25,333 research outputs found
Thematic Annotation: extracting concepts out of documents
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
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
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
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
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
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
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
Pierre Bourdieuâs 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 âcritical sociologyâ
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 âfieldâ, âhabitusâ, variously conceived
notions of âcapitalâ, and âillusioâ (all these concepts and others will
be explicated and assessed in this issue). Yet Bourdieuâs analyses were
scarcely ever received as neutral descriptions within the fields which
he analysed. Bourdieuâs 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 âcritical sociologyâ could
disclose. Coupled with the inveterately combative drive seldom absent
from Bourdieuâs objectifying analysesâand even setting aside the
misprisions to which an external analyst is inevitably subjectâthis
helps explain the resistance which his work recurrently provoked. In
this respect, Bourdieuâs forays into the world of literary studies and his
reception therein can be seen as part of a wider pattern
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