We investigate the numerical approximation of parabolic interface optimal control problems using the stable generalized finite element method (SGFEM). For spatial discretization of the state variable, we employ the SGFEM, while the backward Euler method is utilized for temporal discretization. The control variable is discretized using the variational discretization method. We derive error estimates for the optimal control, state, and adjoint state. Finally, several numerical examples are provided to verify the analysis results.
Defect opening and fracture in high-pressure CO2 pipelines under near-critical and dense-phase conditions involve rapid depressurization, phase-change-related cooling and complex pipe-wall deformation. In this study, three fracture tests were conducted on DN150 X65 pipe sections subjected to pure CO2 release. The initial pressure ranged from 8.2 to 8.7 MPa, and the initial temperature ranged from 18 to 50 degrees C. External axial defects with a depth of approximately 90% of the wall thickness were pre-machined. Pressure, temperature, fracture timing-wire signals and high-speed images were recorded, and the fracture behavior was analyzed using macroscopic morphology, SEM observations, image-based apparent CTOA measurement and decompressionwave prediction. The three tests showed distinct responses: limited axial crack propagation followed by circumferential tearing, defect opening only, and local large deformation without stable crack propagation. Rapid pressure drop, pressure rebound and decompression plateaus were observed during CO2 release, which may be associated with transient phase-change behavior, pressure-wave reflection, rupture-disc opening and release-area evolution. In Tests 1 and 3, the minimum measured temperature in the upstream pipe reached 49.56 degrees C, with the maximum cooling occurring at the pipe bottom, indicating strong vertical thermal stratification. High-speed imaging in Test 1 showed that the image-based apparent CTOA remained within a relatively stable range during the visible crack-opening stage. SEM observations in Test 1 confirmed ductile microvoid coalescence without typical brittle fracture features. The decompression model captured the plateau trend but overestimated the initial wave speed and underestimated the plateau duration. These results provide experimental support for fracture response and depressurization assessment of small- and medium-diameter CO2 pipe sections within the present pressure and temperature range.
Investigating the relationship between the distribution of light and heavy fractions in thermal dissolution soluble portions (SPs) and the composition and structural characteristics of raw coal is crucial for elucidating the depolymerization mechanisms of soluble organic matter in coal. In this study, fourteen medium and low-rank coals from China were thermally dissolved at 320 degrees C using an isometric toluene/methanol mixture as the solvent. The correlations between the relative contents of three fractions (light oil, asphaltenes, and preasphaltenes) in the SPs and the composition and structural characteristics of the raw coals were systematically examined. The results show that the SP yield is positively correlated with the volatile matter content of raw coal. Higher H/C and O/C atomic ratios in the coal samples are associated with increased yields of both SPs and light oil; however, as these ratios increase, the proportion of light oil in the SPs gradually decreases. Fourier transform infrared spectroscopy (FT-IR) analysis further reveals that the proportion of light oil in the SPs increases with the aromaticity of raw coal, but decreases with longer aliphatic side chains, suggesting that extended aliphatic side chains hinder the formation of light oil during thermal dissolution. Additionally, as the oxygen enrichment coefficient increases, the proportion of light oil first decreases and then rises. This study provides important theoretical insight into the depolymerization mechanisms of organic species in coal.
Automated cotton apical bud detection is essential for intelligent topping systems, yet most existing methods rely on single-frame analysis and fail to exploit the temporal redundancy inherent in field video streams. In practice, cotton apical buds are extremely small, weakly textured, and frequently occluded by leaves, while complex illumination, motion blur, and low-resolution acquisition further degrade single-frame features. This leaves a fundamental gap between current static-image detectors and the robustness required for real agricultural video deployment. We present UF-YOLO, a lightweight video object detection framework built on YOLOv11n, together with AgriSOV, a video-level benchmark for cotton apical bud detection that covers five naturally occurring field degradation types together with a derived low-resolution condition. UF-YOLO addresses three key challenges through problem-driven module redesigns. The Local-Semantic Feature Modeling (LSFM) module jointly captures local structure and global semantics to make weak-textured small objects easier to distinguish. The Dynamic Spatial Resampling (DSR) module performs content-aware adaptive resampling to help recover features degraded by motion blur and low resolution. The Spatio-Temporal Aggregation (STA) module exploits inter-frame statistical regularities to enforce temporal consistency without explicit state propagation. On AgriSOV, UF-YOLO reaches 58.44% mAP0.50 with only 3.28M parameters and 4.97 GFLOPs, outperforming both image-based and video-based detectors. Cross-domain evaluation on VisDrone2019-VID and multi-backbone experiments further indicate the transferability of the proposed modules across domains and architectures.
Sodium-ion batteries (SIBs) are promising candidates for large-scale energy storage applications, primarily owing to the abundance of sodium and the cost-effectiveness of their components. Among various anode materials, hard carbons (HCs) have attracted considerable attention due to their high capacity, low cost, and wide availability. With high carbon content and economic viability, coal represents a potential precursor for producing HCs. However, the heterogeneity of coal's maceral groups can significantly influence the electrochemical properties of the resulting hard carbon-a relationship that has been largely overlooked in previous studies. Herein, hard carbons were synthesized from distinct maceral groups of low-rank coal via a straightforward two-step carbonization process, aiming to clarify the impact of maceral variations on sodium storage performance. The findings reveal that the electrochemical behavior of the produced hard carbons is significantly influenced by the ratio between amorphous carbon and graphite-like microcrystalline content within the electrode material. Notably, semifusinite a type of inertinite enhances sodium storage capabilities by introducing structural defects and favorable pore architectures, thereby facilitating improved ion transport and charge storage. The I-1200 electrode demonstrated excellent rate performance, with the highest reversible capacity of 327mAh g- 1 and the lowest interfacial resistance observed at a current rate of 0.1C. These results underscore the potential of tailoring coal maceral groups to optimize the performance of hard carbon anodes in next-generation sodium-ion batteries.
