4,153 research outputs found
On Peres' statement "opposite momenta lead to opposite directions", decaying systems and optical imaging
We re-examine Peres' statement ``opposite momenta lead to opposite
directions''. It will be shown that Peres' statement is only valid in the large
distance or large time limit. In the short distance or short time limit an
additional deviation from perfect alignment occurs due to the uncertainty of
the location of the source. This error contribution plays a major role in
Popper's orginal experimental proposal. Peres' statement applies rather to the
phenomenon of optical imaging, which was regarded by him as a verification of
his statement. This is because this experiment can in a certain sense be seen
as occurring in the large distance limit. We will also reconsider both
experiments from the viewpoint of Bohmian mechanics. In Bohmian mechanics
particles with exactly opposite momenta will move in opposite directions. In
addition it will prove particularly usefull to use Bohmian mechanics because
the Bohmian trajectories coincide with the conceptual trajectories drawn by
Pittman et al. In this way Bohmian mechanics provides a theoretical basis for
these conceptual trajectories.Comment: 20 pages, 3 figures, LaTex, to be published in Found. Phy
GPU-driven recombination and transformation of YCoCg-R video samples
Common programmable Graphics Processing Units (GPU) are capable of more than just rendering real-time effects for games. They can also be used for image processing and the acceleration of video decoding. This paper describes an extended implementation of the H.264/AVC YCoCg-R to RGB color space transformation on the GPU. Both the color space transformation and recombination of the color samples from a nontrivial data layout are performed by the GPU. Using mid- to high-range GPUs, this extended implementation offers a significant gain in processing speed compared to an existing basic GPU version and an optimized CPU implementation. An ATI X1900 GPU was capable of processing more than 73 high-resolution 1080p YCoCg-R frames per second, which is over twice the speed of the CPU-only transformation using a Pentium D 820
Not all adversarial examples require a complex defense : identifying over-optimized adversarial examples with IQR-based logit thresholding
Detecting adversarial examples currently stands as one of the biggest challenges in the field of deep learning. Adversarial attacks, which produce adversarial examples, increase the prediction likelihood of a target class for a particular data point. During this process, the adversarial example can be further optimized, even when it has already been wrongly classified with 100% confidence, thus making the adversarial example even more difficult to detect. For this kind of adversarial examples, which we refer to as over-optimized adversarial examples, we discovered that the logits of the model provide solid clues on whether the data point at hand is adversarial or genuine. In this context, we first discuss the masking effect of the softmax function for the prediction made and explain why the logits of the model are more useful in detecting over-optimized adversarial examples. To identify this type of adversarial examples in practice, we propose a non-parametric and computationally efficient method which relies on interquartile range, with this method becoming more effective as the image resolution increases. We support our observations throughout the paper with detailed experiments for different datasets (MNIST, CIFAR-10, and ImageNet) and several architectures
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