742 research outputs found
Two dimensional semiconductors with possible high room temperature mobility
We calculated the longitudinal acoustic phonon limited electron mobility of
14 two dimensional semiconductors with composition of MX, where M (= Mo, W,
Sn, Hf, Zr and Pt) is the transition metal, and X is S, Se and Te. We treated
the scattering matrix by deformation potential approximation. We found that out
of the 14 compounds, MoTe, HfSe and HfTe, are promising regarding
to the possible high mobility and finite band gap. The phonon limited mobility
can be above 2500 cmVs at room temperature
Inverse spin Hall effect in Nd doped SrTiO3
Conversion of spin to charge current was observed in SrTiO3 doped with Nd
(Nd:STO), which exhibited a metallic behavior even with low concentration
doping. The obvious variation of DC voltages for Py/Nd:STO, obtained by
inverting the spin diffusion direction, demonstrated that the detected signals
contained the contribution from the inverse spin Hall effect (ISHE) induced by
the spin dependent scattering from Nd impurities with strong spin-orbit
interaction. The DC voltages of the ISHE for Nd:STO were measured at different
microwave frequency and power, which revealed that spin currents were
successfully injected into doped STO layer by spin pumping. The linear relation
between the ISHE resistivity and the resistivity induced by impurities implied
that the skew scattering was the dominant contribution in this case, and the
spin Hall angle was estimated to be 0.17%. This work demonstrated that
extrinsic spin dependent scattering in oxides can be used in spintroics besides
that in heavy elements doped metals
Optical Flow Guided Feature: A Fast and Robust Motion Representation for Video Action Recognition
Motion representation plays a vital role in human action recognition in
videos. In this study, we introduce a novel compact motion representation for
video action recognition, named Optical Flow guided Feature (OFF), which
enables the network to distill temporal information through a fast and robust
approach. The OFF is derived from the definition of optical flow and is
orthogonal to the optical flow. The derivation also provides theoretical
support for using the difference between two frames. By directly calculating
pixel-wise spatiotemporal gradients of the deep feature maps, the OFF could be
embedded in any existing CNN based video action recognition framework with only
a slight additional cost. It enables the CNN to extract spatiotemporal
information, especially the temporal information between frames simultaneously.
This simple but powerful idea is validated by experimental results. The network
with OFF fed only by RGB inputs achieves a competitive accuracy of 93.3% on
UCF-101, which is comparable with the result obtained by two streams (RGB and
optical flow), but is 15 times faster in speed. Experimental results also show
that OFF is complementary to other motion modalities such as optical flow. When
the proposed method is plugged into the state-of-the-art video action
recognition framework, it has 96:0% and 74:2% accuracy on UCF-101 and HMDB-51
respectively. The code for this project is available at
https://github.com/kevin-ssy/Optical-Flow-Guided-Feature.Comment: CVPR 2018. code available at
https://github.com/kevin-ssy/Optical-Flow-Guided-Featur
Ethnobotany of Camptotheca Decaisne: New Discoveries of Old Medicinal Uses
Camptotheca trees had been used as fuelwood and an ornamental species in its native China. There were no reports on medicinal uses of Camptotheca in China and thus it was believed the trees had no medicinal before its antitumor activity discovered in 1957. We conducted national surveys of Camptotheca in China from 1994 to 1999. We found that Camptotheca acuminate is commonly known as happytree (xi shu) because the trees can be used as folk medicine to cure stubborn phlegm as well as other diseases, thus making patients “happy”. There are three local names to refer the uses of C. acuminata in China. In addition, there are at least 25 other local names for tree morphology and habitat of the species by 35 ethnic groups. There are two local names for C. lowreyana. The Dong people made paste from fresh leaves or fruits and powder from dry materials from any part of this tree species and mixed some or all with rice wine to cure many stubborn diseases including furunclulosis, skin diseases, and even a liu (probably a kind of cancer). Medicinal and other ethnic uses of Camptotheca trees in China were reported in this study
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