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Aiming at the problem that there is no GNSS signal in the coal mine, the state-of-the-art LiDAR SLAM algorithm is prone to degenerate due to insufficient feature constraints, a tight coupling SLAM algorithm of LiDAR and IMU for the coal mine environment is proposed. First, we design a dynamic feature point extraction method, by detecting whether there is degradation in the underground environment of coal mine to dynamically adjust the number of feature points extracted, build a rich and good feature information constraint matrix, improve the accuracy of pose estimation; then, the factor diagram optimization is used to realize the robust and accurate SLAM in the coal mine. Finally, a wide range of experimental analysis is carried out through the measured data in the coal mine. The results show that the proposed laser SLAM algorithm performs well, the pose estimation error is reduced by 50.93% in the horizontal direction and 42.13% in the vertical direction compared with LIO_SAM, it can provide technical reference for intelligent perception and safety inspection of coal mine robots.

The vibration pretreatment–microwave curing process can achieve high-quality molding under low-pressure conditions and is widely used in the curing of resin-based composites. This study investigated the effects of the vibration pretreatment process parameters on the void content and the fiber weight fraction of T700/TRE231; specifically, their influence on the interlaminar shear strength and impact strength of the composite. Initially, an orthogonal experimental design was employed with interlaminar shear strength as the optimization target, where vibration acceleration was determined as the primary factor and dwell time as the secondary factor. Concurrently, thermogravimetric analysis (TGA) was performed based on process parameters that corresponded to the extremum of interlaminar shear strength, revealing a 2.17% difference in fiber weight fraction among specimens with varying parameters, indicating a minimal effect of fiber weight fraction on mechanical properties. Optical digital microscope (ODM) analysis identified interlaminar large-size voids in specimens treated with vibration energy of 5 g and 15 g, while specimens subjected to a vibration energy of 10 g exhibited numerous small-sized voids within layers, suggesting that vibration acceleration influences void escape pathways. Finally, impact testing revealed the effect of the vibration pretreatment process parameters on the impact strength, implying a positive correlation between interlaminar shear strength and impact strength. [ABSTRACT FROM AUTHOR]

Let $\mathcal {M}$ be an Ahlfors $n$ -regular Riemannian manifold such that either the Ricci curvature is non-negative or the Ricci curvature is bounded from below together with a bound on the gradient of the heat kernel. In the paper [IMRN, 2022, no. 2, 1245-1269] of Brazke–Schikorra–Sire, the authors characterised the BMO function $u : \mathcal {M} \to \mathbb {R}$ by a Carleson measure condition of its $\sigma$ -harmonic extension $U:\mathcal {M}\times \mathbb {R}_+ \to \mathbb {R}$. This paper is concerned with the similar problem under a more general Dirichlet metric measure space setting, and the limiting behaviours of BMO & Carleson measure, where the heat kernel admits only the so-called diagonal upper estimate. More significantly, without the Ricci curvature condition, we relax the Ahlfors regularity to a doubling property, and remove the pointwise bound on the gradient of the heat kernel. Some similar results for the Lipschitz function are also given, and two open problems related to our main result are considered. [ABSTRACT FROM AUTHOR]

The primary challenge during the secondary bonding process of full-height honeycomb sandwich structures is the aramid honeycomb core's height shrinkage. This paper systematically investigated the height evolution behavior of the honeycomb core by using a creep testing machine. The results showed that the out-of-plane compression deformation curve of aramid honeycomb cores is mainly divided into three stages: the dehumidification stage, the pressurization stage and the creep stage. Under conditions of high temperature and pressure, height shrinkage was attributed to the dehydration caused by moisture infiltration, and the compression creep resulted from the slippage of polymer molecular chains. Dehydration shrinkage is stable, whereas compression creep reflects typical viscoelastic polymer characteristics. By employing the viscoelastic Burgers mechanical model and applying the nonlinear surface fitting method, the total height shrinkage deformation behavior of the aramid honeycomb core during the curing process can be accurately predicted by summing the above three stages. This research contributes valuable insights for the manufacturing process of honeycomb sandwich structures. [ABSTRACT FROM AUTHOR]

Ag3PO4 is an effective green photocatalyst that exhibits higher visible light photocatalytic performance for the degradation of various organic pollutants. The photocatalytic performance of Ag3PO4 is affected by the exposed high‐energy crystal facets. Herein, Ag3PO4 with different morphologies and specific surfaces is synthesized via a direct precipitation method in the presence of triethanolamine (TEA). The Ag(TEA)n complex, which served as an intermediate medium, plays a critical role during the morphological transformation. When the molar ratio of Ag+ to TEA is set as 1:12, 18‐facet polyhedral morphology of Ag3PO4 crystals is obtained. The spherical and dodecahedral samples are also obtained by adjusting the molar ratio of Ag+ to TEA as 1:1 and 1:14. The photocatalytic activity of the samples for the degradation of methylene blue (MB) is tested under visible light irradiation. It is demonstrated when the molar ratio of Ag+/TEA is 1:12, Ag3PO4 polyhedra with 18‐facet are fabricated. X‐ray diffraction and scanning electron microscopy results indicate that the 18‐facet polyhedron, with six {100} facets and twelve {110} facets, enjoys the most exposed high‐energy crystal facets. Photocatalytic experiments show that the 18‐facet polyhedron has the best performance, and the degradation of MB by Ag3PO4 polyhedron with 18‐facet morphology reaches 90% within 70 min. [ABSTRACT FROM AUTHOR]