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Scale separation, rolling solutions and entropy bounds
No full textInternational audienceWe revisit scale separation for compactifications of ten- and eleven-dimensional supergravity. For cosmological solutions rolling down flux-generated potentials, we observe that scale separation is achieved as time flows, and is fairly generic. This is realized without the need of orientifolds nor corrections to the classical supergravity approximation. We then confront scale separation with the Covariant Entropy Bound (CEB) and the CKN bound. We show that a naive application of these bounds to vacua hints at the existence of at least two extra dimensions. For rolling solutions, we observe that the CEB is not always respected, but since these examples lack a cosmic horizon, the application of entropy bounds remains delicate
Induced polarization applied to landslides. Part 1: imaging hydraulic barriers
No full textInternational audienceWater content and pore fluid pressure increases have been recognized as important drivers of shallow landslides, especially through the role of strong rainfalls promoting gravitational instabilities. Less recognized is the role of vertical hydraulic barriers impeding the flow of ground water at the feet of areas prone to landslides. Induced polarization is a non-intrusive geophysical technique able to image hydraulic properties of the shallow subsurface. Recently developed petrophysical models bridging the gap between hydraulic and electrical properties of soft sediments, soils and rocks have been developed. Thanks to these relationships, this geophysical method can be used to image the water and clay contents of the formations and their permeability. Therefore, induced polarization can be used to image the occurrence of ver tical per meability barriers. We focus our approach on a large landslide that occurred in March 1931 (reacti v ated in 1971-1972) above Le Châtelard village (Bauges, France). This landslide started inside a kilometer-scale syncline hosting clayey formations and moraines. We performed a 2.2 km profile crossing the syncline and the sliding area including resistivity, induced polarization and self-potential measurements. In addition, 22 samples were taken from the different formations outcropping at the field site including limestones, sandstones and clayey formations. The petrophysical investigations are combined with the field data to image the water content and cation exchange capacity as well as their permeability. The data set shows the existence of a vertical permeability barrier at the bottom of the landslide corresponding to the tight Urgonian limestone formation. We combine the permeability distribution, the resistivity and self-potential data by forward modelling the groundwater flow and electrokinetic response. We then invert the self-potential measurements to refine the image of the Darcy velocity distribution. The results show a strong upflow of the ground water just above the Manauds canyon where several gravitational instabilities occured in the past
In-situ synthesis of Metal Matrix Composite (MMC) by laser powder bed fusion
No full textInternational audienceThe in-situ synthesis of Aluminium Matrix Composites (AMC) via the Global Reactive Synthesis (GRS) has already been demonstrated as a promising approach to control reinforcement size and distribution, as well as to obtain sharp matrix/reinforcement interface. Based on the use of chemical precursors, the GRS is driven by controlled reactivity and thermodynamics enabling the in-situ formation of both the matrix and the reinforcement under basic geometries (cylinders or plates). It has been applied successfully to conventional AMCs like Al-TiC [1] and Al-TiB2. It has also paved the way to a new class of AMCs and the most advanced studies have been focused on Al-Tau3 AMC, where Tau3 is a ternary borocarbide (Al3B48C2) [2,3]. Nowadays the challenge is to combine both the GRS and the novel Additive Manufacturing techniques in order to get near-net shape pieces of AMC with complex geometries, where both the matrix and the reinforcements are formed in-situ during the manufacturing process.The synthesis of MMC via GRS was studied with the Laser Powder Bed Fusion (LPBF) Additive Manufacturing technique. In this talk, we will present the interesting and complex microstructures so obtained and we will discuss the different process parameters, such as precursor composition, high heating and cooling rate, laser speed and power that influence the phases formed, their sizes and distributions as well as their morphologies
Amélioration continue : étude de la maturité des équipes pour renforcer les dynamiques de progrès
