1,721,077 research outputs found
Leader-Following consensus for nonlinear agents with measurement feedback
Full text linkThe leader-following consensus problem is investigated for large classes of nonlinear
identical agents. Sufficient conditions are provided for achieving consensus
via state and measurement feedback laws based on a local (ie, among neighbors)
information exchange. The leader's trajectories are assumed bounded
without knowledge of the containing compact set and the agents' trajectories
possibly unbounded under the action of a bounded input. Generalizations to
heterogeneous agents and robustness are also discussed
Observability of nonlinear time–delay systems and its application to their state realization
Full text linkIn this paper, it is shown that the two notions of weak observability and strong observability may not be sufficient to describe the link between the input/output equation associated to the behaviour of a system and its state space realization. A new notion, called regular observability, is introduced, which is shown to capture essential features of nonlinear time delay systems and the existence of some realization
Feedback linearization of nonlinear time-delay systems over a time window via discontinuous control
Full text linkFeedback linearization is worked out for nonlinear time-delay systems and it is shown that even if the problem can not be solved for all time, it may still be solved over some time windows. The solution then reduces to a discontinuous state feedback. It is foreseen that such piecewise feedback linearization can be instrumental for stabilization by a discontinuous control, although it is not the scope of this paper. The approach used herein may be used to address other classical control problems. It takes advantage of the delays as delays duplicate somehow the number of independent control values at some given time instant
T-Accessibility for a class of nonlinear time–delay systems
No full textObservability and detectability on one hand as well as accessibility and controllability on the other, are related properties and have not been closely investigated for nonlinear–time delay systems until these recent years. Currently accessibility or nonlinear time delay systems is defined as the absence of autonomous functions on the extended state space. Such a property is expressed in terms of the Accessibility matrix rank, extending to the nonlinear context the well known Kalman Criterion. A weaker notion is introduced in this paper which is motivated by the fact that even if autonomous functions exist for the given system, it may be still possible to move from a fixed point to an arbitrary one in some open subset of IRn. The study is performed on the class of driftless single input system
T-accessibility for Nonlinear Time-Delay Systems: The general case
No full textFollowing the results recently obtained for nonlinear driftless systems affected by constant commensurate delays, a partial characterization of t - accessibility is provided for general nonlinear time-delay systems affected by constant commensurate delays. Conditions are given for this new property. The results are stated using the differential representation of time-delay systems
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
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