1,721,145 research outputs found
Corrigendum to “Crystal structure solution of KMg(ND)(ND2): An ordered mixed amide/imide compound” [Int J Hydrogen Energy 39 (2) 2014) 868 - 876]
No full textThis corrigendum to orignal article [Int J Hydrogen Energy 39 (2) 2014) 868 - 876] wants to points out that there are two different way to describe the structure of KMg(ND)(ND2). This was described as an orthorhombic system with space group P212121 (n.19) in the original article. However, after the publication of the article the authors found out that the structure can also be described in higher symmetry using the space group Pnma (n.62) in the orthorhombic system. The corrigendum describes i netails this second possibility.JRC.F.2 - Energy Conversion and Storage Technologie
Crystal structure solution of KMg(ND)(ND2): An ordered mixed amide/imide compound
No full textAn ordered mixed deuterated amide/imide potassiumemagnesium compound was synthesized with the intent of solving its structure using neutron diffraction technique with help of “ab-initio” methods. Obtained powder diffraction patterns were compatible with
the orthorhombic P212121 space group, and lattice parameters a ¼ 9.8896(3) A; b ¼ 9.3496(3) A; c ¼ 3.6630(1) A, respectively.
Assuming a density of 1.91 g/cm3 the investigation has allowed to locate the four constituting elements distributed in seven different sites into Wyckoff general positions 4(a), for a total of 28 atoms in the unit cell. This is the first example of crystal structure solution of amixed imide/amide compound appearing during the dehydrogenation process of a potassium containing amide based hydrogen storage material.JRC.F.2 - Cleaner energ
Structural study of a new B-rich phase obtained by partial hydrogenation of 2NaH + MgB2
No full textThe structure of an unknown crystalline phase observed during the hydrogen absorption reaction of the powder mixtures 2NaH þ MgB2 at high pressure has been studied by abinitio structure determination from powder diffraction. The sequence of un-overlapped peaks extracted from the X-ray powder diffraction pattern could be indexed with a primitive cubic cell with lattice parameter a ¼ 7.319 A°. The diffraction patterns of the peaks are matched with the Pa-3 space group. The stoichiometry of the hydrogen absorption reaction suggests the presence of a high-boron content phase in the compound under investigation. Assuming this phase to be composed only by boron atoms and therefore having a density similar to that found for boron polymorphs, the solution with a space group of Pa-3 leads to reasonable BeB interatomic distances.JRC.F.2 - Cleaner energ
Mechanically activated metathesis reaction in NaNH2–MgH2 powder mixtures
Full text linkThe present work addresses the kinetics of chemical transformations activated by the mechanical processing of powder by ball milling. In particular, attention focuses on the reaction between NaNH2 and MgH2, specific case studies suitably chosen to throw light on the kinetic features emerging in connection with the exchange of anionic ligands induced by mechanical activation. Experimental findings indicate that the mechanical treatment of NaNH2–MgH2 powder mixtures induces a simple metathetic reaction with formation of NaH and Mg(NH2)2 phases. Chemical conversion data obtained by X-ray diffraction analysis have been interpreted using a kinetic model incorporating the statistical character of the mechanical processing by ball milling. The apparent rate constant measuring the reaction rate is related to the volume of powder effectively processed during individual collisions, and tentatively connected with the transfer of mechanical energy across the network formed by the points of contact between the powder particles trapped during collisions.H2020-MSCA-IF-2015 Grant Number #70795
A new mutually destabilized reactive hydride system: LiBH4–Mg2NiH4
No full textIn this work, the hydrogen sorption properties of the LiBH4–Mg2NiH4 composite system with the molar ratio 2:2.5 were thoroughly investigated as a function of the applied temperature and hydrogen pressure. To the best of our knowledge, it has been possible to prove experimentally the mutual destabilization between LiBH4 and Mg2NiH4. A detailed account of the kinetic and thermodynamic features of the dehydrogenation process is reported here.Fil: Bergemann, Nils. Helmholtz zentrum Geesthacht ; AlemaniaFil: Pistidda, Claudio. Helmholtz zentrum Geesthacht ; AlemaniaFil: Uptmoor, Maike. Helmholtz zentrum Geesthacht ; AlemaniaFil: Milanese, Chiara. Universita Degli Studi Di Pavia; ItaliaFil: Santoru, Antonio. Helmholtz zentrum Geesthacht ; AlemaniaFil: Emmler, Thomas. Helmholtz zentrum Geesthacht ; AlemaniaFil: Puszkiel, Julián Atilio. Helmholtz zentrum Geesthacht ; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Dornheim, Martin. Helmholtz zentrum Geesthacht ; AlemaniaFil: Klassen, Thomas. Helmholtz zentrum Geesthacht ; Alemania. Universitat Hamburg; Alemani
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
Kinetics and hydrogen storage performance of Li-Mg-N-H systems doped with Al and AlCl3
Full text linkRecent investigations showed the formation of new amide-chloride phases between LiNH2 and AlCl3 after milling and/or heating under hydrogen pressure. These phases exhibited a key role in the improvement of the hydrogen storage properties of the LiNH2-LiH composite. In the present work, we studied the effects of Al and AlCl3 additives on the hydrogen storage behavior of the Li-Mg-N-H system. The dehydrogenation kinetics and the reaction pathway of Al and AlCl3 modified LiNH2-MgH2 composite were investigated through a combination of kinetic measurements and structural analyses. During the first cycle, the addition of Al catalytically accelerates the hydrogen release at 200 °C. In the subsequent cycles, the formation of a new phase of unknown nature is probably responsible for both increased equilibrium hydrogen pressure and decreased dehydrogenation rate. In contrast, AlCl3 additive reacts with LiNH2-MgH2 through the milling and continues during heating under hydrogen pressure. Addition of AlCl3 leads to the formation of two cubic structures identified in the Li-Al-N-H-Cl system, which improves dehydrogenation rate by modifying the thermodynamic stability of the material. This study evidences positive effect of cation and/or anion substitution on hydrogen storage properties of the Li-Mg-N-H system.This study has been partially supported by bilateral collaboration Project MINCyT-MAE
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