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This paper describes a new single-shear specimen (SSS) and method to characterize the dynamic shear behavior of bulk metals using a traditional Split Hopkinson Pressure Bar (SHPB). By this method, the shear behavior of materials can be tested conveniently over a wide range of strain rates within 105 s−1. This technique was applied to a 304 austenitic stainless steel (ASS) under shear strain rates from 0.001 s−1 to 38700 s−1 at room temperature. Based on finite element (FE) simulations, it was found that the deformation of the specimen shear zone was dominated by shear stress/strain components. Stress state parameters represented by stress triaxiality η and Lode angle parameter θ - were found very close to zero, indicating a deformation mode of simple shear. Besides, an obvious gap existed between the local deformation behavior in the specimen shear zone and the macroscopic stress-strain relations measured by the strain gauges on the SHPB bars. A correction coefficient method was adopted to extract the real shear behavior from the experimentally obtained force-displacement data. Through comparisons between the tested and simulated stress-strain curves, a good agreement was obtained.

Peroxisome proliferator-activated receptor β/ (PPARβ/) activates AMP-activated protein kinase (AMPK) and plays a crucial role in glucose and lipid metabolism. Here, we examined whether the beneficial effects of PPARβ/δ activation depended on growth differentiation factor 15 (GDF15), a stress response cytokine that regulates energy metabolism. Pharmacological PPARβ/δ activation increased GDF15 levels and ameliorated glucose intolerance, fatty acid oxidation, endoplasmic reticulum stress, inflammation and activated AMPK in HFD-fed mice, whereas these effects were abrogated by the injection of a GDF15 neutralizing antibody and in Gdf15-/- mice. The AMPK-p53 pathway was involved in the PPARβ/δ-mediated increase in GDF15, which in turn activated again AMPK. Finally, Gdf15-/- mice showed reduced AMPK activation in skeletal muscle, whereas GDF15 administration resulted in AMPK activation in this organ. Collectively, these data reveal a novel mechanism by which PPARβ/δ activation increases the levels of GDF15 via AMPK and p53, which in turn mediates the metabolic effects of PPARβ/δ by sustaining AMPK activation. Abbreviations: Acadm, acyl-CoA dehydrogenase medium chain; Acox, acyl-CoA oxidase; AMPK, AMP-activated protein kinase; ATF4, activating transcription factor 4; BiP/GRP78, Binding immunoglobulin protein/78-kDa glucose-regulated protein; CC, compound C; Chop, C/EBP homologous protein; Cpt-1, carnitine palmitoyl-transferase 1; eIF2eukaryotic translation initiation factor 2 ER, endoplasmic reticulum; ERK, extracellular signal-regulated kinase; FGF21, fibroblast growth factor 21; GDF15, growth differentiation factor 15; GFRAL, glial-derived neurotrophic factor receptor α-like; HFD, high-fat diet; Pdk4, pyruvate dehydrogenase kinase 4; IRS, insulin receptor substrate; PGC-1PPAR co-activator 1 PPAR peroxisome proliferator-activated receptor; SOCS3, suppressor of cytokine signaling 3; STAT3, signal transducer and activator of transcription 3; Vldlr, very-low density lipoprotein receptor.

