5,569 research outputs found
Non-simplifying Graph Rewriting Termination
So far, a very large amount of work in Natural Language Processing (NLP) rely
on trees as the core mathematical structure to represent linguistic
informations (e.g. in Chomsky's work). However, some linguistic phenomena do
not cope properly with trees. In a former paper, we showed the benefit of
encoding linguistic structures by graphs and of using graph rewriting rules to
compute on those structures. Justified by some linguistic considerations, graph
rewriting is characterized by two features: first, there is no node creation
along computations and second, there are non-local edge modifications. Under
these hypotheses, we show that uniform termination is undecidable and that
non-uniform termination is decidable. We describe two termination techniques
based on weights and we give complexity bound on the derivation length for
these rewriting system.Comment: In Proceedings TERMGRAPH 2013, arXiv:1302.599
Interaction Grammars
Interaction Grammar (IG) is a grammatical formalism based on the notion of
polarity. Polarities express the resource sensitivity of natural languages by
modelling the distinction between saturated and unsaturated syntactic
structures. Syntactic composition is represented as a chemical reaction guided
by the saturation of polarities. It is expressed in a model-theoretic framework
where grammars are constraint systems using the notion of tree description and
parsing appears as a process of building tree description models satisfying
criteria of saturation and minimality
Systemic design of multidisciplinary electrical energy devices: a pedagogical approach
In this paper, we present a complete educative project for illustrating the design and the analysis of hybrid electrical systems. It is based on the study of an ElectroHydrostatic Actuator for flight control application, fed by a power supply associating a PEM fuel cell with a ultracapacitor storage. This system is controlled to achieve a typical energy management strategy of this multi source structure.
Step by step, student can faces typical issues relative to the design of heterogenous and multidisciplinary devices by achieving eight pedagogical objectives. These eight targets are focused on methodological approach for multi domain modelling (Bond Graphs), causal analysis, but also on simulation of complex heterogeneous systems. A typical hybrid system feeding an ElectroHydrostatic Actuator (EHA) for flight control application has to be designed which drives students towards other pedagogical objectives: system based device sizing (fuel cell and ultracapacitor), energy management, system analysis
Geodesics for a class of distances in the space of probability measures
In this paper, we study the characterization of geodesics for a class of
distances between probability measures introduced by Dolbeault, Nazaret and
Savar e. We first prove the existence of a potential function and then give
necessary and suffi cient optimality conditions that take the form of a coupled
system of PDEs somehow similar to the Mean-Field-Games system of Lasry and
Lions. We also consider an equivalent formulation posed in a set of probability
measures over curves
Optimal transportation for the determinant
Among -valued triples of random vectors having fixed marginal
probability laws, what is the best way to jointly draw in such a way
that the simplex generated by has maximal average volume? Motivated
by this simple question, we study optimal transportation problems with several
marginals when the objective function is the determinant or its absolute value
Effective Feature Representation for Clinical Text Concept Extraction
Crucial information about the practice of healthcare is recorded only in
free-form text, which creates an enormous opportunity for high-impact NLP.
However, annotated healthcare datasets tend to be small and expensive to
obtain, which raises the question of how to make maximally efficient uses of
the available data. To this end, we develop an LSTM-CRF model for combining
unsupervised word representations and hand-built feature representations
derived from publicly available healthcare ontologies. We show that this
combined model yields superior performance on five datasets of diverse kinds of
healthcare text (clinical, social, scientific, commercial). Each involves the
labeling of complex, multi-word spans that pick out different healthcare
concepts. We also introduce a new labeled dataset for identifying the treatment
relations between drugs and diseases
Semi-analytical and numerical methods for computing transient waves in 2D acoustic / poroelastic stratified media
Wave propagation in a stratified fluid / porous medium is studied here using
analytical and numerical methods. The semi-analytical method is based on an
exact stiffness matrix method coupled with a matrix conditioning procedure,
preventing the occurrence of poorly conditioned numerical systems. Special
attention is paid to calculating the Fourier integrals. The numerical method is
based on a high order finite-difference time-domain scheme. Mesh refinement is
applied near the interfaces to discretize the slow compressional diffusive wave
predicted by Biot's theory. Lastly, an immersed interface method is used to
discretize the boundary conditions. The numerical benchmarks are based on
realistic soil parameters and on various degrees of hydraulic contact at the
fluid / porous boundary. The time evolution of the acoustic pressure and the
porous velocity is plotted in the case of one and four interfaces. The
excellent level of agreement found to exist between the two approaches confirms
the validity of both methods, which cross-checks them and provides useful tools
for future researches.Comment: Wave Motion (2012) XX
Effects of dissipation rate and diffusion rate of the progress variable on local fuel burning rate in premixed turbulent flames
The validity of the premixed flamelet equations and the dependence of the fuel burning rate on the parameters involved in these equations have been investigated using a large series of direct numerical simulations of turbulent premixed flames in the thin reaction zones (TRZ) and the distributed reaction zones (DRZ) regimes. Methane, toluene, n-heptane, and iso-octane fuels were considered over a wide range of unburnt conditions and turbulence characteristics. Flames with unity and non-unity Lewis numbers were investigated separately to isolate turbulence-chemistry interaction from differential diffusion effects. In both cases, the flamelet equations, which rely on the assumption of a thin reaction zone, are locally valid throughout the TRZ regime, more precisely up to a Karlovitz number at the reaction zone of 10 (based on the definition used in this paper). Consistent with this result, in the unity Lewis number limit, the fuel burning rate is strongly correlated with the dissipation rate of the progress variable, the only parameter in the flamelet equations. In the non-unity Lewis number case, the burning rate is a strong function of both the dissipation rate and the diffusion rate, both of which are parameters in the flamelet equations. In particular, the correlation with these parameters is significantly better than with curvature or tangential strain rate
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