arXiv subjects

Shipeng Hu

Publications and source records attributed to Shipeng Hu.

4 recordsLinked to original sources

arXiv2026

Effects of Competing Reactions on $^{59}\mathrm{Cu}$ and $^{63}\mathrm{Ga}$ on Abundance Distributions in Type I X-Ray Bursts

The composition of X-ray burst ashes affects the thermal transport properties of the neutron star crust, as well as heating and cooling through weak interaction processes. Reaction-rate uncertainties can produce secondary peaks separated from the main peak in final abundance distributions. Using STARLIB reaction rates and their temperature-dependent uncertainties in the K04 one-zone post-processing model, we combine four sets of Monte Carlo calculations with XGBoost classification, SHAP analysis, and reaction-flow analysis to investigate the origins of these secondary peaks. We find that the competing $(p,α)$ and $(p,γ)$ reaction pairs on $^{59}\mathrm{Cu}$ and $^{63}\mathrm{Ga}$ are primarily responsible for secondary peaks outside the central 68\% confidence interval in all 44 isotopes examined. Fixing both pairs at their median rates reduces the fractions of samples in the secondary-peak regions by 96\%--100\%, while the bounds of the central 68\% interval remain largely unchanged for most mass numbers. The $^{59}\mathrm{Cu}$ pair has the larger effect. Enhanced recycling limits the supply of material to heavier isotopes and accelerates proton consumption, while earlier proton exhaustion further suppresses subsequent proton captures. These changes alter the balance between isotope production and destruction, leading to high- or low-abundance secondary peaks over a broad mass range beyond the Ni--Cu and Zn--Ga cycles. These results identify $^{59}\mathrm{Cu}(p,γ)^{60}\mathrm{Zn}$ and the two competing channels on $^{63}\mathrm{Ga}$ as priorities for further nuclear-physics constraints to improve XRB abundance predictions.

astro-ph.HE↗

arXiv2026

O2D-MedNet: An Optimization-Aware Dual-Domain Framework for Robust Medical Image Segmentation

Medical image segmentation (MIS) remains challenging due to composite degradations and multi-scale geometric variations, which jointly impair lesion-background separability, structural consistency, and optimization stability. Existing single-stream frameworks entangle heterogeneous cues within a single representation pathway, while hybrid-stream approaches often rely on generic or static fusion, limiting effective coordination across domains and failing to explicitly address optimization instability. To overcome these limitations, we propose a new optimization-aware dual-domain framework for MIS (O2D-MedNet). First, a degradation-aware dualdomain interaction (DDI) module integrates Fourier - and Wavelet-domain features to suppress degradation-sensitive responses while preserving structural and fine-detail information. Second, a cross-backbone contour-guided fusion (CGF) module enables selective interaction between CNN-based local detail modeling and visual state-space-based global structure modeling, improving boundary accuracy and representation consistency. Third, a gradient-context optimization (GCO) strategy stabilizes training by adaptively adjusting learning dynamics based on loss trends and gradient statistics, mitigating instability caused by class imbalance and heterogeneous sample difficulty. Extensive experiments on six benchmarks demonstrate consistent improvements over state-of-the-art MIS methods across multiple imaging modalities. Further analyses confirm enhanced sensitivity, structural consistency, and optimization stability, validating the effectiveness of the proposed O2D-MedNet for robust MIS under heterogeneous conditions.

cs.CV↗

arXiv2026

Impact of Nuclear Reaction Rate Uncertainties on Type I X-ray Burst Nucleosynthesis: A Monte Carlo Study

Type I X-ray bursts are thermonuclear flashes on the surface of accreting neutron stars, involving hundreds of nuclei and thousands of reactions with larger uncertainties in reaction rate. To investigate the impact of nuclear reaction rate uncertainties on type I X-ray burst nucleosynthesis, comprehensive Monte Carlo simulations were performed with temperature-independent and -dependent variations in reaction rates using the REACLIB and STARLIB libraries, respectively. A total of 1,711 $(p, γ)$, $(p, α)$, $(α, p)$, and $(α, γ)$ reaction rates are varied simultaneously along with their inverse reactions via detailed balance. For the first time, it has been found that Monte Carlo sampling with larger perturbations to these reaction rates may lead to multi-peak abundance distributions for certain isotopes, such as $^{64}$Zn and $^{55}$Co. These multi-peak structures arise not only from coupled reactions but also from single reactions in some cases. Our studies also confirm previously identified key reactions and provide more robust lists that deserve priority consideration in future studies.

astro-ph.HE↗

arXiv2026

Impact of Nuclear Reaction Rates on Calcium Production in Population III Stars: A Global Analysis

We investigate the sensitivity of calcium production to nuclear reaction rates of a 40 solar-mass Population III star using 1D multi-zone stellar models. A comprehensive nuclear reaction network was constructed, and all $(p,γ)$ and $(p,α)$ reaction rates were individually varied by a factor of 10 up and down, identifying 13 preliminary key reactions for calcium production. To propagate the reaction rate uncertainties on calcium production, two sets of Monte Carlo simulations were performed for these key reactions: one adopting STARLIB reaction rates and the other incorporating updated rates from recent experimental data and evaluations. Our results show that Monte Carlo simulations using the updated rates show good agreement with the observed calcium abundance of the extremely iron-poor star SMSS J031300.36-670839.3 within the 68% confidence interval predicted by the models. In contrast, the observed calcium abundance lies marginally outside the 68% C.I. when using the STARLIB rates. Spearman rank-order correlation analysis and SHAP values show that the $(p,γ)$ and $(p,α)$ reactions of F18 and F19 exhibit strong coupled effects on calcium production. These reaction-rate uncertainties need to be reduced to constrain the stellar model predictions. Our study provides insights for future nuclear physics experiments aimed at reducing reaction rate uncertainties in the nucleosynthesis of Population III Stars. Additionally, comparisons between 20 solar-mass and 40 solar-mass Population III stellar models confirm that the latter, with updated reaction rates, is more capable of reproducing the observed Ca abundance and [Ca/Mg] ratio.

astro-ph.SR↗