197,110 research outputs found
The effect of image pixelation on unfamiliar face matching
Low-resolution, pixelated images from CCTV can be used to compare the perpetrators of crime with high-resolution photographs of potential suspects. The current study investigated the accuracy of person identification under these conditions, by comparing high-resolution and pixelated photographs of unfamiliar faces in a series of matching tasks. Performance decreased gradually with different levels of pixelation and was close to chance with a horizontal image resolution of only 8 pixel bands per face (Experiment 1). Matching accuracy could be improved by reducing the size of pixelated faces (Experiment 2) or by varying the size of the to-be-compared-with high-resolution face image (Experiment 3). In addition, pixelation produced effects that appear to be separable from other factors that might affect matching performance, such as changes in face view (Experiment 4). These findings reaffirm that criminal identifications from CCTV must be treated with caution and provide some basic estimates for identification accuracy with different pixelation levels. This study also highlights potential methods for improving performance in this task
Detection and Combining Techniques for Asynchronous Random Access with Time Diversity
Asynchronous random access (RA) protocols are particularly attractive for
their simplicity and avoidance of tight synchronization requirements. Recent
enhancements have shown that the use of successive interference cancellation
(SIC) can largely boost the performance of these schemes. A further step
forward in the performance can be attained when diversity combining techniques
are applied. In order to enable combining, the detection and association of the
packets to their transmitters has to be done prior to decoding. We present a
solution to this problem, that articulates into two phases. Non-coherent
soft-correlation as well as interference-aware soft-correlation are used for
packet detection. We evaluate the detection capabilities of both solutions via
numerical simulations. We also evaluate numerically the spectral efficiency
achieved by the proposed approach, highlighting its benefits.Comment: 6 pages, 7 figures. Work has been submitted to the 11th International
ITG Conference on Systems, Communications and Coding 201
Complementarity of PALM and SOFI for super-resolution live cell imaging of focal adhesions
Live cell imaging of focal adhesions requires a sufficiently high temporal
resolution, which remains a challenging task for super-resolution microscopy.
We have addressed this important issue by combining photo-activated
localization microscopy (PALM) with super-resolution optical fluctuation
imaging (SOFI). Using simulations and fixed cell focal adhesion images, we
investigated the complementarity between PALM and SOFI in terms of spatial and
temporal resolution. This PALM-SOFI framework was used to image focal adhesions
in living cells, while obtaining a temporal resolution below 10 s. We
visualized the dynamics of focal adhesions, and revealed local mean velocities
around 190 nm per minute. The complementarity of PALM and SOFI was assessed in
detail with a methodology that integrates a quantitative resolution and
signal-to-noise metric. This PALM and SOFI concept provides an enlarged
quantitative imaging framework, allowing unprecedented functional exploration
of focal adhesions through the estimation of molecular parameters such as the
fluorophore density and the photo-activation and photo-switching rates
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