1,720,960 research outputs found
La1-xSrxMnO3-δ, La1-xSrxCo1-yFeyO3-δ, Ba1-xSrxCo1-yFeyO3-δ; the Huey, Dewy and Louie of Solid Oxide Fuel Cell cathode materials
No full textMODELLAZIONE E SIMULAZIONE DI IMPEDENZA IN CELLE A COMBUSTIBILE AD OSSIDI SOLIDI
No full textIn questo studio si presenta un modello per la simulazione di spettri di impedenza di elettrodi compositi per celle a combustibile ad ossido solido. Il modello è applicato a catodi compositi porosi di LSM e YSZ che presentano una porosità distribuita lungo lo spessore [1]. La modellazione si basa sull'applicazione di bilanci di massa e carica in condizioni dinamiche, considerando una cinetica elettrochimica tipo Butler-Volmer, il trasporto di carica nelle fasi conduttive e convezione e diffusione (ordinaria e di Knudsen) in fase gas. Il dominio è rappresentato come un continuo, caratterizzato da proprietà effettive di trasporto e reazione correlate alle proprietà microstrutturali attraverso la teoria di percolazione [2]. La simulazione di impedenza è operata applicando sovratensioni sinusoidali a diversa frequenza risolvendo le equazioni nel dominio tempo ottenendo così la densità di corrente.
Gli spettri simulati sono comparati con spettri sperimentali ottenuti per diversi spessori (5-85m) e temperature (650-850°C) [1]. Dal confronto, di cui un esempio è riportato in figura, si valutano il parametro cinetico della reazione elettrochimica ed una capacità macroscopica del doppio strato elettrico all'interfaccia LSM-YSZ, entrambi costanti con lo spessore dell'elettrodo. Mentre il primo presenta un andamento tipo Arrhenius con la temperatura, la capacità del doppio strato, relativa all'arco a bassa frequenza (da 3.5 a 250Hz per temperature comprese tra 650°C e 850°C), non presenta una chiara relazione con la temperatura, suggerendo che essa possa incorporare più fenomeni aventi comportamenti diversi
Electrochemical behaviour of La0.8Sr0.2MnO3-δ-infiltrated Ba0.5Sr0.5Co0.8Fe0.2O3-δ under anodic overpotential
No full textA Boron‐Doped Diamond Anode for the Electrochemical Removal of Parabens in Low‐Conductive Solution: From a Conventional Flow Cell to a Solid Polymer Electrolyte System
No full textSolution conductivity plays a fundamental role for the employment of electrochemical advanced oxidation processes (EAOPs) and in the determination of their energy consumption. In this paper, a conventional flow cell based on BDD anode, which requires the addition of supporting electrolyte, is compared with a cell setup based on solid polymer electrolyte (SPE). The new cell configuration avoids the addition of salt to increase solution conductivity. The two systems performance are compared for treatment of different solutions containing methylparaben, ethylparaben and propylparaben. Both systems are able to remove all the three parabens, but the SPE- system provided a better performance, with a maximum COD removal of 91% and energy consumption of 16.25 kWh m-3 while the conventional one remove a maximum of 81% consuming 10.92 kWh m-3. The influence of parameters such as current density, flow conditions and supporting electrolyte concentration was analyzed, and results confirming that SPE-system is a promising system to treat low conductive solutions polluted by parabens
Morphological and electrochemical modeling of SOFC composite cathodes with distributed porosity
No full textA steady-state mathematical model of charge and mass transport and electrochemical reaction in porous composite cathodes for solid oxide fuel cell application is presented. The model, based on local mass and charge balances, describes the domain as a continuum, characterizing kinetics as well as mass and charge transport using effective properties, related to cathode microstructure and material properties by percolation theory. The distribution of morphological properties along the electrode thickness, as experimentally observed on scanning electron microscope images of the samples investigated, is taken into account. This feature allows the model to reproduce the dependence of electrode thickness and oxygen partial pressure on polarization resistance in the range 600-850. °C. It is found that for cathodes made of strontium-doped lanthanum manganite (LSM) and yttria-stabilized zirconia (YSZ), the exchange current, which represents the kinetic constant of the oxygen reduction reaction, follows an Arrhenius behavior with respect to the temperature and it is dependent on the square root of the oxygen partial pressure
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
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