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2014 Power Systems Computation Conference (PSCC)

作者： Kolosok, Irina Korkina, Elena Buchinsky, Evgeny Energy Syst Inst SB RAS Irkutsk Russia

ISBN: (纸本)9788393580132

The advent of next generation devices for synchronized phasor measurements (voltage and current values in lines) -PMU- makes it possible to realize linear algorithms of state estimation. The paper suggests the development of the test equation technique for linear state estimation of power system facilities that are monitored on the basis of PMU measurements. New algorithms for the construction of the test equations on the basis of PMU measurements are presented. The algorithms are based on the exclusion of unmeasured variables or state vector components from the electrical circuit equations written in the rectangular coordinates. By virtue of linear nature of these equations the obtained test equations are also linear. The paper presents the algorithms for bad data detection in PMU measurements as well as the algorithms for calculation of estimates, using linear test equations which make it possible to obtain a solution within one iteration. Performance of the algorithms was tested on a test network equipped with PMUs. The developed algorithms allow us to make local state estimation of individual power system facilities (power plants, substations, network sections) that are monitored online on the basis of PMU measurements

关键词： state estimation PMU measurements test equation technique linear algorithms

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linear algorithms for Chordal Graphs of Bounded Directed Vertex Leafage

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Electronic Notes in Discrete Mathematics 2009年第C期32卷 99-108页

作者： Habib, Michel Stacho, Juraj LIAFA - CNRS Université Denis Diderot - Paris VII Paris France

The directed vertex leafage of a chordal graph G is the smallest integer k such that G is the intersection graph of subtrees of a rooted directed tree where each subtree has at most k leaves. In this note, we show how to find in time O (k n) an optimal colouring, a maximum independent set, a maximum clique, and an optimal clique cover of an n-vertex chordal graph G with directed vertex leafage k if a representation of G is given. In particular, this implies that for any path graph G, the four problems can be solved in time O (n) given a path representation of G. © 2009 Elsevier B.V. All rights reserved.

关键词： chordal graph clique colouring linear algorithms path graph

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Considerations on Parallelizing Non-negative Matrix Factorization for Hyperspectral Data Unmixing

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IEEE GEOSCIENCE AND REMOTE SENSING LETTERS 2009年第1期6卷 57-61页

作者： Robila, Stefan A. Maciak, Lukasz G. Montclair State Univ Dept Comp Sci Montclair NJ 07043 USA

Nonnegative matrix factorization (NMF) is a recently developed linear unmixing technique that assumes that the original sources and transform were positively defined. Given that the linear mixing model (LMM) for hyperspectral data requires positive endmembers and abundances, with only minor modifications, NMF can be used to solve LMM. Traditionally, NMF solutions include an iterative process resulting in considerable execution times. In this letter, we provide two novel algorithms aimed at speeding the NW through parallel processing: the first based on the traditional multiplicative solution and the second modifying an adaptive projected gradient technique known to provide better convergence. The algorithms' implementations were tested on various data sets;the results suggest that a significant speedup can be achieved without decrease in accuracy. This supports the further use of NMF for linear unmixing.

关键词： Hyperspectral data linear algorithms linear unmixing nonnegative matrix factorization (NMF) parallel processing remote sensing

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Optimal algorithms for detecting network stability 1

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2nd International Workshop on algorithms and Computation

作者： Koukopoulos, Dimitrios Nikolopoulos, Stavros D. Palios, Leonidas Spirakis, Paul G. Univ Ioannina Dept Cultural Heritage Management & New Technol GR-30100 Agrinion Greece Univ Ioannina Dept Comp Sci GR-45110 Ioannina Greece Univ Patras Dept Comp Engn & Informat GR-26500 Patras Greece Univ Patras RACTI GR-26500 Patras Greece

ISBN: (数字)9783540778912

ISBN: (纸本)9783540778905

A packet-switched network is universally stable if, for any greedy protocol and any adversary of injection rate less than 1, the number of packets in the network remains bounded at all times. A natural question that arises is whether there is a fast way to detect if a network is universally stable based on the network's structure. In this work, we study this question in the context of Adversarial Queueing Theory which assumes that an adversary controls the locations and rates of packet injections and determines packet paths. Within this framework, we present optimal algorithms for detecting the universal stability (packet paths do not contain repeated edges but may contain repeated vertices) and the simple-path universal stability (paths contain neither repeated vertices nor repeated edges) of a network. Additionally, we describe an algorithm which decides in constant time whether the addition of a link in a universally stable network leads it to instability;such an algorithm could be useful in detecting intrusion attacks.

