1,721,041 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
Surface soil moisture retrieval using Envisat ASAR global mode data
Get PDFBodenfeuchte als wichtige Größe in den globalen Kreisläufen von Wasser, Energie und Kohlenstoff, ist räumlich und zeitlich hoch variabel. Sie kann mit Hilfe von in-situ Messungen sehr genau bestimmt werden. Der hierfür notwendige organisatorische und finanzielle Aufwand macht wiederholte Messungen auf kontinentaler oder globaler Ebene unmöglich. Als Alternative bieten sich hier Methoden der Radarfernerkundung an, die Daten auf unterschiedlichen zeitlichen und räumlichen Skalen liefern können. Der Zusammenhang zwischen empfangenen Radarsignalen und der Bodenfeuchte ist von verschiedenen Faktoren abhängig und kann mit Hilfe von Modellen abgeleitet werden. Aufgrund der Komplexität des Radarrückstreuvorgangs ist eine vollständige mathematisch-physikalische Beschreibung unrealistisch. Mit Hilfe sogenannter Change-Detection-Methoden wird versucht, diese Probleme zu umgehen, indem lediglich die Änderungen in der Radarrückstreuung über die Zeit ohne Beschreiung der absoluten Rückstreuung beobachtet wird.Die vorliegende Arbeit basiert auf einem ursprünglich für ERS-Scatterometerdaten entwickelten Change-Detection-Modell. Dabei wird die Radarrückstreuung mit Hilfe empirischer Rückstreuparameter zur Ableitung relativer Bodenfeuchtewerte modelliert. Diese Rückstreuparameter beschreiben die Radarrückstreuung für den lageabhängigen Zeitpunkt mit trockene und gesättigte Bodenfeuchtebedingungen. Da im Fall des ERS drei unabhängige Messugen unter verschiedenen Einfallswinkeln zur Verfügung stehen, können saisonabhängige Effekte mit Hilfe des Einfallswinkelverhaltens beschrieben werden. Das invertiere Rückstreumodell kann dann benutzt werden, um einzelne Radarmessungen zwischen Trockenbedingungen (0%) und Feuchtbedingungen (100%) zu skalieren.Im Fall des Envisat ASAR steht lediglich nur eine Radarrückstreumessungen bei einem Einfallswinkel zur Verfügung. Daher musste der ursprüngliche Bodenfeuchtealgorithmus angepasst werden. Die Datenanalyse hat gezeigt, dass saisonale Effekte weniger stark ausgeprägt sind. Außerdem wird eine für Vegetation weniger sensitive Polarisation verwendet. Daher wird zur Vereinfachung angenommen, angenommen, dass die Parameter des Rückstreumodells zeitlich konstant sind und saisonale Effekte durch Änderungen der Vegetation vernachlässigt werden können. Mit Hilfe des angepassten Rückstreumodells wurden Referenzwerte für trockene und gesättigte Bodenfeuchtebedingungen zur Skalierung von Radareinzelmessungen abgeleitet.Die Ergebnisse wurden mit Hilfe von in-situ Bodenfeuchtemessungen des Oklahoma Mesonets und Bodenfeuchtewerten aus ERS Scatterometerdaten validiert. Gute Übereinstimmungen zwischen der relativen oberflächennahen Bodenfeuchte aus ASAR GM- Daten und den Validierungsdaten wurden beobachtet. Beim direkten Vergleich der Ergebnisse zeigt sich, das die Bodenfeuchte aus ERS-Scatterometerdaten etwas bessere Ergebnisse liefert als der ASAR GM Sensor. Als Hauptfehlerquelle wurde die radiometrische Genauigkeit von 1.2 dB identifiziert. Das ist ein im Vergleich zum ERS Scatterometer mit einer radiometrischen Genauigkeit von 0.3 dB relativ hoher Wert. Trotzdem können aus ASAR GM Daten Bodenfeuchtewerte mit wesentlich mehr räumlichen Details als für den ERS Scatterometer abgeleitet werden, die ebenso die zeitliche Dynamik der Bodenfeuchte abbilden wie im Fall des Scatterometers. Die Validierung hat gezeigt, dass die Vernachlässigung saisonaler Vegetationseffekte auf die Radarrückstreuung eine haltbare Vereinfachung darstellt und das ASAR GM Daten für ein operationelles Bodenfeuchtemonitoring mit Hilfe von Change-Detection-Modellen genutzt werden können.Soil moisture, highly variable in space and time, is a key element in the global hydrologic, energy and carbon cycle. Soil moisture can be measured accurately in the field using in-situ measurement techniques. Measuring soil moisture at continental to global scales using in-situ techniques is not feasible. Alternatively, soil moisture can be measured using radar remote sensing at different temporal and spatial scales. The relation between the received radar signals and soil moisture is controlled by a number of factors and can be described by means of modelling. Due to the complexity of the radar backscattering process, a mathematical-physical description is not realistic. Change detection methods try to circumvent these difficulties by solely interpreting backscatter changes at fixed locations over time, without attempting to explain the absolute backscatter level. The presented work is based on a change detection approach originally developed for ERS scatterometer data. It describes radar backscatter in terms of empirical backscatter parameters and the relative surface soil moisture content. The empirical backscatter parameters define radar backscatter at dry and saturated soil moisture conditions. As there are three individual backscatter measurements at different incidence angles available from the ERS scatterometer per acquisition, seasonal effects can be described by exploiting the local incidence angle behaviour. The inverted model can be used to scale individual radar backscatter measurements between dry (0%) and wet (100%) surface soil moisture conditions.In the case of ASAR GM only one backscatter measurement at some incidence angle is being made during each overpass. Therefore the algorithm developed for the ERS scatterometer needed to be adapted accordingly. Data analysis showed that changes in backscatter due to vegetation growth are in general much smaller than changes due to soil moisture. Additionally, ASAR GM is commonly operated in HH polarization which penetrates vegetation better than VV polarization as used by the ERS scatterometer. Therefore, a simplified change detection model is adapted for ASAR GM. It is assumed that, in a first approximation, the backscatter model parameters are constant in time because seasonal vegetation effects are expected to be weak for ASAR GM. This assumption may lead to a seasonally varying error of the retrieval. The adapted change detection backscatter model also scales individual backscatter measurements between a lower backscatter threshold related to dry surface soil moisture conditions and an upper backscatter threshold related to saturated conditions. The results were validated using in-situ soil moisture data from the Oklahoma Mesonet and ERS-1/2 scatterometer derived relative surface soil moisture. Good agreement between ASAR GM relative surface soil moisture and both in-situ soil moisture measurements and ERS-1/2 scatterometer derived soil moisture was observed. The direct comparison of the results shows that the surface soil moisture extracted from ERS-1/2 scatterometer data performs slightly better than the data derived from ASAR GM. As the main source of error, the noise of the ASAR GM data with a value of 1.2 dB has been identified which is relatively high when compared to radiometric resolution of at least 0.3 dB of the ERS scatterometer. Nevertheless, the ASAR GM data offer surface soil moisture data with much more details than the ERS-1/2 scatterometer data and still keeping the capability of the scatterometer data to map temporal surface soil moisture trends. The validation of the remotely sensed soil moisture extracted from ASAR GM data has proven that neglecting seasonal vegetation cover effects can be regarded as a valid assumption and operational use of ASAR GM data for soil moisture retrieval using change detection is possible
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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