1,261 research outputs found
Formation of hot subdwarf B stars with neutron star components
Binary population synthesis predicts the existence of subdwarf B stars (sdBs)
with neutron star (NS) or black hole (BH) companions. We systematically
investigate the formation of sdB+NS binaries from binary evolution and aim to
obtain some clues for a search for such systems. We started from a series of
MS+NS systems and determined the parameter spaces for producing sdB+NS binaries
from the stable Roche-lobe overflow (RLOF) channel and from the common envelope
(CE) ejection channel. Various NS accretion efficiencies and NS masses were
examined to investigate the effects they have. We show the characteristics of
the produced sdB+NS systems, such as the mass of components, orbital period,
the semi-amplitude of the radial velocity (K), and the spin of the NS
component. In the stable RLOF channel, the orbital period of sdB+NS binaries
produced in this way ranges from several days to more than 1000 days and moves
toward the short-period (~ hr) side with increasing initial MS mass. the sdB+NS
systems that result from CE ejection have very short orbital periods and then
high values of K (up to 800km s^-1). Such systems are born in very young
populations (younger than 0.3 Gyr) and are potential gravitational wave sources
that might be resolved by the Laser Interferometer Space Antenna (LISA) in the
future. Gravitational wave radiation may again bring them into contact on a
timescale of only ~Myr. As a consequence, they are rare and hard to discover.
The pulsar signal is likely a feature of sdB+NS systems caused by stable RLOF,
and some NS components in sdB binaries may be millisecond pulsars.Comment: 12 pages, 6 figures, 4 tables. Accepted for publication in A&
CFD-FEM simulation of water entry of aluminium flat stiffened plate structure considering the effects of hydroelasticity
In this paper, the slamming loads and structural response of an aluminium flat stiffened-plate structure during calm water entry considering the hydroelasticity effects are studied by a partitioned CFD-FEM two-way coupled method. The target structure is simplified as one segment of an idealized ship grillage structure, comprising flat plate and stiffeners. The typical numerical results are analyzed such as vertical displacement, velocity, acceleration, impact loads, and structural stress of the flexible flat bottom grillage structure considering the hydroelasticity effect and air cushion effect in different free fall height conditions. Drop test results of the same structure and other existing numerical simulation data by both coupled and uncoupled solutions in the literature are used for comparison with the present numerical simulation results. This study provides a practical means to simulate the slamming behaviour and structural response of ship structures, which is useful for predicting ship hull stiffened panel loads and related structural design
at CEPC: ISR effect with MadGraph
The Circular Electron Positron Collider (CEPC) is a future Higgs factory
proposed by the Chinese high energy physics community. It will operate at a
center-of-mass energy of 240-250 GeV. The CEPC will accumulate an integrated
luminosity of 5 ab in ten years' operation. With GEANT4-based full
simulation samples for CEPC, Higgs boson decaying into electron pair is studied
at the CEPC. The upper limit of could reach
0.024\% at 95\% confidence level. The signal process is generated by MadGraph,
with Initial State Radiation (ISR) implemented, as a first step to adjust
MadGraph for a electron positron Collider.Comment: Accepted version by J.P.
Dense Pixel-to-Pixel Harmonization via Continuous Image Representation
High-resolution (HR) image harmonization is of great significance in
real-world applications such as image synthesis and image editing. However, due
to the high memory costs, existing dense pixel-to-pixel harmonization methods
are mainly focusing on processing low-resolution (LR) images. Some recent works
resort to combining with color-to-color transformations but are either limited
to certain resolutions or heavily depend on hand-crafted image filters. In this
work, we explore leveraging the implicit neural representation (INR) and
propose a novel image Harmonization method based on Implicit neural Networks
(HINet), which to the best of our knowledge, is the first dense pixel-to-pixel
method applicable to HR images without any hand-crafted filter design. Inspired
by the Retinex theory, we decouple the MLPs into two parts to respectively
capture the content and environment of composite images. A Low-Resolution Image
Prior (LRIP) network is designed to alleviate the Boundary Inconsistency
problem, and we also propose new designs for the training and inference
process. Extensive experiments have demonstrated the effectiveness of our
method compared with state-of-the-art methods. Furthermore, some interesting
and practical applications of the proposed method are explored. Our code is
available at https://github.com/WindVChen/INR-Harmonization.Comment: Accepted by IEEE Transactions on Circuits and Systems for Video
Technology (TCSVT
Continuous Cross-resolution Remote Sensing Image Change Detection
Most contemporary supervised Remote Sensing (RS) image Change Detection (CD)
approaches are customized for equal-resolution bitemporal images. Real-world
applications raise the need for cross-resolution change detection, aka, CD
based on bitemporal images with different spatial resolutions. Given training
samples of a fixed bitemporal resolution difference (ratio) between the
high-resolution (HR) image and the low-resolution (LR) one, current
cross-resolution methods may fit a certain ratio but lack adaptation to other
resolution differences. Toward continuous cross-resolution CD, we propose
scale-invariant learning to enforce the model consistently predicting HR
results given synthesized samples of varying resolution differences.
Concretely, we synthesize blurred versions of the HR image by random
downsampled reconstructions to reduce the gap between HR and LR images. We
introduce coordinate-based representations to decode per-pixel predictions by
feeding the coordinate query and corresponding multi-level embedding features
into an MLP that implicitly learns the shape of land cover changes, therefore
benefiting recognizing blurred objects in the LR image. Moreover, considering
that spatial resolution mainly affects the local textures, we apply
local-window self-attention to align bitemporal features during the early
stages of the encoder. Extensive experiments on two synthesized and one
real-world different-resolution CD datasets verify the effectiveness of the
proposed method. Our method significantly outperforms several vanilla CD
methods and two cross-resolution CD methods on the three datasets both in
in-distribution and out-of-distribution settings. The empirical results suggest
that our method could yield relatively consistent HR change predictions
regardless of varying bitemporal resolution ratios. Our code is available at
\url{https://github.com/justchenhao/SILI_CD}.Comment: 21 pages, 11 figures. Accepted article by IEEE TGR
Implicit Ray-Transformers for Multi-view Remote Sensing Image Segmentation
The mainstream CNN-based remote sensing (RS) image semantic segmentation
approaches typically rely on massive labeled training data. Such a paradigm
struggles with the problem of RS multi-view scene segmentation with limited
labeled views due to the lack of considering 3D information within the scene.
In this paper, we propose ''Implicit Ray-Transformer (IRT)'' based on Implicit
Neural Representation (INR), for RS scene semantic segmentation with sparse
labels (such as 4-6 labels per 100 images). We explore a new way of introducing
multi-view 3D structure priors to the task for accurate and view-consistent
semantic segmentation. The proposed method includes a two-stage learning
process. In the first stage, we optimize a neural field to encode the color and
3D structure of the remote sensing scene based on multi-view images. In the
second stage, we design a Ray Transformer to leverage the relations between the
neural field 3D features and 2D texture features for learning better semantic
representations. Different from previous methods that only consider 3D prior or
2D features, we incorporate additional 2D texture information and 3D prior by
broadcasting CNN features to different point features along the sampled ray. To
verify the effectiveness of the proposed method, we construct a challenging
dataset containing six synthetic sub-datasets collected from the Carla platform
and three real sub-datasets from Google Maps. Experiments show that the
proposed method outperforms the CNN-based methods and the state-of-the-art
INR-based segmentation methods in quantitative and qualitative metrics
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