1,721,286 research outputs found
Embedded multivalued control for ceramic manufacturing
No full textThis paper presents the realization of a prototypal embedded system which implements a new control law characterized by a fixed and quantized control set. This effort is motivated by the observation that many industrial plants with high parametric uncertainties, both for constructive simplicity and/or in order to minimize the operation cost, are usually commanded with signals that can only assume a finite number of values. This paper proposes a new multivalued control algorithm which is robust with respect to disturbances and plant's uncertain parameters and consents the plant's output to practically track a given reference trajectory, with preassigned maximum values of the tracking error and its first derivative. Moreover, this paper deals with the digital realization of this new multivalued control law and the key issues associated with its microprocessor implementation. The efficiencies of the methodology and of the design procedure utilized for the realization of the embedded system are shown through a very interesting application: a temperature control system for a ceramic kiln
Practical tracking via finite-valued control for uncertain SISO plants
No full textIn this paper we present a new technique for control design, with controllers characterized by control signals that may assume only a finite number of values, in order to force a SISO linear plant, subject to disturbances and parametric uncertainties, to track a given sufficiently regular reference trajectory.
The used approach is based on Lyapunov method and allows designing a control law, with prescribed levels of the control signal, which guarantees to follow the reference trajectory with specified values of the tracking error and of its derivatives until n-1 , where n is the order of the plant, and in particular with specified values of the error and of its first derivative.
The proposed control law is a generalization of the traditional relay control laws and of the sliding mode ones. It is quite robust, guarantees the convergence of the error in a prefixed time, generally has a relatively low switching frequency and it can be easily realized with a low cost microcontroller.
Moreover, we present a simple example that shows the advantages of the control law obtained with the proposed design methodology with respect to the ones obtained using sliding mode and classical relay approaches
OPTIMAL DESIGN OF ROBUST CONTROL SYSTEMS WITH LARGE BAND REFERENCE SIGNALS
No full textIn this paper, a new technique in controller design is presented. Its aim is to force a linear plant to track, with a prefixed error, a class of reference trajectories characterized by an assigned band. Furthermore, the designed control is robust with respect to parametric uncertainties, disturbances and it guarantees limitations of some internal signals. The design methodology is based on the introduction of an important project parameter, the time delay within which the command can be considered to have been carried out, by a controller structure with sufficient degrees of freedom and by a constrained optimization technique where the initial values of controller parameters are determined by means of the most appropriate techniques of modern control theory. The efficiency of the proposed procedure is illustrated through the design of a realistic control system for the planar laser scanner. In result consistent improvement in performance can be measure
Multi-valued robust control technique for uncertain systems
No full textA variety of plants with high parametric uncertainties are usually controlled with signals that may assume only a finite number of values, both to simplify actuator's construction and minimize the operation cost. The design of multi-valued control laws which provide a control signal that is discontinuous in time and quantized in magnitude is then of particular interest in many practical applications. This paper presents a new technique for robust control design in order to force a SISO linear plant, subject to disturbances and parametric uncertainties, to track a given sufficiently regular reference trajectory. The proposed approach is based on Lyapunov method and allows designing a control law which guarantees to follow the reference trajectory with prefixed values of the tracking error and of its derivatives up to the n1-th, where n is the order of the plant. Moreover, the control law is quite robust and guarantees the convergence of the error in a prefixed time. The technique is applied to design controllers characterized by control signals that may assume only a finite number of values. In this case, the control law can be seen as a generalization of the traditional relay control laws and of the sliding mode ones, with a relatively low switching frequency. Finally, a simple example shows the advantages of the control law obtained with the proposed design methodology with respect to the classical approaches
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
Synaptic alterations associated with depression and schizophrenia: potential as a therapeutic target
No full textIn recent years, the concept of 'synaptopathy' has been extended from neurodegenerative and neurological disorders to psychiatric diseases. According to this nascent line of research, disruption in synaptic structure and function acts as the main determinant of mental illness. Therefore, molecular systems and processes crucial for synaptic activity may represent promising therapeutic targets.
We review data on synaptic structural alterations in depression and schizophrenia and on specific molecular systems and/or mechanisms important for the maintenance of proper synaptic function. Specifically, we examine the involvement of the neuroligin system, the local protein translation, and the neurotrophin BDNF by reviewing clinical and preclinical studies, with particular attention to results provided by using animal models based on the role of stress in psychiatric diseases. Finally, we also discuss the impact of pharmacological treatment on these molecular systems/mechanisms.
The relevance of synaptic dysfunctions in psychiatric diseases is undoubted and the potential to normalize, ameliorate, and shape such alterations by acting on molecular systems crucial to ensure synaptic function property is fascinating. However, future studies are required to elucidate several open issues
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