No full textContinuous Improvement (CI) initiatives rely on an engaged workforce to embrace change and adopt its methods, fulfilling both the roles of source and driver to sustain progress. Yet, despite the extensive body of knowledge surrounding CI methodologies, limited research has focused on the workforce contributions essential to sustaining these programs. This lack of research is particularly evident in the absence of systematic assessments that capture team dynamics, or approaches that extend beyond technical skills and knowledge to grasp a more holistic view of the human factor. To bridge this gap, this thesis aims to develop a conceptual and practical approach to embed the workforce into the CI dynamic through the assessment and improvement of team maturity. This approach is based on team maturity, considering the pivotal role teams hold in initiatives, and the broader implications of maturity, not limited to actions, but also encompassing the reciprocal influence among individuals, teams, organizations, and their surrounding environment. To effectively study team maturity, identifying the characteristics of mature production teams within the CI context enables team maturity to be assessed and further improved. Based on research from various fields - group development and CI domains - and CI expert opinion, this thesis proposes a characterization of team maturity composed of 5 dimensions structuring 16 maturity elements. Building on this identification, a Conceptual Team Maturity Improvement Process (CTMIP) is introduced, encompassing a loop of assessment and improvement. Team maturity assessment is proposed through the development of a Team maturity model and an assessment questionnaire, offering a practical tool to measure team maturity. This questionnaire is designed for members' self-evaluation of their team's maturity. Concerning team maturity improvement, 3 axes of intervention and 11 team maturity influencers are outlined to assist organizations and guide the design of tailored improvement plans. The team maturity approach is analyzed through case studies - featuring 13 production teams - that confirm the feasibility of the assessment and potential to integrate teams into an improvement dynamic and support CI initiatives.La réussite des projets d'amélioration continue (AC) dépend fortement des acteurs humains, de leur engagement face au changement, et de leur implication dans ces projets. Par ailleurs, cette amélioration est souvent initiée et mise en œuvre par les acteurs de terrain eux-mêmes. Cependant, malgré l'importante littérature sur les méthodologies d'AC, assez peu de recherches se sont concentrées sur leurs contributions, pourtant essentielles à la pérennité de ces projets. Ce manque de travaux est particulièrement vrai en ce qui concerne à la fois l'évaluation des dynamiques d'équipes, et l'intégration du facteur humain au-delà des compétences techniques. Cette thèse propose une approche conceptuelle et pratique pour intégrer les acteurs de terrain dans la dynamique de l'AC, à travers un processus d'évaluation et d'amélioration de la maturité des équipes. La maturité d'équipe constitue le fondement de cette approche. En effet, l'équipe joue un rôle central dans les projets d'amélioration et la maturité permet de tenir compte de l'influence réciproque entre les individus, les équipes et leur environnement. Pour étudier cette maturité, il est important d'identifier les caractéristiques des équipes de production matures dans le contexte de l'AC. En s'appuyant sur des publications issues de plusieurs disciplines (domaines du développement de groupe et de l'AC), ainsi que sur des experts terrain de l'AC, cette thèse propose une caractérisation de la maturité d'équipe, composée de 5 dimensions, structurant 16 éléments de maturité. A partir de cette identification, un processus conceptuel d'amélioration de la maturité d'équipe (CTMIP) est proposé, incluant une boucle d'évaluation et d'amélioration. Le développement d'un modèle de maturité et d'un questionnaire d'auto-évaluation permet d'obtenir une mesure de cette maturité d'équipe. Enfin, 3 axes d'intervention et 11 facteurs influençant la maturité sont identifiés pour guider l'élaboration de plans d'amélioration personnalisés. L'approche proposée a été testée sur le terrain à travers des études de cas au sein de 13 équipes de production. Cela a permis de valider la faisabilité de l'évaluation et de confirmer son intérêt pratique en soutien aux initiatives d'AC et à l'intégration des équipes dans un cycle d'amélioration
Leverage points for scaling nature-based adaptation to climate change
