158 research outputs found
Resistivity and AE Response Characteristics in the Failure Process of CGB under Uniaxial Loading
To understand the characteristics of the acoustic emission (AE) and electrical resistivity of cemented coal gangue backfill (CGB) under uniaxial compression, the variations in these characteristics at 1 day, 3 days, and 7 days are analyzed by means of a stress-strain-resistivity-AE test, and the microperformances are investigated. The research results indicate that the AE can reflect the initiation and propagation of cracks and later explain the variation of the resistivity of the specimens under the uniaxial loading. The cumulative energy curve of AE is approximately two straight lines corresponding to the peak stress, and the difference in the linear slope gradually decreased with the increasing curing time due to the lower pore solution content and the compact pore structure. The relationships between the stress and resistivity and the loading condition before and after the peak stress at different curing times were established. Therefore, it is of great significance to predict the stability of the filling body by monitoring the AE and resistivity variations of the filling body. In addition, it is possible to calculate the roof stress using the relation equation between the resistivity and stress
RFD-ECNet: Extreme Underwater Image Compression with Reference to Feature Dictionar
Thriving underwater applications demand efficient extreme compression
technology to realize the transmission of underwater images (UWIs) in very
narrow underwater bandwidth. However, existing image compression methods
achieve inferior performance on UWIs because they do not consider the
characteristics of UWIs: (1) Multifarious underwater styles of color shift and
distance-dependent clarity, caused by the unique underwater physical imaging;
(2) Massive redundancy between different UWIs, caused by the fact that
different UWIs contain several common ocean objects, which have plenty of
similarities in structures and semantics. To remove redundancy among UWIs, we
first construct an exhaustive underwater multi-scale feature dictionary to
provide coarse-to-fine reference features for UWI compression. Subsequently, an
extreme UWI compression network with reference to the feature dictionary
(RFD-ECNet) is creatively proposed, which utilizes feature match and reference
feature variant to significantly remove redundancy among UWIs. To align the
multifarious underwater styles and improve the accuracy of feature match, an
underwater style normalized block (USNB) is proposed, which utilizes underwater
physical priors extracted from the underwater physical imaging model to
normalize the underwater styles of dictionary features toward the input.
Moreover, a reference feature variant module (RFVM) is designed to adaptively
morph the reference features, improving the similarity between the reference
and input features. Experimental results on four UWI datasets show that our
RFD-ECNet is the first work that achieves a significant BD-rate saving of 31%
over the most advanced VVC
Semantic-Preserving Linguistic Steganography by Pivot Translation and Semantic-Aware Bins Coding
Linguistic steganography (LS) aims to embed secret information into a highly
encoded text for covert communication. It can be roughly divided to two main
categories, i.e., modification based LS (MLS) and generation based LS (GLS).
Unlike MLS that hides secret data by slightly modifying a given text without
impairing the meaning of the text, GLS uses a trained language model to
directly generate a text carrying secret data. A common disadvantage for MLS
methods is that the embedding payload is very low, whose return is well
preserving the semantic quality of the text. In contrast, GLS allows the data
hider to embed a high payload, which has to pay the high price of
uncontrollable semantics. In this paper, we propose a novel LS method to modify
a given text by pivoting it between two different languages and embed secret
data by applying a GLS-like information encoding strategy. Our purpose is to
alter the expression of the given text, enabling a high payload to be embedded
while keeping the semantic information unchanged. Experimental results have
shown that the proposed work not only achieves a high embedding payload, but
also shows superior performance in maintaining the semantic consistency and
resisting linguistic steganalysis
Cone Beam Micro-CT System for Small Animal Imaging and Performance Evaluation
A prototype cone-beam micro-CT system for small animal imaging has been developed by our group recently, which consists of a microfocus X-ray source, a three-dimensional programmable stage with object holder, and a flat-panel X-ray detector. It has a large field of view (FOV), which can acquire the whole body imaging of a normal-size mouse in a single scan which usually takes about several minutes or tens of minutes. FDK method is adopted for 3D reconstruction with Graphics Processing Unit (GPU) acceleration. In order to reconstruct images with high spatial resolution and low artifacts, raw data preprocessing and geometry calibration are implemented before reconstruction. A method which utilizes a wire phantom to estimate the residual horizontal offset of the detector is proposed, and 1D point spread function is used to assess the performance of geometric calibration quantitatively. System spatial resolution, image uniformity and noise, and low contrast resolution have been studied. Mouse images with and without contrast agent are illuminated
in this paper. Experimental results show that the system is suitable for small animal imaging and is adequate to provide high-resolution anatomic information for bioluminescence tomography to build a dual modality system
Vertical Stress and Deformation Characteristics of Roadside Backfilling Body in Gob-Side Entry for Thick Coal Seams with Different Pre-Split Angles
Retained gob-side entry (RGE) is a significant improvement for fully-mechanized longwall mining. The environment of surrounding rock directly affects its stability. Roadside backfilling body (RBB), a man-made structure in RGE plays the most important role in successful application of the technology. In the field, however, the vertical deformation of RBB is large during the panel extraction, which leads to malfunction of the RGE. In order to solve the problem, roof pre-split is employed. According to geological conditions as well as the physical modeling of roof behavior and deformation of surrounding rock, the support resistance of RBB is calculated. The environment of surrounding rock, vertical stress and vertical deformation of the RBB in the RGE with different roof pre-split angles are analyzed using FLAC3D software. With the increase of roof pre-split angle, the vertical stresses both in the coal wall and RBB are minimum, and the vertical deformation of RBB also decreases from 110.51 mm to 6.1 mm. Therefore, based on the results of numerical modeling and field observation, roof pre-split angle of 90° is more beneficial to the maintenance of the RGE
Tunable Correlated Chern Insulator and Ferromagnetism in Trilayer Graphene/Boron Nitride Moir\'e Superlattice
Studies on two-dimensional electron systems in a strong magnetic field first
revealed the quantum Hall (QH) effect, a topological state of matter featuring
a finite Chern number (C) and chiral edge states. Haldane later theorized that
Chern insulators with integer QH effects could appear in lattice models with
complex hopping parameters even at zero magnetic field. The ABC-trilayer
graphene/hexagonal boron nitride (TLG/hBN) moir\'e superlattice provides an
attractive platform to explore Chern insulators because it features nearly flat
moir\'e minibands with a valley-dependent electrically tunable Chern number.
Here we report the experimental observation of a correlated Chern insulator in
a TLG/hBN moir\'e superlattice. We show that reversing the direction of the
applied vertical electric field switches TLG/hBN's moir\'e minibands between
zero and finite Chern numbers, as revealed by dramatic changes in
magneto-transport behavior. For topological hole minibands tuned to have a
finite Chern number, we focus on 1/4 filling, corresponding to one hole per
moir\'e unit cell. The Hall resistance is well quantized at h/2e2, i.e. C = 2,
for |B| > 0.4 T. The correlated Chern insulator is ferromagnetic, exhibiting
significant magnetic hysteresis and a large anomalous Hall signal at zero
magnetic field. Our discovery of a C = 2 Chern insulator at zero magnetic field
should open up exciting opportunities for discovering novel correlated
topological states, possibly with novel topological excitations, in nearly flat
and topologically nontrivial moir\'e minibands.Comment: 16 pages, 4 figures, and 2 extended figure
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