1,720,979 research outputs found
Cartographie du potentiel de développement de l'irrigation durable avec des eaux souterraines renouvelables en Afrique pour réduire l'insécurité alimentaire africaine
No full textIn Africa, groundwater irrigation is considered a reliable and affordable means to increase food security. Areas equipped for groundwater irrigation in Africa have however, developed slowly since 1950 and remain very limited. To date, no studies have identified the sustainable development potential of irrigation with renewable groundwater across Africa. This study is based on two approaches to locate and quantify this potential. The quantitative hydrological approach is based on the estimation of the current crop irrigation need and available renewable groundwater for irrigation after all other water needs, including environmental, have been satisfied. This approach shows that the potential is 44.6 x 106 ha or 20.5% of the cropland over the continent. The environmental approach redefines the quantitative potential by considering a set of biophysical and socio-economic factors conducive to sustainable development of groundwater irrigation. The potential is then 19.3 x 106 ha and it is reduced mainly from the equatorial regions where the need for irrigation is limited. In fact, without considering the countries of the Maghreb and South Africa where current irrigation by groundwater exceeds the estimated potential, groundwater irrigated areas could be multiplied by 75. The largest areas which are worthwhile to develop are mainly located along a west-east line from Angola to the north of Mozambique and a line south of the Sahel. The dry regions of the Sahel, East Africa and Southern Africa have limited development potential which is more suitable to small-scale agriculture and could greatly improve food security in Africa.En Afrique, l'irrigation des cultures par les eaux souterraines est considérée comme un outil fiable et abordable pour augmenter la sécurité alimentaire mais les superficies équipées pour l'irrigation par les eaux souterraines restent très limitées. Cette étude se base sur deux approches pour localiser et quantifier le potentiel de développement de l’irrigation des cultures par les eaux souterraines renouvelables sur l'ensemble du continent. L’approche quantitative et hydrologique s’appuie sur l’estimation des eaux souterraines renouvelables disponibles après satisfaction de tous les autres besoins, y compris environnementaux et sur le besoin en irrigation des cultures et montre un potentiel s’élevant à 44.6 x 106 ha soit 20.5% des cultures du continent. L’approche contextuelle redéfinit le potentiel quantitatif en considérant un ensemble de facteurs biophysiques et socio-économiques propices au développement de l’irrigation par les eaux souterraines. Le potentiel s’élève alors à 19,3 x 106 ha et est réduit essentiellement dans les régions équatoriales où le besoin en irrigation est limité. En fait, sans considérer les pays où l’irrigation actuelle par les eaux souterraines excède le potentiel estimé, les surfaces irriguées pourraient être multipliées par 75. Les plus grandes surfaces propices au développement de l'irrigation sont principalement situées le long d’une ligne ouest-est de de l’Angola au nord du Mozambique et d’une ligne au sud du Sahel. Les régions sèches du Sahel et de l’Afrique de l’Est et australe ont un potentiel de développement plus limité, plus adapté à la petite agriculture, qui pourrait améliorer amplement la sécurité alimentaire en Afrique
Cartographie du potentiel de développement de l'irrigation durable avec des eaux souterraines renouvelables en Afrique pour réduire l'insécurité alimentaire africaine
No full textIn Africa, groundwater irrigation is considered a reliable and affordable means to increase food security. Areas equipped for groundwater irrigation in Africa have however, developed slowly since 1950 and remain very limited. To date, no studies have identified the sustainable development potential of irrigation with renewable groundwater across Africa. This study is based on two approaches to locate and quantify this potential. The quantitative hydrological approach is based on the estimation of the current crop irrigation need and available renewable groundwater for irrigation after all other water needs, including environmental, have been satisfied. This approach shows that the potential is 44.6 x 106 ha or 20.5% of the cropland over the continent. The environmental approach redefines the quantitative potential by considering a set of biophysical and socio-economic factors conducive to sustainable development of groundwater irrigation. The potential is then 19.3 x 106 ha and it is reduced mainly from the