1,243 research outputs found
Searching for cosmic string induced stochastic gravitational wave background with the Parkes Pulsar Timing Array
We search for stochastic gravitational wave background emitted from cosmic
strings using the Parkes Pulsar Timing Array data over 15 years. While we find
that the common power-law excess revealed by several pulsar timing array
experiments might be accounted for by the gravitational wave background from
cosmic strings, the lack of the characteristic Hellings-Downs correlation
cannot establish its physical origin yet. The constraints on the cosmic string
model parameters are thus derived with conservative assumption that the common
power-law excess is due to unknown background. Two representative cosmic string
models with different loop distribution functions are considered. We obtain
constraints on the dimensionless string tension parameter
, which is more stringent by two orders of magnitude
than that obtained by the high-frequency LIGO-Virgo experiment for one model,
and less stringent for the other. The results provide the chance to test the
Grand unified theories, with the spontaneous symmetry breaking scale of
being two-to-three orders of magnitude below GeV. The pulsar timing
array experiments are thus quite complementary to the LIGO-Virgo experiment in
probing the cosmic strings and the underlying beyond standard model physics in
the early Universe.Comment: 10 pages, 8 figures, 4 tables. Comments welcom
Direct Inversion: Boosting Diffusion-based Editing with 3 Lines of Code
Text-guided diffusion models have revolutionized image generation and
editing, offering exceptional realism and diversity. Specifically, in the
context of diffusion-based editing, where a source image is edited according to
a target prompt, the process commences by acquiring a noisy latent vector
corresponding to the source image via the diffusion model. This vector is
subsequently fed into separate source and target diffusion branches for
editing. The accuracy of this inversion process significantly impacts the final
editing outcome, influencing both essential content preservation of the source
image and edit fidelity according to the target prompt. Prior inversion
techniques aimed at finding a unified solution in both the source and target
diffusion branches. However, our theoretical and empirical analyses reveal that
disentangling these branches leads to a distinct separation of responsibilities
for preserving essential content and ensuring edit fidelity. Building on this
insight, we introduce "Direct Inversion," a novel technique achieving optimal
performance of both branches with just three lines of code. To assess image
editing performance, we present PIE-Bench, an editing benchmark with 700 images
showcasing diverse scenes and editing types, accompanied by versatile
annotations and comprehensive evaluation metrics. Compared to state-of-the-art
optimization-based inversion techniques, our solution not only yields superior
performance across 8 editing methods but also achieves nearly an order of
speed-up
DUFormer: Solving Power Line Detection Task in Aerial Images using Semantic Segmentation
Unmanned aerial vehicles (UAVs) are frequently used for inspecting power
lines and capturing high-resolution aerial images. However, detecting power
lines in aerial images is difficult,as the foreground data(i.e, power lines) is
small and the background information is abundant.To tackle this problem, we
introduce DUFormer, a semantic segmentation algorithm explicitly designed to
detect power lines in aerial images. We presuppose that it is advantageous to
train an efficient Transformer model with sufficient feature extraction using a
convolutional neural network(CNN) with a strong inductive bias.With this goal
in mind, we introduce a heavy token encoder that performs overlapping feature
remodeling and tokenization. The encoder comprises a pyramid CNN feature
extraction module and a power line feature enhancement module.After successful
local feature extraction for power lines, feature fusion is conducted.Then,the
Transformer block is used for global modeling. The final segmentation result is
achieved by amalgamating local and global features in the decode head.Moreover,
we demonstrate the importance of the joint multi-weight loss function in power
line segmentation. Our experimental results show that our proposed method
outperforms all state-of-the-art methods in power line segmentation on the
publicly accessible TTPLA dataset
Defects engineering simultaneously enhances activity and recyclability of MOFs in selective hydrogenation of biomass
The development of synthetic methodologies towards enhanced performance in biomass conversion is desirable due to the growing energy demand. Here we design two types of Ru impregnated MIL-100-Cr defect engineered metal-organic frameworks (Ru@DEMOFs) by incorporating defective ligands (DLs), aiming at highly efficient catalysts for biomass hydrogenation. Our results show that Ru@DEMOFs simultaneously exhibit boosted recyclability, selectivity and activity with the turnover frequency being about 10 times higher than the reported values of polymer supported Ru towards D-glucose hydrogenation. This work provides in-depth insights into (i) the evolution of various defects in the cationic framework upon DLs incorporation and Ru impregnation, (ii) the special effect of each type of defects on the electron density of Ru nanoparticles and activation of reactants, and (iii) the respective role of defects, confined Ru particles and metal single active sites in the catalytic performance of Ru@DEMOFs for D-glucose selective hydrogenation as well as their synergistic catalytic mechanism
Learning Invariant Molecular Representation in Latent Discrete Space
Molecular representation learning lays the foundation for drug discovery.
