1,721,277 research outputs found

    Going Beyond Counting First Authors in Author Co-citation Analysis

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    The 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

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    “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

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    We 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

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    We 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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    Modulation properties and nonlinear dynamics induced by optical feedback in distributed-feedback quantum cascade lasers

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    This study explores the dynamic behavior of distributed-feedback quantum cascade lasers (QCLs) through numerical simulations based on the Effective Semiconductor Maxwell-Bloch Equations (ESMBEs). First, we analyze the intrinsic intensity modulation response of QCLs, demonstrating that the modulation bandwidth is fundamentally constrained by the population grating induced by the standing-wave pattern in the QCL cavity, namely, spatial hole burning (SHB). We then extend the ESMBEs framework to incorporate the effects of an external target, enabling the investigation of multimode nonlinear dynamics in QCLs subject to external optical feedback (EOF). Our findings identify fast SHB and a non-zero linewidth enhancement factor as key physical mechanisms governing the emergence of complex multimode behavior and the eventual transition to chaos. Notably, we reveal that QCL destabilization under EOF arises from interactions between internal longitudinal modes and external cavity modes, rather than from undamped relaxation oscillations, as typically observed in conventional semiconductor lasers. Furthermore, we examine the evolution of the system's dynamics as a function of feedback strength, demonstrating the onset of photonic chaos at feedback levels two orders of magnitude higher than those required in traditional diode lasers, in agreement with experimental observations existing in the literature. Finally, we assess the correlation dimension of the attractor of the resulting nonlinear dynamics. Beyond fundamental insight, this work introduces the use of ESMBEs as a predictive framework for experimental interpretation and device design, enabling the engineering of QCLs for mid- and long-infrared free-space applications, including high-speed transmission, chaos-based LiDAR, and random number generation. (c) 2025 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International (CC BY-NC-ND) license (https://creativecommons.org/licenses/by-nc-nd/4.0/)
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