An edge coloring of a graph is orientable if and only if it is possible to orient the edges of the graph so that the color of each edge is determined by the head of its corresponding oriented arc. The goals of this pa...
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An edge coloring of a graph is orientable if and only if it is possible to orient the edges of the graph so that the color of each edge is determined by the head of its corresponding oriented arc. The goals of this paper include finding a forbidden substructure characterization of orientable colorings and giving a linear time recognition algorithm for orientable colorings. An edge coloring is lexical if and only if it is possible to number the vertices of the graph so that the color of each edge is determined by its lower endpoint. Lexical colorings are, of course, the orientable colorings in which the underlying orientation is acyclic. Lexical colorings play an important role in Canonical Ramsey theory, and it is this standpoint that motivates the current study. (C) 2010 Elsevier B.V. All rights reserved.
The development of an efficient and practical method to recognize matrices originating from generalized graphs, in the same way that network matrices are defined over directed graphs, remains an open question. In this...
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The development of an efficient and practical method to recognize matrices originating from generalized graphs, in the same way that network matrices are defined over directed graphs, remains an open question. In this paper we present such a recognition procedure for binet matrices which are known to characterize an important class of integral polyhedra. A mathematical programming formulation for the recognition problem is provided, where the special structure of these matrices is expressed via a set of constraints. Finally, given that binet matrices represent certain classes of matroids, we present a set of areas ranging from combinatorial optimization to matroid theory that can benefit from our approach.
Can a directed graph be completed to a directed line graph? If possible, how many arcs must be added? In this paper we address the above questions characterizing partial directed line (PDL) graphs, i.e., partial subgr...
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Can a directed graph be completed to a directed line graph? If possible, how many arcs must be added? In this paper we address the above questions characterizing partial directed line (PDL) graphs, i.e., partial subgraph of directed line graphs. We show that for such class of graphs a forbidden configuration criterion and a Krausz's like theorem are equivalent characterizations. Furthermore, the latter leads to a recognition algorithm that requires O(m) worst case time, where m is the number of arcs in the graph. Given a partial line digraph, our characterization allows us to find a minimum completion to a directed line graph within the same time bound. The class of PDL graphs properly contains the class of directed line graphs, characterized in [J. Blazewicz, A. Hertz, D. Kobler, D. de Werra, On some properties of DNA graphs, Discrete Appl. Math. 98(1-2) (1999) 1-19], hence our results generalize those already known for directed line graphs. In the undirected case, we show that finding a minimum line graph edge completion is NP-hard. while the problem of deciding whether or not an undirected graph is a partial graph of a simple line graph is trivial. (C) 2007 Elsevier B.V. All rights reserved.
We consider the class of (C-4, diamond)-free graphs;graphs in this class do not contain a C-4 or a diamond as an induced subgraph. We provide an efficient recognition algorithm for this class. We count the number of m...
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We consider the class of (C-4, diamond)-free graphs;graphs in this class do not contain a C-4 or a diamond as an induced subgraph. We provide an efficient recognition algorithm for this class. We count the number of maximal cliques in a (C-4, diamond)-free graph and the number of n-vertex, labeled (C-4, diamond)-free graphs. We also give an efficient algorithm for finding a largest clique in the more general class of (house, diamond)-free graphs. (C) 2010 Elsevier B.V. All rights reserved.
Incomplete Monge matrices are a generalization of standard Monge matrices: the values of some entries are not specified and the Monge property only must hold for all specified entries. We derive several combinatorial ...
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Incomplete Monge matrices are a generalization of standard Monge matrices: the values of some entries are not specified and the Monge property only must hold for all specified entries. We derive several combinatorial properties of incomplete Monge matrices and prove that the problem of recognizing permuted incomplete Monge matrices is NP-complete. For the special case of permuted Supnick matrices, we derive a fast recognition algorithm and thereby identify a special case of the n-vertex travelling salesman problem which can be solved in O (n(2) log n) time.
We give a linear-time recognition algorithm for circular-arc graphs based on the algorithm of Eschen and Spinrad (Proceedings of the Fourth Annual ACM-SIAM Symposium on Discrete algorithms (SODA), pp. 128-137, 1993) a...
