Le PNUD et la sécurité humaine

International audienc

A New Fast and Efficient Conformal Mapping Based Technique for Remote Sensing Data Compression and Transmittal

In this paper we deal with a new technique for large data compression. Contour mapping of two dimensional objects is of fundamental importance in remote sensing and computer vision applications. We present extensive algorithms applied to polygonized, simply-connected contours and reproduce desired shapes using an innovative data compression technique based on conformal mapping. In a previous work3,4, through a conformal mapping process, we demonstrated the ability to 1) recognize shapes, and 2) concisely represent shape boundaries using a set of polynomial coefficients derived in the mapping process. In this work we illustrate how these previous results can be applied to data compression. In particular, in the approach outlined herein, a syntactic representation is formed for polygon shapes whose representation we desire to extract and reproduce compactly. Additionally, we present a problem of concavity in shape boundaries and a proposed solution in which polygons are divided into convex subsets and reconstructed accordingly

Noise and thermal stability of vibrating micro-gyrometers preamplifiers

The preamplifier is a critical component of gyrometer's electronics. Indeed the resolution of the sensor is limited by its signal to noise ratio, and the gyrometer's thermal stability is limited by its gain drift. In this paper, five different kinds of preamplifiers are presented and compared. Finally, the design of an integrated preamplifier is shown in order to increase the gain stability while reducing its noise and size.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/EDA-Publishing

3D object classification in baggage computed tomography imagery using randomised clustering forests

We investigate the feasibility of a codebook approach for the automated classification of threats in pre-segmented 3D baggage Computed Tomography (CT) security imagery. We compare the performance of five codebook models, using various combinations of sampling strategies, feature encoding techniques and classifiers, to the current state-of-the-art 3D visual cortex approach [1]. We demonstrate an improvement over the state-of-the-art both in terms of accuracy as well as processing time using a codebook constructed via randomised clustering forests [2], a dense feature sampling strategy and an SVM classifier. Correct classification rates in excess of 98% and false positive rates of less than 1%, in conjunction with a reduction of several orders of magnitude in processing time, make the proposed approach an attractive option for the automated classification of threats in security screening settings

Études paramétriques de la formation des traînées de condensation

Après un bref aperçu du contexte dans lequel s’inscrit le projet de recherche, ce mémoire met en évidence les notions scientifiques nécessaires à la compréhension des phénomènes permettant de réaliser des calculs CFD pour simuler la formation des traînées de condensation. Ainsi, un état de l’art centré sur les modélisations des traînées de condensation présente les problématiques à aborder. Ces problématiques prennent en compte, la dynamique pilotant la dispersion des effluents dans le sillage de l'avion, les réactions chimiques ayant lieu dans le panache formé par les émissions de l’aéronef et enfin les processus microphysiques responsables de la formation des cristaux de glace constituant la traînée de condensation. D’un point de vue méthodologie, le travail effectué s'appuie sur une méthode itérative d’adaptation de maillage permettant d’obtenir un raffinement optimal. L'objectif étant de résoudre les phénomènes physiques avec précision, d'une part et de réduire le coût de calcul, d'autre part. Les résultats présentés dans ce mémoire sont issus de trois études paramétriques : deux d’entre elles faisant varier un paramètre géométrique sur le modèle d’avion étudié, et une autre faisant varier les conditions atmosphériques. Ces résultats permettent de mettre en avant des comportements et des tendances dans la formation des traînées de condensation

