HAL Portal UPPA (University of Pau and the Pays de l'Adour)
Not a member yet
42255 research outputs found
Sort by
L’européanisation de la vie politique nationale par la contestation de l’action de l’Union européenne pour les valeurs de l’article 2 TUE. L’exemple des réactions au rapport Tavares en Hongrie
No full textInternational audienc
Introduction. Le système juridique hongrois devant la Cour de justice de l'Union européenne
No full textInternational audienc
Error analysis for stochastic gradient optimization schemes using modified equations
No full textWe consider a class of stochastic gradient optimization schemes. Assuming that the objective function is strongly convex, we prove weak error estimates which are uniform in time for the error between the solution of the numerical scheme, and the solutions of continuous-time modified (or high-resolution) differential equations at first and second orders, with respect to the time-step size. At first order, the modified equation is deterministic, whereas at second order the modified equation is stochastic and depends on a modified objective function. We go beyond existing results where the error estimates have been considered only on finite time intervals and were not uniform in time. This allows us to then provide a rigorous complexity analysis of the method in the large time and small time-step size regimes. We provide numerical experiments to illustrate the convergence results
VARIANCE OF VECTOR FIELDS -DEFINITION AND PROPERTIES
No full textWe give a self contained presentation of the notion of variance of a vector field introduced by Jean Ecalle and Bruno Vallet in [8] following a previous work of Jean Ecalle and Dana Schlomiuk in [7]. We give complete proofs and definitions of various results stated in these articles. Following J. Ecalle and D. Schlomiuk, We illustrate the interest of the variance by giving a complete proof of the formulas for the mould defining the nilpotent part of a resonant vector field
La sécurité du consommateur : Une notion en constante évolution au regard des impératifs de protection du consommateur
No full textInternational audienc
Land Use Optimization in Small Islands: A Water-Energy-Food Nexus Approach
No full textDue to their isolation, limited resources, and high population density, small islands are particularly vulnerable to multi-sectoral crises. The study of sustainability on small islands raises, among other challenges, the need to balance the use of local resources -such as water, food and energy-while effectively managing urban sprawl. This paper introduces a systemic approach that explores the interdependencies among multiple resources and production systems, framed within the Water-Energy-Food (WEF) nexus, with a specific focus on assessing land use competition driven by the dynamics of land use change. In this paper, we propose a novel approach of the WEF nexus through the optimization of scenarios that make use of Geographical Information Systems (GIS) integrated with a robust optimization model. The contributions include constructing integrated scenarios that encompass agricultural production, electricity production, and urban sprawl dynamics, highlighting their impacts on land use change and their combined effects on energy and food production from several local resources by 2035. The model is applied to Reunion Island, using real-world data to build insightful scenarios that facilitate informed decision-making. Our proposed model functions as a spatial analysis tool, enabling the identification of optimal agricultural parcels for urban development and potential areas for electricity and food production within a systemic approach. Besides, it provides medium-term projections regarding the impact of integrated scenarios on local food and energy production. As such, it serves as a relevant decision-support tool for local policymakers at the island scale
Robust Pickering emulsions stabilized with pH-responsive self-assembled amphiphilic tadpole bottlebrush copolymers: bulk reversibility of the self-assembly is lost at the interface.
No full textInternational audienceHypothesis: The newly synthesized amphiphilic tadpole bottlebrush copolymer can exist in solution as unimers (disassembled polymer chains) or micelles depending on pH. Owing to this specific structure, these assemblies are at thermodynamic equilibrium, allowing for dynamic transitions between unimer and aggregated states. We hypothesize that the same copolymer can stabilize emulsions with distinct properties at varying pH, whether in its unimer or micellar state (Pickering emulsions). Experiments: We characterized the copolymer behavior in aqueous solutions across pH range using dynamic light scattering (DLS), contact angle measurements, and dynamic tensiometry. Dodecane-in-water emulsions were prepared using the copolymer at various pH values. Emulsion characteristics were studied using optical microscopy and laser granulometry, complemented by visual observations to assess stability over time. The adsorption of polymer micelles at the emulsion droplet surface was investigated using transmission electron microscopy (TEM) of freeze-fractured samples. Findings: Above pH 5–6, the copolymer acts as a macromolecular surfactant, resulting in emulsions with short-term stability. At lower pH (pH 2 years) even at low copolymer concentrations (as low as 0.001 wt% with respect to total sample weight). Drop size is tunable with the copolymer concentration. TEM analysis of freeze-fractured emulsions reveals micelle adsorption at the droplet surface at low pH, highlighting their efficiency as Pickering emulsion stabilizers. Despite the copolymer reversible assembly in solution, no emulsion breakup occurs when pH increases to reach the unimer state domain. This unexpected behavior suggests that adsorbed copolymer micelles lose pH-sensitivity at the water-dodecane interface, demonstrating a unique system where interfacial behavior differs from solution behavior
Fulgurance et onde de choc. La temporalité de l’explosion et ses élaborations artistiques
No full textInternational audienc
Towards ultra-low detection limits of lithium by LIBS in LiF atomic layers
No full text"Accord Couperin-Elsevier"International audienceThe growing number of industrial applications requiring thin-film materials is prompting the development of new characterization methods. We demonstrate that laser-induced breakdown spectroscopy (LIBS) enables the verification of the spatial homogeneity of LiF films deposited by atomic layer deposition (ALD), and the quantification of the lithium amount in LiF thin films. In our experimental conditions, we obtained a limit of detection (LOD) of 0.7–4.1 fg.ng−1for the Li I line at 670.8 nm and for single-shot LIBS analysis. Then, an estimate of LOD in the range 0.17–0.93 fg.ng−1 (i.e. 170–930 ppb) was obtained with other acquisition parameters. Given the 100 Hz repetition rate of the laser shots, the LOD decreases by a factor of 10 in one second leading to 0.012–0.065 fg/√Hz. Such level of detection limit paves the way for future utilization of LIBS for the chemical characterization of thin films