1,720,961 research outputs found
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
Extremwellen in der südlichen Nordsee
No full textRogue waves are exceptionally high waves, relative to the surrounding sea state. They occur rarely, which makes them difficult to predict. Due to their particular height and limited predictability, they pose a threat to offshore structures and operations. A first step towards the prediction of rogue waves in a region is the investigation of their occurrence frequency. Knowing whether rogue waves occur as often as expected at random, or more frequently, gives a hint on the mechanisms that may have contributed to their formation. It is likely that different processes can be responsible for rogue wave formation. In deep and intermediate water, rogue wave occurrence frequencies beyond the expectations of common wave height distributions have been explained mathematically and experimentally, for example, by nonlinear focusing. In shallow water, in which wave dynamics experience the influence of the sea floor, the presence of solitons has been suspected as a cause of increased rogue wave occurrence. An improved understanding of the mechanisms that form rogue waves is crucial for their prediction. The prediction of rogue waves can prevent accidents at sea. This thesis concerns rogue waves in the southern North Sea, in both intermediate-water and shallow-water regimes. In an extensive set of surface elevation data from six buoy and five radar measurement stations, rogue waves with exceptional crest and crest-to-trough heights were identified. Their occurrence frequencies were compared to the expectations of common wave height distributions of a Weibull type. The statistical analysis in intermediate water depths revealed that wave buoys did not identify more rogue waves than expected. However, rogue wave frequencies recorded at radar stations exceeded the expectations of the common wave height distributions. The discrepancy between the results might be due to the different measurement techniques. Following the statistical analysis at intermediate-water sites, it was investigated whether nonlinear focusing, that has led to deep-water rogue wave formation in numerical and physical experiments, provides a conceivable explanation for rogue wave generation at the considered sites. An investigation of wave energy spectra at the intermediate-water stations yielded broad-banded conditions in both frequency and angular direction. These are unlikely conditions for nonlinear focusing to occur. In shallow water, the statistics revealed an exceptionally high number of rogue waves at one buoy and one radar device. In the shallow-water time series at these sites, the recorded rogue waves could be associated with the presence of solitons.
The study leads to the conclusion that intermediate-water rogue waves in the southern North Sea are probably not the result of nonlinear focusing. At some sites in shallow water above a sloping sea floor, rogue wave occurrence frequencies exceeding the expectations of common wave height distributions, could be explained by the presence of solitons.Extremwellen oder "Rogue Waves" sind außergewöhnlich hohe Wellen, bezogen auf den umgebenden Seegangszustand. Sie treten selten auf, was ihre Vorhersage erschwert. Auf Grund ihrer ungewöhnlichen Höhe und eingeschränkten Vorhersagbarkeit stellen sie eine Bedrohung für Bauwerke und Tätigkeiten auf See dar. Ein erster Schritt auf dem Weg zur Vorhersage von Extremwellen in einer Region ist die Ermittlung ihrer Häufigkeit. Das Wissen darüber, ob Extremwellen so oft auftreten wie zufällig erwartet, oder häufiger, gibt einen Hinweis darauf, welche Mechanismen zu ihrer Entstehung beigetragen haben könnten. Es ist anzunehmen, dass unterschiedliche Prozesse für das Entstehen von Extremwellen verantwortlich sein können. In großen und mittleren Wassertiefen wird eine Extremwellenhäufigkeit, die über die Erwartungen gebräuchlicher Verteilungen von Wellenhöhen hinausgeht, mathematisch und experimentell beispielsweise durch nichtlineare Fokussierung erklärt. In flachem Wasser, in welchem die Dynamik von Wellen den Einfluss des Meeresbodens erfährt, wird das Vorhandensein von Solitonen als Ursache für eine erhöhte
Extremwellenhäufigkeit in Betracht gezogen. Ein verbessertes Verständnis der Mechanismen, die Extremwellen ausbilden, ist wesentlich für deren Vorhersage. Die Vorhersage von Extremwellen kann Unfällen auf See vorbeugen. Diese Dissertation betrifft Extremwellen in der südlichen Nordsee, sowohl in mittleren, als auch in geringen Wassertiefen. In einem umfangreichen Satz von Wasserspiegelauslenkungsdaten von sechs Bojen- und fünf
