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Contribution à l'optimalisation d'un système à biomasse fixée de traitement d'eaux résiduaires urbaines appliqué à des effluents industriels contenant des composés récalcitrants
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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
Causticizing reactions of sodium fluorosilicate (Na2SiF6) and recovery of by-products to obtain building materials.
No full textL’acide fluorosilicique (H2SiF6) est l’un des déchets rejetés par la production industrielle d'engrais phosphatés et constitue un défi environnemental (toxicité) et économique (traitement des déchets en fin de chaîne) majeur. Il est donc essentiel d'opter pour le recyclage de ce déchet par un système de traitements générant des substances utilisables dans les procédés chimiques. À ce jour, aucune solution industrielle n’est cependant mise en oeuvre pour traiter cet effluent dangereux. Récemment, un procédé en plusieurs étapes pour le traitement et la récupération de l'acide fluorosilicique a été proposé. Il consiste en une première réaction entre l'acide fluorosilicique et le chlorure de sodium qui produit de l'acide chlorhydrique et du fluorosilicate de sodium. Ce dernier réagit avec de la chaux pour former de la lessive de soude et un mélange de deux solides, du fluorure de calcium et du silicate de calcium. Les déchets solides obtenus par le procédé actuel se sont avérés réduire la température à laquelle le ciment est produit tout en réduisant simultanément les émissions de dioxyde de carbone. Cependant, il contient trop de fluorure de calcium pour être utilisé directement, car les clinkers produits présentent une teneur en fluor 50 fois supérieure à la valeur limite maximale. Dans ce présent travail, l'étape de conversion du fluorosilicate de sodium a été revisitée. La méthodologie a consisté à réaliser une étude thermodynamique du procédé aqueux, à l'aide du logiciel géochimique PHREEQC. Les calculs ont été combinés à des tests expérimentaux sur un composé modèle (Na2SiF6 pur), dans un réacteur batch, avec différentes techniques de caractérisation des produits (ICP-AES, DRX, ATG). Ce travail a abouti à la proposition d'une nouvelle étape du procédé, permettant de générer successivement deux produits solides : (i) du fluorure de calcium pur CaF2, utilisable en métallurgie et (ii) un mélange de silicate de calcium hydraté (CSH) à faible teneur en CaF2, qui constitue une matière première prometteuse pour la fabrication de matériaux de construction. Sur la base de ce procédé de transformation de Na2SiF6 en voie aqueuse à deux étapes, la suite des travaux a été dédiée à l’étude de deux voies de valorisation du produit issu de la seconde étape. L’une des pistes de valorisation consiste en une réaction de carbonatation accélérée des CSH pour produire un matériau de construction. L’objectif des travaux a été de caractériser la vitesse et le rendement de la carbonatation des poudres de CSH. L’étude a en particulier permis de montrer que les CSH carbonatent beaucoup plus vite qu’un minerai de référence, la wollastonite (CaSiO3). Cette différence a été attribuée à la présence d’eau liée dans la structure des CSH, qui favorise localement la réaction de carbonatation. Néanmoins, la présence de cette eau liée n’est pas suffisante pour se passer d’une humidification préalable de la poudre. La deuxième piste de valorisation a consisté à utiliser la poudre de CSH et la suspension de CSH + soude obtenue à l’issu de l’étape 2 du nouveau procédé en tant qu’activateur pour les systèmes à base de ciment et de laitier de haut-fourneau. Les essais effectués ont démontré que la poudre de CSH peut être incorporée en faible quantité lors du gâchage du ciment afin d’accroitre les résistances mécaniques à jeune âge. Enfin, l’étude des systèmes à base de laitier a permis de montrer que la résistance à la compression des mortiers augmente avec la quantité (CSH + NaOH). En revanche, les résistances à long terme sont altérées pour des quantités d’activateurs élevéesFluorosilicic acid (H2SiF6) is one of the wastes products released by the industrial production of phosphate fertilizers and constitutes a major environmental (toxicity) and economic (end-of-chain waste treatment) challenge. It is therefore essential to opt for recycling this waste through a treatment system generating substances that can be used in chemical processes. However, up to now, no industrial solution has been implemented to treat this dangerous effluent. Recently, a multistep process for the treatment and recovery of fluorosilicic acid has been proposed. It consists of a first reaction between fluorosilicic acid and sodium chloride which produces hydrochloric acid and sodium fluorosilicate. The latter reacts with lime to form soda and a mixture of two solids, calcium fluoride and calcium silicate. The solid waste obtained by the current process has been proven to reduce the temperature at which cement is produced while simultaneously reducing carbon dioxide emissions. However, it contains too much calcium fluoride to be used directly, because the produced clinkers have a fluorine content 50 times higher than the maximum limit value. In this present work, the sodium fluorosilicate conversion step has been revisited. The methodology consisted in carrying out a thermodynamic study of the aqueous process, using the geochemical software PHREEQC. The calculations were combined with experimental tests on a model compound (pure Na2SiF6), in a batch reactor, with different product characterization techniques (ICP-AES, XRD, TGA). This work led to the proposal of a new step of the process, that allows to successively generate two solid products: (i) pure calcium fluoride CaF2, usable in metallurgy and (ii) a mixture of hydrated calcium silicate (CSH) low in CaF2, which is a promising raw material for the manufacture of building materials. Based on this two-step aqueous process, two ways of upgrading the product from the second step were studied. The first valuation method consisted of an accelerated carbonation reaction of CSH to produce a building material. The objective of the work was to characterize the rate and efficiency of the carbonation of CSH powders. In particular, the study showed that CSH carbonate much faster than a benchmark ore, wollastonite (CaSiO3). This difference has been attributed to the presence of bound water in the structure of CSH, which locally promotes the carbonation reaction. However, the presence of this bound water is not sufficient to dispense with prior moistening of the powder. The second recovery method consisted of using the CSH powder and the CSH + soda suspension obtained at the end of step 2 of the new process as an activator for cement and blast-furnace slag based systems. The tests carried out have shown that the CSH powder can be incorporated in small quantities during the mixing of the cement in order to increase the mechanical resistance at a young age. Finally, the study of slag based systems has shown that the compressive strength of mortars increases with the amount (CSH + NaOH). In contrast, long-term resistance is impaired for high amounts of activators
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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