1,720,980 research outputs found
Investigation of thermal runaway in semibatch chemical reactors by an Early Warning Detection Device
No full textNotwithstanding the numerous studies in the last decades to prevent runaway reactions, the maintenance of stability in chemical reactors is still a current issue in industrial chemical plants. There is an urgent need to implement an efficient and robust algorithm capable of detecting in advance anomalous behaviours of the reactor temperature during exothermic processes, in order to take appropriate countermeasures and avoid accidents occurring.
In this paper we have investigated the behaviour of an early warning detection device, based on the divergence calculation, to control the temperature within a laboratory-scale jacketed reactor, during the methyl methacrylate emulsion polymerization process carried out under semibatch conditions.
In order to test the reliability of the detection system, some failures or malfunctions were simulated, such as the rupture of the agitator or feeding pumps. Results showed that the divergence criterion was able to detect dangerous situations, by distinguishing in advance runaway phenomena from situations under normal operating control. In particular during the simulation of the agitator breakage, the presence of three thermo-resistance sensors located at different positions inside the reactor, allowed to identify the formation of hot-spots due to the missing of stirring. In that case the stability of the emulsion was lost and polymerization occurred with a higher chemical heat flow, with potential dangerous consequences such as the explosion of the reactor
H2 production by selective photo-dehydrogenation of ethanol in gas and liquid phase on CuOx/TiO2 nanocomposites
No full textCuOx/TiO2 nanocomposites prepared by copper photodeposition (1.0 and 2.5 wt% copper loading) on TiO2 (synthesized by three different routes) are studied in the ethanol photo-dehydrogenation in gas- and liquid-phase operations, and characterized in terms of surface area, phase composition by XRD, morphology and copper-oxide nanoparticle size distribution, and copper species by UV-visible diffuse reflectance spectroscopy. Cu2+ ions partially enter into the titania structure leading to the creation of oxygen vacancies responsible for the shift in the band gap, but also the creation of traps for photogenerated holes and electrons. While the band gap shifts to lower energies with the copper content, a maximum photocatalytic activity is shown for the intermediate copper loading. Gas-phase operations allow a higher H2 productivity with respect to liquid-phase operations, and especially a higher selectivity (about 92–93%) to acetaldehyde. It is remarked that the route of photo-dehydrogenation of ethanol to H2 and acetaldehyde has an economic value about 3.0–3.5 times higher than the alternative route of photoreforming to produce H2. Gas-phase operations would be preferable for the photo-dehydrogenation of ethanol
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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