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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
High performances lead batteries with flexible titanium and carbon based curent collectors
No full textCe travail de thèse porte sur le développement d’une technologie Pb-acide de type AGM, avec une conception innovante reposant sur des collecteurs de courant constitués de feuille/grille de titane (électrode positive) et de carbone flexible (électrode négative) couverts d’une couche mince de matériaux actifs. Cette nouvelle approche permet d’augmenter la densité d’énergie et la puissance spécifique de la batterie sans pénaliser sa cyclabilité et sa durée de vie. Des paramètres tels que la résistance électrique et l’utilisation de la matière active ont été évalués avec succès en laboratoire (cyclage profond, cyclage partiel, voltampérométrie cyclique et spectroscopie d’impédance). Ceci en utilisant des cellules plomb-acide et plomb-carbone-acide de petites tailles compressées avec des séparateurs poreux en fibre de verre (AGM). L’épaisseur, la porosité et la quantité d’expandeur sont les paramètres clefs influençant l’évolution de l’utilisation de la matière active négative. Le processus réversible de stockage d’hydrogène à l’intérieur du carbone activé, utilisé comme additif principal dans la plaque négative, est en compétition avec le système Pb/PbSO4 et inhibe son fonctionnement pour une fraction massique supérieure à 9,3 %m. L’utilisation de titane recouvert de SnO2 comme collecteur de courant élimine l’apparition de la corrosion responsable de la défaillance de la cellule. Des modèles multiphysiques basés sur ces données permettront de déterminer la géométrie optimale correspondante à chaque type d’application (énergie, puissance).The aim of this work is to present and proof new concept of high performance lead-acid cells using new thin-plate electrodes. The new approach allows increasing the energy density and the specific power of the battery without a penalty for its cycle and calendar lifetime. Flexible carbon support electroplated with lead and thin surface-modified titanium mesh/foil are used as current collectors. Parameters like electric resistance and active materials utilization have been evaluated successfully in long-term laboratory tests (deep-cycling, micro-cycling, cyclic voltammetry, impedance spectroscopy) using small-scale compressed lead-acid and lead-carbon cells with absorptive glass mat (AGM) separators. The thickness, the porosity and the expander loading are the key parameters which influence the evolution of the negative active material utilization. It has been found that the process of reversible hydrogen storage within the activated carbon used as main dopant of the negative plate competes with the Pb/PbSO4 electrode inhibiting its operation at carbon loading higher than 9.3 %m. The use of SnO2 coated titanium as positive current collector eliminates completely the appearance of corrosion-related battery failure. Multiphysics modeling based on these data will allow fitting to all the battery applications (power, energy)
Gestion et Composants pour Accumulateurs au Plomb Avancés
No full textThe manuscript presents a series of works aimed to optimise the performance of the valve-regulated lead-acid battery (VRLAB) in terms of lifetime and energy and power density. The first direction includes the development of various battery management solutions based on the detailed comprehension of the lead-acid battery electrochemistry. The oxygen recombination current and the oxygen cycle efficiency were measured using a custom-made gassing rate monitoring system. The correlation between the proposed model and the measured data showed that the oxygen cycle is gas-diffusion limited process. It is demonstrated that the integration of reference electrodes for positive plate potential regulation during the charge is one of the best strategies for control over the oxygen cycle and prevention of the thermal runaway phenomenon. Further, the mechanism of the pulse charge of the lead-acid battery was studied separately on the positive and on the negative plate using electrochemical impedance spectroscopy. It is concluded that the pulse charge with a frequency close or equal to the characteristic frequency of the charge reaction leads to an electrochemical resonance corresponding to a maximum of the charge acceptance. The impact of the electrolyte on the positive plate electrochemistry is studied on small-scale “Planté” electrodes and on traction positive plates. It is found that sulphuric acid electrolytes with concentration higher than 5mol/l cause a passivation of the lead dioxide electrode. QCM electrode studies revealed that the passivation is caused by a solid-state PbO2 reduction mechanism taking place with proton insertion. The improvement of the specific power and energy of the battery was accomplished by the replacement of the traditional grids with innovative carbon honeycomb current collectors. They offer high ratio between the surface area of the grid and the quantity of the active materials as well as excellent compatibility with the AGM technology.Ce mémoire présente un recueil de travaux ciblant l’amélioration des performances des accumulateurs au plomb étanches de type AGM-VRLAB en termes de la duré de vie et de densités de puissance et d’énergie. La première direction comprend le développent de solutions de gestion (BMS) basées sur l’électrochimie détaillée de la batterie. Le courant lié à la recombinaison de l’oxygène et l’efficacité du cycle de l’oxygène ont été mesurés à l’aide d’un système de mesure du dégazage pendant le cyclage et la