Multi-agent planning and scheduling, execution monitoring and incremental rescheduling: Application to motorway traffic

This article describes a planning method applicable to agents with great perception and decision-making capabilities and the ability to communicate with other agents. Each agent has a task to fulfill allowing for the actions of other agents in its vicinity. Certain simultaneous actions may cause conflicts because they require the same resource. The agent plans each of its actions and simultaneously transmits these to its neighbors. In a similar way, it receives plans from the other agents and must take account of these plans. The planning method allows us to build a distributed scheduling system. Here, these agents are robot vehicles on a highway communicating by radio. In this environment, conflicts between agents concern the allocation of space in time and are connected with the inertia of the vehicles. Each vehicle made a temporal, spatial, and situated reasoning in order to drive without collision. The flexibility and reactivity of the method presented here allows the agent to generate its plan based on assumptions concerning the other agents and then check these assumptions progressively as plans are received from the other agents. A multi-agent execution monitoring of these plans can be done, using data generated during planning and the multi-agent decision-making algorithm described here. A selective backtrack allows us to perform incremental rescheduling

THE IMPACT OF PRICES ON SEAFOOD TRADE: A PANEL DATA ANALYSIS OF THE FRENCH SEAFOOD MARKET

In the early 1990s, two major crises affected the French fish market. Low import prices were suspected to have affected import levels of fish. Therefore, this paper looks at the empirical economic factors of fish imports in France. Most economic papers related to this field use a demand function of imports for a single product and focus only on trade relations between two countries. In this research, a panel data trade model is used at the multilateral level with many trade partners and products over several years. Results are presented by product groups at both aggregated and disaggregated levels. French imports appear to be very sensitive to internal price competitiveness and nominal exchange rates, with a differentiated impact according to the degree of processing. From that model, simulations show the consequences of the implementation of a single European currency on seafood trade.International Relations/Trade, Resource /Energy Economics and Policy,

The determinants of innovation adoption

Using a sample of 46 000 EU firms from the Community Innovation Survey, this paper analyses the drivers of innovation adoption. In contrast to most empirical studies on innovation diffusion in which a specific technology is analyzed, this study covers several countries and industries in the European Union. Following Van de Ven and Van Praag (1981), Heckman's method is applied in a context of binary endogenous variable to explain the choices made by firms regarding innovation. Distinctions are made between the internal generation of innovation and the adoption of innovation produced by others, as well as between different types of adoption (product vs. process and cooperation-based adoption vs. isolated adoption). The study is focused on the impact of users' features and their cooperation with suppliers on the adoption choices. The results point out that cooperation is a key driver of adoption choices. Usual determinants such as firm size, absorptive capability or exports would foster generation of innovation instead of adoption.Innovation adoption; Innovation diffusion; Community Innovation Survey; Process adoption; Product adoption

Institutional entrepreneurs as translators : a comparative study in an emerging activity.

This paper analyzes the reasons why some institutional entrepreneurship strategies failed to translate an institution while other succeeded, by paying a specific attention to the interaction between material and discursive dimensions in the translation process. A theoretical framework integrating both dimensions of translation is first proposed in order to study strategies of competing entrepreneurs. Then a comparative study of three entrepreneurs translating practices of corporate social evaluation in the French context is used to investigate the processes through which competing translators achieved their objective more or less successfully.neo-institutionalisme; translation; corporate social responsibility;

Numerical study of solid particle axial mixing in a fixed cylindrical drum with rotating paddles

Axial mixture characterization is a wide spread problem in granular particle blending processes such as in an horizontal drum mixer. The homogeneous mixture of particles is obtained by blending the particles via rotating paddles in a fixed cylindrical drum. This problem, common to many technological devices, is crucial in the manufacture of a broad variety of industrial products, such as polypropylene. The granular flow behavior in these systems is still poorly understood and the numerical study of such configurations receives increasing academic and industrial attention. In this paper, a study is conducted to investigate the effects of different aspects of the reactor design on the axial transport of monodisperse, uniform density and spherical polypropylene particles. Results show that principally the shape of the paddles is the important design consideration to enhance the axial transport of particles

Approximate stochastic dynamic programming for hydroelectric production planning

This paper presents a novel approach for approximate stochastic dynamic programming (ASDP) over a continuous state space when the optimization phase has a near-convex structure. The approach entails a simplicial partitioning of the state space. Bounds on the true value function are used to refine the partition. We also provide analytic formulae for the computation of the expectation of the value function in the “uni-basin” case where natural inflows are strongly correlated. The approach is experimented on several configurations of hydro-energy systems. It is also tested against actual industrial data

