13,536 research outputs found
A Challenge Set Approach to Evaluating Machine Translation
Neural machine translation represents an exciting leap forward in translation
quality. But what longstanding weaknesses does it resolve, and which remain? We
address these questions with a challenge set approach to translation evaluation
and error analysis. A challenge set consists of a small set of sentences, each
hand-designed to probe a system's capacity to bridge a particular structural
divergence between languages. To exemplify this approach, we present an
English-French challenge set, and use it to analyze phrase-based and neural
systems. The resulting analysis provides not only a more fine-grained picture
of the strengths of neural systems, but also insight into which linguistic
phenomena remain out of reach.Comment: EMNLP 2017. 28 pages, including appendix. Machine readable data
included in a separate file. This version corrects typos in the challenge se
Discrete embeddings for Lagrangian and Hamiltonian systems
The general topic of the present paper is to study the conservation for some
structural property of a given problem when discretising this problem.
Precisely we are interested with Lagrangian or Hamiltonian structures and thus
with variational problems attached to a least action principle. Considering a
partial differential equation (PDE) deriving from such a variational principle,
a natural question is to know whether this structure at the continuous level is
preserved at the discrete level when discretising the PDE. To address this
question a concept of \textit{coherence} is introduced. Both the differential
equation (the PDE translating the least action principle) and the variational
structure can be embedded at the discrete level. This provides two discrete
embeddings for the original problem. In case these procedures finally provide
the same discrete problem we will say that the discretisation is
\textit{coherent}. Our purpose is illustrated with the Poisson problem.
Coherence for discrete embeddings of Lagrangian structures is studied for
various classical discretisations (finite elements, finite differences and
finite volumes). Hamiltonian structures are shown to provide coherence between
a discrete Hamiltonian structure and the discretisation of the mixed
formulation of the PDE, both for mixed finite elements and mimetic finite
differences methods.Comment: Acta Mathematica Vietnamica, Springer Singapore, A Para{\^i}tr
Raviart-Thomas finite elements of Petrov-Galerkin type
The mixed finite element method for the Poisson problem with the
Raviart-Thomas elements of low-level can be interpreted as a finite volume
method with a non-local gradient. In this contribution, we propose a variant of
Petrov-Galerkin type for this problem to ensure a local computation of the
gradient at the interfaces of the elements. The shape functions are the
Raviart-Thomas finite elements. Our goal is to define test functions that are
in duality with these shape functions: Precisely, the shape and test functions
will be asked to satisfy a L2-orthogonality property. The general theory of
Babu\v{s}ka brings necessary and sufficient stability conditions for a
Petrov-Galerkin mixed problem to be convergent. We propose specific constraints
for the dual test functions in order to ensure stability. With this choice, we
prove that the mixed Petrov-Galerkin scheme is identical to the four point
finite volumes scheme of Herbin, and to the mass lumping approach developed by
Baranger, Maitre and Oudin. Finally, we construct a family of dual test
functions that satisfy the stability conditions. Convergence is proven with the
usual techniques of mixed finite elements
On the uniqueness of the solution of the two-dimensional Navier-Stokes equation with a Dirac mass as initial vorticity
We propose two different proofs of the fact that Oseen's vortex is the unique
solution of the two-dimensional Navier-Stokes equation with a Dirac mass as
initial vorticity. The first argument, due to C.E. Wayne and the second author,
is based on an entropy estimate for the vorticity equation in self-similar
variables. The second proof is new and relies on symmetrization techniques for
parabolic equations.Comment: 9 pages, no figur
Towards an Automatic Dictation System for Translators: the TransTalk Project
Professional translators often dictate their translations orally and have
them typed afterwards. The TransTalk project aims at automating the second part
of this process. Its originality as a dictation system lies in the fact that
both the acoustic signal produced by the translator and the source text under
translation are made available to the system. Probable translations of the
source text can be predicted and these predictions used to help the speech
recognition system in its lexical choices. We present the results of the first
prototype, which show a marked improvement in the performance of the speech
recognition task when translation predictions are taken into account.Comment: Published in proceedings of the International Conference on Spoken
Language Processing (ICSLP) 94. 4 pages, uuencoded compressed latex source
with 4 postscript figure
- …