1,720,959 research outputs found
On some aspects of polynomial dynamical systems
No full textThe aim of this work is to study exact algebraic criteria local/global observability ([HK77], [Ino77]) for polynomial dynamical system by means of algebraic geometry and computational commutative algebra in the vein of [SR76], [Son79a], [Son79b], [Bai80], [Bai81], [Bar95], [Bar99], [Nes98], [Tib04], [KO13], [Bar16].
A key point in this topic is to work with polynomials with real coefficients and their real roots instead of their complex roots, as it is usually the case ([CLO15], [KR00]). A central concept is then the real radical of an ideal [BN93], [Neu98], [LLM+13], along with the Krivine- Dubois-Risler real nullstellensatz for polynomial rings [Kri64], [Dub70], [Ris70], [BCR98]. Underestimating this point leads to incorrect results (see, e.g. [Bar16] remark on [KO13]).
This thesis is therefore devoted to set the necessary algebraic tools in the right context and level of generality (i.e. real algebra and real algebraic geometry) for applications to our dynamical systems and to further develop their exploit in this context.
The first two chapters set the algebraic and algebraic geometry preliminaries. The third chapter is devoted to the applications of the previous algebraic concepts to the study of the ob- servability of polynomial dynamical systems. In the last chapter an approach to the construction of Lyapunov funtions to prove stability in estimation problems is presented
Deligne’s representation theory in complex rank and objects of integral type
No full textUsing Deligne's category Rep(St) we answer questions by B. Kahn and C. Weibel on objects of integral typ
On the minimum distance of AG codes, on Weierstrass semigroups and the smoothability of certain monomial curves in 4–space
No full textIn this paper we treat several topics regarding numerical Weierstrass semigroups and the
theory of Algebraic Geometric Codes associated to a pair (X; P), where X is a projective
curve defined over the algebraic closure of the finite field Fq and P is a Fq-rational point of
X. First we show how to evaluate the Feng-Rao Order Bound, which is a good estimation
for the minimum distance of such codes. This bound is related to the classical Weierstrass
semigroup of the curve X at P. Further we focus our attention on the question to recognize
the Weierstrass semigroups over fields of characteristic 0. After surveying the main tools
(deformations and smoothability of monomial curves) we prove that the semigroups of
embedding dimension four generated by an arithmetic sequence are Weierstrass.
Keywords : AG code, Order Bound, Numerical semigroup, Monomial curve, Deformation, Weierstrass sem
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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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