1,720,956 research outputs found
Li-Promoted La<sub><i>x</i></sub>Sr<sub>2–<i>x</i></sub>FeO<sub>4−δ</sub> Core–Shell Redox Catalysts for Oxidative Dehydrogenation of Ethane under a Cyclic Redox Scheme
No full textChemical
looping oxidative dehydrogenation (CL-ODH) of ethane utilizes
a transition metal oxide based oxygen carrier, also known as a redox
catalyst, to convert ethane into ethylene under an autothermal cyclic
redox scheme. The current study investigates a Li-promoted LaxSr2–xFeO4−δ (LaSrFe) redox catalyst for CL-ODH reactions.
While LaSrFe without Li promoter exhibits low ethylene selectivity,
addition of Li leads to high selectivity/yield and good regenerability.
Up to 61% ethane conversion and 90% ethylene selectivity are achieved
with Li-promoted LaSrFe. Further characterization indicates that the
Li-promoted LaSrFe redox catalyst consists of LiFeO2 (disordered
rock salt) and LaSrFe (Ruddlesden–Popper) phases. Moreover,
the surface of the redox catalysts is enriched with Li cations. It
is also determined the LaSrFe phase contributes to oxygen storage
and donation, whereas the activity and selectivity of the redox catalysts
are modified by the Li promoter: while oxygen for the CL-ODH reaction
is supplied from the lattice of the LaSrFe phase, the enrichment of
Li cations on the surface increases the resistance for O2– diffusion from the bulk and its subsequent evolution into electrophilic
oxygen species on the surface. The nonselective nature of the surface
oxygen species and the inhibition effects of Li promoter on O2– diffusion are further confirmed by pulse experiments.
On the basis of such findings, it is concluded that Li-promoted LaxSr2–xFeO4−δ is an effective redox catalyst for ethane
ODH in the absence of gaseous oxygen. Moreover, the selectivity of
the redox catalysts can be enhanced by the alkali metal oxide promoters
Dynamic Methane Partial Oxidation Using a Fe<sub>2</sub>O<sub>3</sub>@La<sub>0.8</sub>Sr<sub>0.2</sub>FeO<sub>3‑δ</sub> Core–Shell Redox Catalyst in the Absence of Gaseous Oxygen
No full textChemical looping reforming partially
oxidizes methane into syngas
through cyclic redox reactions of an active lattice-oxygen (O2–) containing redox catalyst. The avoidance of direct
contact between methane and steam and/or gaseous oxygen has the potential
to eliminate the energy consumption for generating these oxidants,
thereby increasing methane conversion efficiency. This article investigates
redox catalysts comprised of iron oxide core covered with lanthanum
strontium ferrite (LSF) shell. The iron oxide core serves as the primary
source of lattice-oxygen, whereas the LSF shell provides an active
surface and facilitates O2– and electron conductions.
These core–shell materials have the promise to provide higher
selectivity for methane conversion with lower solid circulation rates
than traditional redox catalysts. Methane oxidation by this catalyst
exhibits four distinct regions, i.e. deep oxidation; competing deep
and selective oxidation; selective oxidation with autoactivation;
and methane decomposition. Further investigations indicate that the
evolution of “loose” lattice oxygen from the bulk contributes
to deep oxidation, whereas reduced surface iron species are responsible
for selective methane oxidation
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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