1,720,957 research outputs found
Accelerations for global optimization methods that use second derivative information
Get PDFTwo new improvements for the algorithm of Breiman & Cutler are presented. Better envelopes can be built up using positive definite quadratic forms. Better utilization of first and second derivative information is attained by combining both global aspects of curvature and local aspects nearthe global optimum. The basis of the results is the geometric viewpoint developed by the first author and can be applied to a number of covering type methods. Improvements in convergence rates are demonstrated empirically on standard test functions
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
Accelerations for a variety of global optimization methods
Get PDFOptimization methods for a given class are easily modified to utilize additional information and work faster on a more restricted class. In particular algorithms that use
only the Lipschitz constant (e.g. Mladineo, Piyavskii, Shubert and Wood) can be modified
to use second derivative bounds or gradient calculations. T he algorithm of Breiman &
Cutler can be modified to use Lipschitz bounds. Test cases illustrating accelerations to
various algorithms are provided
Multidimensional bisection : a dual viewpoint
Get PDFThis paper provides an alternative viewpoint of multidimensional bisection global optimisation methods of Wood. A dual coordinate representation of convex bodies
is introduced which leads to an easy implementation and eliminates the need to see the
geometry of intersecting simplexes. Although developed in the context of global optimisation,
the techniques deal more generally with regions represented as the union of
convex bodies. With this dual framework the algorithm can be implemented efficiently
using any multi-attribute index data structure that allows for quick range queries. A C
version using a "multi-key double linked skip list" based on Pugh's skip list has been
implemented
Customizing methods for global optimization : a geometric viewpoint
Get PDFA new class of global optimization algorithms, extending the multidimensional bisection method of Wood, is described geometrically. New results show how the
geometry of the global minimum relates to performance. Remarkably, the epigraph
of the objective function, turned upside down, plays a key role. Algorithms customized
to take advantage of special information about the objective function belong to the class.
A number of algorithms in the literature, including those of Piyavskii-Shubert, Mladineo,
Wood and Breiman & Cutler, also belong, and simple modifications of them produce
customized algorithms. Comparison of various algorithms in the class is provided
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
Global optimization requires global information
Get PDFThere are many global optimization algorithms which do not use global information. We broaden previous results, showing limitations on such algorithms, even if allowed
to run forever. We show deterministic algorithms must sample a dense set to find the
global optimum value and can never be guaranteed to converge only to global optimizers.
Further, analogous results show introducing a stochastic element does not overcome these
limitations. An example is simulated annealing in practice. Our results show there are
functions for which the probability of success is arbitrarily small
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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