1,720,968 research outputs found
An investigation on the redox kinetics of NH3-SCR over a V/Mo/Ti catalyst: Evidence of a direct role of NO in the re-oxidation step
No full textThis study addresses a kinetic investigation of NH3-SCR on commercial SCR catalysts with composition V2O5/MoO3/TiO2. Objective of the study is an improved kinetic description of the reaction, based on the recognition of the redox nature of the V-site; which calls for an understanding of the effect of O2. At this scope, an extensive experimental investigation over a powdered catalyst was performed at largely varying concentrations of O2 (from 0.06 to 8%) both at high and at low NO and NH3 concentration. It was found that the increase of the O2 feed content promoted NO conversion with asymptotic trend: the promotion was important in the range 0.06–3%, but became moderate in the range 3–8%. Unexpectedly, the effect of O2 was equally important at high NO and NH3 concentration as well as at low NO and NH3 concentration (where a kinetic control from the reduction step and thus a negligible role of the oxidation step were expected). The kinetic analysis revealed that the observed experimental trends can be described by a Mars-van Krevelen rate expression assuming that the rate of re-oxidation depends on NO concentration as well as the rate of reduction does. A molecular rate equation which incorporates a simple linear dependence on NO concentration in the re-oxidation kinetics fully describes the whole bulk of data and is suitable to engineering purposes. The existence of an NH3 inhibiting effect was also included. The global rate expression was successfully validated against independent pilot-scale experiments on slabs
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
Appraising Multinuclear Cu(2+) Structure Formation in Cu‐CHA SCR Catalysts via Low‐T Dry CO Oxidation with Modulated NH(3) Solvation
Full text linkCu(2+) ions (ZCu(2+)(OH)(−), Z(2)Cu(2+)) are regarded as the NH(3)‐SCR (SCR=selective catalytic reduction) active site precursors of Cu‐exchanged chabazite (CHA) which is among the best available catalysts for the abatement of NO(x) from Diesel engines. During SCR operation, copper sites undergo reduction (Reduction half‐cycle, RHC: Cu(2+)→Cu(+)) and oxidation (Oxidaton half‐cycle, OHC: Cu(+)→Cu(2+)) semi cycles, whose associated mechanisms are still debated. We recently proposed CO oxidation to CO(2) as an effective method to probe the formation of multinuclear Cu(2+) species as the initial low‐T RHC step. NH(3) pre‐adsorption determined a net positive effect on the CO(2) production: by solvating ZCu(2+)(OH)(−) ions, ammonia enhances their mobility, favoring their coupling to form binuclear complexes which can catalyze the reaction. In this work, dry CO oxidation experiments, preceded by modulated NH(3) feed phases, clearly showed that CO(2) production enhancements are correlated with the extent of Cu(2+) ion solvation by NH(3). Analogies with the SCR‐RHC phase are evidenced: the NH(3)‐Cu(2+) presence ensures the characteristic dynamics associated with a second order kinetic dependence on the oxidized Cu(2+) fraction. These findings provide novel information on the NH(3) role in the low‐T SCR redox mechanism and on the nature of the related active catalyst sites
Transient CO Oxidation as a Versatile Technique to Investigate Cu2+ Titration, Speciation and Sites Hydrolysis on Cu–CHA Catalysts: The Cu Loading Effect
No full textThe investigation of the ZCu2+(OH)− and Z2Cu2+ ions modifications during NH3-SCR on Cu–CHA catalysts is a key aspect to clarify the still-debated low-T redox SCR mechanism. In previous works, the dry transient CO oxidation protocol has been employed to identify the generation of dinuclear Cu2+ structures under conditions representative of the low-T SCR–RHC: NH3 solvation promotes the inter-cage mobility and coupling of ZCu2+(OH)−, acting as the catalytic centers for the CO oxidation process, while Z2Cu2+ results inactive. Herein the same protocol, with pre-stored NH3, has been applied to a set of Cu–CHA catalysts with variable Cu loading (0.7–2.4% w/w) but fixed Si/Al: an increasing Cu content produced a net positive effect on the CO2 production, coherent with a growing ZCu2+(OH)− population, while a further enhancement was observed in the presence of H2O. The analysis of the integral CO2 production enabled to predict the maximum CO conversion, corresponding to the titration of the whole ZCu2+(OH)− content for each catalyst under dry condition, verifying the initial mechanism. Conversely, in the presence of water, the analysis evaluated an asymptotic titration of the total catalyst Cu2+ contents. This finding permits to generalize a recent study where combined TRMs, DFT and FTIR were used to probe the complete reversible Cu2+ sites hydrolysis and pairing in the presence of H2O and NH3, thus activating the participation of Z2Cu2+ species, too. These results also highlight the versatility and effectiveness of the CO oxidation protocol as a multi-purpose technique to study the Cu2+ ions in Cu–CHA catalysts
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
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