This paper presents a multi-agent system (MAS) approach for automated service restoration for futuristic distribution systems with distributed energy resources (with/without microgrid forming capabilities). The propos...
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ISBN:
(纸本)9781538655832
This paper presents a multi-agent system (MAS) approach for automated service restoration for futuristic distribution systems with distributed energy resources (with/without microgrid forming capabilities). The proposed algorithm provides an architecture for interchangeable agent roles which is more robust and reliable compared to other approaches with rigid agent roles. The restoration algorithm is greedy (loosely based on distributed Prim's algorithm) to form the largest possible online sections. This helps improving system stability and makes it less susceptible to changing load/demand in the system by aggregation. The performance is demonstrated for a 33-bus distribution system with and without DERs. It is seen that algorithm always results in maximum possible loads be connected.
The sparse unmixing problem of greedy algorithms still remains a great challenge at finding an optimal subset of endmembers for the observed data from the spectral library,due to the usually high correlation of the sp...
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The sparse unmixing problem of greedy algorithms still remains a great challenge at finding an optimal subset of endmembers for the observed data from the spectral library,due to the usually high correlation of the spectral *** such circumstances,a novel greedy algorithm for sparse unmixing of hyperspectral data is presented,termed the recursive dictionary-based simultaneous orthogonal matching pursuit(RD-SOMP).The algorithm adopts a block-processing strategy to divide the whole hyperspectral image into several *** each iteration of the block,the spectral library is projected into the orthogonal subspace and renormalized,which can reduce the correlation of the spectral *** RD-SOMP selects a new endmember with the maximum correlation between the current residual and the orthogonal subspace of the spectral *** endmembers picked in all the blocks are associated as the endmember sets of the whole hyperspectral ***,the abundances are estimated using the whole hyperspectral data with the obtained endmember *** can be proved that RD-SOMP can recover the optimal endmembers from the spectral library under certain *** results demonstrate that the RD-SOMP algorithm outperforms the other algorithms,with a better spectral unmixing accuracy.
The reduced basis method (RBM) is a popular certified model reduction approach for solving parametrized partial differential equations. One critical stage of the offline portion of the algorithm is a greedy algorithm,...
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The reduced basis method (RBM) is a popular certified model reduction approach for solving parametrized partial differential equations. One critical stage of the offline portion of the algorithm is a greedy algorithm, requiring maximization of an error estimate over parameter space. In practice this maximization is usually performed by replacing the parameter domain continuum with a discrete "training" set. When the dimension of parameter space is large, it is necessary to significantly increase the size of this training set in order to effectively search parameter space. Large training sets diminish the attractiveness of RBM algorithms since this proportionally increases the cost of the offline phase. In this work we propose novel strategies for offline RBM algorithms that mitigate the computational difficulty of maximizing error estimates over a training set. The main idea is to identify a subset of the training set, a "surrogate training set" (STS), on which to perform greedy algorithms. The STS we construct is much smaller in size than the full training set, yet our examples suggest that it is accurate enough to induce the solution manifold of interest at the current offline RBM iteration. We propose two algorithms to construct the STS: our first algorithm, the successive maximization method, is inspired by inverse transform sampling for non-standard univariate probability distributions. The second constructs an STS by identifying pivots in the Cholesky decomposition of an approximate error correlation matrix. We demonstrate the algorithm through numerical experiments, showing that it is capable of accelerating offline RBM procedures without degrading accuracy, assuming that the solution manifold has rapidly decaying Kolmogorov width.
High-accuracy time-delay estimation is basically noted in several research areas. L1-minimisation is a compressive sensing (CS) approach which solves this problem with high resolution and accuracy in the case of spars...
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High-accuracy time-delay estimation is basically noted in several research areas. L1-minimisation is a compressive sensing (CS) approach which solves this problem with high resolution and accuracy in the case of spars signals. Band excluded orthogonal matching pursuit is another CS method which uses a greedy algorithm to retrieve time delays and has lower complexity compared with the L1-minimisation method;however, it is only applicable when the signals are well spaced or orthogonal. Moreover, both approaches are established on a discrete basis which inherently limits their accuracy for the constraint on the sampling rate of the system. To mitigate these challenges in this study, the authors first incorporate the L1-minimisation method in a greedy algorithm to achieve a high resolution in the discrete grid. In the next step, to overcome the limitation caused by the sampling rate and refine the obtained time delays, the algorithm is combined with a complex continuous basis pursuit (CCBP) by using a polar interpolation. Their simulation and experiment results show that the proposed combination of L1-minimisation-CCBP can recover time delays in very closely spaced echoes not only with high accuracy but also with low computational time and sampling rate.
We propose working-set/greedy algorithms to efficiently solve problems penalized respectively by the total variation on a general weighted graph and its l(0) counterpart the Mumford Shah total level-set boundary size ...