equatorial regions where the need for irrigation is limited. In fact, without considering the countries of the Maghreb and South Africa where current irrigation by groundwater exceeds the estimated potential, groundwater irrigated areas could be multiplied by 75. The largest areas which are worthwhile to develop are mainly located along a west-east line from Angola to the north of Mozambique and a line south of the Sahel. The dry regions of the Sahel, East Africa and Southern Africa have limited development potential which is more suitable to small-scale agriculture and could greatly improve food security in Africa.En Afrique, l'irrigation des cultures par les eaux souterraines est considérée comme un outil fiable et abordable pour augmenter la sécurité alimentaire mais les superficies équipées pour l'irrigation par les eaux souterraines restent très limitées. Cette étude se base sur deux approches pour localiser et quantifier le potentiel de développement de l’irrigation des cultures par les eaux souterraines renouvelables sur l'ensemble du continent. L’approche quantitative et hydrologique s’appuie sur l’estimation des eaux souterraines renouvelables disponibles après satisfaction de tous les autres besoins, y compris environnementaux et sur le besoin en irrigation des cultures et montre un potentiel s’élevant à 44.6 x 106 ha soit 20.5% des cultures du continent. L’approche contextuelle redéfinit le potentiel quantitatif en considérant un ensemble de facteurs biophysiques et socio-économiques propices au développement de l’irrigation par les eaux souterraines. Le potentiel s’élève alors à 19,3 x 106 ha et est réduit essentiellement dans les régions équatoriales où le besoin en irrigation est limité. En fait, sans considérer les pays où l’irrigation actuelle par les eaux souterraines excède le potentiel estimé, les surfaces irriguées pourraient être multipliées par 75. Les plus grandes surfaces propices au développement de l'irrigation sont principalement situées le long d’une ligne ouest-est de de l’Angola au nord du Mozambique et d’une ligne au sud du Sahel. Les régions sèches du Sahel et de l’Afrique de l’Est et australe ont un potentiel de développement plus limité, plus adapté à la petite agriculture, qui pourrait améliorer amplement la sécurité alimentaire en Afrique
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Water resource management in the Olifants Basin of South Africa: previous projects and future prospects
No full textThe Olifants River Basin is located in the north-eastern part of the South Africa and southern to Mozambique.The Olifants River passes through three provinces of South Africa (Gauteng, Mpumalanga, Limpopo Province), through the Kruger National Park, into Mozambique, where it joins the Limpopo . it is the home to nearly 10 % of the total population of South Africa. The climate is semi-arid, with rain falling primarily during the summer (November to March). Precipitation averages 630 mm and potential evaporation is 1700mm. In South Africa, significant mining, industrial and agricultural activities (including intensive irrigation schemes) are concentrated within the catchment, so it is of considerable importance for the country's economy. However, Water is especially scarce in this basin. Like many river basins in South Africa, water resources in the Olifants river basin are almost fully allocated. Water demand management, especially in the agricultural sector, which is the biggest user, is one of the possible solutions being considered by the South African Department of Water Affairs and Forestry (DWAF). The basin also faces significant water quality problems, due to mining activities, industries, power generation and agricultural use of water. The impact of these pollutions (high salinity, high concentrations of metals, low pH) are probably multiple with serious ecological impacts. Particularly of concern in the downstream Kruger National Park which is a major tourist attraction in South Africa and more importantly very worrisome health impacts, since some people are drinking surface water without any treatment. In South Africa it is of prime importance to maintain a minimum level of water quality and quantity in the rivers in order to maintain a healthy biophysical environment (DWAF, 1997). This requirement, referred to as the 'Ecological Reserve', is as important in the South African legislation as meeting the basic human needs and must be met before any other users can abstract water. Main activities on the Olifants basin have been done through the Challenge Program on Water and Food and the WETwin project but not only
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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
- …