Conception et réalisation d'un capteur MEMS multifonctions

La problématique entourant la mise en oeuvre, la conception et le conditionnement de micro-capteurs au sein d'une application embarquée représente un enjeu industriel majeur, consiste en un vaste ensemble de défis techniques et touche à de nombreux champs de recherche scientifiques comme d'applications commerciales. Ce mémoire de thèse compile de manière pédagogique et détaillée la conception, la réalisation et l'évaluation expérimentale d'un capteur MEMS constitué d'un simple micro-filament destiné à la mesure, mutuellement, de la température, de la pression et de l'humidité d'une ambiance gazeuse, en utilisant un même et mutuel étage de conditionnement du signal ce qui en tant que tel constitue une méthode d'intégration particulièrement originale qui est arbitrairement référencée comme "intégration totale". Aussi, le principe physique sous jacent à ce triplet de mesurage est la diffusion par conduction de la chaleur, produite par effet Joule dans l'élément sensible, à travers l'échantillon gazeux l'environnant. Ainsi, le principe de fonctionnement consiste en ce que, la réponse transitoire d'un tel ensemble permet d'une part de mettre en évidence, simultanément et de manière diagonalisable, à une température donnée, l'influence de la pression et de l'humidité sur la conductivité thermique et la capacité calorifique du couple sonde/échantillon. D'autre part, l'élément sensible est spécifiquement prévu pour que dans les conditions initiales du régime transitoire de l'échauffement, sa résistance électrique ne soit sensible qu'à la seule température ambiante, indépendamment des deux mesurandes.Integration of micro sensors within an embedded system is a challenging task in terms of commercial application and deals with many fields of research. This report compiles a novel methodology of multi-sensor integration, from the design to the experimental evaluation. The reported MEMS gas sensor is made from a resistive micro-wire. It is designed to the sensing of temperature, pressure and humidity of a gaseous sample, at the same time, in using only a single sensing part as well as a single conditioning principle which is by itself a new feature arbitrarily called "total integration". The physical principle involved here is heat-diffusion, where heat is produced by Joule effect within the resistive sensing part, sinking through the gaseous sample. The key is that the transient response of such a sensor enables the reading of both the sample thermal conductivity and heat capacity, depending on both humidity and pressure at a given temperature, the later being only depending upon the initial response of the sensor transient response.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

The on-line interpretation of pronouns and repeated names in seven-year-old children

Seven-year-old children performed a cross-modal naming task, in order to investigate the on-line interpretation of subject pronouns and repeated names. Children had to listen to short texts containing two sentences and to read a visual probe which represented the last word of the second sentence. This second sentence began with a subject anaphor which was either a pronoun or a repeated name, and referred either to the subject referent (Subject-Subject condition), or to the object referent (Object-Subject condition) of the first sentence. In agreement with the repeated name penalty predicted from the Gordon and Hendrick’s model (1998) developed for adults, children showed faster naming times for pronouns than for repeated names in Subject-Subject condition, whereas they showed similar naming times to solve pronouns and repeated names in Object-Subject condition. These results suggest that children interpret on-line the pronoun as a specific marker of referential continuity

Differences in the Components and Relations of a Multidimensional Model of Reading Comprehension in Low and Average 8- to 11-Year-Old French Readers.

International audienceIf the simple view of reading earlier characterised reading comprehension as a product of decoding and linguistic comprehension, research has evolved to a more complex simple view including speed or fluency as a major factor of reading comprehension. Through this complex simple view approach, multidimensional models of reading comprehension emerged, which, in addition, proposed the implication of other cognitive skills. The purpose of our study is; Firstly, as we hypothesised a structural theoretical model of the relationships between oral language skills, decoding and word fluency, oral text comprehension, reading fluency and reading comprehension, we want to test if this model fits the data obtained from 8 to 11-year-old French students and to identify the contribution and relations of each skill to reading comprehension. Secondly, we want to explore the relations of text fluency with other components of the model and with reading comprehension. Thirdly, we try to identify variations of the relations between these components according to the average or low level of reading achievement of pupils. The results obtained by studying differences in the relationships between multiple predictors of reading comprehension for low and average primary school readers seem to indicate that proficiency in reading is acquired by passing from an independent participation of the OLS and WLS to reading comprehension, as stated by the simple view of reading, to a more integrated functioning with some links between these two groups of skills, which calls for more complex views of reading

Architecture for Integrated Mems Resonators Quality Factor Measurement

In this paper, an architecture designed for electrical measurement of the quality factor of MEMS resonators is proposed. An estimation of the measurement performance is made using PSPICE simulations taking into account the component's non-idealities. An error on the measured Q value of only several percent is achievable, at a small integration cost, for sufficiently high quality factor values (Q > 100).Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/EDA-Publishing