Hal - Université Grenoble Alpes
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À l’heure où l’on ne prend au sérieux que la voix des canons… Georges Henein, animateur des avant-gardes artistiques et politiques cairotes pendant la guerre
No full textInternational audienc
On design, analysis, and hybrid manufacturing of microstructured blade-like geometries
No full textInternational audienceWith the evolution of new manufacturing technologies such as multi-material 3D printing, one can think of new type of objects that consist of considerably less, yet heterogeneous, material, consequently being porous, lighter and cheaper, while having the very same functionality as the original object when manufactured from one single solid material. We aim at questioning five decades of traditional paradigms in geometric CAD and focus at new generation of CAD objects that are not solid, but contain heterogeneous free-form internal microstructures. We propose a unified manufacturing pipeline that involves all stages, namely design, optimization, manufacturing, and inspection of microstructured free-form geometries. We demonstrate our pipeline on an industrial test case of a blisk blade that sustains the desired pressure limits, yet requires significantly less material when compared to the solid counterpart
Electronic structure and transport in materials with flat bands: 2D materials and quasicrystals
No full textreviewInternational audienceIn this review, we present recent works on materials whose common point is the presence of electronic bands of very low dispersion, called "flat bands", which are due to specific atomic order effects without electron interactions. These states are always indicative of some form of confinement and have significant consequences on the electronic structure, transport properties and magnetism of these materials. A first part is devoted to the cases where this confinement is due to the long-range geometry of the defect-free structure. We have thus studied periodic approximant structures of quasiperiodic Penrose and octagonal tilings, and twisted bilayers of graphene or transition metal dichalcogenides (TMDs) whose rotation angle between the two layers assumes a special value, called "magic angle". In these materials, the flat bands correspond to electronic states distributed over a very large number of atoms (several hundreds or even thousands of atoms) and are very sensitive to small structural distortions such as "heterostrain". We have shown that their electronic transport properties cannot be described by usual Bloch-Boltzmann theories, because the interband terms of the velocity operator dominate the intraband terms as far as quantum diffusion is concerned. In the case of twisted bilayer graphene, flat bands can induce a magnetic state and other electron-electron correlation effects. The second part focuses on two-dimensional nanomaterials in the presence of local point defects that cause resonant electronic states (vacancies, adsorbed atoms or molecules). We present studies on monolayer graphene, twisted or Bernal bilayer graphene, carbon nanotubes, monolayer and multilayer black phosphorene, and monolayer TMDs. A recent result is the discovery that the selective functionalization of a Bernal bilayer graphene sublattice leads to a metallic or insulating behavior depending on the functionalized sublattice type. This result, which seems to be confirmed by very recent experimental measurements, suggests that functionalization can be a key parameter to control the electronic properties of two-dimensional materials
Intermediation Platforms and Geopolitical Asymmetries, Lessons from a Pandemic
No full textInternational audienceTo a large extent, and particularly before vaccines became available, human societies owed their resilience during the COVID-19 pandemic to non-pharmaceutical interventions, i.e. social distancing combined with more invasive digital systems. In this paper, we consider the digital applications developed during 2020-2021, the two first years of the pandemic. We introduce a typology based on the services offered and the data flows they require, between both public and private actors. A detailed timeline of these developments shows that countries’ strategies have evolved in strong coherence with their overall digital policy. Our study demonstrates that this exogenous crisis has reinforced the critical role of intermediation platforms for maintaining society’s essential functions. Their increased centrality has contributed to intensifying information asymmetries and power imbalances, already at stake before the pandemic, both between platforms and states, as well as between countries, leading to new geopolitical equilibria
Observation of production in collisions at = 13 TeV with the ATLAS detector and constraints on anomalous quartic gauge-boson couplings
No full textInternational audienceThis Letter reports the observation of triboson production in 140 fb of data collected by the ATLAS detector from proton-proton collisions at a centre-of-mass energy of = 13 TeV at the LHC. Events with an opposite-charge pair, a high transverse-momentum photon, and significant missing transverse momentum are considered. The observed (expected) significance of the signal is 5.9 (6.0) standard deviations. The measured fiducial cross-section, defined for the final state is 6.2 0.8 (stat.) 0.6 (sys.) fb, in good agreement with the Standard Model prediction of 6.1 fb. Constraints on the Wilson coefficients of 13 dimension-8 operators describing physics beyond the Standard Model through anomalous quartic gauge-boson couplings are derived using the effective field theory framework
Les controverses mémorielles autour de l’héritage du fascisme et l’identité de l’extrême droite en Italie (fin XXe-début XXIe siècle)
No full textInternational audienc
Long induced paths and forbidden patterns: Polylogarithmic bounds
