1,721,026 research outputs found
Combination of chemical separation and data treatment for 55Fe, 63Ni, 99Tc, 137Cs and 90Sr/90Y activity determination in radioactive waste by liquid scintillation
No full textRoutine operations involving nuclear reactors and decommissioning activities require numerous chemical analyses. Most of the procedures developed for these chemical characterisations involve several separation steps to prepare the sample for measurement. Chemical treatments are time- and manpower-consuming, labour intensive and produce significant quantities of waste. In order to address this problem, we evaluate a data treatment procedure (multivariate calibration—PLS), which we propose as a substitute to some of these separation steps. Mixtures of beta emitter radionuclides of increasing complexity (90Sr/90Y—99Tc, 90Sr/90Y—99Tc—63Ni—137Cs and 90Sr/90Y—99Tc—63Ni—137Cs—55Fe) have been measured by liquid scintillation (LS) counting. The influences of quenching and level of activity was evaluated and the activity of unknown samples determined. Despite the spectra overlapping and low resolution of LS, relative errors in the activities quantification of unknown samples inside the range covered by the calibration matrix are lower than 15% whatever the number of radionuclides included in the solution was
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
aging in spin glasses in three, four and infinite dimensions
No full text© 2003 IOP Publishing Ltd. We are indebted with L.A. Fernández and J.J. Ruiz-Lorenzo for discussions. We thank the Spanish MCyT for financial support through research contracts FPA2001-1813, FPA2000-0956, BFM2001-0718 and PB98-0842. V.M.M. is a Ramón y Cajal research fellow (MCyT) and S.J. is a DGA fellow.The SUE machine is used to extend by a factor of 1000 the time-scale of previous studies of the aging, out-of-equilibrium dynamics of the Edwards-Anderson model with binary couplings, on large lattices (L = 60). The correlation function, C(t+t_(w), t_(w)), t_(w) being the time elapsed under a quench from high-temperature, follows nicely a slightly-modified power law for t > t_(w). Very tiny (logarithmic), yet clearly detectable deviations from the full-aging t/t_(w) scaling can be observed. Furthermore, the t < t_(w) data shows clear indications of the presence of more than one time-sector in the aging dynamics. Similar results are found in four-dimensions, but a rather different behaviour is obtained in the infinite-dimensional z = 6 Viana-Bray model. Most surprisingly, our results in infinite dimensions seem incompatible with dynamical ultrametricity. A detailed study of the link correlation function is presented, suggesting that its aging-properties are the same as for the spin correlation-function.Spanish MCyTRamón y Cajal research fellow (MCyT)DGA fellowDepto. de Física TeóricaFac. de Ciencias FísicasTRUEpu
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
Co-electrolysis of steam and carbon dioxide in large area solid oxide cells based on infiltrated mesoporous oxygen electrodes
No full textInfiltration of nano-catalysts in ionic-conductive backbones is receiving increasing attention to fabricate highly performing electrodes for Solid Oxide Cells application. In particular, nanostructured, high surface area scaffolds based on ceria and infiltrated with functional perovskites have already proved their excellent catalytic activity as oxygen electrodes. A major challenge for this type of nanocomposites is keeping the enhanced performance when up-scaling to large area cells and during long term operation. In this work, Ce0.8Gd0.2O1.9-La0.6Sr0.4Co0.2Fe0.8O3-δ infiltrated mesoporous oxygen electrodes were fabricated and tested in state-of-the-art 25 cm2 area fuel electrode supported solid oxide electrolysis cells. Injected currents as high as 11.2 A (0.7 A cm−2) at 1.3 V were measured in co-electrolysis mode at 750 °C showing improved performances with respect to button cell counterparts. Stability tests at injected currents of 8 A (0.5 A cm−2) for more than 600 h yielded a degradation rate of 126 mV kh−1 mainly related to the metallic nickel depletion approaching the fuel electrode-electrolyte interface, proving the stability of the oxygen electrode under highly demanding operating conditions. The excellent results presented here anticipate the relevance of nanostructured infiltrated electrodes for the next generation of enhanced Solid Oxide Cells
Solid oxide cell electrode nanocomposites fabricated by inkjet printing infiltration of ceria scaffolds
Full text linkThe enhancement of solid oxide cell (SOC) oxygen electrode performance through the generation of nanocomposite electrodes via infiltration using wet-chemistry processes has been widely studied in recent years. An efficient oxygen electrode consists of a porous backbone and an active catalyst, which should provide ionic conductivity, high catalytic activity and electronic conductivity. Inkjet printing is a versatile additive manufacturing technique, which can be used for reliable and homogeneous functionalization of SOC electrodes via infiltration for either small-or large-area devices. In this study, we implemented the utilization of an inkjet printer for the automatic functionalization of different gadolinium-doped ceria scaffolds, via infiltration with ethanol:water-based La1−xSrxCo1−yFeyO3−δ (LSCF) ink. Scaffolds based on commercial and mesoporous Gd-doped ceria (CGO) powders were used to demonstrate the versatility of inkjet printing as an infiltration technique. Using yttrium-stabilized zirconia (YSZ) commercial electrolytes, symmetrical LSCF/LSCF– CGO/YSZ/LSCF–CGO/LSCF cells were fabricated via infiltration and characterized by SEM-EDX, XRD and EIS. Microstructural analysis demonstrated the feasibility and reproducibility of the process. Electrochemical characterization lead to an ASR value of ≈1.2 Ω cm2 at 750◦C, in the case of nanosized rare earth-doped ceria scaffolds, with the electrode contributing ≈0.18 Ω cm2. These results demonstrate the feasibility of inkjet printing as an infiltration technique for SOC fabrication
Hybrid-3D printing of symmetric solid oxide cells by inkjet printing and robocasting
No full textWhen processed using state-of-the-art techniques, Solid Oxide Cells (SOCs) fabrication (e.g. tape casting) requires many steps. Recently, Additive Manufacturing (AM) techniques have gained popularity to complement or substitute SOCs fabrication processes. AM allows the combination of different techniques to produce complete cells, minimizing material waste while reducing the number of fabrication steps and improving their reliability. 3D printed symmetrical cells with composition LSM-YSZ/YSZ/LSM-YSZ were prepared by a robocasting and inkjet printing hybrid technology, followed by a co-sintering step. Printability tests and rheological characterization have been made on the robocast LSM-YSZ slurries for the electrodes and on the water-based YSZ ink for inkjet printing to produce the dense electrolyte. This study presents the fabrication of complete cells with self-standing robocast electrodes combined with inkjet printed electrolytes and their co-sintering in one step. After co-sintering, the symmetrical cells were characterized by SEM-EDX, XRD and EIS. The microstructural analysis confirmed the feasibility of the process and its reproducibility. The electrochemical characterization led to an ASR value of ≈ 2.1 Ω cm2 at 750 °C. These remarkable results demonstrate the potential of robocasting and inkjet printing for the fabrication of multi-material energy devices
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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