1,721,042 research outputs found
Matrix measures, stability and contraction theory for dynamical systems on time scales
Get PDFThis paper is concerned with the study of the stability of dynamical systems
evolving on time scales. We first {formalize the notion of matrix measures on
time scales, prove some of their key properties and make use of this notion to
study both linear and nonlinear dynamical systems on time scales.}
Specifically, we start with considering linear time-varying systems and, for
these, we prove a time scale analogous of an upper bound due to Coppel. We make
use of this upper bound to give stability and input-to-state stability
conditions for linear time-varying systems. {Then, we consider nonlinear
time-varying dynamical systems on time scales and} establish a sufficient
condition for the convergence of the solutions. Finally, after linking our
results to the existence of a Lyapunov function, we make use of our approach to
study certain epidemic dynamics and complex networks. For the former, we give a
sufficient condition on the parameters of a SIQR model on time scales ensuring
that its solutions converge to the disease-free solution. For the latter, we
first give a sufficient condition for pinning controllability of complex time
scale networks and then use this condition to study certain collective opinion
dynamics. The theoretical results are complemented with simulations.Comment: 30 pages, 3 figure
Barabanov norms, Lipschitz continuity and monotonicity for the max algebraic joint spectral radius
Get PDFWe present several results describing the interplay between
the max algebraic joint spectral radius (JSR) for compact sets
of matrices and suitably defined matrix norms. In particular,
we extend a classical result for the conventional algebra,
showing that the max algebraic JSR can be described in
terms of induced norms of the matrices in the set. We also
show that for a set generating an irreducible semigroup (in
a cone-theoretic sense), a monotone Barabanov norm always
exists. This fact is then used to show that the max algebraic
JSR is locally Lipschitz continuous on the space of compact
irreducible sets of matrices with respect to the Hausdorff
distance. We then prove that the max algebraic JSR is
locally Hoelder continuous on the space of compact sets of
nonnegative matrices. Finally, we prove a strict monotonicity
property for the max algebraic JSR that echoes a fact for the classical JSR. The single matrix characterisation of the max
algebraic JSR plays a vital role in our proofs
Smart Cities: A Golden Age for Control Theory?
No full textIndustry Perspective: Smart Cities: A Golden Age for Control Theory
Electric and Plug-in Hybrid Vehicle Networks: Optimization and Control
No full texthis book explores the behavior of networks of electric and hybrid vehicles. The topics that are covered include: energy management issues for aggregates of plug-in vehicles; the design of sharing systems to support electro-mobility; context awareness in the operation of electric and hybrid vehicles, and the role that this plays in a Smart City context; and tools to test and design massively large-scale networks of such vehicles. The book also introduces new and interesting control problems that are becoming prevalent in the EV-PHEV's context, as well as identifying some open questions. A particular focus of the book is on the opportunities afforded by networked actuation possibilities in electric and hybrid vehicles, and the role that such actuation may play in air-quality and emissions 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
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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