15771 research outputs found
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Parameterized Inapproximability of Degree Anonymization
No full textin Springer series Lecture Notes in Computer Science, vol. 8894The Degree Anonymity problem arises in the context of combinatorial graph anonymization. It asks, given a graph G and two integers k and s, whether G can be made k-anonymous with at most s modifications. Here, a graph is k-anonymous if the graph contains for every vertex at least k−1 other vertices of the same degree. Complementing recent investigations on its computational complexity, we show that this problem is very hard when studied from the viewpoints of approximation as well as parameterized approximation. In particular, for the optimization variant where one wants to minimize the number of either edge or vertex deletions there is no factor-n1−ε approximation running in polynomial time unless P = NP, for any constant 0<ε≤1. For the variant where one wants to maximize k and the number s of either edge or vertex deletions is given, there is no factor-n1/2−ε approximation running in time f(s)⋅nO(1) unless W[1] = FPT, for any constant 0<ε≤1/2 and any function f. On the positive side, we classify the general decision version as fixed-parameter tractable with respect to the combined parameter solution size s and maximum degree.nonouirechercheInternationa
In Search of the Purpose of Accounting Representation
No full textThis book, dedicated to Prof. Jacques Richard, is about the economic, political, social and even environmental consequences of setting accounting standards, with emphasis of those thar are alleged to be precipitated by the adoption and implementation of IFRS.nonouirechercheInternationa
Multi-dimensional signal approximation with sparse structured priors using split Bregman iterations
No full textThis paper addresses the structurally constrained sparse decomposition of multi-dimensional signals onto overcomplete families of vectors, called dictionaries. The contribution of the paper is threefold. Firstly, a generic spatio-temporal regularization term is designed and used together with the standard ℓ1ℓ1 regularization term to enforce a sparse decomposition preserving the spatio-temporal structure of the signal. Secondly, an optimization algorithm based on the split Bregman approach is proposed to handle the associated optimization problem, and its convergence is analyzed. Our well-founded approach yields same accuracy as the other algorithms at the state of the art, with significant gains in terms of convergence speed. Thirdly, the empirical validation of the approach on artificial and real-world problems demonstrates the generality and effectiveness of the method. On artificial problems, the proposed regularization subsumes the Total Variation minimization and recovers the expected decomposition. On the real-world problem of electro-encephalography brainwave decomposition, the approach outperforms similar approaches in terms of P300 evoked potentials detection, using structured spatial priors to guide the decomposition.nonouirechercheInternationa
Riemannian approaches in Brain-Computer Interfaces: a review
No full textAlthough promising from numerous applications, current Brain-Computer Interfaces (BCIs) still suffer from a number of limitations. In particular, they are sensitive to noise, outliers and the non-stationarity of ElectroEncephaloGraphic (EEG) signals, they require long calibration times and are not reliable. Thus, new approaches and tools, notably at the EEG signal processing and classification level, are necessary to address these limitations. Riemannian approaches, spearheaded by the use of covariance matrices, are such a very promising tool slowly adopted by a growing number of researchers. This article, after a quick introduction to Riemannian geometry and a presentation of the BCI-relevant manifolds, reviews how these approaches have been used for EEG-based BCI, in particular for feature representation and learning, classifier design and calibration time reduction. Finally, relevant challenges and promising research directions for EEG signal classification in BCIs are identified, such as feature tracking on manifold or multi-task learning.nonnonrechercheInternationa
A Multi-Agent Approach for Trust-Based Service Discovery and Selection in Social Networks
No full textService discovery and selection approaches are often done using a centralized registry-based technique, which only captures common Quality of Service criteria. With more and more services offered via social networks, these approaches are not able to evaluate trust in service providers and often fail to comply with new requester's expectations. This is because theses approaches are not able (i) to take into consideration the social dimension and (ii) to capitalize on information resulting from previous experiences. To address these challenges, we propose the use of multi-agent systems as they have demonstrated the capability to use previous interactions, knowledge representation and distributed reasoning, as well as social metaphors like trust. More precisely, in this paper, we enhance service discovery and selection processes by integrating the societal view in trust modeling. Based on relationships between agents, their previous experiences and extracted information from social network, we define a trust model built upon social, expert and recommender-based components. The social-based component judges whether the provider is worthwhile pursuing before using his services (viz. trust in sociability). The expert-based component estimates whether the service behaves well and as expected (viz. trust in expertise). The recommender-based component assesses for an agent whether one's can rely on its recommendations (viz. trust in recommendation). However, when searching for a service in a social network, agents (service requester and service providers) may have no direct interactions or previous experiences. This requires a method to infer trust between them. Based on a probabilistic model, we estimate trust between non adjacent agents while taking into account roles (recommender or provider) of intermediate agents. Moreover, we propose a distributed algorithm for trustworthy service discovery and selection using referral systems in social networks. Experiments demonstrate that our approach is effective and outperforms existing ones, and can deliver more trustworthy results.nonouirechercheInternationa
