1,721,070 research outputs found
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
Study of the effect of noble metal promotion in Ni-based catalyst for the Sabatier reaction
No full textThis paper reports the preparation and the evaluation of the performance of Ni-based powder catalysts with low nickel loading on the CO2 methanation reaction, that is an integral part of the power-to-gas (PtG) technology. CeO2, CeZrO4 and CeO2/SiO2 were selected as possible supports, and the results of this first screening pointed out that 10%Ni/CeO2 catalyst could offer the best reaction performances because of ceria's peculiar characteristics. Moreover, the promotion of this promising formulation with the addition of a small amount of noble metals (Pt, Ru, Rh) was investigated, showing that platinum in particular can enhance the catalyst performances. A further study related to the noble metal loading pointed out that platinum and ruthenium have a different optimum loading condition: this result, together with the activity tests performed on monometallic formulations with only the noble metal, suggested that the two metals are able to catalyse two different reactions, thus promoting two different reaction mechanisms
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
H2 generation via ethanol reforming over CeO2-SiO2 based catalysts
No full textIn this paper, the renewable hydrogen generation through oxidative steam reforming of ethanol has been investigated over bimetallic Pt-Ni/CeO2-SiO2 catalysts, prepared by sequential wet impregnation at different loadings of noble metals (0-3 wt%); temperature ranged from 300 to 600°C and the H2O/C2H5OH as well as O2/C2H5OH ratios were fixed, respectively, to 4 and 0.5. The samples were characterized by BET, XRD and TPR analysis. Despite the very low contact time selected (25 ms), all the bimetallic samples displayed ethanol conversions higher than 50% above 450°C; however, the selectivity in hydrogen generation decreased with the Pt content. It indicates that low platinum loading are sufficient to assure a promising performance for the investigated reaction, thus assuring a considerable reduction of the catalyst cost. An experimental kinetic investigation was also carried out on the most interesting bimetallic sample in comparison with the monometallic catalyst in order to predict the evolution of product species with reaction temperature
Insights in the application of highly conductive structured catalysts to CO2 methanation: Computational study
Full text linkNowadays, the optimization of the heat management in highly exothermic processes is a key issue. In recent years, highly conductive structured catalysts have been widely recognized in recent years as a tool for the process intensification of several technologies of this kind. To the best of our knowledge, despite the great availability of studies (both experimental and computational) on the topic, only the potentiality of this application has been discussed so far. Less attention has been paid to the limitations of structured catalysts systems. This work aims to provide an overview on the application of different types of structured catalysts in highly exothermic reactions using as probe reaction the methanation of CO2, offering a perspective view on the industrialization and scale up of this technology. The transport phenomena of momentum, heat and mass coupled with the chemical reaction have been detailed via computational study and compared to a previous experimental work, highlighting how the potentiality observed on lab scale will lose appeal in a scaled-up configuration, where higher Reynolds numbers are involved. Finally, the study provides a possible solution for the application of structured catalysts on bigger scale, without losing the advantages of thermal conductivity observed in the lab-scale experiments
Kinetics of Oxidative Steam Reforming of Ethanol Over Bimetallic Catalysts Supported on CeO2–SiO2: A Comparative Study
No full textAbstract: The catalytic activity of M(Ag, Ru, Pt)–Ni/CeO2–SiO2 catalysts prepared by wet impregnation at different M loadings (0–3 wt%) for oxidative steam reforming of ethanol (OSR) was investigated at H2O/C2H5OH = 4, O2/C2H5OH = 0.5, T = 300–600 °C and WHSV = 61.7 h−1. Ag deposition on the Ni/CeO2–SiO2 sample resulted in lower H2 yields, whatever the silver content. Conversely, Ru and Pt addition improved the performances of the monometallic sample and catalyst activity was enhanced by the reduction of metals loading. Similar results were recorded over the catalysts prepared at the same metals content and a metal loading of 0.5 wt% was sufficient to reach the highest performance in the investigated temperature interval. The kinetic model able to predict the experimental results obtained over the most promising formulations includes ethanol decomposition, methane oxidation and steam reforming, water gas shift; Pt as well as Ru addition to the Ni/CeO2–SiO2 sample reduced the activation energy of the involved reactions and Ru was demonstrated to be a valid substitute of the Pt for OSR of ethanol. Thus, by employing smaller noble metal content and less expensive materials, it is possible to reduce the catalyst price. Graphical Abstract: [Figure not available: see fulltext.]
Precursor salts influence in Ruthenium catalysts for CO2 hydrogenation to methane
No full textThe intermittency in power generation that characterizes renewable energy sources requires a way to convert the energy surplus. Among all the possibilities, the conversion of power in hydrogen via water electrolysis and then into methane via CO2 methanation represents a competitive storage system. CO2 methanation is an exothermic reaction which requires the use of low temperatures in order to achieve sufficiently high conversions: for this reason, there is a strong need in low-temperature active catalyst. In this work, several Ru/CeO2-ZrO2 and Ru-Ni/CeO2-ZrO2 were prepared and compared with Ni/CeO2-ZrO2, in order to evaluate the effect of Ru loading and Ru precursor salt. The results showed that in monometallic formulations the higher was the Ru amount the better were the reaction performances achieved, particularly at low temperatures. In bimetallic formulations, the presence of Ru enhances the catalyst activity; in particular, the use of the Ru acetylacetonate, for the deposition of the noble metal on support, remarkably reduces the catalyst onset temperature. The effect is due to the templating effect of the precursor molecule, which allows a better dispersion of the active compounds
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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