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Due to the black and glossy appearance of the carbon fiber prepreg bundle surface, the accurate identification of surface defects in automated fiber placement (AFP) presents a high level of difficulty. Currently, the enhanced YOLOv7 algorithm demonstrates certain performance advantages in this detection task, yet issues with missed detections, false alarms, and low confidence levels persist. Therefore, this study proposes an improved YOLOv7 algorithm to further enhance the performance and generalization of surface defect detection in AFP. Firstly, to enhance the model's feature extraction capability, the BiFormer attention mechanism is introduced to make the model pay more attention to small target defects, thereby improving feature discriminability. Next, the AFPN structure is used to replace the PAFPN at the neck layer to strengthen feature fusion, preserve semantic information to a greater extent, and finely integrate multi-scale features. Finally, WIoU is adopted to replace CIoU as the bounding box regression loss function, making it more sensitive to small targets, enabling more accurate prediction of object bounding boxes, and enhancing the model's detection accuracy and generalization capability. Through a series of ablation experiments, the improved YOLOv7 shows a 10.5% increase in mAP and a 14 FPS increase in frame rate, with a maximum detection speed of 35 m/min during the AFP process, meeting the requirements of online detection and thus being able to be applied to surface defect detection in AFP operations. [ABSTRACT FROM AUTHOR]

Gas injection for enhancing gas recovery (GI–EGR) is a multifaceted process that requires a solid theoretical foundation to be implemented orderly. However, there are limited reports on the micro-mechanisms of GI–EGR technology applied to coalbed methane reservoirs, especially for deep strata. To address this gap, this study utilized molecular simulation techniques to construct the organic pore models of anthracite with varying sizes and morphologies, and explored the micro-dynamic behaviors of CH4 and various gas injected components including N2, CO2 and flue gas confined in nanopores. The aim was to reveal the competitive adsorption mechanisms of gases in multi-component systems under shallow and deep geological conditions. The results demonstrated that the isosteric heats of CH4, N2 and CO2 all increased after the transition from shallow to deep, with rising amplitudes of 18.8%, 22.8% and 17.8%, respectively, in the respective single-component systems. In multi-component adsorption models, the isosteric heats remained higher than those under shallow conditions, but there were some small fluctuations due to the interference between various gases. On the other hand, the self-diffusion coefficients of single CH4, N2 and CO2 in the deep condition decreased by 37.6%, 27.2% and 23.1%, respectively, compared to those in conventional shallow conditions. As a consequence, the difference in diffusivity among various gases would get narrowed. The molecular-level observations herein have the potential to improve the understanding of gas occurrence and lay a solid foundation for the GI–EGR technology. [ABSTRACT FROM AUTHOR]

LaNi 3.50 and La 0.80 Mg 0.20 Ni 3.50 hydrogen storage alloys with single-phase Ce 2 Ni 7 -type structure are prepared, respectively. It is found that the expansion of [A 2 B 4 ] subunits volumes of Mg-containing alloy is bigger than that of Mg-free alloy, while the expansion of [AB 5 ] subunits volumes of the two alloys are almost the same, hence the deviation value of [A 2 B 4 ] and [AB 5 ] subunits volumes and strain value of super stacking structure for Mg-containing alloy are obviously higher than those of Mg-free alloy, and Mg-containing alloy is easier to be pulverized during charge/discharge cycles. Mg-containing alloy has more apparent cracks on the surface of alloy at the same cycle numbers, which demonstrate that Mg-containing alloy has poorer anti-pulverization. Besides, the presence of Mg hydroxides with a regular hexagon shape makes the surface of Mg-containing alloy become loose enough to be easily oxidized after charge/discharge cycles. The corrosion current density of Mg-containing alloy is larger than that of Mg-free alloy, so Mg-containing alloy is easier to be oxidized. Therefore, reducing the deviation value of [A 2 B 4 ] and [AB 5 ] subunits of super stacking structure and the corrosion of alloying element Mg is the basic solution to enhance the electrochemical cycling stability of La Mg Ni alloy. [ABSTRACT FROM AUTHOR]