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Evolutionary Algorithms Are Significantly More Robust to Noise When They Ignore It
No full textInternational audienceRandomized search heuristics (RSHs) are known to have a certain robustness to noise. Mathematical analyses trying to quantify rigorously how robust RSHs are to a noisy access to the objective function typically assume that each solution is re-evaluated whenever it is compared to others. This aims at preventing that a single noisy evaluation has a lasting negative effect, but is computationally expensive and requires the user to foresee that noise is present (as in a noise-free setting, one would never re-evaluate solutions). In this work, we conduct the first mathematical runtime analysis of an evolutionary algorithm solving a single-objective noisy problem without re-evaluations. We prove that the (1+1) evolutionary algorithm without re-evaluations can optimize the classic LeadingOnes benchmark with up to constant noise rates, in sharp contrast to the version with re-evaluations, where only noise with rates O(n⁻²log n) can be tolerated. This result suggests that re-evaluations are much less needed than what was previously thought, and that they actually can be highly detrimental. The insights from our mathematical proofs indicate that this similar results are plausible for other classic benchmarks
La construction d’éco-score comme modalité d’exploration de valeur de l’ éco-conception
No full textInternational audienceDans le contexte de l'urgence environnementale, la valeur des éco-innovations sur les marchés constitue un défi majeur, rendant crucial le travail de qualification et de cadrage de leurs échanges. Les dispositifs de labellisation sont souvent présentés comme des outils de cadrage marchand, pourtant, leur prolifération, les controverses qu’ils suscitent et leur efficacité limitée interrogent leur véritable capacité à cadrer. Si le cadrage est un processus collectif et situé, alors la conception même de ces dispositifs et les interactions individuelles qu’elle abrite méritent d’être étudiées. Analysant in-situ le processus de conception collaborative d'un éco-label pour la filière du dispositif médical, notre recherche révèle qu’il constitue un espace de visibilisation des intérêts et de construction de compromis entre des logiques diverses (environnementales, économiques, réglementaires). Elle met également en évidence le rôle d’un acteur fantôme – les pouvoirs publiques –, qui oriente fortement les choix sans participer directement
Refractive indices of Titan, Pluto and Exoplanet photochemical haze analogs from UV to far-IR : a comparative study between the PAMPRE and COSmIC experimental setups
No full textInternational audienceThe observations of planetary atmospheres and surfaces strongly rely on the use of experimental data to understand the interaction between light and particles. The intrinsic optical properties of these particles, also known as the refractive indices, describing light dispersion (i.e., n) and absorption (i.e., k), are required to consider the influence of their chemical composition. Only with these data can we interpret observations and avoid large degeneracy in the retrieval data analyses. Climate modeling is also strongly sensitive to these experimental data as atmospheric particles absorb and scatter radiations, and thus modify the temperature profile.Photochemical hazes are observed in the atmospheres of the different objects in the outer Solar System (Titan, Pluto, Triton, Jupiter, Saturn) as well as in exoplanet atmospheres (e.g., GJ1214 b). The observations of these different objects as well as the modeling suggest that the composition of photochemical hazes varies from one object to the next following changes in the irradiation efficiency, temperature, pressure and gas composition. These differences in composition suggest that the refractive indices of photochemical hazes are also function of pressure, temperature, irradiation