However, existing methods suffer from poor out-of-distribution (OOD)
generalization, particularly when data for training and testing originate from
different environments. To address this issue, we propose a new framework for
learning molecular representations that exhibit invariance and robustness
against distribution shifts. Specifically, we propose a strategy called
``first-encoding-then-separation'' to identify invariant molecule features in
the latent space, which deviates from conventional practices. Prior to the
separation step, we introduce a residual vector quantization module that
mitigates the over-fitting to training data distributions while preserving the
expressivity of encoders. Furthermore, we design a task-agnostic
self-supervised learning objective to encourage precise invariance
identification, which enables our method widely applicable to a variety of
tasks, such as regression and multi-label classification. Extensive experiments
on 18 real-world molecular datasets demonstrate that our model achieves
stronger generalization against state-of-the-art baselines in the presence of
various distribution shifts. Our code is available at
https://github.com/HICAI-ZJU/iMoLD
Analysis of high-speed angular ball bearing lubrication based on bi-directional fluid-solid coupling
The lubrication of angular contact ball bearings under high-speed motion conditions is particularly important to the working performance of rolling bearings. Combining the contact characteristics of fluid domain and solid domain, a lubrication calculation model for angular contact ball bearings is established based on the RNG k-ε method. The pressure and velocity characteristics of the bearing basin under the conditions of rotational speed, number of balls and lubricant parameters are analyzed, and the lubrication conditions and dynamics of the angular contact ball bearings under different working conditions are obtained. The results show that the lubricant film pressure will rise with increasing speed and viscosity of the lubricant. The number of balls affects the pressure and velocity distribution of the flow field inside the bearing but has a small effect on the values of the characteristic parameters of the bearing flow field. The established CFD model provides a new approach to study the effect of fluid flow on bearing performance in angular contact ball bearings
A novel strategy for rapid identification of the fruits of Illicium verum and Illicium anisatum using electronic nose and tongue technology
Purpose: To develop an effective and rapid strategy for the identification of fruits of I. verum and I. anisatum based on their odor and taste.Methods: Electronic nose (E-nose) and electronic tongue (E-tongue) technology was used to identify the fruits of I. verum (FIV) and I. anisatum (FIA). Samples of FIA, FIV, and FIA : FIV mixtures in different proportions (1 : 3, 1 : 1, and 3 : 1) were prepared to evaluate the identification abilities of E-nose and Etongue methods. Samples were powdered and sifted through a standard sieve (aperture size 355 ± 13 μm) for E-nose analysis. Each sample was refluxed with water for 1 h before E-tongue analysis. The acquired data were analyzed by principal component analysis (PCA) and discriminant factor analysis (DFA).Results: Based on the signals acquired by E-nose and E-tongue analyses, a total of 90 data points each were used for PCA. The three principal component values for E-nose analysis were PC1 = 93.89 %, PC2 = 6.08 %, and PC3 = 0.03 %, and those for E-tongue analysis were PC1 = 98.72 %, PC2 = 0.68 %, and PC3 = 0.57 %. The sample data were significantly divided into two groups representing FIV and FIA. Furthermore, E-nose and E-tongue assessments combined with PCA and DFA analyses effectively identified FIV, FIA and their mixtures.Conclusion: The use of E-nose and E-tongue technology is an effective and rapid strategy to identify the fruits of I. verum and I. anisatum and their mixtures. This strategy may also offer an effective method for detection of adulterants.Keywords: Illicium verum, Illicium anisatum, Discrimination, Electronic nose, Electronic tongue, Safety, Principal component analysis, Discriminant factor analysi
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