89 research outputs found
Simulation of Rolling Process of AZ31 Magnesium Alloy Sheet
AbstractTo understand more about the rolling process of an AZ31 magnesium alloy sheet and the difference of simulation results between 2D and 3D, the rolling experiment of AZ31 was carried out and some useful data were obtained, and then the rolling processes were simulated by DEFORM2D and 3D respectively. The simulation results are in good agreement with the experimental results based on selecting the correct parameters of stress-strain relationship of AZ31, the friction factor with or without lubricant and the interfacial heat transfer coefficient. The influences of rolling reduction, workpiece temperature and roller temperature on the rolling load and torque are discussed and the difference of simulation results between 2D and 3D is illustrated
Dynamic Spatial Sparsification for Efficient Vision Transformers and Convolutional Neural Networks
In this paper, we present a new approach for model acceleration by exploiting
spatial sparsity in visual data. We observe that the final prediction in vision
Transformers is only based on a subset of the most informative tokens, which is
sufficient for accurate image recognition. Based on this observation, we
propose a dynamic token sparsification framework to prune redundant tokens
progressively and dynamically based on the input to accelerate vision
Transformers. Specifically, we devise a lightweight prediction module to
estimate the importance score of each token given the current features. The
module is added to different layers to prune redundant tokens hierarchically.
While the framework is inspired by our observation of the sparse attention in
vision Transformers, we find the idea of adaptive and asymmetric computation
can be a general solution for accelerating various architectures. We extend our
method to hierarchical models including CNNs and hierarchical vision
Transformers as well as more complex dense prediction tasks that require
structured feature maps by formulating a more generic dynamic spatial
sparsification framework with progressive sparsification and asymmetric
computation for different spatial locations. By applying lightweight fast paths
to less informative features and using more expressive slow paths to more
important locations, we can maintain the structure of feature maps while
significantly reducing the overall computations. Extensive experiments
demonstrate the effectiveness of our framework on various modern architectures
and different visual recognition tasks. Our results clearly demonstrate that
dynamic spatial sparsification offers a new and more effective dimension for
model acceleration. Code is available at
https://github.com/raoyongming/DynamicViTComment: Accepted to T-PAMI. Journal version of our NeurIPS 2021 work:
arXiv:2106.02034. Code is available at
https://github.com/raoyongming/DynamicVi
Development of a Vacuum Ultra-Violet Laser-Based Angle-Resolved Photoemission System with a Super-High Energy Resolution Better Than 1 meV
The design and performance of the first vacuum ultra-violet (VUV) laser-based
angle-resolved photoemission (ARPES) system are described. The VUV laser with a
photon energy of 6.994 eV and bandwidth of 0.26 meV is achieved from the second
harmonic generation using a novel non-linear optical crystal KBe2BO3F2 (KBBF).
The new VUV laser-based ARPES system exhibits superior performance, including
super-high energy resolution better than 1 meV, high momentum resolution,
super-high photon flux and much enhanced bulk sensitivity, which are
demonstrated from measurements on a typical Bi2Sr2CaCu2O8 high temperature
superconductor. Issues and further development related to the VUV laser-based
photoemission technique are discussed.Comment: 29 pages, 10 figures, submitted to Review of Scientific Instrument
Unusual Fermi Surface Sheet-Dependent Band Splitting in Sr2RuO4 Revealed by High Resolution Angle-Resolved Photoemission
High resolution angle-resolved photoemission measurements have been carried
out on Sr2RuO4. We observe clearly two sets of Fermi surface sheets near the
(\pi,0)-(0,\pi) line which are most likely attributed to the surface and bulk
Fermi surface splitting of the \beta band. This is in strong contrast to the
nearly null surface and bulk Fermi surface splitting of the \alpha band
although both have identical orbital components. Extensive band structure
calculations are performed by considering various scenarios, including
structural distortion, spin-orbit coupling and surface ferromagnetism. However,
none of them can explain such a qualitative difference of the surface and bulk
Fermi surface splitting between the \alpha and \beta sheets. This unusual
behavior points to an unknown order on the surface of Sr2RuO4 that remains to
be uncovered. Its revelation will be important for studying and utilizing novel
quantum phenomena associated with the surface of Sr2RuO4 as a result of its
being a possible p-wave chiral superconductor and a topological superconductor.Comment: 13 pages, 4 figure
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