Approximating multiple class queueing models with loss models

Multiple class queueing models arise in situations where some flexibility is sought through pooling of demands for different services. Earlier research has shown that most of the benefits of flexibility can be obtained with only a small proportion of cross-trained operators. Predicting the performance of a system with different types of demands and operator pools with different skills is very difficult. We present an approximation method that is based on equivalent loss systems. We successively develop approximations for the waiting probability, The average waiting time and the service level. Our approximations are validated using a series of simulations. Along the way we present some interesting insights into some similarities between queueing systems and equivalent loss systems that have to our knowledge never been reported in the literature.

Commune d’Ahun

Dans le cadre de l’étude de l’agglomération d’Acitodunum, la campagne de prospection 2015 a eu pour but de commencer à définir la morphologie de la ville antique. Pour ce faire, trois méthodes d’investigation ont été mises en œuvre : les relevés au sol, l’archéologie aérienne, l’étude du cadastre napoléonien. L’organisation du vicus gallo-romain commence à être mise au jour et plusieurs hypothèses peuvent être avancées (fig. 1 et 2). Fig. 1 – Vue aérienne du bourg d’Ahun Fig. 2 – Hypothèse d..

Measuring the variability in supply chains with the peakedness

This paper introduces a novel way to measure the variability of order flows in supply chains, the peakedness. The peakedness can be used to measure the variability assuming the order flow is a general point pro- cess. We show basic properties of the peakedness, and demonstrate its computation from real-time continuous demand processes, and cumulative demand collected at fixed time intervals as well. We also show that the peakedness can be used to characterize demand, forecast, and inventory variables, to effectively manage the variability. Our results hold for both single stage and multistage inventory systems, and can further be extended to a tree-structured supply chain with a single supplier and multiple retailers. Furthermore, the peakedness can be applied to study traditional inventory problems such as quantifying bullwhip effects and determining safety stock levels. Finally, a numerical study based on real life Belgian supermarket data verifies the effectiveness of the peakedness for measuring the order flow variability, as well as estimating the bullwhip effects.variability, peakedness, supply chain

Breaking of non-Newtonian character in flows through a porous medium

International audienceFrom NMR measurements we show that the velocity field of a yield stress fluid flowing through a disordered well-connected porous medium is very close to that for a Newtonian fluid. In particular, it is shown that no arrested regions exist even at very low velocities, for which the solid regime is expected to be dominant. This suggests that these results obtained for strongly nonlinear fluid can be extrapolated to any nonlinear fluid. We deduce a generalized form of Darcy's law for such materials and provide insight into the physical origin of the coefficients involved in this expression, which are shown to be moments of the second invariant of the strain rate tensor

Slider : un Raisonneur Incrémental Évolutif

National audienceThe main drawbacks of current reasoning methods over ontologies are they struggle to provide scalability for large datasets. The batch processing reasoners who provide the best scalability so far are unable to infer knowledge from evolving data. We contribute to solving these problems by introducing Slider, an efficient incremental reasoner. Slider exhibits a performance improvement by more than a 70% compared to the OWLIM-SE reasoner. Slider is conceived to handle expanding data from streams with a growing background knowledge base. It natively supports ρdf and RDFS, and its architecture allows to extend it to more complex fragments with a minimal effort.Les solutions existantes pour le raisonnement incrémental souffrent principalement de leur incapacité à prendre en charge des ontologies complexes et ne sont pas conçues pour gérer de grandes quantités de connaissances. Dans cet article, nous présentons Slider (Chevalier et al. (2015)), un raisonneur incrémental évolutif par chaînage avant, permettant de raisonner sur des flux de données sémantiques

Hacia la empresa de territorio.

The relationship between an enterprise and the territory is a multifaceted phenomenon. Although a company can be "extractive" and take advantage of the territory for its own benefit in some cases it can inspire local public development policies and mobilize those citizens who seek to commit to an ecological and social transition. The article —based on the dialogue between a researcher and the CEO of a Group— analyses an important social innovation in France considering the trajectory of the Archer group, located in Romans-sur-Isère, Drôme, France. It characterizes its evolution to show how a private organization can contribute to local development. Case study and interview evidence indicate a first approximation to the definition of the 'territory enterprise' as a new organizational form.La vinculación entre una empresa y el territorio configura un fenómeno complejo. Aunque en algunos casos, la empresa puede ser "extractiva" y utilizar el territorio para su propio beneficio, también existen casos en que la empresa puede inspirar políticas públicas locales de desarrollo y movilizar a los ciudadanos que buscan comprometerse en una transición ecológica y social. El artículo —basado en el diálogo entre un investigador y el director de una empresa— analiza una significativa innovación social en Francia a la luz de la trayectoria del grupo Archer localizado en Romans-sur-Isère, Drôme, Francia. Se caracteriza la evolución del grupo y se examina su particularidad, para mostrar en qué medida una organización privada puede contribuir al desarrollo local. El análisis constituye una primera aproximación a la definición de la especificidad de la empresa de territorio como una nueva forma organizativa