1,720,979 research outputs found
Fitting of the Voltage-Li+ insertion curve of LiFePO4
No full textFitting of the voltage vs. insertion curves of the LiFePO4 electrode was based on theoretical expressions describing the Li+ diffusive process in a solid medium. The noninteracting gas model for the chemical potential of ions distributed in a solid matrix was taken into account, and the diffusion coefficient and the energy activation for the diffusion process were accordingly calculated. The polari- zation curves at various discharge stages were theoretically obtained, and a good agreement was found with the experimental data at all discharge rates. A mathematical relation describing the trend of the diffusion resistance vs. insertion degree was also developed
Effect of milling and doping on decomposition of NH3BH3 complex
No full textIn this work we considered three different samples: borane ammonia (BA) complex as received, ball milled BA and, finally, BA subjected to ball milling and doped with 1 mol% of hydrogen hexachloroplatinate hydrate. Their crystalline structure was described by XRD and morphology was investigated using SEM and EDS techniques. In order to describe samples behaviour in hydrogen release we plotted TGA curves and thermal decomposition tests were realized. We verified that ball milling increases the BA cristallinity and changes its morphology enhancing the amount of evolved gas. Both the milled and the doped samples show an increase of the pre-exponential factor in the Arrhenius equation. The activation energy remains almost unchanged for the doped sample and it increases for the milled one. As result it was found that the decomposition of 1 mol% doped sample could be provided by waste heat coming from a PEM fuel cell
Anisotropy and non-universality in kinetic roughening
No full textWe introduce a new model for kinetic roughening which exhibits a non-universal behavior for the roughness exponent, in agreement with many experimental findings. The model, inspired by the chemical etching processes, takes explicitly into account the effect of anisotropy, say the dependence of the growth rule on the local environment conditions. The interplay between anisotropy and non-universality is investigated as well as the relationship with the known universality classes
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
Electrochemical Characterization of a Composite Polymer Electrolyte with Improved Lithium Metal Electrode Interfacial Properties
No full textIn the development of rechargeable lithium polymer batteries it is of paramount importance to control the passivation phenomena occurring at the lithium electrode interface. It is well estabilished that the type and the growth of the lithium passivation layer is unpredictably influenced by the presence of liquid components and/or impurities in the electrolyte. Therefore, one approach to improve the stability of the lithium interface is the use of liquid-free, highly pure electrolytes. The electrochemical properties of a composite polymer electrolyte obtained by hot pressing a mixture of polyethylene oxide (PEO), a lithium salt (lithium tetrafluoroborate, LiBF(4)) and a powdered ceramic additive (gamma-LiAlO(2)), will be presented and discussed. The electrochemical characterization included the determination of the ionic conductivity, the anodic break-down voltage and, most importantly, the stability of the lithium metal electrode interface and the lithium stripping-plating process efficiency. The main feature of this dry, true solid-state electrolyte is a very good compatibility with the lithium metal electrode, demonstrated by a very high lithium cycling efficiency, which approaches a value of 99%
Synthesis and characterization of amorphous hydrated FePO4 and its electrode performance in lithium batteries
No full textAmorphous iron(III) phosphate was synthesized by spontaneous precipitation from equimolar aqueous solutions of Fe(NH4)(2)(SO4)(2).6H(2)O and NH4H2PO4, using hydrogen peroxide as the oxidizing agent. The material was characterized by chemical analysis, thermogravimetrical analysis, differential thermoanalysis, X-ray powder diffraction, and scanning electron microscopy. The material was tested as a cathode in nonaqueous lithium cells. Galvanostatic intermittent titration technique was used to follow the lithium intercalation process. The effect of firing on the specific capacity was also tested. The material fired at 400degreesC showed the best electrochemical performance, delivering about 0.108 Ah g(-1) when cycled at C/10 rate. The capacity fade upon cycling was found as low as 0.075% per cycle. (C) 2002 The Electrochemical Society
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
- …