Radarmessstationen wurden Extremwellen mit außergewöhnlichen Wellenbergen und Wellenhöhen von Berg zu Tal identifiziert. Ihre Häufigkeiten wurden mit den Erwartungen üblicher Wellenhöhen-Verteilungen der Art einer Weibull-Verteilung verglichen. Die statistische Auswertung in mittleren Wassertiefen zeigte, dass Wellenbojen nicht mehr Extremwellen identifizierten als erwartet. Extremwellenhäufigkeiten, die an Radarstationen erfasst wurden, überschritten jedoch die Erwartungen der üblichen Wellenhöhen-Verteilungen. Die Unstimmigkeiten zwischen den Ergebnissen liegen möglicherweise in den unterschiedlichen Messmethoden begründet. Im Anschluss an die statistische Auswertung an Standorten in mittlerer Wassertiefe wurde überprüft, ob nichtlineare Fokussierung, die in numerischen und physikalischen Experimenten zur Entstehung von Extremwellen in tiefem Wasser geführt hat, eine denkbare Erklärung für die Erzeugung von Extremwellen an den betrachteten Standorten bietet. Die Untersuchung von Wellenenergiespektren an den Stationen in mittleren Wassertiefen ergab breitbandige Zustände, sowohl in der Frequenz-, als auch in der Richtungsverteilung. Diese Bedingungen machen die Entstehung nichtlinearer Fokussierung unwahrscheinlich. In flachem Wasser offenbarte die Statistik eine außergewöhnlich hohe Anzahl an Extremwellen an einer Boje, sowie an einem Radargerät. In den Flachwasser-Zeitreihen dieser Standorte konnten die aufgezeichneten Extremwellen mit dem Vorhandensein von Solitonen in Verbindung gebracht werden. Die Studie kommt zu dem Schluss, dass Extremwellen in den mittleren Wassertiefen der südlichen Nordsee wahrscheinlich nicht das Ergebnis nichtlinearer Fokussierung sind. An einigen Standorten in flachemWasser oberhalb eines abschüssigen Meeresbodens konnten Extremwellenhäufigkeiten, die die Erwartungen üblicher Wellenhöhen-Verteilungen überschritten, durch das Vorhandensein von Solitonen erklärt werden
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
Investigation of the Wake Flow behind a stepped circular Cylinder using Particle Image Velocimetry
Full text linkSubject of the present study was the investigation of the wake behind stepped circular cylinders. Experiments were performed using particle image velocimetry (PIV). Cylinder models with diameter ratios D/d=1, D/d=6/5 and D/d=2 were investigated at Reynolds numbers Re_{D}=2243.6, Re_{D}=12820.5 and Re_{D}=51282.1 with respect to the large diameter. Of main interest were the influences of step size and Reynolds number on the formation of vortex shedding cells. Mean flow characteristics and instantaneous captures of the flow field were analyzed in order to gain insight into vortex development in the wake. Spectral analysis was applied to obtain information on the number of forming vortex shedding cells.It was found that an increase in Re_D leads to a decrease in eddy formation length . At the largest investigated Reynolds number, turbulence gained strong influence on the flow characteristics. An increase in stepsize leads to the development of a large and a small diameter wake with distinct eddy formation lengths L_{f,L} and L_{f,S}.Due to a mismatch in vortex shedding frequencies in the two wakes, vortices that come out of phase connect to subsequent vortices on the same side of the step. This occurs more frequently for a higher diameter ratio.Several vortex shedding cells were found in the wake of the step cylinders, their number increasing with the step size and differing for different Reynolds numbers.The wake behind step cylinders was discovered to be strongly three-dimensional. I order to complete the information about flow characteristics, measurements were performed in several parallel vertical and horizontal planes along the cylinder.PIV proved to be a good method for the investigation of flow features in the wake of step cylinders for the chosen model dimensions and Reynolds numbers
Investigation of the Wake Flow behind a stepped circular Cylinder using Particle Image Velocimetry
No full textSubject of the present study was the investigation of the wake behind stepped circular cylinders. Experiments were performed using particle image velocimetry (PIV). Cylinder models with diameter ratios D/d=1, D/d=6/5 and D/d=2 were investigated at Reynolds numbers Re_{D}=2243.6, Re_{D}=12820.5 and Re_{D}=51282.1 with respect to the large diameter. Of main interest were the influences of step size and Reynolds number on the formation of vortex shedding cells. Mean flow characteristics and instantaneous captures of the flow field were analyzed in order to gain insight into vortex development in the wake. Spectral analysis was applied to obtain information on the number of forming vortex shedding cells.It was found that an increase in Re_D leads to a decrease in eddy formation length . At the largest investigated Reynolds number, turbulence gained strong influence on the flow characteristics. An increase in stepsize leads to the development of a large and a small diameter wake with distinct eddy formation lengths L_{f,L} and L_{f,S}.Due to a mismatch in vortex shedding frequencies in the two wakes, vortices that come out of phase connect to subsequent vortices on the same side of the step. This occurs more frequently for a higher diameter ratio.Several vortex shedding cells were found in the wake of the step cylinders, their number increasing with the step size and differing for different Reynolds numbers.The wake behind step cylinders was discovered to be strongly three-dimensional. I order to complete the information about flow characteristics, measurements were performed in several parallel vertical and horizontal planes along the cylinder.PIV proved to be a good method for the investigation of flow features in the wake of step cylinders for the chosen model dimensions and Reynolds numbers
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