Éditeur(s) : HAL CCSD EDP Sciences
Résumé : We propose and we justify a Monte-Carlo algorithm which solves a spatially homogeneous kinetic equation of Boltzmann type that models the fusion reaction between a deuterium ion and a tritium ion, and giving an α particle and a neutron. The proposed algorithm is validated with the use of explicit solutions of the kinetic model obtained by replacing the fusion cross-section by a Maxwellian cross section.
ISSN: 1270-900X

hal-00689821
https://hal.archives-ouvertes.fr/hal-00689821
https://hal.archives-ouvertes.fr/hal-00689821/document
https://hal.archives-ouvertes.fr/hal-00689821/file/proc_versionHAL.pdf

Éditeur(s) : EDP Sciences
Résumé : The diversity of reef ecosystems, the multiplicity of reef resource uses and the breadth of the range of the island socio-cultural contexts concerned make coral reef fisheries (CRF) management in the South Pacific a complex task. The health and state of the targeted resources depend both on ecosystem characteristics (as determined by ecological and biological factors) and on fishing pressure, whose effects are only partly known. Increasing harvests from commercial and recreational fishing increasingly overlap with traditional Subsistence activity, creating an important CRF management challenge. This paper presents a new approach to CRF assessment and monitoring by providing a set of multidisciplinary indicators. The fisheries system is assessed from three different viewpoints: ecology of targeted populations, exploitation and the broader socio-econornic fishery context. The use of complementary indicators chosen from each of these fields could balance the chronic lack of human and financial resources for the management of these fisheries. We suggest the use of these indicators through an assessment grid or an indicator dashboard specifically adapted to given situations and management objectives determined through a participatory approach. The operational efficiency of this dashboard depends on i) dialogue between users, ii) the objectivity of the proposed monitoring, iii) the Visual transcription of divergent/convergent interests amongst stakeholders, and iv) stakeholder involvement in the decision-making process. The use and constraints of such a tool are described with reference to Ouvea atoll (New-Caledonia, South Pacific) for which an analysis of available indicators for assessing fisheries status is presented.
La diversité des écosystèmes coralliens, la multiplicité des modalités d'exploitation de leurs ressources et l'hétérogénéité des contextes socio-culturels insulaires rendent complexe la gestion des pêcheries récifo-lagonaires du Pacifique sud. La santé et l'évolution de ces ressources dépendent, d'une part, des caractéristiques propres de l'écosystème (obéissant à des facteurs biologiques et écologiques) et, d'autre part, de la pression de pêche dont certains effets seulement sont établis. La pêche traditionnelle aux fins de subsistance est aujourd'hui concurrencée par des activités à visées commerciales et récréatives, qui accroissent les prélèvements et soulèvent de nouveaux enjeux de gestion. L'article propose une approche pour l'évaluation et le suivi de ces pêcheries basée sur un ensemble d'indicateurs pluridisciplinaires. Le système « Pêche » est analysé de trois points de vue complémentaires : l'écologie des peuplements exploités, l'exploitation halieutique sensu stricto et le contexte économique et social plus large des pêcheries. La mise en place d'indicateurs issus de ces trois domaines vise à compenser le manque chronique de moyens financiers et humains pour la gestion des pêcheries coralliennes des îles du Pacifique sud. Nous suggérons que leur utilisation s'effectue au travers d'une grille d'évaluation ou tableau de bord répondant à des situations précises et des objectifs de gestion définis lors d'une approche participative. La portée opérationnelle de ce tableau de bord de gestion de la pêche repose sur i) la concertation engagée entre les usagers, ii) l'objectivité du suivi préconisé, iii) la transcription visuelle des intérêts convergents et/ou divergents des acteurs, et iv) leur implication dans le processus de décision. Les modalités et contraintes d'application de cet outil sont décrites sur l'exemple de l'atoll d'Ouvéa (Nouvelle-Calédonie, Pacifique Sud), pour lequel une analyse des indicateurs disponibles pour décrire l'état des pêcheries a été réalisée.
Aquatic Living Resources (0990-7440) (EDP Sciences), 2005-07 , Vol. 18 , N. 3 , P. 199-213

