Numerical methods for RANSE simulations of a self-propelled fish-like body

International audienceThis paper deals with numerical simulations on a self-propelled fish-like body. Firstly, the methods used to achieve such simulations based on the solution of the Reynolds-Averaged-Navier–Stokes Equations are described: resolution of the Newton's law (parameterization, use of a description of the rotation based on a quaternion), regridding strategies linked to body motion and deformation, fluid–motion coupling methods. In the second part, realistic applications are shown. The interaction between the fluid and the body is fully solved since the evolution of the body's position is not imposed but computed. Only the imposed deformation of the shape and its interaction with the fluid produce forces on the body and, consequently, motion

CFD Simulation of PMM Motion in Shallow Water for the DTC Container Ship

International audienceThis paper is devoted to the validation exercises with the ISIS-CFD code conducted for the test cases proposed for the MASHCON conference. CFD simulations have been performed for the 4 different pure yaw and pure sway test cases under shallow water condition. Predicted results are compared with the measurement data provided by FHR

Random sequential adsorption on a dashed line

We study analytically and numerically a model of random sequential adsorption (RSA) of segments on a line, subject to some constraints suggested by two kinds of physical situations: - deposition of dimers on a lattice where the sites have a spatial extension; - deposition of extended particles which must overlap one (or several) adsorbing sites on the substrate. Both systems involve discrete and continuous degrees of freedom, and, in one dimension, are equivalent to our model, which depends on one length parameter. When this parameter is varied, the model interpolates between a variety of known situations : monomers on a lattice, "car-parking" problem, dimers on a lattice. An analysis of the long-time behaviour of the coverage as a function of the parameter exhibits an anomalous 1/t^2 approach to the jamming limit at the transition point between the fast exponential kinetics, characteristic of the lattice model, and the 1/t law of the continuous one.Comment: 14 pages (Latex) + 4 Postscript figure

Thermodynamics of a mixed quantum-classical Heisenberg model in two dimensions

We study the planar antiferromagnetic Heisenberg model on a decorated hexagonal lattice, involving both classical spins (occupying the vertices) and quantum spins (occupying the middle of the links). This study is motivated by the description of a recently synthesized molecular magnetic compound. First, we trace out the spin 1/2 degrees of freedom to obtain a fully classical model with an effective ferromagnetic interaction. Then, using high temperature expansions and Monte Carlo simulations, we analyse its thermal and magnetic properties. We show that it provides a good quantitative description of the magnetic susceptibility of the molecular magnet in its paramagnetic phase.Comment: Revtex, 6 pages, 4 included postscript figures, fig.1 upon request to [email protected] . To appear in J. of Physic C (condensed matter

Large eddy simulation of urban features for Copenhagen metropolitan area

International audienceThe large eddy simulations employing the SUBMESO model with the urban soil layer model SM2-U were performed for the model domain covering the Danish Island of Sealand and including the Copenhagen metropolitan area. Monthly and diurnal cycle variability were studied for the net radiation, sensible and storage heat fluxes, surface's temperatures, and others. These were evaluated for selected urban vs. non urban related types of covers/surfaces and urban districts such as city center, high buildings, industrial, and residential. Results showed strong effects of urban features on temporal and spatial variability. They are useful and applicable for verification of numerical weather prediction models and development of urban canopy parameterizations

Mid Holocene vegetation reconstruction from Vanevan peat (south-eastern shore of Lake Sevan, Armenia)

International audienceA sediment core has been retrieved from Vanevan peat (south-eastern shore of Lake Sevan, Armenia), which is today disconnected from Lake Sevan thanks to an artificial shallowing of the lake. Based on 5 radiocarbon dates, Vanevan record covers the Mid Holocene (from ca. 7800 to ca. 5100 cal. BP). The Late Holocene is today absent in the peat stratigraphy due to modern peat exploitation by surface mining. This study focuses on a multi-proxy approach including pollen, charcoals, and pollen-inferred climate reconstruction. An open-land, steppic vegetation is recorded up to ca. 7700 cal. BP, followed by a more forested landscape during the Mid Holocene (up to ca. 5700 cal. BP), and ending again with an open-land vegetation (to the end of record, 5100 cal. BP). This vegetation dynamics responds to general climate changes documented in the Near East. Whether human activities are documented since ca. 7500 cal. BP (Late Neolithic) in Vanevan, they remain marginal and probably did not affect the area. Early Holocene dry climate, which caused the steppic environment to be widespread through the Near East, is strongly related to low late spring precipitation (PMay–Jun = 180 mm). Mid Holocene forested landscape and increasing lake-level seem related to late spring precipitation (+28%), which is the main change in estimated climate parameters. This has to be linked with reinforcement of the Westerlies and less active Siberian High, which are inversely involved in the following, dry phase starting at ca. 5700 cal. B

