25,333 research outputs found

    Thematic Annotation: extracting concepts out of documents

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    Contrarily to standard approaches to topic annotation, the technique used in this work does not centrally rely on some sort of -- possibly statistical -- keyword extraction. In fact, the proposed annotation algorithm uses a large scale semantic database -- the EDR Electronic Dictionary -- that provides a concept hierarchy based on hyponym and hypernym relations. This concept hierarchy is used to generate a synthetic representation of the document by aggregating the words present in topically homogeneous document segments into a set of concepts best preserving the document's content. This new extraction technique uses an unexplored approach to topic selection. Instead of using semantic similarity measures based on a semantic resource, the later is processed to extract the part of the conceptual hierarchy relevant to the document content. Then this conceptual hierarchy is searched to extract the most relevant set of concepts to represent the topics discussed in the document. Notice that this algorithm is able to extract generic concepts that are not directly present in the document.Comment: Technical report EPFL/LIA. 81 pages, 16 figure

    European Communications at the Crossroads. Report of the CEPS Working Party on electronic communications. CEPS Task Force Reports No. 39, 1 October 2001

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    Community institutions are now busy with the second readings of the proposals for a new regime for regulating the European Communications Industry. While many aspects of the proposed new regulatory arrangements are widely accepted, a number of key choices still have to be made. The regulation of European communications is therefore at a crossroads. This CEPS Working Party Report considers the key choices that lie ahead, with the aim of providing the institutions with some fresh input from well placed observers

    Connecting local active forces to macroscopic stress in elastic media

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    In contrast with ordinary materials, living matter drives its own motion by generating active, out-of-equilibrium internal stresses. These stresses typically originate from localized active elements embedded in an elastic medium, such as molecular motors inside the cell or contractile cells in a tissue. While many large-scale phenomenological theories of such active media have been developed, a systematic understanding of the emergence of stress from the local force-generating elements is lacking. In this paper, we present a rigorous theoretical framework to study this relationship. We show that the medium's macroscopic active stress tensor is equal to the active elements' force dipole tensor per unit volume in both continuum and discrete linear homogeneous media of arbitrary geometries. This relationship is conserved on average in the presence of disorder, but can be violated in nonlinear elastic media. Such effects can lead to either a reinforcement or an attenuation of the active stresses, giving us a glimpse of the ways in which nature might harness microscopic forces to create active materials.Comment: 9 pages, 4 figure

    Multiresolution modeling and simulation of an air-ground combat application

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    The High Level Architecture (HLA) establishes a common modeling and simulation framework facilitating interoperability and reuse of simulation components. Since 1996, ONERA (French Aeronautics and Space Research Centre) carries out several studies on HLA in order to gain a better understanding of the underlying mechanisms of HLA implementations. The first critical step of this initiative was to develop our own RTI from the HLA specifications. In order to evaluate the cost of making a transition from legacy simulations to HLA, we first developed an HLA federation simulating an air-ground combat involving a set of aircraft's engaged against a surface to air defense system. Current studies on HLA distributed simulation include security, WAN simulations and multiresolution. Conventional simulations represent entities at just one single level of resolution. Multiresolution representation of entities consists in maintaining multiple and concurrent representations of entities. In this paper we address the problem of how HLA services may allow to achieve multiresolution modeling and simulation. Our goal is not to provide a general framework as a basis for designing simulations of entities at different levels of resolution concurrently. We focus on experience feedback we have obtained by migrating a single level resolution HLA federation to a multi-level resolution federation. The selected application is an air-ground combat simulation involving aggregated patrols of aircraft's engaged against a surface to air defense system. In this paper, we briefly describe the air-ground combat simulation application. We then detail the multiresolution representation of entities (patrols and aircraft's), and discuss the chosen mechanisms allowing triggering aggregation from an entity-level representation, and conversely, triggering disaggregation from an aggregate representation. We focus on the HLA services we have selected to maintain several levels of representation concurrently and on methodological issues in designing multiresolution HLA simulations. We have tackled some difficulties and we propose a new HLA service that should make easier the user's task. This multiresolution management service can be added to our RTI or written by using existing HLA services. Finally, future trends are discussed

    Interior metric and ray-tracing map in the firework black-to-white hole transition

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    The possibility that a black hole could tunnel into a white hole has recently received attention. Here we present a metric that improves the 'firework' metric: it describes the entire process and solves the Einstein equations everywhere except on a small transition surface that corresponds to the quantum tunnelling. We compute the corresponding ray-tracing map from past infinity to future infinity explicitly.Comment: 5 pages, 10 figure

    Non-Equilibrium Statistical Mechanics of Strongly Anharmonic Chains of Oscillators

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    We study the model of a strongly non-linear chain of particles coupled to two heat baths at different temperatures. Our main result is the existence and uniqueness of a stationary state at all temperatures. This result extends those of Eckmann, Pillet, Rey-Bellet to potentials with essentially arbitrary growth at infinity. This extension is possible by introducing a stronger version of H\"ormander's theorem for Kolmogorov equations to vector fields with polynomially bounded coefficients on unbounded domains.Comment: ~60 pages, 3 figure

    Low-frequency noise impact on CMOS image sensors

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    CMOS image sensors are nowadays extensively used in imaging applications even for high-end applications. This is really possible thanks to a reduction of noise obtained, among others, by Correlated Double Sampling (CDS) readout. Random Telegraph Signal (RTS) noise has thus become an issue for low light level applications especially in the context of downscaling transistor size. This paper describes the analysis of in-pixel source follower transistor RTS noise filtering by CDS circuit. The measurement of a non Gaussian distribution with a positive skew of image sensor output noise is analysed. Impact of dimensions (W and L) of the in-pixel source follower is demonstrated. Circuit to circuit pixel output noise dispersion on 12 circuits coming from 3 different wafers is also analysed and weak dispersion is seen

    Introduction : Bourdieu and the literary field

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    Pierre Bourdieu’s range as a thinker was extremely wide, and it would be misleading to present him primarily as a literary theorist. Trained as a philosopher, he became the leading French sociologist of his generation, and brought under the spotlight of his ‘critical sociology’ a whole series of institutional and discursive universes (education, art, linguistics, public administration, politics, philosophy, journalism, economics and others). Far from representing an intellectual dispersal, these manifold objects of enquiry allowed him to develop and refine a comprehensive theory of social process and power-relations based on distinctive concepts such as ‘field’, ‘habitus’, variously conceived notions of ‘capital’, and ‘illusio’ (all these concepts and others will be explicated and assessed in this issue). Yet Bourdieu’s analyses were scarcely ever received as neutral descriptions within the fields which he analysed. Bourdieu’s abiding agenda was to show how the discursive presuppositions and institutional logics at work in such fields carried but also masked certain social logics that a ‘critical sociology’ could disclose. Coupled with the inveterately combative drive seldom absent from Bourdieu’s objectifying analyses—and even setting aside the misprisions to which an external analyst is inevitably subject—this helps explain the resistance which his work recurrently provoked. In this respect, Bourdieu’s forays into the world of literary studies and his reception therein can be seen as part of a wider pattern
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