Symmetry

Optical Character Recognition (OCR) for Manchu is hindered by large intra-domain variation caused by diverse fonts. Consequently, traditional end-to-end models perform poorly in zero-shot cross-domain scenarios. To address this bottleneck, we propose a two-stage decoupled paradigm, “Normalize-then-Recognize,” and construct the Target-Masked Adversarial Reconstruction Network (TMAR-Net) as a modular visual pre-filter. To address the continuous cursive axis and severe foreground–background imbalance of Manchu script, TMAR-Net utilizes a paired ConvNeXt generator equipped with bottleneck self-attention and introduces a Structure-Aware Hard-Mining Target-Masked Loss (SA-HMTM Loss). Through the joint application of pixel-level masking, instance-level hard mining, and feature-level structural anchoring, this approach reduces broken strokes, long-tail sample collapse, and topological hallucinations during reconstruction. Evaluated on a dataset containing 20,000 words, system-level validation shows that, after lightweight domain adaptation, the end-to-end recognition accuracies of single-font and multi-font baseline models rise to averages of 92.34% and 92.56%, respectively, peaking at 95.52%. This yields an average absolute improvement of over 90 percentage points compared with the direct single-font baseline, closely approaching the 99.81% recognition rate typically achieved under in-domain conditions. This work provides a robust, system-level solution for digitizing high-variance, low-resource minority multi-font documents.

To investigate the effect of prefabricated borehole diameter on the dynamic response of coal–rock composite specimens, split Hopkinson pressure bar (SHPB) tests were conducted on specimens without a borehole and with borehole diameters of 4, 6, and 8 mm. Twelve specimens were tested, with three specimens in each group, under a nominal impact pressure of 0.3 MPa. The average strain rates ranged from 19.64 to 22.36 s⁻¹, while the peak strain rates ranged from 29.79 to 33.10 s⁻¹. The group-mean nominal dynamic peak strengths of the 0, 4, 6, and 8 mm groups were 92.87, 94.68, 78.34, and 77.60 MPa, respectively. The peak strain and peak secant modulus both exhibited non-monotonic variations with borehole diameter. The corresponding group-mean net absorbed energies were 33.96, 35.60, 32.16, and 33.05 J, respectively, also showing a non-monotonic variation. Across the four borehole-diameter groups, the group-mean fitted fragmentation parameter ranged from 1.95 to 2.06, while the group-mean characteristic particle size ranged from 6.95 to 7.76 mm. The Weibull statistical damage model provided a good descriptive representation of the nonlinear stress–strain response within the selected fitting interval, with group-mean coefficients of determination $R^2$ ranging from 0.9895 to 0.9969. Overall, the load-bearing, energy, fragmentation, and nonlinear deformation responses varied among the tested borehole-diameter groups, and the different response indicators did not exhibit a uniform monotonic dependence on borehole diameter.

The aim of the paper is to establish the existence of solutions of a quadratic Hammerstein–Stieltjes integral equation considered on the real half-axis ${\mathbb{R}}_{+}$. We seek solutions in the class of real-valued functions which are continuous and bounded on ${\mathbb{R}}_{+}$ and possess finite limits at infinity. The proof is based on the technique of measures of noncompactness combined with the fixed-point theorem of Darbo type. Our considerations also involve the concepts of bounded variation and the Riemann–Stieltjes integral on an unbounded interval. The obtained result extends previous investigations concerning solutions tending to zero at infinity.