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991.
On a family of pseudorandom binary sequences 总被引:1,自引:0,他引:1
Katalin Gyarmati 《Periodica Mathematica Hungarica》2004,49(2):45-63
Recently, numerous constructions have been given for finite pseudorandom binary sequences. However, in many applications, e.g., in cryptography one needs large families of good pseudorandom sequences. Very Recently L.~Goubin, C.~Mauduit, A.~Sárkzy succeeded in constructing large families of pseudorandom binary sequences based on the Legendre symbol. In this paper we will generate another type of large family of pseudorandom sequences by using the notion of index (discrete logarithm). 相似文献
992.
Csaba Szabó Vera Vé rtesi 《Proceedings of the American Mathematical Society》2004,132(12):3689-3695
We analyze the so-called word-problem for , the ring of matrices over . We prove that the term-equivalence problem for the semigroup (and so for the ring) is coNP-complete.
993.
Yixun Shi 《Numerical Linear Algebra with Applications》2004,11(10):883-893
A recent work of Shi (Numer. Linear Algebra Appl. 2002; 9 : 195–203) proposed a hybrid algorithm which combines a primal‐dual potential reduction algorithm with the use of the steepest descent direction of the potential function. The complexity of the potential reduction algorithm remains valid but the overall computational cost can be reduced. In this paper, we make efforts to further reduce the computational costs. We notice that in order to obtain the steepest descent direction of the potential function, the Hessian matrix of second order partial derivatives of the objective function needs to be computed. To avoid this, we in this paper propose another hybrid algorithm which uses a projected steepest descent direction of the objective function instead of the steepest descent direction of the potential function. The complexity of the original potential reduction algorithm still remains valid but the overall computational cost is further reduced. Our numerical experiments are also reported. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
994.
Jean-Pierre?BarthélemyEmail author Fran?ois?Brucker Christophe?Osswald 《4OR: A Quarterly Journal of Operations Research》2004,2(3):179-219
This paper is devoted to some selected topics relating Combinatorial Optimization and Hierarchical Classification. It is oriented toward extensions of the standard classification schemes (the hierarchies): pyramids, quasi-hierarchies, circular clustering, rigid clustering and others. Bijection theorems between these models and dissimilarity models allow to state some clustering problems as optimization problems. Within the galaxy of optimization we have especially discussed the following: NP-completeness results and search for polynomial instances; problems solved in a polynomial time (e.g. subdominant theory); design, analysis and applications of algorithms. In contrast with the orientation to new clustering problems, the last part discusses some standard algorithmic approaches.Received: July 2004, Revised: September 2004, MSC classification:
62H30, 91C20, 05C65, 90C27, 68R01 相似文献
995.
Alix Munier Kordon 《Operations Research Letters》2004,32(6):557-564
We consider the makespan minimization for a unit execution time task sequencing problem with a bipartite precedence delays graph and a positive precedence delay d. We prove that the associated decision problem is strongly NP-complete and we provide a non-trivial polynomial sub-case. We also give an approximation algorithm with ratio . 相似文献
996.
We consider linear programs in which the objective function (cost) coefficients are independent non-negative random variables, and give upper bounds for the random minimum cost. One application shows that for quadratic assignment problems with such costs certain branch-and-bound algorithms usually take more than exponential time. 相似文献
997.
N. T. Kogabaev 《Siberian Mathematical Journal》2006,47(2):291-297
We study computable Boolean algebras with distinguished ideals (I-algebras for short). We prove that the isomorphism problem for computable I-algebras is Σ 1 1 -complete and show that the computable isomorphism problem and the computable categoricity problem for computable I-algebras are Σ 3 0 -complete. 相似文献
998.
We consider the break minimization problem for fixing home–away assignments in round-robin sports tournaments. First, we show that, for an opponent schedule with n teams and n−1 rounds, there always exists a home–away assignment with at most breaks. Secondly, for infinitely many n, we construct opponent schedules for which at least breaks are necessary. Finally, we prove that break minimization for n teams and a partial opponent schedule with r rounds is an NP-hard problem for r≥3. This is in strong contrast to the case of r=2 rounds, which can be scheduled (in polynomial time) without any breaks. 相似文献
999.
1000.
Dorota Dabrowska. 《Mathematics of Computation》2005,74(249):279-290
The paper deals with recovering band- and energy-limited signals from a finite set of perturbed inner products involving the prolate spheroidal wavefunctions. The measurement noise (bounded by ) and jitter meant as perturbation of the ends of the integration interval (bounded by ) are considered. The upper and lower bounds on the radius of information are established. We show how the error of the best algorithms depends on and . We prove that jitter causes error of order , where is a bandwidth, which is similar to the error caused by jitter in the case of recovering signals from samples.