Global electro-thermal modelling and circuit-type simulation of SiC Mosfet power devices in short-circuit operation for critical system analysis

International audienceThe purpose of this paper is to present, for the first time, a global transient electrothermal model and simulation results of commercially recent silicon carbide (SiC) power MOSFET devices. The developed models aim is faithfully transposing specifically experimental short-circuit (SC) behaviour of the studied components, ready-to-use for the analysis of an inverter-leg malfunctioning. After extensive experimentation, a thermal model of the SiC die allows to develop models of gate-leakage current and drain-source current during SC. After verifying the robustness of the proposed models, an original circuit-type with an easy implementation is performed using a commercial circuit simulation tool

AGING INVESTIGATION OF INVERTER-FED LOW VOLTAGE MOTOR WINDING INSULATION SUBJECTED TO HIGH DV/DT

International audienceThe relevance of this paper determines by oncoming implementation of wide bandgap power semiconductors as SiC in inverters feeding motors. Hence, it is indispensable to investigate the influence of intensified electric stresses on winding insulation. In this regard, comparative corona resistance tests on pulse voltage with µs-and ns-level of rise/fall time were carried out. A novel specimen form for rectangular section wires is proposed. Considerations related to aging of dielectrics subjected to high dV/dt and high frequency pulse voltage are introduced

Monofiber optical probe using Doppler signals detection for Drop Size and Velocity measurement in air assisted atomization

Reliable measurement of droplet/bubble size and velocity distributions in dense flows is desired in a variety of research fields, both for laboratory and industrial use. A new type of single-mode monofiber optical probe manufactured by A2 Photonic Sensors is introduced in this paper: it combines traditional phase detection with the collection of a Doppler signal returned by an incoming gas-liquid interface to provide information on residence times, drop concentration and velocity, which afford then drop chords and liquid flux measurements. Compared with classical optical probes, that new sensor does not require any calibration. The purpose of the present work is to test this technique in assisted atomization in order to provide a mean for spray characterization and ultimately to improve our understanding of atomization mechanisms. The probe has been tested downstream of a coaxial air-assisted atomizer operated at liquid velocity =. to. / , and gas velocity from = to about /. We first analyzed raw signals in various flow conditions. It happens that, when increasing the gas velocity and the number density of drops, the signal experiences very strong fluctuations of the gas level, making the identification of individual droplets more difficult. That leads us to develop a new signal processing routine specifically adapted to such complex working conditions. At = / and for three liquid flow rates, the spatial integration of local liquid fluxes represents 92 to 99% of the injected liquid flow rate. These good results demonstrate that the Doppler probe provides reliable statistics on drops velocity and size

Les plans d\u27urgence dans les bibliothèques patrimoniales françaises : premières recommandations pour les bibliothèques municipales classées par la mission, aux regards des enjeux identifiés dans la note de cadrage

L’IGÉSR (Inspection générale de l’éducation, du sport et de la recherche) publie un rapport sur le chantier d’élaboration et de mise en œuvre de plans d’urgence dans les bibliothèques patrimoniales françaises où la nécessité d’avoir une procédure de sauvetage et d’évacuation maîtrisée des collections patrimoniales reste peu cadrée. Ces recommandations fortes sont destinées à la Bibliothèque nationale de France (BNF), aux bibliothèques des collectivités territoriales, aux bibliothèques universitaires et des grands établissements scientifiques et littéraires, soit environ 660 établissements

Poisoning by Anticoagulant Rodenticides in Humans and Animals: Causes and Consequences

Anticoagulant rodenticides (ARs) are a keystone of the management of rodent populations in the world. The widespread use of these molecules raises questions on exposure and intoxication risks, which define the safety of these products. Exposures and intoxications can affect humans, domestic animals and wildlife. Consequences are different for each group, from the simple issue of intoxication in humans to public health concern if farm animals are exposed. After a rapid presentation of the mechanism of action and the use of anticoagulant rodenticides, this chapter assesses the prominence of poisoning by anticoagulant rodenticides in humans, domestic animals and wildlife

Impact of a Viscous Liquid Drop

We simulate the impact of a viscous liquid drop onto a smooth dry solid surface. As in experiments, when ambient air effects are negligible, impact flattens the falling drop without producing a splash. The no-slip boundary condition at the wall produces a boundary layer inside the liquid. Later, the flattening surface of the drop traces out the boundary layer. As a result, the eventual shape of the drop is a "pancake" of uniform thickness except at the rim, where surface tension effects are significant. The thickness of the pancake is simply the height where the drop surface first collides with the boundary layer.Comment: 5 pages, 3 figures, submitted to Physical Review Letter

