Éditeur(s) : HAL CCSD
Résumé : International audience
IHMA
Lille, France

hal-01313395
https://hal.archives-ouvertes.fr/hal-01313395

Éditeur(s) : HAL CCSD Elsevier Masson
Résumé : Fire-free forest conversion with organic inputs as an alternative to slash-and-burn could improve agro-ecosystem sustainability. We assessed soil carbon mass changes in a sandy-clayey and well-drained soil in French Guiana after forest clearing by the chop-and-mulch method and crop establishment. At the experimental site of Combi, native forest was cut down in October 2008; woody biomass was chopped and incorporated into the top 20 cm of soil. After about one year of legume and grass cover, three forms of land management were compared: grassland (Urochloa ruziziensis), maize/soybean crop rotation with disk tillage and in direct seeding without tillage. There were four replicates. We measured 14.16 kg m(-2) of carbon in 2 mm-sieved soil down to 2 m depth for the initial forest. Forest clearing did not induce significant soil compaction; neither did any specific agricultural practice. In converted soils, C stocks were measured in the 0-30 cm layer after each crop for three years. Carbon mass changes for soil fractions <2 mm (soil C stock) and >2 mm (soil C pool) in the 0-5, 5-10, 10-20 and 20-30 cm soil layers were assessed on an equivalent soil mass basis. One year and 1.5 years after deforestation, higher C stocks (+0.64 to 1.16 kg C m(-2) yr(-1)) and C pools (+0.52 to 0.90 kg C m(-2) yr(-1)) were measured in converted soils, compared to those of the forest into the top 30 cm of soil. However, the masses of carbon in these converted soils declined later. The highest rates of carbon decrease were measured between 1.5 and 2 years after forest conversion in the <2 mm soil fraction, from 0.46 kg Cm-2 yr(-1) (in grassland soils) to 0.71 kg C m(-2) yr(-1) (in cropland under no tillage). The carbon pool declined during the third year at rates of 0.41 kg C m(-2) yr(-1) (cropland under disk tillage) to 0.76 kg C m(-2) yr(-1) (grassland soils). Three years after forest conversion, C masses in the top 30 cm of soils for grassland showed similar values than for forest. In comparison, the carbon stock in cropped soils managed under no tillage in direct seeding (without mulch) was significantly 17% and 16% lower than in forest and grassland soils, respectively. None of the studied agricultural practices succeeded in accumulating carbon from the chopped forest biomass.
ISSN: 0167-8809

hal-01032438
https://hal.archives-ouvertes.fr/hal-01032438
DOI : 10.1016/j.agee.2013.11.009

Éditeur(s) : HAL CCSD Society for Industrial and Applied Mathematics
Résumé : International audience
ISSN: 0363-0129

hal-01147931
https://hal.archives-ouvertes.fr/hal-01147931

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
ISSN: 0006-8993

hal-00690129
https://hal.archives-ouvertes.fr/hal-00690129

Éditeur(s) : HAL CCSD Tsing Hua University
Résumé : International audience
ISSN: 1607-2510

hal-00514916
https://hal.archives-ouvertes.fr/hal-00514916

Éditeur(s) : HAL CCSD
Résumé : International audience
Rendiconti del Circolo Matematico di Palermo

hal-01099638
https://hal.archives-ouvertes.fr/hal-01099638
DOI : 10.1007/s12215-014-0161-y

Éditeur(s) : HAL CCSD
Résumé : En traitement d'image, avant toute exploitation de résultats d'une segmentation d'image, il est souvent nécessaire de réaliser une opération de fusion. Le but est de créer une partition formée de composantes connexes, modélisant les objets présents dans l'image. La segmentation initiale des images est souvent obtenue par l'exploitation d'attributs de bas-niveau (couleur, texture, forme...). La théorie Gestalt permet de prendre en compte des informations d'un niveau supérieur qui s'appuient sur l'organisation spatiale des objets et groupement d'objets initialement segment'es. Dans cet article, nous proposons une méthode de fusion de régions. L'originalité des travaux repose sur l'ajout d'un nouveau critère qui, associé aux critères Gestalt, permet de prendre en compte les objets jugés d'intérêt par le photographe, c'est-'a-dire les objets aux contours nets. Les régions associées aux objets d'intérêts seront alors préservées alors que les régions floues ou aux contours flous, situées dans l'arrière-plan, auront tendance 'a fusionner entre elles.
Journée du GdR Mathématique de l'Optimisation et Application (MOA)
Saint-François, Guadeloupe

