5,914 research outputs found
Designing optimal- and fast-on-average pattern matching algorithms
Given a pattern and a text , the speed of a pattern matching algorithm
over with regard to , is the ratio of the length of to the number of
text accesses performed to search into . We first propose a general
method for computing the limit of the expected speed of pattern matching
algorithms, with regard to , over iid texts. Next, we show how to determine
the greatest speed which can be achieved among a large class of algorithms,
altogether with an algorithm running this speed. Since the complexity of this
determination make it impossible to deal with patterns of length greater than
4, we propose a polynomial heuristic. Finally, our approaches are compared with
9 pre-existing pattern matching algorithms from both a theoretical and a
practical point of view, i.e. both in terms of limit expected speed on iid
texts, and in terms of observed average speed on real data. In all cases, the
pre-existing algorithms are outperformed
Random weighted Sobolev inequalities and application to quantum ergodicity
This paper is a continuation of Poiret-Robert-Thomann (2013) where we studied
a randomisation method based on the Laplacian with harmonic potential. Here we
extend our previous results to the case of any polynomial and confining
potential on . We construct measures, under concentration
type assumptions, on the support of which we prove optimal weighted Sobolev
estimates on . This construction relies on accurate estimates on
the spectral function in a non-compact configuration space. Then we prove
random quantum ergodicity results without specific assumption on the classical
dynamics. Finally, we prove that almost all basis of Hermite functions is
quantum uniquely ergodic.Comment: Clarifications added in the part concerning QU
CompiLIG at SemEval-2017 Task 1: Cross-Language Plagiarism Detection Methods for Semantic Textual Similarity
We present our submitted systems for Semantic Textual Similarity (STS) Track
4 at SemEval-2017. Given a pair of Spanish-English sentences, each system must
estimate their semantic similarity by a score between 0 and 5. In our
submission, we use syntax-based, dictionary-based, context-based, and MT-based
methods. We also combine these methods in unsupervised and supervised way. Our
best run ranked 1st on track 4a with a correlation of 83.02% with human
annotations
Deep Investigation of Cross-Language Plagiarism Detection Methods
This paper is a deep investigation of cross-language plagiarism detection
methods on a new recently introduced open dataset, which contains parallel and
comparable collections of documents with multiple characteristics (different
genres, languages and sizes of texts). We investigate cross-language plagiarism
detection methods for 6 language pairs on 2 granularities of text units in
order to draw robust conclusions on the best methods while deeply analyzing
correlations across document styles and languages.Comment: Accepted to BUCC (10th Workshop on Building and Using Comparable
Corpora) colocated with ACL 201
The various manifestations of collisionless dissipation in wave propagation
The propagation of an electrostatic wave packet inside a collisionless and
initially Maxwellian plasma is always dissipative because of the irreversible
acceleration of the electrons by the wave. Then, in the linear regime, the wave
packet is Landau damped, so that in the reference frame moving at the group
velocity, the wave amplitude decays exponentially with time. In the nonlinear
regime, once phase mixing has occurred and when the electron motion is nearly
adiabatic, the damping rate is strongly reduced compared to the Landau one, so
that the wave amplitude remains nearly constant along the characteristics. Yet,
we show here that the electrons are still globally accelerated by the wave
packet, and, in one dimension, this leads to a non local amplitude dependence
of the group velocity. As a result, a freely propagating wave packet would
shrink, and, therefore, so would its total energy. In more than one dimension,
not only does the magnitude of the group velocity nonlinearly vary, but also
its direction. In the weakly nonlinear regime, when the collisionless damping
rate is still significant compared to its linear value, this leads to an
effective defocussing effect which we quantify, and which we compare to the
self-focussing induced by wave front bowing.Comment: 23 pages, 6 figure
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