Le répertoire des figures

Balzac ne cesse de rattacher ses personnages aux grandes figures du passé, de celles qui sont recueillies dans ces répertoires biographiques que goûte tant la librairie romantique (ainsi de la Biographie Michaud). Les appositions (« Troubert, l’Alexandre VI de Tours »), les antonomases (« une nouvelle Diane de Poitiers »), les listes exemplaires et autres opérateurs analogiques inscrivent les personnages balzaciens dans un jeu dynamique de liaisons, d’apparentements, comme s’il s’agissait de leur donner une légitimité qui leur ferait défaut. Ces traits stylistiques nous disent quelque chose du personnage de roman, de son statut, de la légitimité fragile qui est la sienne au regard des personnages de la fable, des figures héritées de la tradition : sa présence incertaine dans nos mémoires est toujours près d’être dénoncée comme une usurpation.Balzac consistently connects his characters to important figures of the past, like those that are collected in the biographical catalogues that were so appreciated by the Romantic library (such as the Biographie Michaud). Appositions (“Troubert, l’Alexandre VI de Tours”), antonomasia (“une nouvelle Diane de Poitiers”), exemplary lists and other analogical operators place Balzac’s characters in a network of liaisons and affiliations, as if it were a matter of giving them a legitimacy which would be their shortcoming. These stylistic traits reveal something about the character in the novel, about his status, and his fragile legitimacy in relation to the characters of the fable and the inherited figures of tradition. His uncertain presence in our memory is always close to being denounced as usurpation

Genèse d'une communauté de pratique d'étudiants issue d'un forum de discussion : participation, conscience d'autrui et engagement mutuel

National audienceThis paper examines the way bachelor’s degree students in education in an online environment (FORSE, CNED) use a discussion forum, and how a virtual community of practice (CoP, Wenger, 1998/2005) emerges from their written interactions. We gathered and analysed these interactions, which are distributed in one academic year on three periods. Moreover the students were given a questionnaire assessing their practices and opinions on the forum. Three main dimensions were investigated: the actual use of the discussion forum tool; the students’ awareness about each other (actions, thoughts); the extent a virtual CoP can emerge and develop. Results show, first, that the forum tool shapes the communication among students; second, that identity and self-introduction schemes are mainly delivered in the first phase. Eventually, several help or self-organizing behaviours, as well as different levels of involvement were found, supporting Wenger’s theory.Cet article étudie la manière dont une promotion d'étudiants de 3e année de licence en sciences de l'éducation à distance (FORSE, CNED) s'approprie un forum de discussion généraliste et interne à la formation, et comment une communauté de pratique virtuelle peut émerger à partir de leurs interactions. Ces dernières sont recueillies et analysées sur trois périodes au sein d'une année entière et un questionnaire d'opinion est passé. Trois dimensions sont investiguées : l'utilisation de l'outil forum de discussion, la manière dont les participants s'intéressent à autrui et communiquent à propos d'eux-mêmes (awareness) et, enfin, l'émergence et l'entretien d'une communauté de pratique en ligne. Les résultats montrent que le forum est un outil qui structure la CdP, que des éléments personnels de présentation de soi sont principalement diffusés en début d'année, dirigés vers autrui et spécifiques à la distance; enfin, l'existence d'entraide et d'auto-organisation des participants à différents niveaux d'engagement est relevée, conforme en cela à la théorie de Wenger

Algorithms for the Multiclass Network Equilibrium Problem

International audienceWe consider a nonatomic congestion game on a connected graph, with several classes of players. Each player wants to go from its origin vertex to its destination vertex at the minimum cost and all players of a given class share the same characteristics: cost functions on each arc, and origin-destination pair. In the transportation terminology, each class models a distinct mode of transportation, such as cars, trucks, or motorbikes for example.A strategy profile is a mapping determining for each player a route from its origin to its destination. A strategy profile is a (pure) Nash equilibrium if no player would benefit by changing its route. This game enters in the category of nonatomic congestion games with player-specific cost functions, see Milchtaich (Congestion games with player-specific payoff functions, Games Econom. Behavior, 13:111-124, 1996). The problem of finding a Nash equilibrium for such a game is called the Multiclass Network Equilibrium Problem. Under some mild conditions, it is known that a Nash equilibrium exists, but the computation of an equilibrium in the multiclass case is an open problem for general functions. We consider the specific case where the cost functions are affine and stricly increasing. In this case, we write the Multiclass Network Equilibrium Problem as a linear complementarity problem. Our contribution is twofold: - We prove the existence of a polynomial algorithm solving the problem when the graph consists in parallel arcs. The main idea of the algorithm relies on properties of hyperplane arrangements.- We build a pivoting algorithm, adapted from Lemke (Bimatrix equilibrium points and equilibrium programming, Management Science, 11:681-689, 1965), solving the problem for general graphs. To our knowledge, it is the first algorithm solving this problem. We prove its efficiency through computational experiments. Moreover, this algorithm provides the first constructive proof of the existence of an equilibrium for this problem.</p

