1,720,956 research outputs found
Comparison of sine versus pulse waveform effects on fatigue crack growth behavior on Nr, SBR, and BR compounds
No full textFatigue crack growth experiments on carbon black-filled rubber compounds have been carried out to evaluate the influence of testing conditions over different compound formulations. Investigations on the influence of waveform, data
acquisition, and compound formulation have been performed on strip-tensile specimens reproducing the mode I of crack opening. The response of three different compound formulations (based on either natural rubber, butadiene rubber, or
styrene-butadiene rubber) to the application of two different waveforms, pulse and sine, has been analyzed, showing
significant differences in fatigue behavior and ranking of the various compounds. Compared to the sinusoidal waveform, the use of a pulse waveform provided an improved correlation of the tearing energy with the crack propagation speed.
This difference was particularly evident in the case of natural rubber and butadiene rubber, while it resulted negligible
in the case of styrene-butadiene rubber. Such a different behavior could be attributed to differences in macromolecular chains orientation. Fine-tuning of video acquisition parameters provided an accurate observation of the crack growth process, as confirmed by the low standard deviation of the estimated tearing energy and crack growth rate
Produzione in fed-batch ripetuto di acido citrico da Yarrowia lipolytica con riciclo di biomassa per microfiltrazione tangenziale
No full textIn this work, citric acid production by Yarrowia lipolytica ATCC 20346 was studied in a laboratory-scale Membrane Recycle Bioreactor composed of a stirred fermenter coupled to a flat-membrane cross-flow microfiltration (CFMF) unit.
By increasing the number of production cycles, citrate productivity (R-p) tended to reduce in spite of the fact that the production medium had been integrated with vitamins, whereas the yield factor for citric acid production on glucose was found to be approximately constant. By operating with partial cell discharge (when using either the production media enriched with amounts of nitrogen and essential nutrients equivalent to the mass of cells disposed of, or the growth medium), it was possible to obtain the expected microbial biomass with no or very limited citrate excretion.
To minimise the contribution of the cell growth phase to the overall citrate productivity and yield on glucose, it would be convenient to subdivide the process into the following stages: growth phase, yeast recovery by CFMF; Ist prolunged fed-batch production using a pi-I-controller as an indirect feedback of simultaneous substrate and alkaline reagent feeding; yeast recovery by CFMF; 2nd prolunged fed-batch production
Confocal Raman imaging, FTIR spectroscopy and kinetic modelling of the zinc oxide/stearic acid reaction in a vulcanizing rubber
No full textThe reaction of zinc oxide (ZnO) with stearic acid (StA) to form zinc stearate (ZnSt) has been investigated experimentally in a model matrix (unvulcanized styreneebutadiene rubber) by using confocal Raman microscopy and FTIR transmission spectroscopy. The heterogeneous nature of the reacting system has been confirmed. The Raman analysis has revealed the coreeshell structure of the product, which is formed via the gradual shrinkage of the ZnO core and the concurrent formation of a surrounding ZnSt shell of increasing thickness. FTIR spectroscopy has provided information about the molecular state of
aggregation of StA when dissolved in the rubber, as well as quantitative information on the reaction kinetics. The kinetic behaviour of the system has been interpreted using a semi-quantitative heterogeneous reaction model grounded on the Raman imaging results, which was able to catch the essential
features of the phenomenon and to simulate reliably the experimental conversion vs time data at three different temperatures
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
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