A tight bound on the throughput of queueing networks with blocking

In this paper, we present a bounding methodology that allows to compute a tight lower bound on the cycle time of fork--join queueing networks with blocking and with general service time distributions. The methodology relies on two ideas. First, probability masses fitting (PMF) discretizes the service time distributions so that the evolution of the modified network can be modelled by a Markov chain. The PMF discretization is simple: the probability masses on regular intervals are computed and aggregated on a single value in the orresponding interval. Second, we take advantage of the concept of critical path, i.e. the sequence of jobs that covers a sample run. We show that the critical path can be computed with the discretized distributions and that the same sequence of jobs offers a lower bound on the original cycle time. The tightness of the bound is shown on computational experiments. Finally, we discuss the extension to split--and--merge networks and approximate estimations of the cycle time.queueing networks, blocking, throughput, bound, probability masses fitting, critical path.

Probability masses fitting in the analysis of manufacturing flow lines

A new alternative in the analysis of manufacturing systems with finite buffers is presented. We propose and study a new approach in order to build tractable phase-type distributions, which are required by state-of-the-art analytical models. Called "probability masses fitting" (PMF), the approach is quite simple: the probability masses on regular intervals are computed and aggregated on a single value in the corresponding interval, leading to a discrete distribution. PMF shows some interesting properties: it is bounding, monotonic and it conserves the shape of the distribution. After PMF, from the discrete phase-type distributions, state-of-the-art analytical models can be applied. Here, we choose the exactly model the evolution of the system by a Markov chain, and we focus on flow lines. The properties of the global modelling method can be discovered by extending the PMF properties, mainly leading to bounds on the throughput. Finally, the method is shown, by numerical experiments, to compute accurate estimations of the throughput and of various performance measures, reaching accuracy levels of a few tenths of percent.stochastic modelling, flow lines, probability masses fitting, discretization, bounds, performance measures, distributions.

Images de l'Europe dans l'enseignement de la géographie

L'iconographie des livres solaires de géographie participe fortement à la construction des représentations et à l'élaboration d'une conception de l'Europe

Le terrain, les programmes scolaires et les figures du géographe

Fieldwork and practice are at the joining point of pedagogical concern and geographical thought. But, in despite of many pedagogical injunctions from the 1880thies to the 1980thies, fieldworks stay scares at school. This may be related to the different figures of the Geographer: office geographer, open-air geographer and workshop geographer. These three figures of the Geographer can be associated, from the Enlightment to the beginning of the XXIth century, with three modalities for scholar geography: as memory branch of learning, as experimental and general science and as a teaching method based upon documents.Le terrain et les pratiques de terrain sont à la jonction des préoccupations des pédagogues et des géographes. Mais, contrairement à ce qu'il était souvent demandé des années 1880 aux années 1980, les pratiques du terrain sont loin de s'être généralisées dans le cadre de la géographie scolaire. Ceci peut être mis en regard avec les différentes figures du géographe qui apparaissent sur une période plus ample : le géographe de cabinet, le géographe de plein-vent et le géographe d'atelier. Ces trois figures du géographe correspondent à trois régimes de la géographie scolaire : la discipline de mémoire, la géographie leçon de choses et la pédagogie par le document

Enseigner de la géographie aux jeunes écoliers du primaire en France: quelques repères chronologiques

History of the teaching of géography in primary in Francechronologie de l'enseignement de la géographie à l'école primaire en Franc

Enseigner la France en géographie aux jeunes écoliers (1788-2008)

