Application of the ONERA model of dynamic stall

A semiempirical model to predict the unsteady loads on an airfoil that is experiencing dynamic stall, is investigated. The mathematical model is described from an engineering point of view, demonstrates the procedure for obtaining various empirical parameters, and compares the loads predicted by the model with those obtained in the experiment. It is found that the procedure is straightforward, and the final calculations are in qualitative agreement with the experimental results. Comparisons between calculations and measurements also indicate that a decrease in accuracy results when the values of both the reduced frequency and the amplitude of oscillation are large. Potential quantitative improvements in the accuracy of the calculations are discussed for accounting of both the hysteresis in the static data and the effects of stall delay in the governing equations

Electrons on a sphere in disorder potential

We investigate, both analytically and numerically, the behavior of the electron gas on a sphere in the presence of point-like impurities. We find a criterion when the disorder can be regarded as small one and the main effect is the broadening of rotational multiplets. In the latter regime the statistics of one impurity-induced band is studied numerically. The energy level spacing distribution function follows the law P(s) ~ s exp(-a s^b) with 1<b<2. The number variance shows various possibilities, strongly dependent on the chosen model of disorder.Comment: 11 pages, REVTEX, 9 eps figures; references added to Sec.

Pengujian Karakteristik Unjuk Kerja Turbin Mikrohidro Di Desa Ciasmara

Experimental study of performance characteristic of micro-hydro water turbine hasbeen done in Kabitpaten Bogor. In this study performance is defined as a turbine efficiency which isrepresented by ratio between mechanical energy provided by turbine and an available potential energyofwater at a various conditions offlow. The study was limited only at several variation ofwater flowrate because the turbine installation is only equipped by conventional control system. Water level inthe basin was measured by level water meter with the precision is around 10%, while water flow ratewas measured by bridge flow meter. Mechanical energy is calculatedfrom measurement ofrotationalmoment and rotation of shaft. The moment was measured by calibrated hydraulic dynamometer andthe shaft rotation was measured by stroboscope. Based on the test results, at the full capacity (0.305mlIs flow rate and 3.17 mhead) the turbine showed agood performance with the efficiency is around59%

Le concept de maladies virales émergentes : quel risque de zoonose pour La Réunion ?

A La Réunion, le risque d'émergence de maladies virales est constitué par plusieurs zoonoses virales qu'il convient de surveiller: infections à virus Sindbis, virus de l'encéphalite japonaise, virus Wesselsbron, virus Nipah, virus Zika, virus West Nile, virus de la fièvre de la vallée du Rift. La lutte contre ces maladies virales émergentes (MVE) passe par une détection précoce des cas et donc un système de surveillance doté d'un véritable réseau d'information, d'alerte et de prévention international. (Résumé d'auteur

Cardiac Output and Performance during a Marathon Race in Middle-Aged Recreational Runners

Purpose. Despite the increasing popularity of marathon running, there are no data on the responses of stroke volume (SV) and cardiac output (CO) to exercise in this context. We sought to establish whether marathon performance is associated with the ability to sustain high fractional use of maximal SV and CO (i.e, cardiac endurance) and/or CO, per meter (i.e., cardiac cost). Methods. We measured the SV, heart rate (HR), CO, and running speed of 14 recreational runners in an incremental, maximal laboratory test and then during a real marathon race (mean performance: 3 hr 30 min ± 45 min). Results. Our data revealed that HR, SV and CO were all in a high but submaximal steady state during the marathon (87.0 ± 1.6%, 77.2 ± 2.6%, and 68.7 ± 2.8% of maximal values, respectively). Marathon performance was inversely correlated with an upward drift in the CO/speed ratio (mL of CO × m−1) (r = −0.65, P < 0.01) and positively correlated with the runner's ability to complete the race at a high percentage of the speed at maximal SV (r = 0.83, P < 0.0002). Conclusion. Our results showed that marathon performance is inversely correlated with cardiac cost and positively correlated with cardiac endurance. The CO response could be a benchmark for race performance in recreational marathon runners

Présentation du calcul médico-économique à travers des outils biostatistiques et probabilités

International audiencePrésentation du calcul médico-économique à travers des outils biostatistiques et probabilités T. Bastogne, Y. Petot et P. Vallois Présentation du calcul médico-économique à travers des outils biostatistiques et probabilités 2 octobre 201

Record RF performance of standard 90 nm CMOS technology

We have optimized 3 key RF devices realized in standard logic 90 nm CMOS technology and report a record performance in terms of n-MOS maximum oscillation frequency f/sub max/ (280 GHz), varactor tuning range and varactor and inductor quality factor

A ferromagnet with a glass transition

We introduce a finite-connectivity ferromagnetic model with a three-spin interaction which has a crystalline (ferromagnetic) phase as well as a glass phase. The model is not frustrated, it has a ferromagnetic equilibrium phase at low temperature which is not reached dynamically in a quench from the high-temperature phase. Instead it shows a glass transition which can be studied in detail by a one step replica-symmetry broken calculation. This spin model exhibits the main properties of the structural glass transition at a solvable mean-field level.Comment: 7 pages, 2 figures, uses epl.cls (included

THREE-DIMENSIONAL ANALYSIS OF TURBINE ROTOR FLOW INCLUDING TIP CLEARANCE

A 3D Navier-Stokes investigation of a high pressure turbine rotor blade including tip clearance effects is presented. The 3D Navier-Stokes code developed at ONERA solves the three-dimensional unsteady set of mass-averaged Navier-Stokes equations by the finite volume technique. A one step Lax-Wendroff type scheme is used in a rotating frame of reference. An implicit residual smoothing technique has been implemented, which accelerates the convergence towards the steady state. A mixing length model adapted to 3D configurations is used. The turbine rotor flow is calculated at transonic operating conditions. The tip clearance effect is taken into account. The gap region is discretized using more than 55,000 points within a multi-domain approach. The solution accounts for the relative motion of the blade and casing surfaces. The total mesh is composed of five sub-domains and counts 710,000 discretization points