1,720,963 research outputs found
Structure and luminescence properties of Dy2O3 doped bismuth-borate glasses
No full textIn this work heavy bismuth-borate glasses were studied as host matrices of Dy2O3 rare earth, for potential application as scintillator materials in high energy physics experiments and in general radiation detection systems. Glass matrices were prepared from 20BaO-xBi2O3-(80-x)B2O3 (x = 20, 30, 40 mol%) ternary systems and synthesized by the melt-quenching method at different temperatures in order to obtain high density and high transparency in the UV/Vis range. Particularly, the glass manifesting the higher transparency and with sufficiently high density was doped with Dy2O3 (2.5 and 5 mol%) in order to induce the luminescence characteristics. The effects of Bi2O3 and Dy2O3 on density, thermal behaviour, transmission as well as luminescence properties under UV excitation, were investigated. The experimental results show that the synthesized glasses can be considered promising candidate materials as dense scintillators, due to the Dy3 + centres emission
E-LCA of Two Microwave Absorbers Obtained from Slag of Copper Primary Production
No full textPurpose: This research investigates the environmental performance of two products obtained using slag derived from copper primary production (copper slag, CS). The first is a tile produced as a traditional stoneware ceramic plate (CS tile) and the second product is a glass–ceramic sample obtained by melt quenching method (CS bulk sample). The products are intended for use in industrial plants as auxiliary heating elements aimed at absorbing microwave. Methods: The environmental assessment was carried out using LCA methodology, and the obtained outcomes were compared to the results calculated for a traditional tile containing silicon carbide (SiC tile). Results: The analyses show that the innovative products have an environmental load of 74% for the CS tile and 54% for the CS bulk sample lower than the environmental impact calculated for the traditional SiC-based material tile. The latter presents a high environmental load due to the incidence on the total impact of the raw materials production. In fact, LCA analysis proves that copper slag production has an impact of 96% lower with respect to the SiC production. Conclusions: This study identifies a possible waste reduction strategy in accordance with the European end-of-waste criteria, but these results should be supported by a site analysis in order to provide an appropriate context for decision making
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
Fabrication of new glass–ceramic materials from float glass and slag waste by modulation of the cooling rate
No full textThis study explores an alternative route to recycle waste materials from float glass (FG, 30 wt%) and copper slag (CS, 70 wt%). The FG is a silica-rich glass, while the CS is rich in Fe and Zn. They were melted at 1550 °C to obtain a homogeneous glass that was then re-melted and cooled at 10 (low) and 500 (high) °C/h to produce a glass–ceramic. X-Ray Powder Diffraction, Scanning Electron Microscope and Electron microprobe characterisations show that both products contain spinel crystals within an abundant glassy matrix. At 500 °C/h, unexpectedly, the glass–ceramic contains a higher content (30.0 ± 5.5 area%) of tiny and long dendrites (spinifex) of spinels than at 10 °C/h (13.7 ± 2.2 area%); at the low rate, spinels are skeletal (large crystals) to dendritic (tiny and short) and larger than at high rate. This unveils that the estimated crystal growth rate (10−7 cm/s) is higher at 500 °C/h. The crystal-chemistry of spinels results in more enriched Fe and Zn at 10 °C/h than at the high rate. This approach is promising for various applications or for concentrating valuable transition metals (Fe, Zn) as a function of cooling rate and type and quantity of starting waste materials; also, it avoids treatments with additives or fluxing agents and it provides, thanks to the dielectric properties shown, a strong potential for industrial use as a microwave absorber
Lanthanum glass infiltrated alumina/alumina composites for dental prosthetic applications
Full text linkLanthanum glass frits suitable for infiltration in pre-sintered alumina were developed in order to obtain innovative alumina–glass composites, which are promising materials for all-ceramic dental prosthetic restorations, such as single crowns and fixed partial dentures. Glass compositions belonging to the lanthanum-silicate-borate system were synthesized in order to reinforce and give an improved esthetic appearance to the pre-sintered Al2O3.
Fifteen formulations, defined by using a mixture design approach, were melted and quenched in water at room temperature in order to obtain the frits. Those exhibiting the lower melting temperatures were tested for infiltration into Al2O3 to obtain Al2O3/glass composites. The frits and the composites were characterized by X-Ray diffraction, differential thermal analyses, hot stage microscopy, colorimetry (Hunter color scale) and scanning electron microscopy. The mechanical properties of the composites, in terms of flexure strength, were evaluated using a three-point bending tests
V K-Edge XANES Full Multiple Scattering Study of V-Bearing Phosphate Glasses
No full textIn this contribution we analyzed the Vanadium speciation and structural local environment in two V-bearing Na-phosphate glasses by means of V K-edge X-ray Absorption Spectroscopy. The two glasses have starting molar proportions Na2O:V2O5:P2O5 equal to 45:10:45 (NaPV10) and 10:80:10 (NaPV80). Accurate analysis of the pre-edge peak of the two glasses allowed to determine the presence of[4]V5+ and[5]V5+ in NaPV80 and of[5]V4+ and[6]V4+ in NaPV10. EXAFS derived V–O distances for the two glasses are in agreement with literature data for the above mentioned V species. The determined V local geometries and the EXAFS derived bond distances have been used to build four structural models for[4]V5+,[5]V5+,[5]V4+ and[6]V4+ in the studied glasses; these models have been in turn used to calculate theoretical XANES spectra by means of the MXAN code. The partial contributions of each V species have been summed in order to fit the experimental XANES spectra of the two glasses. Iterative fitting of the structural parameters of each structural model resulted in a good agreement between experimental and theoretical XANES data. The analysis strategy used in the present work allowed to gain information of V speciation and on the structural local environment of the[4]V5+,[5]V5+,[5]V4+ and[6]V4+ species present in the analyzed glasses. Combined use of different spectral regions and data analysis routines allowed to successfully simulate XANES spectra and to gain an in depth knowledge of V local environment even in a complex system like amorphous glass containing different V species
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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