1,721,165 research outputs found
Homogeneous: Vs. heterogeneous catalysis for hydrogen evolution by a nickel(ii) bis(diphosphine) complex
No full textNickel(ii) bis(diphosphine) complex 1 bearing carboxylic acid functional groups at the periphery has been prepared and characterized. Its catalytic ability towards the hydrogen evolution reaction (HER) has been evaluated under different experimental conditions: (i) under homogeneous electrocatalysis in acetonitrile using trifluoroacetic acid as the proton source, (ii) under homogeneous photocatalysis in aqueous solution using Ru(bpy)32+ (where bpy = 2,2′-bipyridine) as the sensitizer and ascorbic acid as the sacrificial electron donor, and (iii) under heterogeneous electrochemical conditions upon grafting onto mesoporous TiO2. The results show that complex 1 is a competent and efficient catalyst for the HER under both homogeneous electro- and photochemical conditions, while undergoes rapid deactivation once attached onto the TiO2 surface. This is attributed to both catalyst binding mode and structural rigidity imparted by covalent grafting, which highlights how catalyst design has to be considered for the direct transposition of molecular catalysis on (photo)electrode surfaces
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
Modeling liquidus hypersurfaces through simplicial complexes
No full texttermodinamica dei sistemi amorfi e calcoli di mesh simpliciali con tecniche di guscio convess
Steepest descent path on simplicial meshes of arbitrary dimensions
No full textThe paper introduces an algorithm to compute steepest descent paths on multivariate piecewise-linear functions on Euclidean domains of arbitrary dimensions and topolog
Thermoset Nanocomposites as ablative materials for rocket and military applications
No full textAblative materials are at the base of entire aerospace industry; these sacrificial materials enable the production of propulsion devices [such as liquid and solid rocket motors (SRMs)] or protect vehicles and probes during the hypersonic flight through a planetary atmosphere. They are also known as thermal protection system (TPS) materials. Some nonpolymeric materials have been successfully used as ablatives; however, due to their versatility, polymeric ablative materials (PAMs) represent the widest family of sacrificial TPS materials. In fact, when compared with nonpolymeric ablatives such as high-melting-point metals and inorganic polymers (or metal oxides or carbides), PAMs have some intrinsic advantages such as tunable density, higher heat shock resistance, and lower cost. This chapter covers all main areas related to the science and technology of military PAMs based on thermoset matrices
An Introduction to Ablative Materials and High-Temperature Testing Protocols
No full textAblative materials are at the base of the entire aerospace industry because as sacrificial materials they allow the production of propulsion devices (such as liquid and solid rocket motors [SRMs]) or the protection of vehicles and probes during hypersonic flight through a planetary atmosphere. Some nonpolymeric materials have been successfully used as ablatives but, due to their versatility, polymeric ablative materials represent the widest family of sacrificial thermal protection system (TPS) materials. Thermal analysis such as differential scanning calorimetry, thermogravimetric analysis, thermomechanical analysis, and differential thermal analysis can establish the bases for a proper and comprehensive evaluation of the thermal response of composite TPS materials when exposed to high temperatures, enabling the modeling of the ablation process. However, the aforementioned protocols cannot properly simulate the real conditions of the hyperthermal environment in which TPS materials have to work. Other techniques such as the oxy-acetylene torch test or the simulated solid rocket motor allow to better study the response of ablative materials; these techniques can reproduce in a smaller scale the environmental conditions produced in an SRM. As a result, in light of the specific topic of Section 3 of this book, the purpose of this chapter is to provide readers with relevant generalities on ablative materials and related testing techniques, i.e., to introduce the proper tools to understand the scientific content and uniqueness of the other chapters of this section
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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