Machine translation for subtitling: a large-scale evaluation

This article describes a large-scale evaluation of the use of Statistical Machine Translation for professional subtitling. The work was carried out within the FP7 EU-funded project SUMAT and involved two rounds of evaluation: a quality evaluation and a measure of productivity gain/loss. We present the SMT systems built for the project and the corpora they were trained on, which combine professionally created and crowd-sourced data. Evaluation goals, methodology and results are presented for the eleven translation pairs that were evaluated by professional subtitlers. Overall, a majority of the machine translated subtitles received good quality ratings. The results were also positive in terms of productivity, with a global gain approaching 40%. We also evaluated the impact of applying quality estimation and filtering of poor MT output, which resulted in higher productivity gains for filtered files as opposed to fully machine-translated files. Finally, we present and discuss feedback from the subtitlers who participated in the evaluation, a key aspect for any eventual adoption of machine translation technology in professional subtitlin

Implementation of variance-reduction techniques for Monte Carlo nuclear logging calculations with neutron sources

Monte Carlo simulations for nuclear logging applications are considered to be highly demanding transport problems. In this paper, the implementation of weight-window variance reduction schemes in a 'manual' fashion to improve the efficiency of calculations for a neutron logging tool is presented. The simulations were conducted using MCNP to assess the sensitivity of neutron and gamma flux to the saturation of soil with fresh and salty water and oil. The weight-windows were optimised to enhance the precision in characteristic gamma-ray windows for carbon-oxygen logging and sigma logging. An analysis is under way to incorporate quartz sediments and other oil substances. Future tasks include the assessment of advanced Monte Carlo estimators and optimisation of capture gamma-ray sampling techniques to enhance the variance reduction in nuclear logging calculations

Development and calibration of a gamma-ray density-meter for sediment-like materials

The core-logger PHAROS was designed at Kernfysisch Versneller Instituut, Groningen, the Netherlands to measure activity concentration of sediment like materials. As the core logger was calibrated for a single material density the variations in the density profile in the scanned core can result in erroneous estimations of activity concentrations. To overcome this, a density-meter was developed and implemented on PHAROS. The density measurement should be non-invasive and should cover a wide range of sediment like materials. The most suitable approach is to deploy gamma-ray transmission technique, where the intensity of non-attenuated photons after traversing the core is directly related to its density. Due to the overall complexity of radiation transport through sediment media, the design of the density-meter was assisted by Monte Carlo simulations. They were deployed to model sophisticated and time-consuming experiments in the process of designing the (137)Cs-based source, to generate the pulse-height response functions of the bismuth-germanate (BGO) scintillator and to estimate the systematic uncertainty induced by the core displacement in the process of the measurement. Moreover, the Monte Carlo simulations have demonstrated as a reliable complementary tool for the generation of PHAROS detector calibration curves. The designed density-meter of PHAROS core-logger indicates to be adequate to estimate densities ranging from similar to 1.6 to similar to 2.7 g cm(-3) with the systematic uncertainty within 3%. (C) 2009 Elsevier Ltd. All rights reserved

Monte Carlo simulations to advance characterisation of landmines by pulsed fast/thermal neutron analysis

The performance of a detection system based on the pulsed fast/thermal neutron analysis technique was assessed using Monte Carlo simulations. The aim was to develop and implement simulation methods, to support and advance the data analysis techniques of the characteristic gamma-ray spectra, potentially leading to elemental characterisation of innocuous objects using the full spectrum analysis (FSA) approach. The simulations were carried out with a simplified too], based on a 14 MeV DT pulse-neutron source and a bismuth-germanate detector. A MCNP-based method for decoupling the radiation transport in mixed (n,gamma) fields, to generate separate sets of standard detector gamma-ray responses for individual elements, is outlined. When normalised and experimentally benchmarked in terms of the pulse-neutron source production rate, the standard spectra can be incorporated into algorithms for the FSA of in situ measurements and elemental fingerprinting of the inspected object. (C) 2004 Elsevier Ltd. All rights reserved

Monte Carlo uncertainty analysis of germanium detector response to gamma-rays with energies below 1 MeV

Monte Carlo method was used to simulate the pulse-height response function of high-precision germanium (HPGe) detector for photon energies below 1 MeV. The calculations address the uncertainty estimation due to inadequate specifications of source positioning and to variations in the detector's physical components: dead layer thickness, spectrometer angular positioning and the presence/absence of aluminium holder. A detailed Monte Carlo model was developed using the MCNP4C code. The simulation results indicate that the uncertainty due to the dead layer thickness has larger effect on photons energies below 100 keV, where for 15 keV incident photon energy the total counts are by a factor of 7 times higher when the thickness is 50% larger. Small variations in source position and angular spectrometer have minimum effect on the photon energies modelled. The absence of A1-holder in the Monte Carlo model reduces the Compton region information for higher energy regions. This analysis has indicated that Monte Carlo methods can represent a valuable tool for the quantitative uncertainty analysis of radiation spectrometers. They can furthermore be instrumental in the gamma-ray detector quantitative calibration and benchmarking processes, thus minimizing the need for deployment of radioactive sources. (C) 2004 Elsevier B.V. All rights reserved

Verification of Monte Carlo calculations of the neutron flux in typical irradiation channels of the TRIGA reactor, Ljubljana

An experimental verification of Monte Carlo neutron flux calculations in typical irradiation channels in the TRIGA Mark II reactor at the Jozef Stefan Institute is presented. It was found that the flux, as well as its spectral characteristics, depends rather strongly on the position of the irradiation channel. Comparison of the results for parameter f (thermal-to-epithermal flux ratio), experimentally obtained by the "Cd ratio multimonitor" method and Monte Carlo simulations shows relatively good agreement for most studied configurations except for the channel IC40 in the carousel facility, where differences are relatively large and not understood