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We propose working-set/greedy algorithms to efficiently solve problems penalized respectively by the total variation on a general weighted graph and its l(0) counterpart the Mumford Shah total level-set boundary size when the piecewise constant solutions have a small number of distinct level-sets;this is typically the case when the total level-set boundary size is small, which is encouraged by these two forms of penalization. Our algorithms exploit this structure by recursively splitting the level-sets of a piecewise-constant candidate solution using graph cuts. We obtain significant speed-ups over state-of-the-art algorithms for images that are well approximated with few level-sets.
The classes of large-error bounds that are based on the covariance inequality, in both Bayesian and non-Bayesian approaches, are characterized as projection-based bounds. Tightening of bounds in these classes involves...
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The classes of large-error bounds that are based on the covariance inequality, in both Bayesian and non-Bayesian approaches, are characterized as projection-based bounds. Tightening of bounds in these classes involves high computational complexity due to multidimensional optimization procedure. Consequently, projection-based large-error bounds have little popularity, while small-error bounds are frequently preferred, although they are not necessarily tight. In this letter, we first introduce a unified formulation for Bayesian and non-Bayesian projection-based lower bounds and set a general framework, which allows for their approximation via a greedy-based method. This framework is then used to propose the use of optimized orthogonal matching pursuit approach for computing projection-based large-error bounds. We analyze the complexity of the proposed algorithm and show that it is significantly lower than the complexity of the conventional approach. Finally, we apply the algorithm for the problem of multitone estimation and show that for fixed computational resources, the Weiss-Weinstein bound implemented with the proposed algorithm, provides a tighter bound compared to conventional approaches.
We study the maximum coverage problem with group budget constraints (MCG). The input consists of a ground set X, a collection of subsets of X each of which is associated with a combinatorial structure such that for ev...
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We study the maximum coverage problem with group budget constraints (MCG). The input consists of a ground set X, a collection of subsets of X each of which is associated with a combinatorial structure such that for every set , a cost can be calculated based on the combinatorial structure associated with , a partition of , and budgets , and B. A solution to the problem consists of a subset H of such that and for each , . The objective is to maximize . In our work we use a new and improved analysis of the greedy algorithm to prove that it is a -approximation algorithm, where is the approximation ratio of a given oracle which takes as an input a subset and a group and returns a set which approximates the optimal solution for . This analysis that is shown here to be tight for the greedy algorithm, improves by a factor larger than 2 the analysis of the best known approximation algorithm for MCG.
In this work, we address the bottling scheduling problem that arises in the wine industry when the packing requests from clients need to be allocated to the production lines. This problem also appears in a large varie...
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In this work, we address the bottling scheduling problem that arises in the wine industry when the packing requests from clients need to be allocated to the production lines. This problem also appears in a large variety of industries, but especially in packaged food companies. Based on the operations of a large Chilean winery we worked with, we developed a MIP model that exhibits industry-specific features such as different types of wine resources and oenological process constraints. This model can be reduced to an n job, m parallel machine scheduling problem, which is known to be NP-hard, so we developed a greedy heuristic algorithm in order to find a feasible bottling schedule in a reduced computing time. We show that the proposed solution approach is a very promising alternative to efficient MIP solvers like CPLEX. Particularly, the greedy heuristic is able to schedule all the jobs in 98% of the test instances and the computational times are very reasonable even for large industrial cases. (C) 2016 Elsevier Ltd. All rights reserved.
The number of seismological studies based on artificial neural networks has been increasing. However, neural networks with one hidden layer have almost reached the limit of their capabilities. In the last few years, t...
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The number of seismological studies based on artificial neural networks has been increasing. However, neural networks with one hidden layer have almost reached the limit of their capabilities. In the last few years, there has been a new boom in neuroinformatics associated with the development of third-generation networks, deep neural networks. These networks operate with data at a higher level. Unlabeled data can be used to pretrain the network, i.e., there is no need for an expert to determine in advance the phenomenon to which these data correspond. Final training requires a small amount of labeled data. Deep networks have a higher level of abstraction and produce fewer errors. The same network can be used to solve several tasks at the same time, or it is easy to retrain it from one task to another. The paper discusses the possibility of applying deep networks in seismology. We have described what deep networks are, their advantages, how they are trained, how to adapt them to the features of seismic data, and what prospects are opening up in connection with their use.
Adaptive Fourier decomposition (AFD) has been found to be among the most effective greedy algorithms. AFD shows an outstanding performance in signal analysis and system identification. As compensation of effectiveness...
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Adaptive Fourier decomposition (AFD) has been found to be among the most effective greedy algorithms. AFD shows an outstanding performance in signal analysis and system identification. As compensation of effectiveness, the computation complexity is great, that is especially due to maximal selections of the parameters. In this paper, we explore the discretization of the 1-D AFD integration via with discrete Fourier transform (DFT), incorporating fast Fourier transform (FFT). We show that the new algorithm, called FFT-AFD, reduces the computational complexity from O (MN2) to O (MN log N), the latter being the same as FFT. Through experiments, we verify the effectiveness, accuracy, and robustness of the proposed algorithm. The proposed FFT-based algorithm for AFD lays a foundation for its practical applications. (C) 2017 Elsevier B.V. All rights reserved.
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