Active noise control (ANC) is a methodology for attenuating noise based on adaptive signal processing algorithms. ANC is well assessed for the attenuation of Gaussian noise, but the rejection of non-Gaussian impulsive...
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Active noise control (ANC) is a methodology for attenuating noise based on adaptive signal processing algorithms. ANC is well assessed for the attenuation of Gaussian noise, but the rejection of non-Gaussian impulsive noise signals represents a much more critical task that may even impair algorithm convergence. To overcome this problem the adaptive filter weight update process must be modified by discarding or discounting samples associated with impulsive noise. This can be done either by modeling the impulsive noise with a non-Gaussian distribution such as the Symmetric alpha-stable (S alpha S) distribution or by applying an outlier detection method. With both approaches the accuracy in the noise description appears to be crucial for effective noise reduction. This paper proposes two novel approaches for the attenuation of impulsive noise both for invariant and time-varying noise distributions. The first one is based on the on-line estimation of an S alpha S model of the noise probabilistic description. The second relies on a simple on-line recursive procedure that reliably estimates amplitude thresholds for outlier detection. Both methods compare favorably with competitor approaches, while maintaining a sufficiently low algorithm complexity. Several examples are shown to demonstrate the algorithms' effectiveness. (C) 2011 Elsevier Ltd. All rights reserved.
We study the computational complexity of a Metropolis-Hastings algorithm for Bayesian community detection. We first establish a posterior strong consistency result for a natural prior distribution on stochastic block ...
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We study the computational complexity of a Metropolis-Hastings algorithm for Bayesian community detection. We first establish a posterior strong consistency result for a natural prior distribution on stochastic block models under the optimal signal-to-noise ratio condition in the literature. We then give a set of conditions that guarantee rapidly mixing of a simple Metropolis-Hastings algorithm. The mixing time analysis is based on a careful study of posterior ratios and a canonical path argument to control the spectral gap of the Markov chain.
At the conference CiE 2005, the first author introduced a new model for analog computations, namely interval-valued computations. In this model, computations work on the so-called interval-valued bytes, which are spec...
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At the conference CiE 2005, the first author introduced a new model for analog computations, namely interval-valued computations. In this model, computations work on the so-called interval-valued bytes, which are special subsets of the interval [0, 1) rather than a finite sequence of bits. The question was posed there, which complexity is needed to solve PSPACE-complete problems in this paradigm. In this paper, after formalizing the computational model, we answer this question. We show that the validity problem of quantified propositional formulae is decidable by a linear interval-valued computation. As a consequence, all polynomial space problems are decidable by a polynomial interval-valued computation. Furthermore, it is proven that MACE coincides with the class of languages which are decidable by a restricted polynomial interval-valued computation. (C) 2008 Elsevier B.V. All rights reserved.
This paper presents a sparse factorization for the delay Vandermonde matrix (DVM) along with fast, exact, radix-2, and recursive algorithms to compute the DVM-vector product for wideband multi-beam antenna arrays. The...
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This paper presents a sparse factorization for the delay Vandermonde matrix (DVM) along with fast, exact, radix-2, and recursive algorithms to compute the DVM-vector product for wideband multi-beam antenna arrays. The proposed algorithms enable low-complexity wideband beamformers in emerging millimeter-wave wireless communication networks by reducing the complexity of N-beam wideband beamforming from O (N-2) to O (N log N), where N = 2(r) (r >= 1). As a result, the algorithms are faster than the brute-force computation of the DVM-vector product and more efficient than the direct realization of true-time-delay-based multi-beam beamformers. The proposed low-complexity algorithms' signal flow graph (SFG) is also presented to highlight their suitability for hardware implementations. The 2-D frequency responses of DVM-based beamformers are explained through an array signal processing example. Simulation results suggest that integrated circuit (IC) implementations of the SFG significantly reduce chip area and power consumption.
We present algorithms for testing language inclusion L(A) subset of L(B) between tree automata in time O(vertical bar A vertical bar . vertical bar B vertical bar) where B is deterministic (bottom-up or top-down). We ...
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We present algorithms for testing language inclusion L(A) subset of L(B) between tree automata in time O(vertical bar A vertical bar . vertical bar B vertical bar) where B is deterministic (bottom-up or top-down). We extend our algorithms for testing inclusion of automata for unranked trees A in deterministic DTDs or deterministic EDTDs with restrained competition D in time O(vertical bar A vertical bar . vertical bar Sigma vertical bar . vertical bar D vertical bar). Previous algorithms were less efficient or less general. (C) 2009 Elsevier Inc. All rights reserved.
This article investigates solving the min-max affine fractional programming problem (MAFPP), which arises in systems science and engineering. For globally solving the MAFPP, based on the outer space branching search, ...