Fuzzy along spatial relation in 3D. Application to anatomical structures in maxillofacial CBCT
No full textLecture Notes in Computer Science, Vol. 9279Spatial relations have proved to be of great importance in computer vision and image understanding. One issue is their modeling in the image domain, hence allowing for their integration in segmentation and recognition algorithms. In this paper, we focus on the “along” spatial relation. Based on a previous work in 2D, we propose extensions to 3D. Starting from the inter-objects region, we demonstrate that the elongation of the interface between the objects and this region gives a good evaluation of the alongness degree. We also integrate distance information to take into account only close objects parts. Then we describe how to define the alongness relation within the fuzzy set theory. Our method gives a quantitative satisfaction degree of the relation, reliable for differentiating spatial situations. An original example on the maxillofacial area in Cone-Beam Computed Tomography (CBCT) illustrates how the proposed approach could be used to recognize elongated structures.nonouirechercheInternationa
Abductive reasoning using tableau methods for high-level image interpretation
No full textImage interpretation is a dynamic research domain involving not only the detection of objects in a scene but also the semantic description considering context information in the whole scene. Image interpretation problem can be formalized as an abductive reasoning problem, i.e. an inference to the best explanation using a background knowledge. In this work, we present a framework using a tableau method for generating and selecting potential explanations of the given image when the background knowledge is encoded using a description that is able to handle spatial relations.nonouirechercheInternationa
ShareLab support for collective intelligence. 1 deadline, 11 designers, 1 project
No full textThis paper presents the implementation of a collaborative action research approach aimed to assist in constructing collective intelligence. Named ShareLab, this project was implemented as part of a call to an international competition bringing together different skills originating from varying cultures so as to produce a common project in a very short time. What is the origin of ShareLab? How was it put into play? What are its advantages and limitations? This article aims to answer these questions thanks to the feedback obtained from this competition experience.nonouirechercheInternationa
Por un metodo alternativo del analisis de la difusion de informacion social y medioambiental
No full textThis paper proposes an alternative approach to corporate social disclosure analysis. A survey of the literature dealing with description and explanation of corporate social disclosure practices underlines the inconsistency of the findings. We discuss the relevance of the instrument. In order to improve the description of corporate social practices as well as the explanation of the link between these disclosures and corporate social performance, we propose a qualitative approach. An exploratory study on fifteen French companies outlines the interest of this alternative method.ouinonouirechercheNationa
Aléas de carrière, inégalités et retraite
No full textLa diversité des parcours de vie (âge d’entrée dans la vie active, vie familiale, santé et espérance de vie, inactivité, chômage…) n’est pas sans incidence sur les départs à la retraite et sur le niveau de vie des retraités. Cette diversité est ainsi devenue un thème central dans la réflexion sur les systèmes de retraite. Les parcours professionnels et familiaux sont-ils plus accidentés pour les femmes que les hommes ? Les aléas de carrière sont-ils plus nombreux pour certaines tranches d’âge, pour certaines générations ? Comment faut-il compenser les interruptions d’activité ? Quel est l’impact de ces différents aléas sur le montant des pensions de retraite ? En lien avec ces questions, celle des inégalités de revenus est à l’évidence de premier ordre dans la réflexion. L’étude propose dans un premier temps, à partir des enquêtes Emploi (1990, 1995, 2005) et Patrimoine (2003-2004) de l’Insee, une analyse des accidents de carrière et des inégalités de revenus parmi les actifs et les retraités et ainsi met en évidence de nouvelles tendances quant à l’évolution des trajectoires professionnelles, notamment selon le genre et la génération. La mobilisation de différents indicateurs (notamment le coefficient de Gini) permet ensuite de déterminer les groupes d’actifs et de retraités les plus inégalitaires en fonction de nombreuses caractéristiques socioéconomiques et sociodémographiques. Dans un second temps, une analyse des conséquences des parcours heurtés sur les droits à la retraite est menée. Principalement touchés par les aléas de carrière, les seniors font au préalable l’objet d’une étude spécifique qui permet également de faire le point sur les différents dispositifs en faveur de l’emploi des seniors. Enfin, une évaluation de l’incidence de la prise en compte du RMI et d’un allégement de la décote sur les droits à pension est effectuée.ouinonouirechercheNationa