15771 research outputs found
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Return Migrants in Western Africa: Characteristics and Labour Market Performance
No full textouinonouirechercheInternationa
Optimal Control versus Stochastic Target problems: An Equivalence Result
No full textWithin a general abstract framework, we show that any optimal control problem instandard form can be translated into a stochastic target problem as de ned in [17], whenever the underlying ltered probability space admits a suitable martingale representationproperty. This provides a uni ed way of treating these two classes of stochastic con-trol problems. As an illustration, we show, within a jump di usion framework, how theHamilton-Jacobi-Bellman equations associated to an optimal control problem in standard form can be easily retrieved from the partial di erential equations associated to itsstochastic target counterpart.ouinonouirechercheInternationa
Comment se construisent les problèmes de santé publique
No full textRadiations, infections nosocomiales, périnatalité, canicule, antennes relais de téléphonie mobile, sécurité routière, amiante, chikungunya, éthers de glycol, toxicomanie, bruit, démographie médicale, tremblante du mouton... Alors que la France a connu ces dernières années d'importantes crises sanitaires, nombre de phénomènes tendent à être considérés comme des problèmes de santé publique. Or ni cette qualification ni la mise en œuvre d'une action publique correspondante ne vont de soi. En témoignent les différences de traitement de situations qui sont rendues publiques ou font l'objet d'alertes plus ou moins confidentielles.Les processus par lesquels une situation devient ou non un problème de santé publique et fait ou non l'objet d'une intervention sont abordés de front dans cet ouvrage. La question des « luttes définitionnelles », des acteurs et processus qui construisent et portent ces définitions en constitue le fil conducteur. L'un des apports des contributions rassemblées, qui mobilisent différentes approches de sciences sociales, est de prêter la même attention aux contours publics, voire médiatiques, d'un problème qu'à ses caractéristiques dans des arènes plus dis-crètes lorsqu'il est traité entre spécialistes du domaine. Une attention particulière est aussi accordée à la dynamique de ces processus de définition sur un temps long. Les auteurs montrent également que les luttes ou négociations autour de la définition d'un problème sont aussi des conflits de pouvoir entre différents acteurs ou groupes d'acteurs.Une réflexion qui permet une meilleure compréhension des conditions d'émergence et de reconnaissance des problèmes publics et de l'engagement de l'action publique.nonouirechercheNationa
Pourquoi et comment redresser le système européen des quotas de CO²
No full textnonnonouirechercheNationa
Blockers for the stability number and the chromatic number
No full textGiven an undirected graph G = (V,E) and two positive integers k and d, we are interested in finding a set of edges (resp. non-edges) of size at most k to delete (resp. to add) in such a way that the chromatic number (resp. stability number) in the resulting graph will decrease by at least d compared to the original graph. We investigate these two problems in various classes of graphs (split graphs, threshold graphs, (complement of) bipartite graphs) and determine their computational complexity. In some of the polynomial-time solvable cases, we also give a structural description of a solution.nonouirechercheInternationa
A microeconometric analysis of household savings determinants in Morocco
No full textThis article provides an analysis of the microeconomic determinants of household savings behaviour in Morocco according to geographical household residence. Descriptive statistics seemto indicate a similar savings pattern in both rural and urban areas but the econometric results do not support this conclusion. Current income strongly affects the savings level in the urban area whereas the literacy of the household’s head is determinant in the rural one. However, theresults do not confirm the life cycle hypothesis. The household’s size has a significant negative impact only in the urban case, while women heads of household save more than men, except for highest income levels. The results clearly show that urban and rural households behave differently with regards to savings.nonouirechercheInternationa
Knowledge-Based Programs as Plans: Succinctness and the Complexity of Plan Existence
No full textKnowledge-based programs (KBPs) are high-level protocols describing the course of action an agent should perform as a function of its knowledge. The use of KBPs for expressing action policies in AI planning has been surprisingly over-looked. Given that to each KBP corresponds an equivalent plan and vice versa, KBPs are typically more succinct than standard plans, but imply more on-line computation time. Here we make this argument formal, and prove that there exists an exponential succinctness gap between knowledge-based programs and standard plans. Then we address the complexity of plan existence. Some results trivially follow from results already known from the literature on planning under incomplete knowledge, but many were unknown so far.nonouirechercheInternationa
Marketing viral ou buzz marketing, même combat ? Le marketing viral dans la perspective du marketing interactif
No full textnonouirechercheNationa
Bayesian nonparametric dependent model for partially replicated data: The influence of fuel spills on species diversity
No full textWe introduce a dependent Bayesian nonparametric model for the probabilistic modeling of membership of subgroups in a community based on partially replicated data. The focus here is on species-by-site data, that is, community data where observations at different sites are classified in distinct species. Our aim is to study the impact of additional covariates, for instance, environmental variables, on the data structure, and in particular on the community diversity. To this end, we introduce dependence a priori across the covariates and show that it improves posterior inference. We use a dependent version of the Griffiths–Engen–McCloskey distribution defined via the stick-breaking construction. This distribution is obtained by transforming a Gaussian process whose covariance function controls the desired dependence. The resulting posterior distribution is sampled by Markov chain Monte Carlo. We illustrate the application of our model to a soil microbial data set acquired across a hydrocarbon contamination gradient at the site of a fuel spill in Antarctica. This method allows for inference on a number of quantities of interest in ecotoxicology, such as diversity or effective concentrations, and is broadly applicable to the general problem of community response to environmental variables.nonnonouirechercheInternationa