Search results for "méthodes"
showing 10 items of 77 documents
Data synergy between leaf area index and clumping index Earth Observation products using photon recollision probability theory
2018
International audience; Clumping index (CI) is a measure of foliage aggregation relative to a random distribution of leaves in space. The CI can help with estimating fractions of sunlit and shaded leaves for a given leaf area index (LAI) value. Both the CI and LAI can be obtained from global Earth Observation data from sensors such as the Moderate Resolution Imaging Spectrometer (MODIS). Here, the synergy between a MODIS-based CI and a MODIS LAI product is examined using the theory of spectral invariants, also referred to as photon recollision probability ('p-theory'), along with raw LAI-2000/2200 Plant Canopy Analyzer data from 75 sites distributed across a range of plant functional types.…
Accounting for preferential sampling in species distribution models
2019
D. C., A. L. Q. and F. M. would like to thank the Ministerio de Educación y Ciencia (Spain) for financial support (jointly financed by the European Regional Development Fund) via Research Grants MTM2013‐42323‐P and MTM2016‐77501‐P, and ACOMP/2015/202 from Generalitat Valenciana (Spain). Species distribution models (SDMs) are now being widely used in ecology for management and conservation purposes across terrestrial, freshwater, and marine realms. The increasing interest in SDMs has drawn the attention of ecologists to spatial models and, in particular, to geostatistical models, which are used to associate observations of species occurrence or abundance with environmental covariates in a fi…
Vegetation structure and greenness in Central Africa from Modis multi-temporal data.
2013
African forests within the Congo Basin are generally mapped at regional scale as broad-leaved evergreen forests, with a main distinction between terra-firme and swamp forests types. At the same time, commercial forest inventories, as well as national maps, have highlighted a strong spatial heterogeneity of forest types. A detailed vegetation map generated using consistent methods is needed to inform decision makers about spatial forest organisation and theirs relationships with environmental drivers in the context of global change. We propose a multi-temporal remotely sensed data approach to characterize vegetation types using vegetation index annual profiles. The classifications identified…
la prospection systématique d’un fond de rivière : l’exemple du Doubs
2020
La présentation des méthodes mises en œuvre et des résultats obtenus à l’occasion d’une opération de prospection subaquatique systématique menée sur la rivière Doubs, en amont de Verdun-sur-le-Doubs (Saône-et-Loire), illustre en grandeur réelle l’intérêt de la démarche adoptée, fondée sur des principes simples, dans la perspective d’un inventaire systématique du patrimoine fluvial immergé. La diversité des vestiges découverts et leur répartition sur la longue durée en soulignent la pertinence mais également, s’il en était encore besoin, la réalité du formidable potentiel archéologique que recèlent les cours d’eau. The presentation of the methods used and results obtained during a systematic…
Accélération de la convergence et algorithme proximal
1995
Nous faisons une première étude de la question de savoir s'il est possible d'accélérer des suites issues de l'algorithme proximal ou de la méthode de l'inverse partiel par des méthodes d'extrapolation.
Démarche statistique pour la sélection des indicateurs par Random Forests pour la surveillance de la qualité des sols
2013
The volume of data, and the large number of biological variables to be tested (one hundred), require analytical techniques, such asRandom Forests, which can overcome the problem of multi-colinearity for the selection of indicators, sensitive to various factors.Random Forests methodology is appropriate for the selection of the most discriminant variables. So, we searched for the best wayto select them, by bringing together all biological variables, representing the Microflora and Fauna. This approach focuses on impactindicators from the Bio2 program, indicators of flora and indicators of accumulation (snails) were not included.This work has been implemented on the three factors of discrimina…
PREVISION JOURNALIERE DES POLLENS SUR LE TERRITOIRE NATIONAL FRANÇAIS, AVEC UN OBJECTIF D'INFORMATION SANITAIRE DES POPULATIONS ALLERGIQUES
2008
At present, 16% of French people suffer from allergies to one or several pollens. The corresponding symptoms can be presented as under benign form (rhinitis, conjunctivitis, cough) as under much more serious form : asthma. Forecast of the starting date of an allergic exposure risk to pollens is necessary from a sanitary and preventive standpoint. Forecast has to be more precisely as possible in order to begin anti-allergic treatments at appropriate moment, with a view of effectiveness and reduction of the costs due to this disease. The present study, taking place in all the French territory, concerns four pollen taxa among the most allergenic : ash, birch, grasses and ragweed. This work com…
Devenir chercheur ou enseignant chercheur : le goût pour la recherche des doctorants à l'épreuve du marché du travail
2016
Faire une thèse pour devenir chercheur ou enseignant-chercheur est souvent considéré comme un parcours difficile dont le résultat est incertain. Plus que dans d’autres pays, les diplômés de doctorat en France connaissent de fortes difficultés de stabilisation sur le marché du travail. Notre recherche s’interroge sur les raisons qui conduisent les jeunes à obtenir un doctorat puis à choisir une carrière de chercheur ou d’enseignant-chercheur et enfin, à s’y stabiliser. À partir d’une enquête du Céreq, nos résultats montrent que l’intérêt pour la recherche qu’ils ont manifesté dès le début des études supérieures et le capital social vont fortement structurer leur parcours universitaire et pro…
Rethinking physical and rehabilitation medicine: new technologies induce new learning strategies
2010
International audience; Reeducation consists in training people injured by either illness or the vagaries of life to achieve the best fundionality now possible for them. Strangely, the subject is not taught in the normal educational curricula of the relevant professions. Reeducation thus tends to be developed anew with each patient, without recourse to knowledge of what such training, or assistance in such training, might be. However, new paradigms of reeducation are in fact possible today, thanks to advances in cognitive science and the development of new technologies such as virtual reality and robotics. In turn, they lead to the rethinking of the procedures of physical medicine, as well …
It’s a matter of confidence. Institutions, government stability and economic outcomes
2021
In this paper we analyse the effect of constitutional structures over policy outcomes. In particular, we exploit the heterogeneity in parliamentary systems deriving from the presence and the use of the confidence vote to investigate whether stable and unstable parliamentary systems behave differently in terms of the policies they implement. This finer partition of parliamentary systems allows us to identify effects that are more robust than the ones previously discussed in the literature. We show that the difference between presidential and parliamentary systems documented in previous works is driven by a difference between presidential and stable parliamentary systems. We suggest that poss…