1,720,994 research outputs found
A New Approach To Detectability Of Discrete-time Infinite Markov Jump Linear Systems
No full textThis paper deals with detectability for the class of discrete-time Markov jump linear systems (MJLS) with the underlying Markov chain having countably infinite state space. The formulation here relates the convergence of the output with that of the state variables. Our approach introduces invariant subspaces for the autonomous system and exhibits the role that they play. This allows us to show that detectability can be written equivalently in term of two conditions: stability of the autonomous system in a certain invariant space and convergence of general state trajectories to this invariant space under convergence of input and output variables. This, in turn, provides the tools to show that detectability here generalizes uniform observability ideas as well as previous detectability notions for MJLS with finite state Markov chain, and allows us to solve the jump-linear-quadratic control problem. In addition, it is shown for the MJLS with finite Markov state that the second condition is redundant and that detectability retrieves previously well-known concepts in their respective scenarios. detectability, stochastic systems, Markov jump systems, infinite Markov state space, optimal control © 2005 IEEE.200566626667E. F. COSTA AND J. B. R. DO VAL, On the detectability and observability of discrete-time Markov jump linear systems, Systems Control Lett., 44 (2001), pp. 135-145E. F. COSTA AND J. B. R. DO VAL, On the detectability and observability of continuous-time Markov jump linear systems, SIAM J. Control Optim., 41 (2002), pp. 1295-1314E. F. COSTA AND J. B. R. DO VAL, Weak detectability and the linear quadratic control problem of discrete-time Markov jump linear systems, Int. J. Control, 16/17 (2002), pp. 1282-1292COSTA, E.F., VAL, J.B.R.D., FRAGOSO, M.D., On a detectability concept of discrete-time infinite Markov jump linear systems Stochastic Analysis and Applications, , to appearCOSTA, E.F., VAL, J.B.R.D., FRAGOSO, M.D., On a detectability concept of discrete-time infinite Markov jump linear systems (2002) Proceedings of the 15th Triennal World Congress IFAC, pp. 2660-2665COSTA, O.L.V., Discrete-time coupled Riccati equations for systems with Markov switching parameters (1995) J. Math. Anal. Appl, 194, pp. 197-216COSTA, O.L.V., FRAGOSO, M.D., Discrete-time LQ-optimal control problems for infinite Markov jump parameter systems (1995) IEEE Trans. Automat. Control, 40, pp. 2076-2088FRAGOSO, M.D., BACZYNSKI, J., Optimal control for continuous time problems with infinite Markov jump parameters (2001) SIAM J. Control Optim, 40, pp. 270-297FRAGOSO, M.D., BACZYNSKI, J., Lyapunov coupled equations for continuous-time infinite Markov jump linear systems (2002) J. Math. Anal. Appl, 274, pp. 319-335FRAGOSO, M.D., BACZYNSKI, J., Stochastic versus mean square stability in continuous time linear infinite Markov jump parameter systems (2002) Stochastic Anal. Appl, 20, pp. 347-356Y. JI AND H. J. CHIZECK, Controllability, stabilizability and continuous time Markovian jump linear quadratic control, IEEE Trans. Automat. Control, 35 (1990), pp. 777-788MOROZAN, T., Stability and control for linear systems with jump Markov perturbations (1995) Stochastic Anal. Appl, 13, pp. 91-110W. S. GRAY AND J. P. MESKO, Observability functions for linear and nonlinear systems, Systems Control Lett., 38 (1999), pp. 99-113R. A. HORN AND C. R. JOHNSON, Matrix Analysis, Cambridge University Press, Cambridge, UK, 1990KAILATH, T., (1980) Linear Systems, , Prentice-Hall, Englewood Cliffs, NJKNOPP, K., (1956) Infinite Sequences and Series, , Dover, New YorkPETERSEN, I.R., Notions of observability for uncertain linear systems with structured uncertainty (2002) SIAM J. Control Optim, 41, pp. 345-36
Approximate dynamic programming via direct search in the space of value function approximations
No full textThis paper deals with approximate value iteration (AVI) algorithms applied to discounted dynamic programming (DP) problems. For a fixed control policy, the span semi-norm of the so-called Bellman residual is shown to be convex in the Banach space of candidate solutions to the DP problem. This fact motivates the introduction of an AVI algorithm with local search that seeks to minimize the span semi-norm of the Bellman residual in a convex value function approximation space. The novelty here is that the optimality of a point in the approximation architecture is characterized by means of convex optimization concepts and necessary and sufficient conditions to local optimality are derived. The procedure employs the classical AVI algorithm direction (Bellman residual) combined with a set of independent search directions, to improve the convergence rate. It has guaranteed convergence and satisfies, at least, the necessary optimality conditions over a prescribed set of directions. To illustrate the method, examples are presented that deal with a class of problems from the literature and a large state space queueing problem setting.</p
Weak Detectability And The Lq Problem Of Discrete-time Infinite Markov Jump Linear Systems
No full textThe paper deals with a concept of weak detectability for discrete-tine infinite Markov jump linear systems, which relates the stochastic convergence of the output with the stochastic convergence of the state and generalizes previous concepts. Certain invariant sets are introduced, which allow us to find a related system that is stochastically detectable if and only if the original system is weakly detectable. This provides the necessary tools to show, via an additional assumption, that the weak detectability concept is invariant with respect to linear state feedback control. As an immediate extension, the result provides that linear state feedback controls are stabilizing whenever the associated cost functional is bounded. In addition, it is shown that the detectability concept assures that the solution of the JLQ is stabilizing and the solution of the associated algebraic Riccati equation is unique and stabilizing, thus retrieving the usual role that detectability concepts play in finite dimensional MJLS and linear deterministic systems. Finally, regarding the assumption, the paper shows that: it is not related to the detectability concept, it always holds for finite dimensional Markov jump linear systems, and it holds under a condition of uniform observability on trajectories associated with non-convergent output.657895794Costa, E.F., Do Val, J.B.R., On the detectability and observability of discrete-time Markov jump linear systems (2001) System Control Lett., 44, pp. 135-145Costa, E.F., Do Val, J.B.R., On the detectability and observability of continuous-time Markov jump linear systems (2002) SIAM J. Control Optim., 41 (4), pp. 1295-1314Costa, E.F., Do Val, J.B.R., Weak detectability and the linear quadratic control problem of discrete-time Markov jump linear systems (2002) Internat. J. Control, 75 (16-17), pp. 1282-1292Costa, E.F., Do Val, J.B.R., Fragoso, M.D., On a detectability concept of discrete-time infinite Markov jump linear systems (2002) IFAC 15th World Congress, pp. 2660-2665. , BarcelonaCosta, O.L.V., Fragoso, M.D., Discrete-time LQ-optimal control problems for infinite Markov jump parameter systems (1995) IEEE Trans. Automat. Control, AC-40, pp. 2076-2088Fragoso, M., Baczynski, J., Optimal control for continuous time LQ problems with infinite Markov jump parameters (2001) SIAM J. Control Optim., 40 (1), pp. 270-297Fragoso, M.D., Baczynski, J., Stochastic versus mean square stability in continuous time linear infinite Markov jump parameter systems (2002) Stochastic Anal. Appl., 20 (20), pp. 347-356Golub, G.H., Loan, C.V., (1996) Matrix Computation, , Johns Hopkins Press, London, third editio
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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