surcharge de l’accumulateur. La corrélation entre le modèle proposé et les données expérimentales a montré que la réaction de recombinaison est limitée par la diffusion de l’oxygène. J’ai montré que l’utilisation des électrodes de référence intégrées aux cellules d’accumulateurs est une très bonne stratégie de contrôle du cycle de l’oxygène qui permet d’avoir une prévention continue contre les risques d’emballement thermique en fin de charge. J’ai pu montrer qu’une charge galvanique pulsée effectuée à une fréquence proche de la fréquence caractéristique de la réaction de transfert de charge de l’électrode positive ou négative permettait d’obtenir une acceptance de charge optimale par un effet de « résonance électrochimique ». L’impact de l’électrolyte sur l’électrochimie du système PbO2/PbSO4/H2SO4 a été étudié sur des électrodes de type « Planté » ainsi que sur des plaques positives d’accumulateurs de type « traction ». J’ai prouvé que pour électrolytes de concentration supérieure à 5mol/L le dioxyde de plomb devient passif. Des études effectuées par méthode couplée EQCM ont révélé que la passivation est liée à la réaction de réduction de PbO2 en phase solide provenant d’une insertion des protons dans le volume des particules de PbO2. Finalement, l’amélioration de la puissance et de l’énergie de l’accumulateur au plomb a été obtenue via le remplacement des grilles traditionnelles par des collecteurs de courant de carbone en nid d’abeille possédant une grande surface géométrique
Gestion et Composants pour Accumulateurs au Plomb Avancés
No full textThe manuscript presents a series of works aimed to optimise the performance of the valve-regulated lead-acid battery (VRLAB) in terms of lifetime and energy and power density. The first direction includes the development of various battery management solutions based on the detailed comprehension of the lead-acid battery electrochemistry. The oxygen recombination current and the oxygen cycle efficiency were measured using a custom-made gassing rate monitoring system. The correlation between the proposed model and the measured data showed that the oxygen cycle is gas-diffusion limited process. It is demonstrated that the integration of reference electrodes for positive plate potential regulation during the charge is one of the best strategies for control over the oxygen cycle and prevention of the thermal runaway phenomenon. Further, the mechanism of the pulse charge of the lead-acid battery was studied separately on the positive and on the negative plate using electrochemical impedance spectroscopy. It is concluded that the pulse charge with a frequency close or equal to the characteristic frequency of the charge reaction leads to an electrochemical resonance corresponding to a maximum of the charge acceptance. The impact of the electrolyte on the positive plate electrochemistry is studied on small-scale “Planté” electrodes and on traction positive plates. It is found that sulphuric acid electrolytes with concentration higher than 5mol/l cause a passivation of the lead dioxide electrode. QCM electrode studies revealed that the passivation is caused by a solid-state PbO2 reduction mechanism taking place with proton insertion. The improvement of the specific power and energy of the battery was accomplished by the replacement of the traditional grids with innovative carbon honeycomb current collectors. They offer high ratio between the surface area of the grid and the quantity of the active materials as well as excellent compatibility with the AGM technology.Ce mémoire présente un recueil de travaux ciblant l’amélioration des performances des accumulateurs au plomb étanches de type AGM-VRLAB en termes de la duré de vie et de densités de puissance et d’énergie. La première direction comprend le développent de solutions de gestion (BMS) basées sur l’électrochimie détaillée de la batterie. Le courant lié à la recombinaison de l’oxygène et l’efficacité du cycle de l’oxygène ont été mesurés à l’aide d’un système de mesure du dégazage pendant le cyclage et la surcharge de l’accumulateur. La corrélation entre le modèle proposé et les données expérimentales a montré que la réaction de recombinaison est limitée par la diffusion de l’oxygène. J’ai montré que l’utilisation des électrodes de référence intégrées aux cellules d’accumulateurs est une très bonne stratégie de contrôle du cycle de l’oxygène qui permet d’avoir une prévention continue contre les risques d’emballement thermique en fin de charge. J’ai pu montrer qu’une charge galvanique pulsée effectuée à une fréquence proche de la fréquence caractéristique de la réaction de transfert de charge de l’électrode positive ou négative permettait d’obtenir une acceptance de charge optimale par un effet de « résonance électrochimique ». L’impact de l’électrolyte sur l’électrochimie du système PbO2/PbSO4/H2SO4 a été étudié sur des électrodes de type « Planté » ainsi que sur des plaques positives d’accumulateurs de type « traction ». J’ai prouvé que pour électrolytes de concentration supérieure à 5mol/L le dioxyde de plomb devient passif. Des études effectuées par méthode couplée EQCM ont révélé que la passivation est liée à la réaction de réduction de PbO2 en phase solide provenant d’une insertion des protons dans le volume des particules de PbO2. Finalement, l’amélioration de la puissance et de l’énergie de l’accumulateur au plomb a été obtenue via le remplacement des grilles traditionnelles par des collecteurs de courant de carbone en nid d’abeille possédant une grande surface géométrique
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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