1,720,963 research outputs found
Numerical Groundwater Model to Assess the Fate of Nitrates in the Coastal Aquifer of Arborea (Sardinia, Italy)
Get PDFThe Arborea plain in Sardinia (Italy) is classified as a nitrate vulnerable zone (NVZ). In the present study, the individual work steps that are necessary to progress from the existing 3D hydrogeological model to a 3D numerical groundwater model using the interactive finite-element simulation system FEFLOW 7.4 are shown. The results of the transient flow model highlight the influence of the drainage network on the overall groundwater management: the total water volume drained by the ditches accounted for approximately 58% of the annual outflow volume. The numerical transport simulations conducted from 2012 to 2020 using hypothetical field-based nitrate input scenarios globally underestimated the high concentrations that were observed in the NVZ. However, as observed in the field, the computed nitrate concentrations in December 2020 still varied strongly in space, from several mg L−1 to several hundreds of mg L−1. The origin of these remaining local hotspots is not yet known. The modeling of rainfall fluctuations under the influence of climate change revealed a general long-term decline in the groundwater level of several tens of centimeters in the long term and, in conjunction with a zero-nitrate scenario, led to a significant decrease in nitrate pollution. Although hotspots were attenuated, the concentrations at several monitoring wells still exceeded the limit value of 50 mg L−1
Geochemical modeling of isotopic fractionation : implementation in reactive transport code Hytec and environmental applications
No full textL’éventail des processus géochimiques modélisés par les codes de transport réactif a vocation à s’élargir de plus en plus et permet à ces codes de traiter des problématiques de nature différente (stockage de déchets radioactifs, exploitation minière, pollutions, etc.). Cette dernière décennie a vu l’essor de la modélisation des fractionnements isotopiques par les codes de transport réactif. Cette fonctionnalité permet d’ajouter au suivi de réactions géochimiques leur impact sur la composition isotopique des espèces chimiques. Néanmoins, l’hypothèse classiquement utilisée lors de ces modélisations repose sur l’existence d’un isotope majoritaire au sein des isotopes de l’élément d’intérêt. Ces travaux menés à MINES ParisTech contiennent les développements mathématiques réalisés afin de vérifier que la méthodologie reste valide pour un ensemble d’hypothèses moins contraignantes, vérifiées dans la majorité des systèmes naturels. Plusieurs applications ont été réalisées avec Hytec, code de transport réactif développé à MINES ParisTech. La comparaison de résultats dans le cadre d’un benchmark a permis de valider l’emploi de cette méthodologie avec Hytec. Ensuite, un modèle de dégradation et de migration de solvants chlorés dans un système aquifère-aquitard a été mis au point et permet de simuler les signatures isotopiques du carbone et du chlore au sein de ces composés. Les résultats ont montré que le suivi de la composition isotopique des solvants dans l’aquifère peut renseigner sur leur potentielle dégradation dans l’aquitard. Par ailleurs, ces travaux montrent l’importance de la configuration du modèle numérique utilisé ainsi que le potentiel offert par la modélisation des fractionnements isotopiques combinée à la polyvalence d’Hytec.The scope of geochemical processes modeled by reactive transport codes is widening and allows these codes to address different type of problematics (radioactive waste storage, mining, contamination, etc.). The last decade saw the rise of the isotopic fractionation modeling with reactive transport codes. This functionality allows tracing geochemical processes in amore precise way, using geochemical reactions and the isotopic fractionation they induce. However, the traditionally used hypothesis to model isotopic fractionation relies on the existence of a major isotope for the studied element. This work, prepared at MINES ParisTech, contains mathematical developments to support the methodology a set of less constraining hypotheses, easily verified in the majority of natural systems. Several application cases were performed with Hytec, are active transport code developed at MINES ParisTech. The comparison of isotopic fractionation simulation results in a benchmark study acts as a validation of this methodology with Hytec.Then, a model of degradation and migration of chlorinated solvents in an aquifer-aquitard system was built step by step. This model allows simulating the isotopic signatures of carbon and chlorine in these components. Results showed that data extracted from the aquifer brings information about the reactivity of the aquitard regarding the solvent degradation. Furthermore, results also highlight the importance of the choice of model parameters and the potential of isotopic fractionation modeling combined to theversatility of Hytec
Modélisation géochimique des fractionnements isotopiques avec le code de transport réactif Hytec et applications environnementales
No full textThe scope of geochemical processes modeled by reactive transport codes is widening and allows these codes to address different type of problematics (radioactive waste storage, mining, contamination, etc.). The last decade saw the rise of the isotopic fractionation modeling with reactive transport codes. This functionality allows tracing geochemical processes in amore precise way, using geochemical reactions and the isotopic fractionation they induce. However, the traditionally used hypothesis to model isotopic fractionation relies on the existence of a major isotope for the studied element. This work, prepared at MINES ParisTech, contains mathematical developments to support the methodology a set of less constraining hypotheses, easily verified in the majority of natural systems. Several application cases were performed with Hytec, are active transport code developed at MINES ParisTech. The comparison of isotopic fractionation simulation results in a benchmark study acts as a validation of this methodology with Hytec.Then, a model of degradation and migration of chlorinated solvents in an aquifer-aquitard system was built step by step. This model allows simulating the isotopic signatures of carbon and chlorine in these components. Results showed that data extracted from the aquifer brings information about the reactivity of the aquitard regarding the solvent degradation. Furthermore, results also highlight the importance of the choice of model parameters and the potential of isotopic fractionation modeling combined to theversatility of Hytec.L’éventail des processus géochimiques modélisés par les codes de transport réactif a vocation à s’élargir de plus en plus et permet à ces codes de traiter des problématiques de nature différente (stockage de déchets radioactifs, exploitation minière, pollutions, etc.). Cette dernière décennie a vu l’essor de la modélisation des fractionnements isotopiques par les codes de transport réactif. Cette fonctionnalité permet d’ajouter au suivi de réactions géochimiques leur impact sur la composition isotopique des espèces chimiques. Néanmoins, l’hypothèse classiquement utilisée lors de ces modélisations repose sur l’existence d’un isotope majoritaire au sein des isotopes de l’élément d’intérêt. Ces travaux menés à MINES ParisTech contiennent les développements mathématiques réalisés afin de vérifier que la méthodologie reste valide pour un ensemble d’hypothèses moins contraignantes, vérifiées dans la majorité des systèmes naturels. Plusieurs applications ont été réalisées avec Hytec, code de transport réactif développé à MINES ParisTech. La comparaison de résultats dans le cadre d’un benchmark a permis de valider l’emploi de cette méthodologie avec Hytec. Ensuite, un modèle de dégradation et de migration de solvants chlorés dans un système aquifère-aquitard a été mis au point et permet de simuler les signatures isotopiques du carbone et du chlore au sein de ces composés. Les résultats ont montré que le suivi de la composition isotopique des solvants dans l’aquifère peut renseigner sur leur potentielle dégradation dans l’aquitard. Par ailleurs, ces travaux montrent l’importance de la configuration du modèle numérique utilisé ainsi que le potentiel offert par la modélisation des fractionnements isotopiques combinée à la polyvalence d’Hytec
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
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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