4,452 research outputs found
Low PAPR Pilot for Delay-Doppler Domain Modulation
This paper studies the low PAPR pilot design in delay-Doppler domain
modulation. We adopt a sequence based pilot design instead of the conventional
pulse pilot, to mitigate the PAPR issue. We develop simple channel estimation
algorithm composes of two-stages which are path identification and channel
coefficient estimation. The quantitative analysis on the channel estimation
error model is provided. Based on which the principle of pilot sequence design
in delay-Doppler domain is revealed. Experiment results shows that the proposed
scheme maintains a relatively low PAPR in time domain samples, while the
channel estimation performance approaches the ideal channel estimation in
limited-Doppler-Shift channel model
A Layer Decomposition-Recomposition Framework for Neuron Pruning towards Accurate Lightweight Networks
Neuron pruning is an efficient method to compress the network into a slimmer
one for reducing the computational cost and storage overhead. Most of
state-of-the-art results are obtained in a layer-by-layer optimization mode. It
discards the unimportant input neurons and uses the survived ones to
reconstruct the output neurons approaching to the original ones in a
layer-by-layer manner. However, an unnoticed problem arises that the
information loss is accumulated as layer increases since the survived neurons
still do not encode the entire information as before. A better alternative is
to propagate the entire useful information to reconstruct the pruned layer
instead of directly discarding the less important neurons. To this end, we
propose a novel Layer Decomposition-Recomposition Framework (LDRF) for neuron
pruning, by which each layer's output information is recovered in an embedding
space and then propagated to reconstruct the following pruned layers with
useful information preserved. We mainly conduct our experiments on ILSVRC-12
benchmark with VGG-16 and ResNet-50. What should be emphasized is that our
results before end-to-end fine-tuning are significantly superior owing to the
information-preserving property of our proposed framework.With end-to-end
fine-tuning, we achieve state-of-the-art results of 5.13x and 3x speed-up with
only 0.5% and 0.65% top-5 accuracy drop respectively, which outperform the
existing neuron pruning methods.Comment: accepted by AAAI19 as ora
Vortex patterns and the critical rotational frequency in rotating dipolar Bose-Einstein condensates
Based on the two-dimensional mean-field equations for pancake-shaped dipolar
Bose-Einstein condensates in a rotating frame with both attractive and
repulsive dipole-dipole interaction (DDI) as well as arbitrary polarization
angle, we study the profiles of the single vortex state and show how the
critical rotational frequency change with the s-wave contact interaction
strengths, DDI strengths and the polarization angles. In addition, we find
numerically that at the `magic angle' , the
critical rotational frequency is almost independent of the DDI strength. By
numerically solving the dipolar GPE at high rotational speed, we identify
different patterns of vortex lattices which strongly depend on the polarization
direction. As a result, we undergo a study of vortex lattice structures for the
whole regime of polarization direction and find evidence that the vortex
lattice orientation tends to be aligned with the direction of the dipoles
Analyses on deformation and fracture evolution of zonal disintegration during axial overloading in 3D geomechanical model tests
To investigate the formation of zonal disintegration phenomenon in deep rock mass under high axial geostress, 3D geomechanical model tests for two rock strengths are carried out via capacity of deep rock breakage mechanics and supporting technique model test. Considering the maximum principal stress along the tunnel axis, 3D geomechanical model tests are carried out in a loading procedure of first loading to initial geostress, then excavating the tunnel with blasting construction, and finally overloading the stress along the tunnel. Due to unloading effect, radial strain is tensile and tangential strain is compressive around excavated tunnel after excavation complete, which indicates a radial tension and circumferential compression stress state. With continuous overloading of axial stress, values of both radial tensile strain and tangential compressive strain increase, then ring fracture appears due to large radial tensile strain. After axial overloading, an interval distribution of peaks and troughs is shown in radial tensile strain distribution around excavated tunnel, which indicates a formation of zonal disintegration. By cutting the rectangular cemented sand model, a distinct zonal disintegration phenomenon emerges, and an apparent shrinkage of excavated tunnel is also shown due to radial deformation towards excavated tunnel. The larger the rock strength is, the less the tunnel shrinkage is, the smaller the radius of fracture zone. After statistical analyses of three ring tensile fracture zones, the radius scale factor of fracture zone in zonal disintegration is about 1.28
Time-frequency analyses of blasting vibration signals in single-hole blasting model experiments
With common horseshoe cavern in underground engineering as the prototype, three single-hole blasting model experiments have been carried out. And coupled SPH-FEM approach is adopted for analyzing the limit effect of pre-excavated horseshoe cavern on blasting crater. During the experiment, the blasting vibration signals on the top surface of cemented sand model have been recorded. Then Hilbert-Huang transform has been applied to analyzing the time-frequency characteristics of recorded blasting vibration signals. Both experiment results and numerical cases indicate that the range of blasting crater is controlled effectively by pre-excavating horseshoe cavern, and the limit effect of pre-excavating on blasting crater has a close connection with its length. Moreover, the 50 mm pre-excavated horseshoe cavern presents an amplification effect in blasting vibration effect both along the blasthole direction and perpendicular to the blasthole direction, and it also demonstrates a weaken effect in the main blasting vibration frequency of vertical blasting vibration signal. HHT analyses of vertical blasting vibration signals show that single-hole blasting vibration signals present a centralized distribution in time domain and an uneven distribution in frequency domain. The dominant energy of blasting vibration signal is distributed in several IMF components, where main blasting vibration frequency locates. When cutting the charge, the blasting vibration effect will be reduced, while the main blasting vibration frequency of blasting vibration signal will be increased
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