Amélioration de la méthodologie de calcul de bruit de jet à l'aide de la ZDES mode 3 et d'une méthode de génération de turbulence silencieuse

International audienceThis article presents Zonal Detached Eddy Simulations (ZDES) of a single stream jet. Focus is put on the improvement of the turbulence modelling methodology aimed at taking into account the nozzle internal boundary layer dynamics to better simulate the initial stage of the mixing layer development. To this effect, ZDES mode 3 (acting as a Wall Modelled Large Eddy Simulation, WMLES) is used inside the nozzle and turbulence is triggered with tripping dots implemented in the computation using the Immersed Boundary Condition method. Results are compared to experimental data and a standard ZDES mode 2 simulation (running in URANS mode for the nozzle boundary layer). The novel methodology involving ZDES mode 3 is successful in removing the spurious RANS-to-LES transition noise in the early stages of the mixing layer observed in the ZDES mode 2 simulation which opens the way to the accurate prediction of jet noise on complex aircraft configurations with ZDES

Electro-mechanical Resonant Ice Protection Systems: Initiation of Fractures with Piezoelectric Actuators

Recent research is showing growing interest in low-power electromechanical de-icing systems and, in particular, de-icing systems based on piezoelectric actuators. These systems use the vibrations generated by piezoelectric actuators at resonance frequencies to produce shear stress at the interface between the ice and the support or to produce tensile stress in the ice. Many configurations of de-icing systems using piezoelectric actuators have been tested and showed that piezoelectric actuation may be a viable ice removal system. If the many experimental studies already achieved have the advantage to present tests in different configurations, they often lack analysis of the phenomena, which limits the optimization opportunities. This paper proposes a computational method for estimating voltages and currents of a piezoelectric de-icing system to initiate cohesive fractures in the ice or adhesive fractures at the ice/support interface. The computational method is validated by comparing numerical results with experimental results. Other contributions of this paper are the study of the types of mode (extensional or flexural) and of the frequency range with respect to de-icing performances and the proposal of some general rules for designing such systems while limiting their electric power consumption

EMMPRIN Promotes Melanoma Cells Malignant Properties through a HIF-2alpha Mediated Up-Regulation of VEGF-Receptor-2

EMMPRIN's expression in melanoma tissue was reported to be predictive of poor prognosis. Here we demonstrate that EMMPRIN up-regulated VEGF receptor-2 (VEGFR-2) in two different primary melanoma cell lines and consequently increased migration and proliferation of these cells while inhibiting their apoptosis. SiRNA inhibition of VEGFR-2 expression abrogated these EMMPRIN effects. EMMPRIN regulation of VEGFR-2 was mediated through the over-expression of HIF-2α and its translocation to the nucleus where it forms heterodimers with HIF-1β. These results were supported by an in vivo correlation between the expression of EMMPRIN with that of VEGFR-2 in human melanoma tissues as well as with the extent of HIF-2α localization in the nucleus. They demonstrate a novel mechanism by which EMMPRIN promotes tumor progression through HIF-2α/VEGFR-2 mediated mechanism, with an autocrine role in melanoma cell malignancy. The inhibition of EMMPRIN in cancer may thus simultaneously target both the VEGFR-2/VEGF system and the matrix degrading proteases to block tumor cell growth and invasion

New nonlinear vibration energy harvesters based on PVDF hybrid fluid diaphragm

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Hybrid fluid diaphragm structures for vibration energy harvesting applications

International audienceThis paper deals with the design of a compact, generic membrane structure suitable for vibration energy harvesting (VEH). A hybrid fluid diaphragm architecture is proposed. It allows the resonant frequency to match the classical low frequencies ambient excitations to be harvested. A semi analytical model has been developed and validated so the proposed structure can be easily tuned for a given application. The next step will consist in designing a piezoelectric structure which will be integrated to the HFD

Bimorph hybrid fluid diaphragm device for vibration energy harvesting

International audienceA low resonant frequency piezoelectric energy harvesting using a hybrid fluid diaphragm (HFD) is presented. This paper describes the design, fabrication and characterization of such a device for harvesting energy from vibrations. The PHFD consists in an incompressible fluid confined between two thin piezoelectric membranes. The output voltage and power of the P(VDF-TrFE) HFD are studied based on experimental and simulation results. This device resonates at 164 Hz for low acceleration (10 m/s²). The simulations showed the power production of about 6 µW with a power density of 78.98 µW/cm³ of electroactive material volume

Hybrid fluid diaphragm structures for vibration energy harvesting applications

International audienceThis paper deals with the design of a compact, generic membrane structure suitable for vibration energy harvesting (VEH). A hybrid fluid diaphragm architecture is proposed. It allows the resonant frequency to match the classical low frequencies ambient excitations to be harvested. A semi analytical model has been developed and validated so the proposed structure can be easily tuned for a given application. The next step will consist in designing a piezoelectric structure which will be integrated to the HFD

Is hypertriglyceridemia atherogenic?

International audienceHypertriglyceridemia occurs mainly because of metabolic disorders secondary to diabetes, alcohol intake, and/or overweight. Genetic factors have also been clearly identified in most severe cases. Triglycerides are generally considered as 'bystanders' for cardiovascular diseases. However, biological and basic research provides strong data suggesting that triglyceride-rich lipoproteins could be involved in the pathophysiology of cardiovascular diseases

Total Burden of Events : A New Standard Stressing the Positive Impact of Inflammation Modulation

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