648 research outputs found
A40: An Experimental Study on the Effect of Intelligent Motor Intervention on Motor Ability of Infants with Motor Retardation
Purpose: Early exercise intervention is particularly important for the improvement of motor ability in young children with delayed motor development. In this study, the effect of intelligent exercise online intervention on the motor ability of slow motor development in children aged 3 to 6 years was verified by arranging interesting sports games in the sports APP. Methods: Using the experimental method, interview method and mathematical statistics method, 37 children aged 3-6 years were selected through the motor development questionnaire, and online exercise intervention was carried out around the six themes of balance, coordination, sensitivity, flexibility, jumping and strength. There is a sports theme cycle every week, and the weekend is a parent-child sports game. The overall intervention lasts for 6 months, lasting from 15 to 20 minutes per day. Results: There were highly significant differences in children\u27s exercise ability before and after the experiment (t= -24.859, P \u3c 0.01); the sensitivity, flexibility and coordination were particularly improved, with highly significant differences (t= -25.147, P \u3c 0.01); interviews found that through weekly parent-child exercise games, children and parents increased physical interaction and language communication compared with before intervention. Conclusion: Intelligent exercise online intervention can effectively improve the motor ability of children aged 3 to 6 years, especially the sensitivity, flexibility, and coordination ability. Meanwhile, regular parent-child exercise can improve communication between parents and children and improve the parent-child relationship
Terahertz imaging with sub-wavelength resolution by femtosecond laser filament in air
Terahertz (THz) imaging provides cutting edge technique in biology, medical
sciences and non-destructive evaluation. However, due to the long wavelength of
the THz wave, the obtained resolution of THz imaging is normally a few hundred
microns and is much lower than that of the traditional optical imaging. We
introduce a sub-wavelength resolution THz imaging technique which uses the THz
radiation generated by a femtosecond laser filament in air as the probe. This
method is based on the fact that the femtosecond laser filament forms a
waveguide for the THz wave in air. The diameter of the THz beam, which
propagates inside the filament, varies from 20 {\mu}m to 50 {\mu}m, which is
significantly smaller than the wavelength of the THz wave. Using this highly
spatially confined THz beam as the probe, THz imaging with resolution as high
as 20 {\mu}m (~{\lambda}/38) can be realized.Comment: 10 pages, 7 figure
Terahertz Wave Guiding by Femtosecond Laser Filament in Air
Femtosecond laser filament generates strong terahertz (THz) pulse in air. In
this paper, THz pulse waveform generated by femtosecond laser filament has been
experimentally investigated as a function of the length of the filament.
Superluminal propagation of THz pulse has been uncovered, indicating that the
filament creates a THz waveguide in air. Numerical simulation has confirmed
that the waveguide is formed because of the radially non-uniform refractive
index distribution inside the filament. The underlying physical mechanisms and
the control techniques of this type THz pulse generation method might be
revisited based on our findings. It might also potentially open a new approach
for long-distance propagation of THz wave in air.Comment: 5 pages, 6 figure
Charge transport and electron-hole asymmetry in low-mobility graphene/hexagonal boron nitride heterostructures
Graphene/hexagonal boron nitride (G/-BN) heterostructures offer an
excellent platform for developing nanoelectronic devices and for exploring
correlated states in graphene under modulation by a periodic superlattice
potential. Here, we report on transport measurements of nearly
-twisted G/-BN heterostructures. The heterostructures
investigated are prepared by dry transfer and thermally annealing processes and
are in the low mobility regime (approximately
at 1.9 K). The replica
Dirac spectra and Hofstadter butterfly spectra are observed on the hole
transport side, but not on the electron transport side, of the
heterostructures. We associate the observed electron-hole asymmetry to the
presences of a large difference between the opened gaps in the conduction and
valence bands and a strong enhancement in the interband contribution to the
conductivity on the electron transport side in the low-mobility G/-BN
heterostructures. We also show that the gaps opened at the central Dirac point
and the hole-branch secondary Dirac point are large, suggesting the presence of
strong graphene-substrate interaction and electron-electron interaction in our
G/-BN heterostructures. Our results provide additional helpful insight into
the transport mechanism in G/-BN heterostructures.Comment: 7 pages, 4 figure
Classical and Quantum Security of Elliptic Curve VRF, via Relative Indifferentiability
Verifiable random functions (VRFs) are essentially pseudorandom
functions for which selected outputs can be proved correct and unique,
without compromising the security of other outputs. VRFs have numerous
applications across cryptography, and in particular they have recently
been used to implement committee selection in the Algorand protocol.
Elliptic Curve VRF (ECVRF) is an elegant construction,
originally due to Papadopoulos et al., that is now under consideration
by the Internet Research Task Force. Prior work proved that ECVRF
possesses the main desired security properties of a VRF, under
suitable assumptions. However, several recent versions of ECVRF
include changes that make some of these proofs inapplicable. Moreover,
the prior analysis holds only for *classical* attackers, in the
random-oracle model (ROM); it says nothing about whether any of the
desired properties hold against *quantum* attacks, in the
quantumly accessible ROM. We note that certain important properties
of ECVRF, like uniqueness, do *not* rely on assumptions that are
known to be broken by quantum computers, so it is plausible that these
properties could hold even in the quantum setting.
This work provides a multi-faceted security analysis of recent
versions of ECVRF, in both the classical and quantum settings. First,
we motivate and formally define new security properties for VRFs, like
non-malleability and binding, and prove that recent versions of ECVRF
satisfy them (under standard assumptions). Second, we identify a
subtle obstruction in proving that recent versions of ECVRF have
*uniqueness* via prior indifferentiability definitions and
theorems, even in the classical setting. Third, we fill this gap by
defining a stronger notion called *relative indifferentiability*,
and extend prior work to show that a standard domain extender used in
ECVRF satisfies this notion, in both the classical and quantum
settings. This final contribution is of independent interest and we
believe it should be applicable elsewhere
- …