Selective maintenance for multi-state series-parallel systems under economic dependence

YesThis paper presents a study on selective maintenance for multi-state series-parallel systems with economically dependent components. In the selective maintenance problem, the maintenance manager has to decide which components should receive maintenance activities within a finite break between missions. All the system reliabilities in the next operating mission, the available budget and the maintenance time for each component from its current state to a higher state are taken into account in the optimization models. In addition, the components in series-parallel systems are considered to be economically dependent. Time and cost savings will be achieved when several components are simultaneously repaired in a selective maintenance strategy. As the number of repaired components increases, the saved time and cost will also increase due to the share of setting up between components and another additional reduction amount resulting from the repair of multiple identical components. Different optimization models are derived to find the best maintenance strategy for multi-state series-parallel systems. A genetic algorithm is used to solve the optimization models. The decision makers may select different components to be repaired to different working states based on the maintenance objective, resource availabilities and how dependent the repair time and cost of each component are. © 2013 Elsevier Ltd. All rights reserved.Natural Sciences and Engineering Research Council of Canada (NSERC) and Vietnam International Education Development (VIED

Study of intermixing in a GaAs/AlGaAs quantum-well structure using doped spin-on silica layers

The effect of two different dopants, P and Ga, in spin-on glass (SOG) films on impurity-free vacancy disordering (IFVD) in GaAs/AlGaAs quantum-well structures has been investigated. It is observed that by varying the annealing and baking temperatures, P-doped SOG films created a similar amount of intermixing as the undoped SOG films. This is different from the results of other studies of P-doped SiO₂ and is ascribed to the low doping concentration of P, indicating that the doping concentration of P in the SiO₂ layer is one of the key parameters that may control intermixing. On the other hand, for all the samples encapsulated with Ga-doped SOG layers, significant suppression of the intermixing was observed, making them very promising candidates with which to achieve the selective-area defect engineering that is required for any successful application of IFVD.One of the authors (H.H.T.) acknowledges a fellowship awarded to him by the Australian Research Council

Electromagnetic penguin operators and direct CP violation in K --> pi l^+ l^-

Supersymmetric extensions of the Standard Model predict a large enhancement of the Wilson coefficients of the dimension-five electromagnetic penguin operators affecting the direct CP violation in K_L --> pi^0 e^+ e^- and the charge asymmetry in K^\pm --> pi^\pm l^+ l^-. Here we compute the relevant matrix elements in the chiral quark model and compare these with the ones given by lattice calculationsComment: 12 pages, JHEP style, gluonic corrections to B_T adde

Analyse de la rentabilite economique des systemes de production a base d’Igname : cas des sites de Leo et Midebdo au Burkina Faso

La production de l’igname est confrontée à plusieurs contraintes dont la baisse de la fertilité des sols. Pour améliorer le rendement de leurs cultures, les producteurs d’igname ont alors adopté plusieurs méthodes de gestion. Cette étude a pour objectif d’analyser la rentabilité économique des systèmes de production à base d’igname en relation avec les méthodes de gestion de la fertilité des sols par les exploitants agricoles des communes rurales de Léo et Midebdo au Burkina Faso. Un essai de typologie des systèmes de production à base d’igname a été fait à l’aide d’une analyse en composante Principale (ACP) appliquée à un échantillon de 100 exploitants agricoles. Les résultats montrent qu’il existe deux systèmes de production : i) un système semi-intensif et ii) un système extensif et itinérant. L’analyse de rentabilité économique par les indicateurs tels que la marge brute et le ratio bénéfice/coût, montre que le système de production semi-intensif semble plus rentable que le système extensif. Le ratio bénéfice/coût obtenu avec chacun des systèmes de production est inférieur à 1, ce qui signifie que la production de l’igname dans ces conditions n’est pas économiquement rentable. Une politique de promotion de la culture de l’igname par l’adoption de fertilisants (organiques ou minérales) dans les systèmes de production pour compenser la baisse de la fertilité des sols permettrait aux producteurs d’accroître leurs productions et revenus.Mots clés: Dioscorea, système de production, rentabilité, Burkina FasoEnglish Title: Analysis of the economic profitability of yam-based production systems: the case of Leo and Midebdo sites in Burkina FasoEnglish AbstractFace to the problem of soil infertility, several methods of soil fertility management are used by yam producers to improve their production. This study aims to analyze the economic profitability of yam production systems in relation to soil fertility management methods by farmers in the rural communes of Leo and Midebdo in Burkina Faso. A typology test of yam production systems was carried out using a statistical method based on multivariate analysis. The analysis was applied to a sample of 100 smallholders. The results showed that there were two production systems: i) a semi-intensive system and ii) an extensive and itinerant system. The economic profitability analysis by indicators such as gross margin and the cost/ benefit ratio indicated that the semi-intensive production system was more profitable than the extensive one. The cost/benefit ratio obtained with the two production systems was inferior to 1 indicating that yam production activity under these production systems conditions, was not economically profitable. A policy of promoting yam cultivation through the adoption of fertilizers (organic or mineral) in production systems to compensate for declining soil fertility would allow producers to increase their production and income.Keywords: Yam, production system, profitability, Burkina Fas

Asymptotic Behavior of Ext functors for modules of finite complete intersection dimension

Let $R$ be a local ring, and let $M$ and $N$ be finitely generated $R$-modules such that $M$ has finite complete intersection dimension. In this paper we define and study, under certain conditions, a pairing using the modules \Ext_R^i(M,N) which generalizes Buchweitz's notion of the Herbrand diference. We exploit this pairing to examine the number of consecutive vanishing of \Ext_R^i(M,N) needed to ensure that \Ext_R^i(M,N)=0 for all $i\gg 0$. Our results recover and improve on most of the known bounds in the literature, especially when $R$ has dimension at most two

Analytical approximation for the sphere-sphere Coulomb potential

A simple analytical expression, which closely approximates the Coulomb potential between two uniformly charged spheres, is presented. This expression can be used in the optical potential semiclassical analyses which require that the interaction be analytic on and near the real r-axis.Comment: 4 pages including 3 figures and 1 tabl

The CP-violating asymmetry in \eta\to\pi^+ \pi^- e^+e^-

We study the CP-violating asymmetry {\cal A}_{\rm CP}, which arises, in \eta\to\pi^+\pi^- e^+e^-, from the angular correlation of the e^+ e^- and \pi^+\pi^- planes due to the interference between the magnetic and electric decay amplitudes. With the phenomenologically determined magnetic amplitude and branching ratio as input, the asymmetry, induced by the electric bremsstrahlung amplitude through the CP-violating decay \eta\to\pi^+\pi^-, and by an unconventional tensor type operator, has been estimated respectively. The upper bound of {\cal A}_{\rm CP} from the former is about 10^{-3}, and the asymmetry from the latter might be up to O(10^{-2}). One can therefore expect that this CP asymmetry would be an interesting CP-violating observable for the future precise measurements in the \eta factories.Comment: LaTeX, 6 pages. One reference corrected, and some new references adde

Pair formation and collapse in imbalanced Fermion populations with unequal masses

We present an exact Quantum Monte Carlo study of the effect of unequal masses on pair formation in Fermionic systems with population imbalance loaded into optical lattices. We have considered three forms of the attractive interaction and find in all cases that the system is unstable and collapses as the mass difference increases and that the ground state becomes an inhomogeneous collapsed state. We also address the question of canonical vs grand canonical ensemble and its role, if any, in stabilizing certain phases