1,721,219 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
Structure électronique et propriétés optiques de nanocristaux hétérogènes : théorie et modélisation
No full textL'objectif de ce travail est de décrire la structure électronique et les propriétés optiques de boîtes quantiques de semiconducteurs (nanocristaux) contenant des hétérojonctions, c'est-à-dire des nano-jonctions entre deux semiconducteurs. Ces nanostructures ont des propriétés optiques très intéressantes pour les applications photoniques et photovoltaïques. La description théorique des effets liés à l'interface demande un traitement particulier. Nous commençons par décrire la structure électronique des semiconducteurs massifs en liaisons fortes et nous montrons comment on peut appliquer cette théorie aux nanocristaux. La méthodologie de calcul des spectres optiques en partant de la structure électronique est présentée. Les paramètres de liaisons fortes sont utilisés pour calculer l'évolution de la structure électronique des boîtes quantiques en fonction de leur taille. Le bon accord théorie/expérience obtenu pour la variation de la bande interdite en fonction de la taille valide notre approche théorique. Nous appliquons ensuite ces techniques à des nanocristaux coeur/coquille PbSe/CdSe, après analyse des interfaces présentes dans ces systèmes et discussion des valeurs des discontinuités de bandes. Nos calculs justifient l'hypothèse que CdSe agit comme une barrière de potentiel pour l'électron et le trou. Nous simulons les spectres d'absorption optique des nanocristaux de PbSe, CdSe et PbSe/CdSe. Nos travaux confirment l'existence de transitions optiques intra-bandes photo-induites observées récemment dans des expériences de type pompe-sonde. Ces transitions intra-bandes photo-induites, révélées et étudiées pour la première fois, sont très intéressantes pour des applications en photonique.The main objective of this work is to give a description of the electronic structure and optical properties of semiconductor quantum dots (nanocrystals) containing heterojunctions, i.e. nano-junctions between two semiconductors. These nanostructures have interesting optical properties which are very promising for applications in photonics and photovoltaics. The theoretical description of the effects of the interface demands special attention. We start describing the calculations of the electronic structure of bulk semiconductors using semi-empirical tight-binding, and we show how to apply this technique to semiconductor quantum dots. We develop expressions to connect the discrete levels of energy in a quantum dot and the transitions in optical absorption spectra. The bulk tight-binding parameters are used for the calculation of the electronic structure of quantum dots of single compounds, analyzing the effect of the size variation of the quantum dots. The effectiveness of this method is demonstrated, in particular we obtain good values for the bandgap versus size compared to experiments. We apply this method to calculate the electronic structure of PbSe/CdSe core/shell quantum dots, after an analysis of the different types of interfaces that can appear in this system, and we discuss the issues related to the determination of the band offsets. The results of these calculations validate the assumption of the role of the shell as a potential barrier for the electron and the hole. The electronic structures are used in the last chapter to simulate the absorption spectra of PbSe, CdSe and PbSe/CdSe quantum dots. We give theoretical support to recent experiments in transient absorption spectroscopy, revealing groups of new transitions originated by photo-induced intraband absorption. Our calculations shed light on the nature of these optical transitions which can be of interest for applications in photonics
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
Theoretical study of semiconducting nanowires
No full textLe dopage des nano-fils de semi-conducteurs est un paramètre essentiel gouvernant leurs propriétés optiques et de transport. Alors que dans les fils d'une centaine de nanomètres de diamètre les impuretés servant au dopage se comportent certainement comme dans le matériau massif, les confinements quantique et diélectrique influent fortement sur leur structure électronique pour des dimensions de l'ordre de la dizaine de nanomètres ou en dessous. Les récentes techniques de croissance des nano-fils semi-conducteurs ouvrent de grandes opportunités pour des applications à l'échelle nanométrique. Ils restent semi-conducteurs indépendamment de leur diamètre et de leur orientation, donnant la possibilité de contrôler leurs propriétés par dopage. Alors qu'il n'y a pas de doute que des nano-fils de type p et n peuvent être produits, la question sur «comment leur conductivité électrique dépend du dopage ?» reste largement ouverte. En fait, la plupart des travaux montrant de bonnes propriétés de transport concernent des nano-fils dopés avec une forte concentration de dopants (près de la densité de Mott ou au dessus). Dans ce cadre, notre travail présentera les résultats de calculs de structure électronique d'impuretés hydrogénoïdes dans des nano-fils de silicium. L'évolution de l'énergie de liaison des donneurs et accepteurs sera présentée en fonction de la taille des nano-fils. Des simulations de l'efficacité de dopage à température ambiante permettront de prédire des caractéristiques essentielles du transport électronique dans les nano-fils. Nous montrons que l'énergie de liaison croit, dû aux confinements. Le confinement quantique pour les petites tailles de nano-fils (diamètre < 5 nm) et le confinement dit « diélectrique» qui se produit quand il y a une importante discontinuité entre la constante diélectrique dans le nano- fil et celle de son environnement. Pour les nano- fils dans un environnement avec une faible constante diélectrique, nous montrons que les impuretés ne peuvent être ionisées à température ambiante même pour des diamètres jusqu'à quelques dizaines de nanomètres. Nous expliquons l'origine de ce comportement en considérant l'effet du potentiel de l'impureté et de la self-énergie des porteurs, nous donnons l'énergie d'ionisation dans différentes configurations. Ces résultats nous permettent de conclure qu'un fort dopage est nécessaire pour obtenir de bonnes propriétés électriques dans le nano-fil.Recent breakthroughs in the growth of semiconductor nanowires (SNWs) have opened up great opportunities for nanoscale device applications. SNWs remain semiconducting independent oftheir diameter and orientation, giving the ability to control their properties by doping. Therefore a large number of experimental works have addressed the problem of doping and of its modulation in SNWs. While there is no doubt that p- and n-type SNWs can be produced, the question of how their electrical conductivity depends on the doping level remains largely open. ln fact, most of the works showing good transport properties concern SNWs doped with high impurity concentration, near or above the Mott density. ln order to investigate the doping efficiency in SNWs, we present calculations of the electronic structure of donor and acceptor impurities in Si nanowires. We show that their ionization energy increases due to the confinement, the quantum confinement at small sizes (diameter < 5 nm) and above aIl the so-called dielectric confinement which occurs when there is an important dielectric mismatch between the wire and its surrounding. For SNWs embedded in a material with a low dielectric constant, we obtain that the impurities cannot be ionized at room temperature even for diameters up to several tens of nanometers. We explain the origin of this behavior by considering the effect of the impurity potential and of the self-energy of the carrier, and we make predictions for the ionization energy in different configurations. These results allow us to conclude on the necessity to use heavy doping to obtain good electrical properties in SNWs
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