In October 2020, ETUC adopted a resolution “on the protection of the rights of nonstandard workers and workers in platform companies including the self-employed)”. ETUC calls for a European initiative which provides for a presumption of employment relationship where the burden of proof should be borne by the platform companies, who should abide to their labour and fiscal obligations, including the sectorialagreements negotiated in collective bargaining by social partners. This report provides sound legal support to the feasibility of the ETUC demands. The experts have identified a legal avenue which seeks to improve the situation of workers in platform companies:to put an end to the use by platforms of bogus self-employment contracts by prescribing a presumption of employment relationship and the liability of platforms as companies. The authors have provided national and European example to introduce the mechanism for a strong presumption of employment status to a potential directive regulating platform work. At national level, the most outstanding case for an employment presumption of workers in platform companies can be the Spanish Royal-Decree Law 9/2021, which extends the application of the labour code to workers in delivery platforms. At European level, cases of employment presumption are analysed from the Directive 2009/52/EC on sanctions and measures againstemployers of illegally staying third-country nationals and the Directive 2019/1152 on transparent and predictable working conditions.The authors complete the employment presumption with the need to shifting the burden of the proof on the platform. ETUC recalls that in the context of sex discrimination, the European Court of Justice has been introducing a reversal of the burden’ of proof through its case law and that this was incorporated later in the Directive 2006/54/EC on the implementation of the principle of equal opportunities and equal treatment of men and women in matters of employment and occupation. More recently, article 18 of the Transparent and Predictable Working ConditionsDirective also introduces a reversal of the burden of proof in the competence of labour law (unfair dismissals).The authors also tackle the need to qualify the legal status of the platform as companies, for which an avenue is proposed following the definition of a report of the European Parliament of 2020. To recognize platforms companies as employers when the presumption of employment relationship applies, ETUC proposes the definition of the employing entity as the party that impose labour law obligations and largely determines the terms and conditions.Whereas the clarification of the employment status of workers in platform companies would resolve many other current problems of workers in platform companies (like the de facto coverage by the social protection and the prevention and assessment of risks), specific guarantees appertaining to platform work should be granted to workers when it comes to working time, and information and consultation rights related to the algorithm management. These aspects are also tackled by the report. LV/ID/et Brussels, 24 June 2021 ETUC would like to remind that the views and opinions expressed in this report are those of the authors and do not necessarily reflect the official policy or position our organisation. The report concentrates largely on the extension of some labour law guarantees and social protection to genuine self-employed workers, thus examining how the ETUC resolution can provide for genuine self-employed workers operating through platform companies. ETUC defends the need for a level playing field between employees and the self-employed to prevent the employer from using the latter as cheap labour in opposition to the employee. This also implies taking action in relation to minimum wages and minimum tariffs, in such a way that these are not below the existing minimum wages or sectoral collective agreements, including the cost of social protection, taxes and other costs (such as holidays and professional costs) that the self-employed person will have to finance him/herself.In the accompanying document of the European Commission to the first stage consultation, it stated that “existing EU-level instruments only partially impact the challenges posed by platform work”, notably the employment status, underlining the need for EU action. At the moment of this publication, ETUC and the European employers’ organisations are consulted under Article 154 TFEU on possible action addressing the challenges related to working conditions in platform work. The avenues identified by the researchers are food for thought for the ETUC to prepare its answer for the second phase consultation. ETUC would like to thank the authors Judith Brockmann, Marie-Cécile Escande Varniol, Cécile Nicod and Daniel Pérez del Prado for their good work and their engagement to bring the organising efforts and legal victories of the European trade union movement to a European legislative framework.

International audience; This work proposes a new empirical direct methodology to estimate both the solar flux distribution and intensity on the surface of central receivers. In solar power tower plants with deteriorated heliostats, the numerical simulations to estimate the incident solar flux are not precise. Hence the thermal behaviour of the receivers cannot be determined. In those cases, direct measurement or semi-empirical methodologies are required to characterize the radiant power on the receiver. The new methodology proposed, named "Superposition method", consists in the hourly characterization of the reflected solar beam of each individual heliostat by means of a pyrheliometer, a passive screen, a flux sensor, a camera and digital image analysis. According to the aiming strategy used during receiver operation, each individual solar flux distribution and intensity can be gathered to obtain the total incident radiant power on the solar receiver. This non-real-time method has the advantage of reproducing any solar flux distribution on the receiver at present and past time.

International audience; This paper presents a systematic study of the thermo-viscoplastic behavior of a 304 austenitic stainless steel (ASS). The experiments were conducted over a wide range of strain rates (10 − 3 s − 1 to 3270 s − 1 ) and temperatures (-163°C to 172°C), for which the deformation behavior of 304 ASS becomes more complex due to the strain- induced martensitic transformation (SIMT) effect. Dynamic tests at low/elevated temperatures were conducted using the Hopkinson technique coupled with a cooling device/heating furnace, and temperature distribution within the specimen was verified to be uniform. Experimental results showed that the strain hardening rate of 304 ASS was strongly affected by SIMT effect. For quasi-static tests (10 − 3 s − 1 to 1 s − 1 ) at low temperatures (-163°C to -20°C), the stress-strain relations exhibited an S-shape and a second strain hardening phenomenon. The strain rate sensitivity and temperature sensitivity of 304 ASS were also different from metallic materials deformed by dislocation glide. Several unexpected phenomena including the negative strain rate sensitivity and the changing temperature sensitivity from quasi-static to dynamic tests were observed. Based on experimental results, an extension of the Rusinek-Klepaczko (RK) model considering SIMT effect was used to simulate the deformation behavior of 304 ASS: it predicted flow stress curves of 304 ASS above -60°C correctly. In addition, to validate the extended RK model and the identified model parameters, numerical simulations of ballistic impact tests of 304 ASS plates at various temperatures were carried out, showing a good agreement with experiments.

International audience; With the increasing availability of mobile devices and data generated by end-users, scientific instruments and simulations solving many of our most important scientific and engineering problems require innovative technical solutions. These solutions should provide the whole chain to process data and services from the mobile users to the cloud infrastructure, which must also integrate heterogeneous clouds to provide availability, scalability, and data privacy. This special issue presents the results of particular research works showing advances on mobile, hybrid, and heterogeneous clouds for modern cyberinfrastructures.

