1,720,961 research outputs found
Improving the settleability of a metal sulphide suspension by the application of a magnetic field
No full textGravitational sedimentation of suspensions in various precipitation processes is hindered by colloidal stability. More especially in sulphide precipitation, where high levels of supersaturation dominate and nucleation is favoured. This results in a large number of colloidal particles with a highly negative surface charge, which remain suspended in solution. The high surface charge of the suspension results in strong attraction/interaction between the ions on the particle surface and counter-ions in solution. Moreover, this strong interaction between ions on the particle surface and counter-ions in solution results in a charge build-up that renders the suspension stable. In order to induce gravitational sedimentation of these particles, a redistribution of ions close to the particle surface is required. This study therefore seeks to redistribute ions close to the particle surface by applying a magnetic field. This results in the reduction of inter-particle electrostatic repulsive forces and subsequent increase in the zeta potential of a suspension. For the purposes of this study, a copper sulphide suspension was used. A T-mixer was used as the reaction zone for the precipitation of each suspension. Subsequent to this, the suspended copper sulphide particles were exposed to a range of field strengths for set exposure times and their zeta potential was measured before and after exposure to the magnetic field. The effect of magnetic field strength, exposure time and particle speed on the zeta potential were tested. All particles had an initial zeta potential value equal to or less than - 40 mV prior to magnetic field exposure. A significant increase in zeta potential was observed with values reaching a maximum of - 16.5 mV when exposed to a 2 T field strength for 40 minutes. An increase in the zeta potential corresponds to a reduction in repulsive electrostatic forces between suspended particles due to the Lorentz force exerted by a magnetic field on the particle surface. DLVO plots were used to quantify this reduction in repulsive electrostatic forces
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
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
The effect of energy input on the aggregation rate in an oscillating multi-grid reactor
No full textIncludes bibliographical references.Aggregation is a size enlargement mechanism which can be either desirable or inconvenient depending on the process involved. It involves the coming together or collision of two or more particles to form a larger single particle. It is a mechanism which is poorly understood and much research is still required before the intricacies of the process are fully grasped. Although it is known that aggregation is influenced by energy input (amongst other factors), the relationship between the two has previously been measured in anisotropic turbulent environments. Thus although aggregation is a function of local energy input, it has yet to be measured in environments where the local energy dissipation is well understood, or else it has been studied in low Reynolds number environments. This thesis aims to address this deficiency by studying the effect of local energy input on the aggregation rate in a well characterised environment of isotropic and homogenous turbulence
Effect of antiscalants during eutectic freeze crystallization of a reverse osmosis retentate
No full textIncludes bibliography.Eutectic Freeze Crystallization (EFC) is a separation technique which involves simultaneous crystallization of water and solute under eutectic conditions. It can be applied to treatment of various industrial aqueous streams containing dissolved organic and inorganic contaminants, such as reverse osmosis (RO) retentate brine streams. Since antiscalants are dosed in RO feed streams, these become concentrated in the retentate brine stream and could have an undesirable effect on crystallization kinetics of both ice and salt in EFC. In this study, the impact of a phosphonate antiscalant on the kinetic processes of nucleation and growth in EFC was investigated. Firstly, the effect of an antiscalant on the thermodynamic phase equilibria of a binary Na2SO4 aqueous solution was experimentally determined. The effect of the antiscalant on the nucleation and growth rates of both ice and salt in a continuous EFC process was then established for concentrations of 200, 350 and 500 mg/L of antiscalant. Product quality parameters such as the Crystal Size Distribution (CSD), morphology and purity of crystals were also measured since they are directly affected by the kinetic rate processes investigated
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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