L'influence du vieillissement sur les pratiques touristiques en France

Vieillissement de la population et changements de modes de vie à l'âge de la retraite, le secteur du tourisme est et sera fortement concerné par ces évolutions démographiques et sociales. Clientèle essentielle pour le secteur du tourisme, la catégorie des retraités et pré-retraités connaît de profonds changements, dont l'accroissement numérique ne constitue qu'un élément : élargissement de l'horizon de vie et amélioration de l'état de santé et des revenus, générations de plus en plus intégrées au monde de la consommation et des loisirs, mais générations qui seront aussi préoccupées par le financement des retraites et par les problèmes de mobilité aux grands âges. Comment ont évolué les pratiques touristiques des « seniors » ces dernières années et comment risquent-elles de changer encore dans les années à venir ? Nous présentons les évolutions récentes du tourisme des retraités à partir de données statistiques récentes et essayons d'anticiper les évolutions futures. Sur bien des points les pratiques touristiques des personnes âgées se sont rapprochées de celles des plus jeunes. L'arrivée à la retraite des générations nées après-guerre va entraîner de nouvelles inflexions dans les pratiques touristiques, avec notamment une autonomie plus grande et plus de diversité dans les formes de voyages.Retraité ; Mode de vie ; Tourisme ; Demande ; Effet d'âge ; Effet de génération ; Enquête statistique

Stratogenèse associée à la dynamique des coulées à front pierreux en milieu alpin, La Mortice, Alpes méridionales, France

L'étude des dépôts de pente nappant les versants est et nord-ouest de La Mortice (3170 m, Alpes méridionales, France) met en évidence le rôle de la dynamique des coulées de solifluxion à front pierreux dans le développement d'une stratification. Au sein des coulées, la cryoexpulsion et le lavage produisent la différenciation d'un front caillouteux associé à un pavage superficiel et d'un niveau riche en matrice. Ce dernier progresse par cryoreptation et ensevelit le front pierreux au fur et à mesure de sa constitution, pour former ainsi un lit grossier enterré à structure ouverte. La cryoturbation et des transferts de matière hors du système constitué par la coulée (éluviation de la matrice, expulsion et transit des blocs en surface) s'opèrent pendant le dépôt et perturbent la stratogénèse. La comparaison des dépôts provenant des deux versants de La Mortice ainsi que des exemples déjà connus dans les Andes montre que la stratification est d'autant mieux exprimée que le nombre de cycles gel-dégel annuels est important et que la profondeur d'engel est faible.This paper emphasizes the role of stone-banked sheets in bedding of slope deposits at La Mortice (3170 m). Coarse particles sorting due to frost heaving and runoff occurs within sheets leading to the development of stone banks and surface pavements in connection with matrix-rich beds. Burying of stones at the sheet front by the frost creep induced movement of matrix-rich layers makes it possible the formation of coarse openwork beds. Cryoturbation, heaving of blocky materials and intense leaching of fine particles through the different beds disturb the stratification. A comparison between deposits from the east and the northwest facing slopes of La Mortice and Andean examples clearly shows that bedding is better developped when superficial freeze-thaw cycles are frequent and the depth of seasonal freezing shallow.Das Studium der Hangablagerungen, welche die ôstlichen und nordwestlichen Hànge von La Mortice uberziehen (3170 m, sùdliche Alpen, Frankreich), hebt deutlich die RoIIe der Dynamik des Bodenfliefiens mit steiniger Front bei der Entwicklung einer Schichtung hervor. Innerhalb der Stromungen bewirken Frostauswerfung und Auswaschung die Differenzierung einer kiesartigen Front verbunden mit einer oberflàchlichen Bedeckung und einem an Grundmasse reichen Niveau. Letzteres bewegt sich durch Frostkriechen und beerdigt im Laufe seiner Entstehung die steinige Front, bis es ein grobes eingegrabenes Bett mit offener Struktur bildet. Kryoturbation und Materialtransfer auRerhalb des durch die Strômung gebildeten Systems (Verwitterung der Grundmasse, AusstoB und Transit der Oberflàchenblôcke) finden wàhrend der Ablagerung statt und stôren die Stratogenese. Der Vergleich der Ablagerung von den zwei Hàngen von La Mortice sowie von schon bekannten Beispielen in den Anden zeigt, daf3 die Schichtung umso besser ausgedruckt ist, je bedeutender die Zahl der jâhrlichen Frost- und Tauperioden und je schwacher die Frosttiefe ist

Longitudinal Electrical Near-field generated by a Tapered Coax and studied with a Piezoelectric Film coupled with an Optical Probe

International audienceWe investigated the influence of using a conical end on the longitudinal electrical near-field generated by a coaxial cable. Simulations with Finite Integration Technique show that this influence greatly varies along the longitudinal axis. Experimental measurements were also carried out. To that purpose, we designed a new set-up to measure the electrical field in one direction with a spatial resolution of 100 microns in this direction, with nearly no perturbation by the other components of the field. This set-up uses a piezoelectric sintered PZT film and a heterodyne laser probe