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Décision équitable en contexte professionnel : quelles questions avant la modélisation ?
No full textNational audienceDécision équitable en contexte professionnel : quelles questions avant la modélisation
A two-step XGBoost-based pipeline for seismic event classification
No full textEarly and reliable earthquake detection is crucial for mitigating seismic hazards, particularly in densely populated areas. This study explores a two-stage Seismic Classifier Pipeline, using two XGBoost models for seismic event classification, leveraging station-level recordings to refine event-level predictions. The first model classifies individual station readings, while the second aggregates station-level outputs to provide a final event classification. The dataset is carefully preprocessed, addressing challenges such as data imbalance, sensor variability, and irregular station coverage. To ensure the model's reliability, an extensive hyperparameter tuning pipeline (the Seismic Classifier Hyperparameter selection Pipeline) with a robust 5-fold cross-validation strategy is conducted. The results highlight the effectiveness of the model (global accuracy of 81.48%), with strong recall for large earthquakes, although medium-sized events remain more difficult to distinguish. Along some discussions on the practicality of the use of such classifiers, these findings contribute to the development of scalable and interpretable Earthquake Early Warning (EEW) systems, with potential applications in earthquake-prone regions worldwide.</div
Une méthode de Lagrangien Augmenté assistée par apprentissage par renforcement pour la maintenance d'une ligne d'assemblage hybride série-parallèle
No full textNational audienceUne méthode de Lagrangien Augmenté assistée par apprentissage par renforcement pour la maintenance d'une ligne d'assemblage hybride série-parallèl
Explications Contrefactuelles pour le Problème de Couverture par Ensemble, un cas d’étude Radar
No full textInternational audienceCounterfactual Explanations for the Set Cover Problem, a Radar use cas
Energy-Efficient Orchestration and Placement of 5G Network Slices
No full textInternational audienceThe advent of fifth-generation (5G) mobile networks is accompanied by a massive and hetero-geneous demand for services with stringent requirements. To deliver customizable guarantees,5G adopts the network slicing paradigm, virtualizing isolated sub-networks over a shared phys-ical infrastructure [1]. While slicing increases flexibility, it also raises concerns about energyconsumption in virtualized infrastructures [2]. This work focuses on energy-aware orchestrationand placement of multiple slices under Service Level Agreement (SLA) constraint
Limits on the chiral magnetic effect from the event shape engineering and participant-spectator correlation techniques in Pb-Pb collisions at TeV
No full textInternational audienceThe latest experimental studies related to the search for the Chiral Magnetic Effect (CME) in Pb-Pb collisions at TeV recorded with the ALICE detector at the Large Hadron Collider (LHC) are presented. Charge-dependent two-particle correlations relative to the reaction plane are measured for charged particles in the pseudorapidity range and the transverse-momentum range GeV/. Two approaches have been employed: in the first method, the contribution of the background to the measurement is varied using the event shape engineering (ESE), while the second relies on changing the contribution of the potential CME signal by measuring azimuthal correlations relative to the participant plane, where the background contributions are maximized, and spectator plane, where the CME signal contribution is maximized. Both methods yield results consistent with the absence of a CME signal within the measurement uncertainties. The result obtained from correlations relative to different symmetry planes, a technique applied for the first time at LHC energies, gives the possibility to test independently and confirm the upper limits from previous measurements, while the new limit from the ESE analysis offers improved constraint relative to previous attempts
Comparative performance of ICOPE Step 1 and fried frailty criteria in detecting frailty phenotypes: A cross-sectional study