Vortices catapult droplets in atomization

International audienceA droplet ejection mechanism in planar two-phase mixing layers is examined. Any disturbance on the gas-liquid interface grows into a Kelvin-Helmholtz wave, and the wave crest forms a thin liquid film that flaps as the wave grows downstream. Increasing the gas speed, it is observed that the film breaks up into droplets which are eventually thrown into the gas stream at large angles. In a flow where most of the momentum is in the horizontal direction, it is surprising to observe these large ejection angles. Our experiments and simulations show that a recirculation region grows downstream of the wave and leads to vortex shedding similar to the wake of a backward-facing step. The ejection mechanism results from the interaction between the liquid film and the vortex shedding sequence: a recirculation zone appears in the wake of the wave and a liquid film emerges from the wave crest; the recirculation region detaches into a vortex and the gas flow over the wave momentarily reattaches due to the departure of the vortex; this reattached flow pushes the liquid film down; by now, a new recirculation vortex is being created in the wake of the wave--just where the liquid film is now located; the liquid film is blown up from below by the newly formed recirculation vortex in a manner similar to a bag-breakup event; the resulting droplets are catapulted by the recirculation vortex

Towards the Industrialization of New MDO Methodologies and Tools for Aircraft Design

An overall summary of the Institute of Technology IRT Saint Exupery MDA-MDO project (Multi-Disciplinary Analysis - Multidisciplinary Design Optimization) is presented. The aim of the project is to develop efficient capabilities (methods, tools and a software platform) to enable industrial deployment of MDO methods in industry. At IRT Saint Exupery, industrial and academic partners collaborate in a single place to the development of MDO methodologies; the advantage provided by this mixed organization is to directly benefit from both advanced methods at the cutting edge of research and deep knowledge of industrial needs and constraints. This paper presents the three main goals of the project: the elaboration of innovative MDO methodologies and formulations (also referred to as architectures in the literature 1) adapted to the resolution of industrial aircraft optimization design problems, the development of a MDO platform featuring scalable MDO capabilities for transfer to industry and the achievement of a simulation-based optimization of an aircraft engine pylon with industrial Computational Fluid Dynamics (CFD) and Computational Structural Mechanics (CSM) tools

Management of massive rotator cuff tears: prospective study in 218 patients

BACKGROUND: No consensus exists about the management of massive and symptomatic rotator cuff tears (RCTs). The objective of this study was to compare the 12-month clinical outcomes of various treatment options for massive RCTs. HYPOTHESIS: Arthroscopic surgery has a role to play in the treatment of massive and apparently irreparable RCTs. MATERIAL AND METHODS: A prospective multicentre non-randomised study was performed in patients with massive RCTs managed non-operatively (NONOP) or by arthroscopic tenotomy/tenodesis of the long head of biceps (aTLB), arthroscopic partial tendon repair (aPTR), arthroscopic latissimus dorsi transfer (aLDT), or reverse shoulder arthroplasty (RSA). Clinical outcomes were evaluated based on the Constant score, Subjective Shoulder Value (SSV), and American Shoulder and Elbow Surgeons (ASES) score after 3, 6, and 12 months. RESULTS: The 218 included patients (mean age, 69 years) were distributed as follows: NONOP, n=71; aTLB, n=26; aPTR, n=61; aLDT, n=25; and RSA, n=35. After 12 months, the mean Constant score, SSV, and ASES score values were 70, 68%, and 73, respectively, and had improved significantly versus the preoperative values in all treatment groups. RSA was the only treatment followed by improvements in all Constant score items. Active forwards elevation improved significantly in the NONOP (+25°), aPTR (+26°), and RSA (+66°) groups. An improvement in active external rotation was seen only in the RSA group, where it was small (+10°, p=0.046). Significant increases in internal rotation were seen in the NONOP (+1.6 points) and aPTR (+1.7 points) groups. CONCLUSION: Arthroscopic techniques (aTLB, aPTR, and aLDT) for managing massive irreparable RCTs produce significant functional gains. Partial tendon repair (aPTR) and RSA may provide better outcomes than isolated aTLB or aLDT