Impact of trailing wake drag on the statistical properties and dynamics of finite-sized particle in turbulence

We study by means of an Eulerian-Lagrangian model the statistical properties of velocity and acceleration of a neutrally-buoyant finite-sized particle in a turbulent flow statistically homogeneous and isotropic. The particle equation of motion, beside added mass and steady Stokes drag, keeps into account the unsteady Stokes drag force - known as Basset-Boussinesq history force - and the non-Stokesian drag based on Schiller-Naumann parametrization, together with the finite-size Faxen corrections. We focus on the case of flow at low Taylor-Reynolds number, Re_lambda ~ 31, for which fully resolved numerical data which can be taken as a reference are available (Homann & Bec 651 81-91 J. Fluid Mech. (2010)). Remarkably, we show that while drag forces have always minor effects on the acceleration statistics, their role is important on the velocity behavior. We propose also that the scaling relations for the particle velocity variance as a function of its size, which have been first detected in fully resolved simulations, does not originate from inertial-scale properties of the background turbulent flow but it is likely to arise from the non-Stokesian component of the drag produced by the wake behind the particle. Furthermore, by means of comparison with fully resolved simulations, we show that the Faxen correction to the added mass has a dominant role in the particle acceleration statistics even for particle with size in the inertial range.Comment: 9 pages, 9 figure

Acceleration statistics of finite-sized particles in turbulent flow: the role of Faxen forces

The dynamics of particles in turbulence when the particle-size is larger than the dissipative scale of the carrier flow is studied. Recent experiments have highlighted signatures of particles finiteness on their statistical properties, namely a decrease of their acceleration variance, an increase of correlation times -at increasing the particles size- and an independence of the probability density function of the acceleration once normalized to their variance. These effects are not captured by point particle models. By means of a detailed comparison between numerical simulations and experimental data, we show that a more accurate model is obtained once Faxen corrections are included.Comment: 10 pages, 4 figure

Skin capacitance imaging, a new technique for investigating the skin surface.

Thanks to the recently introduced silicone image sensor technology, skin capacitance imaging has now been made possible. The dedicated device is called SkinChip. This method is easy to handle and provides information about the skin microrelief, the level of stratum corneum hydration and the sweat gland activity. The apparatus sees and measures these parameters with a 50 microm resolution. A series of conditions have been explored using skin capacitance imaging. This review summarizes relevant findings about regional variability on the body, changes occurring with ageing, effects of a hydrating formulation, reactivity kinetics of corneocytes to surfactants, acne and skin pores characteristics, as well as hyperkeratotic dermatoses and tumours

Concept of Event by Heidegger, Vattimo and Badiou

This article analyses the different interpretation held of Heidegger, Vattimo and Badiou about the concept of «Event». For Heidegger and Vattimo, Event (Ereignis) is a form of self-giving of being that differs completely to the western metaphysical tradition’s form of thinking being-and time. This hermeneutical thought can be considered as an active nihilism. The concept of Event in Badiou is quite different. For the French Philosopher, there is some newness in being: it can be possible to think novelty. The philosophy of Badiou can then bring us news instruments to think novelty, radical changes and discontinuity in the historical process.Este artículo analiza las distintas interpretaciones del concepto de «acontecimiento » propuestas por Heidegger, Vattimo y Badiou. Para Heidegger y Vattimo, el acontecimiento es una forma de auto-donación del Ser que difiere radicalmente de la forma en que la tradición metafísica occidental ha pensado el Ser –y el tiempo. Este pensamiento hermenéutico puede ser caracterizado como una forma de nihilismo activo. El concepto de acontecimiento en Badiou es totalmente diferente. Para el filósofo francés, hay alguna novedad en el ser: es posible entonces, a partir de esta premisa, pensar la novedad. La filosofía de Badiou puede entonces proporcionarnos nuevos instrumentos para pensar la novedad, los cambios radicales y la discontinuidad en el proceso de la Histori

Construction and Test of a Flux Modulation Superconducting Machine for Aircraft

International audienceThe increasing of drives towards More Electric Aircraft (MEA) or the development of electric propulsion aircraft calls for MW-class electrical machines with more compact and power dense designs. One way is to explore the use of superconducting materials to create a high magnetic field in order to reduce the mass of ferromagnetic components. This paper presents the construction and the test of a brushless axial flux superconducting machine. The brushless topology satisfies the aeronautics industry requirements in terms of maintenance, while the axial configuration ensures an optimal use of the anisotropic HTS tapes. The machine is classed as partially superconducting, only the inductor is made with superconducting materials. A special design concerning the use of a stationary cryostat is presented. This improvement reduces significantly the electromagnetic air-gap length. A 50kW prototype is manufactured with a minimal mass objective. The prototype constitutes a first step to a scale-up MW-class machine design

Analytical Model for the Magnetic Field Distribution in a Flux Modulation Superconducting Machine

