1,721,064 research outputs found
FTIR analysis of supported catalyst systems related to the reduction of automotive exhaust emissions
No full textFourier transform infrared spectroscopy and mass spectrometry were used in tandem to investigate the surface chemistry and reactivity of three different catalyst systems. The three systems were related by their relevance to current issues in automotive exhaust catalysis and the fact that each system operated under non-steady state conditions. In the first system, isothermal kinetic rate oscillations in the oxidation of carbon monoxide were studied on a series of silica-supported platinum catalysts. It was determined that the oscillations are related to the formation of densely packed islands on the surface of the catalyst that poison a portion of the active sites and that change in dimension during the course of the reaction. The origin of this effect is unknown, but it may be related to the surface phase transition that is responsible for oscillations in the same reaction on platinum single crystals. Second, isothermal kinetic rate oscillations were also studied in the decomposition of nitrous oxide over copper-exchanged ZSM-5 zeolite. In this case, the oscillations were linked to the existence of a nitrate species bound to isolated copper ions associated with the zeolite framework. Catalysts made from aluminum-rich ZSM-5 did not show oscillations due to a de-stabilization of the critical nitrate species under reaction conditions. Finally, a fundamental study of a new class of materials known as nitrogen storage and reduction (NSR) catalysts was performed. These catalysts are designed to remove nitrogen oxides from automotive exhaust in the presence of excess oxygen if the engine is operated in a transient fashion such that the fuel mixture is cycled between a fuel-rich phase and a fuel-lean phase. Many details of the reaction mechanism were uncovered. It was found that interaction between the reactive platinum component and the barium oxide storage component is critical to the activity of the catalyst due to the need for spillover between the two phases. In addition, the use of iron as an additive to the catalyst system was shown to improve the durability of the material to poisoning by sulfur compounds
High throughput screening of supported catalysts using FTIR imaging
No full textThis study focuses on applying high throughput experimentation to study catalysts and reaction kinetics. In order to employ this method successfully new high throughput screening techniques have emerged. Among screening techniques is FTIR imaging. The feasibility of using FTIR imaging to study both adsorbates on supported catalysts and ligands attached to resin beads has been demonstrated. In this study, the technique has been successfully extended to screen gas phase reactants from multiple flow reactors. To accomplish this, detailed design of both flow reactor assembly and a sampling system was completed. After building the system, it was established that the FTIR imaging technique could be applied to both steady state and transient experiments, and the data was successfully used to construct rate equations for CO oxidation, catalyzed by supported metal catalysts. Three different catalysts were studied for the reaction, platinum, rhodium, and ruthenium. For these catalysts, reaction orders and activation energies were established from the steady state experiments and information on the metal dispersion of the catalysts established from the transient experiments
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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