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Démonstration de sauts orbitaux multiples dans un récepteur électrodynamique non linéaire à double mode pour le transfert d'énergie sans fil
No full textInternational audienceThis paper introduces a rotating-magnet based electrodynamic receiver for low-frequency wireless power transfer, capable of operating in two distinct modes: an oscillating mode and a continuous rotation mode. This dual-mode capability, never demonstrated previously in similar systems, enables seamless adaptation to a wide range of input magnetic field characteristics, addressing limitations of existing systems. An analytical model is developed to characterize the system's behavior and predict its performance. Based on this model, an orbit jump strategy to force the transition between modes has been developed, simulated, and experimentally validated. Experimental validation shows that the receiver, within a bounding box of 810 mm³, achieves 16.7 mW at 135 Hz in continuous rotation mode and 4.4 mW at 47 Hz under a 1 mT field in oscillating mode
An ancient DNA perspective on the Russian conquest of Yakutia
No full textInternational audienceYakut communities from northeastern Siberia inhabit some of the coldest environments on Earth, preserving an extraordinary archaeological record. Their history was profoundly reshaped by the Russian conquest, which introduced cereals, pathogens and Christianity beginning in 1632 (refs. 1,2,3,4,5). However, the biological impact of these transformations remains unknown. Here we generated extensive ancient DNA data to elucidate contemporary changes in Yakut genomic diversity and oral microbiomes. We found Yakut origins tracing back to local populations that admixed with Trans-Baikal groups migrating as the Great Mongol Empire spread. Despite the Russian conquest, the Yakut gene pool and oral microbiomes appeared largely stable, although smallpox strains distinct from those documented in Europe by approximately 1650 circulated. Marital practices generally maintained low consanguinity, with the exception of one female bearing the latest markers of traditional shamanism, who was the daughter of second-degree relatives
Homogenization model for a dense elastic medium of cylindrical scatterers and based on a realistic pair correlation function
No full textInternational audienceMultiple scattering effects due to a random distribution of identical cylindrical inclusions in an elastic medium are investigated. The approach is based on the analysis proposed by Fikioris and Waterman. The solution of the developed modal equations yields the effective wavenumbers of elastic coherent waves. Attention is made in this paper to a more realistic description of scatterers’ distribution in the host medium: this distribution is taken into account in modeling by introducing the notion of pair correlation function. The existing Conoir and Norris approach has been established by using the Hole Correction as pair correlation function, which simplifies the description of scatterers’ distribution and may lead to unphysical results for dense media. New formulas for the effective wavenumbers are proposed here by generalization of the latter theory and enable the use of any pair correlation function for possible application to dense media. The new generalized analytical model coupled to a realistic pair correlation function is compared to the previous approach in different materials configurations and validated for concrete structures by comparison to numerical simulations
A new lifetime measurement of the <math altimg="si3.svg"><mrow><mn>15</mn><mo linebreak="goodbreak">/</mo><msubsup><mn>2</mn><mn>1</mn><mo>−</mo></msubsup></mrow></math> octupole state in Pb
No full textInternational audienceA spectroscopic study of the 15/21− isomeric state in 209Pb has been performed to shed more light on the octupole phonons near the doubly-magic nucleus 208Pb. Populated by neutron-transfer reactions 208Pb(d, p)209Pb*, the de-exciting nuclei of interest were measured with the SFγNCS array, a versatile set-up comprising a silicon telescope and 60 NaI(Tl) detectors. Determined with particle-γ-ray coincidences, the branching ratio and multipolarity of the aimed γ-ray transition of the 15/21− state in 209Pb were found to be consistent with the literature. The state lifetime was precisely measured with the delayed coincidence method. The resulting reduced transition probability B(E3,15/21−→9/21+)=24.2(4) W.u. is an order of magnitude more precise than previously reported. An analysis in terms of the particle-octupole-vibration coupling model led to a reevaluation of the neutron E3 effective charge. This new experimental result on the lifetime of the 15/21− octupole state in 209Pb should help future investigations to constrain the nature of states in 207,208,209Pb
Prediction of temperature-dependent nucleation and growth in pure FeCr alloy via a self-consistent Phase Field approach
No full textInternational audienceIn a nucleation and growth process, the nucleation rate dictating the decomposition kinetics is generally modeled using the classical nucleation theory approach, which is only valid near the solubility limit where experiments are very difficult to perform. An alternative to this difficulty is to describe the exact dynamics associated with the decomposition from the metastable state to the stable state. This dynamics depends on the system under consideration and is complex to calculate. The approach presented in this work circumvents these two difficulties. The nucleation rate is calculated using only the knowledge of an effective Hamiltonian within a phase field approach. It then does not require the exact knowledge of the dynamics. The key point of this generic work is to show that only two time scales are sufficient to describe the complex interactions between the nucleation, growth, and coarsening processes. Comparing these scales makes it then possible to simulate microstructures by considering the nucleation process either as an initial condition or as a source term in the phase field equations. This approach is validated by the very good agreement between the simulated and measured 3D microstructures at different times on ultra-pure samples of FeCr, a textbook case of a nucleation-growth process
Performance assessment after long-term irradiation of ATLAS Micromegas detectors using 120 GeV muons at the Gamma Irradiation Facility at CERN
