1,720,956 research outputs found
On the equivalence of model inversion architectures for control applications
No full textThe main inversion-based control architectures are the plant and closed-loop inversion architectures. For scalar continuous-time linear systems, these architectures are shown to be fully equivalent for both the minimum and nonminimum-phase cases when exact stable inverses are used. This equivalence, deduced by using a behavioral approach, dictates that the two architectures deliver the same performances for any disturbance and mis-modeling affecting the controlled plant. A simulation example highlights that the equivalence still holds in practice when a careful truncation of the preaction control is performed
On the structure of the multivariable free response
No full textThe structure of the free (or zero-input) response of multivariable (MIMO) linear time-invariant systems is investigated.
In a behavioral setting, the free response is an autonomous behavior, solution of a homogeneous differential equation. A new closed-form expression of this solution is presented. It is a linear (real) combination of modes associated to the system’s pole minimal polynomial. The vector coefficients of the modes belong to the output mode subspaces. These are characterized by a chain of subspace inclusions for each distinct pole. In the special, but relevant case of the pole minimal polynomial having simple roots the closed-form expression simplifies and admits a phasor interpretation. Examples are included to highlight the paper’s findings
Structured identification for network reconstruction of RC-models
No full textResistive–capacitive (RC) networks are used to model various processes in engineering, physics or biology. We consider the problem of recovering the network connection structure from measured input–output data. We address this problem as a structured identification one, that is, we assume to have a state-space model of the system (identified with standard techniques, such as subspace methods) and find a coordinate transformation that puts the identified system in a form that reveals the nodes connection structure. We characterize the solution set, that is, the set of all possible RC-networks that can be associated to the input–output data. We present a possible solution algorithm and show some computational experiments
On the equivalence of inversion-based control architectures
No full textInversion-based control architectures are feedforward-feedback schemes in which the feedforward control is determined by stable input-output inversion. The main architectures of this type are the plant and the closed-loop inversion architectures. For scalar, linear, nonminimum-phase systems these architectures are shown to be equivalent for any disturbance and any plant perturbation for which the feedback controller ensures closed-loop stability. This equivalence - deduced by using a behavioral approach - also holds in practice when a careful truncation of the preaction control occurs. New output-error-based rules to set the preaction and postaction times of a stable inverse input are introduced. Still holding the equivalence, these rules help in choosing the preferable architecture at the implementation stage. An example with simulation comparisons highlights the paper findings. (c) 2023 European Control Association. Published by Elsevier Ltd. All rights reserved
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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