For the last two centuries, the ways of teaching geography of France to the young French pupils from 9 to 11 years old have known many transformations. The objectives and the finality have changed. These transformations result from the general changes in pedagogical methods at school, but also from the particular changes of how the French conceive their own territory and national identity.Since the beginning of the 19th century Geography taught in primary schools differs from the geography made for colleges and high schools, which has remained for a long time within the tradition of historical geography from the Ancient time to the modern period. At the end of the 19th century the 3rd French Republic put France and its colonies as the centre and the horizon of the geography studies. Geography at school was a main way to build up a national identity.In the 20th century, and more particularly during the sixties, thanks to the development of new media, space as perceived by young children became wider and more various. New curricula have been opened to new spatial dimensions: Europe and the world. The building of a national identity blends with regional, European and world wide scalar levels. Even if the latest curriculum is more focused on France.L'évolution de la façon dont la géographie de la France est présentée aux petits Français âgés de 9 à 11 ans montre les transformations des méthodes pédagogiques, en particulier celles en usage dans la leçon de géographie ; elle témoigne des transformations des finalités de l'enseignement de la géographie à l'école élémentaire et reflète autant l'évolution de l'espace français que la façon dont les Français pensent leur territoire.La géographie destinée aux élèves des écoles communales se différencie d'emblée des savoirs géographiques enseignés dans l'enseignement secondaire en rompant d'emblée avec la tradition de la géographie historique. La IIIe République fait ensuite de la France et de ses colonies l'horizon de la géographie de l'école primaire et le cadre identitaire des jeunes français. Depuis les années soixante l'espace perçu par les jeunes enfants via les différents médias s'est considérablement élargi et diversifié et les programmes scolaires se sont ouverts sur l'Europe et le monde, associant la construction de l'identité nationale avec d'autres niveaux scalaires de référence : la région, l'Europe, le monde ; même si le dernier programme est plus centré sur la France

Meshless modelling of dynamic behaviour of glasses under intense shock loadings: application to matter ejection during high velocity impacts on thin brittle targets

The purpose of this study is to present a new material model adapted to SPH modelling of dynamic behaviour of glasses under shock loadings. This model has the ability to reproduce fragmentation and densification of glasses under compression as well as brittle tensile failure. It has been implemented in Ls-Dyna software and coupled with a SPH code. By comparison with CEA-CESTA experimental data the model has been validated for fused silica and Pyrex glass for stress level up to 35GPa. For Laser MegaJoule applications, the present material model was applied to 3D high velocity impacts on thin brittle targets with good agreement in term of damages and matter ejection with experimental data obtained using CESTA’s double stage light gas gun

Qu’entendre par « grammaire traditionnelle »?

Constatant que l’on emploie souvent le terme de « grammaire traditionnelle » pour désigner une entité assez vague, l’auteur tente de cerner ce qu’il estime un point critique : la naissance de grammaires françaises qui tentent d’adapter les analyses de la Grammaire générale aux besoins nouveaux de l’enseignement définis lors de la création des Écoles centrales, puis des Lycées (fin XVIIIe — début XIXe siècle). Il étudie les points essentiels du dispositif : création d’une syntaxe sémantico-morphologique, d’une conjonction analyse grammaticale/syntaxique. Il estime que les défauts aujourd’hui dénoncés de cette grammaire ont pour origine le rôle trop large donné à cette grammaire qui excédait les capacités d’analyse qu’elle offrait.Having observed that the term "traditional grammar" is often used to designate a rather vague entity, the author tries to circumscribe that which he estimates to be a critical issue: the birth of French Grammars that attempt to adapt the analyses of the "Grammaire Générale" to the new needs of teaching as defined when the "Écoles Centrales" and later the "Lycées" were created (end of the XVIIIth — beginning of the XIXth centuries). He examines the essential points of the disposition: the creation of a semantic-morphological syntax, the conjunction of grammatical/syntactical analysis. He estimates that the defects of traditional grammar which are denounced today have their origin in the over preponderant role accorded to it which far exceded the analytical capabilities it offered

The role of emotional interpretants in Peirce’s theory of belief and doubt

The theory of emotional interpretant is mentioned only a few times in Peirce’s works. My hypothesis is that if Peirce did not develop this concept through and through, and reflected on it only very late in his writings, it is because it had been implicit in almost all his previous epistemological and semiotic works. The qualitative nature which defines belief and doubt makes the whole theory of inquiry rely on feelings, and is a consistent part of the characterization of beliefs as dispositions. In spite of this, objectivity is still preserved.Includes: Comment. Emotion and belief by Henrik Rydenfelt (pp. 496–500)