efficiency and gas composition. In the present work, we produced laboratory analogs of these hazes from various gas mixtures with controlled abundances. We used 6 different gas compositions to mimic the atmospheric compositions of Titan, Pluto and exoplanets. Among the 6 conditions, we modified the N2/CH4 and CO/CH4 abundance ratios in the gas mixture to assess the influence of N2 and CO on the refractive indices of the haze material. In addition, we compared the influence of the experimental setup by using haze analogs produced with the PAMPRE (LATMOS, France) and COSmIC (NASA Ames, USA) experimental setups. This cross-laboratory comparison allows us to assess the influence of temperature, pressure, gas residence time and irradiation which are changing between PAMPRE and COSmIC. Using several optical measurements, we covered a broad spectral range from UV to far-IR (up to 200 microns) which is essential for climate calculations and to interpret the various remote-sensing observations of these planetary bodies.Our results revealed a significant difference between the refractive indices obtained on PAMPRE and COSmIC analogs, even for similar gas compositions. Based on previous elemental analyses of the haze analogs, we know that the COSmIC analogs are richer in nitrogen relative to carbon compared to the PAMPRE analogs. Here, we show that this difference in composition leads to higher n and k values for the COSmlC analogs in the entire spectral range. We found that changes in the CO/CH4 gas ratio have a rather poor influence on the refractive indices compared to the effect of the N2/CH4 ratio. We also found that hazes produced without nitrogen are more transparent in the entire spectral range from UV to IR with very different mid-IR absorption features that could help distinguish between N-rich and N-poor exoplanet atmospheres. These data should be used for future observational analyses and modeling simulations of sub-Neptune atmospheres and Solar System gas giants
Contribution of Geostationary Satellites to the Observation of Atmospheric NH3
No full textInternational audienceAmmonia (NH3) is an atmospheric pollutant mainly emitted by the agricultural sector, which has an effect on public health since it is a precursor of fine particles (PM2.5). The diurnal variability of NH3 in the atmosphere and its transformation into particles are poorly constrained and strongly depend on meteorological parameters, in particular temperature. Polar orbit satellite observations, such as the Infrared Atmospheric Sounder Instrument (IASI), are keys to assess spatio-temporal variabilities of NH3 with observations twice a day. Geostationary instruments offer a comprehensive assessment of NH3 diurnal variability and its dependence on atmospheric temperature. This study analyses the contribution of geostationary instruments to observe ammonia variabilities and their link to atmospheric temperature. We use IASI observations, as well as the Geostationary Interferometric Infrared Sounder (GIIRS) on board China’s FengYun-4B satellite launched in June 2021 that measure atmospheric ammonia over East Asia and parts of South Asia and Southeast Asia every 2 hours at 12 km at nadir. We also evaluate the InfraRed Sounder (IRS) instrument that will be launched onboard the Meteosat Third Generation (MTG) satellite into geostationary orbit over Europe and Africa in late 2025. IRS will offer the ability to assess NH3 diurnal variabilities with frequent measurements (every 30-45 minutes) and better spatially resolved observations than IASI (4 km x 4 km at the Equator and Greenwich meridian). In this work, GIIRS NH3 total columns are validated with IASI observations between July 2022 and June 2024. Then, the link between NH3 variabilities and atmospheric temperature are analyzed over Asia using GIIRS observations. Finally, a NH3 sensitivity analysis considering measurement noises is made for the future IRS-MTG mission and is discussed with respect to IASI.
