Splitting Arabic Texts into Elementary Discourse Units

International audienceIn this article, we propose the first work that investigates the feasibility of Arabic discourse segmentation into elementary discourse units within the segmented discourse representation theory framework. We first describe our annotation scheme that defines a set of principles to guide the segmentation process. Two corpora have been annotated according to this scheme: elementary school textbooks and newspaper documents extracted from the syntactically annotated Arabic Treebank. Then, we propose a multiclass supervised learning approach that predicts nested units. Our approach uses a combination of punctuation, morphological, lexical, and shallow syntactic features. We investigate how each feature contributes to the learning process. We show that an extensive morphological analysis is crucial to achieve good results in both corpora. In addition, we show that adding chunks does not boost the performance of our system

KYHP3O10 : Rietveld refinement using x-ray powder diffraction data and Raman study of the conductivity phase transition

Potassium yttrium hydrogen triphosphate (KYHP3O10) crystallises in the triclinic system P1̄ at room temperature with the following parameters: a=6.8522(2), b=7.6254(2), View the MathML sourceα=106.658(1), β=106.435(2) and γ=82.344(2)°; Z=2. This structure has been refined from X-raypowderdiffractiondata using the Rietveld method, with the isostructural compounds KSmHP3O10 and NH4BiHP3O10 as the starting model. Refinement of 70 parameters by the Rietveld method, using 2447 reflections, led to cRwp=0.138, cRp=0.104 and RB=0.041. This compound is a chain-based structure. The K+ and Y3+ cations are intercalated between chains, formed of (HP3O104−) groups linked by OH⋯O hydrogen bonding along the c-axis. The yttrium atoms are in an eight-fold coordination and also build infinite chains of edge-sharing YO8 polyhedra running parallel to the a-axis. The potassium cations are coordinated by 10 oxygen atoms and build chains of KO10 polyhedra running parallel to the b-axis. A calorimetric study of the title compound shows one endothermal peak, which is detected at 519 K. Samples were examined by impedance and Raman spectroscopy techniques. The Raman spectra of KYHP3O10, recorded at different temperatures in the frequency range 50-1250 cm−1 show the presence of a transition, which is characterised by an unusual high conductivity caused by breaking of the hydrogen bridges and suggests a great dynamic disorder of protons. This permits H+ ions at high temperature to contribute with the potassium cations to the ionic conductivity of the product

High-power CEP-stable few-cycle fiber lasers

Summary form only given. Today, carrier-envelope-phase (CEP) stable laser pulses have become a versatile tool for a plethora of scientific applications. Many years their generation relied on either optical parametric amplification or the use of titanium-sapphire amplifiers. Although impressive results have been achieved using these technologies [1, 2], their main drawback is the restricted average power (and therewith repetition rate for a given energy) due to thermo-optical limitations. Here we report on another approach, the nonlinear compression of ultrafast ytterbium-based high-power fiber lasers [3]. The first commercially available source employing this technology is the HR1 laser constructed for the ELI-ALPS research facility in Szeged, Hungary. The Extreme Light Infrastructure (ELI) is currently being installed in several European countries aiming to provide unique user facilities with beyond state-of-the-art laser systems. The attosecond facility ELI-ALPS in Szeged, for example, will host several laser systems that will be used for attosecond pulse generation at unprecedented pulse parameters (energy and repetition rate). One of these laser systems is the HR1 (high repetition rate) laser that targets pulse parameters of 1mJ, 6fs pulses at 100kHz repetition rate (100W average power) and with CEP stable operation in its first implementation phase.We will show detailed measurements and characterization of the CPA system as well as the compression unit. General scaling properties of hollow-fiber compressors towards multi-mJ operation at kW-level average powers will be discussed. Furthermore, a detailed discussion on the CEP stabilization of the system will be given and supported by the latest measurement results using a stereo ATI device