No full textSource Agritrop Cirad (https://agritrop.cirad.fr/614741/)International audienceDespite ambitious goals and policies, climate change adaptation efforts remain slow and insufficient compared to the pace and magnitude of climate change. Nature-based Solutions (NbS) offer a holistic approach, with assumed co-benefits that jointly address climate change adaptation and mitigation, biodiversity conservation and other societal challenges. NbS are increasingly implemented to enhance local adaptation to climate change; however, they remain mostly marginal and isolated considering the magnitude of the challenge. Therefore, pathways to rapidly scale NbS are urgently needed. We hypothesise that NbS implementors are limited in their scaling strategies by their decision context. We propose an empirical framework for systemic analysis of decision contexts for scaling NbS, showcased for the Grenoble Region in the French Alps. We use mixed qualitative methods—policy and strategy document analysis, interviews and workshops with NbS experts, to explore a pathway to a conducive decision context. To characterize this context and the pathway to scaling, we identified the main leverage points, their underpinning levers and their interactions. According to workshops participants, NbS scaling should be supported by a combination of several deep and some shallow leverage points working simultaneously, including knowledge production and sharing, values and perception, local governance, supportive policies, financial support and landscape planning culture. Our results stress the need for more emphasis on how to support the integration of NbS principles into cultural roots and values; and on how to integrate deep leverage points into adaptation policies and strategies. However, this entails many challenges because of the diversity of actors with different objectives, values and power, and the multiple institutional scales and timeframes. We propose our integrative approach as a way to further support decision-makers in navigating complex decision contexts for scaling NbS and building on simultaneous progress within each leverage point
3D FIB-SEM and TEM characterization of an industrial 0.5-Mo low carbon steel subjected to high temperature hydrogen attack
No full textInternational audienceThis work focuses on the microstructural characterization of an industrial low carbon steel which was submitted to high temperature hydrogen attack for decades in petroleum refineries. Scanning electron microscopy (SEM) was used to make an initial assessment of the attack stage by identifying the defects. Cavities which are probably filled with methane are localized at ferrite-ferrite or ferrite-pearlite grain boundaries as well as at the carbide/matrix interfaces. Cracks are also observed next to zones showing less advanced damage which reflects a heterogeneity of attack. In order to establish a link between the fine-scale microstructure, which may be responsible for this heterogeneity, and the formation of cavities, a 3D visualization of a zone displaying cavities was performed thanks to a 3D focused ion beam (FIB) -SEM analysis. The main result is that cavities are mostly formed at the junction of a transgranular inclusion-enriched plane with a grain boundary or carbides at grain boundaries and in pearlite grain. These inclusion-enriched planes that pass through ferrite or pearlite grains may correspond to former austenitic grain boundaries that have been overwhelmed by subsequent ferrite and pearlite grain boundaries during the steel manufacturing. A transmission electron microscopy (TEM) observation of an attacked pearlite reveals that in most cavities located at carbide/matrix interface, an inclusion of AlN remains stuck. The potential catalytic effect of inclusions as AlN on the trigger of attack is not yet fully understood and will be the subject of further investigations on brand new C-steels
Andorre ou le vélo marketing, une principauté sur deux roues
No full textInternational audienceLa principauté d’Andorre est enserrée entre la France et l’Espagne, dans les Pyrénées centrales. Très fortement aménagée, elle offre de nombreuses possibilités sportives, autant pour la pratique du vélo en loisir que pour l’accueil d’étapes de courses professionnelles, une identité revendiquée par le petit État pyrénéen au cœur d’une stratégie de marketing territorial, le cyclisme est devenu un élément phare de la promotion du territoire andorran
Comprendre et soutenir les enseignants dans leur accompagnement d’élèves orphelins