No full textInternational audienceBackground: Frailty represents a significant public health challenge among aging populations. Early and accurate detection is vital for implementing timely interventions that may delay or prevent functional deterioration. Among the available assessment tools, The Fried frailty phenotype is widely recognized as a reference framework for assessing frailty. In parallel, the WHO's ICOPE Step 1 has been developed as a tool to detect potential declines in intrinsic capacity. Considering its design and purpose, ICOPE Step 1 may be regarded as a feasible option for use as a screening tool in clinical and community settings; however, direct comparative analyses within the same population remain limited. This study aimed to evaluate the concordance between the ICOPE Step 1 tool and Fried criteria to inform and enhance frailty screening practices in both clinical and community-based settings. Methods: This cross-sectional study included 202 community-dwelling older adults aged ≥60 years (mean age 85.0 ± 4.5; 160 [79.2 %] females), categorized as non-frail, pre-frail, or frail based on Fried's frailty phenotype and the WHO ICOPE Step 1 screening tool. The diagnostic performance of the ICOPE tool was assessed in comparison to Fried's criteria by calculating sensitivity, specificity, and the area under the receiver operating characteristic (ROC) curve. Results: Compared to the reference Fried criteria, the ICOPE Step 1 tool identified a higher proportion of individuals as frail (63 % vs. 29 %) and fewer as robust (2 % vs. 18 %). Diagnostic performance analysis showed a sensitivity of 83.9 % and a specificity of 43.8 %, with an area under the ROC curve (AUC) of 0.639, indicating moderate discriminative ability. Conclusion: ICOPEStep 1 demonstrated high sensitivity as a rapid, community-based screening tool for identifying older adults at risk of frailty. While it cannot replace the diagnostic utility of the Fried phenotype due to its limited specificity, it serves as a valuable first-line instrument to guide further comprehensive geriatric assessment, particularly via ICOPE Step 2.</div
GWTC-4.0: Searches for Gravitational-Wave Lensing Signatures
No full textInternational audienceGravitational waves can be gravitationally lensed by massive objects along their path. Depending on the lens mass and the lens--source geometry, this can lead to the observation of a single distorted signal or multiple repeated events with the same frequency evolution. We present the results for gravitational-wave lensing searches on the data from the first part of the fourth LIGO--Virgo--KAGRA observing run (O4a). We search for strongly lensed events in the newly acquired data by (1) searching for an overall phase shift present in an image formed at a saddle point of the lens potential, (2) looking for pairs of detected candidates with consistent frequency evolution, and (3) identifying sub-threshold counterpart candidates to the detected signals. Beyond strong lensing, we also look for lensing-induced distortions in all detected signals using an isolated point-mass model. We do not find evidence for strongly lensed gravitational-wave signals and use this result to constrain the rate of detectable strongly lensed events and the merger rate density of binary black holes at high redshift. In the search for single distorted lensed signals, we find one outlier: GW231123_135430, for which we report more detailed investigations. While this event is interesting, the associated waveform uncertainties make its interpretation complicated, and future observations of the populations of binary black holes and of gravitational lenses will help determine the probability that this event could be lensed
Black Hole Spectroscopy and Tests of General Relativity with GW250114
No full textInternational audienceThe binary black hole signal GW250114, the loudest gravitational wave detected to date, offers a unique opportunity to test Einstein’s general relativity (GR) in the high-velocity, strong-gravity regime and probe whether the remnant conforms to the Kerr metric. Upon perturbation, black holes emit a spectrum of damped sinusoids with specific, complex frequencies. Our analysis of the postmerger signal shows that at least two quasinormal modes are required to explain the data, with the most damped remaining statistically significant for about one cycle. We probe the remnant’s Kerr nature by constraining the spectroscopic pattern of the dominant quadrupolar (ℓ=m=2) mode and its first overtone to match the Kerr prediction to tens of percent at multiple postpeak times. The measured mode amplitudes and phases agree with a numerical-relativity simulation having parameters close to GW250114. By fitting a parametrized waveform that incorporates the full inspiral-merger-ringdown sequence, we constrain the fundamental (ℓ=m=4) mode to tens of percent and bound the quadrupolar frequency to within a few percent of the GR prediction. We perform a suite of tests—spanning inspiral, merger, and ringdown—finding constraints that are comparable to, and in some cases 2–3 times more stringent than those obtained by combining dozens of events in the fourth Gravitational-Wave Transient Catalog. These results constitute the most stringent single-event verification of GR and the Kerr nature of black holes to date, and outline the power of black-hole spectroscopy for future gravitational-wave observations