1,720,960 research outputs found
Constrained control strategies for disturbance rejection in a solar furnaces
No full textThis paper addresses the temperature control problem in a solar furnace. In particular, two control strategies for the disturbances rejection (represented by the variation of the input energy provided by the Sun, mainly because of passing clouds and the solar daily cycle) are proposed, based on a twodegrees-of-freedom scheme. The first one is based on generalized predictive control, where a nonlinear
model is employed for free response prediction while a linearized model is used for the computation of the forced response. Amplitude and slew-rate constraints on both the control variable and the output of the system are taken into account. The second one is a constrained control strategy where both the process input and output constraints are taken into account explicitly. In both cases an adaptation of the most significant process parameter is performed. Simulation and experimental results show the effectiveness of the methodologies
Event-Based PI Plus Feedforward Control Strategies for a Distributed Solar Collector Field
No full textThis brief deals with the application of an event-based proportional-integral (PI) plus feedforward control strategy to a distributed solar collector field. In particular, a symmetric send-on-delta strategy is considered and an event based feedforward action to compensate for the disturbance
represented by changes in the solar radiation is added to the PI control law. Furthermore, we propose a simple strategy, based on the describing function technique, to estimate the model parameters for tuning the controller. The obtained experimental results show that the proposed control strategy permits to obtain a very significant reduction of the events with only a slight decrement of the control performance
A feedback linearization GPC control strategy for a solar furnace
No full textThis paper addresses the temperature control problem in a solar furnace. In particular, a feedback linearization generalized predictive control strategy is presented with the
aim of improving the performance in the reference tracking and in the rejection of disturbances (represented by the variation of the input energy provided by the Sun, mainly because of passing clouds and the solar daily cycle). Physical and security constraints are taken into account in the optimization problem. Simulation results show the effectiveness of the methodology
Implementation of feedback linearization GPC control for a solar furnace
No full textIn this paper the temperature control of a solar furnace is addressed. In particular, we propose the use of a feedback linearization generalized predictive control strategy where both the reference tracking task and the rejection of disturbances (represented by the variation of the input energy provided by the Sun, mainly because of the solar daily cycle and passing clouds) are considered. This allows the physical and security constraints to be explicitly taken into account in the design. Simulation and experimental results show the effectiveness of the methodology and that this kind of plants can be considered as a cheap or alternative option for the material treatment and testing in the industrial context
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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