HAL-INSA Toulouse
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    31239 research outputs found

    A semi-analytical model for low-density impact-based surface treatments: Application to the abrasive waterjet texturing of thermoplastic polymers

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    International audienceSurface roughness is critical for bonding applications, as it directly influences the mechanisms occurring at the adhesive interface. Abrasive Waterjet texturing has emerged as a promising technique for functionalizing surfaces, but predicting the surface characteristics from stochastic impact-based processes remains a challenge. This study aimed to develop a numerical model capable of forecasting key morphological parameters for AWJ-textured surfaces with pilotable treatment coverage. The proposed model was optimized through theoretical analysis and confronted to topographical data from polymer samples treated with low-density AWJ using standard parameters. Profilometry measurements were supported by a custom post-treatment algorithm to remove artefacts and assess the characteristics of individual particle impacts (number, repartition, dimensions). The predicted roughness showed a 94 % concordance to the measured values

    Thermal investigations of supercritical CO 2 jet impingement and its cooling applicability in a machining context

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    International audienceIn recent years, the use of supercritical carbon dioxide (sCO2) as cutting fluid during machining operations has gained attention of the manufacturing community. The present paper intends to address thermal characteristics of sCO2 free jet impingement on a hot plate. An experimental approach has been hereby chosen in order to assess the heat transfer coefficient (HTC) in various experimental conditions. Infrared thermography along with high speed imaging are set up in order to access the cooling of a titanium plate. HTC is then calculated from an analytical solution of the heat transfer equation adapted to the specific conditions of the proposed setup.Investigations are focused on the influence of nozzle-to-plate distance (from 4 to 106 times jet diameter), angle of incidence (from 90° to 50°) and flow initial temperature (40 ◩C to 80 ◩C) and pressure (100 bar to 285 bar).Results provide with metric and dimensionless values of the HTC. Preliminary conclusions are drawn from the presence of solid carbon dioxide at the plate’s surface and leads are proposed to investigate in further detail the effect of the jet nature and structure on its cooling ability

    Experimental Validation of Sensitivity-Aware Trajectory Planning for a Quadrotor UAV Under Parametric Uncertainty

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    International audienceIn this work, we provide an experimental vali-dation of the recent concepts of closed-loop state and inputsensitivity in the context of robust flight control for a quadrotor(UAV) equipped with the popular PX4 controller. Our objectiveis to experimentally assess how the optimization of the referencetrajectory w.r.t. these sensitivity metrics can improve the closed-loop system performance against model uncertainties commonlyaffecting the quadrotor systems. To accomplish this, we presenta series of experiments designed to validate our optimizationapproach on two distinct trajectories, with the primary aimof assessing its precision in guiding the quadrotor through thecenter of a window at relatively high speeds. This approachprovides some interesting insights for increasing the closed-loop robustness of the robot state and inputs against physicalparametric uncertainties that may degrade the system’s perfor-mance

    Extending Guiding Vector Field to track unbounded UAV paths

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    International audienceA recent advance in vector field path following is the introduction of the Parametric Guiding Vector Field method. It allows for singularity-free vector fields with strong convergence guarantees, usable even for self-intersecting paths. However, the method requires significant gain tuning for practical use. In particular, for unbounded paths, the gains will inevitably become ill-suited for efficient path following. We propose a method to overcome this issue by introducing a dynamic step adaptation strategy, which provides additional normalization properties to the field. This allows the following of unbounded curves and reduces the number of gains to tune. The proposed improvements are verified in simulations using the PaparazziUAV software

    Describing carbons

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    International audienc

    Tuning the spin-orbit coupling, magnetic proximity, and band hybridization in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>Fe(001)</mml:mi><mml:mtext>/</mml:mtext><mml:mi>MgO</mml:mi><mml:mtext>/</mml:mtext><mml:msub><mml:mi>MoS</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math> multilayers

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    International audienceWe present first-principles calculations of the electronic structure and spin texture of a MoS2_{2} monolayer in Fe/MgO/MoS2_{2} multilayers. These metal/insulator/semiconductor stackings are subject to an electron transfer from the Fe layer to the MoS2_{2} sheet, giving rise to a two-dimensional (2D) electron gas, the density of which depends on the MgO layer thickness. We describe the consequences of this electron transfer and of the magnetic proximity effect on the occupation of the conduction bands of the MoS2_{2} layer, on the nature of its band gap, and on the splitting and dispersion of its valence bands near the Γ point of the 2D Brillouin zone. The spin splitting and spin texture are reproduced and understood by an effective Hamiltonian, which includes Rashba, Dresselhaus, and Zeeman effects. We finally show that the splitting of the MoS2_{2} valence bands induced near Γ by the spin-orbit coupling is rather different when Fe is replaced by a nonmagnetic transition metal such as vanadium

    Overpressure sensing through acousto-optics: a comparison between a self-mixing interferometer and an all-fiber Michelson interferometer

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    International audienceRecent studies have shown that a compact self-mixing interferometer can be used for the characterization of shock waves.It measures dynamically (&gt; 10 MHz) the changes in the refractive index induced by the shock wave. Associated to anappropriate acousto-optic model, the pressure profile is computed with a 34 mbar resolution. In the present work, wecompare shock wave induced refractive index variations measurements by another method using a Michelson-type fiber-optic interferometer with phase analysis that has been developed for Photonic Doppler Velocimetry applications. Theoutput signals of this system are processed in triature, which consists in analyzing the phase shift between the threeinterferometric signals. This bulkier system provides, in theory, a better resolution than the self-mixing interferometrysensing scheme. In the present paper, we compare these two optical methods to measure a shock wave pressure throughexperiments that were carried out with an open shock tube instrumented with commercial, bandwidth limited, pressuresensors. This configuration creates a spherical shock wave similar to those observed during on-field experiments withexplosives. We describe the two measurement systems and the experimental setup design used for overpressurecharacterizations. Both sensing approaches have been carried out in the same experimental conditions and with shock wavepressure peak amplitudes of a few bars. We detail the two types of signal processing and we discuss the results obtainedwith the two optical methods, which are also compared to a piezoelectric reference sensor

    The threshold phenomena for propagation in fractional Laplacian diffusion equations

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    In this paper, we investigate the threshold phenomenon between extinction and propagation in fractional Laplacian diffusion equations for a class of compactly supported initial data. We provide the first quantitative estimates on the threshold when the reaction nonlinearity is of bistable or ignition type. We mainly use estimates on the fundamental solutions of fractional Laplacian operators together with some accurate upper and lower solutions to show that the solution either propagates or goes extinct

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