37 research outputs found
The optimization of a maintenance policy related to a global service contract
No full textWith refer to a Global Service Contract between a Service Provider and a Logistic Company, the purpose of the present paper is to develop an optimization model aimed to minimize the maintenance related total cost. In particular, such contract requires the supplying of a mandatory set of corrective maintenance services on a set of equal vehicles, in a fixed time horizon. The considered problem is formulated by a non-linear constrained mathematical model that, for large practical systems as the one herein considered, becomes difficult or very hard to solve by mathematical resolution approach. For this reason, a specific resolution approach based on a constrained genetic algorithm is herein developed to solve the treated problem. The obtained results show that meaningful cost reductions can be achieved by using the proposed approach
Civil Liability, Safety and Nuclear Parks: Is Concentrated Management Better?
No full textUltra-hazardous risky activities as nuclear industry cannot be considered as “normal industries” i.e. industries without abnormal environmental and health risks. Consequently, the industrial organization of these specific sectors is of the utmost importance. This paper aims at studying this question. We focus on the associated costs of prevention and civil liability. We analyze how civil liability rules may contribute to extend or to discourage the expansion of nuclear parks to new operators. The paper compares the consequences of extending the management of nuclear stations to several independent operators. This question can apply to the unification process of the European electricity market in which several public and private nuclear power operators are running. The paper shows that the choice between either a monopolistic scheme (one operator managing several plants) or a decentralized one (one operator by station) depends on the condition of application of the legal civil liability regime and on the strength of the safety control exerted by the Nuclear Regulatory Authorities. It is shown that when the control is high, then the safety costs generated by the monopolistic organization are less than the same costs of a decentralized one. However, conditions on the insurance policy can mitigate this result.Strict Liability, Electric Energy, Nuclear Plants
Joint control charts for monitoring location and dispersion
No full textThe T-2 and the generalized variance vertical bar S vertical bar charts are used for monitoring the mean vector and the covariance matrix of multivariate processes. In this article, we propose for bivariate processes the use of the T-2 and the VMAX charts. The points plotted on the VMAX chart correspond to the maximum of the sample variances of the two quality characteristics. The reason to consider the VMAX statistic instead of the generalized variance vertical bar S vertical bar is the user's familiarity with the computation of simple sample variances; we can't say the same with regard to the computation of the generalized variance vertical bar S vertical bar
Joint control charts for monitoring location and dispersion
No full textThe T-2 and the generalized variance vertical bar S vertical bar charts are used for monitoring the mean vector and the covariance matrix of multivariate processes. In this article, we propose for bivariate processes the use of the T-2 and the VMAX charts. The points plotted on the VMAX chart correspond to the maximum of the sample variances of the two quality characteristics. The reason to consider the VMAX statistic instead of the generalized variance vertical bar S vertical bar is the user's familiarity with the computation of simple sample variances; we can't say the same with regard to the computation of the generalized variance vertical bar S vertical bar
Synthetic control chart for monitoring the pprocess mean and variance
No full textIn this article, we consider the synthetic control chart with two-stage sampling (SyTS chart) to control the process mean and variance. During the first stage, one item of the sample is inspected; if its value X, is close to the target value of the process mean, then the sampling is interrupted. Otherwise, the sampling goes on to the second stage, where the remaining items are inspected and the statistic T = Sigma [x(i) - mu(0) + xi sigma(0)](2) is computed taking into account all items of the sample. The design parameter is function of X-1. When the statistic T is larger than a specified value, the sample is classified as nonconforming. According to the synthetic procedure, the signal is based on Conforming Run Length (CRL). The CRL is the number of samples taken from the process since the previous nonconforming sample until the occurrence of the next nonconforming sample. If the CRL is sufficiently small, then a signal is generated. A comparative study shows that the SyTS chart and the joint X and S charts with double sampling are very similar in performance. However, from the practical viewpoint, the SyTS chart is more convenient to administer than the joint charts
Joint control charts for monitoring location and dispersion
No full textThe T-2 and the generalized variance vertical bar S vertical bar charts are used for monitoring the mean vector and the covariance matrix of multivariate processes. In this article, we propose for bivariate processes the use of the T-2 and the VMAX charts. The points plotted on the VMAX chart correspond to the maximum of the sample variances of the two quality characteristics. The reason to consider the VMAX statistic instead of the generalized variance vertical bar S vertical bar is the user's familiarity with the computation of simple sample variances; we can't say the same with regard to the computation of the generalized variance vertical bar S vertical bar.UNESP São Paulo State Univ, BR-12516410 Guaratingueta, SP, BrazilUNESP São Paulo State Univ, BR-12516410 Guaratingueta, SP, Brazi
Synthetic control chart for monitoring the pprocess mean and variance
No full textIn this article, we consider the synthetic control chart with two-stage sampling (SyTS chart) to control the process mean and variance. During the first stage, one item of the sample is inspected; if its value X, is close to the target value of the process mean, then the sampling is interrupted. Otherwise, the sampling goes on to the second stage, where the remaining items are inspected and the statistic T = Sigma [x(i) - mu(0) + xi sigma(0)](2) is computed taking into account all items of the sample. The design parameter is function of X-1. When the statistic T is larger than a specified value, the sample is classified as nonconforming. According to the synthetic procedure, the signal is based on Conforming Run Length (CRL). The CRL is the number of samples taken from the process since the previous nonconforming sample until the occurrence of the next nonconforming sample. If the CRL is sufficiently small, then a signal is generated. A comparative study shows that the SyTS chart and the joint X and S charts with double sampling are very similar in performance. However, from the practical viewpoint, the SyTS chart is more convenient to administer than the joint charts
A synthetic control chart for monitoring the pprocess mean and variance
No full textIn this article, we consider the synthetic control chart with two-stage sampling (SyTS chart) to control the process mean and variance. During the first stage, one item of the sample is inspected; if its value Xl is close to the target value of the process mean, then the sampling is interrupted. Otherwise, the sampling goes on to the second stage, where the remaining items are inspected and the statistic T = Σ [X1 - μ0 + ξσ0]2 is computed taking into account all items of the sample. The design parameter ξ is function of X1. When the statistic T is larger than a specified value, the sample is classified as nonconforming. According to the synthetic procedure, the signal is based on Conforming Run Length (CRL). The CRL is the number of samples taken from the process since the previous nonconforming sample until the occurrence of the next nonconforming sample. If the CRL is sufficiently small, then a signal is generated. A comparative study shows that the SyTS chart and the joint X and S charts with double sampling are very similar in performance. However, from the practical viewpoint, the SyTS chart is more convenient to administer than the joint charts.ENCE, Rio de Janeiro, RJ 20231050Catholic University of Rio de Janeiro, Rio de Janeiro, RJ 22453900UNESP, BR-12516410 Guaratingueta, SP, BrazilUNESP, BR-12516410 Guaratingueta, SP, Brazi
A multi-decision makers approach to select the maintenance plan for a multi-component system.
No full text