Droits : 2005 EDP Sciences, IFREMER, IRD
http://archimer.ifremer.fr/doc/2005/publication-716.pdf
DOI:10.1051/alr:2005026
http://archimer.ifremer.fr/doc/00000/716/

Éditeur(s) : HAL CCSD EDP Sciences
Résumé : International audience
We show that the so-called low-regret (or least-regret) control by J. L. Lions [8] fits on the control of ill-posed problems. At each time, we give the characterization of the so-called no-regret control by means of singular optimality systems. For the backward heat ill-posed problem, no Slater hypothesis is assumed on the admissible set of controls U ad. This work is two pieces, and two methods are considered : the regularization method and the null-controllability method. For the first method, a zero order corrector is used, while for the second method, the passage to the limit is easy. The results presented here generalize the works in [2, 3] to the no-regret control. Résumé. On montre que le contrôlè a moindres regrets de J. L. Lions [8] est bien adapté pour le contrôle des desprobì emes mal posés. A chaque fois, on donne une caractérisation du contrôle sans regret par le moyen de systèmes d'optimalité singuliers. Pour leprobì eme de chaleur rétrograde mal posé, aucune hypothèse de type Slater sur l'ensemble des contrôles admissibles U ad n'est nécessaire. Ce travail est divisé en deux parties, et deux méthodes sont considérées: la méthode de régularisation et celle de la contrôlabilitécontrôlabilitéà zéro. Pour lapremì ere méthode, un correcteur d'ordre zéro est utilisé, alors que pour la seconde méthode le passagè a la limite est simple. Les résultats présentés ici généralisent les travaux dans [2, 3] au contrôle sans regret.
ISSN: 1270-900X

Droits : info:eu-repo/semantics/OpenAccess
hal-01683792
https://hal.univ-antilles.fr/hal-01683792
https://hal.univ-antilles.fr/hal-01683792/document
https://hal.univ-antilles.fr/hal-01683792/file/proc071705.pdf

Éditeur(s) : HAL CCSD EDP Sciences
Résumé : International audience
Aggregation patterns are often visually detected in sets of location data. These clusters may be the result of interesting dynamics or the effect of pure randomness. We build an asymptotically Gaussian test for the hypothesis of randomness corresponding to a homogeneous Poisson point process. We first compute the exact first and second moment of the Ripley K-statistic under the homogeneous Poisson point process model. Then we prove the asymptotic normality of a vector of such statistics for different scales and compute its covariance matrix. From these results, we derive a test statistic that is chi-square distributed. By a Monte-Carlo study, we check that the test is numerically tractable even for large data sets and also correct when only a hundred of points are observed
ISSN: 1292-8100

hal-01502640
https://hal-agroparistech.archives-ouvertes.fr/hal-01502640
DOI : 10.1051/ps/2012027

Éditeur(s) : HAL CCSD Springer Verlag/EDP Sciences
Résumé : International audience
The vibration damping coefficient (tanδ) of wood is an important property for acoustical uses, including musical instruments. Current difficulties in the availability of some of the preferred species call for diversification, but this comes up against the lack of systematic damping coefficient data. * Keeping in mind the possible factors affecting tanδ, could we predict its variations between species, by using indicators that are either easily measured and/or readily available for many species? * Vibrational properties, equilibrium moisture content and colorimetric parameters were assessed on 94 wood types belonging to 76 species. Experimental results were then related to data on chemical contents and physical properties from the CIRAD database. The "standard" relationship between tanδ and specific modulus of elasticity (E'/ρ) explained only half of the variations. Deviations from this trend were correlated to extractives content, yet effects were not directly quantitative. Damping deviations were also correlated to colour and moisture-related properties, especially so with fibre saturation point. * By taking into account a combination of moisture-related properties, colour - or extractives content, and the "standard" relationship between tanδ and E'/ρ, we could propose simple predictive models which explain up to 89% of observed variations in tanδ between 48 species.
ISSN: 1286-4560

hal-00808338
https://hal.archives-ouvertes.fr/hal-00808338
https://hal.archives-ouvertes.fr/hal-00808338/document
https://hal.archives-ouvertes.fr/hal-00808338/file/Physico-chemical_indicators_Bremaud_al.pdf
DOI : 10.1051/forest/2010032

