1,720,994 research outputs found
Cartographie des forêts humides dans la région d’El Kala (Algérie) à l’aide des outils d’observation de la Terre
No full textMapping of wet forests using Earth Observation tools in El Kala area (Algeria).
Wet forests are among the most threatened and degraded wetland ecosystems in the world. In Algeria, they are mainly represented by specific, fragile and rare forest habitats. The region of El Kala (North-East of Algeria) hosts many unique wetlands (e. g. lakes, marshlands, wet meadows, lagoons, etc.) but also some of the most extended wet forests in North Africa. The main objective of this study is to develop a new mapping approach for the location and the delineation of these ecosystems using Earth Observation (EO) tools. This methodology is based on a combination of topographic and hydro-geomorphological indices derived from Digital Elevation Models (DEMs), with spectral variables extracted from Landsat-8 satellite images and in-situ data collected from the field. The final result showed that the studied area hosts more than 3900 ha of wet forests (alder and riparian forests), with an overall accuracy, estimated using field observations, higher than 85 %. This new approach allows mapping the spatial distribution of wet forests at large geographic scales and could be used as a support to facilitate their monitoring, using EO time series, but also to better implement management and conservation measures.Les forêts humides sont parmi les écosystèmes humides les plus dégradés et les plus menacés dans le monde. En Algérie, elles représentent un ensemble d’habitats forestiers singuliers, fragiles et rares. La région d’El Kala, à l’extrême nord-est du pays, abrite de nombreuses zones humides uniques (lacs, marais, prairies humides, lagunes, etc.), parmi lesquelles quelques-unes des plus importantes formations de forêts humides en Afrique du Nord. L’objectif de cette étude est de développer une nouvelle approche cartographique afin de localiser et de délimiter ces formations à l’aide des outils d’observation de la Terre. Elle se base sur une combinaison d’indices topographiques et hydro-géomorphologiques, issus des Modèles Numériques de Terrain (MNT), de variables spectrales calculées à partir des images Landsat-8 et de données collectées sur terrain. Le résultat final a permis de mettre en évidence l’existence de plus de 3900 ha de forêts humides (aulnaies plus ripisylves) sur l’ensemble des bassins versants de la région d’El Kala, avec un niveau de fiabilité, estimé à partir d’observations terrain, supérieur à 85 %. Ainsi, la méthodologie développée ici permet de définir la distribution spatiale des forêts humides sur de grandes échelles territoriales, ce qui pourrait grandement faciliter leur suivi diachronique, avec des analyses rétrospectives rendues possible grâce aux outils de télédétection, mais aussi une meilleure implémentation des outils dédiés à leur gestion et à leur conservation.Kahli Asma, Belhadj Ghania, Gaget Élie, Merle Clément, Guelmami Anis. Cartographie des forêts humides dans la région d’El Kala (Algérie) à l’aide des outils d’observation de la Terre. In: Revue d'Écologie (La Terre et La Vie), tome 73, n°4, 2018. pp. 431-445
Existing areas and past changes of wetland extent in the Mediterranean region: an overview
No full textWe quantified the amount of existing wetlands in the Mediterranean region as well as their losses in the past century. An estimated 18.5 ± 3.5 million ha of wetlands existed in c. 2000, one quarter of them consisting of artificial wetlands, including primarily reservoirs and ricefields. Past losses were estimated to represent c.
50% over the 20th century. Land-cover maps derived from the CORINE Land-Cover system were also used to test whether they could monitor total surface areas, surfaces by wetland types, or wetland losses, at the required scale.Nous avons quantifié la surface de zones humides existant en Méditerranée, ainsi que leurs pertes au cours du siècle passé. Environ 18,5 millions d’hectares (± 3,5 millions) existaient vers l’an 2000, dont environ un quart de zones humides artificielles, principalement des réservoirs et des rizières. Les pertes sont estimées à environ 50 % au cours du XXe siècle. Les cartes d’occupation du sol tirées de CORINE Land-Cover ont aussi été utilisées, afin de tester si elles permettraient de suivre, à l’échelle requise, la surface totale, la surface par type de zones humides, et la perte de ces milieux.Perennou Christian, Beltrame Coralie, Guelmami Anis, Tomàs Vives Pere, Caessteker Pierre. Existing areas and past changes of wetland extent in the Mediterranean region: an overview. In: Ecologia mediterranea, tome 38 n°2, 2012. pp. 53-66
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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