1,720,966 research outputs found
Li/ Li1+xV3O8 secondary batteries. III°. Further characterization of the mechanism of Li+ insertion and of the cycling behaviour.
No full textThe reduction mechanism of the bronze Li1.2V3O8 in nonaqueous Li cells has been elucidated. Upon Li+ insertion, a solid solution is formed with an upper composition of Li3V3O8. Within this composition range, Li+ progressively fills the tetrahedral sites available in the unit cell. Four such sites are supposed to be filled at the upper composition limit. Beyond this, a new phase is nucleated to accommodate excess Li+, this resulting in a constant cell's OCV. Li+ insertions not greater than 3.0 eq/mol are reversible, as shown by the cycling behavior and the x-ray patterns. Owing to the outstanding structure stability and to the high speed of Li+ diffusion in Li1.2V3O8, extended cycling at high rates is achievable with cells based on this bronze. 445 cycles at discharge rates variable in the range of 2-10 mA/cm 2 have been obtained
Richargeable compact Li cells with Li1+xV3O8 , LixCr0.9V0.1S2 and LixMnO2 cathodes and ether based electrolytes
No full textLi/ Li1+xV3O8 batteries. V°. Comparison with other secondary cells and influence of micro- and macro-structural alteration on the cathode performance.
No full textLi/Li1+xV3O8 cells have been compared with analogous cells based on TiS2, V6O13 and β-Na0.17V2O5 cathode. The results have demonstrated thet this bronze can be ranked among the most promising cathode materials for high rate rechargeable Li cells. This has encouraged attempts aimed at improving the electrochemical performance of the bronze through substitution of V witch such transition metals as Cr and Mo, and substitution of Li with Na. None of these substituted materials performed better thet the parent compound. On the other hand, controlled H2O Intercalation within the layers resulted in an increased interlayer distance and in higher capacities. A remarkable improvement in cell performance at high rate (10 mA/Cm2) was obtained with a new technique of cathode preparation
Li/ Li1+xV3O8 secondary batteries. IV°. Evaluation of factors affecting the performance of test cells.
No full textWith the aim of optimizing the performance of Li/Li1+xV3O8 cells, several aspects of cathode preparation have been examined. The influence of synthesis technique nature and amount of conductive additive, compacting pressure, cathode loading, and particle size, has been investigated. Furthermore, the role played by the solutions on cathode efficiency has been outlined. The formulations which perform best are based on small-sized particles blended with about 20% acetylene black and compacted at very high pressures to improve the contact between particles. Such cathodes can provide high capacities at high rate and good cycling efficiencies. The Kinetic loss of capacity, observed during the first few cycles, may be alleviated by choosing solutions with high fluidity and conductivity
Small particle-size lihium-vanadium oxide: an improved cathode material for high rate rechargeable Li batteries.
No full textA Li rechargeable battery with a cathode based on small particle-size Li1+xV3O8 has a high cathode utilization and a long cycle life at high discharge rates. It is shown that decreasing the particle diameter from 10 to 1 μm decreases 10 times the current density really applied to the cathode. This is particularly beneficial by limiting the cathodic capacity losses and thereby increasing the life to several hundreds of cycles. The high rate capability afforded by the use of small particles results in good power energy characteristics
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
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
- …
