1,720,961 research outputs found
Effect of the cobalt-precursor on the reactivity of cobalt-based Fischer-Tropsch catalysts supported on stabilized alumina
No full textThis study investigates the effect of the cobalt precursor (nitrate and acetate) on the catalytic performance in the Fischer-Tropsch synthesis of catalysts supported on stabilized CoAl2O4/Al2O3 pellets. The catalysts are prepared via multi-steps of impregnation of the support with aqueous solutions of cobalt nitrate or acetate followed by calcination in air. The dispersion of the Co3O4 particles obtained via exothermic decomposition of acetate increases if each impregnation is followed by calcination. In fact, halving the calcinations leads to Co3O4 particles even bigger than those formed from cobalt-nitrate. A worsening of the catalytic performances is observed when the Co-acetate catalysts are tested in the FTS. Such a result is explained on the basis of Co0 particles size effect. Pt improves the catalysts reducibility regardless of the Co-precursor. The metallic surface area of the Pt-promoted Co-nitrate catalyst is higher than that of the corresponding Co-acetate catalyst, thus resulting in improved catalytic performances
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
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
Adoption of 3D printed highly conductive periodic open cellular structures as an effective solution to enhance the heat transfer performances of compact Fischer-Tropsch fixed-bed reactors
Full text linkHeat transfer is universally recognized as a key challenge for the intensification of the Fischer-Tropsch (FT) process in compact fixed-bed reactors. For the first time in the scientific literature we demonstrate experimentally that the adoption of a highly conductive periodic open cellular structure (POCS, 3D-printed in AlSi7Mg0.6 by Selective Laser Melting) packed with catalysts pellets is a promising solution to boost heat exchange in fixed-bed FT reactors. This reactor configuration enabled us to assess the performances of a highly active Co/Pt/Al2O3 catalyst packed into the POCS at process conditions relevant to industrial Fischer-Tropsch operation. Unprecedented performances (CO conversion ≈ 80%) could be thus achieved thanks to an outstanding heat management. In fact, almost flat axial and radial temperature profiles were measured along the catalytic bed even under the most severe process conditions (i.e. high CO conversions corresponding to high volumetric heat duties), demonstrating the effective potential of this reactor concept to manage the strong exothermicity of the FT reaction. The heat transfer of the packed-POCS reactor outperformed both packed-bed and packed-foam reactors, granting smaller radial temperature gradients in the catalytic bed, as well as smaller temperature differences at the reactor wall, with larger volumetric power releases. The strengths of the packed-POCS reactor configuration are its regular geometry, which enhances the effective radial thermal conductivity, and the improved contact between the structure and the reactor wall, which governs the limiting wall heat transfer coefficient
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
- …
