On the testability of WCAG 2.0 for beginners

Web accessibility for people with disabilities is a highly visible area of research in the field of ICT accessibility, including many policy activities across many countries. The commonly accepted guidelines for web accessibility (WCAG 1.0) were published in 1999 and have been extensively used by designers, evaluators and legislators. W3C-WAI published a new version of these guidelines (WCAG 2.0) in December 2008. One of the main goals of WCAG 2.0 was testability, that is, WCAG 2.0 should be either machine testable or reliably human testable. In this paper we present an educational experiment performed during an intensive web accessibility course. The goal of the experiment was to assess the testability of the 25 level-A success criteria of WCAG 2.0 by beginners. To do this, the students had to manually evaluate the accessibility of the same web page. The result was that only eight success criteria could be considered to be reliably human testable when evaluators were beginners. We also compare our experiment with a similar study published recently. Our work is not a conclusive experiment, but it does suggest some parts of WCAG 2.0 to which special attention should be paid when training accessibility evaluator

Reduction of internal noise in auditory perceptual learning

This paper examines what mechanisms underlie auditory perceptual learning. Fifteen normal hearing adults performed two-alternative, forced choice, pure tone frequency discrimination for four sessions. External variability was introduced by adding a zero-mean Gaussian random variable to the frequency of each tone. Measures of internal noise, encoding efficiency, bias, and inattentiveness were derived using four methods (model fit, classification boundary, psychometric function, and double-pass consistency). The four methods gave convergent estimates of internal noise, which was found to decrease from 4.52 to 2.93 Hz with practice. No group-mean changes in encoding efficiency, bias, or inattentiveness were observed. It is concluded that learned improvements in frequency discrimination primarily reflect a reduction in internal noise. Data from highly experienced listeners and neural networks performing the same task are also reported. These results also indicated that auditory learning represents internal noise reduction, potentially through the re-weighting of frequency-specific channels

GPU-based Image Analysis on Mobile Devices

With the rapid advances in mobile technology many mobile devices are capable of capturing high quality images and video with their embedded camera. This paper investigates techniques for real-time processing of the resulting images, particularly on-device utilizing a graphical processing unit. Issues and limitations of image processing on mobile devices are discussed, and the performance of graphical processing units on a range of devices measured through a programmable shader implementation of Canny edge detection.Comment: Proceedings of Image and Vision Computing New Zealand 201

The mystery of spectral breaks: Lyman continuum absorption by photon-photon pair production in the Fermi GeV spectra of bright blazars

We reanalyze Fermi/LAT gamma-ray spectra of bright blazars with a higher photon statistics than in previous works and with new Pass 7 data representation. In the spectra of the brightest blazar 3C 454.3 and possibly of 4C +21.35 we detect breaks at 5 GeV (in the rest frame) associated with the photon-photon pair production absorption by He II Lyman continuum (LyC). We also detect confident breaks at 20 GeV associated with hydrogen LyC both in the individual spectra and in the stacked redshift-corrected spectrum of several bright blazars. The detected breaks in the stacked spectra univocally prove that they are associated with atomic ultraviolet emission features of the quasar broad-line region (BLR). The dominance of the absorption by hydrogen Ly complex over He II, rather small detected optical depth, and the break energy consistent with the head-on collisions with LyC photons imply that the gamma-ray emission site is located within the BLR, but most of the BLR emission comes from a flat disk-like structure producing little opacity. Alternatively, the LyC emission region size might be larger than the BLR size measured from reverberation mapping, and/or the gamma-ray emitting region is extended. These solutions would resolve a long-standing issue how the multi-hundred GeV photons can escape from the emission zone without being absorbed by softer photons.Comment: 7 pages, 6 figures; accepted to Ap

A Sunyaev-Zel'Dovich-Selected Sample of the Most Massive Galaxy Clusters in the 2500 deg^2 South Pole Telescope Survey

The South Pole Telescope (SPT) is currently surveying 2500 deg^2 of the southern sky to detect massive galaxy clusters out to the epoch of their formation using the Sunyaev-Zel'dovich (SZ) effect. This paper presents a catalog of the 26 most significant SZ cluster detections in the full survey region. The catalog includes 14 clusters which have been previously identified and 12 that are new discoveries. These clusters were identified in fields observed to two differing noise depths: 1500 deg^2 at the final SPT survey depth of 18 μK arcmin at 150 GHz and 1000 deg^2 at a depth of 54 μK arcmin. Clusters were selected on the basis of their SZ signal-to-noise ratio (S/N) in SPT maps, a quantity which has been demonstrated to correlate tightly with cluster mass. The S/N thresholds were chosen to achieve a comparable mass selection across survey fields of both depths. Cluster redshifts were obtained with optical and infrared imaging and spectroscopy from a variety of ground- and space-based facilities. The redshifts range from 0.098 ≤ z ≤ 1.132 with a median of z_(med) = 0.40. The measured SZ S/N and redshifts lead to unbiased mass estimates ranging from 9.8 × 10^(14) M_☉ h^(–1)_(70) ≤ M _(200(ρmean)) ≤ 3.1 × 10^(15) M_☉ h^(–1)_(70). Based on the SZ mass estimates, we find that none of the clusters are individually in significant tension with the ΛCDM cosmological model. We also test for evidence of non-Gaussianity based on the cluster sample and find the data show no preference for non-Gaussian perturbations