1,720,970 research outputs found
Combined bio-hydrometallurgical process for gold recovery from refractory stibnite
No full textTo examine the recovery of gold by a combined biometallurgical and hydrometallurgical treatment, tests were conducted at laboratory scale using a refractory stibnite ore. After a long leach time, low recovery was obtained by direct cyanidation, while a gold extraction yield of about 80% was achieved combining biometallurgical and hydrometallurgical process. Experimental results show the technical feasibility of the biometallurgical pretreatment prior to the hydrometallurgical process
Removal of iron from quartz sands: A study by column leaching using a complete factorial design
No full textThe aim of the work was to decrease the iron content of ferrous quartz sands by fixed-bed column leaching with recycling of the leaching solutions in order to attain a product suitable for industrial use. Dissolution of iron was achieved by treating the sands in an acid medium with a reducing agent (oxalic acid) to convert Fe-III into Fe-II. The factors assumed to affect dissolution of iron, Such as temperature, oxalic acid concentration, pH and flow-rate, were studied with a 2(4) full factorial design in order to assess the main effects and the interactions among the factors. Removal of 46.1% iron gives a product containing 0.0163% Fe2O3 which is fit for industrial applications
PREPARATORY BIOLEACHING TO THE CONVENTIONAL CYANIDATION OF ARSENICAL GOLD ORES
No full textCyanide leaching is the wide-spread process for the extraction of gold from primary raw-materials. However when gold is associated with metal sulphides, an oxidative thermal or a chemical pretreatment is often needed to access precious metal particles. Bacterial oxidative leaching may be an interesting alternative - low cost and environmentally friendly - to liberate gold from the sulphide matrix and then make it amenable to cyanidation. Bioleaching with Thiobacillus ferrooxidans has been investigated at 30-degrees-C at bench scale on a gold-bearing arsenopyrite (2 g/t Au) ore coming from Golcuck Mine in Turkey. The study was concerned with the influence of the age of the inoculum, pH, pulp density and time of the bacterial leaching at 30-degrees-C on the recovery of gold during the subsequent standard cyanide attack. Direct cyanide leaching of the arsenopyrite ground to -74 mum showed no gold dissolution at all, but with fine grinding to -30 mum, gold recovery increased to about 55.3% after 48 hours of cyanidation. On the contrary, cyanidation performed for 2 days on a bioleached arsenopyrite allowed 90% of gold to be solubilized in 2 hours
Bioxidation of arsenopyrite to improve gold cyanidation: study of some parameters and comparison with grinding
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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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