1,720,964 research outputs found
A globally convergent flow for computing the best low rank approximation of a matrix
No full textDriessel, Kenneth R.. (2007). A globally convergent flow for computing the best low rank approximation of a matrix. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/4360
Linear operators on matrices: Preserving spectrum and displacement structure
No full textDriessel, Kenneth R.; So, Wasin. (1992). Linear operators on matrices: Preserving spectrum and displacement structure. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/2118
Some remarks on the geometry of some surfaces of matrices associated with Toeplitz eigenproblems
No full textDriessel, Kenneth R.. (1992). Some remarks on the geometry of some surfaces of matrices associated with Toeplitz eigenproblems. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/2156
On Preserving Structured Matrices Using Double Bracket Operators: Tridiagonal and Toeplitz Matrices
Get PDFIn the algebra of square matrices over the complex numbers, denotes Two problems are solved: (1) Find all Hermitian matrices M which have the following property: For every Hermitian matrix A, if A is tridiagonal, then so is (2) Find all Hermitian matrices M which have the following property: For every Hermitian matrix A, if A is Toeplitz, then so isThis article is published as Driessel, Kenneth R., Irvin R. Hentzel, and Wasin So. "On Preserving structured matrices using double bracket operators: Tridiagonal and Toeplitz matrices,” JP Journal of Algebra, Number Theory and Applications, 1, no. 2, (2001): 87-114. Posted with permission.</p
The Dynamics of Ski Skating
Get PDFWe discuss the dynamics of ski skating, in particular, the optimization problem: Maximize average speed for a given power. We begin with a mathematical model of ski skating. To simplify the analysis, we limit our attention to ski skating with no poles on a level plane. We also limit our attention to the physics of ski skating; we ignore most biomechanical considerations. In the early days of skating, ski instructors often said: “Take a long glide on a flat ski.” Many skiers interpreted this to mean: “Take a passive glide, then give a short hard push to the side.” As an application of our theory, we show that this advice is wrong. We show that the skier should start pushing to the side as soon as possible.This article is published as Driessel, Kenneth R., Philip Fink, and Irvin R. Hentzel. "The Dynamics of Ski Skating." UMAPJournal (2004): 375. Posted with permission.</p
VaR-implied tail-correlation matrices : [Version October 2013]
No full textEmpirical evidence suggests that asset returns correlate more strongly in bear markets than conventional correlation estimates imply. We propose a method for determining complete tail correlation matrices based on Value-at-Risk (VaR) estimates. We demonstrate how to obtain more efficient tail-correlation estimates by use of overidentification strategies and how to guarantee positive semidefiniteness, a property required for valid risk aggregation and Markowitz{type portfolio optimization. An empirical application to a 30-asset universe illustrates the practical applicability and relevance of the approach in portfolio management
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
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