1,721,259 research outputs found
Modulated RF discharges as effective tool for selecting excited species
No full textModulated NH3-fed rf glow discharges have been investigated; the emissions of the active species NH* and N-2* have been collected during the modulation period (time on+time off). In this study, modulated discharges have been characterized by a constant time on of 7 ms and a tunable time off in the range of 0-1000 ms. It has been found that the power modulation represents an effective tool for selecting excited species: this procedure may be exploited in surface grafting treatments of polymers where high selectivity of chemical groups is requested, e.g., for preferentially grafting -NH2 groups onto polyethylene with respect to all other N-containing functionalities
Process control for plasma processing of polymers
No full textPE-CVD processes of a variety of coatings - fluoropolymers, SiOx, PEO- and Ag-PEO-like, -COOH functional layers - are described, as well as plasma treatments aimed to selectively graft -NH2 groups on polymers, with the use of spectroscopic plasma- and surface-diagnostics parameters of potential use for process transfer and control in industrial applications
NH3 plasma treatments of PET for enhancing Al adhesion
No full textANH3 plasma process has been studied for enhancing the adhesion of aluminum coatings
on polyethyleneterephtalate (PET) films. According to our peel strength results,
NH3 plasmas increase markedly the adhesion of aluminum on PET compared to O2 discharges,
with a much shorter treatment time. A tentative model of nonhindered growth
of Al-coating based on the Lewis basic character of the functionalities grafted by NH3
plasma is proposed for Al-polymer interactions, and for explaining the various steps
in the process. The effects of power input and treatment time on the polymer surface
chemistry and on the metal-polymer peel strength have been evaluated. Treatment times
as short as 0.1 s at 100Wproved to be the best conditions in NH3 plasmas, for a significant
increase in Al/PET adhesion, while longer treatments have a detrimental effect.
This may explain why most authors have not discovered the benefits of NH3 plasmas for
improving the adhesion of metals on PET, and have preferred O2 or air treatments. The
relative basicity of PET grafted with N-containing functionalities has been measured
by means of X-ray Photoelectron Spectroscopy (XPS) analysis of samples exposed to
vapors of trichloromethane, a Lewis acid molecular probe. The Al/PET adhesion was
evaluated by means of a 180± Peel Test
Selective grafting of amine groups on polyethylene by means of modulated RF NH3 plasmas
No full textPlasma treatments in power modulated NH3 RF glow discharges have been performed for modifying the surface of polyethylene (PE). Time Resolved Optical Emission Spectroscopy (TR-OES) has been utilized for monitoring the emission of active species during the modulation period of the discharge, Electron Spectroscopy for Chemical Analysis (ESCA) has been used for studying the surface composition of PE before and after the derivatization of plasma-grafted -NH2 groups. We present our preliminary results here, which show how modulated NH3 plasmas can effectively improve the grafting selectivity of -NH2 respect to all other N-containing groups
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
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