Éditeur(s) : HAL CCSD Springer Verlag/EDP Sciences
Résumé :  
On 10 trees from 10 species of French Guyana tropical rainforest in a clear active process of restoring verticality growth strains were measured in situ in order to determine the occurrence of tension wood within samples. Wood specimens were cut in the vicinity of the growth strains measurements in order to measure some mechanical and physical properties. As suspected, tensile growth strains was very much higher in tension wood zone, because longitudinal modulus of elasticity was slightly higher. Longitudinal shrinkage was also much higher in tension wood than in opposite wood.
ISSN: 1286-4560

hal-01032110
https://hal.archives-ouvertes.fr/hal-01032110
DOI : 10.1051/forest:2007027

Éditeur(s) : HAL CCSD Springer Verlag/EDP Sciences
Résumé : International audience
Key message: Genetic diversity appears to be unaffected by disturbance in a stand of the light-demanding Neotropical treeV. michelii. Although spatial genetic structure is modified in post-disturbance cohorts, mixing of seeds from different mother trees in canopy gaps appears to efficiently maintain genetic admixture. Context: The interplay between genetic and demographic processes has major consequences on population viability. Population size affects demographic trends, while genetic diversity insures viability by reducing risks of inbreeding depression and by maintaining adaptive potential. Yet, the consequences of increases in census size (as opposed to effective size) on genetic diversity of forest populations are poorly known. Aims: We have studied the structure of genetic diversity in populations of saplings of the light-responsive tree, Virola michelii (Myristicaceae, the nutmeg family), in two plots having undergone different levels of canopy-gap opening disturbance. This allowed us to test the “intermediate disturbance” hypothesis, which generally applies to species diversity, at the intra-specific scale. Methods: Levels and distribution of genetic diversity were compared between plots and between life stages. Sapling parentage was analysed to infer each adult tree’s contribution to regeneration. Results: Genetic diversity was higher, and spatial genetic structure was stronger in the post-disturbance than in the control seedling population. Parentage analysis suggested that a limited number of parents contributed to most of the regeneration, but that efficient mixing of their progeny may have enhanced the diversity of saplings occupying canopy gaps. Conclusion: A mixture of demo-genetic processes may contribute to maintain genetic diversity in spite of, or possibly due to, ecosystem disturbance in V. michelii.
ISSN: 1286-4560

hal-01502942
https://hal-agroparistech.archives-ouvertes.fr/hal-01502942
https://hal-agroparistech.archives-ouvertes.fr/hal-01502942/document
https://hal-agroparistech.archives-ouvertes.fr/hal-01502942/file/art_10.1007_s13595-015-0508-3-1_%7B869D58F4-272C-491F-A903-DAD6CDBDC042%7D.pdf
DOI : 10.1007/s13595-015-0508-3

Éditeur(s) : HAL CCSD EDP Sciences
Résumé : International audience
ISSN: 1270-900X

hal-00507812
https://hal.archives-ouvertes.fr/hal-00507812

Éditeur(s) : HAL CCSD Springer Verlag/EDP Sciences
Résumé : International audience
Chlorophyll meters such as the SPAD-502 offer a simple, inexpensive and rapid method to estimate foliar chlorophyll content. However, values provided by SPAD-502 are unitless and require empirical calibrations between SPAD units and extracted chlorophyll values. * Leaves of 13 tree species from the tropical rain forest in French Guiana were sampled to select the most appropriate calibration model among the often-used linear, polynomial and exponential models, in addition to a novel homographic model that has a natural asymptote.* The homographic model best accurately predicted total chlorophyll content (μg cm−2) from SPAD units (R2 = 0.89). Interspecific differences in the homographic model parameters explain less than 7% of the variation in chlorophyll content in our data set. * The utility of the general homographic model for a variety of research and management applications clearly outweighs the slight loss of model accuracy due to the abandon of the species' effect.
ISSN: 1286-4560

