A new airborne Polar Nephelometer for the measurement of optical and microphysical cloud properties. Part II: Preliminary tests

International audienceA new optical sensor, the airborne Polar Nephelometer, has been tested in an open wind tunnel. The wind tunnel was operated in cloudy conditions including either cloud water droplets or ice crystals, or a mixture of these particles. The sensor is designed to measure the optical and microphysical parameters of cloud particles sized from a few micrometers to about 500 µm diameter. Basically, the probe measures the scattering phase function of an ensemble of cloud particles which intersect a collimated laser beam near the focal point of a paraboloidal mirror. From the measured scattering phase function the retrieval of the droplet-size spectra and subsequent derived quantities such as liquid water content and size parameters can be calculated using an inversion method. The particle phase discrimination (water droplets/ice particles) can be derived from the shape of the scattering phase function and the sensitivity of the probe allows the detection of small ice crystals (typically of 5 µm diameter). The paper describes the preliminary results obtained by the prototype version of the Polar Nephelometer in various cloudy conditions. These results are compared with direct microphysical measurements obtained by usual PMS probes also mounted in the wind tunnel. Complementary results obtained in a cold chamber are presented in order to illustrate the reliability of the Polar Nephelometer in the presence of small ice crystals

Modelling and experimental validation of a fluidized bed reactor freeboard region: application to natural gas combustion

A theoretical and experimental study of natural gas-air mixture combustion in a fluidized bed of sand particles is presented. The operating temperatures are lower than a critical temperature of 800 °C above which the combustion occurs in the vicinity of the fluidized bed. Our study focusses on the freeboard zone where most of the methane combustion takes place at such temperatures. Experimental results show the essential role of the projection zone in determining the global thermal efficiency of the reactor. The dense bed temperature, the fluidizing velocity and the mean particle diameter significantly affect the thermal behaviours. A model for natural gas-air mixture combustion in fluidized beds is proposed, counting for interactions between dense and dilute regions of the reactor [Pré et al. (1998)] supplemented with the freeboard region modelling of Kunii-Levenspiel (1990). Thermal exchanges due to the convection between gas and particles, and due to the conduction and radiation phenomena between the gas-particle suspension and the reactor walls are counted. The kinetic scheme for the methane conversion is that proposed by Dryer and Glassman (1973). Model predictions are in good agreement with the measurements

Comprendre les phénomènes migratoires : la mobilité dans un village de l'Hérault de 1836 à 1962

Using a previous reconstitution of families living in the village of Puéchabon (Hérault) and twenty-three lists of its inhabitants from 1836 to 1962 as a base, the author has analyzed the migrations of the villagers accorging to sex, marital status and age group while distinguishing two types of migration : actual departures and entries (permanent or long-term departures, and entries by newcomers or those returning after prolonged absences), and short-term absences and subsequent returns. Using this typology, he brings out three periods of migration for the village résidents : before the War of 1870, there were traditional movements ; between 1870 and World War II, a pronounced rural exodus occurred ; and since then, there has been a less striking but more regular decline in population.En se fondant sur une reconstitution préalable des familles du village de Puéchabon (Hérault) et sur les vingt-trois listes nominatives de 1836 à 1962, l'auteur a analysé les migrations des habitants suivant le sexe, l'état matrimonial et les groupes d'âges, tout en classant les migrations suivant deux types : sorties et entrées proprement dites (sorties définitives ou de longue durée, entrées de l'extérieur ou consécutives à des sorties de longue durée) ; absences de courte durée et retours après ces absences. A partir de cette typologie, il fait ressortir trois périodes dans l'histoire des migrations des villageois de Puéchabon : avant la guerre de 1870, mouvements traditionnels ; entre 1870 et la Seconde Guerre mondiale, exode rural ; et depuis lors, baisse moins marquée et plus régulière.Fournol Henri. Comprendre les phénomènes migratoires : la mobilité dans un village de l'Hérault de 1836 à 1962. In: Annales de démographie historique, 1996. Morbidité, mortalité, santé. pp. 313-336

Le rôle de l'omnipraticien dans les "retraitements" endodontiques

MONTPELLIER-BU Médecine (341722104) / SudocMONTPELLIER-BU Médecine UPM (341722108) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Efficacité à court et à long terme de la vertébroplastie percutanée dans le traitement des fractures vertébrales osteoporotiques hyperalgiques

NICE-BU Médecine Odontologie (060882102) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

A new airborne polar Nephelometer for the measurements of optical and microphysical cloud properties. Part I: Theoretical design

A new optical sensor, the airborne Polar Nephelometer, is described. The sensor is designed to measure the optical and microphysical parameters of clouds containing either water droplets or ice crystals or a mixture of these particles ranging in size from a few micrometers to about 500 µm diameter. The probe measures the scattering phase function of an ensemble of cloud particles intersecting a collimated laser beam near the focal point of a paraboloïdal mirror. The light scattered from polar angles from 3.49° to 169° is reflected onto a circular array of 33 photodiodes. The signal processing electronics and computer storage can provide one measurement of the scattering phase function every 100 ms or every 0.2 ms. The first part of the paper describes the theoretical design of a prototype version of the probe