1,720,961 research outputs found
Étude du potentiel éolien du jet nocturne dans la zone sahélienne à partir des observations de radars profileurs de vent.
No full textSHORT ABSTRACT: This work presents a large study of the wind characteristics and the diurnal and seasonal wind variations obtained from the data of two wind profiler radars installed at Bamako in 2005 and at Niamey in 2006. The nocturnal low level jet peaked at 14 m s-1 at 500 m. It was still obvious at 150 m. Important wind shears were also shown, together with the impacts on aircraft activity. The wind pattern was marked by a strong diurnal cycle as well as a strong seasonal cycle. A wind assessment was made by two methods. The first involved the wind distributions directly observed. The second was based on the Weibull distributions. Day and night were compared. Results showed that the nocturnal low level jet was an interesting source of energy provided that wind turbines were 150 m high and huge-capacity energy storage was used, so that the energy stored at night could be restored during the daytime, when the demand is highest. Harmattan period is most propitious with an output power exceeding 300 W m-2 due to the nocturnal jet. The economic study results showed that this energy was found to be cheap relative to other renewable energy sources.Ce travail présente une étude détaillée des caractéristiques et des variations journalières et saisonnières du vent obtenues à partir des données de deux radars UHF profileurs de vent installés à Bamako en 2005 et à Niamey en 2006. Les pics du jet nocturne observés atteignent 14 ms-1 à 500m d'altitude. Ce jet est aussi présent à 150m. On note la présence d'un important cisaillement de vent aux conséquences aéronautiques non négligeables. Le cycle du vent est caractérisé par un fort cycle diurne ainsi qu'un cycle saisonnier bien distinct. Une évaluation du potentiel éolien est faite suivant deux méthodes : celle s'appuyant sur les distributions de vent observées directement sur les sites et celle utilisant les distributions statistiques de Weibull. Les variations mensuelles du module du vent et les distributions statistiques des vitesses sont présentées, de même que les paramètres de Weibull correspondants et les puissances moyennes récupérables. Les valeurs des paramètres de Weibull du jour et de la nuit sont comparées. Les résultats montrent que le jet nocturne est une importante source d'énergie à condition que les aérogénérateurs soient placés à 150m d'altitude et que de larges capacités de stockage d'énergie soient installées pour que l'énergie produite et stockée la nuit puisse être utilisée pendant la journée. Les résultats de l'étude économique montrent que cette énergie est bon marché en comparaison avec les autres sources d'énergie renouvelables
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
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
Effet des structures des problèmes proposés par les enseignants sur les performances des élèves en résolution de problèmes de physique
No full textThe aim of this study is to determine the effect of problem structures proposed by physical science teachers on their students\u27 performance in solving physics problems. Theoretically, it is based on the differentiation between problem and exercise. It uses a mixed method (qualitative and quantitative). The quantitative method consisted in administering a written test (problem and exercise) to 437 students from six high schools in Niger. The qualitative method involved six focus groups with students and eight individual interviews with teachers. The results showed that there was a statistically significant (p=0.000) difference between students\u27 performance in problem solving and exercise solving. More explicitly, students perform better in exercise solving than in problem solving. Difficult comprehension, the absence of intermediate questions and the lack of precision in the physical laws to be used in the problem statements explain this difference in performance. The problem structures that teachers propose to their students therefore have a negative effect on their students\u27 problem-solving performance. It is therefore necessary to train teachers in problem statement design in order to make their students more competitive on the national and international scene.Cette étude vise à déterminer l’effet des structures des problèmes proposés par les enseignants de sciences physiques sur les performances de leurs élèves en résolution de problèmes de physique. Théoriquement, elle se base sur la différenciation entre problème et exercice. Elle utilise une méthode mixte (méthode qualitative et méthode quantitative). La méthode quantitative a consisté à soumettre un test écrit (en problème et en exercice) auprès de 437 élèves de six établissements du second cycle du secondaire au Niger. Six focus group avec les élèves et huit entretiens individuels avec les enseignants constituent la méthode qualitative. Les résultats ont montré qu’il y a une différence statistiquement significative (p=0.000) entre les performances des élèves en résolution de problème et résolution d’exercice. De façon plus explicite, les élèves réussissent mieux en résolution d’exercice qu’en résolution de problème. La compréhension difficile, l’absence de questions intermédiaires et la non-précision des lois physiques à utiliser dans les énoncés de problèmes expliquent cette différence de performances. Les structures des problèmes que proposent les enseignants à leurs élèves ont donc un effet négatif sur les performances de leurs élèves en résolution de problèmes. Il est donc nécessaire de former les enseignants en conception des énoncés de problèmes afin de rendre plus compétitifs leurs élèves sur la scène nationale et internationale
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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