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Acquiring numerical equality
No full textInternational audienceWe propose to analyze the notion of numerical equality as a complex, Numerical Equality, constituted of three facets ("same number" statements, numeral labels, and one-to-one pairings of collections) all mapping onto a same relation defined on collections, herein referred to as the relation of equal numerosity. With this framework in hand, we review experimental studies assessing whether children correctly map the three facets of Numerical Equality onto the relation of equal numerosity, and whether they understand that these three facets are interrelated. By and large, these studies indicate that children still struggle with various aspects of the Numerical Equality complex as they enter school -and provide no evidence that children represent the relation of equal numerosity itself before the age of 5 years. Our review also identifies significant gaps in the literature, leaving many aspects of children's acquisition of numerical equality open to research
Formation dynamics of an ethylene carbonate-derived solid–electrolyte-interphase in commercial Li-ion batteries
No full textInternational audienceThe importance of the solid–electrolyte-interphase (SEI) is well-established in lithium-ion (Li-ion) batteries, but the technical story behind its formation remains incomplete. Current research has largely focused on the nature of the deposited layer, while the formation dynamics, particularly those occurring in the solution phase, remain elusive. Here, by employing operando infrared fiber evanescent wave spectroscopy (IR-FEWS) to conduct real-time monitoring of the chemical dynamics of ethylene carbonate-based electrolytes and graphite anodes, we reveal that the assembly of the SEI layer follows a classical heterogeneous nucleation and growth process under appropriate kinetic constraints. Our findings, supported by various other in situ/ex situ techniques, show that during charging, the newly generated species (e.g. lithium ethylene dicarbonate (LEDC) and Li2CO3), that are destined for the SEI, can also diffuse away from the graphite–electrolyte interface into the electrolyte. The deposition of the species occurs via a heterogeneous nucleation process with the low-solubility inorganic species (e.g. Li2CO3) preferentially nucleating on the graphite surface, followed by more-soluble organic species (e.g. LEDC). Limiting diffusion to promote the deposition is crucial for facilitating efficient SEI formation with competitive deposition kinetics depending not only on the charging rate and temperature, but also the electrolyte quantity. When the formation parameter-space is intentionally modified by employing a high current pulse during initial charging followed immediately by an ageing step, a more stable SEI with lower resistance is developed, leading to longer lifetimes for the Li-ion pouch cells prepared with this new protocol. Collectively, these findings deepen our mechanistic understanding of SEI formation from the “solution” phase perspective and offer an enriched framework for defining initial charging protocols for battery manufacturing
On the performance of radiocarbon and quartz OSL dating in macrotidal estuarine environments: Four case studies from Western France
No full textInternational audienceThe study of estuarine sedimentary archives provides valuable insights into their geomorphological evolution over the past two centuries, enhancing our understanding of estuarine responses to climate change. Establishing a reliable and precise geochronological framework is therefore essential for monitoring these changes. This study evaluates the performance of quartz Single-Aliquot Regenerative (SAR) OSL and AMS 14C dating in four estuaries along the western coast of France. The results are compared with cartographic data, serving as an independent age control. Of the 14 OSL dated samples, 10 yield depositional ages consistent with cartographic data, whereas the remaining 4 appear to overestimate ages by 20–100 years. In contrast, AMS 14C dating reveals numerous stratigraphic inversions, with at least 12 out of the 16 measured samples overestimating the depositional age in some cases by up to 5000 years, in total disagreement with cartographic data. The discrepancy between the OSL and radiocarbon ages reflects the constant reworking of allochthonous material, to which is added the further uncertainty associated with the local reservoir age. These factors fundamentally limit the reliability of 14C dating regardless of the material analyzed. By contrast, the OSL signal displays remarkable resilience, with any age overestimation linked to partial bleaching remaining minor (on the order of decades) compared with the errors affecting 14C ages. This underscores the capacity of OSL dating to resolve short-term environmental changes and positions it as the most reliable tool for constructing high-resolution chronologies of the last centuries in macrotidal estuarine settings
Flying shape and aerodynamics of a full-scale flexible Olympic windsurf sail
No full textInternational audienceThe introduction of hydrofoils in windsurfing has fundamentally changed the aerodynamic loads on modern rigs. While past studies including recent ones in windsurfing or sailing aerodynamics have relied on reduced-scale rigid sail models and numerical simulations, there is a lack of experimental data on the full-scale flying shape of deformable sails. In particular, iQFOil class - new Olympic windsurf class - still lacks of direct measurements to potentially validate Fluid Structure Interaction model, in order to improve the accuracy of Velocity Program Prediction. The 3D flying shape of a real-scale 8 m iQFOiL class windsurf sail is measured in steady state sailing configurations. The outdoor conditions are simulated in a large-scale wind tunnel and the flying shape is reconstructed with a stereo camera imaging technique. Together with the sail shape, we measure simultaneously the aerodynamic forces and moments applied to the sail. With the measured forces and moments, the lift, drag and roll coefficients are determined for wind velocities ranging from 4 to 8 m/s. A systematic decrease of these coefficients is observed as compared to previous studies on reduced-scale rigid sail model, because of the rigging deformation due to wind loading. We thus establish experimentally benchmark data for the iQFOiL sail and more generally for compliant rigging
Omnidirectional type inference for ML: 5th Workshop on the Implementation of Type Systems
