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991.
This paper considers an aging multi‐state system, where the system failure rate varies with time. After any failure, maintenance is performed by an external repair team. Repair rate and cost of each repair are determined by a corresponding corrective maintenance contract with a repair team. The service market can provide different kinds of maintenance contracts to the system owner, which also can be changed after each specified time period. The owner of the system would like to determine a series of repair contracts during the system life cycle in order to minimize the total expected cost while satisfying the system availability. Operating cost, repair cost and penalty cost for system failures should be taken into account. The paper proposes a method for determining such optimal series of maintenance contracts. The method is based on the piecewise constant approximation for an increasing failure rate function in order to assess lower and upper bounds of the total expected cost and system availability by using Markov models. The genetic algorithm is used as the optimization technique. Numerical example is presented to illustrate the approach. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
992.
递归关系不仅在数学中有广泛应用,而且在计算机算法设计与分析中也有广泛应用.本文对Josephus问题进行了推广,得到一类更广泛的递归关系模型.讨论了这类模型的求解方法,采用d-进制记数法,给出了这类递归关系模型的解. 相似文献
993.
一类具有Watt型功能性反应的捕食系统的极限环与稳定性 总被引:1,自引:0,他引:1
研究一类具有Watt型功能性反应的捕食模型.讨论了该系统正平衡点的存在性以及非负平衡点的性态,应用Poincare-Bendixson定理和张芷芬定理,证明了极限环的存在性和唯一性,并采用构造Dulac函数的方法,获得了正平衡点全局渐近稳定性的一个充分条件. 相似文献
994.
Pablo A. D. Castro Fernando J. Von Zuben 《Journal of Mathematical Modelling and Algorithms》2009,8(2):151-173
Recently, we have proposed a Multi-Objective Bayesian Artificial Immune System (MOBAIS) to deal effectively with building
blocks (high-quality partial solutions coded in the solution vector) in combinatorial multi-objective problems. By replacing
the mutation and cloning operators with a probabilistic model, more specifically a Bayesian network representing the joint
distribution of promising solutions, MOBAIS takes into account the relationships among the variables of the problem, avoiding
the disruption of already obtained high-quality partial solutions. The preliminary results have indicated that our proposal
is able to properly build the Pareto front. Motivated by this scenario, this paper better formalizes the proposal and investigates
its usefulness on more challenging problems. In addition, an important enhancement regarding the Bayesian network learning
was incorporated into the algorithm in order to speed up its execution. To conclude, we compare MOBAIS with state-of-the-art
algorithms taking into account quantitative aspects of the Pareto front found by the algorithms. MOBAIS outperforms the contenders
in terms of the quality of the obtained solutions and requires an amount of computational resource inferior or compatible
with the contenders. 相似文献
995.
Gabriela Jeronimo Guillermo Matera Pablo Solernó Ariel Waissbein 《Foundations of Computational Mathematics》2009,9(1):1-50
We exhibit a probabilistic symbolic algorithm for solving zero-dimensional sparse systems. Our algorithm combines a symbolic
homotopy procedure, based on a flat deformation of a certain morphism of affine varieties, with the polyhedral deformation
of Huber and Sturmfels. The complexity of our algorithm is cubic in the size of the combinatorial structure of the input system.
This size is mainly represented by the cardinality and mixed volume of Newton polytopes of the input polynomials and an arithmetic
analogue of the mixed volume associated to the deformations under consideration.
Research was partially supported by the following grants: UBACyT X112 (2004–2007), UBACyT X847 (2006–2009), PIP CONICET 2461,
PIP CONICET 5852/05, ANPCyT PICT 2005 17-33018, UNGS 30/3005, MTM2004-01167 (2004–2007), MTM2007-62799 and CIC 2007–2008. 相似文献
996.
Much of contemporary research in Artificial Immune Systems (AIS) has partitioned into either algorithmic machine learning
and optimisation, or, modelling biologically plausible dynamical systems, with little overlap between. We propose that this dichotomy is somewhat
to blame for the lack of significant advancement of the field in either direction and demonstrate how a simplistic interpretation
of Perelson’s shape-space formalism may have largely contributed to this dichotomy. In this paper, we motivate and derive
an alternative representational abstraction. To do so we consider the validity of shape-space from both the biological and
machine learning perspectives. We then take steps towards formally integrating these perspectives into a coherent computational
model of notions such as life-long learning, degeneracy, constructive representations and contextual recognition—rhetoric
that has long inspired work in AIS, while remaining largely devoid of operational definition. 相似文献
997.
欧氏空间子空间正交补的代数方法研究 总被引:1,自引:0,他引:1
在n维欧氏空间Rn中,对其任意的非零子空间V1,有子空间V2使V1⊥V2,且Rn=V1V2.本文对这一几何问题利用齐次线性方程组给予了代数方法的又一种证明. 相似文献
998.
Zhenjie Liu 《分析论及其应用》2009,25(4):369-380
This paper investigates the existence of periodic solutions of a three-species food-chain diffusive system with Beddington-DeAngelis
functional responses and time delays in a two-patch environment on time scales. By using a continuation theorem based on coincidence
degree theory, we obtain sufficient criteria for the existence of periodic solutions for the system. Moreover, when the time
scale T is chosen as R or Z, the existence of the periodic solutions of the corresponding continuous and discrete models follows. Therefore, the method
is unified to provide the existence of the desired solutions for continuous differential equations and discrete difference
equations. 相似文献
999.
In this paper, the dynamical behavior of an eco-epidemiological model with distributed delay is studied. Sufficient conditions for the asymptotical stability of all the equilibria are obtained. We prove that there exists a threshold value of the conversion rate h beyond which the positive equilibrium bifurcates towards a periodic solution. We further analyze the orbital stability of the periodic orbits arising from bifurcation by applying Poore’s condition. Numerical simulation with some hypothetical sets of data has been done to support the analytical findings. 相似文献
1000.
The bioconversion of glycerol to 1,3-propanediol is a complex bioprocess. In this study, we aim to explore a novel model for describing the multistage cell growth in batch culture. This is achieved by a modification at the specific rate of cell growth in consideration of its time-dependent changes. The existence, uniqueness and boundedness of solutions to the system and the continuity of solutions with respect to the parameters are discussed. In addition, a parameter identification problem of the system is developed and a feasible optimization algorithm is constructed to solve it. Numerical result shows that the improved model could describe the batch culture well. 相似文献