1,721,077 research outputs found
Fast parallel LQ regulator design for adaptive control
No full textA new fast algorithm for linear quadratic (LQ) control optimization is derived using a partial state formulation and is exploited for the synthesis of long-range predictive controllers. The new algorithm requires O(Nn) computations for an nth-order plant and N-step prediction horizon and is about twice as cheap as existing fast algorithms. Systolic implementation on arrays of O(n) processors is also considered to get an O(N) processing time. Both fast algorithms and systolic implementation can be used to considerably speed up the control design task in adaptive predictive control schemes and thus increase the adaptation bandwidth
Clockwise property of the Nyquist plot with implications for absolute stability
No full textIn this paper the clockwise property of the Nyquist plot of stable transfer functions is addressed. The relationships between clockwise property and modulus and/or phase monotonicity are analyzed. Some necessary and sufficient conditions for a class of stable transfer functions to enjoy the clockwise property are obtained. These results are used to enlarge the class of systems for which the Kalman conjecture on absolute stability of nonlinear systems holds
Convexity properties of polynomials with assigned root location
No full textThis paper presents some geometrical results on the domain of (generalized) stability for a family of nth order polynomials. Regions of root location such that the convex hull of the corresponding domain of stability in the coefficient space is a polyhedron are investigated, and specific regions for which the convex hull is an n+1 vertex polyhedron are derived. The discrete-time stability domain falls in the latter class of regions. Implications of the results for the design of filters solving the robust strict positive realness for families of rational transfer functions with uncertainty in the numerator are also developed
Enhancing strict positive realness condition on families of polynomials by filter design
No full textSome results on strict positive realness of families of polynomials are given. The main motivation for these results is the need for design criteria of filters ensuring the convergence of algorithms in the presence of uncertainty in the plant model in the area of identification and adaptive control. Two main results are given. The first provides analytical conditions under which a family of polynomials with zeros in a prescribed region of the complex plane is strict positive real or can be made strict positive real over an assigned region of the complex plane through the use of a suitable filter. The second is a design result providing a parameterization of a family of filters maximizing the region of the complex plane on which strict positive realness is achievable
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
Design criteria for robust strict positive realness in adaptive schemes
No full textDesign of filters ensuring convergence of recursive estimation algorithms in the presence of uncertainty in the plant model is a key problem in the area of identification and adaptive control. This paper addresses the problem of designing filters ensuring strict positive realness of a family of uncertain polynomials over an assigned region of the complex plane. The uncertainty is assumed to be both structured and unstructured. When the structured uncertainty of the family is represented through regions of root location of a certain shape (for instance, circles centered on the real axis), an optimal solution of the problem is provided. For more general uncertainty regions, a simple procedure for constructing sub-optimal solutions to the filter design problem is proposed. A numerical example is fully developed to show the effectiveness of the proposed approach
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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