关键词： packet-switched communication networks network stability linear algorithms graph theory intrusion detection adversarial queueing theory

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Sequential and parallel feature extraction in hyperspectral data using Nonnegative Matrix Factorization

Sequential and parallel feature extraction in hyperspectral ...

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3rd Annual IEEE Long Island Systems, Applications and Technology Conference

作者： Robila, Stefan A. Maciak, Lukasz G. Montclair State Univ Dept Comp Sci Montclair NJ 07043 USA

ISBN: (纸本)9781424413010

Feature extraction refers to the groups of techniques that, when applied to large dimensional and redundant data result in significant dimensionality reduction while preserving or even enhancing the information content. Among various techniques investigated for feature extraction, of new interest is Nonnegative Matrix Factorization (NMF). In NMF, it is assumed that the data is formed as a linear nonnegative combination of positive sources and the NMF solution recovers the original sources and the mixing matrix. In this paper, we first look at ways NMF can be applied for feature extraction in hyperspectral imagery a data known for large sizes and redundancy. While some of the associations are natural to linear mixing model (LMM - that assumes that hyperspectral images are formed as a linear mixture of endmember information), we also show NMF to be a slow method. To counter this, we investigate alternative solutions such as projected NMF approaches and provide an insight to how parallel implementations would contribute to speedup. Experimental results on various data show projected NMF outperforming regular NMF with parallel implementations providing a promising speedup advantage.

关键词： remote sensing hyperspectral data linear unmixing linear algorithms Nonnegative Matrix Factorization

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A convex analytic approach to system identification

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IEEE TRANSACTIONS ON AUTOMATIC CONTROL 2005年第10期50卷 1550-1566页

作者： Saligrama, V Boston Univ Dept Elect & Comp Engn Boston MA 02215 USA

This paper introduces a new concept for system identification in order to account for random and nonrandom(deterministic/set-membership) uncertainties. While, random/stochastic models are natural for modeling measurement errors, nonrandom uncertainties are well-suited for modeling parametric and nonparametric components. The new concept introduced is distinct from earlier concepts in many respects. First, inspired by the concept of uniform convergence of empirical means developed in machine learning theory, we seek a stronger notion of convergence in that the objective is to obtain probabilistic uniform convergence of model estimates to the minimum possible radius of uncertainty. Second, the formulation lends itself to convex analysis leading to description of optimal algorithms, which turn out to be well-known instrument-variable methods for many of the problems. Third, we characterize conditions on inputs in terms of second-order sample path properties required to achieve the minimum radius of uncertainty. Finally, we present fundamental bounds and optimal algorithms for system identification for a wide variety of standard as well as nonstandard problems that include special structures such as unmodeled dynamics, positive real conditions, bounded sets and linear fractional maps.

关键词： complex systems convex analysis input design linear algorithms robust identification

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An algorithm for partial Grundy number on trees

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DISCRETE MATHEMATICS 2005年第1-3期304卷 108-116页

作者： Shi, Z Goddard, W Hedetniemi, ST Kennedy, K Laskar, R McRae, A Clemson Univ Dept Comp Sci Clemson SC 29634 USA Clemson Univ Dept Math Clemson SC 29634 USA Appalachian State Univ Dept Comp Sci Boone NC 28607 USA

A coloring of a graph G = (V, E) is a partition {V-1, V-2,..., V-k} of V into independent sets or color classes. A vertex v E Vi is a Grundy vertex if it is adjacent to at least one vertex in each color class V-j for every j < i. A coloring is a partial Grundy coloring if every color class contains at least one Grundy vertex, and the partial Grundy number of a graph is the maximum number of colors in a partial Grundy coloring. We derive a natural upper bound on this parameter and show that graphs with sufficiently large girth achieve equality in the bound. In particular, this gives a linear-time algorithm to determine the partial Grundy number of a tree. (c) 2005 Elsevier B.V. All rights reserved.

