85 research outputs found
Non-coherent Massive SIMO Systems in ISI Channels: Constellation Design and Performance Analysis
A massive single-input multiple-output (SIMO) system with a single transmit
antenna and a large number of receive antennas in intersymbol interference
(ISI) channels is considered. Contrast to existing energy detection (ED)-based
non-coherent receiver where conventional pulse amplitude modulation (PAM) is
employed, we propose a constellation design which minimizes the symbol-error
rate (SER) with the knowledge of channel statistics. To make a comparison, we
derive the SERs of the ED-based receiver with both the proposed constellation
and PAM, namely and . Specifically, asymptotic
behaviors of the SER in regimes of a large number of receive antennas and high
signal-to-noise ratio (SNR) are investigated. Analytical results demonstrate
that the logarithms of both and decrease
approximately linearly with the number of receive antennas, while
degrades faster. It is also shown that the proposed design is of less cost,
because compared with PAM, less antennas are required to achieve the same error
rate
The spectrum of low- in heavy ion collisions in a fractal description
Transverse momentum spectrum of particles in hadron gas are affected by flow,
quantum and strong interaction effects. Previously, most models focus on only
one of the three effects but ignore others. The unconsidered effects are taken
into the fitted parameters. In this paper, we study the three effects together
from a new fractal angle by physical calculation instead of data fitting. Near
the critical temperature, the three effects induce and neighboring
meson to form a two-meson structure. We set up a two-particle fractal (TPF)
model to describe this structure. We propose that under the three effects,
- two-meson state, and two-quark states form a
self-similarity structure. With evolution, the two-meson structure
disintegrate. We introduce an influencing factor to describe the
flow, quantum and strong interaction effects and an escort factor to
describe the binding force and the three effects. By solving the probability
and entropy equations, we obtain the values of and at different
collision energies and centrality classes. By substituting the value of
into distribution function, we obtain the transverse momentum
spectrum of low- and find it in good agreement with experimental
data. We also analyze the evolution of with the temperature. It is
found that is larger than 1. This is because the three effects
decrease the number of microstates. We also find decreases with
decreasing the temperature. This is consistent with the fact that with the
system expansion, the influence of the three effects decrease.Comment: 9 pages, 3 figure
Low frequency noise peak near magnon emission energy in magnetic tunnel junctions
We report on the low frequency (LF) noise measurements in magnetic tunnel
junctions (MTJs) below 4 K and at low bias, where the transport is strongly
affected by scattering with magnons emitted by hot tunnelling electrons, as
thermal activation of magnons from the environment is suppressed. For both
CoFeB/MgO/CoFeB and CoFeB/AlO/CoFeB MTJs, enhanced LF noise is observed
at bias voltage around magnon emission energy, forming a peak in the bias
dependence of noise power spectra density, independent of magnetic
configurations. The noise peak is much higher and broader for unannealed
AlO-based MTJ, and besides Lorentzian shape noise spectra in the
frequency domain, random telegraph noise (RTN) is visible in the time traces.
During repeated measurements the noise peak reduces and the RTN becomes
difficult to resolve, suggesting defects being annealed. The Lorentzian shape
noise spectra can be fitted with bias-dependent activation of RTN, with the
attempt frequency in the MHz range, consistent with magnon dynamics. These
findings suggest magnon-assisted activation of defects as the origin of the
enhanced LF noise.Comment: 6 pages, 5 figure
Attentive Mask CLIP
Image token removal is an efficient augmentation strategy for reducing the
cost of computing image features. However, this efficient augmentation strategy
has been found to adversely affect the accuracy of CLIP-based training. We
hypothesize that removing a large portion of image tokens may improperly
discard the semantic content associated with a given text description, thus
constituting an incorrect pairing target in CLIP training. To address this
issue, we propose an attentive token removal approach for CLIP training, which
retains tokens with a high semantic correlation to the text description. The
correlation scores are computed in an online fashion using the EMA version of
the visual encoder. Our experiments show that the proposed attentive masking
approach performs better than the previous method of random token removal for
CLIP training. The approach also makes it efficient to apply multiple
augmentation views to the image, as well as introducing instance contrastive
learning tasks between these views into the CLIP framework. Compared to other
CLIP improvements that combine different pre-training targets such as SLIP and
MaskCLIP, our method is not only more effective, but also much more efficient.
Specifically, using ViT-B and YFCC-15M dataset, our approach achieves
top-1 accuracy on ImageNet-1K zero-shot classification, as well as
and I2T/T2I retrieval accuracy on Flickr30K and MS COCO, which are
, , and higher than the SLIP method, while being
faster. An efficient version of our approach running
faster than the plain CLIP model achieves significant gains of ,
, and on these benchmarks
A randomized comparison of fluoroscopic techniques for implanting pacemaker lead on the right ventricular outflow tract septum
Berberine inhibits enterovirus 71 replication by downregulating the MEK/ERK signaling pathway and autophagy
Primate-specific endogenous retrovirus-driven transcription defines naive-like stem cells
Naive embryonic stem cells hold great promise for research and therapeutics as they have broad and robust developmental potential. While such cells are readily derived from mouse blastocysts it has not been possible to isolate human equivalents easily, although human naive-like cells have been artificially generated (rather than extracted) by coercion of human primed embryonic stem cells by modifying culture conditions or through transgenic modification. Here we show that a sub-population within cultures of human embryonic stem cells (hESCs) and induced pluripotent stem cells (hiPSCs) manifests key properties of naive state cells. These naive-like cells can be genetically tagged, and are associated with elevated transcription of HERVH, a primate-specific endogenous retrovirus. HERVH elements provide functional binding sites for a combination of naive pluripotency transcription factors, including LBP9, recently recognized as relevant to naivety in mice. LBP9-HERVH drives hESC-specific alternative and chimaeric transcripts, including pluripotency-modulating long non-coding RNAs. Disruption of LBP9, HERVH and HERVH-derived transcripts compromises self-renewal. These observations define HERVH expression as a hallmark of naive-like hESCs, and establish novel primate-specific transcriptional circuitry regulating pluripotency
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