1,720,961 research outputs found
Synthesis and chemical-physical characterisation of hybrid, ceramic and glass ceramic luminescent materials
No full textPREPARATION AND CHARACTERIZATION OF LAS GLASS CERAMICS CONTAINING ER3+:ZRO2 NANOPARTICLES
No full textSynthesis, X-ray Diffraction Characterization, and Radiative Properties of Er2O3-ZrO2 Nanocrystals Embedded in LAS Glass Ceramic
No full textLow thermal expansion Li2O−Al2O3−SiO2 (LAS) glass ceramic was examined as a host matrix for erbium ions. ZrO2 was added to the glass since it serves as a nucleating agent and as a good environment for the luminescent ions. The study was carried out on amorphous powders of the Li2O−Al2O3−SiO2/ZrO2/Er2O3 system prepared by the sol−gel method and successively crystallized at different temperatures. X-ray diffraction (XRD), transmission electron microscopy (TEM), and infrared (IR) spectroscopy were employed to study the evolution of the crystalline phases and the distribution of the erbium ions. The TEM micrographs confirmed that, after thermal treatment at 1000 °C, the crystallization of nanoparticles constituted by an Er2O3−ZrO2 solid solution with narrow size distribution could be achieved. On the contrary, erbium silicate was detected in the samples without ZrO2. The repartition constant of Er2O3 between ZrO2 and LAS matrix has been also evaluated
Effect of the microstructure on concentration quenching in heavily doped Tb2O3-ZrO2 nanoparticles embedded in silica
No full textTb3+-doped ZrO2 samples were prepared both as pure compounds and as a nanocomposite made up of sub-5 nm crystalline nanoparticles
developed in an amorphous silica matrix. The materials were characterized by using HRTEM, XRD and luminescence spectroscopy.
The amount of terbium crystallized into the zirconia lattice was determined by the Rietveld method. A significant
improvement of the life time was observed in the nanocomposite with respect to the pure lanthanide doped zirconia particles despite
of the very high (about 20 mol%) rare earth concentration developed
Reduction of concentration-induced luminescence quenching in Eu3+-doped nanoparticles embedded in silica
No full textIn this paper, high concentration (up to 40% of rare earth with respect to the metal oxides) Eu3+-doped ZrO2, Y2O3 and ZrO2–Y2O3
systems were prepared both as bulk material and as nanoparticles embedded in SiO2. The latter nanocomposites were obtained as a result
of a thermal treatment at 1000 C of powder samples prepared by the sol–gel method. The combination of transmission electron microscopy
(TEM), X-ray scattering (WAXS) and photoluminescence (PL) spectroscopy enabled us to obtain detailed information about morphology
and composition of the rare earth-doped nanoparticles. In particular, for nanostructured samples, high luminescence has been
observed in spite of a very high rare earth concentration in the active host
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
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