1,721,186 research outputs found
Bang-Bang Property for Bolza Problems in Two Dimensions
No full textConsider the following Bolza problem: min integral h(x, u)dt, x = F(x) + uG(x), \u\ less-than-or-equal-to 1, x is-an-element-of OMEGA subset-of R2, x(0) = x0, x(1) = x1. We show that, under suitable assumptions on F, G, h, all optimal trajectories are bang-bang. The proof relies on a geometrical approach that works for every smooth two-dimensional manifold. As a corollary, we obtain existence results for nonconvex optimization problems
Minisimposium "Control Problems for Fluidodynamic Models"
No full textThe minisimposium was part of the "6th International Congress on Industrial and Applied Mathematics (ICIAM 2007)'', held in ETH e University of Zurich, on July 2007. It was aimed to put together researchers working in the field of control problem for nonlinear hyperbolic PDEs and in modelization of traffic flow problems and supply chains.
Abstract:
The theory of weak solutions of hyperbolic conservation laws received many foundamental contributions in the last years. In particular, the well-posedness theory for the Cauchy problem and for the mixed initial-boundary value problem is now well established in the case of systems in one space dimension. On the other hand, the study of these equations from the point of view of control theory is still at an early stage. The interest on such problems is motivated by applications to traffic flow models, multicomponent chromatography, as well as in problems of oil resevoir simulation and gas dynamic. Another related interesting area of research regards the control of equations over networks, to address application domain as car traffic flow, telecommunication, irrigation channels, etc.
When studying the effect of the boundary data treated as controls acting on the solutions of a conservation law one cannot expect to achieve in general complete controllability results within the space of discontinuous weak solutions, due to the particular wave-front structure of the solutions of such systems. It is then more appropriate to consider the problem of asymptotic stabilization of an hyperbolic system with boundary controls. Of particular interest for applications are general boundary controllability and stabilizability problems where the control acts only on some of the boundary conditions.
Another relevant direction in which it is being pursued the investigation of hyperbolic control problems is the study of necessary conditions for the optimality of a weak solution where the controls may act through the boundary conditions as well as through the source term of the balance laws. Here, the main source of difficulties stems from the fact that the input-to-trajectory map that associates to a given control the corresponding solution may not be differentiable in any natural Banach space. For this reason to tackle such problems it has been crucial to introduce a suitable variational structure on the flow generated by conservation laws
Feedback Encoding for Efficient Symbolic Control of Dynamical Systems
No full textThe problem of efficiently steering dynamical systems by generating finite input plans is considered. Finite plans are finite--length words constructed on a finite alphabet of input symbols, which could be e.g. transmitted through a limited capacity channel to a remote system, where they can be decoded in suitable control actions. Efficiency is considered in terms of the computational complexity of plans, and in terms of their description length (in number of bits). We show that, by suitable choice of the control encoding, finite plans can be efficiently built for a wide class of dynamical systems, computing arbitrarily close approximations of a desired equilibrium in polynomial time. The paper also investigates how the efficiency of planning is affected by the choice of inputs, and provides some results as to optimal performance in terms of accuracy and range
On the reachability of quantized control systems
No full textIn this paper, we study control systems whose input sets are quantized, i.e., finite or regularly distributed on a mesh. We specifically focus on problems relating to the structure of the reachable set of such systems, which may turn out to be either dense or discrete. We report results on the reachable set of linear quantized systems, and on a particular but interesting class of nonlinear systems, i.e., nonholonomic chained-form systems. For such systems, we provide a complete characterization of the reachable set, and, in case the set is discrete, a computable method to completely and succinctly describe its structure. Implications and open problems in the analysis and synthesis of quantized control systems are addresse
Reachability Analysis for a Class of Quantized Control Systems
No full textWe study control systems whose input sets are quantized. We specifically focus on problems relating to the structure of the reachable set of such systems, which may turn out to be either dense or discrete. We report on some results on the reachable set of linear quantized systems, and study in detail an interesting class of nonlinear systems, forming the discrete counterpart of driftless nonholonomic continuous systems. For such systems, we provide a complete characterization of the reachable set, and, in the case the set is discrete, a computable method to describe its lattice structur
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
Quantized Control Systems and Discrete Nonholonomy
No full textIn this paper we study control systems whose input sets are quantized, and in particular finite or countable but nowhere dense. We specifically focus on problems relating to the structure of the reachable set of such systems, which may turn out to be either dense or discrete. We report results on the rechable set of linear quantized systems, and on a particular but interesting class of nonlinear systems, forming the discrete counterpart of driftless nonholonomic continuous systems. Implications and open problems in the analysis and synthesis of quantized control systems are addressed
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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