1,720,981 research outputs found
A langmuir multi-probe system for the characterization of atmospheric pressure arc plasmas
Full text linkThe 'high-pressure' atmospheric (TIG) arc plasma is studied by means of a multi-Langmuir probe system. In order to determine the appropriate regime of operation, definitions of the plasma parameters for the description of the argon arc are considered and evaluations are presented. A description of the probe basic techniques is followed by an in-depth discussion of the
different regimes of probe operation. The emphasis is put on atmospheric and flowing (arc) regimes. Probe sheath theories are compared and “Nonidealities” like cooling due to plasma-probe motion and probe emission mechanisms are then described.
The extensive literature review reveals that the existing probe theories are
inappropriate for a use in the TIG arc, because of ‘high’ pressure (atmospheric), broad range of ionization across the arc, flowing conditions,
and ultimately, to the uncertainty about onset of Local Thermodynamical Equilibrium.
The Langmuir probe system is built to operate in floating and biased conditions. The present work represents the first extensive investigation of electrostatic probes in arcs where the experimental difficulties and the
primary observed quantities are presented in great detail. Analysis methodologies are introduced and experimental results are presented
towards a unified picture of the resulting arc structure by comparison with data from emission spectroscopy. Results from different measurements are presented and comparison is made with data on TIG arcs present in literature. Probe obtained temperatures are lower than the values obtained from emission spectroscopy and this ‘cooling’ is attributed to electron-ion recombination. However, it is believed that probes can access temperatures
regions not attainable by emission spectroscopy.
Only axial electric potential and electric field are obtained because of the
equipotential-probe requirement. Estimations of the sheath voltage and extension are obtained and a qualitative picture of the ion and electron
current densities within the arc is given
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
Effect of Bottle Storage on Colour, Phenolics and Volatile Composition of Malvasia and Moscato White Wines
No full textThe effect of bottle storage on the colour, phenolics and volatile composition of Malvasia and Muscat wines obtained from grapes grown in Sardinia was evaluated. Colour was evaluated by UV-VIS spectrophotometry and by tristimulus colorimetry. Polyphenols were analysed by UV-VIS spectrophotometry and HPLC-DAD. GC/MS was used to identify and quantify the content of free and bound volatile compounds. As expected, the absorbance values at 420 nm increased significantly for both wines during storage, due to oxidative browning, while difference in colour (DE*) from the beginning of storage and after 18 months was more intense in the Muscat wine than in the Malvasia wine. A significant decrease was observed in different phenolic compounds over time, especially in the Malvasia wine. In-bottle storage for 18 months at 20°C in the dark resulted in a significant decrease in all the classes of free and bound volatiles. These finding enhance knowledge regarding the effects of bottle storage on Muscat and Malvasia wines. This is of interest because, rather surprisingly, this topic has been poorly investigated in relation to these two varieties
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
Free and enzymatically hydrolysed volatile compounds of sweet wines from Malvasia and Muscat grapes (Vitis vinifera L.) grown in Sardinia
No full textEffect of Bottle Storage on Colour, Phenolics and Volatile Composition of Malvasia and Moscato White Wines
No full text- …