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This article investigates solving the min-max affine fractional programming problem (MAFPP), which arises in systems science and engineering. For globally solving the MAFPP, based on the outer space branching search, we design a branch-relaxation-bound algorithm. In the algorithm, we firstly convert the MAFPP into an equivalent problem with linear fractional constraints by introducing some auxiliary parameter variables. Next, to determine and update the lower bound during the branching search process, we construct the linear relaxation problem of the equivalence problem by using a new relaxation technique. The global convergence of the presented algorithm is verified. Also, by analyzing the algorithmic complexity, we give a maximum estimate of iteration times of the presented algorithm. Finally, computational comparison results are reported to demonstrate the effectiveness and feasibility of the presented algorithm.
In this work we deal with the so-calledpath convexities, defined over special collections of paths. For example, the collection of the shortest paths in a graph is associated with the well-knowngeodesic convexity, whi...
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In this work we deal with the so-calledpath convexities, defined over special collections of paths. For example, the collection of the shortest paths in a graph is associated with the well-knowngeodesic convexity, while the collection of the induced paths is associated with themonophonic convexity;and there are many other examples. Besides reviewing the path convexities in the literature, we propose a general path convexity framework, of which most existing path convexities can be viewed as particular cases. Some benefits of the proposed framework are the systematization of the algorithmic study of related problems and the possibility of defining new convexities not yet investigated.
A directed path in a digraph is proper if any two consecutive arcs on the path have distinct colors. An arc-colored digraph D is proper connected if for any two distinct vertices x and y of D, there are both proper (x...
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A directed path in a digraph is proper if any two consecutive arcs on the path have distinct colors. An arc-colored digraph D is proper connected if for any two distinct vertices x and y of D, there are both proper (x, y)-directed paths and proper (y, x)-directed paths in D. The proper connection number -<(p)(c)over right arrow>(D) of a digraph D is the minimum number of colors that can be used to make D proper connected. Obviously, if a digraph has a proper connection number, it must be strongly connected, and -<(p)(c)over right arrow>(D) = 1 if and only if D is complete. Magnant et al. showed that -<(p)(c)over right arrow>(D) <= 3 for all strong digraphs D, and Ducoffe et al. proved that deciding whether a given digraph has proper connection number at most two is NP-complete. In this paper, we give a few classes of strong digraphs with proper connection number two, and from our proofs one can construct an optimal arc-coloring for a digraph of order nin time O(n(3)). (C) 2021 Elsevier B.V. All rights reserved.
AbstractIn recent years, several authors have presented algorithms that locate instances of a given string, or set of strings, within a text. Recently, authors have given less consideration to the complementary proble...
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AbstractIn recent years, several authors have presented algorithms that locate instances of a given string, or set of strings, within a text. Recently, authors have given less consideration to the complementary problem of processing a text to find out what strings appear in the text, without any preconceived notion of what strings might be present. A system called PATRICIA, which was developed two decades ago, is an implementation of a solution to this problem. The design of PATRICIA is very tightly bound to the assumptions that individual string elements are bits and that the user of the system can provide complete lists of starting and stopping places for strings. This paper presents an approach that drops these assumptions. Our method allows different definitions of indivisible string elements for different applications, and the only information the user provides for the determination of the beginning and ends of strings is a specification of a maximum length for output *** paper also describes a portable C implementation of the method, called PORTREP. The primary data structure of PORTREP is a trie represented as a ternary tree. PORTREP has a method for eliminating redundancy from the output, and it can function with a bounded number of nodes by employing a heuristic process that reuses seldom‐visited nodes. Theoretical analysis and empirical studies, reported here, give confidence in the efficiency of the algorithms. PORTREP has the ability to form the basis for a variety of text‐analysis applications, and this paper considers one such application, automatic document index
Action logic is the algebraic logic (inequational theory) of residuated Kleene lattices. One of the operations of this logic is the Kleene star, which is axiomatized by an induction scheme. For a stronger system that ...
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Action logic is the algebraic logic (inequational theory) of residuated Kleene lattices. One of the operations of this logic is the Kleene star, which is axiomatized by an induction scheme. For a stronger system that uses an omega-rule instead (infinitary action logic), Buszkowski and Palka (2007) proved Pi(0)(1)-completeness (thus, undecidability). Decidability of action logic itselfwas an open question, raised by Kozen in 1994. In this article, we show that it is undecidable, more precisely, Sigma(0)(1)-complete. We also prove the same undecidability results for all recursively enumerable logics between action logic and infinitary action logic, for fragments of these logics with only one of the two lattice (additive) connectives, and for action logic extended with the law of distributivity.
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