1,721,046 research outputs found
Homogeneous nucleation of pure phase oxides. Formation of rod-like particles
No full textPure monoclinic ZrO2 powders are obtained following a hydrothermal precipitation route. The reaction involves a slow hydrolysis step of zirconium (IV) occurring at 100°C from chloride-containing solutions. Examination by scanning electron microscopy eveals the dried products to be composed of prism-shaped particles with sharp edges and right angles. The rods appear to be the result of a sintering process taking place during the final drying step. The effects induced, on the morphology, by modifications in the experimental conditions are discussed. © 1991
Temperature effects on rod-like zirconia particles. Morphology, degree of crystallinity and texture
No full textThe paper reports data concerning zirconia samples obtained by coupling a first hydrolysis reaction of ZrCl4 in solution at 100°C with subsequent treatments of the powders at higher temperatures (400-800°C). The products of the reactions are characterized by X-ray diffraction, scanning electron microscopy and N2 adsorption. The samples appear to be composed, at any temperature, of pure baddelyite with a degree of crystallinity which increases with the temperature of preparation. Morphologically, the products have the shape of prismatic rods of variable dimensions. The rods are the result of sintering of the primary particles produced during the precipitation in solution. The general prismatic pattern of the rods is not affected by the temperature of calcination; conversely, the texture of the rods (i.e. the degree of hydration and aggregation of the primary particles) strongly depends on the temperature of the treatment. The nature of the interactions taking place between water and the solid particles, at different temperatures, is discussed. © 1993
Adsorption of Methylene Blue at solid/liquid and water/air interfaces
No full textDeterminations of the adsorption of Methylene Blue (MB) at both solid/liquid and water/air interfaces have been performed. The solid adsorbents were two ZrO2 samples prepared in the laboratory. For both oxides the adsorption isotherms presented a langmuirian shape with a long plateau and a final slight upward bend. Parameters describing the adsorption at the solid surfaces were obtained by processing data by both the Langmuir and the BET equations. At the water/air interface, measurements of the surface tension as a function of the bulk concentration of MB were performed. The resulting isotherm exhibited two regions differing in the slopes of the curves. The orientation, degree of association and packing of the adsorbed MB molecules are discussed, and the data obtained at the two interfaces are compared. © 1993
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
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