No full textInternational audienceThe Damas-Hindley-Milner (ML) type system owes its success to principality, the property that every well-typed expression has a unique most general type. This makes inference predictable and efficient. Yet, principality is fragile: many extensions of ML—GADTs, higher-rank polymorphism, and static overloading—break it by introducing fragile constructs that resist principal inference. Existing approaches recover principality through directional inference algorithms, which propagate known type information in a fixed (or static) order (e.g. as in bidirectional typing) to disambiguate such constructs. However, the rigidity of a static inference order often causes otherwise well-typed programs to be rejected.We propose omnidirectional type inference, where type information flows in a dynamic order. Typing constraints may be solved in any order, suspending when progress requires known type information and resuming once it becomes available, using suspended match constraints. This approach is straightforward for simply typed systems, but extending it to ML is challenging due to let-generalization. Existing ML inference algorithms type let-bindings `let x = e_1 in e_2` in a fixed order—type `e_1`, generalize its type, and then type `e_2`. To overcome this, we introduce incremental instantiation, allowing partially solved type schemes containing suspended constraints to be instantiated, with a mechanism to incrementally update instances as the scheme is refined. Omnidirectionality provides a general framework for restoring principality in the presence of fragile features. We demonstrate its versatility on two fundamentally different features of OCaml: static overloading of record labels and datatype constructors and semi-explicit first-class polymorphism. In both cases, we obtain a principal type inference algorithm that is more expressive than OCaml’s current typechecker
Nondestructive optomechanical detection scheme for Bose-Einstein condensates
No full textInternational audienceWe present a two-tone heterodyne optical readout scheme to extract unequal-time density correlations along an arbitrary stationary interaction path from a pancake-shaped Bose-Einstein condensate, using a modulated laser probe. Analysing the measurement noise both from imprecision and backaction, we identify the standard quantum limit for the signal-extraction scheme, and examine how a class of two-mode squeezed initial states can be used to push beyond this limit. As an application, we show how the readout scheme can be used for an experimental realisation of acceleration-dependence of quantum-vacuum fluctuations in the system, including the analogue spacetime circular motion Unruh effect
Superstition in Translation: Vamps, Vampire-Capitalists, and Vocabularies of Class and Gender in Republican China
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Euclid preparation: Towards a DR1 application of higher-order weak lensing statistics
No full textInternational audienceThis is the second paper in the HOWLS (higher-order weak lensing statistics) series exploring the usage of non-Gaussian statistics for cosmology inference within \textit{Euclid}. With respect to our first paper, we develop a full tomographic analysis based on realistic photometric redshifts which allows us to derive Fisher forecasts in the (, ) plane for a \textit{Euclid}-like data release 1 (DR1) setup. We find that the 5 higher-order statistics (HOSs) that satisfy the Gaussian likelihood assumption of the Fisher formalism (1-point probability distribution function, 1-norm, peak counts, Minkowski functionals, and Betti numbers) each outperform the shear 2-point correlation functions by a factor on the forecasts, with only marginal improvement when used in combination with 2-point estimators, suggesting that every HOS is able to retrieve both the non-Gaussian and Gaussian information of the matter density field. The similar performance of the different estimators\inlinecomment{, with a slight preference for Minkowski functionals and 1-point probability distribution function,} is explained by a homogeneous use of multi-scale and tomographic information, optimized to lower computational costs. These results hold for the mass mapping techniques of the \textit{Euclid} pipeline: aperture mass, Kaiser--Squires, and Kaiser--Squires plus, and are unaffected by the application of realistic star masks. Finally, we explore the use of HOSs with the Bernardeau--Nishimichi--Taruya (BNT) nulling scheme approach, finding promising results towards applying physical scale cuts to HOSs
Thermo-mechanical simulation of L-PBF process at part-scale by coupling grain structure calculation and crystal viscoplasticity
No full textInternational audienceAn integrated numerical framework is proposed to perform a thermomechanical analysis of Laser Powder Bed Fusion (L-PBF) at the part scale, covering the entire construction process. The novelty lies in the fact that the thermomechanical analysis is driven by the evolving grain structure, also predicted at the part scale. The grain structure is first generated using a hybrid - Cellular Automaton (CA) method, which enables the generation of the grain structure on a CA grid at part-scale while incorporating the detailed scanning trajectories. For the thermo-mechanical simulation, a layer-by-layer thermal analysis includes the non-exposed powder, whereas the mechanical analysis only considers the substrate and the part under construction. A crystal plasticity model is employed for the nickel-based superalloy Inconel 718 (IN718), utilizing the CA grain structure referenced by Euler angles. A reduced grain approach is proposed, wherein Euler angles from the CA grid are projected onto the mechanical mesh. The mechanical mesh size is chosen appropriately to balance computational efficiency and accuracy. The calibration of the parameters of the crystal plasticity laws is conducted from room temperature up to 1100 C using tests performed on homogenized IN718 material. Tensile tests on the representative volume elements (RVEs) of grain structures with different laser scanning trajectories are performed to study the mechanical response for each specified texture. Finally, thermo-mechanical simulations are applied to the L-PBF construction of a propeller with single-crystal and polycrystalline grain structures. At each time increment, the temperature field is transferred to the mechanical mesh, and grains are activated according to the part under construction. The influence of local grain texture on anisotropic stress distribution and distortion is analyzed and discussed
