597,467 research outputs found

    Implementing Distributed Controllers for Systems with Priorities

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    Implementing a component-based system in a distributed way so that it ensures some global constraints is a challenging problem. We consider here abstract specifications consisting of a composition of components and a controller given in the form of a set of interactions and a priority order amongst them. In the context of distributed systems, such a controller must be executed in a distributed fashion while still respecting the global constraints imposed by interactions and priorities. We present in this paper an implementation of an algorithm that allows a distributed execution of systems with (binary) interactions and priorities. We also present a comprehensive simulation analysis that shows how sensitive to changes our algorithm is, in particular changes related to the degree of conflict in the system.Comment: In Proceedings FOCLASA 2010, arXiv:1007.499

    Hydrogen vs. Battery in the long-term operation. A comparative between energy management strategies for hybrid renewable microgrids

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    The growth of the world’s energy demand over recent decades in relation to energy intensity and demography is clear. At the same time, the use of renewable energy sources is pursued to address decarbonization targets, but the stochasticity of renewable energy systems produces an increasing need for management systems to supply such energy volume while guaranteeing, at the same time, the security and reliability of the microgrids. Locally distributed energy storage systems (ESS) may provide the capacity to temporarily decouple production and demand. In this sense, the most implemented ESS in local energy districts are small–medium-scale electrochemical batteries. However, hydrogen systems are viable for storing larger energy quantities thanks to its intrinsic high mass-energy density. To match generation, demand and storage, energy management systems (EMSs) become crucial. This paper compares two strategies for an energy management system based on hydrogen-priority vs. battery-priority for the operation of a hybrid renewable microgrid. The overall performance of the two mentioned strategies is compared in the long-term operation via a set of evaluation parameters defined by the unmet load, storage efficiency, operating hours and cumulative energy. The results show that the hydrogen-priority strategy allows the microgrid to be led towards island operation because it saves a higher amount of energy, while the battery-priority strategy reduces the energy efficiency in the storage round trip. The main contribution of this work lies in the demonstration that conventional EMS for microgrids’ operation based on battery-priority strategy should turn into hydrogen-priority to keep the reliability and independence of the microgrid in the long-term operation

    A distributed Real-Time Java system based on CSP

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    CSP is a fundamental concept for developing software for distributed real time systems. The CSP paradigm constitutes a natural addition to object orientation and offers higher order multithreading constructs. The CSP channel concept that has been implemented in Java deals with single- and multi-processor environments and also takes care of the real time priority scheduling requirements. For this, the notion of priority and scheduling has been carefully examined and as a result it was reasoned that priority scheduling should be attached to the communicating channels rather than to the processes. In association with channels, a priority based parallel construct is developed for composing processes: hiding threads and priority indexing from the user. This approach simplifies the use of priorities for the object oriented paradigm. Moreover, in the proposed system, the notion of scheduling is no longer connected to the operating system but has become part of the application instead

    The International Right to Health: What Does It Mean in Legal Practice and How Can It Affect Priority Setting for Universal Health Coverage?

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    The international right to health is enshrined in national and international law. In a growing number of cases, individuals denied access to high-cost medicines and technologies under universal coverage systems have turned to the courts to challenge the denial of access as against their right to health. In some instances, patients seek access to medicines, services, or technologies that they would have access to under universal coverage if not for government, health system, or service delivery shortfalls. In others, patients seek access to medicines, services, or technologies that have not been included or that have been explicitly denied for coverage due to prioritization. In the former, judicialization of the right to health is critical to ensure patients access to the technologies or services to which they are entitled. In the latter, courts may grant patients access to medicines not covered as a result of explicit priority setting to allocate finite resources. By doing so, courts may give priority to those with the means and incentive to turn to the courts, at the expense of the maximization of equity- and population-based health. Evidence- based, informed decision-making processes could ensure that the most clinically and cost-effective products aligning with social value judgments are prioritized. Governments should be equipped to engage in and defend rational priority setting as a means to promote fair allocation of resources to maximize population health. Rational priority setting is an evidence-based form of explicit priority setting, where the priority setting process is deliberate and transparent, the decision makers are specified, relevant stakeholders are involved, and the best available evidence about clinical and cost-effectiveness and social values is considered. The most rational priority setting processes will also account for the benefit to patients, the cost, the ethicality and the fairness. The priority setting process and institutions involved should then be held accountable through an appeals process, allowing independent review by health systems, health care, and other relevant experts, and an opportunity for judicial review. While the implementation of a three-step (1) rational priority setting, (2) appeals, and (3) judicial review process will differ depending on a country’s resource constraints, political systems, and social values, the authors argue that the three stages together will promote the greatest accountability and fairness. As a result, the courts could place greater reliance on the government’s coverage choices, and the population’s health could be most equitably distributed

    Assess program: Interactive data management systems for airborne research

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    Two data systems were developed for use in airborne research. Both have distributed intelligence and are programmed for interactive support among computers and with human operators. The C-141 system (ADAMS) performs flight planning and telescope control functions in addition to its primary role of data acquisition; the CV-990 system (ADDAS) performs data management functions in support of many research experiments operating concurrently. Each system is arranged for maximum reliability in the first priority function, precision data acquisition

    Parametric Schedulability Analysis of Fixed Priority Real-Time Distributed Systems

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    Parametric analysis is a powerful tool for designing modern embedded systems, because it permits to explore the space of design parameters, and to check the robustness of the system with respect to variations of some uncontrollable variable. In this paper, we address the problem of parametric schedulability analysis of distributed real-time systems scheduled by fixed priority. In particular, we propose two different approaches to parametric analysis: the first one is a novel technique based on classical schedulability analysis, whereas the second approach is based on model checking of Parametric Timed Automata (PTA). The proposed analytic method extends existing sensitivity analysis for single processors to the case of a distributed system, supporting preemptive and non-preemptive scheduling, jitters and unconstrained deadlines. Parametric Timed Automata are used to model all possible behaviours of a distributed system, and therefore it is a necessary and sufficient analysis. Both techniques have been implemented in two software tools, and they have been compared with classical holistic analysis on two meaningful test cases. The results show that the analytic method provides results similar to classical holistic analysis in a very efficient way, whereas the PTA approach is slower but covers the entire space of solutions.Comment: Submitted to ECRTS 2013 (http://ecrts.eit.uni-kl.de/ecrts13

    Cost-effective scheduling analysis through discrete event simulation for distributed systems

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    Large computing systems where globally distributed can be best characterized by their dynamic nature particularly in terms of resource provisioning and scheduling. Users of the systems normally aim to maximize their own interest when consuming the shared resources. Apart from that, the pro- cessing requirements that submitted by the systems’ users are diverse in their properties (e.g., size, priority). This condition makes the resources in distributed system overwhelmed by heterogeneity of task to be processed; that leads to fluctuation in resource availability. There are researchers’ proposed scheduling algorithms and evaluated through simulation system in order to improve resource availability. It is because the simulation system is able to save cost rather than real test bed experimental. In response to this, we proposed priority-based scheduling algorithm for improving resource availability that developed using discrete-event simulation approach. We de fined several events in the simulation to represent various execution statuses that used to monitor resource state in the distributed systems. Our simulation system successfully gives better performance in terms of waiting time compared than other works that also used simulation as their experimental platform
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