hal-00706538
https://hal.archives-ouvertes.fr/hal-00706538

Éditeur(s) : HAL CCSD
Résumé : International audience
Revista Colombiana de Matematicas

hal-00514918
https://hal.archives-ouvertes.fr/hal-00514918

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
ISSN: 0764-4442

hal-00515784
https://hal.archives-ouvertes.fr/hal-00515784

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Understanding how communities respond to natural disturbances is fundamental to assess the mechanisms of ecosystem resistance and resilience. However, ecosystem responses to natural disturbances are rarely monitored both through space and time, while the factors promoting ecosystem stability act at various temporal and spatial scales. Hence, assessing both the spatial and temporal variations in species composition is important to comprehensively explore the effects of natural disturbances. Here, we suggest a framework to better scrutinize the mechanisms underlying community responses to disturbances through both time and space. Our analytical approach is based on beta diversity decomposition into two components, replacement and biomass difference. We illustrate this approach using a 9-year monitoring of coral reef fish communities off Moorea Island (French Polynesia), which encompassed two severe natural disturbances: a crown-of-thorns starfish outbreak and a hurricane. These disturbances triggered a fast logistic decline in coral cover, which suffered a 90% decrease on all reefs. However, we found that the coral reef fish composition remained largely stable through time and space whereas compensatory changes in bio-mass among species were responsible for most of the temporal fluctuations, as outlined by the overall high contribution of the replacement component to total beta diversity. This suggests that, despite the severity of the two disturbances, fish communities exhibited high resistance and the ability to reorganize their compositions to maintain the same level of total community biomass as before the disturbances. We further investigated the spatial congruence of this pattern and showed that temporal dynamics involved different species across sites; yet, herbivores controlling the proliferation of algae that compete with coral communities were consistently favored. These results suggest that compensatory changes in bio-mass among species and spatial heterogeneity in species responses can provide further
ISSN: 1932-6203

hal-01212344
https://hal-univ-perp.archives-ouvertes.fr/hal-01212344
https://hal-univ-perp.archives-ouvertes.fr/hal-01212344/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01212344/file/journal.pone.0138696.pdf
DOI : 10.1371/journal.pone.0138696

Éditeur(s) : HAL CCSD
Résumé : 12 pages, in French. Colloque international et interdisciplinaire pour les enjeux et usages des technologies de l'information et de la communication, 2015 (EUTIC 2015)
International audience
The emergence of new communication media such as blogs, online newspapers and social networks allow us to go further in the understanding of human behavior. Indeed, these public exchange spaces are now firmly planted in our modern society and appear to be powerful sensors of social behavior and opinion movements. In this paper, we focus on information spreading and attempt to understand what are the conditions in which a person decides to speak on a subject. For this purpose, we propose a set of measures that aim to characterize the diffusion behavior. Our measures have been used on messages related to two events that took place in January 2015: presentation by Microsoft of a new virtual reality headset and the election of a political party of radical left in Greece.
Colloque international et interdisciplinaire pour les enjeux et usages des technologies de l'information et de la communication, 2015 (EUTIC 2015)
Schoelcher, France

hal-01514258
https://hal.archives-ouvertes.fr/hal-01514258
ARXIV : 1602.00252

Éditeur(s) : HAL CCSD IGI Global
Résumé : International audience
Graph Theoretic Approaches for Analyzing Large-Scale Social Networks

