1,720,993 research outputs found
A study of some bivalent metal divanadates and their catalytic activity in the oxidation of propane
No full textThe divanadates M(2)V(2)O(7) of a virtually unreducible and unoxidizable cation, Mg(2+), of a reducible cation, Cu(2+), and of an oxidizable cation, Mn(2+), have been prepared and characterized by X-ray diffraction, surface area measurements, skeletal IR and UV-vis-NIR spectroscopies, and DTA-TG analyses. These materials have also been tested as catalysts for propane oxidative dehydrogenation at two different contact times. Mg divanadate is more active and more selective than Mn divanadate, while Cu divanadate is a little bit more selective than the Mg compound. The activity is likely mainly associated to the redox behavior of V cations which could be improved by reducible centers. Gas phase phenomena predominate at relatively low contact times and higher temperatures while true catalytic phenomena are observed at higher contact times and lower temperatures
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
A study of Mn-Ti oxide powders and their behaviour in propane oxidation catalysis
No full textMn-Ti mixed oxides with composition Ti(1-x)Mn(x)O(y) (x =0, 0.1, 0.2, 0.5; 0.8, 0.9 and 1) have been prepared. A Mn-TiO(2) monolayer type sample has also been prepared by impregnation, for comparison. Manganese is found to speed up the anatase-to-rutile phase transition,more clearly in the impregnated sample, while titanium tends to slightly hinder the thermodynamically reversible hausmannite-to-bixbyite phase transition upon cooling; The catalytic activity of all samples in propene oxidation decreases by increasing the Ti content: Conversely, the catalytic activity in propane oxidation shows a maximum at intermediate composition
MnOx-TiO2 catalyzers for valatil organic compounds elimination.
No full textMn-Ti mixed oxides with stoichiometry TixMn1-xOy (with x = 0, 0.1, 0.2, 0.5, 0.8, 0.9, 1) have been prepared by a coprecipitation method. Mn3O4 (hausmannite) and TiO2 (anatase) were found to be the main crystalline phases, while solid solutions appeared to be formed at the extreme values of x. Thermal stability of these materials reaches 873 K, transforming into thermodynamically stable phases, TiO2 (rutile) y alpha-Mn2O3, at higher temperatures. From catalytic point of view, they are active in propane and propene oxidation, though the increase of Ti content seems to deactivate Mn oxide for propene oxidation. Conversely, the sample with the Mn/Ti = 1 ratio presents a maximum for propane oxidation
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
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