Search results for " Sampling"

Probability and algorithmics: a focus on some recent developments

2017

Jean-François Coeurjolly, Adeline Leclercq-Samson Eds.; International audience; This article presents different recent theoretical results illustrating the interactions between probability and algorithmics. These contributions deal with various topics: cellular automata and calculability, variable length Markov chains and persistent random walks, perfect sampling via coupling from the past. All of them involve discrete dynamics on complex random structures.; Cet article présente différents résultats récents de nature théorique illustrant les interactions entre probabilités et algorithmique. Ces contributions traitent de sujets variés : automates cellulaires et calculabilité, chaînes de Mark…

Exact simulation of diffusion first exit times: algorithm acceleration

2020

In order to describe or estimate different quantities related to a specific random variable, it is of prime interest to numerically generate such a variate. In specific situations, the exact generation of random variables might be either momentarily unavailable or too expensive in terms of computation time. It therefore needs to be replaced by an approximation procedure. As was previously the case, the ambitious exact simulation of exit times for diffusion processes was unreachable though it concerns many applications in different fields like mathematical finance, neuroscience or reliability. The usual way to describe exit times was to use discretization schemes, that are of course approxim…

Weeds sampling for map reconstruction: a Markov random field approach

2012

In the past 15 years, there has been a growing interest for the study of the spatial repartition of weeds in crops, mainly because this is a prerequisite to herbicides use reduction. There has been a large variety of statistical methods developped for this problem ([5], [7], [10]). However, one common point of all of these methods is that they are based on in situ collection of data about weeds spatial repartition. A crucial problem is then to choose where, in the eld, data should be collected. Since exhaustive sampling of a eld is too costly, a lot of attention has been paid to the development of spatial sampling methods ([12], [4], [6] [9]). Classical spatial stochastic model of weeds cou…

The impact of urban contamination on antibioresistance in microbial communities from periphyton and sediments

2020

International audience; Since the early 20's antibiotics have been massively produced and consumed for the benefit of bothhuman and animal health. Nevertheless, antibiotics have also reached the aquatic environmentthrough diffuse sources (e.g. veterinary treatment, contaminated manure application...) and throughwastewater. Consequently, antibiotics concentrations between the ng/L and μg/L range are regularlydetected in surface water and those molecules have also been found in sediments and aquatic biota.The ubiquitous presence of antibiotics exerts a selective pressure on microbial communities leading tothe acquisition and dissemination of antibioresistance in the environment. While both an…

Ecomic - RMQs : Cartographie de la diversité microbienne des sols à l'échelle de la France

2009

aeres : C-AFF; National audience; no abstract

Extrapolation of the Species Accumulation Curve for Incomplete Species Samplings: A New Nonparametric Approach to Estimate the Degree of Sample Compl…

2015

9 pages; International audience; Incomplete species samplings are deemed to remain the common practice in those groups of animals, such as small or micro- invertebrates, with numerous species that often are more or less difficult to detect in the field. Thus, extrapolating the Species Accumulation Curve as far as possible beyond the actual sample size may thus serve as a useful (although imperfect) surrogate to the desired, but practically inaccessible, complete samplings. In this context, several kinds of theoretical or empirical models for the Species Accumulation Curve and also a lot of estimators of the asymptotic limit of the Curve (i.e. total species richness) have been proposed. The …

Tourism statistics and unobserved tourism: empirical evidences in Sicily

2013

Despite its strategic importance, accurately measuring visitor attendance has been a challenging and problematic exercise for tourism managers for decades. Consequently, the primary aim of tourism statistics of accurately quantify tourism flows has been only partially achieved; indeed at a lower territorial scale tourism statistics appear less precise and accurate. The aim of this paper is: to introduce the concept of unobserved tourism, by highlighting the main limits of official statistical systems (with a special focus on the European statistical system on tourism statistics; to formalize a theoretical model in which tourism nights and trips in a given destination are decomposed intoobse…

Tourism statistics and unobserved tourism: empirical evidences in Sicily

2013

Despite its strategic importance, accurately measuring visitor attendance has been a challenging and problematic exercise for tourism managers for decades. Consequently, the primary aim of tourism statistics of accurately quantify tourism flows has been only partially achieved; indeed at a lower territorial scale tourism statistics appear less precise and accurate. The aim of this paper is: to introduce the concept of unobserved tourism, by highlighting the main limits of official statistical systems (with a special focus on the European statistical system on tourism statistics; to formalize a theoretical model in which tourism nights and trips in a given destination are decomposed into obs…

Acceleration of the AChBP conformational transition using Temperarure Accelerated Molecular Dynamics

2013

Emotional and behavioral difficulties in adolescence: Relationship with emotional well-being, affect, and academic performance

2018

Abstract The main purpose of this study was to examine difficulties in behavioral and emotional adjustment and their relationship to subjective well-being, positive and negative affect, and academic performance in a representative sample of nonclinical adolescents. The sample consisted of a total of 1,664 participants (M = 16.12 years, SD = 1.36, range 14-19 years), selected through stratified cluster sampling. The instruments used were the Strengths and Difficulties Questionnaire (SDQ), the Positive and Negative Affect Schedule for Children (PANAS-C), the Personal Wellbeing Index-School Children (PWI-SC), the ad hoc academic performance questionnaire, and the Oviedo Scale of Response Infre…