Droits : info:eu-repo/semantics/OpenAccess
hal-00883628
https://hal.archives-ouvertes.fr/hal-00883628
https://hal.archives-ouvertes.fr/hal-00883628/document
https://hal.archives-ouvertes.fr/hal-00883628/file/hal-00883628.pdf
DOI : 10.1051/forest/2010020

Éditeur(s) : HAL CCSD EDP Sciences
Résumé : International audience
Modelling environmental problems leads to mathematical systems with missing data. For instance, weather problems have generally missing initial conditions. The paper is concerned with identifying pollution terms arising in the state equation of some dissipative system with incomplete initial condition. To this aim the so-called sentinel method is used. Here, the problem of determining a sentinel is equivalent to a null-controllability problem for which Carleman inequalities are revisited.
ISSN: 1270-900X

hal-00720818
https://hal.univ-antilles.fr/hal-00720818
https://hal.univ-antilles.fr/hal-00720818/document
https://hal.univ-antilles.fr/hal-00720818/file/esaimpr2.pdf

Éditeur(s) : HAL CCSD EDP Sciences
Résumé : International audience
ISSN: 1292-8119

hal-01673090
https://hal.archives-ouvertes.fr/hal-01673090
DOI : 10.1051/cocv/2017024

Éditeur(s) : HAL CCSD EDP Sciences
Résumé : International audience
This paper reports the first outcomes of a research program “Environment and Sustainable Development in the Caribbean space” co-funded by the European Union, the Région Martinique and the Université des Antilles et de la Guyane under the European Union operational programme 2007-2013. Since the middle of the last century, the Caribbean countries, regardless of their great diversity and political fragmentation, are faced with the recurring problem of development. Having explored different paths, they are looking now for new development models. This challenge which becomes obsessive over the decades, is now a major concern: indeed, the Caribbean territories are per se vulnerable and highly exposed to natural risks due to climate change. In addition, this relates to areas where tensions between exploitation and conservation of a rich biodiversity are particularly strong. Based on the promotion of tourism and services as part of an “open regionalism” at the intersection of global and local scales of public action, the current development strategies give rise to a dual approach with, however, rather mixed results: on the one hand, a discursive use of sustainable development, apprehended through its environmental dimension, evidences a new way of looking at the region and a change in the way the region sees itself; on the other hand, a political use of sustainable development through cross-cutting policies, is hindered by the complexity of structures, the multiple levels of action and regulation, and the difficult appropriation of public-policy organization by local communities and people.
Cet article rend compte des premiers résultats d’un programme de recherche « Environnement et développement durable dans l’espace caraïbe » cofinancé par l’Union européenne, la région Martinique et l’Université des Antilles et de la Guyane dans le cadre des programmes opérationnels européens 2007-2013. Il montre que les territoires de la Caraïbe, après avoir exploré plusieurs voies en matière de développement, privilégient désormais des stratégies axées sur le tourisme et les services. S’inscrivant dans un « régionalisme ouvert » au croisement des échelles globale et locale d’intervention en matière d’action publique, ces stratégies débouchent sur une double démarche aux résultats contrastés : d’un côté, une mise en discours du développement durable, appréhendé notamment à travers sa dimension environnementale, témoigne d’un changement de regard sur la région et de celle-ci sur elle-même ; de l’autre, une mise en politique du développement durable à travers des dispositifs à caractère transversal, se heurte à la complexité des structures, à la multiplicité des échelles d’intervention et de régulation ainsi qu’à la difficile appropriation desdits dispositifs par les populations locales.
ISSN: 1240-1307

