261 research outputs found
Med-DANet V2: A Flexible Dynamic Architecture for Efficient Medical Volumetric Segmentation
Recent works have shown that the computational efficiency of 3D medical image
(e.g. CT and MRI) segmentation can be impressively improved by dynamic
inference based on slice-wise complexity. As a pioneering work, a dynamic
architecture network for medical volumetric segmentation (i.e. Med-DANet) has
achieved a favorable accuracy and efficiency trade-off by dynamically selecting
a suitable 2D candidate model from the pre-defined model bank for different
slices. However, the issues of incomplete data analysis, high training costs,
and the two-stage pipeline in Med-DANet require further improvement. To this
end, this paper further explores a unified formulation of the dynamic inference
framework from the perspective of both the data itself and the model structure.
For each slice of the input volume, our proposed method dynamically selects an
important foreground region for segmentation based on the policy generated by
our Decision Network and Crop Position Network. Besides, we propose to insert a
stage-wise quantization selector to the employed segmentation model (e.g.
U-Net) for dynamic architecture adapting. Extensive experiments on BraTS 2019
and 2020 show that our method achieves comparable or better performance than
previous state-of-the-art methods with much less model complexity. Compared
with previous methods Med-DANet and TransBTS with dynamic and static
architecture respectively, our framework improves the model efficiency by up to
nearly 4.1 and 17.3 times with comparable segmentation results on BraTS 2019.Comment: Accepted by WACV 202
Enhance Primordial Black Hole Abundance through the Non-linear Processes around Bounce Point
The non-singular bouncing cosmology is an alternative paradigm to inflation,
wherein the background energy density vanishes at the bounce point, in the
context of Einstein gravity. Therefore, the non-linear effects in the evolution
of density fluctuations () may be strong in the bounce phase,
which potentially provides a mechanism to enhance the abundance of primordial
black holes (PBHs). This article presents a comprehensive illustration for PBH
enhancement due to the bounce phase. To calculate the non-linear evolution of
, the Raychaudhuri equation is numerically solved here. Since the
non-linear processes may lead to a non-Gaussian probability distribution
function for after the bounce point, the PBH abundance is
calculated in a modified Press-Schechter formalism. In this case, the criterion
of PBH formation is complicated, due to complicated non-linear evolutionary
behavior of during the bounce phase. Our results indicate that
the bounce phase indeed has potential to enhance the PBH abundance
sufficiently. Furthermore, the PBH abundance is applied to constrain the
parameters of bounce phase, providing a complementary to the surveys of cosmic
microwave background and large scale structure.Comment: 17 pages, 6 figure
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