1,720,965 research outputs found
Identifying parameters of a sorption model alternative to the Kd approach : field applicability of values obtained in controlled conditions
No full textLa sorption joue un rôle majeur dans le devenir des radionucléides dans les sols. Elle contrôle leur mobilité, leur biodisponibilité et leur impact radiologique. En modélisation opérationnelle, la sorption est généralement décrite par le modèle Kd qui suppose qu'elle est linéaire, instantanée et réversible. Pourtant, il ne permet pas de bien décrire la sorption dans des conditions de non-équilibre ou de non-linéarité. Des approches alternatives ont été proposées pour améliorer cette modélisation. Cependant, ces modèles n’ont pas été complètement validés dans des conditions de sorption du Cs au laboratoire ou in situ. Expérimentalement, la sorption peut être étudiée à travers plusieurs dispositifs de différents degrés de complexité pouvant induire une dépendance des paramètres de sorption du dispositif choisi. Cependant, ces effets du dispositif restent peu identifiés. Les objectifs de ce travail sont de valider un modèle de sorption à deux sites cinétiques et à l’équilibre (EK) et d’étudier son applicabilité dans des conditions expérimentales et sur le terrain. Les résultats obtenus ont suggéré que le non-équilibre permet d’améliorer la modélisation de la migration du Cs in situ mais que les paramètres de sorption sont difficilement identifiables. Au laboratoire, les expériences en réacteurs ouverts ont démontré que la rétention du Cs se fait dans des conditions de non-équilibre et de non-linéarité et que le modèle EK permet de bien la reproduire. La comparaison des trois échelles a suggéré une influence du dispositif expérimental sur les paramètres EK principalement en milieux poreux structurés où des processus non chimiques peuvent influencer la migration du CsSorption plays a major role in the prediction of radionuclides migration in soils. It controls their mobility in the soil, their bioavailability, their radiological impact. In assessment level models, sorption is usually described by the Kd model that assumes that sorption is linear, instantaneous and reversible. However, this model fails to describe sorption reactions in non-equilibrium or nonlinear conditions. Alternative Equilibrium-Kinetic (EK) models have been suggested to improve sorption modelling. However, these models have not been fully validated in laboratory and field sorption conditions for cesium. Experimentally, sorption can be studied using multiple designs with varying levels of complexity and representativity which may lead to a dependence of the sorption parameters to the chosen design. However, these effects of the experimental scale on sorption parameters are not fully understood. This thesis aimed at validating an alternative nonlinear equilibrium-Kinetic (EK) model for cesium sorption and studying its applicability under different experimental and field conditions. The obtained results suggested that non-equilibrium sorption improves the description of 137Cs migration in situ. However, sorption parameters are not easily identifiable in these conditions. In the laboratory, open flow reactor experiments showed that Cs sorption takes place in non-equilibrium or nonlinear conditions and that EK model can successfully reproduce these reactions. The comparison between the three experimental devices suggested that EK parameters can be influenced by the experimental level especially in porous media where non chemical processes can impact Cs migratio
Extraction des paramètres de sorption dans un référentiel de modélisation alternatif au Kd : applicabilité des grandeurs obtenues en milieux contrôlés à des situations réelles
No full textSorption plays a major role in the prediction of solutes migration in soils. It controls their mobility in the soil, their bioavailability, and in the case of radionuclides, their radiological impact.In assessment level models, sorption is usually described by a single parameter model (Kd) that assumes that sorption is linear, instantaneous and reversible. However, this model fails to describe sorption reactions in non-equilibrium or nonlinear conditions. Alternative Equilibrium-Kinetic (EK) models have been suggested to improve modelling of sorption. These models suppose the existence of two or more sorption sites governed by equilibrium or kinetic sorption laws. However, these models have not been fully validated in both laboratoryand field sorption conditions for cesium. Experimentally, sorption can be studied using multiple designs with varying levels of complexity and representativity of field conditions (batch reactor, open flow reactor, soil column, etc.) which may lead to a dependence of the sorption parameters to the experimental scale at which they were identified. However, these effects of the experimental scale on sorption parameters are not fully understood.This thesis aimed at validating an alternative nonlinear equilibrium-Kinetic (EK) model for cesium sorption and studying its applicability under different experimental and field conditions. To do so, EK model was used to reproduce a series of contamination profiles of 137Cs measured in situ and a series of data obtained in the laboratory using three experimental devices (batch reactors, open flow reactors and soil columns). The obtained results suggested that non-equilibrium sorption improves the description of 137Cs migration in situ. However, sorption parameters are not easily identifiable in these conditions. In the laboratory, open flow reactor experiments showed that Cs sorption takesplace in non-equilibrium or nonlinear conditions and that EK model can successfully reproduce theses reactions. The comparison between the three experimental devices suggested that sorption parameters can be influenced by the experimental level especially in porous media where non chemical processes can impact cesium migration.La sorption joue un rôle majeur dans le devenir des solutés dans les sols. Elle contrôle leur mobilité, leur biodisponibilité et, dans les cas des radionucléides, leur impact radiologique.En modélisation opérationnelle, la réaction de sorption est généralement décrite par un modèle à paramètre unique (Kd) qui suppose que la sorption est linéaire, instantanée et réversible. Pourtant, il ne permet pas de bien décrire la sorption dans des conditions de non-équilibre ou de non-linéarité. Des approches alternatives ont été proposées pour améliorer la modélisation de la sorption dans ces conditions. Cependant, ces modèles n’ont pas été complètement validés dans des conditions de sorption du Cs au laboratoire ou in situ.Expérimentalement, la sorption peut être étudiée à l’aide de plusieurs dispositifs de différents degrés de complexité et de représentativité des conditions in situ (batchs, réacteurs ouverts, colonnes, etc.) pouvant induire une dépendance des paramètres de sorption de l’échelle expérimentale sur laquelle ils ont été identifiés. Cependant, ces effets de l’échelle expérimentale sur les paramètres de sorption restent mal compris.Les objectifs de ce travail de thèse sont de valider un modèle de sorption à deux sites cinétiques et à l’équilibre (EK) et d’étudier son applicabilité dans différentes conditions expérimentales et sur le terrain. Pour cela, le modèle EK a été utilisé pour reproduire une série de profils de contamination en 137Cs issus du terrain puis une série de données générées au laboratoire à partir de trois dispositifs (batchs, réacteurs ouverts et colonnes).Les résultats obtenus ont suggéré que le non-équilibre permettait d’améliorer lamodélisation de la migration du 137Cs in situ mais que les paramètres de sorption étaient difficilement identifiables dans ces conditions. Au laboratoire, les expériences en réacteurs ouverts ont démontré que la rétention du Cs se faisait dans des conditions de non-équilibre et de non-linéarité et que le modèle EK permettait de bien reproduire ces réactions. La comparaison des trois échelles expérimentales a suggéré une influence du dispositif expérimental sur les paramètres de sorption principalement en milieux poreux structurés oùd’autres processus non chimiques peuvent influencer la migration du césium
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
