1,721,052 research outputs found
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
Detection, characteristics and predictability of potential strong human impacts events on West African cities : a case study of heat waves
No full textLes vagues de chaleur constituent une réelle menace pour l'Homme et son environnement. Sous l'effet du changement climatique, les vagues de chaleur deviendront plus fréquentes et intenses. Les conditions climatiques en Afrique de l'ouest rendent la région favorable aux vagues de chaleur. La première partie de ce travail a été consacrée au monitoring des vagues de chaleur dans 15 villes ouest-Africaines situées sur les régions côtière et continentale. Trois sources d'incertitude ont été identifiées dans la détection d'une vague de chaleur : la première est liée aux données de réanalyse, la seconde repose sur le choix du seuil utilisé pour la définition de la vague de chaleur, et la dernière est la méthodologie utilisée. Les vagues de chaleur nocturnes associées à Tw sont plus fréquentes que celles détectées avec AT,T2m,UTCI. Ceci montre que l'humidité joue un rôle important dans l'occurrence des vagues de chaleur nocturnes, augmentant ainsi le nombre d'événements concomitants (jour et nuit consécutivement) sur le nord du Sahel. La variabilité inter-annuelle des vagues de chaleur dans les différentes régions a mis en évidence pour les 3 indicateurs (AT,T2m,Tw) des années particulièrement chaudes avec une fréquence élevée d'événements: 1998, 2005, 2010, 2016, 2019 et 2020, correspondant pour la plupart aux années El Nino. La région GU est plus touchée par les vagues de chaleur au cours de la dernière décennie (2012-2020) que les régions CONT et ATL. Toutefois, les vagues de chaleur les plus persistantes et les plus intenses se produisent dans la région CONT. Un renforcement de la fréquence, de la durée et de l'intensité des vagues de chaleur est observé durant la dernière décennie. Dans la deuxième partie de ce travail, nous nous sommes intéressés à l'aspect prédictibilité des vagues de chaleur. Une première étude de la prédictibilité des vagues de chaleur a été conduite en utilisant les modèles de prévision intra-saisonnière à saisonnière du CEPMMT et UKMO. Les modèles de prévision présentent de meilleures performances par rapport à une climatologie de référence, principalement pour les prévisions à court terme (deux semaines à l'avance) dans les trois régions. Les vagues de chaleur nocturnes sont plus prévisibles que les vagues de chaleur diurnes. D'après les valeurs de FAR obtenues, seulement 15 à 30% des jours de vague de chaleur prédits par les modèles sont effectivement observés dans les réanalyses, respectivement pour les semaines 5 et 2. Le modèle du CEPMMT émet moins de fausses alertes que UKMO pour les prévisions à court terme. Bien que les modèles démontrent des performances en matière de détection des vagues de chaleur par rapport à une climatologie de référence, leur capacité à prédire l'intensité des événements reste faible même pour de courtes échéances. La prédictibilité des vagues de chaleur a été effectuée en utilisant des méthodes d'apprentissage automatique. La méthode BRF présente de meilleures performances par rapport aux deux autres. Le modèle BRF présente de meilleures performances pour la détection des vagues de chaleur par rapport aux modèles de prévision intra-saisonnière dans les trois régions.La prédictibilité des vagues de chaleur par méthode de prédicteurs de grande échelle tels que la dépression thermique Saharienne (SHL) a été abordée en utilisant deux modèles de prévision saisonnière du centre européen et Météo-France. Le but de cette étude est d'évaluer la représentation et la prévisibilité de la SHL à l'échelle saisonnière. Les modèles sont capables de représenter le cycle saisonnier moyen de la SHL et de capturer certaines caractéristiques de sa variabilité inter-annuelle comme la tendance au réchauffement observée durant les années 2010. En utilisant les outils de correction de biais, les résultats mettent en évidence la capacité des modèles à représenter la variabilité intra-saisonnière de la SHL,mais les performances des modèles restent faibles pour une échéance supérieure à un mois.Heat waves (HWs) are a real threat to humans and their environment. Due to climate change, heat waves will become more frequent and more intense. Climatic conditions in West Africa make the region more vulnerable to heat waves. West African cities are highly populated centers, and when it comes to the impact of heat waves on human activities, it's important to study these events at these scales. This study aims to monitor heat waves in major West African cities and evaluate their predictability in subseasonal to seasonal forecast models. The first part of this work focuses on monitoring