1,489 research outputs found
ALTN: Word Alignment Features for Cross-Lingual Textual Entailment.
No full textWe present a supervised learning approach to cross-lingual textual entailment that explores statistical word alignment models to predict entailment relations between sentences writ- ten in different languages. Our approach is language independent, and was used to participate in the CLTE task (Task#8) organized within Semeval 2013 (Negri et al., 2013). The four runs submitted, one for each language combination covered by the test data (i.e. Spanish/English, German/English, French/English and Italian/English), achieved encouraging results. In terms of accuracy, performance ranges from 38.8% (for German/English) to 43.2% (for Italian/English). On the Italian/English and Spanish/English test sets our systems ranked second among five participants, close to the top results (respectively 43.4% and 45.4%)
Quasi-static crack propagation by Griffith's criterion
No full textWe consider the propagation of a crack in a brittle material along a prescribed crack path and define a quasi-static evolution by means of stationary points of the free energy. We show that this evolution satisfies Griffith's criterion in a suitable form which takes into account both stable and unstable propagations, as well as an energy balance formula which accounts for dissipation in the unstable regime. If the load is monotonically increasing, this solution is explicit and almost everywhere unique. For more general loads we construct a solution via time discretization. Finally, we consider a finite element discretization of the problem and prove convergence of the discrete solutions
Towards Automatic Subtitling: Assessing the Quality of Old and New Resources
No full textGrowing needs in localising multimedia content for global audiences have resulted in Neural Machine Translation (NMT) gradually becoming an established practice in the field of subtitling in order to reduce costs and turn-around times. Contrary to text translation, subtitling is subject to spatial and temporal constraints, which greatly increase the post-processing effort required to restore the NMT output to a proper subtitle format. In our previous work (Karakanta, Negri, and Turchi 2019), we identified several missing elements in the corpora available for training NMT systems specifically tailored for subtitling. In this work, we compare the previously studied corpora with MuST-Cinema, a corpus enabling end-to-end speech to subtitles translation, in terms of the conformity to the constraints of: 1) length and reading speed; and 2) proper line breaks. We show that MuST-Cinema conforms to these constraints and discuss the recent progress the corpus has facilitated in end-to-end speech to subtitles translation
Quasi-static rate-independent evolutions: characterization, existence, approximation and application to fracture mechanics
No full textWe characterize quasi-static rate-independent evolutions, by means of their graph parametrization, in terms of a couple of equations: the first gives stationarity while the second provides the energy balance. An abstract existence result is given for functionals ℱ of class C1 in reflexive separable Banach spaces. We provide a couple of constructive proofs of existence which share common features with the theory of minimizing movements for gradient flows. Moreover, considering a sequence of functionals ℱn and its Γ-limit ℱ we provide, under suitable assumptions, a convergence result for the associated quasi-static evolutions. Finally, we apply this approach to a phase field model in brittle fracture
From phase field to sharp cracks: Convergence of quasi-static evolutions in a special setting
No full textAbstractWe consider the quasi-static evolution of a straight crack within the recently developed phase-field approach and the classical sharp crack approach, and we show a strong correlation between the outcomes from the two approaches: the corresponding energies, minimizers, energy release rates and quasi-static evolutions converge as the internal length parameter of the phase-field model tends to zero. A crucial point in the proof is a novel representation of the energy release rate, which allows one to pass to the limit under weak convergence of the strains
Quasi-Static Evolutions in Brittle Fracture Generated by Gradient Flows: Sharp Crack and Phase-Field Approaches
No full textConvergence analysis for a smeared crack approach in brittle fracture
No full textOur analysis focuses on the mechanical energies involved in the propagation of fractures: the elastic energy, stored in the bulk, and the fracture energy, concentrated in the crack. We consider a finite element model based on a smeared crack approach: the fracture is approximated geometrically by a stripe of elements and mechanically by a softening constitutive law. We define in this way a discrete free energy Gh (h being the element size) which accounts for both elastic displacements and fractures. Our main interest is the behaviour of Gh as h tends to 0. We prove that, for a suitable choice of the (mesh dependent) constitutive law, Gh converges to a limit functional Gphi with a positive (anisotropic) term concentrated on the crack. We discuss the mesh bias and compute it explicitly in the case of a structured triangulation
A unilateral gradient flow and its quasi-static limit in phase-field fracture by alternate minimization
No full textWe consider an evolution in phase field fracture which combines, in a system of {sc pde}s, an irreversible gradient-flow for the phase-field variable with the equilibrium equation for the displacement field. We introduce a discretization in time and define a discrete solution by means of a 1-step alternate minimization scheme, with a quadratic -penalty in the phase-field variable (i.e.~an alternate minimizing movement). First, we prove that discrete solutions converge to a solution of our system of {sc pde}s. Then, we show that the vanishing viscosity limit is a quasi-static (parametrized) -evolution. All these solutions are described both in terms of energy balance and, equivalently, by {sc pde}s within the natural framework of
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