Droits : info:eu-repo/semantics/OpenAccess
hal-01675012
https://hal.univ-antilles.fr/hal-01675012
https://hal.univ-antilles.fr/hal-01675012/document
https://hal.univ-antilles.fr/hal-01675012/file/NSS_La%20mise%20en%20discours.pdf
DOI : 10.1051/nss/2015043

Éditeur(s) : HAL CCSD Springer Verlag/EDP Sciences
Résumé : International audience
Background : This study examines the radial trend in wood stiffness of tropical rainforest trees. The objective was to determine if the type of growing environment (exposed plantation or dense primary forest) would have an effect on this radial trend. Methods : The axial elastic modulus of wood samples, representing a pith to bark cross-section, of six trees from several French Guianese species (two of Eperua falcata, one of Eperua grandiflora, two of Carapa procera and one of Symphonia gloubulifera) was measured using a dynamic "forced vibration" method. Results : Primary forest trees were observed to have a decrease in wood stiffness from pith to bark, whereas plantation trees, from the same genus or species, displayed a corresponding increase in wood stiffness. Juvenile wood stiffness appears to vary depending on the environment in which the tree had grown. Conclusion : We suggest that the growth strategy of primary forest trees is to produce wood resistant to selfbuckling so that the height of the canopy may be obtained with the maximum of efficiency. In contrast, the growth strategy of the trees growing in an exposed plantation is to produce low-stiffness wood, important to provide flexibility in wind. Further experiments to study the behaviour of more species, with more individuals per species, growing across a range of physical environments, are required.
ISSN: 1286-4560

hal-00644335
https://hal.archives-ouvertes.fr/hal-00644335
https://hal.archives-ouvertes.fr/hal-00644335/document
https://hal.archives-ouvertes.fr/hal-00644335/file/McLean_al.pdf
DOI : 10.1007/s13595-011-0085-z

Éditeur(s) : HAL CCSD EDP Sciences
Résumé : Cette communication présente les principaux résultats du projet ExtraFlo sur l'estimation des pluies et crues extrêmes. A partir d'un jeu de données conséquent de plusieurs milliers de stations, une procédure d'inter-comparaison a permis d'évaluer les performances d'une trentaine d'implémentations différentes issues de différentes combinaisons (modèle probabiliste, méthode d'estimation, cadre local / régional / mixte local et régional). Le projet ExtraFlo a permis de mettre en évidence le manque de robustesse des approches basées sur le traitement statistique d'une série de quelques dizaines d'années d'observation. Des alternatives intéressantes existent, basées sur l'exploitation des records de pluie et de débit à l'échelle d'une région, de la collecte de données historiques quand cela est possible, de méthodes de simulation basées sur le couplage d'un générateur d'averses avec un modèle hydrologique pour la transformation des pluies en débit, ou des traces morphologiques laissées par les crues anciennes.
ISSN: 0018-6368

hal-01054313
https://hal.archives-ouvertes.fr/hal-01054313
DOI : 10.1051/1hb/2014010

Éditeur(s) : HAL CCSD INRA/EDP Sciences
Résumé : 23 ref.
absent
ISSN: 0003-4312

hal-01032359
https://hal.archives-ouvertes.fr/hal-01032359

Éditeur(s) : HAL CCSD EDP sciences
Résumé : International audience
Off road wheelchair riding, a “ hiking boots” : body experience and identity reconfigurations. Feel sensations during the practice of nature sport is not new. However, a disabled person feels similar sensations to an abled person, through access to the mountain with an Off Road Wheelchair Riding (ORWC), is part of a normalization process. This activity appeared in France in the early 1990’s. It allows people who have lost all or part of their mobility, to be able to access to high mountains. The interviewees are quadriplegic and paraplegic after an accident. Their speeches reveal the body uses in ORWC for reliving the sensations in mountain environment. The reconquest of natural areas is the social limitations to overcome, to escape a negative social assignment of the disabled person, but also to regain a self-identity.
La question de l’expérience corporelle lors d’une pratique sportive de pleine nature est récurrente. Cependant, qu’une personne handicapée expérimente sensations similaires à un individu « valide », en accédant à la montagne en Fauteuil Tout Terrain (FFT), participe d’un processus de normalisation. Cette activité, apparue en France au début des années 1990, permet aux personnes qui ont perdu la totalité ou une partie de leur mobilité, d’accéder à la haute montagne. Les enquêtés, accidentés tétraplégiques ou paraplégiques, révèlent des usages du corps en FTT pour revivre des sensations en milieu montagnard. La reconquête des espaces naturels représente les limites sociales à surmonter permettant d’échapper à une assignation sociale négative de la personne handicapée, mais également de reconstituer une identité à soi.
ISSN: 2118-5735

