1,721,017 research outputs found
A study of the influence of free convection on coagulation process
No full textIt was assumed [1, 2] that gravity affects the coagulation process in two ways: free convection, which is hard to be avoided on the ground and sedimentation, which can be greatly reduced by the density-matching method. We present a ground-based experiment set-up to study the influence of convection on the perikinetic coagulation for aqueous polystyrene (PS) dispersions. The turbidity measurement was used to evaluate the relative coagulation rate and convection-driven flows in the solution were checked with a visual-magnification system. The pattern of flow field temperature profile in the sample cell is given. Our experiments show that there was no noticeable difference of coagulation rate observed no matter whether convection flows exist (with the flow speed up to 180 mu m/s) or not
Progress in coagulation rate measurements of colloidal dispersions
No full textThis article reviews recent advances in coagulation rate measurements of colloidal dispersions, with emphasis on the turbidity method. For turbidity method, measurement of the coagulation rate relies upon the turbidity change resulting from the coagulation process, and the measuring sensitivity significantly depends on particle size and the wavelength used. There exists a "zero sensitivity" blind point for measurement at a specific wavelength, suggesting that such measurements should be performed at a wavelength some distance from the blind point. The major difficulty in determining absolute coagulation rate constant (CRC) by light scattering and turbidity measurements is how to theoretically solve the scattering problem of 2-particle aggregates. The T-matrix method accurately solves this problem, showing its superiority over various earlier theoretical approximations (applicable only to small particles). Results from studies on effects of forward scattering, multiple scattering, etc., provide guidelines for choosing proper particle size and volume fraction for the allowed margin of measurement error. Most of these findings on turbidity methods are also valid or applicable to other scattering methods. Finally, we introduce a new microscopic approach to assess the colloidal stability at individual particle levels, by means of directly observing artificially induced collision with the aid of optical tweezers
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
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
Evaluation of influence of multiple scattering effect in light-scattering-based applications
No full textThe extinction cross sections of a system containing two particles are calculated by the T-matrix method, and the results are compared with those of two single particles with single-scattering approximation. The necessity of the correction of the refractive indices of water and polystyrene for different incident wavelengths is particularly addressed in the calculation. By this means, the volume fractions allowed for certain accuracy requirements of single-scattering approximation in the light scattering experiment can be evaluated. The volume fractions calculated with corrected refractive indices are compared with those obtained with fixed refractive indices which have been rather commonly used, showing that fixed refractive indices may cause significant error in evaluating multiple scattering effect. The results also give a simple criterion for selecting the incident wavelength and particle size to avoid the 'blind zone' in the turbidity measurement, where the turbidity change is insensitive to aggregation of two particles
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