Expansions of MSO by cardinality relations

We study expansions of the Weak Monadic Second Order theory of (N,<) by cardinality relations, which are predicates R(X1,...,Xn) whose truth value depends only on the cardinality of the sets X1, ...,Xn. We first provide a (definable) criterion for definability of a cardinality relation in (N,<), and use it to prove that for every cardinality relation R which is not definable in (N,<), there exists a unary cardinality relation which is definable in (N,<,R) and not in (N,<). These results resemble Muchnik and Michaux-Villemaire theorems for Presburger Arithmetic. We prove then that + and x are definable in (N,<,R) for every cardinality relation R which is not definable in (N,<). This implies undecidability of the WMSO theory of (N,<,R). We also consider the related satisfiability problem for the class of finite orderings, namely the question whether an MSO sentence in the language {<,R} admits a finite model M where < is interpreted as a linear ordering, and R as the restriction of some (fixed) cardinality relation to the domain of M. We prove that this problem is undecidable for every cardinality relation R which is not definable in (N,<).Comment: to appear in LMC

Existence of common and upper frequently hypercyclic subspaces

We provide criteria for the existence of upper frequently hypercyclic subspaces and for common hypercyclic subspaces, which include the following consequences. There exist frequently hypercyclic operators with upper-frequently hypercyclic subspaces and no frequently hypercyclic subspace. On the space of entire functions, each differentiation operator induced by a non-constant polynomial supports an upper frequently hypercyclic subspace, and the family of its non-zero scalar multiples has a common hypercyclic subspace. A question of Costakis and Sambarino on the existence of a common hypercyclic subspace for a certain uncountable family of weighted shift operators is also answered.Comment: 30 page

The French research system : which evolution and which borders ?

We analyse the French Research System with the study of the contracts between the CNRS (Centre National de la Recherche Scientifique) and the companies and test the hypothesis of small world in science. Our working material is the data base of the contracts of the units of the CNRS with economic partners, which has been collecting information since 1986 to 2006. This first application of Network methods and tools to the CNRS contracts allows us to obtain some results: at first, the major firms’s scientific network is not "scale-free" as if competition and strategy between the most large firms dominate the behaviour in R&D investments and management of contracts with public research units. However, in second part, we demonstrate that every discipline network is a "small world", i.e. , that it exists several scientific communities in which the diffusion of information is free and easy, even if its forwards through any actors (some labs or some firms). Probably, there are several "small worlds" in this database as in the scientific collaboration networks. Is seems that the industrial research does not disturb too much the properties of scientific network, as it’s well known in the literature of Sciences Studies

La phrase verbale noyau en français

La phrase verbale noyau en français, caractérisée comme la chaîne de mots qui comprend clitiques, auxiliaire, noyau verbal, particules de négation, l'adverbe toujours et la forme tous est étudiée dans un cadre -- libellé 5P -- qui essaye d'intégrer observation, test et calcul -- c'est-à-dire les activités essentielles de toute science du réel -- dans l'étude des phénomènes linguistiques. Le cadre 5P est présenté dans ses caractéristiques essentielles. Les Propriétés permettant de spécifier, sous certaines conditions d'observation, les phrases verbales noyau sont définies, de même que le calcul à effectuer pour générer tous les conséquences de ces Propriétés -- c'est-à-dire les suites qui sont des phrases verbales noyau en français. On montre, par ailleurs, les possibilités de calcul à partir de ces suites. Les caractéristiques de modularité et d'incrémentalité du système sont illustrées, et celui-ci est mis en perspective par rapport à d'autres points de vue qui ont cours en linguistique

Enabling Realistic Cross-Layer Analysis based on Satellite Physical Layer Traces

We present a solution to evaluate the performance of transport protocols as a function of link layer reliability schemes (i.e. ARQ, FEC and Hybrid ARQ) applied to satellite physical layer traces. As modelling such traces is complex and may require approximations, the use of real traces will minimise the potential for erroneous performance evaluations resulting from imperfect models. Our Trace Manager Tool (TMT) produces the corresponding link layer output, which is then used within the ns-2 network simulator via the additionally developed ns-2 interface module. We first present the analytical models for the link layer with bursty erasure packets and for the link layer reliability mechanisms with bursty erasures. Then, we present details of the TMT tool and our validation methodology, demonstrating that the selected performance metrics (recovery delay and throughput efficiency) exhibit a good match between the theoretical results and those obtained with TMT. Finally, we present results showing the impact of different link layer reliability mechanisms on the performance of TCP Cubic transport layer protocol

French Order Without Order

International audienceTo account for the semi-free word order of French, Unification Categorial Grammar is extended in two ways. First, verbal valencies are contained in a set rather than in a list. Second, type-raised NP's are described as two-sided functors. The new framework does not overgenerate, i.e. it accepts all and only the sentences which are grammatical. This follows partly from the elimination of false lexical ambiguities -- i.e. ambiguities introduced in order to account for all the possible positions a word can be in within a sentence -- and partly from a system of features constraining the possible combinations

Propriétés et analyse d'un langage

International audienceNous présentons dans cet article une nouvelle approche, que nous appelons 5P, permettant la description des propriétés d'un langage et son utilisation pour une analyse automatique. Nous montrons comment cette approche permet la prise en compte de la dimension descriptive de la linguistique. Par ailleurs, nous présentons une technique d'analyse, appelée analyse par Filtrage et Fusion, qui tire parti de cette description en propriétés. Nous montrons en quoi ces deux projets (description d'une langue et analyse automatique) convergent et ouvrent de nouvelles perspectives

Les relations entre anciens élèves ingénieurs : réseau personnel ou capital social ?

Cette étude vise à analyser le fonctionnement des réseaux d’anciens élèves ingénieurs et notamment les phénomènes d’entraide et de solidarité entre ingénieurs issus des mêmes Ecoles. L'étude a été conduite dans une ENSI de la région toulousaine auprès d'un échantillon réduit d'anciens élèves afin de retracer leur trajectoire de sociabilité. Cette étude préliminaire a fait apparaître que les relations entre anciens élèves se constituent surtout pendant la formation, sur la base d’activités communes partagées au cours de cette période. De même, les relations entre élèves et diplômés ne sont pas directes – par l’utilisation de l’annuaire par exemple – mais passent par l’Ecole, à l’occasion de stages ou de cours. Il n’y a pas de réflexe de recommandation ou d’esprit de corps proprement dit, c’est-à-dire de contacts entre anciens élèves sans chaine relationnelle préalable tels qu’on peut les retrouver dans d’autres Ecoles, par exemple celles des Arts et Métiers