11,897 research outputs found

    Governing by internet architecture

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    In the past thirty years, the exponential rise in the number of Internet users around the word and the intensive use of the digital networks have brought to light crucial political issues. Internet is now the object of regulations. Namely, it is a policy domain. Yet, its own architecture represents a new regulative structure, one deeply affecting politics and everyday life. This article considers some of the main transformations of the Internet induced by privatization and militarization processes, as well as their consequences on societies and human beings.En los últimos treinta años ha crecido de manera exponencial el número de usuarios de Internet alrededor del mundo y el uso intensivo de conexiones digitales ha traído a la luz cuestiones políticas cruciales. Internet es ahora objeto de regulaciones. Es decir, es un ámbito de la política. Aún su propia arquitectura representa una nueva estructura reguladora, que afecta profundamente la política y la vida cotidiana. Este artículo considera algunas de las principales transformaciones de Internet inducida por procesos de privatización y militarización, como también sus consecuencias en las sociedades y en los seres humanos

    Decentralized Implementation of Centralized Controllers for Interconnected Systems

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    Given a centralized controller associated with a linear time-invariant interconnected system, this paper is concerned with designing a parameterized decentralized controller such that the state and input of the system under the obtained decentralized controller can become arbitrarily close to those of the system under the given centralized controller, by tuning the controller's parameters. To this end, a two-level decentralized controller is designed, where the upper level captures the dynamics of the centralized closed-loop system, and the lower level is an observed-based sub-controller designed based on the new notion of structural initial value observability. The proposed method can decentralize every generic centralized controller, provided the interconnected system satisfies very mild conditions. The efficacy of this work is elucidated by some numerical examples

    A Near-Optimal Decentralized Servomechanism Controller for Hierarchical Interconnected Systems

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    This paper is concerned with decentralized output regulation of hierarchical systems subject to input and output disturbances. It is assumed that the disturbance can be represented as the output of an autonomous LTI system with unknown initial state. The primary objective is to design a decentralized controller with the property that not only does it reject the degrading effect of the disturbance on the output (for a satisfactory steady-state performance), it also results in a small LQ cost function (implying a good transient behavior). To this end, the underlying problem is treated in two phases. In the first step, a number of modified systems are defined in terms of the original system. The problem of designing a LQ centralized controller which stabilizes all the modified systems and rejects the disturbance in the original system is considered, and it is shown that this centralized controller can be efficiently found by solving a LMI problem. In the second step, a method recently presented in the literature is exploited to decentralize the designed centralized controller. It is proved that the obtained controller satisfies the pre-determined design specifications including disturbance rejection. Simulation results elucidate the efficacy of the proposed control law

    Identification and Optimal Control of Large-Scale Systems Using Selective Decentralization

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    In this paper, we explore the capability of selective decentralization in improving the control performance for unknown large-scale systems using model-based approaches. In selective decentralization, we explore all of the possible communication policies among subsystems and show that with the appropriate switching among the resulting multiple identification models (with corresponding communication policies), such selective decentralization significantly outperforms a centralized identification model when the system is weakly interconnected, and performs at least equivalent to the centralized model when the system is strongly interconnected. To derive the sub-optimal control, our control design include two phases. First, we apply system identification to train the approximation model for the unknown system. Second, we find the suboptimal solution of the Halminton-Jacobi-Bellman (HJB) equation to derive the suboptimal control. In linear systems, the HJB equation transforms to the well-solved Riccati equation with closed-form solution. In nonlinear systems, we discretize the approximation model in order to acquire the control unit by using dynamic programming methods for the resulting Markov Decision Process (MDP). We compare the performance among the selective decentralization, the complete decentralization and the centralization in our two-phase control design. Our results show that selective decentralization outperforms the complete decentralization and the centralization approaches when the systems are completely decoupled or strongly interconnected

    The Ecosystem Approach to Fisheries: Issues, Terminology, Principles, Institutional Foundations, Implementation and Outlook

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    Ecosystems are complex and dynamic natural units that produce goods and services beyond those of benefit to fisheries. Because fisheries have a direct impact on the ecosystem, which is also impacted by other human activities, they need to be managed in an ecosystem context. The meaning of the terms 'ecosystem management', 'ecosystem based management', 'ecosystem approach to fisheries'(EAF), etc., are still not universally defined and progressively evolving. The justification of EAF is evident in the characteristics of an exploited ecosystem and the impacts resulting from fisheries and other activities. The rich set of international agreements of relevance to EAF contains a large number of principles and conceptual objectives. Both provide a fundamental guidance and a significant challenge for the implementation of EAF. The available international instruments also provide the institutional foundations for EAF. The FAO Code of Conduct for Responsible Fisheries is particularly important in this respect and contains provisions for practically all aspects of the approach. One major difficulty in defining EAF lies precisely in turning the available concepts and principles into operational objectives from which an EAF management plan would more easily be developed. The paper discusses these together with the types of action needed to achieve them. Experience in EAF implementation is still limited but some issues are already apparent, e.g. in added complexity, insufficient capacity, slow implementation, need for a pragmatic approach, etc. It is argued, in conclusion, that the future of EAF and fisheries depends on the way in which the two fundamental concepts of fisheries management and ecosystem management, and their respective stakeholders, will join efforts or collide
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