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We give a linear-time recognition algorithm for circular-arc graphs based on the algorithm of Eschen and Spinrad (Proceedings of the Fourth Annual ACM-SIAM Symposium on Discrete algorithms (SODA), pp. 128-137, 1993) and Eschen (PhD thesis, 1997). Our algorithm both improves the time bound of Eschen and Spinrad, and fixes some flaws in it. Our algorithm is simpler than the earlier linear-time recognition algorithm of McConnell (algorithmica 37(2):93-147, 2003), which is the only linear time recognition algorithm previously known.
With the acceleration of global warming and energy shortages, the smart grid has become the goal of power grid development, which makes intelligent household appliance control systems essential. To promote the integra...
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With the acceleration of global warming and energy shortages, the smart grid has become the goal of power grid development, which makes intelligent household appliance control systems essential. To promote the integration of traditional household appliances into a new electrical system, this study focused on an appliance recognition algorithm applicable to traditional and typical household appliances. Using sequential appliance power consumption data from intelligent power sockets, this study generalized and extracted the characteristics of occupant behavior and power consumption of typical household appliances. A new recognition algorithm for household appliances, based on a Bayes classification model, is presented in this paper. Seven types of household appliances (refrigerator, electric cooker, air conditioner, television, laptop computer, washing machine, and water dispenser) were analyzed in 15 Beijing households. The proposed algorithm was proven to be applicable for appliance recognition.
The method of Grimson, Lozano Pérez and others for the recognition of polyhedral objects with sparse data, has been developed and implemented on a distributed array processor, the AMT DAP 500, which operates in s...
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The method of Grimson, Lozano Pérez and others for the recognition of polyhedral objects with sparse data, has been developed and implemented on a distributed array processor, the AMT DAP 500, which operates in single instruction-multiple data (SIMD) mode. Measurements involving the location vectors and the surface normals at m data points, considered in pairs, are compared with the corresponding maximum and minimum values associated with n × n pairs of object model faces in a process that exploits n × n parallelism. The overall processing time is essentiallv proportional to m × (m−1) 2 to explore the interpretation tree to its full depth. This paper discusses the nature of the comparisons between object models and data, together with the need to make these comparisons in a particular sequence, and results of test runs with a variety of object models and different geometric constraints are presented herein. Comparison is made with the corresponding sequential process, and with the more costly method of Flynn and Harris, in which n m processing elements are required to acheive, at best a processing time of the same order of magnitude.
We consider the class A of graphs that contain no odd hole, no antihole of length at least 5, and no prism ( a graph consisting of two disjoint triangles with three disjoint paths between them) and the class A' of...
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We consider the class A of graphs that contain no odd hole, no antihole of length at least 5, and no prism ( a graph consisting of two disjoint triangles with three disjoint paths between them) and the class A' of graphs that contain no odd hole, no antihole of length at least 5, and no odd prism ( prism whose three paths are odd). These two classes were introduced by Everett and Reed and are relevant to the study of perfect graphs. We give polynomial-time recognition algorithms for these two classes. In contrast we prove that determining if a general graph contains a prism ( or an even prism, or an odd prism) is NP-complete.
This paper proposes a novel method for recognizing a set of signals with linearly and nonlinearly included parameters from a given ensemble of signals under essential a priori uncertainty. Due to this uncertainty, wel...
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This paper proposes a novel method for recognizing a set of signals with linearly and nonlinearly included parameters from a given ensemble of signals under essential a priori uncertainty. Due to this uncertainty, well-known statistical methods become inapplicable. Signals may be present in an additive mixture containing an observation noise and a singular interference;the distribution law of the noise is unknown, and only its correlation matrix is specified. The novel method is invariant to this interference, does not require traditional state-space expansion, and ensures the decomposition and parallelization of the computational procedure. The signals and interference are represented using conventional linear spectral decompositions with unknown coefficients and given basis functions. Random and methodological errors, as well as the resulting computational effect, are analyzed. An illustrative example is provided.
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