1,721,284 research outputs found
Two-dimensional recursive filtering algorithm with edge-preserving properties and reduced numerical complexity
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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
High-speed imaging investigation of transition phenomena in the pilot arc phase in Hf cathodes for plasma arc cutting
No full textThe behaviour of Hf cathodes has been investigated with high-speed camera (HSC) imaging techniques during the low-current pilot arc phase to highlight phenomena that take place during the transition from an insulating, non-emissive, cold phase to a conductive, emissive, hot phase for Hf-based materials used in electrodes for plasma arc cutting (PAC) of mild steel plates. The different behaviours during the start-up phases of new or used electrodes have been considered. Such phenomena have been partially described on physical bases in the past but can now be fully seen and analysed using diagnostics. Conclusions can be drawn concerning the particular conditions under which heat transfer transients in the cathode tip during the PAC pilot arc take place, giving additional useful information for future design-oriented simulation of such phenomena under different geometric and operating conditions, with the final aim of optimizing the cathode’s expected service life
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
Design oriented simulation for PAC consumables and experimental validation of results
No full textElectrode and nozzle erosion mechanisms in plasma arc cutting processes of mild steel have been studied while designing a prototype mono-gas plasma torch, operating in the range 25-160 A. The correlation between the distribution of different quantities inside the plasma chamber and the erosion mechanisms of the hafnium emitter surface and of the nozzle inner surfaces have been investigated by means of a 2D ANSYS FLUENT-based numerical model, with the final aim of optimizing the overall performances of the prototype. Modelling and numerical simulation have allowed better understanding of the physical phenomena evidenced by experimental results and have suggested successful design solutions for consumables (in particular nozzle, electrode and primary gas diffusers). The correlation between the results of experimental tests and numerical simulations has proven useful in overcoming the critical aspects initially pointed out, significantly improving the expected lifetime of consumables. Results have been analyzed with respect to plasma behaviour, and conclusions have been drawn, concerning the powerfulness of numerical simulation as a tool for designing plasma cutting torches
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
Experimental analysis of the behaviour of high current electrodes in plasma arc cutting during first cycles
No full textThe behaviour of hafnium (Hf) cathodes at the beginning of their service life when operating at high current levels (250 A) in the plasma arc cutting (PAC) process has been experimentally investigated with the final aim of describing the phenomena that take place during those initial cutting cycles (CCs), and optimizing (with respect to expected service life) the initial shape of the electrode emissive surface. The experimental tests were carried out under realistic operative conditions for cutting mild steel plates with oxygen/air as the plasma/shield gas. Starting with an electrode with a new planar emissive surface, subsequent CCs were completed. With each cycle the dimensions of the growing concave recess naturally created on the insert, and the amount of Hf oxide (HfO2) collected on the nozzle surface and on the flat surface around the edge of the recess was recorded. Morphological and compositional analysis of the tested electrodes and nozzles led to a detailed description of Hf erosion mechanisms, modifications of the Hf insert morphological structure, and effects of HfO2 deposits on the nozzle inner surface. High-speed imaging during early stages of the transferred arc mode has been used to highlight the possible presence of non-destructive double-arcing phenomena taking place during the first few CCs as a consequence of deposition of HfO2 on the nozzle. Conclusions can be drawn concerning the optimization of the dimensions of the initial recess of the Hf insert fit to avoid the massive deposition of material on the nozzle inner surface that would cause a strong reduction of electrode and nozzle service life and a rapid degrading of cut quality
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