323,059 research outputs found
Ageing and innovation.Exploring a collective matter of concern
No full textOver the last few years, Science and Technology Studies and socio-gerontology have moved beyond the interventionist logic, whereby users are perceived as «targets» of techno-scientific instruments aimed at solving their needs, contributing decisively to the emergence of an alternative perspective on ageing. This special issue aims to follow this direction. It offers a multifaceted mapping of the current debate about how ageing and techno-scientific innovation shape each other through the involvement of heterogeneous actors such as scientific communities, market and industrial systems, digital media, self-tracking technologies, healthcare professionals, and the elderly and their social networks. Presenting the rationale of the papers that compose the Special Issue, we suggest four themes arising when empirically and theoretically approaching these intricacies: i) ageing research and medicine; ii) ageing, social media, and public discourses; iii) ageing, ICTs, and daily life. Drawing on the discussion of the selected papers, we will argue that ageing emerges as a collective matter of concern marked by multiplicity
Positive real control of two-dimensional systems: Roesser models and linear repetitive processes
No full textThis paper considers the problem of positive real control for two-dimensional (2-D) discrete systems described by the Roesser model and also discrete linear repetitive processes, which are another distinct sub-class of 2-D linear systems of both systems theoretic and applications interest. The purpose of this paper is to design a dynamic output feedback controller such that the resulting closed-loop system is asymptotically stable and the closed-loop system transfer function from the disturbance to the controlled output is extended strictly positive real. We first establish a version of positive realness for 2-D discrete systems described by the Roesser state space model, then a sufficient condition for the existence of the desired output feedback controllers is obtained in terms of four LMIs. When these LMIs are feasible, an explicit parameterization of the desired output feedback controllers is given. We then apply a similar approach to discrete linear repetitive processes represented in their equivalent 1-D state-space form. Finally, we provide numerical examples to demonstrate the applicability of the approach
Time-relevant stability of 2D systems
No full textFor many 2D systems, one of the independent variables plays a distinct role in the evolution of the trajectories; since often this special independent variable is time, we call such systems 'time-relevant'. In this paper, we introduce a stability notion for time-relevant systems described by higher-order difference equations. We give algebraic tests in terms of the location of the zeros of the determinant of a polynomial matrix describing the system. We also give an LMI characterization of time-relevant stability involving only constant matrices
Analyse des notions de stabilité pour les modèles 2D de Roesser et de Fornasini-Marchesini
No full textThis thesis presents the results of research work on different notions of stability used in the literature of multidimensional dynamical systems. More precisely, within the framework of the 2D Roesser and Fornasini-Marchesini models, we analyze the notions of stability in the sense of Lyapunov, asymptotic stability, exponential stability(ies) and structural stability, as well as the relations between these different properties. The first chapter of this thesis carries out a certain number of reminders concerning the definitions of stability and the links which exist between them, with the aim of establishing a solid framework in order to extend these notions from the 1D case to the 2D case. Once these reminders have been established, we present the 2D models that we are studying. The second chapter lists the stability definitions used for the 2D Roesser and Fornasini-Marchesini models and establishes the links between these different definitions. In the third chapter, we propose a necessary and sufficient condition of asymptotic stability for a certain class of linear discrete 2D Fornasini-Marchesini models. The fourth and last chapter proposes a detailed study of a non-linear 1D model which has the rare characteristic of being both attractive and unstable, and we generalize this particular model to the 2D case in order to establish which properties are conserved. or not when passing from the 1D case to the 2D case.Cette thèse présente les résultats de travaux sur lLes différentes notions de stabilité utilisées dans la littérature des systèmes dynamiques multidimensionnels. Plus précisément, dans le cadre des modèles 2D de Roesser et de Fornasini-Marchesini, nous analysons les notions de stabilité au sens de Lyapunov, stabilité asymptotique, stabilité(s) exponentielle(s) et stabilité structurelle, ainsi que les relations entre ces différentes propriétés. Le premier chapitre de ce mémoire effectue un certain nombre de rappels concernant les définitions de stabilité et les liens qui existent entre celles-ci, dans le but d'établir un cadre solide en vue d'étendre ces notions du cas 1D au cas 2D. Une fois ces rappels établis, nous présentons les modèles 2D que nous étudions. Le deuxième chapitre dresse la liste des définitions de stabilité utilisées pour les modèles 2D de Roesser et de Fornasini-Marchesini et établit les liens entre ces différentes définitions. Au cours du troisième chapitre, nous proposons une condition nécessaire et suffisante de stabilité asymptotique pour une certaine classe de modèles de Fornasini-Marchesini 2D discrets linéaires. Le quatrième et dernier chapitre propose une étude détaillée d'un modèle 1D non-linéaire qui possède la particularité rare d'être à la fois attractif et instable, et nous généralisons ce modèle particulier au cas 2D afin d'établir quelles propriétés se conservent ou non lorsque l'on passe du cas 1D au cas 2D
Filtering for uncertain 2-D discrete systems with state delays
No full textThis is the post print version of the article. The official published version can be obtained from the link below - Copyright 2007 Elsevier Ltd.This paper is concerned with the problem of robust H∞ filtering for two-dimensional (2-D) discrete systems with time-delays in states. The 2-D systems under consideration are described in terms of the well-known Fornasini–Marchesini local state-space (FMLSS) models with time-delays. Our attention is focused on the design of a full-order filter such that the filtering error system is guaranteed to be asymptotically stable with a prescribed H∞ disturbance attenuation performance. Sufficient conditions for the existence of desired filters are established by using a linear matrix inequality (LMI) approach, and the corresponding filter design problem is then cast into a convex optimization problem that can be efficiently solved by resorting to some standard numerical software. Furthermore, the obtained results are extended to more general cases where the system matrices contain either polytopic or norm-bounded parameter uncertainties. A simulation example is provided to illustrate the effectiveness of the proposed design method.This work was partially supported by the National Natural Science Foundation of China (60504008), Program for New Century Excellent Talents in University of China and the Postdoctoral Science Foundation of China (20060390231)