International audience; A novel image analysis-based technique applied to unmanned aerial vehicle (UAV) survey data isdescribed to detect and locate individual free-ranging sharks within aggregations. The methodallows rapid collection of data and quantification of fine-scale swimming and collective patternsof sharks. We demonstrate the usefulness of this technique in a small-scale case study exploringthe shoaling tendencies of blacktip reef sharks Carcharhinus melanopterus in a large lagoonwithin Moorea, French Polynesia. Using our approach, we found that C. melanopterus displayedincreased alignment with shoal companions when distributed over a sandflat where they areregularly fed for ecotourism purposes as compared with when they shoaled in a deeper adjacentchannel. Our case study highlights the potential of a relatively low-cost method that combinesUAV survey data and image analysis to detect differences in shoaling patterns of free-rangingsharks in shallow habitats. This approach offers an alternative to current techniques commonlyused in controlled settings that require time-consuming post-processing effort.

In this paper, we observe how the heat equation in a noncylindrical domain can arise as the asymptotic limit of a parabolic problem in a cylindrical domain, by adding a potential that vanishes outside the limit domain. This can be seen as a parabolic version of a previous work by the first and last authors, concerning the stationary case [Alvarez-Caudevilla and Lemenant, Adv. Differ. Equ. 15 (2010) 649-688]. We provide a strong convergence result for the solution by use of energetic methods and Γ-convergence technics. Then, we establish an exponential decay estimate coming from an adaptation of an argument due to B. Simon.

International audience; E. Le Vagueresse présente et explique le parcours qui l'a conduit, lui, professeur de littérature espagnole, à introduire l'étude des médias audiovisuels, et en particulier le cinéma - hispanique - et les séries télévisées, dans ses enseignements et dans son activité de recherche.

This paper presents a novel methodology to find out canting errors in the facets, i.e. mirror modules, of heliostats. An optimization procedure is established to fit simulated heliostat flux distributions to those captured on a white target. On the basis of a convolution-projection optical model, a deterministic algorithm - named DIRECT - has been successfully implemented, reaching correlation coefficients up to 95.8%. In this instance, the procedure has been applied to a THEMIS heliostat presenting canting errors of its, faceted modules. From the optimization results, the heliostat modules were accordingly readjusted. And the heliostat optical quality has been significantly increased, validating the proposed methodology. The authors thank the help provided by Antoine Pérez, Yann Volut and William Baltus during the experimental phase at THEMIS solar power plant. A. Sánchez-González is also indebted to Universidad Carlos III de Madrid for the mobility grant that funded the stay at PROMES-CNRS during spring-summer 2016.

International audience

This paper surveys the rise and fall of the European mercantilist system, and the transition to the modern, well-integrated international economy of the 19th century. It also surveys the literature on the links between trade and economic growth during the period, and on the economic effects of empire.

International audience; In this paper we present a different strategy for generating the trajectory of the swinging leg for a walking humanoid robot which takes into account the effects due to acceleration and velocities of the joints onto the center of mass of the robot. The trajectory of the leg is chosen to be constituted by two forth order polynomials interlaced by a via-point which satisfies the optimality criterium. This approach is validated on a humanoid robot HRP-2.

International audience; This paper addresses the problem of generating dynamic motion for a humanoid between two predefined postures. The humanoid robot starts its motion from a statically stable configuration to another known statically stable configuration when it is necessary to make step; that is, the center of mass (COM) is inside the support polygon at the initial and the goal configurations. A dynamic motion generation method is proposed in order to generate the whole-body robot motion. Zero moment point preview control is used for maintaining dynamic stability while the robot is taking the step and suitable splines are used for generating the hands, neck and foot motion because it is a free motion on the field of gravity; the screw theory is applied under Lie groups for kinematics and dynamics humanoid modeling, which allows smooth and natural humanoid motion. Successful results on the HRP-2 humanoid robot are shown and discussed.

International audience; This paper presents the objectives and the research work carried out in the frame of the ANEMOS project on short-term wind power forecasting. The aim of the project is to develop accurate models that substantially outperform current state-of-the-art methods, for onshore and offshore wind power forecasting, exploiting both statistical and physical modeling approaches. The project focus on prediction horizons up to 48 hours ahead and investigates predictability of wind for higher horizons up to 7 days ahead useful i.e. for maintenance scheduling. Emphasis is given on the integration of high-resolution meteorological forecasts. For the offshore case, marine meteorology is considered as well as information by satellite-radar images. Specific modules are also developed for on-line uncertainty and prediction risk estimation. An integrated software platform, 'ANEMOS', is developed to host the various models. This system will be installed by several end-users for on-line operation at onshore and offshore wind farms for prediction at a local, regional and national scale. The applications include different terrain types and wind climates, on-and offshore cases, and interconnected or island grids. The on-line operation by the utilities will allow validation of the models and an analysis of the value of wind prediction for a competitive integration of wind energy in the developing liberalized electricity markets in the EU.