Board-level employee representation and corporate sustainability: A focus on executive compensation programs
No full textThis paper explores the impact of board-level employee representation (BLER) on Corporate Social Responsibility (CSR) contracting, i.e. the integration of non-financial criteria into top executive officers' compensation. We exploit the enactment of two laws (in 2013 and 2015) that mandated the presence of employee directors in large French companies to identify a causal impact in a staggered difference-in-differences design. Our findings show that BLER significantly increases the likelihood of implementing CSR contracting, especially when employee directors are members of the compensation committee (a unique feature of the French system). In addition, using an instrumental variables (IV) approach, we show that CSR contracting has a significant, positive impact on CSR performance. This study opens up avenues for future research to delve deeper into the role of employee representation in corporate governance and CSR
EU Digital Technologies and Policy Conference (EUDTP 2025) Abstracts and Contributions
No full textInternational audienc
Optical, electrochemical and charge transport properties of fully coplanar diketopyrrolopyrrole thiazole-based semiconductor material
No full textInternational audiencePi-conjugated semiconductor material with multi-alkyl chains composed of thiazole, thiophene and diketopyrrolopyrrole moieties was designed and synthesized, named PDPP-2T-2Tz. Theoretical simulations confirmed that the molecular structure exhibits excellent coplanarity, which is essential for achieving efficient charge carrier transport. A series of photophysical and electrochemical tests were conducted to investigate its absorption characteristics and frontier orbital energy levels. Two-dimensional grazing-incidence wide-angle X-ray scattering (2D-GIWAXS) and atomic force microscopy (AFM) tests verified the high crystallinity and smooth film morphology of the material. The hole mobility of the annealed film-based transistor materials reached 0.33 cm 2 V -1 s -1 , demonstrating its potential applications in organic optoelectronics
RDF Query Answering in the Presence of Access Restrictions
No full textIn this work, we explore algorithms for answering conjunctive RDF queries in the presence of RDFS ontologies and access control. We consider an access control setting where by default all users have access to the complete graph, and a restriction can forbid user a user's access to specific IRIs. Here, restricting for user u the access to an IRI i entails that: no answer to a query by u may contain the IRI i; no triple containing i can be used to compute an answer for a query by i, nor to entail such a triple via reasoning with the ontology. We present a set of query answering algorithms for this novel context, and prove that five among them are correct, i.e., sound and complete, with respect to both the ontology and the access restrictions in place. We have implemented all our algorithms and present experiments comparing their performance
Counterfactual simulations for large scale systems with burnout variables
No full textInternational audienceWe consider large-scale systems influenced by burnout variables-state variables that start active, shape dynamics, and irreversibly deactivate once certain conditions are met. Simulating "what-if" scenarios in such systems is computationally demanding, as alternative trajectories often require sequential processing, which does not scale very well. This challenge arises in settings like online advertising, because of campaigns budgets, complicating counterfactual analysis despite rich data availability. We introduce a new type of algorithms based on what we refer to as uncertainty relaxation, that enables efficient parallel computation, significantly improving scalability for counterfactual estimation in systems with burnout variables
Simulation de la fissuration par champ de phase : Analyse technique de l’initialisation et la propagation de fissures
No full textInternational audienceThis study examines numerical biases in phase-field fracture simulations. More specifically, it investigates the influence of meshing on crack path trajectories in phase-field fracture simulations. A reference problem based on a Pure Shear test with an eccentric initial crack is used to evaluate the impact of spatial discretization on predicted crack trajectories. Phase-field simulations are compared to a reference solution from Linear Elastic Fracture Mechanics, towards which they theoretically converge. Results show that structured meshes introduce artificial anisotropy that forces the crack to follow a mesh-dependent trajectory. Conversely, unstructured meshes enable a more accurate prediction of the expected exponential trajectory. Indeed, the disordered nature of the mesh significantly reduces the artificial anisotropy effects induced by discretization. These observations highlight the importance of mesh selection in crack propagation simulations. Practical recommendations are finally proposed to minimize numerical biases in phase-field simulations.Cette étude propose d’étudier les bias numériques dans les simulations de la fissuration par champ de phase. Plus spécifiquement, elle examine l’influence du maillage sur la trajectoire de fissure. Un problème de référence basé sur un essai de Pure Shear avec fissure initiale excentrée est utilisé pour évaluer l’impact de la discrétisation spatiale sur la trajectoire de fissure prédite. Les simulations par champ de phase sont comparées à une solution de référence issue de la mécanique linéaire élastique de la rupture, vers laquelle elles convergent théoriquement. Les résultats montrent que les maillages structurés introduisent une anisotropie artificielle qui contraint la fissure à suivre une trajectoire dépen- dante du maillage. En revanche, les maillages non structurés permettent une prédiction plus fidèle de la trajectoire exponentielle attendue. En effet, le caractère désordonné du maillage réduit les effets d’ani- sotropie artificiels induits par la discrétisation. Ces observations mettent en évidence l’importance du choix du maillage dans les simulations de propagation de fissures. Des recommandations pratiques sont finalement proposées pour minimiser les biais numériques dans les simulations par champ de phase