97 research outputs found
Local Probes for Quantum Hall Ferroelectrics and Nematics
Two-dimensional multi-valley electronic systems in which the dispersion of
individual pockets has low symmetry give rise to quantum Hall ferroelectric and
nematic states in the presence of strong quantising magnetic fields. We
investigate local signatures of these states arising near impurities that can
be probed via Scanning Tunnelling Microscopy (STM) spectroscopy. For quantum
Hall ferroelectrics, we demonstrate a direct relation between the dipole moment
measured at impurity bound states and the ideal bulk dipole moment obtained
from the modern theory of polarisation. We also study the many-body problem
with a single impurity via exact diagonalization and find that near strong
impurities non-trivial excitonic state can form with specific features that can
be easily identified via STM spectroscopy.Comment: Main: 5 pages, 4 figures; Supplement: 9 pages, 4 figures; published
versio
Stability of fractionally dissipative 2D quasi-geostrophic equation with infinite delay
In this paper, fractionally dissipative 2D quasi-geostrophic equations with an external force containing infinite delay is considered in the space Hs with s ≥ 2 − 2α and α ∈ ( 1 2 , 1). First, we investigate the existence and regularity of solutions by Galerkin approximation and the energy method. The continuity of solutions with respect to initial data and the uniqueness of so lutions are also established. Then we prove the existence and uniqueness of a stationary solution by the Lax-Milgram theorem and the Schauder fixed point theorem. Using the classical Lyapunov method, the construction method of Lyapunov functionals and the Razumikhin-Lyapunov technique, we analyze the local stability of stationary solutions. Finally, the polynomial stability of stationary solutions is verified in a particular case of unbounded variable delay
EDMAE: An Efficient Decoupled Masked Autoencoder for Standard View Identification in Pediatric Echocardiography
This paper introduces the Efficient Decoupled Masked Autoencoder (EDMAE), a
novel self-supervised method for recognizing standard views in pediatric
echocardiography. EDMAE introduces a new proxy task based on the
encoder-decoder structure. The EDMAE encoder is composed of a teacher and a
student encoder. The teacher encoder extracts the potential representation of
the masked image blocks, while the student encoder extracts the potential
representation of the visible image blocks. The loss is calculated between the
feature maps output by the two encoders to ensure consistency in the latent
representations they extract. EDMAE uses pure convolution operations instead of
the ViT structure in the MAE encoder. This improves training efficiency and
convergence speed. EDMAE is pre-trained on a large-scale private dataset of
pediatric echocardiography using self-supervised learning, and then fine-tuned
for standard view recognition. The proposed method achieves high classification
accuracy in 27 standard views of pediatric echocardiography. To further verify
the effectiveness of the proposed method, the authors perform another
downstream task of cardiac ultrasound segmentation on the public dataset CAMUS.
The experimental results demonstrate that the proposed method outperforms some
popular supervised and recent self-supervised methods, and is more competitive
on different downstream tasks.Comment: 15 pages, 5 figures, 8 tables, Published in Biomedical Signal
Processing and Contro
Atrial Septal Defect Detection in Children Based on Ultrasound Video Using Multiple Instances Learning
Purpose: Congenital heart defect (CHD) is the most common birth defect.
Thoracic echocardiography (TTE) can provide sufficient cardiac structure
information, evaluate hemodynamics and cardiac function, and is an effective
method for atrial septal defect (ASD) examination. This paper aims to study a
deep learning method based on cardiac ultrasound video to assist in ASD
diagnosis. Materials and methods: We select two standard views of the atrial
septum (subAS) and low parasternal four-compartment view (LPS4C) as the two
views to identify ASD. We enlist data from 300 children patients as part of a
double-blind experiment for five-fold cross-validation to verify the
performance of our model. In addition, data from 30 children patients (15
positives and 15 negatives) are collected for clinician testing and compared to
our model test results (these 30 samples do not participate in model training).
We propose an echocardiography video-based atrial septal defect diagnosis
system. In our model, we present a block random selection, maximal agreement
decision and frame sampling strategy for training and testing respectively,
resNet18 and r3D networks are used to extract the frame features and aggregate
them to build a rich video-level representation. Results: We validate our model
using our private dataset by five-cross validation. For ASD detection, we
achieve 89.33 AUC, 84.95 accuracy, 85.70 sensitivity, 81.51 specificity and
81.99 F1 score. Conclusion: The proposed model is multiple instances
learning-based deep learning model for video atrial septal defect detection
which effectively improves ASD detection accuracy when compared to the
performances of previous networks and clinical doctors
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