind of a methane emission source, where a co-located tracer gas is released at a known flux rate. Acetylene is a commonly used methane tracer due to its availability, low cost and low atmospheric background. Acetylene mole fraction can be measured using infrared gas analysers such as the cavity ring-down spectroscopy Picarro G2203. However, failure to calibrate tracer gas analysers may influence methane flux estimation, due to inaccurate raw tracer mole fraction measurements. We conducted extensive Picarro G2203 laboratory characterisation testing. Picarro G2203 acetylene measurements were calibrated by diluting a high concentration of acetylene with ambient air. The precise level of acetylene in each dilution blend was determined by diluting a high-concentration methane source in an identical way, with reliable methane mole fraction measurements used to quantify the true level of dilution. A linear calibration fit applied to raw acetylene mole fraction measured by the Picarro G2203 showed that these measurements could be corrected through direct multiplication with a calibration gain factor of 0.94. However, this specific calibration for the Picarro G2203 tested in this study is only valid from an acetylene mole fraction of 1.16 ppb, below which unstable measurements were observed. The same Picarro G2203 was used during a field study to perform 14 successful transects downwind of an active landfill site, where a point-source acetylene release was conducted at a fixed flow rate. Methane fluxes were derived by integrating the methane and acetylene mole fraction plumes, as a function of distance along the sampling road. This resulted in a ±56 % flux variability between different transects which was principally due to errors associated with the tracer release location and downwind sampling positioning. Methane fluxes were also derived using raw uncalibrated Picarro G2203 acetylene mole fraction instead of calibrated measurements, which resulted an average methane emission flux underestimation of approximately 8 % for this specific study, compared to fluxes derived using calibrated measurements. Unlike a random uncertainty, this bias represents a consistent flux underestimation that cannot be reduced by improving the field sampling methodology; the only solution is using calibrated acetylene mole fraction measurements. The magnitude of the bias is principally due to the 0.94 multiplicative gain factor. Therefore, a similar level of methane flux bias can be expected in other studies when using uncalibrated acetylene mole fraction measurements from the Picarro G2203 tested in this work. This study therefore emphasises the equal importance of calibrating target as well as tracer gas measurements, regardless of the instrument being used to obtain these measurements. Otherwise, biases can be induced within target gas flux estimates. For the example of methane, this can influence our understanding of the role of certain facility-scale sources within the global methane budget
Une jeunesse au guichet de l'emploi. Enquête sur le Contrat d'engagement jeune
No full textCe rapport de recherche propose une analyse de la mise en œuvre du Contrat d’engagement jeune (CEJ) à partir d’une enquête qualitative. Ayant vu le jour le 1er mars 2022 et faisant suite à la Garantie jeunes, le CEJ constitue un dispositif d’accompagnement intensif auprès des jeunes qui vise à leur insertion socio-professionnelle. 590 000 contrats ont été signés entre mars 2022 et 2023. Pouvant s’étaler entre six mois et dix-huit mois, ce dispositif est mis en place aussi bien par les agences France Travail que par les missions locales, ainsi que – dans le cadre spécifique du sous-dispositif dit « Jeunes en rupture » – par des partenaires locaux des missions locales, en l’occurrence essentiellement des associations. Dans chacune de ces institutions faisant partie du « service public de l’emploi », les conseillères et conseillers doivent faire en sorte que les jeunes inscrits en CEJ effectuent entre 15 et 20 heures d’activité par semaine dans le cadre de leur projet d’insertion. En effet, le dispositif demande aux jeunes de s’investir dans leur projet socio-professionnel en contrepartie de l’attribution (sous conditions de ressources) d’une allocation.Menée sur trois communes franciliennes, notre enquête de terrain nous a permis de collecter 71 entretiens avec diverses actrices et acteurs prenant part à la mise en œuvre du CEJ, soit des cadres de direction, des conseillères et conseillers, des jeunes. Nous avons également réalisé 19 journées d’observation auprès d’elles et eux. Ce rapport de recherche propose d’interroger la concrétisation de ce nouveau dispositif destiné aux jeunes « éloignés de l’emploi ». Tout un ensemble de questions suivent ce fil conducteur. Les institutions précitées travaillent-elles ensemble dans le cadre du CEJ ? Si oui, comment ? Est-ce qu’une labellisation commune de leur travail produit une homogénéisation de l’activité des conseillères et conseillers, ou bien chacun garde ses spécificités ? Que se joue-t-il dans le recrutement des jeunes qui se présentent au guichet du service public de l’emploi ? De quelles manières les conseillères et conseillers des trois institutions qui assurent la mise en œuvre du CEJ intègrent les jeunes ? Comment prend forme le « suivi intensif » à leur égard ?Ce rapport de recherche montre que le ciblage des jeunes en situation de précarité dans le cadre du CEJ, élaboré « par le haut », soit par les décideurs publics à différentes échelles d’action publique (Europe, France), est retravaillé « par le bas », c’est-à-dire au travers des relations entre les conseillères ou conseillers et leurs destinataires, ainsi que façonné par les conditions matérielles dans lesquelles travaillent les premiers. En ce sens, cette recherche rend compte de la manière par laquelle les institutions construisent, à différents niveaux d’action publique et par des divisions du travail entre elles, la jeunesse à insérer socio-professionnellement. Elle analyse notamment, d’une part, l’entrée des jeunes dans le dispositif au travers de ces diverses entrées au guichet du service public de l’emploi et, d’autre part, le principe d’un accompagnement dit « intensif ». Cette recherche a bénéficié de la participation financière de la Dares, dans le cadre de l'appel à projets de recherche "Suivi qualitatif du recours au contrat d'engagement jeune (CEJ)" qu'elle a lancé
Avatars and metaverse in the professional sphere: experiment to understand user behavior