International audienceThis paper presents a theoretical analysis of an axial field machine using High Temperature Superconductors (HTS) wires and bulks. The air-gap magnetic field obtained with the HTS coil and modulated by the HTS bulks is predicted by two 2D axisymmetric models. Analytical models are based on the solution of Laplace's equation by the separation of variable method. The torque is obtained by a quick numerical integration of the Laplace force that acts on the armature winding. The proposed model is compared with 3D finite element simulations and good agreement is obtained. This model can be used with an optimization design procedure with a large reduction of the computational time

Ethical thinking machines in surgery and the requirement for clinical leadership

No abstract available

Synthesis and anti-microbial potencies of 1-(2-hydroxyethyl)-3-alkylimidazolium chloride ionic liquids: microbial viabilities at different ionic liquids concentrations

Three 1-(2-hydroxyethyl)-3-alkylimidazolium chloride room temperature ionic liquids (ILs) [2OHimCn][Cl]; (n=0, 1, 4) have been synthesized from the appropriate imidazole precursors and characterized by IR and NMR spectroscopies and elemental analysis. Their anti-microbial activities were investigated using the well-diffusion method. The viabilities of Escherichia coli, Aeromonas hydrophila, Listeria monocytogenes and Salmonella enterica as a function of IL concentrations were studied. The minimal inhibitory concentrations (MICs) and EC50 values for the present ILs were within the concentration range from 60 to 125 mM and 23 to 73 mM. The anti-microbial potencies of the present ILs were compared to a standard antibiotic, gentamicin. The finding affords additional perspective on the level of ILs toxicity to aquatic lifeforms and yet, this characteristic can be readily harnessed to detect microbial growth and activity

APRÈS LE DÉLUGE : ÉVOLUTION GÉOMORPHOLOGIQUE DU DELTA DU DANUBE APRÈS LA RECONNEXION MER NOIRE - MÉDITERRANÉE ET SES IMPLICATIONS SUR LE PEUPLEMENT ÉNÉOLITHIQUE / CHALCOLITHIQUE

International audienceIn this work, we document the evolution of the upper Danube delta (i.e. blocked delta) using archaeological, geomorphological and geoarchaeological approaches, after the discovery, in the 90's, of the oldest human settlement (Eneolithic/Chalcolithic) close to Mila 23 district. In-site and out-site fieldwork allows us to refine the Danube delta early evolution from 5,600 to 4,000 cal. yr BC. During this period, it functions like a fresh bayhead delta, flowing into a huge lagoon isolated from the open sea by the Letea-Caraorman spit. Then, lagoon water level rose rapidly due to an eustatic rise, and possibly from an unusual highstand of sealevel resulting from wet conditions. The settlement was then partially flooded and abandoned around 4,450 cal. yr BC.Dans ce travail, l'évolution de la zone interne du delta du Danube est appréhendée à partir de travaux géoarchéologiques et géomorphologiques réalisés dans le district de Mila 23, suite à la découverte de la plus vieille occupation humaine (énéolithique/ chalcolithique) du delta dans les années 90. Les travaux sur site et hors site ont permis de préciser les stades précoces de l'évolution du delta entre 5 600 et 4 000 ans cal. av. J.-C. Celui-ci évolue comme un delta lagunaire en eau douce, s'épandant dans un large lagon séparé de la mer par la ride de Letea-Caraorman. La remontée rapide du niveau lagunaire, sous l'effet de la remontée eustatique et peut-être d'une sur cote liée à un événement humide, ont conduit à une submersion partielle du site et probablement à son abandon vers 4 450 ans cal. av. J.-C

Ultrasonic-Assisted Extraction of Toxic Acidic Components from Acidic Oil Using 1,8-Diazobicyclo[5.4.0]undec-7-ene-Based Ionic Liquids

[Image: see text] Ionic liquids (ILs) show remarkable performance in enhancing the naphthenic acid extraction efficiency and decreasing the extraction time. However, the ultrasonic-assisted IL-based extraction of naphthenic acid is merely addressed previously. Therefore, this study investigated the impact of essential ultrasonic parameters, including amplitude and time, on naphthenic acid extraction using different ILs, and the system was optimized for maximum extraction. The IL 1,8-diazobicyclo[5.4.0]-undec-7-ene (DBU) with thiocyanate anions revealed the highest efficiency in extracting naphthenic acid from a model oil (dodecane) at optimized conditions, and the experimental liquid–liquid equilibrium data were obtained at atmospheric pressure for the mixture of dodecane, [DBU], thiocyanate, and naphthenic acid. In addition, the influence of the chain length of the cation (hexyl, octyl, or decyl) on the extraction efficiency was also evaluated by determining the distribution coefficients, and the conductor-like screening model for real solvents (COSMO-RS) study was carried out at infinite dilution. It was found that [DBU-Dec] [SCN] gives the best extraction efficiency and has a distribution coefficient of 9.2707 and a performance index of 49.48. Based on these values, ILs can be ordered as follows: [DBU-Dec] [SCN] > [DBU-Oct][SCN] > [DBU-Hex][SCN] in the decreasing order of performance index 49.48, 41.58, and 28.13. Moreover, non-random two liquid and Margules thermodynamic models were employed to investigate the interaction parameters between the components. Both models showed excellent agreement with the experimental results and could successfully be used for ultrasonic-assisted IL extraction of naphthenic acid