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21.
Leopoldina Fortunati Mauro Sarrica John O'Sullivan Aukse Balcytiene Halliki Harro-Loit Phil Macgregor Nayia Roussou Ramón Salaverría Federico de Luca 《Journal of Computer-Mediated Communication》2009,14(4):928-963
This study investigates how European journalists evaluate the changes that have occurred in their profession since the Internet has been integrated in newsrooms. How do journalists perceive the features and innovations associated with the Internet? What are the principal changes in the profession? Do practitioners believe that the quality of journalism has been raised or lowered? To answer to these research questions, we carried out a survey across 11 European countries–Cyprus, Estonia, Finland, Greece, Ireland, Italy, Lithuania, United Kingdom, Slovenia, Spain, Sweden–of 239 journalists, working for 40 of the most‐read print/online news outlets in these countries. The survey shows that the opportunity to use the Internet to reinforce the social functions of journalism has not been fully recognised. 相似文献
22.
Triangulation is the means by which an alternate perspective is used to validate, challenge or extend existing findings. It
is frequently used when the field of study is difficult, demanding or contentious and presence research meets all of these
criteria. We distinguish between the use of hard and soft triangulation—the former emphasising the challenging of findings,
the latter being more confirmatory in character. Having reviewed a substantial number of presence papers, we conclude that
strong triangulation is not widely used while soft triangulation is routinely employed. We demonstrate the usefulness of hard
triangulation by contrasting an ontological analysis of in-ness with an empirical study of (computer) game playing. We conclude that presence research would be well served by the wider
use of hard triangulation and for the reporting of anomalous and ill-fitting results.
相似文献
Susan TurnerEmail: |
23.
Attenuation correction is an important part of accurate image reconstruction in positron tomography. The usual correction method involves direct measurement of attenuation correction factors (ACFs). A reconstruct-reproject method, which has been suggested as providing superior noise properties, is sometimes employed; an attenuation image is first reconstructed from the measurement and then ACFs are obtained by reprojection through this image. Here the authors present a model which follows the signal-to-noise ratio (SNR) through the attenuation correction by both the direct and reconstruct-reproject methods. This model is applicable to both 2D and 3D imaging geometry, but applies to the central elements of emission and transmission objects with circular symmetry and constant amplitude. For this simplified geometry, the model predicts that the SNR of the emission image following attenuation correction is the same for both direct and reconstruct-reproject methods, although the SNRs of the ACFs are themselves substantially different. The authors also present the measured SNR at the various steps of attenuation correction for both the direct and reconstruct-reproject methods using simulated transmission and emission data. The measured SNRs agree with the model; no significant difference between the direct and reconstruct-reproject SNRs was observed. 相似文献
24.
The motionless-head parallel-readout optical-disk system is designed to read out two-dimensional bit planes that are stored as one-dimensional Fourier-transform computer-generated holograms distributed radially on the disk active surface. Such a system, when built at full scale, could offer several potential advantages: high data-transfer rates of 1 Gbyte/s and higher, low access times of less than 15 ms, low retrieval times (the time required to read the entire memory) of less than 25 ms, and simple optical implementation. The experimental results of a scaled-down implementation of the system are presented. 相似文献
25.
A photorefractive beam splitter (PRBS) is introduced as an alternative to a polarizing beam splitter (PBS) for coupling optical power into reflective modulators in a free-space optical interconnection system. The PRBS uses a single diffraction grating recorded in a photorefractive material to redirect the incident laser light into the first diffraction order and onto the modulators. Reflected interconnection light not matching the Bragg angle criteria transmits uncoupled through the beam splitter. Experimental results show that the PRBS provides better, more uniform transmission for off-axis beams than the currently used PBS. 相似文献
26.
