Operational monitoring of radioelectric exposure in an urban environment

International audiencePolemics about base stations of cellular telephones have become a recurrent source of conflict among telecommunication companies, city authorities and citizens. Following early work performed within the framework of a doctoral thesis, the french research projet ANR Samper (2008-2011) has set up, for the first time, a network of monitoring stations in an urban environment, whose measurements are processed continuously by geostatistical methods, in order to inform daily the inhabitants on the hourly variations of radioelectric exposure in their surroundings. More precisely, the system uses a kriging of the exposure measurements including as external drift the output of a physical model of the propagation of the radioelectric signal emitted at different frequencies by the base stations. We present the implementation of the ANR Samper pre-operational monitoring system set up during several months in a section of the city of Grenoble

Geostatistics for Gaussian Processes

http://videolectures.net/nipsworkshops09_wackernagel_ggpInternational audienc

Towards a better understanding of clogged steam generators: a sensitivity analysis of dynamic themohydraulic model output

Communication available online at http://hans.wackernagel.free.fr/article_ICONE_final_140311.pdfInternational audienceTube support plate clogging of steam generators affects their operating and requires frequent maintenance operations. A diagnosis method based on dynamic behaviour analysis is under development at EDF to provide means of optimisation of maintenance strategies. Previous work showed that the dynamic response to a power transient of the wide range level measurement contains informations about the clogging state of steam generators. The diagnosis method consists of comparisons of the measured dynamic response with simulations on a mono-dimensional dynamic steam generator model for various input clogging configurations. In order to assess the potential of this method, a sensitivity analysis has been conducted through a quasi-Monte Carlo scheme to compute sensitivity indices for each half tube support plate's clogging ratio. Sensitivity indices are usually defined for scalar model outputs. Principal component analysis has been used to determine a small subset of variables that condense the information about the shape of the response curves. Finally, estimation variability was assessed by construction of bootstrap confidence intervals. The results showed that half of the preselected input variables have negligible influence and allowed to rank the most important ones. Interactions of input variables have been estimated to exert only a small influence on the output. The effects of clogging on the steam generator dynamics has been characterised qualitatively and quantitatively

A 'small-world-like' model for comparing interventions aimed at preventing and controlling influenza pandemics

BACKGROUND: With an influenza pandemic seemingly imminent, we constructed a model simulating the spread of influenza within the community, in order to test the impact of various interventions. METHODS: The model includes an individual level, in which the risk of influenza virus infection and the dynamics of viral shedding are simulated according to age, treatment, and vaccination status; and a community level, in which meetings between individuals are simulated on randomly generated graphs. We used data on real pandemics to calibrate some parameters of the model. The reference scenario assumes no vaccination, no use of antiviral drugs, and no preexisting herd immunity. We explored the impact of interventions such as vaccination, treatment/prophylaxis with neuraminidase inhibitors, quarantine, and closure of schools or workplaces. RESULTS: In the reference scenario, 57% of realizations lead to an explosive outbreak, lasting a mean of 82 days (standard deviation (SD) 12 days) and affecting 46.8% of the population on average. Interventions aimed at reducing the number of meetings, combined with measures reducing individual transmissibility, would be partly effective: coverage of 70% of affected households, with treatment of the index patient, prophylaxis of household contacts, and confinement to home of all household members, would reduce the probability of an outbreak by 52%, and the remaining outbreaks would be limited to 17% of the population (range 0.8%–25%). Reactive vaccination of 70% of the susceptible population would significantly reduce the frequency, size, and mean duration of outbreaks, but the benefit would depend markedly on the interval between identification of the first case and the beginning of mass vaccination. The epidemic would affect 4% of the population if vaccination started immediately, 17% if there was a 14-day delay, and 36% if there was a 28-day delay. Closing schools when the number of infections in the community exceeded 50 would be very effective, limiting the size of outbreaks to 10% of the population (range 0.9%–22%). CONCLUSION: This flexible tool can help to determine the interventions most likely to contain an influenza pandemic. These results support the stockpiling of antiviral drugs and accelerated vaccine development

PROPOSAL OF A SEQUENTIAL METHOD FOR SPATIAL INTERPOLATION OF MODE CHOICE

The main objective of this study is to propose a sequential method for spatial interpolation of mode choice for household locations where choices are unobserved based on Decision Tree analysis and Geostatistics. Initially, Decision Tree analysis was applied in order to estimate the probability of mode choice in surveyed households, thus determining the numeric variable to be estimated by Ordinary Kriging. The data used is from the Origin-Destination Survey and Urban Transportation Evaluation Survey, carried out in 2007/2008 in the city of São Carlos (São Paulo/Brazil). The study area selected for geoestatistical modeling is a small region of the city with 110 sampling points. The mode choice was estimated for the study area revealing a tendency of increasing the probability of car usage from the center to the periphery of region. The proposed method can be an alternative to traditional approaches in both non-spatial modeling, especially for the case of lack of data from stated preference survey, as in spatial modeling, allowing estimation in various geographic coordinates

Géostatistique et assimilation séquentielle de données

Traditional geostatistical space-time geostatistics is not able to take account of the generally strongly non-linear dynamics of multivariate space-time processes. To this effect physico-chemical transport models are in general more suitable. However, as the latter do not fully master the complexity of the processes they attempt to describe, either because of simplifying hypotheses or because the information serving to set up initial and boundary conditions is imperfect, it is appropriate to introduce statistical techniques in order to assimilate a flow of measurements emanating from automatic stations. Recent projects at Centre de Géostatistique of Ecole des Mines de Paris have permitted to explore these techniques in oceanography and air pollution. Soon it became evident that geostatistics could offer concepts and approaches to enhance Sequential Data Assimilation techniques. The thesis of Laurent Bertino as well as subsequent publications have permitted to develop this fruitful theme of which the present synthesis presents an account.La géostatistique spatio-temporelle traditionnelle n'est pas en mesure de décrire adéquatement la dynamique, en général fortement non-linéaire, de processus spatio-temporels multivariables. Pour cela des modèles de transport physico-chimiques sont en général bien mieux adaptés. Cependant, étant donné que ces derniers ne maîtrisent pas totalement la complexité des processus qu'ils cherchent à décrire, soit parce qu'ils sont basés sur des hypothèses simplificatrices, soit parce que l'information servant à établir les conditions initiales et aux limites est imparfaite, il est opportun d'introduire des techniques statistiques servant à les guider pour assimiler un flot de mesures émanant de capteurs automatiques. Des projets récents au Centre de Géostatistique de l'Ecole des Mines de Paris ont permis d'explorer l'application de ces techniques dans le domaine de l'océanographie et en pollution de l'air. Il s'est très vite avéré que la géostatistique offrait des concepts et des approches qui pouvaient contribuer à enrichir les techniques d'Assimilation Séquentielle de Données. La thèse de Laurent Bertino et des publications ultérieures ont permis de développer cette thématique porteuse, dont la présente synthèse établit un compte-rendu

Data assimilation for epidemiological surveillance

International audienc

Geostatistical model, covariance structure and cokriging

International audienc

Multivariate Geostatistics

International audienc