1,721,001 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
Faisceaux vortex et vector-vortex de très haute charge par génération d'harmoniques : génération, caractérisation et amplification dans un plasma de laser X
No full textCe manuscrit présente une étude complète de la caractérisation de faisceaux vortex de lumière intense femtoseconde a été effectuée. Ces faisceaux sont produits par insertion de lame de phase spirale sur le trajet du faisceau infrarouge et caractérisés par un Shack Hartmann. Cette méthode de caractérisation en phase et en amplitude du champ électrique du laser permet une décomposition modale précise et quantitative du faisceau dans la base des modes de Laguerre Gauss. Les lames utilisées permettent d’induire un moment angulaire de la lumière de valeurs entières 1 à 4, en positif ou négatif selon le sens de variation de la phase. Ces faisceaux ont ensuite été utilisés pour générer des harmoniques d’ordres élevés dans une cellule de gaz rare. Les faisceaux extrêmes ultraviolets ainsi produits ont été caractérisés par un Hartmann XUV. Des moments orbitaux aussi élevés que l = 100 peuvent être produits et complètement caractérisés à partir de l’harmonique 25 du faisceau infrarouge initial, vérifiant ainsi la loi indiquant que le moment angulaire orbital du faisceau vortex harmonique est égal au produit du moment du faisceau infrarouge par l’ordre harmonique. Un état plus complexe de la lumière a également été étudié : les faisceaux vecteurs vortex pour lesquels non seulement la phase spatiale du faisceau vérifie une dépendance azimutale mais dont la polarisation varie spatialement. Elle peut être radiale ou azimutale. La caractérisation de faisceaux harmoniques produits par des faisceaux infrarouges vecteur vortex permet de montrer qu’on obtient ainsi des faisceaux vecteur vortex dans l’extrême ultraviolet et qu’ils sont capables de se propager. La structure de ces faisceaux a été complètement décrite par des simulations numériques validées par les résultats expérimentaux. Enfin le dernier chapitre présente les premiers résultats d’amplification d’un vortex harmonique extrême ultraviolet dans un plasma de laser X collisionnel transitoire. Des effets fins de l’effet du moment angulaire orbital sur la propagation du faisceau dans le milieu amplificateur ont été démontrés et analysés, en comparaison avec des codes numériques. Le présent travail démontre que les plasmas de laser X permettent une amplification du faisceau harmonique capable d’en conserver toutes les propriétés spatiales, en particulier le moment angulaire orbital.Controlled generation and manipulation of ultrafast structured light in the extreme-ultraviolet (EUV) and X-ray spectral range is paramount to extending their applications to nanometric spatial and subfemtosecond temporal scales. Here, we focus on the frequency upconversion of near-Infrared (IR) light beams tailored either in their Orbital Angular Momentum (OAM), Spin Angular Momentum (SAM), or simultaneously in their SAM and OAM to the EUV spectral regime via high-order harmonic generation (HHG). Throughout this work, we rely on IR and EUV wavefront sensing to assess and affirm the characteristics of the driving and the HHG beams. First, we demonstrate single-shot amplitude, wavefront, and modal content characterization of IR vortex beams of various topological charges. The experimental results show the multi-modal nature of the IR driving beams arising from the non-ideal behavior of the utilized mode converters. Thereafter, resorting to a low-density 15 mm long generation medium that allowed the production of EUV vortices with high photon flux, we demonstrate the single-shot intensity and wavefront characterization of the selected harmonic order (25th harmonic; λ=32.6 nm) for the IR driver of unit topological charge. Remarkably, these results affirm the topological charge scaling law with harmonic order, indicating that even in an extended generation medium, the upconverted HHG-OAM beam retains its twisted wavefront. We further reinforce this remark by demonstrating the generation and characterization of EUV vortex beams manifesting a topological charge as high as 100, which, to the best of our knowledge, represents the highest topological charge measured in the EUV regime. By driving HHG with vortex beams of topological charges up to 4, we show that the 25th harmonic beam reaches a topological charge of 100, comprising a rich OAM content influenced by the modal purity of the driving beams and the underlying nonperturbative nature of HHG. Interestingly, very high topological charge ultrafast EUV beams may open the route to transfer OAM not only to macroscopic particles but also to clusters or even molecules, bringing in the scenario of light-matter OAM transfer. Following the generation of EUV vector beams tailored in their SAM, we demonstrate a novel structured EUV beam, a vector-vortex beam (VVB) that combines the polarization and phase singularity of vector and vortex beams. We demonstrate that the selection rule for HHG-VVB is governed by the upscaling of the topological Pancharatnam