hal-01637538
https://hal.archives-ouvertes.fr/hal-01637538

Éditeur(s) : HAL CCSD IGI Global
Résumé : International audience
Standard data mining techniques have been applied and adapted for eliciting knowledge from social networks, by achieving classical tasks such as classification, search for frequent patterns or link prediction. Most works have exploited only the network topological structure, and therefore cannot be used to answer questions involving nodes features. For instance, the frequent pattern discovery task generally refers to the search for sub-networks frequently found in a single network or in a set of networks. In the same area, this paper focuses on the concept of frequent link that stands as a regularity found in a network on links between node groups that share common characteristics. The extraction of such links from a social network is a particularly challenging and computationally intensive problem, since it is much dependent on the number of links and attributes. In this study, we propose a solution for reducing the search space of frequent links, by filtering the nodes features on a criterion of frequency. We make the assumption that frequent links occur between sets of features that are themselves frequent. This property is used to reduce the search space and speed up the extraction process. We empirically show that it is well founded. We discuss the efficiency of the solution in terms of computation time and number of frequent patterns found depending on several frequency thresholds.
ISSN: 1947-8186

hal-00786166
https://hal.archives-ouvertes.fr/hal-00786166

Éditeur(s) : HAL CCSD
Résumé : International audience
IEEE-AP/S International Symposium and USNC/URSI National Radio Science Meeting
Washington DC, United States

hal-00770282
https://hal.univ-antilles.fr/hal-00770282

Éditeur(s) : HAL CCSD
Résumé : International audience
Compte Rendu de l'Académie bulgare des Sciences

hal-00514917
https://hal.archives-ouvertes.fr/hal-00514917

Éditeur(s) : HAL CCSD
Résumé : International audience
Traditional network generation models aim to replicate global structural properties observed on various real-world networks (power law degree distribution, short average distance, community structure, etc.) through synthetic link formation mechanisms such as triadic closure or preferential attachment. Nowadays the large amount of data available allows to study more precisely the link formation processes and to compare the models to real situations. In this work, we analyse the communication activities of the users of a mobile telephony operator for studying the link formation process. The communications emitted and received by users are strong indicators for understanding the underlying mechanisms of the link formation process and highlighting how user attributes correlate with the formation process in such a network. In a first study conducted at a global level we show that the traditional mechanisms commonly used in network generation models are not the main link formation mechanisms involved in this network. In a second study, we analyse more precisely the link formation process by searching for correlations between some user attributes and the formation of the new links. These results provide valuable guidelines to the design of more realistic generation models taking into account network structure and node attributes.
IEEE International Conference on Research Challenges in Information Science (RCIS)
Marrakesh, Morocco

hal-01312314
https://hal.archives-ouvertes.fr/hal-01312314
DOI : 10.1109/RCIS.2014.6861065

Éditeur(s) : HAL CCSD
Résumé : International audience
ICGF'2000, the International Conference on Generalized Functions, Linear and nonlinear problems
Pointe-à-pitre, Guadeloupe

hal-01555297
https://hal.archives-ouvertes.fr/hal-01555297

Éditeur(s) : HAL CCSD
Séminaire du laboratoire de mathématiques de l'Université de Bretagne Occidentale

hal-00675038
https://hal.archives-ouvertes.fr/hal-00675038

Éditeur(s) : HAL CCSD
Résumé : Session "Articles"
National audience
Dans cet article, nous présentons une méthode robuste et précise pour détecter 17 points caractéristiques du visage sur des images expressives. Une nouvelle architecture multi-résolution basée sur les récents algorithmes multi-noyau est introduite. Les patches de faibles résolutions codent les informations globales du visage donnant lieu à une détection grossière mais robuste du point désiré. Les patches de grandes résolutions quant à eux utilisent les détails locaux afin d'affiner cette localisation. En combinant une détection indépendante de points et des informations a priori sur les distributions de points, nous proposons un détecteur robuste aux changements d'expressions ainsi qu'aux variations d'illuminations. Ce système a été évalué sur plusieurs bases de données de la littérature. Les résultats présentés améliorent les performances des détecteurs de l'état de l'art
Actes de la conférence RFIA 2012
Lyon, France

hal-00656522
https://hal.archives-ouvertes.fr/hal-00656522
https://hal.archives-ouvertes.fr/hal-00656522/document
https://hal.archives-ouvertes.fr/hal-00656522/file/rfia2012_submission_99.pdf

Éditeur(s) : HAL CCSD
CODE07
Paris, France

hal-00514924
https://hal.archives-ouvertes.fr/hal-00514924