Polynomial inverses of 2D transfer matrices and finite memory realizations via inverse systems
No full textLet G(z1,z2) be a p×m 2D proper rational transfer matrix, with full column rank, and S= (A1,A2,B1,B2,C, D) a state-space realization of its. Necessary and sufficient conditions are presented in this paper, which guarantee that (i) G(z1,z2) admits polynomial left inverses, (ii) such polynomial inverses are transfer matrices of some inverse system of sum. When the above conditions are not fulfilled, the existence of stable and/or proper, possibly delayed, inverses ofG(z1,z2), is also discussed
La memoria della materia, la materia della memoria
No full textThe first part of the paper is devoted to the analysis of dynamical systems performance. Specifically, in these systems the effects of past inputs on the present state may be regarded as a form of memory (whereas a static system can be considered as memoryless). The second part of the paper describes the standard storage devices adopted in the field of computer technology as well as other storing devices for recording words, sounds and images
Analysis of the notions of stability for the 2D Roesser and Fornasini-Marchesini models
No full textCette thèse présente les résultats de travaux sur lLes différentes notions de stabilité utilisées dans la littérature des systèmes dynamiques multidimensionnels. Plus précisément, dans le cadre des modèles 2D de Roesser et de Fornasini-Marchesini, nous analysons les notions de stabilité au sens de Lyapunov, stabilité asymptotique, stabilité(s) exponentielle(s) et stabilité structurelle, ainsi que les relations entre ces différentes propriétés. Le premier chapitre de ce mémoire effectue un certain nombre de rappels concernant les définitions de stabilité et les liens qui existent entre celles-ci, dans le but d'établir un cadre solide en vue d'étendre ces notions du cas 1D au cas 2D. Une fois ces rappels établis, nous présentons les modèles 2D que nous étudions. Le deuxième chapitre dresse la liste des définitions de stabilité utilisées pour les modèles 2D de Roesser et de Fornasini-Marchesini et établit les liens entre ces différentes définitions. Au cours du troisième chapitre, nous proposons une condition nécessaire et suffisante de stabilité asymptotique pour une certaine classe de modèles de Fornasini-Marchesini 2D discrets linéaires. Le quatrième et dernier chapitre propose une étude détaillée d'un modèle 1D non-linéaire qui possède la particularité rare d'être à la fois attractif et instable, et nous généralisons ce modèle particulier au cas 2D afin d'établir quelles propriétés se conservent ou non lorsque l'on passe du cas 1D au cas 2D.This thesis presents the results of research work on different notions of stability used in the literature of multidimensional dynamical systems. More precisely, within the framework of the 2D Roesser and Fornasini-Marchesini models, we analyze the notions of stability in the sense of Lyapunov, asymptotic stability, exponential stability(ies) and structural stability, as well as the relations between these different properties. The first chapter of this thesis carries out a certain number of reminders concerning the definitions of stability and the links which exist between them, with the aim of establishing a solid framework in order to extend these notions from the 1D case to the 2D case. Once these reminders have been established, we present the 2D models that we are studying. The second chapter lists the stability definitions used for the 2D Roesser and Fornasini-Marchesini models and establishes the links between these different definitions. In the third chapter, we propose a necessary and sufficient condition of asymptotic stability for a certain class of linear discrete 2D Fornasini-Marchesini models. The fourth and last chapter proposes a detailed study of a non-linear 1D model which has the rare characteristic of being both attractive and unstable, and we generalize this particular model to the 2D case in order to establish which properties are conserved. or not when passing from the 1D case to the 2D case
Robust synchronization for 2-D discrete-time coupled dynamical networks
No full textThis is the post-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2012 IEEEIn this paper, a new synchronization problem is addressed for an array of 2-D coupled dynamical networks. The class of systems under investigation is described by the 2-D nonlinear state space model which is oriented from the well-known Fornasini–Marchesini second model. For such a new 2-D complex network model, both the network dynamics and the couplings evolve in two independent directions. A new synchronization concept is put forward to account for the phenomenon that the propagations of all 2-D dynamical networks are synchronized in two directions with influence from the coupling strength. The purpose of the problem addressed is to first derive sufficient conditions ensuring the global synchronization and then extend the obtained results to more general cases where the system matrices contain either the norm-bounded or the polytopic parameter uncertainties. An energy-like quadratic function is developed, together with the intensive use of the Kronecker product, to establish the easy-to-verify conditions under which the addressed 2-D complex network model achieves global synchronization. Finally, a numerical example is given to illustrate the theoretical results and the effectiveness of the proposed synchronization scheme.This work was supported in part by the National Natural Science Foundation of China under Grants 61028008 and 61174136, the International Science and Technology Cooperation Project of China under
Grant No. 2009DFA32050, the Natural Science Foundation of Jiangsu Province of China under Grant BK2011598, the Qing Lan Project of Jiangsu Province of China, the Project sponsored by SRF for ROCS of SEM of China, the Engineering and Physical Sciences Research Council (EPSRC) of the U.K. under Grant GR/S27658/01, the Royal Society of the U.K., and the Alexander von Humboldt Foundation of Germany
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