hal-01681326
https://hal.archives-ouvertes.fr/hal-01681326
DOI : 10.1051/sm/2017013

Éditeur(s) : HAL CCSD Springer Verlag/EDP Sciences
Résumé : We characterised the among species variability in leaf gas exchange and morphological traits under controlled conditions of seedlings of 22 tropical rainforest canopy species to understand the origin of the variability in leaf carbon isotope discrimination (Delta) among species with different growth and dynamic characteristics (successional gradient). Our results first suggest that these species pursue a consistent strategy in terms of (Delta) throughout their ontogeny (juveniles grown here versus canopy adult trees from the natural forest). Second, leaf (Delta) was negatively correlated with WUE and N, and positively correlated with gs, but among species differences in (Delta) were mainly explained by differences in WUE. Finally, species belonging to different successional groups display distinct leaf functional and morphological traits. We confirmed that fast growing early successional species maximise carbon assimilation with high stomatal conductance. In contrast, fast and slow growing late successional species are both characterised by low carbon assimilation values, but by distinct stomatal conductance and leaf morphological features. Along the successional gradient, these differences result in much lower (Delta) for the intermediate species (i.e. fast growing late successional) as compared to the two other groups.
ISSN: 1286-4560

hal-01032038
https://hal.archives-ouvertes.fr/hal-01032038
DOI : 10.1051/forest:2006101

Éditeur(s) : Edp Sciences S A
Houille Blanche-revue Internationale De L Eau (0018-6368) (Edp Sciences S A), 2015-02 , N. 1 , P. 109-112

Droits : EDP Sciences
http://archimer.ifremer.fr/doc/00260/37084/35585.pdf
http://archimer.ifremer.fr/doc/00260/37084/

Éditeur(s) : HAL CCSD EDP Sciences
Résumé : S'inscrivant dans une perspective institutionnaliste, notre article porte sur l'analyse des modes de coordination entre acteurs locaux en vue d'une gestion durable des ressources naturelles. En mobilisant les apports de l'économie de la proximité, nous mettons en lumière la manière dont les dynamiques de relations sociales peuvent être activées pour favoriser des pratiques de gestion durable des ressources naturelles. Plus largement, à partir d'une réflexion générale sur les institutions de gestion commune des ressources naturelles et le rôle que jouent sur elles les catégories de la proximité, nous proposons les éléments d'une formalisation de la robustesse des systèmes sociaux écologiques. Nous analysons sous quelles conditions un degré élevé de proximité peut favoriser ou, au contraire, nuire à la pérennité d'un système écologique et social. Notre propos est illustré par un cas d'étude concret : le site Natura 2000 du Mont-Bar (petit territoire forestier auvergnat).
ISSN: 1240-1307

hal-00982722
https://hal-agroparistech.archives-ouvertes.fr/hal-00982722
https://hal-agroparistech.archives-ouvertes.fr/hal-00982722/document
https://hal-agroparistech.archives-ouvertes.fr/hal-00982722/file/2009_NSS_AngeonCaron.pdf
DOI : 10.1051/nss/2009065

Éditeur(s) : HAL CCSD INRA/EDP Sciences
Résumé : absent
ISSN: 0003-4312

hal-01032368
https://hal.archives-ouvertes.fr/hal-01032368