1,721,062 research outputs found
Showcase of a Fuzzy Logic Controller Design
No full textIn this paper a method developed by the authors for defining a Sugeno--Takagi Fuzzy Logic Controller parameters is illustrated. The procedure, based on the Variable Structure System approach, defines an adaptive fuzzy control structure. In order to show the effectiveness of the proposed solution, the controller is applied to a known benchmark control problem and the obtained simulation results are discussed
Multiple-layer variable structure controller with parameter adaptation.
No full textThis paper deals with the design procedure of aMultiple Layer Variable Structure Controller (ML-VSC) with on-lineparameter adaptation.The ML-VSC is obtained by non-linear interpolation of the control lawsof a set of VSC with sliding mode dynamics, each of them designed onthe basis of progressively pessimistic estimates of the parametricuncertainty and disturbance input of the plant.This new structure improves both the robustness and controlperformance of the single VS controller when poor knowledge on plantparameters and disturbance bounds is available.The control algorithm is completed by an on-line adaptation mechanismaiming to achieve fine tuning of the parameters. This mechanism isbased on the trade-off between the ``chattering'' effect and thetracking error. This heuristics, formulated in terms of ``if--then''linguistic rules, is implemented by a Fuzzy Logic (FL) algorithm.The paper also addresses the stability issue of the closed loopsystem, giving sufficient conditions for global stability in thepresence of bounded disturbance and modeling uncertainties. Finally, asimple simulation example illustrates the main design steps of thecontrol approach propose
Adaptive Fuzzy Logic Controller Synthesis Via Sliding Mode Approach
No full textThe VSC (Variable Structure Control) with SM (Sliding Mode) dynamics is a well known theory used to define a robust controller for a plant in the presence of model uncertainty and disturbance input. In this paper a method for defining a Sugeno type of Fuzzy Logic Controller (FLC) parameters, derived from VSC design considerations, is proposed. The idea is to generate a set of VSC controllers, related to different bounds on model uncertainties and disturbances, and use the interpolatory capability of the fuzzy paradigm to merge the VSC behavior in only one structure. Moreover a heuristic algorithm for the on-line FC parameter tuning is given. The global stability of the proposed controller is also demonstrated.Simulations show that the FC obtained performs better than the basic VSC counterpart in the presence of unmodeled dynamics and disturbances
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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