1,354,286 research outputs found
Improvement of the dispatching preplanning process in day-ahead electricity market using a sequential method
No full textThis paper proposes a sequential loading method, which finds the hourly changes of frequency and optimal load distribution between power stations. The method solves to minimize the aggregate cost in the electric power system (EPS). The method also calculates the surplus or deficit of an active power in EPS, hourly power flows of each transmission lines, active power losses in the networks. Computed and analyzed the optimal regimes of Mongolian EPS by the proposed method. The result confirmed that the method can potentially benefit to supply of frequency regulation. Developed software allows doing day-ahead market planning and intraday market preplanning in EPS, which improves electricity market model
A Digital Protection Procedure for Smart Grid Reconfiguration after Faults
No full textSmart grids can be considered as active, meshed
networks. In order to increase the continuity level of power supply in
these systems, it is of fundamental importance to quickly detect the
presence and location of a fault and afterwards to reconfigure the
network automatically, eliminating the faulted line-segment as fast as
possible. Therefore, it is particularly important to draw up a
selectivity plan which could prove accurate and valid for most
possible faults. From this point of view indeed, the use of a proper
selectivity coordination and the adoption of new-generation digital
relays may substantially increase the supply continuity level of smart
grids, which are being more and more widely implemented. The
paper presents a fast, robust method based on a particular logic
selectivity procedure that can be advantageously used also in the
presence of Distributed Generation (DG). Moreover, the operation
zones and setting of the proposed digital protection system are
presented and explained. Finally, some problems of protection
systems in the presence of DG are also discussed and commented
The Prosumer Node in Modelling Unit Commitment Technology
No full textThe described model allows to calculate Unit Commitment (hereafter - UC), providing for compliance with all technical limitations in electric power generation and electricity regime parameters to ensure minimization of total costs, as determined on the basis of a prosumer node’s parameters and filed with the participants of UC market price bids, including the cost of power units. A prosumer node, usually a smart home or building, can be considered at the same time as a producer and consumer of energy where automatic energy management systems can be both very effective and profitable. The proposed optimization method, which can be applied to traditional power stations, distributed generation and prosumer nodes, is described and shortly commented also with reference to its practical application
Optimization of Electrochemical Storage in a Prosumer Node
No full textIt is well known that renewable (wind and solar) distributed sources are normally random and intermittent. That is why at certain times of the day the Distribution System Operator (DSO) of a smart grid may have to handle energy surpluses that are difficult to control and could eventually undermine the whole operation of a local distribution system. This problem can be solved, of course, using properly dimensioned, efficient storage systems. The issue may affect either one individual prosumer node or more complex systems, consisting of a smart grid and a number of prosumer nodes connected to it. In any case, regardless of their complexity, modern electrical systems are to be managed through automatic integrated controls, able to take into account at the same time also how much energy is to be produced, consumed and stored. In addition, reference should be made to predictive methods, which have to take into consideration such other factors as local weather conditions, the habits of the people occupying the building and current energy prices. In this work, a storage control system is described with a management model consisting of a single prosumer node interfaced with a smart grid DSO. In order to better identify the model representing the behavior of a storage battery, reference is to be made to charging and discharging processes, which do not take place simultaneously and therefore allow the requested models to be defined independently. For the control system to operate correctly, it is necessary to acquire information about the status of the storage system, such as the charge level and the instantaneous power delivered or absorbed by the batteries. The proposed automatic management system was analyzed through numerical simulations, which are also reported and commented
The unit commitment model for the smart grid
No full textThis mathematical model allows calculation of Unit Commitment (hereinafter - UC), providing for
compliance with all technical limitations in the equipment state and electricity regime parameters to ensure the
minimization of the total cost of electric power generation, as determined on the basis of notifications
wholesale market participants on the composition and parameters of the generating equipment and filed with
the participants of market price bids UC including the cost of power units. Finally, a dynamic model of
investment for the smart grid is formulated, using UC technology
Neuromodulatory actions on ion channels of neuronal populations of the reticular activating system
No full textThe pedunculopontine nucleus (PPN) is a cholinergic area of the reticular activating system (RAS). It contributes to regulation of sleep-wakefulness cycles and movement, as it is a part of the mesencephalic locomotor region (MLR). Rostral serotonergic members of the RAS are the dorsal and median raphe nuclei (DR and MR, respectively) which also targeted by cholinergic neuromodulation and play important role in regulation of sleep-wakefulness cycles, movement and affective states.
We showed that deletion of KCNQ4 leads to alterations in adaptation of activity to light-darkness cycles. Although the M-current is an electrophysiological hallmark of the cholinergic neurons, only a subpopulation of these neurons possessed KCNQ4-dependent M-current. It synchronizes neighboring PPN neurons and inhibition of the M-current decreases neuronal synchronization.
Serotonergic neurons with M-current are located rostrally in the DR and dorsally in the MR. The M-current seems to have a strong impact on firing properties of certain serotonergic neuronal subpopulations and it might serve as an effective contributor to cholinergic and local serotonergic neuromodulatory actions.
The MLR is a functionally-defined midbrain area consisted of the PPN and the cuneiform nucleus (CnF). We showed that CnF glutamatergic neurons are electrophysiologically more homogeneous than PPN neurons. PPN neurons composed a heterogeneous group displaying a range of adapting responses, whereas the majority of CnF neurons are fast-adapting; suggesting a greater diversity of neuronal profiles than the CnF
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Momentum trading in cryptocurrencies: Short-term returns and diversification benefits
No full textWe test for the presence of momentum effects in cryptocurrency market and estimate dynamic conditional correlations (DCCs) of returns between momentum portfolios of cryptocurrencies and traditional assets. First, investment portfolios are constructed adherent to the classic J/K momentum strategy, using daily data from twelve cryptocurrencies for over a period of three years. We identify the existence of momentum effect, which is highly significant for short-term portfolios but disappears over the longer term. Second, we show that cross correlations of weekly returns between momentum portfolio of cryptocurrencies and traditional assets are unlike correlations of returns between traditional assets. Third, we find that momentum portfolios of cryptocurrencies not only offer diversification benefits but also can be a hedge and safe haven for traditional assets
Variations on the Author
No full text“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
No full textWe 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
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