A simple account of multiagent epistemic planning

International audienceA realistic model of multiagent planning must allow us to model notions which are absent in classical planning such as communication and knowledge. We investigate multiagent planning based on a simple logic of action and knowledge that is based on the visibility of propositional variables. Using such a formal logic allows us to deduce the validity of a plan from the validity of the individual actions which compose it. We present a coding of multiagent planning problems expressed in this logic into the classical planning language PDDL. Feeding the resulting problem into a PDDL planner provides a provably correct plan for the original multiagent planning problem. We use the gossip problem as a running example

Media réactif comprenant un support poreux imprégné d’un composé organique capable de former des clathrates de gaz, et son utilisation pour la séparation et le stockage de CO2

L'invention concerne un média réactif comprenant un support poreux sur lequel est déposé, sous forme solide, un composé organique capable de former des clathrates de gaz. L'invention concerne également un procédé de séparation du CO2, présent dans un mélange de gaz, dans lequel une capture du CO2 est réalisée par enclathration au moyen dudit média réactif. L'invention porte aussi sur des réacteurs permettant la mise en oeuvre dudit procédé

Artémidore, Daldis et les divinités locales sur les émissions provinciales romaines

Comprendre le milieu dans lequel Artémidore de Daldis a pu baigner permet de saisir sa personnalité, ou, tout au moins, certains des traits de caractères qu’il a laissé transparaître, volontairement ou pas, dans son ouvre, les Oneirokritika. L’auteur se dit « de Daldis », sa patrie par sa mère bien qu’il fût citoyen d’Éphèse. Ses passages à Daldis durant son enfance et son adolescence, cité grecque de la Lydie intérieure (région d’Asie Mineure occidentale, intégrée à la province d’Asie pour l..

50 dates historiques de la Grèce antique

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The epistemic gossip problem

International audienceIn the gossip problem information (‘secrets’) must be shared among a certain number of agents using the minimum number of calls. We extend the gossip problem to arbitrary epistemic depths. For example, we may require not only that all agents know all secrets but also that all agents know that all agents know all secrets. We give optimal protocols for various versions of this epistemic gossip problem, depending on the graph of communication links, in the case of two-way communication, one-way communication and parallel communication. We show, among other things, that increasing epistemic depth from 1 (all agents know all secrets) to 2 (so that all agents know that all agents know all secrets) does not double the required number of calls but increases this number by 3/2 (for a complete graph). We also show that the following counterintuitive result generalises to the epistemic gossip problem: asymptotically the same number of calls are required whether calls are two-way or one-way

Acetylene semi-hydrogenation over Pd-Zn/CeO2: Relevance of CO adsorption and methanation as descriptors of selectivity

SSCI-VIDE+ING+FRM:MMF:YSCInternational audienceSelective hydrogenatio

Stable Au-Ag alloy nanoparticles encapsulated in single crystal multi-hollow zeolites: application to CO removal at low temperature studied by operando IR spectroscopy

MICROSCOPIE+ING+RAT:ATU:LBU:FRMInternational audienceThe preparation of well-defined and stable alloy nanoparticle remains a challenge. We have shown that it was possible to prepare well-defined alloy nanoparticles encapsulated in single crystal hollow zeolite nanoboxes that were stable at 500°C in the presence of steam. The overall metal loading in these single hollow nanoboxes had yet to be kept low if the preparation of small particles was sought. We have recently reported a novel method to prepare well-dispersed nickel nanoparticles at high loading (i.e. 6 wt.%) using multi-hollow single crystal zeolites.The present contribution reports for the first time the preparation of Au and Au-Ag nanoparticles dispersed in multi-hollow silicalite-1 single crystals, derived from the method reported earlier2. Highly dispersed Au and Au-Ag nanoparticles with a diameter around 3 nm were obtained, even after calcination at 550°C.The CO oxidation activity and the species present at the surface of the catalyst were evaluated using a diffuse reflectance FT-IR spectroscopic (DRIFTS) cell described elsewhere. The Au and Au-Ag materials exhibited a maximum of activity, as expected1. Surprisingly, the Au-only sample was as active as the Au-Ag sample at lower temperatures, possibly due to a large fraction of low coordination sites that are able to adsorb and activate CO. This was confirmed by the operando DRIFTS data, which showed a significantly higher band at 2134 cm-1, corresponding to CO adsorbed on step and corner sites4. The proportion of these sites was lower on the Au-Ag sample, but the alloy exhibited partially oxidised Ag sites (bands at 2189 and 2172 cm-1) that could too adsorb CO. The activity of an Ag-only sample was significantly lower over this temperature range, stressing again the synergy existing between Au and Ag for CO oxidation.This work shows that it is possible to prepare highly dispersed and stable Au and Au-Ag nanoparticles in multi-hollow zeolites that exhibit interesting activity for CO oxidation at room temperature

