1,720,955 research outputs found
Hybrid film: a case analysis of the sol-gel technology for improved mechanical properties application
No full textThe paper deals with the analysis of the mechanical characteristics of hybrid coating obtained through the sol-gel synthesis starting from CH3Si(OCH3)3 and C6H5Si(OCH3)3 with colloidal silica, α-Al2O3, and HNO3 as catalyst. The experimental conditions refer to a not-optimized reaction parameters trying to obtain a greater sensibility on their variations. On the base of the kinetic reaction pathway the surface morphology, analysed by SEM, the hardness, the abrasion, the film porosity and the contact angles, are interpreted. Indeed the temperature appears a relevant parameter in the control of the surface aspect and the mechanical behaviour. The roles of the colloidal silica and of the nanometric α-Al2O3 were analysed. The results demonstrate the strong enclosing of the silica particle in the hybrid polymer network. On the contrary α-Al2O3 decreases the abrasion resistance due to the lack of chemical bonds with the network
Evolution of Two Acid Steps Sol-Gel Phases by FTIR Technology.
No full textAbstract FTIR has been used to follow the evolution of a
sol–gel preparation accomplished with two acid/acid steps.
The reaction of methyltrimethoxysilane mixed with colloidal
silica was taken as an example, aiming at proving the
use of IR spectroscopy for the determination of reaction
aspects like the kinetic behaviour that is essential for the
scale-up of the application. The steps were carried out for
60 min each and samples were taken in each step at variable
time intervals. For the spectroscopy analysis the dispersion
samples were deposited on a spinning disc of KBr
or ZnSe obtaining thin hybrid organic/inorganic films. The
signals at 950 cm-1 and 1,000–1,100 cm-1 related to the
hydrolysis and condensation reaction, respectively were
recorded at variable time and their intensity normalised to
the 1,273 cm-1band of Si-CH3 group not involved in the
hydrolysis nor condensation reaction. The effects of pH
and temperature have been investigated showing that reliable
effective data on the reaction extent of SiO2-doped
sol–gel dispersions can be obtained by the FTIR spectroscopy.
The data have been supported and interpreted
also by SEM observations. The reactions degree of the
(poly)condensation sharply increases after the addition of
more alkoxysilane. Short reaction times can be designed
that could be compatible with industrial production
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
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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