382 research outputs found
Une Toolbox Abaqus pour le calcul de propriétés effectives de milieux hétérogènes
National audienceSee http://hal.archives-ouvertes.fr/docs/00/59/28/66/ANNEX/r_89TN22OL.pd
How to improve robustness in Kohonen maps and display additional information in Factorial Analysis: application to text mining
This article is an extended version of a paper presented in the WSOM'2012
conference [1]. We display a combination of factorial projections, SOM
algorithm and graph techniques applied to a text mining problem. The corpus
contains 8 medieval manuscripts which were used to teach arithmetic techniques
to merchants. Among the techniques for Data Analysis, those used for
Lexicometry (such as Factorial Analysis) highlight the discrepancies between
manuscripts. The reason for this is that they focus on the deviation from the
independence between words and manuscripts. Still, we also want to discover and
characterize the common vocabulary among the whole corpus. Using the properties
of stochastic Kohonen maps, which define neighborhood between inputs in a
non-deterministic way, we highlight the words which seem to play a special role
in the vocabulary. We call them fickle and use them to improve both Kohonen map
robustness and significance of FCA visualization. Finally we use graph
algorithmic to exploit this fickleness for classification of words
Structure génétique des populations : modèle amérindien et les haplotypes du chromosome X
Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal
Can species richness be maintained in logged endemic Acacia Heterophylla forests (Reunion Island, Indian Ocean) ?
It is assumed that forests can serve multiple uses, including wood production and maintenance of high biodiversity level. We tested this hypothesis by studying eradication methods of invasive plants currently implemented in exploited endemic Acacia heterophylla forests located in a tropical highland forest region on the island of Réunion. We also compared species richness in logged (over time) and natural forests. Our results show that all individuals of the widespread alien invasive plant Rubus alceifolius were generated from cuttings. We quantifi ed the high growth capability of this species by comparing with those of Acacia heterophylla along with Rubus apetalus var. apetalus, a close non-invasive congener. The substantial multiplicative and vegetative growth ability of R. alceifolius enabled it to form monospecific patches in only 2.5 years. The species richness of the exploited Acacia heterophylla forest was thus very affected. Although the species richness increased over time after logging, the extent of the resulting richness was not as great as that in natural forests which, moreover, included numerous exotic plants. The authors assess the impact of highly disturbing logging operations and, based on the results of the comparisons, are very pessimistic about the possibility of maintaining species richness in logged forests. Nevertheless, the results indicate that the situation is not beyond hope and an eradication program specifi cally tailored to this kind of forest is proposed if exploitation will stop
Modélisation de structures multi-rubans pour applications spatiales
National audienceOn s'intéresse à la modélisation de structures multi-rubans déployables. Partant d'un modèle 1D spécifique, on établit un outil métier capable de modéliser un mètre ruban seul afin d'effectuer une analyse des réponses possibles pour un jeu de conditions limites imposé. Cet outil sera par la suite étendu à la modélisation de structures multi-rubans, pour conduire une étude comparative de diverses solutions de déploiement envisagées
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