1,721,202 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
BOS-based three-dimensional reconstruction of rotor blade tip vortices
No full textLAUREA MAGISTRALEUn argomento di ricerca dell'istituto di aerodinamica di Gottinga è l'investigazione dei vortici di punta di pala creati dal rotore di un elicottero. Questi vortici sono
analizzati sia su elicotteri in volo libero in diverse condizioni di volo, sia su un apparato rotorico. La tecnica di misura che è stata utilizzata per visualizzare questi vortici è la background-oriented schlieren (BOS).
Lo scopo di questo lavoro è stato la ricostruzione tridimensionale dei vortici a partire da misure stereoscopiche BOS. Si è dunque sviluppato uno schema di ricostruzione basato sulla geometria epipolare, applicato ai filamenti dei vortici registrati in due esperimenti differenti. La prima analisi si è focalizzata sul modello di un elicottero in volo libero ed è stato possibile ricostruire parti significative del sistema di vortici fino a un'età di vortice, Ψv, superiore a 600° durante una manovra di decollo non stazionaria in effetto suolo. Lo schema sviluppato è stato successivamente adattato ed applicato ad un sistema di vortici generato da un apparato rotorico con controllo di pitch ciclico. I filamenti dei vortici del rotore in condizioni di pitch sono stati ricostruiti e la loro convezione è stata esaminata. La valutazione di 200 immagini di misura, in condizioni quasi stazionarie, ha evidenziato uno scatter significativo nella posizione dei vortici, in accordo con precedenti risultati. Lo schema di ricostruzione sviluppato permetterà l'estrazione automatica della posizione dei vortici per una moltitudine di diverse prove all'apparato rotorico per studi futuri.A research topic of the Institute of Aerodynamics and Flow Technology in Göttingen is the investigation of blade tip vortices created by helicopter rotors. These vortices
are investigated both on free-flying helicopters in different flight situations and on a rotor test stand. A measurement technique that is used to visualize these vortices is the density based background-oriented schlieren (BOS) method.
The subject of this work is the three-dimensional vortex reconstruction based on stereoscopic BOS measurements. Therefore, a reconstruction scheme based on epipolar geometry was developed and applied to vortex filaments that were recorded in two different experiments. First, a model helicopter in free flight was investigated and it was possible to reconstruct significant parts of the vortex system up to a maximum vortex age Ψv above 600° during an unsteady takeoff maneuver in ground effect. The developed evaluation scheme was subsequently adapted and applied to the vortex system generated by a rotor test stand with cyclic pitch control. Vortex filaments of the rotor in cyclic pitch conditions were reconstructed and the vortex convection was investigated. The evaluation of a larger sample number of 200 measurement images in quasi-steady conditions showed a significant scatter in the vortex locations, which is in agreement with previous findings. The developed reconstruction scheme allows an automated extraction of vortex positions for a multitude of test conditions at the rotor test stand for future investigations
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
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