1,720,982 research outputs found
Performance Oriented Adaptive Architectures with Guaranteed Bounds
Full text linkWhile adaptive control has been used in numerous applications to achieve given system stabilization or command following criteria, the ability to obtain a predictable transient performance is a challenging problem when there is no a priori knowledge about system uncertainties (e.g., their upper bounds and/or domains). In order to address this problem, a new method is presented in [1, 2] utilizing artificial basis functions in the update law of an adaptive control design. This approach is predicated on a gradient minimization procedure and achieves a predictable transient performance without inducing oscillations in the system response as the constant gain due to the nature of this minimization approach is judiciously increased. However, selection of this gain is problem dependent and may need to be adjusted for each different design. To address this problem, we present a new approach which has an ability to auto-tune an adaptive control design with artificial basis functions employed when the controlled system is about to violate a given design constraint on error dynamics (i.e., only when it is necessary). In particular, our approach is based on a controller architecture that allows the assignment of a priori known (user-defined) transient performance bounds. These bounds are constructed through a restricted potential function approach [3] that yields to an error dependent gain to adjust system performance for time instants when it is required to meet given design criteria. In addition to the theoretical results based on Lyapunov stability arguments highlighting transient performance of an uncertain system that stays within a priori given performance bounds, an illustrative example is provided to demonstrate the efficacy of the proposed framework
A Non-Conservative Approach for the Estimation of the Region of Operation of Uncertain Adaptive Control Systems
No full textA challenging problem for Model Reference Adaptive Control Systems is the accurate characterization of the transient response in the presence of large uncertainties. Early prior research by the authors has demonstrated that using a projection mechanism for parameters adaptation the tracking error dynamics behaves as a linear system perturbed by bounded uncertainties. This brings the benefit that the stability analysis can be cast in terms of a convex optimization problem with LMI constraints so that efficient numerical tools can be used for the adaptive controller design. A possible limitation of the approach is that the design is restricted to quadratic control Lyapunov functions that could produce a conservative estimation of the regions of operation for the actual uncertain adaptive system. In this paper this approach is extended to arbitrary high degree polynomial Lyapunov functions by translating the design and performance requirements in terms of Sum of Square (SOS) inequalities and then using SOS optimization tools for the design. In this effort the new SOS approach is introduced and compared with the previous one. A numerical example based on the short period longitudinal dynamics of the F16 aircraft is used to demonstrate the efficacy of the novel method
Model Reference Neuroadaptive Control Revisited: How to Keep the System Trajectories on a Given Compact Set
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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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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