1,721,057 research outputs found
Methane Activation on Oxyhalogenated Rare-earth System: Effect of Pr3+ Substitution in LaOCl Host Struture on CO2 Formation
No full textCatalytic activity of LnOX (Ln = Sm, La or Nd; X = Cl or Br) and Ln(1-x)Lm(x)OX (Ln = La and Lm = Pr, 0 less than or equal to x less than or equal to1) catalysts has been studied using a continuous flow reactor system. Methane oxidation using LnOX results in an increase of CO2 selectivity in the order Nd > La > Pr > Sm, while using Ln(1-x)Lm(x)OX systems CO2 selectivity is enhanced by increasing partial lanthanum substitution with praseodymium. A decrease in CO and Ct hydrocarbons selectivities is also observed at isoconversion. The different compounds structures studied do not change with time under reaction conditions within the temperature range at which the catalysts are stable
Isothermal Reduction Behaviour of Undoped and Ca, K and P-Doped NiMoO4 Phases Used for Selective Propane Oxydehydrogenation
No full textIsothermal reduction under hydrogen of polymorphic NiMoO4 system has been studied at different temperatures using thermogravimetry. Evidences found by TG (oxygen depletion rate) have shown a dependence on lattice oxygen mobility and source due to the crystal structure and temperature.
Relative to the undoped NiMoO4 phases, it has been found that the presence of K2O, CaO and P2O5 promoters simultaneously affects both the reduction rate and the oxygen source.
Monolayer lattice oxygen mobility of undoped and doped NiMoO4 material was investigated by oxydehydrogenation of light alkanes performed by using a periodic flow micro-reactor. The alkane activity has been found to be linked to the reduction behaviour of the different undoped and doped NiMoO4 phases
Dielectric characterization of La1-xAgxMnO3+δ (x = 0; 0.2) perovskites in the frequency range 200MHz-3GHz
No full textLa1-xAgxMnO3+δ (x = 0; 0.2) perovskites have been prepared using a microwaves process (MWhyd) by comparing the heating time and reaction temperature with the same factor under conventional thermal process (CHhyd). Experiments have been conducted using hydrothermal method at medium pressure (T = 200°C, P = 2.06 MPa.) followed by a conventional treatment of the precursor at 700°C (10h). While MWhyd and CHhyd powders exhibited the same XRD patterns indexed as pure perovskite structure, their physico-chemical properties were found to be strongly influenced by the preparation method. La1-xAgxMnO3+δ perovskites were characterised using x-ray diffraction (XRD), BET sorption, temperature programmed reduction-mass spectrometry (TPR-MS), x-ray photoelectron spectroscopy (XPS), and dielectric measurements in the frequency range 200 MHz-3GHz
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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