No full textFNEGE 4, ABS 2International audiencePurpose - Virtual worlds have undergone considerable technological advances in recent years, from the personalization of avatars to the enrichment of haptic technologies, enabling a ten-fold increase in the sensory characteristics of the environment in which individuals are immersed. The metaverse is used in various fields, ranging from aerospace and healthcare to employee and student training. This research aimed to analyze the perception of the advantages and limitations of avatars in the professional use of the metaverse. Design/methodology/approach - To address the research objective, we conducted an exploratory qualitative study with thirteen employees. First, non-participant observations were used to identify respondents’ behaviors, reactions and emotions as they created their avatars and took their first steps into the metaverse. Second, semi-structured interviews were conducted using an interview guide to analyze emerging emotions and explain the metaverse’s acceptability to employees. Findings - The professional usage context defines the limitations of avatar creation; users showed a conservative approach in designing their avatars, expressed in three types: those who approve, those who are reluctant and those who oppose. Originality/value - This study is the first to empirically examine how professionals with no prior metaverse experience create avatars for workplace use, conceptualizing these avatars as professional digital twins shaped by social norms. It introduces a novel typology of avatar behaviors – approver, reluctant and opposer. Methodologically, the study advances experiential research by combining non-participant observation and interviews, while also extending technology acceptance models by identifying context-specific motivations and barriers to professional metaverse adoption
Exploring self-sovereign identity solutions for improved identity and access management in the European Union
No full textInternational audienceSelf-sovereign identity is an emerging digital concept that grants individuals greater control over their data. The implementation and regulation of SSI in the European Union face challenges due to the diverse policies and legal regulations, including the General Data Protection Regulation and eIDAS. This systematic literature review allows us to appreciate the extent to which SSI can potentially enhance identity access management while identifying the benefits, challenges, and limitations associated with its implementation and adoption within the EU’s legal framework. By synthesizing existing research, this work seeks to inform both IS literature in four key areas (technical, legal, policy and behavioral) as well as practice
Deep Generative Models for Discrete Genotype Simulation
No full textDeep generative models for simulating realistic genomic data while preserving privacy and addressing data accessibility constraints. While previous studies have primarily focused on generating gene expression or haplotype data, this study explores generating genotype data in both unconditioned and phenotype-conditioned settings, which is inherently more challenging due to the discrete nature of genotype data. In this work, we developed and evaluated commonly used generative models, including Variational Autoencoders (VAEs), Diffusion Models, and Generative Adversarial Networks (GANs), and proposed adaptation tailored to discrete genotype data. We conducted extensive experiments on large-scale datasets, including all chromosomes from cow and multiple chromosomes from human. Model performance was assessed using a well-established set of metrics drawn from both deep learning and quantitative genetics literature. Our results show that these models can effectively capture genetic patterns and preserve genotype-phenotype association. Our findings provide a comprehensive comparison of these models and offer practical guidelines for future research in genotype simulation. We have made our code publicly available at https://github.com/SihanXXX/DiscreteGenoGen
A distribution-free-based approach for stochastic food closed-loop supply chain
No full textInternational audienceResource scarcity has driven growing interest in circular economy (CE). Closed-loop supply chain (CLSC) with returnable transport items (RTIs) in the food industry is an important component of CE. However, existing works on food CLSC with RTIs have not simultaneously considered the perishability, facility location, and uncertain demand under limited information. Therefore, this work addresses a new food CLSC optimisation problem. We first propose a non-linear chance-constrained programming model. It is then transformed into a mixed-integer linear programming model via using the distribution-free (DF) method and sample average approximation (SAA) method, respectively. An illustrative example reveals that the DF method needs only 10.50% of the computation time of the SAA method. To address large-scale problems, an improved Lagrangian relaxation (LR) method is developed. To address the computational challenge in large-scale problems, an improved Lagrangian relaxation (LR) algorithm is developed. Results show that CPLEX achieves a gap of 75.57%, while the LR surpasses it by finding near-optimal solutions with a gap of 1.22%, using only 31.82% of the computation time required by CPLEX. For this work, the main insights are summarised: (1) extending product shelf life can reduce the total cost; and (2) to alleviate uncertain demand and production risks, production capacity and product inventory capacity can be appropriately expanded, but excessive investment may not improve returns
Variants of Tissue P Systems with Prescribed Teams of Channel Rules
No full textInternational audienceIn this paper we consider tissue P systems with prescribed teams of channel rules, with the application of the channel rules possibly depending on some given condition. A channel rule opens a channel from one cell to another one for one object to pass through it, and the channel is only open for one step. A team of channel rules then is a multiset of such channel rules. We especially investigate two variants of how the rules in the teams can be applied: in the enforcing mode, the opened channel has to be used by the object it has been opened for, whereas in the permitting mode an open channel has to be used if possible, but can also remain unused if no object exists which could pass through. We show how multiset grammars using evolution rules equipped with random context conditions can easily be simulated by teams of channel rules, as well as how variants of purely communicating (tissue) P systems can be interpreted in this framework of tissue P systems with prescribed teams of channel rules. Moreover, we prove computational completeness results for various models of purely communicating (tissue) P systems, often based on already proven results, some even with all channel rules working the enforcing mode without applicability conditions. We also show how computations on strings can be carried out by tissue P systems with prescribed teams of channel rules. Finally, we also discuss how these systems allow for “going beyond Turing”