Evaluating the association between extreme heat and mortality in urban Southwestern Ontario using different temperature data sources

Urban areas have complex thermal distribution. We examined the association between extreme temperature and mortality in urban Ontario, using two temperature data sources: high-resolution and weather station data. We used distributed lag non-linear Poisson models to examine census division-specific temperature–mortality associations between May and September 2005–2012. We used random-effect multivariate meta-analysis to pool results, adjusted for air pollution and temporal trends, and presented risks at the 99th percentile compared to minimum mortality temperature. As additional analyses, we varied knots, examined associations using different temperature metrics (humidex and minimum temperature), and explored relationships using different referent values (most frequent temperature, 75th percentile of temperature distribution). Weather stations yielded lower temperatures across study months. U-shaped associations between temperature and mortality were observed using both high-resolution and weather station data. Temperature–mortality relationships were not statistically significant; however, weather stations yielded estimates with wider confidence intervals. Similar findings were noted in additional analyses. In urban environmental health studies, high-resolution temperature data is ideal where station observations do not fully capture population exposure or where the magnitude of exposure at a local level is important. If focused upon temperature–mortality associations using time series, either source produces similar temperature–mortality relationships

Adsorption of Line Segments on a Square Lattice

We study the deposition of line segments on a two-dimensional square lattice. The estimates for the coverage at jamming obtained by Monte-Carlo simulations and by $7^{th}$-order time-series expansion are successfully compared. The non-trivial limit of adsorption of infinitely long segments is studied, and the lattice coverage is consistently obtained using these two approaches.Comment: 19 pages in Latex+5 postscript files sent upon request ; PTB93_

Complicanze infettive locali precoci e tardive nella chirurgia otologica

La via retroauricolare rappresenta l’approccio di scelta nel trattamento dell’otite media cronica. Nelle procedure “sporche” l’incidenza della complicanza infettiva locale è del 10%. Il presente studio analizza le infezioni del sito chirurgico dopo la chirurgia dell’otite media cronica e ne investiga i potenziali fattori predittivi. Il presente studio, dal design osservazionale prospettico, ha incluso pazienti affetti da otite media cronica e candidati alla chirurgia mediante approccio retroauricolare. Sono state definite precoci le complicanze postoperatorie insorte entro i 30 giorni e tardive quelle insorte oltre i 30 giorni. Sono stati analizzati i dati di 102 pazienti. Sono stati registrati 4 casi (3,9%) di infezione precoce, per la quale è stata evidenziata un’associazione significativa con l’antibioticoterapia preoperatoria, l’orecchio in fase secernente all’esame otoscopico preoperatorio, una classe III (contaminato) nella classificazione delle ferite chirurgiche, indice NNIS (National Nosocomial Infection Surveillance) >1 e assunzione di antibiotici per OS nel postoperatorio. Sono state inoltre registrate 7 complicanze tardive (7,1%), occorse fra i 90 e i 160 giorni dall’intervento, significativamente correlate alla presenza di otorrea nei sei mesi precedenti la chirurgia, una durata del tempo chirurgico inferiore o uguale a 60 minuti, una tecnica aperta e all’uso della colla di fibrina. L’infezione del sito chirurgico sembra essere associata ai fattori correlati allo stato infiammatorio dell’orecchio medio al momento della chirurgia nelle infezioni precoci e all’infiammazione cronica nelle infezioni tardive

TOWARDS UNSTEADY APPROACH FOR FUTURE FLUTTER CALCULATIONS

International audienc