162 research outputs found

    An exact relaxation of AC-OPF problem for battery-integrated power grids

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    Renewable energy resources and power electronics-interfaced loads introduce fast dynamics in distribution networks. These dynamics cannot be regulated by slow conventional solutions and require fast controllable energy resources such as Battery Energy Storage Systems (BESSs). To compensate for the high costs associated to BESSs, their energy and power management should be optimized. In this paper, a convex iterative optimization approach is developed to find the optimal active and reactive power setpoints of BESSs in active distribution networks. The objective is to minimize the total cost of energy purchase from the grid. Round-trip and life-time characteristics of BESSs are modelled accurately and integrated into a relaxed and exact formulation of the AC power flow, resulting into a Modified Augmented Relaxed Optimal Power Flow (MAROP) problem. The feasibility and optimality of the solution under the grid security limits and technical constraints of BESSs is proven analytically. A 32-bus IEEE test benchmark is used to illustrate the performance of the developed approach in comparison to the alternative approaches existing in the literature

    Model-based networked control for finite-time stability of nonlinear systems: the stochastic case

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    In this paper we analyze model-based networked control systems for a discrete-time nonlinear plant model, operating in the presence of stochastic dropout of state observations. The dropout is modeled as a Markov chain, and sufficient conditions for finite-time stochastic stability are provided using the stochastic version of Lyapunov second method. In a companion paper we model the dropout as a deterministic sequence

    Finite-time stability of discrete-time nonlinear systems: analysis and design

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    Finite-time stability of nonlinear discrete-time systems is studied. Some new analysis results are developed and applied to controller design

    Stability and finite-time stability analysis of discrete-time nonlinear networked control systems

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    In this paper we present an approach to model networked control systems with a discrete-time nonlinear plant, operating in the presence of arbitrary but finite data dropout of state observations. Sufficient conditions for stability of the global system and finite-time stability over transmission intervals are provided

    Different carbohydrate sources affect swine performance and post-prandial glycaemic response

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    The type of starch and fibre in the diet affects several parameters, including glycaemic and insulin response, that are involved in pig growth performance. Four experimental diets for growing pigs differing for carbohydrates source (corn, barley, faba bean and pea) were tested. The diets were analysed in vitro to assess the carbohydrates characteristics, and they were administered to 56 crossbreed growing pigs (Landrace × Large White) randomly divided into four groups (mean age of 95 ± 6 days; body weight 80 kg ± 4 days). Clinical examination and average daily gain were performed before recruitment and after 40 days of experiment. The metabolic effects were investigated by blood count and serum biochemical parameters and by the glycaemic and insulin post-prandial response. The study revealed substantial differences among the diets, suggesting that alternative feedstuffs for swine affect several parameters, including glycaemic and insulin response, with no negative effects on growing performance. The Barley group showed the highest daily weight gain (p <.05) associated with the highest glycaemic (p <.05) and insulin response at 1 and 2 h post-prandial (p <.01), suggesting that the barley-based diet can support performance comparable to that of the corn-based diet in growing pig. By contrast, the lowest glycaemia was observed in the Faba bean group (p <.05), confirming the capacity of this legume to modulate post-prandial glucose levels. Moreover, the ability of some ingredients in lowering glucose and insulin response enriches the knowledge on functional nutrients for animal diets and to prevent the incidence of enteric diseases.Highlights The type of starch and fibre used in the diet highly affected some blood parameters, such as glycaemic and insulin responses. The Barley group showed the highest daily weight gain. Lower glycaemia levels were observed in the Faba bean group compared to the Corn one. Alternative protein sources for swine diets can limit the glycaemic and insulin response with no negative effects on growing performance

    Parity Effect in a Small Superconducting Particle

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    Matveev and Larkin calculated the parity effect on the ground state energy of a small superconducting particle in the regimes where the mean level spacing is either large or small compared to the bulk gap. We perform a numerical calculation which extends their results into the intermediate regime, where the level spacing is of the same order as the bulk gap.Comment: 6 LaTeX pages, including 2 EPS figures; corrected reference and spellin

    An Overview of Quasi-Monte Carlo Methods in Control Systems

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    Many control problems are so complex that analytic techniques fail to solve them [2]. Furthermore, even when analytic solutions are available, they may be computationally costly [2] and generally result in very high-order compensators [3]. Due to these reasons, we tend to accept approximate answers which provide us with certain performance guarantees for such problems. Sampling methods thus come into the picture to try and remedy the “cost of solution” problem by drawing samples from an appropriate space, and providing an approximate answer. For many years, random sampling has dominated the afore mentioned arena [8, 11, 4]. Random sample generation, with a uniform underlying distribution, however tends to cluster the samples on the boundary of the sample space in higher dimensions. It is for this reason that we are interested in presenting a method that distributes the points regularly in the sample space while providing deterministic guarantees on the error involved. Recently, deterministic or quasi-Monte Carlo (QMC) methods have proven superior to random methods in several applications such as the calculation of certain integrals [6], financial derivatives [7] and motion planning in robotics [10]. They have also been used for stability analysis of high speed networks [9]. In this work, we provide an overview of such deterministic quasi-Monte Carlo method of sampling, and their applications to control systems analysis and design. We present the basic concepts pertaining to quasi-Monte Carlo deterministic sampling. Such concepts include the following: Indicator functions, performance objective, generation of point sets, total variation, and error bounds

    Effects of low-frequency noise cross-correlations in coupled superconducting qubits

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    We study the effects of correlated low frequency noise sources acting on a two qubit gate in a fixed coupling scheme. A phenomenological model for the spatial and cross-talk correlations is introduced. The decoherence inside the SWAP subspace is analysed by combining analytic results based on the adiabatic approximation and numerical simulations. Results critically depend on amplitude of the low frequency noise with respect to the qubits coupling strength. Correlations between noise sources induce qualitative different behaviors depending on the values of the above parameters. The possibility to reduce dephasing due to correlated low frequency noise by a recalibration protocol is discussed.Comment: 18 pages, 7 figure

    Broadband noise decoherence in solid-state complex architectures

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    Broadband noise represents a severe limitation towards the implementation of a solid-state quantum information processor. Considering common spectral forms, we propose a classification of noise sources based on the effects produced instead of on their microscopic origin. We illustrate a multi-stage approach to broadband noise which systematically includes only the relevant information on the environment, out of the huge parametrization needed for a microscopic description. We apply this technique to a solid-state two-qubit gate in a fixed coupling implementation scheme.Comment: Proceedings of Nobel Symposium 141: Qubits for Future Quantum Informatio

    A case report of osteochondroma of the frontotemporosphenoidal suture.

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    Osteochondroma, also known as osteocartilaginous exostosis, is the most frequent benign bone tumour of the skeletal system. Despite its preference for long bones (tibia and femur), osteochondroma may occur in some short bones developing endochondral ossification. Seventy-five percent of the patients present only with a single lesion, whereas 25% have multiple lesions; this last clinical condition, defined as osteochondromatosis (disorder of autosomal dominant inheritance) shows a high risk of malignant transformation (about 11%). In the craniofacial area this tumour is very rare. The sites of predilection are the coronoid process and mandibular condyle, even though osteochondromas arising from the base of the skull, maxillary sinus and zygomatic arch have been previously described. However, an osteochondroma originating from the frontotemporosphenoidal suture has not been reported before in the literature. We present a unique case of osteochondroma of the frontotemporosphenoidal suture. Moreover, the relevant international literature has been reviewed and all diagnostic and surgical matters have been discussed
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