1,720,958 research outputs found
Dramatic mitigation of capacity decay and volume variation in vanadium redox flow batteries through modified preparation of electrolytes
Full text linkElectrolyte imbalance caused by the undesired vanadium-ions cross-over and water transport through the membrane is one of the main critical issues of vanadium redox flow batteries, leading to battery capacity loss and electrolytes volume variation. In this work, the evolution of discharged capacity and electrolyte volume variation were firstly investigated adopting commercial electrolyte for hundreds of charge-discharge cycles in vanadium redox flow batteries employing different membranes, varying thickness and equivalent weight. Subsequently, with the support of a 1D physics-based model, the origin of the main phenomena regulating capacity decay and volume variation has been identified and different modifications in the preparation of electrolytes have been proposed. Electrolytes characterized by an equal proton concentration between the two tanks at the beginning of cycling operation turned out to limit capacity decay, while increasing electrolyte proton concentration was effective also in the mitigation of volume variation. The most promising electrolyte preparation combined the effect of high proton concentration and null osmotic pressure gradient between the two tanks: compared to commercial electrolyte this preparation reduced the capacity decay from 47.7% to 20.9%, increased the coulombic efficiency from 96.2% to 98.9% and the energy one from 79.9% to 83.4%, and also implied a negligible volume variation during cycles. The effectiveness of this electrolyte preparation has been verified with different membranes, increasing the range of validity of the results, that could be thus applied in a real system regardless of the adopted membrane
A comprehensive experimental and modelling approach for the evaluation of cross-over fluxes in Vanadium Redox Flow Battery
Full text linkVanadium cross-over is a critical issue in Vanadium Redox Flow Battery consisting in a complex interplay of different mechanisms of which a complete comprehension has not been reached yet. Due to the complexity of the involved phenomena, several models have been developed in literature to investigate vanadium cross-over. However, the conventional approaches for model calibration present a limited set of experiments for the validation preventing a complete understanding of cross-over phenomena. In this work a new and comprehensive approach is proposed. It is based on charge-discharge cycles with fixed exchanged capacity, able to isolate the capacity loss induced by cross-over fluxes, and on the measure of the self-discharge of the single electrolyte solutions by exploiting through-plate reference electrodes. Moreover, a 1D physically-based model of the operation of the battery is developed and calibrated on the data of electrolyte imbalance during charge-discharge cycles at three different current densities to obtain model parameters able to accurately describe the involved physics in different operating conditions. The model is then exploited to investigate the main vanadium transport mechanisms through the membrane and to evaluate the influence of the current density on the vanadium crossover fluxes, net vanadium transport and self-discharge rate of the electrolyte
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
Efficacy of 190 mcg fluocinolone acetonide intravitreal implant: microperimetry and OCT real-life data
Full text linkObjective: Fluocinolone acetonide is a valid alternative treatment for patients with chronic diabetic macular edema (DME) with poor response to anti-vascular endothelial growth factor (VEGF) therapy. The purpose of this study is to report the efficacy and safety of ILUVIEN® implant in pseudophakic eyes with persistent DME. Patients and methods: This is a single-centre pilot-study of 8 patients with persistent DME treated with the ILUVIEN implant, despite previous anti-vascular endothelial growth factor and/or steroid treatment. Best-corrected visual acuity (BCVA), optical coherence tomography (OCT) central retinal thickness, intraocular pressure (IOP) and microperimetric data were evaluated at baseline and month 1, 3 and 6 post treatment. Results: All data are presented as mean and standard deviation. At baseline, 1, 3 and 6 months, we had BCVA of 0.26±0.22, 0.38±0.27, 0.48±0.27 and 0.46±0.24; IOP of 15.00±2.67, 15.50±3.16, 14.88±2.42 and 15.63±2.67 mmHg; macular thickness of 652±231, 487±278, 475±287 and 413±211 μm; macular sensitivity of 6.83±4.20, 6.13±3.72, 7.68±3.40 and 7.71±3.33 dB; bivariate contour elliptic area (BCEA) 95.4% 3.8±3.42, 6.06±10.06, 3.05±2.46 and 2.59±2.19°2. Conclusions: According to the results of our study, fluocinolone acetonide (FAc) is a valid therapy option despite some limitations. It has been evidenced that FAc is more effective in patients with mild central macular thickening, while in those with modest to severe central macular thickness (CMT), different therapy strategies should be considered
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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