1,721,000 research outputs found
Effective Ce-based catalysts deposition on ceramic open cell foams
No full textIn this work, ceramic powder dispersion was achieved by using a glycerol/water solution as dispersion medium and polyvinyl alcohol as binder and rheology modifier. Five different powders were dispersed and they were deposited onto open cell ceramic foams: the bare carrier (i.e. cerium oxide) and four catalytically active powders (i.e. nickel, cobalt, iron and copper oxides supported on eerie). Catalysts powders have been extensively characterized and were demonstrated to be suitable samples candidates of model powders for the deposition onto open-cell foams. Rheological properties were found to be related to the dispersed powder, thus directly affecting washcoat load. Multiple depositions were performed by means of dip-coating on 20, 30 and 40 PPI Y-stabilized ZrO2 open cell foams. Depending on formulation and foam pore density, coating loads in the 6-30 % wt. range were obtained. Washcoat layers were found to be quite homogeneous and well adherent therefore suitable for catalytic applications, such as for instance the methane steam reforming synthesis for Ni-based catalysts
Investigation of packed conductive foams as a novel reactor configuration for methane steam reforming
Full text linkIn this work, a novel fixed bed reactor configuration is proposed and tested for the steam reforming of methane; the proposed solution consists of filling the voids of highly conductive metallic open-cell foams with small catalytic pellets. This reactor layout aims at enhancing the radial heat transfer of the tubular reactor by exploiting the thermal conductivity of the solid interconnected matrix, while keeping a target catalyst inventory and avoiding issues related to washcoating of metallic structures. Tests were performed using a Rh/Al2O3 catalyst in the form of alumina egg-shell particles, with diameter of 600 μm. FeCrAlY open cell foams of 12 PPI and copper open cell foams of 10 and 40 PPI were compared to a conventional packed bed system; experiments were performed at GHSV of 5000 and 10000 h−1 at oven temperatures in the 600–800 °C range. Experiments demonstrated a benefit in terms of the thermal management of the reactor and an increase of productivity at the same furnace temperature in kinetically-limited conditions. A heat transfer model of the packed foams was developed based on the approach of electric equivalent circuit; the model incorporates independently estimated lumped or effective parameters and provides an engineering rationale of the observed reduction of temperature gradients across the catalytic bed
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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