Search results for "Simulation"
showing 10 items of 5095 documents
Modelling the spatial-temporal progression of the 2009 A/H1N1 influenza pandemic in Chile
2016
A spatial-temporal transmission model of 2009 A/H1N1 pandemic influenza across Chile, a country that spans a large latitudinal range, is developed to characterize the spatial variation in peak timing of that pandemic as a function of local transmission rates, spatial connectivity assumptions for Chilean regions, and the putative location of introduction of the novel virus into the country. Specifically, a metapopulation SEIR (susceptible-exposed-infected-removed) compartmental model that tracks the transmission dynamics of influenza in 15 Chilean regions is calibrated. The model incorporates population mobility among neighboring regions and indirect mobility to and from other regions via th…
Dendrochemical assessment of mercury releases from a pond and dredged-sediment landfill impacted by a chlor-alkali plant.
2016
International audience; Although current Hg emissions from industrial activities may be accurately monitored, evidence of past releases to the atmosphere must rely on one or more environmental proxies. We used Hg concentrations in tree cores collected from poplars and willows to investigate the historical changes of Hg emissions from a dredged sediment landfill and compared them to a nearby control location. Our results demonstrated the potential value of using dendrochemistry to record historical Hg emissions from past industrial activities.
Experimental and numerical investigations on the effect of fracture geometry and fracture aperture distribution on flow and solute transport in natur…
2018
The impact of fracture geometry and aperture distribution on fluid movement and on non-reactive solute transport was investigated experimentally and numerically in single fractures. For this purpose a hydrothermally altered and an unaltered granite drill core with axial fractures were investigated. Using three injection and three extraction locations at top and bottom of the fractured cores, different dipole flow fields were examined. The conservative tracer (Amino-G) breakthrough curves were measured using fluorescence spectroscopy. Based on 3-D digital data obtained by micro-computed tomography 2.5-D numerical models were generated for both fractures by mapping the measured aperture distr…
Stochastic dynamical modelling of spot freight rates
2014
Based on empirical analysis of the Capesize and Panamax indices, we propose different continuous-time stochastic processes to model their dynamics. The models go beyond the standard geometric Brownian motion, and incorporate observed effects like heavy-tailed returns, stochastic volatility and memory. In particular, we suggest stochastic dynamics based on exponential Levy processes with normal inverse Gaussian distributed logarithmic returns. The Barndorff-Nielsen and Shephard stochastic volatility model is shown to capture time-varying volatility in the data. Finally, continuous-time autoregressive processes provide a class of models sufficiently rich to incorporate short-term persistence …
Hybrid WENO schemes for polydisperse sedimentation models
2015
International audience; Polydisperse sedimentation models can be described by a strongly coupled system of conservation laws for the concentration of each species of solids. Typical solutions for the sedimentation model considered for batch settling in a column include stationary kinematic shocks separating layers of sediment of different composition. This phenomenon, known as segregation of species, is a specially demanding task for numerical simulation due to the need of accurate numerical simulations. Very high-order accurate solutions can be constructed by incorporating characteristic information, available due to the hyperbolicity analysis made in Donat and Mulet [A secular equation fo…
Simulations of Glassforming Network Fluids: Classical Molecular Dynamics versus Car-Parrinello Molecular Dynamics
2010
Abstract Static and dynamic Properties of molten germanium dioxide are studied by two simulation methods, classical Molecular Dynamics (MD) using the Oeffner-Elliott (OE) potential, and “ab initio” Car-Parrinello Molecular Dynamics (CPMD). While CPMD provides a (presumably) more accurate description of the local structure and the forces, it severely suffers from finite size effects when the structure beyond the first neighbor shells is considered. For glassforming fluids, the demanding equilibrium needs are a further reason, why simply MD is still preferable, when a “good” effective potential is available.
Benefits of a dance group intervention on institutionalized elder people: A Bayesian network approach
2018
[EN] The present study aims to explore the effects of an adapted classical dance intervention on the psychological and functional status of institutionalized elder people using a Bayesian network. All participants were assessed at baseline and after the 9 weeks period of the intervention. Measures included balance and gait, psychological well-being, depression, and emotional distress. According to the Bayesian network obtained, the dance intervention increased the likelihood of presenting better psychological well-being, balance, and gait. Besides, it also decreased the probabilities of presenting emotional distress and depression. These findings demonstrate that dancing has functional and …
Continuous Glucose Monitoring in Type 1 Diabetes
2016
Background: Continuous glucose monitoring (CGM) patient systems have been shown to improve diabetes self-treatment when used consistently. The meaningful integration of this technology into everyday life, however, can vary greatly among CGM users and not all people with diabetes use CGM to its full potential. To address this issue, the study pursued 2 aims: first, to identify patient characteristics that underlie the acceptance of CGM in people with type 1 diabetes and, second, to examine the effects of different levels of experience with CGM use. Methods: Guided by a model based on the technology acceptance model (TAM), structural equation modeling (SEM) was employed to model the patient c…
Mathematical modeling of fetal limb growth
1989
Using ultrasound measurements of the femur, tibia, humerus, radius (N = 515), and fibula and ulna (N = 385) from normal fetuses between 12 and 40 completed weeks of gestation, growth models were determined for each bone by computer analysis. On the basis of residual analysis, growth of fetal limb bones could best be expressed as a function of tangens hyperbolicus. Growth profiles and growth data are shown with 5th, 10th, 50th, 90th, and 95th percentiles. These results are compared with previous investigations of limb bone measurements.
Exact simulation of first exit times for one-dimensional diffusion processes
2019
International audience; The simulation of exit times for diffusion processes is a challenging task since it concerns many applications in different fields like mathematical finance, neuroscience, reliability horizontal ellipsis The usual procedure is to use discretization schemes which unfortunately introduce some error in the target distribution. Our aim is to present a new algorithm which simulates exactly the exit time for one-dimensional diffusions. This acceptance-rejection algorithm requires to simulate exactly the exit time of the Brownian motion on one side and the Brownian position at a given time, constrained not to have exit before, on the other side. Crucial tools in this study …