1,720,980 research outputs found
Cinetica del rigonfiamento di matrici polimeriche vetrose indotta dall'assorbimento di gas o vapori
No full textLa cinetica di assorbimento di specie a basso peso molecolare in polimeri vetrosi è qui interpretata sulla base dell'approccio del Non-Equilibrium Lattice Fluid e della adozione di un modello viscoelastico per il rilassamento di volume della matrice polimerica. Il lavoro prende in considerazione in particolare il caso del processo di assorbimento in campioni polimerici di dimensioni caratteristiche sufficientemente piccole perchè si possa considerare trascurabile il tempo caratteristico di diffusione rispetto al tempo caratteristico del rilassamento di volume. I risultati del modello sono confrontati con i dati sperimentali di massa assorbita in funzione del tempo per il caso della cinetica di assorbimento di n-esano in sferette submicrometriche di polistirene a diverse temperature
Stress effects on mass transport in polymers: a model for volume relaxation
No full textA model is introduced here for volume relaxation in glassy polymers, induced by sorption of low molecular weight species. The model relies on description of thermodynamic properties of glassy mixtures obtained through NET-GP model and it considers simple linear viscoelastic laws to interpret the stress–strain relation for the polymeric material. Results for the case of sorption kinetics in constant fugacity processes, obtained from the model, are compared with experimental values for vapour sorption in glassy polymeric microspheres. Satisfactory representations were obtained both for instant solute content measured in experimental run and for mass uptake registered in ‘relaxation stage’ of sorption processes. Viscosity data obtained from fitting of sorption experimental results are finally discussed in terms of temperature dependence and compared with values obtained form purely mechanical volume relaxation experiments
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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