No full textInternational audienceEn France, un élève par classe en moyenne est en situation d’orphelinage précoce. Néanmoins, à l’heure où l’école se veut plus inclusive, les dispositifs propres à l’accompagnement de ces élèves restent absents et la formation des enseignants sur ces thématiques est faible, voire inexistante. Dès lors, comment les professionnels de l’Education nationale s’organisent-ils pour prendre en charge cette problématique ? À partir d’entretiens semi-directifs réalisés auprès de 24 enseignants et personnels éducatifs, l’article révèle une méconnaissance des enjeux liés à l’orphelinage et une mauvaise définition de cette notion au sein du milieu scolaire, qui participe de son invisibilisation. Il montre aussi comment les différents acteurs bricolent dans l’urgence des stratégies individuelles, qui reposent essentiellement sur leurs expériences vécues et sur des compétences relationnelles, plutôt que techniques. Pour cela, ils mobilisent différents registres d’action : celui de l’attention et de l’observation, de l’écoute, ainsi que de l’expérience et du vécu personnel. L’étude révèle par ailleurs des résistances quant à la mobilisation du registre d’écoute, accompagnées d’une tendance à déléguer à autrui la prise en charge des élèves orphelins. Par ces actions, les acteurs de l’Éducation nationale semblent chercher à se protéger au sein d’un univers professionnel où leur individualité est mobilisée comme outil de travail
Unveiling the shape of the Ne nucleus by measuring the flow coefficients with cumulants in PbNe and PbAr collisions at GeV
No full textInternational audienceThe anisotropic flow coefficients quantify the collective medium response to the initial spatial anisotropy of the overlapping region in ion collisions and serve as sensitive probes of both the medium properties and shape of nuclear initial states. In this analysis, the and parameters of prompt charged particles are measured using the multiparticle cumulant method in fixed-target PbNe and PbAr collisions at GeV, collected by LHCb using the SMOG2 gas-target system during the 2024 LHC lead-beam run. The cumulant method is first validated using 2018 PbPb collision data, successfully reproducing previous measurements obtained via the two-particle correlation method. Results for the fixed-target collisions are then presented, showing a significantly larger value of the elliptic flow coefficient in central PbNe with respect to PbAr collisions. This is qualitatively consistent with 3+1D hydrodynamic predictions including ab-initio descriptions of the nuclear structure. The results provide the first experimental confirmation of the distinctive bowling-pin shape of the ground-state Ne nucleus, validating at the same time the hydrodynamic description of the hot medium formed in high-energy collisions involving light ions
Citizen Voices: a transdisciplinary experiment for a sustainable transition in the Vercors range
No full textInternational audienceThe Vercors is a mountain range in Franch Prealps, facing strong residential and tourist pressure, in a context of climate change that is reflected in a decline in average snow cover and a growing scarcity of water resources. Over the past few years, a large-scale project to create a new tourist unit for a high-end clientele has generated considerable controversy among the local population. Initially formed in opposition to this project, the “Vercors citoyens” collective set about building a project for the range, including diagnostics and prospec- tive visions from local residents in all their diversity. To carry out this process, the collective approached the University of Grenoble and the Labex ITTEM. From a transdisciplinary perspective, a steering committee was set up, with researchers, members of the citizens’ collective and representatives of the Union Nationale des Acteurs du Développement Local (UNADEL – a national network of associations promoting local development). Inspired by a method developed by UNADEL (territorial listening), the citizen listening approach was deployed along the way, supported by the methodological support of researchers. The idea is simple: citizens listen to other citizens in pairs. To put this into practice, various tools were proposed and then co-constructed: a listener’s guide, an interview guide, an analysis guide, and so on. Analysis of the 80 listening sessions carried out over 6 months has enabled us to draw up a summary of the findings and visions gathered. The results are presented at “mirror meetings”, at which the transdisciplinary team presents the initial findings to the population and gathers new contributions. This experience was underpinned by the strong will of a collective of citizens. The mobilization was made possible by the existence of a strong controversy over the future of this territory. We can deduce from this that the territorial issues of adaptation to global change, through the tensions they generate, are conducive to the emergence of innovative transdisciplinary approaches. In the case of the approach presented here, however, we can ask the remoteness of the spheres of local public action, and therefore of the ability of deci- sion-makers to take this dynamic into account