No full textInternational audienceThe ATLAS muon spectrometer will face an increased particle rate as a result of the increased instantaneous luminosity expected during the High-Luminosity LHC (HL-LHC) upgrade. The HL-LHC will provide a luminosity of L=7.5×1034cm−2s−1 and 3000fb−1 of integrated luminosity in 10 years, about 9 times more data of the ones so far collected by the ATLAS experiment. Micromegas chambers are used in the New Small Wheel(s), the first forward muon spectrometer station, to provide tracking and triggering at the intense particle rates expected. The detectors are operated with a ternary gas mixture composed of Ar+5%CO2+2%iC4H10, providing good high voltage stability and a large pulse height, important for inclined track reconstruction of particles crossing the detector. To ensure the long-term stable operation of the detector during the whole HL-LHC period, and due to the hydrocarbon content in the mixture, an extensive aging campaign has been ongoing since 2021 at the CERN Gamma Irradiation Facility, where spare production chambers are long-term exposed to a 14 TBq 137Csγ-source, accumulating so far, a charge equivalent to five years of HL-LHC operations under the highest expected background rate. This paper describes the results of the Micromegas chamber performance studies after two years of gamma irradiation and using the SPS/H4 120 GeV muon beams at CERN
Experimental and numerical investigation of the impact force generated by cylindrical ice water pellets
No full textInternational audienceThis study focuses on the force-time response of cylindrical water ice specimens subjected to impact loadings. Spherical specimens are traditionally used to characterize the impact behavior of water ice. However, they cannot be used to study the geometric effects induced by a cylindrical shape. Impact tests were carried out on a Hopkinson bar at 30 m.s -1 . These tests have demonstrated the importance of the impact angle in terms of both the increase in the load and the peak force at impact. Contrarily to what was observed for tensile spalling test, porosity has no noticeable impact on the maximum peak force measured here. The importance of the impact angle is illustrated by comparing the mechanical response of ice spheres with pellet cylinders for equivalent kinetic energies and temperatures
Technological trajectories in iron smelting: slag signatures, recipes, and traditions from Phnom Dek (Cambodia, 7th–20th c. CE)
No full textInternational audienceThis study investigates the long-term dynamics of bloomery iron smelting practices across the Phnom Dek region of Cambodia, a major metallurgical landscape active from at least the 7th to 20th centuries CE. Based on pXRF analysis of more than 1,700 slag samples, it develops an interpretive framework that integrates multiple scales of evidence, combining chemical composition, spatial distribution, technical features, and chronological context. At the core of this approach is the identification of coherent chemical signatures in slag, which, by using multivariate analyses, function as proxies for metallurgical recipes, and, at a broader level, enduring technological traditions shaped by the social organization of production. These signatures serve as comparative units for tracing production behaviors across sites and time periods. Through the categories of practice and recipe, the analysis aims to identify patterns of continuity, adaptation, and transformation in iron-making processes or smelting behavior over time. Results point to significant changes in ore procurement and recipe during the 11th–12th centuries, likely linked to wider transformations within Angkorian state dynamics. The persistence of specific chemical profiles and regionally shared smelting practices beyond this period suggests a bloomery tradition sustained across the landscape. Ultimately, the study argues that the chemistry of slag, as a material trace of smelting activities derived from technical, spatial, and chronological contexts, has unique capabilities to acquire interpretive significance when analyzed across these dimensions. This approach enables the discussion of technological trajectories in iron production and the socio-technical logics that shaped the evolution of the Phnom Dek metallurgical landscape
On the limitations of CFD modelling of flow boiling at high flow velocities and high heat fluxes
No full textInternational audienceThe ability of computational fluid dynamics (CFD) models to predict flow boiling at high heat flux and high flow velocity conditions has been investigated. High heat fluxes of about 10 MW/m 2 and high flow velocities of about 10 m/s typically appear in water cooling channels of divertor target elements in fusion reactors. In particular, the heat flux partitioning model used in the two-fluid CFD formulation was studied. CFD simulations of flow boiling in realistic divertor target cooling channels were performed and compared with conservative single-phase simulations. The predictive capability of CFD models for boiling was evaluated using experimental data, covering a wide range of flow velocities and heat fluxes. Existing CFD models correctly predicted void fraction and wall temperature at low flow velocities, but showed physically irrelevant results at higher velocities (above 3 m/s) leading to wall temperature overestimation. The study identified the wall heat flux partitioning model as the main contributor to the mispredictions and thoroughly discussed the main modelling shortcomings. By analysing the impact of operating conditions, some key boiling parameters, and state-of-the-art heat flux partitioning models, improvements of the model parameters are proposed. The simulations and model analyses are performed within the framework of the ANSYS CFX code and the results are compared with flow boiling experiments in uniformly and top-heated flow channels.</div
Search for b hadron decays to long-lived particles in the CMS endcap muon detectors
No full textInternational audienceA search for long-lived particles originating from the decay of b hadrons produced in proton-proton collisions with a center-of-mass energy of 13 TeV at the LHC is presented. The analysis is performed on a data set recorded in 2018, corresponding to an integrated luminosity of 41.6 fb. Interactions of the long-lived particles in the CMS endcap muon system would create hadronic or electromagnetic showers, producing clusters of detector hits. Selected events contain at least one such high-multiplicity cluster in the muon endcaps and require the presence of a displaced muon. The most stringent upper limits to date on the branching fraction (B K), where the long-lived particle decays to a pair of hadrons, are obtained for masses of 0.33.0 GeV and mean proper decay lengths in the range of 1500 cm