charge that accounts both for the SAM and OAM of the IR driver. Interestingly, numerical results reveal the possibility of synthesizing attosecond light springs with spatially varying polarization, thus providing a new degree of freedom in attosecond beams. To increase the photon flux of HHG beams, we investigate the amplification of EUV OAM beams in a Ne-like Ti solid-target plasma-based X-ray laser (XRL). First, for XRL seeded by a conventional Gaussian HHG beam, we demonstrate a reduction of amplification duration resulting from collisional ionization gating through a controlled increase of the electron density in the gain region. Our work shows that a coherently-seeded high electron density XRL can deliver coherent and energetic EUV radiation with few hundreds of femtosecond pulse duration. Concerning HHG-OAM seeded XRL, experimental results supported by 3D Bloch-Maxwell simulations indicate that the OAM of the harmonic seeding pulse is retained during amplification in plasma-based XRL. Consequently, our work opens the prospect of amplifying EUV vector-vortex beams that are simultaneously tailored in their SAM and OAM in a plasma-based lasing medium. Interestingly, HHG-vortex and HHG-vector-vortex seeded XRL pave the way for obtaining ultrafast structured EUV light pulses with microjoule level energy, thus further widening the prospect of these advanced table-top light sources for numerous applications
Export and Economic Growth in India: Causal Interpretation
Get PDFThe present study focuses on the cointegration between Export and Gross Domestic Product and its components at current and constant prices. Time series data for Export and Gross Domestic Product and its components has been taken for the period 1950-51 to 2001-02. In the long run export and GDP reveal that export and GDP at constant prices are not cointegrable while export and GDP at current prices are cointegrable and also the direction of causality is positive. In the short run, through error correction mechanism it has been observed that GDP as dependent variable and export as an independent variable show that short run changes in export have affected positively to GDP and its components
Globalization and WTO: Impact on India’s economic growth and export
Get PDFThe roots of newly emerging forces of globalization exist in specific economic and political development in the late 1980s and early1990s. From other regulatory measures to correct the prevailing distortions in the Indian economy, government of India introduced Structural Adjustment Programmes (SAPs) in July 1991. The World Trade Organization (WTO) which came into existence on January 1, 1995 with a view to ensure global cooperative trade environment, to raise incomes and to create ample job opportunity for the nations through fair and open trade. In order to estimate growth of Indian exports as well as Gross Domestic Product (GDP) for the period 1985-86 to 2004-05 keeping view the structural reform of 1991 and WTO Settlement in 1995, we have employed OLS technique based on dummy variables. The empirical evidences of the present paper has scanned Gross Domestic Product and export performance of the Indian economy for the period 1985-86 to 2004-05 with an attempt to isolate the impacts of Economic reforms and WTO
Uttar Pradesh: State Economy (AT A Glance)
Get PDFUttar Pradesh is India`s fourth largest and the most populated state in India. With an area of 93,933 sq mi (243,286 square km), Uttar Pradesh covers a large part of the highly fertile and densely populated upper Gangetic plain. There is an average population density of 828 persons per km² i.e. 2,146 per sq meters. Uttar Pradesh shares an international border with Nepal to the north. Other states along Uttar Pradesh's border include Uttarakhand, Haryana and Delhi to the north and northwest; Rajasthan on the west; Madhya Pradesh on the south; Chhattisgarh and Jharkhand on the south east; and Bihar on the east. As Uttar Pradesh shares an international boundary it assumes strategic importance as far as its defence is concerned. The administrative and legislative capital of Uttar Pradesh is Lucknow
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
Export and Economic Growth in India: Causal Interpretation
Get PDFThe present study focuses on the cointegration between Export and Gross Domestic Product and its components at current and constant prices. Time series data for Export and Gross Domestic Product and its components has been taken for the period 1950-51 to 2001-02. In the long run export and GDP reveal that export and GDP at constant prices are not cointegrable while export and GDP at current prices are cointegrable and also the direction of causality is positive. In the short run, through error correction mechanism it has been observed that GDP as dependent variable and export as an independent variable show that short run changes in export have affected positively to GDP and its components.Gross Domestic Product, Export, Unit root test, Cointegration, Error Correction Model, Time series
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