Acetylene semi-hydrogenation over PdZn/CeO2: CO methanation as unequivocal descriptor of selectivation

SSCI-VIDE+ING+FRM:YSCInternational audienceThe semi-hydrogenation of acetylene to ethylene can be achieved over bulk CeO21 and ZnO-supported PdZn2, the latter being active below 100°C. To our knowledge, PdZn/CeO2 has not yet been investigated for this reaction. The effect of Zn alloying with Pd and the selectivation of the sample with reduction temperature is presented here. PdZn samples free of Pd-Pd ensembles (showing no bridged CO) were prepared, since the most selective PdZn surfaces were proposed to be intermetallic that exhibited only Pd-Zn-Pd units2.Pd and Pd+Zn were impregnated over a custom-made ceria. Acetylene hydrogenation was carried out in a tubular stainless steel reactor using a feed composed of 1.2% C2H2 + 4.3% H2 + 32% C2H4 in He. A diffuse reflectance FT-IR (DRIFTS) cell was used to investigate CO hydrogenation to methane and determine CO adsorption mode and heat in operando conditions.All samples were highly active for acetylene hydrogenation (70°C < T50% < 85°C). Zn-free Pd/CeO2 led to negative selectivities, as acetylene and some of the ethylene fed into the reactor were hydrogenated to ethane (Fig. 1, left). PdZn/CeO2 reduced at 400 and 500°C exhibited only a moderate selectivity of ca. 50%, despite the fact that these samples did not exhibit any bridged CO (Fig. 1, top right). Bridged CO is thus not a satisfactory descriptor. PdZn/CeO2 reduced at 550 and 650°C led to near 100% selectivity up to full conversion, but were too dark to be investigated by IR. CO methanation (Fig. 1, bottom right) was shown to be a suitable selectivity descriptor, as only the highly selective PdZn/CeO2 reduced at 550 and 650°C led to no measurable methane formation

Acetylene semi-hydrogenation over PdZn/CeO2: CO methanation as unequivocal descriptor of selectivation

SSCI-VIDE+ING+FRM:YSCInternational audienceThe semi-hydrogenation of acetylene to ethylene can be achieved over bulk CeO21 and ZnO-supported PdZn2, the latter being active below 100°C. To our knowledge, PdZn/CeO2 has not yet been investigated for this reaction. The effect of Zn alloying with Pd and the selectivation of the sample with reduction temperature is presented here. PdZn samples free of Pd-Pd ensembles (showing no bridged CO) were prepared, since the most selective PdZn surfaces were proposed to be intermetallic that exhibited only Pd-Zn-Pd units2.Pd and Pd+Zn were impregnated over a custom-made ceria. Acetylene hydrogenation was carried out in a tubular stainless steel reactor using a feed composed of 1.2% C2H2 + 4.3% H2 + 32% C2H4 in He. A diffuse reflectance FT-IR (DRIFTS) cell was used to investigate CO hydrogenation to methane and determine CO adsorption mode and heat in operando conditions.All samples were highly active for acetylene hydrogenation (70°C < T50% < 85°C). Zn-free Pd/CeO2 led to negative selectivities, as acetylene and some of the ethylene fed into the reactor were hydrogenated to ethane (Fig. 1, left). PdZn/CeO2 reduced at 400 and 500°C exhibited only a moderate selectivity of ca. 50%, despite the fact that these samples did not exhibit any bridged CO (Fig. 1, top right). Bridged CO is thus not a satisfactory descriptor. PdZn/CeO2 reduced at 550 and 650°C led to near 100% selectivity up to full conversion, but were too dark to be investigated by IR. CO methanation (Fig. 1, bottom right) was shown to be a suitable selectivity descriptor, as only the highly selective PdZn/CeO2 reduced at 550 and 650°C led to no measurable methane formation

Simple epistemic planning: generalised gossiping

International audienceThe gossip problem, in which information (secrets) must be shared among a certain number of agents using the minimum number of calls, is of interest in the conception of communication networks and protocols. We extend the gossip problem to arbitrary epistemic depths. For example, we may require not only that all agents know all secrets but also that all agents know that all agents know all secrets. We give optimal protocols for the generalised gossip problem, in the case of two-way communications, one-way communications and parallel communication. In the presence of negative goals testing the existence of a successful protocol is NP-complete