This paper focuses on the adaptive observer design for nonlinear discrete‐time MIMO systems with unknown time‐delay and nonlinear dynamics. The delayed states involved in the system are arguments of a nonlinear function and only the estimated delay is utilized. By constructing an appropriate Lyapunov–Krasovskii function, the delay estimation error is considered in the observer parameter design. The proposed method is then extended to the system with a nonlinear output measurement equation and the delayed dynamics. With the help of a high‐order neural network (HONN), the requirement for a precise system model, the linear‐in‐the‐parameters (LIP) assumption of the delayed states, the Lipschitz or norm‐boundedness assumption of unknown nonlinearities are removed. A novel converse Lyapunov technical lemma is also developed and used to prove the uniform ultimate boundedness of the proposed observer. The effectiveness of the proposed results is verified by simulations. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
27.
Translating between dissimilar languages requires an account of the use of divergent word orders when expressing the same
semantic content. Reordering poses a serious problem for statistical machine translation systems and has generated a considerable
body of research aimed at meeting its challenges. Direct evaluation of reordering requires automatic metrics that explicitly
measure the quality of word order choices in translations. Current metrics, such as BLEU, only evaluate reordering indirectly.
We analyse the ability of current metrics to capture reordering performance. We then introduce permutation distance metrics
as a direct method for measuring word order similarity between translations and reference sentences. By correlating all metrics
with a novel method for eliciting human judgements of reordering quality, we show that current metrics are largely influenced
by lexical choice, and that they are not able to distinguish between different reordering scenarios. Also, we show that permutation
distance metrics correlate very well with human judgements, and are impervious to lexical differences. 相似文献
28.
Abhishek Arun Barry Haddow Philipp Koehn Adam Lopez Chris Dyer Phil Blunsom 《Machine Translation》2010,24(2):103-121
Recent advances in statistical machine translation have used approximate beam search for NP-complete inference within probabilistic
translation models. We present an alternative approach of sampling from the posterior distribution defined by a translation
model. We define a novel Gibbs sampler for sampling translations given a source sentence and show that it effectively explores
this posterior distribution. In doing so we overcome the limitations of heuristic beam search and obtain theoretically sound
solutions to inference problems such as finding the maximum probability translation and minimum risk training and decoding. 相似文献
29.
Edward Farhi Jeffrey Goldstone David Gosset Harvey B. Meyer 《Computer Physics Communications》2011,(8):1663-1673
In this paper we explore ways to study the zero temperature limit of quantum statistical mechanics using Quantum Monte Carlo simulations. We develop a Quantum Monte Carlo method in which one fixes the ground state energy as a parameter. The Hamiltonians we consider are of the form H=H0+λV with ground state energy E. For fixed H0 and V, one can view E as a function of λ whereas we view λ as a function of E. We fix E and define a path integral Quantum Monte Carlo method in which a path makes no reference to the times (discrete or continuous) at which transitions occur between states. For fixed E we can determine λ(E) and other ground state properties of H. 相似文献
30.
Nelsestuen GL Harvey SB Zhang Y Kasthuri RS Sinaiko AR Ely EW Bernard GR Homoncik M Jilma B 《Proteomics. Clinical applications》2008,2(2):158-166
Although numerous protein biomarkers have been correlated with advanced disease states, no new clinical assays have been developed. Goals often anticipate disease-specific protein changes that exceed values among healthy individuals, a property common to acute phase reactants. This review considers somewhat different approaches. It focuses on intact protein isoform ratios that present a biomarker without change in the total concentration of the protein. These will seldom be detected by peptide level analysis or by most antibody-based assays. For example, application of an inexpensive method to large sample groups resulted in observation of several polymorphisms, including the first structural polymorphism of apolipoprotein C1. Isoform distribution of this protein was altered and was eventually linked to increased obesity. Numerous other protein isoforms included C- and N-terminal proteolysis, changes of glycoisoform ratios and certain types of sulfhydryl oxidation. While many of these gave excellent statistical correlation with advanced disease, clinical utility was not apparent. More important may be that protein isoform ratios were very stable in each individual. Diagnosis by longitudinal analysis of the same individual might increase sensitivity of protein biomarkers by 20-fold or more. Protein changes that exceed the range of values found among healthy individuals may be uncommon. 相似文献