1,721,016 research outputs found
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
Inhomogénéités locales dans les couches minces de CuIn1-xGaxSe2 à grand gap
No full textLes cellules solaires à base de CuIn1-xGaxSe2 sont des dispositifs en couches minces permettant d’atteindre des hauts rendements de conversion photovoltaïque. Le CuIn1-xGaxSe2 est un absorbeur permettant d’adapter l’énergie de la bande interdite de la cellule solaire en changeant la teneur en Ga. Le rendement record de conversion photovoltaïque actuel a été obtenu pour x~0.3, alors que la théorie indique qu’il devrait être obtenu pour un x~0.7. L’origine de cette limite pour x élevé reste en débat. Dans cette thèse, on étudie deux origines liées aux interfaces internes de CuIn1-xGaxSe2 à savoir i) le changement d’élément ségrégé aux joints de grains pour des fortes et faibles teneurs en Ga et ii) la ségrégation défavorable du séléniure du cuivre au volume ou à la surface. Dans une première partie, une étude par premiers principes (DFT) montre que la ségrégation substitutionnelle de l’In par Ga (ou de Ga par In) n’est pas favorisée dans un joint de macle. Dans le cas plus général d’une surface notre étude sur les forces motrices de ségrégation montre qu’il est plus facile de faire ségréger une impureté d’In qui se trouve dans une matrice de CuGaSe2 que l’inverse. Dans la seconde partie, les résultats expérimentaux du CuIn1-xGaxSe2 indiquent qu’en augmentant le taux de Ga la couche devient plus inhomogène. Cela est dû aux inhomogénéités locales de concentration en Cu dans la couche. L’origine de ce phénomène est liée à la cinétique de la formation de CuGaSe2 qui est lente et à la faible diffusion du Cu et du Ga. Nous proposons une étape de relaxation supplémentaire pendant la co-évaporation de CuIn1-xGaxSe2 qui permet de faciliter la croissance des grains, d’améliorer l’homogénéité de la couche et d’atteindre l’équilibre attendu.Amongst the different semiconductor materials used as absorber layers, polycrystalline CuIn1-xGaxSe2 is one of the most promising materials in the thin-film photovoltaic technology. Due to the high efficiency, stability and band gap tunability with x, thin-film solar cells based on CuIn1-xGaxSe2 absorber layer are already industrially implemented. Moreover, in the multi-junction solar cell technology the aim of reaching higher efficiencies while keeping the fabrication costs low, makes the wide band gap indium-free CuGaSe2 absorber layer an interesting candidate as a top cell in a hybrid tandem solar cell based on c-Si bottom cell. However, the actual energy conversion efficiency strongly decreases for x larger than 0.3 and it does not follow the theoretical predictions indicating better performances for x around 0.7. The difficulty to obtain a high device performance for large x has been a worldwide question for several years and many theories have been proposed to explain the limited conversion efficiency. A possible cause of the limited CuIn1-xGaxSe2 performance for large x involves the local inhomogeneities at the inter- or intra-grain regions, since the nature of the accumulated species or compound at the interfaces can be detrimental or beneficial for the solar cell efficiency. In this thesis we investigate two possible phenomena that are likely to occur at the CIGSe interfaces i) a preferential elemental segregation at the grain boundaries and ii) the detrimental copper selenide surface segregation or bulk precipitation. In this work, the elemental segregation is investigated at equilibrium by coupling ab initio calculations and thermodynamic modeling. Our results indicate that substitutional (InGa or GaIn antisite) cannot be expected in the most frequently present interfaces such as the twin grain boundaries. A complementary and simple analysis of the main segregation driving forces was also studied in order to understand the segregation in the more general cases, such as the surface segregation. Our calculations show that In is slightly more favorable to segregate at the surface rather than Ga. The experimental analysis on CuIn1-xGaxSe2 films at intermediate and large x reveals that increasing x the Cu content in the CuIn1-xGaxSe2 film can locally differ, creating detrimental Cu-enriched domains within the bulk of the film. This phenomenon is due to the slow kinetics at large x and the reduced Cu and Ga interdiffusion. In this work, we propose a strategy to avoid these local inhomogeneities by applying a relaxation stage during the CuIn1-xGaxSe2 deposition process. This stage improves the photovoltaic performance, since it leads to a long-range equilibration, grain growth, annihilation of voids and a close to stoichiometry bulk which was expecte
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
Segregation in co-deposited bimetallic nanowires : finite-size effects and equilibrium distribution