Uniqueness of equilibrium on rings

We consider congestion games on networks with nonatomic users and user-specific costs. We are interested in the uniqueness property defined by Milchtaich [Milchtaich, I. 2005. Topological conditions for uniqueness of equilibrium in networks. Math. Oper. Res. 30 225-244] as the uniqueness of equilibrium flows for all assignments of strictly increasing cost functions. He settled the case with two-terminal networks. In the present work we characterize completely bidirectional rings for which the uniqueness property holds. The main result is that it holds precisely for nine networks and those obtained from them by elementary operations. For other bidirectional rings, we exhibit affine cost functions yielding to two distinct equilibrium flows. Related results are also proven

Genèse d'une communauté de pratique d'étudiants issue d'un forum de discussion : participation, conscience d'autrui et engagement mutuel

National audienceThis paper examines the way bachelor’s degree students in education in an online environment (FORSE, CNED) use a discussion forum, and how a virtual community of practice (CoP, Wenger, 1998/2005) emerges from their written interactions. We gathered and analysed these interactions, which are distributed in one academic year on three periods. Moreover the students were given a questionnaire assessing their practices and opinions on the forum. Three main dimensions were investigated: the actual use of the discussion forum tool; the students’ awareness about each other (actions, thoughts); the extent a virtual CoP can emerge and develop. Results show, first, that the forum tool shapes the communication among students; second, that identity and self-introduction schemes are mainly delivered in the first phase. Eventually, several help or self-organizing behaviours, as well as different levels of involvement were found, supporting Wenger’s theory.Cet article étudie la manière dont une promotion d'étudiants de 3e année de licence en sciences de l'éducation à distance (FORSE, CNED) s'approprie un forum de discussion généraliste et interne à la formation, et comment une communauté de pratique virtuelle peut émerger à partir de leurs interactions. Ces dernières sont recueillies et analysées sur trois périodes au sein d'une année entière et un questionnaire d'opinion est passé. Trois dimensions sont investiguées : l'utilisation de l'outil forum de discussion, la manière dont les participants s'intéressent à autrui et communiquent à propos d'eux-mêmes (awareness) et, enfin, l'émergence et l'entretien d'une communauté de pratique en ligne. Les résultats montrent que le forum est un outil qui structure la CdP, que des éléments personnels de présentation de soi sont principalement diffusés en début d'année, dirigés vers autrui et spécifiques à la distance; enfin, l'existence d'entraide et d'auto-organisation des participants à différents niveaux d'engagement est relevée, conforme en cela à la théorie de Wenger

A Lemke-like algorithm for the Multiclass Network Equilibrium Problem

14 pagesWe consider a nonatomic congestion game on a connected graph, with several classes of players. Each player wants to go from its origin vertex to its destination vertex at the minimum cost and all players of a given class share the same characteristics: cost functions on each arc, and origin-destination pair. Under some mild conditions, it is known that a Nash equilibrium exists, but the computation of an equilibrium in the multiclass case is an open problem for general functions. We consider the specific case where the cost functions are affine and propose an extension of Lemke's algorithm able to solve this problem. At the same time, it provides a constructive proof of the existence of an equilibrium in this case

Bounding the price of anarchy for games with player-specific cost functions

9 pagesWe study the efficiency of equilibria in atomic splittable congestion games on networks. We consider the general case where players are not affected in the same way by the congestion. Extending a result by Cominetti, Correa, and Stier-Moses (The impact of oligopolistic competition in networks, Oper. Res., 57, 1421--1437 (2009)), we prove a general bound on the price of anarchy for games with player-specific cost functions. This bound generalizes some of their results, especially the bound they obtain for the affine case. However our bound still requires some dependence between the cost functions of the players. In the general case, we prove that the price of anarchy is unbounded, by exhibiting an example with affine cost functions and only two players