heat waves in fifteen cities over West Africa located in coastal and continental regions. Three sources of uncertainty encountered in the heat wave detection process were identified: the first related to reanalysis data, the second to the choice of threshold used to define a heat wave, and the last to the methodology adopted. The inter-annual variability of heat waves in the different regions highlighted particularly hot years with a high frequency of heat wave events for all the three indicators AT, T2m,Tw: 1998, 2005, 2010, 2016, 2019 and 2020, mostly corresponding to El Nino years. The GU region has been more affected by heat waves over the past decade (2012-2020) than the CONT and ATL regions. However, the most persistent and intense heat waves occurred in the CONT region. An increase in the frequency, duration and intensity of heat waves has been observed over the last decade (2012-2020), probably due to global warming acting on extreme events." In the second part of this study, we focused on the predictability aspect of heat waves. A preliminary study of the predictability of heat waves has been carried out for the period 2001-2020 using subseasonal to seasonal forecast models from the European Centre for Medium-Range Weather Forecasts (ECMWF) and the United Kingdom Meteorological Office (UKMO). The forecast models perform better than a reference climatology, particularly for short-term forecasts (up to two weeks) in all the three regions. Nighttime heatwaves are more predictable than daytime heatwaves. According to the FAR values, only 15 to 30% of the predicted heatwave days by the models are actually observed in the reanalyses, respectively for lead weeks 5 and 2. This suggests that the models overestimate the duration of heat waves compared with ERA5 reanalysis. ECMWF issues fewer false alarms than UKMO for short-term forecasts. Although the models show skills to detect heat waves compared to a reference climatology, their ability to forecast the intensity of events remains weak even for a short lead time. The predictability of heat waves was performed using machine learning methods. The BRF model demonstrated better heat wave detection skills than subseasonal forecast models in all the three regions. The BRF model considerably improves heat wave detection in forecast models, but on the other hand it generates a high rate of false alarms. The predictability of heat waves using large-scale predictors such as the Saharan Heat Low (SHL) was investigated using two seasonal forecast models: the fifth version of the European Center Seasonal Forecast Model "SEAS5" and the seventh version of the Météo-France Seasonal Forecast Model "MF7". The models show skills on the representation of the mean seasonal cycle of the SHL and capture some characteristics of its inter-annual variability, such as the warming trend observed during the 2010s. SEAS5 makes a more realistic representation of the climatic trend of the SHL compared to MF7. Using bias correction techniques, the results highlight the capacity of the models to represent the intra-seasonal variability of the SHL. Bias correction helps to improve the Continuous Ranked Probability Score (CRPS), but the skills of the model remain low for lead times beyond one month
Early Warning of Drought in Europe
Get PDFThe performances of the first month of the ECMWF probabilistic extended forecast and the seasonal forecast to predict droughts over Europe are compared. The Standardized Precipitation Index is used to quantify droughts. It can be shown that on average the extended forecast has higher skill than the seasonal forecast whilst both outperform climatology. No significant spatial or temporal patterns can be observed but the scores are improved when we focus on large scale droughts.
This report further analyses several different methods to convert the probabilistic forecasts of SPI into a Boolean drought warning. It can be demonstrated that methodologies which convert low percentiles of the forecasted cumulative distribution function of SPI into warnings are superior in comparison to alternatives such as the mean or the median of the ensemble. This work demonstrates that around 40% of droughts in Europe are correctly forecasted one month in advance. Nevertheless, due to the lack of the significant difference between the distributions of the ensemble members for false alarms or misses on one hand side and correct forecasts on the other hand side, it is not yet possible to quantify the uncertainty of the drought forecasts.JRC.H.7 - Climate Risk Managemen
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
De la compréhension des systèmes météorologiques violents aux développement d'outils d'aide à la décision en Afrique de l'Ouest
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