关键词： partial Grundy coloring linear algorithms graph algorithms tree

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Fast and accurate algorithms for projective multi-image structure from motion

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IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE 2001年第6期23卷 546-559页

作者： Oliensis, J Genc, Y NEC Res Inst Princeton NJ 08540 USA Siemens Res Princeton NJ 08540 USA

We describe algorithms for computing projective structure and motion from a multi-image sequence of tracked points. The algorithms are essentially linear, work for any motion of moderate size, and give accuracies similar to those of a maximum-likelihood estimate. They give better results than the Sturm/Triggs factorization approach and are equally fast and they are much faster than bundle adjustment. Our experiments show that the (iterated) Sturm/Triggs approach often fails for linear camera motions. In addition, we study experimentally the common situation where the calibration is fixed and approximately known, comparing the projective versions of our algorithms to mixed projective/Euclidean strategies. We clarify the nature of dominant-plane compensation, showing that it can be considered a small-translation approximation rather than an approximation that the scene is planar. We show that projective algorithms accurately recover the (projected) inverse depths and homographies despite the possibility of transforming the structure and motion by a projective transformation.

关键词： projective multiframe structure from motion structure from motion projective geometry factorization linear algorithms Sturm/Triggs factorization dominant plane bundle adjustment shape from X low level vision

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Convex-round and concave-round graphs

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SIAM JOURNAL ON DISCRETE MATHEMATICS 2000年第2期13卷 179-193页

作者： Bang-Jensen, J Huang, J Yeo, A Odense Univ Dept Math & Comp Sci DK-5230 Odense Denmark Univ Victoria Dept Math & Stat Victoria BC V8W 3P4 Canada Univ Aarhus Dept Comp Sci Brics DK-8000 Aarhus C Denmark

We introduce two new classes of graphs which we call convex-round, respectively concave-round graphs. Convex-round (concave-round) graphs are those graphs whose vertices can be circularly enumerated so that the (closed) neighborhood of each vertex forms an interval in the enumeration. Hence the two classes transform into each other by taking complements. We show that both classes of graphs have nice structural properties. We observe that the class of concave-round graphs properly contains the class of proper circular arc graphs and, by a result of Tucker [Pacific J. Math., 39 (1971), pp. 535-545] is properly contained in the class of general circular arc graphs. We point out that convex-round and concave-round graphs can be recognized in O(n + m) time (here n denotes the number of vertices and m the number of edges of the graph in question). We show that the chromatic number of a graph which is convex-round (concave-round) can be found in time O(n + m) (O(n(2))). We describe optimal O(n + m) time algorithms for finding a maximum clique, a maximum matching, and a Hamiltonian cycle (if one exists) for the class of convex-round graphs. Finally, we pose a number of open problems and conjectures concerning the structure and algorithmic properties of the two new classes and a related third class of graphs.

关键词： proper circular arc graphs round graphs round enumeration Hamiltonian cycle coloring maximum matching maximum clique linear algorithms recognition

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Finiteness theorems for graphs and posets obtained by compositions

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ORDER-A JOURNAL ON THE THEORY OF ORDERED SETS AND ITS APPLICATIONS 1998年第3期15卷 203-220页

作者： Gustedt, J Tech Univ Berlin D-10623 Berlin Germany

We investigate classes of graphs and posets that admit decompositions to obtain or disprove finiteness results for obstruction sets. To do so we develop a theory of minimal infinite antichains that allows us to characterize such antichains by means of the set of elements below it. In particular we show that the following classes have infinite antichains with respect to the induced subgraph/poset relation: interval graphs and orders, N-free orders, orders with bounded decomposition width. On the other hand for orders with bounded decomposition diameter finiteness of all antichains is shown. As a consequence those classes with infinite antichains have undecidable hereditary properties whereas those with finite antichains have fast algorithms for all such properties.

关键词： decidability linear algorithms suborder relation substitution decomposition well-quasi-ordering

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