No full textLes nano-objets unidimensionnels alliés présentent des propriétés physiques spécifiques qui résultent à la fois de leur morphologie, de leur taille et de la répartition chimique des atomes. Nous exploitons un modèle d’Ising sur réseau qui rend compte en particulier des effets de ségrégation au sein de nanofils bimétalliques pour obtenir une compréhension fine des effets gouvernant cette répartition à l’équilibre.Dans une première section, nous détaillons l’équilibre d’un nanofil en fonction de sa taille et de sa composition, de manière à mettre en évidence le rôle des effets de taille finie sur la thermodynamique d’équilibre d’objets bimétalliques 1D. Contrairement aux systèmes infinis, l’équilibre dépend de l’ensemble statistique considéré. Ainsi la ségrégation est plus marquée dans l’ensemble canonique, où la concentration du nanofil est imposée, que dans l’ensemble pseudo-Grand Canonique (p-GC) où le nanofil est en équilibre avec un réservoir qui fixe la différence de potentiel chimique entre les espèces. De même, la contrainte de composition dans l’ensemble canonique induit des corrélations chimiques d’occupation des sites qui favorisent davantage les paires hétéroatomiques. Nous montrons que l’écart observé entre les isothermes des deux ensembles croît avec la courbure de l’isotherme canonique et avec l’amplitude des fluctuations de la concentration nominale dans l’ensemble p-GC. Ces fluctuations diminuant avec la taille du nanofil considéré, l’écart entre les ensembles s’annule à la limite thermodynamique. Les effets de taille finie se traduisent par ailleurs par l’apparition, à basse température et pour de petits nanofils, d’une coexistence d’un mode pur en l’espèce ségrégeante et d’un mode de faible concentration nominale constitué principalement de configurations de type cœur-coquille et Janus. Nous développons alors un formalisme permettant de caractériser cette bimodalité.Alors que les résultats évoqués précédemment concernent un nanofil considéré seul, nous étudions dans la deuxième section l’équilibre de l’ensemble des nanofils formant un co-dépôt unidimensionnel inférieur à la mono-couche. Nous montrons que la distribution en taille de ces nanofils varie globalement selon une loi de puissance, quelle que soit la composition du codépôt, de sorte que la ségrégation n’a que peu d’influence sur la microstructure observée. Par contre, en raison du rapport surface/volume et des corrélations chimiques dans ces objets, la composition des nanofils du co-dépôt varie très fortement selon leur taille, les petits nanofils étant plus riches en l’espèce ségrégeante que les plus grands. Enfin, nous étendons le diagramme de bimodalité d’un nanofil seul à l’ensemble des nanofils du co-dépôt et montrons que cette bimodalité est difficilement observable car elle ne concerne que des amas de petite taille qui sont très minoritaires du fait de la cohésion atomique.The chemical configuration and the specific shape of 1D bimetallic nano-objects endow them with physical properties (such as magnetic ones) that strongly differ from their bulk counterparts. To get a deep insight of the parameters that govern the equilibrium configuration, we consider a rigid lattice-gas Ising model that accounts for segregation effects within bimetallic nanowires that decorate a step edge.In a first section, we detail the equilibrium of a nanowire as a function of both its size and composition in order to specify the role of finite-size effects onto the equilibrium thermodynamics of 1D bimetallic objects. Contrary to infinite systems, this equilibrium depends on the statistical ensemble to be considered. The segregation profile is indeed stiffer in the canonical ensemble where the nanowire concentration is imposed, than in the semi-grand-canonical ensemble (s-GC) where the nanowire is in equibrium with a reservoir that sets the difference of chemical potentials between the species. Moreover, the composition constraint in the canonical ensemble yields chemical correlations between occupation sites that favor heteroatomic pairs. We show that the deviation observed between the isotherms related to the two ensembles increases with the curvature of the canonical isotherm and with the amplitude of the fluctuations of the nominal concentration within the s-GC ensemble. As these fluctuations decrease with the nanowire size, the deviation between ensembles vanishes at the thermodynamical limit. The finite-size effects also imply at low temperature for small nanowires, that a pure mode of the segregating species coexists with a low-concentration mode that mainly corresponds to core-shell and Janus configurations. We develop a framework to characterize the resulting two-mode density of compositions.While the abovementioned results deal with a fixed-size nanowire, we study in the second section the equilibrium of the set of nanowires that forms a submonolayer 1D-codeposit. We show that the size distribution of these nanowires globally varies as a power law, whatever the codeposit composition, so that segregation has a slight influence onto the observed microstructure. However, due to the surface/volume ratio and chemical correlations within these objects, the composition of the nanowires of the codeposit varies strongly with their size, the smaller the richer in the segregating species. Finally we extend the two-mode diagram of the single nanowire to the set of nanowires forming the codeposit and show that this two-mode distribution is hardly visible as it concerns only short nanowires which are very rare, mainly due to atomic cohesion that is reinforced at low temperature
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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