1,721,030 research outputs found
Topological String, Supersymmetric Gauge Theory and BPS Counting
No full textIn this thesis we study the Donaldson-Thomas theory on the local curve geometry, which arises in the context of geometric engineering of supersymmetric gauge theory from type IIA string compactification. The topological A-model amplitude gives the F-term interaction of the com-pactified theory. In particular, it is related to the instanton partition function via Nekrasov conjecture. We will introduce ADHM sheaves on curve, as an alternative description of local Donaldson-Thomas theory. We derive the wallcrossing of ADHM invariants and their refinements. We show that it is equivalent to the semi-primitive wallcrossing from supergravity, and the Kontsevich-Soibelman wallcrossing formula. As an application, we discuss the connection between ADHM moduli space with Hitchin system. In particular we give a recursive formula for the Poincare polynomial of Hitchin system in terms of instanton partition function, from refined wallcrossing. We also introduce higher rank generalization of Donaldson-Thomas invariant in the context of ADHM sheaves. We study their wallcrossing and discuss their physical interpretation via string duality
Hydrodynamic benefit of cephalic fins in a self-propelled flexible manta ray
No full textThe hydrodynamic benefit of cephalic fins in manta ray was explored using the penalty immersed boundary method. When manta rays feed, they open their cephalic fins and lower them to their mouth. As they swim forward, the cephalic fins are straightened in the forward direction. The smooth body of manta rays was modeled as a flexible plate. A self-propelled flexible plate was realized by enforcing a prescribed harmonic oscillation in the vertical direction but allowing the plate to move freely in the horizontal direction. Simulations without cephalic fins were also performed for comparison. Vortical structures and pressure distributions were visualized to elucidate the hydrodynamic benefits of cephalic fins. The fins generated streamwise vortices that resulted in negative pressure and enhanced the average cruising speed and thrust. The effect of the gap distance (g/L, where g is the gap distance between the two cephalic fins and L is the length of the plate) was examined in detail. The underlying propulsion mechanism was analyzed by examining the phase of the heaving stroke. The effects of the g/L were scrutinized by visualizing the contours of vorticity (omega(x), omega(y), omega(z)) and pressure (p) around the flexible plate. A maximum cruising speed was obtained at g/L = 0.6, where the average cruising speed increased by more than 62.8%.
Features of PAN Guang-dan′s Imperial Examination Research
No full text潘光旦站在学术研究的立场上,实事求是地研究科举史。他在科举研究中一以贯之以人文主义的优生学思想,强调科举制度的人文选择功能。他的科举研究运用现代家谱分析法和社会统计方法,注重对家谱和硃卷等文献的开发。这些具有开创性的科举研究特色对终结盲目批判科举的时代、对在科举研究中更广泛和深入地运用现代相关学科的理论和研究方法、对更广泛和深入地开发科举文献,有很重要的启发。PAN Guang-dan holds the stand of academic research,researching imperial examination history with the spirit of seeking truth from facts.He fills humanistic eugenics thought in his imperial examination research,highlighting humanistic selective function of imperial examination system.He uses modern genealogic analysis and social statistic approach in his imperial examination research,laying emphasis on the development of imperial examination documents,such as "zhujuan",etc.These pioneering features are of important significance for ending the blindness in imperial examination criticism,developing theory and research of modern relevant disciplines and developing examination documents more extensively and more intensively
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
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