No full textSome material from arXiv:2304.09679 has been reused (such as definitions and remarks), so text overlap is to be expectedInternational audienceConsider a graph with a long path . When is it the case that also contains a long induced path? This question has been investigated in general as well as within a number of different graph classes since the 80s. We have recently observed in a companion paper (Long induced paths in sparse graphs and graphs with forbidden patterns, arXiv:2411.08685, 2024) that most existing results can recovered in a simple way by considering forbidden ordered patterns of edges along the path . In particular we proved that if we forbid some fixed ordered matching along a path of order in a graph , then must contain an induced path of order . Moreover, we completely characterized the forbidden ordered patterns forcing the existence of an induced path of polynomial size. The purpose of the present paper is to completely characterize the ordered patterns such that forbidding along a path of order implies the existence of an induced path of order . These patterns are star forests with some specific ordering, which we called constellations. As a direct consequence of our result, we show that if a graph has a path of length and does not contain as a topological minor, then contains an induced path of order . The previously best known bound was for some unspecified function depending on the Topological Minor Structure Theorem of Grohe and Marx (2015)
Detailed Manufacturing Design of REBCO Insert and Cooling Performance of 33T Cryogen-Free Superconducting Magnet
No full textInternational audienceThe 33T Cryogen-Free Superconducting Magnet (33T-CSM) project is progressing at Institute for Materials Research, Tohoku University. The 33T-CSM consists of a 19 T REBCO coil (HTS) with a 68 mm bore and a 14 T Nb3Sn+NbTi Rutherford coil (LTS) with a 320 mm bore. The 14 T-LTS coil was completed in 2024 and its stand-alone test was successfully performed. The 19 T-HTS coil design, which involves winding REBCO tape conductors in a two-layer bundle and impregnating only the end faces, has been completed and is expected to enter the manufacturing phase soon. This design reduces the risk of local degradation, which can cause hotspots, and optimizes the stress distribution within the coil to minimize maximum stress. Following these concepts, detailed manufacturing design of specific stacking methods of the pancakes and connections between the pancakes is discussed. In addition, the evaluation of the cooling capacity of the GM-JT and GM cryocoolers used for gas circulation cooling of the HTS and LTS coils in the cryostat of the 33 T-CSM, as well as the future scalability, will be presented
An informational account of anticipatory coarticulation – theoretical considerations and empirical plausibility
No full textInternational audienceIn speech, the realization of a phoneme is influenced by its preceding and forthcoming neighbors, a phenomenon called coarticulation. While influences from past actions (carryover coarticulation) can be explained by a combination of physical causalities and motor planning, influences from future action goals can only be fully explained by active anticipatory processes in speech motor control. Current modeling accounts view coarticulation as a side effect of efficiency objectives of control or properties of the planning algorithm.Here, we propose that anticipatory coarticulation provides prospective sensory cues usable for feedback-dependent speech control. To support this notion, we characterized the dynamics of carryover and anticipatory coarticulation in three French speakers in both acoustic and articulator data as measured by Electromagnetic Articulography using General Additive Models. Our data show that anticipatory coarticulation effects dominate over carryover coarticulation effects and allow to reliably differentiate between upcoming phonemes at least 200 ms before the canonical phoneme onset.These findings are compatible with an anticipatory feedback-dependent control strategy, as sensory information about future actions is available early enough to influence ongoing actions in spite of sensorimotor delays. Such considerations weaken the necessity for fully fledged internal predictive forward models for the control of fast actions
The role of Al addition on the hydrogen sorption properties of TiVZrNbHf high entropy alloy
No full textDiamond Light Source , B18 under the Energy Materials Block Allocation Group (BAG)International audienceRefractory BCC high entropy alloy TiVZrNbHf is a promising material for solid-state hydrogen storage with high hydrogen sorption capacity but unfavourable thermodynamics of hydride phase, i.e. too stable hydride that need high temperature to reversibly recover the absorbed hydrogen. As an attempt to destabilize the hydride phase, this study reports on the effect of Al addition (limited concentrations: 5 and 10 at.%) into this alloy on the physicochemical and hydrogen sorption properties. Despite traces of a V-Al secondary phase, the BCC (TiVZrNbHf)1-xAlx alloys are random solid solutions which form high-capacity FCC hydride phases under hydrogen atmosphere at room temperature, as proven by synchrotron and neutron diffraction. Although Al decreases the hydrogen sorption capacity, the presence of p element destabilizes the FCC hydride phase. A comparison with previous literature data helps understanding the role of Al which strongly depends on the chemical composition of the initial alloys. XANES studies allowed access to details of the electronic structure of the unoccupied levels complemented by density functional theory calculations. Moreover, the addition of Al favours the formation of larger open volume defects during hydride formation than the initial Al-free alloy which might explain the faster absorption kinetics in Al-containing alloys